From e5662ba6525c27248d57d8265e9c6c3a46f95c7e Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Wed, 5 Aug 2020 21:26:17 +0200
Subject: [PATCH 001/188] Add a flag to start the REPL on evaluation errors
This allows interactively inspecting the state of the evaluator at the
point of failure.
Example:
$ nix eval path:///home/eelco/Dev/nix/flake2#modules.hello-closure._final --start-repl-on-eval-errors
error: --- TypeError -------------------------------------------------------------------------------------------------------------------------------------------------------------------- nix
at: (20:53) in file: /nix/store/4264z41dxfdiqr95svmpnxxxwhfplhy0-source/flake.nix
19|
20| _final = builtins.foldl' (xs: mod: xs // (mod._module.config { config = _final; })) _defaults _allModules;
| ^
21| };
attempt to call something which is not a function but a set
Starting REPL to allow you to inspect the current state of the evaluator.
The following extra variables are in scope: arg, fun
Welcome to Nix version 2.4. Type :? for help.
nix-repl> fun
error: --- EvalError -------------------------------------------------------------------------------------------------------------------------------------------------------------------- nix
at: (150:28) in file: /nix/store/4264z41dxfdiqr95svmpnxxxwhfplhy0-source/flake.nix
149|
150| tarballClosure = (module {
| ^
151| extends = [ self.modules.derivation ];
attribute 'derivation' missing
nix-repl> :t fun
a set
nix-repl> builtins.attrNames fun
[ "tarballClosure" ]
nix-repl>
---
src/libexpr/eval.cc | 13 ++++++--
src/nix/command.cc | 24 ++++++++++++++
src/nix/command.hh | 8 +++++
src/nix/installables.cc | 7 ----
src/nix/repl.cc | 71 ++++++++++++++++++++++++++++-------------
5 files changed, 91 insertions(+), 32 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 0123070d1..5d71e5466 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -1171,6 +1171,8 @@ void EvalState::callPrimOp(Value & fun, Value & arg, Value & v, const Pos & pos)
}
}
+std::function<void(const Error & error, const std::map<std::string, Value *> & env)> debuggerHook;
+
void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & pos)
{
auto trace = evalSettings.traceFunctionCalls ? std::make_unique<FunctionCallTrace>(pos) : nullptr;
@@ -1198,8 +1200,15 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
}
}
- if (fun.type != tLambda)
- throwTypeError(pos, "attempt to call something which is not a function but %1%", fun);
+ if (fun.type != tLambda) {
+ auto error = TypeError({
+ .hint = hintfmt("attempt to call something which is not a function but %1%", showType(fun)),
+ .errPos = pos
+ });
+ if (debuggerHook)
+ debuggerHook(error, {{"fun", &fun}, {"arg", &arg}});
+ throw error;
+ }
ExprLambda & lambda(*fun.lambda.fun);
diff --git a/src/nix/command.cc b/src/nix/command.cc
index af36dda89..8b69948b6 100644
--- a/src/nix/command.cc
+++ b/src/nix/command.cc
@@ -31,6 +31,30 @@ void StoreCommand::run()
run(getStore());
}
+EvalCommand::EvalCommand()
+{
+ addFlag({
+ .longName = "start-repl-on-eval-errors",
+ .description = "start an interactive environment if evaluation fails",
+ .handler = {&startReplOnEvalErrors, true},
+ });
+}
+
+extern std::function<void(const Error & error, const std::map<std::string, Value *> & env)> debuggerHook;
+
+ref<EvalState> EvalCommand::getEvalState()
+{
+ if (!evalState) {
+ evalState = std::make_shared<EvalState>(searchPath, getStore());
+ if (startReplOnEvalErrors)
+ debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error & error, const std::map<std::string, Value *> & env) {
+ printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error.what());
+ runRepl(evalState, env);
+ };
+ }
+ return ref<EvalState>(evalState);
+}
+
StorePathsCommand::StorePathsCommand(bool recursive)
: recursive(recursive)
{
diff --git a/src/nix/command.hh b/src/nix/command.hh
index bc46a2028..fe1cd2799 100644
--- a/src/nix/command.hh
+++ b/src/nix/command.hh
@@ -36,8 +36,12 @@ private:
struct EvalCommand : virtual StoreCommand, MixEvalArgs
{
+ bool startReplOnEvalErrors = false;
+
ref<EvalState> getEvalState();
+ EvalCommand();
+
std::shared_ptr<EvalState> evalState;
};
@@ -251,4 +255,8 @@ void printClosureDiff(
const StorePath & afterPath,
std::string_view indent);
+void runRepl(
+ ref<EvalState> evalState,
+ const std::map<std::string, Value *> & extraEnv);
+
}
diff --git a/src/nix/installables.cc b/src/nix/installables.cc
index 59b52ce95..926cac2f8 100644
--- a/src/nix/installables.cc
+++ b/src/nix/installables.cc
@@ -234,13 +234,6 @@ void completeFlakeRefWithFragment(
completeFlakeRef(evalState->store, prefix);
}
-ref<EvalState> EvalCommand::getEvalState()
-{
- if (!evalState)
- evalState = std::make_shared<EvalState>(searchPath, getStore());
- return ref<EvalState>(evalState);
-}
-
void completeFlakeRef(ref<Store> store, std::string_view prefix)
{
if (prefix == "")
diff --git a/src/nix/repl.cc b/src/nix/repl.cc
index fb9050d0d..8409c7574 100644
--- a/src/nix/repl.cc
+++ b/src/nix/repl.cc
@@ -41,7 +41,7 @@ namespace nix {
struct NixRepl : gc
{
string curDir;
- std::unique_ptr<EvalState> state;
+ ref<EvalState> state;
Bindings * autoArgs;
Strings loadedFiles;
@@ -54,7 +54,7 @@ struct NixRepl : gc
const Path historyFile;
- NixRepl(const Strings & searchPath, nix::ref<Store> store);
+ NixRepl(ref<EvalState> state);
~NixRepl();
void mainLoop(const std::vector<std::string> & files);
StringSet completePrefix(string prefix);
@@ -65,13 +65,13 @@ struct NixRepl : gc
void initEnv();
void reloadFiles();
void addAttrsToScope(Value & attrs);
- void addVarToScope(const Symbol & name, Value & v);
+ void addVarToScope(const Symbol & name, Value * v);
Expr * parseString(string s);
void evalString(string s, Value & v);
typedef set<Value *> ValuesSeen;
- std::ostream & printValue(std::ostream & str, Value & v, unsigned int maxDepth);
- std::ostream & printValue(std::ostream & str, Value & v, unsigned int maxDepth, ValuesSeen & seen);
+ std::ostream & printValue(std::ostream & str, Value & v, unsigned int maxDepth);
+ std::ostream & printValue(std::ostream & str, Value & v, unsigned int maxDepth, ValuesSeen & seen);
};
@@ -84,8 +84,8 @@ string removeWhitespace(string s)
}
-NixRepl::NixRepl(const Strings & searchPath, nix::ref<Store> store)
- : state(std::make_unique<EvalState>(searchPath, store))
+NixRepl::NixRepl(ref<EvalState> state)
+ : state(state)
, staticEnv(false, &state->staticBaseEnv)
, historyFile(getDataDir() + "/nix/repl-history")
{
@@ -176,11 +176,13 @@ void NixRepl::mainLoop(const std::vector<std::string> & files)
string error = ANSI_RED "error:" ANSI_NORMAL " ";
std::cout << "Welcome to Nix version " << nixVersion << ". Type :? for help." << std::endl << std::endl;
- for (auto & i : files)
- loadedFiles.push_back(i);
+ if (!files.empty()) {
+ for (auto & i : files)
+ loadedFiles.push_back(i);
- reloadFiles();
- if (!loadedFiles.empty()) std::cout << std::endl;
+ reloadFiles();
+ if (!loadedFiles.empty()) std::cout << std::endl;
+ }
// Allow nix-repl specific settings in .inputrc
rl_readline_name = "nix-repl";
@@ -516,10 +518,10 @@ bool NixRepl::processLine(string line)
isVarName(name = removeWhitespace(string(line, 0, p))))
{
Expr * e = parseString(string(line, p + 1));
- Value & v(*state->allocValue());
- v.type = tThunk;
- v.thunk.env = env;
- v.thunk.expr = e;
+ auto v = state->allocValue();
+ v->type = tThunk;
+ v->thunk.env = env;
+ v->thunk.expr = e;
addVarToScope(state->symbols.create(name), v);
} else {
Value v;
@@ -577,17 +579,17 @@ void NixRepl::addAttrsToScope(Value & attrs)
{
state->forceAttrs(attrs);
for (auto & i : *attrs.attrs)
- addVarToScope(i.name, *i.value);
+ addVarToScope(i.name, i.value);
std::cout << format("Added %1% variables.") % attrs.attrs->size() << std::endl;
}
-void NixRepl::addVarToScope(const Symbol & name, Value & v)
+void NixRepl::addVarToScope(const Symbol & name, Value * v)
{
if (displ >= envSize)
throw Error("environment full; cannot add more variables");
staticEnv.vars[name] = displ;
- env->values[displ++] = &v;
+ env->values[displ++] = v;
varNames.insert((string) name);
}
@@ -754,6 +756,26 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
return str;
}
+void runRepl(
+ ref<EvalState> evalState,
+ const std::map<std::string, Value *> & extraEnv)
+{
+ auto repl = std::make_unique<NixRepl>(evalState);
+
+ repl->initEnv();
+
+ std::set<std::string> names;
+
+ for (auto & [name, value] : extraEnv) {
+ names.insert(ANSI_BOLD + name + ANSI_NORMAL);
+ repl->addVarToScope(repl->state->symbols.create(name), value);
+ }
+
+ printError("The following extra variables are in scope: %s\n", concatStringsSep(", ", names));
+
+ repl->mainLoop({});
+}
+
struct CmdRepl : StoreCommand, MixEvalArgs
{
std::vector<std::string> files;
@@ -775,17 +797,20 @@ struct CmdRepl : StoreCommand, MixEvalArgs
Examples examples() override
{
return {
- Example{
- "Display all special commands within the REPL:",
- "nix repl\n nix-repl> :?"
- }
+ {
+ "Display all special commands within the REPL:",
+ "nix repl\n nix-repl> :?"
+ }
};
}
void run(ref<Store> store) override
{
evalSettings.pureEval = false;
- auto repl = std::make_unique<NixRepl>(searchPath, openStore());
+
+ auto evalState = make_ref<EvalState>(searchPath, store);
+
+ auto repl = std::make_unique<NixRepl>(evalState);
repl->autoArgs = getAutoArgs(*repl->state);
repl->mainLoop(files);
}
From e486996cef871337ef14991e709d7f2cc6611e4e Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Mon, 1 Feb 2021 15:50:58 +0100
Subject: [PATCH 002/188] Rename to --debugger
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Co-authored-by: Domen Kožar <domen@dev.si>
---
src/nix/command.cc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/nix/command.cc b/src/nix/command.cc
index 8b69948b6..c2bd5b13c 100644
--- a/src/nix/command.cc
+++ b/src/nix/command.cc
@@ -34,7 +34,7 @@ void StoreCommand::run()
EvalCommand::EvalCommand()
{
addFlag({
- .longName = "start-repl-on-eval-errors",
+ .longName = "debugger",
.description = "start an interactive environment if evaluation fails",
.handler = {&startReplOnEvalErrors, true},
});
From 57c2dd5d8581f37392df369493b00794b619304e Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Wed, 28 Apr 2021 09:55:08 -0600
Subject: [PATCH 003/188] fixes
---
src/libexpr/eval.cc | 2 +-
src/nix/repl.cc | 4 ++--
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index a92adc3c0..37fb6ed18 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -1278,7 +1278,7 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
if (!fun.isLambda()) {
auto error = TypeError({
// .hint = hintfmt("attempt to call something which is not a function but %1%", showType(fun)),
- .hint = hintfmt("attempt to call something which is not a function but %1%", fun),
+ .msg = hintfmt("attempt to call something which is not a function but %1%", fun),
.errPos = pos
});
if (debuggerHook)
diff --git a/src/nix/repl.cc b/src/nix/repl.cc
index bb067e935..b1f250e73 100644
--- a/src/nix/repl.cc
+++ b/src/nix/repl.cc
@@ -537,8 +537,8 @@ bool NixRepl::processLine(string line)
isVarName(name = removeWhitespace(string(line, 0, p))))
{
Expr * e = parseString(string(line, p + 1));
- Value & v(*state->allocValue());
- v.mkThunk(env, e);
+ Value *v = new Value(*state->allocValue());
+ v->mkThunk(env, e);
addVarToScope(state->symbols.create(name), v);
} else {
Value v;
From f32c687f03e9764e55831d894b719fdf0104cf25 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Wed, 28 Apr 2021 15:50:11 -0600
Subject: [PATCH 004/188] move repl.cc to libcmd for linkage
---
src/libcmd/command.cc | 37 +++++++++++++++++++++++++++++++++++++
src/libcmd/local.mk | 6 +++---
src/{nix => libcmd}/repl.cc | 0
3 files changed, 40 insertions(+), 3 deletions(-)
rename src/{nix => libcmd}/repl.cc (100%)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 644c9c3b0..d790bb51d 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -54,6 +54,7 @@ void StoreCommand::run()
run(getStore());
}
+/*
EvalCommand::EvalCommand()
{
addFlag({
@@ -77,6 +78,42 @@ ref<EvalState> EvalCommand::getEvalState()
}
return ref<EvalState>(evalState);
}
+*/
+EvalCommand::EvalCommand()
+{
+ addFlag({
+ .longName = "debugger",
+ .description = "start an interactive environment if evaluation fails",
+ .handler = {&startReplOnEvalErrors, true},
+ });
+}
+// ref<EvalState> EvalCommand::getEvalState()
+// {
+// if (!evalState)
+// evalState = std::make_shared<EvalState>(searchPath, getStore());
+// return ref<EvalState>(evalState);
+// }
+extern std::function<void(const Error & error, const std::map<std::string, Value *> & env)> debuggerHook;
+
+ref<EvalState> EvalCommand::getEvalState()
+{
+ if (!evalState) {
+ evalState = std::make_shared<EvalState>(searchPath, getStore());
+ if (startReplOnEvalErrors)
+ debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error & error, const std::map<std::string, Value *> & env) {
+ printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error.what());
+ runRepl(evalState, env);
+ };
+ }
+ return ref<EvalState>(evalState);
+}
+
+EvalCommand::~EvalCommand()
+{
+ if (evalState)
+ evalState->printStats();
+}
+
RealisedPathsCommand::RealisedPathsCommand(bool recursive)
: recursive(recursive)
diff --git a/src/libcmd/local.mk b/src/libcmd/local.mk
index ab0e0e43d..c282499b1 100644
--- a/src/libcmd/local.mk
+++ b/src/libcmd/local.mk
@@ -6,10 +6,10 @@ libcmd_DIR := $(d)
libcmd_SOURCES := $(wildcard $(d)/*.cc)
-libcmd_CXXFLAGS += -I src/libutil -I src/libstore -I src/libexpr -I src/libmain -I src/libfetchers
+libcmd_CXXFLAGS += -I src/libutil -I src/libstore -I src/libexpr -I src/libmain -I src/libfetchers -I src/nix
-libcmd_LDFLAGS = -llowdown
+libcmd_LDFLAGS = $(EDITLINE_LIBS) -llowdown
-libcmd_LIBS = libstore libutil libexpr libmain libfetchers
+libcmd_LIBS = libstore libutil libexpr libmain libfetchers libnix libwut
$(eval $(call install-file-in, $(d)/nix-cmd.pc, $(prefix)/lib/pkgconfig, 0644))
diff --git a/src/nix/repl.cc b/src/libcmd/repl.cc
similarity index 100%
rename from src/nix/repl.cc
rename to src/libcmd/repl.cc
From 2dd61411af903e374566e0cf5d06257ad240662e Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Mon, 3 May 2021 14:37:33 -0600
Subject: [PATCH 005/188] debugger on autoCallFunction error
---
src/libcmd/command.cc | 20 ++++++++++++--------
src/libexpr/eval.cc | 20 ++++++++++++++++++--
2 files changed, 30 insertions(+), 10 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index d790bb51d..51a071d25 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -79,24 +79,28 @@ ref<EvalState> EvalCommand::getEvalState()
return ref<EvalState>(evalState);
}
*/
-EvalCommand::EvalCommand()
-{
- addFlag({
- .longName = "debugger",
- .description = "start an interactive environment if evaluation fails",
- .handler = {&startReplOnEvalErrors, true},
- });
-}
// ref<EvalState> EvalCommand::getEvalState()
// {
// if (!evalState)
// evalState = std::make_shared<EvalState>(searchPath, getStore());
// return ref<EvalState>(evalState);
// }
+
+
+EvalCommand::EvalCommand()
+{
+ // std::cout << "EvalCommand::EvalCommand()" << std::endl;
+ addFlag({
+ .longName = "debugger",
+ .description = "start an interactive environment if evaluation fails",
+ .handler = {&startReplOnEvalErrors, true},
+ });
+}
extern std::function<void(const Error & error, const std::map<std::string, Value *> & env)> debuggerHook;
ref<EvalState> EvalCommand::getEvalState()
{
+ std::cout << " EvalCommand::getEvalState()" << startReplOnEvalErrors << std::endl;
if (!evalState) {
evalState = std::make_shared<EvalState>(searchPath, getStore());
if (startReplOnEvalErrors)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 37fb6ed18..51feef923 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -1398,12 +1398,28 @@ void EvalState::autoCallFunction(Bindings & args, Value & fun, Value & res)
if (j != args.end()) {
actualArgs->attrs->push_back(*j);
} else if (!i.def) {
- throwMissingArgumentError(i.pos, R"(cannot evaluate a function that has an argument without a value ('%1%')
+ auto error = MissingArgumentError({
+ .msg = hintfmt(R"(cannot evaluate a function that has an argument without a value ('%1%')
Nix attempted to evaluate a function as a top level expression; in
this case it must have its arguments supplied either by default
values, or passed explicitly with '--arg' or '--argstr'. See
-https://nixos.org/manual/nix/stable/#ss-functions.)", i.name);
+https://nixos.org/manual/nix/stable/#ss-functions.)", i.name),
+ .errPos = i.pos
+ });
+
+// throwMissingArgumentError(i.pos
+// , R"(cannot evaluate a function that has an argument without a value ('%1%')
+
+// Nix attempted to evaluate a function as a top level expression; in
+// this case it must have its arguments supplied either by default
+// values, or passed explicitly with '--arg' or '--argstr'. See
+// https://nixos.org/manual/nix/stable/#ss-functions.)", i.name);
+
+ if (debuggerHook)
+ debuggerHook(error, {{"fun", &fun}});
+
+ throw error;
}
}
From a8fef9a6b10c34e450d4251f7e9808c906e2f488 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Mon, 10 May 2021 18:36:57 -0600
Subject: [PATCH 006/188] throwTypeError with debugger/env
---
src/libexpr/eval.cc | 123 ++++++++++++++++++++++++++++++--------------
1 file changed, 85 insertions(+), 38 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 51feef923..a48c38e0d 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -17,6 +17,7 @@
#include <sys/resource.h>
#include <iostream>
#include <fstream>
+#include <optional>
#include <sys/resource.h>
@@ -35,6 +36,7 @@
namespace nix {
+std::function<void(const Error & error, const std::map<std::string, Value *> & env)> debuggerHook;
static char * dupString(const char * s)
{
@@ -615,7 +617,6 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
return {};
}
-
/* Every "format" object (even temporary) takes up a few hundred bytes
of stack space, which is a real killer in the recursive
evaluator. So here are some helper functions for throwing
@@ -656,22 +657,46 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & p1, const char * s, const
});
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s))
+// #define valmap(x) std::optional<const std::map<std::string, Value *>>
+
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const std::optional<const std::map<std::string, Value *>> & env))
{
- throw TypeError({
+ auto error = TypeError({
.msg = hintfmt(s),
.errPos = pos
});
+
+ if (debuggerHook)
+ debuggerHook(error, *env);
+ throw error;
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const ExprLambda & fun, const Symbol & s2))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v, const std::optional<const std::map<std::string, Value *>> & env))
{
- throw TypeError({
+ auto error = TypeError({
+ .msg = hintfmt(s, v),
+ .errPos = pos
+ });
+
+ if (debuggerHook)
+ debuggerHook(error, *env);
+ throw error;
+}
+
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const ExprLambda & fun, const Symbol & s2, const std::optional<const std::map<std::string, Value *>> & env))
+{
+ auto error = TypeError({
.msg = hintfmt(s, fun.showNamePos(), s2),
.errPos = pos
});
+
+ if (debuggerHook)
+ debuggerHook(error, *env);
+ throw error;
}
+
+
LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s, const string & s1))
{
throw AssertionError({
@@ -688,12 +713,16 @@ LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char *
});
}
-LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char * s, const string & s1))
+LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char * s, const string & s1, const std::optional<const std::map<std::string, Value *>> & env))
{
- throw MissingArgumentError({
+ auto error = MissingArgumentError({
.msg = hintfmt(s, s1),
.errPos = pos
});
+
+ if (debuggerHook)
+ debuggerHook(error, *env);
+ throw error;
}
LocalNoInline(void addErrorTrace(Error & e, const char * s, const string & s2))
@@ -1246,7 +1275,6 @@ void EvalState::callPrimOp(Value & fun, Value & arg, Value & v, const Pos & pos)
}
}
-std::function<void(const Error & error, const std::map<std::string, Value *> & env)> debuggerHook;
void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & pos)
{
@@ -1276,14 +1304,20 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
}
if (!fun.isLambda()) {
- auto error = TypeError({
- // .hint = hintfmt("attempt to call something which is not a function but %1%", showType(fun)),
- .msg = hintfmt("attempt to call something which is not a function but %1%", fun),
- .errPos = pos
- });
- if (debuggerHook)
- debuggerHook(error, {{"fun", &fun}, {"arg", &arg}});
- throw error;
+ throwTypeError(
+ pos,
+ "attempt to call something which is not a function but %1%",
+ fun,
+ std::optional<const std::map<std::string, Value *>>({{"fun", &fun}, {"arg", &arg}}));
+
+ // auto error = TypeError({
+ // // .hint = hintfmt("attempt to call something which is not a function but %1%", showType(fun)),
+ // .msg = hintfmt("attempt to call something which is not a function but %1%", fun),
+ // .errPos = pos
+ // });
+ // if (debuggerHook)
+ // debuggerHook(error, {{"fun", &fun}, {"arg", &arg}});
+ // throw error;
}
ExprLambda & lambda(*fun.lambda.fun);
@@ -1312,8 +1346,13 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
for (auto & i : lambda.formals->formals) {
Bindings::iterator j = arg.attrs->find(i.name);
if (j == arg.attrs->end()) {
- if (!i.def) throwTypeError(pos, "%1% called without required argument '%2%'",
- lambda, i.name);
+ if (!i.def)
+ throwTypeError(
+ pos,
+ "%1% called without required argument '%2%'",
+ lambda,
+ i.name,
+ std::optional<const std::map<std::string, Value *>>({{"fun", &fun}, {"arg", &arg}}));
env2.values[displ++] = i.def->maybeThunk(*this, env2);
} else {
attrsUsed++;
@@ -1328,7 +1367,11 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
user. */
for (auto & i : *arg.attrs)
if (lambda.formals->argNames.find(i.name) == lambda.formals->argNames.end())
- throwTypeError(pos, "%1% called with unexpected argument '%2%'", lambda, i.name);
+ throwTypeError(pos,
+ "%1% called with unexpected argument '%2%'",
+ lambda,
+ i.name,
+ std::optional<const std::map<std::string, Value *>>({{"fun", &fun}, {"arg", &arg}}));
abort(); // can't happen
}
}
@@ -1398,16 +1441,14 @@ void EvalState::autoCallFunction(Bindings & args, Value & fun, Value & res)
if (j != args.end()) {
actualArgs->attrs->push_back(*j);
} else if (!i.def) {
- auto error = MissingArgumentError({
- .msg = hintfmt(R"(cannot evaluate a function that has an argument without a value ('%1%')
+ throwMissingArgumentError(i.pos, R"(cannot evaluate a function that has an argument without a value ('%1%')
Nix attempted to evaluate a function as a top level expression; in
this case it must have its arguments supplied either by default
values, or passed explicitly with '--arg' or '--argstr'. See
-https://nixos.org/manual/nix/stable/#ss-functions.)", i.name),
- .errPos = i.pos
- });
-
+https://nixos.org/manual/nix/stable/#ss-functions.)", i.name,
+ std::optional<const std::map<std::string, Value *>>({{"fun", &fun}})); // todo add bindings.
+
// throwMissingArgumentError(i.pos
// , R"(cannot evaluate a function that has an argument without a value ('%1%')
@@ -1416,10 +1457,11 @@ https://nixos.org/manual/nix/stable/#ss-functions.)", i.name),
// values, or passed explicitly with '--arg' or '--argstr'. See
// https://nixos.org/manual/nix/stable/#ss-functions.)", i.name);
- if (debuggerHook)
- debuggerHook(error, {{"fun", &fun}});
+ // if (debuggerHook)
+ // // debuggerHook(error, args);
+ // debuggerHook(error, {{"fun", &fun}});
- throw error;
+ // throw error;
}
}
@@ -1673,7 +1715,8 @@ NixInt EvalState::forceInt(Value & v, const Pos & pos)
{
forceValue(v, pos);
if (v.type() != nInt)
- throwTypeError(pos, "value is %1% while an integer was expected", v);
+ throwTypeError(pos, "value is %1% while an integer was expected", v,
+ std::optional<const std::map<std::string, Value *>>({{"value", &v}}));
return v.integer;
}
@@ -1684,7 +1727,8 @@ NixFloat EvalState::forceFloat(Value & v, const Pos & pos)
if (v.type() == nInt)
return v.integer;
else if (v.type() != nFloat)
- throwTypeError(pos, "value is %1% while a float was expected", v);
+ throwTypeError(pos, "value is %1% while a float was expected", v,
+ std::optional<const std::map<std::string, Value *>>({{"value", &v}}));
return v.fpoint;
}
@@ -1693,7 +1737,8 @@ bool EvalState::forceBool(Value & v, const Pos & pos)
{
forceValue(v, pos);
if (v.type() != nBool)
- throwTypeError(pos, "value is %1% while a Boolean was expected", v);
+ throwTypeError(pos, "value is %1% while a Boolean was expected", v,
+ std::optional<const std::map<std::string, Value *>>({{"value", &v}}));
return v.boolean;
}
@@ -1708,7 +1753,8 @@ void EvalState::forceFunction(Value & v, const Pos & pos)
{
forceValue(v, pos);
if (v.type() != nFunction && !isFunctor(v))
- throwTypeError(pos, "value is %1% while a function was expected", v);
+ throwTypeError(pos, "value is %1% while a function was expected", v,
+ std::optional<const std::map<std::string, Value *>>({{"value", &v}}));
}
@@ -1716,10 +1762,8 @@ string EvalState::forceString(Value & v, const Pos & pos)
{
forceValue(v, pos);
if (v.type() != nString) {
- if (pos)
- throwTypeError(pos, "value is %1% while a string was expected", v);
- else
- throwTypeError("value is %1% while a string was expected", v);
+ throwTypeError(pos, "value is %1% while a string was expected", v,
+ std::optional<const std::map<std::string, Value *>>({{"value", &v}}));
}
return string(v.string.s);
}
@@ -1826,7 +1870,9 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
return *maybeString;
}
auto i = v.attrs->find(sOutPath);
- if (i == v.attrs->end()) throwTypeError(pos, "cannot coerce a set to a string");
+ if (i == v.attrs->end())
+ throwTypeError(pos, "cannot coerce a set to a string",
+ std::optional<const std::map<std::string, Value *>>({{"value", &v}}));
return coerceToString(pos, *i->value, context, coerceMore, copyToStore);
}
@@ -1857,7 +1903,8 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
}
}
- throwTypeError(pos, "cannot coerce %1% to a string", v);
+ throwTypeError(pos, "cannot coerce %1% to a string", v,
+ std::optional<const std::map<std::string, Value *>>({{"value", &v}}));
}
From e7847ad7a1268bbe6962a36a29b044ee841f1874 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Tue, 11 May 2021 15:38:49 -0600
Subject: [PATCH 007/188] map1/2 for stack usage
---
Makefile | 2 +-
src/libexpr/eval.cc | 56 +++++++++++++++++++++------------------------
2 files changed, 27 insertions(+), 31 deletions(-)
diff --git a/Makefile b/Makefile
index 68ec3ab0c..bc2684eaa 100644
--- a/Makefile
+++ b/Makefile
@@ -31,4 +31,4 @@ endif
include mk/lib.mk
-GLOBAL_CXXFLAGS += -g -Wall -include config.h -std=c++17
+GLOBAL_CXXFLAGS += -g -Wall -include config.h -std=c++17 -fstack-usage
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index a48c38e0d..f8391cd77 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -17,7 +17,6 @@
#include <sys/resource.h>
#include <iostream>
#include <fstream>
-#include <optional>
#include <sys/resource.h>
@@ -617,6 +616,19 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
return {};
}
+static std::optional<const std::map<std::string, Value *>> map1(const char *name, Value *v) __attribute__((noinline));
+std::optional<const std::map<std::string, Value *>> map1(const char *name, Value *v)
+{
+ return std::optional<const std::map<std::string, Value *>>({{name, v}});
+}
+
+
+static std::optional<const std::map<std::string, Value *>> map2(const char *name1, Value *v1, const char *name2, Value *v2) __attribute__((noinline));
+std::optional<const std::map<std::string, Value *>> map2(const char *name1, Value *v1, const char *name2, Value *v2)
+{
+ return std::optional<const std::map<std::string, Value *>>({{name1, v1},{name2, v2}});
+}
+
/* Every "format" object (even temporary) takes up a few hundred bytes
of stack space, which is a real killer in the recursive
evaluator. So here are some helper functions for throwing
@@ -657,8 +669,6 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & p1, const char * s, const
});
}
-// #define valmap(x) std::optional<const std::map<std::string, Value *>>
-
LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const std::optional<const std::map<std::string, Value *>> & env))
{
auto error = TypeError({
@@ -1308,7 +1318,7 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
pos,
"attempt to call something which is not a function but %1%",
fun,
- std::optional<const std::map<std::string, Value *>>({{"fun", &fun}, {"arg", &arg}}));
+ map2("fun", &fun, "arg", &arg));
// auto error = TypeError({
// // .hint = hintfmt("attempt to call something which is not a function but %1%", showType(fun)),
@@ -1352,7 +1362,7 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
"%1% called without required argument '%2%'",
lambda,
i.name,
- std::optional<const std::map<std::string, Value *>>({{"fun", &fun}, {"arg", &arg}}));
+ map2("fun", &fun, "arg", &arg));
env2.values[displ++] = i.def->maybeThunk(*this, env2);
} else {
attrsUsed++;
@@ -1371,7 +1381,7 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
"%1% called with unexpected argument '%2%'",
lambda,
i.name,
- std::optional<const std::map<std::string, Value *>>({{"fun", &fun}, {"arg", &arg}}));
+ map2("fun", &fun, "arg", &arg));
abort(); // can't happen
}
}
@@ -1446,23 +1456,9 @@ void EvalState::autoCallFunction(Bindings & args, Value & fun, Value & res)
Nix attempted to evaluate a function as a top level expression; in
this case it must have its arguments supplied either by default
values, or passed explicitly with '--arg' or '--argstr'. See
-https://nixos.org/manual/nix/stable/#ss-functions.)", i.name,
- std::optional<const std::map<std::string, Value *>>({{"fun", &fun}})); // todo add bindings.
-
-// throwMissingArgumentError(i.pos
-// , R"(cannot evaluate a function that has an argument without a value ('%1%')
-
-// Nix attempted to evaluate a function as a top level expression; in
-// this case it must have its arguments supplied either by default
-// values, or passed explicitly with '--arg' or '--argstr'. See
-// https://nixos.org/manual/nix/stable/#ss-functions.)", i.name);
-
- // if (debuggerHook)
- // // debuggerHook(error, args);
- // debuggerHook(error, {{"fun", &fun}});
-
- // throw error;
-
+https://nixos.org/manual/nix/stable/#ss-functions.)",
+ i.name,
+ map1("fun", &fun)); // todo add bindings.
}
}
}
@@ -1716,7 +1712,7 @@ NixInt EvalState::forceInt(Value & v, const Pos & pos)
forceValue(v, pos);
if (v.type() != nInt)
throwTypeError(pos, "value is %1% while an integer was expected", v,
- std::optional<const std::map<std::string, Value *>>({{"value", &v}}));
+ map1("value", &v));
return v.integer;
}
@@ -1728,7 +1724,7 @@ NixFloat EvalState::forceFloat(Value & v, const Pos & pos)
return v.integer;
else if (v.type() != nFloat)
throwTypeError(pos, "value is %1% while a float was expected", v,
- std::optional<const std::map<std::string, Value *>>({{"value", &v}}));
+ map1("value", &v));
return v.fpoint;
}
@@ -1738,7 +1734,7 @@ bool EvalState::forceBool(Value & v, const Pos & pos)
forceValue(v, pos);
if (v.type() != nBool)
throwTypeError(pos, "value is %1% while a Boolean was expected", v,
- std::optional<const std::map<std::string, Value *>>({{"value", &v}}));
+ map1("value", &v));
return v.boolean;
}
@@ -1754,7 +1750,7 @@ void EvalState::forceFunction(Value & v, const Pos & pos)
forceValue(v, pos);
if (v.type() != nFunction && !isFunctor(v))
throwTypeError(pos, "value is %1% while a function was expected", v,
- std::optional<const std::map<std::string, Value *>>({{"value", &v}}));
+ map1("value", &v));
}
@@ -1763,7 +1759,7 @@ string EvalState::forceString(Value & v, const Pos & pos)
forceValue(v, pos);
if (v.type() != nString) {
throwTypeError(pos, "value is %1% while a string was expected", v,
- std::optional<const std::map<std::string, Value *>>({{"value", &v}}));
+ map1("value", &v));
}
return string(v.string.s);
}
@@ -1872,7 +1868,7 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
auto i = v.attrs->find(sOutPath);
if (i == v.attrs->end())
throwTypeError(pos, "cannot coerce a set to a string",
- std::optional<const std::map<std::string, Value *>>({{"value", &v}}));
+ map1("value", &v));
return coerceToString(pos, *i->value, context, coerceMore, copyToStore);
}
@@ -1904,7 +1900,7 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
}
throwTypeError(pos, "cannot coerce %1% to a string", v,
- std::optional<const std::map<std::string, Value *>>({{"value", &v}}));
+ map1("value", &v));
}
From 0c2265da85bd094376279aea5e282974784218b3 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Wed, 12 May 2021 09:43:58 -0600
Subject: [PATCH 008/188] unique_ptr for valmap
---
src/libexpr/eval.cc | 24 ++++++++++++++----------
1 file changed, 14 insertions(+), 10 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index f8391cd77..531e3f752 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -616,17 +616,21 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
return {};
}
-static std::optional<const std::map<std::string, Value *>> map1(const char *name, Value *v) __attribute__((noinline));
-std::optional<const std::map<std::string, Value *>> map1(const char *name, Value *v)
+// typedef std::optional<const std::map<std::string, Value *>> valmap;
+typedef const std::map<std::string, Value *> valmap;
+
+static std::unique_ptr<valmap> map1(const char *name, Value *v) __attribute__((noinline));
+std::unique_ptr<valmap> map1(const char *name, Value *v)
{
- return std::optional<const std::map<std::string, Value *>>({{name, v}});
+ // return new valmap({{name, v}});
+ return std::unique_ptr<valmap>(new valmap({{name, v}}));
}
-static std::optional<const std::map<std::string, Value *>> map2(const char *name1, Value *v1, const char *name2, Value *v2) __attribute__((noinline));
-std::optional<const std::map<std::string, Value *>> map2(const char *name1, Value *v1, const char *name2, Value *v2)
+static std::unique_ptr<valmap> map2(const char *name1, Value *v1, const char *name2, Value *v2) __attribute__((noinline));
+std::unique_ptr<valmap> map2(const char *name1, Value *v1, const char *name2, Value *v2)
{
- return std::optional<const std::map<std::string, Value *>>({{name1, v1},{name2, v2}});
+ return std::unique_ptr<valmap>(new valmap({{name1, v1}, {name2, v2}}));
}
/* Every "format" object (even temporary) takes up a few hundred bytes
@@ -669,7 +673,7 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & p1, const char * s, const
});
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const std::optional<const std::map<std::string, Value *>> & env))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, std::unique_ptr<valmap> env))
{
auto error = TypeError({
.msg = hintfmt(s),
@@ -681,7 +685,7 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
throw error;
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v, const std::optional<const std::map<std::string, Value *>> & env))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v, std::unique_ptr<valmap> env))
{
auto error = TypeError({
.msg = hintfmt(s, v),
@@ -693,7 +697,7 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
throw error;
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const ExprLambda & fun, const Symbol & s2, const std::optional<const std::map<std::string, Value *>> & env))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const ExprLambda & fun, const Symbol & s2, std::unique_ptr<valmap> env))
{
auto error = TypeError({
.msg = hintfmt(s, fun.showNamePos(), s2),
@@ -723,7 +727,7 @@ LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char *
});
}
-LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char * s, const string & s1, const std::optional<const std::map<std::string, Value *>> & env))
+LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char * s, const string & s1, std::unique_ptr<valmap> env))
{
auto error = MissingArgumentError({
.msg = hintfmt(s, s1),
From 459bccc750616f07c9d55d6c12211e07c2369f1a Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Wed, 12 May 2021 11:33:31 -0600
Subject: [PATCH 009/188] plain env pointer
---
src/libexpr/eval.cc | 23 +++++++++++++----------
1 file changed, 13 insertions(+), 10 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 531e3f752..3f73c24a1 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -619,18 +619,18 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
// typedef std::optional<const std::map<std::string, Value *>> valmap;
typedef const std::map<std::string, Value *> valmap;
-static std::unique_ptr<valmap> map1(const char *name, Value *v) __attribute__((noinline));
-std::unique_ptr<valmap> map1(const char *name, Value *v)
+static valmap* map1(const char *name, Value *v) __attribute__((noinline));
+valmap* map1(const char *name, Value *v)
{
// return new valmap({{name, v}});
- return std::unique_ptr<valmap>(new valmap({{name, v}}));
+ return new valmap({{name, v}});
}
-static std::unique_ptr<valmap> map2(const char *name1, Value *v1, const char *name2, Value *v2) __attribute__((noinline));
-std::unique_ptr<valmap> map2(const char *name1, Value *v1, const char *name2, Value *v2)
+static valmap* map2(const char *name1, Value *v1, const char *name2, Value *v2) __attribute__((noinline));
+valmap* map2(const char *name1, Value *v1, const char *name2, Value *v2)
{
- return std::unique_ptr<valmap>(new valmap({{name1, v1}, {name2, v2}}));
+ return new valmap({{name1, v1}, {name2, v2}});
}
/* Every "format" object (even temporary) takes up a few hundred bytes
@@ -673,8 +673,9 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & p1, const char * s, const
});
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, std::unique_ptr<valmap> env))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, valmap* env))
{
+ auto delenv = std::unique_ptr<valmap>(env);
auto error = TypeError({
.msg = hintfmt(s),
.errPos = pos
@@ -685,8 +686,9 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, std::
throw error;
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v, std::unique_ptr<valmap> env))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v, valmap* env))
{
+ auto delenv = std::unique_ptr<valmap>(env);
auto error = TypeError({
.msg = hintfmt(s, v),
.errPos = pos
@@ -697,8 +699,9 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
throw error;
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const ExprLambda & fun, const Symbol & s2, std::unique_ptr<valmap> env))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const ExprLambda & fun, const Symbol & s2, valmap* env))
{
+ auto delenv = std::unique_ptr<valmap>(env);
auto error = TypeError({
.msg = hintfmt(s, fun.showNamePos(), s2),
.errPos = pos
@@ -727,7 +730,7 @@ LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char *
});
}
-LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char * s, const string & s1, std::unique_ptr<valmap> env))
+LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char * s, const string & s1, valmap* env))
{
auto error = MissingArgumentError({
.msg = hintfmt(s, s1),
From ab19d1685dd67a19c91eb3af346b9ac86f34b7d1 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Thu, 13 May 2021 16:00:48 -0600
Subject: [PATCH 010/188] throwEvalError; mapBindings
---
src/libexpr/eval.cc | 79 ++++++++++++++++++++++++++++++++-------------
1 file changed, 57 insertions(+), 22 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 3f73c24a1..29b2721fe 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -617,20 +617,43 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
}
// typedef std::optional<const std::map<std::string, Value *>> valmap;
-typedef const std::map<std::string, Value *> valmap;
+typedef std::map<std::string, Value *> valmap;
-static valmap* map1(const char *name, Value *v) __attribute__((noinline));
-valmap* map1(const char *name, Value *v)
+static valmap * map0() __attribute__((noinline));
+valmap * map0()
{
- // return new valmap({{name, v}});
- return new valmap({{name, v}});
+ return new valmap();
+}
+
+static valmap * map1(const char *name, Value *v) __attribute__((noinline));
+valmap * map1(const char *name, Value *v)
+{
+ // return new valmap({{name, v}});
+ return new valmap({{name, v}});
}
-static valmap* map2(const char *name1, Value *v1, const char *name2, Value *v2) __attribute__((noinline));
-valmap* map2(const char *name1, Value *v1, const char *name2, Value *v2)
+static valmap * map2(const char *name1, Value *v1, const char *name2, Value *v2) __attribute__((noinline));
+valmap * map2(const char *name1, Value *v1, const char *name2, Value *v2)
{
- return new valmap({{name1, v1}, {name2, v2}});
+ return new valmap({{name1, v1}, {name2, v2}});
+}
+
+static valmap * mapBindings(Bindings *b) __attribute__((noinline));
+valmap * mapBindings(Bindings *b)
+{
+ auto map = new valmap();
+
+ // auto v = new Value;
+
+ for (auto i = b->begin(); i != b->end(); ++i)
+ {
+ std::string s = i->name;
+ (*map)[s] = i->value;
+ // map->insert({std::string("wat"), v});
+ }
+
+ return map;
}
/* Every "format" object (even temporary) takes up a few hundred bytes
@@ -638,17 +661,27 @@ valmap* map2(const char *name1, Value *v1, const char *name2, Value *v2)
evaluator. So here are some helper functions for throwing
exceptions. */
-LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2))
+LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, valmap * env))
{
- throw EvalError(s, s2);
+ auto delenv = std::unique_ptr<valmap>(env);
+ auto error = EvalError(s, s2);
+
+ if (debuggerHook)
+ debuggerHook(error, *env);
+ throw error;
}
-LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2))
+LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2, valmap * env))
{
- throw EvalError({
+ auto delenv = std::unique_ptr<valmap>(env);
+ auto error = EvalError({
.msg = hintfmt(s, s2),
.errPos = pos
});
+
+ if (debuggerHook)
+ debuggerHook(error, *env);
+ throw error;
}
LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, const string & s3))
@@ -673,7 +706,7 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & p1, const char * s, const
});
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, valmap* env))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, valmap * env))
{
auto delenv = std::unique_ptr<valmap>(env);
auto error = TypeError({
@@ -686,7 +719,7 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, valma
throw error;
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v, valmap* env))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v, valmap * env))
{
auto delenv = std::unique_ptr<valmap>(env);
auto error = TypeError({
@@ -699,7 +732,7 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
throw error;
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const ExprLambda & fun, const Symbol & s2, valmap* env))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const ExprLambda & fun, const Symbol & s2, valmap * env))
{
auto delenv = std::unique_ptr<valmap>(env);
auto error = TypeError({
@@ -730,7 +763,7 @@ LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char *
});
}
-LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char * s, const string & s1, valmap* env))
+LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char * s, const string & s1, valmap * env))
{
auto error = MissingArgumentError({
.msg = hintfmt(s, s1),
@@ -1198,7 +1231,7 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
} else {
state.forceAttrs(*vAttrs, pos);
if ((j = vAttrs->attrs->find(name)) == vAttrs->attrs->end())
- throwEvalError(pos, "attribute '%1%' missing", name);
+ throwEvalError(pos, "attribute '%1%' missing", name, mapBindings(vAttrs->attrs));
}
vAttrs = j->value;
pos2 = j->pos;
@@ -1463,7 +1496,7 @@ void EvalState::autoCallFunction(Bindings & args, Value & fun, Value & res)
Nix attempted to evaluate a function as a top level expression; in
this case it must have its arguments supplied either by default
values, or passed explicitly with '--arg' or '--argstr'. See
-https://nixos.org/manual/nix/stable/#ss-functions.)",
+https://nixos.org/manual/nix/stable/#ss-functions.)",
i.name,
map1("fun", &fun)); // todo add bindings.
}
@@ -1651,14 +1684,14 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
nf = n;
nf += vTmp.fpoint;
} else
- throwEvalError(pos, "cannot add %1% to an integer", showType(vTmp));
+ throwEvalError(pos, "cannot add %1% to an integer", showType(vTmp), map0());
} else if (firstType == nFloat) {
if (vTmp.type() == nInt) {
nf += vTmp.integer;
} else if (vTmp.type() == nFloat) {
nf += vTmp.fpoint;
} else
- throwEvalError(pos, "cannot add %1% to a float", showType(vTmp));
+ throwEvalError(pos, "cannot add %1% to a float", showType(vTmp), map0());
} else
s << state.coerceToString(pos, vTmp, context, false, firstType == nString);
}
@@ -1914,7 +1947,9 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
string EvalState::copyPathToStore(PathSet & context, const Path & path)
{
if (nix::isDerivation(path))
- throwEvalError("file names are not allowed to end in '%1%'", drvExtension);
+ throwEvalError("file names are not allowed to end in '%1%'",
+ drvExtension,
+ map0());
Path dstPath;
auto i = srcToStore.find(path);
@@ -1938,7 +1973,7 @@ Path EvalState::coerceToPath(const Pos & pos, Value & v, PathSet & context)
{
string path = coerceToString(pos, v, context, false, false);
if (path == "" || path[0] != '/')
- throwEvalError(pos, "string '%1%' doesn't represent an absolute path", path);
+ throwEvalError(pos, "string '%1%' doesn't represent an absolute path", path, map1("value", &v));
return path;
}
From 989a4181a8f3fb830bae5018c18a13dc535b395a Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Fri, 14 May 2021 11:06:20 -0600
Subject: [PATCH 011/188] throwEvalError form 2
---
src/libexpr/eval.cc | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 29b2721fe..1ae88ea1f 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -684,9 +684,14 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const
throw error;
}
-LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, const string & s3))
+LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, const string & s3, valmap * env))
{
- throw EvalError(s, s2, s3);
+ auto delenv = std::unique_ptr<valmap>(env);
+ auto error = EvalError(s, s2, s3);
+
+ if (debuggerHook)
+ debuggerHook(error, *env);
+ throw error;
}
LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2, const string & s3))
@@ -1498,7 +1503,7 @@ this case it must have its arguments supplied either by default
values, or passed explicitly with '--arg' or '--argstr'. See
https://nixos.org/manual/nix/stable/#ss-functions.)",
i.name,
- map1("fun", &fun)); // todo add bindings.
+ map1("fun", &fun)); // todo add bindings + fun
}
}
}
@@ -1850,10 +1855,10 @@ string EvalState::forceStringNoCtx(Value & v, const Pos & pos)
if (v.string.context) {
if (pos)
throwEvalError(pos, "the string '%1%' is not allowed to refer to a store path (such as '%2%')",
- v.string.s, v.string.context[0]);
+ v.string.s, v.string.context[0]);
else
throwEvalError("the string '%1%' is not allowed to refer to a store path (such as '%2%')",
- v.string.s, v.string.context[0]);
+ v.string.s, v.string.context[0], map1("value", &v));
}
return s;
}
@@ -2052,7 +2057,8 @@ bool EvalState::eqValues(Value & v1, Value & v2)
return v1.fpoint == v2.fpoint;
default:
- throwEvalError("cannot compare %1% with %2%", showType(v1), showType(v2));
+ throwEvalError("cannot compare %1% with %2%", showType(v1), showType(v2),
+ map2("value1", &v1, "value2", &v2));
}
}
From ed74eaa07f6f7b5e87a1b96eff94990551ff488e Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Fri, 14 May 2021 11:09:18 -0600
Subject: [PATCH 012/188] throwEvalError form 3
---
src/libexpr/eval.cc | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 1ae88ea1f..592f89fdf 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -694,12 +694,17 @@ LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, con
throw error;
}
-LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2, const string & s3))
+LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2, const string & s3, valmap * env))
{
- throw EvalError({
+ auto delenv = std::unique_ptr<valmap>(env);
+ auto error = EvalError({
.msg = hintfmt(s, s2, s3),
.errPos = pos
});
+
+ if (debuggerHook)
+ debuggerHook(error, *env);
+ throw error;
}
LocalNoInlineNoReturn(void throwEvalError(const Pos & p1, const char * s, const Symbol & sym, const Pos & p2))
@@ -1855,7 +1860,7 @@ string EvalState::forceStringNoCtx(Value & v, const Pos & pos)
if (v.string.context) {
if (pos)
throwEvalError(pos, "the string '%1%' is not allowed to refer to a store path (such as '%2%')",
- v.string.s, v.string.context[0]);
+ v.string.s, v.string.context[0], map1("value", &v));
else
throwEvalError("the string '%1%' is not allowed to refer to a store path (such as '%2%')",
v.string.s, v.string.context[0], map1("value", &v));
From d041dd874eddef8e56822ecb0806ad53db1fdacc Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Fri, 14 May 2021 11:15:24 -0600
Subject: [PATCH 013/188] throwEvalError form 4
---
src/libexpr/eval.cc | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 592f89fdf..8c96b6ba2 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -707,13 +707,18 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const
throw error;
}
-LocalNoInlineNoReturn(void throwEvalError(const Pos & p1, const char * s, const Symbol & sym, const Pos & p2))
+LocalNoInlineNoReturn(void throwEvalError(const Pos & p1, const char * s, const Symbol & sym, const Pos & p2, valmap * env))
{
// p1 is where the error occurred; p2 is a position mentioned in the message.
- throw EvalError({
+ auto delenv = std::unique_ptr<valmap>(env);
+ auto error = EvalError({
.msg = hintfmt(s, sym, p2),
.errPos = p1
});
+
+ if (debuggerHook)
+ debuggerHook(error, *env);
+ throw error;
}
LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, valmap * env))
@@ -1151,7 +1156,8 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
Symbol nameSym = state.symbols.create(nameVal.string.s);
Bindings::iterator j = v.attrs->find(nameSym);
if (j != v.attrs->end())
- throwEvalError(i.pos, "dynamic attribute '%1%' already defined at %2%", nameSym, *j->pos);
+ throwEvalError(i.pos, "dynamic attribute '%1%' already defined at %2%", nameSym, *j->pos,
+ map1("value", &v)); // TODO dynamicAttrs to env?
i.valueExpr->setName(nameSym);
/* Keep sorted order so find can catch duplicates */
From 17af7dc3260216aa279a1bb6f506b537aaef7bc3 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Fri, 14 May 2021 11:29:26 -0600
Subject: [PATCH 014/188] throwAssertionError, throwUndefinedError ->
valmap-ized
---
src/libexpr/eval.cc | 25 +++++++++++++++++--------
1 file changed, 17 insertions(+), 8 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 8c96b6ba2..671b07dcd 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -760,26 +760,35 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
throw error;
}
-
-
-LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s, const string & s1))
+LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s, const string & s1, valmap * env))
{
- throw AssertionError({
+ auto delenv = std::unique_ptr<valmap>(env);
+ auto error = AssertionError({
.msg = hintfmt(s, s1),
.errPos = pos
});
+
+ if (debuggerHook)
+ debuggerHook(error, *env);
+ throw error;
}
-LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char * s, const string & s1))
+LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char * s, const string & s1, valmap * env))
{
- throw UndefinedVarError({
+ auto delenv = std::unique_ptr<valmap>(env);
+ auto error = UndefinedVarError({
.msg = hintfmt(s, s1),
.errPos = pos
});
+
+ if (debuggerHook)
+ debuggerHook(error, *env);
+ throw error;
}
LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char * s, const string & s1, valmap * env))
{
+ auto delenv = std::unique_ptr<valmap>(env);
auto error = MissingArgumentError({
.msg = hintfmt(s, s1),
.errPos = pos
@@ -848,7 +857,7 @@ inline Value * EvalState::lookupVar(Env * env, const ExprVar & var, bool noEval)
return j->value;
}
if (!env->prevWith)
- throwUndefinedVarError(var.pos, "undefined variable '%1%'", var.name);
+ throwUndefinedVarError(var.pos, "undefined variable '%1%'", var.name, map0()); // TODO: env.attrs?
for (size_t l = env->prevWith; l; --l, env = env->up) ;
}
}
@@ -1548,7 +1557,7 @@ void ExprAssert::eval(EvalState & state, Env & env, Value & v)
if (!state.evalBool(env, cond, pos)) {
std::ostringstream out;
cond->show(out);
- throwAssertionError(pos, "assertion '%1%' failed", out.str());
+ throwAssertionError(pos, "assertion '%1%' failed", out.str(), map0());
}
body->eval(state, env, v);
}
From 644567cf7ea810f86bd8e0328567b39c4757bc14 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Fri, 14 May 2021 13:40:00 -0600
Subject: [PATCH 015/188] clean up w LocalNoInline macro
---
src/libexpr/eval.cc | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 671b07dcd..897444360 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -619,28 +619,24 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
// typedef std::optional<const std::map<std::string, Value *>> valmap;
typedef std::map<std::string, Value *> valmap;
-static valmap * map0() __attribute__((noinline));
-valmap * map0()
+LocalNoInline(valmap * map0())
{
return new valmap();
}
-static valmap * map1(const char *name, Value *v) __attribute__((noinline));
-valmap * map1(const char *name, Value *v)
+LocalNoInline(valmap * map1(const char *name, Value *v))
{
// return new valmap({{name, v}});
return new valmap({{name, v}});
}
-static valmap * map2(const char *name1, Value *v1, const char *name2, Value *v2) __attribute__((noinline));
-valmap * map2(const char *name1, Value *v1, const char *name2, Value *v2)
+LocalNoInline(valmap * map2(const char *name1, Value *v1, const char *name2, Value *v2))
{
return new valmap({{name1, v1}, {name2, v2}});
}
-static valmap * mapBindings(Bindings *b) __attribute__((noinline));
-valmap * mapBindings(Bindings *b)
+LocalNoInline(valmap * mapBindings(Bindings *b))
{
auto map = new valmap();
From 99304334caa833b32712ad02e04f1a0e9c8322fe Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Fri, 14 May 2021 18:09:30 -0600
Subject: [PATCH 016/188] showType(fun)
---
src/libexpr/eval.cc | 11 +----------
1 file changed, 1 insertion(+), 10 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 897444360..9bb43f522 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -1378,17 +1378,8 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
throwTypeError(
pos,
"attempt to call something which is not a function but %1%",
- fun,
+ showType(fun),
map2("fun", &fun, "arg", &arg));
-
- // auto error = TypeError({
- // // .hint = hintfmt("attempt to call something which is not a function but %1%", showType(fun)),
- // .msg = hintfmt("attempt to call something which is not a function but %1%", fun),
- // .errPos = pos
- // });
- // if (debuggerHook)
- // debuggerHook(error, {{"fun", &fun}, {"arg", &arg}});
- // throw error;
}
ExprLambda & lambda(*fun.lambda.fun);
From ff2e72054f741f51c07e737d82c8eff920342488 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Tue, 8 Jun 2021 14:44:41 -0600
Subject: [PATCH 017/188] another throwTypeError form
---
src/libexpr/eval.cc | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 9bb43f522..f296550d0 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -743,6 +743,19 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
throw error;
}
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const char * t, valmap * env))
+{
+ auto delenv = std::unique_ptr<valmap>(env);
+ auto error = TypeError({
+ .msg = hintfmt(s, t),
+ .errPos = pos
+ });
+
+ if (debuggerHook)
+ debuggerHook(error, *env);
+ throw error;
+}
+
LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const ExprLambda & fun, const Symbol & s2, valmap * env))
{
auto delenv = std::unique_ptr<valmap>(env);
@@ -1378,7 +1391,7 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
throwTypeError(
pos,
"attempt to call something which is not a function but %1%",
- showType(fun),
+ showType(fun).c_str(),
map2("fun", &fun, "arg", &arg));
}
From a8df23975293a9c0b4d7a55b46d0047f955e0f1c Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Tue, 8 Jun 2021 14:44:53 -0600
Subject: [PATCH 018/188] highlight the extra vars
---
src/libcmd/repl.cc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index b1f250e73..29be71e13 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -785,7 +785,7 @@ void runRepl(
repl->addVarToScope(repl->state->symbols.create(name), value);
}
- printError("The following extra variables are in scope: %s\n", concatStringsSep(", ", names));
+ printError(hintfmt("The following extra variables are in scope: %s\n", concatStringsSep(", ", names)).str());
repl->mainLoop({});
}
From ebf530d31ecc2e01238737be8cf41c9d80962c99 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Tue, 8 Jun 2021 18:17:58 -0600
Subject: [PATCH 019/188] line endings
---
src/libexpr/eval.cc | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index f296550d0..cef0f0bc3 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -642,9 +642,9 @@ LocalNoInline(valmap * mapBindings(Bindings *b))
// auto v = new Value;
- for (auto i = b->begin(); i != b->end(); ++i)
+ for (auto i = b->begin(); i != b->end(); ++i)
{
- std::string s = i->name;
+ std::string s = i->name;
(*map)[s] = i->value;
// map->insert({std::string("wat"), v});
}
@@ -1174,7 +1174,7 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
Symbol nameSym = state.symbols.create(nameVal.string.s);
Bindings::iterator j = v.attrs->find(nameSym);
if (j != v.attrs->end())
- throwEvalError(i.pos, "dynamic attribute '%1%' already defined at %2%", nameSym, *j->pos,
+ throwEvalError(i.pos, "dynamic attribute '%1%' already defined at %2%", nameSym, *j->pos,
map1("value", &v)); // TODO dynamicAttrs to env?
i.valueExpr->setName(nameSym);
@@ -2077,7 +2077,7 @@ bool EvalState::eqValues(Value & v1, Value & v2)
return v1.fpoint == v2.fpoint;
default:
- throwEvalError("cannot compare %1% with %2%", showType(v1), showType(v2),
+ throwEvalError("cannot compare %1% with %2%", showType(v1), showType(v2),
map2("value1", &v1, "value2", &v2));
}
}
From 93ca9381dac7b95cdab005e653f3051c74968d51 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Tue, 8 Jun 2021 18:37:28 -0600
Subject: [PATCH 020/188] formatting; string arg for throwTypeError
---
src/libexpr/eval.cc | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index cef0f0bc3..85bff6ee5 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -743,11 +743,11 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
throw error;
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const char * t, valmap * env))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const string &s2, valmap * env))
{
auto delenv = std::unique_ptr<valmap>(env);
auto error = TypeError({
- .msg = hintfmt(s, t),
+ .msg = hintfmt(s, s2),
.errPos = pos
});
@@ -1516,7 +1516,7 @@ void EvalState::autoCallFunction(Bindings & args, Value & fun, Value & res)
if (j != args.end()) {
actualArgs->attrs->push_back(*j);
} else if (!i.def) {
- throwMissingArgumentError(i.pos, R"(cannot evaluate a function that has an argument without a value ('%1%')
+ throwMissingArgumentError(i.pos, R"(cannot evaluate a function that has an argument without a value ('%1%')
Nix attempted to evaluate a function as a top level expression; in
this case it must have its arguments supplied either by default
@@ -1965,7 +1965,7 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
}
throwTypeError(pos, "cannot coerce %1% to a string", v,
- map1("value", &v));
+ map1("value", &v));
}
@@ -2077,8 +2077,10 @@ bool EvalState::eqValues(Value & v1, Value & v2)
return v1.fpoint == v2.fpoint;
default:
- throwEvalError("cannot compare %1% with %2%", showType(v1), showType(v2),
- map2("value1", &v1, "value2", &v2));
+ throwEvalError("cannot compare %1% with %2%",
+ showType(v1),
+ showType(v2),
+ map2("value1", &v1, "value2", &v2));
}
}
From d22de1dd0c060971cb2cbeb9e49cae84c8d395cb Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Wed, 9 Jun 2021 15:38:08 -0600
Subject: [PATCH 021/188] remove dead code
---
src/libexpr/eval.cc | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 85bff6ee5..f8fe0f309 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -616,7 +616,6 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
return {};
}
-// typedef std::optional<const std::map<std::string, Value *>> valmap;
typedef std::map<std::string, Value *> valmap;
LocalNoInline(valmap * map0())
@@ -626,7 +625,6 @@ LocalNoInline(valmap * map0())
LocalNoInline(valmap * map1(const char *name, Value *v))
{
- // return new valmap({{name, v}});
return new valmap({{name, v}});
}
@@ -640,13 +638,10 @@ LocalNoInline(valmap * mapBindings(Bindings *b))
{
auto map = new valmap();
- // auto v = new Value;
-
for (auto i = b->begin(); i != b->end(); ++i)
{
std::string s = i->name;
(*map)[s] = i->value;
- // map->insert({std::string("wat"), v});
}
return map;
@@ -866,7 +861,8 @@ inline Value * EvalState::lookupVar(Env * env, const ExprVar & var, bool noEval)
return j->value;
}
if (!env->prevWith)
- throwUndefinedVarError(var.pos, "undefined variable '%1%'", var.name, map0()); // TODO: env.attrs?
+ // TODO: env.attrs?
+ throwUndefinedVarError(var.pos, "undefined variable '%1%'", var.name, map0());
for (size_t l = env->prevWith; l; --l, env = env->up) ;
}
}
From 129dd760e63d1be33e99d847e759d8a1e4c2dee7 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Fri, 11 Jun 2021 18:55:15 -0600
Subject: [PATCH 022/188] mapEnvBindings
---
src/libexpr/eval.cc | 53 +++++++++++++++++++++++++++++++++------------
1 file changed, 39 insertions(+), 14 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index f8fe0f309..6dcdbb2bd 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -618,6 +618,15 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
typedef std::map<std::string, Value *> valmap;
+/*void addEnv(Value * v, valmap &vmap)
+{
+ if (v.isThunk()) {
+ Env * env = v.thunk.env;
+
+ Expr * expr = v.thunk.expr;
+
+}
+*/
LocalNoInline(valmap * map0())
{
return new valmap();
@@ -628,17 +637,16 @@ LocalNoInline(valmap * map1(const char *name, Value *v))
return new valmap({{name, v}});
}
-
LocalNoInline(valmap * map2(const char *name1, Value *v1, const char *name2, Value *v2))
{
return new valmap({{name1, v1}, {name2, v2}});
}
-LocalNoInline(valmap * mapBindings(Bindings *b))
+LocalNoInline(valmap * mapBindings(Bindings &b))
{
auto map = new valmap();
- for (auto i = b->begin(); i != b->end(); ++i)
+ for (auto i = b.begin(); i != b.end(); ++i)
{
std::string s = i->name;
(*map)[s] = i->value;
@@ -647,6 +655,15 @@ LocalNoInline(valmap * mapBindings(Bindings *b))
return map;
}
+LocalNoInline(valmap * mapEnvBindings(Env &env))
+{
+ if (env.values[0]->type() == nAttrs) {
+ return mapBindings(*env.values[0]->attrs);
+ } else {
+ return map0();
+ }
+}
+
/* Every "format" object (even temporary) takes up a few hundred bytes
of stack space, which is a real killer in the recursive
evaluator. So here are some helper functions for throwing
@@ -813,13 +830,11 @@ LocalNoInline(void addErrorTrace(Error & e, const Pos & pos, const char * s, con
e.addTrace(pos, s, s2);
}
-
void mkString(Value & v, const char * s)
{
v.mkString(dupString(s));
}
-
Value & mkString(Value & v, std::string_view s, const PathSet & context)
{
v.mkString(dupStringWithLen(s.data(), s.size()));
@@ -862,7 +877,8 @@ inline Value * EvalState::lookupVar(Env * env, const ExprVar & var, bool noEval)
}
if (!env->prevWith)
// TODO: env.attrs?
- throwUndefinedVarError(var.pos, "undefined variable '%1%'", var.name, map0());
+ throwUndefinedVarError(var.pos, "undefined variable '%1%'", var.name,
+ mapEnvBindings(*env));
for (size_t l = env->prevWith; l; --l, env = env->up) ;
}
}
@@ -1171,7 +1187,8 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
Bindings::iterator j = v.attrs->find(nameSym);
if (j != v.attrs->end())
throwEvalError(i.pos, "dynamic attribute '%1%' already defined at %2%", nameSym, *j->pos,
- map1("value", &v)); // TODO dynamicAttrs to env?
+ mapEnvBindings(env));
+ // map1("value", &v)); // TODO dynamicAttrs to env?
i.valueExpr->setName(nameSym);
/* Keep sorted order so find can catch duplicates */
@@ -1261,7 +1278,9 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
} else {
state.forceAttrs(*vAttrs, pos);
if ((j = vAttrs->attrs->find(name)) == vAttrs->attrs->end())
- throwEvalError(pos, "attribute '%1%' missing", name, mapBindings(vAttrs->attrs));
+ throwEvalError(pos, "attribute '%1%' missing", name,
+ mapEnvBindings(env));
+ // mapBindings(*vAttrs->attrs));
}
vAttrs = j->value;
pos2 = j->pos;
@@ -1519,7 +1538,8 @@ this case it must have its arguments supplied either by default
values, or passed explicitly with '--arg' or '--argstr'. See
https://nixos.org/manual/nix/stable/#ss-functions.)",
i.name,
- map1("fun", &fun)); // todo add bindings + fun
+ mapBindings(args));
+ // map1("fun", &fun)); // todo add bindings + fun
}
}
}
@@ -1704,15 +1724,20 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
firstType = nFloat;
nf = n;
nf += vTmp.fpoint;
- } else
- throwEvalError(pos, "cannot add %1% to an integer", showType(vTmp), map0());
+ } else {
+ std::cerr << "envtype: " << showType(env.values[0]->type()) << std::endl;
+
+ throwEvalError(pos, "cannot add %1% to an integer", showType(vTmp),
+ mapEnvBindings(env));
+ }
} else if (firstType == nFloat) {
if (vTmp.type() == nInt) {
nf += vTmp.integer;
} else if (vTmp.type() == nFloat) {
nf += vTmp.fpoint;
} else
- throwEvalError(pos, "cannot add %1% to a float", showType(vTmp), map0());
+ throwEvalError(pos, "cannot add %1% to a float", showType(vTmp),
+ mapEnvBindings(env));
} else
s << state.coerceToString(pos, vTmp, context, false, firstType == nString);
}
@@ -1871,10 +1896,10 @@ string EvalState::forceStringNoCtx(Value & v, const Pos & pos)
if (v.string.context) {
if (pos)
throwEvalError(pos, "the string '%1%' is not allowed to refer to a store path (such as '%2%')",
- v.string.s, v.string.context[0], map1("value", &v));
+ v.string.s, v.string.context[0], map1("value", &v));
else
throwEvalError("the string '%1%' is not allowed to refer to a store path (such as '%2%')",
- v.string.s, v.string.context[0], map1("value", &v));
+ v.string.s, v.string.context[0], map1("value", &v));
}
return s;
}
From edb5a280243974c2094ed62cec104b55b97add43 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Fri, 11 Jun 2021 18:55:40 -0600
Subject: [PATCH 023/188] hintfmt for eye searing varnames
---
src/libcmd/repl.cc | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 29be71e13..57174bf0e 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -781,11 +781,13 @@ void runRepl(
std::set<std::string> names;
for (auto & [name, value] : extraEnv) {
- names.insert(ANSI_BOLD + name + ANSI_NORMAL);
+ // names.insert(ANSI_BOLD + name + ANSI_NORMAL);
+ names.insert(name);
repl->addVarToScope(repl->state->symbols.create(name), value);
}
printError(hintfmt("The following extra variables are in scope: %s\n", concatStringsSep(", ", names)).str());
+ // printError("The following extra variables are in scope: %s\n", concatStringsSep(", ", names));
repl->mainLoop({});
}
From 89264d20e63effa8d10f84a5f989d962f5df36f5 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Fri, 6 Aug 2021 11:09:27 -0600
Subject: [PATCH 024/188] move valmap to hh; add to env
---
src/libexpr/eval.cc | 168 ++++++++++++++++++++++++++++++++++++--------
src/libexpr/eval.hh | 3 +
src/nix/flake.cc | 1 +
3 files changed, 142 insertions(+), 30 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 6dcdbb2bd..48bff8dce 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -78,6 +78,8 @@ void printValue(std::ostream & str, std::set<const Value *> & active, const Valu
return;
}
+ str << "internal type: " << v.internalType << std::endl;
+
switch (v.internalType) {
case tInt:
str << v.integer;
@@ -404,7 +406,7 @@ EvalState::EvalState(const Strings & _searchPath, ref<Store> store)
assert(gcInitialised);
- static_assert(sizeof(Env) <= 16, "environment must be <= 16 bytes");
+ static_assert(sizeof(Env) <= 16 + sizeof(std::unique_ptr<void*>), "environment must be <= 16 bytes");
/* Initialise the Nix expression search path. */
if (!evalSettings.pureEval) {
@@ -616,7 +618,7 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
return {};
}
-typedef std::map<std::string, Value *> valmap;
+// typedef std::map<std::string, Value *> valmap;
/*void addEnv(Value * v, valmap &vmap)
{
@@ -655,13 +657,44 @@ LocalNoInline(valmap * mapBindings(Bindings &b))
return map;
}
+LocalNoInline(void addBindings(string prefix, Bindings &b, valmap &valmap))
+{
+ for (auto i = b.begin(); i != b.end(); ++i)
+ {
+ std::string s = prefix;
+ s += i->name;
+ valmap[s] = i->value;
+ }
+}
+
LocalNoInline(valmap * mapEnvBindings(Env &env))
{
- if (env.values[0]->type() == nAttrs) {
- return mapBindings(*env.values[0]->attrs);
- } else {
- return map0();
+ // NOT going to use this
+ if (env.staticEnv) {
+ std::cout << "got static env" << std::endl;
}
+
+// std::cout << "envsize: " << env.values.size() << std::endl;
+
+ // std::cout << "size_t size: " << sizeof(size_t) << std::endl;
+ // std::cout << "envsize: " << env.size << std::endl;
+ // std::cout << "envup: " << env.up << std::endl;
+
+ valmap *vm = env.up ? mapEnvBindings(*env.up) : new valmap();
+
+ /*
+ size_t i=0;
+ do {
+ std::cout << "env: " << i << " value: " << showType(*env.values[i]) << std::endl;
+ // std::cout << *env.values[i] << std::endl;
+ ++i;
+ } while(i < (std::min(env.size, (size_t)100)));
+
+
+ if (env.values[0]->type() == nAttrs)
+ addBindings(std::to_string((int)env.size), *env.values[0]->attrs, *vm);
+ */
+ return vm;
}
/* Every "format" object (even temporary) takes up a few hundred bytes
@@ -876,7 +909,6 @@ inline Value * EvalState::lookupVar(Env * env, const ExprVar & var, bool noEval)
return j->value;
}
if (!env->prevWith)
- // TODO: env.attrs?
throwUndefinedVarError(var.pos, "undefined variable '%1%'", var.name,
mapEnvBindings(*env));
for (size_t l = env->prevWith; l; --l, env = env->up) ;
@@ -902,14 +934,28 @@ Value * EvalState::allocValue()
Env & EvalState::allocEnv(size_t size)
{
+
nrEnvs++;
nrValuesInEnvs += size;
- Env * env = (Env *) allocBytes(sizeof(Env) + size * sizeof(Value *));
- env->type = Env::Plain;
+ // if (debuggerHook)
+ // {
+ // Env * env = (Env *) allocBytes(sizeof(DebugEnv) + size * sizeof(Value *));
+ // // Env * env = new DebugEnv;
+ // env->type = Env::Plain;
+ // /* We assume that env->values has been cleared by the allocator; maybeThunk() and lookupVar fromWith expect this. */
- /* We assume that env->values has been cleared by the allocator; maybeThunk() and lookupVar fromWith expect this. */
+ // return *env;
+ // } else {
+ Env * env = (Env *) allocBytes(sizeof(Env) + size * sizeof(Value *));
+ env->type = Env::Plain;
+ // env->size = size;
- return *env;
+ /* We assume that env->values has been cleared by the allocator; maybeThunk() and lookupVar fromWith expect this. */
+
+ return *env;
+ // }
+
+
}
@@ -1126,6 +1172,11 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
env2.up = &env;
dynamicEnv = &env2;
+ // TODO; deal with the below overrides or whatever
+ if (debuggerHook) {
+ env2.valuemap = mapBindings(attrs);
+ }
+
AttrDefs::iterator overrides = attrs.find(state.sOverrides);
bool hasOverrides = overrides != attrs.end();
@@ -1207,6 +1258,9 @@ void ExprLet::eval(EvalState & state, Env & env, Value & v)
Env & env2(state.allocEnv(attrs->attrs.size()));
env2.up = &env;
+ if (debuggerHook) {
+ env2.valuemap = mapBindings(attrs);
+ }
/* The recursive attributes are evaluated in the new environment,
while the inherited attributes are evaluated in the original
environment. */
@@ -1420,9 +1474,11 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
size_t displ = 0;
- if (!lambda.matchAttrs)
+ if (!lambda.matchAttrs){
+ // TODO: what is this arg? empty argument?
+ // add empty valmap here?
env2.values[displ++] = &arg;
-
+ }
else {
forceAttrs(arg, pos);
@@ -1432,23 +1488,51 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
/* For each formal argument, get the actual argument. If
there is no matching actual argument but the formal
argument has a default, use the default. */
- size_t attrsUsed = 0;
- for (auto & i : lambda.formals->formals) {
- Bindings::iterator j = arg.attrs->find(i.name);
- if (j == arg.attrs->end()) {
- if (!i.def)
- throwTypeError(
- pos,
- "%1% called without required argument '%2%'",
- lambda,
- i.name,
- map2("fun", &fun, "arg", &arg));
- env2.values[displ++] = i.def->maybeThunk(*this, env2);
- } else {
- attrsUsed++;
- env2.values[displ++] = j->value;
+ if (debuggerHook) {
+ size_t attrsUsed = 0;
+ for (auto & i : lambda.formals->formals) {
+ Bindings::iterator j = arg.attrs->find(i.name);
+ if (j == arg.attrs->end()) {
+ if (!i.def)
+ throwTypeError(
+ pos,
+ "%1% called without required argument '%2%'",
+ lambda,
+ i.name,
+ map2("fun", &fun, "arg", &arg));
+ env2.values[displ++] = i.def->maybeThunk(*this, env2);
+ } else {
+ attrsUsed++;
+ env2.values[displ++] = j->value;
+ }
}
}
+ else {
+ auto map = new valmap();
+
+ size_t attrsUsed = 0;
+ for (auto & i : lambda.formals->formals) {
+ Bindings::iterator j = arg.attrs->find(i.name);
+ if (j == arg.attrs->end()) {
+ if (!i.def)
+ throwTypeError(
+ pos,
+ "%1% called without required argument '%2%'",
+ lambda,
+ i.name,
+ map2("fun", &fun, "arg", &arg));
+ env2.values[displ++] = i.def->maybeThunk(*this, env2);
+ } else {
+ attrsUsed++;
+ env2.values[displ++] = j->value;
+
+ // add to debugger name-value map
+ std::string s = i->name;
+ (*map)[s] = i->value;
+ }
+ }
+ env2.valuemap = map;
+ }
/* Check that each actual argument is listed as a formal
argument (unless the attribute match specifies a `...'). */
@@ -1558,6 +1642,8 @@ void ExprWith::eval(EvalState & state, Env & env, Value & v)
env2.type = Env::HasWithExpr;
env2.values[0] = (Value *) attrs;
+ env2.valuemap = mapBindings(attrs)
+
body->eval(state, env2, v);
}
@@ -1896,14 +1982,36 @@ string EvalState::forceStringNoCtx(Value & v, const Pos & pos)
if (v.string.context) {
if (pos)
throwEvalError(pos, "the string '%1%' is not allowed to refer to a store path (such as '%2%')",
- v.string.s, v.string.context[0], map1("value", &v));
+ v.string.s, v.string.context[0],
+ // b.has_value() ? mapBindings(*b.get()) : map0());
+ map1("value", &v));
else
throwEvalError("the string '%1%' is not allowed to refer to a store path (such as '%2%')",
- v.string.s, v.string.context[0], map1("value", &v));
+ v.string.s, v.string.context[0],
+ // b.has_value() ? mapBindings(*b.get()) : map0());
+ map1("value", &v));
}
return s;
}
+/*string EvalState::forceStringNoCtx(std::optional<Bindings*> b, Value & v, const Pos & pos)
+{
+ string s = forceString(v, pos);
+ if (v.string.context) {
+ if (pos)
+ throwEvalError(pos, "the string '%1%' is not allowed to refer to a store path (such as '%2%')",
+ v.string.s, v.string.context[0],
+ b.has_value() ? mapBindings(*b.get()) : map0());
+ // map1("value", &v));
+ else
+ throwEvalError("the string '%1%' is not allowed to refer to a store path (such as '%2%')",
+ v.string.s, v.string.context[0],
+ b.has_value() ? mapBindings(*b.get()) : map0());
+ // map1("value", &v));
+ }
+ return s;
+}*/
+
bool EvalState::isDerivation(Value & v)
{
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index e3eaed6d3..448f41def 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -33,12 +33,14 @@ struct PrimOp
const char * doc = nullptr;
};
+typedef std::map<std::string, Value *> valmap;
struct Env
{
Env * up;
unsigned short prevWith:14; // nr of levels up to next `with' environment
enum { Plain = 0, HasWithExpr, HasWithAttrs } type:2;
+ std::unique_ptr<valmap> valuemap; // TODO: rename
Value * values[0];
};
@@ -204,6 +206,7 @@ public:
string forceString(Value & v, const Pos & pos = noPos);
string forceString(Value & v, PathSet & context, const Pos & pos = noPos);
string forceStringNoCtx(Value & v, const Pos & pos = noPos);
+ // string forceStringNoCtx(std::optional<Bindings*> b, Value & v, const Pos & pos = noPos);
/* Return true iff the value `v' denotes a derivation (i.e. a
set with attribute `type = "derivation"'). */
diff --git a/src/nix/flake.cc b/src/nix/flake.cc
index 62a413e27..6af052008 100644
--- a/src/nix/flake.cc
+++ b/src/nix/flake.cc
@@ -408,6 +408,7 @@ struct CmdFlakeCheck : FlakeCommand
if (auto attr = v.attrs->get(state->symbols.create("description")))
state->forceStringNoCtx(*attr->value, *attr->pos);
+ // state->forceStringNoCtx(std::optional(v.attrs), *attr->value, *attr->pos);
else
throw Error("template '%s' lacks attribute 'description'", attrPath);
From 030271184fecbbe9dd871b71d92c61e163254646 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Mon, 9 Aug 2021 14:30:47 -0600
Subject: [PATCH 025/188] trying env args; but unecessary?
---
src/libcmd/command.cc | 3 +-
src/libexpr/eval.cc | 148 ++++++++++++++++++++----------------------
2 files changed, 74 insertions(+), 77 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 51a071d25..86b6f37f8 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -96,7 +96,8 @@ EvalCommand::EvalCommand()
.handler = {&startReplOnEvalErrors, true},
});
}
-extern std::function<void(const Error & error, const std::map<std::string, Value *> & env)> debuggerHook;
+// extern std::function<void(const Error & error, const std::map<std::string, Value *> & env)> debuggerHook;
+extern std::function<void(const Error & error, const Env & env)> debuggerHook;
ref<EvalState> EvalCommand::getEvalState()
{
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 48bff8dce..464022372 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -35,7 +35,8 @@
namespace nix {
-std::function<void(const Error & error, const std::map<std::string, Value *> & env)> debuggerHook;
+// std::function<void(const Error & error, const std::map<std::string, Value *> & env)> debuggerHook;
+std::function<void(const Error & error, const Env & env)> debuggerHook;
static char * dupString(const char * s)
{
@@ -667,189 +668,189 @@ LocalNoInline(void addBindings(string prefix, Bindings &b, valmap &valmap))
}
}
-LocalNoInline(valmap * mapEnvBindings(Env &env))
-{
- // NOT going to use this
- if (env.staticEnv) {
- std::cout << "got static env" << std::endl;
- }
+// LocalNoInline(valmap * mapEnvBindings(Env &env))
+// {
+// // NOT going to use this
+// if (env.valuemap) {
+// std::cout << "got static env" << std::endl;
+// }
-// std::cout << "envsize: " << env.values.size() << std::endl;
+// // std::cout << "envsize: " << env.values.size() << std::endl;
- // std::cout << "size_t size: " << sizeof(size_t) << std::endl;
- // std::cout << "envsize: " << env.size << std::endl;
- // std::cout << "envup: " << env.up << std::endl;
+// // std::cout << "size_t size: " << sizeof(size_t) << std::endl;
+// // std::cout << "envsize: " << env.size << std::endl;
+// // std::cout << "envup: " << env.up << std::endl;
- valmap *vm = env.up ? mapEnvBindings(*env.up) : new valmap();
+// valmap *vm = env.up ? mapEnvBindings(*env.up) : new valmap();
- /*
- size_t i=0;
- do {
- std::cout << "env: " << i << " value: " << showType(*env.values[i]) << std::endl;
- // std::cout << *env.values[i] << std::endl;
- ++i;
- } while(i < (std::min(env.size, (size_t)100)));
+// /*
+// size_t i=0;
+// do {
+// std::cout << "env: " << i << " value: " << showType(*env.values[i]) << std::endl;
+// // std::cout << *env.values[i] << std::endl;
+// ++i;
+// } while(i < (std::min(env.size, (size_t)100)));
- if (env.values[0]->type() == nAttrs)
- addBindings(std::to_string((int)env.size), *env.values[0]->attrs, *vm);
- */
- return vm;
-}
+// if (env.values[0]->type() == nAttrs)
+// addBindings(std::to_string((int)env.size), *env.values[0]->attrs, *vm);
+// */
+// return vm;
+// }
/* Every "format" object (even temporary) takes up a few hundred bytes
of stack space, which is a real killer in the recursive
evaluator. So here are some helper functions for throwing
exceptions. */
-LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, valmap * env))
+LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, Env & env))
{
- auto delenv = std::unique_ptr<valmap>(env);
+ // auto delenv = std::unique_ptr<valmap>(env);
auto error = EvalError(s, s2);
if (debuggerHook)
- debuggerHook(error, *env);
+ debuggerHook(error, env);
throw error;
}
-LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2, valmap * env))
+LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2, Env & env))
{
- auto delenv = std::unique_ptr<valmap>(env);
+ // auto delenv = std::unique_ptr<valmap>(env);
auto error = EvalError({
.msg = hintfmt(s, s2),
.errPos = pos
});
if (debuggerHook)
- debuggerHook(error, *env);
+ debuggerHook(error, env);
throw error;
}
-LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, const string & s3, valmap * env))
+LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, const string & s3, Env & env))
{
- auto delenv = std::unique_ptr<valmap>(env);
+ // auto delenv = std::unique_ptr<valmap>(env);
auto error = EvalError(s, s2, s3);
if (debuggerHook)
- debuggerHook(error, *env);
+ debuggerHook(error, env);
throw error;
}
-LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2, const string & s3, valmap * env))
+LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2, const string & s3, Env & env))
{
- auto delenv = std::unique_ptr<valmap>(env);
+ // auto delenv = std::unique_ptr<valmap>(env);
auto error = EvalError({
.msg = hintfmt(s, s2, s3),
.errPos = pos
});
if (debuggerHook)
- debuggerHook(error, *env);
+ debuggerHook(error, env);
throw error;
}
-LocalNoInlineNoReturn(void throwEvalError(const Pos & p1, const char * s, const Symbol & sym, const Pos & p2, valmap * env))
+LocalNoInlineNoReturn(void throwEvalError(const Pos & p1, const char * s, const Symbol & sym, const Pos & p2, Env & env))
{
// p1 is where the error occurred; p2 is a position mentioned in the message.
- auto delenv = std::unique_ptr<valmap>(env);
+ // auto delenv = std::unique_ptr<valmap>(env);
auto error = EvalError({
.msg = hintfmt(s, sym, p2),
.errPos = p1
});
if (debuggerHook)
- debuggerHook(error, *env);
+ debuggerHook(error, env);
throw error;
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, valmap * env))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, Env & env))
{
- auto delenv = std::unique_ptr<valmap>(env);
+ // auto delenv = std::unique_ptr<valmap>(env);
auto error = TypeError({
.msg = hintfmt(s),
.errPos = pos
});
if (debuggerHook)
- debuggerHook(error, *env);
+ debuggerHook(error, env);
throw error;
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v, valmap * env))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v, Env & env))
{
- auto delenv = std::unique_ptr<valmap>(env);
+ // auto delenv = std::unique_ptr<valmap>(env);
auto error = TypeError({
.msg = hintfmt(s, v),
.errPos = pos
});
if (debuggerHook)
- debuggerHook(error, *env);
+ debuggerHook(error, env);
throw error;
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const string &s2, valmap * env))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const string &s2, Env & env))
{
- auto delenv = std::unique_ptr<valmap>(env);
+ // auto delenv = std::unique_ptr<valmap>(env);
auto error = TypeError({
.msg = hintfmt(s, s2),
.errPos = pos
});
if (debuggerHook)
- debuggerHook(error, *env);
+ debuggerHook(error, env);
throw error;
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const ExprLambda & fun, const Symbol & s2, valmap * env))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const ExprLambda & fun, const Symbol & s2, Env & env))
{
- auto delenv = std::unique_ptr<valmap>(env);
+ // auto delenv = std::unique_ptr<valmap>(env);
auto error = TypeError({
.msg = hintfmt(s, fun.showNamePos(), s2),
.errPos = pos
});
if (debuggerHook)
- debuggerHook(error, *env);
+ debuggerHook(error, env);
throw error;
}
-LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s, const string & s1, valmap * env))
+LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s, const string & s1, Env & env))
{
- auto delenv = std::unique_ptr<valmap>(env);
+ // auto delenv = std::unique_ptr<valmap>(env);
auto error = AssertionError({
.msg = hintfmt(s, s1),
.errPos = pos
});
if (debuggerHook)
- debuggerHook(error, *env);
+ debuggerHook(error, env);
throw error;
}
-LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char * s, const string & s1, valmap * env))
+LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char * s, const string & s1, Env & env))
{
- auto delenv = std::unique_ptr<valmap>(env);
+ // auto delenv = std::unique_ptr<valmap>(env);
auto error = UndefinedVarError({
.msg = hintfmt(s, s1),
.errPos = pos
});
if (debuggerHook)
- debuggerHook(error, *env);
+ debuggerHook(error, env);
throw error;
}
-LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char * s, const string & s1, valmap * env))
+LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char * s, const string & s1, Env & env))
{
- auto delenv = std::unique_ptr<valmap>(env);
+ // auto delenv = std::unique_ptr<valmap>(env);
auto error = MissingArgumentError({
.msg = hintfmt(s, s1),
.errPos = pos
});
if (debuggerHook)
- debuggerHook(error, *env);
+ debuggerHook(error, env);
throw error;
}
@@ -909,8 +910,7 @@ inline Value * EvalState::lookupVar(Env * env, const ExprVar & var, bool noEval)
return j->value;
}
if (!env->prevWith)
- throwUndefinedVarError(var.pos, "undefined variable '%1%'", var.name,
- mapEnvBindings(*env));
+ throwUndefinedVarError(var.pos, "undefined variable '%1%'", var.name, *env);
for (size_t l = env->prevWith; l; --l, env = env->up) ;
}
}
@@ -1238,7 +1238,7 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
Bindings::iterator j = v.attrs->find(nameSym);
if (j != v.attrs->end())
throwEvalError(i.pos, "dynamic attribute '%1%' already defined at %2%", nameSym, *j->pos,
- mapEnvBindings(env));
+ env);
// map1("value", &v)); // TODO dynamicAttrs to env?
i.valueExpr->setName(nameSym);
@@ -1332,8 +1332,7 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
} else {
state.forceAttrs(*vAttrs, pos);
if ((j = vAttrs->attrs->find(name)) == vAttrs->attrs->end())
- throwEvalError(pos, "attribute '%1%' missing", name,
- mapEnvBindings(env));
+ throwEvalError(pos, "attribute '%1%' missing", name, env);
// mapBindings(*vAttrs->attrs));
}
vAttrs = j->value;
@@ -1622,7 +1621,8 @@ this case it must have its arguments supplied either by default
values, or passed explicitly with '--arg' or '--argstr'. See
https://nixos.org/manual/nix/stable/#ss-functions.)",
i.name,
- mapBindings(args));
+ fun.lambda.env);
+ // mapBindings(args));
// map1("fun", &fun)); // todo add bindings + fun
}
}
@@ -1642,7 +1642,7 @@ void ExprWith::eval(EvalState & state, Env & env, Value & v)
env2.type = Env::HasWithExpr;
env2.values[0] = (Value *) attrs;
- env2.valuemap = mapBindings(attrs)
+ env2.valuemap = mapBindings(*attrs)
body->eval(state, env2, v);
}
@@ -1813,8 +1813,7 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
} else {
std::cerr << "envtype: " << showType(env.values[0]->type()) << std::endl;
- throwEvalError(pos, "cannot add %1% to an integer", showType(vTmp),
- mapEnvBindings(env));
+ throwEvalError(pos, "cannot add %1% to an integer", showType(vTmp), env);
}
} else if (firstType == nFloat) {
if (vTmp.type() == nInt) {
@@ -1822,8 +1821,7 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
} else if (vTmp.type() == nFloat) {
nf += vTmp.fpoint;
} else
- throwEvalError(pos, "cannot add %1% to a float", showType(vTmp),
- mapEnvBindings(env));
+ throwEvalError(pos, "cannot add %1% to a float", showType(vTmp), env);
} else
s << state.coerceToString(pos, vTmp, context, false, firstType == nString);
}
@@ -2061,8 +2059,7 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
}
auto i = v.attrs->find(sOutPath);
if (i == v.attrs->end())
- throwTypeError(pos, "cannot coerce a set to a string",
- map1("value", &v));
+ throwTypeError(pos, "cannot coerce a set to a string", map1("value", &v));
return coerceToString(pos, *i->value, context, coerceMore, copyToStore);
}
@@ -2093,12 +2090,11 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
}
}
- throwTypeError(pos, "cannot coerce %1% to a string", v,
- map1("value", &v));
+ throwTypeError(pos, "cannot coerce %1% to a string", v, map1("value", &v));
}
-string EvalState::copyPathToStore(PathSet & context, const Path & path)
+string EvalState::copyPathToStore(Env &env, PathSet & context, const Path & path)
{
if (nix::isDerivation(path))
throwEvalError("file names are not allowed to end in '%1%'",
From b6eb38016b9d16cf206f3f2b0cd4bce4dea40345 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Tue, 17 Aug 2021 14:39:50 -0600
Subject: [PATCH 026/188] moving towards env in exceptions
---
src/libcmd/command.cc | 2 +-
src/libexpr/eval.cc | 43 ++++++++++++++++++++++++++++---------------
2 files changed, 29 insertions(+), 16 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 86b6f37f8..59ab1f874 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -105,7 +105,7 @@ ref<EvalState> EvalCommand::getEvalState()
if (!evalState) {
evalState = std::make_shared<EvalState>(searchPath, getStore());
if (startReplOnEvalErrors)
- debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error & error, const std::map<std::string, Value *> & env) {
+ debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error & error, const Env & env) {
printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error.what());
runRepl(evalState, env);
};
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 464022372..f799ee7db 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -1172,11 +1172,6 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
env2.up = &env;
dynamicEnv = &env2;
- // TODO; deal with the below overrides or whatever
- if (debuggerHook) {
- env2.valuemap = mapBindings(attrs);
- }
-
AttrDefs::iterator overrides = attrs.find(state.sOverrides);
bool hasOverrides = overrides != attrs.end();
@@ -1195,6 +1190,11 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
v.attrs->push_back(Attr(i.first, vAttr, &i.second.pos));
}
+ // TODO; deal with the below overrides or whatever
+ if (debuggerHook) {
+ env2.valuemap.reset(mapBindings(*v.attrs));
+ }
+
/* If the rec contains an attribute called `__overrides', then
evaluate it, and add the attributes in that set to the rec.
This allows overriding of recursive attributes, which is
@@ -1258,9 +1258,6 @@ void ExprLet::eval(EvalState & state, Env & env, Value & v)
Env & env2(state.allocEnv(attrs->attrs.size()));
env2.up = &env;
- if (debuggerHook) {
- env2.valuemap = mapBindings(attrs);
- }
/* The recursive attributes are evaluated in the new environment,
while the inherited attributes are evaluated in the original
environment. */
@@ -1268,6 +1265,18 @@ void ExprLet::eval(EvalState & state, Env & env, Value & v)
for (auto & i : attrs->attrs)
env2.values[displ++] = i.second.e->maybeThunk(state, i.second.inherited ? env : env2);
+ if (debuggerHook) {
+ auto map = new valmap();
+
+ displ = 0;
+ for (auto & i : attrs->attrs)
+ {
+ // std::string s = i->name;
+ (*map)[i.first] = env2.values[displ++];
+ }
+ env2.valuemap.reset(map);
+ }
+
body->eval(state, env2, v);
}
@@ -1460,6 +1469,7 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
pos,
"attempt to call something which is not a function but %1%",
showType(fun).c_str(),
+ // fun.env);
map2("fun", &fun, "arg", &arg));
}
@@ -1498,7 +1508,8 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
"%1% called without required argument '%2%'",
lambda,
i.name,
- map2("fun", &fun, "arg", &arg));
+ fun.lambda.env);
+ // map2("fun", &fun, "arg", &arg));
env2.values[displ++] = i.def->maybeThunk(*this, env2);
} else {
attrsUsed++;
@@ -1519,18 +1530,19 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
"%1% called without required argument '%2%'",
lambda,
i.name,
- map2("fun", &fun, "arg", &arg));
+ fun.env);
+ // map2("fun", &fun, "arg", &arg));
env2.values[displ++] = i.def->maybeThunk(*this, env2);
} else {
attrsUsed++;
env2.values[displ++] = j->value;
// add to debugger name-value map
- std::string s = i->name;
- (*map)[s] = i->value;
+ std::string s = i.name;
+ (*map)[s] = i.value;
}
}
- env2.valuemap = map;
+ env2.valuemap.reset(map);
}
/* Check that each actual argument is listed as a formal
@@ -1544,7 +1556,8 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
"%1% called with unexpected argument '%2%'",
lambda,
i.name,
- map2("fun", &fun, "arg", &arg));
+ fun.env);
+ // map2("fun", &fun, "arg", &arg));
abort(); // can't happen
}
}
@@ -1621,7 +1634,7 @@ this case it must have its arguments supplied either by default
values, or passed explicitly with '--arg' or '--argstr'. See
https://nixos.org/manual/nix/stable/#ss-functions.)",
i.name,
- fun.lambda.env);
+ *fun.lambda.env);
// mapBindings(args));
// map1("fun", &fun)); // todo add bindings + fun
}
From e82cf13b1e94a27b2d6402ff6850a5a11d18fb92 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Wed, 18 Aug 2021 17:53:10 -0600
Subject: [PATCH 027/188] switch to fakeenvs
---
src/libexpr/eval.cc | 68 ++++++++++++++++++++++++++++++++-------------
1 file changed, 48 insertions(+), 20 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index f799ee7db..48546e8ad 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -958,6 +958,16 @@ Env & EvalState::allocEnv(size_t size)
}
+Env & fakeEnv(size_t size)
+{
+ // making a fake Env so we'll have one to pass to exception ftns.
+ // a placeholder until we can pass real envs everywhere they're needed.
+ Env * env = (Env *) allocBytes(sizeof(Env) + size * sizeof(Value *));
+ env->type = Env::Plain;
+
+ return *env;
+}
+
void EvalState::mkList(Value & v, size_t size)
{
@@ -1469,8 +1479,9 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
pos,
"attempt to call something which is not a function but %1%",
showType(fun).c_str(),
+ fakeEnv(1));
// fun.env);
- map2("fun", &fun, "arg", &arg));
+ // map2("fun", &fun, "arg", &arg));
}
ExprLambda & lambda(*fun.lambda.fun);
@@ -1508,7 +1519,7 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
"%1% called without required argument '%2%'",
lambda,
i.name,
- fun.lambda.env);
+ *fun.lambda.env);
// map2("fun", &fun, "arg", &arg));
env2.values[displ++] = i.def->maybeThunk(*this, env2);
} else {
@@ -1530,7 +1541,7 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
"%1% called without required argument '%2%'",
lambda,
i.name,
- fun.env);
+ *fun.lambda.env);
// map2("fun", &fun, "arg", &arg));
env2.values[displ++] = i.def->maybeThunk(*this, env2);
} else {
@@ -1539,7 +1550,7 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
// add to debugger name-value map
std::string s = i.name;
- (*map)[s] = i.value;
+ (*map)[s] = j->value;
}
}
env2.valuemap.reset(map);
@@ -1556,7 +1567,7 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
"%1% called with unexpected argument '%2%'",
lambda,
i.name,
- fun.env);
+ *fun.lambda.env);
// map2("fun", &fun, "arg", &arg));
abort(); // can't happen
}
@@ -1655,7 +1666,11 @@ void ExprWith::eval(EvalState & state, Env & env, Value & v)
env2.type = Env::HasWithExpr;
env2.values[0] = (Value *) attrs;
- env2.valuemap = mapBindings(*attrs)
+ if (debuggerHook) {
+ forceAttrs(attrs);
+ env2.valuemap = mapBindings(attrs->attrs);
+ }
+
body->eval(state, env2, v);
}
@@ -1672,7 +1687,7 @@ void ExprAssert::eval(EvalState & state, Env & env, Value & v)
if (!state.evalBool(env, cond, pos)) {
std::ostringstream out;
cond->show(out);
- throwAssertionError(pos, "assertion '%1%' failed", out.str(), map0());
+ throwAssertionError(pos, "assertion '%1%' failed", out.str(), env);
}
body->eval(state, env, v);
}
@@ -1895,7 +1910,8 @@ NixInt EvalState::forceInt(Value & v, const Pos & pos)
forceValue(v, pos);
if (v.type() != nInt)
throwTypeError(pos, "value is %1% while an integer was expected", v,
- map1("value", &v));
+ fakeEnv(1));
+ // map1("value", &v));
return v.integer;
}
@@ -1907,7 +1923,8 @@ NixFloat EvalState::forceFloat(Value & v, const Pos & pos)
return v.integer;
else if (v.type() != nFloat)
throwTypeError(pos, "value is %1% while a float was expected", v,
- map1("value", &v));
+ fakeEnv(1));
+ // map1("value", &v));
return v.fpoint;
}
@@ -1916,8 +1933,9 @@ bool EvalState::forceBool(Value & v, const Pos & pos)
{
forceValue(v, pos);
if (v.type() != nBool)
- throwTypeError(pos, "value is %1% while a Boolean was expected", v,
- map1("value", &v));
+ throwTypeError(pos, "value is %1% while a Boolean was expected", v,
+ fakeEnv(1));
+ // map1("value", &v));
return v.boolean;
}
@@ -1933,7 +1951,8 @@ void EvalState::forceFunction(Value & v, const Pos & pos)
forceValue(v, pos);
if (v.type() != nFunction && !isFunctor(v))
throwTypeError(pos, "value is %1% while a function was expected", v,
- map1("value", &v));
+ fakeEnv(1));
+ // map1("value", &v));
}
@@ -1942,7 +1961,8 @@ string EvalState::forceString(Value & v, const Pos & pos)
forceValue(v, pos);
if (v.type() != nString) {
throwTypeError(pos, "value is %1% while a string was expected", v,
- map1("value", &v));
+ fakeEnv(1));
+ // map1("value", &v));
}
return string(v.string.s);
}
@@ -1995,12 +2015,14 @@ string EvalState::forceStringNoCtx(Value & v, const Pos & pos)
throwEvalError(pos, "the string '%1%' is not allowed to refer to a store path (such as '%2%')",
v.string.s, v.string.context[0],
// b.has_value() ? mapBindings(*b.get()) : map0());
- map1("value", &v));
+ fakeEnv(1));
+ // map1("value", &v));
else
throwEvalError("the string '%1%' is not allowed to refer to a store path (such as '%2%')",
v.string.s, v.string.context[0],
// b.has_value() ? mapBindings(*b.get()) : map0());
- map1("value", &v));
+ fakeEnv(1));
+ // map1("value", &v));
}
return s;
}
@@ -2072,7 +2094,9 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
}
auto i = v.attrs->find(sOutPath);
if (i == v.attrs->end())
- throwTypeError(pos, "cannot coerce a set to a string", map1("value", &v));
+ throwTypeError(pos, "cannot coerce a set to a string",
+ fakeEnv(1));
+ // map1("value", &v));
return coerceToString(pos, *i->value, context, coerceMore, copyToStore);
}
@@ -2080,7 +2104,6 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
return v.external->coerceToString(pos, context, coerceMore, copyToStore);
if (coerceMore) {
-
/* Note that `false' is represented as an empty string for
shell scripting convenience, just like `null'. */
if (v.type() == nBool && v.boolean) return "1";
@@ -2103,7 +2126,9 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
}
}
- throwTypeError(pos, "cannot coerce %1% to a string", v, map1("value", &v));
+ throwTypeError(pos, "cannot coerce %1% to a string", v,
+ fakeEnv(1));
+ // map1("value", &v));
}
@@ -2136,7 +2161,9 @@ Path EvalState::coerceToPath(const Pos & pos, Value & v, PathSet & context)
{
string path = coerceToString(pos, v, context, false, false);
if (path == "" || path[0] != '/')
- throwEvalError(pos, "string '%1%' doesn't represent an absolute path", path, map1("value", &v));
+ throwEvalError(pos, "string '%1%' doesn't represent an absolute path", path,
+ fakeEnv(1));
+ // map1("value", &v));
return path;
}
@@ -2218,7 +2245,8 @@ bool EvalState::eqValues(Value & v1, Value & v2)
throwEvalError("cannot compare %1% with %2%",
showType(v1),
showType(v2),
- map2("value1", &v1, "value2", &v2));
+ fakeEnv(1));
+ // map2("value1", &v1, "value2", &v2));
}
}
From 22720215366ada555f077ffb8eb810029ec93a04 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Wed, 18 Aug 2021 20:02:23 -0600
Subject: [PATCH 028/188] more error fixes
---
src/libexpr/eval.cc | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 48546e8ad..eef4974e5 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -1667,8 +1667,8 @@ void ExprWith::eval(EvalState & state, Env & env, Value & v)
env2.values[0] = (Value *) attrs;
if (debuggerHook) {
- forceAttrs(attrs);
- env2.valuemap = mapBindings(attrs->attrs);
+ state.forceAttrs(*env2.values[0]);
+ env2.valuemap.reset(mapBindings(*env2.values[0]->attrs));
}
@@ -2132,12 +2132,13 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
}
-string EvalState::copyPathToStore(Env &env, PathSet & context, const Path & path)
+string EvalState::copyPathToStore(PathSet & context, const Path & path)
{
if (nix::isDerivation(path))
throwEvalError("file names are not allowed to end in '%1%'",
drvExtension,
- map0());
+ fakeEnv(1));
+ // map0());
Path dstPath;
auto i = srcToStore.find(path);
From 4b5f9b35f06754aaf578a2d4b3d730949964ef05 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Wed, 18 Aug 2021 21:25:26 -0600
Subject: [PATCH 029/188] env to bindings
---
src/libcmd/command.cc | 5 ++++-
src/libexpr/eval.cc | 25 +++++++++++++++++++++++--
src/libexpr/eval.hh | 1 +
3 files changed, 28 insertions(+), 3 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 59ab1f874..a32c4a24b 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -99,6 +99,8 @@ EvalCommand::EvalCommand()
// extern std::function<void(const Error & error, const std::map<std::string, Value *> & env)> debuggerHook;
extern std::function<void(const Error & error, const Env & env)> debuggerHook;
+
+
ref<EvalState> EvalCommand::getEvalState()
{
std::cout << " EvalCommand::getEvalState()" << startReplOnEvalErrors << std::endl;
@@ -107,7 +109,8 @@ ref<EvalState> EvalCommand::getEvalState()
if (startReplOnEvalErrors)
debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error & error, const Env & env) {
printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error.what());
- runRepl(evalState, env);
+ auto vm = mapEnvBindings(env);
+ runRepl(evalState, *vm);
};
}
return ref<EvalState>(evalState);
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index eef4974e5..2e885bb7c 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -668,6 +668,28 @@ LocalNoInline(void addBindings(string prefix, Bindings &b, valmap &valmap))
}
}
+
+
+void mapEnvBindings(const Env &env, valmap & vm)
+{
+ // add bindings for the next level up first.
+ if (env.up) {
+ mapEnvBindings(*env.up, vm);
+ }
+
+ // merge - and write over - higher level bindings.
+ vm.merge(*env.valuemap);
+}
+
+valmap * mapEnvBindings(const Env &env)
+{
+ auto vm = new valmap();
+
+ mapEnvBindings(env, *vm);
+
+ return vm;
+}
+
// LocalNoInline(valmap * mapEnvBindings(Env &env))
// {
// // NOT going to use this
@@ -1508,8 +1530,8 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
/* For each formal argument, get the actual argument. If
there is no matching actual argument but the formal
argument has a default, use the default. */
+ size_t attrsUsed = 0;
if (debuggerHook) {
- size_t attrsUsed = 0;
for (auto & i : lambda.formals->formals) {
Bindings::iterator j = arg.attrs->find(i.name);
if (j == arg.attrs->end()) {
@@ -1531,7 +1553,6 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
else {
auto map = new valmap();
- size_t attrsUsed = 0;
for (auto & i : lambda.formals->formals) {
Bindings::iterator j = arg.attrs->find(i.name);
if (j == arg.attrs->end()) {
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 448f41def..2d167e6eb 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -44,6 +44,7 @@ struct Env
Value * values[0];
};
+valmap * mapEnvBindings(const Env &env);
Value & mkString(Value & v, std::string_view s, const PathSet & context = PathSet());
From bd3b5329f91e6caff387cf361a5c779468f34f88 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Tue, 24 Aug 2021 16:32:54 -0600
Subject: [PATCH 030/188] print env bindings
---
src/libcmd/command.cc | 1 +
src/libexpr/eval.cc | 72 ++++++++++++++++++++++++++++++++++++++-----
src/libexpr/eval.hh | 1 +
3 files changed, 67 insertions(+), 7 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index a32c4a24b..1a59dff77 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -109,6 +109,7 @@ ref<EvalState> EvalCommand::getEvalState()
if (startReplOnEvalErrors)
debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error & error, const Env & env) {
printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error.what());
+ printEnvBindings(env);
auto vm = mapEnvBindings(env);
runRepl(evalState, *vm);
};
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 2e885bb7c..7fee1168c 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -669,6 +669,26 @@ LocalNoInline(void addBindings(string prefix, Bindings &b, valmap &valmap))
}
+void printEnvBindings(const Env &env, int lv )
+{
+ if (env.values[0]->type() == nAttrs) {
+ Bindings::iterator j = env.values[0]->attrs->begin();
+
+ while (j != env.values[0]->attrs->end()) {
+ std::cout << lv << " env binding: " << j->name << std::endl;
+ // if (countCalls && j->pos) attrSelects[*j->pos]++;
+ // return j->value;
+ j++;
+ }
+
+ }
+
+ std::cout << "next env : " << env.up << std::endl;
+
+ if (env.up) {
+ printEnvBindings(*env.up, ++lv);
+ }
+}
void mapEnvBindings(const Env &env, valmap & vm)
{
@@ -678,14 +698,38 @@ void mapEnvBindings(const Env &env, valmap & vm)
}
// merge - and write over - higher level bindings.
- vm.merge(*env.valuemap);
+ if (env.valuemap)
+ vm.merge(*env.valuemap);
}
+// void mapEnvBindings(const Env &env, valmap & vm)
+// {
+// // add bindings for the next level up first.
+// if (env.up) {
+// mapEnvBindings(*env.up, vm);
+// }
+
+// // merge - and write over - higher level bindings.
+// if (env.valuemap)
+// vm.merge(*env.valuemap);
+// }
+
valmap * mapEnvBindings(const Env &env)
{
auto vm = new valmap();
+ // segfault!
+ std::cout << "before mapenv" << std::endl;
+ if (env.valuemap) {
+ std::cout << "valuemap" << std::endl;
+ std::cout << "mapenv count" << env.valuemap->size() << std::endl;
+ } else
+ {
+ std::cout << "novaluemap" << std::endl;
+ }
+
mapEnvBindings(env, *vm);
+ std::cout << "after mapenv" << std::endl;
return vm;
}
@@ -852,6 +896,8 @@ LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s,
LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char * s, const string & s1, Env & env))
{
+ std::cout << "throwUndefinedVarError" << std::endl;
+
// auto delenv = std::unique_ptr<valmap>(env);
auto error = UndefinedVarError({
.msg = hintfmt(s, s1),
@@ -914,6 +960,8 @@ void mkPath(Value & v, const char * s)
inline Value * EvalState::lookupVar(Env * env, const ExprVar & var, bool noEval)
{
+ // std::cout << " EvalState::lookupVar" << std::endl;
+
for (size_t l = var.level; l; --l, env = env->up) ;
if (!var.fromWith) return env->values[var.displ];
@@ -931,8 +979,10 @@ inline Value * EvalState::lookupVar(Env * env, const ExprVar & var, bool noEval)
if (countCalls && j->pos) attrSelects[*j->pos]++;
return j->value;
}
- if (!env->prevWith)
+ if (!env->prevWith) {
+ std::cout << "pre throwUndefinedVarError" << std::endl;
throwUndefinedVarError(var.pos, "undefined variable '%1%'", var.name, *env);
+ }
for (size_t l = env->prevWith; l; --l, env = env->up) ;
}
}
@@ -1681,16 +1731,24 @@ https://nixos.org/manual/nix/stable/#ss-functions.)",
void ExprWith::eval(EvalState & state, Env & env, Value & v)
{
+ // std::cout << "ExprWith::eval" << std::endl;
Env & env2(state.allocEnv(1));
env2.up = &env;
env2.prevWith = prevWith;
env2.type = Env::HasWithExpr;
- env2.values[0] = (Value *) attrs;
+ env2.values[0] = (Value *) attrs; // ok DAG nasty. just smoosh this in.
+ // presumably evaluate later, lazily.
+ // std::cout << "ExprWith::eval2" << std::endl;
- if (debuggerHook) {
- state.forceAttrs(*env2.values[0]);
- env2.valuemap.reset(mapBindings(*env2.values[0]->attrs));
- }
+ // can't load the valuemap until they've been evaled, which is not yet.
+ // if (debuggerHook) {
+ // std::cout << "ExprWith::eval3.0" << std::endl;
+ // std::cout << "ExprWith attrs" << *attrs << std::endl;
+ // state.forceAttrs(*(Value*) attrs);
+ // std::cout << "ExprWith::eval3.5" << std::endl;
+ // env2.valuemap.reset(mapBindings(*env2.values[0]->attrs));
+ // std::cout << "ExprWith::eval4" << std::endl;
+ // }
body->eval(state, env2, v);
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 2d167e6eb..f5c685edf 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -44,6 +44,7 @@ struct Env
Value * values[0];
};
+void printEnvBindings(const Env &env, int lv = 0);
valmap * mapEnvBindings(const Env &env);
Value & mkString(Value & v, std::string_view s, const PathSet & context = PathSet());
From d8a977a22ebd8884124a0a80e6b1523228f70f4b Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Wed, 25 Aug 2021 11:19:09 -0600
Subject: [PATCH 031/188] adding all the value names from env.values[0]
---
src/libcmd/command.cc | 2 +-
src/libexpr/eval.cc | 24 +++++++++++-------------
2 files changed, 12 insertions(+), 14 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 1a59dff77..45665b555 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -103,7 +103,7 @@ extern std::function<void(const Error & error, const Env & env)> debuggerHook;
ref<EvalState> EvalCommand::getEvalState()
{
- std::cout << " EvalCommand::getEvalState()" << startReplOnEvalErrors << std::endl;
+ std::cout << "EvalCommand::getEvalState()" << startReplOnEvalErrors << std::endl;
if (!evalState) {
evalState = std::make_shared<EvalState>(searchPath, getStore());
if (startReplOnEvalErrors)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 7fee1168c..6eb7f2cb9 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -698,21 +698,19 @@ void mapEnvBindings(const Env &env, valmap & vm)
}
// merge - and write over - higher level bindings.
- if (env.valuemap)
- vm.merge(*env.valuemap);
+ if (env.values[0]->type() == nAttrs) {
+ auto map = valmap();
+
+ Bindings::iterator j = env.values[0]->attrs->begin();
+
+ while (j != env.values[0]->attrs->end()) {
+ map[j->name] = j->value;
+ j++;
+ }
+ vm.merge(map);
+ }
}
-// void mapEnvBindings(const Env &env, valmap & vm)
-// {
-// // add bindings for the next level up first.
-// if (env.up) {
-// mapEnvBindings(*env.up, vm);
-// }
-
-// // merge - and write over - higher level bindings.
-// if (env.valuemap)
-// vm.merge(*env.valuemap);
-// }
valmap * mapEnvBindings(const Env &env)
{
From 310c689d317d1eb4bcf50cd11d84165fe2ffd512 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Wed, 25 Aug 2021 13:18:27 -0600
Subject: [PATCH 032/188] remove more explicit valmap code
---
src/libexpr/eval.cc | 148 ++++++++++++++------------------------------
src/libexpr/eval.hh | 1 -
2 files changed, 47 insertions(+), 102 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 6eb7f2cb9..c6fb052f4 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -630,43 +630,43 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
}
*/
-LocalNoInline(valmap * map0())
-{
- return new valmap();
-}
+// LocalNoInline(valmap * map0())
+// {
+// return new valmap();
+// }
-LocalNoInline(valmap * map1(const char *name, Value *v))
-{
- return new valmap({{name, v}});
-}
+// LocalNoInline(valmap * map1(const char *name, Value *v))
+// {
+// return new valmap({{name, v}});
+// }
-LocalNoInline(valmap * map2(const char *name1, Value *v1, const char *name2, Value *v2))
-{
- return new valmap({{name1, v1}, {name2, v2}});
-}
+// LocalNoInline(valmap * map2(const char *name1, Value *v1, const char *name2, Value *v2))
+// {
+// return new valmap({{name1, v1}, {name2, v2}});
+// }
-LocalNoInline(valmap * mapBindings(Bindings &b))
-{
- auto map = new valmap();
+// LocalNoInline(valmap * mapBindings(Bindings &b))
+// {
+// auto map = new valmap();
- for (auto i = b.begin(); i != b.end(); ++i)
- {
- std::string s = i->name;
- (*map)[s] = i->value;
- }
+// for (auto i = b.begin(); i != b.end(); ++i)
+// {
+// std::string s = i->name;
+// (*map)[s] = i->value;
+// }
- return map;
-}
+// return map;
+// }
-LocalNoInline(void addBindings(string prefix, Bindings &b, valmap &valmap))
-{
- for (auto i = b.begin(); i != b.end(); ++i)
- {
- std::string s = prefix;
- s += i->name;
- valmap[s] = i->value;
- }
-}
+// LocalNoInline(void addBindings(string prefix, Bindings &b, valmap &valmap))
+// {
+// for (auto i = b.begin(); i != b.end(); ++i)
+// {
+// std::string s = prefix;
+// s += i->name;
+// valmap[s] = i->value;
+// }
+// }
void printEnvBindings(const Env &env, int lv )
@@ -698,6 +698,7 @@ void mapEnvBindings(const Env &env, valmap & vm)
}
// merge - and write over - higher level bindings.
+ // note; skipping HasWithExpr that haven't been evaled yet.
if (env.values[0]->type() == nAttrs) {
auto map = valmap();
@@ -716,18 +717,7 @@ valmap * mapEnvBindings(const Env &env)
{
auto vm = new valmap();
- // segfault!
- std::cout << "before mapenv" << std::endl;
- if (env.valuemap) {
- std::cout << "valuemap" << std::endl;
- std::cout << "mapenv count" << env.valuemap->size() << std::endl;
- } else
- {
- std::cout << "novaluemap" << std::endl;
- }
-
mapEnvBindings(env, *vm);
- std::cout << "after mapenv" << std::endl;
return vm;
}
@@ -1270,11 +1260,6 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
v.attrs->push_back(Attr(i.first, vAttr, &i.second.pos));
}
- // TODO; deal with the below overrides or whatever
- if (debuggerHook) {
- env2.valuemap.reset(mapBindings(*v.attrs));
- }
-
/* If the rec contains an attribute called `__overrides', then
evaluate it, and add the attributes in that set to the rec.
This allows overriding of recursive attributes, which is
@@ -1345,18 +1330,6 @@ void ExprLet::eval(EvalState & state, Env & env, Value & v)
for (auto & i : attrs->attrs)
env2.values[displ++] = i.second.e->maybeThunk(state, i.second.inherited ? env : env2);
- if (debuggerHook) {
- auto map = new valmap();
-
- displ = 0;
- for (auto & i : attrs->attrs)
- {
- // std::string s = i->name;
- (*map)[i.first] = env2.values[displ++];
- }
- env2.valuemap.reset(map);
- }
-
body->eval(state, env2, v);
}
@@ -1579,51 +1552,24 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
there is no matching actual argument but the formal
argument has a default, use the default. */
size_t attrsUsed = 0;
- if (debuggerHook) {
- for (auto & i : lambda.formals->formals) {
- Bindings::iterator j = arg.attrs->find(i.name);
- if (j == arg.attrs->end()) {
- if (!i.def)
- throwTypeError(
- pos,
- "%1% called without required argument '%2%'",
- lambda,
- i.name,
- *fun.lambda.env);
- // map2("fun", &fun, "arg", &arg));
- env2.values[displ++] = i.def->maybeThunk(*this, env2);
- } else {
- attrsUsed++;
- env2.values[displ++] = j->value;
- }
+ for (auto & i : lambda.formals->formals) {
+ Bindings::iterator j = arg.attrs->find(i.name);
+ if (j == arg.attrs->end()) {
+ if (!i.def)
+ throwTypeError(
+ pos,
+ "%1% called without required argument '%2%'",
+ lambda,
+ i.name,
+ *fun.lambda.env);
+ // map2("fun", &fun, "arg", &arg));
+ env2.values[displ++] = i.def->maybeThunk(*this, env2);
+ } else {
+ attrsUsed++;
+ env2.values[displ++] = j->value;
}
}
- else {
- auto map = new valmap();
-
- for (auto & i : lambda.formals->formals) {
- Bindings::iterator j = arg.attrs->find(i.name);
- if (j == arg.attrs->end()) {
- if (!i.def)
- throwTypeError(
- pos,
- "%1% called without required argument '%2%'",
- lambda,
- i.name,
- *fun.lambda.env);
- // map2("fun", &fun, "arg", &arg));
- env2.values[displ++] = i.def->maybeThunk(*this, env2);
- } else {
- attrsUsed++;
- env2.values[displ++] = j->value;
- // add to debugger name-value map
- std::string s = i.name;
- (*map)[s] = j->value;
- }
- }
- env2.valuemap.reset(map);
- }
/* Check that each actual argument is listed as a formal
argument (unless the attribute match specifies a `...'). */
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index f5c685edf..ca3a7b742 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -40,7 +40,6 @@ struct Env
Env * up;
unsigned short prevWith:14; // nr of levels up to next `with' environment
enum { Plain = 0, HasWithExpr, HasWithAttrs } type:2;
- std::unique_ptr<valmap> valuemap; // TODO: rename
Value * values[0];
};
From 176911102ce2c0be06bbfed9099f364d71c3c679 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Mon, 13 Sep 2021 11:57:25 -0600
Subject: [PATCH 033/188] printEnvPosChain
---
doc/manual/manual.html | 8926 ++++++++
doc/manual/manual.is-valid | 0
doc/manual/manual.xmli | 20139 ++++++++++++++++++
doc/manual/src/command-ref/conf-file.md.tmp | 52 +
doc/manual/src/command-ref/nix.md | 3021 +++
doc/manual/src/expressions/builtins.md.tmp | 16 +
doc/manual/version.txt | 1 +
src/libcmd/command.cc | 1 +
src/libexpr/eval.cc | 34 +-
src/libexpr/eval.hh | 1 +
src/libutil/error.hh | 6 +
11 files changed, 32193 insertions(+), 4 deletions(-)
create mode 100644 doc/manual/manual.html
create mode 100644 doc/manual/manual.is-valid
create mode 100644 doc/manual/manual.xmli
create mode 100644 doc/manual/src/command-ref/conf-file.md.tmp
create mode 100644 doc/manual/src/command-ref/nix.md
create mode 100644 doc/manual/src/expressions/builtins.md.tmp
create mode 100644 doc/manual/version.txt
diff --git a/doc/manual/manual.html b/doc/manual/manual.html
new file mode 100644
index 000000000..2396756ef
--- /dev/null
+++ b/doc/manual/manual.html
@@ -0,0 +1,8926 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Nix Package Manager Guide</title><meta name="generator" content="DocBook XSL Stylesheets V1.79.2" /></head><body><div class="book"><div class="titlepage"><div><div><h1 class="title"><a id="idm139733328760992"></a>Nix Package Manager Guide</h1></div><div><h2 class="subtitle">Version 3.0</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Eelco</span> <span class="surname">Dolstra</span></h3></div></div><div><p class="copyright">Copyright © 2004-2018 Eelco Dolstra</p></div></div><hr /></div><div class="toc"><dl class="toc"><dt><span class="part"><a href="#chap-introduction">I. Introduction</a></span></dt><dd><dl><dt><span class="chapter"><a href="#ch-about-nix">1. About Nix</a></span></dt><dt><span class="chapter"><a href="#chap-quick-start">2. Quick Start</a></span></dt></dl></dd><dt><span class="part"><a href="#chap-installation">II. Installation</a></span></dt><dd><dl><dt><span class="chapter"><a href="#ch-supported-platforms">3. Supported Platforms</a></span></dt><dt><span class="chapter"><a href="#ch-installing-binary">4. Installing a Binary Distribution</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-single-user-installation">4.1. Single User Installation</a></span></dt><dt><span class="section"><a href="#sect-multi-user-installation">4.2. Multi User Installation</a></span></dt><dt><span class="section"><a href="#sect-macos-installation">4.3. macOS Installation</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-macos-installation-change-store-prefix">4.3.1. Change the Nix store path prefix</a></span></dt><dt><span class="section"><a href="#sect-macos-installation-encrypted-volume">4.3.2. Use a separate encrypted volume</a></span></dt><dt><span class="section"><a href="#sect-macos-installation-symlink">4.3.3. Symlink the Nix store to a custom location</a></span></dt><dt><span class="section"><a href="#sect-macos-installation-recommended-notes">4.3.4. Notes on the recommended approach</a></span></dt></dl></dd><dt><span class="section"><a href="#sect-nix-install-pinned-version-url">4.4. Installing a pinned Nix version from a URL</a></span></dt><dt><span class="section"><a href="#sect-nix-install-binary-tarball">4.5. Installing from a binary tarball</a></span></dt></dl></dd><dt><span class="chapter"><a href="#ch-installing-source">5. Installing Nix from Source</a></span></dt><dd><dl><dt><span class="section"><a href="#sec-prerequisites-source">5.1. Prerequisites</a></span></dt><dt><span class="section"><a href="#sec-obtaining-source">5.2. Obtaining a Source Distribution</a></span></dt><dt><span class="section"><a href="#sec-building-source">5.3. Building Nix from Source</a></span></dt></dl></dd><dt><span class="chapter"><a href="#ch-nix-security">6. Security</a></span></dt><dd><dl><dt><span class="section"><a href="#sec-single-user">6.1. Single-User Mode</a></span></dt><dt><span class="section"><a href="#ssec-multi-user">6.2. Multi-User Mode</a></span></dt></dl></dd><dt><span class="chapter"><a href="#ch-env-variables">7. Environment Variables</a></span></dt><dd><dl><dt><span class="section"><a href="#sec-nix-ssl-cert-file">7.1. <code class="envar">NIX_SSL_CERT_FILE</code></a></span></dt><dd><dl><dt><span class="section"><a href="#sec-nix-ssl-cert-file-with-nix-daemon-and-macos">7.1.1. <code class="envar">NIX_SSL_CERT_FILE</code> with macOS and the Nix daemon</a></span></dt><dt><span class="section"><a href="#sec-installer-proxy-settings">7.1.2. Proxy Environment Variables</a></span></dt></dl></dd></dl></dd></dl></dd><dt><span class="chapter"><a href="#ch-upgrading-nix">8. Upgrading Nix</a></span></dt><dt><span class="part"><a href="#chap-package-management">III. Package Management</a></span></dt><dd><dl><dt><span class="chapter"><a href="#ch-basic-package-mgmt">9. Basic Package Management</a></span></dt><dt><span class="chapter"><a href="#sec-profiles">10. Profiles</a></span></dt><dt><span class="chapter"><a href="#sec-garbage-collection">11. Garbage Collection</a></span></dt><dd><dl><dt><span class="section"><a href="#ssec-gc-roots">11.1. Garbage Collector Roots</a></span></dt></dl></dd><dt><span class="chapter"><a href="#sec-channels">12. Channels</a></span></dt><dt><span class="chapter"><a href="#sec-sharing-packages">13. Sharing Packages Between Machines</a></span></dt><dd><dl><dt><span class="section"><a href="#ssec-binary-cache-substituter">13.1. Serving a Nix store via HTTP</a></span></dt><dt><span class="section"><a href="#ssec-copy-closure">13.2. Copying Closures Via SSH</a></span></dt><dt><span class="section"><a href="#ssec-ssh-substituter">13.3. Serving a Nix store via SSH</a></span></dt><dt><span class="section"><a href="#ssec-s3-substituter">13.4. Serving a Nix store via AWS S3 or S3-compatible Service</a></span></dt><dd><dl><dt><span class="section"><a href="#ssec-s3-substituter-anonymous-reads">13.4.1. Anonymous Reads to your S3-compatible binary cache</a></span></dt><dt><span class="section"><a href="#ssec-s3-substituter-authenticated-reads">13.4.2. Authenticated Reads to your S3 binary cache</a></span></dt><dt><span class="section"><a href="#ssec-s3-substituter-authenticated-writes">13.4.3. Authenticated Writes to your S3-compatible binary cache</a></span></dt></dl></dd></dl></dd></dl></dd><dt><span class="part"><a href="#chap-writing-nix-expressions">IV. Writing Nix Expressions</a></span></dt><dd><dl><dt><span class="chapter"><a href="#ch-simple-expression">14. A Simple Nix Expression</a></span></dt><dd><dl><dt><span class="section"><a href="#sec-expression-syntax">14.1. Expression Syntax</a></span></dt><dt><span class="section"><a href="#sec-build-script">14.2. Build Script</a></span></dt><dt><span class="section"><a href="#sec-arguments">14.3. Arguments and Variables</a></span></dt><dt><span class="section"><a href="#sec-building-simple">14.4. Building and Testing</a></span></dt><dt><span class="section"><a href="#sec-generic-builder">14.5. Generic Builder Syntax</a></span></dt></dl></dd><dt><span class="chapter"><a href="#ch-expression-language">15. Nix Expression Language</a></span></dt><dd><dl><dt><span class="section"><a href="#ssec-values">15.1. Values</a></span></dt><dt><span class="section"><a href="#sec-constructs">15.2. Language Constructs</a></span></dt><dt><span class="section"><a href="#sec-language-operators">15.3. Operators</a></span></dt><dt><span class="section"><a href="#ssec-derivation">15.4. Derivations</a></span></dt><dd><dl><dt><span class="section"><a href="#sec-advanced-attributes">15.4.1. Advanced Attributes</a></span></dt></dl></dd><dt><span class="section"><a href="#ssec-builtins">15.5. Built-in Functions</a></span></dt></dl></dd></dl></dd><dt><span class="part"><a href="#part-advanced-topics">V. Advanced Topics</a></span></dt><dd><dl><dt><span class="chapter"><a href="#chap-distributed-builds">16. Remote Builds</a></span></dt><dt><span class="chapter"><a href="#chap-tuning-cores-and-jobs">17. Tuning Cores and Jobs</a></span></dt><dt><span class="chapter"><a href="#chap-diff-hook">18. Verifying Build Reproducibility with <code class="option"><a class="option" href="#conf-diff-hook">diff-hook</a></code></a></span></dt><dd><dl><dt><span class="section"><a href="#idm139733300510624">18.1.
+ Spot-Checking Build Determinism
+ </a></span></dt><dt><span class="section"><a href="#idm139733300495744">18.2.
+ Automatic and Optionally Enforced Determinism Verification
+ </a></span></dt></dl></dd><dt><span class="chapter"><a href="#chap-post-build-hook">19. Using the <code class="option"><a class="option" href="#conf-post-build-hook">post-build-hook</a></code></a></span></dt><dd><dl><dt><span class="section"><a href="#chap-post-build-hook-caveats">19.1. Implementation Caveats</a></span></dt><dt><span class="section"><a href="#idm139733300481840">19.2. Prerequisites</a></span></dt><dt><span class="section"><a href="#idm139733300479440">19.3. Set up a Signing Key</a></span></dt><dt><span class="section"><a href="#idm139733300473952">19.4. Implementing the build hook</a></span></dt><dt><span class="section"><a href="#idm139733300467040">19.5. Updating Nix Configuration</a></span></dt><dt><span class="section"><a href="#idm139733300464016">19.6. Testing</a></span></dt><dt><span class="section"><a href="#idm139733300459088">19.7. Conclusion</a></span></dt></dl></dd></dl></dd><dt><span class="part"><a href="#part-command-ref">VI. Command Reference</a></span></dt><dd><dl><dt><span class="chapter"><a href="#sec-common-options">20. Common Options</a></span></dt><dt><span class="chapter"><a href="#sec-common-env">21. Common Environment Variables</a></span></dt><dt><span class="chapter"><a href="#ch-main-commands">22. Main Commands</a></span></dt><dd><dl><dt><span class="refentrytitle"><a href="#sec-nix-env">nix-env</a></span><span class="refpurpose"> — manipulate or query Nix user environments</span></dt><dt><span class="refentrytitle"><a href="#sec-nix-build">nix-build</a></span><span class="refpurpose"> — build a Nix expression</span></dt><dt><span class="refentrytitle"><a href="#sec-nix-shell">nix-shell</a></span><span class="refpurpose"> — start an interactive shell based on a Nix expression</span></dt><dt><span class="refentrytitle"><a href="#sec-nix-store">nix-store</a></span><span class="refpurpose"> — manipulate or query the Nix store</span></dt></dl></dd><dt><span class="chapter"><a href="#ch-utilities">23. Utilities</a></span></dt><dd><dl><dt><span class="refentrytitle"><a href="#sec-nix-channel">nix-channel</a></span><span class="refpurpose"> — manage Nix channels</span></dt><dt><span class="refentrytitle"><a href="#sec-nix-collect-garbage">nix-collect-garbage</a></span><span class="refpurpose"> — delete unreachable store paths</span></dt><dt><span class="refentrytitle"><a href="#sec-nix-copy-closure">nix-copy-closure</a></span><span class="refpurpose"> — copy a closure to or from a remote machine via SSH</span></dt><dt><span class="refentrytitle"><a href="#sec-nix-daemon">nix-daemon</a></span><span class="refpurpose"> — Nix multi-user support daemon</span></dt><dt><span class="refentrytitle"><a href="#sec-nix-hash">nix-hash</a></span><span class="refpurpose"> — compute the cryptographic hash of a path</span></dt><dt><span class="refentrytitle"><a href="#sec-nix-instantiate">nix-instantiate</a></span><span class="refpurpose"> — instantiate store derivations from Nix expressions</span></dt><dt><span class="refentrytitle"><a href="#sec-nix-prefetch-url">nix-prefetch-url</a></span><span class="refpurpose"> — copy a file from a URL into the store and print its hash</span></dt></dl></dd><dt><span class="chapter"><a href="#ch-files">24. Files</a></span></dt><dd><dl><dt><span class="refentrytitle"><a href="#sec-conf-file">nix.conf</a></span><span class="refpurpose"> — Nix configuration file</span></dt></dl></dd></dl></dd><dt><span class="appendix"><a href="#part-glossary">A. Glossary</a></span></dt><dt><span class="appendix"><a href="#chap-hacking">B. Hacking</a></span></dt><dt><span class="appendix"><a href="#sec-relnotes">C. Nix Release Notes</a></span></dt><dd><dl><dt><span class="section"><a href="#ssec-relnotes-2.3">C.1. Release 2.3 (2019-09-04)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-2.2">C.2. Release 2.2 (2019-01-11)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-2.1">C.3. Release 2.1 (2018-09-02)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-2.0">C.4. Release 2.0 (2018-02-22)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.11.10">C.5. Release 1.11.10 (2017-06-12)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.11">C.6. Release 1.11 (2016-01-19)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.10">C.7. Release 1.10 (2015-09-03)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.9">C.8. Release 1.9 (2015-06-12)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.8">C.9. Release 1.8 (2014-12-14)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.7">C.10. Release 1.7 (2014-04-11)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.6.1">C.11. Release 1.6.1 (2013-10-28)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.6.0">C.12. Release 1.6 (2013-09-10)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.5.2">C.13. Release 1.5.2 (2013-05-13)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.5">C.14. Release 1.5 (2013-02-27)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.4">C.15. Release 1.4 (2013-02-26)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.3">C.16. Release 1.3 (2013-01-04)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.2">C.17. Release 1.2 (2012-12-06)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.1">C.18. Release 1.1 (2012-07-18)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.0">C.19. Release 1.0 (2012-05-11)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-0.16">C.20. Release 0.16 (2010-08-17)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-0.15">C.21. Release 0.15 (2010-03-17)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-0.14">C.22. Release 0.14 (2010-02-04)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-0.13">C.23. Release 0.13 (2009-11-05)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-0.12">C.24. Release 0.12 (2008-11-20)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-0.11">C.25. Release 0.11 (2007-12-31)</a></span></dt><dt><span class="section"><a href="#ch-relnotes-0.10.1">C.26. Release 0.10.1 (2006-10-11)</a></span></dt><dt><span class="section"><a href="#ch-relnotes-0.10">C.27. Release 0.10 (2006-10-06)</a></span></dt><dt><span class="section"><a href="#ch-relnotes-0.9.2">C.28. Release 0.9.2 (2005-09-21)</a></span></dt><dt><span class="section"><a href="#ch-relnotes-0.9.1">C.29. Release 0.9.1 (2005-09-20)</a></span></dt><dt><span class="section"><a href="#ch-relnotes-0.9">C.30. Release 0.9 (2005-09-16)</a></span></dt><dt><span class="section"><a href="#ch-relnotes-0.8.1">C.31. Release 0.8.1 (2005-04-13)</a></span></dt><dt><span class="section"><a href="#ch-relnotes-0.8">C.32. Release 0.8 (2005-04-11)</a></span></dt><dt><span class="section"><a href="#ch-relnotes-0.7">C.33. Release 0.7 (2005-01-12)</a></span></dt><dt><span class="section"><a href="#ch-relnotes-0.6">C.34. Release 0.6 (2004-11-14)</a></span></dt><dt><span class="section"><a href="#ch-relnotes-0.5">C.35. Release 0.5 and earlier</a></span></dt></dl></dd></dl></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a id="chap-introduction"></a>Part I. Introduction</h1></div></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-about-nix"></a>Chapter 1. About Nix</h2></div></div></div><p>Nix is a <span class="emphasis"><em>purely functional package manager</em></span>.
+This means that it treats packages like values in purely functional
+programming languages such as Haskell — they are built by functions
+that don’t have side-effects, and they never change after they have
+been built. Nix stores packages in the <span class="emphasis"><em>Nix
+store</em></span>, usually the directory
+<code class="filename">/nix/store</code>, where each package has its own unique
+subdirectory such as
+
+</p><pre class="programlisting">
+/nix/store/b6gvzjyb2pg0kjfwrjmg1vfhh54ad73z-firefox-33.1/
+</pre><p>
+
+where <code class="literal">b6gvzjyb2pg0…</code> is a unique identifier for the
+package that captures all its dependencies (it’s a cryptographic hash
+of the package’s build dependency graph). This enables many powerful
+features.</p><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733302010000"></a>Multiple versions</h2></div></div></div><p>You can have multiple versions or variants of a package
+installed at the same time. This is especially important when
+different applications have dependencies on different versions of the
+same package — it prevents the “DLL hell”. Because of the hashing
+scheme, different versions of a package end up in different paths in
+the Nix store, so they don’t interfere with each other.</p><p>An important consequence is that operations like upgrading or
+uninstalling an application cannot break other applications, since
+these operations never “destructively” update or delete files that are
+used by other packages.</p></div><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733302007296"></a>Complete dependencies</h2></div></div></div><p>Nix helps you make sure that package dependency specifications
+are complete. In general, when you’re making a package for a package
+management system like RPM, you have to specify for each package what
+its dependencies are, but there are no guarantees that this
+specification is complete. If you forget a dependency, then the
+package will build and work correctly on <span class="emphasis"><em>your</em></span>
+machine if you have the dependency installed, but not on the end
+user's machine if it's not there.</p><p>Since Nix on the other hand doesn’t install packages in “global”
+locations like <code class="filename">/usr/bin</code> but in package-specific
+directories, the risk of incomplete dependencies is greatly reduced.
+This is because tools such as compilers don’t search in per-packages
+directories such as
+<code class="filename">/nix/store/5lbfaxb722zp…-openssl-0.9.8d/include</code>,
+so if a package builds correctly on your system, this is because you
+specified the dependency explicitly. This takes care of the build-time
+dependencies.</p><p>Once a package is built, runtime dependencies are found by
+scanning binaries for the hash parts of Nix store paths (such as
+<code class="literal">r8vvq9kq…</code>). This sounds risky, but it works
+extremely well.</p></div><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733302002080"></a>Multi-user support</h2></div></div></div><p>Nix has multi-user support. This means that non-privileged
+users can securely install software. Each user can have a different
+<span class="emphasis"><em>profile</em></span>, a set of packages in the Nix store that
+appear in the user’s <code class="envar">PATH</code>. If a user installs a
+package that another user has already installed previously, the
+package won’t be built or downloaded a second time. At the same time,
+it is not possible for one user to inject a Trojan horse into a
+package that might be used by another user.</p></div><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733301999344"></a>Atomic upgrades and rollbacks</h2></div></div></div><p>Since package management operations never overwrite packages in
+the Nix store but just add new versions in different paths, they are
+<span class="emphasis"><em>atomic</em></span>. So during a package upgrade, there is no
+time window in which the package has some files from the old version
+and some files from the new version — which would be bad because a
+program might well crash if it’s started during that period.</p><p>And since packages aren’t overwritten, the old versions are still
+there after an upgrade. This means that you can <span class="emphasis"><em>roll
+back</em></span> to the old version:</p><pre class="screen">
+$ nix-env --upgrade <em class="replaceable"><code>some-packages</code></em>
+$ nix-env --rollback
+</pre></div><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733301995248"></a>Garbage collection</h2></div></div></div><p>When you uninstall a package like this…
+
+</p><pre class="screen">
+$ nix-env --uninstall firefox
+</pre><p>
+
+the package isn’t deleted from the system right away (after all, you
+might want to do a rollback, or it might be in the profiles of other
+users). Instead, unused packages can be deleted safely by running the
+<span class="emphasis"><em>garbage collector</em></span>:
+
+</p><pre class="screen">
+$ nix-collect-garbage
+</pre><p>
+
+This deletes all packages that aren’t in use by any user profile or by
+a currently running program.</p></div><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733301992112"></a>Functional package language</h2></div></div></div><p>Packages are built from <span class="emphasis"><em>Nix expressions</em></span>,
+which is a simple functional language. A Nix expression describes
+everything that goes into a package build action (a “derivation”):
+other packages, sources, the build script, environment variables for
+the build script, etc. Nix tries very hard to ensure that Nix
+expressions are <span class="emphasis"><em>deterministic</em></span>: building a Nix
+expression twice should yield the same result.</p><p>Because it’s a functional language, it’s easy to support
+building variants of a package: turn the Nix expression into a
+function and call it any number of times with the appropriate
+arguments. Due to the hashing scheme, variants don’t conflict with
+each other in the Nix store.</p></div><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733301988512"></a>Transparent source/binary deployment</h2></div></div></div><p>Nix expressions generally describe how to build a package from
+source, so an installation action like
+
+</p><pre class="screen">
+$ nix-env --install firefox
+</pre><p>
+
+<span class="emphasis"><em>could</em></span> cause quite a bit of build activity, as not
+only Firefox but also all its dependencies (all the way up to the C
+library and the compiler) would have to built, at least if they are
+not already in the Nix store. This is a <span class="emphasis"><em>source deployment
+model</em></span>. For most users, building from source is not very
+pleasant as it takes far too long. However, Nix can automatically
+skip building from source and instead use a <span class="emphasis"><em>binary
+cache</em></span>, a web server that provides pre-built binaries. For
+instance, when asked to build
+<code class="literal">/nix/store/b6gvzjyb2pg0…-firefox-33.1</code> from source,
+Nix would first check if the file
+<code class="uri">https://cache.nixos.org/b6gvzjyb2pg0….narinfo</code> exists, and
+if so, fetch the pre-built binary referenced from there; otherwise, it
+would fall back to building from source.</p></div><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733301983504"></a>Nix Packages collection</h2></div></div></div><p>We provide a large set of Nix expressions containing hundreds of
+existing Unix packages, the <span class="emphasis"><em>Nix Packages
+collection</em></span> (Nixpkgs).</p></div><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733301981888"></a>Managing build environments</h2></div></div></div><p>Nix is extremely useful for developers as it makes it easy to
+automatically set up the build environment for a package. Given a
+Nix expression that describes the dependencies of your package, the
+command <span class="command"><strong>nix-shell</strong></span> will build or download those
+dependencies if they’re not already in your Nix store, and then start
+a Bash shell in which all necessary environment variables (such as
+compiler search paths) are set.</p><p>For example, the following command gets all dependencies of the
+Pan newsreader, as described by <a class="link" href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/networking/newsreaders/pan/default.nix" target="_top">its
+Nix expression</a>:</p><pre class="screen">
+$ nix-shell '<nixpkgs>' -A pan
+</pre><p>You’re then dropped into a shell where you can edit, build and test
+the package:</p><pre class="screen">
+[nix-shell]$ tar xf $src
+[nix-shell]$ cd pan-*
+[nix-shell]$ ./configure
+[nix-shell]$ make
+[nix-shell]$ ./pan/gui/pan
+</pre></div><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733301976352"></a>Portability</h2></div></div></div><p>Nix runs on Linux and macOS.</p></div><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733301975296"></a>NixOS</h2></div></div></div><p>NixOS is a Linux distribution based on Nix. It uses Nix not
+just for package management but also to manage the system
+configuration (e.g., to build configuration files in
+<code class="filename">/etc</code>). This means, among other things, that it
+is easy to roll back the entire configuration of the system to an
+earlier state. Also, users can install software without root
+privileges. For more information and downloads, see the <a class="link" href="http://nixos.org/" target="_top">NixOS homepage</a>.</p></div><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733301972848"></a>License</h2></div></div></div><p>Nix is released under the terms of the <a class="link" href="http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html" target="_top">GNU
+LGPLv2.1 or (at your option) any later version</a>.</p></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="chap-quick-start"></a>Chapter 2. Quick Start</h2></div></div></div><p>This chapter is for impatient people who don't like reading
+documentation. For more in-depth information you are kindly referred
+to subsequent chapters.</p><div class="procedure"><ol class="procedure" type="1"><li class="step"><p>Install single-user Nix by running the following:
+
+</p><pre class="screen">
+$ bash <(curl -L https://nixos.org/nix/install)
+</pre><p>
+
+This will install Nix in <code class="filename">/nix</code>. The install script
+will create <code class="filename">/nix</code> using <span class="command"><strong>sudo</strong></span>,
+so make sure you have sufficient rights. (For other installation
+methods, see <a class="xref" href="#chap-installation" title="Part II. Installation">Part II, “Installation”</a>.)</p></li><li class="step"><p>See what installable packages are currently available
+in the channel:
+
+</p><pre class="screen">
+$ nix-env -qa
+docbook-xml-4.3
+docbook-xml-4.5
+firefox-33.0.2
+hello-2.9
+libxslt-1.1.28
+<em class="replaceable"><code>...</code></em></pre><p>
+
+</p></li><li class="step"><p>Install some packages from the channel:
+
+</p><pre class="screen">
+$ nix-env -i hello</pre><p>
+
+This should download pre-built packages; it should not build them
+locally (if it does, something went wrong).</p></li><li class="step"><p>Test that they work:
+
+</p><pre class="screen">
+$ which hello
+/home/eelco/.nix-profile/bin/hello
+$ hello
+Hello, world!
+</pre><p>
+
+</p></li><li class="step"><p>Uninstall a package:
+
+</p><pre class="screen">
+$ nix-env -e hello</pre><p>
+
+</p></li><li class="step"><p>You can also test a package without installing it:
+
+</p><pre class="screen">
+$ nix-shell -p hello
+</pre><p>
+
+This builds or downloads GNU Hello and its dependencies, then drops
+you into a Bash shell where the <span class="command"><strong>hello</strong></span> command is
+present, all without affecting your normal environment:
+
+</p><pre class="screen">
+[nix-shell:~]$ hello
+Hello, world!
+
+[nix-shell:~]$ exit
+
+$ hello
+hello: command not found
+</pre><p>
+
+</p></li><li class="step"><p>To keep up-to-date with the channel, do:
+
+</p><pre class="screen">
+$ nix-channel --update nixpkgs
+$ nix-env -u '*'</pre><p>
+
+The latter command will upgrade each installed package for which there
+is a “newer” version (as determined by comparing the version
+numbers).</p></li><li class="step"><p>If you're unhappy with the result of a
+<span class="command"><strong>nix-env</strong></span> action (e.g., an upgraded package turned
+out not to work properly), you can go back:
+
+</p><pre class="screen">
+$ nix-env --rollback</pre><p>
+
+</p></li><li class="step"><p>You should periodically run the Nix garbage collector
+to get rid of unused packages, since uninstalls or upgrades don't
+actually delete them:
+
+</p><pre class="screen">
+$ nix-collect-garbage -d</pre><p>
+
+
+
+</p></li></ol></div></div></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a id="chap-installation"></a>Part II. Installation</h1></div></div></div><div class="partintro"><div></div><p>This section describes how to install and configure Nix for first-time use.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-supported-platforms"></a>Chapter 3. Supported Platforms</h2></div></div></div><p>Nix is currently supported on the following platforms:
+
+</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Linux (i686, x86_64, aarch64).</p></li><li class="listitem"><p>macOS (x86_64).</p></li></ul></div><p>
+
+</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-installing-binary"></a>Chapter 4. Installing a Binary Distribution</h2></div></div></div><p>
+ If you are using Linux or macOS versions up to 10.14 (Mojave), the
+ easiest way to install Nix is to run the following command:
+</p><pre class="screen">
+ $ sh <(curl -L https://nixos.org/nix/install)
+</pre><p>
+ If you're using macOS 10.15 (Catalina) or newer, consult
+ <a class="link" href="#sect-macos-installation" title="4.3. macOS Installation">the macOS installation instructions</a>
+ before installing.
+</p><p>
+ As of Nix 2.1.0, the Nix installer will always default to creating a
+ single-user installation, however opting in to the multi-user
+ installation is highly recommended.
+
+</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sect-single-user-installation"></a>4.1. Single User Installation</h2></div></div></div><p>
+ To explicitly select a single-user installation on your system:
+
+ </p><pre class="screen">
+ sh <(curl -L https://nixos.org/nix/install) --no-daemon
+</pre><p>
+ </p><p>
+This will perform a single-user installation of Nix, meaning that
+<code class="filename">/nix</code> is owned by the invoking user. You should
+run this under your usual user account, <span class="emphasis"><em>not</em></span> as
+root. The script will invoke <span class="command"><strong>sudo</strong></span> to create
+<code class="filename">/nix</code> if it doesn’t already exist. If you don’t
+have <span class="command"><strong>sudo</strong></span>, you should manually create
+<code class="filename">/nix</code> first as root, e.g.:
+
+</p><pre class="screen">
+$ mkdir /nix
+$ chown alice /nix
+</pre><p>
+
+The install script will modify the first writable file from amongst
+<code class="filename">.bash_profile</code>, <code class="filename">.bash_login</code>
+and <code class="filename">.profile</code> to source
+<code class="filename">~/.nix-profile/etc/profile.d/nix.sh</code>. You can set
+the <code class="envar">NIX_INSTALLER_NO_MODIFY_PROFILE</code> environment
+variable before executing the install script to disable this
+behaviour.
+</p><p>You can uninstall Nix simply by running:
+
+</p><pre class="screen">
+$ rm -rf /nix
+</pre><p>
+
+</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sect-multi-user-installation"></a>4.2. Multi User Installation</h2></div></div></div><p>
+ The multi-user Nix installation creates system users, and a system
+ service for the Nix daemon.
+ </p><div class="itemizedlist"><p class="title"><strong>Supported Systems</strong></p><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Linux running systemd, with SELinux disabled</p></li><li class="listitem"><p>macOS</p></li></ul></div><p>
+ You can instruct the installer to perform a multi-user
+ installation on your system:
+ </p><pre class="screen">sh <(curl -L https://nixos.org/nix/install) --daemon</pre><p>
+ The multi-user installation of Nix will create build users between
+ the user IDs 30001 and 30032, and a group with the group ID 30000.
+
+ You should run this under your usual user account,
+ <span class="emphasis"><em>not</em></span> as root. The script will invoke
+ <span class="command"><strong>sudo</strong></span> as needed.
+ </p><div class="note"><h3 class="title">Note</h3><p>
+ If you need Nix to use a different group ID or user ID set, you
+ will have to download the tarball manually and <a class="link" href="#sect-nix-install-binary-tarball" title="4.5. Installing from a binary tarball">edit the install
+ script</a>.
+ </p></div><p>
+ The installer will modify <code class="filename">/etc/bashrc</code>, and
+ <code class="filename">/etc/zshrc</code> if they exist. The installer will
+ first back up these files with a
+ <code class="literal">.backup-before-nix</code> extension. The installer
+ will also create <code class="filename">/etc/profile.d/nix.sh</code>.
+ </p><p>You can uninstall Nix with the following commands:
+
+</p><pre class="screen">
+sudo rm -rf /etc/profile/nix.sh /etc/nix /nix ~root/.nix-profile ~root/.nix-defexpr ~root/.nix-channels ~/.nix-profile ~/.nix-defexpr ~/.nix-channels
+
+# If you are on Linux with systemd, you will need to run:
+sudo systemctl stop nix-daemon.socket
+sudo systemctl stop nix-daemon.service
+sudo systemctl disable nix-daemon.socket
+sudo systemctl disable nix-daemon.service
+sudo systemctl daemon-reload
+
+# If you are on macOS, you will need to run:
+sudo launchctl unload /Library/LaunchDaemons/org.nixos.nix-daemon.plist
+sudo rm /Library/LaunchDaemons/org.nixos.nix-daemon.plist
+</pre><p>
+
+ There may also be references to Nix in
+ <code class="filename">/etc/profile</code>,
+ <code class="filename">/etc/bashrc</code>, and
+ <code class="filename">/etc/zshrc</code> which you may remove.
+ </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sect-macos-installation"></a>4.3. macOS Installation</h2></div></div></div><p>
+ Starting with macOS 10.15 (Catalina), the root filesystem is read-only.
+ This means <code class="filename">/nix</code> can no longer live on your system
+ volume, and that you'll need a workaround to install Nix.
+ </p><p>
+ The recommended approach, which creates an unencrypted APFS volume
+ for your Nix store and a "synthetic" empty directory to mount it
+ over at <code class="filename">/nix</code>, is least likely to impair Nix
+ or your system.
+ </p><div class="note"><h3 class="title">Note</h3><p>
+ With all separate-volume approaches, it's possible something on
+ your system (particularly daemons/services and restored apps) may
+ need access to your Nix store before the volume is mounted. Adding
+ additional encryption makes this more likely.
+ </p></div><p>
+ If you're using a recent Mac with a
+ <a class="link" href="https://www.apple.com/euro/mac/shared/docs/Apple_T2_Security_Chip_Overview.pdf" target="_top">T2 chip</a>,
+ your drive will still be encrypted at rest (in which case "unencrypted"
+ is a bit of a misnomer). To use this approach, just install Nix with:
+ </p><pre class="screen">$ sh <(curl -L https://nixos.org/nix/install) --darwin-use-unencrypted-nix-store-volume</pre><p>
+ If you don't like the sound of this, you'll want to weigh the
+ other approaches and tradeoffs detailed in this section.
+ </p><div class="note"><h3 class="title">Eventual solutions?</h3><p>
+ All of the known workarounds have drawbacks, but we hope
+ better solutions will be available in the future. Some that
+ we have our eye on are:
+ </p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
+ A true firmlink would enable the Nix store to live on the
+ primary data volume without the build problems caused by
+ the symlink approach. End users cannot currently
+ create true firmlinks.
+ </p></li><li class="listitem"><p>
+ If the Nix store volume shared FileVault encryption
+ with the primary data volume (probably by using the same
+ volume group and role), FileVault encryption could be
+ easily supported by the installer without requiring
+ manual setup by each user.
+ </p></li></ol></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="sect-macos-installation-change-store-prefix"></a>4.3.1. Change the Nix store path prefix</h3></div></div></div><p>
+ Changing the default prefix for the Nix store is a simple
+ approach which enables you to leave it on your root volume,
+ where it can take full advantage of FileVault encryption if
+ enabled. Unfortunately, this approach also opts your device out
+ of some benefits that are enabled by using the same prefix
+ across systems:
+
+ </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
+ Your system won't be able to take advantage of the binary
+ cache (unless someone is able to stand up and support
+ duplicate caching infrastructure), which means you'll
+ spend more time waiting for builds.
+ </p></li><li class="listitem"><p>
+ It's harder to build and deploy packages to Linux systems.
+ </p></li></ul></div><p>
+
+
+
+ It would also possible (and often requested) to just apply this
+ change ecosystem-wide, but it's an intrusive process that has
+ side effects we want to avoid for now.
+
+ </p><p>
+ </p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="sect-macos-installation-encrypted-volume"></a>4.3.2. Use a separate encrypted volume</h3></div></div></div><p>
+ If you like, you can also add encryption to the recommended
+ approach taken by the installer. You can do this by pre-creating
+ an encrypted volume before you run the installer--or you can
+ run the installer and encrypt the volume it creates later.
+
+ </p><p>
+ In either case, adding encryption to a second volume isn't quite
+ as simple as enabling FileVault for your boot volume. Before you
+ dive in, there are a few things to weigh:
+ </p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
+ The additional volume won't be encrypted with your existing
+ FileVault key, so you'll need another mechanism to decrypt
+ the volume.
+ </p></li><li class="listitem"><p>
+ You can store the password in Keychain to automatically
+ decrypt the volume on boot--but it'll have to wait on Keychain
+ and may not mount before your GUI apps restore. If any of
+ your launchd agents or apps depend on Nix-installed software
+ (for example, if you use a Nix-installed login shell), the
+ restore may fail or break.
+ </p><p>
+ On a case-by-case basis, you may be able to work around this
+ problem by using <span class="command"><strong>wait4path</strong></span> to block
+ execution until your executable is available.
+ </p><p>
+ It's also possible to decrypt and mount the volume earlier
+ with a login hook--but this mechanism appears to be
+ deprecated and its future is unclear.
+ </p></li><li class="listitem"><p>
+ You can hard-code the password in the clear, so that your
+ store volume can be decrypted before Keychain is available.
+ </p></li></ol></div><p>
+ If you are comfortable navigating these tradeoffs, you can encrypt the volume with
+ something along the lines of:
+
+ </p><pre class="screen">alice$ diskutil apfs enableFileVault /nix -user disk</pre></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="sect-macos-installation-symlink"></a>4.3.3. Symlink the Nix store to a custom location</h3></div></div></div><p>
+ Another simple approach is using <code class="filename">/etc/synthetic.conf</code>
+ to symlink the Nix store to the data volume. This option also
+ enables your store to share any configured FileVault encryption.
+ Unfortunately, builds that resolve the symlink may leak the
+ canonical path or even fail.
+ </p><p>
+ Because of these downsides, we can't recommend this approach.
+ </p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="sect-macos-installation-recommended-notes"></a>4.3.4. Notes on the recommended approach</h3></div></div></div><p>
+ This section goes into a little more detail on the recommended
+ approach. You don't need to understand it to run the installer,
+ but it can serve as a helpful reference if you run into trouble.
+ </p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
+ In order to compose user-writable locations into the new
+ read-only system root, Apple introduced a new concept called
+ <code class="literal">firmlinks</code>, which it describes as a
+ "bi-directional wormhole" between two filesystems. You can
+ see the current firmlinks in <code class="filename">/usr/share/firmlinks</code>.
+ Unfortunately, firmlinks aren't (currently?) user-configurable.
+ </p><p>
+ For special cases like NFS mount points or package manager roots,
+ <a class="link" href="https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man5/synthetic.conf.5.html" target="_top">synthetic.conf(5)</a>
+ supports limited user-controlled file-creation (of symlinks,
+ and synthetic empty directories) at <code class="filename">/</code>.
+ To create a synthetic empty directory for mounting at <code class="filename">/nix</code>,
+ add the following line to <code class="filename">/etc/synthetic.conf</code>
+ (create it if necessary):
+ </p><pre class="screen">nix</pre></li><li class="listitem"><p>
+ This configuration is applied at boot time, but you can use
+ <span class="command"><strong>apfs.util</strong></span> to trigger creation (not deletion)
+ of new entries without a reboot:
+ </p><pre class="screen">alice$ /System/Library/Filesystems/apfs.fs/Contents/Resources/apfs.util -B</pre></li><li class="listitem"><p>
+ Create the new APFS volume with diskutil:
+ </p><pre class="screen">alice$ sudo diskutil apfs addVolume diskX APFS 'Nix Store' -mountpoint /nix</pre></li><li class="listitem"><p>
+ Using <span class="command"><strong>vifs</strong></span>, add the new mount to
+ <code class="filename">/etc/fstab</code>. If it doesn't already have
+ other entries, it should look something like:
+ </p><pre class="screen">
+#
+# Warning - this file should only be modified with vifs(8)
+#
+# Failure to do so is unsupported and may be destructive.
+#
+LABEL=Nix\040Store /nix apfs rw,nobrowse
+</pre><p>
+ The nobrowse setting will keep Spotlight from indexing this
+ volume, and keep it from showing up on your desktop.
+ </p></li></ol></div></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sect-nix-install-pinned-version-url"></a>4.4. Installing a pinned Nix version from a URL</h2></div></div></div><p>
+ NixOS.org hosts version-specific installation URLs for all Nix
+ versions since 1.11.16, at
+ <code class="literal">https://releases.nixos.org/nix/nix-<em class="replaceable"><code>version</code></em>/install</code>.
+ </p><p>
+ These install scripts can be used the same as the main
+ NixOS.org installation script:
+
+ </p><pre class="screen">
+ sh <(curl -L https://nixos.org/nix/install)
+</pre><p>
+ </p><p>
+ In the same directory of the install script are sha256 sums, and
+ gpg signature files.
+ </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sect-nix-install-binary-tarball"></a>4.5. Installing from a binary tarball</h2></div></div></div><p>
+ You can also download a binary tarball that contains Nix and all
+ its dependencies. (This is what the install script at
+ <code class="uri">https://nixos.org/nix/install</code> does automatically.) You
+ should unpack it somewhere (e.g. in <code class="filename">/tmp</code>),
+ and then run the script named <span class="command"><strong>install</strong></span> inside
+ the binary tarball:
+
+
+</p><pre class="screen">
+alice$ cd /tmp
+alice$ tar xfj nix-1.8-x86_64-darwin.tar.bz2
+alice$ cd nix-1.8-x86_64-darwin
+alice$ ./install
+</pre><p>
+ </p><p>
+ If you need to edit the multi-user installation script to use
+ different group ID or a different user ID range, modify the
+ variables set in the file named
+ <code class="filename">install-multi-user</code>.
+ </p></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-installing-source"></a>Chapter 5. Installing Nix from Source</h2></div></div></div><p>If no binary package is available, you can download and compile
+a source distribution.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-prerequisites-source"></a>5.1. Prerequisites</h2></div></div></div><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>GNU Autoconf
+ (<a class="link" href="https://www.gnu.org/software/autoconf/" target="_top">https://www.gnu.org/software/autoconf/</a>)
+ and the autoconf-archive macro collection
+ (<a class="link" href="https://www.gnu.org/software/autoconf-archive/" target="_top">https://www.gnu.org/software/autoconf-archive/</a>).
+ These are only needed to run the bootstrap script, and are not necessary
+ if your source distribution came with a pre-built
+ <code class="literal">./configure</code> script.</p></li><li class="listitem"><p>GNU Make.</p></li><li class="listitem"><p>Bash Shell. The <code class="literal">./configure</code> script
+ relies on bashisms, so Bash is required.</p></li><li class="listitem"><p>A version of GCC or Clang that supports C++17.</p></li><li class="listitem"><p><span class="command"><strong>pkg-config</strong></span> to locate
+ dependencies. If your distribution does not provide it, you can get
+ it from <a class="link" href="http://www.freedesktop.org/wiki/Software/pkg-config" target="_top">http://www.freedesktop.org/wiki/Software/pkg-config</a>.</p></li><li class="listitem"><p>The OpenSSL library to calculate cryptographic hashes.
+ If your distribution does not provide it, you can get it from <a class="link" href="https://www.openssl.org" target="_top">https://www.openssl.org</a>.</p></li><li class="listitem"><p>The <code class="literal">libbrotlienc</code> and
+ <code class="literal">libbrotlidec</code> libraries to provide implementation
+ of the Brotli compression algorithm. They are available for download
+ from the official repository <a class="link" href="https://github.com/google/brotli" target="_top">https://github.com/google/brotli</a>.</p></li><li class="listitem"><p>The bzip2 compressor program and the
+ <code class="literal">libbz2</code> library. Thus you must have bzip2
+ installed, including development headers and libraries. If your
+ distribution does not provide these, you can obtain bzip2 from <a class="link" href="https://web.archive.org/web/20180624184756/http://www.bzip.org/" target="_top">https://web.archive.org/web/20180624184756/http://www.bzip.org/</a>.</p></li><li class="listitem"><p><code class="literal">liblzma</code>, which is provided by
+ XZ Utils. If your distribution does not provide this, you can
+ get it from <a class="link" href="https://tukaani.org/xz/" target="_top">https://tukaani.org/xz/</a>.</p></li><li class="listitem"><p>cURL and its library. If your distribution does not
+ provide it, you can get it from <a class="link" href="https://curl.haxx.se/" target="_top">https://curl.haxx.se/</a>.</p></li><li class="listitem"><p>The SQLite embedded database library, version 3.6.19
+ or higher. If your distribution does not provide it, please install
+ it from <a class="link" href="http://www.sqlite.org/" target="_top">http://www.sqlite.org/</a>.</p></li><li class="listitem"><p>The <a class="link" href="http://www.hboehm.info/gc/" target="_top">Boehm
+ garbage collector</a> to reduce the evaluator’s memory
+ consumption (optional). To enable it, install
+ <code class="literal">pkgconfig</code> and the Boehm garbage collector, and
+ pass the flag <code class="option">--enable-gc</code> to
+ <span class="command"><strong>configure</strong></span>.</p></li><li class="listitem"><p>The <code class="literal">boost</code> library of version
+ 1.66.0 or higher. It can be obtained from the official web site
+ <a class="link" href="https://www.boost.org/" target="_top">https://www.boost.org/</a>.</p></li><li class="listitem"><p>The <code class="literal">editline</code> library of version
+ 1.14.0 or higher. It can be obtained from the its repository
+ <a class="link" href="https://github.com/troglobit/editline" target="_top">https://github.com/troglobit/editline</a>.</p></li><li class="listitem"><p>The <span class="command"><strong>xmllint</strong></span> and
+ <span class="command"><strong>xsltproc</strong></span> programs to build this manual and the
+ man-pages. These are part of the <code class="literal">libxml2</code> and
+ <code class="literal">libxslt</code> packages, respectively. You also need
+ the <a class="link" href="http://docbook.sourceforge.net/projects/xsl/" target="_top">DocBook
+ XSL stylesheets</a> and optionally the <a class="link" href="http://www.docbook.org/schemas/5x" target="_top"> DocBook 5.0 RELAX NG
+ schemas</a>. Note that these are only required if you modify the
+ manual sources or when you are building from the Git
+ repository.</p></li><li class="listitem"><p>Recent versions of Bison and Flex to build the
+ parser. (This is because Nix needs GLR support in Bison and
+ reentrancy support in Flex.) For Bison, you need version 2.6, which
+ can be obtained from the <a class="link" href="ftp://alpha.gnu.org/pub/gnu/bison" target="_top">GNU FTP
+ server</a>. For Flex, you need version 2.5.35, which is
+ available on <a class="link" href="http://lex.sourceforge.net/" target="_top">SourceForge</a>.
+ Slightly older versions may also work, but ancient versions like the
+ ubiquitous 2.5.4a won't. Note that these are only required if you
+ modify the parser or when you are building from the Git
+ repository.</p></li><li class="listitem"><p>The <code class="literal">libseccomp</code> is used to provide
+ syscall filtering on Linux. This is an optional dependency and can
+ be disabled passing a <code class="option">--disable-seccomp-sandboxing</code>
+ option to the <span class="command"><strong>configure</strong></span> script (Not recommended
+ unless your system doesn't support
+ <code class="literal">libseccomp</code>). To get the library, visit <a class="link" href="https://github.com/seccomp/libseccomp" target="_top">https://github.com/seccomp/libseccomp</a>.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-obtaining-source"></a>5.2. Obtaining a Source Distribution</h2></div></div></div><p>The source tarball of the most recent stable release can be
+downloaded from the <a class="link" href="http://nixos.org/nix/download.html" target="_top">Nix homepage</a>.
+You can also grab the <a class="link" href="http://hydra.nixos.org/job/nix/master/release/latest-finished#tabs-constituents" target="_top">most
+recent development release</a>.</p><p>Alternatively, the most recent sources of Nix can be obtained
+from its <a class="link" href="https://github.com/NixOS/nix" target="_top">Git
+repository</a>. For example, the following command will check out
+the latest revision into a directory called
+<code class="filename">nix</code>:</p><pre class="screen">
+$ git clone https://github.com/NixOS/nix</pre><p>Likewise, specific releases can be obtained from the <a class="link" href="https://github.com/NixOS/nix/tags" target="_top">tags</a> of the
+repository.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-building-source"></a>5.3. Building Nix from Source</h2></div></div></div><p>After unpacking or checking out the Nix sources, issue the
+following commands:
+
+</p><pre class="screen">
+$ ./configure <em class="replaceable"><code>options...</code></em>
+$ make
+$ make install</pre><p>
+
+Nix requires GNU Make so you may need to invoke
+<span class="command"><strong>gmake</strong></span> instead.</p><p>When building from the Git repository, these should be preceded
+by the command:
+
+</p><pre class="screen">
+$ ./bootstrap.sh</pre><p>
+
+</p><p>The installation path can be specified by passing the
+<code class="option">--prefix=<em class="replaceable"><code>prefix</code></em></code> to
+<span class="command"><strong>configure</strong></span>. The default installation directory is
+<code class="filename">/usr/local</code>. You can change this to any location
+you like. You must have write permission to the
+<em class="replaceable"><code>prefix</code></em> path.</p><p>Nix keeps its <span class="emphasis"><em>store</em></span> (the place where
+packages are stored) in <code class="filename">/nix/store</code> by default.
+This can be changed using
+<code class="option">--with-store-dir=<em class="replaceable"><code>path</code></em></code>.</p><div class="warning"><h3 class="title">Warning</h3><p>It is best <span class="emphasis"><em>not</em></span> to change the Nix
+store from its default, since doing so makes it impossible to use
+pre-built binaries from the standard Nixpkgs channels — that is, all
+packages will need to be built from source.</p></div><p>Nix keeps state (such as its database and log files) in
+<code class="filename">/nix/var</code> by default. This can be changed using
+<code class="option">--localstatedir=<em class="replaceable"><code>path</code></em></code>.</p></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-nix-security"></a>Chapter 6. Security</h2></div></div></div><p>Nix has two basic security models. First, it can be used in
+“single-user mode”, which is similar to what most other package
+management tools do: there is a single user (typically <code class="systemitem">root</code>) who performs all package
+management operations. All other users can then use the installed
+packages, but they cannot perform package management operations
+themselves.</p><p>Alternatively, you can configure Nix in “multi-user mode”. In
+this model, all users can perform package management operations — for
+instance, every user can install software without requiring root
+privileges. Nix ensures that this is secure. For instance, it’s not
+possible for one user to overwrite a package used by another user with
+a Trojan horse.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-single-user"></a>6.1. Single-User Mode</h2></div></div></div><p>In single-user mode, all Nix operations that access the database
+in <code class="filename"><em class="replaceable"><code>prefix</code></em>/var/nix/db</code>
+or modify the Nix store in
+<code class="filename"><em class="replaceable"><code>prefix</code></em>/store</code> must be
+performed under the user ID that owns those directories. This is
+typically <code class="systemitem">root</code>. (If you
+install from RPM packages, that’s in fact the default ownership.)
+However, on single-user machines, it is often convenient to
+<span class="command"><strong>chown</strong></span> those directories to your normal user account
+so that you don’t have to <span class="command"><strong>su</strong></span> to <code class="systemitem">root</code> all the time.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-multi-user"></a>6.2. Multi-User Mode</h2></div></div></div><p>To allow a Nix store to be shared safely among multiple users,
+it is important that users are not able to run builders that modify
+the Nix store or database in arbitrary ways, or that interfere with
+builds started by other users. If they could do so, they could
+install a Trojan horse in some package and compromise the accounts of
+other users.</p><p>To prevent this, the Nix store and database are owned by some
+privileged user (usually <code class="literal">root</code>) and builders are
+executed under special user accounts (usually named
+<code class="literal">nixbld1</code>, <code class="literal">nixbld2</code>, etc.). When a
+unprivileged user runs a Nix command, actions that operate on the Nix
+store (such as builds) are forwarded to a <span class="emphasis"><em>Nix
+daemon</em></span> running under the owner of the Nix store/database
+that performs the operation.</p><div class="note"><h3 class="title">Note</h3><p>Multi-user mode has one important limitation: only
+<code class="systemitem">root</code> and a set of trusted
+users specified in <code class="filename">nix.conf</code> can specify arbitrary
+binary caches. So while unprivileged users may install packages from
+arbitrary Nix expressions, they may not get pre-built
+binaries.</p></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301775792"></a>Setting up the build users</h3></div></div></div><p>The <span class="emphasis"><em>build users</em></span> are the special UIDs under
+which builds are performed. They should all be members of the
+<span class="emphasis"><em>build users group</em></span> <code class="literal">nixbld</code>.
+This group should have no other members. The build users should not
+be members of any other group. On Linux, you can create the group and
+users as follows:
+
+</p><pre class="screen">
+$ groupadd -r nixbld
+$ for n in $(seq 1 10); do useradd -c "Nix build user $n" \
+ -d /var/empty -g nixbld -G nixbld -M -N -r -s "$(which nologin)" \
+ nixbld$n; done
+</pre><p>
+
+This creates 10 build users. There can never be more concurrent builds
+than the number of build users, so you may want to increase this if
+you expect to do many builds at the same time.</p></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301772240"></a>Running the daemon</h3></div></div></div><p>The <a class="link" href="#sec-nix-daemon" title="nix-daemon">Nix daemon</a> should be
+started as follows (as <code class="literal">root</code>):
+
+</p><pre class="screen">
+$ nix-daemon</pre><p>
+
+You’ll want to put that line somewhere in your system’s boot
+scripts.</p><p>To let unprivileged users use the daemon, they should set the
+<a class="link" href="#envar-remote"><code class="envar">NIX_REMOTE</code> environment
+variable</a> to <code class="literal">daemon</code>. So you should put a
+line like
+
+</p><pre class="programlisting">
+export NIX_REMOTE=daemon</pre><p>
+
+into the users’ login scripts.</p></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301766816"></a>Restricting access</h3></div></div></div><p>To limit which users can perform Nix operations, you can use the
+permissions on the directory
+<code class="filename">/nix/var/nix/daemon-socket</code>. For instance, if you
+want to restrict the use of Nix to the members of a group called
+<code class="literal">nix-users</code>, do
+
+</p><pre class="screen">
+$ chgrp nix-users /nix/var/nix/daemon-socket
+$ chmod ug=rwx,o= /nix/var/nix/daemon-socket
+</pre><p>
+
+This way, users who are not in the <code class="literal">nix-users</code> group
+cannot connect to the Unix domain socket
+<code class="filename">/nix/var/nix/daemon-socket/socket</code>, so they cannot
+perform Nix operations.</p></div></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-env-variables"></a>Chapter 7. Environment Variables</h2></div></div></div><p>To use Nix, some environment variables should be set. In
+particular, <code class="envar">PATH</code> should contain the directories
+<code class="filename"><em class="replaceable"><code>prefix</code></em>/bin</code> and
+<code class="filename">~/.nix-profile/bin</code>. The first directory contains
+the Nix tools themselves, while <code class="filename">~/.nix-profile</code> is
+a symbolic link to the current <span class="emphasis"><em>user environment</em></span>
+(an automatically generated package consisting of symlinks to
+installed packages). The simplest way to set the required environment
+variables is to include the file
+<code class="filename"><em class="replaceable"><code>prefix</code></em>/etc/profile.d/nix.sh</code>
+in your <code class="filename">~/.profile</code> (or similar), like this:</p><pre class="screen">
+source <em class="replaceable"><code>prefix</code></em>/etc/profile.d/nix.sh</pre><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-nix-ssl-cert-file"></a>7.1. <code class="envar">NIX_SSL_CERT_FILE</code></h2></div></div></div><p>If you need to specify a custom certificate bundle to account
+for an HTTPS-intercepting man in the middle proxy, you must specify
+the path to the certificate bundle in the environment variable
+<code class="envar">NIX_SSL_CERT_FILE</code>.</p><p>If you don't specify a <code class="envar">NIX_SSL_CERT_FILE</code>
+manually, Nix will install and use its own certificate
+bundle.</p><div class="procedure"><ol class="procedure" type="1"><li class="step"><p>Set the environment variable and install Nix</p><pre class="screen">
+$ export NIX_SSL_CERT_FILE=/etc/ssl/my-certificate-bundle.crt
+$ sh <(curl -L https://nixos.org/nix/install)
+</pre></li><li class="step"><p>In the shell profile and rc files (for example,
+ <code class="filename">/etc/bashrc</code>, <code class="filename">/etc/zshrc</code>),
+ add the following line:</p><pre class="programlisting">
+export NIX_SSL_CERT_FILE=/etc/ssl/my-certificate-bundle.crt
+</pre></li></ol></div><div class="note"><h3 class="title">Note</h3><p>You must not add the export and then do the install, as
+the Nix installer will detect the presense of Nix configuration, and
+abort.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="sec-nix-ssl-cert-file-with-nix-daemon-and-macos"></a>7.1.1. <code class="envar">NIX_SSL_CERT_FILE</code> with macOS and the Nix daemon</h3></div></div></div><p>On macOS you must specify the environment variable for the Nix
+daemon service, then restart it:</p><pre class="screen">
+$ sudo launchctl setenv NIX_SSL_CERT_FILE /etc/ssl/my-certificate-bundle.crt
+$ sudo launchctl kickstart -k system/org.nixos.nix-daemon
+</pre></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="sec-installer-proxy-settings"></a>7.1.2. Proxy Environment Variables</h3></div></div></div><p>The Nix installer has special handling for these proxy-related
+environment variables:
+<code class="varname">http_proxy</code>, <code class="varname">https_proxy</code>,
+<code class="varname">ftp_proxy</code>, <code class="varname">no_proxy</code>,
+<code class="varname">HTTP_PROXY</code>, <code class="varname">HTTPS_PROXY</code>,
+<code class="varname">FTP_PROXY</code>, <code class="varname">NO_PROXY</code>.
+</p><p>If any of these variables are set when running the Nix installer,
+then the installer will create an override file at
+<code class="filename">/etc/systemd/system/nix-daemon.service.d/override.conf</code>
+so <span class="command"><strong>nix-daemon</strong></span> will use them.
+</p></div></div></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a id="ch-upgrading-nix"></a>Chapter 8. Upgrading Nix</h1></div></div></div><p>
+ Multi-user Nix users on macOS can upgrade Nix by running:
+ <span class="command"><strong>sudo -i sh -c 'nix-channel --update &&
+ nix-env -iA nixpkgs.nix &&
+ launchctl remove org.nixos.nix-daemon &&
+ launchctl load /Library/LaunchDaemons/org.nixos.nix-daemon.plist'</strong></span>
+ </p><p>
+ Single-user installations of Nix should run this:
+ <span class="command"><strong>nix-channel --update; nix-env -iA nixpkgs.nix nixpkgs.cacert</strong></span>
+ </p><p>
+ Multi-user Nix users on Linux should run this with sudo:
+ <span class="command"><strong>nix-channel --update; nix-env -iA nixpkgs.nix nixpkgs.cacert; systemctl daemon-reload; systemctl restart nix-daemon</strong></span>
+ </p></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a id="chap-package-management"></a>Part III. Package Management</h1></div></div></div><div class="partintro"><div></div><p>This chapter discusses how to do package management with Nix,
+i.e., how to obtain, install, upgrade, and erase packages. This is
+the “user’s” perspective of the Nix system — people
+who want to <span class="emphasis"><em>create</em></span> packages should consult
+<a class="xref" href="#chap-writing-nix-expressions" title="Part IV. Writing Nix Expressions">Part IV, “Writing Nix Expressions”</a>.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-basic-package-mgmt"></a>Chapter 9. Basic Package Management</h2></div></div></div><p>The main command for package management is <a class="link" href="#sec-nix-env" title="nix-env"><span class="command"><strong>nix-env</strong></span></a>. You can use
+it to install, upgrade, and erase packages, and to query what
+packages are installed or are available for installation.</p><p>In Nix, different users can have different “views”
+on the set of installed applications. That is, there might be lots of
+applications present on the system (possibly in many different
+versions), but users can have a specific selection of those active —
+where “active” just means that it appears in a directory
+in the user’s <code class="envar">PATH</code>. Such a view on the set of
+installed applications is called a <span class="emphasis"><em>user
+environment</em></span>, which is just a directory tree consisting of
+symlinks to the files of the active applications. </p><p>Components are installed from a set of <span class="emphasis"><em>Nix
+expressions</em></span> that tell Nix how to build those packages,
+including, if necessary, their dependencies. There is a collection of
+Nix expressions called the Nixpkgs package collection that contains
+packages ranging from basic development stuff such as GCC and Glibc,
+to end-user applications like Mozilla Firefox. (Nix is however not
+tied to the Nixpkgs package collection; you could write your own Nix
+expressions based on Nixpkgs, or completely new ones.)</p><p>You can manually download the latest version of Nixpkgs from
+<a class="link" href="http://nixos.org/nixpkgs/download.html" target="_top">http://nixos.org/nixpkgs/download.html</a>. However,
+it’s much more convenient to use the Nixpkgs
+<span class="emphasis"><em>channel</em></span>, since it makes it easy to stay up to
+date with new versions of Nixpkgs. (Channels are described in more
+detail in <a class="xref" href="#sec-channels" title="Chapter 12. Channels">Chapter 12, <em>Channels</em></a>.) Nixpkgs is automatically
+added to your list of “subscribed” channels when you install
+Nix. If this is not the case for some reason, you can add it as
+follows:
+
+</p><pre class="screen">
+$ nix-channel --add https://nixos.org/channels/nixpkgs-unstable
+$ nix-channel --update
+</pre><p>
+
+</p><div class="note"><h3 class="title">Note</h3><p>On NixOS, you’re automatically subscribed to a NixOS
+channel corresponding to your NixOS major release
+(e.g. <code class="uri">http://nixos.org/channels/nixos-14.12</code>). A NixOS
+channel is identical to the Nixpkgs channel, except that it contains
+only Linux binaries and is updated only if a set of regression tests
+succeed.</p></div><p>You can view the set of available packages in Nixpkgs:
+
+</p><pre class="screen">
+$ nix-env -qa
+aterm-2.2
+bash-3.0
+binutils-2.15
+bison-1.875d
+blackdown-1.4.2
+bzip2-1.0.2
+…</pre><p>
+
+The flag <code class="option">-q</code> specifies a query operation, and
+<code class="option">-a</code> means that you want to show the “available” (i.e.,
+installable) packages, as opposed to the installed packages. If you
+downloaded Nixpkgs yourself, or if you checked it out from GitHub,
+then you need to pass the path to your Nixpkgs tree using the
+<code class="option">-f</code> flag:
+
+</p><pre class="screen">
+$ nix-env -qaf <em class="replaceable"><code>/path/to/nixpkgs</code></em>
+</pre><p>
+
+where <em class="replaceable"><code>/path/to/nixpkgs</code></em> is where you’ve
+unpacked or checked out Nixpkgs.</p><p>You can select specific packages by name:
+
+</p><pre class="screen">
+$ nix-env -qa firefox
+firefox-34.0.5
+firefox-with-plugins-34.0.5
+</pre><p>
+
+and using regular expressions:
+
+</p><pre class="screen">
+$ nix-env -qa 'firefox.*'
+</pre><p>
+
+</p><p>It is also possible to see the <span class="emphasis"><em>status</em></span> of
+available packages, i.e., whether they are installed into the user
+environment and/or present in the system:
+
+</p><pre class="screen">
+$ nix-env -qas
+…
+-PS bash-3.0
+--S binutils-2.15
+IPS bison-1.875d
+…</pre><p>
+
+The first character (<code class="literal">I</code>) indicates whether the
+package is installed in your current user environment. The second
+(<code class="literal">P</code>) indicates whether it is present on your system
+(in which case installing it into your user environment would be a
+very quick operation). The last one (<code class="literal">S</code>) indicates
+whether there is a so-called <span class="emphasis"><em>substitute</em></span> for the
+package, which is Nix’s mechanism for doing binary deployment. It
+just means that Nix knows that it can fetch a pre-built package from
+somewhere (typically a network server) instead of building it
+locally.</p><p>You can install a package using <code class="literal">nix-env -i</code>.
+For instance,
+
+</p><pre class="screen">
+$ nix-env -i subversion</pre><p>
+
+will install the package called <code class="literal">subversion</code> (which
+is, of course, the <a class="link" href="http://subversion.tigris.org/" target="_top">Subversion version
+management system</a>).</p><div class="note"><h3 class="title">Note</h3><p>When you ask Nix to install a package, it will first try
+to get it in pre-compiled form from a <span class="emphasis"><em>binary
+cache</em></span>. By default, Nix will use the binary cache
+<code class="uri">https://cache.nixos.org</code>; it contains binaries for most
+packages in Nixpkgs. Only if no binary is available in the binary
+cache, Nix will build the package from source. So if <code class="literal">nix-env
+-i subversion</code> results in Nix building stuff from source,
+then either the package is not built for your platform by the Nixpkgs
+build servers, or your version of Nixpkgs is too old or too new. For
+instance, if you have a very recent checkout of Nixpkgs, then the
+Nixpkgs build servers may not have had a chance to build everything
+and upload the resulting binaries to
+<code class="uri">https://cache.nixos.org</code>. The Nixpkgs channel is only
+updated after all binaries have been uploaded to the cache, so if you
+stick to the Nixpkgs channel (rather than using a Git checkout of the
+Nixpkgs tree), you will get binaries for most packages.</p></div><p>Naturally, packages can also be uninstalled:
+
+</p><pre class="screen">
+$ nix-env -e subversion</pre><p>
+
+</p><p>Upgrading to a new version is just as easy. If you have a new
+release of Nix Packages, you can do:
+
+</p><pre class="screen">
+$ nix-env -u subversion</pre><p>
+
+This will <span class="emphasis"><em>only</em></span> upgrade Subversion if there is a
+“newer” version in the new set of Nix expressions, as
+defined by some pretty arbitrary rules regarding ordering of version
+numbers (which generally do what you’d expect of them). To just
+unconditionally replace Subversion with whatever version is in the Nix
+expressions, use <em class="parameter"><code>-i</code></em> instead of
+<em class="parameter"><code>-u</code></em>; <em class="parameter"><code>-i</code></em> will remove
+whatever version is already installed.</p><p>You can also upgrade all packages for which there are newer
+versions:
+
+</p><pre class="screen">
+$ nix-env -u</pre><p>
+
+</p><p>Sometimes it’s useful to be able to ask what
+<span class="command"><strong>nix-env</strong></span> would do, without actually doing it. For
+instance, to find out what packages would be upgraded by
+<code class="literal">nix-env -u</code>, you can do
+
+</p><pre class="screen">
+$ nix-env -u --dry-run
+(dry run; not doing anything)
+upgrading `libxslt-1.1.0' to `libxslt-1.1.10'
+upgrading `graphviz-1.10' to `graphviz-1.12'
+upgrading `coreutils-5.0' to `coreutils-5.2.1'</pre><p>
+
+</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="sec-profiles"></a>Chapter 10. Profiles</h2></div></div></div><p>Profiles and user environments are Nix’s mechanism for
+implementing the ability to allow different users to have different
+configurations, and to do atomic upgrades and rollbacks. To
+understand how they work, it’s useful to know a bit about how Nix
+works. In Nix, packages are stored in unique locations in the
+<span class="emphasis"><em>Nix store</em></span> (typically,
+<code class="filename">/nix/store</code>). For instance, a particular version
+of the Subversion package might be stored in a directory
+<code class="filename">/nix/store/dpmvp969yhdqs7lm2r1a3gng7pyq6vy4-subversion-1.1.3/</code>,
+while another version might be stored in
+<code class="filename">/nix/store/5mq2jcn36ldlmh93yj1n8s9c95pj7c5s-subversion-1.1.2</code>.
+The long strings prefixed to the directory names are cryptographic
+hashes<a href="#ftn.idm139733301692864" class="footnote" id="idm139733301692864"><sup class="footnote">[1]</sup></a> of
+<span class="emphasis"><em>all</em></span> inputs involved in building the package —
+sources, dependencies, compiler flags, and so on. So if two
+packages differ in any way, they end up in different locations in
+the file system, so they don’t interfere with each other. <a class="xref" href="#fig-user-environments" title="Figure 10.1. User environments">Figure 10.1, “User environments”</a> shows a part of a typical Nix
+store.</p><div class="figure"><a id="fig-user-environments"></a><p class="title"><strong>Figure 10.1. User environments</strong></p><div class="figure-contents"><div class="mediaobject"><img src="figures/user-environments.png" alt="User environments" /></div></div></div><br class="figure-break" /><p>Of course, you wouldn’t want to type
+
+</p><pre class="screen">
+$ /nix/store/dpmvp969yhdq...-subversion-1.1.3/bin/svn</pre><p>
+
+every time you want to run Subversion. Of course we could set up the
+<code class="envar">PATH</code> environment variable to include the
+<code class="filename">bin</code> directory of every package we want to use,
+but this is not very convenient since changing <code class="envar">PATH</code>
+doesn’t take effect for already existing processes. The solution Nix
+uses is to create directory trees of symlinks to
+<span class="emphasis"><em>activated</em></span> packages. These are called
+<span class="emphasis"><em>user environments</em></span> and they are packages
+themselves (though automatically generated by
+<span class="command"><strong>nix-env</strong></span>), so they too reside in the Nix store. For
+instance, in <a class="xref" href="#fig-user-environments" title="Figure 10.1. User environments">Figure 10.1, “User environments”</a> the user
+environment <code class="filename">/nix/store/0c1p5z4kda11...-user-env</code>
+contains a symlink to just Subversion 1.1.2 (arrows in the figure
+indicate symlinks). This would be what we would obtain if we had done
+
+</p><pre class="screen">
+$ nix-env -i subversion</pre><p>
+
+on a set of Nix expressions that contained Subversion 1.1.2.</p><p>This doesn’t in itself solve the problem, of course; you
+wouldn’t want to type
+<code class="filename">/nix/store/0c1p5z4kda11...-user-env/bin/svn</code>
+either. That’s why there are symlinks outside of the store that point
+to the user environments in the store; for instance, the symlinks
+<code class="filename">default-42-link</code> and
+<code class="filename">default-43-link</code> in the example. These are called
+<span class="emphasis"><em>generations</em></span> since every time you perform a
+<span class="command"><strong>nix-env</strong></span> operation, a new user environment is
+generated based on the current one. For instance, generation 43 was
+created from generation 42 when we did
+
+</p><pre class="screen">
+$ nix-env -i subversion firefox</pre><p>
+
+on a set of Nix expressions that contained Firefox and a new version
+of Subversion.</p><p>Generations are grouped together into
+<span class="emphasis"><em>profiles</em></span> so that different users don’t interfere
+with each other if they don’t want to. For example:
+
+</p><pre class="screen">
+$ ls -l /nix/var/nix/profiles/
+...
+lrwxrwxrwx 1 eelco ... default-42-link -> /nix/store/0c1p5z4kda11...-user-env
+lrwxrwxrwx 1 eelco ... default-43-link -> /nix/store/3aw2pdyx2jfc...-user-env
+lrwxrwxrwx 1 eelco ... default -> default-43-link</pre><p>
+
+This shows a profile called <code class="filename">default</code>. The file
+<code class="filename">default</code> itself is actually a symlink that points
+to the current generation. When we do a <span class="command"><strong>nix-env</strong></span>
+operation, a new user environment and generation link are created
+based on the current one, and finally the <code class="filename">default</code>
+symlink is made to point at the new generation. This last step is
+atomic on Unix, which explains how we can do atomic upgrades. (Note
+that the building/installing of new packages doesn’t interfere in
+any way with old packages, since they are stored in different
+locations in the Nix store.)</p><p>If you find that you want to undo a <span class="command"><strong>nix-env</strong></span>
+operation, you can just do
+
+</p><pre class="screen">
+$ nix-env --rollback</pre><p>
+
+which will just make the current generation link point at the previous
+link. E.g., <code class="filename">default</code> would be made to point at
+<code class="filename">default-42-link</code>. You can also switch to a
+specific generation:
+
+</p><pre class="screen">
+$ nix-env --switch-generation 43</pre><p>
+
+which in this example would roll forward to generation 43 again. You
+can also see all available generations:
+
+</p><pre class="screen">
+$ nix-env --list-generations</pre><p>You generally wouldn’t have
+<code class="filename">/nix/var/nix/profiles/<em class="replaceable"><code>some-profile</code></em>/bin</code>
+in your <code class="envar">PATH</code>. Rather, there is a symlink
+<code class="filename">~/.nix-profile</code> that points to your current
+profile. This means that you should put
+<code class="filename">~/.nix-profile/bin</code> in your <code class="envar">PATH</code>
+(and indeed, that’s what the initialisation script
+<code class="filename">/nix/etc/profile.d/nix.sh</code> does). This makes it
+easier to switch to a different profile. You can do that using the
+command <span class="command"><strong>nix-env --switch-profile</strong></span>:
+
+</p><pre class="screen">
+$ nix-env --switch-profile /nix/var/nix/profiles/my-profile
+
+$ nix-env --switch-profile /nix/var/nix/profiles/default</pre><p>
+
+These commands switch to the <code class="filename">my-profile</code> and
+default profile, respectively. If the profile doesn’t exist, it will
+be created automatically. You should be careful about storing a
+profile in another location than the <code class="filename">profiles</code>
+directory, since otherwise it might not be used as a root of the
+garbage collector (see <a class="xref" href="#sec-garbage-collection" title="Chapter 11. Garbage Collection">Chapter 11, <em>Garbage Collection</em></a>).</p><p>All <span class="command"><strong>nix-env</strong></span> operations work on the profile
+pointed to by <span class="command"><strong>~/.nix-profile</strong></span>, but you can override
+this using the <code class="option">--profile</code> option (abbreviation
+<code class="option">-p</code>):
+
+</p><pre class="screen">
+$ nix-env -p /nix/var/nix/profiles/other-profile -i subversion</pre><p>
+
+This will <span class="emphasis"><em>not</em></span> change the
+<span class="command"><strong>~/.nix-profile</strong></span> symlink.</p><div class="footnotes"><br /><hr style="width:100; text-align:left;margin-left: 0" /><div id="ftn.idm139733301692864" class="footnote"><p><a href="#idm139733301692864" class="para"><sup class="para">[1] </sup></a>160-bit truncations of SHA-256 hashes encoded in
+a base-32 notation, to be precise.</p></div></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="sec-garbage-collection"></a>Chapter 11. Garbage Collection</h2></div></div></div><p><span class="command"><strong>nix-env</strong></span> operations such as upgrades
+(<code class="option">-u</code>) and uninstall (<code class="option">-e</code>) never
+actually delete packages from the system. All they do (as shown
+above) is to create a new user environment that no longer contains
+symlinks to the “deleted” packages.</p><p>Of course, since disk space is not infinite, unused packages
+should be removed at some point. You can do this by running the Nix
+garbage collector. It will remove from the Nix store any package
+not used (directly or indirectly) by any generation of any
+profile.</p><p>Note however that as long as old generations reference a
+package, it will not be deleted. After all, we wouldn’t be able to
+do a rollback otherwise. So in order for garbage collection to be
+effective, you should also delete (some) old generations. Of course,
+this should only be done if you are certain that you will not need to
+roll back.</p><p>To delete all old (non-current) generations of your current
+profile:
+
+</p><pre class="screen">
+$ nix-env --delete-generations old</pre><p>
+
+Instead of <code class="literal">old</code> you can also specify a list of
+generations, e.g.,
+
+</p><pre class="screen">
+$ nix-env --delete-generations 10 11 14</pre><p>
+
+To delete all generations older than a specified number of days
+(except the current generation), use the <code class="literal">d</code>
+suffix. For example,
+
+</p><pre class="screen">
+$ nix-env --delete-generations 14d</pre><p>
+
+deletes all generations older than two weeks.</p><p>After removing appropriate old generations you can run the
+garbage collector as follows:
+
+</p><pre class="screen">
+$ nix-store --gc</pre><p>
+
+The behaviour of the gargage collector is affected by the
+<code class="literal">keep-derivations</code> (default: true) and <code class="literal">keep-outputs</code>
+(default: false) options in the Nix configuration file. The defaults will ensure
+that all derivations that are build-time dependencies of garbage collector roots
+will be kept and that all output paths that are runtime dependencies
+will be kept as well. All other derivations or paths will be collected.
+(This is usually what you want, but while you are developing
+it may make sense to keep outputs to ensure that rebuild times are quick.)
+
+If you are feeling uncertain, you can also first view what files would
+be deleted:
+
+</p><pre class="screen">
+$ nix-store --gc --print-dead</pre><p>
+
+Likewise, the option <code class="option">--print-live</code> will show the paths
+that <span class="emphasis"><em>won’t</em></span> be deleted.</p><p>There is also a convenient little utility
+<span class="command"><strong>nix-collect-garbage</strong></span>, which when invoked with the
+<code class="option">-d</code> (<code class="option">--delete-old</code>) switch deletes all
+old generations of all profiles in
+<code class="filename">/nix/var/nix/profiles</code>. So
+
+</p><pre class="screen">
+$ nix-collect-garbage -d</pre><p>
+
+is a quick and easy way to clean up your system.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-gc-roots"></a>11.1. Garbage Collector Roots</h2></div></div></div><p>The roots of the garbage collector are all store paths to which
+there are symlinks in the directory
+<code class="filename"><em class="replaceable"><code>prefix</code></em>/nix/var/nix/gcroots</code>.
+For instance, the following command makes the path
+<code class="filename">/nix/store/d718ef...-foo</code> a root of the collector:
+
+</p><pre class="screen">
+$ ln -s /nix/store/d718ef...-foo /nix/var/nix/gcroots/bar</pre><p>
+
+That is, after this command, the garbage collector will not remove
+<code class="filename">/nix/store/d718ef...-foo</code> or any of its
+dependencies.</p><p>Subdirectories of
+<code class="filename"><em class="replaceable"><code>prefix</code></em>/nix/var/nix/gcroots</code>
+are also searched for symlinks. Symlinks to non-store paths are
+followed and searched for roots, but symlinks to non-store paths
+<span class="emphasis"><em>inside</em></span> the paths reached in that way are not
+followed to prevent infinite recursion.</p></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="sec-channels"></a>Chapter 12. Channels</h2></div></div></div><p>If you want to stay up to date with a set of packages, it’s not
+very convenient to manually download the latest set of Nix expressions
+for those packages and upgrade using <span class="command"><strong>nix-env</strong></span>.
+Fortunately, there’s a better way: <span class="emphasis"><em>Nix
+channels</em></span>.</p><p>A Nix channel is just a URL that points to a place that contains
+a set of Nix expressions and a manifest. Using the command <a class="link" href="#sec-nix-channel" title="nix-channel"><span class="command"><strong>nix-channel</strong></span></a> you
+can automatically stay up to date with whatever is available at that
+URL.</p><p>To see the list of official NixOS channels, visit <a class="link" href="https://nixos.org/channels" target="_top">https://nixos.org/channels</a>.</p><p>You can “subscribe” to a channel using
+<span class="command"><strong>nix-channel --add</strong></span>, e.g.,
+
+</p><pre class="screen">
+$ nix-channel --add https://nixos.org/channels/nixpkgs-unstable</pre><p>
+
+subscribes you to a channel that always contains that latest version
+of the Nix Packages collection. (Subscribing really just means that
+the URL is added to the file <code class="filename">~/.nix-channels</code>,
+where it is read by subsequent calls to <span class="command"><strong>nix-channel
+--update</strong></span>.) You can “unsubscribe” using <span class="command"><strong>nix-channel
+--remove</strong></span>:
+
+</p><pre class="screen">
+$ nix-channel --remove nixpkgs
+</pre><p>
+</p><p>To obtain the latest Nix expressions available in a channel, do
+
+</p><pre class="screen">
+$ nix-channel --update</pre><p>
+
+This downloads and unpacks the Nix expressions in every channel
+(downloaded from <code class="literal"><em class="replaceable"><code>url</code></em>/nixexprs.tar.bz2</code>).
+It also makes the union of each channel’s Nix expressions available by
+default to <span class="command"><strong>nix-env</strong></span> operations (via the symlink
+<code class="filename">~/.nix-defexpr/channels</code>). Consequently, you can
+then say
+
+</p><pre class="screen">
+$ nix-env -u</pre><p>
+
+to upgrade all packages in your profile to the latest versions
+available in the subscribed channels.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="sec-sharing-packages"></a>Chapter 13. Sharing Packages Between Machines</h2></div></div></div><p>Sometimes you want to copy a package from one machine to
+another. Or, you want to install some packages and you know that
+another machine already has some or all of those packages or their
+dependencies. In that case there are mechanisms to quickly copy
+packages between machines.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-binary-cache-substituter"></a>13.1. Serving a Nix store via HTTP</h2></div></div></div><p>You can easily share the Nix store of a machine via HTTP. This
+allows other machines to fetch store paths from that machine to speed
+up installations. It uses the same <span class="emphasis"><em>binary cache</em></span>
+mechanism that Nix usually uses to fetch pre-built binaries from
+<code class="uri">https://cache.nixos.org</code>.</p><p>The daemon that handles binary cache requests via HTTP,
+<span class="command"><strong>nix-serve</strong></span>, is not part of the Nix distribution, but
+you can install it from Nixpkgs:
+
+</p><pre class="screen">
+$ nix-env -i nix-serve
+</pre><p>
+
+You can then start the server, listening for HTTP connections on
+whatever port you like:
+
+</p><pre class="screen">
+$ nix-serve -p 8080
+</pre><p>
+
+To check whether it works, try the following on the client:
+
+</p><pre class="screen">
+$ curl http://avalon:8080/nix-cache-info
+</pre><p>
+
+which should print something like:
+
+</p><pre class="screen">
+StoreDir: /nix/store
+WantMassQuery: 1
+Priority: 30
+</pre><p>
+
+</p><p>On the client side, you can tell Nix to use your binary cache
+using <code class="option">--option extra-binary-caches</code>, e.g.:
+
+</p><pre class="screen">
+$ nix-env -i firefox --option extra-binary-caches http://avalon:8080/
+</pre><p>
+
+The option <code class="option">extra-binary-caches</code> tells Nix to use this
+binary cache in addition to your default caches, such as
+<code class="uri">https://cache.nixos.org</code>. Thus, for any path in the closure
+of Firefox, Nix will first check if the path is available on the
+server <code class="literal">avalon</code> or another binary caches. If not, it
+will fall back to building from source.</p><p>You can also tell Nix to always use your binary cache by adding
+a line to the <code class="filename"><a class="filename" href="#sec-conf-file" title="nix.conf">nix.conf</a></code>
+configuration file like this:
+
+</p><pre class="programlisting">
+binary-caches = http://avalon:8080/ https://cache.nixos.org/
+</pre><p>
+
+</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-copy-closure"></a>13.2. Copying Closures Via SSH</h2></div></div></div><p>The command <span class="command"><strong><a class="command" href="#sec-nix-copy-closure" title="nix-copy-closure">nix-copy-closure</a></strong></span> copies a Nix
+store path along with all its dependencies to or from another machine
+via the SSH protocol. It doesn’t copy store paths that are already
+present on the target machine. For example, the following command
+copies Firefox with all its dependencies:
+
+</p><pre class="screen">
+$ nix-copy-closure --to alice@itchy.example.org $(type -p firefox)</pre><p>
+
+See <a class="xref" href="#sec-nix-copy-closure" title="nix-copy-closure"><span class="refentrytitle">nix-copy-closure</span>(1)</a> for details.</p><p>With <span class="command"><strong><a class="command" href="#refsec-nix-store-export" title="Operation --export">nix-store
+--export</a></strong></span> and <span class="command"><strong><a class="command" href="#refsec-nix-store-import" title="Operation --import">nix-store --import</a></strong></span> you can
+write the closure of a store path (that is, the path and all its
+dependencies) to a file, and then unpack that file into another Nix
+store. For example,
+
+</p><pre class="screen">
+$ nix-store --export $(nix-store -qR $(type -p firefox)) > firefox.closure</pre><p>
+
+writes the closure of Firefox to a file. You can then copy this file
+to another machine and install the closure:
+
+</p><pre class="screen">
+$ nix-store --import < firefox.closure</pre><p>
+
+Any store paths in the closure that are already present in the target
+store are ignored. It is also possible to pipe the export into
+another command, e.g. to copy and install a closure directly to/on
+another machine:
+
+</p><pre class="screen">
+$ nix-store --export $(nix-store -qR $(type -p firefox)) | bzip2 | \
+ ssh alice@itchy.example.org "bunzip2 | nix-store --import"</pre><p>
+
+However, <span class="command"><strong>nix-copy-closure</strong></span> is generally more
+efficient because it only copies paths that are not already present in
+the target Nix store.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-ssh-substituter"></a>13.3. Serving a Nix store via SSH</h2></div></div></div><p>You can tell Nix to automatically fetch needed binaries from a
+remote Nix store via SSH. For example, the following installs Firefox,
+automatically fetching any store paths in Firefox’s closure if they
+are available on the server <code class="literal">avalon</code>:
+
+</p><pre class="screen">
+$ nix-env -i firefox --substituters ssh://alice@avalon
+</pre><p>
+
+This works similar to the binary cache substituter that Nix usually
+uses, only using SSH instead of HTTP: if a store path
+<code class="literal">P</code> is needed, Nix will first check if it’s available
+in the Nix store on <code class="literal">avalon</code>. If not, it will fall
+back to using the binary cache substituter, and then to building from
+source.</p><div class="note"><h3 class="title">Note</h3><p>The SSH substituter currently does not allow you to enter
+an SSH passphrase interactively. Therefore, you should use
+<span class="command"><strong>ssh-add</strong></span> to load the decrypted private key into
+<span class="command"><strong>ssh-agent</strong></span>.</p></div><p>You can also copy the closure of some store path, without
+installing it into your profile, e.g.
+
+</p><pre class="screen">
+$ nix-store -r /nix/store/m85bxg…-firefox-34.0.5 --substituters ssh://alice@avalon
+</pre><p>
+
+This is essentially equivalent to doing
+
+</p><pre class="screen">
+$ nix-copy-closure --from alice@avalon /nix/store/m85bxg…-firefox-34.0.5
+</pre><p>
+
+</p><p>You can use SSH’s <span class="emphasis"><em>forced command</em></span> feature to
+set up a restricted user account for SSH substituter access, allowing
+read-only access to the local Nix store, but nothing more. For
+example, add the following lines to <code class="filename">sshd_config</code>
+to restrict the user <code class="literal">nix-ssh</code>:
+
+</p><pre class="programlisting">
+Match User nix-ssh
+ AllowAgentForwarding no
+ AllowTcpForwarding no
+ PermitTTY no
+ PermitTunnel no
+ X11Forwarding no
+ ForceCommand nix-store --serve
+Match All
+</pre><p>
+
+On NixOS, you can accomplish the same by adding the following to your
+<code class="filename">configuration.nix</code>:
+
+</p><pre class="programlisting">
+nix.sshServe.enable = true;
+nix.sshServe.keys = [ "ssh-dss AAAAB3NzaC1k... bob@example.org" ];
+</pre><p>
+
+where the latter line lists the public keys of users that are allowed
+to connect.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-s3-substituter"></a>13.4. Serving a Nix store via AWS S3 or S3-compatible Service</h2></div></div></div><p>Nix has built-in support for storing and fetching store paths
+from Amazon S3 and S3 compatible services. This uses the same
+<span class="emphasis"><em>binary</em></span> cache mechanism that Nix usually uses to
+fetch prebuilt binaries from <code class="uri">cache.nixos.org</code>.</p><p>The following options can be specified as URL parameters to
+the S3 URL:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">profile</code></span></dt><dd><p>
+ The name of the AWS configuration profile to use. By default
+ Nix will use the <code class="literal">default</code> profile.
+ </p></dd><dt><span class="term"><code class="literal">region</code></span></dt><dd><p>
+ The region of the S3 bucket. <code class="literal">us–east-1</code> by
+ default.
+ </p><p>
+ If your bucket is not in <code class="literal">us–east-1</code>, you
+ should always explicitly specify the region parameter.
+ </p></dd><dt><span class="term"><code class="literal">endpoint</code></span></dt><dd><p>
+ The URL to your S3-compatible service, for when not using
+ Amazon S3. Do not specify this value if you're using Amazon
+ S3.
+ </p><div class="note"><h3 class="title">Note</h3><p>This endpoint must support HTTPS and will use
+ path-based addressing instead of virtual host based
+ addressing.</p></div></dd><dt><span class="term"><code class="literal">scheme</code></span></dt><dd><p>
+ The scheme used for S3 requests, <code class="literal">https</code>
+ (default) or <code class="literal">http</code>. This option allows you to
+ disable HTTPS for binary caches which don't support it.
+ </p><div class="note"><h3 class="title">Note</h3><p>HTTPS should be used if the cache might contain
+ sensitive information.</p></div></dd></dl></div><p>In this example we will use the bucket named
+<code class="literal">example-nix-cache</code>.</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="ssec-s3-substituter-anonymous-reads"></a>13.4.1. Anonymous Reads to your S3-compatible binary cache</h3></div></div></div><p>If your binary cache is publicly accessible and does not
+ require authentication, the simplest and easiest way to use Nix with
+ your S3 compatible binary cache is to use the HTTP URL for that
+ cache.</p><p>For AWS S3 the binary cache URL for example bucket will be
+ exactly <code class="uri">https://example-nix-cache.s3.amazonaws.com</code> or
+ <code class="uri">s3://example-nix-cache</code>. For S3 compatible binary caches,
+ consult that cache's documentation.</p><p>Your bucket will need the following bucket policy:</p><pre class="programlisting">
+{
+ "Id": "DirectReads",
+ "Version": "2012-10-17",
+ "Statement": [
+ {
+ "Sid": "AllowDirectReads",
+ "Action": [
+ "s3:GetObject",
+ "s3:GetBucketLocation"
+ ],
+ "Effect": "Allow",
+ "Resource": [
+ "arn:aws:s3:::example-nix-cache",
+ "arn:aws:s3:::example-nix-cache/*"
+ ],
+ "Principal": "*"
+ }
+ ]
+}
+</pre></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="ssec-s3-substituter-authenticated-reads"></a>13.4.2. Authenticated Reads to your S3 binary cache</h3></div></div></div><p>For AWS S3 the binary cache URL for example bucket will be
+ exactly <code class="uri">s3://example-nix-cache</code>.</p><p>Nix will use the <a class="link" href="https://docs.aws.amazon.com/sdk-for-cpp/v1/developer-guide/credentials.html" target="_top">default
+ credential provider chain</a> for authenticating requests to
+ Amazon S3.</p><p>Nix supports authenticated reads from Amazon S3 and S3
+ compatible binary caches.</p><p>Your bucket will need a bucket policy allowing the desired
+ users to perform the <code class="literal">s3:GetObject</code> and
+ <code class="literal">s3:GetBucketLocation</code> action on all objects in the
+ bucket. The anonymous policy in <a class="xref" href="#ssec-s3-substituter-anonymous-reads" title="13.4.1. Anonymous Reads to your S3-compatible binary cache">Section 13.4.1, “Anonymous Reads to your S3-compatible binary cache”</a> can be updated to
+ have a restricted <code class="literal">Principal</code> to support
+ this.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="ssec-s3-substituter-authenticated-writes"></a>13.4.3. Authenticated Writes to your S3-compatible binary cache</h3></div></div></div><p>Nix support fully supports writing to Amazon S3 and S3
+ compatible buckets. The binary cache URL for our example bucket will
+ be <code class="uri">s3://example-nix-cache</code>.</p><p>Nix will use the <a class="link" href="https://docs.aws.amazon.com/sdk-for-cpp/v1/developer-guide/credentials.html" target="_top">default
+ credential provider chain</a> for authenticating requests to
+ Amazon S3.</p><p>Your account will need the following IAM policy to
+ upload to the cache:</p><pre class="programlisting">
+{
+ "Version": "2012-10-17",
+ "Statement": [
+ {
+ "Sid": "UploadToCache",
+ "Effect": "Allow",
+ "Action": [
+ "s3:AbortMultipartUpload",
+ "s3:GetBucketLocation",
+ "s3:GetObject",
+ "s3:ListBucket",
+ "s3:ListBucketMultipartUploads",
+ "s3:ListMultipartUploadParts",
+ "s3:PutObject"
+ ],
+ "Resource": [
+ "arn:aws:s3:::example-nix-cache",
+ "arn:aws:s3:::example-nix-cache/*"
+ ]
+ }
+ ]
+}
+</pre><div class="example"><a id="idm139733301558256"></a><p class="title"><strong>Example 13.1. Uploading with a specific credential profile for Amazon S3</strong></p><div class="example-contents"><p><span class="command"><strong>nix copy --to 's3://example-nix-cache?profile=cache-upload&region=eu-west-2' nixpkgs.hello</strong></span></p></div></div><br class="example-break" /><div class="example"><a id="idm139733301556896"></a><p class="title"><strong>Example 13.2. Uploading to an S3-Compatible Binary Cache</strong></p><div class="example-contents"><p><span class="command"><strong>nix copy --to 's3://example-nix-cache?profile=cache-upload&scheme=https&endpoint=minio.example.com' nixpkgs.hello</strong></span></p></div></div><br class="example-break" /></div></div></div></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a id="chap-writing-nix-expressions"></a>Part IV. Writing Nix Expressions</h1></div></div></div><div class="partintro"><div></div><p>This chapter shows you how to write Nix expressions, which
+instruct Nix how to build packages. It starts with a
+simple example (a Nix expression for GNU Hello), and then moves
+on to a more in-depth look at the Nix expression language.</p><div class="note"><h3 class="title">Note</h3><p>This chapter is mostly about the Nix expression language.
+For more extensive information on adding packages to the Nix Packages
+collection (such as functions in the standard environment and coding
+conventions), please consult <a class="link" href="http://nixos.org/nixpkgs/manual/" target="_top">its
+manual</a>.</p></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-simple-expression"></a>Chapter 14. A Simple Nix Expression</h2></div></div></div><p>This section shows how to add and test the <a class="link" href="http://www.gnu.org/software/hello/hello.html" target="_top">GNU Hello
+package</a> to the Nix Packages collection. Hello is a program
+that prints out the text <span class="quote">“<span class="quote">Hello, world!</span>”</span>.</p><p>To add a package to the Nix Packages collection, you generally
+need to do three things:
+
+</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Write a Nix expression for the package. This is a
+ file that describes all the inputs involved in building the package,
+ such as dependencies, sources, and so on.</p></li><li class="listitem"><p>Write a <span class="emphasis"><em>builder</em></span>. This is a
+ shell script<a href="#ftn.idm139733301545648" class="footnote" id="idm139733301545648"><sup class="footnote">[2]</sup></a> that actually builds the package from
+ the inputs.</p></li><li class="listitem"><p>Add the package to the file
+ <code class="filename">pkgs/top-level/all-packages.nix</code>. The Nix
+ expression written in the first step is a
+ <span class="emphasis"><em>function</em></span>; it requires other packages in order
+ to build it. In this step you put it all together, i.e., you call
+ the function with the right arguments to build the actual
+ package.</p></li></ol></div><p>
+
+</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-expression-syntax"></a>14.1. Expression Syntax</h2></div></div></div><div class="example"><a id="ex-hello-nix"></a><p class="title"><strong>Example 14.1. Nix expression for GNU Hello
+(<code class="filename">default.nix</code>)</strong></p><div class="example-contents"><pre class="programlisting">
+{ stdenv, fetchurl, perl }: <a id="ex-hello-nix-co-1"></a>(1)
+
+stdenv.mkDerivation { <a id="ex-hello-nix-co-2"></a>(2)
+ name = "hello-2.1.1"; <a id="ex-hello-nix-co-3"></a>(3)
+ builder = ./builder.sh; <a id="ex-hello-nix-co-4"></a>(4)
+ src = fetchurl { <a id="ex-hello-nix-co-5"></a>(5)
+ url = "ftp://ftp.nluug.nl/pub/gnu/hello/hello-2.1.1.tar.gz";
+ sha256 = "1md7jsfd8pa45z73bz1kszpp01yw6x5ljkjk2hx7wl800any6465";
+ };
+ inherit perl; <a id="ex-hello-nix-co-6"></a>(6)
+}</pre></div></div><br class="example-break" /><p><a class="xref" href="#ex-hello-nix" title="Example 14.1. Nix expression for GNU Hello (default.nix)">Example 14.1, “Nix expression for GNU Hello
+(<code class="filename">default.nix</code>)”</a> shows a Nix expression for GNU
+Hello. It's actually already in the Nix Packages collection in
+<code class="filename">pkgs/applications/misc/hello/ex-1/default.nix</code>.
+It is customary to place each package in a separate directory and call
+the single Nix expression in that directory
+<code class="filename">default.nix</code>. The file has the following elements
+(referenced from the figure by number):
+
+</p><div class="calloutlist"><table border="0" summary="Callout list"><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-nix-co-1">(1)</a> </p></td><td valign="top" align="left"><p>This states that the expression is a
+ <span class="emphasis"><em>function</em></span> that expects to be called with three
+ arguments: <code class="varname">stdenv</code>, <code class="varname">fetchurl</code>,
+ and <code class="varname">perl</code>. They are needed to build Hello, but
+ we don't know how to build them here; that's why they are function
+ arguments. <code class="varname">stdenv</code> is a package that is used
+ by almost all Nix Packages packages; it provides a
+ <span class="quote">“<span class="quote">standard</span>”</span> environment consisting of the things you
+ would expect in a basic Unix environment: a C/C++ compiler (GCC,
+ to be precise), the Bash shell, fundamental Unix tools such as
+ <span class="command"><strong>cp</strong></span>, <span class="command"><strong>grep</strong></span>,
+ <span class="command"><strong>tar</strong></span>, etc. <code class="varname">fetchurl</code> is a
+ function that downloads files. <code class="varname">perl</code> is the
+ Perl interpreter.</p><p>Nix functions generally have the form <code class="literal">{ x, y, ...,
+ z }: e</code> where <code class="varname">x</code>, <code class="varname">y</code>,
+ etc. are the names of the expected arguments, and where
+ <em class="replaceable"><code>e</code></em> is the body of the function. So
+ here, the entire remainder of the file is the body of the
+ function; when given the required arguments, the body should
+ describe how to build an instance of the Hello package.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-nix-co-2">(2)</a> </p></td><td valign="top" align="left"><p>So we have to build a package. Building something from
+ other stuff is called a <span class="emphasis"><em>derivation</em></span> in Nix (as
+ opposed to sources, which are built by humans instead of
+ computers). We perform a derivation by calling
+ <code class="varname">stdenv.mkDerivation</code>.
+ <code class="varname">mkDerivation</code> is a function provided by
+ <code class="varname">stdenv</code> that builds a package from a set of
+ <span class="emphasis"><em>attributes</em></span>. A set is just a list of
+ key/value pairs where each key is a string and each value is an
+ arbitrary Nix expression. They take the general form <code class="literal">{
+ <em class="replaceable"><code>name1</code></em> =
+ <em class="replaceable"><code>expr1</code></em>; <em class="replaceable"><code>...</code></em>
+ <em class="replaceable"><code>nameN</code></em> =
+ <em class="replaceable"><code>exprN</code></em>; }</code>.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-nix-co-3">(3)</a> </p></td><td valign="top" align="left"><p>The attribute <code class="varname">name</code> specifies the symbolic
+ name and version of the package. Nix doesn't really care about
+ these things, but they are used by for instance <span class="command"><strong>nix-env
+ -q</strong></span> to show a <span class="quote">“<span class="quote">human-readable</span>”</span> name for
+ packages. This attribute is required by
+ <code class="varname">mkDerivation</code>.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-nix-co-4">(4)</a> </p></td><td valign="top" align="left"><p>The attribute <code class="varname">builder</code> specifies the
+ builder. This attribute can sometimes be omitted, in which case
+ <code class="varname">mkDerivation</code> will fill in a default builder
+ (which does a <code class="literal">configure; make; make install</code>, in
+ essence). Hello is sufficiently simple that the default builder
+ would suffice, but in this case, we will show an actual builder
+ for educational purposes. The value
+ <span class="command"><strong>./builder.sh</strong></span> refers to the shell script shown
+ in <a class="xref" href="#ex-hello-builder" title="Example 14.2. Build script for GNU Hello (builder.sh)">Example 14.2, “Build script for GNU Hello
+(<code class="filename">builder.sh</code>)”</a>, discussed below.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-nix-co-5">(5)</a> </p></td><td valign="top" align="left"><p>The builder has to know what the sources of the package
+ are. Here, the attribute <code class="varname">src</code> is bound to the
+ result of a call to the <span class="command"><strong>fetchurl</strong></span> function.
+ Given a URL and a SHA-256 hash of the expected contents of the file
+ at that URL, this function builds a derivation that downloads the
+ file and checks its hash. So the sources are a dependency that
+ like all other dependencies is built before Hello itself is
+ built.</p><p>Instead of <code class="varname">src</code> any other name could have
+ been used, and in fact there can be any number of sources (bound
+ to different attributes). However, <code class="varname">src</code> is
+ customary, and it's also expected by the default builder (which we
+ don't use in this example).</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-nix-co-6">(6)</a> </p></td><td valign="top" align="left"><p>Since the derivation requires Perl, we have to pass the
+ value of the <code class="varname">perl</code> function argument to the
+ builder. All attributes in the set are actually passed as
+ environment variables to the builder, so declaring an attribute
+
+ </p><pre class="programlisting">
+perl = perl;</pre><p>
+
+ will do the trick: it binds an attribute <code class="varname">perl</code>
+ to the function argument which also happens to be called
+ <code class="varname">perl</code>. However, it looks a bit silly, so there
+ is a shorter syntax. The <code class="literal">inherit</code> keyword
+ causes the specified attributes to be bound to whatever variables
+ with the same name happen to be in scope.</p></td></tr></table></div><p>
+
+</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-build-script"></a>14.2. Build Script</h2></div></div></div><div class="example"><a id="ex-hello-builder"></a><p class="title"><strong>Example 14.2. Build script for GNU Hello
+(<code class="filename">builder.sh</code>)</strong></p><div class="example-contents"><pre class="programlisting">
+source $stdenv/setup <a id="ex-hello-builder-co-1"></a>(1)
+
+PATH=$perl/bin:$PATH <a id="ex-hello-builder-co-2"></a>(2)
+
+tar xvfz $src <a id="ex-hello-builder-co-3"></a>(3)
+cd hello-*
+./configure --prefix=$out <a id="ex-hello-builder-co-4"></a>(4)
+make <a id="ex-hello-builder-co-5"></a>(5)
+make install</pre></div></div><br class="example-break" /><p><a class="xref" href="#ex-hello-builder" title="Example 14.2. Build script for GNU Hello (builder.sh)">Example 14.2, “Build script for GNU Hello
+(<code class="filename">builder.sh</code>)”</a> shows the builder referenced
+from Hello's Nix expression (stored in
+<code class="filename">pkgs/applications/misc/hello/ex-1/builder.sh</code>).
+The builder can actually be made a lot shorter by using the
+<span class="emphasis"><em>generic builder</em></span> functions provided by
+<code class="varname">stdenv</code>, but here we write out the build steps to
+elucidate what a builder does. It performs the following
+steps:</p><div class="calloutlist"><table border="0" summary="Callout list"><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-builder-co-1">(1)</a> </p></td><td valign="top" align="left"><p>When Nix runs a builder, it initially completely clears the
+ environment (except for the attributes declared in the
+ derivation). For instance, the <code class="envar">PATH</code> variable is
+ empty<a href="#ftn.idm139733301492640" class="footnote" id="idm139733301492640"><sup class="footnote">[3]</sup></a>. This is done to prevent
+ undeclared inputs from being used in the build process. If for
+ example the <code class="envar">PATH</code> contained
+ <code class="filename">/usr/bin</code>, then you might accidentally use
+ <code class="filename">/usr/bin/gcc</code>.</p><p>So the first step is to set up the environment. This is
+ done by calling the <code class="filename">setup</code> script of the
+ standard environment. The environment variable
+ <code class="envar">stdenv</code> points to the location of the standard
+ environment being used. (It wasn't specified explicitly as an
+ attribute in <a class="xref" href="#ex-hello-nix" title="Example 14.1. Nix expression for GNU Hello (default.nix)">Example 14.1, “Nix expression for GNU Hello
+(<code class="filename">default.nix</code>)”</a>, but
+ <code class="varname">mkDerivation</code> adds it automatically.)</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-builder-co-2">(2)</a> </p></td><td valign="top" align="left"><p>Since Hello needs Perl, we have to make sure that Perl is in
+ the <code class="envar">PATH</code>. The <code class="envar">perl</code> environment
+ variable points to the location of the Perl package (since it
+ was passed in as an attribute to the derivation), so
+ <code class="filename"><em class="replaceable"><code>$perl</code></em>/bin</code> is the
+ directory containing the Perl interpreter.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-builder-co-3">(3)</a> </p></td><td valign="top" align="left"><p>Now we have to unpack the sources. The
+ <code class="varname">src</code> attribute was bound to the result of
+ fetching the Hello source tarball from the network, so the
+ <code class="envar">src</code> environment variable points to the location in
+ the Nix store to which the tarball was downloaded. After
+ unpacking, we <span class="command"><strong>cd</strong></span> to the resulting source
+ directory.</p><p>The whole build is performed in a temporary directory
+ created in <code class="varname">/tmp</code>, by the way. This directory is
+ removed after the builder finishes, so there is no need to clean
+ up the sources afterwards. Also, the temporary directory is
+ always newly created, so you don't have to worry about files from
+ previous builds interfering with the current build.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-builder-co-4">(4)</a> </p></td><td valign="top" align="left"><p>GNU Hello is a typical Autoconf-based package, so we first
+ have to run its <code class="filename">configure</code> script. In Nix
+ every package is stored in a separate location in the Nix store,
+ for instance
+ <code class="filename">/nix/store/9a54ba97fb71b65fda531012d0443ce2-hello-2.1.1</code>.
+ Nix computes this path by cryptographically hashing all attributes
+ of the derivation. The path is passed to the builder through the
+ <code class="envar">out</code> environment variable. So here we give
+ <code class="filename">configure</code> the parameter
+ <code class="literal">--prefix=$out</code> to cause Hello to be installed in
+ the expected location.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-builder-co-5">(5)</a> </p></td><td valign="top" align="left"><p>Finally we build Hello (<code class="literal">make</code>) and install
+ it into the location specified by <code class="envar">out</code>
+ (<code class="literal">make install</code>).</p></td></tr></table></div><p>If you are wondering about the absence of error checking on the
+result of various commands called in the builder: this is because the
+shell script is evaluated with Bash's <code class="option">-e</code> option,
+which causes the script to be aborted if any command fails without an
+error check.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-arguments"></a>14.3. Arguments and Variables</h2></div></div></div><div class="example"><a id="ex-hello-composition"></a><p class="title"><strong>Example 14.3. Composing GNU Hello
+(<code class="filename">all-packages.nix</code>)</strong></p><div class="example-contents"><pre class="programlisting">
+...
+
+rec { <a id="ex-hello-composition-co-1"></a>(1)
+
+ hello = import ../applications/misc/hello/ex-1 <a id="ex-hello-composition-co-2"></a>(2) { <a id="ex-hello-composition-co-3"></a>(3)
+ inherit fetchurl stdenv perl;
+ };
+
+ perl = import ../development/interpreters/perl { <a id="ex-hello-composition-co-4"></a>(4)
+ inherit fetchurl stdenv;
+ };
+
+ fetchurl = import ../build-support/fetchurl {
+ inherit stdenv; ...
+ };
+
+ stdenv = ...;
+
+}
+</pre></div></div><br class="example-break" /><p>The Nix expression in <a class="xref" href="#ex-hello-nix" title="Example 14.1. Nix expression for GNU Hello (default.nix)">Example 14.1, “Nix expression for GNU Hello
+(<code class="filename">default.nix</code>)”</a> is a
+function; it is missing some arguments that have to be filled in
+somewhere. In the Nix Packages collection this is done in the file
+<code class="filename">pkgs/top-level/all-packages.nix</code>, where all
+Nix expressions for packages are imported and called with the
+appropriate arguments. <a class="xref" href="#ex-hello-composition" title="Example 14.3. Composing GNU Hello (all-packages.nix)">Example 14.3, “Composing GNU Hello
+(<code class="filename">all-packages.nix</code>)”</a> shows
+some fragments of
+<code class="filename">all-packages.nix</code>.</p><div class="calloutlist"><table border="0" summary="Callout list"><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-composition-co-1">(1)</a> </p></td><td valign="top" align="left"><p>This file defines a set of attributes, all of which are
+ concrete derivations (i.e., not functions). In fact, we define a
+ <span class="emphasis"><em>mutually recursive</em></span> set of attributes. That
+ is, the attributes can refer to each other. This is precisely
+ what we want since we want to <span class="quote">“<span class="quote">plug</span>”</span> the
+ various packages into each other.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-composition-co-2">(2)</a> </p></td><td valign="top" align="left"><p>Here we <span class="emphasis"><em>import</em></span> the Nix expression for
+ GNU Hello. The import operation just loads and returns the
+ specified Nix expression. In fact, we could just have put the
+ contents of <a class="xref" href="#ex-hello-nix" title="Example 14.1. Nix expression for GNU Hello (default.nix)">Example 14.1, “Nix expression for GNU Hello
+(<code class="filename">default.nix</code>)”</a> in
+ <code class="filename">all-packages.nix</code> at this point. That
+ would be completely equivalent, but it would make the file rather
+ bulky.</p><p>Note that we refer to
+ <code class="filename">../applications/misc/hello/ex-1</code>, not
+ <code class="filename">../applications/misc/hello/ex-1/default.nix</code>.
+ When you try to import a directory, Nix automatically appends
+ <code class="filename">/default.nix</code> to the file name.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-composition-co-3">(3)</a> </p></td><td valign="top" align="left"><p>This is where the actual composition takes place. Here we
+ <span class="emphasis"><em>call</em></span> the function imported from
+ <code class="filename">../applications/misc/hello/ex-1</code> with a set
+ containing the things that the function expects, namely
+ <code class="varname">fetchurl</code>, <code class="varname">stdenv</code>, and
+ <code class="varname">perl</code>. We use inherit again to use the
+ attributes defined in the surrounding scope (we could also have
+ written <code class="literal">fetchurl = fetchurl;</code>, etc.).</p><p>The result of this function call is an actual derivation
+ that can be built by Nix (since when we fill in the arguments of
+ the function, what we get is its body, which is the call to
+ <code class="varname">stdenv.mkDerivation</code> in <a class="xref" href="#ex-hello-nix" title="Example 14.1. Nix expression for GNU Hello (default.nix)">Example 14.1, “Nix expression for GNU Hello
+(<code class="filename">default.nix</code>)”</a>).</p><div class="note"><h3 class="title">Note</h3><p>Nixpkgs has a convenience function
+ <code class="function">callPackage</code> that imports and calls a
+ function, filling in any missing arguments by passing the
+ corresponding attribute from the Nixpkgs set, like this:
+
+</p><pre class="programlisting">
+hello = callPackage ../applications/misc/hello/ex-1 { };
+</pre><p>
+
+ If necessary, you can set or override arguments:
+
+</p><pre class="programlisting">
+hello = callPackage ../applications/misc/hello/ex-1 { stdenv = myStdenv; };
+</pre><p>
+
+ </p></div></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-composition-co-4">(4)</a> </p></td><td valign="top" align="left"><p>Likewise, we have to instantiate Perl,
+ <code class="varname">fetchurl</code>, and the standard environment.</p></td></tr></table></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-building-simple"></a>14.4. Building and Testing</h2></div></div></div><p>You can now try to build Hello. Of course, you could do
+<code class="literal">nix-env -i hello</code>, but you may not want to install a
+possibly broken package just yet. The best way to test the package is by
+using the command <span class="command"><strong><a class="command" href="#sec-nix-build" title="nix-build">nix-build</a></strong></span>,
+which builds a Nix expression and creates a symlink named
+<code class="filename">result</code> in the current directory:
+
+</p><pre class="screen">
+$ nix-build -A hello
+building path `/nix/store/632d2b22514d...-hello-2.1.1'
+hello-2.1.1/
+hello-2.1.1/intl/
+hello-2.1.1/intl/ChangeLog
+<em class="replaceable"><code>...</code></em>
+
+$ ls -l result
+lrwxrwxrwx ... 2006-09-29 10:43 result -> /nix/store/632d2b22514d...-hello-2.1.1
+
+$ ./result/bin/hello
+Hello, world!</pre><p>
+
+The <a class="link" href="#opt-attr"><code class="option">-A</code></a> option selects
+the <code class="literal">hello</code> attribute. This is faster than using the
+symbolic package name specified by the <code class="literal">name</code>
+attribute (which also happens to be <code class="literal">hello</code>) and is
+unambiguous (there can be multiple packages with the symbolic name
+<code class="literal">hello</code>, but there can be only one attribute in a set
+named <code class="literal">hello</code>).</p><p><span class="command"><strong>nix-build</strong></span> registers the
+<code class="filename">./result</code> symlink as a garbage collection root, so
+unless and until you delete the <code class="filename">./result</code> symlink,
+the output of the build will be safely kept on your system. You can
+use <span class="command"><strong>nix-build</strong></span>’s <code class="option"><a class="option" href="#opt-out-link">-o</a></code> switch to give the symlink another
+name.</p><p>Nix has transactional semantics. Once a build finishes
+successfully, Nix makes a note of this in its database: it registers
+that the path denoted by <code class="envar">out</code> is now
+<span class="quote">“<span class="quote">valid</span>”</span>. If you try to build the derivation again, Nix
+will see that the path is already valid and finish immediately. If a
+build fails, either because it returns a non-zero exit code, because
+Nix or the builder are killed, or because the machine crashes, then
+the output paths will not be registered as valid. If you try to build
+the derivation again, Nix will remove the output paths if they exist
+(e.g., because the builder died half-way through <code class="literal">make
+install</code>) and try again. Note that there is no
+<span class="quote">“<span class="quote">negative caching</span>”</span>: Nix doesn't remember that a build
+failed, and so a failed build can always be repeated. This is because
+Nix cannot distinguish between permanent failures (e.g., a compiler
+error due to a syntax error in the source) and transient failures
+(e.g., a disk full condition).</p><p>Nix also performs locking. If you run multiple Nix builds
+simultaneously, and they try to build the same derivation, the first
+Nix instance that gets there will perform the build, while the others
+block (or perform other derivations if available) until the build
+finishes:
+
+</p><pre class="screen">
+$ nix-build -A hello
+waiting for lock on `/nix/store/0h5b7hp8d4hqfrw8igvx97x1xawrjnac-hello-2.1.1x'</pre><p>
+
+So it is always safe to run multiple instances of Nix in parallel
+(which isn’t the case with, say, <span class="command"><strong>make</strong></span>).</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-generic-builder"></a>14.5. Generic Builder Syntax</h2></div></div></div><p>Recall from <a class="xref" href="#ex-hello-builder" title="Example 14.2. Build script for GNU Hello (builder.sh)">Example 14.2, “Build script for GNU Hello
+(<code class="filename">builder.sh</code>)”</a> that the builder
+looked something like this:
+
+</p><pre class="programlisting">
+PATH=$perl/bin:$PATH
+tar xvfz $src
+cd hello-*
+./configure --prefix=$out
+make
+make install</pre><p>
+
+The builders for almost all Unix packages look like this — set up some
+environment variables, unpack the sources, configure, build, and
+install. For this reason the standard environment provides some Bash
+functions that automate the build process. A builder using the
+generic build facilities in shown in <a class="xref" href="#ex-hello-builder2" title="Example 14.4. Build script using the generic build functions">Example 14.4, “Build script using the generic
+build functions”</a>.</p><div class="example"><a id="ex-hello-builder2"></a><p class="title"><strong>Example 14.4. Build script using the generic
+build functions</strong></p><div class="example-contents"><pre class="programlisting">
+buildInputs="$perl" <a id="ex-hello-builder2-co-1"></a>(1)
+
+source $stdenv/setup <a id="ex-hello-builder2-co-2"></a>(2)
+
+genericBuild <a id="ex-hello-builder2-co-3"></a>(3)</pre></div></div><br class="example-break" /><div class="calloutlist"><table border="0" summary="Callout list"><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-builder2-co-1">(1)</a> </p></td><td valign="top" align="left"><p>The <code class="envar">buildInputs</code> variable tells
+ <code class="filename">setup</code> to use the indicated packages as
+ <span class="quote">“<span class="quote">inputs</span>”</span>. This means that if a package provides a
+ <code class="filename">bin</code> subdirectory, it's added to
+ <code class="envar">PATH</code>; if it has a <code class="filename">include</code>
+ subdirectory, it's added to GCC's header search path; and so
+ on.<a href="#ftn.idm139733301420112" class="footnote" id="idm139733301420112"><sup class="footnote">[4]</sup></a>
+ </p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-builder2-co-2">(2)</a> </p></td><td valign="top" align="left"><p>The function <code class="function">genericBuild</code> is defined in
+ the file <code class="literal">$stdenv/setup</code>.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-builder2-co-3">(3)</a> </p></td><td valign="top" align="left"><p>The final step calls the shell function
+ <code class="function">genericBuild</code>, which performs the steps that
+ were done explicitly in <a class="xref" href="#ex-hello-builder" title="Example 14.2. Build script for GNU Hello (builder.sh)">Example 14.2, “Build script for GNU Hello
+(<code class="filename">builder.sh</code>)”</a>. The
+ generic builder is smart enough to figure out whether to unpack
+ the sources using <span class="command"><strong>gzip</strong></span>,
+ <span class="command"><strong>bzip2</strong></span>, etc. It can be customised in many ways;
+ see the Nixpkgs manual for details.</p></td></tr></table></div><p>Discerning readers will note that the
+<code class="envar">buildInputs</code> could just as well have been set in the Nix
+expression, like this:
+
+</p><pre class="programlisting">
+ buildInputs = [ perl ];</pre><p>
+
+The <code class="varname">perl</code> attribute can then be removed, and the
+builder becomes even shorter:
+
+</p><pre class="programlisting">
+source $stdenv/setup
+genericBuild</pre><p>
+
+In fact, <code class="varname">mkDerivation</code> provides a default builder
+that looks exactly like that, so it is actually possible to omit the
+builder for Hello entirely.</p></div><div class="footnotes"><br /><hr style="width:100; text-align:left;margin-left: 0" /><div id="ftn.idm139733301545648" class="footnote"><p><a href="#idm139733301545648" class="para"><sup class="para">[2] </sup></a>In fact, it can be written in any
+ language, but typically it's a <span class="command"><strong>bash</strong></span> shell
+ script.</p></div><div id="ftn.idm139733301492640" class="footnote"><p><a href="#idm139733301492640" class="para"><sup class="para">[3] </sup></a>Actually, it's initialised to
+ <code class="filename">/path-not-set</code> to prevent Bash from setting it
+ to a default value.</p></div><div id="ftn.idm139733301420112" class="footnote"><p><a href="#idm139733301420112" class="para"><sup class="para">[4] </sup></a>How does it work? <code class="filename">setup</code>
+ tries to source the file
+ <code class="filename"><em class="replaceable"><code>pkg</code></em>/nix-support/setup-hook</code>
+ of all dependencies. These “setup hooks” can then set up whatever
+ environment variables they want; for instance, the setup hook for
+ Perl sets the <code class="envar">PERL5LIB</code> environment variable to
+ contain the <code class="filename">lib/site_perl</code> directories of all
+ inputs.</p></div></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-expression-language"></a>Chapter 15. Nix Expression Language</h2></div></div></div><p>The Nix expression language is a pure, lazy, functional
+language. Purity means that operations in the language don't have
+side-effects (for instance, there is no variable assignment).
+Laziness means that arguments to functions are evaluated only when
+they are needed. Functional means that functions are
+<span class="quote">“<span class="quote">normal</span>”</span> values that can be passed around and manipulated
+in interesting ways. The language is not a full-featured, general
+purpose language. Its main job is to describe packages,
+compositions of packages, and the variability within
+packages.</p><p>This section presents the various features of the
+language.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-values"></a>15.1. Values</h2></div></div></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301403360"></a>Simple Values</h3></div></div></div><p>Nix has the following basic data types:
+
+</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><span class="emphasis"><em>Strings</em></span> can be written in three
+ ways.</p><p>The most common way is to enclose the string between double
+ quotes, e.g., <code class="literal">"foo bar"</code>. Strings can span
+ multiple lines. The special characters <code class="literal">"</code> and
+ <code class="literal">\</code> and the character sequence
+ <code class="literal">${</code> must be escaped by prefixing them with a
+ backslash (<code class="literal">\</code>). Newlines, carriage returns and
+ tabs can be written as <code class="literal">\n</code>,
+ <code class="literal">\r</code> and <code class="literal">\t</code>,
+ respectively.</p><p>You can include the result of an expression into a string by
+ enclosing it in
+ <code class="literal">${<em class="replaceable"><code>...</code></em>}</code>, a feature
+ known as <span class="emphasis"><em>antiquotation</em></span>. The enclosed
+ expression must evaluate to something that can be coerced into a
+ string (meaning that it must be a string, a path, or a
+ derivation). For instance, rather than writing
+
+</p><pre class="programlisting">
+"--with-freetype2-library=" + freetype + "/lib"</pre><p>
+
+ (where <code class="varname">freetype</code> is a derivation), you can
+ instead write the more natural
+
+</p><pre class="programlisting">
+"--with-freetype2-library=${freetype}/lib"</pre><p>
+
+ The latter is automatically translated to the former. A more
+ complicated example (from the Nix expression for <a class="link" href="http://www.trolltech.com/products/qt" target="_top">Qt</a>):
+
+</p><pre class="programlisting">
+configureFlags = "
+ -system-zlib -system-libpng -system-libjpeg
+ ${if openglSupport then "-dlopen-opengl
+ -L${mesa}/lib -I${mesa}/include
+ -L${libXmu}/lib -I${libXmu}/include" else ""}
+ ${if threadSupport then "-thread" else "-no-thread"}
+";</pre><p>
+
+ Note that Nix expressions and strings can be arbitrarily nested;
+ in this case the outer string contains various antiquotations that
+ themselves contain strings (e.g., <code class="literal">"-thread"</code>),
+ some of which in turn contain expressions (e.g.,
+ <code class="literal">${mesa}</code>).</p><p>The second way to write string literals is as an
+ <span class="emphasis"><em>indented string</em></span>, which is enclosed between
+ pairs of <span class="emphasis"><em>double single-quotes</em></span>, like so:
+
+</p><pre class="programlisting">
+''
+ This is the first line.
+ This is the second line.
+ This is the third line.
+''</pre><p>
+
+ This kind of string literal intelligently strips indentation from
+ the start of each line. To be precise, it strips from each line a
+ number of spaces equal to the minimal indentation of the string as
+ a whole (disregarding the indentation of empty lines). For
+ instance, the first and second line are indented two space, while
+ the third line is indented four spaces. Thus, two spaces are
+ stripped from each line, so the resulting string is
+
+</p><pre class="programlisting">
+"This is the first line.\nThis is the second line.\n This is the third line.\n"</pre><p>
+
+ </p><p>Note that the whitespace and newline following the opening
+ <code class="literal">''</code> is ignored if there is no non-whitespace
+ text on the initial line.</p><p>Antiquotation
+ (<code class="literal">${<em class="replaceable"><code>expr</code></em>}</code>) is
+ supported in indented strings.</p><p>Since <code class="literal">${</code> and <code class="literal">''</code> have
+ special meaning in indented strings, you need a way to quote them.
+ <code class="literal">$</code> can be escaped by prefixing it with
+ <code class="literal">''</code> (that is, two single quotes), i.e.,
+ <code class="literal">''$</code>. <code class="literal">''</code> can be escaped by
+ prefixing it with <code class="literal">'</code>, i.e.,
+ <code class="literal">'''</code>. <code class="literal">$</code> removes any special meaning
+ from the following <code class="literal">$</code>. Linefeed, carriage-return and tab
+ characters can be written as <code class="literal">''\n</code>,
+ <code class="literal">''\r</code>, <code class="literal">''\t</code>, and <code class="literal">''\</code>
+ escapes any other character.
+
+ </p><p>Indented strings are primarily useful in that they allow
+ multi-line string literals to follow the indentation of the
+ enclosing Nix expression, and that less escaping is typically
+ necessary for strings representing languages such as shell scripts
+ and configuration files because <code class="literal">''</code> is much less
+ common than <code class="literal">"</code>. Example:
+
+</p><pre class="programlisting">
+stdenv.mkDerivation {
+ <em class="replaceable"><code>...</code></em>
+ postInstall =
+ ''
+ mkdir $out/bin $out/etc
+ cp foo $out/bin
+ echo "Hello World" > $out/etc/foo.conf
+ ${if enableBar then "cp bar $out/bin" else ""}
+ '';
+ <em class="replaceable"><code>...</code></em>
+}
+</pre><p>
+
+ </p><p>Finally, as a convenience, <span class="emphasis"><em>URIs</em></span> as
+ defined in appendix B of <a class="link" href="http://www.ietf.org/rfc/rfc2396.txt" target="_top">RFC 2396</a>
+ can be written <span class="emphasis"><em>as is</em></span>, without quotes. For
+ instance, the string
+ <code class="literal">"http://example.org/foo.tar.bz2"</code>
+ can also be written as
+ <code class="literal">http://example.org/foo.tar.bz2</code>.</p></li><li class="listitem"><p>Numbers, which can be <span class="emphasis"><em>integers</em></span> (like
+ <code class="literal">123</code>) or <span class="emphasis"><em>floating point</em></span> (like
+ <code class="literal">123.43</code> or <code class="literal">.27e13</code>).</p><p>Numbers are type-compatible: pure integer operations will always
+ return integers, whereas any operation involving at least one floating point
+ number will have a floating point number as a result.</p></li><li class="listitem"><p><span class="emphasis"><em>Paths</em></span>, e.g.,
+ <code class="filename">/bin/sh</code> or <code class="filename">./builder.sh</code>.
+ A path must contain at least one slash to be recognised as such; for
+ instance, <code class="filename">builder.sh</code> is not a
+ path<a href="#ftn.idm139733301368560" class="footnote" id="idm139733301368560"><sup class="footnote">[5]</sup></a>. If the file name is
+ relative, i.e., if it does not begin with a slash, it is made
+ absolute at parse time relative to the directory of the Nix
+ expression that contained it. For instance, if a Nix expression in
+ <code class="filename">/foo/bar/bla.nix</code> refers to
+ <code class="filename">../xyzzy/fnord.nix</code>, the absolute path is
+ <code class="filename">/foo/xyzzy/fnord.nix</code>.</p><p>If the first component of a path is a <code class="literal">~</code>,
+ it is interpreted as if the rest of the path were relative to the
+ user's home directory. e.g. <code class="filename">~/foo</code> would be
+ equivalent to <code class="filename">/home/edolstra/foo</code> for a user
+ whose home directory is <code class="filename">/home/edolstra</code>.
+ </p><p>Paths can also be specified between angle brackets, e.g.
+ <code class="literal"><nixpkgs></code>. This means that the directories
+ listed in the environment variable
+ <code class="envar"><a class="envar" href="#env-NIX_PATH">NIX_PATH</a></code> will be searched
+ for the given file or directory name.
+ </p></li><li class="listitem"><p><span class="emphasis"><em>Booleans</em></span> with values
+ <code class="literal">true</code> and
+ <code class="literal">false</code>.</p></li><li class="listitem"><p>The null value, denoted as
+ <code class="literal">null</code>.</p></li></ul></div><p>
+
+</p></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301358208"></a>Lists</h3></div></div></div><p>Lists are formed by enclosing a whitespace-separated list of
+values between square brackets. For example,
+
+</p><pre class="programlisting">
+[ 123 ./foo.nix "abc" (f { x = y; }) ]</pre><p>
+
+defines a list of four elements, the last being the result of a call
+to the function <code class="varname">f</code>. Note that function calls have
+to be enclosed in parentheses. If they had been omitted, e.g.,
+
+</p><pre class="programlisting">
+[ 123 ./foo.nix "abc" f { x = y; } ]</pre><p>
+
+the result would be a list of five elements, the fourth one being a
+function and the fifth being a set.</p><p>Note that lists are only lazy in values, and they are strict in length.
+</p></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301354960"></a>Sets</h3></div></div></div><p>Sets are really the core of the language, since ultimately the
+Nix language is all about creating derivations, which are really just
+sets of attributes to be passed to build scripts.</p><p>Sets are just a list of name/value pairs (called
+<span class="emphasis"><em>attributes</em></span>) enclosed in curly brackets, where
+each value is an arbitrary expression terminated by a semicolon. For
+example:
+
+</p><pre class="programlisting">
+{ x = 123;
+ text = "Hello";
+ y = f { bla = 456; };
+}</pre><p>
+
+This defines a set with attributes named <code class="varname">x</code>,
+<code class="varname">text</code>, <code class="varname">y</code>. The order of the
+attributes is irrelevant. An attribute name may only occur
+once.</p><p>Attributes can be selected from a set using the
+<code class="literal">.</code> operator. For instance,
+
+</p><pre class="programlisting">
+{ a = "Foo"; b = "Bar"; }.a</pre><p>
+
+evaluates to <code class="literal">"Foo"</code>. It is possible to provide a
+default value in an attribute selection using the
+<code class="literal">or</code> keyword. For example,
+
+</p><pre class="programlisting">
+{ a = "Foo"; b = "Bar"; }.c or "Xyzzy"</pre><p>
+
+will evaluate to <code class="literal">"Xyzzy"</code> because there is no
+<code class="varname">c</code> attribute in the set.</p><p>You can use arbitrary double-quoted strings as attribute
+names:
+
+</p><pre class="programlisting">
+{ "foo ${bar}" = 123; "nix-1.0" = 456; }."foo ${bar}"
+</pre><p>
+
+This will evaluate to <code class="literal">123</code> (Assuming
+<code class="literal">bar</code> is antiquotable). In the case where an
+attribute name is just a single antiquotation, the quotes can be
+dropped:
+
+</p><pre class="programlisting">
+{ foo = 123; }.${bar} or 456 </pre><p>
+
+This will evaluate to <code class="literal">123</code> if
+<code class="literal">bar</code> evaluates to <code class="literal">"foo"</code> when
+coerced to a string and <code class="literal">456</code> otherwise (again
+assuming <code class="literal">bar</code> is antiquotable).</p><p>In the special case where an attribute name inside of a set declaration
+evaluates to <code class="literal">null</code> (which is normally an error, as
+<code class="literal">null</code> is not antiquotable), that attribute is simply not
+added to the set:
+
+</p><pre class="programlisting">
+{ ${if foo then "bar" else null} = true; }</pre><p>
+
+This will evaluate to <code class="literal">{}</code> if <code class="literal">foo</code>
+evaluates to <code class="literal">false</code>.</p><p>A set that has a <code class="literal">__functor</code> attribute whose value
+is callable (i.e. is itself a function or a set with a
+<code class="literal">__functor</code> attribute whose value is callable) can be
+applied as if it were a function, with the set itself passed in first
+, e.g.,
+
+</p><pre class="programlisting">
+let add = { __functor = self: x: x + self.x; };
+ inc = add // { x = 1; };
+in inc 1
+</pre><p>
+
+evaluates to <code class="literal">2</code>. This can be used to attach metadata to a
+function without the caller needing to treat it specially, or to implement
+a form of object-oriented programming, for example.
+
+</p></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-constructs"></a>15.2. Language Constructs</h2></div></div></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301335376"></a>Recursive sets</h3></div></div></div><p>Recursive sets are just normal sets, but the attributes can
+refer to each other. For example,
+
+</p><pre class="programlisting">
+rec {
+ x = y;
+ y = 123;
+}.x
+</pre><p>
+
+evaluates to <code class="literal">123</code>. Note that without
+<code class="literal">rec</code> the binding <code class="literal">x = y;</code> would
+refer to the variable <code class="varname">y</code> in the surrounding scope,
+if one exists, and would be invalid if no such variable exists. That
+is, in a normal (non-recursive) set, attributes are not added to the
+lexical scope; in a recursive set, they are.</p><p>Recursive sets of course introduce the danger of infinite
+recursion. For example,
+
+</p><pre class="programlisting">
+rec {
+ x = y;
+ y = x;
+}.x</pre><p>
+
+does not terminate<a href="#ftn.idm139733301331328" class="footnote" id="idm139733301331328"><sup class="footnote">[6]</sup></a>.</p></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="sect-let-expressions"></a>Let-expressions</h3></div></div></div><p>A let-expression allows you to define local variables for an
+expression. For instance,
+
+</p><pre class="programlisting">
+let
+ x = "foo";
+ y = "bar";
+in x + y</pre><p>
+
+evaluates to <code class="literal">"foobar"</code>.
+
+</p></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301327568"></a>Inheriting attributes</h3></div></div></div><p>When defining a set or in a let-expression it is often convenient to copy variables
+from the surrounding lexical scope (e.g., when you want to propagate
+attributes). This can be shortened using the
+<code class="literal">inherit</code> keyword. For instance,
+
+</p><pre class="programlisting">
+let x = 123; in
+{ inherit x;
+ y = 456;
+}</pre><p>
+
+is equivalent to
+
+</p><pre class="programlisting">
+let x = 123; in
+{ x = x;
+ y = 456;
+}</pre><p>
+
+and both evaluate to <code class="literal">{ x = 123; y = 456; }</code>. (Note that
+this works because <code class="varname">x</code> is added to the lexical scope
+by the <code class="literal">let</code> construct.) It is also possible to
+inherit attributes from another set. For instance, in this fragment
+from <code class="filename">all-packages.nix</code>,
+
+</p><pre class="programlisting">
+ graphviz = (import ../tools/graphics/graphviz) {
+ inherit fetchurl stdenv libpng libjpeg expat x11 yacc;
+ inherit (xlibs) libXaw;
+ };
+
+ xlibs = {
+ libX11 = ...;
+ libXaw = ...;
+ ...
+ }
+
+ libpng = ...;
+ libjpg = ...;
+ ...</pre><p>
+
+the set used in the function call to the function defined in
+<code class="filename">../tools/graphics/graphviz</code> inherits a number of
+variables from the surrounding scope (<code class="varname">fetchurl</code>
+... <code class="varname">yacc</code>), but also inherits
+<code class="varname">libXaw</code> (the X Athena Widgets) from the
+<code class="varname">xlibs</code> (X11 client-side libraries) set.</p><p>
+Summarizing the fragment
+
+</p><pre class="programlisting">
+...
+inherit x y z;
+inherit (src-set) a b c;
+...</pre><p>
+
+is equivalent to
+
+</p><pre class="programlisting">
+...
+x = x; y = y; z = z;
+a = src-set.a; b = src-set.b; c = src-set.c;
+...</pre><p>
+
+when used while defining local variables in a let-expression or
+while defining a set.</p></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="ss-functions"></a>Functions</h3></div></div></div><p>Functions have the following form:
+
+</p><pre class="programlisting">
+<em class="replaceable"><code>pattern</code></em>: <em class="replaceable"><code>body</code></em></pre><p>
+
+The pattern specifies what the argument of the function must look
+like, and binds variables in the body to (parts of) the
+argument. There are three kinds of patterns:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>If a pattern is a single identifier, then the
+ function matches any argument. Example:
+
+ </p><pre class="programlisting">
+let negate = x: !x;
+ concat = x: y: x + y;
+in if negate true then concat "foo" "bar" else ""</pre><p>
+
+ Note that <code class="function">concat</code> is a function that takes one
+ argument and returns a function that takes another argument. This
+ allows partial parameterisation (i.e., only filling some of the
+ arguments of a function); e.g.,
+
+ </p><pre class="programlisting">
+map (concat "foo") [ "bar" "bla" "abc" ]</pre><p>
+
+ evaluates to <code class="literal">[ "foobar" "foobla"
+ "fooabc" ]</code>.</p></li><li class="listitem"><p>A <span class="emphasis"><em>set pattern</em></span> of the form
+ <code class="literal">{ name1, name2, …, nameN }</code> matches a set
+ containing the listed attributes, and binds the values of those
+ attributes to variables in the function body. For example, the
+ function
+
+</p><pre class="programlisting">
+{ x, y, z }: z + y + x</pre><p>
+
+ can only be called with a set containing exactly the attributes
+ <code class="varname">x</code>, <code class="varname">y</code> and
+ <code class="varname">z</code>. No other attributes are allowed. If you want
+ to allow additional arguments, you can use an ellipsis
+ (<code class="literal">...</code>):
+
+</p><pre class="programlisting">
+{ x, y, z, ... }: z + y + x</pre><p>
+
+ This works on any set that contains at least the three named
+ attributes.</p><p>It is possible to provide <span class="emphasis"><em>default values</em></span>
+ for attributes, in which case they are allowed to be missing. A
+ default value is specified by writing
+ <code class="literal"><em class="replaceable"><code>name</code></em> ?
+ <em class="replaceable"><code>e</code></em></code>, where
+ <em class="replaceable"><code>e</code></em> is an arbitrary expression. For example,
+
+</p><pre class="programlisting">
+{ x, y ? "foo", z ? "bar" }: z + y + x</pre><p>
+
+ specifies a function that only requires an attribute named
+ <code class="varname">x</code>, but optionally accepts <code class="varname">y</code>
+ and <code class="varname">z</code>.</p></li><li class="listitem"><p>An <code class="literal">@</code>-pattern provides a means of referring
+ to the whole value being matched:
+
+</p><pre class="programlisting"> args@{ x, y, z, ... }: z + y + x + args.a</pre><p>
+
+but can also be written as:
+
+</p><pre class="programlisting"> { x, y, z, ... } @ args: z + y + x + args.a</pre><p>
+
+ Here <code class="varname">args</code> is bound to the entire argument, which
+ is further matched against the pattern <code class="literal">{ x, y, z,
+ ... }</code>. <code class="literal">@</code>-pattern makes mainly sense with an
+ ellipsis(<code class="literal">...</code>) as you can access attribute names as
+ <code class="literal">a</code>, using <code class="literal">args.a</code>, which was given as an
+ additional attribute to the function.
+ </p><div class="warning"><h3 class="title">Warning</h3><p>
+ The <code class="literal">args@</code> expression is bound to the argument passed to the function which
+ means that attributes with defaults that aren't explicitly specified in the function call
+ won't cause an evaluation error, but won't exist in <code class="literal">args</code>.
+ </p><p>
+ For instance
+</p><pre class="programlisting">
+let
+ function = args@{ a ? 23, ... }: args;
+in
+ function {}
+</pre><p>
+ will evaluate to an empty attribute set.
+ </p></div></li></ul></div><p>Note that functions do not have names. If you want to give them
+a name, you can bind them to an attribute, e.g.,
+
+</p><pre class="programlisting">
+let concat = { x, y }: x + y;
+in concat { x = "foo"; y = "bar"; }</pre><p>
+
+</p></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301295536"></a>Conditionals</h3></div></div></div><p>Conditionals look like this:
+
+</p><pre class="programlisting">
+if <em class="replaceable"><code>e1</code></em> then <em class="replaceable"><code>e2</code></em> else <em class="replaceable"><code>e3</code></em></pre><p>
+
+where <em class="replaceable"><code>e1</code></em> is an expression that should
+evaluate to a Boolean value (<code class="literal">true</code> or
+<code class="literal">false</code>).</p></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301291568"></a>Assertions</h3></div></div></div><p>Assertions are generally used to check that certain requirements
+on or between features and dependencies hold. They look like this:
+
+</p><pre class="programlisting">
+assert <em class="replaceable"><code>e1</code></em>; <em class="replaceable"><code>e2</code></em></pre><p>
+
+where <em class="replaceable"><code>e1</code></em> is an expression that should
+evaluate to a Boolean value. If it evaluates to
+<code class="literal">true</code>, <em class="replaceable"><code>e2</code></em> is returned;
+otherwise expression evaluation is aborted and a backtrace is printed.</p><div class="example"><a id="ex-subversion-nix"></a><p class="title"><strong>Example 15.1. Nix expression for Subversion</strong></p><div class="example-contents"><pre class="programlisting">
+{ localServer ? false
+, httpServer ? false
+, sslSupport ? false
+, pythonBindings ? false
+, javaSwigBindings ? false
+, javahlBindings ? false
+, stdenv, fetchurl
+, openssl ? null, httpd ? null, db4 ? null, expat, swig ? null, j2sdk ? null
+}:
+
+assert localServer -> db4 != null; <a id="ex-subversion-nix-co-1"></a>(1)
+assert httpServer -> httpd != null && httpd.expat == expat; <a id="ex-subversion-nix-co-2"></a>(2)
+assert sslSupport -> openssl != null && (httpServer -> httpd.openssl == openssl); <a id="ex-subversion-nix-co-3"></a>(3)
+assert pythonBindings -> swig != null && swig.pythonSupport;
+assert javaSwigBindings -> swig != null && swig.javaSupport;
+assert javahlBindings -> j2sdk != null;
+
+stdenv.mkDerivation {
+ name = "subversion-1.1.1";
+ ...
+ openssl = if sslSupport then openssl else null; <a id="ex-subversion-nix-co-4"></a>(4)
+ ...
+}</pre></div></div><br class="example-break" /><p><a class="xref" href="#ex-subversion-nix" title="Example 15.1. Nix expression for Subversion">Example 15.1, “Nix expression for Subversion”</a> show how assertions are
+used in the Nix expression for Subversion.</p><div class="calloutlist"><table border="0" summary="Callout list"><tr><td width="5%" valign="top" align="left"><p><a href="#ex-subversion-nix-co-1">(1)</a> </p></td><td valign="top" align="left"><p>This assertion states that if Subversion is to have support
+ for local repositories, then Berkeley DB is needed. So if the
+ Subversion function is called with the
+ <code class="varname">localServer</code> argument set to
+ <code class="literal">true</code> but the <code class="varname">db4</code> argument
+ set to <code class="literal">null</code>, then the evaluation fails.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-subversion-nix-co-2">(2)</a> </p></td><td valign="top" align="left"><p>This is a more subtle condition: if Subversion is built with
+ Apache (<code class="literal">httpServer</code>) support, then the Expat
+ library (an XML library) used by Subversion should be same as the
+ one used by Apache. This is because in this configuration
+ Subversion code ends up being linked with Apache code, and if the
+ Expat libraries do not match, a build- or runtime link error or
+ incompatibility might occur.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-subversion-nix-co-3">(3)</a> </p></td><td valign="top" align="left"><p>This assertion says that in order for Subversion to have SSL
+ support (so that it can access <code class="literal">https</code> URLs), an
+ OpenSSL library must be passed. Additionally, it says that
+ <span class="emphasis"><em>if</em></span> Apache support is enabled, then Apache's
+ OpenSSL should match Subversion's. (Note that if Apache support
+ is not enabled, we don't care about Apache's OpenSSL.)</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-subversion-nix-co-4">(4)</a> </p></td><td valign="top" align="left"><p>The conditional here is not really related to assertions,
+ but is worth pointing out: it ensures that if SSL support is
+ disabled, then the Subversion derivation is not dependent on
+ OpenSSL, even if a non-<code class="literal">null</code> value was passed.
+ This prevents an unnecessary rebuild of Subversion if OpenSSL
+ changes.</p></td></tr></table></div></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301272384"></a>With-expressions</h3></div></div></div><p>A <span class="emphasis"><em>with-expression</em></span>,
+
+</p><pre class="programlisting">
+with <em class="replaceable"><code>e1</code></em>; <em class="replaceable"><code>e2</code></em></pre><p>
+
+introduces the set <em class="replaceable"><code>e1</code></em> into the lexical
+scope of the expression <em class="replaceable"><code>e2</code></em>. For instance,
+
+</p><pre class="programlisting">
+let as = { x = "foo"; y = "bar"; };
+in with as; x + y</pre><p>
+
+evaluates to <code class="literal">"foobar"</code> since the
+<code class="literal">with</code> adds the <code class="varname">x</code> and
+<code class="varname">y</code> attributes of <code class="varname">as</code> to the
+lexical scope in the expression <code class="literal">x + y</code>. The most
+common use of <code class="literal">with</code> is in conjunction with the
+<code class="function">import</code> function. E.g.,
+
+</p><pre class="programlisting">
+with (import ./definitions.nix); ...</pre><p>
+
+makes all attributes defined in the file
+<code class="filename">definitions.nix</code> available as if they were defined
+locally in a <code class="literal">let</code>-expression.</p><p>The bindings introduced by <code class="literal">with</code> do not shadow bindings
+introduced by other means, e.g.
+
+</p><pre class="programlisting">
+let a = 3; in with { a = 1; }; let a = 4; in with { a = 2; }; ...</pre><p>
+
+establishes the same scope as
+
+</p><pre class="programlisting">
+let a = 1; in let a = 2; in let a = 3; in let a = 4; in ...</pre><p>
+
+</p></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301261632"></a>Comments</h3></div></div></div><p>Comments can be single-line, started with a <code class="literal">#</code>
+character, or inline/multi-line, enclosed within <code class="literal">/*
+... */</code>.</p></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-language-operators"></a>15.3. Operators</h2></div></div></div><p><a class="xref" href="#table-operators" title="Table 15.1. Operators">Table 15.1, “Operators”</a> lists the operators in the
+Nix expression language, in order of precedence (from strongest to
+weakest binding).</p><div class="table"><a id="table-operators"></a><p class="title"><strong>Table 15.1. Operators</strong></p><div class="table-contents"><table class="table" summary="Operators" border="1"><colgroup><col /><col /><col /></colgroup><thead><tr><th>Name</th><th>Syntax</th><th>Associativity</th><th>Description</th><th>Precedence</th></tr></thead><tbody><tr><td>Select</td><td><em class="replaceable"><code>e</code></em> <code class="literal">.</code>
+ <em class="replaceable"><code>attrpath</code></em>
+ [ <code class="literal">or</code> <em class="replaceable"><code>def</code></em> ]
+ </td><td>none</td><td>Select attribute denoted by the attribute path
+ <em class="replaceable"><code>attrpath</code></em> from set
+ <em class="replaceable"><code>e</code></em>. (An attribute path is a
+ dot-separated list of attribute names.) If the attribute
+ doesn’t exist, return <em class="replaceable"><code>def</code></em> if
+ provided, otherwise abort evaluation.</td><td>1</td></tr><tr><td>Application</td><td><em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></td><td>left</td><td>Call function <em class="replaceable"><code>e1</code></em> with
+ argument <em class="replaceable"><code>e2</code></em>.</td><td>2</td></tr><tr><td>Arithmetic Negation</td><td><code class="literal">-</code> <em class="replaceable"><code>e</code></em></td><td>none</td><td>Arithmetic negation.</td><td>3</td></tr><tr><td>Has Attribute</td><td><em class="replaceable"><code>e</code></em> <code class="literal">?</code>
+ <em class="replaceable"><code>attrpath</code></em></td><td>none</td><td>Test whether set <em class="replaceable"><code>e</code></em> contains
+ the attribute denoted by <em class="replaceable"><code>attrpath</code></em>;
+ return <code class="literal">true</code> or
+ <code class="literal">false</code>.</td><td>4</td></tr><tr><td>List Concatenation</td><td><em class="replaceable"><code>e1</code></em> <code class="literal">++</code> <em class="replaceable"><code>e2</code></em></td><td>right</td><td>List concatenation.</td><td>5</td></tr><tr><td>Multiplication</td><td>
+ <em class="replaceable"><code>e1</code></em> <code class="literal">*</code> <em class="replaceable"><code>e2</code></em>,
+ </td><td>left</td><td>Arithmetic multiplication.</td><td>6</td></tr><tr><td>Division</td><td>
+ <em class="replaceable"><code>e1</code></em> <code class="literal">/</code> <em class="replaceable"><code>e2</code></em>
+ </td><td>left</td><td>Arithmetic division.</td><td>6</td></tr><tr><td>Addition</td><td>
+ <em class="replaceable"><code>e1</code></em> <code class="literal">+</code> <em class="replaceable"><code>e2</code></em>
+ </td><td>left</td><td>Arithmetic addition.</td><td>7</td></tr><tr><td>Subtraction</td><td>
+ <em class="replaceable"><code>e1</code></em> <code class="literal">-</code> <em class="replaceable"><code>e2</code></em>
+ </td><td>left</td><td>Arithmetic subtraction.</td><td>7</td></tr><tr><td>String Concatenation</td><td>
+ <em class="replaceable"><code>string1</code></em> <code class="literal">+</code> <em class="replaceable"><code>string2</code></em>
+ </td><td>left</td><td>String concatenation.</td><td>7</td></tr><tr><td>Not</td><td><code class="literal">!</code> <em class="replaceable"><code>e</code></em></td><td>none</td><td>Boolean negation.</td><td>8</td></tr><tr><td>Update</td><td><em class="replaceable"><code>e1</code></em> <code class="literal">//</code>
+ <em class="replaceable"><code>e2</code></em></td><td>right</td><td>Return a set consisting of the attributes in
+ <em class="replaceable"><code>e1</code></em> and
+ <em class="replaceable"><code>e2</code></em> (with the latter taking
+ precedence over the former in case of equally named
+ attributes).</td><td>9</td></tr><tr><td>Less Than</td><td>
+ <em class="replaceable"><code>e1</code></em> <code class="literal"><</code> <em class="replaceable"><code>e2</code></em>,
+ </td><td>none</td><td>Arithmetic comparison.</td><td>10</td></tr><tr><td>Less Than or Equal To</td><td>
+ <em class="replaceable"><code>e1</code></em> <code class="literal"><=</code> <em class="replaceable"><code>e2</code></em>
+ </td><td>none</td><td>Arithmetic comparison.</td><td>10</td></tr><tr><td>Greater Than</td><td>
+ <em class="replaceable"><code>e1</code></em> <code class="literal">></code> <em class="replaceable"><code>e2</code></em>
+ </td><td>none</td><td>Arithmetic comparison.</td><td>10</td></tr><tr><td>Greater Than or Equal To</td><td>
+ <em class="replaceable"><code>e1</code></em> <code class="literal">>=</code> <em class="replaceable"><code>e2</code></em>
+ </td><td>none</td><td>Arithmetic comparison.</td><td>10</td></tr><tr><td>Equality</td><td>
+ <em class="replaceable"><code>e1</code></em> <code class="literal">==</code> <em class="replaceable"><code>e2</code></em>
+ </td><td>none</td><td>Equality.</td><td>11</td></tr><tr><td>Inequality</td><td>
+ <em class="replaceable"><code>e1</code></em> <code class="literal">!=</code> <em class="replaceable"><code>e2</code></em>
+ </td><td>none</td><td>Inequality.</td><td>11</td></tr><tr><td>Logical AND</td><td><em class="replaceable"><code>e1</code></em> <code class="literal">&&</code>
+ <em class="replaceable"><code>e2</code></em></td><td>left</td><td>Logical AND.</td><td>12</td></tr><tr><td>Logical OR</td><td><em class="replaceable"><code>e1</code></em> <code class="literal">||</code>
+ <em class="replaceable"><code>e2</code></em></td><td>left</td><td>Logical OR.</td><td>13</td></tr><tr><td>Logical Implication</td><td><em class="replaceable"><code>e1</code></em> <code class="literal">-></code>
+ <em class="replaceable"><code>e2</code></em></td><td>none</td><td>Logical implication (equivalent to
+ <code class="literal">!<em class="replaceable"><code>e1</code></em> ||
+ <em class="replaceable"><code>e2</code></em></code>).</td><td>14</td></tr></tbody></table></div></div><br class="table-break" /></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-derivation"></a>15.4. Derivations</h2></div></div></div><p>The most important built-in function is
+<code class="function">derivation</code>, which is used to describe a single
+derivation (a build action). It takes as input a set, the attributes
+of which specify the inputs of the build.</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><a id="attr-system"></a>There must be an attribute named
+ <code class="varname">system</code> whose value must be a string specifying a
+ Nix platform identifier, such as <code class="literal">"i686-linux"</code> or
+ <code class="literal">"x86_64-darwin"</code><a href="#ftn.idm139733301168656" class="footnote" id="idm139733301168656"><sup class="footnote">[7]</sup></a> The build
+ can only be performed on a machine and operating system matching the
+ platform identifier. (Nix can automatically forward builds for
+ other platforms by forwarding them to other machines; see <a class="xref" href="#chap-distributed-builds" title="Chapter 16. Remote Builds">Chapter 16, <em>Remote Builds</em></a>.)</p></li><li class="listitem"><p>There must be an attribute named
+ <code class="varname">name</code> whose value must be a string. This is used
+ as a symbolic name for the package by <span class="command"><strong>nix-env</strong></span>,
+ and it is appended to the output paths of the
+ derivation.</p></li><li class="listitem"><p>There must be an attribute named
+ <code class="varname">builder</code> that identifies the program that is
+ executed to perform the build. It can be either a derivation or a
+ source (a local file reference, e.g.,
+ <code class="filename">./builder.sh</code>).</p></li><li class="listitem"><p>Every attribute is passed as an environment variable
+ to the builder. Attribute values are translated to environment
+ variables as follows:
+
+ </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Strings and numbers are just passed
+ verbatim.</p></li><li class="listitem"><p>A <span class="emphasis"><em>path</em></span> (e.g.,
+ <code class="filename">../foo/sources.tar</code>) causes the referenced
+ file to be copied to the store; its location in the store is put
+ in the environment variable. The idea is that all sources
+ should reside in the Nix store, since all inputs to a derivation
+ should reside in the Nix store.</p></li><li class="listitem"><p>A <span class="emphasis"><em>derivation</em></span> causes that
+ derivation to be built prior to the present derivation; its
+ default output path is put in the environment
+ variable.</p></li><li class="listitem"><p>Lists of the previous types are also allowed.
+ They are simply concatenated, separated by
+ spaces.</p></li><li class="listitem"><p><code class="literal">true</code> is passed as the string
+ <code class="literal">1</code>, <code class="literal">false</code> and
+ <code class="literal">null</code> are passed as an empty string.
+ </p></li></ul></div><p>
+
+ </p></li><li class="listitem"><p>The optional attribute <code class="varname">args</code>
+ specifies command-line arguments to be passed to the builder. It
+ should be a list.</p></li><li class="listitem"><p>The optional attribute <code class="varname">outputs</code>
+ specifies a list of symbolic outputs of the derivation. By default,
+ a derivation produces a single output path, denoted as
+ <code class="literal">out</code>. However, derivations can produce multiple
+ output paths. This is useful because it allows outputs to be
+ downloaded or garbage-collected separately. For instance, imagine a
+ library package that provides a dynamic library, header files, and
+ documentation. A program that links against the library doesn’t
+ need the header files and documentation at runtime, and it doesn’t
+ need the documentation at build time. Thus, the library package
+ could specify:
+</p><pre class="programlisting">
+outputs = [ "lib" "headers" "doc" ];
+</pre><p>
+ This will cause Nix to pass environment variables
+ <code class="literal">lib</code>, <code class="literal">headers</code> and
+ <code class="literal">doc</code> to the builder containing the intended store
+ paths of each output. The builder would typically do something like
+</p><pre class="programlisting">
+./configure --libdir=$lib/lib --includedir=$headers/include --docdir=$doc/share/doc
+</pre><p>
+ for an Autoconf-style package. You can refer to each output of a
+ derivation by selecting it as an attribute, e.g.
+</p><pre class="programlisting">
+buildInputs = [ pkg.lib pkg.headers ];
+</pre><p>
+ The first element of <code class="varname">outputs</code> determines the
+ <span class="emphasis"><em>default output</em></span>. Thus, you could also write
+</p><pre class="programlisting">
+buildInputs = [ pkg pkg.headers ];
+</pre><p>
+ since <code class="literal">pkg</code> is equivalent to
+ <code class="literal">pkg.lib</code>.</p></li></ul></div><p>The function <code class="function">mkDerivation</code> in the Nixpkgs
+standard environment is a wrapper around
+<code class="function">derivation</code> that adds a default value for
+<code class="varname">system</code> and always uses Bash as the builder, to
+which the supplied builder is passed as a command-line argument. See
+the Nixpkgs manual for details.</p><p>The builder is executed as follows:
+
+</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>A temporary directory is created under the directory
+ specified by <code class="envar">TMPDIR</code> (default
+ <code class="filename">/tmp</code>) where the build will take place. The
+ current directory is changed to this directory.</p></li><li class="listitem"><p>The environment is cleared and set to the derivation
+ attributes, as specified above.</p></li><li class="listitem"><p>In addition, the following variables are set:
+
+ </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p><code class="envar">NIX_BUILD_TOP</code> contains the path of
+ the temporary directory for this build.</p></li><li class="listitem"><p>Also, <code class="envar">TMPDIR</code>,
+ <code class="envar">TEMPDIR</code>, <code class="envar">TMP</code>, <code class="envar">TEMP</code>
+ are set to point to the temporary directory. This is to prevent
+ the builder from accidentally writing temporary files anywhere
+ else. Doing so might cause interference by other
+ processes.</p></li><li class="listitem"><p><code class="envar">PATH</code> is set to
+ <code class="filename">/path-not-set</code> to prevent shells from
+ initialising it to their built-in default value.</p></li><li class="listitem"><p><code class="envar">HOME</code> is set to
+ <code class="filename">/homeless-shelter</code> to prevent programs from
+ using <code class="filename">/etc/passwd</code> or the like to find the
+ user's home directory, which could cause impurity. Usually, when
+ <code class="envar">HOME</code> is set, it is used as the location of the home
+ directory, even if it points to a non-existent
+ path.</p></li><li class="listitem"><p><code class="envar">NIX_STORE</code> is set to the path of the
+ top-level Nix store directory (typically,
+ <code class="filename">/nix/store</code>).</p></li><li class="listitem"><p>For each output declared in
+ <code class="varname">outputs</code>, the corresponding environment variable
+ is set to point to the intended path in the Nix store for that
+ output. Each output path is a concatenation of the cryptographic
+ hash of all build inputs, the <code class="varname">name</code> attribute
+ and the output name. (The output name is omitted if it’s
+ <code class="literal">out</code>.)</p></li></ul></div><p>
+
+ </p></li><li class="listitem"><p>If an output path already exists, it is removed.
+ Also, locks are acquired to prevent multiple Nix instances from
+ performing the same build at the same time.</p></li><li class="listitem"><p>A log of the combined standard output and error is
+ written to <code class="filename">/nix/var/log/nix</code>.</p></li><li class="listitem"><p>The builder is executed with the arguments specified
+ by the attribute <code class="varname">args</code>. If it exits with exit
+ code 0, it is considered to have succeeded.</p></li><li class="listitem"><p>The temporary directory is removed (unless the
+ <code class="option">-K</code> option was specified).</p></li><li class="listitem"><p>If the build was successful, Nix scans each output
+ path for references to input paths by looking for the hash parts of
+ the input paths. Since these are potential runtime dependencies,
+ Nix registers them as dependencies of the output
+ paths.</p></li><li class="listitem"><p>After the build, Nix sets the last-modified
+ timestamp on all files in the build result to 1 (00:00:01 1/1/1970
+ UTC), sets the group to the default group, and sets the mode of the
+ file to 0444 or 0555 (i.e., read-only, with execute permission
+ enabled if the file was originally executable). Note that possible
+ <code class="literal">setuid</code> and <code class="literal">setgid</code> bits are
+ cleared. Setuid and setgid programs are not currently supported by
+ Nix. This is because the Nix archives used in deployment have no
+ concept of ownership information, and because it makes the build
+ result dependent on the user performing the build.</p></li></ul></div><p>
+
+</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="sec-advanced-attributes"></a>15.4.1. Advanced Attributes</h3></div></div></div><p>Derivations can declare some infrequently used optional
+attributes.</p><div class="variablelist"><dl class="variablelist"><dt><a id="adv-attr-allowedReferences"></a><span class="term"><code class="varname">allowedReferences</code></span></dt><dd><p>The optional attribute
+ <code class="varname">allowedReferences</code> specifies a list of legal
+ references (dependencies) of the output of the builder. For
+ example,
+
+</p><pre class="programlisting">
+allowedReferences = [];
+</pre><p>
+
+ enforces that the output of a derivation cannot have any runtime
+ dependencies on its inputs. To allow an output to have a runtime
+ dependency on itself, use <code class="literal">"out"</code> as a list item.
+ This is used in NixOS to check that generated files such as
+ initial ramdisks for booting Linux don’t have accidental
+ dependencies on other paths in the Nix store.</p></dd><dt><a id="adv-attr-allowedRequisites"></a><span class="term"><code class="varname">allowedRequisites</code></span></dt><dd><p>This attribute is similar to
+ <code class="varname">allowedReferences</code>, but it specifies the legal
+ requisites of the whole closure, so all the dependencies
+ recursively. For example,
+
+</p><pre class="programlisting">
+allowedRequisites = [ foobar ];
+</pre><p>
+
+ enforces that the output of a derivation cannot have any other
+ runtime dependency than <code class="varname">foobar</code>, and in addition
+ it enforces that <code class="varname">foobar</code> itself doesn't
+ introduce any other dependency itself.</p></dd><dt><a id="adv-attr-disallowedReferences"></a><span class="term"><code class="varname">disallowedReferences</code></span></dt><dd><p>The optional attribute
+ <code class="varname">disallowedReferences</code> specifies a list of illegal
+ references (dependencies) of the output of the builder. For
+ example,
+
+</p><pre class="programlisting">
+disallowedReferences = [ foo ];
+</pre><p>
+
+ enforces that the output of a derivation cannot have a direct runtime
+ dependencies on the derivation <code class="varname">foo</code>.</p></dd><dt><a id="adv-attr-disallowedRequisites"></a><span class="term"><code class="varname">disallowedRequisites</code></span></dt><dd><p>This attribute is similar to
+ <code class="varname">disallowedReferences</code>, but it specifies illegal
+ requisites for the whole closure, so all the dependencies
+ recursively. For example,
+
+</p><pre class="programlisting">
+disallowedRequisites = [ foobar ];
+</pre><p>
+
+ enforces that the output of a derivation cannot have any
+ runtime dependency on <code class="varname">foobar</code> or any other derivation
+ depending recursively on <code class="varname">foobar</code>.</p></dd><dt><a id="adv-attr-exportReferencesGraph"></a><span class="term"><code class="varname">exportReferencesGraph</code></span></dt><dd><p>This attribute allows builders access to the
+ references graph of their inputs. The attribute is a list of
+ inputs in the Nix store whose references graph the builder needs
+ to know. The value of this attribute should be a list of pairs
+ <code class="literal">[ <em class="replaceable"><code>name1</code></em>
+ <em class="replaceable"><code>path1</code></em> <em class="replaceable"><code>name2</code></em>
+ <em class="replaceable"><code>path2</code></em> <em class="replaceable"><code>...</code></em>
+ ]</code>. The references graph of each
+ <em class="replaceable"><code>pathN</code></em> will be stored in a text file
+ <em class="replaceable"><code>nameN</code></em> in the temporary build directory.
+ The text files have the format used by <span class="command"><strong>nix-store
+ --register-validity</strong></span> (with the deriver fields left
+ empty). For example, when the following derivation is built:
+
+</p><pre class="programlisting">
+derivation {
+ ...
+ exportReferencesGraph = [ "libfoo-graph" libfoo ];
+};
+</pre><p>
+
+ the references graph of <code class="literal">libfoo</code> is placed in the
+ file <code class="filename">libfoo-graph</code> in the temporary build
+ directory.</p><p><code class="varname">exportReferencesGraph</code> is useful for
+ builders that want to do something with the closure of a store
+ path. Examples include the builders in NixOS that generate the
+ initial ramdisk for booting Linux (a <span class="command"><strong>cpio</strong></span>
+ archive containing the closure of the boot script) and the
+ ISO-9660 image for the installation CD (which is populated with a
+ Nix store containing the closure of a bootable NixOS
+ configuration).</p></dd><dt><a id="adv-attr-impureEnvVars"></a><span class="term"><code class="varname">impureEnvVars</code></span></dt><dd><p>This attribute allows you to specify a list of
+ environment variables that should be passed from the environment
+ of the calling user to the builder. Usually, the environment is
+ cleared completely when the builder is executed, but with this
+ attribute you can allow specific environment variables to be
+ passed unmodified. For example, <code class="function">fetchurl</code> in
+ Nixpkgs has the line
+
+</p><pre class="programlisting">
+impureEnvVars = [ "http_proxy" "https_proxy" <em class="replaceable"><code>...</code></em> ];
+</pre><p>
+
+ to make it use the proxy server configuration specified by the
+ user in the environment variables <code class="envar">http_proxy</code> and
+ friends.</p><p>This attribute is only allowed in <a class="link" href="#fixed-output-drvs">fixed-output derivations</a>, where
+ impurities such as these are okay since (the hash of) the output
+ is known in advance. It is ignored for all other
+ derivations.</p><div class="warning"><h3 class="title">Warning</h3><p><code class="varname">impureEnvVars</code> implementation takes
+ environment variables from the current builder process. When a daemon is
+ building its environmental variables are used. Without the daemon, the
+ environmental variables come from the environment of the
+ <span class="command"><strong>nix-build</strong></span>.</p></div></dd><dt><a id="fixed-output-drvs"></a><span class="term"><a id="adv-attr-outputHash"></a><code class="varname">outputHash</code>, </span><span class="term"><a id="adv-attr-outputHashAlgo"></a><code class="varname">outputHashAlgo</code>, </span><span class="term"><a id="adv-attr-outputHashMode"></a><code class="varname">outputHashMode</code></span></dt><dd><p>These attributes declare that the derivation is a
+ so-called <span class="emphasis"><em>fixed-output derivation</em></span>, which
+ means that a cryptographic hash of the output is already known in
+ advance. When the build of a fixed-output derivation finishes,
+ Nix computes the cryptographic hash of the output and compares it
+ to the hash declared with these attributes. If there is a
+ mismatch, the build fails.</p><p>The rationale for fixed-output derivations is derivations
+ such as those produced by the <code class="function">fetchurl</code>
+ function. This function downloads a file from a given URL. To
+ ensure that the downloaded file has not been modified, the caller
+ must also specify a cryptographic hash of the file. For example,
+
+</p><pre class="programlisting">
+fetchurl {
+ url = "http://ftp.gnu.org/pub/gnu/hello/hello-2.1.1.tar.gz";
+ sha256 = "1md7jsfd8pa45z73bz1kszpp01yw6x5ljkjk2hx7wl800any6465";
+}
+</pre><p>
+
+ It sometimes happens that the URL of the file changes, e.g.,
+ because servers are reorganised or no longer available. We then
+ must update the call to <code class="function">fetchurl</code>, e.g.,
+
+</p><pre class="programlisting">
+fetchurl {
+ url = "ftp://ftp.nluug.nl/pub/gnu/hello/hello-2.1.1.tar.gz";
+ sha256 = "1md7jsfd8pa45z73bz1kszpp01yw6x5ljkjk2hx7wl800any6465";
+}
+</pre><p>
+
+ If a <code class="function">fetchurl</code> derivation was treated like a
+ normal derivation, the output paths of the derivation and
+ <span class="emphasis"><em>all derivations depending on it</em></span> would change.
+ For instance, if we were to change the URL of the Glibc source
+ distribution in Nixpkgs (a package on which almost all other
+ packages depend) massive rebuilds would be needed. This is
+ unfortunate for a change which we know cannot have a real effect
+ as it propagates upwards through the dependency graph.</p><p>For fixed-output derivations, on the other hand, the name of
+ the output path only depends on the <code class="varname">outputHash*</code>
+ and <code class="varname">name</code> attributes, while all other attributes
+ are ignored for the purpose of computing the output path. (The
+ <code class="varname">name</code> attribute is included because it is part
+ of the path.)</p><p>As an example, here is the (simplified) Nix expression for
+ <code class="varname">fetchurl</code>:
+
+</p><pre class="programlisting">
+{ stdenv, curl }: # The <span class="command"><strong>curl</strong></span> program is used for downloading.
+
+{ url, sha256 }:
+
+stdenv.mkDerivation {
+ name = baseNameOf (toString url);
+ builder = ./builder.sh;
+ buildInputs = [ curl ];
+
+ # This is a fixed-output derivation; the output must be a regular
+ # file with SHA256 hash <code class="varname">sha256</code>.
+ outputHashMode = "flat";
+ outputHashAlgo = "sha256";
+ outputHash = sha256;
+
+ inherit url;
+}
+</pre><p>
+
+ </p><p>The <code class="varname">outputHashAlgo</code> attribute specifies
+ the hash algorithm used to compute the hash. It can currently be
+ <code class="literal">"sha1"</code>, <code class="literal">"sha256"</code> or
+ <code class="literal">"sha512"</code>.</p><p>The <code class="varname">outputHashMode</code> attribute determines
+ how the hash is computed. It must be one of the following two
+ values:
+
+ </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">"flat"</code></span></dt><dd><p>The output must be a non-executable regular
+ file. If it isn’t, the build fails. The hash is simply
+ computed over the contents of that file (so it’s equal to what
+ Unix commands like <span class="command"><strong>sha256sum</strong></span> or
+ <span class="command"><strong>sha1sum</strong></span> produce).</p><p>This is the default.</p></dd><dt><span class="term"><code class="literal">"recursive"</code></span></dt><dd><p>The hash is computed over the NAR archive dump
+ of the output (i.e., the result of <a class="link" href="#refsec-nix-store-dump" title="Operation --dump"><span class="command"><strong>nix-store
+ --dump</strong></span></a>). In this case, the output can be
+ anything, including a directory tree.</p></dd></dl></div><p>
+
+ </p><p>The <code class="varname">outputHash</code> attribute, finally, must
+ be a string containing the hash in either hexadecimal or base-32
+ notation. (See the <a class="link" href="#sec-nix-hash" title="nix-hash"><span class="command"><strong>nix-hash</strong></span> command</a>
+ for information about converting to and from base-32
+ notation.)</p></dd><dt><a id="adv-attr-passAsFile"></a><span class="term"><code class="varname">passAsFile</code></span></dt><dd><p>A list of names of attributes that should be
+ passed via files rather than environment variables. For example,
+ if you have
+
+ </p><pre class="programlisting">
+passAsFile = ["big"];
+big = "a very long string";
+ </pre><p>
+
+ then when the builder runs, the environment variable
+ <code class="envar">bigPath</code> will contain the absolute path to a
+ temporary file containing <code class="literal">a very long
+ string</code>. That is, for any attribute
+ <em class="replaceable"><code>x</code></em> listed in
+ <code class="varname">passAsFile</code>, Nix will pass an environment
+ variable <code class="envar"><em class="replaceable"><code>x</code></em>Path</code> holding
+ the path of the file containing the value of attribute
+ <em class="replaceable"><code>x</code></em>. This is useful when you need to pass
+ large strings to a builder, since most operating systems impose a
+ limit on the size of the environment (typically, a few hundred
+ kilobyte).</p></dd><dt><a id="adv-attr-preferLocalBuild"></a><span class="term"><code class="varname">preferLocalBuild</code></span></dt><dd><p>If this attribute is set to
+ <code class="literal">true</code> and <a class="link" href="#chap-distributed-builds" title="Chapter 16. Remote Builds">distributed building is
+ enabled</a>, then, if possible, the derivaton will be built
+ locally instead of forwarded to a remote machine. This is
+ appropriate for trivial builders where the cost of doing a
+ download or remote build would exceed the cost of building
+ locally.</p></dd><dt><a id="adv-attr-allowSubstitutes"></a><span class="term"><code class="varname">allowSubstitutes</code></span></dt><dd><p>If this attribute is set to
+ <code class="literal">false</code>, then Nix will always build this
+ derivation; it will not try to substitute its outputs. This is
+ useful for very trivial derivations (such as
+ <code class="function">writeText</code> in Nixpkgs) that are cheaper to
+ build than to substitute from a binary cache.</p><div class="note"><h3 class="title">Note</h3><p>You need to have a builder configured which satisfies
+ the derivation’s <code class="literal">system</code> attribute, since the
+ derivation cannot be substituted. Thus it is usually a good idea
+ to align <code class="literal">system</code> with
+ <code class="literal">builtins.currentSystem</code> when setting
+ <code class="literal">allowSubstitutes</code> to <code class="literal">false</code>.
+ For most trivial derivations this should be the case.
+ </p></div></dd></dl></div></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-builtins"></a>15.5. Built-in Functions</h2></div></div></div><p>This section lists the functions and constants built into the
+Nix expression evaluator. (The built-in function
+<code class="function">derivation</code> is discussed above.) Some built-ins,
+such as <code class="function">derivation</code>, are always in scope of every
+Nix expression; you can just access them right away. But to prevent
+polluting the namespace too much, most built-ins are not in scope.
+Instead, you can access them through the <code class="varname">builtins</code>
+built-in value, which is a set that contains all built-in functions
+and values. For instance, <code class="function">derivation</code> is also
+available as <code class="function">builtins.derivation</code>.</p><div class="variablelist"><dl class="variablelist"><dt><a id="builtin-abort"></a><span class="term"><code class="function">abort</code> <em class="replaceable"><code>s</code></em>, </span><span class="term"><code class="function">builtins.abort</code> <em class="replaceable"><code>s</code></em></span></dt><dd><p>Abort Nix expression evaluation, print error
+ message <em class="replaceable"><code>s</code></em>.</p></dd><dt><a id="builtin-add"></a><span class="term"><code class="function">builtins.add</code>
+ <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em>
+ </span></dt><dd><p>Return the sum of the numbers
+ <em class="replaceable"><code>e1</code></em> and
+ <em class="replaceable"><code>e2</code></em>.</p></dd><dt><a id="builtin-all"></a><span class="term"><code class="function">builtins.all</code>
+ <em class="replaceable"><code>pred</code></em> <em class="replaceable"><code>list</code></em></span></dt><dd><p>Return <code class="literal">true</code> if the function
+ <em class="replaceable"><code>pred</code></em> returns <code class="literal">true</code>
+ for all elements of <em class="replaceable"><code>list</code></em>,
+ and <code class="literal">false</code> otherwise.</p></dd><dt><a id="builtin-any"></a><span class="term"><code class="function">builtins.any</code>
+ <em class="replaceable"><code>pred</code></em> <em class="replaceable"><code>list</code></em></span></dt><dd><p>Return <code class="literal">true</code> if the function
+ <em class="replaceable"><code>pred</code></em> returns <code class="literal">true</code>
+ for at least one element of <em class="replaceable"><code>list</code></em>,
+ and <code class="literal">false</code> otherwise.</p></dd><dt><a id="builtin-attrNames"></a><span class="term"><code class="function">builtins.attrNames</code>
+ <em class="replaceable"><code>set</code></em></span></dt><dd><p>Return the names of the attributes in the set
+ <em class="replaceable"><code>set</code></em> in an alphabetically sorted list. For instance,
+ <code class="literal">builtins.attrNames { y = 1; x = "foo"; }</code>
+ evaluates to <code class="literal">[ "x" "y" ]</code>.</p></dd><dt><a id="builtin-attrValues"></a><span class="term"><code class="function">builtins.attrValues</code>
+ <em class="replaceable"><code>set</code></em></span></dt><dd><p>Return the values of the attributes in the set
+ <em class="replaceable"><code>set</code></em> in the order corresponding to the
+ sorted attribute names.</p></dd><dt><a id="builtin-baseNameOf"></a><span class="term"><code class="function">baseNameOf</code> <em class="replaceable"><code>s</code></em></span></dt><dd><p>Return the <span class="emphasis"><em>base name</em></span> of the
+ string <em class="replaceable"><code>s</code></em>, that is, everything following
+ the final slash in the string. This is similar to the GNU
+ <span class="command"><strong>basename</strong></span> command.</p></dd><dt><a id="builtin-bitAnd"></a><span class="term"><code class="function">builtins.bitAnd</code>
+ <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>Return the bitwise AND of the integers
+ <em class="replaceable"><code>e1</code></em> and
+ <em class="replaceable"><code>e2</code></em>.</p></dd><dt><a id="builtin-bitOr"></a><span class="term"><code class="function">builtins.bitOr</code>
+ <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>Return the bitwise OR of the integers
+ <em class="replaceable"><code>e1</code></em> and
+ <em class="replaceable"><code>e2</code></em>.</p></dd><dt><a id="builtin-bitXor"></a><span class="term"><code class="function">builtins.bitXor</code>
+ <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>Return the bitwise XOR of the integers
+ <em class="replaceable"><code>e1</code></em> and
+ <em class="replaceable"><code>e2</code></em>.</p></dd><dt><a id="builtin-builtins"></a><span class="term"><code class="varname">builtins</code></span></dt><dd><p>The set <code class="varname">builtins</code> contains all
+ the built-in functions and values. You can use
+ <code class="varname">builtins</code> to test for the availability of
+ features in the Nix installation, e.g.,
+
+</p><pre class="programlisting">
+if builtins ? getEnv then builtins.getEnv "PATH" else ""</pre><p>
+
+ This allows a Nix expression to fall back gracefully on older Nix
+ installations that don’t have the desired built-in
+ function.</p></dd><dt><a id="builtin-compareVersions"></a><span class="term"><code class="function">builtins.compareVersions</code>
+ <em class="replaceable"><code>s1</code></em> <em class="replaceable"><code>s2</code></em></span></dt><dd><p>Compare two strings representing versions and
+ return <code class="literal">-1</code> if version
+ <em class="replaceable"><code>s1</code></em> is older than version
+ <em class="replaceable"><code>s2</code></em>, <code class="literal">0</code> if they are
+ the same, and <code class="literal">1</code> if
+ <em class="replaceable"><code>s1</code></em> is newer than
+ <em class="replaceable"><code>s2</code></em>. The version comparison algorithm
+ is the same as the one used by <a class="link" href="#ssec-version-comparisons" title="Versions"><span class="command"><strong>nix-env
+ -u</strong></span></a>.</p></dd><dt><a id="builtin-concatLists"></a><span class="term"><code class="function">builtins.concatLists</code>
+ <em class="replaceable"><code>lists</code></em></span></dt><dd><p>Concatenate a list of lists into a single
+ list.</p></dd><dt><a id="builtin-concatStringsSep"></a><span class="term"><code class="function">builtins.concatStringsSep</code>
+ <em class="replaceable"><code>separator</code></em> <em class="replaceable"><code>list</code></em></span></dt><dd><p>Concatenate a list of strings with a separator
+ between each element, e.g. <code class="literal">concatStringsSep "/"
+ ["usr" "local" "bin"] == "usr/local/bin"</code></p></dd><dt><a id="builtin-currentSystem"></a><span class="term"><code class="varname">builtins.currentSystem</code></span></dt><dd><p>The built-in value <code class="varname">currentSystem</code>
+ evaluates to the Nix platform identifier for the Nix installation
+ on which the expression is being evaluated, such as
+ <code class="literal">"i686-linux"</code> or
+ <code class="literal">"x86_64-darwin"</code>.</p></dd><dt><a id="builtin-deepSeq"></a><span class="term"><code class="function">builtins.deepSeq</code>
+ <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>This is like <code class="literal">seq
+ <em class="replaceable"><code>e1</code></em>
+ <em class="replaceable"><code>e2</code></em></code>, except that
+ <em class="replaceable"><code>e1</code></em> is evaluated
+ <span class="emphasis"><em>deeply</em></span>: if it’s a list or set, its elements
+ or attributes are also evaluated recursively.</p></dd><dt><a id="builtin-derivation"></a><span class="term"><code class="function">derivation</code>
+ <em class="replaceable"><code>attrs</code></em>, </span><span class="term"><code class="function">builtins.derivation</code>
+ <em class="replaceable"><code>attrs</code></em></span></dt><dd><p><code class="function">derivation</code> is described in
+ <a class="xref" href="#ssec-derivation" title="15.4. Derivations">Section 15.4, “Derivations”</a>.</p></dd><dt><a id="builtin-dirOf"></a><span class="term"><code class="function">dirOf</code> <em class="replaceable"><code>s</code></em>, </span><span class="term"><code class="function">builtins.dirOf</code> <em class="replaceable"><code>s</code></em></span></dt><dd><p>Return the directory part of the string
+ <em class="replaceable"><code>s</code></em>, that is, everything before the final
+ slash in the string. This is similar to the GNU
+ <span class="command"><strong>dirname</strong></span> command.</p></dd><dt><a id="builtin-div"></a><span class="term"><code class="function">builtins.div</code>
+ <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>Return the quotient of the numbers
+ <em class="replaceable"><code>e1</code></em> and
+ <em class="replaceable"><code>e2</code></em>.</p></dd><dt><a id="builtin-elem"></a><span class="term"><code class="function">builtins.elem</code>
+ <em class="replaceable"><code>x</code></em> <em class="replaceable"><code>xs</code></em></span></dt><dd><p>Return <code class="literal">true</code> if a value equal to
+ <em class="replaceable"><code>x</code></em> occurs in the list
+ <em class="replaceable"><code>xs</code></em>, and <code class="literal">false</code>
+ otherwise.</p></dd><dt><a id="builtin-elemAt"></a><span class="term"><code class="function">builtins.elemAt</code>
+ <em class="replaceable"><code>xs</code></em> <em class="replaceable"><code>n</code></em></span></dt><dd><p>Return element <em class="replaceable"><code>n</code></em> from
+ the list <em class="replaceable"><code>xs</code></em>. Elements are counted
+ starting from 0. A fatal error occurs if the index is out of
+ bounds.</p></dd><dt><a id="builtin-fetchurl"></a><span class="term"><code class="function">builtins.fetchurl</code>
+ <em class="replaceable"><code>url</code></em></span></dt><dd><p>Download the specified URL and return the path of
+ the downloaded file. This function is not available if <a class="link" href="#conf-restrict-eval">restricted evaluation mode</a> is
+ enabled.</p></dd><dt><a id="builtin-fetchTarball"></a><span class="term"><code class="function">fetchTarball</code>
+ <em class="replaceable"><code>url</code></em>, </span><span class="term"><code class="function">builtins.fetchTarball</code>
+ <em class="replaceable"><code>url</code></em></span></dt><dd><p>Download the specified URL, unpack it and return
+ the path of the unpacked tree. The file must be a tape archive
+ (<code class="filename">.tar</code>) compressed with
+ <code class="literal">gzip</code>, <code class="literal">bzip2</code> or
+ <code class="literal">xz</code>. The top-level path component of the files
+ in the tarball is removed, so it is best if the tarball contains a
+ single directory at top level. The typical use of the function is
+ to obtain external Nix expression dependencies, such as a
+ particular version of Nixpkgs, e.g.
+
+</p><pre class="programlisting">
+with import (fetchTarball https://github.com/NixOS/nixpkgs/archive/nixos-14.12.tar.gz) {};
+
+stdenv.mkDerivation { … }
+</pre><p>
+ </p><p>The fetched tarball is cached for a certain amount of time
+ (1 hour by default) in <code class="filename">~/.cache/nix/tarballs/</code>.
+ You can change the cache timeout either on the command line with
+ <code class="option">--option tarball-ttl <em class="replaceable"><code>number of seconds</code></em></code> or
+ in the Nix configuration file with this option:
+ <code class="literal"><a class="xref" href="#conf-tarball-ttl"><code class="literal">tarball-ttl</code></a> <em class="replaceable"><code>number of seconds to cache</code></em></code>.
+ </p><p>Note that when obtaining the hash with <code class="varname">nix-prefetch-url
+ </code> the option <code class="varname">--unpack</code> is required.
+ </p><p>This function can also verify the contents against a hash.
+ In that case, the function takes a set instead of a URL. The set
+ requires the attribute <code class="varname">url</code> and the attribute
+ <code class="varname">sha256</code>, e.g.
+
+</p><pre class="programlisting">
+with import (fetchTarball {
+ url = "https://github.com/NixOS/nixpkgs/archive/nixos-14.12.tar.gz";
+ sha256 = "1jppksrfvbk5ypiqdz4cddxdl8z6zyzdb2srq8fcffr327ld5jj2";
+}) {};
+
+stdenv.mkDerivation { … }
+</pre><p>
+
+ </p><p>This function is not available if <a class="link" href="#conf-restrict-eval">restricted evaluation mode</a> is
+ enabled.</p></dd><dt><a id="builtin-fetchGit"></a><span class="term">
+ <code class="function">builtins.fetchGit</code>
+ <em class="replaceable"><code>args</code></em>
+ </span></dt><dd><p>
+ Fetch a path from git. <em class="replaceable"><code>args</code></em> can be
+ a URL, in which case the HEAD of the repo at that URL is
+ fetched. Otherwise, it can be an attribute with the following
+ attributes (all except <code class="varname">url</code> optional):
+ </p><div class="variablelist"><dl class="variablelist"><dt><span class="term">url</span></dt><dd><p>
+ The URL of the repo.
+ </p></dd><dt><span class="term">name</span></dt><dd><p>
+ The name of the directory the repo should be exported to
+ in the store. Defaults to the basename of the URL.
+ </p></dd><dt><span class="term">rev</span></dt><dd><p>
+ The git revision to fetch. Defaults to the tip of
+ <code class="varname">ref</code>.
+ </p></dd><dt><span class="term">ref</span></dt><dd><p>
+ The git ref to look for the requested revision under.
+ This is often a branch or tag name. Defaults to
+ <code class="literal">HEAD</code>.
+ </p><p>
+ By default, the <code class="varname">ref</code> value is prefixed
+ with <code class="literal">refs/heads/</code>. As of Nix 2.3.0
+ Nix will not prefix <code class="literal">refs/heads/</code> if
+ <code class="varname">ref</code> starts with <code class="literal">refs/</code>.
+ </p></dd><dt><span class="term">submodules</span></dt><dd><p>
+ A Boolean parameter that specifies whether submodules
+ should be checked out. Defaults to
+ <code class="literal">false</code>.
+ </p></dd></dl></div><div class="example"><a id="idm139733300931888"></a><p class="title"><strong>Example 15.2. Fetching a private repository over SSH</strong></p><div class="example-contents"><pre class="programlisting">builtins.fetchGit {
+ url = "git@github.com:my-secret/repository.git";
+ ref = "master";
+ rev = "adab8b916a45068c044658c4158d81878f9ed1c3";
+}</pre></div></div><br class="example-break" /><div class="example"><a id="idm139733300930528"></a><p class="title"><strong>Example 15.3. Fetching an arbitrary ref</strong></p><div class="example-contents"><pre class="programlisting">builtins.fetchGit {
+ url = "https://github.com/NixOS/nix.git";
+ ref = "refs/heads/0.5-release";
+}</pre></div></div><br class="example-break" /><div class="example"><a id="idm139733300929216"></a><p class="title"><strong>Example 15.4. Fetching a repository's specific commit on an arbitrary branch</strong></p><div class="example-contents"><p>
+ If the revision you're looking for is in the default branch
+ of the git repository you don't strictly need to specify
+ the branch name in the <code class="varname">ref</code> attribute.
+ </p><p>
+ However, if the revision you're looking for is in a future
+ branch for the non-default branch you will need to specify
+ the the <code class="varname">ref</code> attribute as well.
+ </p><pre class="programlisting">builtins.fetchGit {
+ url = "https://github.com/nixos/nix.git";
+ rev = "841fcbd04755c7a2865c51c1e2d3b045976b7452";
+ ref = "1.11-maintenance";
+}</pre><div class="note"><h3 class="title">Note</h3><p>
+ It is nice to always specify the branch which a revision
+ belongs to. Without the branch being specified, the
+ fetcher might fail if the default branch changes.
+ Additionally, it can be confusing to try a commit from a
+ non-default branch and see the fetch fail. If the branch
+ is specified the fault is much more obvious.
+ </p></div></div></div><br class="example-break" /><div class="example"><a id="idm139733300924656"></a><p class="title"><strong>Example 15.5. Fetching a repository's specific commit on the default branch</strong></p><div class="example-contents"><p>
+ If the revision you're looking for is in the default branch
+ of the git repository you may omit the
+ <code class="varname">ref</code> attribute.
+ </p><pre class="programlisting">builtins.fetchGit {
+ url = "https://github.com/nixos/nix.git";
+ rev = "841fcbd04755c7a2865c51c1e2d3b045976b7452";
+}</pre></div></div><br class="example-break" /><div class="example"><a id="idm139733300922352"></a><p class="title"><strong>Example 15.6. Fetching a tag</strong></p><div class="example-contents"><pre class="programlisting">builtins.fetchGit {
+ url = "https://github.com/nixos/nix.git";
+ ref = "refs/tags/1.9";
+}</pre></div></div><br class="example-break" /><div class="example"><a id="idm139733300921056"></a><p class="title"><strong>Example 15.7. Fetching the latest version of a remote branch</strong></p><div class="example-contents"><p>
+ <code class="function">builtins.fetchGit</code> can behave impurely
+ fetch the latest version of a remote branch.
+ </p><div class="note"><h3 class="title">Note</h3><p>Nix will refetch the branch in accordance to
+ <a class="xref" href="#conf-tarball-ttl"><code class="literal">tarball-ttl</code></a>.</p></div><div class="note"><h3 class="title">Note</h3><p>This behavior is disabled in
+ <span class="emphasis"><em>Pure evaluation mode</em></span>.</p></div><pre class="programlisting">builtins.fetchGit {
+ url = "ssh://git@github.com/nixos/nix.git";
+ ref = "master";
+}</pre></div></div><br class="example-break" /></dd><dt><span class="term"><code class="function">builtins.filter</code>
+ <em class="replaceable"><code>f</code></em> <em class="replaceable"><code>xs</code></em></span></dt><dd><p>Return a list consisting of the elements of
+ <em class="replaceable"><code>xs</code></em> for which the function
+ <em class="replaceable"><code>f</code></em> returns
+ <code class="literal">true</code>.</p></dd><dt><a id="builtin-filterSource"></a><span class="term"><code class="function">builtins.filterSource</code>
+ <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>This function allows you to copy sources into the Nix
+ store while filtering certain files. For instance, suppose that
+ you want to use the directory <code class="filename">source-dir</code> as
+ an input to a Nix expression, e.g.
+
+</p><pre class="programlisting">
+stdenv.mkDerivation {
+ ...
+ src = ./source-dir;
+}
+</pre><p>
+
+ However, if <code class="filename">source-dir</code> is a Subversion
+ working copy, then all those annoying <code class="filename">.svn</code>
+ subdirectories will also be copied to the store. Worse, the
+ contents of those directories may change a lot, causing lots of
+ spurious rebuilds. With <code class="function">filterSource</code> you
+ can filter out the <code class="filename">.svn</code> directories:
+
+</p><pre class="programlisting">
+ src = builtins.filterSource
+ (path: type: type != "directory" || baseNameOf path != ".svn")
+ ./source-dir;
+</pre><p>
+
+ </p><p>Thus, the first argument <em class="replaceable"><code>e1</code></em>
+ must be a predicate function that is called for each regular
+ file, directory or symlink in the source tree
+ <em class="replaceable"><code>e2</code></em>. If the function returns
+ <code class="literal">true</code>, the file is copied to the Nix store,
+ otherwise it is omitted. The function is called with two
+ arguments. The first is the full path of the file. The second
+ is a string that identifies the type of the file, which is
+ either <code class="literal">"regular"</code>,
+ <code class="literal">"directory"</code>, <code class="literal">"symlink"</code> or
+ <code class="literal">"unknown"</code> (for other kinds of files such as
+ device nodes or fifos — but note that those cannot be copied to
+ the Nix store, so if the predicate returns
+ <code class="literal">true</code> for them, the copy will fail). If you
+ exclude a directory, the entire corresponding subtree of
+ <em class="replaceable"><code>e2</code></em> will be excluded.</p></dd><dt><a id="builtin-foldl-prime"></a><span class="term"><code class="function">builtins.foldl’</code>
+ <em class="replaceable"><code>op</code></em> <em class="replaceable"><code>nul</code></em> <em class="replaceable"><code>list</code></em></span></dt><dd><p>Reduce a list by applying a binary operator, from
+ left to right, e.g. <code class="literal">foldl’ op nul [x0 x1 x2 ...] = op (op
+ (op nul x0) x1) x2) ...</code>. The operator is applied
+ strictly, i.e., its arguments are evaluated first. For example,
+ <code class="literal">foldl’ (x: y: x + y) 0 [1 2 3]</code> evaluates to
+ 6.</p></dd><dt><a id="builtin-functionArgs"></a><span class="term"><code class="function">builtins.functionArgs</code>
+ <em class="replaceable"><code>f</code></em></span></dt><dd><p>
+ Return a set containing the names of the formal arguments expected
+ by the function <em class="replaceable"><code>f</code></em>.
+ The value of each attribute is a Boolean denoting whether the corresponding
+ argument has a default value. For instance,
+ <code class="literal">functionArgs ({ x, y ? 123}: ...) = { x = false; y = true; }</code>.
+ </p><p>"Formal argument" here refers to the attributes pattern-matched by
+ the function. Plain lambdas are not included, e.g.
+ <code class="literal">functionArgs (x: ...) = { }</code>.
+ </p></dd><dt><a id="builtin-fromJSON"></a><span class="term"><code class="function">builtins.fromJSON</code> <em class="replaceable"><code>e</code></em></span></dt><dd><p>Convert a JSON string to a Nix
+ value. For example,
+
+</p><pre class="programlisting">
+builtins.fromJSON ''{"x": [1, 2, 3], "y": null}''
+</pre><p>
+
+ returns the value <code class="literal">{ x = [ 1 2 3 ]; y = null;
+ }</code>.</p></dd><dt><a id="builtin-genList"></a><span class="term"><code class="function">builtins.genList</code>
+ <em class="replaceable"><code>generator</code></em> <em class="replaceable"><code>length</code></em></span></dt><dd><p>Generate list of size
+ <em class="replaceable"><code>length</code></em>, with each element
+ <em class="replaceable"><code>i</code></em> equal to the value returned by
+ <em class="replaceable"><code>generator</code></em> <code class="literal">i</code>. For
+ example,
+
+</p><pre class="programlisting">
+builtins.genList (x: x * x) 5
+</pre><p>
+
+ returns the list <code class="literal">[ 0 1 4 9 16 ]</code>.</p></dd><dt><a id="builtin-getAttr"></a><span class="term"><code class="function">builtins.getAttr</code>
+ <em class="replaceable"><code>s</code></em> <em class="replaceable"><code>set</code></em></span></dt><dd><p><code class="function">getAttr</code> returns the attribute
+ named <em class="replaceable"><code>s</code></em> from
+ <em class="replaceable"><code>set</code></em>. Evaluation aborts if the
+ attribute doesn’t exist. This is a dynamic version of the
+ <code class="literal">.</code> operator, since <em class="replaceable"><code>s</code></em>
+ is an expression rather than an identifier.</p></dd><dt><a id="builtin-getEnv"></a><span class="term"><code class="function">builtins.getEnv</code>
+ <em class="replaceable"><code>s</code></em></span></dt><dd><p><code class="function">getEnv</code> returns the value of
+ the environment variable <em class="replaceable"><code>s</code></em>, or an empty
+ string if the variable doesn’t exist. This function should be
+ used with care, as it can introduce all sorts of nasty environment
+ dependencies in your Nix expression.</p><p><code class="function">getEnv</code> is used in Nix Packages to
+ locate the file <code class="filename">~/.nixpkgs/config.nix</code>, which
+ contains user-local settings for Nix Packages. (That is, it does
+ a <code class="literal">getEnv "HOME"</code> to locate the user’s home
+ directory.)</p></dd><dt><a id="builtin-hasAttr"></a><span class="term"><code class="function">builtins.hasAttr</code>
+ <em class="replaceable"><code>s</code></em> <em class="replaceable"><code>set</code></em></span></dt><dd><p><code class="function">hasAttr</code> returns
+ <code class="literal">true</code> if <em class="replaceable"><code>set</code></em> has an
+ attribute named <em class="replaceable"><code>s</code></em>, and
+ <code class="literal">false</code> otherwise. This is a dynamic version of
+ the <code class="literal">?</code> operator, since
+ <em class="replaceable"><code>s</code></em> is an expression rather than an
+ identifier.</p></dd><dt><a id="builtin-hashString"></a><span class="term"><code class="function">builtins.hashString</code>
+ <em class="replaceable"><code>type</code></em> <em class="replaceable"><code>s</code></em></span></dt><dd><p>Return a base-16 representation of the
+ cryptographic hash of string <em class="replaceable"><code>s</code></em>. The
+ hash algorithm specified by <em class="replaceable"><code>type</code></em> must
+ be one of <code class="literal">"md5"</code>, <code class="literal">"sha1"</code>,
+ <code class="literal">"sha256"</code> or <code class="literal">"sha512"</code>.</p></dd><dt><a id="builtin-hashFile"></a><span class="term"><code class="function">builtins.hashFile</code>
+ <em class="replaceable"><code>type</code></em> <em class="replaceable"><code>p</code></em></span></dt><dd><p>Return a base-16 representation of the
+ cryptographic hash of the file at path <em class="replaceable"><code>p</code></em>. The
+ hash algorithm specified by <em class="replaceable"><code>type</code></em> must
+ be one of <code class="literal">"md5"</code>, <code class="literal">"sha1"</code>,
+ <code class="literal">"sha256"</code> or <code class="literal">"sha512"</code>.</p></dd><dt><a id="builtin-head"></a><span class="term"><code class="function">builtins.head</code>
+ <em class="replaceable"><code>list</code></em></span></dt><dd><p>Return the first element of a list; abort
+ evaluation if the argument isn’t a list or is an empty list. You
+ can test whether a list is empty by comparing it with
+ <code class="literal">[]</code>.</p></dd><dt><a id="builtin-import"></a><span class="term"><code class="function">import</code>
+ <em class="replaceable"><code>path</code></em>, </span><span class="term"><code class="function">builtins.import</code>
+ <em class="replaceable"><code>path</code></em></span></dt><dd><p>Load, parse and return the Nix expression in the
+ file <em class="replaceable"><code>path</code></em>. If <em class="replaceable"><code>path
+ </code></em> is a directory, the file <code class="filename">default.nix
+ </code> in that directory is loaded. Evaluation aborts if the
+ file doesn’t exist or contains an incorrect Nix expression.
+ <code class="function">import</code> implements Nix’s module system: you
+ can put any Nix expression (such as a set or a function) in a
+ separate file, and use it from Nix expressions in other
+ files.</p><div class="note"><h3 class="title">Note</h3><p>Unlike some languages, <code class="function">import</code> is a regular
+ function in Nix. Paths using the angle bracket syntax (e.g., <code class="function">
+ import</code> <em class="replaceable"><code><foo></code></em>) are normal path
+ values (see <a class="xref" href="#ssec-values" title="15.1. Values">Section 15.1, “Values”</a>).</p></div><p>A Nix expression loaded by <code class="function">import</code> must
+ not contain any <span class="emphasis"><em>free variables</em></span> (identifiers
+ that are not defined in the Nix expression itself and are not
+ built-in). Therefore, it cannot refer to variables that are in
+ scope at the call site. For instance, if you have a calling
+ expression
+
+</p><pre class="programlisting">
+rec {
+ x = 123;
+ y = import ./foo.nix;
+}</pre><p>
+
+ then the following <code class="filename">foo.nix</code> will give an
+ error:
+
+</p><pre class="programlisting">
+x + 456</pre><p>
+
+ since <code class="varname">x</code> is not in scope in
+ <code class="filename">foo.nix</code>. If you want <code class="varname">x</code>
+ to be available in <code class="filename">foo.nix</code>, you should pass
+ it as a function argument:
+
+</p><pre class="programlisting">
+rec {
+ x = 123;
+ y = import ./foo.nix x;
+}</pre><p>
+
+ and
+
+</p><pre class="programlisting">
+x: x + 456</pre><p>
+
+ (The function argument doesn’t have to be called
+ <code class="varname">x</code> in <code class="filename">foo.nix</code>; any name
+ would work.)</p></dd><dt><a id="builtin-intersectAttrs"></a><span class="term"><code class="function">builtins.intersectAttrs</code>
+ <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>Return a set consisting of the attributes in the
+ set <em class="replaceable"><code>e2</code></em> that also exist in the set
+ <em class="replaceable"><code>e1</code></em>.</p></dd><dt><a id="builtin-isAttrs"></a><span class="term"><code class="function">builtins.isAttrs</code>
+ <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return <code class="literal">true</code> if
+ <em class="replaceable"><code>e</code></em> evaluates to a set, and
+ <code class="literal">false</code> otherwise.</p></dd><dt><a id="builtin-isList"></a><span class="term"><code class="function">builtins.isList</code>
+ <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return <code class="literal">true</code> if
+ <em class="replaceable"><code>e</code></em> evaluates to a list, and
+ <code class="literal">false</code> otherwise.</p></dd><dt><a id="builtin-isFunction"></a><span class="term"><code class="function">builtins.isFunction</code>
+ <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return <code class="literal">true</code> if
+ <em class="replaceable"><code>e</code></em> evaluates to a function, and
+ <code class="literal">false</code> otherwise.</p></dd><dt><a id="builtin-isString"></a><span class="term"><code class="function">builtins.isString</code>
+ <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return <code class="literal">true</code> if
+ <em class="replaceable"><code>e</code></em> evaluates to a string, and
+ <code class="literal">false</code> otherwise.</p></dd><dt><a id="builtin-isInt"></a><span class="term"><code class="function">builtins.isInt</code>
+ <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return <code class="literal">true</code> if
+ <em class="replaceable"><code>e</code></em> evaluates to an int, and
+ <code class="literal">false</code> otherwise.</p></dd><dt><a id="builtin-isFloat"></a><span class="term"><code class="function">builtins.isFloat</code>
+ <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return <code class="literal">true</code> if
+ <em class="replaceable"><code>e</code></em> evaluates to a float, and
+ <code class="literal">false</code> otherwise.</p></dd><dt><a id="builtin-isBool"></a><span class="term"><code class="function">builtins.isBool</code>
+ <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return <code class="literal">true</code> if
+ <em class="replaceable"><code>e</code></em> evaluates to a bool, and
+ <code class="literal">false</code> otherwise.</p></dd><dt><span class="term"><code class="function">builtins.isPath</code>
+ <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return <code class="literal">true</code> if
+ <em class="replaceable"><code>e</code></em> evaluates to a path, and
+ <code class="literal">false</code> otherwise.</p></dd><dt><a id="builtin-isNull"></a><span class="term"><code class="function">isNull</code>
+ <em class="replaceable"><code>e</code></em>, </span><span class="term"><code class="function">builtins.isNull</code>
+ <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return <code class="literal">true</code> if
+ <em class="replaceable"><code>e</code></em> evaluates to <code class="literal">null</code>,
+ and <code class="literal">false</code> otherwise.</p><div class="warning"><h3 class="title">Warning</h3><p>This function is <span class="emphasis"><em>deprecated</em></span>;
+ just write <code class="literal">e == null</code> instead.</p></div></dd><dt><a id="builtin-length"></a><span class="term"><code class="function">builtins.length</code>
+ <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return the length of the list
+ <em class="replaceable"><code>e</code></em>.</p></dd><dt><a id="builtin-lessThan"></a><span class="term"><code class="function">builtins.lessThan</code>
+ <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>Return <code class="literal">true</code> if the number
+ <em class="replaceable"><code>e1</code></em> is less than the number
+ <em class="replaceable"><code>e2</code></em>, and <code class="literal">false</code>
+ otherwise. Evaluation aborts if either
+ <em class="replaceable"><code>e1</code></em> or <em class="replaceable"><code>e2</code></em>
+ does not evaluate to a number.</p></dd><dt><a id="builtin-listToAttrs"></a><span class="term"><code class="function">builtins.listToAttrs</code>
+ <em class="replaceable"><code>e</code></em></span></dt><dd><p>Construct a set from a list specifying the names
+ and values of each attribute. Each element of the list should be
+ a set consisting of a string-valued attribute
+ <code class="varname">name</code> specifying the name of the attribute, and
+ an attribute <code class="varname">value</code> specifying its value.
+ Example:
+
+</p><pre class="programlisting">
+builtins.listToAttrs
+ [ { name = "foo"; value = 123; }
+ { name = "bar"; value = 456; }
+ ]
+</pre><p>
+
+ evaluates to
+
+</p><pre class="programlisting">
+{ foo = 123; bar = 456; }
+</pre><p>
+
+ </p></dd><dt><a id="builtin-map"></a><span class="term"><code class="function">map</code>
+ <em class="replaceable"><code>f</code></em> <em class="replaceable"><code>list</code></em>, </span><span class="term"><code class="function">builtins.map</code>
+ <em class="replaceable"><code>f</code></em> <em class="replaceable"><code>list</code></em></span></dt><dd><p>Apply the function <em class="replaceable"><code>f</code></em> to
+ each element in the list <em class="replaceable"><code>list</code></em>. For
+ example,
+
+</p><pre class="programlisting">
+map (x: "foo" + x) [ "bar" "bla" "abc" ]</pre><p>
+
+ evaluates to <code class="literal">[ "foobar" "foobla" "fooabc"
+ ]</code>.</p></dd><dt><a id="builtin-match"></a><span class="term"><code class="function">builtins.match</code>
+ <em class="replaceable"><code>regex</code></em> <em class="replaceable"><code>str</code></em></span></dt><dd><p>Returns a list if the <a class="link" href="http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_04" target="_top">extended
+ POSIX regular expression</a> <em class="replaceable"><code>regex</code></em>
+ matches <em class="replaceable"><code>str</code></em> precisely, otherwise returns
+ <code class="literal">null</code>. Each item in the list is a regex group.
+
+</p><pre class="programlisting">
+builtins.match "ab" "abc"
+</pre><p>
+
+Evaluates to <code class="literal">null</code>.
+
+</p><pre class="programlisting">
+builtins.match "abc" "abc"
+</pre><p>
+
+Evaluates to <code class="literal">[ ]</code>.
+
+</p><pre class="programlisting">
+builtins.match "a(b)(c)" "abc"
+</pre><p>
+
+Evaluates to <code class="literal">[ "b" "c" ]</code>.
+
+</p><pre class="programlisting">
+builtins.match "[[:space:]]+([[:upper:]]+)[[:space:]]+" " FOO "
+</pre><p>
+
+Evaluates to <code class="literal">[ "foo" ]</code>.
+
+ </p></dd><dt><a id="builtin-mul"></a><span class="term"><code class="function">builtins.mul</code>
+ <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>Return the product of the numbers
+ <em class="replaceable"><code>e1</code></em> and
+ <em class="replaceable"><code>e2</code></em>.</p></dd><dt><a id="builtin-parseDrvName"></a><span class="term"><code class="function">builtins.parseDrvName</code>
+ <em class="replaceable"><code>s</code></em></span></dt><dd><p>Split the string <em class="replaceable"><code>s</code></em> into
+ a package name and version. The package name is everything up to
+ but not including the first dash followed by a digit, and the
+ version is everything following that dash. The result is returned
+ in a set <code class="literal">{ name, version }</code>. Thus,
+ <code class="literal">builtins.parseDrvName "nix-0.12pre12876"</code>
+ returns <code class="literal">{ name = "nix"; version = "0.12pre12876";
+ }</code>.</p></dd><dt><a id="builtin-path"></a><span class="term">
+ <code class="function">builtins.path</code>
+ <em class="replaceable"><code>args</code></em>
+ </span></dt><dd><p>
+ An enrichment of the built-in path type, based on the attributes
+ present in <em class="replaceable"><code>args</code></em>. All are optional
+ except <code class="varname">path</code>:
+ </p><div class="variablelist"><dl class="variablelist"><dt><span class="term">path</span></dt><dd><p>The underlying path.</p></dd><dt><span class="term">name</span></dt><dd><p>
+ The name of the path when added to the store. This can
+ used to reference paths that have nix-illegal characters
+ in their names, like <code class="literal">@</code>.
+ </p></dd><dt><span class="term">filter</span></dt><dd><p>
+ A function of the type expected by
+ <a class="link" href="#builtin-filterSource">builtins.filterSource</a>,
+ with the same semantics.
+ </p></dd><dt><span class="term">recursive</span></dt><dd><p>
+ When <code class="literal">false</code>, when
+ <code class="varname">path</code> is added to the store it is with a
+ flat hash, rather than a hash of the NAR serialization of
+ the file. Thus, <code class="varname">path</code> must refer to a
+ regular file, not a directory. This allows similar
+ behavior to <code class="literal">fetchurl</code>. Defaults to
+ <code class="literal">true</code>.
+ </p></dd><dt><span class="term">sha256</span></dt><dd><p>
+ When provided, this is the expected hash of the file at
+ the path. Evaluation will fail if the hash is incorrect,
+ and providing a hash allows
+ <code class="literal">builtins.path</code> to be used even when the
+ <code class="literal">pure-eval</code> nix config option is on.
+ </p></dd></dl></div></dd><dt><a id="builtin-pathExists"></a><span class="term"><code class="function">builtins.pathExists</code>
+ <em class="replaceable"><code>path</code></em></span></dt><dd><p>Return <code class="literal">true</code> if the path
+ <em class="replaceable"><code>path</code></em> exists at evaluation time, and
+ <code class="literal">false</code> otherwise.</p></dd><dt><a id="builtin-placeholder"></a><span class="term"><code class="function">builtins.placeholder</code>
+ <em class="replaceable"><code>output</code></em></span></dt><dd><p>Return a placeholder string for the specified
+ <em class="replaceable"><code>output</code></em> that will be substituted by the
+ corresponding output path at build time. Typical outputs would be
+ <code class="literal">"out"</code>, <code class="literal">"bin"</code> or
+ <code class="literal">"dev"</code>.</p></dd><dt><a id="builtin-readDir"></a><span class="term"><code class="function">builtins.readDir</code>
+ <em class="replaceable"><code>path</code></em></span></dt><dd><p>Return the contents of the directory
+ <em class="replaceable"><code>path</code></em> as a set mapping directory entries
+ to the corresponding file type. For instance, if directory
+ <code class="filename">A</code> contains a regular file
+ <code class="filename">B</code> and another directory
+ <code class="filename">C</code>, then <code class="literal">builtins.readDir
+ ./A</code> will return the set
+
+</p><pre class="programlisting">
+{ B = "regular"; C = "directory"; }</pre><p>
+
+ The possible values for the file type are
+ <code class="literal">"regular"</code>, <code class="literal">"directory"</code>,
+ <code class="literal">"symlink"</code> and
+ <code class="literal">"unknown"</code>.</p></dd><dt><a id="builtin-readFile"></a><span class="term"><code class="function">builtins.readFile</code>
+ <em class="replaceable"><code>path</code></em></span></dt><dd><p>Return the contents of the file
+ <em class="replaceable"><code>path</code></em> as a string.</p></dd><dt><a id="builtin-removeAttrs"></a><span class="term"><code class="function">removeAttrs</code>
+ <em class="replaceable"><code>set</code></em> <em class="replaceable"><code>list</code></em>, </span><span class="term"><code class="function">builtins.removeAttrs</code>
+ <em class="replaceable"><code>set</code></em> <em class="replaceable"><code>list</code></em></span></dt><dd><p>Remove the attributes listed in
+ <em class="replaceable"><code>list</code></em> from
+ <em class="replaceable"><code>set</code></em>. The attributes don’t have to
+ exist in <em class="replaceable"><code>set</code></em>. For instance,
+
+</p><pre class="programlisting">
+removeAttrs { x = 1; y = 2; z = 3; } [ "a" "x" "z" ]</pre><p>
+
+ evaluates to <code class="literal">{ y = 2; }</code>.</p></dd><dt><a id="builtin-replaceStrings"></a><span class="term"><code class="function">builtins.replaceStrings</code>
+ <em class="replaceable"><code>from</code></em> <em class="replaceable"><code>to</code></em> <em class="replaceable"><code>s</code></em></span></dt><dd><p>Given string <em class="replaceable"><code>s</code></em>, replace
+ every occurrence of the strings in <em class="replaceable"><code>from</code></em>
+ with the corresponding string in
+ <em class="replaceable"><code>to</code></em>. For example,
+
+</p><pre class="programlisting">
+builtins.replaceStrings ["oo" "a"] ["a" "i"] "foobar"
+</pre><p>
+
+ evaluates to <code class="literal">"fabir"</code>.</p></dd><dt><a id="builtin-seq"></a><span class="term"><code class="function">builtins.seq</code>
+ <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>Evaluate <em class="replaceable"><code>e1</code></em>, then
+ evaluate and return <em class="replaceable"><code>e2</code></em>. This ensures
+ that a computation is strict in the value of
+ <em class="replaceable"><code>e1</code></em>.</p></dd><dt><a id="builtin-sort"></a><span class="term"><code class="function">builtins.sort</code>
+ <em class="replaceable"><code>comparator</code></em> <em class="replaceable"><code>list</code></em></span></dt><dd><p>Return <em class="replaceable"><code>list</code></em> in sorted
+ order. It repeatedly calls the function
+ <em class="replaceable"><code>comparator</code></em> with two elements. The
+ comparator should return <code class="literal">true</code> if the first
+ element is less than the second, and <code class="literal">false</code>
+ otherwise. For example,
+
+</p><pre class="programlisting">
+builtins.sort builtins.lessThan [ 483 249 526 147 42 77 ]
+</pre><p>
+
+ produces the list <code class="literal">[ 42 77 147 249 483 526
+ ]</code>.</p><p>This is a stable sort: it preserves the relative order of
+ elements deemed equal by the comparator.</p></dd><dt><a id="builtin-split"></a><span class="term"><code class="function">builtins.split</code>
+ <em class="replaceable"><code>regex</code></em> <em class="replaceable"><code>str</code></em></span></dt><dd><p>Returns a list composed of non matched strings interleaved
+ with the lists of the <a class="link" href="http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_04" target="_top">extended
+ POSIX regular expression</a> <em class="replaceable"><code>regex</code></em> matches
+ of <em class="replaceable"><code>str</code></em>. Each item in the lists of matched
+ sequences is a regex group.
+
+</p><pre class="programlisting">
+builtins.split "(a)b" "abc"
+</pre><p>
+
+Evaluates to <code class="literal">[ "" [ "a" ] "c" ]</code>.
+
+</p><pre class="programlisting">
+builtins.split "([ac])" "abc"
+</pre><p>
+
+Evaluates to <code class="literal">[ "" [ "a" ] "b" [ "c" ] "" ]</code>.
+
+</p><pre class="programlisting">
+builtins.split "(a)|(c)" "abc"
+</pre><p>
+
+Evaluates to <code class="literal">[ "" [ "a" null ] "b" [ null "c" ] "" ]</code>.
+
+</p><pre class="programlisting">
+builtins.split "([[:upper:]]+)" " FOO "
+</pre><p>
+
+Evaluates to <code class="literal">[ " " [ "FOO" ] " " ]</code>.
+
+ </p></dd><dt><a id="builtin-splitVersion"></a><span class="term"><code class="function">builtins.splitVersion</code>
+ <em class="replaceable"><code>s</code></em></span></dt><dd><p>Split a string representing a version into its
+ components, by the same version splitting logic underlying the
+ version comparison in <a class="link" href="#ssec-version-comparisons" title="Versions">
+ <span class="command"><strong>nix-env -u</strong></span></a>.</p></dd><dt><a id="builtin-stringLength"></a><span class="term"><code class="function">builtins.stringLength</code>
+ <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return the length of the string
+ <em class="replaceable"><code>e</code></em>. If <em class="replaceable"><code>e</code></em> is
+ not a string, evaluation is aborted.</p></dd><dt><a id="builtin-sub"></a><span class="term"><code class="function">builtins.sub</code>
+ <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>Return the difference between the numbers
+ <em class="replaceable"><code>e1</code></em> and
+ <em class="replaceable"><code>e2</code></em>.</p></dd><dt><a id="builtin-substring"></a><span class="term"><code class="function">builtins.substring</code>
+ <em class="replaceable"><code>start</code></em> <em class="replaceable"><code>len</code></em>
+ <em class="replaceable"><code>s</code></em></span></dt><dd><p>Return the substring of
+ <em class="replaceable"><code>s</code></em> from character position
+ <em class="replaceable"><code>start</code></em> (zero-based) up to but not
+ including <em class="replaceable"><code>start + len</code></em>. If
+ <em class="replaceable"><code>start</code></em> is greater than the length of the
+ string, an empty string is returned, and if <em class="replaceable"><code>start +
+ len</code></em> lies beyond the end of the string, only the
+ substring up to the end of the string is returned.
+ <em class="replaceable"><code>start</code></em> must be
+ non-negative. For example,
+
+</p><pre class="programlisting">
+builtins.substring 0 3 "nixos"
+</pre><p>
+
+ evaluates to <code class="literal">"nix"</code>.
+ </p></dd><dt><a id="builtin-tail"></a><span class="term"><code class="function">builtins.tail</code>
+ <em class="replaceable"><code>list</code></em></span></dt><dd><p>Return the second to last elements of a list;
+ abort evaluation if the argument isn’t a list or is an empty
+ list.</p></dd><dt><a id="builtin-throw"></a><span class="term"><code class="function">throw</code>
+ <em class="replaceable"><code>s</code></em>, </span><span class="term"><code class="function">builtins.throw</code>
+ <em class="replaceable"><code>s</code></em></span></dt><dd><p>Throw an error message
+ <em class="replaceable"><code>s</code></em>. This usually aborts Nix expression
+ evaluation, but in <span class="command"><strong>nix-env -qa</strong></span> and other
+ commands that try to evaluate a set of derivations to get
+ information about those derivations, a derivation that throws an
+ error is silently skipped (which is not the case for
+ <code class="function">abort</code>).</p></dd><dt><a id="builtin-toFile"></a><span class="term"><code class="function">builtins.toFile</code>
+ <em class="replaceable"><code>name</code></em>
+ <em class="replaceable"><code>s</code></em></span></dt><dd><p>Store the string <em class="replaceable"><code>s</code></em> in a
+ file in the Nix store and return its path. The file has suffix
+ <em class="replaceable"><code>name</code></em>. This file can be used as an
+ input to derivations. One application is to write builders
+ “inline”. For instance, the following Nix expression combines
+ <a class="xref" href="#ex-hello-nix" title="Example 14.1. Nix expression for GNU Hello (default.nix)">Example 14.1, “Nix expression for GNU Hello
+(<code class="filename">default.nix</code>)”</a> and <a class="xref" href="#ex-hello-builder" title="Example 14.2. Build script for GNU Hello (builder.sh)">Example 14.2, “Build script for GNU Hello
+(<code class="filename">builder.sh</code>)”</a> into one file:
+
+</p><pre class="programlisting">
+{ stdenv, fetchurl, perl }:
+
+stdenv.mkDerivation {
+ name = "hello-2.1.1";
+
+ builder = builtins.toFile "builder.sh" "
+ source $stdenv/setup
+
+ PATH=$perl/bin:$PATH
+
+ tar xvfz $src
+ cd hello-*
+ ./configure --prefix=$out
+ make
+ make install
+ ";
+
+ src = fetchurl {
+ url = "http://ftp.nluug.nl/pub/gnu/hello/hello-2.1.1.tar.gz";
+ sha256 = "1md7jsfd8pa45z73bz1kszpp01yw6x5ljkjk2hx7wl800any6465";
+ };
+ inherit perl;
+}</pre><p>
+
+ </p><p>It is even possible for one file to refer to another, e.g.,
+
+</p><pre class="programlisting">
+ builder = let
+ configFile = builtins.toFile "foo.conf" "
+ # This is some dummy configuration file.
+ <em class="replaceable"><code>...</code></em>
+ ";
+ in builtins.toFile "builder.sh" "
+ source $stdenv/setup
+ <em class="replaceable"><code>...</code></em>
+ cp ${configFile} $out/etc/foo.conf
+ ";</pre><p>
+
+ Note that <code class="literal">${configFile}</code> is an antiquotation
+ (see <a class="xref" href="#ssec-values" title="15.1. Values">Section 15.1, “Values”</a>), so the result of the
+ expression <code class="literal">configFile</code> (i.e., a path like
+ <code class="filename">/nix/store/m7p7jfny445k...-foo.conf</code>) will be
+ spliced into the resulting string.</p><p>It is however <span class="emphasis"><em>not</em></span> allowed to have files
+ mutually referring to each other, like so:
+
+</p><pre class="programlisting">
+let
+ foo = builtins.toFile "foo" "...${bar}...";
+ bar = builtins.toFile "bar" "...${foo}...";
+in foo</pre><p>
+
+ This is not allowed because it would cause a cyclic dependency in
+ the computation of the cryptographic hashes for
+ <code class="varname">foo</code> and <code class="varname">bar</code>.</p><p>It is also not possible to reference the result of a derivation.
+ If you are using Nixpkgs, the <code class="literal">writeTextFile</code> function is able to
+ do that.</p></dd><dt><a id="builtin-toJSON"></a><span class="term"><code class="function">builtins.toJSON</code> <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return a string containing a JSON representation
+ of <em class="replaceable"><code>e</code></em>. Strings, integers, floats, booleans,
+ nulls and lists are mapped to their JSON equivalents. Sets
+ (except derivations) are represented as objects. Derivations are
+ translated to a JSON string containing the derivation’s output
+ path. Paths are copied to the store and represented as a JSON
+ string of the resulting store path.</p></dd><dt><a id="builtin-toPath"></a><span class="term"><code class="function">builtins.toPath</code> <em class="replaceable"><code>s</code></em></span></dt><dd><p> DEPRECATED. Use <code class="literal">/. + "/path"</code>
+ to convert a string into an absolute path. For relative paths,
+ use <code class="literal">./. + "/path"</code>.
+ </p></dd><dt><a id="builtin-toString"></a><span class="term"><code class="function">toString</code> <em class="replaceable"><code>e</code></em>, </span><span class="term"><code class="function">builtins.toString</code> <em class="replaceable"><code>e</code></em></span></dt><dd><p>Convert the expression
+ <em class="replaceable"><code>e</code></em> to a string.
+ <em class="replaceable"><code>e</code></em> can be:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>A string (in which case the string is returned unmodified).</p></li><li class="listitem"><p>A path (e.g., <code class="literal">toString /foo/bar</code> yields <code class="literal">"/foo/bar"</code>.</p></li><li class="listitem"><p>A set containing <code class="literal">{ __toString = self: ...; }</code>.</p></li><li class="listitem"><p>An integer.</p></li><li class="listitem"><p>A list, in which case the string representations of its elements are joined with spaces.</p></li><li class="listitem"><p>A Boolean (<code class="literal">false</code> yields <code class="literal">""</code>, <code class="literal">true</code> yields <code class="literal">"1"</code>).</p></li><li class="listitem"><p><code class="literal">null</code>, which yields the empty string.</p></li></ul></div></dd><dt><a id="builtin-toXML"></a><span class="term"><code class="function">builtins.toXML</code> <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return a string containing an XML representation
+ of <em class="replaceable"><code>e</code></em>. The main application for
+ <code class="function">toXML</code> is to communicate information with the
+ builder in a more structured format than plain environment
+ variables.</p><p><a class="xref" href="#ex-toxml" title="Example 15.8. Passing information to a builder using toXML">Example 15.8, “Passing information to a builder
+ using <code class="function">toXML</code>”</a> shows an example where this is
+ the case. The builder is supposed to generate the configuration
+ file for a <a class="link" href="http://jetty.mortbay.org/" target="_top">Jetty
+ servlet container</a>. A servlet container contains a number
+ of servlets (<code class="filename">*.war</code> files) each exported under
+ a specific URI prefix. So the servlet configuration is a list of
+ sets containing the <code class="varname">path</code> and
+ <code class="varname">war</code> of the servlet (<a class="xref" href="#ex-toxml-co-servlets">(3)</a>). This kind of information is
+ difficult to communicate with the normal method of passing
+ information through an environment variable, which just
+ concatenates everything together into a string (which might just
+ work in this case, but wouldn’t work if fields are optional or
+ contain lists themselves). Instead the Nix expression is
+ converted to an XML representation with
+ <code class="function">toXML</code>, which is unambiguous and can easily be
+ processed with the appropriate tools. For instance, in the
+ example an XSLT stylesheet (<a class="xref" href="#ex-toxml-co-stylesheet">(2)</a>) is applied to it (<a class="xref" href="#ex-toxml-co-apply">(1)</a>) to
+ generate the XML configuration file for the Jetty server. The XML
+ representation produced from <a class="xref" href="#ex-toxml-co-servlets">(3)</a> by <code class="function">toXML</code> is shown in <a class="xref" href="#ex-toxml-result" title="Example 15.9. XML representation produced by toXML">Example 15.9, “XML representation produced by
+ <code class="function">toXML</code>”</a>.</p><p>Note that <a class="xref" href="#ex-toxml" title="Example 15.8. Passing information to a builder using toXML">Example 15.8, “Passing information to a builder
+ using <code class="function">toXML</code>”</a> uses the <code class="function"><a class="function" href="#builtin-toFile">toFile</a></code> built-in to write the
+ builder and the stylesheet “inline” in the Nix expression. The
+ path of the stylesheet is spliced into the builder at
+ <code class="literal">xsltproc ${stylesheet}
+ <em class="replaceable"><code>...</code></em></code>.</p><div class="example"><a id="ex-toxml"></a><p class="title"><strong>Example 15.8. Passing information to a builder
+ using <code class="function">toXML</code></strong></p><div class="example-contents"><pre class="programlisting">
+{ stdenv, fetchurl, libxslt, jira, uberwiki }:
+
+stdenv.mkDerivation (rec {
+ name = "web-server";
+
+ buildInputs = [ libxslt ];
+
+ builder = builtins.toFile "builder.sh" "
+ source $stdenv/setup
+ mkdir $out
+ echo "$servlets" | xsltproc ${stylesheet} - > $out/server-conf.xml <a id="ex-toxml-co-apply"></a>(1)
+ ";
+
+ stylesheet = builtins.toFile "stylesheet.xsl" <a id="ex-toxml-co-stylesheet"></a>(2)
+ "<?xml version='1.0' encoding='UTF-8'?>
+ <xsl:stylesheet xmlns:xsl='http://www.w3.org/1999/XSL/Transform' version='1.0'>
+ <xsl:template match='/'>
+ <Configure>
+ <xsl:for-each select='/expr/list/attrs'>
+ <Call name='addWebApplication'>
+ <Arg><xsl:value-of select=\"attr[@name = 'path']/string/@value\" /></Arg>
+ <Arg><xsl:value-of select=\"attr[@name = 'war']/path/@value\" /></Arg>
+ </Call>
+ </xsl:for-each>
+ </Configure>
+ </xsl:template>
+ </xsl:stylesheet>
+ ";
+
+ servlets = builtins.toXML [ <a id="ex-toxml-co-servlets"></a>(3)
+ { path = "/bugtracker"; war = jira + "/lib/atlassian-jira.war"; }
+ { path = "/wiki"; war = uberwiki + "/uberwiki.war"; }
+ ];
+})</pre></div></div><br class="example-break" /><div class="example"><a id="ex-toxml-result"></a><p class="title"><strong>Example 15.9. XML representation produced by
+ <code class="function">toXML</code></strong></p><div class="example-contents"><pre class="programlisting"><?xml version='1.0' encoding='utf-8'?>
+<expr>
+ <list>
+ <attrs>
+ <attr name="path">
+ <string value="/bugtracker" />
+ </attr>
+ <attr name="war">
+ <path value="/nix/store/d1jh9pasa7k2...-jira/lib/atlassian-jira.war" />
+ </attr>
+ </attrs>
+ <attrs>
+ <attr name="path">
+ <string value="/wiki" />
+ </attr>
+ <attr name="war">
+ <path value="/nix/store/y6423b1yi4sx...-uberwiki/uberwiki.war" />
+ </attr>
+ </attrs>
+ </list>
+</expr></pre></div></div><br class="example-break" /></dd><dt><a id="builtin-trace"></a><span class="term"><code class="function">builtins.trace</code>
+ <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>Evaluate <em class="replaceable"><code>e1</code></em> and print its
+ abstract syntax representation on standard error. Then return
+ <em class="replaceable"><code>e2</code></em>. This function is useful for
+ debugging.</p></dd><dt><a id="builtin-tryEval"></a><span class="term"><code class="function">builtins.tryEval</code>
+ <em class="replaceable"><code>e</code></em></span></dt><dd><p>Try to shallowly evaluate <em class="replaceable"><code>e</code></em>.
+ Return a set containing the attributes <code class="literal">success</code>
+ (<code class="literal">true</code> if <em class="replaceable"><code>e</code></em> evaluated
+ successfully, <code class="literal">false</code> if an error was thrown) and
+ <code class="literal">value</code>, equalling <em class="replaceable"><code>e</code></em>
+ if successful and <code class="literal">false</code> otherwise. Note that this
+ doesn't evaluate <em class="replaceable"><code>e</code></em> deeply, so
+ <code class="literal">let e = { x = throw ""; }; in (builtins.tryEval e).success
+ </code> will be <code class="literal">true</code>. Using <code class="literal">builtins.deepSeq
+ </code> one can get the expected result: <code class="literal">let e = { x = throw "";
+ }; in (builtins.tryEval (builtins.deepSeq e e)).success</code> will be
+ <code class="literal">false</code>.
+ </p></dd><dt><a id="builtin-typeOf"></a><span class="term"><code class="function">builtins.typeOf</code>
+ <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return a string representing the type of the value
+ <em class="replaceable"><code>e</code></em>, namely <code class="literal">"int"</code>,
+ <code class="literal">"bool"</code>, <code class="literal">"string"</code>,
+ <code class="literal">"path"</code>, <code class="literal">"null"</code>,
+ <code class="literal">"set"</code>, <code class="literal">"list"</code>,
+ <code class="literal">"lambda"</code> or
+ <code class="literal">"float"</code>.</p></dd></dl></div></div><div class="footnotes"><br /><hr style="width:100; text-align:left;margin-left: 0" /><div id="ftn.idm139733301368560" class="footnote"><p><a href="#idm139733301368560" class="para"><sup class="para">[5] </sup></a>It's parsed as an expression that selects the
+ attribute <code class="varname">sh</code> from the variable
+ <code class="varname">builder</code>.</p></div><div id="ftn.idm139733301331328" class="footnote"><p><a href="#idm139733301331328" class="para"><sup class="para">[6] </sup></a>Actually, Nix detects infinite
+recursion in this case and aborts (<span class="quote">“<span class="quote">infinite recursion
+encountered</span>”</span>).</p></div><div id="ftn.idm139733301168656" class="footnote"><p><a href="#idm139733301168656" class="para"><sup class="para">[7] </sup></a>To figure out
+ your platform identifier, look at the line <span class="quote">“<span class="quote">Checking for the
+ canonical Nix system name</span>”</span> in the output of Nix's
+ <code class="filename">configure</code> script.</p></div></div></div></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a id="part-advanced-topics"></a>Part V. Advanced Topics</h1></div></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="chap-distributed-builds"></a>Chapter 16. Remote Builds</h2></div></div></div><p>Nix supports remote builds, where a local Nix installation can
+forward Nix builds to other machines. This allows multiple builds to
+be performed in parallel and allows Nix to perform multi-platform
+builds in a semi-transparent way. For instance, if you perform a
+build for a <code class="literal">x86_64-darwin</code> on an
+<code class="literal">i686-linux</code> machine, Nix can automatically forward
+the build to a <code class="literal">x86_64-darwin</code> machine, if
+available.</p><p>To forward a build to a remote machine, it’s required that the
+remote machine is accessible via SSH and that it has Nix
+installed. You can test whether connecting to the remote Nix instance
+works, e.g.
+
+</p><pre class="screen">
+$ nix ping-store --store ssh://mac
+</pre><p>
+
+will try to connect to the machine named <code class="literal">mac</code>. It is
+possible to specify an SSH identity file as part of the remote store
+URI, e.g.
+
+</p><pre class="screen">
+$ nix ping-store --store ssh://mac?ssh-key=/home/alice/my-key
+</pre><p>
+
+Since builds should be non-interactive, the key should not have a
+passphrase. Alternatively, you can load identities ahead of time into
+<span class="command"><strong>ssh-agent</strong></span> or <span class="command"><strong>gpg-agent</strong></span>.</p><p>If you get the error
+
+</p><pre class="screen">
+bash: nix-store: command not found
+error: cannot connect to 'mac'
+</pre><p>
+
+then you need to ensure that the <code class="envar">PATH</code> of
+non-interactive login shells contains Nix.</p><div class="warning"><h3 class="title">Warning</h3><p>If you are building via the Nix daemon, it is the Nix
+daemon user account (that is, <code class="literal">root</code>) that should
+have SSH access to the remote machine. If you can’t or don’t want to
+configure <code class="literal">root</code> to be able to access to remote
+machine, you can use a private Nix store instead by passing
+e.g. <code class="literal">--store ~/my-nix</code>.</p></div><p>The list of remote machines can be specified on the command line
+or in the Nix configuration file. The former is convenient for
+testing. For example, the following command allows you to build a
+derivation for <code class="literal">x86_64-darwin</code> on a Linux machine:
+
+</p><pre class="screen">
+$ uname
+Linux
+
+$ nix build \
+ '(with import <nixpkgs> { system = "x86_64-darwin"; }; runCommand "foo" {} "uname > $out")' \
+ --builders 'ssh://mac x86_64-darwin'
+[1/0/1 built, 0.0 MiB DL] building foo on ssh://mac
+
+$ cat ./result
+Darwin
+</pre><p>
+
+It is possible to specify multiple builders separated by a semicolon
+or a newline, e.g.
+
+</p><pre class="screen">
+ --builders 'ssh://mac x86_64-darwin ; ssh://beastie x86_64-freebsd'
+</pre><p>
+</p><p>Each machine specification consists of the following elements,
+separated by spaces. Only the first element is required.
+To leave a field at its default, set it to <code class="literal">-</code>.
+
+</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>The URI of the remote store in the format
+ <code class="literal">ssh://[<em class="replaceable"><code>username</code></em>@]<em class="replaceable"><code>hostname</code></em></code>,
+ e.g. <code class="literal">ssh://nix@mac</code> or
+ <code class="literal">ssh://mac</code>. For backward compatibility,
+ <code class="literal">ssh://</code> may be omitted. The hostname may be an
+ alias defined in your
+ <code class="filename">~/.ssh/config</code>.</p></li><li class="listitem"><p>A comma-separated list of Nix platform type
+ identifiers, such as <code class="literal">x86_64-darwin</code>. It is
+ possible for a machine to support multiple platform types, e.g.,
+ <code class="literal">i686-linux,x86_64-linux</code>. If omitted, this
+ defaults to the local platform type.</p></li><li class="listitem"><p>The SSH identity file to be used to log in to the
+ remote machine. If omitted, SSH will use its regular
+ identities.</p></li><li class="listitem"><p>The maximum number of builds that Nix will execute
+ in parallel on the machine. Typically this should be equal to the
+ number of CPU cores. For instance, the machine
+ <code class="literal">itchy</code> in the example will execute up to 8 builds
+ in parallel.</p></li><li class="listitem"><p>The “speed factor”, indicating the relative speed of
+ the machine. If there are multiple machines of the right type, Nix
+ will prefer the fastest, taking load into account.</p></li><li class="listitem"><p>A comma-separated list of <span class="emphasis"><em>supported
+ features</em></span>. If a derivation has the
+ <code class="varname">requiredSystemFeatures</code> attribute, then Nix will
+ only perform the derivation on a machine that has the specified
+ features. For instance, the attribute
+
+</p><pre class="programlisting">
+requiredSystemFeatures = [ "kvm" ];
+</pre><p>
+
+ will cause the build to be performed on a machine that has the
+ <code class="literal">kvm</code> feature.</p></li><li class="listitem"><p>A comma-separated list of <span class="emphasis"><em>mandatory
+ features</em></span>. A machine will only be used to build a
+ derivation if all of the machine’s mandatory features appear in the
+ derivation’s <code class="varname">requiredSystemFeatures</code>
+ attribute..</p></li></ol></div><p>
+
+For example, the machine specification
+
+</p><pre class="programlisting">
+nix@scratchy.labs.cs.uu.nl i686-linux /home/nix/.ssh/id_scratchy_auto 8 1 kvm
+nix@itchy.labs.cs.uu.nl i686-linux /home/nix/.ssh/id_scratchy_auto 8 2
+nix@poochie.labs.cs.uu.nl i686-linux /home/nix/.ssh/id_scratchy_auto 1 2 kvm benchmark
+</pre><p>
+
+specifies several machines that can perform
+<code class="literal">i686-linux</code> builds. However,
+<code class="literal">poochie</code> will only do builds that have the attribute
+
+</p><pre class="programlisting">
+requiredSystemFeatures = [ "benchmark" ];
+</pre><p>
+
+or
+
+</p><pre class="programlisting">
+requiredSystemFeatures = [ "benchmark" "kvm" ];
+</pre><p>
+
+<code class="literal">itchy</code> cannot do builds that require
+<code class="literal">kvm</code>, but <code class="literal">scratchy</code> does support
+such builds. For regular builds, <code class="literal">itchy</code> will be
+preferred over <code class="literal">scratchy</code> because it has a higher
+speed factor.</p><p>Remote builders can also be configured in
+<code class="filename">nix.conf</code>, e.g.
+
+</p><pre class="programlisting">
+builders = ssh://mac x86_64-darwin ; ssh://beastie x86_64-freebsd
+</pre><p>
+
+Finally, remote builders can be configured in a separate configuration
+file included in <code class="option">builders</code> via the syntax
+<code class="literal">@<em class="replaceable"><code>file</code></em></code>. For example,
+
+</p><pre class="programlisting">
+builders = @/etc/nix/machines
+</pre><p>
+
+causes the list of machines in <code class="filename">/etc/nix/machines</code>
+to be included. (This is the default.)</p><p>If you want the builders to use caches, you likely want to set
+the option <a class="link" href="#conf-builders-use-substitutes"><code class="literal">builders-use-substitutes</code></a>
+in your local <code class="filename">nix.conf</code>.</p><p>To build only on remote builders and disable building on the local machine,
+you can use the option <code class="option">--max-jobs 0</code>.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="chap-tuning-cores-and-jobs"></a>Chapter 17. Tuning Cores and Jobs</h2></div></div></div><p>Nix has two relevant settings with regards to how your CPU cores
+will be utilized: <a class="xref" href="#conf-cores"><code class="literal">cores</code></a> and
+<a class="xref" href="#conf-max-jobs"><code class="literal">max-jobs</code></a>. This chapter will talk about what
+they are, how they interact, and their configuration trade-offs.</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><a class="xref" href="#conf-max-jobs"><code class="literal">max-jobs</code></a></span></dt><dd><p>
+ Dictates how many separate derivations will be built at the same
+ time. If you set this to zero, the local machine will do no
+ builds. Nix will still substitute from binary caches, and build
+ remotely if remote builders are configured.
+ </p></dd><dt><span class="term"><a class="xref" href="#conf-cores"><code class="literal">cores</code></a></span></dt><dd><p>
+ Suggests how many cores each derivation should use. Similar to
+ <span class="command"><strong>make -j</strong></span>.
+ </p></dd></dl></div><p>The <a class="xref" href="#conf-cores"><code class="literal">cores</code></a> setting determines the value of
+<code class="envar">NIX_BUILD_CORES</code>. <code class="envar">NIX_BUILD_CORES</code> is equal
+to <a class="xref" href="#conf-cores"><code class="literal">cores</code></a>, unless <a class="xref" href="#conf-cores"><code class="literal">cores</code></a>
+equals <code class="literal">0</code>, in which case <code class="envar">NIX_BUILD_CORES</code>
+will be the total number of cores in the system.</p><p>The maximum number of consumed cores is a simple multiplication,
+<a class="xref" href="#conf-max-jobs"><code class="literal">max-jobs</code></a> * <code class="envar">NIX_BUILD_CORES</code>.</p><p>The balance on how to set these two independent variables depends
+upon each builder's workload and hardware. Here are a few example
+scenarios on a machine with 24 cores:</p><div class="table"><a id="idm139733300537552"></a><p class="title"><strong>Table 17.1. Balancing 24 Build Cores</strong></p><div class="table-contents"><table><thead><tr>
+ <th><a class="xref" href="#conf-max-jobs"><code class="literal">max-jobs</code></a></th>
+ <th><a class="xref" href="#conf-cores"><code class="literal">cores</code></a></th>
+ <th><code class="envar">NIX_BUILD_CORES</code></th>
+ <th>Maximum Processes</th>
+ <th>Result</th>
+ </tr></thead><tbody><tr>
+ <td>1</td>
+ <td>24</td>
+ <td>24</td>
+ <td>24</td>
+ <td>
+ One derivation will be built at a time, each one can use 24
+ cores. Undersold if a job can’t use 24 cores.
+ </td>
+ </tr><tr>
+ <td>4</td>
+ <td>6</td>
+ <td>6</td>
+ <td>24</td>
+ <td>
+ Four derivations will be built at once, each given access to
+ six cores.
+ </td>
+ </tr><tr>
+ <td>12</td>
+ <td>6</td>
+ <td>6</td>
+ <td>72</td>
+ <td>
+ 12 derivations will be built at once, each given access to six
+ cores. This configuration is over-sold. If all 12 derivations
+ being built simultaneously try to use all six cores, the
+ machine's performance will be degraded due to extensive context
+ switching between the 12 builds.
+ </td>
+ </tr><tr>
+ <td>24</td>
+ <td>1</td>
+ <td>1</td>
+ <td>24</td>
+ <td>
+ 24 derivations can build at the same time, each using a single
+ core. Never oversold, but derivations which require many cores
+ will be very slow to compile.
+ </td>
+ </tr><tr>
+ <td>24</td>
+ <td>0</td>
+ <td>24</td>
+ <td>576</td>
+ <td>
+ 24 derivations can build at the same time, each using all the
+ available cores of the machine. Very likely to be oversold,
+ and very likely to suffer context switches.
+ </td>
+ </tr></tbody></table></div></div><br class="table-break" /><p>It is up to the derivations' build script to respect
+host's requested cores-per-build by following the value of the
+<code class="envar">NIX_BUILD_CORES</code> environment variable.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="chap-diff-hook"></a>Chapter 18. Verifying Build Reproducibility with <code class="option"><a class="option" href="#conf-diff-hook">diff-hook</a></code></h2></div><div><h3 class="subtitle"><em>Check build reproducibility by running builds multiple times
+and comparing their results.</em></h3></div></div></div><p>Specify a program with Nix's <a class="xref" href="#conf-diff-hook"><code class="literal">diff-hook</code></a> to
+compare build results when two builds produce different results. Note:
+this hook is only executed if the results are not the same, this hook
+is not used for determining if the results are the same.</p><p>For purposes of demonstration, we'll use the following Nix file,
+<code class="filename">deterministic.nix</code> for testing:</p><pre class="programlisting">
+let
+ inherit (import <nixpkgs> {}) runCommand;
+in {
+ stable = runCommand "stable" {} ''
+ touch $out
+ '';
+
+ unstable = runCommand "unstable" {} ''
+ echo $RANDOM > $out
+ '';
+}
+</pre><p>Additionally, <code class="filename">nix.conf</code> contains:
+
+</p><pre class="programlisting">
+diff-hook = /etc/nix/my-diff-hook
+run-diff-hook = true
+</pre><p>
+
+where <code class="filename">/etc/nix/my-diff-hook</code> is an executable
+file containing:
+
+</p><pre class="programlisting">
+#!/bin/sh
+exec >&2
+echo "For derivation $3:"
+/run/current-system/sw/bin/diff -r "$1" "$2"
+</pre><p>
+
+</p><p>The diff hook is executed by the same user and group who ran the
+build. However, the diff hook does not have write access to the store
+path just built.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733300510624"></a>18.1.
+ Spot-Checking Build Determinism
+ </h2></div></div></div><p>
+ Verify a path which already exists in the Nix store by passing
+ <code class="option">--check</code> to the build command.
+ </p><p>If the build passes and is deterministic, Nix will exit with a
+ status code of 0:</p><pre class="screen">
+$ nix-build ./deterministic.nix -A stable
+this derivation will be built:
+ /nix/store/z98fasz2jqy9gs0xbvdj939p27jwda38-stable.drv
+building '/nix/store/z98fasz2jqy9gs0xbvdj939p27jwda38-stable.drv'...
+/nix/store/yyxlzw3vqaas7wfp04g0b1xg51f2czgq-stable
+
+$ nix-build ./deterministic.nix -A stable --check
+checking outputs of '/nix/store/z98fasz2jqy9gs0xbvdj939p27jwda38-stable.drv'...
+/nix/store/yyxlzw3vqaas7wfp04g0b1xg51f2czgq-stable
+</pre><p>If the build is not deterministic, Nix will exit with a status
+ code of 1:</p><pre class="screen">
+$ nix-build ./deterministic.nix -A unstable
+this derivation will be built:
+ /nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv
+building '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv'...
+/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable
+
+$ nix-build ./deterministic.nix -A unstable --check
+checking outputs of '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv'...
+error: derivation '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv' may not be deterministic: output '/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable' differs
+</pre><p>In the Nix daemon's log, we will now see:
+</p><pre class="screen">
+For derivation /nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv:
+1c1
+< 8108
+---
+> 30204
+</pre><p>
+</p><p>Using <code class="option">--check</code> with <code class="option">--keep-failed</code>
+ will cause Nix to keep the second build's output in a special,
+ <code class="literal">.check</code> path:</p><pre class="screen">
+$ nix-build ./deterministic.nix -A unstable --check --keep-failed
+checking outputs of '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv'...
+note: keeping build directory '/tmp/nix-build-unstable.drv-0'
+error: derivation '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv' may not be deterministic: output '/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable' differs from '/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable.check'
+</pre><p>In particular, notice the
+ <code class="literal">/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable.check</code>
+ output. Nix has copied the build results to that directory where you
+ can examine it.</p><div class="note"><h3 class="title"><a id="check-dirs-are-unregistered"></a><code class="literal">.check</code> paths are not registered store paths</h3><p>Check paths are not protected against garbage collection,
+ and this path will be deleted on the next garbage collection.</p><p>The path is guaranteed to be alive for the duration of
+ <a class="xref" href="#conf-diff-hook"><code class="literal">diff-hook</code></a>'s execution, but may be deleted
+ any time after.</p><p>If the comparison is performed as part of automated tooling,
+ please use the diff-hook or author your tooling to handle the case
+ where the build was not deterministic and also a check path does
+ not exist.</p></div><p>
+ <code class="option">--check</code> is only usable if the derivation has
+ been built on the system already. If the derivation has not been
+ built Nix will fail with the error:
+ </p><pre class="screen">
+error: some outputs of '/nix/store/hzi1h60z2qf0nb85iwnpvrai3j2w7rr6-unstable.drv' are not valid, so checking is not possible
+</pre><p>
+
+ Run the build without <code class="option">--check</code>, and then try with
+ <code class="option">--check</code> again.
+ </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733300495744"></a>18.2.
+ Automatic and Optionally Enforced Determinism Verification
+ </h2></div></div></div><p>
+ Automatically verify every build at build time by executing the
+ build multiple times.
+ </p><p>
+ Setting <a class="xref" href="#conf-repeat"><code class="literal">repeat</code></a> and
+ <a class="xref" href="#conf-enforce-determinism"><code class="literal">enforce-determinism</code></a> in your
+ <code class="filename">nix.conf</code> permits the automated verification
+ of every build Nix performs.
+ </p><p>
+ The following configuration will run each build three times, and
+ will require the build to be deterministic:
+
+ </p><pre class="programlisting">
+enforce-determinism = true
+repeat = 2
+</pre><p>
+ </p><p>
+ Setting <a class="xref" href="#conf-enforce-determinism"><code class="literal">enforce-determinism</code></a> to false as in
+ the following configuration will run the build multiple times,
+ execute the build hook, but will allow the build to succeed even
+ if it does not build reproducibly:
+
+ </p><pre class="programlisting">
+enforce-determinism = false
+repeat = 1
+</pre><p>
+ </p><p>
+ An example output of this configuration:
+ </p><pre class="screen">
+$ nix-build ./test.nix -A unstable
+this derivation will be built:
+ /nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv
+building '/nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv' (round 1/2)...
+building '/nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv' (round 2/2)...
+output '/nix/store/6xg356v9gl03hpbbg8gws77n19qanh02-unstable' of '/nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv' differs from '/nix/store/6xg356v9gl03hpbbg8gws77n19qanh02-unstable.check' from previous round
+/nix/store/6xg356v9gl03hpbbg8gws77n19qanh02-unstable
+</pre><p>
+ </p></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="chap-post-build-hook"></a>Chapter 19. Using the <code class="option"><a class="option" href="#conf-post-build-hook">post-build-hook</a></code></h2></div><div><h3 class="subtitle"><em>Uploading to an S3-compatible binary cache after each build</em></h3></div></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="chap-post-build-hook-caveats"></a>19.1. Implementation Caveats</h2></div></div></div><p>Here we use the post-build hook to upload to a binary cache.
+ This is a simple and working example, but it is not suitable for all
+ use cases.</p><p>The post build hook program runs after each executed build,
+ and blocks the build loop. The build loop exits if the hook program
+ fails.</p><p>Concretely, this implementation will make Nix slow or unusable
+ when the internet is slow or unreliable.</p><p>A more advanced implementation might pass the store paths to a
+ user-supplied daemon or queue for processing the store paths outside
+ of the build loop.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733300481840"></a>19.2. Prerequisites</h2></div></div></div><p>
+ This tutorial assumes you have configured an S3-compatible binary cache
+ according to the instructions at
+ <a class="xref" href="#ssec-s3-substituter-authenticated-writes" title="13.4.3. Authenticated Writes to your S3-compatible binary cache">Section 13.4.3, “Authenticated Writes to your S3-compatible binary cache”</a>, and
+ that the <code class="literal">root</code> user's default AWS profile can
+ upload to the bucket.
+ </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733300479440"></a>19.3. Set up a Signing Key</h2></div></div></div><p>Use <span class="command"><strong>nix-store --generate-binary-cache-key</strong></span> to
+ create our public and private signing keys. We will sign paths
+ with the private key, and distribute the public key for verifying
+ the authenticity of the paths.</p><pre class="screen">
+# nix-store --generate-binary-cache-key example-nix-cache-1 /etc/nix/key.private /etc/nix/key.public
+# cat /etc/nix/key.public
+example-nix-cache-1:1/cKDz3QCCOmwcztD2eV6Coggp6rqc9DGjWv7C0G+rM=
+</pre><p>Then, add the public key and the cache URL to your
+<code class="filename">nix.conf</code>'s <a class="xref" href="#conf-trusted-public-keys"><code class="literal">trusted-public-keys</code></a>
+and <a class="xref" href="#conf-substituters"><code class="literal">substituters</code></a> like:</p><pre class="programlisting">
+substituters = https://cache.nixos.org/ s3://example-nix-cache
+trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= example-nix-cache-1:1/cKDz3QCCOmwcztD2eV6Coggp6rqc9DGjWv7C0G+rM=
+</pre><p>We will restart the Nix daemon in a later step.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733300473952"></a>19.4. Implementing the build hook</h2></div></div></div><p>Write the following script to
+ <code class="filename">/etc/nix/upload-to-cache.sh</code>:
+ </p><pre class="programlisting">
+#!/bin/sh
+
+set -eu
+set -f # disable globbing
+export IFS=' '
+
+echo "Signing paths" $OUT_PATHS
+nix sign-paths --key-file /etc/nix/key.private $OUT_PATHS
+echo "Uploading paths" $OUT_PATHS
+exec nix copy --to 's3://example-nix-cache' $OUT_PATHS
+</pre><div class="note"><h3 class="title">Should <code class="literal">$OUT_PATHS</code> be quoted?</h3><p>
+ The <code class="literal">$OUT_PATHS</code> variable is a space-separated
+ list of Nix store paths. In this case, we expect and want the
+ shell to perform word splitting to make each output path its
+ own argument to <span class="command"><strong>nix sign-paths</strong></span>. Nix guarantees
+ the paths will not contain any spaces, however a store path
+ might contain glob characters. The <span class="command"><strong>set -f</strong></span>
+ disables globbing in the shell.
+ </p></div><p>
+ Then make sure the hook program is executable by the <code class="literal">root</code> user:
+ </p><pre class="screen">
+# chmod +x /etc/nix/upload-to-cache.sh
+</pre></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733300467040"></a>19.5. Updating Nix Configuration</h2></div></div></div><p>Edit <code class="filename">/etc/nix/nix.conf</code> to run our hook,
+ by adding the following configuration snippet at the end:</p><pre class="programlisting">
+post-build-hook = /etc/nix/upload-to-cache.sh
+</pre><p>Then, restart the <span class="command"><strong>nix-daemon</strong></span>.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733300464016"></a>19.6. Testing</h2></div></div></div><p>Build any derivation, for example:</p><pre class="screen">
+$ nix-build -E '(import <nixpkgs> {}).writeText "example" (builtins.toString builtins.currentTime)'
+this derivation will be built:
+ /nix/store/s4pnfbkalzy5qz57qs6yybna8wylkig6-example.drv
+building '/nix/store/s4pnfbkalzy5qz57qs6yybna8wylkig6-example.drv'...
+running post-build-hook '/home/grahamc/projects/github.com/NixOS/nix/post-hook.sh'...
+post-build-hook: Signing paths /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
+post-build-hook: Uploading paths /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
+/nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
+</pre><p>Then delete the path from the store, and try substituting it from the binary cache:</p><pre class="screen">
+$ rm ./result
+$ nix-store --delete /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
+</pre><p>Now, copy the path back from the cache:</p><pre class="screen">
+$ nix-store --realise /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
+copying path '/nix/store/m8bmqwrch6l3h8s0k3d673xpmipcdpsa-example from 's3://example-nix-cache'...
+warning: you did not specify '--add-root'; the result might be removed by the garbage collector
+/nix/store/m8bmqwrch6l3h8s0k3d673xpmipcdpsa-example
+</pre></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733300459088"></a>19.7. Conclusion</h2></div></div></div><p>
+ We now have a Nix installation configured to automatically sign and
+ upload every local build to a remote binary cache.
+ </p><p>
+ Before deploying this to production, be sure to consider the
+ implementation caveats in <a class="xref" href="#chap-post-build-hook-caveats" title="19.1. Implementation Caveats">Section 19.1, “Implementation Caveats”</a>.
+ </p></div></div></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a id="part-command-ref"></a>Part VI. Command Reference</h1></div></div></div><div class="partintro"><div></div><p>This section lists commands and options that you can use when you
+work with Nix.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="sec-common-options"></a>Chapter 20. Common Options</h2></div></div></div><p>Most Nix commands accept the following command-line options:</p><div class="variablelist"><a id="opt-common"></a><dl class="variablelist"><dt><span class="term"><code class="option">--help</code></span></dt><dd><p>Prints out a summary of the command syntax and
+ exits.</p></dd><dt><span class="term"><code class="option">--version</code></span></dt><dd><p>Prints out the Nix version number on standard output
+ and exits.</p></dd><dt><span class="term"><code class="option">--verbose</code> / <code class="option">-v</code></span></dt><dd><p>Increases the level of verbosity of diagnostic messages
+ printed on standard error. For each Nix operation, the information
+ printed on standard output is well-defined; any diagnostic
+ information is printed on standard error, never on standard
+ output.</p><p>This option may be specified repeatedly. Currently, the
+ following verbosity levels exist:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term">0</span></dt><dd><p>“Errors only”: only print messages
+ explaining why the Nix invocation failed.</p></dd><dt><span class="term">1</span></dt><dd><p>“Informational”: print
+ <span class="emphasis"><em>useful</em></span> messages about what Nix is doing.
+ This is the default.</p></dd><dt><span class="term">2</span></dt><dd><p>“Talkative”: print more informational
+ messages.</p></dd><dt><span class="term">3</span></dt><dd><p>“Chatty”: print even more
+ informational messages.</p></dd><dt><span class="term">4</span></dt><dd><p>“Debug”: print debug
+ information.</p></dd><dt><span class="term">5</span></dt><dd><p>“Vomit”: print vast amounts of debug
+ information.</p></dd></dl></div></dd><dt><span class="term"><code class="option">--quiet</code></span></dt><dd><p>Decreases the level of verbosity of diagnostic messages
+ printed on standard error. This is the inverse option to
+ <code class="option">-v</code> / <code class="option">--verbose</code>.
+ </p><p>This option may be specified repeatedly. See the previous
+ verbosity levels list.</p></dd><dt><a id="opt-log-format"></a><span class="term"><code class="option">--log-format</code> <em class="replaceable"><code>format</code></em></span></dt><dd><p>This option can be used to change the output of the log format, with
+ <em class="replaceable"><code>format</code></em> being one of:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term">raw</span></dt><dd><p>This is the raw format, as outputted by nix-build.</p></dd><dt><span class="term">internal-json</span></dt><dd><p>Outputs the logs in a structured manner. NOTE: the json schema is not guarantees to be stable between releases.</p></dd><dt><span class="term">bar</span></dt><dd><p>Only display a progress bar during the builds.</p></dd><dt><span class="term">bar-with-logs</span></dt><dd><p>Display the raw logs, with the progress bar at the bottom.</p></dd></dl></div></dd><dt><span class="term"><code class="option">--no-build-output</code> / <code class="option">-Q</code></span></dt><dd><p>By default, output written by builders to standard
+ output and standard error is echoed to the Nix command's standard
+ error. This option suppresses this behaviour. Note that the
+ builder's standard output and error are always written to a log file
+ in
+ <code class="filename"><em class="replaceable"><code>prefix</code></em>/nix/var/log/nix</code>.</p></dd><dt><a id="opt-max-jobs"></a><span class="term"><code class="option">--max-jobs</code> / <code class="option">-j</code>
+<em class="replaceable"><code>number</code></em></span></dt><dd><p>Sets the maximum number of build jobs that Nix will
+ perform in parallel to the specified number. Specify
+ <code class="literal">auto</code> to use the number of CPUs in the system.
+ The default is specified by the <a class="link" href="#conf-max-jobs"><code class="literal">max-jobs</code></a>
+ configuration setting, which itself defaults to
+ <code class="literal">1</code>. A higher value is useful on SMP systems or to
+ exploit I/O latency.</p><p> Setting it to <code class="literal">0</code> disallows building on the local
+ machine, which is useful when you want builds to happen only on remote
+ builders.</p></dd><dt><a id="opt-cores"></a><span class="term"><code class="option">--cores</code></span></dt><dd><p>Sets the value of the <code class="envar">NIX_BUILD_CORES</code>
+ environment variable in the invocation of builders. Builders can
+ use this variable at their discretion to control the maximum amount
+ of parallelism. For instance, in Nixpkgs, if the derivation
+ attribute <code class="varname">enableParallelBuilding</code> is set to
+ <code class="literal">true</code>, the builder passes the
+ <code class="option">-j<em class="replaceable"><code>N</code></em></code> flag to GNU Make.
+ It defaults to the value of the <a class="link" href="#conf-cores"><code class="literal">cores</code></a>
+ configuration setting, if set, or <code class="literal">1</code> otherwise.
+ The value <code class="literal">0</code> means that the builder should use all
+ available CPU cores in the system.</p></dd><dt><a id="opt-max-silent-time"></a><span class="term"><code class="option">--max-silent-time</code></span></dt><dd><p>Sets the maximum number of seconds that a builder
+ can go without producing any data on standard output or standard
+ error. The default is specified by the <a class="link" href="#conf-max-silent-time"><code class="literal">max-silent-time</code></a>
+ configuration setting. <code class="literal">0</code> means no
+ time-out.</p></dd><dt><a id="opt-timeout"></a><span class="term"><code class="option">--timeout</code></span></dt><dd><p>Sets the maximum number of seconds that a builder
+ can run. The default is specified by the <a class="link" href="#conf-timeout"><code class="literal">timeout</code></a>
+ configuration setting. <code class="literal">0</code> means no
+ timeout.</p></dd><dt><span class="term"><code class="option">--keep-going</code> / <code class="option">-k</code></span></dt><dd><p>Keep going in case of failed builds, to the
+ greatest extent possible. That is, if building an input of some
+ derivation fails, Nix will still build the other inputs, but not the
+ derivation itself. Without this option, Nix stops if any build
+ fails (except for builds of substitutes), possibly killing builds in
+ progress (in case of parallel or distributed builds).</p></dd><dt><span class="term"><code class="option">--keep-failed</code> / <code class="option">-K</code></span></dt><dd><p>Specifies that in case of a build failure, the
+ temporary directory (usually in <code class="filename">/tmp</code>) in which
+ the build takes place should not be deleted. The path of the build
+ directory is printed as an informational message.
+ </p></dd><dt><span class="term"><code class="option">--fallback</code></span></dt><dd><p>Whenever Nix attempts to build a derivation for which
+ substitutes are known for each output path, but realising the output
+ paths through the substitutes fails, fall back on building the
+ derivation.</p><p>The most common scenario in which this is useful is when we
+ have registered substitutes in order to perform binary distribution
+ from, say, a network repository. If the repository is down, the
+ realisation of the derivation will fail. When this option is
+ specified, Nix will build the derivation instead. Thus,
+ installation from binaries falls back on installation from source.
+ This option is not the default since it is generally not desirable
+ for a transient failure in obtaining the substitutes to lead to a
+ full build from source (with the related consumption of
+ resources).</p></dd><dt><span class="term"><code class="option">--no-build-hook</code></span></dt><dd><p>Disables the build hook mechanism. This allows to ignore remote
+ builders if they are setup on the machine.</p><p>It's useful in cases where the bandwidth between the client and the
+ remote builder is too low. In that case it can take more time to upload the
+ sources to the remote builder and fetch back the result than to do the
+ computation locally.</p></dd><dt><span class="term"><code class="option">--readonly-mode</code></span></dt><dd><p>When this option is used, no attempt is made to open
+ the Nix database. Most Nix operations do need database access, so
+ those operations will fail.</p></dd><dt><span class="term"><code class="option">--arg</code> <em class="replaceable"><code>name</code></em> <em class="replaceable"><code>value</code></em></span></dt><dd><p>This option is accepted by
+ <span class="command"><strong>nix-env</strong></span>, <span class="command"><strong>nix-instantiate</strong></span>,
+ <span class="command"><strong>nix-shell</strong></span> and <span class="command"><strong>nix-build</strong></span>.
+ When evaluating Nix expressions, the expression evaluator will
+ automatically try to call functions that
+ it encounters. It can automatically call functions for which every
+ argument has a <a class="link" href="#ss-functions" title="Functions">default value</a>
+ (e.g., <code class="literal">{ <em class="replaceable"><code>argName</code></em> ?
+ <em class="replaceable"><code>defaultValue</code></em> }:
+ <em class="replaceable"><code>...</code></em></code>). With
+ <code class="option">--arg</code>, you can also call functions that have
+ arguments without a default value (or override a default value).
+ That is, if the evaluator encounters a function with an argument
+ named <em class="replaceable"><code>name</code></em>, it will call it with value
+ <em class="replaceable"><code>value</code></em>.</p><p>For instance, the top-level <code class="literal">default.nix</code> in
+ Nixpkgs is actually a function:
+
+</p><pre class="programlisting">
+{ # The system (e.g., `i686-linux') for which to build the packages.
+ system ? builtins.currentSystem
+ <em class="replaceable"><code>...</code></em>
+}: <em class="replaceable"><code>...</code></em></pre><p>
+
+ So if you call this Nix expression (e.g., when you do
+ <code class="literal">nix-env -i <em class="replaceable"><code>pkgname</code></em></code>),
+ the function will be called automatically using the value <a class="link" href="#builtin-currentSystem"><code class="literal">builtins.currentSystem</code></a>
+ for the <code class="literal">system</code> argument. You can override this
+ using <code class="option">--arg</code>, e.g., <code class="literal">nix-env -i
+ <em class="replaceable"><code>pkgname</code></em> --arg system
+ \"i686-freebsd\"</code>. (Note that since the argument is a Nix
+ string literal, you have to escape the quotes.)</p></dd><dt><span class="term"><code class="option">--argstr</code> <em class="replaceable"><code>name</code></em> <em class="replaceable"><code>value</code></em></span></dt><dd><p>This option is like <code class="option">--arg</code>, only the
+ value is not a Nix expression but a string. So instead of
+ <code class="literal">--arg system \"i686-linux\"</code> (the outer quotes are
+ to keep the shell happy) you can say <code class="literal">--argstr system
+ i686-linux</code>.</p></dd><dt><a id="opt-attr"></a><span class="term"><code class="option">--attr</code> / <code class="option">-A</code>
+<em class="replaceable"><code>attrPath</code></em></span></dt><dd><p>Select an attribute from the top-level Nix
+ expression being evaluated. (<span class="command"><strong>nix-env</strong></span>,
+ <span class="command"><strong>nix-instantiate</strong></span>, <span class="command"><strong>nix-build</strong></span> and
+ <span class="command"><strong>nix-shell</strong></span> only.) The <span class="emphasis"><em>attribute
+ path</em></span> <em class="replaceable"><code>attrPath</code></em> is a sequence of
+ attribute names separated by dots. For instance, given a top-level
+ Nix expression <em class="replaceable"><code>e</code></em>, the attribute path
+ <code class="literal">xorg.xorgserver</code> would cause the expression
+ <code class="literal"><em class="replaceable"><code>e</code></em>.xorg.xorgserver</code> to
+ be used. See <a class="link" href="#refsec-nix-env-install-examples" title="Examples"><span class="command"><strong>nix-env
+ --install</strong></span></a> for some concrete examples.</p><p>In addition to attribute names, you can also specify array
+ indices. For instance, the attribute path
+ <code class="literal">foo.3.bar</code> selects the <code class="literal">bar</code>
+ attribute of the fourth element of the array in the
+ <code class="literal">foo</code> attribute of the top-level
+ expression.</p></dd><dt><span class="term"><code class="option">--expr</code> / <code class="option">-E</code></span></dt><dd><p>Interpret the command line arguments as a list of
+ Nix expressions to be parsed and evaluated, rather than as a list
+ of file names of Nix expressions.
+ (<span class="command"><strong>nix-instantiate</strong></span>, <span class="command"><strong>nix-build</strong></span>
+ and <span class="command"><strong>nix-shell</strong></span> only.)</p><p>For <span class="command"><strong>nix-shell</strong></span>, this option is commonly used
+ to give you a shell in which you can build the packages returned
+ by the expression. If you want to get a shell which contain the
+ <span class="emphasis"><em>built</em></span> packages ready for use, give your
+ expression to the <span class="command"><strong>nix-shell -p</strong></span> convenience flag
+ instead.</p></dd><dt><a id="opt-I"></a><span class="term"><code class="option">-I</code> <em class="replaceable"><code>path</code></em></span></dt><dd><p>Add a path to the Nix expression search path. This
+ option may be given multiple times. See the <code class="envar"><a class="envar" href="#env-NIX_PATH">NIX_PATH</a></code> environment variable for
+ information on the semantics of the Nix search path. Paths added
+ through <code class="option">-I</code> take precedence over
+ <code class="envar">NIX_PATH</code>.</p></dd><dt><span class="term"><code class="option">--option</code> <em class="replaceable"><code>name</code></em> <em class="replaceable"><code>value</code></em></span></dt><dd><p>Set the Nix configuration option
+ <em class="replaceable"><code>name</code></em> to <em class="replaceable"><code>value</code></em>.
+ This overrides settings in the Nix configuration file (see
+ <span class="citerefentry"><span class="refentrytitle">nix.conf</span>(5)</span>).</p></dd><dt><span class="term"><code class="option">--repair</code></span></dt><dd><p>Fix corrupted or missing store paths by
+ redownloading or rebuilding them. Note that this is slow because it
+ requires computing a cryptographic hash of the contents of every
+ path in the closure of the build. Also note the warning under
+ <span class="command"><strong>nix-store --repair-path</strong></span>.</p></dd></dl></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="sec-common-env"></a>Chapter 21. Common Environment Variables</h2></div></div></div><p>Most Nix commands interpret the following environment variables:</p><div class="variablelist"><a id="env-common"></a><dl class="variablelist"><dt><span class="term"><code class="envar">IN_NIX_SHELL</code></span></dt><dd><p>Indicator that tells if the current environment was set up by
+ <span class="command"><strong>nix-shell</strong></span>. Since Nix 2.0 the values are
+ <code class="literal">"pure"</code> and <code class="literal">"impure"</code></p></dd><dt><a id="env-NIX_PATH"></a><span class="term"><code class="envar">NIX_PATH</code></span></dt><dd><p>A colon-separated list of directories used to look up Nix
+ expressions enclosed in angle brackets (i.e.,
+ <code class="literal"><<em class="replaceable"><code>path</code></em>></code>). For
+ instance, the value
+
+ </p><pre class="screen">
+/home/eelco/Dev:/etc/nixos</pre><p>
+
+ will cause Nix to look for paths relative to
+ <code class="filename">/home/eelco/Dev</code> and
+ <code class="filename">/etc/nixos</code>, in this order. It is also
+ possible to match paths against a prefix. For example, the value
+
+ </p><pre class="screen">
+nixpkgs=/home/eelco/Dev/nixpkgs-branch:/etc/nixos</pre><p>
+
+ will cause Nix to search for
+ <code class="literal"><nixpkgs/<em class="replaceable"><code>path</code></em>></code> in
+ <code class="filename">/home/eelco/Dev/nixpkgs-branch/<em class="replaceable"><code>path</code></em></code>
+ and
+ <code class="filename">/etc/nixos/nixpkgs/<em class="replaceable"><code>path</code></em></code>.</p><p>If a path in the Nix search path starts with
+ <code class="literal">http://</code> or <code class="literal">https://</code>, it is
+ interpreted as the URL of a tarball that will be downloaded and
+ unpacked to a temporary location. The tarball must consist of a
+ single top-level directory. For example, setting
+ <code class="envar">NIX_PATH</code> to
+
+ </p><pre class="screen">
+nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-15.09.tar.gz</pre><p>
+
+ tells Nix to download the latest revision in the Nixpkgs/NixOS
+ 15.09 channel.</p><p>A following shorthand can be used to refer to the official channels:
+
+ </p><pre class="screen">nixpkgs=channel:nixos-15.09</pre><p>
+ </p><p>The search path can be extended using the <code class="option"><a class="option" href="#opt-I">-I</a></code> option, which takes precedence over
+ <code class="envar">NIX_PATH</code>.</p></dd><dt><span class="term"><code class="envar">NIX_IGNORE_SYMLINK_STORE</code></span></dt><dd><p>Normally, the Nix store directory (typically
+ <code class="filename">/nix/store</code>) is not allowed to contain any
+ symlink components. This is to prevent “impure” builds. Builders
+ sometimes “canonicalise” paths by resolving all symlink components.
+ Thus, builds on different machines (with
+ <code class="filename">/nix/store</code> resolving to different locations)
+ could yield different results. This is generally not a problem,
+ except when builds are deployed to machines where
+ <code class="filename">/nix/store</code> resolves differently. If you are
+ sure that you’re not going to do that, you can set
+ <code class="envar">NIX_IGNORE_SYMLINK_STORE</code> to <code class="envar">1</code>.</p><p>Note that if you’re symlinking the Nix store so that you can
+ put it on another file system than the root file system, on Linux
+ you’re better off using <code class="literal">bind</code> mount points, e.g.,
+
+ </p><pre class="screen">
+$ mkdir /nix
+$ mount -o bind /mnt/otherdisk/nix /nix</pre><p>
+
+ Consult the <span class="citerefentry"><span class="refentrytitle">mount</span>(8)</span> manual page for details.</p></dd><dt><span class="term"><code class="envar">NIX_STORE_DIR</code></span></dt><dd><p>Overrides the location of the Nix store (default
+ <code class="filename"><em class="replaceable"><code>prefix</code></em>/store</code>).</p></dd><dt><span class="term"><code class="envar">NIX_DATA_DIR</code></span></dt><dd><p>Overrides the location of the Nix static data
+ directory (default
+ <code class="filename"><em class="replaceable"><code>prefix</code></em>/share</code>).</p></dd><dt><span class="term"><code class="envar">NIX_LOG_DIR</code></span></dt><dd><p>Overrides the location of the Nix log directory
+ (default <code class="filename"><em class="replaceable"><code>prefix</code></em>/var/log/nix</code>).</p></dd><dt><span class="term"><code class="envar">NIX_STATE_DIR</code></span></dt><dd><p>Overrides the location of the Nix state directory
+ (default <code class="filename"><em class="replaceable"><code>prefix</code></em>/var/nix</code>).</p></dd><dt><span class="term"><code class="envar">NIX_CONF_DIR</code></span></dt><dd><p>Overrides the location of the system Nix configuration
+ directory (default
+ <code class="filename"><em class="replaceable"><code>prefix</code></em>/etc/nix</code>).</p></dd><dt><span class="term"><code class="envar">NIX_USER_CONF_FILES</code></span></dt><dd><p>Overrides the location of the user Nix configuration files
+ to load from (defaults to the XDG spec locations). The variable is treated
+ as a list separated by the <code class="literal">:</code> token.</p></dd><dt><span class="term"><code class="envar">TMPDIR</code></span></dt><dd><p>Use the specified directory to store temporary
+ files. In particular, this includes temporary build directories;
+ these can take up substantial amounts of disk space. The default is
+ <code class="filename">/tmp</code>.</p></dd><dt><a id="envar-remote"></a><span class="term"><code class="envar">NIX_REMOTE</code></span></dt><dd><p>This variable should be set to
+ <code class="literal">daemon</code> if you want to use the Nix daemon to
+ execute Nix operations. This is necessary in <a class="link" href="#ssec-multi-user" title="6.2. Multi-User Mode">multi-user Nix installations</a>.
+ If the Nix daemon's Unix socket is at some non-standard path,
+ this variable should be set to <code class="literal">unix://path/to/socket</code>.
+ Otherwise, it should be left unset.</p></dd><dt><span class="term"><code class="envar">NIX_SHOW_STATS</code></span></dt><dd><p>If set to <code class="literal">1</code>, Nix will print some
+ evaluation statistics, such as the number of values
+ allocated.</p></dd><dt><span class="term"><code class="envar">NIX_COUNT_CALLS</code></span></dt><dd><p>If set to <code class="literal">1</code>, Nix will print how
+ often functions were called during Nix expression evaluation. This
+ is useful for profiling your Nix expressions.</p></dd><dt><span class="term"><code class="envar">GC_INITIAL_HEAP_SIZE</code></span></dt><dd><p>If Nix has been configured to use the Boehm garbage
+ collector, this variable sets the initial size of the heap in bytes.
+ It defaults to 384 MiB. Setting it to a low value reduces memory
+ consumption, but will increase runtime due to the overhead of
+ garbage collection.</p></dd></dl></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-main-commands"></a>Chapter 22. Main Commands</h2></div></div></div><p>This section lists commands and options that you can use when you
+work with Nix.</p><div class="refentry"><a id="sec-nix-env"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix-env — manipulate or query Nix user environments</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">nix-env</code> [<code class="option">--help</code>] [<code class="option">--version</code>] [
+ { <code class="option">--verbose</code> | <code class="option">-v</code> }
+...] [
+ <code class="option">--quiet</code>
+] [
+ <code class="option">--log-format</code>
+ <em class="replaceable"><code>format</code></em>
+] [
+ <code class="option">--no-build-output</code> | <code class="option">-Q</code>
+] [
+ { <code class="option">--max-jobs</code> | <code class="option">-j</code> }
+ <em class="replaceable"><code>number</code></em>
+] [
+ <code class="option">--cores</code>
+ <em class="replaceable"><code>number</code></em>
+] [
+ <code class="option">--max-silent-time</code>
+ <em class="replaceable"><code>number</code></em>
+] [
+ <code class="option">--timeout</code>
+ <em class="replaceable"><code>number</code></em>
+] [
+ <code class="option">--keep-going</code> | <code class="option">-k</code>
+] [
+ <code class="option">--keep-failed</code> | <code class="option">-K</code>
+] [<code class="option">--fallback</code>] [<code class="option">--readonly-mode</code>] [
+ <code class="option">-I</code>
+ <em class="replaceable"><code>path</code></em>
+] [
+ <code class="option">--option</code>
+ <em class="replaceable"><code>name</code></em>
+ <em class="replaceable"><code>value</code></em>
+]<br /> [<code class="option">--arg</code> <em class="replaceable"><code>name</code></em> <em class="replaceable"><code>value</code></em>] [<code class="option">--argstr</code> <em class="replaceable"><code>name</code></em> <em class="replaceable"><code>value</code></em>] [
+ { <code class="option">--file</code> | <code class="option">-f</code> }
+ <em class="replaceable"><code>path</code></em>
+ ] [
+ { <code class="option">--profile</code> | <code class="option">-p</code> }
+ <em class="replaceable"><code>path</code></em>
+ ] [
+ <code class="option">--system-filter</code>
+ <em class="replaceable"><code>system</code></em>
+ ] [<code class="option">--dry-run</code>] <em class="replaceable"><code>operation</code></em> [<em class="replaceable"><code>options</code></em>...] [<em class="replaceable"><code>arguments</code></em>...]</p></div></div><div class="refsection"><a id="idm139733300260096"></a><h2>Description</h2><p>The command <span class="command"><strong>nix-env</strong></span> is used to manipulate Nix
+user environments. User environments are sets of software packages
+available to a user at some point in time. In other words, they are a
+synthesised view of the programs available in the Nix store. There
+may be many user environments: different users can have different
+environments, and individual users can switch between different
+environments.</p><p><span class="command"><strong>nix-env</strong></span> takes exactly one
+<span class="emphasis"><em>operation</em></span> flag which indicates the subcommand to
+be performed. These are documented below.</p></div><div class="refsection"><a id="idm139733300256528"></a><h2>Selectors</h2><p>Several commands, such as <span class="command"><strong>nix-env -q</strong></span> and
+<span class="command"><strong>nix-env -i</strong></span>, take a list of arguments that specify
+the packages on which to operate. These are extended regular
+expressions that must match the entire name of the package. (For
+details on regular expressions, see
+<span class="citerefentry"><span class="refentrytitle">regex</span>(7)</span>.)
+The match is case-sensitive. The regular expression can optionally be
+followed by a dash and a version number; if omitted, any version of
+the package will match. Here are some examples:
+
+</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">firefox</code></span></dt><dd><p>Matches the package name
+ <code class="literal">firefox</code> and any version.</p></dd><dt><span class="term"><code class="literal">firefox-32.0</code></span></dt><dd><p>Matches the package name
+ <code class="literal">firefox</code> and version
+ <code class="literal">32.0</code>.</p></dd><dt><span class="term"><code class="literal">gtk\\+</code></span></dt><dd><p>Matches the package name
+ <code class="literal">gtk+</code>. The <code class="literal">+</code> character must
+ be escaped using a backslash to prevent it from being interpreted
+ as a quantifier, and the backslash must be escaped in turn with
+ another backslash to ensure that the shell passes it
+ on.</p></dd><dt><span class="term"><code class="literal">.\*</code></span></dt><dd><p>Matches any package name. This is the default for
+ most commands.</p></dd><dt><span class="term"><code class="literal">'.*zip.*'</code></span></dt><dd><p>Matches any package name containing the string
+ <code class="literal">zip</code>. Note the dots: <code class="literal">'*zip*'</code>
+ does not work, because in a regular expression, the character
+ <code class="literal">*</code> is interpreted as a
+ quantifier.</p></dd><dt><span class="term"><code class="literal">'.*(firefox|chromium).*'</code></span></dt><dd><p>Matches any package name containing the strings
+ <code class="literal">firefox</code> or
+ <code class="literal">chromium</code>.</p></dd></dl></div><p>
+
+</p></div><div class="refsection"><a id="idm139733300238960"></a><h2>Common options</h2><p>This section lists the options that are common to all
+operations. These options are allowed for every subcommand, though
+they may not always have an effect. <span class="phrase">See
+also <a class="xref" href="#sec-common-options" title="Chapter 20. Common Options">Chapter 20, <em>Common Options</em></a>.</span></p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--file</code> / <code class="option">-f</code> <em class="replaceable"><code>path</code></em></span></dt><dd><p>Specifies the Nix expression (designated below as
+ the <span class="emphasis"><em>active Nix expression</em></span>) used by the
+ <code class="option">--install</code>, <code class="option">--upgrade</code>, and
+ <code class="option">--query --available</code> operations to obtain
+ derivations. The default is
+ <code class="filename">~/.nix-defexpr</code>.</p><p>If the argument starts with <code class="literal">http://</code> or
+ <code class="literal">https://</code>, it is interpreted as the URL of a
+ tarball that will be downloaded and unpacked to a temporary
+ location. The tarball must include a single top-level directory
+ containing at least a file named <code class="filename">default.nix</code>.</p></dd><dt><span class="term"><code class="option">--profile</code> / <code class="option">-p</code> <em class="replaceable"><code>path</code></em></span></dt><dd><p>Specifies the profile to be used by those
+ operations that operate on a profile (designated below as the
+ <span class="emphasis"><em>active profile</em></span>). A profile is a sequence of
+ user environments called <span class="emphasis"><em>generations</em></span>, one of
+ which is the <span class="emphasis"><em>current
+ generation</em></span>.</p></dd><dt><span class="term"><code class="option">--dry-run</code></span></dt><dd><p>For the <code class="option">--install</code>,
+ <code class="option">--upgrade</code>, <code class="option">--uninstall</code>,
+ <code class="option">--switch-generation</code>,
+ <code class="option">--delete-generations</code> and
+ <code class="option">--rollback</code> operations, this flag will cause
+ <span class="command"><strong>nix-env</strong></span> to print what
+ <span class="emphasis"><em>would</em></span> be done if this flag had not been
+ specified, without actually doing it.</p><p><code class="option">--dry-run</code> also prints out which paths will
+ be <a class="link" href="#gloss-substitute" title="substitute">substituted</a> (i.e.,
+ downloaded) and which paths will be built from source (because no
+ substitute is available).</p></dd><dt><span class="term"><code class="option">--system-filter</code> <em class="replaceable"><code>system</code></em></span></dt><dd><p>By default, operations such as <code class="option">--query
+ --available</code> show derivations matching any platform. This
+ option allows you to use derivations for the specified platform
+ <em class="replaceable"><code>system</code></em>.</p></dd></dl></div></div><div class="refsection"><a id="idm139733300216432"></a><h2>Files</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="filename">~/.nix-defexpr</code></span></dt><dd><p>The source for the default Nix
+ expressions used by the <code class="option">--install</code>,
+ <code class="option">--upgrade</code>, and <code class="option">--query
+ --available</code> operations to obtain derivations. The
+ <code class="option">--file</code> option may be used to override this
+ default.</p><p>If <code class="filename">~/.nix-defexpr</code> is a file,
+ it is loaded as a Nix expression. If the expression
+ is a set, it is used as the default Nix expression.
+ If the expression is a function, an empty set is passed
+ as argument and the return value is used as
+ the default Nix expression.</p><p>If <code class="filename">~/.nix-defexpr</code> is a directory
+ containing a <code class="filename">default.nix</code> file, that file
+ is loaded as in the above paragraph.</p><p>If <code class="filename">~/.nix-defexpr</code> is a directory without
+ a <code class="filename">default.nix</code> file, then its contents
+ (both files and subdirectories) are loaded as Nix expressions.
+ The expressions are combined into a single set, each expression
+ under an attribute with the same name as the original file
+ or subdirectory.
+ </p><p>For example, if <code class="filename">~/.nix-defexpr</code> contains
+ two files, <code class="filename">foo.nix</code> and <code class="filename">bar.nix</code>,
+ then the default Nix expression will essentially be
+
+</p><pre class="programlisting">
+{
+ foo = import ~/.nix-defexpr/foo.nix;
+ bar = import ~/.nix-defexpr/bar.nix;
+}</pre><p>
+
+ </p><p>The file <code class="filename">manifest.nix</code> is always ignored.
+ Subdirectories without a <code class="filename">default.nix</code> file
+ are traversed recursively in search of more Nix expressions,
+ but the names of these intermediate directories are not
+ added to the attribute paths of the default Nix expression.</p><p>The command <span class="command"><strong>nix-channel</strong></span> places symlinks
+ to the downloaded Nix expressions from each subscribed channel in
+ this directory.</p></dd><dt><span class="term"><code class="filename">~/.nix-profile</code></span></dt><dd><p>A symbolic link to the user's current profile. By
+ default, this symlink points to
+ <code class="filename"><em class="replaceable"><code>prefix</code></em>/var/nix/profiles/default</code>.
+ The <code class="envar">PATH</code> environment variable should include
+ <code class="filename">~/.nix-profile/bin</code> for the user environment
+ to be visible to the user.</p></dd></dl></div></div><div class="refsection"><a id="rsec-nix-env-install"></a><h2>Operation <code class="option">--install</code></h2><div class="refsection"><a id="idm139733300198432"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-env</code> { <code class="option">--install</code> | <code class="option">-i</code> } [
+ { <code class="option">--prebuilt-only</code> | <code class="option">-b</code> }
+ ] [
+ { <code class="option">--attr</code> | <code class="option">-A</code> }
+ ] [<code class="option">--from-expression</code>] [<code class="option">-E</code>] [<code class="option">--from-profile</code> <em class="replaceable"><code>path</code></em>] [ <code class="option">--preserve-installed</code> | <code class="option">-P</code> ] [ <code class="option">--remove-all</code> | <code class="option">-r</code> ] <em class="replaceable"><code>args</code></em>... </p></div></div><div class="refsection"><a id="idm139733300182432"></a><h3>Description</h3><p>The install operation creates a new user environment, based on
+the current generation of the active profile, to which a set of store
+paths described by <em class="replaceable"><code>args</code></em> is added. The
+arguments <em class="replaceable"><code>args</code></em> map to store paths in a
+number of possible ways:
+
+</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>By default, <em class="replaceable"><code>args</code></em> is a set
+ of derivation names denoting derivations in the active Nix
+ expression. These are realised, and the resulting output paths are
+ installed. Currently installed derivations with a name equal to the
+ name of a derivation being added are removed unless the option
+ <code class="option">--preserve-installed</code> is
+ specified.</p><p>If there are multiple derivations matching a name in
+ <em class="replaceable"><code>args</code></em> that have the same name (e.g.,
+ <code class="literal">gcc-3.3.6</code> and <code class="literal">gcc-4.1.1</code>), then
+ the derivation with the highest <span class="emphasis"><em>priority</em></span> is
+ used. A derivation can define a priority by declaring the
+ <code class="varname">meta.priority</code> attribute. This attribute should
+ be a number, with a higher value denoting a lower priority. The
+ default priority is <code class="literal">0</code>.</p><p>If there are multiple matching derivations with the same
+ priority, then the derivation with the highest version will be
+ installed.</p><p>You can force the installation of multiple derivations with
+ the same name by being specific about the versions. For instance,
+ <code class="literal">nix-env -i gcc-3.3.6 gcc-4.1.1</code> will install both
+ version of GCC (and will probably cause a user environment
+ conflict!).</p></li><li class="listitem"><p>If <a class="link" href="#opt-attr"><code class="option">--attr</code></a>
+ (<code class="option">-A</code>) is specified, the arguments are
+ <span class="emphasis"><em>attribute paths</em></span> that select attributes from the
+ top-level Nix expression. This is faster than using derivation
+ names and unambiguous. To find out the attribute paths of available
+ packages, use <code class="literal">nix-env -qaP</code>.</p></li><li class="listitem"><p>If <code class="option">--from-profile</code>
+ <em class="replaceable"><code>path</code></em> is given,
+ <em class="replaceable"><code>args</code></em> is a set of names denoting installed
+ store paths in the profile <em class="replaceable"><code>path</code></em>. This is
+ an easy way to copy user environment elements from one profile to
+ another.</p></li><li class="listitem"><p>If <code class="option">--from-expression</code> is given,
+ <em class="replaceable"><code>args</code></em> are Nix <a class="link" href="#ss-functions" title="Functions">functions</a> that are called with the
+ active Nix expression as their single argument. The derivations
+ returned by those function calls are installed. This allows
+ derivations to be specified in an unambiguous way, which is necessary
+ if there are multiple derivations with the same
+ name.</p></li><li class="listitem"><p>If <em class="replaceable"><code>args</code></em> are store
+ derivations, then these are <a class="link" href="#rsec-nix-store-realise" title="Operation --realise">realised</a>, and the resulting
+ output paths are installed.</p></li><li class="listitem"><p>If <em class="replaceable"><code>args</code></em> are store paths
+ that are not store derivations, then these are <a class="link" href="#rsec-nix-store-realise" title="Operation --realise">realised</a> and
+ installed.</p></li><li class="listitem"><p>By default all outputs are installed for each derivation.
+ That can be reduced by setting <code class="literal">meta.outputsToInstall</code>.
+ </p></li></ul></div><p>
+
+</p></div><div class="refsection"><a id="idm139733300160752"></a><h3>Flags</h3><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--prebuilt-only</code> / <code class="option">-b</code></span></dt><dd><p>Use only derivations for which a substitute is
+ registered, i.e., there is a pre-built binary available that can
+ be downloaded in lieu of building the derivation. Thus, no
+ packages will be built from source.</p></dd><dt><span class="term"><code class="option">--preserve-installed</code>, </span><span class="term"><code class="option">-P</code></span></dt><dd><p>Do not remove derivations with a name matching one
+ of the derivations being installed. Usually, trying to have two
+ versions of the same package installed in the same generation of a
+ profile will lead to an error in building the generation, due to
+ file name clashes between the two versions. However, this is not
+ the case for all packages.</p></dd><dt><span class="term"><code class="option">--remove-all</code>, </span><span class="term"><code class="option">-r</code></span></dt><dd><p>Remove all previously installed packages first.
+ This is equivalent to running <code class="literal">nix-env -e '.*'</code>
+ first, except that everything happens in a single
+ transaction.</p></dd></dl></div></div><div class="refsection"><a id="refsec-nix-env-install-examples"></a><h3>Examples</h3><p>To install a specific version of <span class="command"><strong>gcc</strong></span> from the
+active Nix expression:
+
+</p><pre class="screen">
+$ nix-env --install gcc-3.3.2
+installing `gcc-3.3.2'
+uninstalling `gcc-3.1'</pre><p>
+
+Note the previously installed version is removed, since
+<code class="option">--preserve-installed</code> was not specified.</p><p>To install an arbitrary version:
+
+</p><pre class="screen">
+$ nix-env --install gcc
+installing `gcc-3.3.2'</pre><p>
+
+</p><p>To install using a specific attribute:
+
+</p><pre class="screen">
+$ nix-env -i -A gcc40mips
+$ nix-env -i -A xorg.xorgserver</pre><p>
+
+</p><p>To install all derivations in the Nix expression <code class="filename">foo.nix</code>:
+
+</p><pre class="screen">
+$ nix-env -f ~/foo.nix -i '.*'</pre><p>
+
+</p><p>To copy the store path with symbolic name <code class="literal">gcc</code>
+from another profile:
+
+</p><pre class="screen">
+$ nix-env -i --from-profile /nix/var/nix/profiles/foo gcc</pre><p>
+
+</p><p>To install a specific store derivation (typically created by
+<span class="command"><strong>nix-instantiate</strong></span>):
+
+</p><pre class="screen">
+$ nix-env -i /nix/store/fibjb1bfbpm5mrsxc4mh2d8n37sxh91i-gcc-3.4.3.drv</pre><p>
+
+</p><p>To install a specific output path:
+
+</p><pre class="screen">
+$ nix-env -i /nix/store/y3cgx0xj1p4iv9x0pnnmdhr8iyg741vk-gcc-3.4.3</pre><p>
+
+</p><p>To install from a Nix expression specified on the command-line:
+
+</p><pre class="screen">
+$ nix-env -f ./foo.nix -i -E \
+ 'f: (f {system = "i686-linux";}).subversionWithJava'</pre><p>
+
+I.e., this evaluates to <code class="literal">(f: (f {system =
+"i686-linux";}).subversionWithJava) (import ./foo.nix)</code>, thus
+selecting the <code class="literal">subversionWithJava</code> attribute from the
+set returned by calling the function defined in
+<code class="filename">./foo.nix</code>.</p><p>A dry-run tells you which paths will be downloaded or built from
+source:
+
+</p><pre class="screen">
+$ nix-env -f '<nixpkgs>' -iA hello --dry-run
+(dry run; not doing anything)
+installing ‘hello-2.10’
+this path will be fetched (0.04 MiB download, 0.19 MiB unpacked):
+ /nix/store/wkhdf9jinag5750mqlax6z2zbwhqb76n-hello-2.10
+ <em class="replaceable"><code>...</code></em></pre><p>
+
+</p><p>To install Firefox from the latest revision in the Nixpkgs/NixOS
+14.12 channel:
+
+</p><pre class="screen">
+$ nix-env -f https://github.com/NixOS/nixpkgs/archive/nixos-14.12.tar.gz -iA firefox
+</pre><p>
+
+</p></div></div><div class="refsection"><a id="rsec-nix-env-upgrade"></a><h2>Operation <code class="option">--upgrade</code></h2><div class="refsection"><a id="idm139733300136496"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-env</code> { <code class="option">--upgrade</code> | <code class="option">-u</code> } [
+ { <code class="option">--prebuilt-only</code> | <code class="option">-b</code> }
+ ] [
+ { <code class="option">--attr</code> | <code class="option">-A</code> }
+ ] [<code class="option">--from-expression</code>] [<code class="option">-E</code>] [<code class="option">--from-profile</code> <em class="replaceable"><code>path</code></em>] [ <code class="option">--lt</code> | <code class="option">--leq</code> | <code class="option">--eq</code> | <code class="option">--always</code> ] <em class="replaceable"><code>args</code></em>... </p></div></div><div class="refsection"><a id="idm139733300121104"></a><h3>Description</h3><p>The upgrade operation creates a new user environment, based on
+the current generation of the active profile, in which all store paths
+are replaced for which there are newer versions in the set of paths
+described by <em class="replaceable"><code>args</code></em>. Paths for which there
+are no newer versions are left untouched; this is not an error. It is
+also not an error if an element of <em class="replaceable"><code>args</code></em>
+matches no installed derivations.</p><p>For a description of how <em class="replaceable"><code>args</code></em> is
+mapped to a set of store paths, see <a class="link" href="#rsec-nix-env-install" title="Operation --install"><code class="option">--install</code></a>. If
+<em class="replaceable"><code>args</code></em> describes multiple store paths with
+the same symbolic name, only the one with the highest version is
+installed.</p></div><div class="refsection"><a id="idm139733300116496"></a><h3>Flags</h3><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--lt</code></span></dt><dd><p>Only upgrade a derivation to newer versions. This
+ is the default.</p></dd><dt><span class="term"><code class="option">--leq</code></span></dt><dd><p>In addition to upgrading to newer versions, also
+ “upgrade” to derivations that have the same version. Version are
+ not a unique identification of a derivation, so there may be many
+ derivations that have the same version. This flag may be useful
+ to force “synchronisation” between the installed and available
+ derivations.</p></dd><dt><span class="term"><code class="option">--eq</code></span></dt><dd><p><span class="emphasis"><em>Only</em></span> “upgrade” to derivations
+ that have the same version. This may not seem very useful, but it
+ actually is, e.g., when there is a new release of Nixpkgs and you
+ want to replace installed applications with the same versions
+ built against newer dependencies (to reduce the number of
+ dependencies floating around on your system).</p></dd><dt><span class="term"><code class="option">--always</code></span></dt><dd><p>In addition to upgrading to newer versions, also
+ “upgrade” to derivations that have the same or a lower version.
+ I.e., derivations may actually be downgraded depending on what is
+ available in the active Nix expression.</p></dd></dl></div><p>For the other flags, see <code class="option"><a class="option" href="#rsec-nix-env-install" title="Operation --install">--install</a></code>.</p></div><div class="refsection"><a id="idm139733300106960"></a><h3>Examples</h3><pre class="screen">
+$ nix-env --upgrade gcc
+upgrading `gcc-3.3.1' to `gcc-3.4'
+
+$ nix-env -u gcc-3.3.2 --always <em class="lineannotation"><span class="lineannotation">(switch to a specific version)</span></em>
+upgrading `gcc-3.4' to `gcc-3.3.2'
+
+$ nix-env --upgrade pan
+<em class="lineannotation"><span class="lineannotation">(no upgrades available, so nothing happens)</span></em>
+
+$ nix-env -u <em class="lineannotation"><span class="lineannotation">(try to upgrade everything)</span></em>
+upgrading `hello-2.1.2' to `hello-2.1.3'
+upgrading `mozilla-1.2' to `mozilla-1.4'</pre></div><div class="refsection"><a id="ssec-version-comparisons"></a><h3>Versions</h3><p>The upgrade operation determines whether a derivation
+<code class="varname">y</code> is an upgrade of a derivation
+<code class="varname">x</code> by looking at their respective
+<code class="literal">name</code> attributes. The names (e.g.,
+<code class="literal">gcc-3.3.1</code> are split into two parts: the package
+name (<code class="literal">gcc</code>), and the version
+(<code class="literal">3.3.1</code>). The version part starts after the first
+dash not followed by a letter. <code class="varname">x</code> is considered an
+upgrade of <code class="varname">y</code> if their package names match, and the
+version of <code class="varname">y</code> is higher that that of
+<code class="varname">x</code>.</p><p>The versions are compared by splitting them into contiguous
+components of numbers and letters. E.g., <code class="literal">3.3.1pre5</code>
+is split into <code class="literal">[3, 3, 1, "pre", 5]</code>. These lists are
+then compared lexicographically (from left to right). Corresponding
+components <code class="varname">a</code> and <code class="varname">b</code> are compared
+as follows. If they are both numbers, integer comparison is used. If
+<code class="varname">a</code> is an empty string and <code class="varname">b</code> is a
+number, <code class="varname">a</code> is considered less than
+<code class="varname">b</code>. The special string component
+<code class="literal">pre</code> (for <span class="emphasis"><em>pre-release</em></span>) is
+considered to be less than other components. String components are
+considered less than number components. Otherwise, they are compared
+lexicographically (i.e., using case-sensitive string comparison).</p><p>This is illustrated by the following examples:
+
+</p><pre class="screen">
+1.0 < 2.3
+2.1 < 2.3
+2.3 = 2.3
+2.5 > 2.3
+3.1 > 2.3
+2.3.1 > 2.3
+2.3.1 > 2.3a
+2.3pre1 < 2.3
+2.3pre3 < 2.3pre12
+2.3a < 2.3c
+2.3pre1 < 2.3c
+2.3pre1 < 2.3q</pre><p>
+
+</p></div></div><div class="refsection"><a id="idm139733300091392"></a><h2>Operation <code class="option">--uninstall</code></h2><div class="refsection"><a id="idm139733300090560"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-env</code> { <code class="option">--uninstall</code> | <code class="option">-e</code> } <em class="replaceable"><code>drvnames</code></em>... </p></div></div><div class="refsection"><a id="idm139733300085776"></a><h3>Description</h3><p>The uninstall operation creates a new user environment, based on
+the current generation of the active profile, from which the store
+paths designated by the symbolic names
+<em class="replaceable"><code>names</code></em> are removed.</p></div><div class="refsection"><a id="idm139733300084080"></a><h3>Examples</h3><pre class="screen">
+$ nix-env --uninstall gcc
+$ nix-env -e '.*' <em class="lineannotation"><span class="lineannotation">(remove everything)</span></em></pre></div></div><div class="refsection"><a id="rsec-nix-env-set"></a><h2>Operation <code class="option">--set</code></h2><div class="refsection"><a id="idm139733300080928"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-env</code> <code class="option">--set</code> <em class="replaceable"><code>drvname</code></em> </p></div></div><div class="refsection"><a id="idm139733300077824"></a><h3>Description</h3><p>The <code class="option">--set</code> operation modifies the current generation of a
+profile so that it contains exactly the specified derivation, and nothing else.
+</p></div><div class="refsection"><a id="idm139733300076176"></a><h3>Examples</h3><p>
+The following updates a profile such that its current generation will contain
+just Firefox:
+
+</p><pre class="screen">
+$ nix-env -p /nix/var/nix/profiles/browser --set firefox</pre><p>
+
+</p></div></div><div class="refsection"><a id="rsec-nix-env-set-flag"></a><h2>Operation <code class="option">--set-flag</code></h2><div class="refsection"><a id="idm139733300072736"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-env</code> <code class="option">--set-flag</code> <em class="replaceable"><code>name</code></em> <em class="replaceable"><code>value</code></em> <em class="replaceable"><code>drvnames</code></em>... </p></div></div><div class="refsection"><a id="idm139733300067728"></a><h3>Description</h3><p>The <code class="option">--set-flag</code> operation allows meta attributes
+of installed packages to be modified. There are several attributes
+that can be usefully modified, because they affect the behaviour of
+<span class="command"><strong>nix-env</strong></span> or the user environment build
+script:
+
+</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><code class="varname">priority</code> can be changed to
+ resolve filename clashes. The user environment build script uses
+ the <code class="varname">meta.priority</code> attribute of derivations to
+ resolve filename collisions between packages. Lower priority values
+ denote a higher priority. For instance, the GCC wrapper package and
+ the Binutils package in Nixpkgs both have a file
+ <code class="filename">bin/ld</code>, so previously if you tried to install
+ both you would get a collision. Now, on the other hand, the GCC
+ wrapper declares a higher priority than Binutils, so the former’s
+ <code class="filename">bin/ld</code> is symlinked in the user
+ environment.</p></li><li class="listitem"><p><code class="varname">keep</code> can be set to
+ <code class="literal">true</code> to prevent the package from being upgraded
+ or replaced. This is useful if you want to hang on to an older
+ version of a package.</p></li><li class="listitem"><p><code class="varname">active</code> can be set to
+ <code class="literal">false</code> to “disable” the package. That is, no
+ symlinks will be generated to the files of the package, but it
+ remains part of the profile (so it won’t be garbage-collected). It
+ can be set back to <code class="literal">true</code> to re-enable the
+ package.</p></li></ul></div><p>
+
+</p></div><div class="refsection"><a id="idm139733300058816"></a><h3>Examples</h3><p>To prevent the currently installed Firefox from being upgraded:
+
+</p><pre class="screen">
+$ nix-env --set-flag keep true firefox</pre><p>
+
+After this, <span class="command"><strong>nix-env -u</strong></span> will ignore Firefox.</p><p>To disable the currently installed Firefox, then install a new
+Firefox while the old remains part of the profile:
+
+</p><pre class="screen">
+$ nix-env -q
+firefox-2.0.0.9 <em class="lineannotation"><span class="lineannotation">(the current one)</span></em>
+
+$ nix-env --preserve-installed -i firefox-2.0.0.11
+installing `firefox-2.0.0.11'
+building path(s) `/nix/store/myy0y59q3ig70dgq37jqwg1j0rsapzsl-user-environment'
+collision between `/nix/store/<em class="replaceable"><code>...</code></em>-firefox-2.0.0.11/bin/firefox'
+ and `/nix/store/<em class="replaceable"><code>...</code></em>-firefox-2.0.0.9/bin/firefox'.
+<em class="lineannotation"><span class="lineannotation">(i.e., can’t have two active at the same time)</span></em>
+
+$ nix-env --set-flag active false firefox
+setting flag on `firefox-2.0.0.9'
+
+$ nix-env --preserve-installed -i firefox-2.0.0.11
+installing `firefox-2.0.0.11'
+
+$ nix-env -q
+firefox-2.0.0.11 <em class="lineannotation"><span class="lineannotation">(the enabled one)</span></em>
+firefox-2.0.0.9 <em class="lineannotation"><span class="lineannotation">(the disabled one)</span></em></pre><p>
+
+</p><p>To make files from <code class="literal">binutils</code> take precedence
+over files from <code class="literal">gcc</code>:
+
+</p><pre class="screen">
+$ nix-env --set-flag priority 5 binutils
+$ nix-env --set-flag priority 10 gcc</pre><p>
+
+</p></div></div><div class="refsection"><a id="idm139733300050640"></a><h2>Operation <code class="option">--query</code></h2><div class="refsection"><a id="idm139733300049808"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-env</code> { <code class="option">--query</code> | <code class="option">-q</code> } [ <code class="option">--installed</code> | <code class="option">--available</code> | <code class="option">-a</code> ]<br /> [
+ { <code class="option">--status</code> | <code class="option">-s</code> }
+ ] [
+ { <code class="option">--attr-path</code> | <code class="option">-P</code> }
+ ] [<code class="option">--no-name</code>] [
+ { <code class="option">--compare-versions</code> | <code class="option">-c</code> }
+ ] [<code class="option">--system</code>] [<code class="option">--drv-path</code>] [<code class="option">--out-path</code>] [<code class="option">--description</code>] [<code class="option">--meta</code>]<br /> [<code class="option">--xml</code>] [<code class="option">--json</code>] [
+ { <code class="option">--prebuilt-only</code> | <code class="option">-b</code> }
+ ] [
+ { <code class="option">--attr</code> | <code class="option">-A</code> }
+ <em class="replaceable"><code>attribute-path</code></em>
+ ]<br /> <em class="replaceable"><code>names</code></em>... </p></div></div><div class="refsection"><a id="idm139733300023312"></a><h3>Description</h3><p>The query operation displays information about either the store
+paths that are installed in the current generation of the active
+profile (<code class="option">--installed</code>), or the derivations that are
+available for installation in the active Nix expression
+(<code class="option">--available</code>). It only prints information about
+derivations whose symbolic name matches one of
+<em class="replaceable"><code>names</code></em>.</p><p>The derivations are sorted by their <code class="literal">name</code>
+attributes.</p></div><div class="refsection"><a id="idm139733300019760"></a><h3>Source selection</h3><p>The following flags specify the set of things on which the query
+operates.</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--installed</code></span></dt><dd><p>The query operates on the store paths that are
+ installed in the current generation of the active profile. This
+ is the default.</p></dd><dt><span class="term"><code class="option">--available</code>, </span><span class="term"><code class="option">-a</code></span></dt><dd><p>The query operates on the derivations that are
+ available in the active Nix expression.</p></dd></dl></div></div><div class="refsection"><a id="idm139733300014832"></a><h3>Queries</h3><p>The following flags specify what information to display about
+the selected derivations. Multiple flags may be specified, in which
+case the information is shown in the order given here. Note that the
+name of the derivation is shown unless <code class="option">--no-name</code> is
+specified.</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--xml</code></span></dt><dd><p>Print the result in an XML representation suitable
+ for automatic processing by other tools. The root element is
+ called <code class="literal">items</code>, which contains a
+ <code class="literal">item</code> element for each available or installed
+ derivation. The fields discussed below are all stored in
+ attributes of the <code class="literal">item</code>
+ elements.</p></dd><dt><span class="term"><code class="option">--json</code></span></dt><dd><p>Print the result in a JSON representation suitable
+ for automatic processing by other tools.</p></dd><dt><span class="term"><code class="option">--prebuilt-only</code> / <code class="option">-b</code></span></dt><dd><p>Show only derivations for which a substitute is
+ registered, i.e., there is a pre-built binary available that can
+ be downloaded in lieu of building the derivation. Thus, this
+ shows all packages that probably can be installed
+ quickly.</p></dd><dt><span class="term"><code class="option">--status</code>, </span><span class="term"><code class="option">-s</code></span></dt><dd><p>Print the <span class="emphasis"><em>status</em></span> of the
+ derivation. The status consists of three characters. The first
+ is <code class="literal">I</code> or <code class="literal">-</code>, indicating
+ whether the derivation is currently installed in the current
+ generation of the active profile. This is by definition the case
+ for <code class="option">--installed</code>, but not for
+ <code class="option">--available</code>. The second is <code class="literal">P</code>
+ or <code class="literal">-</code>, indicating whether the derivation is
+ present on the system. This indicates whether installation of an
+ available derivation will require the derivation to be built. The
+ third is <code class="literal">S</code> or <code class="literal">-</code>, indicating
+ whether a substitute is available for the
+ derivation.</p></dd><dt><span class="term"><code class="option">--attr-path</code>, </span><span class="term"><code class="option">-P</code></span></dt><dd><p>Print the <span class="emphasis"><em>attribute path</em></span> of
+ the derivation, which can be used to unambiguously select it using
+ the <a class="link" href="#opt-attr"><code class="option">--attr</code> option</a>
+ available in commands that install derivations like
+ <code class="literal">nix-env --install</code>. This option only works
+ together with <code class="option">--available</code></p></dd><dt><span class="term"><code class="option">--no-name</code></span></dt><dd><p>Suppress printing of the <code class="literal">name</code>
+ attribute of each derivation.</p></dd><dt><span class="term"><code class="option">--compare-versions</code> /
+ <code class="option">-c</code></span></dt><dd><p>Compare installed versions to available versions,
+ or vice versa (if <code class="option">--available</code> is given). This is
+ useful for quickly seeing whether upgrades for installed
+ packages are available in a Nix expression. A column is added
+ with the following meaning:
+
+ </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal"><</code> <em class="replaceable"><code>version</code></em></span></dt><dd><p>A newer version of the package is available
+ or installed.</p></dd><dt><span class="term"><code class="literal">=</code> <em class="replaceable"><code>version</code></em></span></dt><dd><p>At most the same version of the package is
+ available or installed.</p></dd><dt><span class="term"><code class="literal">></code> <em class="replaceable"><code>version</code></em></span></dt><dd><p>Only older versions of the package are
+ available or installed.</p></dd><dt><span class="term"><code class="literal">- ?</code></span></dt><dd><p>No version of the package is available or
+ installed.</p></dd></dl></div><p>
+
+ </p></dd><dt><span class="term"><code class="option">--system</code></span></dt><dd><p>Print the <code class="literal">system</code> attribute of
+ the derivation.</p></dd><dt><span class="term"><code class="option">--drv-path</code></span></dt><dd><p>Print the path of the store
+ derivation.</p></dd><dt><span class="term"><code class="option">--out-path</code></span></dt><dd><p>Print the output path of the
+ derivation.</p></dd><dt><span class="term"><code class="option">--description</code></span></dt><dd><p>Print a short (one-line) description of the
+ derivation, if available. The description is taken from the
+ <code class="literal">meta.description</code> attribute of the
+ derivation.</p></dd><dt><span class="term"><code class="option">--meta</code></span></dt><dd><p>Print all of the meta-attributes of the
+ derivation. This option is only available with
+ <code class="option">--xml</code> or <code class="option">--json</code>.</p></dd></dl></div></div><div class="refsection"><a id="idm139733299975552"></a><h3>Examples</h3><p>To show installed packages:
+
+</p><pre class="screen">
+$ nix-env -q
+bison-1.875c
+docbook-xml-4.2
+firefox-1.0.4
+MPlayer-1.0pre7
+ORBit2-2.8.3
+<em class="replaceable"><code>…</code></em>
+</pre><p>
+
+</p><p>To show available packages:
+
+</p><pre class="screen">
+$ nix-env -qa
+firefox-1.0.7
+GConf-2.4.0.1
+MPlayer-1.0pre7
+ORBit2-2.8.3
+<em class="replaceable"><code>…</code></em>
+</pre><p>
+
+</p><p>To show the status of available packages:
+
+</p><pre class="screen">
+$ nix-env -qas
+-P- firefox-1.0.7 <em class="lineannotation"><span class="lineannotation">(not installed but present)</span></em>
+--S GConf-2.4.0.1 <em class="lineannotation"><span class="lineannotation">(not present, but there is a substitute for fast installation)</span></em>
+--S MPlayer-1.0pre3 <em class="lineannotation"><span class="lineannotation">(i.e., this is not the installed MPlayer, even though the version is the same!)</span></em>
+IP- ORBit2-2.8.3 <em class="lineannotation"><span class="lineannotation">(installed and by definition present)</span></em>
+<em class="replaceable"><code>…</code></em>
+</pre><p>
+
+</p><p>To show available packages in the Nix expression <code class="filename">foo.nix</code>:
+
+</p><pre class="screen">
+$ nix-env -f ./foo.nix -qa
+foo-1.2.3
+</pre><p>
+
+</p><p>To compare installed versions to what’s available:
+
+</p><pre class="screen">
+$ nix-env -qc
+<em class="replaceable"><code>...</code></em>
+acrobat-reader-7.0 - ? <em class="lineannotation"><span class="lineannotation">(package is not available at all)</span></em>
+autoconf-2.59 = 2.59 <em class="lineannotation"><span class="lineannotation">(same version)</span></em>
+firefox-1.0.4 < 1.0.7 <em class="lineannotation"><span class="lineannotation">(a more recent version is available)</span></em>
+<em class="replaceable"><code>...</code></em>
+</pre><p>
+
+</p><p>To show all packages with “<code class="literal">zip</code>” in the name:
+
+</p><pre class="screen">
+$ nix-env -qa '.*zip.*'
+bzip2-1.0.6
+gzip-1.6
+zip-3.0
+<em class="replaceable"><code>…</code></em>
+</pre><p>
+
+</p><p>To show all packages with “<code class="literal">firefox</code>” or
+“<code class="literal">chromium</code>” in the name:
+
+</p><pre class="screen">
+$ nix-env -qa '.*(firefox|chromium).*'
+chromium-37.0.2062.94
+chromium-beta-38.0.2125.24
+firefox-32.0.3
+firefox-with-plugins-13.0.1
+<em class="replaceable"><code>…</code></em>
+</pre><p>
+
+</p><p>To show all packages in the latest revision of the Nixpkgs
+repository:
+
+</p><pre class="screen">
+$ nix-env -f https://github.com/NixOS/nixpkgs/archive/master.tar.gz -qa
+</pre><p>
+
+</p></div></div><div class="refsection"><a id="idm139733299959008"></a><h2>Operation <code class="option">--switch-profile</code></h2><div class="refsection"><a id="idm139733299958176"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-env</code> { <code class="option">--switch-profile</code> | <code class="option">-S</code> } {<em class="replaceable"><code>path</code></em>}</p></div></div><div class="refsection"><a id="idm139733299953696"></a><h3>Description</h3><p>This operation makes <em class="replaceable"><code>path</code></em> the current
+profile for the user. That is, the symlink
+<code class="filename">~/.nix-profile</code> is made to point to
+<em class="replaceable"><code>path</code></em>.</p></div><div class="refsection"><a id="idm139733299951328"></a><h3>Examples</h3><pre class="screen">
+$ nix-env -S ~/my-profile</pre></div></div><div class="refsection"><a id="idm139733299949648"></a><h2>Operation <code class="option">--list-generations</code></h2><div class="refsection"><a id="idm139733299948816"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-env</code> <code class="option">--list-generations</code> </p></div></div><div class="refsection"><a id="idm139733299946528"></a><h3>Description</h3><p>This operation print a list of all the currently existing
+generations for the active profile. These may be switched to using
+the <code class="option">--switch-generation</code> operation. It also prints
+the creation date of the generation, and indicates the current
+generation.</p></div><div class="refsection"><a id="idm139733299944800"></a><h3>Examples</h3><pre class="screen">
+$ nix-env --list-generations
+ 95 2004-02-06 11:48:24
+ 96 2004-02-06 11:49:01
+ 97 2004-02-06 16:22:45
+ 98 2004-02-06 16:24:33 (current)</pre></div></div><div class="refsection"><a id="idm139733299943088"></a><h2>Operation <code class="option">--delete-generations</code></h2><div class="refsection"><a id="idm139733299942256"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-env</code> <code class="option">--delete-generations</code> <em class="replaceable"><code>generations</code></em>... </p></div></div><div class="refsection"><a id="idm139733299938880"></a><h3>Description</h3><p>This operation deletes the specified generations of the current
+profile. The generations can be a list of generation numbers, the
+special value <code class="literal">old</code> to delete all non-current
+generations, a value such as <code class="literal">30d</code> to delete all
+generations older than the specified number of days (except for the
+generation that was active at that point in time), or a value such as
+<code class="literal">+5</code> to keep the last <code class="literal">5</code> generations
+ignoring any newer than current, e.g., if <code class="literal">30</code> is the current
+generation <code class="literal">+5</code> will delete generation <code class="literal">25</code>
+and all older generations.
+Periodically deleting old generations is important to make garbage collection
+effective.</p></div><div class="refsection"><a id="idm139733299934384"></a><h3>Examples</h3><pre class="screen">
+$ nix-env --delete-generations 3 4 8
+
+$ nix-env --delete-generations +5
+
+$ nix-env --delete-generations 30d
+
+$ nix-env -p other_profile --delete-generations old</pre></div></div><div class="refsection"><a id="idm139733299932576"></a><h2>Operation <code class="option">--switch-generation</code></h2><div class="refsection"><a id="idm139733299931744"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-env</code> { <code class="option">--switch-generation</code> | <code class="option">-G</code> } {<em class="replaceable"><code>generation</code></em>}</p></div></div><div class="refsection"><a id="idm139733299927264"></a><h3>Description</h3><p>This operation makes generation number
+<em class="replaceable"><code>generation</code></em> the current generation of the
+active profile. That is, if the
+<code class="filename"><em class="replaceable"><code>profile</code></em></code> is the path to
+the active profile, then the symlink
+<code class="filename"><em class="replaceable"><code>profile</code></em></code> is made to
+point to
+<code class="filename"><em class="replaceable"><code>profile</code></em>-<em class="replaceable"><code>generation</code></em>-link</code>,
+which is in turn a symlink to the actual user environment in the Nix
+store.</p><p>Switching will fail if the specified generation does not exist.</p></div><div class="refsection"><a id="idm139733299922880"></a><h3>Examples</h3><pre class="screen">
+$ nix-env -G 42
+switching from generation 50 to 42</pre></div></div><div class="refsection"><a id="idm139733299921184"></a><h2>Operation <code class="option">--rollback</code></h2><div class="refsection"><a id="idm139733299920352"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-env</code> <code class="option">--rollback</code> </p></div></div><div class="refsection"><a id="idm139733299918064"></a><h3>Description</h3><p>This operation switches to the “previous” generation of the
+active profile, that is, the highest numbered generation lower than
+the current generation, if it exists. It is just a convenience
+wrapper around <code class="option">--list-generations</code> and
+<code class="option">--switch-generation</code>.</p></div><div class="refsection"><a id="idm139733299915712"></a><h3>Examples</h3><pre class="screen">
+$ nix-env --rollback
+switching from generation 92 to 91
+
+$ nix-env --rollback
+error: no generation older than the current (91) exists</pre></div></div></div><div class="refentry"><div class="refentry.separator"><hr /></div><a id="sec-nix-build"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix-build — build a Nix expression</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">nix-build</code> [<code class="option">--help</code>] [<code class="option">--version</code>] [
+ { <code class="option">--verbose</code> | <code class="option">-v</code> }
+...] [
+ <code class="option">--quiet</code>
+] [
+ <code class="option">--log-format</code>
+ <em class="replaceable"><code>format</code></em>
+] [
+ <code class="option">--no-build-output</code> | <code class="option">-Q</code>
+] [
+ { <code class="option">--max-jobs</code> | <code class="option">-j</code> }
+ <em class="replaceable"><code>number</code></em>
+] [
+ <code class="option">--cores</code>
+ <em class="replaceable"><code>number</code></em>
+] [
+ <code class="option">--max-silent-time</code>
+ <em class="replaceable"><code>number</code></em>
+] [
+ <code class="option">--timeout</code>
+ <em class="replaceable"><code>number</code></em>
+] [
+ <code class="option">--keep-going</code> | <code class="option">-k</code>
+] [
+ <code class="option">--keep-failed</code> | <code class="option">-K</code>
+] [<code class="option">--fallback</code>] [<code class="option">--readonly-mode</code>] [
+ <code class="option">-I</code>
+ <em class="replaceable"><code>path</code></em>
+] [
+ <code class="option">--option</code>
+ <em class="replaceable"><code>name</code></em>
+ <em class="replaceable"><code>value</code></em>
+]<br /> [<code class="option">--arg</code> <em class="replaceable"><code>name</code></em> <em class="replaceable"><code>value</code></em>] [<code class="option">--argstr</code> <em class="replaceable"><code>name</code></em> <em class="replaceable"><code>value</code></em>] [
+ { <code class="option">--attr</code> | <code class="option">-A</code> }
+ <em class="replaceable"><code>attrPath</code></em>
+ ] [<code class="option">--no-out-link</code>] [<code class="option">--dry-run</code>] [
+ { <code class="option">--out-link</code> | <code class="option">-o</code> }
+ <em class="replaceable"><code>outlink</code></em>
+ ] <em class="replaceable"><code>paths</code></em>... </p></div></div><div class="refsection"><a id="idm139733299874432"></a><h2>Description</h2><p>The <span class="command"><strong>nix-build</strong></span> command builds the derivations
+described by the Nix expressions in <em class="replaceable"><code>paths</code></em>.
+If the build succeeds, it places a symlink to the result in the
+current directory. The symlink is called <code class="filename">result</code>.
+If there are multiple Nix expressions, or the Nix expressions evaluate
+to multiple derivations, multiple sequentially numbered symlinks are
+created (<code class="filename">result</code>, <code class="filename">result-2</code>,
+and so on).</p><p>If no <em class="replaceable"><code>paths</code></em> are specified, then
+<span class="command"><strong>nix-build</strong></span> will use <code class="filename">default.nix</code>
+in the current directory, if it exists.</p><p>If an element of <em class="replaceable"><code>paths</code></em> starts with
+<code class="literal">http://</code> or <code class="literal">https://</code>, it is
+interpreted as the URL of a tarball that will be downloaded and
+unpacked to a temporary location. The tarball must include a single
+top-level directory containing at least a file named
+<code class="filename">default.nix</code>.</p><p><span class="command"><strong>nix-build</strong></span> is essentially a wrapper around
+<a class="link" href="#sec-nix-instantiate" title="nix-instantiate"><span class="command"><strong>nix-instantiate</strong></span></a>
+(to translate a high-level Nix expression to a low-level store
+derivation) and <a class="link" href="#rsec-nix-store-realise" title="Operation --realise"><span class="command"><strong>nix-store
+--realise</strong></span></a> (to build the store derivation).</p><div class="warning"><h3 class="title">Warning</h3><p>The result of the build is automatically registered as
+a root of the Nix garbage collector. This root disappears
+automatically when the <code class="filename">result</code> symlink is deleted
+or renamed. So don’t rename the symlink.</p></div></div><div class="refsection"><a id="idm139733299863072"></a><h2>Options</h2><p>All options not listed here are passed to <span class="command"><strong>nix-store
+--realise</strong></span>, except for <code class="option">--arg</code> and
+<code class="option">--attr</code> / <code class="option">-A</code> which are passed to
+<span class="command"><strong>nix-instantiate</strong></span>. <span class="phrase">See
+also <a class="xref" href="#sec-common-options" title="Chapter 20. Common Options">Chapter 20, <em>Common Options</em></a>.</span></p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--no-out-link</code></span></dt><dd><p>Do not create a symlink to the output path. Note
+ that as a result the output does not become a root of the garbage
+ collector, and so might be deleted by <span class="command"><strong>nix-store
+ --gc</strong></span>.</p></dd><dt><span class="term"><code class="option">--dry-run</code></span></dt><dd><p>Show what store paths would be built or downloaded.</p></dd><dt><a id="opt-out-link"></a><span class="term"><code class="option">--out-link</code> /
+ <code class="option">-o</code> <em class="replaceable"><code>outlink</code></em></span></dt><dd><p>Change the name of the symlink to the output path
+ created from <code class="filename">result</code> to
+ <em class="replaceable"><code>outlink</code></em>.</p></dd></dl></div><p>The following common options are supported:</p></div><div class="refsection"><a id="idm139733299851056"></a><h2>Examples</h2><pre class="screen">
+$ nix-build '<nixpkgs>' -A firefox
+store derivation is /nix/store/qybprl8sz2lc...-firefox-1.5.0.7.drv
+/nix/store/d18hyl92g30l...-firefox-1.5.0.7
+
+$ ls -l result
+lrwxrwxrwx <em class="replaceable"><code>...</code></em> result -> /nix/store/d18hyl92g30l...-firefox-1.5.0.7
+
+$ ls ./result/bin/
+firefox firefox-config</pre><p>If a derivation has multiple outputs,
+<span class="command"><strong>nix-build</strong></span> will build the default (first) output.
+You can also build all outputs:
+</p><pre class="screen">
+$ nix-build '<nixpkgs>' -A openssl.all
+</pre><p>
+This will create a symlink for each output named
+<code class="filename">result-<em class="replaceable"><code>outputname</code></em></code>.
+The suffix is omitted if the output name is <code class="literal">out</code>.
+So if <code class="literal">openssl</code> has outputs <code class="literal">out</code>,
+<code class="literal">bin</code> and <code class="literal">man</code>,
+<span class="command"><strong>nix-build</strong></span> will create symlinks
+<code class="literal">result</code>, <code class="literal">result-bin</code> and
+<code class="literal">result-man</code>. It’s also possible to build a specific
+output:
+</p><pre class="screen">
+$ nix-build '<nixpkgs>' -A openssl.man
+</pre><p>
+This will create a symlink <code class="literal">result-man</code>.</p><p>Build a Nix expression given on the command line:
+
+</p><pre class="screen">
+$ nix-build -E 'with import <nixpkgs> { }; runCommand "foo" { } "echo bar > $out"'
+$ cat ./result
+bar
+</pre><p>
+
+</p><p>Build the GNU Hello package from the latest revision of the
+master branch of Nixpkgs:
+
+</p><pre class="screen">
+$ nix-build https://github.com/NixOS/nixpkgs/archive/master.tar.gz -A hello
+</pre><p>
+
+</p></div></div><div class="refentry"><div class="refentry.separator"><hr /></div><a id="sec-nix-shell"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix-shell — start an interactive shell based on a Nix expression</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">nix-shell</code> [<code class="option">--arg</code> <em class="replaceable"><code>name</code></em> <em class="replaceable"><code>value</code></em>] [<code class="option">--argstr</code> <em class="replaceable"><code>name</code></em> <em class="replaceable"><code>value</code></em>] [
+ { <code class="option">--attr</code> | <code class="option">-A</code> }
+ <em class="replaceable"><code>attrPath</code></em>
+ ] [<code class="option">--command</code> <em class="replaceable"><code>cmd</code></em>] [<code class="option">--run</code> <em class="replaceable"><code>cmd</code></em>] [<code class="option">--exclude</code> <em class="replaceable"><code>regexp</code></em>] [<code class="option">--pure</code>] [<code class="option">--keep</code> <em class="replaceable"><code>name</code></em>] {
+ { <code class="option">--packages</code> | <code class="option">-p</code> }
+
+ { <em class="replaceable"><code>packages</code></em> | <em class="replaceable"><code>expressions</code></em> }
+ ...
+ | [<em class="replaceable"><code>path</code></em>]}</p></div></div><div class="refsection"><a id="idm139733299816608"></a><h2>Description</h2><p>The command <span class="command"><strong>nix-shell</strong></span> will build the
+dependencies of the specified derivation, but not the derivation
+itself. It will then start an interactive shell in which all
+environment variables defined by the derivation
+<em class="replaceable"><code>path</code></em> have been set to their corresponding
+values, and the script <code class="literal">$stdenv/setup</code> has been
+sourced. This is useful for reproducing the environment of a
+derivation for development.</p><p>If <em class="replaceable"><code>path</code></em> is not given,
+<span class="command"><strong>nix-shell</strong></span> defaults to
+<code class="filename">shell.nix</code> if it exists, and
+<code class="filename">default.nix</code> otherwise.</p><p>If <em class="replaceable"><code>path</code></em> starts with
+<code class="literal">http://</code> or <code class="literal">https://</code>, it is
+interpreted as the URL of a tarball that will be downloaded and
+unpacked to a temporary location. The tarball must include a single
+top-level directory containing at least a file named
+<code class="filename">default.nix</code>.</p><p>If the derivation defines the variable
+<code class="varname">shellHook</code>, it will be evaluated after
+<code class="literal">$stdenv/setup</code> has been sourced. Since this hook is
+not executed by regular Nix builds, it allows you to perform
+initialisation specific to <span class="command"><strong>nix-shell</strong></span>. For example,
+the derivation attribute
+
+</p><pre class="programlisting">
+shellHook =
+ ''
+ echo "Hello shell"
+ '';
+</pre><p>
+
+will cause <span class="command"><strong>nix-shell</strong></span> to print <code class="literal">Hello shell</code>.</p></div><div class="refsection"><a id="idm139733299806096"></a><h2>Options</h2><p>All options not listed here are passed to <span class="command"><strong>nix-store
+--realise</strong></span>, except for <code class="option">--arg</code> and
+<code class="option">--attr</code> / <code class="option">-A</code> which are passed to
+<span class="command"><strong>nix-instantiate</strong></span>. <span class="phrase">See
+also <a class="xref" href="#sec-common-options" title="Chapter 20. Common Options">Chapter 20, <em>Common Options</em></a>.</span></p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--command</code> <em class="replaceable"><code>cmd</code></em></span></dt><dd><p>In the environment of the derivation, run the
+ shell command <em class="replaceable"><code>cmd</code></em>. This command is
+ executed in an interactive shell. (Use <code class="option">--run</code> to
+ use a non-interactive shell instead.) However, a call to
+ <code class="literal">exit</code> is implicitly added to the command, so the
+ shell will exit after running the command. To prevent this, add
+ <code class="literal">return</code> at the end; e.g. <code class="literal">--command
+ "echo Hello; return"</code> will print <code class="literal">Hello</code>
+ and then drop you into the interactive shell. This can be useful
+ for doing any additional initialisation.</p></dd><dt><span class="term"><code class="option">--run</code> <em class="replaceable"><code>cmd</code></em></span></dt><dd><p>Like <code class="option">--command</code>, but executes the
+ command in a non-interactive shell. This means (among other
+ things) that if you hit Ctrl-C while the command is running, the
+ shell exits.</p></dd><dt><span class="term"><code class="option">--exclude</code> <em class="replaceable"><code>regexp</code></em></span></dt><dd><p>Do not build any dependencies whose store path
+ matches the regular expression <em class="replaceable"><code>regexp</code></em>.
+ This option may be specified multiple times.</p></dd><dt><span class="term"><code class="option">--pure</code></span></dt><dd><p>If this flag is specified, the environment is
+ almost entirely cleared before the interactive shell is started,
+ so you get an environment that more closely corresponds to the
+ “real” Nix build. A few variables, in particular
+ <code class="envar">HOME</code>, <code class="envar">USER</code> and
+ <code class="envar">DISPLAY</code>, are retained. Note that
+ <code class="filename">~/.bashrc</code> and (depending on your Bash
+ installation) <code class="filename">/etc/bashrc</code> are still sourced,
+ so any variables set there will affect the interactive
+ shell.</p></dd><dt><span class="term"><code class="option">--packages</code> / <code class="option">-p</code> <em class="replaceable"><code>packages</code></em>…</span></dt><dd><p>Set up an environment in which the specified
+ packages are present. The command line arguments are interpreted
+ as attribute names inside the Nix Packages collection. Thus,
+ <code class="literal">nix-shell -p libjpeg openjdk</code> will start a shell
+ in which the packages denoted by the attribute names
+ <code class="varname">libjpeg</code> and <code class="varname">openjdk</code> are
+ present.</p></dd><dt><span class="term"><code class="option">-i</code> <em class="replaceable"><code>interpreter</code></em></span></dt><dd><p>The chained script interpreter to be invoked by
+ <span class="command"><strong>nix-shell</strong></span>. Only applicable in
+ <code class="literal">#!</code>-scripts (described <a class="link" href="#ssec-nix-shell-shebang" title="Use as a #!-interpreter">below</a>).</p></dd><dt><span class="term"><code class="option">--keep</code> <em class="replaceable"><code>name</code></em></span></dt><dd><p>When a <code class="option">--pure</code> shell is started,
+ keep the listed environment variables.</p></dd></dl></div><p>The following common options are supported:</p></div><div class="refsection"><a id="idm139733299777888"></a><h2>Environment variables</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="envar">NIX_BUILD_SHELL</code></span></dt><dd><p>Shell used to start the interactive environment.
+ Defaults to the <span class="command"><strong>bash</strong></span> found in <code class="envar">PATH</code>.</p></dd></dl></div></div><div class="refsection"><a id="idm139733299774576"></a><h2>Examples</h2><p>To build the dependencies of the package Pan, and start an
+interactive shell in which to build it:
+
+</p><pre class="screen">
+$ nix-shell '<nixpkgs>' -A pan
+[nix-shell]$ unpackPhase
+[nix-shell]$ cd pan-*
+[nix-shell]$ configurePhase
+[nix-shell]$ buildPhase
+[nix-shell]$ ./pan/gui/pan
+</pre><p>
+
+To clear the environment first, and do some additional automatic
+initialisation of the interactive shell:
+
+</p><pre class="screen">
+$ nix-shell '<nixpkgs>' -A pan --pure \
+ --command 'export NIX_DEBUG=1; export NIX_CORES=8; return'
+</pre><p>
+
+Nix expressions can also be given on the command line using the
+<span class="command"><strong>-E</strong></span> and <span class="command"><strong>-p</strong></span> flags.
+For instance, the following starts a shell containing the packages
+<code class="literal">sqlite</code> and <code class="literal">libX11</code>:
+
+</p><pre class="screen">
+$ nix-shell -E 'with import <nixpkgs> { }; runCommand "dummy" { buildInputs = [ sqlite xorg.libX11 ]; } ""'
+</pre><p>
+
+A shorter way to do the same is:
+
+</p><pre class="screen">
+$ nix-shell -p sqlite xorg.libX11
+[nix-shell]$ echo $NIX_LDFLAGS
+… -L/nix/store/j1zg5v…-sqlite-3.8.0.2/lib -L/nix/store/0gmcz9…-libX11-1.6.1/lib …
+</pre><p>
+
+Note that <span class="command"><strong>-p</strong></span> accepts multiple full nix expressions that
+are valid in the <code class="literal">buildInputs = [ ... ]</code> shown above,
+not only package names. So the following is also legal:
+
+</p><pre class="screen">
+$ nix-shell -p sqlite 'git.override { withManual = false; }'
+</pre><p>
+
+The <span class="command"><strong>-p</strong></span> flag looks up Nixpkgs in the Nix search
+path. You can override it by passing <code class="option">-I</code> or setting
+<code class="envar">NIX_PATH</code>. For example, the following gives you a shell
+containing the Pan package from a specific revision of Nixpkgs:
+
+</p><pre class="screen">
+$ nix-shell -p pan -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/8a3eea054838b55aca962c3fbde9c83c102b8bf2.tar.gz
+
+[nix-shell:~]$ pan --version
+Pan 0.139
+</pre><p>
+
+</p></div><div class="refsection"><a id="ssec-nix-shell-shebang"></a><h2>Use as a <code class="literal">#!</code>-interpreter</h2><p>You can use <span class="command"><strong>nix-shell</strong></span> as a script interpreter
+to allow scripts written in arbitrary languages to obtain their own
+dependencies via Nix. This is done by starting the script with the
+following lines:
+
+</p><pre class="programlisting">
+#! /usr/bin/env nix-shell
+#! nix-shell -i <em class="replaceable"><code>real-interpreter</code></em> -p <em class="replaceable"><code>packages</code></em>
+</pre><p>
+
+where <em class="replaceable"><code>real-interpreter</code></em> is the “real” script
+interpreter that will be invoked by <span class="command"><strong>nix-shell</strong></span> after
+it has obtained the dependencies and initialised the environment, and
+<em class="replaceable"><code>packages</code></em> are the attribute names of the
+dependencies in Nixpkgs.</p><p>The lines starting with <code class="literal">#! nix-shell</code> specify
+<span class="command"><strong>nix-shell</strong></span> options (see above). Note that you cannot
+write <code class="literal">#! /usr/bin/env nix-shell -i ...</code> because
+many operating systems only allow one argument in
+<code class="literal">#!</code> lines.</p><p>For example, here is a Python script that depends on Python and
+the <code class="literal">prettytable</code> package:
+
+</p><pre class="programlisting">
+#! /usr/bin/env nix-shell
+#! nix-shell -i python -p python pythonPackages.prettytable
+
+import prettytable
+
+# Print a simple table.
+t = prettytable.PrettyTable(["N", "N^2"])
+for n in range(1, 10): t.add_row([n, n * n])
+print t
+</pre><p>
+
+</p><p>Similarly, the following is a Perl script that specifies that it
+requires Perl and the <code class="literal">HTML::TokeParser::Simple</code> and
+<code class="literal">LWP</code> packages:
+
+</p><pre class="programlisting">
+#! /usr/bin/env nix-shell
+#! nix-shell -i perl -p perl perlPackages.HTMLTokeParserSimple perlPackages.LWP
+
+use HTML::TokeParser::Simple;
+
+# Fetch nixos.org and print all hrefs.
+my $p = HTML::TokeParser::Simple->new(url => 'http://nixos.org/');
+
+while (my $token = $p->get_tag("a")) {
+ my $href = $token->get_attr("href");
+ print "$href\n" if $href;
+}
+</pre><p>
+
+</p><p>Sometimes you need to pass a simple Nix expression to customize
+a package like Terraform:
+
+</p><pre class="programlisting">
+#! /usr/bin/env nix-shell
+#! nix-shell -i bash -p "terraform.withPlugins (plugins: [ plugins.openstack ])"
+
+terraform apply
+</pre><p>
+
+</p><div class="note"><h3 class="title">Note</h3><p>You must use double quotes (<code class="literal">"</code>) when
+passing a simple Nix expression in a nix-shell shebang.</p></div><p>
+</p><p>Finally, using the merging of multiple nix-shell shebangs the
+following Haskell script uses a specific branch of Nixpkgs/NixOS (the
+18.03 stable branch):
+
+</p><pre class="programlisting">
+#! /usr/bin/env nix-shell
+#! nix-shell -i runghc -p "haskellPackages.ghcWithPackages (ps: [ps.HTTP ps.tagsoup])"
+#! nix-shell -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-18.03.tar.gz
+
+import Network.HTTP
+import Text.HTML.TagSoup
+
+-- Fetch nixos.org and print all hrefs.
+main = do
+ resp <- Network.HTTP.simpleHTTP (getRequest "http://nixos.org/")
+ body <- getResponseBody resp
+ let tags = filter (isTagOpenName "a") $ parseTags body
+ let tags' = map (fromAttrib "href") tags
+ mapM_ putStrLn $ filter (/= "") tags'
+</pre><p>
+
+If you want to be even more precise, you can specify a specific
+revision of Nixpkgs:
+
+</p><pre class="programlisting">
+#! nix-shell -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/0672315759b3e15e2121365f067c1c8c56bb4722.tar.gz
+</pre><p>
+
+</p><p>The examples above all used <code class="option">-p</code> to get
+dependencies from Nixpkgs. You can also use a Nix expression to build
+your own dependencies. For example, the Python example could have been
+written as:
+
+</p><pre class="programlisting">
+#! /usr/bin/env nix-shell
+#! nix-shell deps.nix -i python
+</pre><p>
+
+where the file <code class="filename">deps.nix</code> in the same directory
+as the <code class="literal">#!</code>-script contains:
+
+</p><pre class="programlisting">
+with import <nixpkgs> {};
+
+runCommand "dummy" { buildInputs = [ python pythonPackages.prettytable ]; } ""
+</pre><p>
+
+</p></div></div><div class="refentry"><div class="refentry.separator"><hr /></div><a id="sec-nix-store"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix-store — manipulate or query the Nix store</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">nix-store</code> [<code class="option">--help</code>] [<code class="option">--version</code>] [
+ { <code class="option">--verbose</code> | <code class="option">-v</code> }
+...] [
+ <code class="option">--quiet</code>
+] [
+ <code class="option">--log-format</code>
+ <em class="replaceable"><code>format</code></em>
+] [
+ <code class="option">--no-build-output</code> | <code class="option">-Q</code>
+] [
+ { <code class="option">--max-jobs</code> | <code class="option">-j</code> }
+ <em class="replaceable"><code>number</code></em>
+] [
+ <code class="option">--cores</code>
+ <em class="replaceable"><code>number</code></em>
+] [
+ <code class="option">--max-silent-time</code>
+ <em class="replaceable"><code>number</code></em>
+] [
+ <code class="option">--timeout</code>
+ <em class="replaceable"><code>number</code></em>
+] [
+ <code class="option">--keep-going</code> | <code class="option">-k</code>
+] [
+ <code class="option">--keep-failed</code> | <code class="option">-K</code>
+] [<code class="option">--fallback</code>] [<code class="option">--readonly-mode</code>] [
+ <code class="option">-I</code>
+ <em class="replaceable"><code>path</code></em>
+] [
+ <code class="option">--option</code>
+ <em class="replaceable"><code>name</code></em>
+ <em class="replaceable"><code>value</code></em>
+]<br /> [<code class="option">--add-root</code> <em class="replaceable"><code>path</code></em>] [<code class="option">--indirect</code>] <em class="replaceable"><code>operation</code></em> [<em class="replaceable"><code>options</code></em>...] [<em class="replaceable"><code>arguments</code></em>...]</p></div></div><div class="refsection"><a id="idm139733299713504"></a><h2>Description</h2><p>The command <span class="command"><strong>nix-store</strong></span> performs primitive
+operations on the Nix store. You generally do not need to run this
+command manually.</p><p><span class="command"><strong>nix-store</strong></span> takes exactly one
+<span class="emphasis"><em>operation</em></span> flag which indicates the subcommand to
+be performed. These are documented below.</p></div><div class="refsection"><a id="idm139733299710208"></a><h2>Common options</h2><p>This section lists the options that are common to all
+operations. These options are allowed for every subcommand, though
+they may not always have an effect. <span class="phrase">See
+also <a class="xref" href="#sec-common-options" title="Chapter 20. Common Options">Chapter 20, <em>Common Options</em></a> for a list of common
+options.</span></p><div class="variablelist"><dl class="variablelist"><dt><a id="opt-add-root"></a><span class="term"><code class="option">--add-root</code> <em class="replaceable"><code>path</code></em></span></dt><dd><p>Causes the result of a realisation
+ (<code class="option">--realise</code> and <code class="option">--force-realise</code>)
+ to be registered as a root of the garbage collector<span class="phrase"> (see <a class="xref" href="#ssec-gc-roots" title="11.1. Garbage Collector Roots">Section 11.1, “Garbage Collector Roots”</a>)</span>. The root is stored in
+ <em class="replaceable"><code>path</code></em>, which must be inside a directory
+ that is scanned for roots by the garbage collector (i.e.,
+ typically in a subdirectory of
+ <code class="filename">/nix/var/nix/gcroots/</code>)
+ <span class="emphasis"><em>unless</em></span> the <code class="option">--indirect</code> flag
+ is used.</p><p>If there are multiple results, then multiple symlinks will
+ be created by sequentially numbering symlinks beyond the first one
+ (e.g., <code class="filename">foo</code>, <code class="filename">foo-2</code>,
+ <code class="filename">foo-3</code>, and so on).</p></dd><dt><span class="term"><code class="option">--indirect</code></span></dt><dd><p>In conjunction with <code class="option">--add-root</code>, this option
+ allows roots to be stored <span class="emphasis"><em>outside</em></span> of the GC
+ roots directory. This is useful for commands such as
+ <span class="command"><strong>nix-build</strong></span> that place a symlink to the build
+ result in the current directory; such a build result should not be
+ garbage-collected unless the symlink is removed.</p><p>The <code class="option">--indirect</code> flag causes a uniquely named
+ symlink to <em class="replaceable"><code>path</code></em> to be stored in
+ <code class="filename">/nix/var/nix/gcroots/auto/</code>. For instance,
+
+ </p><pre class="screen">
+$ nix-store --add-root /home/eelco/bla/result --indirect -r <em class="replaceable"><code>...</code></em>
+
+$ ls -l /nix/var/nix/gcroots/auto
+lrwxrwxrwx 1 ... 2005-03-13 21:10 dn54lcypm8f8... -> /home/eelco/bla/result
+
+$ ls -l /home/eelco/bla/result
+lrwxrwxrwx 1 ... 2005-03-13 21:10 /home/eelco/bla/result -> /nix/store/1r11343n6qd4...-f-spot-0.0.10</pre><p>
+
+ Thus, when <code class="filename">/home/eelco/bla/result</code> is removed,
+ the GC root in the <code class="filename">auto</code> directory becomes a
+ dangling symlink and will be ignored by the collector.</p><div class="warning"><h3 class="title">Warning</h3><p>Note that it is not possible to move or rename
+ indirect GC roots, since the symlink in the
+ <code class="filename">auto</code> directory will still point to the old
+ location.</p></div></dd></dl></div></div><div class="refsection"><a id="rsec-nix-store-realise"></a><h2>Operation <code class="option">--realise</code></h2><div class="refsection"><a id="idm139733299689136"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> { <code class="option">--realise</code> | <code class="option">-r</code> } <em class="replaceable"><code>paths</code></em>... [<code class="option">--dry-run</code>]</p></div></div><div class="refsection"><a id="idm139733299683808"></a><h3>Description</h3><p>The operation <code class="option">--realise</code> essentially “builds”
+the specified store paths. Realisation is a somewhat overloaded term:
+
+</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>If the store path is a
+ <span class="emphasis"><em>derivation</em></span>, realisation ensures that the output
+ paths of the derivation are <a class="link" href="#gloss-validity" title="validity">valid</a> (i.e., the output path and its
+ closure exist in the file system). This can be done in several
+ ways. First, it is possible that the outputs are already valid, in
+ which case we are done immediately. Otherwise, there may be <a class="link" href="#gloss-substitute" title="substitute">substitutes</a> that produce the
+ outputs (e.g., by downloading them). Finally, the outputs can be
+ produced by performing the build action described by the
+ derivation.</p></li><li class="listitem"><p>If the store path is not a derivation, realisation
+ ensures that the specified path is valid (i.e., it and its closure
+ exist in the file system). If the path is already valid, we are
+ done immediately. Otherwise, the path and any missing paths in its
+ closure may be produced through substitutes. If there are no
+ (successful) subsitutes, realisation fails.</p></li></ul></div><p>
+
+</p><p>The output path of each derivation is printed on standard
+output. (For non-derivations argument, the argument itself is
+printed.)</p><p>The following flags are available:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--dry-run</code></span></dt><dd><p>Print on standard error a description of what
+ packages would be built or downloaded, without actually performing
+ the operation.</p></dd><dt><span class="term"><code class="option">--ignore-unknown</code></span></dt><dd><p>If a non-derivation path does not have a
+ substitute, then silently ignore it.</p></dd><dt><span class="term"><code class="option">--check</code></span></dt><dd><p>This option allows you to check whether a
+ derivation is deterministic. It rebuilds the specified derivation
+ and checks whether the result is bitwise-identical with the
+ existing outputs, printing an error if that’s not the case. The
+ outputs of the specified derivation must already exist. When used
+ with <code class="option">-K</code>, if an output path is not identical to
+ the corresponding output from the previous build, the new output
+ path is left in
+ <code class="filename">/nix/store/<em class="replaceable"><code>name</code></em>.check.</code></p><p>See also the <code class="option">build-repeat</code> configuration
+ option, which repeats a derivation a number of times and prevents
+ its outputs from being registered as “valid” in the Nix store
+ unless they are identical.</p></dd></dl></div><p>Special exit codes:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">100</code></span></dt><dd><p>Generic build failure, the builder process
+ returned with a non-zero exit code.</p></dd><dt><span class="term"><code class="literal">101</code></span></dt><dd><p>Build timeout, the build was aborted because it
+ did not complete within the specified <a class="link" href="#conf-timeout"><code class="literal">timeout</code></a>.
+ </p></dd><dt><span class="term"><code class="literal">102</code></span></dt><dd><p>Hash mismatch, the build output was rejected
+ because it does not match the specified <a class="link" href="#fixed-output-drvs"><code class="varname">outputHash</code></a>.
+ </p></dd><dt><span class="term"><code class="literal">104</code></span></dt><dd><p>Not deterministic, the build succeeded in check
+ mode but the resulting output is not binary reproducable.</p></dd></dl></div><p>With the <code class="option">--keep-going</code> flag it's possible for
+multiple failures to occur, in this case the 1xx status codes are or combined
+using binary or. </p><pre class="screen">
+1100100
+ ^^^^
+ |||`- timeout
+ ||`-- output hash mismatch
+ |`--- build failure
+ `---- not deterministic
+</pre></div><div class="refsection"><a id="idm139733299659648"></a><h3>Examples</h3><p>This operation is typically used to build store derivations
+produced by <a class="link" href="#sec-nix-instantiate" title="nix-instantiate"><span class="command"><strong>nix-instantiate</strong></span></a>:
+
+</p><pre class="screen">
+$ nix-store -r $(nix-instantiate ./test.nix)
+/nix/store/31axcgrlbfsxzmfff1gyj1bf62hvkby2-aterm-2.3.1</pre><p>
+
+This is essentially what <a class="link" href="#sec-nix-build" title="nix-build"><span class="command"><strong>nix-build</strong></span></a> does.</p><p>To test whether a previously-built derivation is deterministic:
+
+</p><pre class="screen">
+$ nix-build '<nixpkgs>' -A hello --check -K
+</pre><p>
+
+</p></div></div><div class="refsection"><a id="rsec-nix-store-serve"></a><h2>Operation <code class="option">--serve</code></h2><div class="refsection"><a id="idm139733299653424"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--serve</code> [<code class="option">--write</code>]</p></div></div><div class="refsection"><a id="idm139733299650592"></a><h3>Description</h3><p>The operation <code class="option">--serve</code> provides access to
+the Nix store over stdin and stdout, and is intended to be used
+as a means of providing Nix store access to a restricted ssh user.
+</p><p>The following flags are available:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--write</code></span></dt><dd><p>Allow the connected client to request the realization
+ of derivations. In effect, this can be used to make the host act
+ as a remote builder.</p></dd></dl></div></div><div class="refsection"><a id="idm139733299646640"></a><h3>Examples</h3><p>To turn a host into a build server, the
+<code class="filename">authorized_keys</code> file can be used to provide build
+access to a given SSH public key:
+
+</p><pre class="screen">
+$ cat <<EOF >>/root/.ssh/authorized_keys
+command="nice -n20 nix-store --serve --write" ssh-rsa AAAAB3NzaC1yc2EAAAA...
+EOF
+</pre><p>
+
+</p></div></div><div class="refsection"><a id="rsec-nix-store-gc"></a><h2>Operation <code class="option">--gc</code></h2><div class="refsection"><a id="idm139733299642624"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--gc</code> [ <code class="option">--print-roots</code> | <code class="option">--print-live</code> | <code class="option">--print-dead</code> ] [<code class="option">--max-freed</code> <em class="replaceable"><code>bytes</code></em>]</p></div></div><div class="refsection"><a id="idm139733299636544"></a><h3>Description</h3><p>Without additional flags, the operation <code class="option">--gc</code>
+performs a garbage collection on the Nix store. That is, all paths in
+the Nix store not reachable via file system references from a set of
+“roots”, are deleted.</p><p>The following suboperations may be specified:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--print-roots</code></span></dt><dd><p>This operation prints on standard output the set
+ of roots used by the garbage collector. What constitutes a root
+ is described in <a class="xref" href="#ssec-gc-roots" title="11.1. Garbage Collector Roots">Section 11.1, “Garbage Collector Roots”</a>.</p></dd><dt><span class="term"><code class="option">--print-live</code></span></dt><dd><p>This operation prints on standard output the set
+ of “live” store paths, which are all the store paths reachable
+ from the roots. Live paths should never be deleted, since that
+ would break consistency — it would become possible that
+ applications are installed that reference things that are no
+ longer present in the store.</p></dd><dt><span class="term"><code class="option">--print-dead</code></span></dt><dd><p>This operation prints out on standard output the
+ set of “dead” store paths, which is just the opposite of the set
+ of live paths: any path in the store that is not live (with
+ respect to the roots) is dead.</p></dd></dl></div><p>By default, all unreachable paths are deleted. The following
+options control what gets deleted and in what order:
+
+</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--max-freed</code> <em class="replaceable"><code>bytes</code></em></span></dt><dd><p>Keep deleting paths until at least
+ <em class="replaceable"><code>bytes</code></em> bytes have been deleted, then
+ stop. The argument <em class="replaceable"><code>bytes</code></em> can be
+ followed by the multiplicative suffix <code class="literal">K</code>,
+ <code class="literal">M</code>, <code class="literal">G</code> or
+ <code class="literal">T</code>, denoting KiB, MiB, GiB or TiB
+ units.</p></dd></dl></div><p>
+
+</p><p>The behaviour of the collector is also influenced by the <a class="link" href="#conf-keep-outputs"><code class="literal">keep-outputs</code></a>
+and <a class="link" href="#conf-keep-derivations"><code class="literal">keep-derivations</code></a>
+variables in the Nix configuration file.</p><p>By default, the collector prints the total number of freed bytes
+when it finishes (or when it is interrupted). With
+<code class="option">--print-dead</code>, it prints the number of bytes that would
+be freed.</p></div><div class="refsection"><a id="idm139733299619488"></a><h3>Examples</h3><p>To delete all unreachable paths, just do:
+
+</p><pre class="screen">
+$ nix-store --gc
+deleting `/nix/store/kq82idx6g0nyzsp2s14gfsc38npai7lf-cairo-1.0.4.tar.gz.drv'
+<em class="replaceable"><code>...</code></em>
+8825586 bytes freed (8.42 MiB)</pre><p>
+
+</p><p>To delete at least 100 MiBs of unreachable paths:
+
+</p><pre class="screen">
+$ nix-store --gc --max-freed $((100 * 1024 * 1024))</pre><p>
+
+</p></div></div><div class="refsection"><a id="idm139733299615968"></a><h2>Operation <code class="option">--delete</code></h2><div class="refsection"><a id="idm139733299615136"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--delete</code> [<code class="option">--ignore-liveness</code>] <em class="replaceable"><code>paths</code></em>... </p></div></div><div class="refsection"><a id="idm139733299611216"></a><h3>Description</h3><p>The operation <code class="option">--delete</code> deletes the store paths
+<em class="replaceable"><code>paths</code></em> from the Nix store, but only if it is
+safe to do so; that is, when the path is not reachable from a root of
+the garbage collector. This means that you can only delete paths that
+would also be deleted by <code class="literal">nix-store --gc</code>. Thus,
+<code class="literal">--delete</code> is a more targeted version of
+<code class="literal">--gc</code>.</p><p>With the option <code class="option">--ignore-liveness</code>, reachability
+from the roots is ignored. However, the path still won’t be deleted
+if there are other paths in the store that refer to it (i.e., depend
+on it).</p></div><div class="refsection"><a id="idm139733299606528"></a><h3>Example</h3><pre class="screen">
+$ nix-store --delete /nix/store/zq0h41l75vlb4z45kzgjjmsjxvcv1qk7-mesa-6.4
+0 bytes freed (0.00 MiB)
+error: cannot delete path `/nix/store/zq0h41l75vlb4z45kzgjjmsjxvcv1qk7-mesa-6.4' since it is still alive</pre></div></div><div class="refsection"><a id="refsec-nix-store-query"></a><h2>Operation <code class="option">--query</code></h2><div class="refsection"><a id="idm139733299603504"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> { <code class="option">--query</code> | <code class="option">-q</code> } { <code class="option">--outputs</code> | <code class="option">--requisites</code> | <code class="option">-R</code> | <code class="option">--references</code> | <code class="option">--referrers</code> | <code class="option">--referrers-closure</code> | <code class="option">--deriver</code> | <code class="option">-d</code> | <code class="option">--graph</code> | <code class="option">--tree</code> | <code class="option">--binding</code> <em class="replaceable"><code>name</code></em> | <code class="option">-b</code> <em class="replaceable"><code>name</code></em> | <code class="option">--hash</code> | <code class="option">--size</code> | <code class="option">--roots</code> } [<code class="option">--use-output</code>] [<code class="option">-u</code>] [<code class="option">--force-realise</code>] [<code class="option">-f</code>] <em class="replaceable"><code>paths</code></em>... </p></div></div><div class="refsection"><a id="idm139733299583008"></a><h3>Description</h3><p>The operation <code class="option">--query</code> displays various bits of
+information about the store paths . The queries are described below. At
+most one query can be specified. The default query is
+<code class="option">--outputs</code>.</p><p>The paths <em class="replaceable"><code>paths</code></em> may also be symlinks
+from outside of the Nix store, to the Nix store. In that case, the
+query is applied to the target of the symlink.</p></div><div class="refsection"><a id="idm139733299579920"></a><h3>Common query options</h3><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--use-output</code>, </span><span class="term"><code class="option">-u</code></span></dt><dd><p>For each argument to the query that is a store
+ derivation, apply the query to the output path of the derivation
+ instead.</p></dd><dt><span class="term"><code class="option">--force-realise</code>, </span><span class="term"><code class="option">-f</code></span></dt><dd><p>Realise each argument to the query first (see
+ <a class="link" href="#rsec-nix-store-realise" title="Operation --realise"><span class="command"><strong>nix-store
+ --realise</strong></span></a>).</p></dd></dl></div></div><div class="refsection"><a id="nixref-queries"></a><h3>Queries</h3><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--outputs</code></span></dt><dd><p>Prints out the <a class="link" href="#gloss-output-path" title="output path">output paths</a> of the store
+ derivations <em class="replaceable"><code>paths</code></em>. These are the paths
+ that will be produced when the derivation is
+ built.</p></dd><dt><span class="term"><code class="option">--requisites</code>, </span><span class="term"><code class="option">-R</code></span></dt><dd><p>Prints out the <a class="link" href="#gloss-closure" title="closure">closure</a> of the store path
+ <em class="replaceable"><code>paths</code></em>.</p><p>This query has one option:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--include-outputs</code></span></dt><dd><p>Also include the output path of store
+ derivations, and their closures.</p></dd></dl></div><p>This query can be used to implement various kinds of
+ deployment. A <span class="emphasis"><em>source deployment</em></span> is obtained
+ by distributing the closure of a store derivation. A
+ <span class="emphasis"><em>binary deployment</em></span> is obtained by distributing
+ the closure of an output path. A <span class="emphasis"><em>cache
+ deployment</em></span> (combined source/binary deployment,
+ including binaries of build-time-only dependencies) is obtained by
+ distributing the closure of a store derivation and specifying the
+ option <code class="option">--include-outputs</code>.</p></dd><dt><span class="term"><code class="option">--references</code></span></dt><dd><p>Prints the set of <a class="link" href="#gloss-reference" title="reference">references</a> of the store paths
+ <em class="replaceable"><code>paths</code></em>, that is, their immediate
+ dependencies. (For <span class="emphasis"><em>all</em></span> dependencies, use
+ <code class="option">--requisites</code>.)</p></dd><dt><span class="term"><code class="option">--referrers</code></span></dt><dd><p>Prints the set of <span class="emphasis"><em>referrers</em></span> of
+ the store paths <em class="replaceable"><code>paths</code></em>, that is, the
+ store paths currently existing in the Nix store that refer to one
+ of <em class="replaceable"><code>paths</code></em>. Note that contrary to the
+ references, the set of referrers is not constant; it can change as
+ store paths are added or removed.</p></dd><dt><span class="term"><code class="option">--referrers-closure</code></span></dt><dd><p>Prints the closure of the set of store paths
+ <em class="replaceable"><code>paths</code></em> under the referrers relation; that
+ is, all store paths that directly or indirectly refer to one of
+ <em class="replaceable"><code>paths</code></em>. These are all the path currently
+ in the Nix store that are dependent on
+ <em class="replaceable"><code>paths</code></em>.</p></dd><dt><span class="term"><code class="option">--deriver</code>, </span><span class="term"><code class="option">-d</code></span></dt><dd><p>Prints the <a class="link" href="#gloss-deriver" title="deriver">deriver</a> of the store paths
+ <em class="replaceable"><code>paths</code></em>. If the path has no deriver
+ (e.g., if it is a source file), or if the deriver is not known
+ (e.g., in the case of a binary-only deployment), the string
+ <code class="literal">unknown-deriver</code> is printed.</p></dd><dt><span class="term"><code class="option">--graph</code></span></dt><dd><p>Prints the references graph of the store paths
+ <em class="replaceable"><code>paths</code></em> in the format of the
+ <span class="command"><strong>dot</strong></span> tool of AT&T's <a class="link" href="http://www.graphviz.org/" target="_top">Graphviz package</a>.
+ This can be used to visualise dependency graphs. To obtain a
+ build-time dependency graph, apply this to a store derivation. To
+ obtain a runtime dependency graph, apply it to an output
+ path.</p></dd><dt><span class="term"><code class="option">--tree</code></span></dt><dd><p>Prints the references graph of the store paths
+ <em class="replaceable"><code>paths</code></em> as a nested ASCII tree.
+ References are ordered by descending closure size; this tends to
+ flatten the tree, making it more readable. The query only
+ recurses into a store path when it is first encountered; this
+ prevents a blowup of the tree representation of the
+ graph.</p></dd><dt><span class="term"><code class="option">--graphml</code></span></dt><dd><p>Prints the references graph of the store paths
+ <em class="replaceable"><code>paths</code></em> in the <a class="link" href="http://graphml.graphdrawing.org/" target="_top">GraphML</a> file format.
+ This can be used to visualise dependency graphs. To obtain a
+ build-time dependency graph, apply this to a store derivation. To
+ obtain a runtime dependency graph, apply it to an output
+ path.</p></dd><dt><span class="term"><code class="option">--binding</code> <em class="replaceable"><code>name</code></em>, </span><span class="term"><code class="option">-b</code> <em class="replaceable"><code>name</code></em></span></dt><dd><p>Prints the value of the attribute
+ <em class="replaceable"><code>name</code></em> (i.e., environment variable) of
+ the store derivations <em class="replaceable"><code>paths</code></em>. It is an
+ error for a derivation to not have the specified
+ attribute.</p></dd><dt><span class="term"><code class="option">--hash</code></span></dt><dd><p>Prints the SHA-256 hash of the contents of the
+ store paths <em class="replaceable"><code>paths</code></em> (that is, the hash of
+ the output of <span class="command"><strong>nix-store --dump</strong></span> on the given
+ paths). Since the hash is stored in the Nix database, this is a
+ fast operation.</p></dd><dt><span class="term"><code class="option">--size</code></span></dt><dd><p>Prints the size in bytes of the contents of the
+ store paths <em class="replaceable"><code>paths</code></em> — to be precise, the
+ size of the output of <span class="command"><strong>nix-store --dump</strong></span> on the
+ given paths. Note that the actual disk space required by the
+ store paths may be higher, especially on filesystems with large
+ cluster sizes.</p></dd><dt><span class="term"><code class="option">--roots</code></span></dt><dd><p>Prints the garbage collector roots that point,
+ directly or indirectly, at the store paths
+ <em class="replaceable"><code>paths</code></em>.</p></dd></dl></div></div><div class="refsection"><a id="idm139733299531008"></a><h3>Examples</h3><p>Print the closure (runtime dependencies) of the
+<span class="command"><strong>svn</strong></span> program in the current user environment:
+
+</p><pre class="screen">
+$ nix-store -qR $(which svn)
+/nix/store/5mbglq5ldqld8sj57273aljwkfvj22mc-subversion-1.1.4
+/nix/store/9lz9yc6zgmc0vlqmn2ipcpkjlmbi51vv-glibc-2.3.4
+<em class="replaceable"><code>...</code></em></pre><p>
+
+</p><p>Print the build-time dependencies of <span class="command"><strong>svn</strong></span>:
+
+</p><pre class="screen">
+$ nix-store -qR $(nix-store -qd $(which svn))
+/nix/store/02iizgn86m42q905rddvg4ja975bk2i4-grep-2.5.1.tar.bz2.drv
+/nix/store/07a2bzxmzwz5hp58nf03pahrv2ygwgs3-gcc-wrapper.sh
+/nix/store/0ma7c9wsbaxahwwl04gbw3fcd806ski4-glibc-2.3.4.drv
+<em class="replaceable"><code>... lots of other paths ...</code></em></pre><p>
+
+The difference with the previous example is that we ask the closure of
+the derivation (<code class="option">-qd</code>), not the closure of the output
+path that contains <span class="command"><strong>svn</strong></span>.</p><p>Show the build-time dependencies as a tree:
+
+</p><pre class="screen">
+$ nix-store -q --tree $(nix-store -qd $(which svn))
+/nix/store/7i5082kfb6yjbqdbiwdhhza0am2xvh6c-subversion-1.1.4.drv
++---/nix/store/d8afh10z72n8l1cr5w42366abiblgn54-builder.sh
++---/nix/store/fmzxmpjx2lh849ph0l36snfj9zdibw67-bash-3.0.drv
+| +---/nix/store/570hmhmx3v57605cqg9yfvvyh0nnb8k8-bash
+| +---/nix/store/p3srsbd8dx44v2pg6nbnszab5mcwx03v-builder.sh
+<em class="replaceable"><code>...</code></em></pre><p>
+
+</p><p>Show all paths that depend on the same OpenSSL library as
+<span class="command"><strong>svn</strong></span>:
+
+</p><pre class="screen">
+$ nix-store -q --referrers $(nix-store -q --binding openssl $(nix-store -qd $(which svn)))
+/nix/store/23ny9l9wixx21632y2wi4p585qhva1q8-sylpheed-1.0.0
+/nix/store/5mbglq5ldqld8sj57273aljwkfvj22mc-subversion-1.1.4
+/nix/store/dpmvp969yhdqs7lm2r1a3gng7pyq6vy4-subversion-1.1.3
+/nix/store/l51240xqsgg8a7yrbqdx1rfzyv6l26fx-lynx-2.8.5</pre><p>
+
+</p><p>Show all paths that directly or indirectly depend on the Glibc
+(C library) used by <span class="command"><strong>svn</strong></span>:
+
+</p><pre class="screen">
+$ nix-store -q --referrers-closure $(ldd $(which svn) | grep /libc.so | awk '{print $3}')
+/nix/store/034a6h4vpz9kds5r6kzb9lhh81mscw43-libgnomeprintui-2.8.2
+/nix/store/15l3yi0d45prm7a82pcrknxdh6nzmxza-gawk-3.1.4
+<em class="replaceable"><code>...</code></em></pre><p>
+
+Note that <span class="command"><strong>ldd</strong></span> is a command that prints out the
+dynamic libraries used by an ELF executable.</p><p>Make a picture of the runtime dependency graph of the current
+user environment:
+
+</p><pre class="screen">
+$ nix-store -q --graph ~/.nix-profile | dot -Tps > graph.ps
+$ gv graph.ps</pre><p>
+
+</p><p>Show every garbage collector root that points to a store path
+that depends on <span class="command"><strong>svn</strong></span>:
+
+</p><pre class="screen">
+$ nix-store -q --roots $(which svn)
+/nix/var/nix/profiles/default-81-link
+/nix/var/nix/profiles/default-82-link
+/nix/var/nix/profiles/per-user/eelco/profile-97-link
+</pre><p>
+
+</p></div></div><div class="refsection"><a id="idm139733299516176"></a><h2>Operation <code class="option">--add</code></h2><div class="refsection"><a id="idm139733299515344"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--add</code> <em class="replaceable"><code>paths</code></em>... </p></div></div><div class="refsection"><a id="idm139733299511968"></a><h3>Description</h3><p>The operation <code class="option">--add</code> adds the specified paths to
+the Nix store. It prints the resulting paths in the Nix store on
+standard output.</p></div><div class="refsection"><a id="idm139733299510336"></a><h3>Example</h3><pre class="screen">
+$ nix-store --add ./foo.c
+/nix/store/m7lrha58ph6rcnv109yzx1nk1cj7k7zf-foo.c</pre></div></div><div class="refsection"><a id="idm139733299508688"></a><h2>Operation <code class="option">--add-fixed</code></h2><div class="refsection"><a id="idm139733299507856"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> [<code class="option">--recursive</code>] <code class="option">--add-fixed</code> <em class="replaceable"><code>algorithm</code></em> <em class="replaceable"><code>paths</code></em>... </p></div></div><div class="refsection"><a id="idm139733299503120"></a><h3>Description</h3><p>The operation <code class="option">--add-fixed</code> adds the specified paths to
+the Nix store. Unlike <code class="option">--add</code> paths are registered using the
+specified hashing algorithm, resulting in the same output path as a fixed-output
+derivation. This can be used for sources that are not available from a public
+url or broke since the download expression was written.
+</p><p>This operation has the following options:
+
+</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--recursive</code></span></dt><dd><p>
+ Use recursive instead of flat hashing mode, used when adding directories
+ to the store.
+ </p></dd></dl></div><p>
+
+</p></div><div class="refsection"><a id="idm139733299498592"></a><h3>Example</h3><pre class="screen">
+$ nix-store --add-fixed sha256 ./hello-2.10.tar.gz
+/nix/store/3x7dwzq014bblazs7kq20p9hyzz0qh8g-hello-2.10.tar.gz</pre></div></div><div class="refsection"><a id="refsec-nix-store-verify"></a><h2>Operation <code class="option">--verify</code></h2><div class="refsection"><a id="idm139733299495712"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--verify</code> [<code class="option">--check-contents</code>] [<code class="option">--repair</code>]</p></div></div><div class="refsection"><a id="idm139733299492208"></a><h3>Description</h3><p>The operation <code class="option">--verify</code> verifies the internal
+consistency of the Nix database, and the consistency between the Nix
+database and the Nix store. Any inconsistencies encountered are
+automatically repaired. Inconsistencies are generally the result of
+the Nix store or database being modified by non-Nix tools, or of bugs
+in Nix itself.</p><p>This operation has the following options:
+
+</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--check-contents</code></span></dt><dd><p>Checks that the contents of every valid store path
+ has not been altered by computing a SHA-256 hash of the contents
+ and comparing it with the hash stored in the Nix database at build
+ time. Paths that have been modified are printed out. For large
+ stores, <code class="option">--check-contents</code> is obviously quite
+ slow.</p></dd><dt><span class="term"><code class="option">--repair</code></span></dt><dd><p>If any valid path is missing from the store, or
+ (if <code class="option">--check-contents</code> is given) the contents of a
+ valid path has been modified, then try to repair the path by
+ redownloading it. See <span class="command"><strong>nix-store --repair-path</strong></span>
+ for details.</p></dd></dl></div><p>
+
+</p></div></div><div class="refsection"><a id="idm139733299484592"></a><h2>Operation <code class="option">--verify-path</code></h2><div class="refsection"><a id="idm139733299483760"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--verify-path</code> <em class="replaceable"><code>paths</code></em>... </p></div></div><div class="refsection"><a id="idm139733299480256"></a><h3>Description</h3><p>The operation <code class="option">--verify-path</code> compares the
+contents of the given store paths to their cryptographic hashes stored
+in Nix’s database. For every changed path, it prints a warning
+message. The exit status is 0 if no path has changed, and 1
+otherwise.</p></div><div class="refsection"><a id="idm139733299478288"></a><h3>Example</h3><p>To verify the integrity of the <span class="command"><strong>svn</strong></span> command and all its dependencies:
+
+</p><pre class="screen">
+$ nix-store --verify-path $(nix-store -qR $(which svn))
+</pre><p>
+
+</p></div></div><div class="refsection"><a id="idm139733299475792"></a><h2>Operation <code class="option">--repair-path</code></h2><div class="refsection"><a id="idm139733299474960"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--repair-path</code> <em class="replaceable"><code>paths</code></em>... </p></div></div><div class="refsection"><a id="idm139733299471456"></a><h3>Description</h3><p>The operation <code class="option">--repair-path</code> attempts to
+“repair” the specified paths by redownloading them using the available
+substituters. If no substitutes are available, then repair is not
+possible.</p><div class="warning"><h3 class="title">Warning</h3><p>During repair, there is a very small time window during
+which the old path (if it exists) is moved out of the way and replaced
+with the new path. If repair is interrupted in between, then the
+system may be left in a broken state (e.g., if the path contains a
+critical system component like the GNU C Library).</p></div></div><div class="refsection"><a id="idm139733299468768"></a><h3>Example</h3><pre class="screen">
+$ nix-store --verify-path /nix/store/dj7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13
+path `/nix/store/dj7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13' was modified!
+ expected hash `2db57715ae90b7e31ff1f2ecb8c12ec1cc43da920efcbe3b22763f36a1861588',
+ got `481c5aa5483ebc97c20457bb8bca24deea56550d3985cda0027f67fe54b808e4'
+
+$ nix-store --repair-path /nix/store/dj7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13
+fetching path `/nix/store/d7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13'...
+…
+</pre></div></div><div class="refsection"><a id="refsec-nix-store-dump"></a><h2>Operation <code class="option">--dump</code></h2><div class="refsection"><a id="idm139733299465056"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--dump</code> <em class="replaceable"><code>path</code></em> </p></div></div><div class="refsection"><a id="idm139733299461824"></a><h3>Description</h3><p>The operation <code class="option">--dump</code> produces a NAR (Nix
+ARchive) file containing the contents of the file system tree rooted
+at <em class="replaceable"><code>path</code></em>. The archive is written to
+standard output.</p><p>A NAR archive is like a TAR or Zip archive, but it contains only
+the information that Nix considers important. For instance,
+timestamps are elided because all files in the Nix store have their
+timestamp set to 0 anyway. Likewise, all permissions are left out
+except for the execute bit, because all files in the Nix store have
+444 or 555 permission.</p><p>Also, a NAR archive is <span class="emphasis"><em>canonical</em></span>, meaning
+that “equal” paths always produce the same NAR archive. For instance,
+directory entries are always sorted so that the actual on-disk order
+doesn’t influence the result. This means that the cryptographic hash
+of a NAR dump of a path is usable as a fingerprint of the contents of
+the path. Indeed, the hashes of store paths stored in Nix’s database
+(see <a class="link" href="#refsec-nix-store-query" title="Operation --query"><code class="literal">nix-store -q
+--hash</code></a>) are SHA-256 hashes of the NAR dump of each
+store path.</p><p>NAR archives support filenames of unlimited length and 64-bit
+file sizes. They can contain regular files, directories, and symbolic
+links, but not other types of files (such as device nodes).</p><p>A Nix archive can be unpacked using <code class="literal">nix-store
+--restore</code>.</p></div></div><div class="refsection"><a id="idm139733299454672"></a><h2>Operation <code class="option">--restore</code></h2><div class="refsection"><a id="idm139733299453840"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--restore</code> <em class="replaceable"><code>path</code></em> </p></div></div><div class="refsection"><a id="idm139733299450608"></a><h3>Description</h3><p>The operation <code class="option">--restore</code> unpacks a NAR archive
+to <em class="replaceable"><code>path</code></em>, which must not already exist. The
+archive is read from standard input.</p></div></div><div class="refsection"><a id="refsec-nix-store-export"></a><h2>Operation <code class="option">--export</code></h2><div class="refsection"><a id="idm139733299446736"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--export</code> <em class="replaceable"><code>paths</code></em>... </p></div></div><div class="refsection"><a id="idm139733299443232"></a><h3>Description</h3><p>The operation <code class="option">--export</code> writes a serialisation
+of the specified store paths to standard output in a format that can
+be imported into another Nix store with <span class="command"><strong><a class="command" href="#refsec-nix-store-import" title="Operation --import">nix-store --import</a></strong></span>. This
+is like <span class="command"><strong><a class="command" href="#refsec-nix-store-dump" title="Operation --dump">nix-store
+--dump</a></strong></span>, except that the NAR archive produced by that command
+doesn’t contain the necessary meta-information to allow it to be
+imported into another Nix store (namely, the set of references of the
+path).</p><p>This command does not produce a <span class="emphasis"><em>closure</em></span> of
+the specified paths, so if a store path references other store paths
+that are missing in the target Nix store, the import will fail. To
+copy a whole closure, do something like:
+
+</p><pre class="screen">
+$ nix-store --export $(nix-store -qR <em class="replaceable"><code>paths</code></em>) > out</pre><p>
+
+To import the whole closure again, run:
+
+</p><pre class="screen">
+$ nix-store --import < out</pre><p>
+
+</p></div></div><div class="refsection"><a id="refsec-nix-store-import"></a><h2>Operation <code class="option">--import</code></h2><div class="refsection"><a id="idm139733299435520"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--import</code> </p></div></div><div class="refsection"><a id="idm139733299433104"></a><h3>Description</h3><p>The operation <code class="option">--import</code> reads a serialisation of
+a set of store paths produced by <span class="command"><strong><a class="command" href="#refsec-nix-store-export" title="Operation --export">nix-store --export</a></strong></span> from
+standard input and adds those store paths to the Nix store. Paths
+that already exist in the Nix store are ignored. If a path refers to
+another path that doesn’t exist in the Nix store, the import
+fails.</p></div></div><div class="refsection"><a id="idm139733299429888"></a><h2>Operation <code class="option">--optimise</code></h2><div class="refsection"><a id="idm139733299429056"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--optimise</code> </p></div></div><div class="refsection"><a id="idm139733299426640"></a><h3>Description</h3><p>The operation <code class="option">--optimise</code> reduces Nix store disk
+space usage by finding identical files in the store and hard-linking
+them to each other. It typically reduces the size of the store by
+something like 25-35%. Only regular files and symlinks are
+hard-linked in this manner. Files are considered identical when they
+have the same NAR archive serialisation: that is, regular files must
+have the same contents and permission (executable or non-executable),
+and symlinks must have the same contents.</p><p>After completion, or when the command is interrupted, a report
+on the achieved savings is printed on standard error.</p><p>Use <code class="option">-vv</code> or <code class="option">-vvv</code> to get some
+progress indication.</p></div><div class="refsection"><a id="idm139733299423328"></a><h3>Example</h3><pre class="screen">
+$ nix-store --optimise
+hashing files in `/nix/store/qhqx7l2f1kmwihc9bnxs7rc159hsxnf3-gcc-4.1.1'
+<em class="replaceable"><code>...</code></em>
+541838819 bytes (516.74 MiB) freed by hard-linking 54143 files;
+there are 114486 files with equal contents out of 215894 files in total
+</pre></div></div><div class="refsection"><a id="idm139733299421120"></a><h2>Operation <code class="option">--read-log</code></h2><div class="refsection"><a id="idm139733299420288"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> { <code class="option">--read-log</code> | <code class="option">-l</code> } <em class="replaceable"><code>paths</code></em>... </p></div></div><div class="refsection"><a id="idm139733299415376"></a><h3>Description</h3><p>The operation <code class="option">--read-log</code> prints the build log
+of the specified store paths on standard output. The build log is
+whatever the builder of a derivation wrote to standard output and
+standard error. If a store path is not a derivation, the deriver of
+the store path is used.</p><p>Build logs are kept in
+<code class="filename">/nix/var/log/nix/drvs</code>. However, there is no
+guarantee that a build log is available for any particular store path.
+For instance, if the path was downloaded as a pre-built binary through
+a substitute, then the log is unavailable.</p></div><div class="refsection"><a id="idm139733299412560"></a><h3>Example</h3><pre class="screen">
+$ nix-store -l $(which ktorrent)
+building /nix/store/dhc73pvzpnzxhdgpimsd9sw39di66ph1-ktorrent-2.2.1
+unpacking sources
+unpacking source archive /nix/store/p8n1jpqs27mgkjw07pb5269717nzf5f8-ktorrent-2.2.1.tar.gz
+ktorrent-2.2.1/
+ktorrent-2.2.1/NEWS
+<em class="replaceable"><code>...</code></em>
+</pre></div></div><div class="refsection"><a id="idm139733299410368"></a><h2>Operation <code class="option">--dump-db</code></h2><div class="refsection"><a id="idm139733299409536"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--dump-db</code> [<em class="replaceable"><code>paths</code></em>...]</p></div></div><div class="refsection"><a id="idm139733299406304"></a><h3>Description</h3><p>The operation <code class="option">--dump-db</code> writes a dump of the
+Nix database to standard output. It can be loaded into an empty Nix
+store using <code class="option">--load-db</code>. This is useful for making
+backups and when migrating to different database schemas.</p><p>By default, <code class="option">--dump-db</code> will dump the entire Nix
+database. When one or more store paths is passed, only the subset of
+the Nix database for those store paths is dumped. As with
+<code class="option">--export</code>, the user is responsible for passing all the
+store paths for a closure. See <code class="option">--export</code> for an
+example.</p></div></div><div class="refsection"><a id="idm139733299401712"></a><h2>Operation <code class="option">--load-db</code></h2><div class="refsection"><a id="idm139733299400880"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--load-db</code> </p></div></div><div class="refsection"><a id="idm139733299398464"></a><h3>Description</h3><p>The operation <code class="option">--load-db</code> reads a dump of the Nix
+database created by <code class="option">--dump-db</code> from standard input and
+loads it into the Nix database.</p></div></div><div class="refsection"><a id="idm139733299395904"></a><h2>Operation <code class="option">--print-env</code></h2><div class="refsection"><a id="idm139733299395072"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--print-env</code> <em class="replaceable"><code>drvpath</code></em> </p></div></div><div class="refsection"><a id="idm139733299391840"></a><h3>Description</h3><p>The operation <code class="option">--print-env</code> prints out the
+environment of a derivation in a format that can be evaluated by a
+shell. The command line arguments of the builder are placed in the
+variable <code class="envar">_args</code>.</p></div><div class="refsection"><a id="idm139733299389744"></a><h3>Example</h3><pre class="screen">
+$ nix-store --print-env $(nix-instantiate '<nixpkgs>' -A firefox)
+<em class="replaceable"><code>…</code></em>
+export src; src='/nix/store/plpj7qrwcz94z2psh6fchsi7s8yihc7k-firefox-12.0.source.tar.bz2'
+export stdenv; stdenv='/nix/store/7c8asx3yfrg5dg1gzhzyq2236zfgibnn-stdenv'
+export system; system='x86_64-linux'
+export _args; _args='-e /nix/store/9krlzvny65gdc8s7kpb6lkx8cd02c25c-default-builder.sh'
+</pre></div></div><div class="refsection"><a id="rsec-nix-store-generate-binary-cache-key"></a><h2>Operation <code class="option">--generate-binary-cache-key</code></h2><div class="refsection"><a id="idm139733299386016"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code>
+ <code class="option">--generate-binary-cache-key</code>
+ <code class="option">key-name</code>
+ <code class="option">secret-key-file</code>
+ <code class="option">public-key-file</code>
+ </p></div></div><div class="refsection"><a id="idm139733299382080"></a><h3>Description</h3><p>This command generates an <a class="link" href="http://ed25519.cr.yp.to/" target="_top">Ed25519 key pair</a> that can
+be used to create a signed binary cache. It takes three mandatory
+parameters:
+
+</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>A key name, such as
+ <code class="literal">cache.example.org-1</code>, that is used to look up keys
+ on the client when it verifies signatures. It can be anything, but
+ it’s suggested to use the host name of your cache
+ (e.g. <code class="literal">cache.example.org</code>) with a suffix denoting
+ the number of the key (to be incremented every time you need to
+ revoke a key).</p></li><li class="listitem"><p>The file name where the secret key is to be
+ stored.</p></li><li class="listitem"><p>The file name where the public key is to be
+ stored.</p></li></ol></div><p>
+
+</p></div></div></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-utilities"></a>Chapter 23. Utilities</h2></div></div></div><p>This section lists utilities that you can use when you
+work with Nix.</p><div class="refentry"><a id="sec-nix-channel"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix-channel — manage Nix channels</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">nix-channel</code> { <code class="option">--add</code> <em class="replaceable"><code>url</code></em> [<em class="replaceable"><code>name</code></em>] | <code class="option">--remove</code> <em class="replaceable"><code>name</code></em> | <code class="option">--list</code> | <code class="option">--update</code> [<em class="replaceable"><code>names</code></em>...] | <code class="option">--rollback</code> [<em class="replaceable"><code>generation</code></em>] }</p></div></div><div class="refsection"><a id="idm139733299360672"></a><h2>Description</h2><p>A Nix channel is a mechanism that allows you to automatically
+stay up-to-date with a set of pre-built Nix expressions. A Nix
+channel is just a URL that points to a place containing a set of Nix
+expressions. <span class="phrase">See also <a class="xref" href="#sec-channels" title="Chapter 12. Channels">Chapter 12, <em>Channels</em></a>.</span></p><p>To see the list of official NixOS channels, visit <a class="link" href="https://nixos.org/channels" target="_top">https://nixos.org/channels</a>.</p><p>This command has the following operations:
+
+</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--add</code> <em class="replaceable"><code>url</code></em> [<em class="replaceable"><code>name</code></em>]</span></dt><dd><p>Adds a channel named
+ <em class="replaceable"><code>name</code></em> with URL
+ <em class="replaceable"><code>url</code></em> to the list of subscribed channels.
+ If <em class="replaceable"><code>name</code></em> is omitted, it defaults to the
+ last component of <em class="replaceable"><code>url</code></em>, with the
+ suffixes <code class="literal">-stable</code> or
+ <code class="literal">-unstable</code> removed.</p></dd><dt><span class="term"><code class="option">--remove</code> <em class="replaceable"><code>name</code></em></span></dt><dd><p>Removes the channel named
+ <em class="replaceable"><code>name</code></em> from the list of subscribed
+ channels.</p></dd><dt><span class="term"><code class="option">--list</code></span></dt><dd><p>Prints the names and URLs of all subscribed
+ channels on standard output.</p></dd><dt><span class="term"><code class="option">--update</code> [<em class="replaceable"><code>names</code></em>…]</span></dt><dd><p>Downloads the Nix expressions of all subscribed
+ channels (or only those included in
+ <em class="replaceable"><code>names</code></em> if specified) and makes them the
+ default for <span class="command"><strong>nix-env</strong></span> operations (by symlinking
+ them from the directory
+ <code class="filename">~/.nix-defexpr</code>).</p></dd><dt><span class="term"><code class="option">--rollback</code> [<em class="replaceable"><code>generation</code></em>]</span></dt><dd><p>Reverts the previous call to <span class="command"><strong>nix-channel
+ --update</strong></span>. Optionally, you can specify a specific channel
+ generation number to restore.</p></dd></dl></div><p>
+
+</p><p>Note that <code class="option">--add</code> does not automatically perform
+an update.</p><p>The list of subscribed channels is stored in
+<code class="filename">~/.nix-channels</code>.</p></div><div class="refsection"><a id="idm139733299340240"></a><h2>Examples</h2><p>To subscribe to the Nixpkgs channel and install the GNU Hello package:</p><pre class="screen">
+$ nix-channel --add https://nixos.org/channels/nixpkgs-unstable
+$ nix-channel --update
+$ nix-env -iA nixpkgs.hello</pre><p>You can revert channel updates using <code class="option">--rollback</code>:</p><pre class="screen">
+$ nix-instantiate --eval -E '(import <nixpkgs> {}).lib.version'
+"14.04.527.0e935f1"
+
+$ nix-channel --rollback
+switching from generation 483 to 482
+
+$ nix-instantiate --eval -E '(import <nixpkgs> {}).lib.version'
+"14.04.526.dbadfad"
+</pre></div><div class="refsection"><a id="idm139733299336912"></a><h2>Files</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="filename">/nix/var/nix/profiles/per-user/<em class="replaceable"><code>username</code></em>/channels</code></span></dt><dd><p><span class="command"><strong>nix-channel</strong></span> uses a
+ <span class="command"><strong>nix-env</strong></span> profile to keep track of previous
+ versions of the subscribed channels. Every time you run
+ <span class="command"><strong>nix-channel --update</strong></span>, a new channel generation
+ (that is, a symlink to the channel Nix expressions in the Nix store)
+ is created. This enables <span class="command"><strong>nix-channel --rollback</strong></span>
+ to revert to previous versions.</p></dd><dt><span class="term"><code class="filename">~/.nix-defexpr/channels</code></span></dt><dd><p>This is a symlink to
+ <code class="filename">/nix/var/nix/profiles/per-user/<em class="replaceable"><code>username</code></em>/channels</code>. It
+ ensures that <span class="command"><strong>nix-env</strong></span> can find your channels. In
+ a multi-user installation, you may also have
+ <code class="filename">~/.nix-defexpr/channels_root</code>, which links to
+ the channels of the root user.</p></dd></dl></div></div><div class="refsection"><a id="idm139733299328928"></a><h2>Channel format</h2><p>A channel URL should point to a directory containing the
+following files:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="filename">nixexprs.tar.xz</code></span></dt><dd><p>A tarball containing Nix expressions and files
+ referenced by them (such as build scripts and patches). At the
+ top level, the tarball should contain a single directory. That
+ directory must contain a file <code class="filename">default.nix</code>
+ that serves as the channel’s “entry point”.</p></dd></dl></div></div></div><div class="refentry"><div class="refentry.separator"><hr /></div><a id="sec-nix-collect-garbage"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix-collect-garbage — delete unreachable store paths</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">nix-collect-garbage</code> [<code class="option">--delete-old</code>] [<code class="option">-d</code>] [<code class="option">--delete-older-than</code> <em class="replaceable"><code>period</code></em>] [<code class="option">--max-freed</code> <em class="replaceable"><code>bytes</code></em>] [<code class="option">--dry-run</code>]</p></div></div><div class="refsection"><a id="idm139733299315776"></a><h2>Description</h2><p>The command <span class="command"><strong>nix-collect-garbage</strong></span> is mostly an
+alias of <a class="link" href="#rsec-nix-store-gc" title="Operation --gc"><span class="command"><strong>nix-store
+--gc</strong></span></a>, that is, it deletes all unreachable paths in
+the Nix store to clean up your system. However, it provides two
+additional options: <code class="option">-d</code> (<code class="option">--delete-old</code>),
+which deletes all old generations of all profiles in
+<code class="filename">/nix/var/nix/profiles</code> by invoking
+<code class="literal">nix-env --delete-generations old</code> on all profiles
+(of course, this makes rollbacks to previous configurations
+impossible); and
+<code class="option">--delete-older-than</code> <em class="replaceable"><code>period</code></em>,
+where period is a value such as <code class="literal">30d</code>, which deletes
+all generations older than the specified number of days in all profiles
+in <code class="filename">/nix/var/nix/profiles</code> (except for the generations
+that were active at that point in time).
+</p></div><div class="refsection"><a id="idm139733299309536"></a><h2>Example</h2><p>To delete from the Nix store everything that is not used by the
+current generations of each profile, do
+
+</p><pre class="screen">
+$ nix-collect-garbage -d</pre><p>
+
+</p></div></div><div class="refentry"><div class="refentry.separator"><hr /></div><a id="sec-nix-copy-closure"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix-copy-closure — copy a closure to or from a remote machine via SSH</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">nix-copy-closure</code> [ <code class="option">--to</code> | <code class="option">--from</code> ] [<code class="option">--gzip</code>] [<code class="option">--include-outputs</code>] [ <code class="option">--use-substitutes</code> | <code class="option">-s</code> ] [<code class="option">-v</code>]
+ <em class="replaceable"><code>user@</code></em><em class="replaceable"><code>machine</code></em>
+ <em class="replaceable"><code>paths</code></em> </p></div></div><div class="refsection"><a id="idm139733299294048"></a><h2>Description</h2><p><span class="command"><strong>nix-copy-closure</strong></span> gives you an easy and
+efficient way to exchange software between machines. Given one or
+more Nix store <em class="replaceable"><code>paths</code></em> on the local
+machine, <span class="command"><strong>nix-copy-closure</strong></span> computes the closure of
+those paths (i.e. all their dependencies in the Nix store), and copies
+all paths in the closure to the remote machine via the
+<span class="command"><strong>ssh</strong></span> (Secure Shell) command. With the
+<code class="option">--from</code>, the direction is reversed:
+the closure of <em class="replaceable"><code>paths</code></em> on a remote machine is
+copied to the Nix store on the local machine.</p><p>This command is efficient because it only sends the store paths
+that are missing on the target machine.</p><p>Since <span class="command"><strong>nix-copy-closure</strong></span> calls
+<span class="command"><strong>ssh</strong></span>, you may be asked to type in the appropriate
+password or passphrase. In fact, you may be asked
+<span class="emphasis"><em>twice</em></span> because <span class="command"><strong>nix-copy-closure</strong></span>
+currently connects twice to the remote machine, first to get the set
+of paths missing on the target machine, and second to send the dump of
+those paths. If this bothers you, use
+<span class="command"><strong>ssh-agent</strong></span>.</p><div class="refsection"><a id="idm139733299286896"></a><h3>Options</h3><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--to</code></span></dt><dd><p>Copy the closure of
+ <em class="replaceable"><code>paths</code></em> from the local Nix store to the
+ Nix store on <em class="replaceable"><code>machine</code></em>. This is the
+ default.</p></dd><dt><span class="term"><code class="option">--from</code></span></dt><dd><p>Copy the closure of
+ <em class="replaceable"><code>paths</code></em> from the Nix store on
+ <em class="replaceable"><code>machine</code></em> to the local Nix
+ store.</p></dd><dt><span class="term"><code class="option">--gzip</code></span></dt><dd><p>Enable compression of the SSH
+ connection.</p></dd><dt><span class="term"><code class="option">--include-outputs</code></span></dt><dd><p>Also copy the outputs of store derivations
+ included in the closure.</p></dd><dt><span class="term"><code class="option">--use-substitutes</code> / <code class="option">-s</code></span></dt><dd><p>Attempt to download missing paths on the target
+ machine using Nix’s substitute mechanism. Any paths that cannot
+ be substituted on the target are still copied normally from the
+ source. This is useful, for instance, if the connection between
+ the source and target machine is slow, but the connection between
+ the target machine and <code class="literal">nixos.org</code> (the default
+ binary cache server) is fast.</p></dd><dt><span class="term"><code class="option">-v</code></span></dt><dd><p>Show verbose output.</p></dd></dl></div></div><div class="refsection"><a id="idm139733299274272"></a><h3>Environment variables</h3><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="envar">NIX_SSHOPTS</code></span></dt><dd><p>Additional options to be passed to
+ <span class="command"><strong>ssh</strong></span> on the command line.</p></dd></dl></div></div><div class="refsection"><a id="idm139733299271440"></a><h3>Examples</h3><p>Copy Firefox with all its dependencies to a remote machine:
+
+</p><pre class="screen">
+$ nix-copy-closure --to alice@itchy.labs $(type -tP firefox)</pre><p>
+
+</p><p>Copy Subversion from a remote machine and then install it into a
+user environment:
+
+</p><pre class="screen">
+$ nix-copy-closure --from alice@itchy.labs \
+ /nix/store/0dj0503hjxy5mbwlafv1rsbdiyx1gkdy-subversion-1.4.4
+$ nix-env -i /nix/store/0dj0503hjxy5mbwlafv1rsbdiyx1gkdy-subversion-1.4.4
+</pre><p>
+
+</p></div></div></div><div class="refentry"><div class="refentry.separator"><hr /></div><a id="sec-nix-daemon"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix-daemon — Nix multi-user support daemon</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">nix-daemon</code> </p></div></div><div class="refsection"><a id="idm139733299262736"></a><h2>Description</h2><p>The Nix daemon is necessary in multi-user Nix installations. It
+performs build actions and other operations on the Nix store on behalf
+of unprivileged users.</p></div></div><div class="refentry"><div class="refentry.separator"><hr /></div><a id="sec-nix-hash"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix-hash — compute the cryptographic hash of a path</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">nix-hash</code> [<code class="option">--flat</code>] [<code class="option">--base32</code>] [<code class="option">--truncate</code>] [<code class="option">--type</code> <em class="replaceable"><code>hashAlgo</code></em>] <em class="replaceable"><code>path</code></em>... </p></div><div class="cmdsynopsis"><p><code class="command">nix-hash</code> <code class="option">--to-base16</code> <em class="replaceable"><code>hash</code></em>... </p></div><div class="cmdsynopsis"><p><code class="command">nix-hash</code> <code class="option">--to-base32</code> <em class="replaceable"><code>hash</code></em>... </p></div></div><div class="refsection"><a id="idm139733299246496"></a><h2>Description</h2><p>The command <span class="command"><strong>nix-hash</strong></span> computes the
+cryptographic hash of the contents of each
+<em class="replaceable"><code>path</code></em> and prints it on standard output. By
+default, it computes an MD5 hash, but other hash algorithms are
+available as well. The hash is printed in hexadecimal. To generate
+the same hash as <span class="command"><strong>nix-prefetch-url</strong></span> you have to
+specify multiple arguments, see below for an example.</p><p>The hash is computed over a <span class="emphasis"><em>serialisation</em></span>
+of each path: a dump of the file system tree rooted at the path. This
+allows directories and symlinks to be hashed as well as regular files.
+The dump is in the <span class="emphasis"><em>NAR format</em></span> produced by <a class="link" href="#refsec-nix-store-dump" title="Operation --dump"><span class="command"><strong>nix-store</strong></span>
+<code class="option">--dump</code></a>. Thus, <code class="literal">nix-hash
+<em class="replaceable"><code>path</code></em></code> yields the same
+cryptographic hash as <code class="literal">nix-store --dump
+<em class="replaceable"><code>path</code></em> | md5sum</code>.</p></div><div class="refsection"><a id="idm139733299239440"></a><h2>Options</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--flat</code></span></dt><dd><p>Print the cryptographic hash of the contents of
+ each regular file <em class="replaceable"><code>path</code></em>. That is, do
+ not compute the hash over the dump of
+ <em class="replaceable"><code>path</code></em>. The result is identical to that
+ produced by the GNU commands <span class="command"><strong>md5sum</strong></span> and
+ <span class="command"><strong>sha1sum</strong></span>.</p></dd><dt><span class="term"><code class="option">--base32</code></span></dt><dd><p>Print the hash in a base-32 representation rather
+ than hexadecimal. This base-32 representation is more compact and
+ can be used in Nix expressions (such as in calls to
+ <code class="function">fetchurl</code>).</p></dd><dt><span class="term"><code class="option">--truncate</code></span></dt><dd><p>Truncate hashes longer than 160 bits (such as
+ SHA-256) to 160 bits.</p></dd><dt><span class="term"><code class="option">--type</code> <em class="replaceable"><code>hashAlgo</code></em></span></dt><dd><p>Use the specified cryptographic hash algorithm,
+ which can be one of <code class="literal">md5</code>,
+ <code class="literal">sha1</code>, and
+ <code class="literal">sha256</code>.</p></dd><dt><span class="term"><code class="option">--to-base16</code></span></dt><dd><p>Don’t hash anything, but convert the base-32 hash
+ representation <em class="replaceable"><code>hash</code></em> to
+ hexadecimal.</p></dd><dt><span class="term"><code class="option">--to-base32</code></span></dt><dd><p>Don’t hash anything, but convert the hexadecimal
+ hash representation <em class="replaceable"><code>hash</code></em> to
+ base-32.</p></dd></dl></div></div><div class="refsection"><a id="idm139733299224832"></a><h2>Examples</h2><p>Computing the same hash as <span class="command"><strong>nix-prefetch-url</strong></span>:
+</p><pre class="screen">
+$ nix-prefetch-url file://<(echo test)
+1lkgqb6fclns49861dwk9rzb6xnfkxbpws74mxnx01z9qyv1pjpj
+$ nix-hash --type sha256 --flat --base32 <(echo test)
+1lkgqb6fclns49861dwk9rzb6xnfkxbpws74mxnx01z9qyv1pjpj
+</pre><p>
+</p><p>Computing hashes:
+
+</p><pre class="screen">
+$ mkdir test
+$ echo "hello" > test/world
+
+$ nix-hash test/ <em class="lineannotation"><span class="lineannotation">(MD5 hash; default)</span></em>
+8179d3caeff1869b5ba1744e5a245c04
+
+$ nix-store --dump test/ | md5sum <em class="lineannotation"><span class="lineannotation">(for comparison)</span></em>
+8179d3caeff1869b5ba1744e5a245c04 -
+
+$ nix-hash --type sha1 test/
+e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
+
+$ nix-hash --type sha1 --base32 test/
+nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
+
+$ nix-hash --type sha256 --flat test/
+error: reading file `test/': Is a directory
+
+$ nix-hash --type sha256 --flat test/world
+5891b5b522d5df086d0ff0b110fbd9d21bb4fc7163af34d08286a2e846f6be03</pre><p>
+
+</p><p>Converting between hexadecimal and base-32:
+
+</p><pre class="screen">
+$ nix-hash --type sha1 --to-base32 e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
+nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
+
+$ nix-hash --type sha1 --to-base16 nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
+e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6</pre><p>
+
+</p></div></div><div class="refentry"><div class="refentry.separator"><hr /></div><a id="sec-nix-instantiate"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix-instantiate — instantiate store derivations from Nix expressions</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">nix-instantiate</code> [ <code class="option">--parse</code> |
+ <code class="option">--eval</code>
+ [<code class="option">--strict</code>]
+ [<code class="option">--json</code>]
+ [<code class="option">--xml</code>]
+ ] [<code class="option">--read-write-mode</code>] [<code class="option">--arg</code> <em class="replaceable"><code>name</code></em> <em class="replaceable"><code>value</code></em>] [
+ { <code class="option">--attr</code> | <code class="option">-A</code> }
+ <em class="replaceable"><code>attrPath</code></em>
+ ] [<code class="option">--add-root</code> <em class="replaceable"><code>path</code></em>] [<code class="option">--indirect</code>] [ <code class="option">--expr</code> | <code class="option">-E</code> ] <em class="replaceable"><code>files</code></em>... </p></div><div class="cmdsynopsis"><p><code class="command">nix-instantiate</code> <code class="option">--find-file</code> <em class="replaceable"><code>files</code></em>... </p></div></div><div class="refsection"><a id="idm139733299196816"></a><h2>Description</h2><p>The command <span class="command"><strong>nix-instantiate</strong></span> generates <a class="link" href="#gloss-derivation" title="derivation">store derivations</a> from (high-level)
+Nix expressions. It evaluates the Nix expressions in each of
+<em class="replaceable"><code>files</code></em> (which defaults to
+<em class="replaceable"><code>./default.nix</code></em>). Each top-level expression
+should evaluate to a derivation, a list of derivations, or a set of
+derivations. The paths of the resulting store derivations are printed
+on standard output.</p><p>If <em class="replaceable"><code>files</code></em> is the character
+<code class="literal">-</code>, then a Nix expression will be read from standard
+input.</p><p>See also <a class="xref" href="#sec-common-options" title="Chapter 20. Common Options">Chapter 20, <em>Common Options</em></a> for a list of common options.</p></div><div class="refsection"><a id="idm139733299190864"></a><h2>Options</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--add-root</code> <em class="replaceable"><code>path</code></em>, </span><span class="term"><code class="option">--indirect</code></span></dt><dd><p>See the <a class="link" href="#opt-add-root">corresponding
+ options</a> in <span class="command"><strong>nix-store</strong></span>.</p></dd><dt><span class="term"><code class="option">--parse</code></span></dt><dd><p>Just parse the input files, and print their
+ abstract syntax trees on standard output in ATerm
+ format.</p></dd><dt><span class="term"><code class="option">--eval</code></span></dt><dd><p>Just parse and evaluate the input files, and print
+ the resulting values on standard output. No instantiation of
+ store derivations takes place.</p></dd><dt><span class="term"><code class="option">--find-file</code></span></dt><dd><p>Look up the given files in Nix’s search path (as
+ specified by the <code class="envar"><a class="envar" href="#env-NIX_PATH">NIX_PATH</a></code>
+ environment variable). If found, print the corresponding absolute
+ paths on standard output. For instance, if
+ <code class="envar">NIX_PATH</code> is
+ <code class="literal">nixpkgs=/home/alice/nixpkgs</code>, then
+ <code class="literal">nix-instantiate --find-file nixpkgs/default.nix</code>
+ will print
+ <code class="literal">/home/alice/nixpkgs/default.nix</code>.</p></dd><dt><span class="term"><code class="option">--strict</code></span></dt><dd><p>When used with <code class="option">--eval</code>,
+ recursively evaluate list elements and attributes. Normally, such
+ sub-expressions are left unevaluated (since the Nix expression
+ language is lazy).</p><div class="warning"><h3 class="title">Warning</h3><p>This option can cause non-termination, because lazy
+ data structures can be infinitely large.</p></div></dd><dt><span class="term"><code class="option">--json</code></span></dt><dd><p>When used with <code class="option">--eval</code>, print the resulting
+ value as an JSON representation of the abstract syntax tree rather
+ than as an ATerm.</p></dd><dt><span class="term"><code class="option">--xml</code></span></dt><dd><p>When used with <code class="option">--eval</code>, print the resulting
+ value as an XML representation of the abstract syntax tree rather than as
+ an ATerm. The schema is the same as that used by the <a class="link" href="#builtin-toXML"><code class="function">toXML</code> built-in</a>.
+ </p></dd><dt><span class="term"><code class="option">--read-write-mode</code></span></dt><dd><p>When used with <code class="option">--eval</code>, perform
+ evaluation in read/write mode so nix language features that
+ require it will still work (at the cost of needing to do
+ instantiation of every evaluated derivation). If this option is
+ not enabled, there may be uninstantiated store paths in the final
+ output.</p></dd></dl></div></div><div class="refsection"><a id="idm139733299169472"></a><h2>Examples</h2><p>Instantiating store derivations from a Nix expression, and
+building them using <span class="command"><strong>nix-store</strong></span>:
+
+</p><pre class="screen">
+$ nix-instantiate test.nix <em class="lineannotation"><span class="lineannotation">(instantiate)</span></em>
+/nix/store/cigxbmvy6dzix98dxxh9b6shg7ar5bvs-perl-BerkeleyDB-0.26.drv
+
+$ nix-store -r $(nix-instantiate test.nix) <em class="lineannotation"><span class="lineannotation">(build)</span></em>
+<em class="replaceable"><code>...</code></em>
+/nix/store/qhqk4n8ci095g3sdp93x7rgwyh9rdvgk-perl-BerkeleyDB-0.26 <em class="lineannotation"><span class="lineannotation">(output path)</span></em>
+
+$ ls -l /nix/store/qhqk4n8ci095g3sdp93x7rgwyh9rdvgk-perl-BerkeleyDB-0.26
+dr-xr-xr-x 2 eelco users 4096 1970-01-01 01:00 lib
+...</pre><p>
+
+</p><p>You can also give a Nix expression on the command line:
+
+</p><pre class="screen">
+$ nix-instantiate -E 'with import <nixpkgs> { }; hello'
+/nix/store/j8s4zyv75a724q38cb0r87rlczaiag4y-hello-2.8.drv
+</pre><p>
+
+This is equivalent to:
+
+</p><pre class="screen">
+$ nix-instantiate '<nixpkgs>' -A hello
+</pre><p>
+
+</p><p>Parsing and evaluating Nix expressions:
+
+</p><pre class="screen">
+$ nix-instantiate --parse -E '1 + 2'
+1 + 2
+
+$ nix-instantiate --eval -E '1 + 2'
+3
+
+$ nix-instantiate --eval --xml -E '1 + 2'
+<?xml version='1.0' encoding='utf-8'?>
+<expr>
+ <int value="3" />
+</expr></pre><p>
+
+</p><p>The difference between non-strict and strict evaluation:
+
+</p><pre class="screen">
+$ nix-instantiate --eval --xml -E 'rec { x = "foo"; y = x; }'
+<em class="replaceable"><code>...</code></em>
+ <attr name="x">
+ <string value="foo" />
+ </attr>
+ <attr name="y">
+ <unevaluated />
+ </attr>
+<em class="replaceable"><code>...</code></em></pre><p>
+
+Note that <code class="varname">y</code> is left unevaluated (the XML
+representation doesn’t attempt to show non-normal forms).
+
+</p><pre class="screen">
+$ nix-instantiate --eval --xml --strict -E 'rec { x = "foo"; y = x; }'
+<em class="replaceable"><code>...</code></em>
+ <attr name="x">
+ <string value="foo" />
+ </attr>
+ <attr name="y">
+ <string value="foo" />
+ </attr>
+<em class="replaceable"><code>...</code></em></pre><p>
+
+</p></div></div><div class="refentry"><div class="refentry.separator"><hr /></div><a id="sec-nix-prefetch-url"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix-prefetch-url — copy a file from a URL into the store and print its hash</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">nix-prefetch-url</code> [<code class="option">--version</code>] [<code class="option">--type</code> <em class="replaceable"><code>hashAlgo</code></em>] [<code class="option">--print-path</code>] [<code class="option">--unpack</code>] [<code class="option">--name</code> <em class="replaceable"><code>name</code></em>] <em class="replaceable"><code>url</code></em> [<em class="replaceable"><code>hash</code></em>]</p></div></div><div class="refsection"><a id="idm139733299148080"></a><h2>Description</h2><p>The command <span class="command"><strong>nix-prefetch-url</strong></span> downloads the
+file referenced by the URL <em class="replaceable"><code>url</code></em>, prints its
+cryptographic hash, and copies it into the Nix store. The file name
+in the store is
+<code class="filename"><em class="replaceable"><code>hash</code></em>-<em class="replaceable"><code>baseName</code></em></code>,
+where <em class="replaceable"><code>baseName</code></em> is everything following the
+final slash in <em class="replaceable"><code>url</code></em>.</p><p>This command is just a convenience for Nix expression writers.
+Often a Nix expression fetches some source distribution from the
+network using the <code class="literal">fetchurl</code> expression contained in
+Nixpkgs. However, <code class="literal">fetchurl</code> requires a
+cryptographic hash. If you don't know the hash, you would have to
+download the file first, and then <code class="literal">fetchurl</code> would
+download it again when you build your Nix expression. Since
+<code class="literal">fetchurl</code> uses the same name for the downloaded file
+as <span class="command"><strong>nix-prefetch-url</strong></span>, the redundant download can be
+avoided.</p><p>If <em class="replaceable"><code>hash</code></em> is specified, then a download
+is not performed if the Nix store already contains a file with the
+same hash and base name. Otherwise, the file is downloaded, and an
+error is signaled if the actual hash of the file does not match the
+specified hash.</p><p>This command prints the hash on standard output. Additionally,
+if the option <code class="option">--print-path</code> is used, the path of the
+downloaded file in the Nix store is also printed.</p></div><div class="refsection"><a id="idm139733299139072"></a><h2>Options</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--type</code> <em class="replaceable"><code>hashAlgo</code></em></span></dt><dd><p>Use the specified cryptographic hash algorithm,
+ which can be one of <code class="literal">md5</code>,
+ <code class="literal">sha1</code>, and
+ <code class="literal">sha256</code>.</p></dd><dt><span class="term"><code class="option">--print-path</code></span></dt><dd><p>Print the store path of the downloaded file on
+ standard output.</p></dd><dt><span class="term"><code class="option">--unpack</code></span></dt><dd><p>Unpack the archive (which must be a tarball or zip
+ file) and add the result to the Nix store. The resulting hash can
+ be used with functions such as Nixpkgs’s
+ <code class="varname">fetchzip</code> or
+ <code class="varname">fetchFromGitHub</code>.</p></dd><dt><span class="term"><code class="option">--name</code> <em class="replaceable"><code>name</code></em></span></dt><dd><p>Override the name of the file in the Nix store. By
+ default, this is
+ <code class="literal"><em class="replaceable"><code>hash</code></em>-<em class="replaceable"><code>basename</code></em></code>,
+ where <em class="replaceable"><code>basename</code></em> is the last component of
+ <em class="replaceable"><code>url</code></em>. Overriding the name is necessary
+ when <em class="replaceable"><code>basename</code></em> contains characters that
+ are not allowed in Nix store paths.</p></dd></dl></div></div><div class="refsection"><a id="idm139733299126752"></a><h2>Examples</h2><pre class="screen">
+$ nix-prefetch-url ftp://ftp.gnu.org/pub/gnu/hello/hello-2.10.tar.gz
+0ssi1wpaf7plaswqqjwigppsg5fyh99vdlb9kzl7c9lng89ndq1i
+
+$ nix-prefetch-url --print-path mirror://gnu/hello/hello-2.10.tar.gz
+0ssi1wpaf7plaswqqjwigppsg5fyh99vdlb9kzl7c9lng89ndq1i
+/nix/store/3x7dwzq014bblazs7kq20p9hyzz0qh8g-hello-2.10.tar.gz
+
+$ nix-prefetch-url --unpack --print-path https://github.com/NixOS/patchelf/archive/0.8.tar.gz
+079agjlv0hrv7fxnx9ngipx14gyncbkllxrp9cccnh3a50fxcmy7
+/nix/store/19zrmhm3m40xxaw81c8cqm6aljgrnwj2-0.8.tar.gz
+</pre></div></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-files"></a>Chapter 24. Files</h2></div></div></div><p>This section lists configuration files that you can use when you
+work with Nix.</p><div class="refentry"><a id="sec-conf-file"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix.conf — Nix configuration file</p></div><div class="refsection"><a id="idm139733299118992"></a><h2>Description</h2><p>By default Nix reads settings from the following places:</p><p>The system-wide configuration file
+<code class="filename"><em class="replaceable"><code>sysconfdir</code></em>/nix/nix.conf</code>
+(i.e. <code class="filename">/etc/nix/nix.conf</code> on most systems), or
+<code class="filename">$NIX_CONF_DIR/nix.conf</code> if
+<code class="envar">NIX_CONF_DIR</code> is set. Values loaded in this file are not forwarded to the Nix daemon. The
+client assumes that the daemon has already loaded them.
+</p><p>User-specific configuration files:</p><p>
+ If <code class="envar">NIX_USER_CONF_FILES</code> is set, then each path separated by
+ <code class="literal">:</code> will be loaded in reverse order.
+</p><p>
+ Otherwise it will look for <code class="filename">nix/nix.conf</code> files in
+ <code class="envar">XDG_CONFIG_DIRS</code> and <code class="envar">XDG_CONFIG_HOME</code>.
+
+ The default location is <code class="filename">$HOME/.config/nix.conf</code> if
+ those environment variables are unset.
+</p><p>The configuration files consist of
+<code class="literal"><em class="replaceable"><code>name</code></em> =
+<em class="replaceable"><code>value</code></em></code> pairs, one per line. Other
+files can be included with a line like <code class="literal">include
+<em class="replaceable"><code>path</code></em></code>, where
+<em class="replaceable"><code>path</code></em> is interpreted relative to the current
+conf file and a missing file is an error unless
+<code class="literal">!include</code> is used instead.
+Comments start with a <code class="literal">#</code> character. Here is an
+example configuration file:</p><pre class="programlisting">
+keep-outputs = true # Nice for developers
+keep-derivations = true # Idem
+</pre><p>You can override settings on the command line using the
+<code class="option">--option</code> flag, e.g. <code class="literal">--option keep-outputs
+false</code>.</p><p>The following settings are currently available:
+
+</p><div class="variablelist"><dl class="variablelist"><dt><a id="conf-allowed-uris"></a><span class="term"><code class="literal">allowed-uris</code></span></dt><dd><p>A list of URI prefixes to which access is allowed in
+ restricted evaluation mode. For example, when set to
+ <code class="literal">https://github.com/NixOS</code>, builtin functions
+ such as <code class="function">fetchGit</code> are allowed to access
+ <code class="literal">https://github.com/NixOS/patchelf.git</code>.</p></dd><dt><a id="conf-allow-import-from-derivation"></a><span class="term"><code class="literal">allow-import-from-derivation</code></span></dt><dd><p>By default, Nix allows you to <code class="function">import</code> from a derivation,
+ allowing building at evaluation time. With this option set to false, Nix will throw an error
+ when evaluating an expression that uses this feature, allowing users to ensure their evaluation
+ will not require any builds to take place.</p></dd><dt><a id="conf-allow-new-privileges"></a><span class="term"><code class="literal">allow-new-privileges</code></span></dt><dd><p>(Linux-specific.) By default, builders on Linux
+ cannot acquire new privileges by calling setuid/setgid programs or
+ programs that have file capabilities. For example, programs such
+ as <span class="command"><strong>sudo</strong></span> or <span class="command"><strong>ping</strong></span> will
+ fail. (Note that in sandbox builds, no such programs are available
+ unless you bind-mount them into the sandbox via the
+ <code class="option">sandbox-paths</code> option.) You can allow the
+ use of such programs by enabling this option. This is impure and
+ usually undesirable, but may be useful in certain scenarios
+ (e.g. to spin up containers or set up userspace network interfaces
+ in tests).</p></dd><dt><a id="conf-allowed-users"></a><span class="term"><code class="literal">allowed-users</code></span></dt><dd><p>A list of names of users (separated by whitespace) that
+ are allowed to connect to the Nix daemon. As with the
+ <code class="option">trusted-users</code> option, you can specify groups by
+ prefixing them with <code class="literal">@</code>. Also, you can allow
+ all users by specifying <code class="literal">*</code>. The default is
+ <code class="literal">*</code>.</p><p>Note that trusted users are always allowed to connect.</p></dd><dt><a id="conf-auto-optimise-store"></a><span class="term"><code class="literal">auto-optimise-store</code></span></dt><dd><p>If set to <code class="literal">true</code>, Nix
+ automatically detects files in the store that have identical
+ contents, and replaces them with hard links to a single copy.
+ This saves disk space. If set to <code class="literal">false</code> (the
+ default), you can still run <span class="command"><strong>nix-store
+ --optimise</strong></span> to get rid of duplicate
+ files.</p></dd><dt><a id="conf-builders"></a><span class="term"><code class="literal">builders</code></span></dt><dd><p>A list of machines on which to perform builds. <span class="phrase">See <a class="xref" href="#chap-distributed-builds" title="Chapter 16. Remote Builds">Chapter 16, <em>Remote Builds</em></a> for details.</span></p></dd><dt><a id="conf-builders-use-substitutes"></a><span class="term"><code class="literal">builders-use-substitutes</code></span></dt><dd><p>If set to <code class="literal">true</code>, Nix will instruct
+ remote build machines to use their own binary substitutes if available. In
+ practical terms, this means that remote hosts will fetch as many build
+ dependencies as possible from their own substitutes (e.g, from
+ <code class="literal">cache.nixos.org</code>), instead of waiting for this host to
+ upload them all. This can drastically reduce build times if the network
+ connection between this computer and the remote build host is slow. Defaults
+ to <code class="literal">false</code>.</p></dd><dt><a id="conf-build-users-group"></a><span class="term"><code class="literal">build-users-group</code></span></dt><dd><p>This options specifies the Unix group containing
+ the Nix build user accounts. In multi-user Nix installations,
+ builds should not be performed by the Nix account since that would
+ allow users to arbitrarily modify the Nix store and database by
+ supplying specially crafted builders; and they cannot be performed
+ by the calling user since that would allow him/her to influence
+ the build result.</p><p>Therefore, if this option is non-empty and specifies a valid
+ group, builds will be performed under the user accounts that are a
+ member of the group specified here (as listed in
+ <code class="filename">/etc/group</code>). Those user accounts should not
+ be used for any other purpose!</p><p>Nix will never run two builds under the same user account at
+ the same time. This is to prevent an obvious security hole: a
+ malicious user writing a Nix expression that modifies the build
+ result of a legitimate Nix expression being built by another user.
+ Therefore it is good to have as many Nix build user accounts as
+ you can spare. (Remember: uids are cheap.)</p><p>The build users should have permission to create files in
+ the Nix store, but not delete them. Therefore,
+ <code class="filename">/nix/store</code> should be owned by the Nix
+ account, its group should be the group specified here, and its
+ mode should be <code class="literal">1775</code>.</p><p>If the build users group is empty, builds will be performed
+ under the uid of the Nix process (that is, the uid of the caller
+ if <code class="envar">NIX_REMOTE</code> is empty, the uid under which the Nix
+ daemon runs if <code class="envar">NIX_REMOTE</code> is
+ <code class="literal">daemon</code>). Obviously, this should not be used in
+ multi-user settings with untrusted users.</p></dd><dt><a id="conf-compress-build-log"></a><span class="term"><code class="literal">compress-build-log</code></span></dt><dd><p>If set to <code class="literal">true</code> (the default),
+ build logs written to <code class="filename">/nix/var/log/nix/drvs</code>
+ will be compressed on the fly using bzip2. Otherwise, they will
+ not be compressed.</p></dd><dt><a id="conf-connect-timeout"></a><span class="term"><code class="literal">connect-timeout</code></span></dt><dd><p>The timeout (in seconds) for establishing connections in
+ the binary cache substituter. It corresponds to
+ <span class="command"><strong>curl</strong></span>’s <code class="option">--connect-timeout</code>
+ option.</p></dd><dt><a id="conf-cores"></a><span class="term"><code class="literal">cores</code></span></dt><dd><p>Sets the value of the
+ <code class="envar">NIX_BUILD_CORES</code> environment variable in the
+ invocation of builders. Builders can use this variable at their
+ discretion to control the maximum amount of parallelism. For
+ instance, in Nixpkgs, if the derivation attribute
+ <code class="varname">enableParallelBuilding</code> is set to
+ <code class="literal">true</code>, the builder passes the
+ <code class="option">-j<em class="replaceable"><code>N</code></em></code> flag to GNU Make.
+ It can be overridden using the <code class="option"><a class="option" href="#opt-cores">--cores</a></code> command line switch and
+ defaults to <code class="literal">1</code>. The value <code class="literal">0</code>
+ means that the builder should use all available CPU cores in the
+ system.</p><p>See also <a class="xref" href="#chap-tuning-cores-and-jobs" title="Chapter 17. Tuning Cores and Jobs">Chapter 17, <em>Tuning Cores and Jobs</em></a>.</p></dd><dt><a id="conf-diff-hook"></a><span class="term"><code class="literal">diff-hook</code></span></dt><dd><p>
+ Absolute path to an executable capable of diffing build results.
+ The hook executes if <a class="xref" href="#conf-run-diff-hook"><code class="literal">run-diff-hook</code></a> is
+ true, and the output of a build is known to not be the same.
+ This program is not executed to determine if two results are the
+ same.
+ </p><p>
+ The diff hook is executed by the same user and group who ran the
+ build. However, the diff hook does not have write access to the
+ store path just built.
+ </p><p>The diff hook program receives three parameters:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
+ A path to the previous build's results
+ </p></li><li class="listitem"><p>
+ A path to the current build's results
+ </p></li><li class="listitem"><p>
+ The path to the build's derivation
+ </p></li><li class="listitem"><p>
+ The path to the build's scratch directory. This directory
+ will exist only if the build was run with
+ <code class="option">--keep-failed</code>.
+ </p></li></ol></div><p>
+ The stderr and stdout output from the diff hook will not be
+ displayed to the user. Instead, it will print to the nix-daemon's
+ log.
+ </p><p>When using the Nix daemon, <code class="literal">diff-hook</code> must
+ be set in the <code class="filename">nix.conf</code> configuration file, and
+ cannot be passed at the command line.
+ </p></dd><dt><a id="conf-enforce-determinism"></a><span class="term"><code class="literal">enforce-determinism</code></span></dt><dd><p>See <a class="xref" href="#conf-repeat"><code class="literal">repeat</code></a>.</p></dd><dt><a id="conf-extra-sandbox-paths"></a><span class="term"><code class="literal">extra-sandbox-paths</code></span></dt><dd><p>A list of additional paths appended to
+ <code class="option">sandbox-paths</code>. Useful if you want to extend
+ its default value.</p></dd><dt><a id="conf-extra-platforms"></a><span class="term"><code class="literal">extra-platforms</code></span></dt><dd><p>Platforms other than the native one which
+ this machine is capable of building for. This can be useful for
+ supporting additional architectures on compatible machines:
+ i686-linux can be built on x86_64-linux machines (and the default
+ for this setting reflects this); armv7 is backwards-compatible with
+ armv6 and armv5tel; some aarch64 machines can also natively run
+ 32-bit ARM code; and qemu-user may be used to support non-native
+ platforms (though this may be slow and buggy). Most values for this
+ are not enabled by default because build systems will often
+ misdetect the target platform and generate incompatible code, so you
+ may wish to cross-check the results of using this option against
+ proper natively-built versions of your
+ derivations.</p></dd><dt><a id="conf-extra-substituters"></a><span class="term"><code class="literal">extra-substituters</code></span></dt><dd><p>Additional binary caches appended to those
+ specified in <code class="option">substituters</code>. When used by
+ unprivileged users, untrusted substituters (i.e. those not listed
+ in <code class="option">trusted-substituters</code>) are silently
+ ignored.</p></dd><dt><a id="conf-fallback"></a><span class="term"><code class="literal">fallback</code></span></dt><dd><p>If set to <code class="literal">true</code>, Nix will fall
+ back to building from source if a binary substitute fails. This
+ is equivalent to the <code class="option">--fallback</code> flag. The
+ default is <code class="literal">false</code>.</p></dd><dt><a id="conf-fsync-metadata"></a><span class="term"><code class="literal">fsync-metadata</code></span></dt><dd><p>If set to <code class="literal">true</code>, changes to the
+ Nix store metadata (in <code class="filename">/nix/var/nix/db</code>) are
+ synchronously flushed to disk. This improves robustness in case
+ of system crashes, but reduces performance. The default is
+ <code class="literal">true</code>.</p></dd><dt><a id="conf-hashed-mirrors"></a><span class="term"><code class="literal">hashed-mirrors</code></span></dt><dd><p>A list of web servers used by
+ <code class="function">builtins.fetchurl</code> to obtain files by hash.
+ Given a hash type <em class="replaceable"><code>ht</code></em> and a base-16 hash
+ <em class="replaceable"><code>h</code></em>, Nix will try to download the file
+ from
+ <code class="literal">hashed-mirror/<em class="replaceable"><code>ht</code></em>/<em class="replaceable"><code>h</code></em></code>.
+ This allows files to be downloaded even if they have disappeared
+ from their original URI. For example, given the hashed mirror
+ <code class="literal">http://tarballs.example.com/</code>, when building the
+ derivation
+
+</p><pre class="programlisting">
+builtins.fetchurl {
+ url = "https://example.org/foo-1.2.3.tar.xz";
+ sha256 = "2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae";
+}
+</pre><p>
+
+ Nix will attempt to download this file from
+ <code class="literal">http://tarballs.example.com/sha256/2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae</code>
+ first. If it is not available there, if will try the original URI.</p></dd><dt><a id="conf-http-connections"></a><span class="term"><code class="literal">http-connections</code></span></dt><dd><p>The maximum number of parallel TCP connections
+ used to fetch files from binary caches and by other downloads. It
+ defaults to 25. 0 means no limit.</p></dd><dt><a id="conf-keep-build-log"></a><span class="term"><code class="literal">keep-build-log</code></span></dt><dd><p>If set to <code class="literal">true</code> (the default),
+ Nix will write the build log of a derivation (i.e. the standard
+ output and error of its builder) to the directory
+ <code class="filename">/nix/var/log/nix/drvs</code>. The build log can be
+ retrieved using the command <span class="command"><strong>nix-store -l
+ <em class="replaceable"><code>path</code></em></strong></span>.</p></dd><dt><a id="conf-keep-derivations"></a><span class="term"><code class="literal">keep-derivations</code></span></dt><dd><p>If <code class="literal">true</code> (default), the garbage
+ collector will keep the derivations from which non-garbage store
+ paths were built. If <code class="literal">false</code>, they will be
+ deleted unless explicitly registered as a root (or reachable from
+ other roots).</p><p>Keeping derivation around is useful for querying and
+ traceability (e.g., it allows you to ask with what dependencies or
+ options a store path was built), so by default this option is on.
+ Turn it off to save a bit of disk space (or a lot if
+ <code class="literal">keep-outputs</code> is also turned on).</p></dd><dt><a id="conf-keep-env-derivations"></a><span class="term"><code class="literal">keep-env-derivations</code></span></dt><dd><p>If <code class="literal">false</code> (default), derivations
+ are not stored in Nix user environments. That is, the derivations of
+ any build-time-only dependencies may be garbage-collected.</p><p>If <code class="literal">true</code>, when you add a Nix derivation to
+ a user environment, the path of the derivation is stored in the
+ user environment. Thus, the derivation will not be
+ garbage-collected until the user environment generation is deleted
+ (<span class="command"><strong>nix-env --delete-generations</strong></span>). To prevent
+ build-time-only dependencies from being collected, you should also
+ turn on <code class="literal">keep-outputs</code>.</p><p>The difference between this option and
+ <code class="literal">keep-derivations</code> is that this one is
+ “sticky”: it applies to any user environment created while this
+ option was enabled, while <code class="literal">keep-derivations</code>
+ only applies at the moment the garbage collector is
+ run.</p></dd><dt><a id="conf-keep-outputs"></a><span class="term"><code class="literal">keep-outputs</code></span></dt><dd><p>If <code class="literal">true</code>, the garbage collector
+ will keep the outputs of non-garbage derivations. If
+ <code class="literal">false</code> (default), outputs will be deleted unless
+ they are GC roots themselves (or reachable from other roots).</p><p>In general, outputs must be registered as roots separately.
+ However, even if the output of a derivation is registered as a
+ root, the collector will still delete store paths that are used
+ only at build time (e.g., the C compiler, or source tarballs
+ downloaded from the network). To prevent it from doing so, set
+ this option to <code class="literal">true</code>.</p></dd><dt><a id="conf-max-build-log-size"></a><span class="term"><code class="literal">max-build-log-size</code></span></dt><dd><p>This option defines the maximum number of bytes that a
+ builder can write to its stdout/stderr. If the builder exceeds
+ this limit, it’s killed. A value of <code class="literal">0</code> (the
+ default) means that there is no limit.</p></dd><dt><a id="conf-max-free"></a><span class="term"><code class="literal">max-free</code></span></dt><dd><p>When a garbage collection is triggered by the
+ <code class="literal">min-free</code> option, it stops as soon as
+ <code class="literal">max-free</code> bytes are available. The default is
+ infinity (i.e. delete all garbage).</p></dd><dt><a id="conf-max-jobs"></a><span class="term"><code class="literal">max-jobs</code></span></dt><dd><p>This option defines the maximum number of jobs
+ that Nix will try to build in parallel. The default is
+ <code class="literal">1</code>. The special value <code class="literal">auto</code>
+ causes Nix to use the number of CPUs in your system. <code class="literal">0</code>
+ is useful when using remote builders to prevent any local builds (except for
+ <code class="literal">preferLocalBuild</code> derivation attribute which executes locally
+ regardless). It can be
+ overridden using the <code class="option"><a class="option" href="#opt-max-jobs">--max-jobs</a></code> (<code class="option">-j</code>)
+ command line switch.</p><p>See also <a class="xref" href="#chap-tuning-cores-and-jobs" title="Chapter 17. Tuning Cores and Jobs">Chapter 17, <em>Tuning Cores and Jobs</em></a>.</p></dd><dt><a id="conf-max-silent-time"></a><span class="term"><code class="literal">max-silent-time</code></span></dt><dd><p>This option defines the maximum number of seconds that a
+ builder can go without producing any data on standard output or
+ standard error. This is useful (for instance in an automated
+ build system) to catch builds that are stuck in an infinite
+ loop, or to catch remote builds that are hanging due to network
+ problems. It can be overridden using the <code class="option"><a class="option" href="#opt-max-silent-time">--max-silent-time</a></code> command
+ line switch.</p><p>The value <code class="literal">0</code> means that there is no
+ timeout. This is also the default.</p></dd><dt><a id="conf-min-free"></a><span class="term"><code class="literal">min-free</code></span></dt><dd><p>When free disk space in <code class="filename">/nix/store</code>
+ drops below <code class="literal">min-free</code> during a build, Nix
+ performs a garbage-collection until <code class="literal">max-free</code>
+ bytes are available or there is no more garbage. A value of
+ <code class="literal">0</code> (the default) disables this feature.</p></dd><dt><a id="conf-narinfo-cache-negative-ttl"></a><span class="term"><code class="literal">narinfo-cache-negative-ttl</code></span></dt><dd><p>The TTL in seconds for negative lookups. If a store path is
+ queried from a substituter but was not found, there will be a
+ negative lookup cached in the local disk cache database for the
+ specified duration.</p></dd><dt><a id="conf-narinfo-cache-positive-ttl"></a><span class="term"><code class="literal">narinfo-cache-positive-ttl</code></span></dt><dd><p>The TTL in seconds for positive lookups. If a store path is
+ queried from a substituter, the result of the query will be cached
+ in the local disk cache database including some of the NAR
+ metadata. The default TTL is a month, setting a shorter TTL for
+ positive lookups can be useful for binary caches that have
+ frequent garbage collection, in which case having a more frequent
+ cache invalidation would prevent trying to pull the path again and
+ failing with a hash mismatch if the build isn't reproducible.
+ </p></dd><dt><a id="conf-netrc-file"></a><span class="term"><code class="literal">netrc-file</code></span></dt><dd><p>If set to an absolute path to a <code class="filename">netrc</code>
+ file, Nix will use the HTTP authentication credentials in this file when
+ trying to download from a remote host through HTTP or HTTPS. Defaults to
+ <code class="filename">$NIX_CONF_DIR/netrc</code>.</p><p>The <code class="filename">netrc</code> file consists of a list of
+ accounts in the following format:
+
+</p><pre class="screen">
+machine <em class="replaceable"><code>my-machine</code></em>
+login <em class="replaceable"><code>my-username</code></em>
+password <em class="replaceable"><code>my-password</code></em>
+</pre><p>
+
+ For the exact syntax, see <a class="link" href="https://ec.haxx.se/usingcurl-netrc.html" target="_top">the
+ <code class="literal">curl</code> documentation.</a></p><div class="note"><h3 class="title">Note</h3><p>This must be an absolute path, and <code class="literal">~</code>
+ is not resolved. For example, <code class="filename">~/.netrc</code> won't
+ resolve to your home directory's <code class="filename">.netrc</code>.</p></div></dd><dt><a id="conf-plugin-files"></a><span class="term"><code class="literal">plugin-files</code></span></dt><dd><p>
+ A list of plugin files to be loaded by Nix. Each of these
+ files will be dlopened by Nix, allowing them to affect
+ execution through static initialization. In particular, these
+ plugins may construct static instances of RegisterPrimOp to
+ add new primops or constants to the expression language,
+ RegisterStoreImplementation to add new store implementations,
+ RegisterCommand to add new subcommands to the
+ <code class="literal">nix</code> command, and RegisterSetting to add new
+ nix config settings. See the constructors for those types for
+ more details.
+ </p><p>
+ Since these files are loaded into the same address space as
+ Nix itself, they must be DSOs compatible with the instance of
+ Nix running at the time (i.e. compiled against the same
+ headers, not linked to any incompatible libraries). They
+ should not be linked to any Nix libs directly, as those will
+ be available already at load time.
+ </p><p>
+ If an entry in the list is a directory, all files in the
+ directory are loaded as plugins (non-recursively).
+ </p></dd><dt><a id="conf-pre-build-hook"></a><span class="term"><code class="literal">pre-build-hook</code></span></dt><dd><p>If set, the path to a program that can set extra
+ derivation-specific settings for this system. This is used for settings
+ that can't be captured by the derivation model itself and are too variable
+ between different versions of the same system to be hard-coded into nix.
+ </p><p>The hook is passed the derivation path and, if sandboxes are enabled,
+ the sandbox directory. It can then modify the sandbox and send a series of
+ commands to modify various settings to stdout. The currently recognized
+ commands are:</p><div class="variablelist"><dl class="variablelist"><dt><a id="extra-sandbox-paths"></a><span class="term"><code class="literal">extra-sandbox-paths</code></span></dt><dd><p>Pass a list of files and directories to be included in the
+ sandbox for this build. One entry per line, terminated by an empty
+ line. Entries have the same format as
+ <code class="literal">sandbox-paths</code>.</p></dd></dl></div></dd><dt><a id="conf-post-build-hook"></a><span class="term"><code class="literal">post-build-hook</code></span></dt><dd><p>Optional. The path to a program to execute after each build.</p><p>This option is only settable in the global
+ <code class="filename">nix.conf</code>, or on the command line by trusted
+ users.</p><p>When using the nix-daemon, the daemon executes the hook as
+ <code class="literal">root</code>. If the nix-daemon is not involved, the
+ hook runs as the user executing the nix-build.</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>The hook executes after an evaluation-time build.</p></li><li class="listitem"><p>The hook does not execute on substituted paths.</p></li><li class="listitem"><p>The hook's output always goes to the user's terminal.</p></li><li class="listitem"><p>If the hook fails, the build succeeds but no further builds execute.</p></li><li class="listitem"><p>The hook executes synchronously, and blocks other builds from progressing while it runs.</p></li></ul></div><p>The program executes with no arguments. The program's environment
+ contains the following environment variables:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="envar">DRV_PATH</code></span></dt><dd><p>The derivation for the built paths.</p><p>Example:
+ <code class="literal">/nix/store/5nihn1a7pa8b25l9zafqaqibznlvvp3f-bash-4.4-p23.drv</code>
+ </p></dd><dt><span class="term"><code class="envar">OUT_PATHS</code></span></dt><dd><p>Output paths of the built derivation, separated by a space character.</p><p>Example:
+ <code class="literal">/nix/store/zf5lbh336mnzf1nlswdn11g4n2m8zh3g-bash-4.4-p23-dev
+ /nix/store/rjxwxwv1fpn9wa2x5ssk5phzwlcv4mna-bash-4.4-p23-doc
+ /nix/store/6bqvbzjkcp9695dq0dpl5y43nvy37pq1-bash-4.4-p23-info
+ /nix/store/r7fng3kk3vlpdlh2idnrbn37vh4imlj2-bash-4.4-p23-man
+ /nix/store/xfghy8ixrhz3kyy6p724iv3cxji088dx-bash-4.4-p23</code>.
+ </p></dd></dl></div><p>See <a class="xref" href="#chap-post-build-hook" title="Chapter 19. Using the post-build-hook">Chapter 19, <em>Using the <code class="option"><a class="option" href="#conf-post-build-hook">post-build-hook</a></code></em></a> for an example
+ implementation.</p></dd><dt><a id="conf-repeat"></a><span class="term"><code class="literal">repeat</code></span></dt><dd><p>How many times to repeat builds to check whether
+ they are deterministic. The default value is 0. If the value is
+ non-zero, every build is repeated the specified number of
+ times. If the contents of any of the runs differs from the
+ previous ones and <a class="xref" href="#conf-enforce-determinism"><code class="literal">enforce-determinism</code></a> is
+ true, the build is rejected and the resulting store paths are not
+ registered as “valid” in Nix’s database.</p></dd><dt><a id="conf-require-sigs"></a><span class="term"><code class="literal">require-sigs</code></span></dt><dd><p>If set to <code class="literal">true</code> (the default),
+ any non-content-addressed path added or copied to the Nix store
+ (e.g. when substituting from a binary cache) must have a valid
+ signature, that is, be signed using one of the keys listed in
+ <code class="option">trusted-public-keys</code> or
+ <code class="option">secret-key-files</code>. Set to <code class="literal">false</code>
+ to disable signature checking.</p></dd><dt><a id="conf-restrict-eval"></a><span class="term"><code class="literal">restrict-eval</code></span></dt><dd><p>If set to <code class="literal">true</code>, the Nix evaluator will
+ not allow access to any files outside of the Nix search path (as
+ set via the <code class="envar">NIX_PATH</code> environment variable or the
+ <code class="option">-I</code> option), or to URIs outside of
+ <code class="option">allowed-uri</code>. The default is
+ <code class="literal">false</code>.</p></dd><dt><a id="conf-run-diff-hook"></a><span class="term"><code class="literal">run-diff-hook</code></span></dt><dd><p>
+ If true, enable the execution of <a class="xref" href="#conf-diff-hook"><code class="literal">diff-hook</code></a>.
+ </p><p>
+ When using the Nix daemon, <code class="literal">run-diff-hook</code> must
+ be set in the <code class="filename">nix.conf</code> configuration file,
+ and cannot be passed at the command line.
+ </p></dd><dt><a id="conf-sandbox"></a><span class="term"><code class="literal">sandbox</code></span></dt><dd><p>If set to <code class="literal">true</code>, builds will be
+ performed in a <span class="emphasis"><em>sandboxed environment</em></span>, i.e.,
+ they’re isolated from the normal file system hierarchy and will
+ only see their dependencies in the Nix store, the temporary build
+ directory, private versions of <code class="filename">/proc</code>,
+ <code class="filename">/dev</code>, <code class="filename">/dev/shm</code> and
+ <code class="filename">/dev/pts</code> (on Linux), and the paths configured with the
+ <a class="link" href="#conf-sandbox-paths"><code class="literal">sandbox-paths</code>
+ option</a>. This is useful to prevent undeclared dependencies
+ on files in directories such as <code class="filename">/usr/bin</code>. In
+ addition, on Linux, builds run in private PID, mount, network, IPC
+ and UTS namespaces to isolate them from other processes in the
+ system (except that fixed-output derivations do not run in private
+ network namespace to ensure they can access the network).</p><p>Currently, sandboxing only work on Linux and macOS. The use
+ of a sandbox requires that Nix is run as root (so you should use
+ the <a class="link" href="#conf-build-users-group">“build users”
+ feature</a> to perform the actual builds under different users
+ than root).</p><p>If this option is set to <code class="literal">relaxed</code>, then
+ fixed-output derivations and derivations that have the
+ <code class="varname">__noChroot</code> attribute set to
+ <code class="literal">true</code> do not run in sandboxes.</p><p>The default is <code class="literal">true</code> on Linux and
+ <code class="literal">false</code> on all other platforms.</p></dd><dt><a id="conf-sandbox-dev-shm-size"></a><span class="term"><code class="literal">sandbox-dev-shm-size</code></span></dt><dd><p>This option determines the maximum size of the
+ <code class="literal">tmpfs</code> filesystem mounted on
+ <code class="filename">/dev/shm</code> in Linux sandboxes. For the format,
+ see the description of the <code class="option">size</code> option of
+ <code class="literal">tmpfs</code> in
+ <span class="citerefentry"><span class="refentrytitle">mount</span>(8)</span>. The
+ default is <code class="literal">50%</code>.</p></dd><dt><a id="conf-sandbox-paths"></a><span class="term"><code class="literal">sandbox-paths</code></span></dt><dd><p>A list of paths bind-mounted into Nix sandbox
+ environments. You can use the syntax
+ <code class="literal"><em class="replaceable"><code>target</code></em>=<em class="replaceable"><code>source</code></em></code>
+ to mount a path in a different location in the sandbox; for
+ instance, <code class="literal">/bin=/nix-bin</code> will mount the path
+ <code class="literal">/nix-bin</code> as <code class="literal">/bin</code> inside the
+ sandbox. If <em class="replaceable"><code>source</code></em> is followed by
+ <code class="literal">?</code>, then it is not an error if
+ <em class="replaceable"><code>source</code></em> does not exist; for example,
+ <code class="literal">/dev/nvidiactl?</code> specifies that
+ <code class="filename">/dev/nvidiactl</code> will only be mounted in the
+ sandbox if it exists in the host filesystem.</p><p>Depending on how Nix was built, the default value for this option
+ may be empty or provide <code class="filename">/bin/sh</code> as a
+ bind-mount of <span class="command"><strong>bash</strong></span>.</p></dd><dt><a id="conf-secret-key-files"></a><span class="term"><code class="literal">secret-key-files</code></span></dt><dd><p>A whitespace-separated list of files containing
+ secret (private) keys. These are used to sign locally-built
+ paths. They can be generated using <span class="command"><strong>nix-store
+ --generate-binary-cache-key</strong></span>. The corresponding public
+ key can be distributed to other users, who can add it to
+ <code class="option">trusted-public-keys</code> in their
+ <code class="filename">nix.conf</code>.</p></dd><dt><a id="conf-show-trace"></a><span class="term"><code class="literal">show-trace</code></span></dt><dd><p>Causes Nix to print out a stack trace in case of Nix
+ expression evaluation errors.</p></dd><dt><a id="conf-substitute"></a><span class="term"><code class="literal">substitute</code></span></dt><dd><p>If set to <code class="literal">true</code> (default), Nix
+ will use binary substitutes if available. This option can be
+ disabled to force building from source.</p></dd><dt><a id="conf-stalled-download-timeout"></a><span class="term"><code class="literal">stalled-download-timeout</code></span></dt><dd><p>The timeout (in seconds) for receiving data from servers
+ during download. Nix cancels idle downloads after this timeout's
+ duration.</p></dd><dt><a id="conf-substituters"></a><span class="term"><code class="literal">substituters</code></span></dt><dd><p>A list of URLs of substituters, separated by
+ whitespace. The default is
+ <code class="literal">https://cache.nixos.org</code>.</p></dd><dt><a id="conf-system"></a><span class="term"><code class="literal">system</code></span></dt><dd><p>This option specifies the canonical Nix system
+ name of the current installation, such as
+ <code class="literal">i686-linux</code> or
+ <code class="literal">x86_64-darwin</code>. Nix can only build derivations
+ whose <code class="literal">system</code> attribute equals the value
+ specified here. In general, it never makes sense to modify this
+ value from its default, since you can use it to ‘lie’ about the
+ platform you are building on (e.g., perform a Mac OS build on a
+ Linux machine; the result would obviously be wrong). It only
+ makes sense if the Nix binaries can run on multiple platforms,
+ e.g., ‘universal binaries’ that run on <code class="literal">x86_64-linux</code> and
+ <code class="literal">i686-linux</code>.</p><p>It defaults to the canonical Nix system name detected by
+ <code class="filename">configure</code> at build time.</p></dd><dt><a id="conf-system-features"></a><span class="term"><code class="literal">system-features</code></span></dt><dd><p>A set of system “features” supported by this
+ machine, e.g. <code class="literal">kvm</code>. Derivations can express a
+ dependency on such features through the derivation attribute
+ <code class="varname">requiredSystemFeatures</code>. For example, the
+ attribute
+
+</p><pre class="programlisting">
+requiredSystemFeatures = [ "kvm" ];
+</pre><p>
+
+ ensures that the derivation can only be built on a machine with
+ the <code class="literal">kvm</code> feature.</p><p>This setting by default includes <code class="literal">kvm</code> if
+ <code class="filename">/dev/kvm</code> is accessible, and the
+ pseudo-features <code class="literal">nixos-test</code>,
+ <code class="literal">benchmark</code> and <code class="literal">big-parallel</code>
+ that are used in Nixpkgs to route builds to specific
+ machines.</p></dd><dt><a id="conf-tarball-ttl"></a><span class="term"><code class="literal">tarball-ttl</code></span></dt><dd><p>Default: <code class="literal">3600</code> seconds.</p><p>The number of seconds a downloaded tarball is considered
+ fresh. If the cached tarball is stale, Nix will check whether
+ it is still up to date using the ETag header. Nix will download
+ a new version if the ETag header is unsupported, or the
+ cached ETag doesn't match.
+ </p><p>Setting the TTL to <code class="literal">0</code> forces Nix to always
+ check if the tarball is up to date.</p><p>Nix caches tarballs in
+ <code class="filename">$XDG_CACHE_HOME/nix/tarballs</code>.</p><p>Files fetched via <code class="envar">NIX_PATH</code>,
+ <code class="function">fetchGit</code>, <code class="function">fetchMercurial</code>,
+ <code class="function">fetchTarball</code>, and <code class="function">fetchurl</code>
+ respect this TTL.
+ </p></dd><dt><a id="conf-timeout"></a><span class="term"><code class="literal">timeout</code></span></dt><dd><p>This option defines the maximum number of seconds that a
+ builder can run. This is useful (for instance in an automated
+ build system) to catch builds that are stuck in an infinite loop
+ but keep writing to their standard output or standard error. It
+ can be overridden using the <code class="option"><a class="option" href="#opt-timeout">--timeout</a></code> command line
+ switch.</p><p>The value <code class="literal">0</code> means that there is no
+ timeout. This is also the default.</p></dd><dt><a id="conf-trace-function-calls"></a><span class="term"><code class="literal">trace-function-calls</code></span></dt><dd><p>Default: <code class="literal">false</code>.</p><p>If set to <code class="literal">true</code>, the Nix evaluator will
+ trace every function call. Nix will print a log message at the
+ "vomit" level for every function entrance and function exit.</p><div class="informalexample"><pre class="screen">
+function-trace entered undefined position at 1565795816999559622
+function-trace exited undefined position at 1565795816999581277
+function-trace entered /nix/store/.../example.nix:226:41 at 1565795253249935150
+function-trace exited /nix/store/.../example.nix:226:41 at 1565795253249941684
+</pre></div><p>The <code class="literal">undefined position</code> means the function
+ call is a builtin.</p><p>Use the <code class="literal">contrib/stack-collapse.py</code> script
+ distributed with the Nix source code to convert the trace logs
+ in to a format suitable for <span class="command"><strong>flamegraph.pl</strong></span>.</p></dd><dt><a id="conf-trusted-public-keys"></a><span class="term"><code class="literal">trusted-public-keys</code></span></dt><dd><p>A whitespace-separated list of public keys. When
+ paths are copied from another Nix store (such as a binary cache),
+ they must be signed with one of these keys. For example:
+ <code class="literal">cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
+ hydra.nixos.org-1:CNHJZBh9K4tP3EKF6FkkgeVYsS3ohTl+oS0Qa8bezVs=</code>.</p></dd><dt><a id="conf-trusted-substituters"></a><span class="term"><code class="literal">trusted-substituters</code></span></dt><dd><p>A list of URLs of substituters, separated by
+ whitespace. These are not used by default, but can be enabled by
+ users of the Nix daemon by specifying <code class="literal">--option
+ substituters <em class="replaceable"><code>urls</code></em></code> on the
+ command line. Unprivileged users are only allowed to pass a
+ subset of the URLs listed in <code class="literal">substituters</code> and
+ <code class="literal">trusted-substituters</code>.</p></dd><dt><a id="conf-trusted-users"></a><span class="term"><code class="literal">trusted-users</code></span></dt><dd><p>A list of names of users (separated by whitespace) that
+ have additional rights when connecting to the Nix daemon, such
+ as the ability to specify additional binary caches, or to import
+ unsigned NARs. You can also specify groups by prefixing them
+ with <code class="literal">@</code>; for instance,
+ <code class="literal">@wheel</code> means all users in the
+ <code class="literal">wheel</code> group. The default is
+ <code class="literal">root</code>.</p><div class="warning"><h3 class="title">Warning</h3><p>Adding a user to <code class="option">trusted-users</code>
+ is essentially equivalent to giving that user root access to the
+ system. For example, the user can set
+ <code class="option">sandbox-paths</code> and thereby obtain read access to
+ directories that are otherwise inacessible to
+ them.</p></div></dd></dl></div><p>
+</p><div class="refsection"><a id="idm139733298856336"></a><h3>Deprecated Settings</h3><p>
+
+</p><div class="variablelist"><dl class="variablelist"><dt><a id="conf-binary-caches"></a><span class="term"><code class="literal">binary-caches</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
+ <code class="literal">binary-caches</code> is now an alias to
+ <a class="xref" href="#conf-substituters"><code class="literal">substituters</code></a>.</p></dd><dt><a id="conf-binary-cache-public-keys"></a><span class="term"><code class="literal">binary-cache-public-keys</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
+ <code class="literal">binary-cache-public-keys</code> is now an alias to
+ <a class="xref" href="#conf-trusted-public-keys"><code class="literal">trusted-public-keys</code></a>.</p></dd><dt><a id="conf-build-compress-log"></a><span class="term"><code class="literal">build-compress-log</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
+ <code class="literal">build-compress-log</code> is now an alias to
+ <a class="xref" href="#conf-compress-build-log"><code class="literal">compress-build-log</code></a>.</p></dd><dt><a id="conf-build-cores"></a><span class="term"><code class="literal">build-cores</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
+ <code class="literal">build-cores</code> is now an alias to
+ <a class="xref" href="#conf-cores"><code class="literal">cores</code></a>.</p></dd><dt><a id="conf-build-extra-chroot-dirs"></a><span class="term"><code class="literal">build-extra-chroot-dirs</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
+ <code class="literal">build-extra-chroot-dirs</code> is now an alias to
+ <a class="xref" href="#conf-extra-sandbox-paths"><code class="literal">extra-sandbox-paths</code></a>.</p></dd><dt><a id="conf-build-extra-sandbox-paths"></a><span class="term"><code class="literal">build-extra-sandbox-paths</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
+ <code class="literal">build-extra-sandbox-paths</code> is now an alias to
+ <a class="xref" href="#conf-extra-sandbox-paths"><code class="literal">extra-sandbox-paths</code></a>.</p></dd><dt><a id="conf-build-fallback"></a><span class="term"><code class="literal">build-fallback</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
+ <code class="literal">build-fallback</code> is now an alias to
+ <a class="xref" href="#conf-fallback"><code class="literal">fallback</code></a>.</p></dd><dt><a id="conf-build-max-jobs"></a><span class="term"><code class="literal">build-max-jobs</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
+ <code class="literal">build-max-jobs</code> is now an alias to
+ <a class="xref" href="#conf-max-jobs"><code class="literal">max-jobs</code></a>.</p></dd><dt><a id="conf-build-max-log-size"></a><span class="term"><code class="literal">build-max-log-size</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
+ <code class="literal">build-max-log-size</code> is now an alias to
+ <a class="xref" href="#conf-max-build-log-size"><code class="literal">max-build-log-size</code></a>.</p></dd><dt><a id="conf-build-max-silent-time"></a><span class="term"><code class="literal">build-max-silent-time</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
+ <code class="literal">build-max-silent-time</code> is now an alias to
+ <a class="xref" href="#conf-max-silent-time"><code class="literal">max-silent-time</code></a>.</p></dd><dt><a id="conf-build-repeat"></a><span class="term"><code class="literal">build-repeat</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
+ <code class="literal">build-repeat</code> is now an alias to
+ <a class="xref" href="#conf-repeat"><code class="literal">repeat</code></a>.</p></dd><dt><a id="conf-build-timeout"></a><span class="term"><code class="literal">build-timeout</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
+ <code class="literal">build-timeout</code> is now an alias to
+ <a class="xref" href="#conf-timeout"><code class="literal">timeout</code></a>.</p></dd><dt><a id="conf-build-use-chroot"></a><span class="term"><code class="literal">build-use-chroot</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
+ <code class="literal">build-use-chroot</code> is now an alias to
+ <a class="xref" href="#conf-sandbox"><code class="literal">sandbox</code></a>.</p></dd><dt><a id="conf-build-use-sandbox"></a><span class="term"><code class="literal">build-use-sandbox</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
+ <code class="literal">build-use-sandbox</code> is now an alias to
+ <a class="xref" href="#conf-sandbox"><code class="literal">sandbox</code></a>.</p></dd><dt><a id="conf-build-use-substitutes"></a><span class="term"><code class="literal">build-use-substitutes</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
+ <code class="literal">build-use-substitutes</code> is now an alias to
+ <a class="xref" href="#conf-substitute"><code class="literal">substitute</code></a>.</p></dd><dt><a id="conf-gc-keep-derivations"></a><span class="term"><code class="literal">gc-keep-derivations</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
+ <code class="literal">gc-keep-derivations</code> is now an alias to
+ <a class="xref" href="#conf-keep-derivations"><code class="literal">keep-derivations</code></a>.</p></dd><dt><a id="conf-gc-keep-outputs"></a><span class="term"><code class="literal">gc-keep-outputs</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
+ <code class="literal">gc-keep-outputs</code> is now an alias to
+ <a class="xref" href="#conf-keep-outputs"><code class="literal">keep-outputs</code></a>.</p></dd><dt><a id="conf-env-keep-derivations"></a><span class="term"><code class="literal">env-keep-derivations</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
+ <code class="literal">env-keep-derivations</code> is now an alias to
+ <a class="xref" href="#conf-keep-env-derivations"><code class="literal">keep-env-derivations</code></a>.</p></dd><dt><a id="conf-extra-binary-caches"></a><span class="term"><code class="literal">extra-binary-caches</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
+ <code class="literal">extra-binary-caches</code> is now an alias to
+ <a class="xref" href="#conf-extra-substituters"><code class="literal">extra-substituters</code></a>.</p></dd><dt><a id="conf-trusted-binary-caches"></a><span class="term"><code class="literal">trusted-binary-caches</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
+ <code class="literal">trusted-binary-caches</code> is now an alias to
+ <a class="xref" href="#conf-trusted-substituters"><code class="literal">trusted-substituters</code></a>.</p></dd></dl></div><p>
+</p></div></div></div></div></div><div class="appendix"><div class="titlepage"><div><div><h1 class="title"><a id="part-glossary"></a>Appendix A. Glossary</h1></div></div></div><div class="glosslist"><dl><dt><a id="gloss-derivation"></a><span class="glossterm">derivation</span></dt><dd class="glossdef"><p>A description of a build action. The result of a
+ derivation is a store object. Derivations are typically specified
+ in Nix expressions using the <a class="link" href="#ssec-derivation" title="15.4. Derivations"><code class="function">derivation</code>
+ primitive</a>. These are translated into low-level
+ <span class="emphasis"><em>store derivations</em></span> (implicitly by
+ <span class="command"><strong>nix-env</strong></span> and <span class="command"><strong>nix-build</strong></span>, or
+ explicitly by <span class="command"><strong>nix-instantiate</strong></span>).</p></dd><dt><span class="glossterm">store</span></dt><dd class="glossdef"><p>The location in the file system where store objects
+ live. Typically <code class="filename">/nix/store</code>.</p></dd><dt><span class="glossterm">store path</span></dt><dd class="glossdef"><p>The location in the file system of a store object,
+ i.e., an immediate child of the Nix store
+ directory.</p></dd><dt><span class="glossterm">store object</span></dt><dd class="glossdef"><p>A file that is an immediate child of the Nix store
+ directory. These can be regular files, but also entire directory
+ trees. Store objects can be sources (objects copied from outside of
+ the store), derivation outputs (objects produced by running a build
+ action), or derivations (files describing a build
+ action).</p></dd><dt><a id="gloss-substitute"></a><span class="glossterm">substitute</span></dt><dd class="glossdef"><p>A substitute is a command invocation stored in the
+ Nix database that describes how to build a store object, bypassing
+ the normal build mechanism (i.e., derivations). Typically, the
+ substitute builds the store object by downloading a pre-built
+ version of the store object from some server.</p></dd><dt><span class="glossterm">purity</span></dt><dd class="glossdef"><p>The assumption that equal Nix derivations when run
+ always produce the same output. This cannot be guaranteed in
+ general (e.g., a builder can rely on external inputs such as the
+ network or the system time) but the Nix model assumes
+ it.</p></dd><dt><span class="glossterm">Nix expression</span></dt><dd class="glossdef"><p>A high-level description of software packages and
+ compositions thereof. Deploying software using Nix entails writing
+ Nix expressions for your packages. Nix expressions are translated
+ to derivations that are stored in the Nix store. These derivations
+ can then be built.</p></dd><dt><a id="gloss-reference"></a><span class="glossterm">reference</span></dt><dd class="glossdef"><p>A store path <code class="varname">P</code> is said to have a
+ reference to a store path <code class="varname">Q</code> if the store object
+ at <code class="varname">P</code> contains the path <code class="varname">Q</code>
+ somewhere. The <span class="emphasis"><em>references</em></span> of a store path are
+ the set of store paths to which it has a reference.
+ </p><p>A derivation can reference other derivations and sources
+ (but not output paths), whereas an output path only references other
+ output paths.
+ </p></dd><dt><a id="gloss-reachable"></a><span class="glossterm">reachable</span></dt><dd class="glossdef"><p>A store path <code class="varname">Q</code> is reachable from
+ another store path <code class="varname">P</code> if <code class="varname">Q</code> is in the
+ <a class="link" href="#gloss-closure" title="closure">closure</a> of the
+ <a class="link" href="#gloss-reference" title="reference">references</a> relation.
+ </p></dd><dt><a id="gloss-closure"></a><span class="glossterm">closure</span></dt><dd class="glossdef"><p>The closure of a store path is the set of store
+ paths that are directly or indirectly “reachable” from that store
+ path; that is, it’s the closure of the path under the <a class="link" href="#gloss-reference" title="reference">references</a> relation. For a package, the
+ closure of its derivation is equivalent to the build-time
+ dependencies, while the closure of its output path is equivalent to its
+ runtime dependencies. For correct deployment it is necessary to deploy whole
+ closures, since otherwise at runtime files could be missing. The command
+ <span class="command"><strong>nix-store -qR</strong></span> prints out closures of store paths.
+ </p><p>As an example, if the store object at path <code class="varname">P</code> contains
+ a reference to path <code class="varname">Q</code>, then <code class="varname">Q</code> is
+ in the closure of <code class="varname">P</code>. Further, if <code class="varname">Q</code>
+ references <code class="varname">R</code> then <code class="varname">R</code> is also in
+ the closure of <code class="varname">P</code>.
+ </p></dd><dt><a id="gloss-output-path"></a><span class="glossterm">output path</span></dt><dd class="glossdef"><p>A store path produced by a derivation.</p></dd><dt><a id="gloss-deriver"></a><span class="glossterm">deriver</span></dt><dd class="glossdef"><p>The deriver of an <a class="link" href="#gloss-output-path" title="output path">output path</a> is the store
+ derivation that built it.</p></dd><dt><a id="gloss-validity"></a><span class="glossterm">validity</span></dt><dd class="glossdef"><p>A store path is considered
+ <span class="emphasis"><em>valid</em></span> if it exists in the file system, is
+ listed in the Nix database as being valid, and if all paths in its
+ closure are also valid.</p></dd><dt><a id="gloss-user-env"></a><span class="glossterm">user environment</span></dt><dd class="glossdef"><p>An automatically generated store object that
+ consists of a set of symlinks to “active” applications, i.e., other
+ store paths. These are generated automatically by <a class="link" href="#sec-nix-env" title="nix-env"><span class="command"><strong>nix-env</strong></span></a>. See <a class="xref" href="#sec-profiles" title="Chapter 10. Profiles">Chapter 10, <em>Profiles</em></a>.</p></dd><dt><a id="gloss-profile"></a><span class="glossterm">profile</span></dt><dd class="glossdef"><p>A symlink to the current <a class="link" href="#gloss-user-env" title="user environment">user environment</a> of a user, e.g.,
+ <code class="filename">/nix/var/nix/profiles/default</code>.</p></dd><dt><a id="gloss-nar"></a><span class="glossterm">NAR</span></dt><dd class="glossdef"><p>A <span class="emphasis"><em>N</em></span>ix
+ <span class="emphasis"><em>AR</em></span>chive. This is a serialisation of a path in
+ the Nix store. It can contain regular files, directories and
+ symbolic links. NARs are generated and unpacked using
+ <span class="command"><strong>nix-store --dump</strong></span> and <span class="command"><strong>nix-store
+ --restore</strong></span>.</p></dd></dl></div></div><div class="appendix"><div class="titlepage"><div><div><h1 class="title"><a id="chap-hacking"></a>Appendix B. Hacking</h1></div></div></div><p>This section provides some notes on how to hack on Nix. To get
+the latest version of Nix from GitHub:
+</p><pre class="screen">
+$ git clone https://github.com/NixOS/nix.git
+$ cd nix
+</pre><p>
+</p><p>To build Nix for the current operating system/architecture use
+
+</p><pre class="screen">
+$ nix-build
+</pre><p>
+
+or if you have a flakes-enabled nix:
+
+</p><pre class="screen">
+$ nix build
+</pre><p>
+
+This will build <code class="literal">defaultPackage</code> attribute defined in the <code class="literal">flake.nix</code> file.
+
+To build for other platforms add one of the following suffixes to it: aarch64-linux,
+i686-linux, x86_64-darwin, x86_64-linux.
+
+i.e.
+
+</p><pre class="screen">
+nix-build -A defaultPackage.x86_64-linux
+</pre><p>
+
+</p><p>To build all dependencies and start a shell in which all
+environment variables are set up so that those dependencies can be
+found:
+</p><pre class="screen">
+$ nix-shell
+</pre><p>
+To build Nix itself in this shell:
+</p><pre class="screen">
+[nix-shell]$ ./bootstrap.sh
+[nix-shell]$ ./configure $configureFlags
+[nix-shell]$ make -j $NIX_BUILD_CORES
+</pre><p>
+To install it in <code class="literal">$(pwd)/inst</code> and test it:
+</p><pre class="screen">
+[nix-shell]$ make install
+[nix-shell]$ make installcheck
+[nix-shell]$ ./inst/bin/nix --version
+nix (Nix) 2.4
+</pre><p>
+
+If you have a flakes-enabled nix you can replace:
+
+</p><pre class="screen">
+$ nix-shell
+</pre><p>
+
+by:
+
+</p><pre class="screen">
+$ nix develop
+</pre><p>
+
+</p></div><div class="appendix"><div class="titlepage"><div><div><h1 class="title"><a id="sec-relnotes"></a>Appendix C. Nix Release Notes</h1></div></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-2.3"></a>C.1. Release 2.3 (2019-09-04)</h2></div></div></div><p>This is primarily a bug fix release. However, it makes some
+incompatible changes:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Nix now uses BSD file locks instead of POSIX file
+ locks. Because of this, you should not use Nix 2.3 and previous
+ releases at the same time on a Nix store.</p></li></ul></div><p>It also has the following changes:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><code class="function">builtins.fetchGit</code>'s <code class="varname">ref</code>
+ argument now allows specifying an absolute remote ref.
+ Nix will automatically prefix <code class="varname">ref</code> with
+ <code class="literal">refs/heads</code> only if <code class="varname">ref</code> doesn't
+ already begin with <code class="literal">refs/</code>.
+ </p></li><li class="listitem"><p>The installer now enables sandboxing by default on Linux when the
+ system has the necessary kernel support.
+ </p></li><li class="listitem"><p>The <code class="literal">max-jobs</code> setting now defaults to 1.</p></li><li class="listitem"><p>New builtin functions:
+ <code class="literal">builtins.isPath</code>,
+ <code class="literal">builtins.hashFile</code>.
+ </p></li><li class="listitem"><p>The <span class="command"><strong>nix</strong></span> command has a new
+ <code class="option">--print-build-logs</code> (<code class="option">-L</code>) flag to
+ print build log output to stderr, rather than showing the last log
+ line in the progress bar. To distinguish between concurrent
+ builds, log lines are prefixed by the name of the package.
+ </p></li><li class="listitem"><p>Builds are now executed in a pseudo-terminal, and the
+ <code class="envar">TERM</code> environment variable is set to
+ <code class="literal">xterm-256color</code>. This allows many programs
+ (e.g. <span class="command"><strong>gcc</strong></span>, <span class="command"><strong>clang</strong></span>,
+ <span class="command"><strong>cmake</strong></span>) to print colorized log output.</p></li><li class="listitem"><p>Add <code class="option">--no-net</code> convenience flag. This flag
+ disables substituters; sets the <code class="literal">tarball-ttl</code>
+ setting to infinity (ensuring that any previously downloaded files
+ are considered current); and disables retrying downloads and sets
+ the connection timeout to the minimum. This flag is enabled
+ automatically if there are no configured non-loopback network
+ interfaces.</p></li><li class="listitem"><p>Add a <code class="literal">post-build-hook</code> setting to run a
+ program after a build has succeeded.</p></li><li class="listitem"><p>Add a <code class="literal">trace-function-calls</code> setting to log
+ the duration of Nix function calls to stderr.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-2.2"></a>C.2. Release 2.2 (2019-01-11)</h2></div></div></div><p>This is primarily a bug fix release. It also has the following
+changes:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>In derivations that use structured attributes (i.e. that
+ specify set the <code class="varname">__structuredAttrs</code> attribute to
+ <code class="literal">true</code> to cause all attributes to be passed to
+ the builder in JSON format), you can now specify closure checks
+ per output, e.g.:
+
+</p><pre class="programlisting">
+outputChecks."out" = {
+ # The closure of 'out' must not be larger than 256 MiB.
+ maxClosureSize = 256 * 1024 * 1024;
+
+ # It must not refer to C compiler or to the 'dev' output.
+ disallowedRequisites = [ stdenv.cc "dev" ];
+};
+
+outputChecks."dev" = {
+ # The 'dev' output must not be larger than 128 KiB.
+ maxSize = 128 * 1024;
+};
+</pre><p>
+
+ </p></li><li class="listitem"><p>The derivation attribute
+ <code class="varname">requiredSystemFeatures</code> is now enforced for
+ local builds, and not just to route builds to remote builders.
+ The supported features of a machine can be specified through the
+ configuration setting <code class="varname">system-features</code>.</p><p>By default, <code class="varname">system-features</code> includes
+ <code class="literal">kvm</code> if <code class="filename">/dev/kvm</code>
+ exists. For compatibility, it also includes the pseudo-features
+ <code class="literal">nixos-test</code>, <code class="literal">benchmark</code> and
+ <code class="literal">big-parallel</code> which are used by Nixpkgs to route
+ builds to particular Hydra build machines.</p></li><li class="listitem"><p>Sandbox builds are now enabled by default on Linux.</p></li><li class="listitem"><p>The new command <span class="command"><strong>nix doctor</strong></span> shows
+ potential issues with your Nix installation.</p></li><li class="listitem"><p>The <code class="literal">fetchGit</code> builtin function now uses a
+ caching scheme that puts different remote repositories in distinct
+ local repositories, rather than a single shared repository. This
+ may require more disk space but is faster.</p></li><li class="listitem"><p>The <code class="literal">dirOf</code> builtin function now works on
+ relative paths.</p></li><li class="listitem"><p>Nix now supports <a class="link" href="https://www.w3.org/TR/SRI/" target="_top">SRI hashes</a>,
+ allowing the hash algorithm and hash to be specified in a single
+ string. For example, you can write:
+
+</p><pre class="programlisting">
+import <nix/fetchurl.nix> {
+ url = https://nixos.org/releases/nix/nix-2.1.3/nix-2.1.3.tar.xz;
+ hash = "sha256-XSLa0FjVyADWWhFfkZ2iKTjFDda6mMXjoYMXLRSYQKQ=";
+};
+</pre><p>
+
+ instead of
+
+</p><pre class="programlisting">
+import <nix/fetchurl.nix> {
+ url = https://nixos.org/releases/nix/nix-2.1.3/nix-2.1.3.tar.xz;
+ sha256 = "5d22dad058d5c800d65a115f919da22938c50dd6ba98c5e3a183172d149840a4";
+};
+</pre><p>
+
+ </p><p>In fixed-output derivations, the
+ <code class="varname">outputHashAlgo</code> attribute is no longer mandatory
+ if <code class="varname">outputHash</code> specifies the hash.</p><p><span class="command"><strong>nix hash-file</strong></span> and <span class="command"><strong>nix
+ hash-path</strong></span> now print hashes in SRI format by
+ default. They also use SHA-256 by default instead of SHA-512
+ because that's what we use most of the time in Nixpkgs.</p></li><li class="listitem"><p>Integers are now 64 bits on all platforms.</p></li><li class="listitem"><p>The evaluator now prints profiling statistics (enabled via
+ the <code class="envar">NIX_SHOW_STATS</code> and
+ <code class="envar">NIX_COUNT_CALLS</code> environment variables) in JSON
+ format.</p></li><li class="listitem"><p>The option <code class="option">--xml</code> in <span class="command"><strong>nix-store
+ --query</strong></span> has been removed. Instead, there now is an
+ option <code class="option">--graphml</code> to output the dependency graph
+ in GraphML format.</p></li><li class="listitem"><p>All <code class="filename">nix-*</code> commands are now symlinks to
+ <code class="filename">nix</code>. This saves a bit of disk space.</p></li><li class="listitem"><p><span class="command"><strong>nix repl</strong></span> now uses
+ <code class="literal">libeditline</code> or
+ <code class="literal">libreadline</code>.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-2.1"></a>C.3. Release 2.1 (2018-09-02)</h2></div></div></div><p>This is primarily a bug fix release. It also reduces memory
+consumption in certain situations. In addition, it has the following
+new features:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>The Nix installer will no longer default to the Multi-User
+ installation for macOS. You can still <a class="link" href="#sect-multi-user-installation" title="4.2. Multi User Installation">instruct the installer to
+ run in multi-user mode</a>.
+ </p></li><li class="listitem"><p>The Nix installer now supports performing a Multi-User
+ installation for Linux computers which are running systemd. You
+ can <a class="link" href="#sect-multi-user-installation" title="4.2. Multi User Installation">select a Multi-User installation</a> by passing the
+ <code class="option">--daemon</code> flag to the installer: <span class="command"><strong>sh <(curl
+ https://nixos.org/nix/install) --daemon</strong></span>.
+ </p><p>The multi-user installer cannot handle systems with SELinux.
+ If your system has SELinux enabled, you can <a class="link" href="#sect-single-user-installation" title="4.1. Single User Installation">force the installer to run
+ in single-user mode</a>.</p></li><li class="listitem"><p>New builtin functions:
+ <code class="literal">builtins.bitAnd</code>,
+ <code class="literal">builtins.bitOr</code>,
+ <code class="literal">builtins.bitXor</code>,
+ <code class="literal">builtins.fromTOML</code>,
+ <code class="literal">builtins.concatMap</code>,
+ <code class="literal">builtins.mapAttrs</code>.
+ </p></li><li class="listitem"><p>The S3 binary cache store now supports uploading NARs larger
+ than 5 GiB.</p></li><li class="listitem"><p>The S3 binary cache store now supports uploading to
+ S3-compatible services with the <code class="literal">endpoint</code>
+ option.</p></li><li class="listitem"><p>The flag <code class="option">--fallback</code> is no longer required
+ to recover from disappeared NARs in binary caches.</p></li><li class="listitem"><p><span class="command"><strong>nix-daemon</strong></span> now respects
+ <code class="option">--store</code>.</p></li><li class="listitem"><p><span class="command"><strong>nix run</strong></span> now respects
+ <code class="varname">nix-support/propagated-user-env-packages</code>.</p></li></ul></div><p>This release has contributions from
+
+Adrien Devresse,
+Aleksandr Pashkov,
+Alexandre Esteves,
+Amine Chikhaoui,
+Andrew Dunham,
+Asad Saeeduddin,
+aszlig,
+Ben Challenor,
+Ben Gamari,
+Benjamin Hipple,
+Bogdan Seniuc,
+Corey O'Connor,
+Daiderd Jordan,
+Daniel Peebles,
+Daniel Poelzleithner,
+Danylo Hlynskyi,
+Dmitry Kalinkin,
+Domen Kožar,
+Doug Beardsley,
+Eelco Dolstra,
+Erik Arvstedt,
+Félix Baylac-Jacqué,
+Gleb Peregud,
+Graham Christensen,
+Guillaume Maudoux,
+Ivan Kozik,
+John Arnold,
+Justin Humm,
+Linus Heckemann,
+Lorenzo Manacorda,
+Matthew Justin Bauer,
+Matthew O'Gorman,
+Maximilian Bosch,
+Michael Bishop,
+Michael Fiano,
+Michael Mercier,
+Michael Raskin,
+Michael Weiss,
+Nicolas Dudebout,
+Peter Simons,
+Ryan Trinkle,
+Samuel Dionne-Riel,
+Sean Seefried,
+Shea Levy,
+Symphorien Gibol,
+Tim Engler,
+Tim Sears,
+Tuomas Tynkkynen,
+volth,
+Will Dietz,
+Yorick van Pelt and
+zimbatm.
+</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-2.0"></a>C.4. Release 2.0 (2018-02-22)</h2></div></div></div><p>The following incompatible changes have been made:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>The manifest-based substituter mechanism
+ (<span class="command"><strong>download-using-manifests</strong></span>) has been <a class="link" href="https://github.com/NixOS/nix/commit/867967265b80946dfe1db72d40324b4f9af988ed" target="_top">removed</a>. It
+ has been superseded by the binary cache substituter mechanism
+ since several years. As a result, the following programs have been
+ removed:
+
+ </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p><span class="command"><strong>nix-pull</strong></span></p></li><li class="listitem"><p><span class="command"><strong>nix-generate-patches</strong></span></p></li><li class="listitem"><p><span class="command"><strong>bsdiff</strong></span></p></li><li class="listitem"><p><span class="command"><strong>bspatch</strong></span></p></li></ul></div><p>
+ </p></li><li class="listitem"><p>The “copy from other stores” substituter mechanism
+ (<span class="command"><strong>copy-from-other-stores</strong></span> and the
+ <code class="envar">NIX_OTHER_STORES</code> environment variable) has been
+ removed. It was primarily used by the NixOS installer to copy
+ available paths from the installation medium. The replacement is
+ to use a chroot store as a substituter
+ (e.g. <code class="literal">--substituters /mnt</code>), or to build into a
+ chroot store (e.g. <code class="literal">--store /mnt --substituters /</code>).</p></li><li class="listitem"><p>The command <span class="command"><strong>nix-push</strong></span> has been removed as
+ part of the effort to eliminate Nix's dependency on Perl. You can
+ use <span class="command"><strong>nix copy</strong></span> instead, e.g. <code class="literal">nix copy
+ --to file:///tmp/my-binary-cache <em class="replaceable"><code>paths…</code></em></code></p></li><li class="listitem"><p>The “nested” log output feature (<code class="option">--log-type
+ pretty</code>) has been removed. As a result,
+ <span class="command"><strong>nix-log2xml</strong></span> was also removed.</p></li><li class="listitem"><p>OpenSSL-based signing has been <a class="link" href="https://github.com/NixOS/nix/commit/f435f8247553656774dd1b2c88e9de5d59cab203" target="_top">removed</a>. This
+ feature was never well-supported. A better alternative is provided
+ by the <code class="option">secret-key-files</code> and
+ <code class="option">trusted-public-keys</code> options.</p></li><li class="listitem"><p>Failed build caching has been <a class="link" href="https://github.com/NixOS/nix/commit/8cffec84859cec8b610a2a22ab0c4d462a9351ff" target="_top">removed</a>. This
+ feature was introduced to support the Hydra continuous build
+ system, but Hydra no longer uses it.</p></li><li class="listitem"><p><code class="filename">nix-mode.el</code> has been removed from
+ Nix. It is now <a class="link" href="https://github.com/NixOS/nix-mode" target="_top">a separate
+ repository</a> and can be installed through the MELPA package
+ repository.</p></li></ul></div><p>This release has the following new features:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>It introduces a new command named <span class="command"><strong>nix</strong></span>,
+ which is intended to eventually replace all
+ <span class="command"><strong>nix-*</strong></span> commands with a more consistent and
+ better designed user interface. It currently provides replacements
+ for some (but not all) of the functionality provided by
+ <span class="command"><strong>nix-store</strong></span>, <span class="command"><strong>nix-build</strong></span>,
+ <span class="command"><strong>nix-shell -p</strong></span>, <span class="command"><strong>nix-env -qa</strong></span>,
+ <span class="command"><strong>nix-instantiate --eval</strong></span>,
+ <span class="command"><strong>nix-push</strong></span> and
+ <span class="command"><strong>nix-copy-closure</strong></span>. It has the following major
+ features:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Unlike the legacy commands, it has a consistent way to
+ refer to packages and package-like arguments (like store
+ paths). For example, the following commands all copy the GNU
+ Hello package to a remote machine:
+
+ </p><pre class="screen">nix copy --to ssh://machine nixpkgs.hello</pre><p>
+ </p><pre class="screen">nix copy --to ssh://machine /nix/store/0i2jd68mp5g6h2sa5k9c85rb80sn8hi9-hello-2.10</pre><p>
+ </p><pre class="screen">nix copy --to ssh://machine '(with import <nixpkgs> {}; hello)'</pre><p>
+
+ By contrast, <span class="command"><strong>nix-copy-closure</strong></span> only accepted
+ store paths as arguments.</p></li><li class="listitem"><p>It is self-documenting: <code class="option">--help</code> shows
+ all available command-line arguments. If
+ <code class="option">--help</code> is given after a subcommand, it shows
+ examples for that subcommand. <span class="command"><strong>nix
+ --help-config</strong></span> shows all configuration
+ options.</p></li><li class="listitem"><p>It is much less verbose. By default, it displays a
+ single-line progress indicator that shows how many packages
+ are left to be built or downloaded, and (if there are running
+ builds) the most recent line of builder output. If a build
+ fails, it shows the last few lines of builder output. The full
+ build log can be retrieved using <span class="command"><strong>nix
+ log</strong></span>.</p></li><li class="listitem"><p>It <a class="link" href="https://github.com/NixOS/nix/commit/b8283773bd64d7da6859ed520ee19867742a03ba" target="_top">provides</a>
+ all <code class="filename">nix.conf</code> configuration options as
+ command line flags. For example, instead of <code class="literal">--option
+ http-connections 100</code> you can write
+ <code class="literal">--http-connections 100</code>. Boolean options can
+ be written as
+ <code class="literal">--<em class="replaceable"><code>foo</code></em></code> or
+ <code class="literal">--no-<em class="replaceable"><code>foo</code></em></code>
+ (e.g. <code class="option">--no-auto-optimise-store</code>).</p></li><li class="listitem"><p>Many subcommands have a <code class="option">--json</code> flag to
+ write results to stdout in JSON format.</p></li></ul></div><div class="warning"><h3 class="title">Warning</h3><p>Please note that the <span class="command"><strong>nix</strong></span> command
+ is a work in progress and the interface is subject to
+ change.</p></div><p>It provides the following high-level (“porcelain”)
+ subcommands:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p><span class="command"><strong>nix build</strong></span> is a replacement for
+ <span class="command"><strong>nix-build</strong></span>.</p></li><li class="listitem"><p><span class="command"><strong>nix run</strong></span> executes a command in an
+ environment in which the specified packages are available. It
+ is (roughly) a replacement for <span class="command"><strong>nix-shell
+ -p</strong></span>. Unlike that command, it does not execute the
+ command in a shell, and has a flag (<span class="command"><strong>-c</strong></span>)
+ that specifies the unquoted command line to be
+ executed.</p><p>It is particularly useful in conjunction with chroot
+ stores, allowing Linux users who do not have permission to
+ install Nix in <span class="command"><strong>/nix/store</strong></span> to still use
+ binary substitutes that assume
+ <span class="command"><strong>/nix/store</strong></span>. For example,
+
+ </p><pre class="screen">nix run --store ~/my-nix nixpkgs.hello -c hello --greeting 'Hi everybody!'</pre><p>
+
+ downloads (or if not substitutes are available, builds) the
+ GNU Hello package into
+ <code class="filename">~/my-nix/nix/store</code>, then runs
+ <span class="command"><strong>hello</strong></span> in a mount namespace where
+ <code class="filename">~/my-nix/nix/store</code> is mounted onto
+ <span class="command"><strong>/nix/store</strong></span>.</p></li><li class="listitem"><p><span class="command"><strong>nix search</strong></span> replaces <span class="command"><strong>nix-env
+ -qa</strong></span>. It searches the available packages for
+ occurrences of a search string in the attribute name, package
+ name or description. Unlike <span class="command"><strong>nix-env -qa</strong></span>, it
+ has a cache to speed up subsequent searches.</p></li><li class="listitem"><p><span class="command"><strong>nix copy</strong></span> copies paths between
+ arbitrary Nix stores, generalising
+ <span class="command"><strong>nix-copy-closure</strong></span> and
+ <span class="command"><strong>nix-push</strong></span>.</p></li><li class="listitem"><p><span class="command"><strong>nix repl</strong></span> replaces the external
+ program <span class="command"><strong>nix-repl</strong></span>. It provides an
+ interactive environment for evaluating and building Nix
+ expressions. Note that it uses <code class="literal">linenoise-ng</code>
+ instead of GNU Readline.</p></li><li class="listitem"><p><span class="command"><strong>nix upgrade-nix</strong></span> upgrades Nix to the
+ latest stable version. This requires that Nix is installed in
+ a profile. (Thus it won’t work on NixOS, or if it’s installed
+ outside of the Nix store.)</p></li><li class="listitem"><p><span class="command"><strong>nix verify</strong></span> checks whether store paths
+ are unmodified and/or “trusted” (see below). It replaces
+ <span class="command"><strong>nix-store --verify</strong></span> and <span class="command"><strong>nix-store
+ --verify-path</strong></span>.</p></li><li class="listitem"><p><span class="command"><strong>nix log</strong></span> shows the build log of a
+ package or path. If the build log is not available locally, it
+ will try to obtain it from the configured substituters (such
+ as <code class="uri">cache.nixos.org</code>, which now provides build
+ logs).</p></li><li class="listitem"><p><span class="command"><strong>nix edit</strong></span> opens the source code of a
+ package in your editor.</p></li><li class="listitem"><p><span class="command"><strong>nix eval</strong></span> replaces
+ <span class="command"><strong>nix-instantiate --eval</strong></span>.</p></li><li class="listitem"><p><span class="command"><strong><a class="command" href="https://github.com/NixOS/nix/commit/d41c5eb13f4f3a37d80dbc6d3888644170c3b44a" target="_top">nix
+ why-depends</a></strong></span> shows why one store path has another in
+ its closure. This is primarily useful to finding the causes of
+ closure bloat. For example,
+
+ </p><pre class="screen">nix why-depends nixpkgs.vlc nixpkgs.libdrm.dev</pre><p>
+
+ shows a chain of files and fragments of file contents that
+ cause the VLC package to have the “dev” output of
+ <code class="literal">libdrm</code> in its closure — an undesirable
+ situation.</p></li><li class="listitem"><p><span class="command"><strong>nix path-info</strong></span> shows information about
+ store paths, replacing <span class="command"><strong>nix-store -q</strong></span>. A
+ useful feature is the option <code class="option">--closure-size</code>
+ (<code class="option">-S</code>). For example, the following command show
+ the closure sizes of every path in the current NixOS system
+ closure, sorted by size:
+
+ </p><pre class="screen">nix path-info -rS /run/current-system | sort -nk2</pre><p>
+
+ </p></li><li class="listitem"><p><span class="command"><strong>nix optimise-store</strong></span> replaces
+ <span class="command"><strong>nix-store --optimise</strong></span>. The main difference
+ is that it has a progress indicator.</p></li></ul></div><p>A number of low-level (“plumbing”) commands are also
+ available:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p><span class="command"><strong>nix ls-store</strong></span> and <span class="command"><strong>nix
+ ls-nar</strong></span> list the contents of a store path or NAR
+ file. The former is primarily useful in conjunction with
+ remote stores, e.g.
+
+ </p><pre class="screen">nix ls-store --store https://cache.nixos.org/ -lR /nix/store/0i2jd68mp5g6h2sa5k9c85rb80sn8hi9-hello-2.10</pre><p>
+
+ lists the contents of path in a binary cache.</p></li><li class="listitem"><p><span class="command"><strong>nix cat-store</strong></span> and <span class="command"><strong>nix
+ cat-nar</strong></span> allow extracting a file from a store path or
+ NAR file.</p></li><li class="listitem"><p><span class="command"><strong>nix dump-path</strong></span> writes the contents of
+ a store path to stdout in NAR format. This replaces
+ <span class="command"><strong>nix-store --dump</strong></span>.</p></li><li class="listitem"><p><span class="command"><strong><a class="command" href="https://github.com/NixOS/nix/commit/e8d6ee7c1b90a2fe6d824f1a875acc56799ae6e2" target="_top">nix
+ show-derivation</a></strong></span> displays a store derivation in JSON
+ format. This is an alternative to
+ <span class="command"><strong>pp-aterm</strong></span>.</p></li><li class="listitem"><p><span class="command"><strong><a class="command" href="https://github.com/NixOS/nix/commit/970366266b8df712f5f9cedb45af183ef5a8357f" target="_top">nix
+ add-to-store</a></strong></span> replaces <span class="command"><strong>nix-store
+ --add</strong></span>.</p></li><li class="listitem"><p><span class="command"><strong>nix sign-paths</strong></span> signs store
+ paths.</p></li><li class="listitem"><p><span class="command"><strong>nix copy-sigs</strong></span> copies signatures from
+ one store to another.</p></li><li class="listitem"><p><span class="command"><strong>nix show-config</strong></span> shows all
+ configuration options and their current values.</p></li></ul></div></li><li class="listitem"><p>The store abstraction that Nix has had for a long time to
+ support store access via the Nix daemon has been extended
+ significantly. In particular, substituters (which used to be
+ external programs such as
+ <span class="command"><strong>download-from-binary-cache</strong></span>) are now subclasses
+ of the abstract <code class="classname">Store</code> class. This allows
+ many Nix commands to operate on such store types. For example,
+ <span class="command"><strong>nix path-info</strong></span> shows information about paths in
+ your local Nix store, while <span class="command"><strong>nix path-info --store
+ https://cache.nixos.org/</strong></span> shows information about paths
+ in the specified binary cache. Similarly,
+ <span class="command"><strong>nix-copy-closure</strong></span>, <span class="command"><strong>nix-push</strong></span>
+ and substitution are all instances of the general notion of
+ copying paths between different kinds of Nix stores.</p><p>Stores are specified using an URI-like syntax,
+ e.g. <code class="uri">https://cache.nixos.org/</code> or
+ <code class="uri">ssh://machine</code>. The following store types are supported:
+
+ </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p><code class="classname">LocalStore</code> (stori URI
+ <code class="literal">local</code> or an absolute path) and the misnamed
+ <code class="classname">RemoteStore</code> (<code class="literal">daemon</code>)
+ provide access to a local Nix store, the latter via the Nix
+ daemon. You can use <code class="literal">auto</code> or the empty
+ string to auto-select a local or daemon store depending on
+ whether you have write permission to the Nix store. It is no
+ longer necessary to set the <code class="envar">NIX_REMOTE</code>
+ environment variable to use the Nix daemon.</p><p>As noted above, <code class="classname">LocalStore</code> now
+ supports chroot builds, allowing the “physical” location of
+ the Nix store
+ (e.g. <code class="filename">/home/alice/nix/store</code>) to differ
+ from its “logical” location (typically
+ <code class="filename">/nix/store</code>). This allows non-root users
+ to use Nix while still getting the benefits from prebuilt
+ binaries from <code class="uri">cache.nixos.org</code>.</p></li><li class="listitem"><p><code class="classname">BinaryCacheStore</code> is the abstract
+ superclass of all binary cache stores. It supports writing
+ build logs and NAR content listings in JSON format.</p></li><li class="listitem"><p><code class="classname">HttpBinaryCacheStore</code>
+ (<code class="literal">http://</code>, <code class="literal">https://</code>)
+ supports binary caches via HTTP or HTTPS. If the server
+ supports <code class="literal">PUT</code> requests, it supports
+ uploading store paths via commands such as <span class="command"><strong>nix
+ copy</strong></span>.</p></li><li class="listitem"><p><code class="classname">LocalBinaryCacheStore</code>
+ (<code class="literal">file://</code>) supports binary caches in the
+ local filesystem.</p></li><li class="listitem"><p><code class="classname">S3BinaryCacheStore</code>
+ (<code class="literal">s3://</code>) supports binary caches stored in
+ Amazon S3, if enabled at compile time.</p></li><li class="listitem"><p><code class="classname">LegacySSHStore</code> (<code class="literal">ssh://</code>)
+ is used to implement remote builds and
+ <span class="command"><strong>nix-copy-closure</strong></span>.</p></li><li class="listitem"><p><code class="classname">SSHStore</code>
+ (<code class="literal">ssh-ng://</code>) supports arbitrary Nix
+ operations on a remote machine via the same protocol used by
+ <span class="command"><strong>nix-daemon</strong></span>.</p></li></ul></div><p>
+
+ </p></li><li class="listitem"><p>Security has been improved in various ways:
+
+ </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Nix now stores signatures for local store
+ paths. When paths are copied between stores (e.g., copied from
+ a binary cache to a local store), signatures are
+ propagated.</p><p>Locally-built paths are signed automatically using the
+ secret keys specified by the <code class="option">secret-key-files</code>
+ store option. Secret/public key pairs can be generated using
+ <span class="command"><strong>nix-store
+ --generate-binary-cache-key</strong></span>.</p><p>In addition, locally-built store paths are marked as
+ “ultimately trusted”, but this bit is not propagated when
+ paths are copied between stores.</p></li><li class="listitem"><p>Content-addressable store paths no longer require
+ signatures — they can be imported into a store by unprivileged
+ users even if they lack signatures.</p></li><li class="listitem"><p>The command <span class="command"><strong>nix verify</strong></span> checks whether
+ the specified paths are trusted, i.e., have a certain number
+ of trusted signatures, are ultimately trusted, or are
+ content-addressed.</p></li><li class="listitem"><p>Substitutions from binary caches <a class="link" href="https://github.com/NixOS/nix/commit/ecbc3fedd3d5bdc5a0e1a0a51b29062f2874ac8b" target="_top">now</a>
+ require signatures by default. This was already the case on
+ NixOS.</p></li><li class="listitem"><p>In Linux sandbox builds, we <a class="link" href="https://github.com/NixOS/nix/commit/eba840c8a13b465ace90172ff76a0db2899ab11b" target="_top">now</a>
+ use <code class="filename">/build</code> instead of
+ <code class="filename">/tmp</code> as the temporary build
+ directory. This fixes potential security problems when a build
+ accidentally stores its <code class="envar">TMPDIR</code> in some
+ security-sensitive place, such as an RPATH.</p></li></ul></div><p>
+
+ </p></li><li class="listitem"><p><span class="emphasis"><em>Pure evaluation mode</em></span>. With the
+ <code class="literal">--pure-eval</code> flag, Nix enables a variant of the existing
+ restricted evaluation mode that forbids access to anything that could cause
+ different evaluations of the same command line arguments to produce a
+ different result. This includes builtin functions such as
+ <code class="function">builtins.getEnv</code>, but more importantly,
+ <span class="emphasis"><em>all</em></span> filesystem or network access unless a content hash
+ or commit hash is specified. For example, calls to
+ <code class="function">builtins.fetchGit</code> are only allowed if a
+ <code class="varname">rev</code> attribute is specified.</p><p>The goal of this feature is to enable true reproducibility
+ and traceability of builds (including NixOS system configurations)
+ at the evaluation level. For example, in the future,
+ <span class="command"><strong>nixos-rebuild</strong></span> might build configurations from a
+ Nix expression in a Git repository in pure mode. That expression
+ might fetch other repositories such as Nixpkgs via
+ <code class="function">builtins.fetchGit</code>. The commit hash of the
+ top-level repository then uniquely identifies a running system,
+ and, in conjunction with that repository, allows it to be
+ reproduced or modified.</p></li><li class="listitem"><p>There are several new features to support binary
+ reproducibility (i.e. to help ensure that multiple builds of the
+ same derivation produce exactly the same output). When
+ <code class="option">enforce-determinism</code> is set to
+ <code class="literal">false</code>, it’s <a class="link" href="https://github.com/NixOS/nix/commit/8bdf83f936adae6f2c907a6d2541e80d4120f051" target="_top">no
+ longer</a> a fatal error if build rounds produce different
+ output. Also, a hook named <code class="option">diff-hook</code> is <a class="link" href="https://github.com/NixOS/nix/commit/9a313469a4bdea2d1e8df24d16289dc2a172a169" target="_top">provided</a>
+ to allow you to run tools such as <span class="command"><strong>diffoscope</strong></span>
+ when build rounds produce different output.</p></li><li class="listitem"><p>Configuring remote builds is a lot easier now. Provided you
+ are not using the Nix daemon, you can now just specify a remote
+ build machine on the command line, e.g. <code class="literal">--option builders
+ 'ssh://my-mac x86_64-darwin'</code>. The environment variable
+ <code class="envar">NIX_BUILD_HOOK</code> has been removed and is no longer
+ needed. The environment variable <code class="envar">NIX_REMOTE_SYSTEMS</code>
+ is still supported for compatibility, but it is also possible to
+ specify builders in <span class="command"><strong>nix.conf</strong></span> by setting the
+ option <code class="literal">builders =
+ @<em class="replaceable"><code>path</code></em></code>.</p></li><li class="listitem"><p>If a fixed-output derivation produces a result with an
+ incorrect hash, the output path is moved to the location
+ corresponding to the actual hash and registered as valid. Thus, a
+ subsequent build of the fixed-output derivation with the correct
+ hash is unnecessary.</p></li><li class="listitem"><p><span class="command"><strong>nix-shell</strong></span> <a class="link" href="https://github.com/NixOS/nix/commit/ea59f39326c8e9dc42dfed4bcbf597fbce58797c" target="_top">now</a>
+ sets the <code class="varname">IN_NIX_SHELL</code> environment variable
+ during evaluation and in the shell itself. This can be used to
+ perform different actions depending on whether you’re in a Nix
+ shell or in a regular build. Nixpkgs provides
+ <code class="varname">lib.inNixShell</code> to check this variable during
+ evaluation.</p></li><li class="listitem"><p><code class="envar">NIX_PATH</code> is now lazy, so URIs in the path are
+ only downloaded if they are needed for evaluation.</p></li><li class="listitem"><p>You can now use
+ <code class="uri">channel:<em class="replaceable"><code>channel-name</code></em></code> as a
+ short-hand for
+ <code class="uri">https://nixos.org/channels/<em class="replaceable"><code>channel-name</code></em>/nixexprs.tar.xz</code>. For
+ example, <code class="literal">nix-build channel:nixos-15.09 -A hello</code>
+ will build the GNU Hello package from the
+ <code class="literal">nixos-15.09</code> channel. In the future, this may
+ use Git to fetch updates more efficiently.</p></li><li class="listitem"><p>When <code class="option">--no-build-output</code> is given, the last
+ 10 lines of the build log will be shown if a build
+ fails.</p></li><li class="listitem"><p>Networking has been improved:
+
+ </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>HTTP/2 is now supported. This makes binary cache lookups
+ <a class="link" href="https://github.com/NixOS/nix/commit/90ad02bf626b885a5dd8967894e2eafc953bdf92" target="_top">much
+ more efficient</a>.</p></li><li class="listitem"><p>We now retry downloads on many HTTP errors, making
+ binary caches substituters more resilient to temporary
+ failures.</p></li><li class="listitem"><p>HTTP credentials can now be configured via the standard
+ <code class="filename">netrc</code> mechanism.</p></li><li class="listitem"><p>If S3 support is enabled at compile time,
+ <code class="uri">s3://</code> URIs are <a class="link" href="https://github.com/NixOS/nix/commit/9ff9c3f2f80ba4108e9c945bbfda2c64735f987b" target="_top">supported</a>
+ in all places where Nix allows URIs.</p></li><li class="listitem"><p>Brotli compression is now supported. In particular,
+ <code class="uri">cache.nixos.org</code> build logs are now compressed using
+ Brotli.</p></li></ul></div><p>
+
+ </p></li><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> <a class="link" href="https://github.com/NixOS/nix/commit/b0cb11722626e906a73f10dd9a0c9eea29faf43a" target="_top">now</a>
+ ignores packages with bad derivation names (in particular those
+ starting with a digit or containing a dot).</p></li><li class="listitem"><p>Many configuration options have been renamed, either because
+ they were unnecessarily verbose
+ (e.g. <code class="option">build-use-sandbox</code> is now just
+ <code class="option">sandbox</code>) or to reflect generalised behaviour
+ (e.g. <code class="option">binary-caches</code> is now
+ <code class="option">substituters</code> because it allows arbitrary store
+ URIs). The old names are still supported for compatibility.</p></li><li class="listitem"><p>The <code class="option">max-jobs</code> option can <a class="link" href="https://github.com/NixOS/nix/commit/7251d048fa812d2551b7003bc9f13a8f5d4c95a5" target="_top">now</a>
+ be set to <code class="literal">auto</code> to use the number of CPUs in the
+ system.</p></li><li class="listitem"><p>Hashes can <a class="link" href="https://github.com/NixOS/nix/commit/c0015e87af70f539f24d2aa2bc224a9d8b84276b" target="_top">now</a>
+ be specified in base-64 format, in addition to base-16 and the
+ non-standard base-32.</p></li><li class="listitem"><p><span class="command"><strong>nix-shell</strong></span> now uses
+ <code class="varname">bashInteractive</code> from Nixpkgs, rather than the
+ <span class="command"><strong>bash</strong></span> command that happens to be in the caller’s
+ <code class="envar">PATH</code>. This is especially important on macOS where
+ the <span class="command"><strong>bash</strong></span> provided by the system is seriously
+ outdated and cannot execute <code class="literal">stdenv</code>’s setup
+ script.</p></li><li class="listitem"><p>Nix can now automatically trigger a garbage collection if
+ free disk space drops below a certain level during a build. This
+ is configured using the <code class="option">min-free</code> and
+ <code class="option">max-free</code> options.</p></li><li class="listitem"><p><span class="command"><strong>nix-store -q --roots</strong></span> and
+ <span class="command"><strong>nix-store --gc --print-roots</strong></span> now show temporary
+ and in-memory roots.</p></li><li class="listitem"><p>
+ Nix can now be extended with plugins. See the documentation of
+ the <code class="option">plugin-files</code> option for more details.
+ </p></li></ul></div><p>The Nix language has the following new features:
+
+</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>It supports floating point numbers. They are based on the
+ C++ <code class="literal">float</code> type and are supported by the
+ existing numerical operators. Export and import to and from JSON
+ and XML works, too.</p></li><li class="listitem"><p>Derivation attributes can now reference the outputs of the
+ derivation using the <code class="function">placeholder</code> builtin
+ function. For example, the attribute
+
+</p><pre class="programlisting">
+configureFlags = "--prefix=${placeholder "out"} --includedir=${placeholder "dev"}";
+</pre><p>
+
+ will cause the <code class="envar">configureFlags</code> environment variable
+ to contain the actual store paths corresponding to the
+ <code class="literal">out</code> and <code class="literal">dev</code> outputs.</p></li></ul></div><p>
+
+</p><p>The following builtin functions are new or extended:
+
+</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><code class="function"><a class="function" href="https://github.com/NixOS/nix/commit/38539b943a060d9cdfc24d6e5d997c0885b8aa2f" target="_top">builtins.fetchGit</a></code>
+ allows Git repositories to be fetched at evaluation time. Thus it
+ differs from the <code class="function">fetchgit</code> function in
+ Nixpkgs, which fetches at build time and cannot be used to fetch
+ Nix expressions during evaluation. A typical use case is to import
+ external NixOS modules from your configuration, e.g.
+
+ </p><pre class="programlisting">imports = [ (builtins.fetchGit https://github.com/edolstra/dwarffs + "/module.nix") ];</pre><p>
+
+ </p></li><li class="listitem"><p>Similarly, <code class="function">builtins.fetchMercurial</code>
+ allows you to fetch Mercurial repositories.</p></li><li class="listitem"><p><code class="function">builtins.path</code> generalises
+ <code class="function">builtins.filterSource</code> and path literals
+ (e.g. <code class="literal">./foo</code>). It allows specifying a store path
+ name that differs from the source path name
+ (e.g. <code class="literal">builtins.path { path = ./foo; name = "bar";
+ }</code>) and also supports filtering out unwanted
+ files.</p></li><li class="listitem"><p><code class="function">builtins.fetchurl</code> and
+ <code class="function">builtins.fetchTarball</code> now support
+ <code class="varname">sha256</code> and <code class="varname">name</code>
+ attributes.</p></li><li class="listitem"><p><code class="function"><a class="function" href="https://github.com/NixOS/nix/commit/b8867a0239b1930a16f9ef3f7f3e864b01416dff" target="_top">builtins.split</a></code>
+ splits a string using a POSIX extended regular expression as the
+ separator.</p></li><li class="listitem"><p><code class="function"><a class="function" href="https://github.com/NixOS/nix/commit/26d92017d3b36cff940dcb7d1611c42232edb81a" target="_top">builtins.partition</a></code>
+ partitions the elements of a list into two lists, depending on a
+ Boolean predicate.</p></li><li class="listitem"><p><code class="literal"><nix/fetchurl.nix></code> now uses the
+ content-addressable tarball cache at
+ <code class="uri">http://tarballs.nixos.org/</code>, just like
+ <code class="function">fetchurl</code> in
+ Nixpkgs. (f2682e6e18a76ecbfb8a12c17e3a0ca15c084197)</p></li><li class="listitem"><p>In restricted and pure evaluation mode, builtin functions
+ that download from the network (such as
+ <code class="function">fetchGit</code>) are permitted to fetch underneath a
+ list of URI prefixes specified in the option
+ <code class="option">allowed-uris</code>.</p></li></ul></div><p>
+
+</p><p>The Nix build environment has the following changes:
+
+</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Values such as Booleans, integers, (nested) lists and
+ attribute sets can <a class="link" href="https://github.com/NixOS/nix/commit/6de33a9c675b187437a2e1abbcb290981a89ecb1" target="_top">now</a>
+ be passed to builders in a non-lossy way. If the special attribute
+ <code class="varname">__structuredAttrs</code> is set to
+ <code class="literal">true</code>, the other derivation attributes are
+ serialised in JSON format and made available to the builder via
+ the file <code class="envar">.attrs.json</code> in the builder’s temporary
+ directory. This obviates the need for
+ <code class="varname">passAsFile</code> since JSON files have no size
+ restrictions, unlike process environments.</p><p><a class="link" href="https://github.com/NixOS/nix/commit/2d5b1b24bf70a498e4c0b378704cfdb6471cc699" target="_top">As
+ a convenience to Bash builders</a>, Nix writes a script named
+ <code class="envar">.attrs.sh</code> to the builder’s directory that
+ initialises shell variables corresponding to all attributes that
+ are representable in Bash. This includes non-nested (associative)
+ arrays. For example, the attribute <code class="literal">hardening.format =
+ true</code> ends up as the Bash associative array element
+ <code class="literal">${hardening[format]}</code>.</p></li><li class="listitem"><p>Builders can <a class="link" href="https://github.com/NixOS/nix/commit/88e6bb76de5564b3217be9688677d1c89101b2a3" target="_top">now</a>
+ communicate what build phase they are in by writing messages to
+ the file descriptor specified in <code class="envar">NIX_LOG_FD</code>. The
+ current phase is shown by the <span class="command"><strong>nix</strong></span> progress
+ indicator.
+ </p></li><li class="listitem"><p>In Linux sandbox builds, we <a class="link" href="https://github.com/NixOS/nix/commit/a2d92bb20e82a0957067ede60e91fab256948b41" target="_top">now</a>
+ provide a default <code class="filename">/bin/sh</code> (namely
+ <code class="filename">ash</code> from BusyBox).</p></li><li class="listitem"><p>In structured attribute mode,
+ <code class="varname">exportReferencesGraph</code> <a class="link" href="https://github.com/NixOS/nix/commit/c2b0d8749f7e77afc1c4b3e8dd36b7ee9720af4a" target="_top">exports</a>
+ extended information about closures in JSON format. In particular,
+ it includes the sizes and hashes of paths. This is primarily
+ useful for NixOS image builders.</p></li><li class="listitem"><p>Builds are <a class="link" href="https://github.com/NixOS/nix/commit/21948deed99a3295e4d5666e027a6ca42dc00b40" target="_top">now</a>
+ killed as soon as Nix receives EOF on the builder’s stdout or
+ stderr. This fixes a bug that allowed builds to hang Nix
+ indefinitely, regardless of
+ timeouts.</p></li><li class="listitem"><p>The <code class="option">sandbox-paths</code> configuration
+ option can now specify optional paths by appending a
+ <code class="literal">?</code>, e.g. <code class="literal">/dev/nvidiactl?</code> will
+ bind-mount <code class="varname">/dev/nvidiactl</code> only if it
+ exists.</p></li><li class="listitem"><p>On Linux, builds are now executed in a user
+ namespace with UID 1000 and GID 100.</p></li></ul></div><p>
+
+</p><p>A number of significant internal changes were made:
+
+</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Nix no longer depends on Perl and all Perl components have
+ been rewritten in C++ or removed. The Perl bindings that used to
+ be part of Nix have been moved to a separate package,
+ <code class="literal">nix-perl</code>.</p></li><li class="listitem"><p>All <code class="classname">Store</code> classes are now
+ thread-safe. <code class="classname">RemoteStore</code> supports multiple
+ concurrent connections to the daemon. This is primarily useful in
+ multi-threaded programs such as
+ <span class="command"><strong>hydra-queue-runner</strong></span>.</p></li></ul></div><p>
+
+</p><p>This release has contributions from
+
+Adrien Devresse,
+Alexander Ried,
+Alex Cruice,
+Alexey Shmalko,
+AmineChikhaoui,
+Andy Wingo,
+Aneesh Agrawal,
+Anthony Cowley,
+Armijn Hemel,
+aszlig,
+Ben Gamari,
+Benjamin Hipple,
+Benjamin Staffin,
+Benno Fünfstück,
+Bjørn Forsman,
+Brian McKenna,
+Charles Strahan,
+Chase Adams,
+Chris Martin,
+Christian Theune,
+Chris Warburton,
+Daiderd Jordan,
+Dan Connolly,
+Daniel Peebles,
+Dan Peebles,
+davidak,
+David McFarland,
+Dmitry Kalinkin,
+Domen Kožar,
+Eelco Dolstra,
+Emery Hemingway,
+Eric Litak,
+Eric Wolf,
+Fabian Schmitthenner,
+Frederik Rietdijk,
+Gabriel Gonzalez,
+Giorgio Gallo,
+Graham Christensen,
+Guillaume Maudoux,
+Harmen,
+Iavael,
+James Broadhead,
+James Earl Douglas,
+Janus Troelsen,
+Jeremy Shaw,
+Joachim Schiele,
+Joe Hermaszewski,
+Joel Moberg,
+Johannes 'fish' Ziemke,
+Jörg Thalheim,
+Jude Taylor,
+kballou,
+Keshav Kini,
+Kjetil Orbekk,
+Langston Barrett,
+Linus Heckemann,
+Ludovic Courtès,
+Manav Rathi,
+Marc Scholten,
+Markus Hauck,
+Matt Audesse,
+Matthew Bauer,
+Matthias Beyer,
+Matthieu Coudron,
+N1X,
+Nathan Zadoks,
+Neil Mayhew,
+Nicolas B. Pierron,
+Niklas Hambüchen,
+Nikolay Amiantov,
+Ole Jørgen Brønner,
+Orivej Desh,
+Peter Simons,
+Peter Stuart,
+Pyry Jahkola,
+regnat,
+Renzo Carbonara,
+Rhys,
+Robert Vollmert,
+Scott Olson,
+Scott R. Parish,
+Sergei Trofimovich,
+Shea Levy,
+Sheena Artrip,
+Spencer Baugh,
+Stefan Junker,
+Susan Potter,
+Thomas Tuegel,
+Timothy Allen,
+Tristan Hume,
+Tuomas Tynkkynen,
+tv,
+Tyson Whitehead,
+Vladimír Čunát,
+Will Dietz,
+wmertens,
+Wout Mertens,
+zimbatm and
+Zoran Plesivčak.
+</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.11.10"></a>C.5. Release 1.11.10 (2017-06-12)</h2></div></div></div><p>This release fixes a security bug in Nix’s “build user” build
+isolation mechanism. Previously, Nix builders had the ability to
+create setuid binaries owned by a <code class="literal">nixbld</code>
+user. Such a binary could then be used by an attacker to assume a
+<code class="literal">nixbld</code> identity and interfere with subsequent
+builds running under the same UID.</p><p>To prevent this issue, Nix now disallows builders to create
+setuid and setgid binaries. On Linux, this is done using a seccomp BPF
+filter. Note that this imposes a small performance penalty (e.g. 1%
+when building GNU Hello). Using seccomp, we now also prevent the
+creation of extended attributes and POSIX ACLs since these cannot be
+represented in the NAR format and (in the case of POSIX ACLs) allow
+bypassing regular Nix store permissions. On macOS, the restriction is
+implemented using the existing sandbox mechanism, which now uses a
+minimal “allow all except the creation of setuid/setgid binaries”
+profile when regular sandboxing is disabled. On other platforms, the
+“build user” mechanism is now disabled.</p><p>Thanks go to Linus Heckemann for discovering and reporting this
+bug.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.11"></a>C.6. Release 1.11 (2016-01-19)</h2></div></div></div><p>This is primarily a bug fix release. It also has a number of new
+features:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><span class="command"><strong>nix-prefetch-url</strong></span> can now download URLs
+ specified in a Nix expression. For example,
+
+</p><pre class="screen">
+$ nix-prefetch-url -A hello.src
+</pre><p>
+
+ will prefetch the file specified by the
+ <code class="function">fetchurl</code> call in the attribute
+ <code class="literal">hello.src</code> from the Nix expression in the
+ current directory, and print the cryptographic hash of the
+ resulting file on stdout. This differs from <code class="literal">nix-build -A
+ hello.src</code> in that it doesn't verify the hash, and is
+ thus useful when you’re updating a Nix expression.</p><p>You can also prefetch the result of functions that unpack a
+ tarball, such as <code class="function">fetchFromGitHub</code>. For example:
+
+</p><pre class="screen">
+$ nix-prefetch-url --unpack https://github.com/NixOS/patchelf/archive/0.8.tar.gz
+</pre><p>
+
+ or from a Nix expression:
+
+</p><pre class="screen">
+$ nix-prefetch-url -A nix-repl.src
+</pre><p>
+
+ </p></li><li class="listitem"><p>The builtin function
+ <code class="function"><nix/fetchurl.nix></code> now supports
+ downloading and unpacking NARs. This removes the need to have
+ multiple downloads in the Nixpkgs stdenv bootstrap process (like a
+ separate busybox binary for Linux, or curl/mkdir/sh/bzip2 for
+ Darwin). Now all those files can be combined into a single NAR,
+ optionally compressed using <span class="command"><strong>xz</strong></span>.</p></li><li class="listitem"><p>Nix now supports SHA-512 hashes for verifying fixed-output
+ derivations, and in <code class="function">builtins.hashString</code>.</p></li><li class="listitem"><p>
+ The new flag <code class="option">--option build-repeat
+ <em class="replaceable"><code>N</code></em></code> will cause every build to
+ be executed <em class="replaceable"><code>N</code></em>+1 times. If the build
+ output differs between any round, the build is rejected, and the
+ output paths are not registered as valid. This is primarily
+ useful to verify build determinism. (We already had a
+ <code class="option">--check</code> option to repeat a previously succeeded
+ build. However, with <code class="option">--check</code>, non-deterministic
+ builds are registered in the DB. Preventing that is useful for
+ Hydra to ensure that non-deterministic builds don't end up
+ getting published to the binary cache.)
+ </p></li><li class="listitem"><p>
+ The options <code class="option">--check</code> and <code class="option">--option
+ build-repeat <em class="replaceable"><code>N</code></em></code>, if they
+ detect a difference between two runs of the same derivation and
+ <code class="option">-K</code> is given, will make the output of the other
+ run available under
+ <code class="filename"><em class="replaceable"><code>store-path</code></em>-check</code>. This
+ makes it easier to investigate the non-determinism using tools
+ like <span class="command"><strong>diffoscope</strong></span>, e.g.,
+
+</p><pre class="screen">
+$ nix-build pkgs/stdenv/linux -A stage1.pkgs.zlib --check -K
+error: derivation ‘/nix/store/l54i8wlw2265…-zlib-1.2.8.drv’ may not
+be deterministic: output ‘/nix/store/11a27shh6n2i…-zlib-1.2.8’
+differs from ‘/nix/store/11a27shh6n2i…-zlib-1.2.8-check’
+
+$ diffoscope /nix/store/11a27shh6n2i…-zlib-1.2.8 /nix/store/11a27shh6n2i…-zlib-1.2.8-check
+…
+├── lib/libz.a
+│ ├── metadata
+│ │ @@ -1,15 +1,15 @@
+│ │ -rw-r--r-- 30001/30000 3096 Jan 12 15:20 2016 adler32.o
+…
+│ │ +rw-r--r-- 30001/30000 3096 Jan 12 15:28 2016 adler32.o
+…
+</pre><p>
+
+ </p></li><li class="listitem"><p>Improved FreeBSD support.</p></li><li class="listitem"><p><span class="command"><strong>nix-env -qa --xml --meta</strong></span> now prints
+ license information.</p></li><li class="listitem"><p>The maximum number of parallel TCP connections that the
+ binary cache substituter will use has been decreased from 150 to
+ 25. This should prevent upsetting some broken NAT routers, and
+ also improves performance.</p></li><li class="listitem"><p>All "chroot"-containing strings got renamed to "sandbox".
+ In particular, some Nix options got renamed, but the old names
+ are still accepted as lower-priority aliases.
+ </p></li></ul></div><p>This release has contributions from Anders Claesson, Anthony
+Cowley, Bjørn Forsman, Brian McKenna, Danny Wilson, davidak, Eelco Dolstra,
+Fabian Schmitthenner, FrankHB, Ilya Novoselov, janus, Jim Garrison, John
+Ericson, Jude Taylor, Ludovic Courtès, Manuel Jacob, Mathnerd314,
+Pascal Wittmann, Peter Simons, Philip Potter, Preston Bennes, Rommel
+M. Martinez, Sander van der Burg, Shea Levy, Tim Cuthbertson, Tuomas
+Tynkkynen, Utku Demir and Vladimír Čunát.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.10"></a>C.7. Release 1.10 (2015-09-03)</h2></div></div></div><p>This is primarily a bug fix release. It also has a number of new
+features:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>A number of builtin functions have been added to reduce
+ Nixpkgs/NixOS evaluation time and memory consumption:
+ <code class="function">all</code>,
+ <code class="function">any</code>,
+ <code class="function">concatStringsSep</code>,
+ <code class="function">foldl’</code>,
+ <code class="function">genList</code>,
+ <code class="function">replaceStrings</code>,
+ <code class="function">sort</code>.
+ </p></li><li class="listitem"><p>The garbage collector is more robust when the disk is full.</p></li><li class="listitem"><p>Nix supports a new API for building derivations that doesn’t
+ require a <code class="literal">.drv</code> file to be present on disk; it
+ only requires an in-memory representation of the derivation. This
+ is used by the Hydra continuous build system to make remote builds
+ more efficient.</p></li><li class="listitem"><p>The function <code class="literal"><nix/fetchurl.nix></code> now
+ uses a <span class="emphasis"><em>builtin</em></span> builder (i.e. it doesn’t
+ require starting an external process; the download is performed by
+ Nix itself). This ensures that derivation paths don’t change when
+ Nix is upgraded, and obviates the need for ugly hacks to support
+ chroot execution.</p></li><li class="listitem"><p><code class="option">--version -v</code> now prints some configuration
+ information, in particular what compile-time optional features are
+ enabled, and the paths of various directories.</p></li><li class="listitem"><p>Build users have their supplementary groups set correctly.</p></li></ul></div><p>This release has contributions from Eelco Dolstra, Guillaume
+Maudoux, Iwan Aucamp, Jaka Hudoklin, Kirill Elagin, Ludovic Courtès,
+Manolis Ragkousis, Nicolas B. Pierron and Shea Levy.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.9"></a>C.8. Release 1.9 (2015-06-12)</h2></div></div></div><p>In addition to the usual bug fixes, this release has the
+following new features:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Signed binary cache support. You can enable signature
+ checking by adding the following to <code class="filename">nix.conf</code>:
+
+</p><pre class="programlisting">
+signed-binary-caches = *
+binary-cache-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
+</pre><p>
+
+ This will prevent Nix from downloading any binary from the cache
+ that is not signed by one of the keys listed in
+ <code class="option">binary-cache-public-keys</code>.</p><p>Signature checking is only supported if you built Nix with
+ the <code class="literal">libsodium</code> package.</p><p>Note that while Nix has had experimental support for signed
+ binary caches since version 1.7, this release changes the
+ signature format in a backwards-incompatible way.</p></li><li class="listitem"><p>Automatic downloading of Nix expression tarballs. In various
+ places, you can now specify the URL of a tarball containing Nix
+ expressions (such as Nixpkgs), which will be downloaded and
+ unpacked automatically. For example:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>In <span class="command"><strong>nix-env</strong></span>:
+
+</p><pre class="screen">
+$ nix-env -f https://github.com/NixOS/nixpkgs-channels/archive/nixos-14.12.tar.gz -iA firefox
+</pre><p>
+
+ This installs Firefox from the latest tested and built revision
+ of the NixOS 14.12 channel.</p></li><li class="listitem"><p>In <span class="command"><strong>nix-build</strong></span> and
+ <span class="command"><strong>nix-shell</strong></span>:
+
+</p><pre class="screen">
+$ nix-build https://github.com/NixOS/nixpkgs/archive/master.tar.gz -A hello
+</pre><p>
+
+ This builds GNU Hello from the latest revision of the Nixpkgs
+ master branch.</p></li><li class="listitem"><p>In the Nix search path (as specified via
+ <code class="envar">NIX_PATH</code> or <code class="option">-I</code>). For example, to
+ start a shell containing the Pan package from a specific version
+ of Nixpkgs:
+
+</p><pre class="screen">
+$ nix-shell -p pan -I nixpkgs=https://github.com/NixOS/nixpkgs-channels/archive/8a3eea054838b55aca962c3fbde9c83c102b8bf2.tar.gz
+</pre><p>
+
+ </p></li><li class="listitem"><p>In <span class="command"><strong>nixos-rebuild</strong></span> (on NixOS):
+
+</p><pre class="screen">
+$ nixos-rebuild test -I nixpkgs=https://github.com/NixOS/nixpkgs-channels/archive/nixos-unstable.tar.gz
+</pre><p>
+
+ </p></li><li class="listitem"><p>In Nix expressions, via the new builtin function <code class="function">fetchTarball</code>:
+
+</p><pre class="programlisting">
+with import (fetchTarball https://github.com/NixOS/nixpkgs-channels/archive/nixos-14.12.tar.gz) {}; …
+</pre><p>
+
+ (This is not allowed in restricted mode.)</p></li></ul></div></li><li class="listitem"><p><span class="command"><strong>nix-shell</strong></span> improvements:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p><span class="command"><strong>nix-shell</strong></span> now has a flag
+ <code class="option">--run</code> to execute a command in the
+ <span class="command"><strong>nix-shell</strong></span> environment,
+ e.g. <code class="literal">nix-shell --run make</code>. This is like
+ the existing <code class="option">--command</code> flag, except that it
+ uses a non-interactive shell (ensuring that hitting Ctrl-C won’t
+ drop you into the child shell).</p></li><li class="listitem"><p><span class="command"><strong>nix-shell</strong></span> can now be used as
+ a <code class="literal">#!</code>-interpreter. This allows you to write
+ scripts that dynamically fetch their own dependencies. For
+ example, here is a Haskell script that, when invoked, first
+ downloads GHC and the Haskell packages on which it depends:
+
+</p><pre class="programlisting">
+#! /usr/bin/env nix-shell
+#! nix-shell -i runghc -p haskellPackages.ghc haskellPackages.HTTP
+
+import Network.HTTP
+
+main = do
+ resp <- Network.HTTP.simpleHTTP (getRequest "http://nixos.org/")
+ body <- getResponseBody resp
+ print (take 100 body)
+</pre><p>
+
+ Of course, the dependencies are cached in the Nix store, so the
+ second invocation of this script will be much
+ faster.</p></li></ul></div></li><li class="listitem"><p>Chroot improvements:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Chroot builds are now supported on Mac OS X
+ (using its sandbox mechanism).</p></li><li class="listitem"><p>If chroots are enabled, they are now used for
+ all derivations, including fixed-output derivations (such as
+ <code class="function">fetchurl</code>). The latter do have network
+ access, but can no longer access the host filesystem. If you
+ need the old behaviour, you can set the option
+ <code class="option">build-use-chroot</code> to
+ <code class="literal">relaxed</code>.</p></li><li class="listitem"><p>On Linux, if chroots are enabled, builds are
+ performed in a private PID namespace once again. (This
+ functionality was lost in Nix 1.8.)</p></li><li class="listitem"><p>Store paths listed in
+ <code class="option">build-chroot-dirs</code> are now automatically
+ expanded to their closure. For instance, if you want
+ <code class="filename">/nix/store/…-bash/bin/sh</code> mounted in your
+ chroot as <code class="filename">/bin/sh</code>, you only need to say
+ <code class="literal">build-chroot-dirs =
+ /bin/sh=/nix/store/…-bash/bin/sh</code>; it is no longer
+ necessary to specify the dependencies of Bash.</p></li></ul></div></li><li class="listitem"><p>The new derivation attribute
+ <code class="varname">passAsFile</code> allows you to specify that the
+ contents of derivation attributes should be passed via files rather
+ than environment variables. This is useful if you need to pass very
+ long strings that exceed the size limit of the environment. The
+ Nixpkgs function <code class="function">writeTextFile</code> uses
+ this.</p></li><li class="listitem"><p>You can now use <code class="literal">~</code> in Nix file
+ names to refer to your home directory, e.g. <code class="literal">import
+ ~/.nixpkgs/config.nix</code>.</p></li><li class="listitem"><p>Nix has a new option <code class="option">restrict-eval</code>
+ that allows limiting what paths the Nix evaluator has access to. By
+ passing <code class="literal">--option restrict-eval true</code> to Nix, the
+ evaluator will throw an exception if an attempt is made to access
+ any file outside of the Nix search path. This is primarily intended
+ for Hydra to ensure that a Hydra jobset only refers to its declared
+ inputs (and is therefore reproducible).</p></li><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> now only creates a new
+ “generation” symlink in <code class="filename">/nix/var/nix/profiles</code>
+ if something actually changed.</p></li><li class="listitem"><p>The environment variable <code class="envar">NIX_PAGER</code>
+ can now be set to override <code class="envar">PAGER</code>. You can set it to
+ <code class="literal">cat</code> to disable paging for Nix commands
+ only.</p></li><li class="listitem"><p>Failing <code class="literal"><...></code>
+ lookups now show position information.</p></li><li class="listitem"><p>Improved Boehm GC use: we disabled scanning for
+ interior pointers, which should reduce the “<code class="literal">Repeated
+ allocation of very large block</code>” warnings and associated
+ retention of memory.</p></li></ul></div><p>This release has contributions from aszlig, Benjamin Staffin,
+Charles Strahan, Christian Theune, Daniel Hahler, Danylo Hlynskyi
+Daniel Peebles, Dan Peebles, Domen Kožar, Eelco Dolstra, Harald van
+Dijk, Hoang Xuan Phu, Jaka Hudoklin, Jeff Ramnani, j-keck, Linquize,
+Luca Bruno, Michael Merickel, Oliver Dunkl, Rob Vermaas, Rok Garbas,
+Shea Levy, Tobias Geerinckx-Rice and William A. Kennington III.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.8"></a>C.9. Release 1.8 (2014-12-14)</h2></div></div></div><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Breaking change: to address a race condition, the
+ remote build hook mechanism now uses <span class="command"><strong>nix-store
+ --serve</strong></span> on the remote machine. This requires build slaves
+ to be updated to Nix 1.8.</p></li><li class="listitem"><p>Nix now uses HTTPS instead of HTTP to access the
+ default binary cache,
+ <code class="literal">cache.nixos.org</code>.</p></li><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> selectors are now regular
+ expressions. For instance, you can do
+
+</p><pre class="screen">
+$ nix-env -qa '.*zip.*'
+</pre><p>
+
+ to query all packages with a name containing
+ <code class="literal">zip</code>.</p></li><li class="listitem"><p><span class="command"><strong>nix-store --read-log</strong></span> can now
+ fetch remote build logs. If a build log is not available locally,
+ then ‘nix-store -l’ will now try to download it from the servers
+ listed in the ‘log-servers’ option in nix.conf. For instance, if you
+ have the configuration option
+
+</p><pre class="programlisting">
+log-servers = http://hydra.nixos.org/log
+</pre><p>
+
+then it will try to get logs from
+<code class="literal">http://hydra.nixos.org/log/<em class="replaceable"><code>base name of the
+store path</code></em></code>. This allows you to do things like:
+
+</p><pre class="screen">
+$ nix-store -l $(which xterm)
+</pre><p>
+
+ and get a log even if <span class="command"><strong>xterm</strong></span> wasn't built
+ locally.</p></li><li class="listitem"><p>New builtin functions:
+ <code class="function">attrValues</code>, <code class="function">deepSeq</code>,
+ <code class="function">fromJSON</code>, <code class="function">readDir</code>,
+ <code class="function">seq</code>.</p></li><li class="listitem"><p><span class="command"><strong>nix-instantiate --eval</strong></span> now has a
+ <code class="option">--json</code> flag to print the resulting value in JSON
+ format.</p></li><li class="listitem"><p><span class="command"><strong>nix-copy-closure</strong></span> now uses
+ <span class="command"><strong>nix-store --serve</strong></span> on the remote side to send or
+ receive closures. This fixes a race condition between
+ <span class="command"><strong>nix-copy-closure</strong></span> and the garbage
+ collector.</p></li><li class="listitem"><p>Derivations can specify the new special attribute
+ <code class="varname">allowedRequisites</code>, which has a similar meaning to
+ <code class="varname">allowedReferences</code>. But instead of only enforcing
+ to explicitly specify the immediate references, it requires the
+ derivation to specify all the dependencies recursively (hence the
+ name, requisites) that are used by the resulting
+ output.</p></li><li class="listitem"><p>On Mac OS X, Nix now handles case collisions when
+ importing closures from case-sensitive file systems. This is mostly
+ useful for running NixOps on Mac OS X.</p></li><li class="listitem"><p>The Nix daemon has new configuration options
+ <code class="option">allowed-users</code> (specifying the users and groups that
+ are allowed to connect to the daemon) and
+ <code class="option">trusted-users</code> (specifying the users and groups that
+ can perform privileged operations like specifying untrusted binary
+ caches).</p></li><li class="listitem"><p>The configuration option
+ <code class="option">build-cores</code> now defaults to the number of available
+ CPU cores.</p></li><li class="listitem"><p>Build users are now used by default when Nix is
+ invoked as root. This prevents builds from accidentally running as
+ root.</p></li><li class="listitem"><p>Nix now includes systemd units and Upstart
+ jobs.</p></li><li class="listitem"><p>Speed improvements to <span class="command"><strong>nix-store
+ --optimise</strong></span>.</p></li><li class="listitem"><p>Language change: the <code class="literal">==</code> operator
+ now ignores string contexts (the “dependencies” of a
+ string).</p></li><li class="listitem"><p>Nix now filters out Nix-specific ANSI escape
+ sequences on standard error. They are supposed to be invisible, but
+ some terminals show them anyway.</p></li><li class="listitem"><p>Various commands now automatically pipe their output
+ into the pager as specified by the <code class="envar">PAGER</code> environment
+ variable.</p></li><li class="listitem"><p>Several improvements to reduce memory consumption in
+ the evaluator.</p></li></ul></div><p>This release has contributions from Adam Szkoda, Aristid
+Breitkreuz, Bob van der Linden, Charles Strahan, darealshinji, Eelco
+Dolstra, Gergely Risko, Joel Taylor, Ludovic Courtès, Marko Durkovic,
+Mikey Ariel, Paul Colomiets, Ricardo M. Correia, Ricky Elrod, Robert
+Helgesson, Rob Vermaas, Russell O'Connor, Shea Levy, Shell Turner,
+Sönke Hahn, Steve Purcell, Vladimír Čunát and Wout Mertens.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.7"></a>C.10. Release 1.7 (2014-04-11)</h2></div></div></div><p>In addition to the usual bug fixes, this release has the
+following new features:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Antiquotation is now allowed inside of quoted attribute
+ names (e.g. <code class="literal">set."${foo}"</code>). In the case where
+ the attribute name is just a single antiquotation, the quotes can
+ be dropped (e.g. the above example can be written
+ <code class="literal">set.${foo}</code>). If an attribute name inside of a
+ set declaration evaluates to <code class="literal">null</code> (e.g.
+ <code class="literal">{ ${null} = false; }</code>), then that attribute is
+ not added to the set.</p></li><li class="listitem"><p>Experimental support for cryptographically signed binary
+ caches. See <a class="link" href="https://github.com/NixOS/nix/commit/0fdf4da0e979f992db75cc17376e455ddc5a96d8" target="_top">the
+ commit for details</a>.</p></li><li class="listitem"><p>An experimental new substituter,
+ <span class="command"><strong>download-via-ssh</strong></span>, that fetches binaries from
+ remote machines via SSH. Specifying the flags <code class="literal">--option
+ use-ssh-substituter true --option ssh-substituter-hosts
+ <em class="replaceable"><code>user@hostname</code></em></code> will cause Nix
+ to download binaries from the specified machine, if it has
+ them.</p></li><li class="listitem"><p><span class="command"><strong>nix-store -r</strong></span> and
+ <span class="command"><strong>nix-build</strong></span> have a new flag,
+ <code class="option">--check</code>, that builds a previously built
+ derivation again, and prints an error message if the output is not
+ exactly the same. This helps to verify whether a derivation is
+ truly deterministic. For example:
+
+</p><pre class="screen">
+$ nix-build '<nixpkgs>' -A patchelf
+<em class="replaceable"><code>…</code></em>
+$ nix-build '<nixpkgs>' -A patchelf --check
+<em class="replaceable"><code>…</code></em>
+error: derivation `/nix/store/1ipvxs…-patchelf-0.6' may not be deterministic:
+ hash mismatch in output `/nix/store/4pc1dm…-patchelf-0.6.drv'
+</pre><p>
+
+ </p></li><li class="listitem"><p>The <span class="command"><strong>nix-instantiate</strong></span> flags
+ <code class="option">--eval-only</code> and <code class="option">--parse-only</code>
+ have been renamed to <code class="option">--eval</code> and
+ <code class="option">--parse</code>, respectively.</p></li><li class="listitem"><p><span class="command"><strong>nix-instantiate</strong></span>,
+ <span class="command"><strong>nix-build</strong></span> and <span class="command"><strong>nix-shell</strong></span> now
+ have a flag <code class="option">--expr</code> (or <code class="option">-E</code>) that
+ allows you to specify the expression to be evaluated as a command
+ line argument. For instance, <code class="literal">nix-instantiate --eval -E
+ '1 + 2'</code> will print <code class="literal">3</code>.</p></li><li class="listitem"><p><span class="command"><strong>nix-shell</strong></span> improvements:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>It has a new flag, <code class="option">--packages</code> (or
+ <code class="option">-p</code>), that sets up a build environment
+ containing the specified packages from Nixpkgs. For example,
+ the command
+
+</p><pre class="screen">
+$ nix-shell -p sqlite xorg.libX11 hello
+</pre><p>
+
+ will start a shell in which the given packages are
+ present.</p></li><li class="listitem"><p>It now uses <code class="filename">shell.nix</code> as the
+ default expression, falling back to
+ <code class="filename">default.nix</code> if the former doesn’t
+ exist. This makes it convenient to have a
+ <code class="filename">shell.nix</code> in your project to set up a
+ nice development environment.</p></li><li class="listitem"><p>It evaluates the derivation attribute
+ <code class="varname">shellHook</code>, if set. Since
+ <code class="literal">stdenv</code> does not normally execute this hook,
+ it allows you to do <span class="command"><strong>nix-shell</strong></span>-specific
+ setup.</p></li><li class="listitem"><p>It preserves the user’s timezone setting.</p></li></ul></div></li><li class="listitem"><p>In chroots, Nix now sets up a <code class="filename">/dev</code>
+ containing only a minimal set of devices (such as
+ <code class="filename">/dev/null</code>). Note that it only does this if
+ you <span class="emphasis"><em>don’t</em></span> have <code class="filename">/dev</code>
+ listed in your <code class="option">build-chroot-dirs</code> setting;
+ otherwise, it will bind-mount the <code class="literal">/dev</code> from
+ outside the chroot.</p><p>Similarly, if you don’t have <code class="filename">/dev/pts</code> listed
+ in <code class="option">build-chroot-dirs</code>, Nix will mount a private
+ <code class="literal">devpts</code> filesystem on the chroot’s
+ <code class="filename">/dev/pts</code>.</p></li><li class="listitem"><p>New built-in function: <code class="function">builtins.toJSON</code>,
+ which returns a JSON representation of a value.</p></li><li class="listitem"><p><span class="command"><strong>nix-env -q</strong></span> has a new flag
+ <code class="option">--json</code> to print a JSON representation of the
+ installed or available packages.</p></li><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> now supports meta attributes with
+ more complex values, such as attribute sets.</p></li><li class="listitem"><p>The <code class="option">-A</code> flag now allows attribute names with
+ dots in them, e.g.
+
+</p><pre class="screen">
+$ nix-instantiate --eval '<nixos>' -A 'config.systemd.units."nscd.service".text'
+</pre><p>
+
+ </p></li><li class="listitem"><p>The <code class="option">--max-freed</code> option to
+ <span class="command"><strong>nix-store --gc</strong></span> now accepts a unit
+ specifier. For example, <code class="literal">nix-store --gc --max-freed
+ 1G</code> will free up to 1 gigabyte of disk space.</p></li><li class="listitem"><p><span class="command"><strong>nix-collect-garbage</strong></span> has a new flag
+ <code class="option">--delete-older-than</code>
+ <em class="replaceable"><code>N</code></em><code class="literal">d</code>, which deletes
+ all user environment generations older than
+ <em class="replaceable"><code>N</code></em> days. Likewise, <span class="command"><strong>nix-env
+ --delete-generations</strong></span> accepts a
+ <em class="replaceable"><code>N</code></em><code class="literal">d</code> age limit.</p></li><li class="listitem"><p>Nix now heuristically detects whether a build failure was
+ due to a disk-full condition. In that case, the build is not
+ flagged as “permanently failed”. This is mostly useful for Hydra,
+ which needs to distinguish between permanent and transient build
+ failures.</p></li><li class="listitem"><p>There is a new symbol <code class="literal">__curPos</code> that
+ expands to an attribute set containing its file name and line and
+ column numbers, e.g. <code class="literal">{ file = "foo.nix"; line = 10;
+ column = 5; }</code>. There also is a new builtin function,
+ <code class="varname">unsafeGetAttrPos</code>, that returns the position of
+ an attribute. This is used by Nixpkgs to provide location
+ information in error messages, e.g.
+
+</p><pre class="screen">
+$ nix-build '<nixpkgs>' -A libreoffice --argstr system x86_64-darwin
+error: the package ‘libreoffice-4.0.5.2’ in ‘.../applications/office/libreoffice/default.nix:263’
+ is not supported on ‘x86_64-darwin’
+</pre><p>
+
+ </p></li><li class="listitem"><p>The garbage collector is now more concurrent with other Nix
+ processes because it releases certain locks earlier.</p></li><li class="listitem"><p>The binary tarball installer has been improved. You can now
+ install Nix by running:
+
+</p><pre class="screen">
+$ bash <(curl https://nixos.org/nix/install)
+</pre><p>
+
+ </p></li><li class="listitem"><p>More evaluation errors include position information. For
+ instance, selecting a missing attribute will print something like
+
+</p><pre class="screen">
+error: attribute `nixUnstabl' missing, at /etc/nixos/configurations/misc/eelco/mandark.nix:216:15
+</pre><p>
+
+ </p></li><li class="listitem"><p>The command <span class="command"><strong>nix-setuid-helper</strong></span> is
+ gone.</p></li><li class="listitem"><p>Nix no longer uses Automake, but instead has a
+ non-recursive, GNU Make-based build system.</p></li><li class="listitem"><p>All installed libraries now have the prefix
+ <code class="literal">libnix</code>. In particular, this gets rid of
+ <code class="literal">libutil</code>, which could clash with libraries with
+ the same name from other packages.</p></li><li class="listitem"><p>Nix now requires a compiler that supports C++11.</p></li></ul></div><p>This release has contributions from Danny Wilson, Domen Kožar,
+Eelco Dolstra, Ian-Woo Kim, Ludovic Courtès, Maxim Ivanov, Petr
+Rockai, Ricardo M. Correia and Shea Levy.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.6.1"></a>C.11. Release 1.6.1 (2013-10-28)</h2></div></div></div><p>This is primarily a bug fix release. Changes of interest
+are:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Nix 1.6 accidentally changed the semantics of antiquoted
+ paths in strings, such as <code class="literal">"${/foo}/bar"</code>. This
+ release reverts to the Nix 1.5.3 behaviour.</p></li><li class="listitem"><p>Previously, Nix optimised expressions such as
+ <code class="literal">"${<em class="replaceable"><code>expr</code></em>}"</code> to
+ <em class="replaceable"><code>expr</code></em>. Thus it neither checked whether
+ <em class="replaceable"><code>expr</code></em> could be coerced to a string, nor
+ applied such coercions. This meant that
+ <code class="literal">"${123}"</code> evaluatued to <code class="literal">123</code>,
+ and <code class="literal">"${./foo}"</code> evaluated to
+ <code class="literal">./foo</code> (even though
+ <code class="literal">"${./foo} "</code> evaluates to
+ <code class="literal">"/nix/store/<em class="replaceable"><code>hash</code></em>-foo "</code>).
+ Nix now checks the type of antiquoted expressions and
+ applies coercions.</p></li><li class="listitem"><p>Nix now shows the exact position of undefined variables. In
+ particular, undefined variable errors in a <code class="literal">with</code>
+ previously didn't show <span class="emphasis"><em>any</em></span> position
+ information, so this makes it a lot easier to fix such
+ errors.</p></li><li class="listitem"><p>Undefined variables are now treated consistently.
+ Previously, the <code class="function">tryEval</code> function would catch
+ undefined variables inside a <code class="literal">with</code> but not
+ outside. Now <code class="function">tryEval</code> never catches undefined
+ variables.</p></li><li class="listitem"><p>Bash completion in <span class="command"><strong>nix-shell</strong></span> now works
+ correctly.</p></li><li class="listitem"><p>Stack traces are less verbose: they no longer show calls to
+ builtin functions and only show a single line for each derivation
+ on the call stack.</p></li><li class="listitem"><p>New built-in function: <code class="function">builtins.typeOf</code>,
+ which returns the type of its argument as a string.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.6.0"></a>C.12. Release 1.6 (2013-09-10)</h2></div></div></div><p>In addition to the usual bug fixes, this release has several new
+features:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>The command <span class="command"><strong>nix-build --run-env</strong></span> has been
+ renamed to <span class="command"><strong>nix-shell</strong></span>.</p></li><li class="listitem"><p><span class="command"><strong>nix-shell</strong></span> now sources
+ <code class="filename">$stdenv/setup</code> <span class="emphasis"><em>inside</em></span> the
+ interactive shell, rather than in a parent shell. This ensures
+ that shell functions defined by <code class="literal">stdenv</code> can be
+ used in the interactive shell.</p></li><li class="listitem"><p><span class="command"><strong>nix-shell</strong></span> has a new flag
+ <code class="option">--pure</code> to clear the environment, so you get an
+ environment that more closely corresponds to the “real” Nix build.
+ </p></li><li class="listitem"><p><span class="command"><strong>nix-shell</strong></span> now sets the shell prompt
+ (<code class="envar">PS1</code>) to ensure that Nix shells are distinguishable
+ from your regular shells.</p></li><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> no longer requires a
+ <code class="literal">*</code> argument to match all packages, so
+ <code class="literal">nix-env -qa</code> is equivalent to <code class="literal">nix-env
+ -qa '*'</code>.</p></li><li class="listitem"><p><span class="command"><strong>nix-env -i</strong></span> has a new flag
+ <code class="option">--remove-all</code> (<code class="option">-r</code>) to remove all
+ previous packages from the profile. This makes it easier to do
+ declarative package management similar to NixOS’s
+ <code class="option">environment.systemPackages</code>. For instance, if you
+ have a specification <code class="filename">my-packages.nix</code> like this:
+
+</p><pre class="programlisting">
+with import <nixpkgs> {};
+[ thunderbird
+ geeqie
+ ...
+]
+</pre><p>
+
+ then after any change to this file, you can run:
+
+</p><pre class="screen">
+$ nix-env -f my-packages.nix -ir
+</pre><p>
+
+ to update your profile to match the specification.</p></li><li class="listitem"><p>The ‘<code class="literal">with</code>’ language construct is now more
+ lazy. It only evaluates its argument if a variable might actually
+ refer to an attribute in the argument. For instance, this now
+ works:
+
+</p><pre class="programlisting">
+let
+ pkgs = with pkgs; { foo = "old"; bar = foo; } // overrides;
+ overrides = { foo = "new"; };
+in pkgs.bar
+</pre><p>
+
+ This evaluates to <code class="literal">"new"</code>, while previously it
+ gave an “infinite recursion” error.</p></li><li class="listitem"><p>Nix now has proper integer arithmetic operators. For
+ instance, you can write <code class="literal">x + y</code> instead of
+ <code class="literal">builtins.add x y</code>, or <code class="literal">x <
+ y</code> instead of <code class="literal">builtins.lessThan x y</code>.
+ The comparison operators also work on strings.</p></li><li class="listitem"><p>On 64-bit systems, Nix integers are now 64 bits rather than
+ 32 bits.</p></li><li class="listitem"><p>When using the Nix daemon, the <span class="command"><strong>nix-daemon</strong></span>
+ worker process now runs on the same CPU as the client, on systems
+ that support setting CPU affinity. This gives a significant speedup
+ on some systems.</p></li><li class="listitem"><p>If a stack overflow occurs in the Nix evaluator, you now get
+ a proper error message (rather than “Segmentation fault”) on some
+ systems.</p></li><li class="listitem"><p>In addition to directories, you can now bind-mount regular
+ files in chroots through the (now misnamed) option
+ <code class="option">build-chroot-dirs</code>.</p></li></ul></div><p>This release has contributions from Domen Kožar, Eelco Dolstra,
+Florian Friesdorf, Gergely Risko, Ivan Kozik, Ludovic Courtès and Shea
+Levy.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.5.2"></a>C.13. Release 1.5.2 (2013-05-13)</h2></div></div></div><p>This is primarily a bug fix release. It has contributions from
+Eelco Dolstra, Lluís Batlle i Rossell and Shea Levy.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.5"></a>C.14. Release 1.5 (2013-02-27)</h2></div></div></div><p>This is a brown paper bag release to fix a regression introduced
+by the hard link security fix in 1.4.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.4"></a>C.15. Release 1.4 (2013-02-26)</h2></div></div></div><p>This release fixes a security bug in multi-user operation. It
+was possible for derivations to cause the mode of files outside of the
+Nix store to be changed to 444 (read-only but world-readable) by
+creating hard links to those files (<a class="link" href="https://github.com/NixOS/nix/commit/5526a282b5b44e9296e61e07d7d2626a79141ac4" target="_top">details</a>).</p><p>There are also the following improvements:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>New built-in function:
+ <code class="function">builtins.hashString</code>.</p></li><li class="listitem"><p>Build logs are now stored in
+ <code class="filename">/nix/var/log/nix/drvs/<em class="replaceable"><code>XX</code></em>/</code>,
+ where <em class="replaceable"><code>XX</code></em> is the first two characters of
+ the derivation. This is useful on machines that keep a lot of build
+ logs (such as Hydra servers).</p></li><li class="listitem"><p>The function <code class="function">corepkgs/fetchurl</code>
+ can now make the downloaded file executable. This will allow
+ getting rid of all bootstrap binaries in the Nixpkgs source
+ tree.</p></li><li class="listitem"><p>Language change: The expression <code class="literal">"${./path}
+ ..."</code> now evaluates to a string instead of a
+ path.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.3"></a>C.16. Release 1.3 (2013-01-04)</h2></div></div></div><p>This is primarily a bug fix release. When this version is first
+run on Linux, it removes any immutable bits from the Nix store and
+increases the schema version of the Nix store. (The previous release
+removed support for setting the immutable bit; this release clears any
+remaining immutable bits to make certain operations more
+efficient.)</p><p>This release has contributions from Eelco Dolstra and Stuart
+Pernsteiner.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.2"></a>C.17. Release 1.2 (2012-12-06)</h2></div></div></div><p>This release has the following improvements and changes:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Nix has a new binary substituter mechanism: the
+ <span class="emphasis"><em>binary cache</em></span>. A binary cache contains
+ pre-built binaries of Nix packages. Whenever Nix wants to build a
+ missing Nix store path, it will check a set of binary caches to
+ see if any of them has a pre-built binary of that path. The
+ configuration setting <code class="option">binary-caches</code> contains a
+ list of URLs of binary caches. For instance, doing
+</p><pre class="screen">
+$ nix-env -i thunderbird --option binary-caches http://cache.nixos.org
+</pre><p>
+ will install Thunderbird and its dependencies, using the available
+ pre-built binaries in <code class="uri">http://cache.nixos.org</code>.
+ The main advantage over the old “manifest”-based method of getting
+ pre-built binaries is that you don’t have to worry about your
+ manifest being in sync with the Nix expressions you’re installing
+ from; i.e., you don’t need to run <span class="command"><strong>nix-pull</strong></span> to
+ update your manifest. It’s also more scalable because you don’t
+ need to redownload a giant manifest file every time.
+ </p><p>A Nix channel can provide a binary cache URL that will be
+ used automatically if you subscribe to that channel. If you use
+ the Nixpkgs or NixOS channels
+ (<code class="uri">http://nixos.org/channels</code>) you automatically get the
+ cache <code class="uri">http://cache.nixos.org</code>.</p><p>Binary caches are created using <span class="command"><strong>nix-push</strong></span>.
+ For details on the operation and format of binary caches, see the
+ <span class="command"><strong>nix-push</strong></span> manpage. More details are provided in
+ <a class="link" href="https://nixos.org/nix-dev/2012-September/009826.html" target="_top">this
+ nix-dev posting</a>.</p></li><li class="listitem"><p>Multiple output support should now be usable. A derivation
+ can declare that it wants to produce multiple store paths by
+ saying something like
+</p><pre class="programlisting">
+outputs = [ "lib" "headers" "doc" ];
+</pre><p>
+ This will cause Nix to pass the intended store path of each output
+ to the builder through the environment variables
+ <code class="literal">lib</code>, <code class="literal">headers</code> and
+ <code class="literal">doc</code>. Other packages can refer to a specific
+ output by referring to
+ <code class="literal"><em class="replaceable"><code>pkg</code></em>.<em class="replaceable"><code>output</code></em></code>,
+ e.g.
+</p><pre class="programlisting">
+buildInputs = [ pkg.lib pkg.headers ];
+</pre><p>
+ If you install a package with multiple outputs using
+ <span class="command"><strong>nix-env</strong></span>, each output path will be symlinked
+ into the user environment.</p></li><li class="listitem"><p>Dashes are now valid as part of identifiers and attribute
+ names.</p></li><li class="listitem"><p>The new operation <span class="command"><strong>nix-store --repair-path</strong></span>
+ allows corrupted or missing store paths to be repaired by
+ redownloading them. <span class="command"><strong>nix-store --verify --check-contents
+ --repair</strong></span> will scan and repair all paths in the Nix
+ store. Similarly, <span class="command"><strong>nix-env</strong></span>,
+ <span class="command"><strong>nix-build</strong></span>, <span class="command"><strong>nix-instantiate</strong></span>
+ and <span class="command"><strong>nix-store --realise</strong></span> have a
+ <code class="option">--repair</code> flag to detect and fix bad paths by
+ rebuilding or redownloading them.</p></li><li class="listitem"><p>Nix no longer sets the immutable bit on files in the Nix
+ store. Instead, the recommended way to guard the Nix store
+ against accidental modification on Linux is to make it a read-only
+ bind mount, like this:
+
+</p><pre class="screen">
+$ mount --bind /nix/store /nix/store
+$ mount -o remount,ro,bind /nix/store
+</pre><p>
+
+ Nix will automatically make <code class="filename">/nix/store</code>
+ writable as needed (using a private mount namespace) to allow
+ modifications.</p></li><li class="listitem"><p>Store optimisation (replacing identical files in the store
+ with hard links) can now be done automatically every time a path
+ is added to the store. This is enabled by setting the
+ configuration option <code class="literal">auto-optimise-store</code> to
+ <code class="literal">true</code> (disabled by default).</p></li><li class="listitem"><p>Nix now supports <span class="command"><strong>xz</strong></span> compression for NARs
+ in addition to <span class="command"><strong>bzip2</strong></span>. It compresses about 30%
+ better on typical archives and decompresses about twice as
+ fast.</p></li><li class="listitem"><p>Basic Nix expression evaluation profiling: setting the
+ environment variable <code class="envar">NIX_COUNT_CALLS</code> to
+ <code class="literal">1</code> will cause Nix to print how many times each
+ primop or function was executed.</p></li><li class="listitem"><p>New primops: <code class="varname">concatLists</code>,
+ <code class="varname">elem</code>, <code class="varname">elemAt</code> and
+ <code class="varname">filter</code>.</p></li><li class="listitem"><p>The command <span class="command"><strong>nix-copy-closure</strong></span> has a new
+ flag <code class="option">--use-substitutes</code> (<code class="option">-s</code>) to
+ download missing paths on the target machine using the substitute
+ mechanism.</p></li><li class="listitem"><p>The command <span class="command"><strong>nix-worker</strong></span> has been renamed
+ to <span class="command"><strong>nix-daemon</strong></span>. Support for running the Nix
+ worker in “slave” mode has been removed.</p></li><li class="listitem"><p>The <code class="option">--help</code> flag of every Nix command now
+ invokes <span class="command"><strong>man</strong></span>.</p></li><li class="listitem"><p>Chroot builds are now supported on systemd machines.</p></li></ul></div><p>This release has contributions from Eelco Dolstra, Florian
+Friesdorf, Mats Erik Andersson and Shea Levy.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.1"></a>C.18. Release 1.1 (2012-07-18)</h2></div></div></div><p>This release has the following improvements:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>On Linux, when doing a chroot build, Nix now uses various
+ namespace features provided by the Linux kernel to improve
+ build isolation. Namely:
+ </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>The private network namespace ensures that
+ builders cannot talk to the outside world (or vice versa): each
+ build only sees a private loopback interface. This also means
+ that two concurrent builds can listen on the same port (e.g. as
+ part of a test) without conflicting with each
+ other.</p></li><li class="listitem"><p>The PID namespace causes each build to start as
+ PID 1. Processes outside of the chroot are not visible to those
+ on the inside. On the other hand, processes inside the chroot
+ <span class="emphasis"><em>are</em></span> visible from the outside (though with
+ different PIDs).</p></li><li class="listitem"><p>The IPC namespace prevents the builder from
+ communicating with outside processes using SysV IPC mechanisms
+ (shared memory, message queues, semaphores). It also ensures
+ that all IPC objects are destroyed when the builder
+ exits.</p></li><li class="listitem"><p>The UTS namespace ensures that builders see a
+ hostname of <code class="literal">localhost</code> rather than the actual
+ hostname.</p></li><li class="listitem"><p>The private mount namespace was already used by
+ Nix to ensure that the bind-mounts used to set up the chroot are
+ cleaned up automatically.</p></li></ul></div><p>
+ </p></li><li class="listitem"><p>Build logs are now compressed using
+ <span class="command"><strong>bzip2</strong></span>. The command <span class="command"><strong>nix-store
+ -l</strong></span> decompresses them on the fly. This can be disabled
+ by setting the option <code class="literal">build-compress-log</code> to
+ <code class="literal">false</code>.</p></li><li class="listitem"><p>The creation of build logs in
+ <code class="filename">/nix/var/log/nix/drvs</code> can be disabled by
+ setting the new option <code class="literal">build-keep-log</code> to
+ <code class="literal">false</code>. This is useful, for instance, for Hydra
+ build machines.</p></li><li class="listitem"><p>Nix now reserves some space in
+ <code class="filename">/nix/var/nix/db/reserved</code> to ensure that the
+ garbage collector can run successfully if the disk is full. This
+ is necessary because SQLite transactions fail if the disk is
+ full.</p></li><li class="listitem"><p>Added a basic <code class="function">fetchurl</code> function. This
+ is not intended to replace the <code class="function">fetchurl</code> in
+ Nixpkgs, but is useful for bootstrapping; e.g., it will allow us
+ to get rid of the bootstrap binaries in the Nixpkgs source tree
+ and download them instead. You can use it by doing
+ <code class="literal">import <nix/fetchurl.nix> { url =
+ <em class="replaceable"><code>url</code></em>; sha256 =
+ "<em class="replaceable"><code>hash</code></em>"; }</code>. (Shea Levy)</p></li><li class="listitem"><p>Improved RPM spec file. (Michel Alexandre Salim)</p></li><li class="listitem"><p>Support for on-demand socket-based activation in the Nix
+ daemon with <span class="command"><strong>systemd</strong></span>.</p></li><li class="listitem"><p>Added a manpage for
+ <span class="citerefentry"><span class="refentrytitle">nix.conf</span>(5)</span>.</p></li><li class="listitem"><p>When using the Nix daemon, the <code class="option">-s</code> flag in
+ <span class="command"><strong>nix-env -qa</strong></span> is now much faster.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.0"></a>C.19. Release 1.0 (2012-05-11)</h2></div></div></div><p>There have been numerous improvements and bug fixes since the
+previous release. Here are the most significant:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Nix can now optionally use the Boehm garbage collector.
+ This significantly reduces the Nix evaluator’s memory footprint,
+ especially when evaluating large NixOS system configurations. It
+ can be enabled using the <code class="option">--enable-gc</code> configure
+ option.</p></li><li class="listitem"><p>Nix now uses SQLite for its database. This is faster and
+ more flexible than the old <span class="emphasis"><em>ad hoc</em></span> format.
+ SQLite is also used to cache the manifests in
+ <code class="filename">/nix/var/nix/manifests</code>, resulting in a
+ significant speedup.</p></li><li class="listitem"><p>Nix now has an search path for expressions. The search path
+ is set using the environment variable <code class="envar">NIX_PATH</code> and
+ the <code class="option">-I</code> command line option. In Nix expressions,
+ paths between angle brackets are used to specify files that must
+ be looked up in the search path. For instance, the expression
+ <code class="literal"><nixpkgs/default.nix></code> looks for a file
+ <code class="filename">nixpkgs/default.nix</code> relative to every element
+ in the search path.</p></li><li class="listitem"><p>The new command <span class="command"><strong>nix-build --run-env</strong></span>
+ builds all dependencies of a derivation, then starts a shell in an
+ environment containing all variables from the derivation. This is
+ useful for reproducing the environment of a derivation for
+ development.</p></li><li class="listitem"><p>The new command <span class="command"><strong>nix-store --verify-path</strong></span>
+ verifies that the contents of a store path have not
+ changed.</p></li><li class="listitem"><p>The new command <span class="command"><strong>nix-store --print-env</strong></span>
+ prints out the environment of a derivation in a format that can be
+ evaluated by a shell.</p></li><li class="listitem"><p>Attribute names can now be arbitrary strings. For instance,
+ you can write <code class="literal">{ "foo-1.2" = …; "bla bla" = …; }."bla
+ bla"</code>.</p></li><li class="listitem"><p>Attribute selection can now provide a default value using
+ the <code class="literal">or</code> operator. For instance, the expression
+ <code class="literal">x.y.z or e</code> evaluates to the attribute
+ <code class="literal">x.y.z</code> if it exists, and <code class="literal">e</code>
+ otherwise.</p></li><li class="listitem"><p>The right-hand side of the <code class="literal">?</code> operator can
+ now be an attribute path, e.g., <code class="literal">attrs ?
+ a.b.c</code>.</p></li><li class="listitem"><p>On Linux, Nix will now make files in the Nix store immutable
+ on filesystems that support it. This prevents accidental
+ modification of files in the store by the root user.</p></li><li class="listitem"><p>Nix has preliminary support for derivations with multiple
+ outputs. This is useful because it allows parts of a package to
+ be deployed and garbage-collected separately. For instance,
+ development parts of a package such as header files or static
+ libraries would typically not be part of the closure of an
+ application, resulting in reduced disk usage and installation
+ time.</p></li><li class="listitem"><p>The Nix store garbage collector is faster and holds the
+ global lock for a shorter amount of time.</p></li><li class="listitem"><p>The option <code class="option">--timeout</code> (corresponding to the
+ configuration setting <code class="literal">build-timeout</code>) allows you
+ to set an absolute timeout on builds — if a build runs for more than
+ the given number of seconds, it is terminated. This is useful for
+ recovering automatically from builds that are stuck in an infinite
+ loop but keep producing output, and for which
+ <code class="literal">--max-silent-time</code> is ineffective.</p></li><li class="listitem"><p>Nix development has moved to GitHub (<a class="link" href="https://github.com/NixOS/nix" target="_top">https://github.com/NixOS/nix</a>).</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-0.16"></a>C.20. Release 0.16 (2010-08-17)</h2></div></div></div><p>This release has the following improvements:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>The Nix expression evaluator is now much faster in most
+ cases: typically, <a class="link" href="http://www.mail-archive.com/nix-dev@cs.uu.nl/msg04113.html" target="_top">3
+ to 8 times compared to the old implementation</a>. It also
+ uses less memory. It no longer depends on the ATerm
+ library.</p></li><li class="listitem"><p>
+ Support for configurable parallelism inside builders. Build
+ scripts have always had the ability to perform multiple build
+ actions in parallel (for instance, by running <span class="command"><strong>make -j
+ 2</strong></span>), but this was not desirable because the number of
+ actions to be performed in parallel was not configurable. Nix
+ now has an option <code class="option">--cores
+ <em class="replaceable"><code>N</code></em></code> as well as a configuration
+ setting <code class="varname">build-cores =
+ <em class="replaceable"><code>N</code></em></code> that causes the
+ environment variable <code class="envar">NIX_BUILD_CORES</code> to be set to
+ <em class="replaceable"><code>N</code></em> when the builder is invoked. The
+ builder can use this at its discretion to perform a parallel
+ build, e.g., by calling <span class="command"><strong>make -j
+ <em class="replaceable"><code>N</code></em></strong></span>. In Nixpkgs, this can be
+ enabled on a per-package basis by setting the derivation
+ attribute <code class="varname">enableParallelBuilding</code> to
+ <code class="literal">true</code>.
+ </p></li><li class="listitem"><p><span class="command"><strong>nix-store -q</strong></span> now supports XML output
+ through the <code class="option">--xml</code> flag.</p></li><li class="listitem"><p>Several bug fixes.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-0.15"></a>C.21. Release 0.15 (2010-03-17)</h2></div></div></div><p>This is a bug-fix release. Among other things, it fixes
+building on Mac OS X (Snow Leopard), and improves the contents of
+<code class="filename">/etc/passwd</code> and <code class="filename">/etc/group</code>
+in <code class="literal">chroot</code> builds.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-0.14"></a>C.22. Release 0.14 (2010-02-04)</h2></div></div></div><p>This release has the following improvements:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>The garbage collector now starts deleting garbage much
+ faster than before. It no longer determines liveness of all paths
+ in the store, but does so on demand.</p></li><li class="listitem"><p>Added a new operation, <span class="command"><strong>nix-store --query
+ --roots</strong></span>, that shows the garbage collector roots that
+ directly or indirectly point to the given store paths.</p></li><li class="listitem"><p>Removed support for converting Berkeley DB-based Nix
+ databases to the new schema.</p></li><li class="listitem"><p>Removed the <code class="option">--use-atime</code> and
+ <code class="option">--max-atime</code> garbage collector options. They were
+ not very useful in practice.</p></li><li class="listitem"><p>On Windows, Nix now requires Cygwin 1.7.x.</p></li><li class="listitem"><p>A few bug fixes.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-0.13"></a>C.23. Release 0.13 (2009-11-05)</h2></div></div></div><p>This is primarily a bug fix release. It has some new
+features:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Syntactic sugar for writing nested attribute sets. Instead of
+
+</p><pre class="programlisting">
+{
+ foo = {
+ bar = 123;
+ xyzzy = true;
+ };
+ a = { b = { c = "d"; }; };
+}
+</pre><p>
+
+ you can write
+
+</p><pre class="programlisting">
+{
+ foo.bar = 123;
+ foo.xyzzy = true;
+ a.b.c = "d";
+}
+</pre><p>
+
+ This is useful, for instance, in NixOS configuration files.</p></li><li class="listitem"><p>Support for Nix channels generated by Hydra, the Nix-based
+ continuous build system. (Hydra generates NAR archives on the
+ fly, so the size and hash of these archives isn’t known in
+ advance.)</p></li><li class="listitem"><p>Support <code class="literal">i686-linux</code> builds directly on
+ <code class="literal">x86_64-linux</code> Nix installations. This is
+ implemented using the <code class="function">personality()</code> syscall,
+ which causes <span class="command"><strong>uname</strong></span> to return
+ <code class="literal">i686</code> in child processes.</p></li><li class="listitem"><p>Various improvements to the <code class="literal">chroot</code>
+ support. Building in a <code class="literal">chroot</code> works quite well
+ now.</p></li><li class="listitem"><p>Nix no longer blocks if it tries to build a path and another
+ process is already building the same path. Instead it tries to
+ build another buildable path first. This improves
+ parallelism.</p></li><li class="listitem"><p>Support for large (> 4 GiB) files in NAR archives.</p></li><li class="listitem"><p>Various (performance) improvements to the remote build
+ mechanism.</p></li><li class="listitem"><p>New primops: <code class="varname">builtins.addErrorContext</code> (to
+ add a string to stack traces — useful for debugging),
+ <code class="varname">builtins.isBool</code>,
+ <code class="varname">builtins.isString</code>,
+ <code class="varname">builtins.isInt</code>,
+ <code class="varname">builtins.intersectAttrs</code>.</p></li><li class="listitem"><p>OpenSolaris support (Sander van der Burg).</p></li><li class="listitem"><p>Stack traces are no longer displayed unless the
+ <code class="option">--show-trace</code> option is used.</p></li><li class="listitem"><p>The scoping rules for <code class="literal">inherit
+ (<em class="replaceable"><code>e</code></em>) ...</code> in recursive
+ attribute sets have changed. The expression
+ <em class="replaceable"><code>e</code></em> can now refer to the attributes
+ defined in the containing set.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-0.12"></a>C.24. Release 0.12 (2008-11-20)</h2></div></div></div><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Nix no longer uses Berkeley DB to store Nix store metadata.
+ The principal advantages of the new storage scheme are: it works
+ properly over decent implementations of NFS (allowing Nix stores
+ to be shared between multiple machines); no recovery is needed
+ when a Nix process crashes; no write access is needed for
+ read-only operations; no more running out of Berkeley DB locks on
+ certain operations.</p><p>You still need to compile Nix with Berkeley DB support if
+ you want Nix to automatically convert your old Nix store to the
+ new schema. If you don’t need this, you can build Nix with the
+ <code class="filename">configure</code> option
+ <code class="option">--disable-old-db-compat</code>.</p><p>After the automatic conversion to the new schema, you can
+ delete the old Berkeley DB files:
+
+ </p><pre class="screen">
+$ cd /nix/var/nix/db
+$ rm __db* log.* derivers references referrers reserved validpaths DB_CONFIG</pre><p>
+
+ The new metadata is stored in the directories
+ <code class="filename">/nix/var/nix/db/info</code> and
+ <code class="filename">/nix/var/nix/db/referrer</code>. Though the
+ metadata is stored in human-readable plain-text files, they are
+ not intended to be human-editable, as Nix is rather strict about
+ the format.</p><p>The new storage schema may or may not require less disk
+ space than the Berkeley DB environment, mostly depending on the
+ cluster size of your file system. With 1 KiB clusters (which
+ seems to be the <code class="literal">ext3</code> default nowadays) it
+ usually takes up much less space.</p></li><li class="listitem"><p>There is a new substituter that copies paths
+ directly from other (remote) Nix stores mounted somewhere in the
+ filesystem. For instance, you can speed up an installation by
+ mounting some remote Nix store that already has the packages in
+ question via NFS or <code class="literal">sshfs</code>. The environment
+ variable <code class="envar">NIX_OTHER_STORES</code> specifies the locations of
+ the remote Nix directories,
+ e.g. <code class="literal">/mnt/remote-fs/nix</code>.</p></li><li class="listitem"><p>New <span class="command"><strong>nix-store</strong></span> operations
+ <code class="option">--dump-db</code> and <code class="option">--load-db</code> to dump
+ and reload the Nix database.</p></li><li class="listitem"><p>The garbage collector has a number of new options to
+ allow only some of the garbage to be deleted. The option
+ <code class="option">--max-freed <em class="replaceable"><code>N</code></em></code> tells the
+ collector to stop after at least <em class="replaceable"><code>N</code></em> bytes
+ have been deleted. The option <code class="option">--max-links
+ <em class="replaceable"><code>N</code></em></code> tells it to stop after the
+ link count on <code class="filename">/nix/store</code> has dropped below
+ <em class="replaceable"><code>N</code></em>. This is useful for very large Nix
+ stores on filesystems with a 32000 subdirectories limit (like
+ <code class="literal">ext3</code>). The option <code class="option">--use-atime</code>
+ causes store paths to be deleted in order of ascending last access
+ time. This allows non-recently used stuff to be deleted. The
+ option <code class="option">--max-atime <em class="replaceable"><code>time</code></em></code>
+ specifies an upper limit to the last accessed time of paths that may
+ be deleted. For instance,
+
+ </p><pre class="screen">
+ $ nix-store --gc -v --max-atime $(date +%s -d "2 months ago")</pre><p>
+
+ deletes everything that hasn’t been accessed in two months.</p></li><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> now uses optimistic
+ profile locking when performing an operation like installing or
+ upgrading, instead of setting an exclusive lock on the profile.
+ This allows multiple <span class="command"><strong>nix-env -i / -u / -e</strong></span>
+ operations on the same profile in parallel. If a
+ <span class="command"><strong>nix-env</strong></span> operation sees at the end that the profile
+ was changed in the meantime by another process, it will just
+ restart. This is generally cheap because the build results are
+ still in the Nix store.</p></li><li class="listitem"><p>The option <code class="option">--dry-run</code> is now
+ supported by <span class="command"><strong>nix-store -r</strong></span> and
+ <span class="command"><strong>nix-build</strong></span>.</p></li><li class="listitem"><p>The information previously shown by
+ <code class="option">--dry-run</code> (i.e., which derivations will be built
+ and which paths will be substituted) is now always shown by
+ <span class="command"><strong>nix-env</strong></span>, <span class="command"><strong>nix-store -r</strong></span> and
+ <span class="command"><strong>nix-build</strong></span>. The total download size of
+ substitutable paths is now also shown. For instance, a build will
+ show something like
+
+ </p><pre class="screen">
+the following derivations will be built:
+ /nix/store/129sbxnk5n466zg6r1qmq1xjv9zymyy7-activate-configuration.sh.drv
+ /nix/store/7mzy971rdm8l566ch8hgxaf89x7lr7ik-upstart-jobs.drv
+ ...
+the following paths will be downloaded/copied (30.02 MiB):
+ /nix/store/4m8pvgy2dcjgppf5b4cj5l6wyshjhalj-samba-3.2.4
+ /nix/store/7h1kwcj29ip8vk26rhmx6bfjraxp0g4l-libunwind-0.98.6
+ ...</pre><p>
+
+ </p></li><li class="listitem"><p>Language features:
+
+ </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>@-patterns as in Haskell. For instance, in a
+ function definition
+
+ </p><pre class="programlisting">f = args @ {x, y, z}: <em class="replaceable"><code>...</code></em>;</pre><p>
+
+ <code class="varname">args</code> refers to the argument as a whole, which
+ is further pattern-matched against the attribute set pattern
+ <code class="literal">{x, y, z}</code>.</p></li><li class="listitem"><p>“<code class="literal">...</code>” (ellipsis) patterns.
+ An attribute set pattern can now say <code class="literal">...</code> at
+ the end of the attribute name list to specify that the function
+ takes <span class="emphasis"><em>at least</em></span> the listed attributes, while
+ ignoring additional attributes. For instance,
+
+ </p><pre class="programlisting">{stdenv, fetchurl, fuse, ...}: <em class="replaceable"><code>...</code></em></pre><p>
+
+ defines a function that accepts any attribute set that includes
+ at least the three listed attributes.</p></li><li class="listitem"><p>New primops:
+ <code class="varname">builtins.parseDrvName</code> (split a package name
+ string like <code class="literal">"nix-0.12pre12876"</code> into its name
+ and version components, e.g. <code class="literal">"nix"</code> and
+ <code class="literal">"0.12pre12876"</code>),
+ <code class="varname">builtins.compareVersions</code> (compare two version
+ strings using the same algorithm that <span class="command"><strong>nix-env</strong></span>
+ uses), <code class="varname">builtins.length</code> (efficiently compute
+ the length of a list), <code class="varname">builtins.mul</code> (integer
+ multiplication), <code class="varname">builtins.div</code> (integer
+ division).
+
+ </p></li></ul></div><p>
+
+ </p></li><li class="listitem"><p><span class="command"><strong>nix-prefetch-url</strong></span> now supports
+ <code class="literal">mirror://</code> URLs, provided that the environment
+ variable <code class="envar">NIXPKGS_ALL</code> points at a Nixpkgs
+ tree.</p></li><li class="listitem"><p>Removed the commands
+ <span class="command"><strong>nix-pack-closure</strong></span> and
+ <span class="command"><strong>nix-unpack-closure</strong></span>. You can do almost the same
+ thing but much more efficiently by doing <code class="literal">nix-store --export
+ $(nix-store -qR <em class="replaceable"><code>paths</code></em>) > closure</code> and
+ <code class="literal">nix-store --import <
+ closure</code>.</p></li><li class="listitem"><p>Lots of bug fixes, including a big performance bug in
+ the handling of <code class="literal">with</code>-expressions.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-0.11"></a>C.25. Release 0.11 (2007-12-31)</h2></div></div></div><p>Nix 0.11 has many improvements over the previous stable release.
+The most important improvement is secure multi-user support. It also
+features many usability enhancements and language extensions, many of
+them prompted by NixOS, the purely functional Linux distribution based
+on Nix. Here is an (incomplete) list:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Secure multi-user support. A single Nix store can
+ now be shared between multiple (possible untrusted) users. This is
+ an important feature for NixOS, where it allows non-root users to
+ install software. The old setuid method for sharing a store between
+ multiple users has been removed. Details for setting up a
+ multi-user store can be found in the manual.</p></li><li class="listitem"><p>The new command <span class="command"><strong>nix-copy-closure</strong></span>
+ gives you an easy and efficient way to exchange software between
+ machines. It copies the missing parts of the closure of a set of
+ store path to or from a remote machine via
+ <span class="command"><strong>ssh</strong></span>.</p></li><li class="listitem"><p>A new kind of string literal: strings between double
+ single-quotes (<code class="literal">''</code>) have indentation
+ “intelligently” removed. This allows large strings (such as shell
+ scripts or configuration file fragments in NixOS) to cleanly follow
+ the indentation of the surrounding expression. It also requires
+ much less escaping, since <code class="literal">''</code> is less common in
+ most languages than <code class="literal">"</code>.</p></li><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> <code class="option">--set</code>
+ modifies the current generation of a profile so that it contains
+ exactly the specified derivation, and nothing else. For example,
+ <code class="literal">nix-env -p /nix/var/nix/profiles/browser --set
+ firefox</code> lets the profile named
+ <code class="filename">browser</code> contain just Firefox.</p></li><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> now maintains
+ meta-information about installed packages in profiles. The
+ meta-information is the contents of the <code class="varname">meta</code>
+ attribute of derivations, such as <code class="varname">description</code> or
+ <code class="varname">homepage</code>. The command <code class="literal">nix-env -q --xml
+ --meta</code> shows all meta-information.</p></li><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> now uses the
+ <code class="varname">meta.priority</code> attribute of derivations to resolve
+ filename collisions between packages. Lower priority values denote
+ a higher priority. For instance, the GCC wrapper package and the
+ Binutils package in Nixpkgs both have a file
+ <code class="filename">bin/ld</code>, so previously if you tried to install
+ both you would get a collision. Now, on the other hand, the GCC
+ wrapper declares a higher priority than Binutils, so the former’s
+ <code class="filename">bin/ld</code> is symlinked in the user
+ environment.</p></li><li class="listitem"><p><span class="command"><strong>nix-env -i / -u</strong></span>: instead of
+ breaking package ties by version, break them by priority and version
+ number. That is, if there are multiple packages with the same name,
+ then pick the package with the highest priority, and only use the
+ version if there are multiple packages with the same
+ priority.</p><p>This makes it possible to mark specific versions/variant in
+ Nixpkgs more or less desirable than others. A typical example would
+ be a beta version of some package (e.g.,
+ <code class="literal">gcc-4.2.0rc1</code>) which should not be installed even
+ though it is the highest version, except when it is explicitly
+ selected (e.g., <code class="literal">nix-env -i
+ gcc-4.2.0rc1</code>).</p></li><li class="listitem"><p><span class="command"><strong>nix-env --set-flag</strong></span> allows meta
+ attributes of installed packages to be modified. There are several
+ attributes that can be usefully modified, because they affect the
+ behaviour of <span class="command"><strong>nix-env</strong></span> or the user environment
+ build script:
+
+ </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p><code class="varname">meta.priority</code> can be changed
+ to resolve filename clashes (see above).</p></li><li class="listitem"><p><code class="varname">meta.keep</code> can be set to
+ <code class="literal">true</code> to prevent the package from being
+ upgraded or replaced. Useful if you want to hang on to an older
+ version of a package.</p></li><li class="listitem"><p><code class="varname">meta.active</code> can be set to
+ <code class="literal">false</code> to “disable” the package. That is, no
+ symlinks will be generated to the files of the package, but it
+ remains part of the profile (so it won’t be garbage-collected).
+ Set it back to <code class="literal">true</code> to re-enable the
+ package.</p></li></ul></div><p>
+
+ </p></li><li class="listitem"><p><span class="command"><strong>nix-env -q</strong></span> now has a flag
+ <code class="option">--prebuilt-only</code> (<code class="option">-b</code>) that causes
+ <span class="command"><strong>nix-env</strong></span> to show only those derivations whose
+ output is already in the Nix store or that can be substituted (i.e.,
+ downloaded from somewhere). In other words, it shows the packages
+ that can be installed “quickly”, i.e., don’t need to be built from
+ source. The <code class="option">-b</code> flag is also available in
+ <span class="command"><strong>nix-env -i</strong></span> and <span class="command"><strong>nix-env -u</strong></span> to
+ filter out derivations for which no pre-built binary is
+ available.</p></li><li class="listitem"><p>The new option <code class="option">--argstr</code> (in
+ <span class="command"><strong>nix-env</strong></span>, <span class="command"><strong>nix-instantiate</strong></span> and
+ <span class="command"><strong>nix-build</strong></span>) is like <code class="option">--arg</code>, except
+ that the value is a string. For example, <code class="literal">--argstr system
+ i686-linux</code> is equivalent to <code class="literal">--arg system
+ \"i686-linux\"</code> (note that <code class="option">--argstr</code>
+ prevents annoying quoting around shell arguments).</p></li><li class="listitem"><p><span class="command"><strong>nix-store</strong></span> has a new operation
+ <code class="option">--read-log</code> (<code class="option">-l</code>)
+ <em class="parameter"><code>paths</code></em> that shows the build log of the given
+ paths.</p></li><li class="listitem"><p>Nix now uses Berkeley DB 4.5. The database is
+ upgraded automatically, but you should be careful not to use old
+ versions of Nix that still use Berkeley DB 4.4.</p></li><li class="listitem"><p>The option <code class="option">--max-silent-time</code>
+ (corresponding to the configuration setting
+ <code class="literal">build-max-silent-time</code>) allows you to set a
+ timeout on builds — if a build produces no output on
+ <code class="literal">stdout</code> or <code class="literal">stderr</code> for the given
+ number of seconds, it is terminated. This is useful for recovering
+ automatically from builds that are stuck in an infinite
+ loop.</p></li><li class="listitem"><p><span class="command"><strong>nix-channel</strong></span>: each subscribed
+ channel is its own attribute in the top-level expression generated
+ for the channel. This allows disambiguation (e.g. <code class="literal">nix-env
+ -i -A nixpkgs_unstable.firefox</code>).</p></li><li class="listitem"><p>The substitutes table has been removed from the
+ database. This makes operations such as <span class="command"><strong>nix-pull</strong></span>
+ and <span class="command"><strong>nix-channel --update</strong></span> much, much
+ faster.</p></li><li class="listitem"><p><span class="command"><strong>nix-pull</strong></span> now supports
+ bzip2-compressed manifests. This speeds up
+ channels.</p></li><li class="listitem"><p><span class="command"><strong>nix-prefetch-url</strong></span> now has a
+ limited form of caching. This is used by
+ <span class="command"><strong>nix-channel</strong></span> to prevent unnecessary downloads when
+ the channel hasn’t changed.</p></li><li class="listitem"><p><span class="command"><strong>nix-prefetch-url</strong></span> now by default
+ computes the SHA-256 hash of the file instead of the MD5 hash. In
+ calls to <code class="function">fetchurl</code> you should pass the
+ <code class="literal">sha256</code> attribute instead of
+ <code class="literal">md5</code>. You can pass either a hexadecimal or a
+ base-32 encoding of the hash.</p></li><li class="listitem"><p>Nix can now perform builds in an automatically
+ generated “chroot”. This prevents a builder from accessing stuff
+ outside of the Nix store, and thus helps ensure purity. This is an
+ experimental feature.</p></li><li class="listitem"><p>The new command <span class="command"><strong>nix-store
+ --optimise</strong></span> reduces Nix store disk space usage by finding
+ identical files in the store and hard-linking them to each other.
+ It typically reduces the size of the store by something like
+ 25-35%.</p></li><li class="listitem"><p><code class="filename">~/.nix-defexpr</code> can now be a
+ directory, in which case the Nix expressions in that directory are
+ combined into an attribute set, with the file names used as the
+ names of the attributes. The command <span class="command"><strong>nix-env
+ --import</strong></span> (which set the
+ <code class="filename">~/.nix-defexpr</code> symlink) is
+ removed.</p></li><li class="listitem"><p>Derivations can specify the new special attribute
+ <code class="varname">allowedReferences</code> to enforce that the references
+ in the output of a derivation are a subset of a declared set of
+ paths. For example, if <code class="varname">allowedReferences</code> is an
+ empty list, then the output must not have any references. This is
+ used in NixOS to check that generated files such as initial ramdisks
+ for booting Linux don’t have any dependencies.</p></li><li class="listitem"><p>The new attribute
+ <code class="varname">exportReferencesGraph</code> allows builders access to
+ the references graph of their inputs. This is used in NixOS for
+ tasks such as generating ISO-9660 images that contain a Nix store
+ populated with the closure of certain paths.</p></li><li class="listitem"><p>Fixed-output derivations (like
+ <code class="function">fetchurl</code>) can define the attribute
+ <code class="varname">impureEnvVars</code> to allow external environment
+ variables to be passed to builders. This is used in Nixpkgs to
+ support proxy configuration, among other things.</p></li><li class="listitem"><p>Several new built-in functions:
+ <code class="function">builtins.attrNames</code>,
+ <code class="function">builtins.filterSource</code>,
+ <code class="function">builtins.isAttrs</code>,
+ <code class="function">builtins.isFunction</code>,
+ <code class="function">builtins.listToAttrs</code>,
+ <code class="function">builtins.stringLength</code>,
+ <code class="function">builtins.sub</code>,
+ <code class="function">builtins.substring</code>,
+ <code class="function">throw</code>,
+ <code class="function">builtins.trace</code>,
+ <code class="function">builtins.readFile</code>.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ch-relnotes-0.10.1"></a>C.26. Release 0.10.1 (2006-10-11)</h2></div></div></div><p>This release fixes two somewhat obscure bugs that occur when
+evaluating Nix expressions that are stored inside the Nix store
+(<code class="literal">NIX-67</code>). These do not affect most users.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ch-relnotes-0.10"></a>C.27. Release 0.10 (2006-10-06)</h2></div></div></div><div class="note"><h3 class="title">Note</h3><p>This version of Nix uses Berkeley DB 4.4 instead of 4.3.
+The database is upgraded automatically, but you should be careful not
+to use old versions of Nix that still use Berkeley DB 4.3. In
+particular, if you use a Nix installed through Nix, you should run
+
+</p><pre class="screen">
+$ nix-store --clear-substitutes</pre><p>
+
+first.</p></div><div class="warning"><h3 class="title">Warning</h3><p>Also, the database schema has changed slighted to fix a
+performance issue (see below). When you run any Nix 0.10 command for
+the first time, the database will be upgraded automatically. This is
+irreversible.</p></div><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> usability improvements:
+
+ </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>An option <code class="option">--compare-versions</code>
+ (or <code class="option">-c</code>) has been added to <span class="command"><strong>nix-env
+ --query</strong></span> to allow you to compare installed versions of
+ packages to available versions, or vice versa. An easy way to
+ see if you are up to date with what’s in your subscribed
+ channels is <code class="literal">nix-env -qc \*</code>.</p></li><li class="listitem"><p><code class="literal">nix-env --query</code> now takes as
+ arguments a list of package names about which to show
+ information, just like <code class="option">--install</code>, etc.: for
+ example, <code class="literal">nix-env -q gcc</code>. Note that to show
+ all derivations, you need to specify
+ <code class="literal">\*</code>.</p></li><li class="listitem"><p><code class="literal">nix-env -i
+ <em class="replaceable"><code>pkgname</code></em></code> will now install
+ the highest available version of
+ <em class="replaceable"><code>pkgname</code></em>, rather than installing all
+ available versions (which would probably give collisions)
+ (<code class="literal">NIX-31</code>).</p></li><li class="listitem"><p><code class="literal">nix-env (-i|-u) --dry-run</code> now
+ shows exactly which missing paths will be built or
+ substituted.</p></li><li class="listitem"><p><code class="literal">nix-env -qa --description</code>
+ shows human-readable descriptions of packages, provided that
+ they have a <code class="literal">meta.description</code> attribute (which
+ most packages in Nixpkgs don’t have yet).</p></li></ul></div><p>
+
+ </p></li><li class="listitem"><p>New language features:
+
+ </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Reference scanning (which happens after each
+ build) is much faster and takes a constant amount of
+ memory.</p></li><li class="listitem"><p>String interpolation. Expressions like
+
+</p><pre class="programlisting">
+"--with-freetype2-library=" + freetype + "/lib"</pre><p>
+
+ can now be written as
+
+</p><pre class="programlisting">
+"--with-freetype2-library=${freetype}/lib"</pre><p>
+
+ You can write arbitrary expressions within
+ <code class="literal">${<em class="replaceable"><code>...</code></em>}</code>, not just
+ identifiers.</p></li><li class="listitem"><p>Multi-line string literals.</p></li><li class="listitem"><p>String concatenations can now involve
+ derivations, as in the example <code class="code">"--with-freetype2-library="
+ + freetype + "/lib"</code>. This was not previously possible
+ because we need to register that a derivation that uses such a
+ string is dependent on <code class="literal">freetype</code>. The
+ evaluator now properly propagates this information.
+ Consequently, the subpath operator (<code class="literal">~</code>) has
+ been deprecated.</p></li><li class="listitem"><p>Default values of function arguments can now
+ refer to other function arguments; that is, all arguments are in
+ scope in the default values
+ (<code class="literal">NIX-45</code>).</p></li><li class="listitem"><p>Lots of new built-in primitives, such as
+ functions for list manipulation and integer arithmetic. See the
+ manual for a complete list. All primops are now available in
+ the set <code class="varname">builtins</code>, allowing one to test for
+ the availability of primop in a backwards-compatible
+ way.</p></li><li class="listitem"><p>Real let-expressions: <code class="literal">let x = ...;
+ ... z = ...; in ...</code>.</p></li></ul></div><p>
+
+ </p></li><li class="listitem"><p>New commands <span class="command"><strong>nix-pack-closure</strong></span> and
+ <span class="command"><strong>nix-unpack-closure</strong></span> than can be used to easily
+ transfer a store path with all its dependencies to another machine.
+ Very convenient whenever you have some package on your machine and
+ you want to copy it somewhere else.</p></li><li class="listitem"><p>XML support:
+
+ </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p><code class="literal">nix-env -q --xml</code> prints the
+ installed or available packages in an XML representation for
+ easy processing by other tools.</p></li><li class="listitem"><p><code class="literal">nix-instantiate --eval-only
+ --xml</code> prints an XML representation of the resulting
+ term. (The new flag <code class="option">--strict</code> forces ‘deep’
+ evaluation of the result, i.e., list elements and attributes are
+ evaluated recursively.)</p></li><li class="listitem"><p>In Nix expressions, the primop
+ <code class="function">builtins.toXML</code> converts a term to an XML
+ representation. This is primarily useful for passing structured
+ information to builders.</p></li></ul></div><p>
+
+ </p></li><li class="listitem"><p>You can now unambiguously specify which derivation to
+ build or install in <span class="command"><strong>nix-env</strong></span>,
+ <span class="command"><strong>nix-instantiate</strong></span> and <span class="command"><strong>nix-build</strong></span>
+ using the <code class="option">--attr</code> / <code class="option">-A</code> flags, which
+ takes an attribute name as argument. (Unlike symbolic package names
+ such as <code class="literal">subversion-1.4.0</code>, attribute names in an
+ attribute set are unique.) For instance, a quick way to perform a
+ test build of a package in Nixpkgs is <code class="literal">nix-build
+ pkgs/top-level/all-packages.nix -A
+ <em class="replaceable"><code>foo</code></em></code>. <code class="literal">nix-env -q
+ --attr</code> shows the attribute names corresponding to each
+ derivation.</p></li><li class="listitem"><p>If the top-level Nix expression used by
+ <span class="command"><strong>nix-env</strong></span>, <span class="command"><strong>nix-instantiate</strong></span> or
+ <span class="command"><strong>nix-build</strong></span> evaluates to a function whose arguments
+ all have default values, the function will be called automatically.
+ Also, the new command-line switch <code class="option">--arg
+ <em class="replaceable"><code>name</code></em>
+ <em class="replaceable"><code>value</code></em></code> can be used to specify
+ function arguments on the command line.</p></li><li class="listitem"><p><code class="literal">nix-install-package --url
+ <em class="replaceable"><code>URL</code></em></code> allows a package to be
+ installed directly from the given URL.</p></li><li class="listitem"><p>Nix now works behind an HTTP proxy server; just set
+ the standard environment variables <code class="envar">http_proxy</code>,
+ <code class="envar">https_proxy</code>, <code class="envar">ftp_proxy</code> or
+ <code class="envar">all_proxy</code> appropriately. Functions such as
+ <code class="function">fetchurl</code> in Nixpkgs also respect these
+ variables.</p></li><li class="listitem"><p><code class="literal">nix-build -o
+ <em class="replaceable"><code>symlink</code></em></code> allows the symlink to
+ the build result to be named something other than
+ <code class="literal">result</code>.</p></li><li class="listitem"><p>Platform support:
+
+ </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Support for 64-bit platforms, provided a <a class="link" href="http://bugzilla.sen.cwi.nl:8080/show_bug.cgi?id=606" target="_top">suitably
+ patched ATerm library</a> is used. Also, files larger than 2
+ GiB are now supported.</p></li><li class="listitem"><p>Added support for Cygwin (Windows,
+ <code class="literal">i686-cygwin</code>), Mac OS X on Intel
+ (<code class="literal">i686-darwin</code>) and Linux on PowerPC
+ (<code class="literal">powerpc-linux</code>).</p></li><li class="listitem"><p>Users of SMP and multicore machines will
+ appreciate that the number of builds to be performed in parallel
+ can now be specified in the configuration file in the
+ <code class="literal">build-max-jobs</code> setting.</p></li></ul></div><p>
+
+ </p></li><li class="listitem"><p>Garbage collector improvements:
+
+ </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Open files (such as running programs) are now
+ used as roots of the garbage collector. This prevents programs
+ that have been uninstalled from being garbage collected while
+ they are still running. The script that detects these
+ additional runtime roots
+ (<code class="filename">find-runtime-roots.pl</code>) is inherently
+ system-specific, but it should work on Linux and on all
+ platforms that have the <span class="command"><strong>lsof</strong></span>
+ utility.</p></li><li class="listitem"><p><code class="literal">nix-store --gc</code>
+ (a.k.a. <span class="command"><strong>nix-collect-garbage</strong></span>) prints out the
+ number of bytes freed on standard output. <code class="literal">nix-store
+ --gc --print-dead</code> shows how many bytes would be freed
+ by an actual garbage collection.</p></li><li class="listitem"><p><code class="literal">nix-collect-garbage -d</code>
+ removes all old generations of <span class="emphasis"><em>all</em></span> profiles
+ before calling the actual garbage collector (<code class="literal">nix-store
+ --gc</code>). This is an easy way to get rid of all old
+ packages in the Nix store.</p></li><li class="listitem"><p><span class="command"><strong>nix-store</strong></span> now has an
+ operation <code class="option">--delete</code> to delete specific paths
+ from the Nix store. It won’t delete reachable (non-garbage)
+ paths unless <code class="option">--ignore-liveness</code> is
+ specified.</p></li></ul></div><p>
+
+ </p></li><li class="listitem"><p>Berkeley DB 4.4’s process registry feature is used
+ to recover from crashed Nix processes.</p></li><li class="listitem"><p>A performance issue has been fixed with the
+ <code class="literal">referer</code> table, which stores the inverse of the
+ <code class="literal">references</code> table (i.e., it tells you what store
+ paths refer to a given path). Maintaining this table could take a
+ quadratic amount of time, as well as a quadratic amount of Berkeley
+ DB log file space (in particular when running the garbage collector)
+ (<code class="literal">NIX-23</code>).</p></li><li class="listitem"><p>Nix now catches the <code class="literal">TERM</code> and
+ <code class="literal">HUP</code> signals in addition to the
+ <code class="literal">INT</code> signal. So you can now do a <code class="literal">killall
+ nix-store</code> without triggering a database
+ recovery.</p></li><li class="listitem"><p><span class="command"><strong>bsdiff</strong></span> updated to version
+ 4.3.</p></li><li class="listitem"><p>Substantial performance improvements in expression
+ evaluation and <code class="literal">nix-env -qa</code>, all thanks to <a class="link" href="http://valgrind.org/" target="_top">Valgrind</a>. Memory use has
+ been reduced by a factor 8 or so. Big speedup by memoisation of
+ path hashing.</p></li><li class="listitem"><p>Lots of bug fixes, notably:
+
+ </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Make sure that the garbage collector can run
+ successfully when the disk is full
+ (<code class="literal">NIX-18</code>).</p></li><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> now locks the profile
+ to prevent races between concurrent <span class="command"><strong>nix-env</strong></span>
+ operations on the same profile
+ (<code class="literal">NIX-7</code>).</p></li><li class="listitem"><p>Removed misleading messages from
+ <code class="literal">nix-env -i</code> (e.g., <code class="literal">installing
+ `foo'</code> followed by <code class="literal">uninstalling
+ `foo'</code>) (<code class="literal">NIX-17</code>).</p></li></ul></div><p>
+
+ </p></li><li class="listitem"><p>Nix source distributions are a lot smaller now since
+ we no longer include a full copy of the Berkeley DB source
+ distribution (but only the bits we need).</p></li><li class="listitem"><p>Header files are now installed so that external
+ programs can use the Nix libraries.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ch-relnotes-0.9.2"></a>C.28. Release 0.9.2 (2005-09-21)</h2></div></div></div><p>This bug fix release fixes two problems on Mac OS X:
+
+</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>If Nix was linked against statically linked versions
+ of the ATerm or Berkeley DB library, there would be dynamic link
+ errors at runtime.</p></li><li class="listitem"><p><span class="command"><strong>nix-pull</strong></span> and
+ <span class="command"><strong>nix-push</strong></span> intermittently failed due to race
+ conditions involving pipes and child processes with error messages
+ such as <code class="literal">open2: open(GLOB(0x180b2e4), >&=9) failed: Bad
+ file descriptor at /nix/bin/nix-pull line 77</code> (issue
+ <code class="literal">NIX-14</code>).</p></li></ul></div><p>
+
+</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ch-relnotes-0.9.1"></a>C.29. Release 0.9.1 (2005-09-20)</h2></div></div></div><p>This bug fix release addresses a problem with the ATerm library
+when the <code class="option">--with-aterm</code> flag in
+<span class="command"><strong>configure</strong></span> was <span class="emphasis"><em>not</em></span> used.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ch-relnotes-0.9"></a>C.30. Release 0.9 (2005-09-16)</h2></div></div></div><p>NOTE: this version of Nix uses Berkeley DB 4.3 instead of 4.2.
+The database is upgraded automatically, but you should be careful not
+to use old versions of Nix that still use Berkeley DB 4.2. In
+particular, if you use a Nix installed through Nix, you should run
+
+</p><pre class="screen">
+$ nix-store --clear-substitutes</pre><p>
+
+first.</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Unpacking of patch sequences is much faster now
+ since we no longer do redundant unpacking and repacking of
+ intermediate paths.</p></li><li class="listitem"><p>Nix now uses Berkeley DB 4.3.</p></li><li class="listitem"><p>The <code class="function">derivation</code> primitive is
+ lazier. Attributes of dependent derivations can mutually refer to
+ each other (as long as there are no data dependencies on the
+ <code class="varname">outPath</code> and <code class="varname">drvPath</code> attributes
+ computed by <code class="function">derivation</code>).</p><p>For example, the expression <code class="literal">derivation
+ attrs</code> now evaluates to (essentially)
+
+ </p><pre class="programlisting">
+attrs // {
+ type = "derivation";
+ outPath = derivation! attrs;
+ drvPath = derivation! attrs;
+}</pre><p>
+
+ where <code class="function">derivation!</code> is a primop that does the
+ actual derivation instantiation (i.e., it does what
+ <code class="function">derivation</code> used to do). The advantage is that
+ it allows commands such as <span class="command"><strong>nix-env -qa</strong></span> and
+ <span class="command"><strong>nix-env -i</strong></span> to be much faster since they no longer
+ need to instantiate all derivations, just the
+ <code class="varname">name</code> attribute.</p><p>Also, it allows derivations to cyclically reference each
+ other, for example,
+
+ </p><pre class="programlisting">
+webServer = derivation {
+ ...
+ hostName = "svn.cs.uu.nl";
+ services = [svnService];
+};
+
+svnService = derivation {
+ ...
+ hostName = webServer.hostName;
+};</pre><p>
+
+ Previously, this would yield a black hole (infinite recursion).</p></li><li class="listitem"><p><span class="command"><strong>nix-build</strong></span> now defaults to using
+ <code class="filename">./default.nix</code> if no Nix expression is
+ specified.</p></li><li class="listitem"><p><span class="command"><strong>nix-instantiate</strong></span>, when applied to
+ a Nix expression that evaluates to a function, will call the
+ function automatically if all its arguments have
+ defaults.</p></li><li class="listitem"><p>Nix now uses libtool to build dynamic libraries.
+ This reduces the size of executables.</p></li><li class="listitem"><p>A new list concatenation operator
+ <code class="literal">++</code>. For example, <code class="literal">[1 2 3] ++ [4 5
+ 6]</code> evaluates to <code class="literal">[1 2 3 4 5
+ 6]</code>.</p></li><li class="listitem"><p>Some currently undocumented primops to support
+ low-level build management using Nix (i.e., using Nix as a Make
+ replacement). See the commit messages for <code class="literal">r3578</code>
+ and <code class="literal">r3580</code>.</p></li><li class="listitem"><p>Various bug fixes and performance
+ improvements.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ch-relnotes-0.8.1"></a>C.31. Release 0.8.1 (2005-04-13)</h2></div></div></div><p>This is a bug fix release.</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Patch downloading was broken.</p></li><li class="listitem"><p>The garbage collector would not delete paths that
+ had references from invalid (but substitutable)
+ paths.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ch-relnotes-0.8"></a>C.32. Release 0.8 (2005-04-11)</h2></div></div></div><p>NOTE: the hashing scheme in Nix 0.8 changed (as detailed below).
+As a result, <span class="command"><strong>nix-pull</strong></span> manifests and channels built
+for Nix 0.7 and below will not work anymore. However, the Nix
+expression language has not changed, so you can still build from
+source. Also, existing user environments continue to work. Nix 0.8
+will automatically upgrade the database schema of previous
+installations when it is first run.</p><p>If you get the error message
+
+</p><pre class="screen">
+you have an old-style manifest `/nix/var/nix/manifests/[...]'; please
+delete it</pre><p>
+
+you should delete previously downloaded manifests:
+
+</p><pre class="screen">
+$ rm /nix/var/nix/manifests/*</pre><p>
+
+If <span class="command"><strong>nix-channel</strong></span> gives the error message
+
+</p><pre class="screen">
+manifest `http://catamaran.labs.cs.uu.nl/dist/nix/channels/[channel]/MANIFEST'
+is too old (i.e., for Nix <= 0.7)</pre><p>
+
+then you should unsubscribe from the offending channel
+(<span class="command"><strong>nix-channel --remove
+<em class="replaceable"><code>URL</code></em></strong></span>; leave out
+<code class="literal">/MANIFEST</code>), and subscribe to the same URL, with
+<code class="literal">channels</code> replaced by <code class="literal">channels-v3</code>
+(e.g., <a class="link" href="http://catamaran.labs.cs.uu.nl/dist/nix/channels-v3/nixpkgs-unstable" target="_top">http://catamaran.labs.cs.uu.nl/dist/nix/channels-v3/nixpkgs-unstable</a>).</p><p>Nix 0.8 has the following improvements:
+
+</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>The cryptographic hashes used in store paths are now
+ 160 bits long, but encoded in base-32 so that they are still only 32
+ characters long (e.g.,
+ <code class="filename">/nix/store/csw87wag8bqlqk7ipllbwypb14xainap-atk-1.9.0</code>).
+ (This is actually a 160 bit truncation of a SHA-256
+ hash.)</p></li><li class="listitem"><p>Big cleanups and simplifications of the basic store
+ semantics. The notion of “closure store expressions” is gone (and
+ so is the notion of “successors”); the file system references of a
+ store path are now just stored in the database.</p><p>For instance, given any store path, you can query its closure:
+
+ </p><pre class="screen">
+$ nix-store -qR $(which firefox)
+... lots of paths ...</pre><p>
+
+ Also, Nix now remembers for each store path the derivation that
+ built it (the “deriver”):
+
+ </p><pre class="screen">
+$ nix-store -qR $(which firefox)
+/nix/store/4b0jx7vq80l9aqcnkszxhymsf1ffa5jd-firefox-1.0.1.drv</pre><p>
+
+ So to see the build-time dependencies, you can do
+
+ </p><pre class="screen">
+$ nix-store -qR $(nix-store -qd $(which firefox))</pre><p>
+
+ or, in a nicer format:
+
+ </p><pre class="screen">
+$ nix-store -q --tree $(nix-store -qd $(which firefox))</pre><p>
+
+ </p><p>File system references are also stored in reverse. For
+ instance, you can query all paths that directly or indirectly use a
+ certain Glibc:
+
+ </p><pre class="screen">
+$ nix-store -q --referrers-closure \
+ /nix/store/8lz9yc6zgmc0vlqmn2ipcpkjlmbi51vv-glibc-2.3.4</pre><p>
+
+ </p></li><li class="listitem"><p>The concept of fixed-output derivations has been
+ formalised. Previously, functions such as
+ <code class="function">fetchurl</code> in Nixpkgs used a hack (namely,
+ explicitly specifying a store path hash) to prevent changes to, say,
+ the URL of the file from propagating upwards through the dependency
+ graph, causing rebuilds of everything. This can now be done cleanly
+ by specifying the <code class="varname">outputHash</code> and
+ <code class="varname">outputHashAlgo</code> attributes. Nix itself checks
+ that the content of the output has the specified hash. (This is
+ important for maintaining certain invariants necessary for future
+ work on secure shared stores.)</p></li><li class="listitem"><p>One-click installation :-) It is now possible to
+ install any top-level component in Nixpkgs directly, through the web
+ — see, e.g., <a class="link" href="http://catamaran.labs.cs.uu.nl/dist/nixpkgs-0.8/" target="_top">http://catamaran.labs.cs.uu.nl/dist/nixpkgs-0.8/</a>.
+ All you have to do is associate
+ <code class="filename">/nix/bin/nix-install-package</code> with the MIME type
+ <code class="literal">application/nix-package</code> (or the extension
+ <code class="filename">.nixpkg</code>), and clicking on a package link will
+ cause it to be installed, with all appropriate dependencies. If you
+ just want to install some specific application, this is easier than
+ subscribing to a channel.</p></li><li class="listitem"><p><span class="command"><strong>nix-store -r
+ <em class="replaceable"><code>PATHS</code></em></strong></span> now builds all the
+ derivations PATHS in parallel. Previously it did them sequentially
+ (though exploiting possible parallelism between subderivations).
+ This is nice for build farms.</p></li><li class="listitem"><p><span class="command"><strong>nix-channel</strong></span> has new operations
+ <code class="option">--list</code> and
+ <code class="option">--remove</code>.</p></li><li class="listitem"><p>New ways of installing components into user
+ environments:
+
+ </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Copy from another user environment:
+
+ </p><pre class="screen">
+$ nix-env -i --from-profile .../other-profile firefox</pre><p>
+
+ </p></li><li class="listitem"><p>Install a store derivation directly (bypassing the
+ Nix expression language entirely):
+
+ </p><pre class="screen">
+$ nix-env -i /nix/store/z58v41v21xd3...-aterm-2.3.1.drv</pre><p>
+
+ (This is used to implement <span class="command"><strong>nix-install-package</strong></span>,
+ which is therefore immune to evolution in the Nix expression
+ language.)</p></li><li class="listitem"><p>Install an already built store path directly:
+
+ </p><pre class="screen">
+$ nix-env -i /nix/store/hsyj5pbn0d9i...-aterm-2.3.1</pre><p>
+
+ </p></li><li class="listitem"><p>Install the result of a Nix expression specified
+ as a command-line argument:
+
+ </p><pre class="screen">
+$ nix-env -f .../i686-linux.nix -i -E 'x: x.firefoxWrapper'</pre><p>
+
+ The difference with the normal installation mode is that
+ <code class="option">-E</code> does not use the <code class="varname">name</code>
+ attributes of derivations. Therefore, this can be used to
+ disambiguate multiple derivations with the same
+ name.</p></li></ul></div></li><li class="listitem"><p>A hash of the contents of a store path is now stored
+ in the database after a successful build. This allows you to check
+ whether store paths have been tampered with: <span class="command"><strong>nix-store
+ --verify --check-contents</strong></span>.</p></li><li class="listitem"><p>Implemented a concurrent garbage collector. It is now
+ always safe to run the garbage collector, even if other Nix
+ operations are happening simultaneously.</p><p>However, there can still be GC races if you use
+ <span class="command"><strong>nix-instantiate</strong></span> and <span class="command"><strong>nix-store
+ --realise</strong></span> directly to build things. To prevent races,
+ use the <code class="option">--add-root</code> flag of those commands.</p></li><li class="listitem"><p>The garbage collector now finally deletes paths in
+ the right order (i.e., topologically sorted under the “references”
+ relation), thus making it safe to interrupt the collector without
+ risking a store that violates the closure
+ invariant.</p></li><li class="listitem"><p>Likewise, the substitute mechanism now downloads
+ files in the right order, thus preserving the closure invariant at
+ all times.</p></li><li class="listitem"><p>The result of <span class="command"><strong>nix-build</strong></span> is now
+ registered as a root of the garbage collector. If the
+ <code class="filename">./result</code> link is deleted, the GC root
+ disappears automatically.</p></li><li class="listitem"><p>The behaviour of the garbage collector can be changed
+ globally by setting options in
+ <code class="filename">/nix/etc/nix/nix.conf</code>.
+
+ </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p><code class="literal">gc-keep-derivations</code> specifies
+ whether deriver links should be followed when searching for live
+ paths.</p></li><li class="listitem"><p><code class="literal">gc-keep-outputs</code> specifies
+ whether outputs of derivations should be followed when searching
+ for live paths.</p></li><li class="listitem"><p><code class="literal">env-keep-derivations</code>
+ specifies whether user environments should store the paths of
+ derivations when they are added (thus keeping the derivations
+ alive).</p></li></ul></div><p>
+
+ </p></li><li class="listitem"><p>New <span class="command"><strong>nix-env</strong></span> query flags
+ <code class="option">--drv-path</code> and
+ <code class="option">--out-path</code>.</p></li><li class="listitem"><p><span class="command"><strong>fetchurl</strong></span> allows SHA-1 and SHA-256
+ in addition to MD5. Just specify the attribute
+ <code class="varname">sha1</code> or <code class="varname">sha256</code> instead of
+ <code class="varname">md5</code>.</p></li><li class="listitem"><p>Manual updates.</p></li></ul></div><p>
+
+</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ch-relnotes-0.7"></a>C.33. Release 0.7 (2005-01-12)</h2></div></div></div><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Binary patching. When upgrading components using
+ pre-built binaries (through nix-pull / nix-channel), Nix can
+ automatically download and apply binary patches to already installed
+ components instead of full downloads. Patching is “smart”: if there
+ is a <span class="emphasis"><em>sequence</em></span> of patches to an installed
+ component, Nix will use it. Patches are currently generated
+ automatically between Nixpkgs (pre-)releases.</p></li><li class="listitem"><p>Simplifications to the substitute
+ mechanism.</p></li><li class="listitem"><p>Nix-pull now stores downloaded manifests in
+ <code class="filename">/nix/var/nix/manifests</code>.</p></li><li class="listitem"><p>Metadata on files in the Nix store is canonicalised
+ after builds: the last-modified timestamp is set to 0 (00:00:00
+ 1/1/1970), the mode is set to 0444 or 0555 (readable and possibly
+ executable by all; setuid/setgid bits are dropped), and the group is
+ set to the default. This ensures that the result of a build and an
+ installation through a substitute is the same; and that timestamp
+ dependencies are revealed.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ch-relnotes-0.6"></a>C.34. Release 0.6 (2004-11-14)</h2></div></div></div><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Rewrite of the normalisation engine.
+
+ </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Multiple builds can now be performed in parallel
+ (option <code class="option">-j</code>).</p></li><li class="listitem"><p>Distributed builds. Nix can now call a shell
+ script to forward builds to Nix installations on remote
+ machines, which may or may not be of the same platform
+ type.</p></li><li class="listitem"><p>Option <code class="option">--fallback</code> allows
+ recovery from broken substitutes.</p></li><li class="listitem"><p>Option <code class="option">--keep-going</code> causes
+ building of other (unaffected) derivations to continue if one
+ failed.</p></li></ul></div><p>
+
+ </p></li><li class="listitem"><p>Improvements to the garbage collector (i.e., it
+ should actually work now).</p></li><li class="listitem"><p>Setuid Nix installations allow a Nix store to be
+ shared among multiple users.</p></li><li class="listitem"><p>Substitute registration is much faster
+ now.</p></li><li class="listitem"><p>A utility <span class="command"><strong>nix-build</strong></span> to build a
+ Nix expression and create a symlink to the result int the current
+ directory; useful for testing Nix derivations.</p></li><li class="listitem"><p>Manual updates.</p></li><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> changes:
+
+ </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Derivations for other platforms are filtered out
+ (which can be overridden using
+ <code class="option">--system-filter</code>).</p></li><li class="listitem"><p><code class="option">--install</code> by default now
+ uninstall previous derivations with the same
+ name.</p></li><li class="listitem"><p><code class="option">--upgrade</code> allows upgrading to a
+ specific version.</p></li><li class="listitem"><p>New operation
+ <code class="option">--delete-generations</code> to remove profile
+ generations (necessary for effective garbage
+ collection).</p></li><li class="listitem"><p>Nicer output (sorted,
+ columnised).</p></li></ul></div><p>
+
+ </p></li><li class="listitem"><p>More sensible verbosity levels all around (builder
+ output is now shown always, unless <code class="option">-Q</code> is
+ given).</p></li><li class="listitem"><p>Nix expression language changes:
+
+ </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>New language construct: <code class="literal">with
+ <em class="replaceable"><code>E1</code></em>;
+ <em class="replaceable"><code>E2</code></em></code> brings all attributes
+ defined in the attribute set <em class="replaceable"><code>E1</code></em> in
+ scope in <em class="replaceable"><code>E2</code></em>.</p></li><li class="listitem"><p>Added a <code class="function">map</code>
+ function.</p></li><li class="listitem"><p>Various new operators (e.g., string
+ concatenation).</p></li></ul></div><p>
+
+ </p></li><li class="listitem"><p>Expression evaluation is much
+ faster.</p></li><li class="listitem"><p>An Emacs mode for editing Nix expressions (with
+ syntax highlighting and indentation) has been
+ added.</p></li><li class="listitem"><p>Many bug fixes.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ch-relnotes-0.5"></a>C.35. Release 0.5 and earlier</h2></div></div></div><p>Please refer to the Subversion commit log messages.</p></div></div></div></body></html>
\ No newline at end of file
diff --git a/doc/manual/manual.is-valid b/doc/manual/manual.is-valid
new file mode 100644
index 000000000..e69de29bb
diff --git a/doc/manual/manual.xmli b/doc/manual/manual.xmli
new file mode 100644
index 000000000..241eef2cc
--- /dev/null
+++ b/doc/manual/manual.xmli
@@ -0,0 +1,20139 @@
+<?xml version="1.0"?>
+<book xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0">
+
+ <info>
+ <title>Nix Package Manager Guide</title>
+ <subtitle>Version 3.0</subtitle>
+
+ <author>
+ <personname>
+ <firstname>Eelco</firstname>
+ <surname>Dolstra</surname>
+ </personname>
+ <contrib>Author</contrib>
+ </author>
+
+ <copyright>
+ <year>2004-2018</year>
+ <holder>Eelco Dolstra</holder>
+ </copyright>
+
+ </info>
+
+ <!--
+ <preface>
+ <title>Preface</title>
+ <para>This manual describes how to set up and use the Nix package
+ manager.</para>
+ </preface>
+ -->
+
+ <part xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="chap-introduction" xml:base="introduction/introduction.xml">
+
+<title>Introduction</title>
+
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-about-nix">
+
+<title>About Nix</title>
+
+<para>Nix is a <emphasis>purely functional package manager</emphasis>.
+This means that it treats packages like values in purely functional
+programming languages such as Haskell — they are built by functions
+that don’t have side-effects, and they never change after they have
+been built. Nix stores packages in the <emphasis>Nix
+store</emphasis>, usually the directory
+<filename>/nix/store</filename>, where each package has its own unique
+subdirectory such as
+
+<programlisting>
+/nix/store/b6gvzjyb2pg0kjfwrjmg1vfhh54ad73z-firefox-33.1/
+</programlisting>
+
+where <literal>b6gvzjyb2pg0…</literal> is a unique identifier for the
+package that captures all its dependencies (it’s a cryptographic hash
+of the package’s build dependency graph). This enables many powerful
+features.</para>
+
+
+<simplesect><title>Multiple versions</title>
+
+<para>You can have multiple versions or variants of a package
+installed at the same time. This is especially important when
+different applications have dependencies on different versions of the
+same package — it prevents the “DLL hell”. Because of the hashing
+scheme, different versions of a package end up in different paths in
+the Nix store, so they don’t interfere with each other.</para>
+
+<para>An important consequence is that operations like upgrading or
+uninstalling an application cannot break other applications, since
+these operations never “destructively” update or delete files that are
+used by other packages.</para>
+
+</simplesect>
+
+
+<simplesect><title>Complete dependencies</title>
+
+<para>Nix helps you make sure that package dependency specifications
+are complete. In general, when you’re making a package for a package
+management system like RPM, you have to specify for each package what
+its dependencies are, but there are no guarantees that this
+specification is complete. If you forget a dependency, then the
+package will build and work correctly on <emphasis>your</emphasis>
+machine if you have the dependency installed, but not on the end
+user's machine if it's not there.</para>
+
+<para>Since Nix on the other hand doesn’t install packages in “global”
+locations like <filename>/usr/bin</filename> but in package-specific
+directories, the risk of incomplete dependencies is greatly reduced.
+This is because tools such as compilers don’t search in per-packages
+directories such as
+<filename>/nix/store/5lbfaxb722zp…-openssl-0.9.8d/include</filename>,
+so if a package builds correctly on your system, this is because you
+specified the dependency explicitly. This takes care of the build-time
+dependencies.</para>
+
+<para>Once a package is built, runtime dependencies are found by
+scanning binaries for the hash parts of Nix store paths (such as
+<literal>r8vvq9kq…</literal>). This sounds risky, but it works
+extremely well.</para>
+
+</simplesect>
+
+
+<simplesect><title>Multi-user support</title>
+
+<para>Nix has multi-user support. This means that non-privileged
+users can securely install software. Each user can have a different
+<emphasis>profile</emphasis>, a set of packages in the Nix store that
+appear in the user’s <envar>PATH</envar>. If a user installs a
+package that another user has already installed previously, the
+package won’t be built or downloaded a second time. At the same time,
+it is not possible for one user to inject a Trojan horse into a
+package that might be used by another user.</para>
+
+</simplesect>
+
+
+<simplesect><title>Atomic upgrades and rollbacks</title>
+
+<para>Since package management operations never overwrite packages in
+the Nix store but just add new versions in different paths, they are
+<emphasis>atomic</emphasis>. So during a package upgrade, there is no
+time window in which the package has some files from the old version
+and some files from the new version — which would be bad because a
+program might well crash if it’s started during that period.</para>
+
+<para>And since packages aren’t overwritten, the old versions are still
+there after an upgrade. This means that you can <emphasis>roll
+back</emphasis> to the old version:</para>
+
+<screen>
+$ nix-env --upgrade <replaceable>some-packages</replaceable>
+$ nix-env --rollback
+</screen>
+
+</simplesect>
+
+
+<simplesect><title>Garbage collection</title>
+
+<para>When you uninstall a package like this…
+
+<screen>
+$ nix-env --uninstall firefox
+</screen>
+
+the package isn’t deleted from the system right away (after all, you
+might want to do a rollback, or it might be in the profiles of other
+users). Instead, unused packages can be deleted safely by running the
+<emphasis>garbage collector</emphasis>:
+
+<screen>
+$ nix-collect-garbage
+</screen>
+
+This deletes all packages that aren’t in use by any user profile or by
+a currently running program.</para>
+
+</simplesect>
+
+
+<simplesect><title>Functional package language</title>
+
+<para>Packages are built from <emphasis>Nix expressions</emphasis>,
+which is a simple functional language. A Nix expression describes
+everything that goes into a package build action (a “derivation”):
+other packages, sources, the build script, environment variables for
+the build script, etc. Nix tries very hard to ensure that Nix
+expressions are <emphasis>deterministic</emphasis>: building a Nix
+expression twice should yield the same result.</para>
+
+<para>Because it’s a functional language, it’s easy to support
+building variants of a package: turn the Nix expression into a
+function and call it any number of times with the appropriate
+arguments. Due to the hashing scheme, variants don’t conflict with
+each other in the Nix store.</para>
+
+</simplesect>
+
+
+<simplesect><title>Transparent source/binary deployment</title>
+
+<para>Nix expressions generally describe how to build a package from
+source, so an installation action like
+
+<screen>
+$ nix-env --install firefox
+</screen>
+
+<emphasis>could</emphasis> cause quite a bit of build activity, as not
+only Firefox but also all its dependencies (all the way up to the C
+library and the compiler) would have to built, at least if they are
+not already in the Nix store. This is a <emphasis>source deployment
+model</emphasis>. For most users, building from source is not very
+pleasant as it takes far too long. However, Nix can automatically
+skip building from source and instead use a <emphasis>binary
+cache</emphasis>, a web server that provides pre-built binaries. For
+instance, when asked to build
+<literal>/nix/store/b6gvzjyb2pg0…-firefox-33.1</literal> from source,
+Nix would first check if the file
+<uri>https://cache.nixos.org/b6gvzjyb2pg0….narinfo</uri> exists, and
+if so, fetch the pre-built binary referenced from there; otherwise, it
+would fall back to building from source.</para>
+
+</simplesect>
+
+
+<!--
+<simplesect><title>Binary patching</title>
+
+<para>In addition to downloading binaries automatically if they’re
+available, Nix can download binary deltas that patch an existing
+package in the Nix store into a new version. This speeds up
+upgrades.</para>
+
+</simplesect>
+-->
+
+
+<simplesect><title>Nix Packages collection</title>
+
+<para>We provide a large set of Nix expressions containing hundreds of
+existing Unix packages, the <emphasis>Nix Packages
+collection</emphasis> (Nixpkgs).</para>
+
+</simplesect>
+
+
+<simplesect><title>Managing build environments</title>
+
+<para>Nix is extremely useful for developers as it makes it easy to
+automatically set up the build environment for a package. Given a
+Nix expression that describes the dependencies of your package, the
+command <command>nix-shell</command> will build or download those
+dependencies if they’re not already in your Nix store, and then start
+a Bash shell in which all necessary environment variables (such as
+compiler search paths) are set.</para>
+
+<para>For example, the following command gets all dependencies of the
+Pan newsreader, as described by <link xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/networking/newsreaders/pan/default.nix">its
+Nix expression</link>:</para>
+
+<screen>
+$ nix-shell '<nixpkgs>' -A pan
+</screen>
+
+<para>You’re then dropped into a shell where you can edit, build and test
+the package:</para>
+
+<screen>
+[nix-shell]$ tar xf $src
+[nix-shell]$ cd pan-*
+[nix-shell]$ ./configure
+[nix-shell]$ make
+[nix-shell]$ ./pan/gui/pan
+</screen>
+
+<!--
+<para>Since Nix packages are reproducible and have complete dependency
+specifications, Nix makes an excellent basis for <a
+href="[%root%]hydra">a continuous build system</a>.</para>
+-->
+
+</simplesect>
+
+
+<simplesect><title>Portability</title>
+
+<para>Nix runs on Linux and macOS.</para>
+
+</simplesect>
+
+
+<simplesect><title>NixOS</title>
+
+<para>NixOS is a Linux distribution based on Nix. It uses Nix not
+just for package management but also to manage the system
+configuration (e.g., to build configuration files in
+<filename>/etc</filename>). This means, among other things, that it
+is easy to roll back the entire configuration of the system to an
+earlier state. Also, users can install software without root
+privileges. For more information and downloads, see the <link xlink:href="http://nixos.org/">NixOS homepage</link>.</para>
+
+</simplesect>
+
+
+<simplesect><title>License</title>
+
+<para>Nix is released under the terms of the <link xlink:href="http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html">GNU
+LGPLv2.1 or (at your option) any later version</link>.</para>
+
+</simplesect>
+
+
+</chapter>
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="chap-quick-start">
+
+<title>Quick Start</title>
+
+<para>This chapter is for impatient people who don't like reading
+documentation. For more in-depth information you are kindly referred
+to subsequent chapters.</para>
+
+<procedure>
+
+<step><para>Install single-user Nix by running the following:
+
+<screen>
+$ bash <(curl -L https://nixos.org/nix/install)
+</screen>
+
+This will install Nix in <filename>/nix</filename>. The install script
+will create <filename>/nix</filename> using <command>sudo</command>,
+so make sure you have sufficient rights. (For other installation
+methods, see <xref linkend="chap-installation"/>.)</para></step>
+
+<step><para>See what installable packages are currently available
+in the channel:
+
+<screen>
+$ nix-env -qa
+docbook-xml-4.3
+docbook-xml-4.5
+firefox-33.0.2
+hello-2.9
+libxslt-1.1.28
+<replaceable>...</replaceable></screen>
+
+</para></step>
+
+<step><para>Install some packages from the channel:
+
+<screen>
+$ nix-env -i hello</screen>
+
+This should download pre-built packages; it should not build them
+locally (if it does, something went wrong).</para></step>
+
+<step><para>Test that they work:
+
+<screen>
+$ which hello
+/home/eelco/.nix-profile/bin/hello
+$ hello
+Hello, world!
+</screen>
+
+</para></step>
+
+<step><para>Uninstall a package:
+
+<screen>
+$ nix-env -e hello</screen>
+
+</para></step>
+
+<step><para>You can also test a package without installing it:
+
+<screen>
+$ nix-shell -p hello
+</screen>
+
+This builds or downloads GNU Hello and its dependencies, then drops
+you into a Bash shell where the <command>hello</command> command is
+present, all without affecting your normal environment:
+
+<screen>
+[nix-shell:~]$ hello
+Hello, world!
+
+[nix-shell:~]$ exit
+
+$ hello
+hello: command not found
+</screen>
+
+</para></step>
+
+<step><para>To keep up-to-date with the channel, do:
+
+<screen>
+$ nix-channel --update nixpkgs
+$ nix-env -u '*'</screen>
+
+The latter command will upgrade each installed package for which there
+is a “newer” version (as determined by comparing the version
+numbers).</para></step>
+
+<step><para>If you're unhappy with the result of a
+<command>nix-env</command> action (e.g., an upgraded package turned
+out not to work properly), you can go back:
+
+<screen>
+$ nix-env --rollback</screen>
+
+</para></step>
+
+<step><para>You should periodically run the Nix garbage collector
+to get rid of unused packages, since uninstalls or upgrades don't
+actually delete them:
+
+<screen>
+$ nix-collect-garbage -d</screen>
+
+<!--
+The first command deletes old “generations” of your profile (making
+rollbacks impossible, but also making the packages in those old
+generations available for garbage collection), while the second
+command actually deletes them.-->
+
+</para></step>
+
+</procedure>
+
+</chapter>
+
+</part>
+ <part xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="chap-installation" xml:base="installation/installation.xml">
+
+<title>Installation</title>
+
+<partintro>
+<para>This section describes how to install and configure Nix for first-time use.</para>
+</partintro>
+
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-supported-platforms">
+
+<title>Supported Platforms</title>
+
+<para>Nix is currently supported on the following platforms:
+
+<itemizedlist>
+
+ <listitem><para>Linux (i686, x86_64, aarch64).</para></listitem>
+
+ <listitem><para>macOS (x86_64).</para></listitem>
+
+ <!--
+ <listitem><para>FreeBSD (only tested on Intel).</para></listitem>
+ -->
+
+ <!--
+ <listitem><para>Windows through <link
+ xlink:href="http://www.cygwin.com/">Cygwin</link>.</para>
+
+ <warning><para>On Cygwin, Nix <emphasis>must</emphasis> be installed
+ on an NTFS partition. It will not work correctly on a FAT
+ partition.</para></warning>
+
+ </listitem>
+ -->
+
+</itemizedlist>
+
+</para>
+
+</chapter>
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-installing-binary">
+
+<title>Installing a Binary Distribution</title>
+
+<para>
+ If you are using Linux or macOS versions up to 10.14 (Mojave), the
+ easiest way to install Nix is to run the following command:
+</para>
+
+<screen>
+ $ sh <(curl -L https://nixos.org/nix/install)
+</screen>
+
+<para>
+ If you're using macOS 10.15 (Catalina) or newer, consult
+ <link linkend="sect-macos-installation">the macOS installation instructions</link>
+ before installing.
+</para>
+
+<para>
+ As of Nix 2.1.0, the Nix installer will always default to creating a
+ single-user installation, however opting in to the multi-user
+ installation is highly recommended.
+ <!-- TODO: this explains *neither* why the default version is
+ single-user, nor why we'd recommend multi-user over the default.
+ True prospective users don't have much basis for evaluating this.
+ What's it to me? Who should pick which? Why? What if I pick wrong?
+ -->
+</para>
+
+<section xml:id="sect-single-user-installation">
+ <title>Single User Installation</title>
+
+ <para>
+ To explicitly select a single-user installation on your system:
+
+ <screen>
+ sh <(curl -L https://nixos.org/nix/install) --no-daemon
+</screen>
+ </para>
+
+<para>
+This will perform a single-user installation of Nix, meaning that
+<filename>/nix</filename> is owned by the invoking user. You should
+run this under your usual user account, <emphasis>not</emphasis> as
+root. The script will invoke <command>sudo</command> to create
+<filename>/nix</filename> if it doesn’t already exist. If you don’t
+have <command>sudo</command>, you should manually create
+<filename>/nix</filename> first as root, e.g.:
+
+<screen>
+$ mkdir /nix
+$ chown alice /nix
+</screen>
+
+The install script will modify the first writable file from amongst
+<filename>.bash_profile</filename>, <filename>.bash_login</filename>
+and <filename>.profile</filename> to source
+<filename>~/.nix-profile/etc/profile.d/nix.sh</filename>. You can set
+the <envar>NIX_INSTALLER_NO_MODIFY_PROFILE</envar> environment
+variable before executing the install script to disable this
+behaviour.
+</para>
+
+
+<para>You can uninstall Nix simply by running:
+
+<screen>
+$ rm -rf /nix
+</screen>
+
+</para>
+</section>
+
+<section xml:id="sect-multi-user-installation">
+ <title>Multi User Installation</title>
+ <para>
+ The multi-user Nix installation creates system users, and a system
+ service for the Nix daemon.
+ </para>
+
+ <itemizedlist>
+ <title>Supported Systems</title>
+
+ <listitem>
+ <para>Linux running systemd, with SELinux disabled</para>
+ </listitem>
+ <listitem><para>macOS</para></listitem>
+ </itemizedlist>
+
+ <para>
+ You can instruct the installer to perform a multi-user
+ installation on your system:
+ </para>
+
+ <screen>sh <(curl -L https://nixos.org/nix/install) --daemon</screen>
+
+ <para>
+ The multi-user installation of Nix will create build users between
+ the user IDs 30001 and 30032, and a group with the group ID 30000.
+
+ You should run this under your usual user account,
+ <emphasis>not</emphasis> as root. The script will invoke
+ <command>sudo</command> as needed.
+ </para>
+
+ <note><para>
+ If you need Nix to use a different group ID or user ID set, you
+ will have to download the tarball manually and <link linkend="sect-nix-install-binary-tarball">edit the install
+ script</link>.
+ </para></note>
+
+ <para>
+ The installer will modify <filename>/etc/bashrc</filename>, and
+ <filename>/etc/zshrc</filename> if they exist. The installer will
+ first back up these files with a
+ <literal>.backup-before-nix</literal> extension. The installer
+ will also create <filename>/etc/profile.d/nix.sh</filename>.
+ </para>
+
+ <para>You can uninstall Nix with the following commands:
+
+<screen>
+sudo rm -rf /etc/profile/nix.sh /etc/nix /nix ~root/.nix-profile ~root/.nix-defexpr ~root/.nix-channels ~/.nix-profile ~/.nix-defexpr ~/.nix-channels
+
+# If you are on Linux with systemd, you will need to run:
+sudo systemctl stop nix-daemon.socket
+sudo systemctl stop nix-daemon.service
+sudo systemctl disable nix-daemon.socket
+sudo systemctl disable nix-daemon.service
+sudo systemctl daemon-reload
+
+# If you are on macOS, you will need to run:
+sudo launchctl unload /Library/LaunchDaemons/org.nixos.nix-daemon.plist
+sudo rm /Library/LaunchDaemons/org.nixos.nix-daemon.plist
+</screen>
+
+ There may also be references to Nix in
+ <filename>/etc/profile</filename>,
+ <filename>/etc/bashrc</filename>, and
+ <filename>/etc/zshrc</filename> which you may remove.
+ </para>
+
+</section>
+
+<section xml:id="sect-macos-installation">
+ <title>macOS Installation</title>
+
+ <para>
+ Starting with macOS 10.15 (Catalina), the root filesystem is read-only.
+ This means <filename>/nix</filename> can no longer live on your system
+ volume, and that you'll need a workaround to install Nix.
+ </para>
+
+ <para>
+ The recommended approach, which creates an unencrypted APFS volume
+ for your Nix store and a "synthetic" empty directory to mount it
+ over at <filename>/nix</filename>, is least likely to impair Nix
+ or your system.
+ </para>
+
+ <note><para>
+ With all separate-volume approaches, it's possible something on
+ your system (particularly daemons/services and restored apps) may
+ need access to your Nix store before the volume is mounted. Adding
+ additional encryption makes this more likely.
+ </para></note>
+
+ <para>
+ If you're using a recent Mac with a
+ <link xlink:href="https://www.apple.com/euro/mac/shared/docs/Apple_T2_Security_Chip_Overview.pdf">T2 chip</link>,
+ your drive will still be encrypted at rest (in which case "unencrypted"
+ is a bit of a misnomer). To use this approach, just install Nix with:
+ </para>
+
+ <screen>$ sh <(curl -L https://nixos.org/nix/install) --darwin-use-unencrypted-nix-store-volume</screen>
+
+ <para>
+ If you don't like the sound of this, you'll want to weigh the
+ other approaches and tradeoffs detailed in this section.
+ </para>
+
+ <note>
+ <title>Eventual solutions?</title>
+ <para>
+ All of the known workarounds have drawbacks, but we hope
+ better solutions will be available in the future. Some that
+ we have our eye on are:
+ </para>
+ <orderedlist>
+ <listitem>
+ <para>
+ A true firmlink would enable the Nix store to live on the
+ primary data volume without the build problems caused by
+ the symlink approach. End users cannot currently
+ create true firmlinks.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ If the Nix store volume shared FileVault encryption
+ with the primary data volume (probably by using the same
+ volume group and role), FileVault encryption could be
+ easily supported by the installer without requiring
+ manual setup by each user.
+ </para>
+ </listitem>
+ </orderedlist>
+ </note>
+
+ <section xml:id="sect-macos-installation-change-store-prefix">
+ <title>Change the Nix store path prefix</title>
+ <para>
+ Changing the default prefix for the Nix store is a simple
+ approach which enables you to leave it on your root volume,
+ where it can take full advantage of FileVault encryption if
+ enabled. Unfortunately, this approach also opts your device out
+ of some benefits that are enabled by using the same prefix
+ across systems:
+
+ <itemizedlist>
+ <listitem>
+ <para>
+ Your system won't be able to take advantage of the binary
+ cache (unless someone is able to stand up and support
+ duplicate caching infrastructure), which means you'll
+ spend more time waiting for builds.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ It's harder to build and deploy packages to Linux systems.
+ </para>
+ </listitem>
+ <!-- TODO: may be more here -->
+ </itemizedlist>
+
+ <!-- TODO: Yes, but how?! -->
+
+ It would also possible (and often requested) to just apply this
+ change ecosystem-wide, but it's an intrusive process that has
+ side effects we want to avoid for now.
+ <!-- magnificent hand-wavy gesture -->
+ </para>
+ <para>
+ </para>
+ </section>
+
+ <section xml:id="sect-macos-installation-encrypted-volume">
+ <title>Use a separate encrypted volume</title>
+ <para>
+ If you like, you can also add encryption to the recommended
+ approach taken by the installer. You can do this by pre-creating
+ an encrypted volume before you run the installer--or you can
+ run the installer and encrypt the volume it creates later.
+ <!-- TODO: see later note about whether this needs both add-encryption and from-scratch directions -->
+ </para>
+ <para>
+ In either case, adding encryption to a second volume isn't quite
+ as simple as enabling FileVault for your boot volume. Before you
+ dive in, there are a few things to weigh:
+ </para>
+ <orderedlist>
+ <listitem>
+ <para>
+ The additional volume won't be encrypted with your existing
+ FileVault key, so you'll need another mechanism to decrypt
+ the volume.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ You can store the password in Keychain to automatically
+ decrypt the volume on boot--but it'll have to wait on Keychain
+ and may not mount before your GUI apps restore. If any of
+ your launchd agents or apps depend on Nix-installed software
+ (for example, if you use a Nix-installed login shell), the
+ restore may fail or break.
+ </para>
+ <para>
+ On a case-by-case basis, you may be able to work around this
+ problem by using <command>wait4path</command> to block
+ execution until your executable is available.
+ </para>
+ <para>
+ It's also possible to decrypt and mount the volume earlier
+ with a login hook--but this mechanism appears to be
+ deprecated and its future is unclear.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ You can hard-code the password in the clear, so that your
+ store volume can be decrypted before Keychain is available.
+ </para>
+ </listitem>
+ </orderedlist>
+ <para>
+ If you are comfortable navigating these tradeoffs, you can encrypt the volume with
+ something along the lines of:
+ <!-- TODO:
+ I don't know if this also needs from-scratch instructions?
+ can we just recommend use-the-installer-and-then-encrypt?
+ -->
+ </para>
+ <!--
+ TODO: it looks like this option can be encryptVolume|encrypt|enableFileVault
+
+ It may be more clear to use encryptVolume, here? FileVault seems
+ heavily associated with the boot-volume behavior; I worry
+ a little that it can mislead here, especially as it gets
+ copied around minus doc context...?
+ -->
+ <screen>alice$ diskutil apfs enableFileVault /nix -user disk</screen>
+
+ <!-- TODO: and then go into detail on the mount/decrypt approaches? -->
+ </section>
+
+ <section xml:id="sect-macos-installation-symlink">
+ <!--
+ Maybe a good razor is: if we'd hate having to support someone who
+ installed Nix this way, it shouldn't even be detailed?
+ -->
+ <title>Symlink the Nix store to a custom location</title>
+ <para>
+ Another simple approach is using <filename>/etc/synthetic.conf</filename>
+ to symlink the Nix store to the data volume. This option also
+ enables your store to share any configured FileVault encryption.
+ Unfortunately, builds that resolve the symlink may leak the
+ canonical path or even fail.
+ </para>
+ <para>
+ Because of these downsides, we can't recommend this approach.
+ </para>
+ <!-- Leaving out instructions for this one. -->
+ </section>
+
+ <section xml:id="sect-macos-installation-recommended-notes">
+ <title>Notes on the recommended approach</title>
+ <para>
+ This section goes into a little more detail on the recommended
+ approach. You don't need to understand it to run the installer,
+ but it can serve as a helpful reference if you run into trouble.
+ </para>
+ <orderedlist>
+ <listitem>
+ <para>
+ In order to compose user-writable locations into the new
+ read-only system root, Apple introduced a new concept called
+ <literal>firmlinks</literal>, which it describes as a
+ "bi-directional wormhole" between two filesystems. You can
+ see the current firmlinks in <filename>/usr/share/firmlinks</filename>.
+ Unfortunately, firmlinks aren't (currently?) user-configurable.
+ </para>
+
+ <para>
+ For special cases like NFS mount points or package manager roots,
+ <link xlink:href="https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man5/synthetic.conf.5.html">synthetic.conf(5)</link>
+ supports limited user-controlled file-creation (of symlinks,
+ and synthetic empty directories) at <filename>/</filename>.
+ To create a synthetic empty directory for mounting at <filename>/nix</filename>,
+ add the following line to <filename>/etc/synthetic.conf</filename>
+ (create it if necessary):
+ </para>
+
+ <screen>nix</screen>
+ </listitem>
+
+ <listitem>
+ <para>
+ This configuration is applied at boot time, but you can use
+ <command>apfs.util</command> to trigger creation (not deletion)
+ of new entries without a reboot:
+ </para>
+
+ <screen>alice$ /System/Library/Filesystems/apfs.fs/Contents/Resources/apfs.util -B</screen>
+ </listitem>
+
+ <listitem>
+ <para>
+ Create the new APFS volume with diskutil:
+ </para>
+
+ <screen>alice$ sudo diskutil apfs addVolume diskX APFS 'Nix Store' -mountpoint /nix</screen>
+ </listitem>
+
+ <listitem>
+ <para>
+ Using <command>vifs</command>, add the new mount to
+ <filename>/etc/fstab</filename>. If it doesn't already have
+ other entries, it should look something like:
+ </para>
+
+<screen>
+#
+# Warning - this file should only be modified with vifs(8)
+#
+# Failure to do so is unsupported and may be destructive.
+#
+LABEL=Nix\040Store /nix apfs rw,nobrowse
+</screen>
+
+ <para>
+ The nobrowse setting will keep Spotlight from indexing this
+ volume, and keep it from showing up on your desktop.
+ </para>
+ </listitem>
+ </orderedlist>
+ </section>
+
+</section>
+
+<section xml:id="sect-nix-install-pinned-version-url">
+ <title>Installing a pinned Nix version from a URL</title>
+
+ <para>
+ NixOS.org hosts version-specific installation URLs for all Nix
+ versions since 1.11.16, at
+ <literal>https://releases.nixos.org/nix/nix-<replaceable>version</replaceable>/install</literal>.
+ </para>
+
+ <para>
+ These install scripts can be used the same as the main
+ NixOS.org installation script:
+
+ <screen>
+ sh <(curl -L https://nixos.org/nix/install)
+</screen>
+ </para>
+
+ <para>
+ In the same directory of the install script are sha256 sums, and
+ gpg signature files.
+ </para>
+</section>
+
+<section xml:id="sect-nix-install-binary-tarball">
+ <title>Installing from a binary tarball</title>
+
+ <para>
+ You can also download a binary tarball that contains Nix and all
+ its dependencies. (This is what the install script at
+ <uri>https://nixos.org/nix/install</uri> does automatically.) You
+ should unpack it somewhere (e.g. in <filename>/tmp</filename>),
+ and then run the script named <command>install</command> inside
+ the binary tarball:
+
+
+<screen>
+alice$ cd /tmp
+alice$ tar xfj nix-1.8-x86_64-darwin.tar.bz2
+alice$ cd nix-1.8-x86_64-darwin
+alice$ ./install
+</screen>
+ </para>
+
+ <para>
+ If you need to edit the multi-user installation script to use
+ different group ID or a different user ID range, modify the
+ variables set in the file named
+ <filename>install-multi-user</filename>.
+ </para>
+</section>
+</chapter>
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-installing-source">
+
+<title>Installing Nix from Source</title>
+
+<para>If no binary package is available, you can download and compile
+a source distribution.</para>
+
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-prerequisites-source">
+
+<title>Prerequisites</title>
+
+<itemizedlist>
+
+ <listitem><para>GNU Autoconf
+ (<link xlink:href="https://www.gnu.org/software/autoconf/"/>)
+ and the autoconf-archive macro collection
+ (<link xlink:href="https://www.gnu.org/software/autoconf-archive/"/>).
+ These are only needed to run the bootstrap script, and are not necessary
+ if your source distribution came with a pre-built
+ <literal>./configure</literal> script.</para></listitem>
+
+ <listitem><para>GNU Make.</para></listitem>
+
+ <listitem><para>Bash Shell. The <literal>./configure</literal> script
+ relies on bashisms, so Bash is required.</para></listitem>
+
+ <listitem><para>A version of GCC or Clang that supports C++17.</para></listitem>
+
+ <listitem><para><command>pkg-config</command> to locate
+ dependencies. If your distribution does not provide it, you can get
+ it from <link xlink:href="http://www.freedesktop.org/wiki/Software/pkg-config"/>.</para></listitem>
+
+ <listitem><para>The OpenSSL library to calculate cryptographic hashes.
+ If your distribution does not provide it, you can get it from <link xlink:href="https://www.openssl.org"/>.</para></listitem>
+
+ <listitem><para>The <literal>libbrotlienc</literal> and
+ <literal>libbrotlidec</literal> libraries to provide implementation
+ of the Brotli compression algorithm. They are available for download
+ from the official repository <link xlink:href="https://github.com/google/brotli"/>.</para></listitem>
+
+ <listitem><para>The bzip2 compressor program and the
+ <literal>libbz2</literal> library. Thus you must have bzip2
+ installed, including development headers and libraries. If your
+ distribution does not provide these, you can obtain bzip2 from <link xlink:href="https://web.archive.org/web/20180624184756/http://www.bzip.org/"/>.</para></listitem>
+
+ <listitem><para><literal>liblzma</literal>, which is provided by
+ XZ Utils. If your distribution does not provide this, you can
+ get it from <link xlink:href="https://tukaani.org/xz/"/>.</para></listitem>
+
+ <listitem><para>cURL and its library. If your distribution does not
+ provide it, you can get it from <link xlink:href="https://curl.haxx.se/"/>.</para></listitem>
+
+ <listitem><para>The SQLite embedded database library, version 3.6.19
+ or higher. If your distribution does not provide it, please install
+ it from <link xlink:href="http://www.sqlite.org/"/>.</para></listitem>
+
+ <listitem><para>The <link xlink:href="http://www.hboehm.info/gc/">Boehm
+ garbage collector</link> to reduce the evaluator’s memory
+ consumption (optional). To enable it, install
+ <literal>pkgconfig</literal> and the Boehm garbage collector, and
+ pass the flag <option>--enable-gc</option> to
+ <command>configure</command>.</para></listitem>
+
+ <listitem><para>The <literal>boost</literal> library of version
+ 1.66.0 or higher. It can be obtained from the official web site
+ <link xlink:href="https://www.boost.org/"/>.</para></listitem>
+
+ <listitem><para>The <literal>editline</literal> library of version
+ 1.14.0 or higher. It can be obtained from the its repository
+ <link xlink:href="https://github.com/troglobit/editline"/>.</para></listitem>
+
+ <listitem><para>The <command>xmllint</command> and
+ <command>xsltproc</command> programs to build this manual and the
+ man-pages. These are part of the <literal>libxml2</literal> and
+ <literal>libxslt</literal> packages, respectively. You also need
+ the <link xlink:href="http://docbook.sourceforge.net/projects/xsl/">DocBook
+ XSL stylesheets</link> and optionally the <link xlink:href="http://www.docbook.org/schemas/5x"> DocBook 5.0 RELAX NG
+ schemas</link>. Note that these are only required if you modify the
+ manual sources or when you are building from the Git
+ repository.</para></listitem>
+
+ <listitem><para>Recent versions of Bison and Flex to build the
+ parser. (This is because Nix needs GLR support in Bison and
+ reentrancy support in Flex.) For Bison, you need version 2.6, which
+ can be obtained from the <link xlink:href="ftp://alpha.gnu.org/pub/gnu/bison">GNU FTP
+ server</link>. For Flex, you need version 2.5.35, which is
+ available on <link xlink:href="http://lex.sourceforge.net/">SourceForge</link>.
+ Slightly older versions may also work, but ancient versions like the
+ ubiquitous 2.5.4a won't. Note that these are only required if you
+ modify the parser or when you are building from the Git
+ repository.</para></listitem>
+
+ <listitem><para>The <literal>libseccomp</literal> is used to provide
+ syscall filtering on Linux. This is an optional dependency and can
+ be disabled passing a <option>--disable-seccomp-sandboxing</option>
+ option to the <command>configure</command> script (Not recommended
+ unless your system doesn't support
+ <literal>libseccomp</literal>). To get the library, visit <link xlink:href="https://github.com/seccomp/libseccomp"/>.</para></listitem>
+
+</itemizedlist>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-obtaining-source">
+
+<title>Obtaining a Source Distribution</title>
+
+<para>The source tarball of the most recent stable release can be
+downloaded from the <link xlink:href="http://nixos.org/nix/download.html">Nix homepage</link>.
+You can also grab the <link xlink:href="http://hydra.nixos.org/job/nix/master/release/latest-finished#tabs-constituents">most
+recent development release</link>.</para>
+
+<para>Alternatively, the most recent sources of Nix can be obtained
+from its <link xlink:href="https://github.com/NixOS/nix">Git
+repository</link>. For example, the following command will check out
+the latest revision into a directory called
+<filename>nix</filename>:</para>
+
+<screen>
+$ git clone https://github.com/NixOS/nix</screen>
+
+<para>Likewise, specific releases can be obtained from the <link xlink:href="https://github.com/NixOS/nix/tags">tags</link> of the
+repository.</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-building-source">
+
+<title>Building Nix from Source</title>
+
+<para>After unpacking or checking out the Nix sources, issue the
+following commands:
+
+<screen>
+$ ./configure <replaceable>options...</replaceable>
+$ make
+$ make install</screen>
+
+Nix requires GNU Make so you may need to invoke
+<command>gmake</command> instead.</para>
+
+<para>When building from the Git repository, these should be preceded
+by the command:
+
+<screen>
+$ ./bootstrap.sh</screen>
+
+</para>
+
+<para>The installation path can be specified by passing the
+<option>--prefix=<replaceable>prefix</replaceable></option> to
+<command>configure</command>. The default installation directory is
+<filename>/usr/local</filename>. You can change this to any location
+you like. You must have write permission to the
+<replaceable>prefix</replaceable> path.</para>
+
+<para>Nix keeps its <emphasis>store</emphasis> (the place where
+packages are stored) in <filename>/nix/store</filename> by default.
+This can be changed using
+<option>--with-store-dir=<replaceable>path</replaceable></option>.</para>
+
+<warning><para>It is best <emphasis>not</emphasis> to change the Nix
+store from its default, since doing so makes it impossible to use
+pre-built binaries from the standard Nixpkgs channels — that is, all
+packages will need to be built from source.</para></warning>
+
+<para>Nix keeps state (such as its database and log files) in
+<filename>/nix/var</filename> by default. This can be changed using
+<option>--localstatedir=<replaceable>path</replaceable></option>.</para>
+
+</section>
+
+</chapter>
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-nix-security">
+
+<title>Security</title>
+
+<para>Nix has two basic security models. First, it can be used in
+“single-user mode”, which is similar to what most other package
+management tools do: there is a single user (typically <systemitem class="username">root</systemitem>) who performs all package
+management operations. All other users can then use the installed
+packages, but they cannot perform package management operations
+themselves.</para>
+
+<para>Alternatively, you can configure Nix in “multi-user mode”. In
+this model, all users can perform package management operations — for
+instance, every user can install software without requiring root
+privileges. Nix ensures that this is secure. For instance, it’s not
+possible for one user to overwrite a package used by another user with
+a Trojan horse.</para>
+
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-single-user">
+
+<title>Single-User Mode</title>
+
+<para>In single-user mode, all Nix operations that access the database
+in <filename><replaceable>prefix</replaceable>/var/nix/db</filename>
+or modify the Nix store in
+<filename><replaceable>prefix</replaceable>/store</filename> must be
+performed under the user ID that owns those directories. This is
+typically <systemitem class="username">root</systemitem>. (If you
+install from RPM packages, that’s in fact the default ownership.)
+However, on single-user machines, it is often convenient to
+<command>chown</command> those directories to your normal user account
+so that you don’t have to <command>su</command> to <systemitem class="username">root</systemitem> all the time.</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-multi-user">
+
+<title>Multi-User Mode</title>
+
+<para>To allow a Nix store to be shared safely among multiple users,
+it is important that users are not able to run builders that modify
+the Nix store or database in arbitrary ways, or that interfere with
+builds started by other users. If they could do so, they could
+install a Trojan horse in some package and compromise the accounts of
+other users.</para>
+
+<para>To prevent this, the Nix store and database are owned by some
+privileged user (usually <literal>root</literal>) and builders are
+executed under special user accounts (usually named
+<literal>nixbld1</literal>, <literal>nixbld2</literal>, etc.). When a
+unprivileged user runs a Nix command, actions that operate on the Nix
+store (such as builds) are forwarded to a <emphasis>Nix
+daemon</emphasis> running under the owner of the Nix store/database
+that performs the operation.</para>
+
+<note><para>Multi-user mode has one important limitation: only
+<systemitem class="username">root</systemitem> and a set of trusted
+users specified in <filename>nix.conf</filename> can specify arbitrary
+binary caches. So while unprivileged users may install packages from
+arbitrary Nix expressions, they may not get pre-built
+binaries.</para></note>
+
+
+<simplesect>
+
+<title>Setting up the build users</title>
+
+<para>The <emphasis>build users</emphasis> are the special UIDs under
+which builds are performed. They should all be members of the
+<emphasis>build users group</emphasis> <literal>nixbld</literal>.
+This group should have no other members. The build users should not
+be members of any other group. On Linux, you can create the group and
+users as follows:
+
+<screen>
+$ groupadd -r nixbld
+$ for n in $(seq 1 10); do useradd -c "Nix build user $n" \
+ -d /var/empty -g nixbld -G nixbld -M -N -r -s "$(which nologin)" \
+ nixbld$n; done
+</screen>
+
+This creates 10 build users. There can never be more concurrent builds
+than the number of build users, so you may want to increase this if
+you expect to do many builds at the same time.</para>
+
+</simplesect>
+
+
+<simplesect>
+
+<title>Running the daemon</title>
+
+<para>The <link linkend="sec-nix-daemon">Nix daemon</link> should be
+started as follows (as <literal>root</literal>):
+
+<screen>
+$ nix-daemon</screen>
+
+You’ll want to put that line somewhere in your system’s boot
+scripts.</para>
+
+<para>To let unprivileged users use the daemon, they should set the
+<link linkend="envar-remote"><envar>NIX_REMOTE</envar> environment
+variable</link> to <literal>daemon</literal>. So you should put a
+line like
+
+<programlisting>
+export NIX_REMOTE=daemon</programlisting>
+
+into the users’ login scripts.</para>
+
+</simplesect>
+
+
+<simplesect>
+
+<title>Restricting access</title>
+
+<para>To limit which users can perform Nix operations, you can use the
+permissions on the directory
+<filename>/nix/var/nix/daemon-socket</filename>. For instance, if you
+want to restrict the use of Nix to the members of a group called
+<literal>nix-users</literal>, do
+
+<screen>
+$ chgrp nix-users /nix/var/nix/daemon-socket
+$ chmod ug=rwx,o= /nix/var/nix/daemon-socket
+</screen>
+
+This way, users who are not in the <literal>nix-users</literal> group
+cannot connect to the Unix domain socket
+<filename>/nix/var/nix/daemon-socket/socket</filename>, so they cannot
+perform Nix operations.</para>
+
+</simplesect>
+
+
+</section>
+
+</chapter>
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-env-variables">
+
+<title>Environment Variables</title>
+
+<para>To use Nix, some environment variables should be set. In
+particular, <envar>PATH</envar> should contain the directories
+<filename><replaceable>prefix</replaceable>/bin</filename> and
+<filename>~/.nix-profile/bin</filename>. The first directory contains
+the Nix tools themselves, while <filename>~/.nix-profile</filename> is
+a symbolic link to the current <emphasis>user environment</emphasis>
+(an automatically generated package consisting of symlinks to
+installed packages). The simplest way to set the required environment
+variables is to include the file
+<filename><replaceable>prefix</replaceable>/etc/profile.d/nix.sh</filename>
+in your <filename>~/.profile</filename> (or similar), like this:</para>
+
+<screen>
+source <replaceable>prefix</replaceable>/etc/profile.d/nix.sh</screen>
+
+<section xml:id="sec-nix-ssl-cert-file">
+
+<title><envar>NIX_SSL_CERT_FILE</envar></title>
+
+<para>If you need to specify a custom certificate bundle to account
+for an HTTPS-intercepting man in the middle proxy, you must specify
+the path to the certificate bundle in the environment variable
+<envar>NIX_SSL_CERT_FILE</envar>.</para>
+
+
+<para>If you don't specify a <envar>NIX_SSL_CERT_FILE</envar>
+manually, Nix will install and use its own certificate
+bundle.</para>
+
+<procedure>
+ <step><para>Set the environment variable and install Nix</para>
+ <screen>
+$ export NIX_SSL_CERT_FILE=/etc/ssl/my-certificate-bundle.crt
+$ sh <(curl -L https://nixos.org/nix/install)
+</screen></step>
+
+ <step><para>In the shell profile and rc files (for example,
+ <filename>/etc/bashrc</filename>, <filename>/etc/zshrc</filename>),
+ add the following line:</para>
+<programlisting>
+export NIX_SSL_CERT_FILE=/etc/ssl/my-certificate-bundle.crt
+</programlisting>
+</step>
+</procedure>
+
+<note><para>You must not add the export and then do the install, as
+the Nix installer will detect the presense of Nix configuration, and
+abort.</para></note>
+
+<section xml:id="sec-nix-ssl-cert-file-with-nix-daemon-and-macos">
+<title><envar>NIX_SSL_CERT_FILE</envar> with macOS and the Nix daemon</title>
+
+<para>On macOS you must specify the environment variable for the Nix
+daemon service, then restart it:</para>
+
+<screen>
+$ sudo launchctl setenv NIX_SSL_CERT_FILE /etc/ssl/my-certificate-bundle.crt
+$ sudo launchctl kickstart -k system/org.nixos.nix-daemon
+</screen>
+</section>
+
+<section xml:id="sec-installer-proxy-settings">
+
+<title>Proxy Environment Variables</title>
+
+<para>The Nix installer has special handling for these proxy-related
+environment variables:
+<varname>http_proxy</varname>, <varname>https_proxy</varname>,
+<varname>ftp_proxy</varname>, <varname>no_proxy</varname>,
+<varname>HTTP_PROXY</varname>, <varname>HTTPS_PROXY</varname>,
+<varname>FTP_PROXY</varname>, <varname>NO_PROXY</varname>.
+</para>
+<para>If any of these variables are set when running the Nix installer,
+then the installer will create an override file at
+<filename>/etc/systemd/system/nix-daemon.service.d/override.conf</filename>
+so <command>nix-daemon</command> will use them.
+</para>
+</section>
+
+</section>
+</chapter>
+
+<!-- TODO: should be updated
+<section><title>Upgrading Nix through Nix</title>
+
+<para>You can install the latest stable version of Nix through Nix
+itself by subscribing to the channel <link
+xlink:href="http://nixos.org/releases/nix/channels/nix-stable" />,
+or the latest unstable version by subscribing to the channel <link
+xlink:href="http://nixos.org/releases/nix/channels/nix-unstable" />.
+You can also do a <link linkend="sec-one-click">one-click
+installation</link> by clicking on the package links at <link
+xlink:href="http://nixos.org/releases/full-index-nix.html" />.</para>
+
+</section>
+-->
+
+</part>
+ <chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-upgrading-nix" xml:base="installation/upgrading.xml">
+
+ <title>Upgrading Nix</title>
+
+ <para>
+ Multi-user Nix users on macOS can upgrade Nix by running:
+ <command>sudo -i sh -c 'nix-channel --update &&
+ nix-env -iA nixpkgs.nix &&
+ launchctl remove org.nixos.nix-daemon &&
+ launchctl load /Library/LaunchDaemons/org.nixos.nix-daemon.plist'</command>
+ </para>
+
+
+ <para>
+ Single-user installations of Nix should run this:
+ <command>nix-channel --update; nix-env -iA nixpkgs.nix nixpkgs.cacert</command>
+ </para>
+
+ <para>
+ Multi-user Nix users on Linux should run this with sudo:
+ <command>nix-channel --update; nix-env -iA nixpkgs.nix nixpkgs.cacert; systemctl daemon-reload; systemctl restart nix-daemon</command>
+ </para>
+</chapter>
+ <part xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="chap-package-management" xml:base="packages/package-management.xml">
+
+<title>Package Management</title>
+
+<partintro>
+<para>This chapter discusses how to do package management with Nix,
+i.e., how to obtain, install, upgrade, and erase packages. This is
+the “user’s” perspective of the Nix system — people
+who want to <emphasis>create</emphasis> packages should consult
+<xref linkend="chap-writing-nix-expressions"/>.</para>
+</partintro>
+
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-basic-package-mgmt">
+
+<title>Basic Package Management</title>
+
+<para>The main command for package management is <link linkend="sec-nix-env"><command>nix-env</command></link>. You can use
+it to install, upgrade, and erase packages, and to query what
+packages are installed or are available for installation.</para>
+
+<para>In Nix, different users can have different “views”
+on the set of installed applications. That is, there might be lots of
+applications present on the system (possibly in many different
+versions), but users can have a specific selection of those active —
+where “active” just means that it appears in a directory
+in the user’s <envar>PATH</envar>. Such a view on the set of
+installed applications is called a <emphasis>user
+environment</emphasis>, which is just a directory tree consisting of
+symlinks to the files of the active applications. </para>
+
+<para>Components are installed from a set of <emphasis>Nix
+expressions</emphasis> that tell Nix how to build those packages,
+including, if necessary, their dependencies. There is a collection of
+Nix expressions called the Nixpkgs package collection that contains
+packages ranging from basic development stuff such as GCC and Glibc,
+to end-user applications like Mozilla Firefox. (Nix is however not
+tied to the Nixpkgs package collection; you could write your own Nix
+expressions based on Nixpkgs, or completely new ones.)</para>
+
+<para>You can manually download the latest version of Nixpkgs from
+<link xlink:href="http://nixos.org/nixpkgs/download.html"/>. However,
+it’s much more convenient to use the Nixpkgs
+<emphasis>channel</emphasis>, since it makes it easy to stay up to
+date with new versions of Nixpkgs. (Channels are described in more
+detail in <xref linkend="sec-channels"/>.) Nixpkgs is automatically
+added to your list of “subscribed” channels when you install
+Nix. If this is not the case for some reason, you can add it as
+follows:
+
+<screen>
+$ nix-channel --add https://nixos.org/channels/nixpkgs-unstable
+$ nix-channel --update
+</screen>
+
+</para>
+
+<note><para>On NixOS, you’re automatically subscribed to a NixOS
+channel corresponding to your NixOS major release
+(e.g. <uri>http://nixos.org/channels/nixos-14.12</uri>). A NixOS
+channel is identical to the Nixpkgs channel, except that it contains
+only Linux binaries and is updated only if a set of regression tests
+succeed.</para></note>
+
+<para>You can view the set of available packages in Nixpkgs:
+
+<screen>
+$ nix-env -qa
+aterm-2.2
+bash-3.0
+binutils-2.15
+bison-1.875d
+blackdown-1.4.2
+bzip2-1.0.2
+…</screen>
+
+The flag <option>-q</option> specifies a query operation, and
+<option>-a</option> means that you want to show the “available” (i.e.,
+installable) packages, as opposed to the installed packages. If you
+downloaded Nixpkgs yourself, or if you checked it out from GitHub,
+then you need to pass the path to your Nixpkgs tree using the
+<option>-f</option> flag:
+
+<screen>
+$ nix-env -qaf <replaceable>/path/to/nixpkgs</replaceable>
+</screen>
+
+where <replaceable>/path/to/nixpkgs</replaceable> is where you’ve
+unpacked or checked out Nixpkgs.</para>
+
+<para>You can select specific packages by name:
+
+<screen>
+$ nix-env -qa firefox
+firefox-34.0.5
+firefox-with-plugins-34.0.5
+</screen>
+
+and using regular expressions:
+
+<screen>
+$ nix-env -qa 'firefox.*'
+</screen>
+
+</para>
+
+<para>It is also possible to see the <emphasis>status</emphasis> of
+available packages, i.e., whether they are installed into the user
+environment and/or present in the system:
+
+<screen>
+$ nix-env -qas
+…
+-PS bash-3.0
+--S binutils-2.15
+IPS bison-1.875d
+…</screen>
+
+The first character (<literal>I</literal>) indicates whether the
+package is installed in your current user environment. The second
+(<literal>P</literal>) indicates whether it is present on your system
+(in which case installing it into your user environment would be a
+very quick operation). The last one (<literal>S</literal>) indicates
+whether there is a so-called <emphasis>substitute</emphasis> for the
+package, which is Nix’s mechanism for doing binary deployment. It
+just means that Nix knows that it can fetch a pre-built package from
+somewhere (typically a network server) instead of building it
+locally.</para>
+
+<para>You can install a package using <literal>nix-env -i</literal>.
+For instance,
+
+<screen>
+$ nix-env -i subversion</screen>
+
+will install the package called <literal>subversion</literal> (which
+is, of course, the <link xlink:href="http://subversion.tigris.org/">Subversion version
+management system</link>).</para>
+
+<note><para>When you ask Nix to install a package, it will first try
+to get it in pre-compiled form from a <emphasis>binary
+cache</emphasis>. By default, Nix will use the binary cache
+<uri>https://cache.nixos.org</uri>; it contains binaries for most
+packages in Nixpkgs. Only if no binary is available in the binary
+cache, Nix will build the package from source. So if <literal>nix-env
+-i subversion</literal> results in Nix building stuff from source,
+then either the package is not built for your platform by the Nixpkgs
+build servers, or your version of Nixpkgs is too old or too new. For
+instance, if you have a very recent checkout of Nixpkgs, then the
+Nixpkgs build servers may not have had a chance to build everything
+and upload the resulting binaries to
+<uri>https://cache.nixos.org</uri>. The Nixpkgs channel is only
+updated after all binaries have been uploaded to the cache, so if you
+stick to the Nixpkgs channel (rather than using a Git checkout of the
+Nixpkgs tree), you will get binaries for most packages.</para></note>
+
+<para>Naturally, packages can also be uninstalled:
+
+<screen>
+$ nix-env -e subversion</screen>
+
+</para>
+
+<para>Upgrading to a new version is just as easy. If you have a new
+release of Nix Packages, you can do:
+
+<screen>
+$ nix-env -u subversion</screen>
+
+This will <emphasis>only</emphasis> upgrade Subversion if there is a
+“newer” version in the new set of Nix expressions, as
+defined by some pretty arbitrary rules regarding ordering of version
+numbers (which generally do what you’d expect of them). To just
+unconditionally replace Subversion with whatever version is in the Nix
+expressions, use <parameter>-i</parameter> instead of
+<parameter>-u</parameter>; <parameter>-i</parameter> will remove
+whatever version is already installed.</para>
+
+<para>You can also upgrade all packages for which there are newer
+versions:
+
+<screen>
+$ nix-env -u</screen>
+
+</para>
+
+<para>Sometimes it’s useful to be able to ask what
+<command>nix-env</command> would do, without actually doing it. For
+instance, to find out what packages would be upgraded by
+<literal>nix-env -u</literal>, you can do
+
+<screen>
+$ nix-env -u --dry-run
+(dry run; not doing anything)
+upgrading `libxslt-1.1.0' to `libxslt-1.1.10'
+upgrading `graphviz-1.10' to `graphviz-1.12'
+upgrading `coreutils-5.0' to `coreutils-5.2.1'</screen>
+
+</para>
+
+</chapter>
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-profiles">
+
+<title>Profiles</title>
+
+<para>Profiles and user environments are Nix’s mechanism for
+implementing the ability to allow different users to have different
+configurations, and to do atomic upgrades and rollbacks. To
+understand how they work, it’s useful to know a bit about how Nix
+works. In Nix, packages are stored in unique locations in the
+<emphasis>Nix store</emphasis> (typically,
+<filename>/nix/store</filename>). For instance, a particular version
+of the Subversion package might be stored in a directory
+<filename>/nix/store/dpmvp969yhdqs7lm2r1a3gng7pyq6vy4-subversion-1.1.3/</filename>,
+while another version might be stored in
+<filename>/nix/store/5mq2jcn36ldlmh93yj1n8s9c95pj7c5s-subversion-1.1.2</filename>.
+The long strings prefixed to the directory names are cryptographic
+hashes<footnote><para>160-bit truncations of SHA-256 hashes encoded in
+a base-32 notation, to be precise.</para></footnote> of
+<emphasis>all</emphasis> inputs involved in building the package —
+sources, dependencies, compiler flags, and so on. So if two
+packages differ in any way, they end up in different locations in
+the file system, so they don’t interfere with each other. <xref linkend="fig-user-environments"/> shows a part of a typical Nix
+store.</para>
+
+<figure xml:id="fig-user-environments"><title>User environments</title>
+ <mediaobject>
+ <imageobject>
+ <imagedata fileref="../figures/user-environments.png" format="PNG"/>
+ </imageobject>
+ </mediaobject>
+</figure>
+
+<para>Of course, you wouldn’t want to type
+
+<screen>
+$ /nix/store/dpmvp969yhdq...-subversion-1.1.3/bin/svn</screen>
+
+every time you want to run Subversion. Of course we could set up the
+<envar>PATH</envar> environment variable to include the
+<filename>bin</filename> directory of every package we want to use,
+but this is not very convenient since changing <envar>PATH</envar>
+doesn’t take effect for already existing processes. The solution Nix
+uses is to create directory trees of symlinks to
+<emphasis>activated</emphasis> packages. These are called
+<emphasis>user environments</emphasis> and they are packages
+themselves (though automatically generated by
+<command>nix-env</command>), so they too reside in the Nix store. For
+instance, in <xref linkend="fig-user-environments"/> the user
+environment <filename>/nix/store/0c1p5z4kda11...-user-env</filename>
+contains a symlink to just Subversion 1.1.2 (arrows in the figure
+indicate symlinks). This would be what we would obtain if we had done
+
+<screen>
+$ nix-env -i subversion</screen>
+
+on a set of Nix expressions that contained Subversion 1.1.2.</para>
+
+<para>This doesn’t in itself solve the problem, of course; you
+wouldn’t want to type
+<filename>/nix/store/0c1p5z4kda11...-user-env/bin/svn</filename>
+either. That’s why there are symlinks outside of the store that point
+to the user environments in the store; for instance, the symlinks
+<filename>default-42-link</filename> and
+<filename>default-43-link</filename> in the example. These are called
+<emphasis>generations</emphasis> since every time you perform a
+<command>nix-env</command> operation, a new user environment is
+generated based on the current one. For instance, generation 43 was
+created from generation 42 when we did
+
+<screen>
+$ nix-env -i subversion firefox</screen>
+
+on a set of Nix expressions that contained Firefox and a new version
+of Subversion.</para>
+
+<para>Generations are grouped together into
+<emphasis>profiles</emphasis> so that different users don’t interfere
+with each other if they don’t want to. For example:
+
+<screen>
+$ ls -l /nix/var/nix/profiles/
+...
+lrwxrwxrwx 1 eelco ... default-42-link -> /nix/store/0c1p5z4kda11...-user-env
+lrwxrwxrwx 1 eelco ... default-43-link -> /nix/store/3aw2pdyx2jfc...-user-env
+lrwxrwxrwx 1 eelco ... default -> default-43-link</screen>
+
+This shows a profile called <filename>default</filename>. The file
+<filename>default</filename> itself is actually a symlink that points
+to the current generation. When we do a <command>nix-env</command>
+operation, a new user environment and generation link are created
+based on the current one, and finally the <filename>default</filename>
+symlink is made to point at the new generation. This last step is
+atomic on Unix, which explains how we can do atomic upgrades. (Note
+that the building/installing of new packages doesn’t interfere in
+any way with old packages, since they are stored in different
+locations in the Nix store.)</para>
+
+<para>If you find that you want to undo a <command>nix-env</command>
+operation, you can just do
+
+<screen>
+$ nix-env --rollback</screen>
+
+which will just make the current generation link point at the previous
+link. E.g., <filename>default</filename> would be made to point at
+<filename>default-42-link</filename>. You can also switch to a
+specific generation:
+
+<screen>
+$ nix-env --switch-generation 43</screen>
+
+which in this example would roll forward to generation 43 again. You
+can also see all available generations:
+
+<screen>
+$ nix-env --list-generations</screen></para>
+
+<para>You generally wouldn’t have
+<filename>/nix/var/nix/profiles/<replaceable>some-profile</replaceable>/bin</filename>
+in your <envar>PATH</envar>. Rather, there is a symlink
+<filename>~/.nix-profile</filename> that points to your current
+profile. This means that you should put
+<filename>~/.nix-profile/bin</filename> in your <envar>PATH</envar>
+(and indeed, that’s what the initialisation script
+<filename>/nix/etc/profile.d/nix.sh</filename> does). This makes it
+easier to switch to a different profile. You can do that using the
+command <command>nix-env --switch-profile</command>:
+
+<screen>
+$ nix-env --switch-profile /nix/var/nix/profiles/my-profile
+
+$ nix-env --switch-profile /nix/var/nix/profiles/default</screen>
+
+These commands switch to the <filename>my-profile</filename> and
+default profile, respectively. If the profile doesn’t exist, it will
+be created automatically. You should be careful about storing a
+profile in another location than the <filename>profiles</filename>
+directory, since otherwise it might not be used as a root of the
+garbage collector (see <xref linkend="sec-garbage-collection"/>).</para>
+
+<para>All <command>nix-env</command> operations work on the profile
+pointed to by <command>~/.nix-profile</command>, but you can override
+this using the <option>--profile</option> option (abbreviation
+<option>-p</option>):
+
+<screen>
+$ nix-env -p /nix/var/nix/profiles/other-profile -i subversion</screen>
+
+This will <emphasis>not</emphasis> change the
+<command>~/.nix-profile</command> symlink.</para>
+
+</chapter>
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-garbage-collection">
+
+<title>Garbage Collection</title>
+
+<para><command>nix-env</command> operations such as upgrades
+(<option>-u</option>) and uninstall (<option>-e</option>) never
+actually delete packages from the system. All they do (as shown
+above) is to create a new user environment that no longer contains
+symlinks to the “deleted” packages.</para>
+
+<para>Of course, since disk space is not infinite, unused packages
+should be removed at some point. You can do this by running the Nix
+garbage collector. It will remove from the Nix store any package
+not used (directly or indirectly) by any generation of any
+profile.</para>
+
+<para>Note however that as long as old generations reference a
+package, it will not be deleted. After all, we wouldn’t be able to
+do a rollback otherwise. So in order for garbage collection to be
+effective, you should also delete (some) old generations. Of course,
+this should only be done if you are certain that you will not need to
+roll back.</para>
+
+<para>To delete all old (non-current) generations of your current
+profile:
+
+<screen>
+$ nix-env --delete-generations old</screen>
+
+Instead of <literal>old</literal> you can also specify a list of
+generations, e.g.,
+
+<screen>
+$ nix-env --delete-generations 10 11 14</screen>
+
+To delete all generations older than a specified number of days
+(except the current generation), use the <literal>d</literal>
+suffix. For example,
+
+<screen>
+$ nix-env --delete-generations 14d</screen>
+
+deletes all generations older than two weeks.</para>
+
+<para>After removing appropriate old generations you can run the
+garbage collector as follows:
+
+<screen>
+$ nix-store --gc</screen>
+
+The behaviour of the gargage collector is affected by the
+<literal>keep-derivations</literal> (default: true) and <literal>keep-outputs</literal>
+(default: false) options in the Nix configuration file. The defaults will ensure
+that all derivations that are build-time dependencies of garbage collector roots
+will be kept and that all output paths that are runtime dependencies
+will be kept as well. All other derivations or paths will be collected.
+(This is usually what you want, but while you are developing
+it may make sense to keep outputs to ensure that rebuild times are quick.)
+
+If you are feeling uncertain, you can also first view what files would
+be deleted:
+
+<screen>
+$ nix-store --gc --print-dead</screen>
+
+Likewise, the option <option>--print-live</option> will show the paths
+that <emphasis>won’t</emphasis> be deleted.</para>
+
+<para>There is also a convenient little utility
+<command>nix-collect-garbage</command>, which when invoked with the
+<option>-d</option> (<option>--delete-old</option>) switch deletes all
+old generations of all profiles in
+<filename>/nix/var/nix/profiles</filename>. So
+
+<screen>
+$ nix-collect-garbage -d</screen>
+
+is a quick and easy way to clean up your system.</para>
+
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-gc-roots">
+
+<title>Garbage Collector Roots</title>
+
+<para>The roots of the garbage collector are all store paths to which
+there are symlinks in the directory
+<filename><replaceable>prefix</replaceable>/nix/var/nix/gcroots</filename>.
+For instance, the following command makes the path
+<filename>/nix/store/d718ef...-foo</filename> a root of the collector:
+
+<screen>
+$ ln -s /nix/store/d718ef...-foo /nix/var/nix/gcroots/bar</screen>
+
+That is, after this command, the garbage collector will not remove
+<filename>/nix/store/d718ef...-foo</filename> or any of its
+dependencies.</para>
+
+<para>Subdirectories of
+<filename><replaceable>prefix</replaceable>/nix/var/nix/gcroots</filename>
+are also searched for symlinks. Symlinks to non-store paths are
+followed and searched for roots, but symlinks to non-store paths
+<emphasis>inside</emphasis> the paths reached in that way are not
+followed to prevent infinite recursion.</para>
+
+</section>
+
+</chapter>
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-channels">
+
+<title>Channels</title>
+
+<para>If you want to stay up to date with a set of packages, it’s not
+very convenient to manually download the latest set of Nix expressions
+for those packages and upgrade using <command>nix-env</command>.
+Fortunately, there’s a better way: <emphasis>Nix
+channels</emphasis>.</para>
+
+<para>A Nix channel is just a URL that points to a place that contains
+a set of Nix expressions and a manifest. Using the command <link linkend="sec-nix-channel"><command>nix-channel</command></link> you
+can automatically stay up to date with whatever is available at that
+URL.</para>
+
+<para>To see the list of official NixOS channels, visit <link xlink:href="https://nixos.org/channels"/>.</para>
+
+<para>You can “subscribe” to a channel using
+<command>nix-channel --add</command>, e.g.,
+
+<screen>
+$ nix-channel --add https://nixos.org/channels/nixpkgs-unstable</screen>
+
+subscribes you to a channel that always contains that latest version
+of the Nix Packages collection. (Subscribing really just means that
+the URL is added to the file <filename>~/.nix-channels</filename>,
+where it is read by subsequent calls to <command>nix-channel
+--update</command>.) You can “unsubscribe” using <command>nix-channel
+--remove</command>:
+
+<screen>
+$ nix-channel --remove nixpkgs
+</screen>
+</para>
+
+<para>To obtain the latest Nix expressions available in a channel, do
+
+<screen>
+$ nix-channel --update</screen>
+
+This downloads and unpacks the Nix expressions in every channel
+(downloaded from <literal><replaceable>url</replaceable>/nixexprs.tar.bz2</literal>).
+It also makes the union of each channel’s Nix expressions available by
+default to <command>nix-env</command> operations (via the symlink
+<filename>~/.nix-defexpr/channels</filename>). Consequently, you can
+then say
+
+<screen>
+$ nix-env -u</screen>
+
+to upgrade all packages in your profile to the latest versions
+available in the subscribed channels.</para>
+
+</chapter>
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-sharing-packages">
+
+<title>Sharing Packages Between Machines</title>
+
+<para>Sometimes you want to copy a package from one machine to
+another. Or, you want to install some packages and you know that
+another machine already has some or all of those packages or their
+dependencies. In that case there are mechanisms to quickly copy
+packages between machines.</para>
+
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-binary-cache-substituter">
+
+<title>Serving a Nix store via HTTP</title>
+
+<para>You can easily share the Nix store of a machine via HTTP. This
+allows other machines to fetch store paths from that machine to speed
+up installations. It uses the same <emphasis>binary cache</emphasis>
+mechanism that Nix usually uses to fetch pre-built binaries from
+<uri>https://cache.nixos.org</uri>.</para>
+
+<para>The daemon that handles binary cache requests via HTTP,
+<command>nix-serve</command>, is not part of the Nix distribution, but
+you can install it from Nixpkgs:
+
+<screen>
+$ nix-env -i nix-serve
+</screen>
+
+You can then start the server, listening for HTTP connections on
+whatever port you like:
+
+<screen>
+$ nix-serve -p 8080
+</screen>
+
+To check whether it works, try the following on the client:
+
+<screen>
+$ curl http://avalon:8080/nix-cache-info
+</screen>
+
+which should print something like:
+
+<screen>
+StoreDir: /nix/store
+WantMassQuery: 1
+Priority: 30
+</screen>
+
+</para>
+
+<para>On the client side, you can tell Nix to use your binary cache
+using <option>--option extra-binary-caches</option>, e.g.:
+
+<screen>
+$ nix-env -i firefox --option extra-binary-caches http://avalon:8080/
+</screen>
+
+The option <option>extra-binary-caches</option> tells Nix to use this
+binary cache in addition to your default caches, such as
+<uri>https://cache.nixos.org</uri>. Thus, for any path in the closure
+of Firefox, Nix will first check if the path is available on the
+server <literal>avalon</literal> or another binary caches. If not, it
+will fall back to building from source.</para>
+
+<para>You can also tell Nix to always use your binary cache by adding
+a line to the <filename linkend="sec-conf-file">nix.conf</filename>
+configuration file like this:
+
+<programlisting>
+binary-caches = http://avalon:8080/ https://cache.nixos.org/
+</programlisting>
+
+</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-copy-closure">
+
+<title>Copying Closures Via SSH</title>
+
+<para>The command <command linkend="sec-nix-copy-closure">nix-copy-closure</command> copies a Nix
+store path along with all its dependencies to or from another machine
+via the SSH protocol. It doesn’t copy store paths that are already
+present on the target machine. For example, the following command
+copies Firefox with all its dependencies:
+
+<screen>
+$ nix-copy-closure --to alice@itchy.example.org $(type -p firefox)</screen>
+
+See <xref linkend="sec-nix-copy-closure"/> for details.</para>
+
+<para>With <command linkend="refsec-nix-store-export">nix-store
+--export</command> and <command linkend="refsec-nix-store-import">nix-store --import</command> you can
+write the closure of a store path (that is, the path and all its
+dependencies) to a file, and then unpack that file into another Nix
+store. For example,
+
+<screen>
+$ nix-store --export $(nix-store -qR $(type -p firefox)) > firefox.closure</screen>
+
+writes the closure of Firefox to a file. You can then copy this file
+to another machine and install the closure:
+
+<screen>
+$ nix-store --import < firefox.closure</screen>
+
+Any store paths in the closure that are already present in the target
+store are ignored. It is also possible to pipe the export into
+another command, e.g. to copy and install a closure directly to/on
+another machine:
+
+<screen>
+$ nix-store --export $(nix-store -qR $(type -p firefox)) | bzip2 | \
+ ssh alice@itchy.example.org "bunzip2 | nix-store --import"</screen>
+
+However, <command>nix-copy-closure</command> is generally more
+efficient because it only copies paths that are not already present in
+the target Nix store.</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-ssh-substituter">
+
+<title>Serving a Nix store via SSH</title>
+
+<para>You can tell Nix to automatically fetch needed binaries from a
+remote Nix store via SSH. For example, the following installs Firefox,
+automatically fetching any store paths in Firefox’s closure if they
+are available on the server <literal>avalon</literal>:
+
+<screen>
+$ nix-env -i firefox --substituters ssh://alice@avalon
+</screen>
+
+This works similar to the binary cache substituter that Nix usually
+uses, only using SSH instead of HTTP: if a store path
+<literal>P</literal> is needed, Nix will first check if it’s available
+in the Nix store on <literal>avalon</literal>. If not, it will fall
+back to using the binary cache substituter, and then to building from
+source.</para>
+
+<note><para>The SSH substituter currently does not allow you to enter
+an SSH passphrase interactively. Therefore, you should use
+<command>ssh-add</command> to load the decrypted private key into
+<command>ssh-agent</command>.</para></note>
+
+<para>You can also copy the closure of some store path, without
+installing it into your profile, e.g.
+
+<screen>
+$ nix-store -r /nix/store/m85bxg…-firefox-34.0.5 --substituters ssh://alice@avalon
+</screen>
+
+This is essentially equivalent to doing
+
+<screen>
+$ nix-copy-closure --from alice@avalon /nix/store/m85bxg…-firefox-34.0.5
+</screen>
+
+</para>
+
+<para>You can use SSH’s <emphasis>forced command</emphasis> feature to
+set up a restricted user account for SSH substituter access, allowing
+read-only access to the local Nix store, but nothing more. For
+example, add the following lines to <filename>sshd_config</filename>
+to restrict the user <literal>nix-ssh</literal>:
+
+<programlisting>
+Match User nix-ssh
+ AllowAgentForwarding no
+ AllowTcpForwarding no
+ PermitTTY no
+ PermitTunnel no
+ X11Forwarding no
+ ForceCommand nix-store --serve
+Match All
+</programlisting>
+
+On NixOS, you can accomplish the same by adding the following to your
+<filename>configuration.nix</filename>:
+
+<programlisting>
+nix.sshServe.enable = true;
+nix.sshServe.keys = [ "ssh-dss AAAAB3NzaC1k... bob@example.org" ];
+</programlisting>
+
+where the latter line lists the public keys of users that are allowed
+to connect.</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-s3-substituter">
+
+<title>Serving a Nix store via AWS S3 or S3-compatible Service</title>
+
+<para>Nix has built-in support for storing and fetching store paths
+from Amazon S3 and S3 compatible services. This uses the same
+<emphasis>binary</emphasis> cache mechanism that Nix usually uses to
+fetch prebuilt binaries from <uri>cache.nixos.org</uri>.</para>
+
+<para>The following options can be specified as URL parameters to
+the S3 URL:</para>
+
+<variablelist>
+ <varlistentry><term><literal>profile</literal></term>
+ <listitem>
+ <para>
+ The name of the AWS configuration profile to use. By default
+ Nix will use the <literal>default</literal> profile.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry><term><literal>region</literal></term>
+ <listitem>
+ <para>
+ The region of the S3 bucket. <literal>us–east-1</literal> by
+ default.
+ </para>
+
+ <para>
+ If your bucket is not in <literal>us–east-1</literal>, you
+ should always explicitly specify the region parameter.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry><term><literal>endpoint</literal></term>
+ <listitem>
+ <para>
+ The URL to your S3-compatible service, for when not using
+ Amazon S3. Do not specify this value if you're using Amazon
+ S3.
+ </para>
+ <note><para>This endpoint must support HTTPS and will use
+ path-based addressing instead of virtual host based
+ addressing.</para></note>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry><term><literal>scheme</literal></term>
+ <listitem>
+ <para>
+ The scheme used for S3 requests, <literal>https</literal>
+ (default) or <literal>http</literal>. This option allows you to
+ disable HTTPS for binary caches which don't support it.
+ </para>
+ <note><para>HTTPS should be used if the cache might contain
+ sensitive information.</para></note>
+ </listitem>
+ </varlistentry>
+</variablelist>
+
+<para>In this example we will use the bucket named
+<literal>example-nix-cache</literal>.</para>
+
+<section xml:id="ssec-s3-substituter-anonymous-reads">
+ <title>Anonymous Reads to your S3-compatible binary cache</title>
+
+ <para>If your binary cache is publicly accessible and does not
+ require authentication, the simplest and easiest way to use Nix with
+ your S3 compatible binary cache is to use the HTTP URL for that
+ cache.</para>
+
+ <para>For AWS S3 the binary cache URL for example bucket will be
+ exactly <uri>https://example-nix-cache.s3.amazonaws.com</uri> or
+ <uri>s3://example-nix-cache</uri>. For S3 compatible binary caches,
+ consult that cache's documentation.</para>
+
+ <para>Your bucket will need the following bucket policy:</para>
+
+ <programlisting><![CDATA[
+{
+ "Id": "DirectReads",
+ "Version": "2012-10-17",
+ "Statement": [
+ {
+ "Sid": "AllowDirectReads",
+ "Action": [
+ "s3:GetObject",
+ "s3:GetBucketLocation"
+ ],
+ "Effect": "Allow",
+ "Resource": [
+ "arn:aws:s3:::example-nix-cache",
+ "arn:aws:s3:::example-nix-cache/*"
+ ],
+ "Principal": "*"
+ }
+ ]
+}
+]]></programlisting>
+</section>
+
+<section xml:id="ssec-s3-substituter-authenticated-reads">
+ <title>Authenticated Reads to your S3 binary cache</title>
+
+ <para>For AWS S3 the binary cache URL for example bucket will be
+ exactly <uri>s3://example-nix-cache</uri>.</para>
+
+ <para>Nix will use the <link xlink:href="https://docs.aws.amazon.com/sdk-for-cpp/v1/developer-guide/credentials.html">default
+ credential provider chain</link> for authenticating requests to
+ Amazon S3.</para>
+
+ <para>Nix supports authenticated reads from Amazon S3 and S3
+ compatible binary caches.</para>
+
+ <para>Your bucket will need a bucket policy allowing the desired
+ users to perform the <literal>s3:GetObject</literal> and
+ <literal>s3:GetBucketLocation</literal> action on all objects in the
+ bucket. The anonymous policy in <xref linkend="ssec-s3-substituter-anonymous-reads"/> can be updated to
+ have a restricted <literal>Principal</literal> to support
+ this.</para>
+</section>
+
+
+<section xml:id="ssec-s3-substituter-authenticated-writes">
+ <title>Authenticated Writes to your S3-compatible binary cache</title>
+
+ <para>Nix support fully supports writing to Amazon S3 and S3
+ compatible buckets. The binary cache URL for our example bucket will
+ be <uri>s3://example-nix-cache</uri>.</para>
+
+ <para>Nix will use the <link xlink:href="https://docs.aws.amazon.com/sdk-for-cpp/v1/developer-guide/credentials.html">default
+ credential provider chain</link> for authenticating requests to
+ Amazon S3.</para>
+
+ <para>Your account will need the following IAM policy to
+ upload to the cache:</para>
+
+ <programlisting><![CDATA[
+{
+ "Version": "2012-10-17",
+ "Statement": [
+ {
+ "Sid": "UploadToCache",
+ "Effect": "Allow",
+ "Action": [
+ "s3:AbortMultipartUpload",
+ "s3:GetBucketLocation",
+ "s3:GetObject",
+ "s3:ListBucket",
+ "s3:ListBucketMultipartUploads",
+ "s3:ListMultipartUploadParts",
+ "s3:PutObject"
+ ],
+ "Resource": [
+ "arn:aws:s3:::example-nix-cache",
+ "arn:aws:s3:::example-nix-cache/*"
+ ]
+ }
+ ]
+}
+]]></programlisting>
+
+
+ <example><title>Uploading with a specific credential profile for Amazon S3</title>
+ <para><command>nix copy --to 's3://example-nix-cache?profile=cache-upload&region=eu-west-2' nixpkgs.hello</command></para>
+ </example>
+
+ <example><title>Uploading to an S3-Compatible Binary Cache</title>
+ <para><command>nix copy --to 's3://example-nix-cache?profile=cache-upload&scheme=https&endpoint=minio.example.com' nixpkgs.hello</command></para>
+ </example>
+</section>
+</section>
+
+</chapter>
+
+</part>
+ <part xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="chap-writing-nix-expressions" xml:base="expressions/writing-nix-expressions.xml">
+
+<title>Writing Nix Expressions</title>
+
+<partintro>
+<para>This chapter shows you how to write Nix expressions, which
+instruct Nix how to build packages. It starts with a
+simple example (a Nix expression for GNU Hello), and then moves
+on to a more in-depth look at the Nix expression language.</para>
+
+<note><para>This chapter is mostly about the Nix expression language.
+For more extensive information on adding packages to the Nix Packages
+collection (such as functions in the standard environment and coding
+conventions), please consult <link xlink:href="http://nixos.org/nixpkgs/manual/">its
+manual</link>.</para></note>
+</partintro>
+
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-simple-expression">
+
+<title>A Simple Nix Expression</title>
+
+<para>This section shows how to add and test the <link xlink:href="http://www.gnu.org/software/hello/hello.html">GNU Hello
+package</link> to the Nix Packages collection. Hello is a program
+that prints out the text <quote>Hello, world!</quote>.</para>
+
+<para>To add a package to the Nix Packages collection, you generally
+need to do three things:
+
+<orderedlist>
+
+ <listitem><para>Write a Nix expression for the package. This is a
+ file that describes all the inputs involved in building the package,
+ such as dependencies, sources, and so on.</para></listitem>
+
+ <listitem><para>Write a <emphasis>builder</emphasis>. This is a
+ shell script<footnote><para>In fact, it can be written in any
+ language, but typically it's a <command>bash</command> shell
+ script.</para></footnote> that actually builds the package from
+ the inputs.</para></listitem>
+
+ <listitem><para>Add the package to the file
+ <filename>pkgs/top-level/all-packages.nix</filename>. The Nix
+ expression written in the first step is a
+ <emphasis>function</emphasis>; it requires other packages in order
+ to build it. In this step you put it all together, i.e., you call
+ the function with the right arguments to build the actual
+ package.</para></listitem>
+
+</orderedlist>
+
+</para>
+
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-expression-syntax">
+
+<title>Expression Syntax</title>
+
+<example xml:id="ex-hello-nix"><title>Nix expression for GNU Hello
+(<filename>default.nix</filename>)</title>
+<programlisting>
+{ stdenv, fetchurl, perl }: <co xml:id="ex-hello-nix-co-1"/>
+
+stdenv.mkDerivation { <co xml:id="ex-hello-nix-co-2"/>
+ name = "hello-2.1.1"; <co xml:id="ex-hello-nix-co-3"/>
+ builder = ./builder.sh; <co xml:id="ex-hello-nix-co-4"/>
+ src = fetchurl { <co xml:id="ex-hello-nix-co-5"/>
+ url = "ftp://ftp.nluug.nl/pub/gnu/hello/hello-2.1.1.tar.gz";
+ sha256 = "1md7jsfd8pa45z73bz1kszpp01yw6x5ljkjk2hx7wl800any6465";
+ };
+ inherit perl; <co xml:id="ex-hello-nix-co-6"/>
+}</programlisting>
+</example>
+
+<para><xref linkend="ex-hello-nix"/> shows a Nix expression for GNU
+Hello. It's actually already in the Nix Packages collection in
+<filename>pkgs/applications/misc/hello/ex-1/default.nix</filename>.
+It is customary to place each package in a separate directory and call
+the single Nix expression in that directory
+<filename>default.nix</filename>. The file has the following elements
+(referenced from the figure by number):
+
+<calloutlist>
+
+ <callout arearefs="ex-hello-nix-co-1">
+
+ <para>This states that the expression is a
+ <emphasis>function</emphasis> that expects to be called with three
+ arguments: <varname>stdenv</varname>, <varname>fetchurl</varname>,
+ and <varname>perl</varname>. They are needed to build Hello, but
+ we don't know how to build them here; that's why they are function
+ arguments. <varname>stdenv</varname> is a package that is used
+ by almost all Nix Packages packages; it provides a
+ <quote>standard</quote> environment consisting of the things you
+ would expect in a basic Unix environment: a C/C++ compiler (GCC,
+ to be precise), the Bash shell, fundamental Unix tools such as
+ <command>cp</command>, <command>grep</command>,
+ <command>tar</command>, etc. <varname>fetchurl</varname> is a
+ function that downloads files. <varname>perl</varname> is the
+ Perl interpreter.</para>
+
+ <para>Nix functions generally have the form <literal>{ x, y, ...,
+ z }: e</literal> where <varname>x</varname>, <varname>y</varname>,
+ etc. are the names of the expected arguments, and where
+ <replaceable>e</replaceable> is the body of the function. So
+ here, the entire remainder of the file is the body of the
+ function; when given the required arguments, the body should
+ describe how to build an instance of the Hello package.</para>
+
+ </callout>
+
+ <callout arearefs="ex-hello-nix-co-2">
+
+ <para>So we have to build a package. Building something from
+ other stuff is called a <emphasis>derivation</emphasis> in Nix (as
+ opposed to sources, which are built by humans instead of
+ computers). We perform a derivation by calling
+ <varname>stdenv.mkDerivation</varname>.
+ <varname>mkDerivation</varname> is a function provided by
+ <varname>stdenv</varname> that builds a package from a set of
+ <emphasis>attributes</emphasis>. A set is just a list of
+ key/value pairs where each key is a string and each value is an
+ arbitrary Nix expression. They take the general form <literal>{
+ <replaceable>name1</replaceable> =
+ <replaceable>expr1</replaceable>; <replaceable>...</replaceable>
+ <replaceable>nameN</replaceable> =
+ <replaceable>exprN</replaceable>; }</literal>.</para>
+
+ </callout>
+
+ <callout arearefs="ex-hello-nix-co-3">
+
+ <para>The attribute <varname>name</varname> specifies the symbolic
+ name and version of the package. Nix doesn't really care about
+ these things, but they are used by for instance <command>nix-env
+ -q</command> to show a <quote>human-readable</quote> name for
+ packages. This attribute is required by
+ <varname>mkDerivation</varname>.</para>
+
+ </callout>
+
+ <callout arearefs="ex-hello-nix-co-4">
+
+ <para>The attribute <varname>builder</varname> specifies the
+ builder. This attribute can sometimes be omitted, in which case
+ <varname>mkDerivation</varname> will fill in a default builder
+ (which does a <literal>configure; make; make install</literal>, in
+ essence). Hello is sufficiently simple that the default builder
+ would suffice, but in this case, we will show an actual builder
+ for educational purposes. The value
+ <command>./builder.sh</command> refers to the shell script shown
+ in <xref linkend="ex-hello-builder"/>, discussed below.</para>
+
+ </callout>
+
+ <callout arearefs="ex-hello-nix-co-5">
+
+ <para>The builder has to know what the sources of the package
+ are. Here, the attribute <varname>src</varname> is bound to the
+ result of a call to the <command>fetchurl</command> function.
+ Given a URL and a SHA-256 hash of the expected contents of the file
+ at that URL, this function builds a derivation that downloads the
+ file and checks its hash. So the sources are a dependency that
+ like all other dependencies is built before Hello itself is
+ built.</para>
+
+ <para>Instead of <varname>src</varname> any other name could have
+ been used, and in fact there can be any number of sources (bound
+ to different attributes). However, <varname>src</varname> is
+ customary, and it's also expected by the default builder (which we
+ don't use in this example).</para>
+
+ </callout>
+
+ <callout arearefs="ex-hello-nix-co-6">
+
+ <para>Since the derivation requires Perl, we have to pass the
+ value of the <varname>perl</varname> function argument to the
+ builder. All attributes in the set are actually passed as
+ environment variables to the builder, so declaring an attribute
+
+ <programlisting>
+perl = perl;</programlisting>
+
+ will do the trick: it binds an attribute <varname>perl</varname>
+ to the function argument which also happens to be called
+ <varname>perl</varname>. However, it looks a bit silly, so there
+ is a shorter syntax. The <literal>inherit</literal> keyword
+ causes the specified attributes to be bound to whatever variables
+ with the same name happen to be in scope.</para>
+
+ </callout>
+
+</calloutlist>
+
+</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-build-script">
+
+<title>Build Script</title>
+
+<example xml:id="ex-hello-builder"><title>Build script for GNU Hello
+(<filename>builder.sh</filename>)</title>
+<programlisting>
+source $stdenv/setup <co xml:id="ex-hello-builder-co-1"/>
+
+PATH=$perl/bin:$PATH <co xml:id="ex-hello-builder-co-2"/>
+
+tar xvfz $src <co xml:id="ex-hello-builder-co-3"/>
+cd hello-*
+./configure --prefix=$out <co xml:id="ex-hello-builder-co-4"/>
+make <co xml:id="ex-hello-builder-co-5"/>
+make install</programlisting>
+</example>
+
+<para><xref linkend="ex-hello-builder"/> shows the builder referenced
+from Hello's Nix expression (stored in
+<filename>pkgs/applications/misc/hello/ex-1/builder.sh</filename>).
+The builder can actually be made a lot shorter by using the
+<emphasis>generic builder</emphasis> functions provided by
+<varname>stdenv</varname>, but here we write out the build steps to
+elucidate what a builder does. It performs the following
+steps:</para>
+
+<calloutlist>
+
+ <callout arearefs="ex-hello-builder-co-1">
+
+ <para>When Nix runs a builder, it initially completely clears the
+ environment (except for the attributes declared in the
+ derivation). For instance, the <envar>PATH</envar> variable is
+ empty<footnote><para>Actually, it's initialised to
+ <filename>/path-not-set</filename> to prevent Bash from setting it
+ to a default value.</para></footnote>. This is done to prevent
+ undeclared inputs from being used in the build process. If for
+ example the <envar>PATH</envar> contained
+ <filename>/usr/bin</filename>, then you might accidentally use
+ <filename>/usr/bin/gcc</filename>.</para>
+
+ <para>So the first step is to set up the environment. This is
+ done by calling the <filename>setup</filename> script of the
+ standard environment. The environment variable
+ <envar>stdenv</envar> points to the location of the standard
+ environment being used. (It wasn't specified explicitly as an
+ attribute in <xref linkend="ex-hello-nix"/>, but
+ <varname>mkDerivation</varname> adds it automatically.)</para>
+
+ </callout>
+
+ <callout arearefs="ex-hello-builder-co-2">
+
+ <para>Since Hello needs Perl, we have to make sure that Perl is in
+ the <envar>PATH</envar>. The <envar>perl</envar> environment
+ variable points to the location of the Perl package (since it
+ was passed in as an attribute to the derivation), so
+ <filename><replaceable>$perl</replaceable>/bin</filename> is the
+ directory containing the Perl interpreter.</para>
+
+ </callout>
+
+ <callout arearefs="ex-hello-builder-co-3">
+
+ <para>Now we have to unpack the sources. The
+ <varname>src</varname> attribute was bound to the result of
+ fetching the Hello source tarball from the network, so the
+ <envar>src</envar> environment variable points to the location in
+ the Nix store to which the tarball was downloaded. After
+ unpacking, we <command>cd</command> to the resulting source
+ directory.</para>
+
+ <para>The whole build is performed in a temporary directory
+ created in <varname>/tmp</varname>, by the way. This directory is
+ removed after the builder finishes, so there is no need to clean
+ up the sources afterwards. Also, the temporary directory is
+ always newly created, so you don't have to worry about files from
+ previous builds interfering with the current build.</para>
+
+ </callout>
+
+ <callout arearefs="ex-hello-builder-co-4">
+
+ <para>GNU Hello is a typical Autoconf-based package, so we first
+ have to run its <filename>configure</filename> script. In Nix
+ every package is stored in a separate location in the Nix store,
+ for instance
+ <filename>/nix/store/9a54ba97fb71b65fda531012d0443ce2-hello-2.1.1</filename>.
+ Nix computes this path by cryptographically hashing all attributes
+ of the derivation. The path is passed to the builder through the
+ <envar>out</envar> environment variable. So here we give
+ <filename>configure</filename> the parameter
+ <literal>--prefix=$out</literal> to cause Hello to be installed in
+ the expected location.</para>
+
+ </callout>
+
+ <callout arearefs="ex-hello-builder-co-5">
+
+ <para>Finally we build Hello (<literal>make</literal>) and install
+ it into the location specified by <envar>out</envar>
+ (<literal>make install</literal>).</para>
+
+ </callout>
+
+</calloutlist>
+
+<para>If you are wondering about the absence of error checking on the
+result of various commands called in the builder: this is because the
+shell script is evaluated with Bash's <option>-e</option> option,
+which causes the script to be aborted if any command fails without an
+error check.</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-arguments">
+
+<title>Arguments and Variables</title>
+
+<example xml:id="ex-hello-composition">
+
+<title>Composing GNU Hello
+(<filename>all-packages.nix</filename>)</title>
+<programlisting>
+...
+
+rec { <co xml:id="ex-hello-composition-co-1"/>
+
+ hello = import ../applications/misc/hello/ex-1 <co xml:id="ex-hello-composition-co-2"/> { <co xml:id="ex-hello-composition-co-3"/>
+ inherit fetchurl stdenv perl;
+ };
+
+ perl = import ../development/interpreters/perl { <co xml:id="ex-hello-composition-co-4"/>
+ inherit fetchurl stdenv;
+ };
+
+ fetchurl = import ../build-support/fetchurl {
+ inherit stdenv; ...
+ };
+
+ stdenv = ...;
+
+}
+</programlisting>
+</example>
+
+<para>The Nix expression in <xref linkend="ex-hello-nix"/> is a
+function; it is missing some arguments that have to be filled in
+somewhere. In the Nix Packages collection this is done in the file
+<filename>pkgs/top-level/all-packages.nix</filename>, where all
+Nix expressions for packages are imported and called with the
+appropriate arguments. <xref linkend="ex-hello-composition"/> shows
+some fragments of
+<filename>all-packages.nix</filename>.</para>
+
+<calloutlist>
+
+ <callout arearefs="ex-hello-composition-co-1">
+
+ <para>This file defines a set of attributes, all of which are
+ concrete derivations (i.e., not functions). In fact, we define a
+ <emphasis>mutually recursive</emphasis> set of attributes. That
+ is, the attributes can refer to each other. This is precisely
+ what we want since we want to <quote>plug</quote> the
+ various packages into each other.</para>
+
+ </callout>
+
+ <callout arearefs="ex-hello-composition-co-2">
+
+ <para>Here we <emphasis>import</emphasis> the Nix expression for
+ GNU Hello. The import operation just loads and returns the
+ specified Nix expression. In fact, we could just have put the
+ contents of <xref linkend="ex-hello-nix"/> in
+ <filename>all-packages.nix</filename> at this point. That
+ would be completely equivalent, but it would make the file rather
+ bulky.</para>
+
+ <para>Note that we refer to
+ <filename>../applications/misc/hello/ex-1</filename>, not
+ <filename>../applications/misc/hello/ex-1/default.nix</filename>.
+ When you try to import a directory, Nix automatically appends
+ <filename>/default.nix</filename> to the file name.</para>
+
+ </callout>
+
+ <callout arearefs="ex-hello-composition-co-3">
+
+ <para>This is where the actual composition takes place. Here we
+ <emphasis>call</emphasis> the function imported from
+ <filename>../applications/misc/hello/ex-1</filename> with a set
+ containing the things that the function expects, namely
+ <varname>fetchurl</varname>, <varname>stdenv</varname>, and
+ <varname>perl</varname>. We use inherit again to use the
+ attributes defined in the surrounding scope (we could also have
+ written <literal>fetchurl = fetchurl;</literal>, etc.).</para>
+
+ <para>The result of this function call is an actual derivation
+ that can be built by Nix (since when we fill in the arguments of
+ the function, what we get is its body, which is the call to
+ <varname>stdenv.mkDerivation</varname> in <xref linkend="ex-hello-nix"/>).</para>
+
+ <note><para>Nixpkgs has a convenience function
+ <function>callPackage</function> that imports and calls a
+ function, filling in any missing arguments by passing the
+ corresponding attribute from the Nixpkgs set, like this:
+
+<programlisting>
+hello = callPackage ../applications/misc/hello/ex-1 { };
+</programlisting>
+
+ If necessary, you can set or override arguments:
+
+<programlisting>
+hello = callPackage ../applications/misc/hello/ex-1 { stdenv = myStdenv; };
+</programlisting>
+
+ </para></note>
+
+ </callout>
+
+ <callout arearefs="ex-hello-composition-co-4">
+
+ <para>Likewise, we have to instantiate Perl,
+ <varname>fetchurl</varname>, and the standard environment.</para>
+
+ </callout>
+
+</calloutlist>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-building-simple">
+
+<title>Building and Testing</title>
+
+<para>You can now try to build Hello. Of course, you could do
+<literal>nix-env -i hello</literal>, but you may not want to install a
+possibly broken package just yet. The best way to test the package is by
+using the command <command linkend="sec-nix-build">nix-build</command>,
+which builds a Nix expression and creates a symlink named
+<filename>result</filename> in the current directory:
+
+<screen>
+$ nix-build -A hello
+building path `/nix/store/632d2b22514d...-hello-2.1.1'
+hello-2.1.1/
+hello-2.1.1/intl/
+hello-2.1.1/intl/ChangeLog
+<replaceable>...</replaceable>
+
+$ ls -l result
+lrwxrwxrwx ... 2006-09-29 10:43 result -> /nix/store/632d2b22514d...-hello-2.1.1
+
+$ ./result/bin/hello
+Hello, world!</screen>
+
+The <link linkend="opt-attr"><option>-A</option></link> option selects
+the <literal>hello</literal> attribute. This is faster than using the
+symbolic package name specified by the <literal>name</literal>
+attribute (which also happens to be <literal>hello</literal>) and is
+unambiguous (there can be multiple packages with the symbolic name
+<literal>hello</literal>, but there can be only one attribute in a set
+named <literal>hello</literal>).</para>
+
+<para><command>nix-build</command> registers the
+<filename>./result</filename> symlink as a garbage collection root, so
+unless and until you delete the <filename>./result</filename> symlink,
+the output of the build will be safely kept on your system. You can
+use <command>nix-build</command>’s <option linkend="opt-out-link">-o</option> switch to give the symlink another
+name.</para>
+
+<para>Nix has transactional semantics. Once a build finishes
+successfully, Nix makes a note of this in its database: it registers
+that the path denoted by <envar>out</envar> is now
+<quote>valid</quote>. If you try to build the derivation again, Nix
+will see that the path is already valid and finish immediately. If a
+build fails, either because it returns a non-zero exit code, because
+Nix or the builder are killed, or because the machine crashes, then
+the output paths will not be registered as valid. If you try to build
+the derivation again, Nix will remove the output paths if they exist
+(e.g., because the builder died half-way through <literal>make
+install</literal>) and try again. Note that there is no
+<quote>negative caching</quote>: Nix doesn't remember that a build
+failed, and so a failed build can always be repeated. This is because
+Nix cannot distinguish between permanent failures (e.g., a compiler
+error due to a syntax error in the source) and transient failures
+(e.g., a disk full condition).</para>
+
+<para>Nix also performs locking. If you run multiple Nix builds
+simultaneously, and they try to build the same derivation, the first
+Nix instance that gets there will perform the build, while the others
+block (or perform other derivations if available) until the build
+finishes:
+
+<screen>
+$ nix-build -A hello
+waiting for lock on `/nix/store/0h5b7hp8d4hqfrw8igvx97x1xawrjnac-hello-2.1.1x'</screen>
+
+So it is always safe to run multiple instances of Nix in parallel
+(which isn’t the case with, say, <command>make</command>).</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-generic-builder">
+
+<title>Generic Builder Syntax</title>
+
+<para>Recall from <xref linkend="ex-hello-builder"/> that the builder
+looked something like this:
+
+<programlisting>
+PATH=$perl/bin:$PATH
+tar xvfz $src
+cd hello-*
+./configure --prefix=$out
+make
+make install</programlisting>
+
+The builders for almost all Unix packages look like this — set up some
+environment variables, unpack the sources, configure, build, and
+install. For this reason the standard environment provides some Bash
+functions that automate the build process. A builder using the
+generic build facilities in shown in <xref linkend="ex-hello-builder2"/>.</para>
+
+<example xml:id="ex-hello-builder2"><title>Build script using the generic
+build functions</title>
+<programlisting>
+buildInputs="$perl" <co xml:id="ex-hello-builder2-co-1"/>
+
+source $stdenv/setup <co xml:id="ex-hello-builder2-co-2"/>
+
+genericBuild <co xml:id="ex-hello-builder2-co-3"/></programlisting>
+</example>
+
+<calloutlist>
+
+ <callout arearefs="ex-hello-builder2-co-1">
+
+ <para>The <envar>buildInputs</envar> variable tells
+ <filename>setup</filename> to use the indicated packages as
+ <quote>inputs</quote>. This means that if a package provides a
+ <filename>bin</filename> subdirectory, it's added to
+ <envar>PATH</envar>; if it has a <filename>include</filename>
+ subdirectory, it's added to GCC's header search path; and so
+ on.<footnote><para>How does it work? <filename>setup</filename>
+ tries to source the file
+ <filename><replaceable>pkg</replaceable>/nix-support/setup-hook</filename>
+ of all dependencies. These “setup hooks” can then set up whatever
+ environment variables they want; for instance, the setup hook for
+ Perl sets the <envar>PERL5LIB</envar> environment variable to
+ contain the <filename>lib/site_perl</filename> directories of all
+ inputs.</para></footnote>
+ </para>
+
+ </callout>
+
+ <callout arearefs="ex-hello-builder2-co-2">
+
+ <para>The function <function>genericBuild</function> is defined in
+ the file <literal>$stdenv/setup</literal>.</para>
+
+ </callout>
+
+ <callout arearefs="ex-hello-builder2-co-3">
+
+ <para>The final step calls the shell function
+ <function>genericBuild</function>, which performs the steps that
+ were done explicitly in <xref linkend="ex-hello-builder"/>. The
+ generic builder is smart enough to figure out whether to unpack
+ the sources using <command>gzip</command>,
+ <command>bzip2</command>, etc. It can be customised in many ways;
+ see the Nixpkgs manual for details.</para>
+
+ </callout>
+
+</calloutlist>
+
+<para>Discerning readers will note that the
+<envar>buildInputs</envar> could just as well have been set in the Nix
+expression, like this:
+
+<programlisting>
+ buildInputs = [ perl ];</programlisting>
+
+The <varname>perl</varname> attribute can then be removed, and the
+builder becomes even shorter:
+
+<programlisting>
+source $stdenv/setup
+genericBuild</programlisting>
+
+In fact, <varname>mkDerivation</varname> provides a default builder
+that looks exactly like that, so it is actually possible to omit the
+builder for Hello entirely.</para>
+
+</section>
+
+</chapter>
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-expression-language">
+
+<title>Nix Expression Language</title>
+
+<para>The Nix expression language is a pure, lazy, functional
+language. Purity means that operations in the language don't have
+side-effects (for instance, there is no variable assignment).
+Laziness means that arguments to functions are evaluated only when
+they are needed. Functional means that functions are
+<quote>normal</quote> values that can be passed around and manipulated
+in interesting ways. The language is not a full-featured, general
+purpose language. Its main job is to describe packages,
+compositions of packages, and the variability within
+packages.</para>
+
+<para>This section presents the various features of the
+language.</para>
+
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-values">
+
+<title>Values</title>
+
+
+<simplesect><title>Simple Values</title>
+
+<para>Nix has the following basic data types:
+
+<itemizedlist>
+
+ <listitem>
+
+ <para><emphasis>Strings</emphasis> can be written in three
+ ways.</para>
+
+ <para>The most common way is to enclose the string between double
+ quotes, e.g., <literal>"foo bar"</literal>. Strings can span
+ multiple lines. The special characters <literal>"</literal> and
+ <literal>\</literal> and the character sequence
+ <literal>${</literal> must be escaped by prefixing them with a
+ backslash (<literal>\</literal>). Newlines, carriage returns and
+ tabs can be written as <literal>\n</literal>,
+ <literal>\r</literal> and <literal>\t</literal>,
+ respectively.</para>
+
+ <para>You can include the result of an expression into a string by
+ enclosing it in
+ <literal>${<replaceable>...</replaceable>}</literal>, a feature
+ known as <emphasis>antiquotation</emphasis>. The enclosed
+ expression must evaluate to something that can be coerced into a
+ string (meaning that it must be a string, a path, or a
+ derivation). For instance, rather than writing
+
+<programlisting>
+"--with-freetype2-library=" + freetype + "/lib"</programlisting>
+
+ (where <varname>freetype</varname> is a derivation), you can
+ instead write the more natural
+
+<programlisting>
+"--with-freetype2-library=${freetype}/lib"</programlisting>
+
+ The latter is automatically translated to the former. A more
+ complicated example (from the Nix expression for <link xlink:href="http://www.trolltech.com/products/qt">Qt</link>):
+
+<programlisting>
+configureFlags = "
+ -system-zlib -system-libpng -system-libjpeg
+ ${if openglSupport then "-dlopen-opengl
+ -L${mesa}/lib -I${mesa}/include
+ -L${libXmu}/lib -I${libXmu}/include" else ""}
+ ${if threadSupport then "-thread" else "-no-thread"}
+";</programlisting>
+
+ Note that Nix expressions and strings can be arbitrarily nested;
+ in this case the outer string contains various antiquotations that
+ themselves contain strings (e.g., <literal>"-thread"</literal>),
+ some of which in turn contain expressions (e.g.,
+ <literal>${mesa}</literal>).</para>
+
+ <para>The second way to write string literals is as an
+ <emphasis>indented string</emphasis>, which is enclosed between
+ pairs of <emphasis>double single-quotes</emphasis>, like so:
+
+<programlisting>
+''
+ This is the first line.
+ This is the second line.
+ This is the third line.
+''</programlisting>
+
+ This kind of string literal intelligently strips indentation from
+ the start of each line. To be precise, it strips from each line a
+ number of spaces equal to the minimal indentation of the string as
+ a whole (disregarding the indentation of empty lines). For
+ instance, the first and second line are indented two space, while
+ the third line is indented four spaces. Thus, two spaces are
+ stripped from each line, so the resulting string is
+
+<programlisting>
+"This is the first line.\nThis is the second line.\n This is the third line.\n"</programlisting>
+
+ </para>
+
+ <para>Note that the whitespace and newline following the opening
+ <literal>''</literal> is ignored if there is no non-whitespace
+ text on the initial line.</para>
+
+ <para>Antiquotation
+ (<literal>${<replaceable>expr</replaceable>}</literal>) is
+ supported in indented strings.</para>
+
+ <para>Since <literal>${</literal> and <literal>''</literal> have
+ special meaning in indented strings, you need a way to quote them.
+ <literal>$</literal> can be escaped by prefixing it with
+ <literal>''</literal> (that is, two single quotes), i.e.,
+ <literal>''$</literal>. <literal>''</literal> can be escaped by
+ prefixing it with <literal>'</literal>, i.e.,
+ <literal>'''</literal>. <literal>$</literal> removes any special meaning
+ from the following <literal>$</literal>. Linefeed, carriage-return and tab
+ characters can be written as <literal>''\n</literal>,
+ <literal>''\r</literal>, <literal>''\t</literal>, and <literal>''\</literal>
+ escapes any other character.
+
+ </para>
+
+ <para>Indented strings are primarily useful in that they allow
+ multi-line string literals to follow the indentation of the
+ enclosing Nix expression, and that less escaping is typically
+ necessary for strings representing languages such as shell scripts
+ and configuration files because <literal>''</literal> is much less
+ common than <literal>"</literal>. Example:
+
+<programlisting>
+stdenv.mkDerivation {
+ <replaceable>...</replaceable>
+ postInstall =
+ ''
+ mkdir $out/bin $out/etc
+ cp foo $out/bin
+ echo "Hello World" > $out/etc/foo.conf
+ ${if enableBar then "cp bar $out/bin" else ""}
+ '';
+ <replaceable>...</replaceable>
+}
+</programlisting>
+
+ </para>
+
+ <para>Finally, as a convenience, <emphasis>URIs</emphasis> as
+ defined in appendix B of <link xlink:href="http://www.ietf.org/rfc/rfc2396.txt">RFC 2396</link>
+ can be written <emphasis>as is</emphasis>, without quotes. For
+ instance, the string
+ <literal>"http://example.org/foo.tar.bz2"</literal>
+ can also be written as
+ <literal>http://example.org/foo.tar.bz2</literal>.</para>
+
+ </listitem>
+
+ <listitem><para>Numbers, which can be <emphasis>integers</emphasis> (like
+ <literal>123</literal>) or <emphasis>floating point</emphasis> (like
+ <literal>123.43</literal> or <literal>.27e13</literal>).</para>
+
+ <para>Numbers are type-compatible: pure integer operations will always
+ return integers, whereas any operation involving at least one floating point
+ number will have a floating point number as a result.</para></listitem>
+
+ <listitem><para><emphasis>Paths</emphasis>, e.g.,
+ <filename>/bin/sh</filename> or <filename>./builder.sh</filename>.
+ A path must contain at least one slash to be recognised as such; for
+ instance, <filename>builder.sh</filename> is not a
+ path<footnote><para>It's parsed as an expression that selects the
+ attribute <varname>sh</varname> from the variable
+ <varname>builder</varname>.</para></footnote>. If the file name is
+ relative, i.e., if it does not begin with a slash, it is made
+ absolute at parse time relative to the directory of the Nix
+ expression that contained it. For instance, if a Nix expression in
+ <filename>/foo/bar/bla.nix</filename> refers to
+ <filename>../xyzzy/fnord.nix</filename>, the absolute path is
+ <filename>/foo/xyzzy/fnord.nix</filename>.</para>
+
+ <para>If the first component of a path is a <literal>~</literal>,
+ it is interpreted as if the rest of the path were relative to the
+ user's home directory. e.g. <filename>~/foo</filename> would be
+ equivalent to <filename>/home/edolstra/foo</filename> for a user
+ whose home directory is <filename>/home/edolstra</filename>.
+ </para>
+
+ <para>Paths can also be specified between angle brackets, e.g.
+ <literal><nixpkgs></literal>. This means that the directories
+ listed in the environment variable
+ <envar linkend="env-NIX_PATH">NIX_PATH</envar> will be searched
+ for the given file or directory name.
+ </para>
+
+ </listitem>
+
+ <listitem><para><emphasis>Booleans</emphasis> with values
+ <literal>true</literal> and
+ <literal>false</literal>.</para></listitem>
+
+ <listitem><para>The null value, denoted as
+ <literal>null</literal>.</para></listitem>
+
+</itemizedlist>
+
+</para>
+
+</simplesect>
+
+
+<simplesect><title>Lists</title>
+
+<para>Lists are formed by enclosing a whitespace-separated list of
+values between square brackets. For example,
+
+<programlisting>
+[ 123 ./foo.nix "abc" (f { x = y; }) ]</programlisting>
+
+defines a list of four elements, the last being the result of a call
+to the function <varname>f</varname>. Note that function calls have
+to be enclosed in parentheses. If they had been omitted, e.g.,
+
+<programlisting>
+[ 123 ./foo.nix "abc" f { x = y; } ]</programlisting>
+
+the result would be a list of five elements, the fourth one being a
+function and the fifth being a set.</para>
+
+<para>Note that lists are only lazy in values, and they are strict in length.
+</para>
+
+</simplesect>
+
+
+<simplesect><title>Sets</title>
+
+<para>Sets are really the core of the language, since ultimately the
+Nix language is all about creating derivations, which are really just
+sets of attributes to be passed to build scripts.</para>
+
+<para>Sets are just a list of name/value pairs (called
+<emphasis>attributes</emphasis>) enclosed in curly brackets, where
+each value is an arbitrary expression terminated by a semicolon. For
+example:
+
+<programlisting>
+{ x = 123;
+ text = "Hello";
+ y = f { bla = 456; };
+}</programlisting>
+
+This defines a set with attributes named <varname>x</varname>,
+<varname>text</varname>, <varname>y</varname>. The order of the
+attributes is irrelevant. An attribute name may only occur
+once.</para>
+
+<para>Attributes can be selected from a set using the
+<literal>.</literal> operator. For instance,
+
+<programlisting>
+{ a = "Foo"; b = "Bar"; }.a</programlisting>
+
+evaluates to <literal>"Foo"</literal>. It is possible to provide a
+default value in an attribute selection using the
+<literal>or</literal> keyword. For example,
+
+<programlisting>
+{ a = "Foo"; b = "Bar"; }.c or "Xyzzy"</programlisting>
+
+will evaluate to <literal>"Xyzzy"</literal> because there is no
+<varname>c</varname> attribute in the set.</para>
+
+<para>You can use arbitrary double-quoted strings as attribute
+names:
+
+<programlisting>
+{ "foo ${bar}" = 123; "nix-1.0" = 456; }."foo ${bar}"
+</programlisting>
+
+This will evaluate to <literal>123</literal> (Assuming
+<literal>bar</literal> is antiquotable). In the case where an
+attribute name is just a single antiquotation, the quotes can be
+dropped:
+
+<programlisting>
+{ foo = 123; }.${bar} or 456 </programlisting>
+
+This will evaluate to <literal>123</literal> if
+<literal>bar</literal> evaluates to <literal>"foo"</literal> when
+coerced to a string and <literal>456</literal> otherwise (again
+assuming <literal>bar</literal> is antiquotable).</para>
+
+<para>In the special case where an attribute name inside of a set declaration
+evaluates to <literal>null</literal> (which is normally an error, as
+<literal>null</literal> is not antiquotable), that attribute is simply not
+added to the set:
+
+<programlisting>
+{ ${if foo then "bar" else null} = true; }</programlisting>
+
+This will evaluate to <literal>{}</literal> if <literal>foo</literal>
+evaluates to <literal>false</literal>.</para>
+
+<para>A set that has a <literal>__functor</literal> attribute whose value
+is callable (i.e. is itself a function or a set with a
+<literal>__functor</literal> attribute whose value is callable) can be
+applied as if it were a function, with the set itself passed in first
+, e.g.,
+
+<programlisting>
+let add = { __functor = self: x: x + self.x; };
+ inc = add // { x = 1; };
+in inc 1
+</programlisting>
+
+evaluates to <literal>2</literal>. This can be used to attach metadata to a
+function without the caller needing to treat it specially, or to implement
+a form of object-oriented programming, for example.
+
+</para>
+
+</simplesect>
+
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-constructs">
+
+<title>Language Constructs</title>
+
+<simplesect><title>Recursive sets</title>
+
+<para>Recursive sets are just normal sets, but the attributes can
+refer to each other. For example,
+
+<programlisting>
+rec {
+ x = y;
+ y = 123;
+}.x
+</programlisting>
+
+evaluates to <literal>123</literal>. Note that without
+<literal>rec</literal> the binding <literal>x = y;</literal> would
+refer to the variable <varname>y</varname> in the surrounding scope,
+if one exists, and would be invalid if no such variable exists. That
+is, in a normal (non-recursive) set, attributes are not added to the
+lexical scope; in a recursive set, they are.</para>
+
+<para>Recursive sets of course introduce the danger of infinite
+recursion. For example,
+
+<programlisting>
+rec {
+ x = y;
+ y = x;
+}.x</programlisting>
+
+does not terminate<footnote><para>Actually, Nix detects infinite
+recursion in this case and aborts (<quote>infinite recursion
+encountered</quote>).</para></footnote>.</para>
+
+</simplesect>
+
+
+<simplesect xml:id="sect-let-expressions"><title>Let-expressions</title>
+
+<para>A let-expression allows you to define local variables for an
+expression. For instance,
+
+<programlisting>
+let
+ x = "foo";
+ y = "bar";
+in x + y</programlisting>
+
+evaluates to <literal>"foobar"</literal>.
+
+</para>
+
+</simplesect>
+
+
+<simplesect><title>Inheriting attributes</title>
+
+<para>When defining a set or in a let-expression it is often convenient to copy variables
+from the surrounding lexical scope (e.g., when you want to propagate
+attributes). This can be shortened using the
+<literal>inherit</literal> keyword. For instance,
+
+<programlisting>
+let x = 123; in
+{ inherit x;
+ y = 456;
+}</programlisting>
+
+is equivalent to
+
+<programlisting>
+let x = 123; in
+{ x = x;
+ y = 456;
+}</programlisting>
+
+and both evaluate to <literal>{ x = 123; y = 456; }</literal>. (Note that
+this works because <varname>x</varname> is added to the lexical scope
+by the <literal>let</literal> construct.) It is also possible to
+inherit attributes from another set. For instance, in this fragment
+from <filename>all-packages.nix</filename>,
+
+<programlisting>
+ graphviz = (import ../tools/graphics/graphviz) {
+ inherit fetchurl stdenv libpng libjpeg expat x11 yacc;
+ inherit (xlibs) libXaw;
+ };
+
+ xlibs = {
+ libX11 = ...;
+ libXaw = ...;
+ ...
+ }
+
+ libpng = ...;
+ libjpg = ...;
+ ...</programlisting>
+
+the set used in the function call to the function defined in
+<filename>../tools/graphics/graphviz</filename> inherits a number of
+variables from the surrounding scope (<varname>fetchurl</varname>
+... <varname>yacc</varname>), but also inherits
+<varname>libXaw</varname> (the X Athena Widgets) from the
+<varname>xlibs</varname> (X11 client-side libraries) set.</para>
+
+<para>
+Summarizing the fragment
+
+<programlisting>
+...
+inherit x y z;
+inherit (src-set) a b c;
+...</programlisting>
+
+is equivalent to
+
+<programlisting>
+...
+x = x; y = y; z = z;
+a = src-set.a; b = src-set.b; c = src-set.c;
+...</programlisting>
+
+when used while defining local variables in a let-expression or
+while defining a set.</para>
+
+</simplesect>
+
+
+<simplesect xml:id="ss-functions"><title>Functions</title>
+
+<para>Functions have the following form:
+
+<programlisting>
+<replaceable>pattern</replaceable>: <replaceable>body</replaceable></programlisting>
+
+The pattern specifies what the argument of the function must look
+like, and binds variables in the body to (parts of) the
+argument. There are three kinds of patterns:</para>
+
+<itemizedlist>
+
+
+ <listitem><para>If a pattern is a single identifier, then the
+ function matches any argument. Example:
+
+ <programlisting>
+let negate = x: !x;
+ concat = x: y: x + y;
+in if negate true then concat "foo" "bar" else ""</programlisting>
+
+ Note that <function>concat</function> is a function that takes one
+ argument and returns a function that takes another argument. This
+ allows partial parameterisation (i.e., only filling some of the
+ arguments of a function); e.g.,
+
+ <programlisting>
+map (concat "foo") [ "bar" "bla" "abc" ]</programlisting>
+
+ evaluates to <literal>[ "foobar" "foobla"
+ "fooabc" ]</literal>.</para></listitem>
+
+
+ <listitem><para>A <emphasis>set pattern</emphasis> of the form
+ <literal>{ name1, name2, …, nameN }</literal> matches a set
+ containing the listed attributes, and binds the values of those
+ attributes to variables in the function body. For example, the
+ function
+
+<programlisting>
+{ x, y, z }: z + y + x</programlisting>
+
+ can only be called with a set containing exactly the attributes
+ <varname>x</varname>, <varname>y</varname> and
+ <varname>z</varname>. No other attributes are allowed. If you want
+ to allow additional arguments, you can use an ellipsis
+ (<literal>...</literal>):
+
+<programlisting>
+{ x, y, z, ... }: z + y + x</programlisting>
+
+ This works on any set that contains at least the three named
+ attributes.</para>
+
+ <para>It is possible to provide <emphasis>default values</emphasis>
+ for attributes, in which case they are allowed to be missing. A
+ default value is specified by writing
+ <literal><replaceable>name</replaceable> ?
+ <replaceable>e</replaceable></literal>, where
+ <replaceable>e</replaceable> is an arbitrary expression. For example,
+
+<programlisting>
+{ x, y ? "foo", z ? "bar" }: z + y + x</programlisting>
+
+ specifies a function that only requires an attribute named
+ <varname>x</varname>, but optionally accepts <varname>y</varname>
+ and <varname>z</varname>.</para></listitem>
+
+
+ <listitem><para>An <literal>@</literal>-pattern provides a means of referring
+ to the whole value being matched:
+
+<programlisting> args@{ x, y, z, ... }: z + y + x + args.a</programlisting>
+
+but can also be written as:
+
+<programlisting> { x, y, z, ... } @ args: z + y + x + args.a</programlisting>
+
+ Here <varname>args</varname> is bound to the entire argument, which
+ is further matched against the pattern <literal>{ x, y, z,
+ ... }</literal>. <literal>@</literal>-pattern makes mainly sense with an
+ ellipsis(<literal>...</literal>) as you can access attribute names as
+ <literal>a</literal>, using <literal>args.a</literal>, which was given as an
+ additional attribute to the function.
+ </para>
+
+ <warning>
+ <para>
+ The <literal>args@</literal> expression is bound to the argument passed to the function which
+ means that attributes with defaults that aren't explicitly specified in the function call
+ won't cause an evaluation error, but won't exist in <literal>args</literal>.
+ </para>
+ <para>
+ For instance
+<programlisting>
+let
+ function = args@{ a ? 23, ... }: args;
+in
+ function {}
+</programlisting>
+ will evaluate to an empty attribute set.
+ </para>
+ </warning></listitem>
+
+</itemizedlist>
+
+<para>Note that functions do not have names. If you want to give them
+a name, you can bind them to an attribute, e.g.,
+
+<programlisting>
+let concat = { x, y }: x + y;
+in concat { x = "foo"; y = "bar"; }</programlisting>
+
+</para>
+
+</simplesect>
+
+
+<simplesect><title>Conditionals</title>
+
+<para>Conditionals look like this:
+
+<programlisting>
+if <replaceable>e1</replaceable> then <replaceable>e2</replaceable> else <replaceable>e3</replaceable></programlisting>
+
+where <replaceable>e1</replaceable> is an expression that should
+evaluate to a Boolean value (<literal>true</literal> or
+<literal>false</literal>).</para>
+
+</simplesect>
+
+
+<simplesect><title>Assertions</title>
+
+<para>Assertions are generally used to check that certain requirements
+on or between features and dependencies hold. They look like this:
+
+<programlisting>
+assert <replaceable>e1</replaceable>; <replaceable>e2</replaceable></programlisting>
+
+where <replaceable>e1</replaceable> is an expression that should
+evaluate to a Boolean value. If it evaluates to
+<literal>true</literal>, <replaceable>e2</replaceable> is returned;
+otherwise expression evaluation is aborted and a backtrace is printed.</para>
+
+<example xml:id="ex-subversion-nix"><title>Nix expression for Subversion</title>
+<programlisting>
+{ localServer ? false
+, httpServer ? false
+, sslSupport ? false
+, pythonBindings ? false
+, javaSwigBindings ? false
+, javahlBindings ? false
+, stdenv, fetchurl
+, openssl ? null, httpd ? null, db4 ? null, expat, swig ? null, j2sdk ? null
+}:
+
+assert localServer -> db4 != null; <co xml:id="ex-subversion-nix-co-1"/>
+assert httpServer -> httpd != null && httpd.expat == expat; <co xml:id="ex-subversion-nix-co-2"/>
+assert sslSupport -> openssl != null && (httpServer -> httpd.openssl == openssl); <co xml:id="ex-subversion-nix-co-3"/>
+assert pythonBindings -> swig != null && swig.pythonSupport;
+assert javaSwigBindings -> swig != null && swig.javaSupport;
+assert javahlBindings -> j2sdk != null;
+
+stdenv.mkDerivation {
+ name = "subversion-1.1.1";
+ ...
+ openssl = if sslSupport then openssl else null; <co xml:id="ex-subversion-nix-co-4"/>
+ ...
+}</programlisting>
+</example>
+
+<para><xref linkend="ex-subversion-nix"/> show how assertions are
+used in the Nix expression for Subversion.</para>
+
+<calloutlist>
+
+ <callout arearefs="ex-subversion-nix-co-1">
+ <para>This assertion states that if Subversion is to have support
+ for local repositories, then Berkeley DB is needed. So if the
+ Subversion function is called with the
+ <varname>localServer</varname> argument set to
+ <literal>true</literal> but the <varname>db4</varname> argument
+ set to <literal>null</literal>, then the evaluation fails.</para>
+ </callout>
+
+ <callout arearefs="ex-subversion-nix-co-2">
+ <para>This is a more subtle condition: if Subversion is built with
+ Apache (<literal>httpServer</literal>) support, then the Expat
+ library (an XML library) used by Subversion should be same as the
+ one used by Apache. This is because in this configuration
+ Subversion code ends up being linked with Apache code, and if the
+ Expat libraries do not match, a build- or runtime link error or
+ incompatibility might occur.</para>
+ </callout>
+
+ <callout arearefs="ex-subversion-nix-co-3">
+ <para>This assertion says that in order for Subversion to have SSL
+ support (so that it can access <literal>https</literal> URLs), an
+ OpenSSL library must be passed. Additionally, it says that
+ <emphasis>if</emphasis> Apache support is enabled, then Apache's
+ OpenSSL should match Subversion's. (Note that if Apache support
+ is not enabled, we don't care about Apache's OpenSSL.)</para>
+ </callout>
+
+ <callout arearefs="ex-subversion-nix-co-4">
+ <para>The conditional here is not really related to assertions,
+ but is worth pointing out: it ensures that if SSL support is
+ disabled, then the Subversion derivation is not dependent on
+ OpenSSL, even if a non-<literal>null</literal> value was passed.
+ This prevents an unnecessary rebuild of Subversion if OpenSSL
+ changes.</para>
+ </callout>
+
+</calloutlist>
+
+</simplesect>
+
+
+
+<simplesect><title>With-expressions</title>
+
+<para>A <emphasis>with-expression</emphasis>,
+
+<programlisting>
+with <replaceable>e1</replaceable>; <replaceable>e2</replaceable></programlisting>
+
+introduces the set <replaceable>e1</replaceable> into the lexical
+scope of the expression <replaceable>e2</replaceable>. For instance,
+
+<programlisting>
+let as = { x = "foo"; y = "bar"; };
+in with as; x + y</programlisting>
+
+evaluates to <literal>"foobar"</literal> since the
+<literal>with</literal> adds the <varname>x</varname> and
+<varname>y</varname> attributes of <varname>as</varname> to the
+lexical scope in the expression <literal>x + y</literal>. The most
+common use of <literal>with</literal> is in conjunction with the
+<function>import</function> function. E.g.,
+
+<programlisting>
+with (import ./definitions.nix); ...</programlisting>
+
+makes all attributes defined in the file
+<filename>definitions.nix</filename> available as if they were defined
+locally in a <literal>let</literal>-expression.</para>
+
+<para>The bindings introduced by <literal>with</literal> do not shadow bindings
+introduced by other means, e.g.
+
+<programlisting>
+let a = 3; in with { a = 1; }; let a = 4; in with { a = 2; }; ...</programlisting>
+
+establishes the same scope as
+
+<programlisting>
+let a = 1; in let a = 2; in let a = 3; in let a = 4; in ...</programlisting>
+
+</para>
+
+</simplesect>
+
+
+<simplesect><title>Comments</title>
+
+<para>Comments can be single-line, started with a <literal>#</literal>
+character, or inline/multi-line, enclosed within <literal>/*
+... */</literal>.</para>
+
+</simplesect>
+
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-language-operators">
+
+<title>Operators</title>
+
+<para><xref linkend="table-operators"/> lists the operators in the
+Nix expression language, in order of precedence (from strongest to
+weakest binding).</para>
+
+<table xml:id="table-operators">
+ <title>Operators</title>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Name</entry>
+ <entry>Syntax</entry>
+ <entry>Associativity</entry>
+ <entry>Description</entry>
+ <entry>Precedence</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>Select</entry>
+ <entry><replaceable>e</replaceable> <literal>.</literal>
+ <replaceable>attrpath</replaceable>
+ [ <literal>or</literal> <replaceable>def</replaceable> ]
+ </entry>
+ <entry>none</entry>
+ <entry>Select attribute denoted by the attribute path
+ <replaceable>attrpath</replaceable> from set
+ <replaceable>e</replaceable>. (An attribute path is a
+ dot-separated list of attribute names.) If the attribute
+ doesn’t exist, return <replaceable>def</replaceable> if
+ provided, otherwise abort evaluation.</entry>
+ <entry>1</entry>
+ </row>
+ <row>
+ <entry>Application</entry>
+ <entry><replaceable>e1</replaceable> <replaceable>e2</replaceable></entry>
+ <entry>left</entry>
+ <entry>Call function <replaceable>e1</replaceable> with
+ argument <replaceable>e2</replaceable>.</entry>
+ <entry>2</entry>
+ </row>
+ <row>
+ <entry>Arithmetic Negation</entry>
+ <entry><literal>-</literal> <replaceable>e</replaceable></entry>
+ <entry>none</entry>
+ <entry>Arithmetic negation.</entry>
+ <entry>3</entry>
+ </row>
+ <row>
+ <entry>Has Attribute</entry>
+ <entry><replaceable>e</replaceable> <literal>?</literal>
+ <replaceable>attrpath</replaceable></entry>
+ <entry>none</entry>
+ <entry>Test whether set <replaceable>e</replaceable> contains
+ the attribute denoted by <replaceable>attrpath</replaceable>;
+ return <literal>true</literal> or
+ <literal>false</literal>.</entry>
+ <entry>4</entry>
+ </row>
+ <row>
+ <entry>List Concatenation</entry>
+ <entry><replaceable>e1</replaceable> <literal>++</literal> <replaceable>e2</replaceable></entry>
+ <entry>right</entry>
+ <entry>List concatenation.</entry>
+ <entry>5</entry>
+ </row>
+ <row>
+ <entry>Multiplication</entry>
+ <entry>
+ <replaceable>e1</replaceable> <literal>*</literal> <replaceable>e2</replaceable>,
+ </entry>
+ <entry>left</entry>
+ <entry>Arithmetic multiplication.</entry>
+ <entry>6</entry>
+ </row>
+ <row>
+ <entry>Division</entry>
+ <entry>
+ <replaceable>e1</replaceable> <literal>/</literal> <replaceable>e2</replaceable>
+ </entry>
+ <entry>left</entry>
+ <entry>Arithmetic division.</entry>
+ <entry>6</entry>
+ </row>
+ <row>
+ <entry>Addition</entry>
+ <entry>
+ <replaceable>e1</replaceable> <literal>+</literal> <replaceable>e2</replaceable>
+ </entry>
+ <entry>left</entry>
+ <entry>Arithmetic addition.</entry>
+ <entry>7</entry>
+ </row>
+ <row>
+ <entry>Subtraction</entry>
+ <entry>
+ <replaceable>e1</replaceable> <literal>-</literal> <replaceable>e2</replaceable>
+ </entry>
+ <entry>left</entry>
+ <entry>Arithmetic subtraction.</entry>
+ <entry>7</entry>
+ </row>
+ <row>
+ <entry>String Concatenation</entry>
+ <entry>
+ <replaceable>string1</replaceable> <literal>+</literal> <replaceable>string2</replaceable>
+ </entry>
+ <entry>left</entry>
+ <entry>String concatenation.</entry>
+ <entry>7</entry>
+ </row>
+ <row>
+ <entry>Not</entry>
+ <entry><literal>!</literal> <replaceable>e</replaceable></entry>
+ <entry>none</entry>
+ <entry>Boolean negation.</entry>
+ <entry>8</entry>
+ </row>
+ <row>
+ <entry>Update</entry>
+ <entry><replaceable>e1</replaceable> <literal>//</literal>
+ <replaceable>e2</replaceable></entry>
+ <entry>right</entry>
+ <entry>Return a set consisting of the attributes in
+ <replaceable>e1</replaceable> and
+ <replaceable>e2</replaceable> (with the latter taking
+ precedence over the former in case of equally named
+ attributes).</entry>
+ <entry>9</entry>
+ </row>
+ <row>
+ <entry>Less Than</entry>
+ <entry>
+ <replaceable>e1</replaceable> <literal><</literal> <replaceable>e2</replaceable>,
+ </entry>
+ <entry>none</entry>
+ <entry>Arithmetic comparison.</entry>
+ <entry>10</entry>
+ </row>
+ <row>
+ <entry>Less Than or Equal To</entry>
+ <entry>
+ <replaceable>e1</replaceable> <literal><=</literal> <replaceable>e2</replaceable>
+ </entry>
+ <entry>none</entry>
+ <entry>Arithmetic comparison.</entry>
+ <entry>10</entry>
+ </row>
+ <row>
+ <entry>Greater Than</entry>
+ <entry>
+ <replaceable>e1</replaceable> <literal>></literal> <replaceable>e2</replaceable>
+ </entry>
+ <entry>none</entry>
+ <entry>Arithmetic comparison.</entry>
+ <entry>10</entry>
+ </row>
+ <row>
+ <entry>Greater Than or Equal To</entry>
+ <entry>
+ <replaceable>e1</replaceable> <literal>>=</literal> <replaceable>e2</replaceable>
+ </entry>
+ <entry>none</entry>
+ <entry>Arithmetic comparison.</entry>
+ <entry>10</entry>
+ </row>
+ <row>
+ <entry>Equality</entry>
+ <entry>
+ <replaceable>e1</replaceable> <literal>==</literal> <replaceable>e2</replaceable>
+ </entry>
+ <entry>none</entry>
+ <entry>Equality.</entry>
+ <entry>11</entry>
+ </row>
+ <row>
+ <entry>Inequality</entry>
+ <entry>
+ <replaceable>e1</replaceable> <literal>!=</literal> <replaceable>e2</replaceable>
+ </entry>
+ <entry>none</entry>
+ <entry>Inequality.</entry>
+ <entry>11</entry>
+ </row>
+ <row>
+ <entry>Logical AND</entry>
+ <entry><replaceable>e1</replaceable> <literal>&&</literal>
+ <replaceable>e2</replaceable></entry>
+ <entry>left</entry>
+ <entry>Logical AND.</entry>
+ <entry>12</entry>
+ </row>
+ <row>
+ <entry>Logical OR</entry>
+ <entry><replaceable>e1</replaceable> <literal>||</literal>
+ <replaceable>e2</replaceable></entry>
+ <entry>left</entry>
+ <entry>Logical OR.</entry>
+ <entry>13</entry>
+ </row>
+ <row>
+ <entry>Logical Implication</entry>
+ <entry><replaceable>e1</replaceable> <literal>-></literal>
+ <replaceable>e2</replaceable></entry>
+ <entry>none</entry>
+ <entry>Logical implication (equivalent to
+ <literal>!<replaceable>e1</replaceable> ||
+ <replaceable>e2</replaceable></literal>).</entry>
+ <entry>14</entry>
+ </row>
+ </tbody>
+ </tgroup>
+</table>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-derivation">
+
+<title>Derivations</title>
+
+<para>The most important built-in function is
+<function>derivation</function>, which is used to describe a single
+derivation (a build action). It takes as input a set, the attributes
+of which specify the inputs of the build.</para>
+
+<itemizedlist>
+
+ <listitem xml:id="attr-system"><para>There must be an attribute named
+ <varname>system</varname> whose value must be a string specifying a
+ Nix platform identifier, such as <literal>"i686-linux"</literal> or
+ <literal>"x86_64-darwin"</literal><footnote><para>To figure out
+ your platform identifier, look at the line <quote>Checking for the
+ canonical Nix system name</quote> in the output of Nix's
+ <filename>configure</filename> script.</para></footnote> The build
+ can only be performed on a machine and operating system matching the
+ platform identifier. (Nix can automatically forward builds for
+ other platforms by forwarding them to other machines; see <xref linkend="chap-distributed-builds"/>.)</para></listitem>
+
+ <listitem><para>There must be an attribute named
+ <varname>name</varname> whose value must be a string. This is used
+ as a symbolic name for the package by <command>nix-env</command>,
+ and it is appended to the output paths of the
+ derivation.</para></listitem>
+
+ <listitem><para>There must be an attribute named
+ <varname>builder</varname> that identifies the program that is
+ executed to perform the build. It can be either a derivation or a
+ source (a local file reference, e.g.,
+ <filename>./builder.sh</filename>).</para></listitem>
+
+ <listitem><para>Every attribute is passed as an environment variable
+ to the builder. Attribute values are translated to environment
+ variables as follows:
+
+ <itemizedlist>
+
+ <listitem><para>Strings and numbers are just passed
+ verbatim.</para></listitem>
+
+ <listitem><para>A <emphasis>path</emphasis> (e.g.,
+ <filename>../foo/sources.tar</filename>) causes the referenced
+ file to be copied to the store; its location in the store is put
+ in the environment variable. The idea is that all sources
+ should reside in the Nix store, since all inputs to a derivation
+ should reside in the Nix store.</para></listitem>
+
+ <listitem><para>A <emphasis>derivation</emphasis> causes that
+ derivation to be built prior to the present derivation; its
+ default output path is put in the environment
+ variable.</para></listitem>
+
+ <listitem><para>Lists of the previous types are also allowed.
+ They are simply concatenated, separated by
+ spaces.</para></listitem>
+
+ <listitem><para><literal>true</literal> is passed as the string
+ <literal>1</literal>, <literal>false</literal> and
+ <literal>null</literal> are passed as an empty string.
+ </para></listitem>
+ </itemizedlist>
+
+ </para></listitem>
+
+ <listitem><para>The optional attribute <varname>args</varname>
+ specifies command-line arguments to be passed to the builder. It
+ should be a list.</para></listitem>
+
+ <listitem><para>The optional attribute <varname>outputs</varname>
+ specifies a list of symbolic outputs of the derivation. By default,
+ a derivation produces a single output path, denoted as
+ <literal>out</literal>. However, derivations can produce multiple
+ output paths. This is useful because it allows outputs to be
+ downloaded or garbage-collected separately. For instance, imagine a
+ library package that provides a dynamic library, header files, and
+ documentation. A program that links against the library doesn’t
+ need the header files and documentation at runtime, and it doesn’t
+ need the documentation at build time. Thus, the library package
+ could specify:
+<programlisting>
+outputs = [ "lib" "headers" "doc" ];
+</programlisting>
+ This will cause Nix to pass environment variables
+ <literal>lib</literal>, <literal>headers</literal> and
+ <literal>doc</literal> to the builder containing the intended store
+ paths of each output. The builder would typically do something like
+<programlisting>
+./configure --libdir=$lib/lib --includedir=$headers/include --docdir=$doc/share/doc
+</programlisting>
+ for an Autoconf-style package. You can refer to each output of a
+ derivation by selecting it as an attribute, e.g.
+<programlisting>
+buildInputs = [ pkg.lib pkg.headers ];
+</programlisting>
+ The first element of <varname>outputs</varname> determines the
+ <emphasis>default output</emphasis>. Thus, you could also write
+<programlisting>
+buildInputs = [ pkg pkg.headers ];
+</programlisting>
+ since <literal>pkg</literal> is equivalent to
+ <literal>pkg.lib</literal>.</para></listitem>
+
+</itemizedlist>
+
+<para>The function <function>mkDerivation</function> in the Nixpkgs
+standard environment is a wrapper around
+<function>derivation</function> that adds a default value for
+<varname>system</varname> and always uses Bash as the builder, to
+which the supplied builder is passed as a command-line argument. See
+the Nixpkgs manual for details.</para>
+
+<para>The builder is executed as follows:
+
+<itemizedlist>
+
+ <listitem><para>A temporary directory is created under the directory
+ specified by <envar>TMPDIR</envar> (default
+ <filename>/tmp</filename>) where the build will take place. The
+ current directory is changed to this directory.</para></listitem>
+
+ <listitem><para>The environment is cleared and set to the derivation
+ attributes, as specified above.</para></listitem>
+
+ <listitem><para>In addition, the following variables are set:
+
+ <itemizedlist>
+
+ <listitem><para><envar>NIX_BUILD_TOP</envar> contains the path of
+ the temporary directory for this build.</para></listitem>
+
+ <listitem><para>Also, <envar>TMPDIR</envar>,
+ <envar>TEMPDIR</envar>, <envar>TMP</envar>, <envar>TEMP</envar>
+ are set to point to the temporary directory. This is to prevent
+ the builder from accidentally writing temporary files anywhere
+ else. Doing so might cause interference by other
+ processes.</para></listitem>
+
+ <listitem><para><envar>PATH</envar> is set to
+ <filename>/path-not-set</filename> to prevent shells from
+ initialising it to their built-in default value.</para></listitem>
+
+ <listitem><para><envar>HOME</envar> is set to
+ <filename>/homeless-shelter</filename> to prevent programs from
+ using <filename>/etc/passwd</filename> or the like to find the
+ user's home directory, which could cause impurity. Usually, when
+ <envar>HOME</envar> is set, it is used as the location of the home
+ directory, even if it points to a non-existent
+ path.</para></listitem>
+
+ <listitem><para><envar>NIX_STORE</envar> is set to the path of the
+ top-level Nix store directory (typically,
+ <filename>/nix/store</filename>).</para></listitem>
+
+ <listitem><para>For each output declared in
+ <varname>outputs</varname>, the corresponding environment variable
+ is set to point to the intended path in the Nix store for that
+ output. Each output path is a concatenation of the cryptographic
+ hash of all build inputs, the <varname>name</varname> attribute
+ and the output name. (The output name is omitted if it’s
+ <literal>out</literal>.)</para></listitem>
+
+ </itemizedlist>
+
+ </para></listitem>
+
+ <listitem><para>If an output path already exists, it is removed.
+ Also, locks are acquired to prevent multiple Nix instances from
+ performing the same build at the same time.</para></listitem>
+
+ <listitem><para>A log of the combined standard output and error is
+ written to <filename>/nix/var/log/nix</filename>.</para></listitem>
+
+ <listitem><para>The builder is executed with the arguments specified
+ by the attribute <varname>args</varname>. If it exits with exit
+ code 0, it is considered to have succeeded.</para></listitem>
+
+ <listitem><para>The temporary directory is removed (unless the
+ <option>-K</option> option was specified).</para></listitem>
+
+ <listitem><para>If the build was successful, Nix scans each output
+ path for references to input paths by looking for the hash parts of
+ the input paths. Since these are potential runtime dependencies,
+ Nix registers them as dependencies of the output
+ paths.</para></listitem>
+
+ <listitem><para>After the build, Nix sets the last-modified
+ timestamp on all files in the build result to 1 (00:00:01 1/1/1970
+ UTC), sets the group to the default group, and sets the mode of the
+ file to 0444 or 0555 (i.e., read-only, with execute permission
+ enabled if the file was originally executable). Note that possible
+ <literal>setuid</literal> and <literal>setgid</literal> bits are
+ cleared. Setuid and setgid programs are not currently supported by
+ Nix. This is because the Nix archives used in deployment have no
+ concept of ownership information, and because it makes the build
+ result dependent on the user performing the build.</para></listitem>
+
+</itemizedlist>
+
+</para>
+
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-advanced-attributes">
+
+<title>Advanced Attributes</title>
+
+<para>Derivations can declare some infrequently used optional
+attributes.</para>
+
+<variablelist>
+
+ <varlistentry xml:id="adv-attr-allowedReferences"><term><varname>allowedReferences</varname></term>
+
+ <listitem><para>The optional attribute
+ <varname>allowedReferences</varname> specifies a list of legal
+ references (dependencies) of the output of the builder. For
+ example,
+
+<programlisting>
+allowedReferences = [];
+</programlisting>
+
+ enforces that the output of a derivation cannot have any runtime
+ dependencies on its inputs. To allow an output to have a runtime
+ dependency on itself, use <literal>"out"</literal> as a list item.
+ This is used in NixOS to check that generated files such as
+ initial ramdisks for booting Linux don’t have accidental
+ dependencies on other paths in the Nix store.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="adv-attr-allowedRequisites"><term><varname>allowedRequisites</varname></term>
+
+ <listitem><para>This attribute is similar to
+ <varname>allowedReferences</varname>, but it specifies the legal
+ requisites of the whole closure, so all the dependencies
+ recursively. For example,
+
+<programlisting>
+allowedRequisites = [ foobar ];
+</programlisting>
+
+ enforces that the output of a derivation cannot have any other
+ runtime dependency than <varname>foobar</varname>, and in addition
+ it enforces that <varname>foobar</varname> itself doesn't
+ introduce any other dependency itself.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="adv-attr-disallowedReferences"><term><varname>disallowedReferences</varname></term>
+
+ <listitem><para>The optional attribute
+ <varname>disallowedReferences</varname> specifies a list of illegal
+ references (dependencies) of the output of the builder. For
+ example,
+
+<programlisting>
+disallowedReferences = [ foo ];
+</programlisting>
+
+ enforces that the output of a derivation cannot have a direct runtime
+ dependencies on the derivation <varname>foo</varname>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="adv-attr-disallowedRequisites"><term><varname>disallowedRequisites</varname></term>
+
+ <listitem><para>This attribute is similar to
+ <varname>disallowedReferences</varname>, but it specifies illegal
+ requisites for the whole closure, so all the dependencies
+ recursively. For example,
+
+<programlisting>
+disallowedRequisites = [ foobar ];
+</programlisting>
+
+ enforces that the output of a derivation cannot have any
+ runtime dependency on <varname>foobar</varname> or any other derivation
+ depending recursively on <varname>foobar</varname>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="adv-attr-exportReferencesGraph"><term><varname>exportReferencesGraph</varname></term>
+
+ <listitem><para>This attribute allows builders access to the
+ references graph of their inputs. The attribute is a list of
+ inputs in the Nix store whose references graph the builder needs
+ to know. The value of this attribute should be a list of pairs
+ <literal>[ <replaceable>name1</replaceable>
+ <replaceable>path1</replaceable> <replaceable>name2</replaceable>
+ <replaceable>path2</replaceable> <replaceable>...</replaceable>
+ ]</literal>. The references graph of each
+ <replaceable>pathN</replaceable> will be stored in a text file
+ <replaceable>nameN</replaceable> in the temporary build directory.
+ The text files have the format used by <command>nix-store
+ --register-validity</command> (with the deriver fields left
+ empty). For example, when the following derivation is built:
+
+<programlisting>
+derivation {
+ ...
+ exportReferencesGraph = [ "libfoo-graph" libfoo ];
+};
+</programlisting>
+
+ the references graph of <literal>libfoo</literal> is placed in the
+ file <filename>libfoo-graph</filename> in the temporary build
+ directory.</para>
+
+ <para><varname>exportReferencesGraph</varname> is useful for
+ builders that want to do something with the closure of a store
+ path. Examples include the builders in NixOS that generate the
+ initial ramdisk for booting Linux (a <command>cpio</command>
+ archive containing the closure of the boot script) and the
+ ISO-9660 image for the installation CD (which is populated with a
+ Nix store containing the closure of a bootable NixOS
+ configuration).</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="adv-attr-impureEnvVars"><term><varname>impureEnvVars</varname></term>
+
+ <listitem><para>This attribute allows you to specify a list of
+ environment variables that should be passed from the environment
+ of the calling user to the builder. Usually, the environment is
+ cleared completely when the builder is executed, but with this
+ attribute you can allow specific environment variables to be
+ passed unmodified. For example, <function>fetchurl</function> in
+ Nixpkgs has the line
+
+<programlisting>
+impureEnvVars = [ "http_proxy" "https_proxy" <replaceable>...</replaceable> ];
+</programlisting>
+
+ to make it use the proxy server configuration specified by the
+ user in the environment variables <envar>http_proxy</envar> and
+ friends.</para>
+
+ <para>This attribute is only allowed in <link linkend="fixed-output-drvs">fixed-output derivations</link>, where
+ impurities such as these are okay since (the hash of) the output
+ is known in advance. It is ignored for all other
+ derivations.</para>
+
+ <warning><para><varname>impureEnvVars</varname> implementation takes
+ environment variables from the current builder process. When a daemon is
+ building its environmental variables are used. Without the daemon, the
+ environmental variables come from the environment of the
+ <command>nix-build</command>.</para></warning></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="fixed-output-drvs">
+ <term xml:id="adv-attr-outputHash"><varname>outputHash</varname></term>
+ <term xml:id="adv-attr-outputHashAlgo"><varname>outputHashAlgo</varname></term>
+ <term xml:id="adv-attr-outputHashMode"><varname>outputHashMode</varname></term>
+
+ <listitem><para>These attributes declare that the derivation is a
+ so-called <emphasis>fixed-output derivation</emphasis>, which
+ means that a cryptographic hash of the output is already known in
+ advance. When the build of a fixed-output derivation finishes,
+ Nix computes the cryptographic hash of the output and compares it
+ to the hash declared with these attributes. If there is a
+ mismatch, the build fails.</para>
+
+ <para>The rationale for fixed-output derivations is derivations
+ such as those produced by the <function>fetchurl</function>
+ function. This function downloads a file from a given URL. To
+ ensure that the downloaded file has not been modified, the caller
+ must also specify a cryptographic hash of the file. For example,
+
+<programlisting>
+fetchurl {
+ url = "http://ftp.gnu.org/pub/gnu/hello/hello-2.1.1.tar.gz";
+ sha256 = "1md7jsfd8pa45z73bz1kszpp01yw6x5ljkjk2hx7wl800any6465";
+}
+</programlisting>
+
+ It sometimes happens that the URL of the file changes, e.g.,
+ because servers are reorganised or no longer available. We then
+ must update the call to <function>fetchurl</function>, e.g.,
+
+<programlisting>
+fetchurl {
+ url = "ftp://ftp.nluug.nl/pub/gnu/hello/hello-2.1.1.tar.gz";
+ sha256 = "1md7jsfd8pa45z73bz1kszpp01yw6x5ljkjk2hx7wl800any6465";
+}
+</programlisting>
+
+ If a <function>fetchurl</function> derivation was treated like a
+ normal derivation, the output paths of the derivation and
+ <emphasis>all derivations depending on it</emphasis> would change.
+ For instance, if we were to change the URL of the Glibc source
+ distribution in Nixpkgs (a package on which almost all other
+ packages depend) massive rebuilds would be needed. This is
+ unfortunate for a change which we know cannot have a real effect
+ as it propagates upwards through the dependency graph.</para>
+
+ <para>For fixed-output derivations, on the other hand, the name of
+ the output path only depends on the <varname>outputHash*</varname>
+ and <varname>name</varname> attributes, while all other attributes
+ are ignored for the purpose of computing the output path. (The
+ <varname>name</varname> attribute is included because it is part
+ of the path.)</para>
+
+ <para>As an example, here is the (simplified) Nix expression for
+ <varname>fetchurl</varname>:
+
+<programlisting>
+{ stdenv, curl }: # The <command>curl</command> program is used for downloading.
+
+{ url, sha256 }:
+
+stdenv.mkDerivation {
+ name = baseNameOf (toString url);
+ builder = ./builder.sh;
+ buildInputs = [ curl ];
+
+ # This is a fixed-output derivation; the output must be a regular
+ # file with SHA256 hash <varname>sha256</varname>.
+ outputHashMode = "flat";
+ outputHashAlgo = "sha256";
+ outputHash = sha256;
+
+ inherit url;
+}
+</programlisting>
+
+ </para>
+
+ <para>The <varname>outputHashAlgo</varname> attribute specifies
+ the hash algorithm used to compute the hash. It can currently be
+ <literal>"sha1"</literal>, <literal>"sha256"</literal> or
+ <literal>"sha512"</literal>.</para>
+
+ <para>The <varname>outputHashMode</varname> attribute determines
+ how the hash is computed. It must be one of the following two
+ values:
+
+ <variablelist>
+
+ <varlistentry><term><literal>"flat"</literal></term>
+
+ <listitem><para>The output must be a non-executable regular
+ file. If it isn’t, the build fails. The hash is simply
+ computed over the contents of that file (so it’s equal to what
+ Unix commands like <command>sha256sum</command> or
+ <command>sha1sum</command> produce).</para>
+
+ <para>This is the default.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><literal>"recursive"</literal></term>
+
+ <listitem><para>The hash is computed over the NAR archive dump
+ of the output (i.e., the result of <link linkend="refsec-nix-store-dump"><command>nix-store
+ --dump</command></link>). In this case, the output can be
+ anything, including a directory tree.</para></listitem>
+
+ </varlistentry>
+
+ </variablelist>
+
+ </para>
+
+ <para>The <varname>outputHash</varname> attribute, finally, must
+ be a string containing the hash in either hexadecimal or base-32
+ notation. (See the <link linkend="sec-nix-hash"><command>nix-hash</command> command</link>
+ for information about converting to and from base-32
+ notation.)</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="adv-attr-passAsFile"><term><varname>passAsFile</varname></term>
+
+ <listitem><para>A list of names of attributes that should be
+ passed via files rather than environment variables. For example,
+ if you have
+
+ <programlisting>
+passAsFile = ["big"];
+big = "a very long string";
+ </programlisting>
+
+ then when the builder runs, the environment variable
+ <envar>bigPath</envar> will contain the absolute path to a
+ temporary file containing <literal>a very long
+ string</literal>. That is, for any attribute
+ <replaceable>x</replaceable> listed in
+ <varname>passAsFile</varname>, Nix will pass an environment
+ variable <envar><replaceable>x</replaceable>Path</envar> holding
+ the path of the file containing the value of attribute
+ <replaceable>x</replaceable>. This is useful when you need to pass
+ large strings to a builder, since most operating systems impose a
+ limit on the size of the environment (typically, a few hundred
+ kilobyte).</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="adv-attr-preferLocalBuild"><term><varname>preferLocalBuild</varname></term>
+
+ <listitem><para>If this attribute is set to
+ <literal>true</literal> and <link linkend="chap-distributed-builds">distributed building is
+ enabled</link>, then, if possible, the derivaton will be built
+ locally instead of forwarded to a remote machine. This is
+ appropriate for trivial builders where the cost of doing a
+ download or remote build would exceed the cost of building
+ locally.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="adv-attr-allowSubstitutes"><term><varname>allowSubstitutes</varname></term>
+
+ <listitem>
+ <para>If this attribute is set to
+ <literal>false</literal>, then Nix will always build this
+ derivation; it will not try to substitute its outputs. This is
+ useful for very trivial derivations (such as
+ <function>writeText</function> in Nixpkgs) that are cheaper to
+ build than to substitute from a binary cache.</para>
+
+ <note><para>You need to have a builder configured which satisfies
+ the derivation’s <literal>system</literal> attribute, since the
+ derivation cannot be substituted. Thus it is usually a good idea
+ to align <literal>system</literal> with
+ <literal>builtins.currentSystem</literal> when setting
+ <literal>allowSubstitutes</literal> to <literal>false</literal>.
+ For most trivial derivations this should be the case.
+ </para></note>
+ </listitem>
+
+ </varlistentry>
+
+
+</variablelist>
+
+</section>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-builtins">
+
+<title>Built-in Functions</title>
+
+<para>This section lists the functions and constants built into the
+Nix expression evaluator. (The built-in function
+<function>derivation</function> is discussed above.) Some built-ins,
+such as <function>derivation</function>, are always in scope of every
+Nix expression; you can just access them right away. But to prevent
+polluting the namespace too much, most built-ins are not in scope.
+Instead, you can access them through the <varname>builtins</varname>
+built-in value, which is a set that contains all built-in functions
+and values. For instance, <function>derivation</function> is also
+available as <function>builtins.derivation</function>.</para>
+
+
+<variablelist>
+
+
+ <varlistentry xml:id="builtin-abort">
+ <term><function>abort</function> <replaceable>s</replaceable></term>
+ <term><function>builtins.abort</function> <replaceable>s</replaceable></term>
+
+ <listitem><para>Abort Nix expression evaluation, print error
+ message <replaceable>s</replaceable>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-add">
+ <term><function>builtins.add</function>
+ <replaceable>e1</replaceable> <replaceable>e2</replaceable>
+ </term>
+
+ <listitem><para>Return the sum of the numbers
+ <replaceable>e1</replaceable> and
+ <replaceable>e2</replaceable>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-all">
+ <term><function>builtins.all</function>
+ <replaceable>pred</replaceable> <replaceable>list</replaceable></term>
+
+ <listitem><para>Return <literal>true</literal> if the function
+ <replaceable>pred</replaceable> returns <literal>true</literal>
+ for all elements of <replaceable>list</replaceable>,
+ and <literal>false</literal> otherwise.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-any">
+ <term><function>builtins.any</function>
+ <replaceable>pred</replaceable> <replaceable>list</replaceable></term>
+
+ <listitem><para>Return <literal>true</literal> if the function
+ <replaceable>pred</replaceable> returns <literal>true</literal>
+ for at least one element of <replaceable>list</replaceable>,
+ and <literal>false</literal> otherwise.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-attrNames">
+ <term><function>builtins.attrNames</function>
+ <replaceable>set</replaceable></term>
+
+ <listitem><para>Return the names of the attributes in the set
+ <replaceable>set</replaceable> in an alphabetically sorted list. For instance,
+ <literal>builtins.attrNames { y = 1; x = "foo"; }</literal>
+ evaluates to <literal>[ "x" "y" ]</literal>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-attrValues">
+ <term><function>builtins.attrValues</function>
+ <replaceable>set</replaceable></term>
+
+ <listitem><para>Return the values of the attributes in the set
+ <replaceable>set</replaceable> in the order corresponding to the
+ sorted attribute names.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-baseNameOf">
+ <term><function>baseNameOf</function> <replaceable>s</replaceable></term>
+
+ <listitem><para>Return the <emphasis>base name</emphasis> of the
+ string <replaceable>s</replaceable>, that is, everything following
+ the final slash in the string. This is similar to the GNU
+ <command>basename</command> command.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-bitAnd">
+ <term><function>builtins.bitAnd</function>
+ <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+
+ <listitem><para>Return the bitwise AND of the integers
+ <replaceable>e1</replaceable> and
+ <replaceable>e2</replaceable>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-bitOr">
+ <term><function>builtins.bitOr</function>
+ <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+
+ <listitem><para>Return the bitwise OR of the integers
+ <replaceable>e1</replaceable> and
+ <replaceable>e2</replaceable>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-bitXor">
+ <term><function>builtins.bitXor</function>
+ <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+
+ <listitem><para>Return the bitwise XOR of the integers
+ <replaceable>e1</replaceable> and
+ <replaceable>e2</replaceable>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-builtins">
+ <term><varname>builtins</varname></term>
+
+ <listitem><para>The set <varname>builtins</varname> contains all
+ the built-in functions and values. You can use
+ <varname>builtins</varname> to test for the availability of
+ features in the Nix installation, e.g.,
+
+<programlisting>
+if builtins ? getEnv then builtins.getEnv "PATH" else ""</programlisting>
+
+ This allows a Nix expression to fall back gracefully on older Nix
+ installations that don’t have the desired built-in
+ function.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-compareVersions">
+ <term><function>builtins.compareVersions</function>
+ <replaceable>s1</replaceable> <replaceable>s2</replaceable></term>
+
+ <listitem><para>Compare two strings representing versions and
+ return <literal>-1</literal> if version
+ <replaceable>s1</replaceable> is older than version
+ <replaceable>s2</replaceable>, <literal>0</literal> if they are
+ the same, and <literal>1</literal> if
+ <replaceable>s1</replaceable> is newer than
+ <replaceable>s2</replaceable>. The version comparison algorithm
+ is the same as the one used by <link linkend="ssec-version-comparisons"><command>nix-env
+ -u</command></link>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-concatLists">
+ <term><function>builtins.concatLists</function>
+ <replaceable>lists</replaceable></term>
+
+ <listitem><para>Concatenate a list of lists into a single
+ list.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="builtin-concatStringsSep">
+ <term><function>builtins.concatStringsSep</function>
+ <replaceable>separator</replaceable> <replaceable>list</replaceable></term>
+
+ <listitem><para>Concatenate a list of strings with a separator
+ between each element, e.g. <literal>concatStringsSep "/"
+ ["usr" "local" "bin"] == "usr/local/bin"</literal></para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="builtin-currentSystem">
+ <term><varname>builtins.currentSystem</varname></term>
+
+ <listitem><para>The built-in value <varname>currentSystem</varname>
+ evaluates to the Nix platform identifier for the Nix installation
+ on which the expression is being evaluated, such as
+ <literal>"i686-linux"</literal> or
+ <literal>"x86_64-darwin"</literal>.</para></listitem>
+
+ </varlistentry>
+
+
+ <!--
+ <varlistentry><term><function>currentTime</function></term>
+
+ <listitem><para>The built-in value <varname>currentTime</varname>
+ returns the current system time in seconds since 00:00:00 1/1/1970
+ UTC. Due to the evaluation model of Nix expressions
+ (<emphasis>maximal laziness</emphasis>), it always yields the same
+ value within an execution of Nix.</para></listitem>
+
+ </varlistentry>
+ -->
+
+
+ <!--
+ <varlistentry><term><function>dependencyClosure</function></term>
+
+ <listitem><para>TODO</para></listitem>
+
+ </varlistentry>
+ -->
+
+
+ <varlistentry xml:id="builtin-deepSeq">
+ <term><function>builtins.deepSeq</function>
+ <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+
+ <listitem><para>This is like <literal>seq
+ <replaceable>e1</replaceable>
+ <replaceable>e2</replaceable></literal>, except that
+ <replaceable>e1</replaceable> is evaluated
+ <emphasis>deeply</emphasis>: if it’s a list or set, its elements
+ or attributes are also evaluated recursively.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-derivation">
+ <term><function>derivation</function>
+ <replaceable>attrs</replaceable></term>
+ <term><function>builtins.derivation</function>
+ <replaceable>attrs</replaceable></term>
+
+ <listitem><para><function>derivation</function> is described in
+ <xref linkend="ssec-derivation"/>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-dirOf">
+ <term><function>dirOf</function> <replaceable>s</replaceable></term>
+ <term><function>builtins.dirOf</function> <replaceable>s</replaceable></term>
+
+ <listitem><para>Return the directory part of the string
+ <replaceable>s</replaceable>, that is, everything before the final
+ slash in the string. This is similar to the GNU
+ <command>dirname</command> command.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-div">
+ <term><function>builtins.div</function>
+ <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+
+ <listitem><para>Return the quotient of the numbers
+ <replaceable>e1</replaceable> and
+ <replaceable>e2</replaceable>.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="builtin-elem">
+ <term><function>builtins.elem</function>
+ <replaceable>x</replaceable> <replaceable>xs</replaceable></term>
+
+ <listitem><para>Return <literal>true</literal> if a value equal to
+ <replaceable>x</replaceable> occurs in the list
+ <replaceable>xs</replaceable>, and <literal>false</literal>
+ otherwise.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-elemAt">
+ <term><function>builtins.elemAt</function>
+ <replaceable>xs</replaceable> <replaceable>n</replaceable></term>
+
+ <listitem><para>Return element <replaceable>n</replaceable> from
+ the list <replaceable>xs</replaceable>. Elements are counted
+ starting from 0. A fatal error occurs if the index is out of
+ bounds.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-fetchurl">
+ <term><function>builtins.fetchurl</function>
+ <replaceable>url</replaceable></term>
+
+ <listitem><para>Download the specified URL and return the path of
+ the downloaded file. This function is not available if <link linkend="conf-restrict-eval">restricted evaluation mode</link> is
+ enabled.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-fetchTarball">
+ <term><function>fetchTarball</function>
+ <replaceable>url</replaceable></term>
+ <term><function>builtins.fetchTarball</function>
+ <replaceable>url</replaceable></term>
+
+ <listitem><para>Download the specified URL, unpack it and return
+ the path of the unpacked tree. The file must be a tape archive
+ (<filename>.tar</filename>) compressed with
+ <literal>gzip</literal>, <literal>bzip2</literal> or
+ <literal>xz</literal>. The top-level path component of the files
+ in the tarball is removed, so it is best if the tarball contains a
+ single directory at top level. The typical use of the function is
+ to obtain external Nix expression dependencies, such as a
+ particular version of Nixpkgs, e.g.
+
+<programlisting>
+with import (fetchTarball https://github.com/NixOS/nixpkgs/archive/nixos-14.12.tar.gz) {};
+
+stdenv.mkDerivation { … }
+</programlisting>
+ </para>
+
+ <para>The fetched tarball is cached for a certain amount of time
+ (1 hour by default) in <filename>~/.cache/nix/tarballs/</filename>.
+ You can change the cache timeout either on the command line with
+ <option>--option tarball-ttl <replaceable>number of seconds</replaceable></option> or
+ in the Nix configuration file with this option:
+ <literal><xref linkend="conf-tarball-ttl"/> <replaceable>number of seconds to cache</replaceable></literal>.
+ </para>
+
+ <para>Note that when obtaining the hash with <varname>nix-prefetch-url
+ </varname> the option <varname>--unpack</varname> is required.
+ </para>
+
+ <para>This function can also verify the contents against a hash.
+ In that case, the function takes a set instead of a URL. The set
+ requires the attribute <varname>url</varname> and the attribute
+ <varname>sha256</varname>, e.g.
+
+<programlisting>
+with import (fetchTarball {
+ url = "https://github.com/NixOS/nixpkgs/archive/nixos-14.12.tar.gz";
+ sha256 = "1jppksrfvbk5ypiqdz4cddxdl8z6zyzdb2srq8fcffr327ld5jj2";
+}) {};
+
+stdenv.mkDerivation { … }
+</programlisting>
+
+ </para>
+
+ <para>This function is not available if <link linkend="conf-restrict-eval">restricted evaluation mode</link> is
+ enabled.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="builtin-fetchGit">
+ <term>
+ <function>builtins.fetchGit</function>
+ <replaceable>args</replaceable>
+ </term>
+
+ <listitem>
+ <para>
+ Fetch a path from git. <replaceable>args</replaceable> can be
+ a URL, in which case the HEAD of the repo at that URL is
+ fetched. Otherwise, it can be an attribute with the following
+ attributes (all except <varname>url</varname> optional):
+ </para>
+
+ <variablelist>
+ <varlistentry>
+ <term>url</term>
+ <listitem>
+ <para>
+ The URL of the repo.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>name</term>
+ <listitem>
+ <para>
+ The name of the directory the repo should be exported to
+ in the store. Defaults to the basename of the URL.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>rev</term>
+ <listitem>
+ <para>
+ The git revision to fetch. Defaults to the tip of
+ <varname>ref</varname>.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ref</term>
+ <listitem>
+ <para>
+ The git ref to look for the requested revision under.
+ This is often a branch or tag name. Defaults to
+ <literal>HEAD</literal>.
+ </para>
+
+ <para>
+ By default, the <varname>ref</varname> value is prefixed
+ with <literal>refs/heads/</literal>. As of Nix 2.3.0
+ Nix will not prefix <literal>refs/heads/</literal> if
+ <varname>ref</varname> starts with <literal>refs/</literal>.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>submodules</term>
+ <listitem>
+ <para>
+ A Boolean parameter that specifies whether submodules
+ should be checked out. Defaults to
+ <literal>false</literal>.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ <example>
+ <title>Fetching a private repository over SSH</title>
+ <programlisting>builtins.fetchGit {
+ url = "git@github.com:my-secret/repository.git";
+ ref = "master";
+ rev = "adab8b916a45068c044658c4158d81878f9ed1c3";
+}</programlisting>
+ </example>
+
+ <example>
+ <title>Fetching an arbitrary ref</title>
+ <programlisting>builtins.fetchGit {
+ url = "https://github.com/NixOS/nix.git";
+ ref = "refs/heads/0.5-release";
+}</programlisting>
+ </example>
+
+ <example>
+ <title>Fetching a repository's specific commit on an arbitrary branch</title>
+ <para>
+ If the revision you're looking for is in the default branch
+ of the git repository you don't strictly need to specify
+ the branch name in the <varname>ref</varname> attribute.
+ </para>
+ <para>
+ However, if the revision you're looking for is in a future
+ branch for the non-default branch you will need to specify
+ the the <varname>ref</varname> attribute as well.
+ </para>
+ <programlisting>builtins.fetchGit {
+ url = "https://github.com/nixos/nix.git";
+ rev = "841fcbd04755c7a2865c51c1e2d3b045976b7452";
+ ref = "1.11-maintenance";
+}</programlisting>
+ <note>
+ <para>
+ It is nice to always specify the branch which a revision
+ belongs to. Without the branch being specified, the
+ fetcher might fail if the default branch changes.
+ Additionally, it can be confusing to try a commit from a
+ non-default branch and see the fetch fail. If the branch
+ is specified the fault is much more obvious.
+ </para>
+ </note>
+ </example>
+
+ <example>
+ <title>Fetching a repository's specific commit on the default branch</title>
+ <para>
+ If the revision you're looking for is in the default branch
+ of the git repository you may omit the
+ <varname>ref</varname> attribute.
+ </para>
+ <programlisting>builtins.fetchGit {
+ url = "https://github.com/nixos/nix.git";
+ rev = "841fcbd04755c7a2865c51c1e2d3b045976b7452";
+}</programlisting>
+ </example>
+
+ <example>
+ <title>Fetching a tag</title>
+ <programlisting>builtins.fetchGit {
+ url = "https://github.com/nixos/nix.git";
+ ref = "refs/tags/1.9";
+}</programlisting>
+ </example>
+
+ <example>
+ <title>Fetching the latest version of a remote branch</title>
+ <para>
+ <function>builtins.fetchGit</function> can behave impurely
+ fetch the latest version of a remote branch.
+ </para>
+ <note><para>Nix will refetch the branch in accordance to
+ <xref linkend="conf-tarball-ttl"/>.</para></note>
+ <note><para>This behavior is disabled in
+ <emphasis>Pure evaluation mode</emphasis>.</para></note>
+ <programlisting>builtins.fetchGit {
+ url = "ssh://git@github.com/nixos/nix.git";
+ ref = "master";
+}</programlisting>
+ </example>
+ </listitem>
+ </varlistentry>
+
+
+ <varlistentry><term><function>builtins.filter</function>
+ <replaceable>f</replaceable> <replaceable>xs</replaceable></term>
+
+ <listitem><para>Return a list consisting of the elements of
+ <replaceable>xs</replaceable> for which the function
+ <replaceable>f</replaceable> returns
+ <literal>true</literal>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-filterSource">
+ <term><function>builtins.filterSource</function>
+ <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+
+ <listitem>
+
+ <para>This function allows you to copy sources into the Nix
+ store while filtering certain files. For instance, suppose that
+ you want to use the directory <filename>source-dir</filename> as
+ an input to a Nix expression, e.g.
+
+<programlisting>
+stdenv.mkDerivation {
+ ...
+ src = ./source-dir;
+}
+</programlisting>
+
+ However, if <filename>source-dir</filename> is a Subversion
+ working copy, then all those annoying <filename>.svn</filename>
+ subdirectories will also be copied to the store. Worse, the
+ contents of those directories may change a lot, causing lots of
+ spurious rebuilds. With <function>filterSource</function> you
+ can filter out the <filename>.svn</filename> directories:
+
+<programlisting>
+ src = builtins.filterSource
+ (path: type: type != "directory" || baseNameOf path != ".svn")
+ ./source-dir;
+</programlisting>
+
+ </para>
+
+ <para>Thus, the first argument <replaceable>e1</replaceable>
+ must be a predicate function that is called for each regular
+ file, directory or symlink in the source tree
+ <replaceable>e2</replaceable>. If the function returns
+ <literal>true</literal>, the file is copied to the Nix store,
+ otherwise it is omitted. The function is called with two
+ arguments. The first is the full path of the file. The second
+ is a string that identifies the type of the file, which is
+ either <literal>"regular"</literal>,
+ <literal>"directory"</literal>, <literal>"symlink"</literal> or
+ <literal>"unknown"</literal> (for other kinds of files such as
+ device nodes or fifos — but note that those cannot be copied to
+ the Nix store, so if the predicate returns
+ <literal>true</literal> for them, the copy will fail). If you
+ exclude a directory, the entire corresponding subtree of
+ <replaceable>e2</replaceable> will be excluded.</para>
+
+ </listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-foldl-prime">
+ <term><function>builtins.foldl’</function>
+ <replaceable>op</replaceable> <replaceable>nul</replaceable> <replaceable>list</replaceable></term>
+
+ <listitem><para>Reduce a list by applying a binary operator, from
+ left to right, e.g. <literal>foldl’ op nul [x0 x1 x2 ...] = op (op
+ (op nul x0) x1) x2) ...</literal>. The operator is applied
+ strictly, i.e., its arguments are evaluated first. For example,
+ <literal>foldl’ (x: y: x + y) 0 [1 2 3]</literal> evaluates to
+ 6.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-functionArgs">
+ <term><function>builtins.functionArgs</function>
+ <replaceable>f</replaceable></term>
+
+ <listitem><para>
+ Return a set containing the names of the formal arguments expected
+ by the function <replaceable>f</replaceable>.
+ The value of each attribute is a Boolean denoting whether the corresponding
+ argument has a default value. For instance,
+ <literal>functionArgs ({ x, y ? 123}: ...) = { x = false; y = true; }</literal>.
+ </para>
+
+ <para>"Formal argument" here refers to the attributes pattern-matched by
+ the function. Plain lambdas are not included, e.g.
+ <literal>functionArgs (x: ...) = { }</literal>.
+ </para></listitem>
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-fromJSON">
+ <term><function>builtins.fromJSON</function> <replaceable>e</replaceable></term>
+
+ <listitem><para>Convert a JSON string to a Nix
+ value. For example,
+
+<programlisting>
+builtins.fromJSON ''{"x": [1, 2, 3], "y": null}''
+</programlisting>
+
+ returns the value <literal>{ x = [ 1 2 3 ]; y = null;
+ }</literal>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-genList">
+ <term><function>builtins.genList</function>
+ <replaceable>generator</replaceable> <replaceable>length</replaceable></term>
+
+ <listitem><para>Generate list of size
+ <replaceable>length</replaceable>, with each element
+ <replaceable>i</replaceable> equal to the value returned by
+ <replaceable>generator</replaceable> <literal>i</literal>. For
+ example,
+
+<programlisting>
+builtins.genList (x: x * x) 5
+</programlisting>
+
+ returns the list <literal>[ 0 1 4 9 16 ]</literal>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-getAttr">
+ <term><function>builtins.getAttr</function>
+ <replaceable>s</replaceable> <replaceable>set</replaceable></term>
+
+ <listitem><para><function>getAttr</function> returns the attribute
+ named <replaceable>s</replaceable> from
+ <replaceable>set</replaceable>. Evaluation aborts if the
+ attribute doesn’t exist. This is a dynamic version of the
+ <literal>.</literal> operator, since <replaceable>s</replaceable>
+ is an expression rather than an identifier.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-getEnv">
+ <term><function>builtins.getEnv</function>
+ <replaceable>s</replaceable></term>
+
+ <listitem><para><function>getEnv</function> returns the value of
+ the environment variable <replaceable>s</replaceable>, or an empty
+ string if the variable doesn’t exist. This function should be
+ used with care, as it can introduce all sorts of nasty environment
+ dependencies in your Nix expression.</para>
+
+ <para><function>getEnv</function> is used in Nix Packages to
+ locate the file <filename>~/.nixpkgs/config.nix</filename>, which
+ contains user-local settings for Nix Packages. (That is, it does
+ a <literal>getEnv "HOME"</literal> to locate the user’s home
+ directory.)</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-hasAttr">
+ <term><function>builtins.hasAttr</function>
+ <replaceable>s</replaceable> <replaceable>set</replaceable></term>
+
+ <listitem><para><function>hasAttr</function> returns
+ <literal>true</literal> if <replaceable>set</replaceable> has an
+ attribute named <replaceable>s</replaceable>, and
+ <literal>false</literal> otherwise. This is a dynamic version of
+ the <literal>?</literal> operator, since
+ <replaceable>s</replaceable> is an expression rather than an
+ identifier.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-hashString">
+ <term><function>builtins.hashString</function>
+ <replaceable>type</replaceable> <replaceable>s</replaceable></term>
+
+ <listitem><para>Return a base-16 representation of the
+ cryptographic hash of string <replaceable>s</replaceable>. The
+ hash algorithm specified by <replaceable>type</replaceable> must
+ be one of <literal>"md5"</literal>, <literal>"sha1"</literal>,
+ <literal>"sha256"</literal> or <literal>"sha512"</literal>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-hashFile">
+ <term><function>builtins.hashFile</function>
+ <replaceable>type</replaceable> <replaceable>p</replaceable></term>
+
+ <listitem><para>Return a base-16 representation of the
+ cryptographic hash of the file at path <replaceable>p</replaceable>. The
+ hash algorithm specified by <replaceable>type</replaceable> must
+ be one of <literal>"md5"</literal>, <literal>"sha1"</literal>,
+ <literal>"sha256"</literal> or <literal>"sha512"</literal>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-head">
+ <term><function>builtins.head</function>
+ <replaceable>list</replaceable></term>
+
+ <listitem><para>Return the first element of a list; abort
+ evaluation if the argument isn’t a list or is an empty list. You
+ can test whether a list is empty by comparing it with
+ <literal>[]</literal>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-import">
+ <term><function>import</function>
+ <replaceable>path</replaceable></term>
+ <term><function>builtins.import</function>
+ <replaceable>path</replaceable></term>
+
+ <listitem><para>Load, parse and return the Nix expression in the
+ file <replaceable>path</replaceable>. If <replaceable>path
+ </replaceable> is a directory, the file <filename>default.nix
+ </filename> in that directory is loaded. Evaluation aborts if the
+ file doesn’t exist or contains an incorrect Nix expression.
+ <function>import</function> implements Nix’s module system: you
+ can put any Nix expression (such as a set or a function) in a
+ separate file, and use it from Nix expressions in other
+ files.</para>
+
+ <note><para>Unlike some languages, <function>import</function> is a regular
+ function in Nix. Paths using the angle bracket syntax (e.g., <function>
+ import</function> <replaceable><foo></replaceable>) are normal path
+ values (see <xref linkend="ssec-values"/>).</para></note>
+
+ <para>A Nix expression loaded by <function>import</function> must
+ not contain any <emphasis>free variables</emphasis> (identifiers
+ that are not defined in the Nix expression itself and are not
+ built-in). Therefore, it cannot refer to variables that are in
+ scope at the call site. For instance, if you have a calling
+ expression
+
+<programlisting>
+rec {
+ x = 123;
+ y = import ./foo.nix;
+}</programlisting>
+
+ then the following <filename>foo.nix</filename> will give an
+ error:
+
+<programlisting>
+x + 456</programlisting>
+
+ since <varname>x</varname> is not in scope in
+ <filename>foo.nix</filename>. If you want <varname>x</varname>
+ to be available in <filename>foo.nix</filename>, you should pass
+ it as a function argument:
+
+<programlisting>
+rec {
+ x = 123;
+ y = import ./foo.nix x;
+}</programlisting>
+
+ and
+
+<programlisting>
+x: x + 456</programlisting>
+
+ (The function argument doesn’t have to be called
+ <varname>x</varname> in <filename>foo.nix</filename>; any name
+ would work.)</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-intersectAttrs">
+ <term><function>builtins.intersectAttrs</function>
+ <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+
+ <listitem><para>Return a set consisting of the attributes in the
+ set <replaceable>e2</replaceable> that also exist in the set
+ <replaceable>e1</replaceable>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-isAttrs">
+ <term><function>builtins.isAttrs</function>
+ <replaceable>e</replaceable></term>
+
+ <listitem><para>Return <literal>true</literal> if
+ <replaceable>e</replaceable> evaluates to a set, and
+ <literal>false</literal> otherwise.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-isList">
+ <term><function>builtins.isList</function>
+ <replaceable>e</replaceable></term>
+
+ <listitem><para>Return <literal>true</literal> if
+ <replaceable>e</replaceable> evaluates to a list, and
+ <literal>false</literal> otherwise.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-isFunction"><term><function>builtins.isFunction</function>
+ <replaceable>e</replaceable></term>
+
+ <listitem><para>Return <literal>true</literal> if
+ <replaceable>e</replaceable> evaluates to a function, and
+ <literal>false</literal> otherwise.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-isString">
+ <term><function>builtins.isString</function>
+ <replaceable>e</replaceable></term>
+
+ <listitem><para>Return <literal>true</literal> if
+ <replaceable>e</replaceable> evaluates to a string, and
+ <literal>false</literal> otherwise.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-isInt">
+ <term><function>builtins.isInt</function>
+ <replaceable>e</replaceable></term>
+
+ <listitem><para>Return <literal>true</literal> if
+ <replaceable>e</replaceable> evaluates to an int, and
+ <literal>false</literal> otherwise.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-isFloat">
+ <term><function>builtins.isFloat</function>
+ <replaceable>e</replaceable></term>
+
+ <listitem><para>Return <literal>true</literal> if
+ <replaceable>e</replaceable> evaluates to a float, and
+ <literal>false</literal> otherwise.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-isBool">
+ <term><function>builtins.isBool</function>
+ <replaceable>e</replaceable></term>
+
+ <listitem><para>Return <literal>true</literal> if
+ <replaceable>e</replaceable> evaluates to a bool, and
+ <literal>false</literal> otherwise.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><function>builtins.isPath</function>
+ <replaceable>e</replaceable></term>
+
+ <listitem><para>Return <literal>true</literal> if
+ <replaceable>e</replaceable> evaluates to a path, and
+ <literal>false</literal> otherwise.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="builtin-isNull">
+ <term><function>isNull</function>
+ <replaceable>e</replaceable></term>
+ <term><function>builtins.isNull</function>
+ <replaceable>e</replaceable></term>
+
+ <listitem><para>Return <literal>true</literal> if
+ <replaceable>e</replaceable> evaluates to <literal>null</literal>,
+ and <literal>false</literal> otherwise.</para>
+
+ <warning><para>This function is <emphasis>deprecated</emphasis>;
+ just write <literal>e == null</literal> instead.</para></warning>
+
+ </listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-length">
+ <term><function>builtins.length</function>
+ <replaceable>e</replaceable></term>
+
+ <listitem><para>Return the length of the list
+ <replaceable>e</replaceable>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-lessThan">
+ <term><function>builtins.lessThan</function>
+ <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+
+ <listitem><para>Return <literal>true</literal> if the number
+ <replaceable>e1</replaceable> is less than the number
+ <replaceable>e2</replaceable>, and <literal>false</literal>
+ otherwise. Evaluation aborts if either
+ <replaceable>e1</replaceable> or <replaceable>e2</replaceable>
+ does not evaluate to a number.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-listToAttrs">
+ <term><function>builtins.listToAttrs</function>
+ <replaceable>e</replaceable></term>
+
+ <listitem><para>Construct a set from a list specifying the names
+ and values of each attribute. Each element of the list should be
+ a set consisting of a string-valued attribute
+ <varname>name</varname> specifying the name of the attribute, and
+ an attribute <varname>value</varname> specifying its value.
+ Example:
+
+<programlisting>
+builtins.listToAttrs
+ [ { name = "foo"; value = 123; }
+ { name = "bar"; value = 456; }
+ ]
+</programlisting>
+
+ evaluates to
+
+<programlisting>
+{ foo = 123; bar = 456; }
+</programlisting>
+
+ </para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="builtin-map">
+ <term><function>map</function>
+ <replaceable>f</replaceable> <replaceable>list</replaceable></term>
+ <term><function>builtins.map</function>
+ <replaceable>f</replaceable> <replaceable>list</replaceable></term>
+
+ <listitem><para>Apply the function <replaceable>f</replaceable> to
+ each element in the list <replaceable>list</replaceable>. For
+ example,
+
+<programlisting>
+map (x: "foo" + x) [ "bar" "bla" "abc" ]</programlisting>
+
+ evaluates to <literal>[ "foobar" "foobla" "fooabc"
+ ]</literal>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-match">
+ <term><function>builtins.match</function>
+ <replaceable>regex</replaceable> <replaceable>str</replaceable></term>
+
+ <listitem><para>Returns a list if the <link xlink:href="http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_04">extended
+ POSIX regular expression</link> <replaceable>regex</replaceable>
+ matches <replaceable>str</replaceable> precisely, otherwise returns
+ <literal>null</literal>. Each item in the list is a regex group.
+
+<programlisting>
+builtins.match "ab" "abc"
+</programlisting>
+
+Evaluates to <literal>null</literal>.
+
+<programlisting>
+builtins.match "abc" "abc"
+</programlisting>
+
+Evaluates to <literal>[ ]</literal>.
+
+<programlisting>
+builtins.match "a(b)(c)" "abc"
+</programlisting>
+
+Evaluates to <literal>[ "b" "c" ]</literal>.
+
+<programlisting>
+builtins.match "[[:space:]]+([[:upper:]]+)[[:space:]]+" " FOO "
+</programlisting>
+
+Evaluates to <literal>[ "foo" ]</literal>.
+
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="builtin-mul">
+ <term><function>builtins.mul</function>
+ <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+
+ <listitem><para>Return the product of the numbers
+ <replaceable>e1</replaceable> and
+ <replaceable>e2</replaceable>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-parseDrvName">
+ <term><function>builtins.parseDrvName</function>
+ <replaceable>s</replaceable></term>
+
+ <listitem><para>Split the string <replaceable>s</replaceable> into
+ a package name and version. The package name is everything up to
+ but not including the first dash followed by a digit, and the
+ version is everything following that dash. The result is returned
+ in a set <literal>{ name, version }</literal>. Thus,
+ <literal>builtins.parseDrvName "nix-0.12pre12876"</literal>
+ returns <literal>{ name = "nix"; version = "0.12pre12876";
+ }</literal>.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="builtin-path">
+ <term>
+ <function>builtins.path</function>
+ <replaceable>args</replaceable>
+ </term>
+
+ <listitem>
+ <para>
+ An enrichment of the built-in path type, based on the attributes
+ present in <replaceable>args</replaceable>. All are optional
+ except <varname>path</varname>:
+ </para>
+
+ <variablelist>
+ <varlistentry>
+ <term>path</term>
+ <listitem>
+ <para>The underlying path.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>name</term>
+ <listitem>
+ <para>
+ The name of the path when added to the store. This can
+ used to reference paths that have nix-illegal characters
+ in their names, like <literal>@</literal>.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>filter</term>
+ <listitem>
+ <para>
+ A function of the type expected by
+ <link linkend="builtin-filterSource">builtins.filterSource</link>,
+ with the same semantics.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>recursive</term>
+ <listitem>
+ <para>
+ When <literal>false</literal>, when
+ <varname>path</varname> is added to the store it is with a
+ flat hash, rather than a hash of the NAR serialization of
+ the file. Thus, <varname>path</varname> must refer to a
+ regular file, not a directory. This allows similar
+ behavior to <literal>fetchurl</literal>. Defaults to
+ <literal>true</literal>.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>sha256</term>
+ <listitem>
+ <para>
+ When provided, this is the expected hash of the file at
+ the path. Evaluation will fail if the hash is incorrect,
+ and providing a hash allows
+ <literal>builtins.path</literal> to be used even when the
+ <literal>pure-eval</literal> nix config option is on.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="builtin-pathExists">
+ <term><function>builtins.pathExists</function>
+ <replaceable>path</replaceable></term>
+
+ <listitem><para>Return <literal>true</literal> if the path
+ <replaceable>path</replaceable> exists at evaluation time, and
+ <literal>false</literal> otherwise.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="builtin-placeholder">
+ <term><function>builtins.placeholder</function>
+ <replaceable>output</replaceable></term>
+
+ <listitem><para>Return a placeholder string for the specified
+ <replaceable>output</replaceable> that will be substituted by the
+ corresponding output path at build time. Typical outputs would be
+ <literal>"out"</literal>, <literal>"bin"</literal> or
+ <literal>"dev"</literal>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="builtin-readDir">
+ <term><function>builtins.readDir</function>
+ <replaceable>path</replaceable></term>
+
+ <listitem><para>Return the contents of the directory
+ <replaceable>path</replaceable> as a set mapping directory entries
+ to the corresponding file type. For instance, if directory
+ <filename>A</filename> contains a regular file
+ <filename>B</filename> and another directory
+ <filename>C</filename>, then <literal>builtins.readDir
+ ./A</literal> will return the set
+
+<programlisting>
+{ B = "regular"; C = "directory"; }</programlisting>
+
+ The possible values for the file type are
+ <literal>"regular"</literal>, <literal>"directory"</literal>,
+ <literal>"symlink"</literal> and
+ <literal>"unknown"</literal>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-readFile">
+ <term><function>builtins.readFile</function>
+ <replaceable>path</replaceable></term>
+
+ <listitem><para>Return the contents of the file
+ <replaceable>path</replaceable> as a string.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-removeAttrs">
+ <term><function>removeAttrs</function>
+ <replaceable>set</replaceable> <replaceable>list</replaceable></term>
+ <term><function>builtins.removeAttrs</function>
+ <replaceable>set</replaceable> <replaceable>list</replaceable></term>
+
+ <listitem><para>Remove the attributes listed in
+ <replaceable>list</replaceable> from
+ <replaceable>set</replaceable>. The attributes don’t have to
+ exist in <replaceable>set</replaceable>. For instance,
+
+<programlisting>
+removeAttrs { x = 1; y = 2; z = 3; } [ "a" "x" "z" ]</programlisting>
+
+ evaluates to <literal>{ y = 2; }</literal>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-replaceStrings">
+ <term><function>builtins.replaceStrings</function>
+ <replaceable>from</replaceable> <replaceable>to</replaceable> <replaceable>s</replaceable></term>
+
+ <listitem><para>Given string <replaceable>s</replaceable>, replace
+ every occurrence of the strings in <replaceable>from</replaceable>
+ with the corresponding string in
+ <replaceable>to</replaceable>. For example,
+
+<programlisting>
+builtins.replaceStrings ["oo" "a"] ["a" "i"] "foobar"
+</programlisting>
+
+ evaluates to <literal>"fabir"</literal>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-seq">
+ <term><function>builtins.seq</function>
+ <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+
+ <listitem><para>Evaluate <replaceable>e1</replaceable>, then
+ evaluate and return <replaceable>e2</replaceable>. This ensures
+ that a computation is strict in the value of
+ <replaceable>e1</replaceable>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-sort">
+ <term><function>builtins.sort</function>
+ <replaceable>comparator</replaceable> <replaceable>list</replaceable></term>
+
+ <listitem><para>Return <replaceable>list</replaceable> in sorted
+ order. It repeatedly calls the function
+ <replaceable>comparator</replaceable> with two elements. The
+ comparator should return <literal>true</literal> if the first
+ element is less than the second, and <literal>false</literal>
+ otherwise. For example,
+
+<programlisting>
+builtins.sort builtins.lessThan [ 483 249 526 147 42 77 ]
+</programlisting>
+
+ produces the list <literal>[ 42 77 147 249 483 526
+ ]</literal>.</para>
+
+ <para>This is a stable sort: it preserves the relative order of
+ elements deemed equal by the comparator.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-split">
+ <term><function>builtins.split</function>
+ <replaceable>regex</replaceable> <replaceable>str</replaceable></term>
+
+ <listitem><para>Returns a list composed of non matched strings interleaved
+ with the lists of the <link xlink:href="http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_04">extended
+ POSIX regular expression</link> <replaceable>regex</replaceable> matches
+ of <replaceable>str</replaceable>. Each item in the lists of matched
+ sequences is a regex group.
+
+<programlisting>
+builtins.split "(a)b" "abc"
+</programlisting>
+
+Evaluates to <literal>[ "" [ "a" ] "c" ]</literal>.
+
+<programlisting>
+builtins.split "([ac])" "abc"
+</programlisting>
+
+Evaluates to <literal>[ "" [ "a" ] "b" [ "c" ] "" ]</literal>.
+
+<programlisting>
+builtins.split "(a)|(c)" "abc"
+</programlisting>
+
+Evaluates to <literal>[ "" [ "a" null ] "b" [ null "c" ] "" ]</literal>.
+
+<programlisting>
+builtins.split "([[:upper:]]+)" " FOO "
+</programlisting>
+
+Evaluates to <literal>[ " " [ "FOO" ] " " ]</literal>.
+
+ </para></listitem>
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-splitVersion">
+ <term><function>builtins.splitVersion</function>
+ <replaceable>s</replaceable></term>
+
+ <listitem><para>Split a string representing a version into its
+ components, by the same version splitting logic underlying the
+ version comparison in <link linkend="ssec-version-comparisons">
+ <command>nix-env -u</command></link>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-stringLength">
+ <term><function>builtins.stringLength</function>
+ <replaceable>e</replaceable></term>
+
+ <listitem><para>Return the length of the string
+ <replaceable>e</replaceable>. If <replaceable>e</replaceable> is
+ not a string, evaluation is aborted.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-sub">
+ <term><function>builtins.sub</function>
+ <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+
+ <listitem><para>Return the difference between the numbers
+ <replaceable>e1</replaceable> and
+ <replaceable>e2</replaceable>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-substring">
+ <term><function>builtins.substring</function>
+ <replaceable>start</replaceable> <replaceable>len</replaceable>
+ <replaceable>s</replaceable></term>
+
+ <listitem><para>Return the substring of
+ <replaceable>s</replaceable> from character position
+ <replaceable>start</replaceable> (zero-based) up to but not
+ including <replaceable>start + len</replaceable>. If
+ <replaceable>start</replaceable> is greater than the length of the
+ string, an empty string is returned, and if <replaceable>start +
+ len</replaceable> lies beyond the end of the string, only the
+ substring up to the end of the string is returned.
+ <replaceable>start</replaceable> must be
+ non-negative. For example,
+
+<programlisting>
+builtins.substring 0 3 "nixos"
+</programlisting>
+
+ evaluates to <literal>"nix"</literal>.
+ </para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-tail">
+ <term><function>builtins.tail</function>
+ <replaceable>list</replaceable></term>
+
+ <listitem><para>Return the second to last elements of a list;
+ abort evaluation if the argument isn’t a list or is an empty
+ list.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-throw">
+ <term><function>throw</function>
+ <replaceable>s</replaceable></term>
+ <term><function>builtins.throw</function>
+ <replaceable>s</replaceable></term>
+
+ <listitem><para>Throw an error message
+ <replaceable>s</replaceable>. This usually aborts Nix expression
+ evaluation, but in <command>nix-env -qa</command> and other
+ commands that try to evaluate a set of derivations to get
+ information about those derivations, a derivation that throws an
+ error is silently skipped (which is not the case for
+ <function>abort</function>).</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-toFile">
+ <term><function>builtins.toFile</function>
+ <replaceable>name</replaceable>
+ <replaceable>s</replaceable></term>
+
+ <listitem><para>Store the string <replaceable>s</replaceable> in a
+ file in the Nix store and return its path. The file has suffix
+ <replaceable>name</replaceable>. This file can be used as an
+ input to derivations. One application is to write builders
+ “inline”. For instance, the following Nix expression combines
+ <xref linkend="ex-hello-nix"/> and <xref linkend="ex-hello-builder"/> into one file:
+
+<programlisting>
+{ stdenv, fetchurl, perl }:
+
+stdenv.mkDerivation {
+ name = "hello-2.1.1";
+
+ builder = builtins.toFile "builder.sh" "
+ source $stdenv/setup
+
+ PATH=$perl/bin:$PATH
+
+ tar xvfz $src
+ cd hello-*
+ ./configure --prefix=$out
+ make
+ make install
+ ";
+
+ src = fetchurl {
+ url = "http://ftp.nluug.nl/pub/gnu/hello/hello-2.1.1.tar.gz";
+ sha256 = "1md7jsfd8pa45z73bz1kszpp01yw6x5ljkjk2hx7wl800any6465";
+ };
+ inherit perl;
+}</programlisting>
+
+ </para>
+
+ <para>It is even possible for one file to refer to another, e.g.,
+
+<programlisting>
+ builder = let
+ configFile = builtins.toFile "foo.conf" "
+ # This is some dummy configuration file.
+ <replaceable>...</replaceable>
+ ";
+ in builtins.toFile "builder.sh" "
+ source $stdenv/setup
+ <replaceable>...</replaceable>
+ cp ${configFile} $out/etc/foo.conf
+ ";</programlisting>
+
+ Note that <literal>${configFile}</literal> is an antiquotation
+ (see <xref linkend="ssec-values"/>), so the result of the
+ expression <literal>configFile</literal> (i.e., a path like
+ <filename>/nix/store/m7p7jfny445k...-foo.conf</filename>) will be
+ spliced into the resulting string.</para>
+
+ <para>It is however <emphasis>not</emphasis> allowed to have files
+ mutually referring to each other, like so:
+
+<programlisting>
+let
+ foo = builtins.toFile "foo" "...${bar}...";
+ bar = builtins.toFile "bar" "...${foo}...";
+in foo</programlisting>
+
+ This is not allowed because it would cause a cyclic dependency in
+ the computation of the cryptographic hashes for
+ <varname>foo</varname> and <varname>bar</varname>.</para>
+ <para>It is also not possible to reference the result of a derivation.
+ If you are using Nixpkgs, the <literal>writeTextFile</literal> function is able to
+ do that.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-toJSON">
+ <term><function>builtins.toJSON</function> <replaceable>e</replaceable></term>
+
+ <listitem><para>Return a string containing a JSON representation
+ of <replaceable>e</replaceable>. Strings, integers, floats, booleans,
+ nulls and lists are mapped to their JSON equivalents. Sets
+ (except derivations) are represented as objects. Derivations are
+ translated to a JSON string containing the derivation’s output
+ path. Paths are copied to the store and represented as a JSON
+ string of the resulting store path.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-toPath">
+ <term><function>builtins.toPath</function> <replaceable>s</replaceable></term>
+
+ <listitem><para> DEPRECATED. Use <literal>/. + "/path"</literal>
+ to convert a string into an absolute path. For relative paths,
+ use <literal>./. + "/path"</literal>.
+ </para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-toString">
+ <term><function>toString</function> <replaceable>e</replaceable></term>
+ <term><function>builtins.toString</function> <replaceable>e</replaceable></term>
+
+ <listitem><para>Convert the expression
+ <replaceable>e</replaceable> to a string.
+ <replaceable>e</replaceable> can be:</para>
+ <itemizedlist>
+ <listitem><para>A string (in which case the string is returned unmodified).</para></listitem>
+ <listitem><para>A path (e.g., <literal>toString /foo/bar</literal> yields <literal>"/foo/bar"</literal>.</para></listitem>
+ <listitem><para>A set containing <literal>{ __toString = self: ...; }</literal>.</para></listitem>
+ <listitem><para>An integer.</para></listitem>
+ <listitem><para>A list, in which case the string representations of its elements are joined with spaces.</para></listitem>
+ <listitem><para>A Boolean (<literal>false</literal> yields <literal>""</literal>, <literal>true</literal> yields <literal>"1"</literal>).</para></listitem>
+ <listitem><para><literal>null</literal>, which yields the empty string.</para></listitem>
+ </itemizedlist>
+ </listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-toXML">
+ <term><function>builtins.toXML</function> <replaceable>e</replaceable></term>
+
+ <listitem><para>Return a string containing an XML representation
+ of <replaceable>e</replaceable>. The main application for
+ <function>toXML</function> is to communicate information with the
+ builder in a more structured format than plain environment
+ variables.</para>
+
+ <!-- TODO: more formally describe the schema of the XML
+ representation -->
+
+ <para><xref linkend="ex-toxml"/> shows an example where this is
+ the case. The builder is supposed to generate the configuration
+ file for a <link xlink:href="http://jetty.mortbay.org/">Jetty
+ servlet container</link>. A servlet container contains a number
+ of servlets (<filename>*.war</filename> files) each exported under
+ a specific URI prefix. So the servlet configuration is a list of
+ sets containing the <varname>path</varname> and
+ <varname>war</varname> of the servlet (<xref linkend="ex-toxml-co-servlets"/>). This kind of information is
+ difficult to communicate with the normal method of passing
+ information through an environment variable, which just
+ concatenates everything together into a string (which might just
+ work in this case, but wouldn’t work if fields are optional or
+ contain lists themselves). Instead the Nix expression is
+ converted to an XML representation with
+ <function>toXML</function>, which is unambiguous and can easily be
+ processed with the appropriate tools. For instance, in the
+ example an XSLT stylesheet (<xref linkend="ex-toxml-co-stylesheet"/>) is applied to it (<xref linkend="ex-toxml-co-apply"/>) to
+ generate the XML configuration file for the Jetty server. The XML
+ representation produced from <xref linkend="ex-toxml-co-servlets"/> by <function>toXML</function> is shown in <xref linkend="ex-toxml-result"/>.</para>
+
+ <para>Note that <xref linkend="ex-toxml"/> uses the <function linkend="builtin-toFile">toFile</function> built-in to write the
+ builder and the stylesheet “inline” in the Nix expression. The
+ path of the stylesheet is spliced into the builder at
+ <literal>xsltproc ${stylesheet}
+ <replaceable>...</replaceable></literal>.</para>
+
+ <example xml:id="ex-toxml"><title>Passing information to a builder
+ using <function>toXML</function></title>
+
+<programlisting><![CDATA[
+{ stdenv, fetchurl, libxslt, jira, uberwiki }:
+
+stdenv.mkDerivation (rec {
+ name = "web-server";
+
+ buildInputs = [ libxslt ];
+
+ builder = builtins.toFile "builder.sh" "
+ source $stdenv/setup
+ mkdir $out
+ echo "$servlets" | xsltproc ${stylesheet} - > $out/server-conf.xml]]> <co xml:id="ex-toxml-co-apply"/> <![CDATA[
+ ";
+
+ stylesheet = builtins.toFile "stylesheet.xsl"]]> <co xml:id="ex-toxml-co-stylesheet"/> <![CDATA[
+ "<?xml version='1.0' encoding='UTF-8'?>
+ <xsl:stylesheet xmlns:xsl='http://www.w3.org/1999/XSL/Transform' version='1.0'>
+ <xsl:template match='/'>
+ <Configure>
+ <xsl:for-each select='/expr/list/attrs'>
+ <Call name='addWebApplication'>
+ <Arg><xsl:value-of select=\"attr[@name = 'path']/string/@value\" /></Arg>
+ <Arg><xsl:value-of select=\"attr[@name = 'war']/path/@value\" /></Arg>
+ </Call>
+ </xsl:for-each>
+ </Configure>
+ </xsl:template>
+ </xsl:stylesheet>
+ ";
+
+ servlets = builtins.toXML []]> <co xml:id="ex-toxml-co-servlets"/> <![CDATA[
+ { path = "/bugtracker"; war = jira + "/lib/atlassian-jira.war"; }
+ { path = "/wiki"; war = uberwiki + "/uberwiki.war"; }
+ ];
+})]]></programlisting>
+
+ </example>
+
+ <example xml:id="ex-toxml-result"><title>XML representation produced by
+ <function>toXML</function></title>
+
+<programlisting><![CDATA[<?xml version='1.0' encoding='utf-8'?>
+<expr>
+ <list>
+ <attrs>
+ <attr name="path">
+ <string value="/bugtracker" />
+ </attr>
+ <attr name="war">
+ <path value="/nix/store/d1jh9pasa7k2...-jira/lib/atlassian-jira.war" />
+ </attr>
+ </attrs>
+ <attrs>
+ <attr name="path">
+ <string value="/wiki" />
+ </attr>
+ <attr name="war">
+ <path value="/nix/store/y6423b1yi4sx...-uberwiki/uberwiki.war" />
+ </attr>
+ </attrs>
+ </list>
+</expr>]]></programlisting>
+
+ </example>
+
+ </listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-trace">
+ <term><function>builtins.trace</function>
+ <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+
+ <listitem><para>Evaluate <replaceable>e1</replaceable> and print its
+ abstract syntax representation on standard error. Then return
+ <replaceable>e2</replaceable>. This function is useful for
+ debugging.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="builtin-tryEval">
+ <term><function>builtins.tryEval</function>
+ <replaceable>e</replaceable></term>
+
+ <listitem><para>Try to shallowly evaluate <replaceable>e</replaceable>.
+ Return a set containing the attributes <literal>success</literal>
+ (<literal>true</literal> if <replaceable>e</replaceable> evaluated
+ successfully, <literal>false</literal> if an error was thrown) and
+ <literal>value</literal>, equalling <replaceable>e</replaceable>
+ if successful and <literal>false</literal> otherwise. Note that this
+ doesn't evaluate <replaceable>e</replaceable> deeply, so
+ <literal>let e = { x = throw ""; }; in (builtins.tryEval e).success
+ </literal> will be <literal>true</literal>. Using <literal>builtins.deepSeq
+ </literal> one can get the expected result: <literal>let e = { x = throw "";
+ }; in (builtins.tryEval (builtins.deepSeq e e)).success</literal> will be
+ <literal>false</literal>.
+ </para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="builtin-typeOf">
+ <term><function>builtins.typeOf</function>
+ <replaceable>e</replaceable></term>
+
+ <listitem><para>Return a string representing the type of the value
+ <replaceable>e</replaceable>, namely <literal>"int"</literal>,
+ <literal>"bool"</literal>, <literal>"string"</literal>,
+ <literal>"path"</literal>, <literal>"null"</literal>,
+ <literal>"set"</literal>, <literal>"list"</literal>,
+ <literal>"lambda"</literal> or
+ <literal>"float"</literal>.</para></listitem>
+
+ </varlistentry>
+
+
+</variablelist>
+
+
+</section>
+
+
+</chapter>
+
+</part>
+ <part xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" xml:id="part-advanced-topics" version="5.0" xml:base="advanced-topics/advanced-topics.xml">
+
+<title>Advanced Topics</title>
+
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="chap-distributed-builds">
+
+<title>Remote Builds</title>
+
+<para>Nix supports remote builds, where a local Nix installation can
+forward Nix builds to other machines. This allows multiple builds to
+be performed in parallel and allows Nix to perform multi-platform
+builds in a semi-transparent way. For instance, if you perform a
+build for a <literal>x86_64-darwin</literal> on an
+<literal>i686-linux</literal> machine, Nix can automatically forward
+the build to a <literal>x86_64-darwin</literal> machine, if
+available.</para>
+
+<para>To forward a build to a remote machine, it’s required that the
+remote machine is accessible via SSH and that it has Nix
+installed. You can test whether connecting to the remote Nix instance
+works, e.g.
+
+<screen>
+$ nix ping-store --store ssh://mac
+</screen>
+
+will try to connect to the machine named <literal>mac</literal>. It is
+possible to specify an SSH identity file as part of the remote store
+URI, e.g.
+
+<screen>
+$ nix ping-store --store ssh://mac?ssh-key=/home/alice/my-key
+</screen>
+
+Since builds should be non-interactive, the key should not have a
+passphrase. Alternatively, you can load identities ahead of time into
+<command>ssh-agent</command> or <command>gpg-agent</command>.</para>
+
+<para>If you get the error
+
+<screen>
+bash: nix-store: command not found
+error: cannot connect to 'mac'
+</screen>
+
+then you need to ensure that the <envar>PATH</envar> of
+non-interactive login shells contains Nix.</para>
+
+<warning><para>If you are building via the Nix daemon, it is the Nix
+daemon user account (that is, <literal>root</literal>) that should
+have SSH access to the remote machine. If you can’t or don’t want to
+configure <literal>root</literal> to be able to access to remote
+machine, you can use a private Nix store instead by passing
+e.g. <literal>--store ~/my-nix</literal>.</para></warning>
+
+<para>The list of remote machines can be specified on the command line
+or in the Nix configuration file. The former is convenient for
+testing. For example, the following command allows you to build a
+derivation for <literal>x86_64-darwin</literal> on a Linux machine:
+
+<screen>
+$ uname
+Linux
+
+$ nix build \
+ '(with import <nixpkgs> { system = "x86_64-darwin"; }; runCommand "foo" {} "uname > $out")' \
+ --builders 'ssh://mac x86_64-darwin'
+[1/0/1 built, 0.0 MiB DL] building foo on ssh://mac
+
+$ cat ./result
+Darwin
+</screen>
+
+It is possible to specify multiple builders separated by a semicolon
+or a newline, e.g.
+
+<screen>
+ --builders 'ssh://mac x86_64-darwin ; ssh://beastie x86_64-freebsd'
+</screen>
+</para>
+
+<para>Each machine specification consists of the following elements,
+separated by spaces. Only the first element is required.
+To leave a field at its default, set it to <literal>-</literal>.
+
+<orderedlist>
+
+ <listitem><para>The URI of the remote store in the format
+ <literal>ssh://[<replaceable>username</replaceable>@]<replaceable>hostname</replaceable></literal>,
+ e.g. <literal>ssh://nix@mac</literal> or
+ <literal>ssh://mac</literal>. For backward compatibility,
+ <literal>ssh://</literal> may be omitted. The hostname may be an
+ alias defined in your
+ <filename>~/.ssh/config</filename>.</para></listitem>
+
+ <listitem><para>A comma-separated list of Nix platform type
+ identifiers, such as <literal>x86_64-darwin</literal>. It is
+ possible for a machine to support multiple platform types, e.g.,
+ <literal>i686-linux,x86_64-linux</literal>. If omitted, this
+ defaults to the local platform type.</para></listitem>
+
+ <listitem><para>The SSH identity file to be used to log in to the
+ remote machine. If omitted, SSH will use its regular
+ identities.</para></listitem>
+
+ <listitem><para>The maximum number of builds that Nix will execute
+ in parallel on the machine. Typically this should be equal to the
+ number of CPU cores. For instance, the machine
+ <literal>itchy</literal> in the example will execute up to 8 builds
+ in parallel.</para></listitem>
+
+ <listitem><para>The “speed factor”, indicating the relative speed of
+ the machine. If there are multiple machines of the right type, Nix
+ will prefer the fastest, taking load into account.</para></listitem>
+
+ <listitem><para>A comma-separated list of <emphasis>supported
+ features</emphasis>. If a derivation has the
+ <varname>requiredSystemFeatures</varname> attribute, then Nix will
+ only perform the derivation on a machine that has the specified
+ features. For instance, the attribute
+
+<programlisting>
+requiredSystemFeatures = [ "kvm" ];
+</programlisting>
+
+ will cause the build to be performed on a machine that has the
+ <literal>kvm</literal> feature.</para></listitem>
+
+ <listitem><para>A comma-separated list of <emphasis>mandatory
+ features</emphasis>. A machine will only be used to build a
+ derivation if all of the machine’s mandatory features appear in the
+ derivation’s <varname>requiredSystemFeatures</varname>
+ attribute..</para></listitem>
+
+</orderedlist>
+
+For example, the machine specification
+
+<programlisting>
+nix@scratchy.labs.cs.uu.nl i686-linux /home/nix/.ssh/id_scratchy_auto 8 1 kvm
+nix@itchy.labs.cs.uu.nl i686-linux /home/nix/.ssh/id_scratchy_auto 8 2
+nix@poochie.labs.cs.uu.nl i686-linux /home/nix/.ssh/id_scratchy_auto 1 2 kvm benchmark
+</programlisting>
+
+specifies several machines that can perform
+<literal>i686-linux</literal> builds. However,
+<literal>poochie</literal> will only do builds that have the attribute
+
+<programlisting>
+requiredSystemFeatures = [ "benchmark" ];
+</programlisting>
+
+or
+
+<programlisting>
+requiredSystemFeatures = [ "benchmark" "kvm" ];
+</programlisting>
+
+<literal>itchy</literal> cannot do builds that require
+<literal>kvm</literal>, but <literal>scratchy</literal> does support
+such builds. For regular builds, <literal>itchy</literal> will be
+preferred over <literal>scratchy</literal> because it has a higher
+speed factor.</para>
+
+<para>Remote builders can also be configured in
+<filename>nix.conf</filename>, e.g.
+
+<programlisting>
+builders = ssh://mac x86_64-darwin ; ssh://beastie x86_64-freebsd
+</programlisting>
+
+Finally, remote builders can be configured in a separate configuration
+file included in <option>builders</option> via the syntax
+<literal>@<replaceable>file</replaceable></literal>. For example,
+
+<programlisting>
+builders = @/etc/nix/machines
+</programlisting>
+
+causes the list of machines in <filename>/etc/nix/machines</filename>
+to be included. (This is the default.)</para>
+
+<para>If you want the builders to use caches, you likely want to set
+the option <link linkend="conf-builders-use-substitutes"><literal>builders-use-substitutes</literal></link>
+in your local <filename>nix.conf</filename>.</para>
+
+<para>To build only on remote builders and disable building on the local machine,
+you can use the option <option>--max-jobs 0</option>.</para>
+
+</chapter>
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="chap-tuning-cores-and-jobs">
+
+<title>Tuning Cores and Jobs</title>
+
+<para>Nix has two relevant settings with regards to how your CPU cores
+will be utilized: <xref linkend="conf-cores"/> and
+<xref linkend="conf-max-jobs"/>. This chapter will talk about what
+they are, how they interact, and their configuration trade-offs.</para>
+
+<variablelist>
+ <varlistentry>
+ <term><xref linkend="conf-max-jobs"/></term>
+ <listitem><para>
+ Dictates how many separate derivations will be built at the same
+ time. If you set this to zero, the local machine will do no
+ builds. Nix will still substitute from binary caches, and build
+ remotely if remote builders are configured.
+ </para></listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><xref linkend="conf-cores"/></term>
+ <listitem><para>
+ Suggests how many cores each derivation should use. Similar to
+ <command>make -j</command>.
+ </para></listitem>
+ </varlistentry>
+</variablelist>
+
+<para>The <xref linkend="conf-cores"/> setting determines the value of
+<envar>NIX_BUILD_CORES</envar>. <envar>NIX_BUILD_CORES</envar> is equal
+to <xref linkend="conf-cores"/>, unless <xref linkend="conf-cores"/>
+equals <literal>0</literal>, in which case <envar>NIX_BUILD_CORES</envar>
+will be the total number of cores in the system.</para>
+
+<para>The maximum number of consumed cores is a simple multiplication,
+<xref linkend="conf-max-jobs"/> * <envar>NIX_BUILD_CORES</envar>.</para>
+
+<para>The balance on how to set these two independent variables depends
+upon each builder's workload and hardware. Here are a few example
+scenarios on a machine with 24 cores:</para>
+
+<table>
+ <caption>Balancing 24 Build Cores</caption>
+ <thead>
+ <tr>
+ <th><xref linkend="conf-max-jobs"/></th>
+ <th><xref linkend="conf-cores"/></th>
+ <th><envar>NIX_BUILD_CORES</envar></th>
+ <th>Maximum Processes</th>
+ <th>Result</th>
+ </tr>
+ </thead>
+ <tbody>
+ <tr>
+ <td>1</td>
+ <td>24</td>
+ <td>24</td>
+ <td>24</td>
+ <td>
+ One derivation will be built at a time, each one can use 24
+ cores. Undersold if a job can’t use 24 cores.
+ </td>
+ </tr>
+
+ <tr>
+ <td>4</td>
+ <td>6</td>
+ <td>6</td>
+ <td>24</td>
+ <td>
+ Four derivations will be built at once, each given access to
+ six cores.
+ </td>
+ </tr>
+ <tr>
+ <td>12</td>
+ <td>6</td>
+ <td>6</td>
+ <td>72</td>
+ <td>
+ 12 derivations will be built at once, each given access to six
+ cores. This configuration is over-sold. If all 12 derivations
+ being built simultaneously try to use all six cores, the
+ machine's performance will be degraded due to extensive context
+ switching between the 12 builds.
+ </td>
+ </tr>
+ <tr>
+ <td>24</td>
+ <td>1</td>
+ <td>1</td>
+ <td>24</td>
+ <td>
+ 24 derivations can build at the same time, each using a single
+ core. Never oversold, but derivations which require many cores
+ will be very slow to compile.
+ </td>
+ </tr>
+ <tr>
+ <td>24</td>
+ <td>0</td>
+ <td>24</td>
+ <td>576</td>
+ <td>
+ 24 derivations can build at the same time, each using all the
+ available cores of the machine. Very likely to be oversold,
+ and very likely to suffer context switches.
+ </td>
+ </tr>
+ </tbody>
+</table>
+
+<para>It is up to the derivations' build script to respect
+host's requested cores-per-build by following the value of the
+<envar>NIX_BUILD_CORES</envar> environment variable.</para>
+
+</chapter>
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" xml:id="chap-diff-hook" version="5.0">
+
+<title>Verifying Build Reproducibility with <option linkend="conf-diff-hook">diff-hook</option></title>
+
+<subtitle>Check build reproducibility by running builds multiple times
+and comparing their results.</subtitle>
+
+<para>Specify a program with Nix's <xref linkend="conf-diff-hook"/> to
+compare build results when two builds produce different results. Note:
+this hook is only executed if the results are not the same, this hook
+is not used for determining if the results are the same.</para>
+
+<para>For purposes of demonstration, we'll use the following Nix file,
+<filename>deterministic.nix</filename> for testing:</para>
+
+<programlisting>
+let
+ inherit (import <nixpkgs> {}) runCommand;
+in {
+ stable = runCommand "stable" {} ''
+ touch $out
+ '';
+
+ unstable = runCommand "unstable" {} ''
+ echo $RANDOM > $out
+ '';
+}
+</programlisting>
+
+<para>Additionally, <filename>nix.conf</filename> contains:
+
+<programlisting>
+diff-hook = /etc/nix/my-diff-hook
+run-diff-hook = true
+</programlisting>
+
+where <filename>/etc/nix/my-diff-hook</filename> is an executable
+file containing:
+
+<programlisting>
+#!/bin/sh
+exec >&2
+echo "For derivation $3:"
+/run/current-system/sw/bin/diff -r "$1" "$2"
+</programlisting>
+
+</para>
+
+<para>The diff hook is executed by the same user and group who ran the
+build. However, the diff hook does not have write access to the store
+path just built.</para>
+
+<section>
+ <title>
+ Spot-Checking Build Determinism
+ </title>
+
+ <para>
+ Verify a path which already exists in the Nix store by passing
+ <option>--check</option> to the build command.
+ </para>
+
+ <para>If the build passes and is deterministic, Nix will exit with a
+ status code of 0:</para>
+
+ <screen>
+$ nix-build ./deterministic.nix -A stable
+this derivation will be built:
+ /nix/store/z98fasz2jqy9gs0xbvdj939p27jwda38-stable.drv
+building '/nix/store/z98fasz2jqy9gs0xbvdj939p27jwda38-stable.drv'...
+/nix/store/yyxlzw3vqaas7wfp04g0b1xg51f2czgq-stable
+
+$ nix-build ./deterministic.nix -A stable --check
+checking outputs of '/nix/store/z98fasz2jqy9gs0xbvdj939p27jwda38-stable.drv'...
+/nix/store/yyxlzw3vqaas7wfp04g0b1xg51f2czgq-stable
+</screen>
+
+ <para>If the build is not deterministic, Nix will exit with a status
+ code of 1:</para>
+
+ <screen>
+$ nix-build ./deterministic.nix -A unstable
+this derivation will be built:
+ /nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv
+building '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv'...
+/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable
+
+$ nix-build ./deterministic.nix -A unstable --check
+checking outputs of '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv'...
+error: derivation '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv' may not be deterministic: output '/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable' differs
+</screen>
+
+<para>In the Nix daemon's log, we will now see:
+<screen>
+For derivation /nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv:
+1c1
+< 8108
+---
+> 30204
+</screen>
+</para>
+
+ <para>Using <option>--check</option> with <option>--keep-failed</option>
+ will cause Nix to keep the second build's output in a special,
+ <literal>.check</literal> path:</para>
+
+ <screen>
+$ nix-build ./deterministic.nix -A unstable --check --keep-failed
+checking outputs of '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv'...
+note: keeping build directory '/tmp/nix-build-unstable.drv-0'
+error: derivation '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv' may not be deterministic: output '/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable' differs from '/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable.check'
+</screen>
+
+ <para>In particular, notice the
+ <literal>/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable.check</literal>
+ output. Nix has copied the build results to that directory where you
+ can examine it.</para>
+
+ <note xml:id="check-dirs-are-unregistered">
+ <title><literal>.check</literal> paths are not registered store paths</title>
+
+ <para>Check paths are not protected against garbage collection,
+ and this path will be deleted on the next garbage collection.</para>
+
+ <para>The path is guaranteed to be alive for the duration of
+ <xref linkend="conf-diff-hook"/>'s execution, but may be deleted
+ any time after.</para>
+
+ <para>If the comparison is performed as part of automated tooling,
+ please use the diff-hook or author your tooling to handle the case
+ where the build was not deterministic and also a check path does
+ not exist.</para>
+ </note>
+
+ <para>
+ <option>--check</option> is only usable if the derivation has
+ been built on the system already. If the derivation has not been
+ built Nix will fail with the error:
+ <screen>
+error: some outputs of '/nix/store/hzi1h60z2qf0nb85iwnpvrai3j2w7rr6-unstable.drv' are not valid, so checking is not possible
+</screen>
+
+ Run the build without <option>--check</option>, and then try with
+ <option>--check</option> again.
+ </para>
+</section>
+
+<section>
+ <title>
+ Automatic and Optionally Enforced Determinism Verification
+ </title>
+
+ <para>
+ Automatically verify every build at build time by executing the
+ build multiple times.
+ </para>
+
+ <para>
+ Setting <xref linkend="conf-repeat"/> and
+ <xref linkend="conf-enforce-determinism"/> in your
+ <filename>nix.conf</filename> permits the automated verification
+ of every build Nix performs.
+ </para>
+
+ <para>
+ The following configuration will run each build three times, and
+ will require the build to be deterministic:
+
+ <programlisting>
+enforce-determinism = true
+repeat = 2
+</programlisting>
+ </para>
+
+ <para>
+ Setting <xref linkend="conf-enforce-determinism"/> to false as in
+ the following configuration will run the build multiple times,
+ execute the build hook, but will allow the build to succeed even
+ if it does not build reproducibly:
+
+ <programlisting>
+enforce-determinism = false
+repeat = 1
+</programlisting>
+ </para>
+
+ <para>
+ An example output of this configuration:
+ <screen>
+$ nix-build ./test.nix -A unstable
+this derivation will be built:
+ /nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv
+building '/nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv' (round 1/2)...
+building '/nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv' (round 2/2)...
+output '/nix/store/6xg356v9gl03hpbbg8gws77n19qanh02-unstable' of '/nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv' differs from '/nix/store/6xg356v9gl03hpbbg8gws77n19qanh02-unstable.check' from previous round
+/nix/store/6xg356v9gl03hpbbg8gws77n19qanh02-unstable
+</screen>
+ </para>
+</section>
+</chapter>
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" xml:id="chap-post-build-hook" version="5.0">
+
+<title>Using the <option linkend="conf-post-build-hook">post-build-hook</option></title>
+<subtitle>Uploading to an S3-compatible binary cache after each build</subtitle>
+
+
+<section xml:id="chap-post-build-hook-caveats">
+ <title>Implementation Caveats</title>
+ <para>Here we use the post-build hook to upload to a binary cache.
+ This is a simple and working example, but it is not suitable for all
+ use cases.</para>
+
+ <para>The post build hook program runs after each executed build,
+ and blocks the build loop. The build loop exits if the hook program
+ fails.</para>
+
+ <para>Concretely, this implementation will make Nix slow or unusable
+ when the internet is slow or unreliable.</para>
+
+ <para>A more advanced implementation might pass the store paths to a
+ user-supplied daemon or queue for processing the store paths outside
+ of the build loop.</para>
+</section>
+
+<section>
+ <title>Prerequisites</title>
+
+ <para>
+ This tutorial assumes you have configured an S3-compatible binary cache
+ according to the instructions at
+ <xref linkend="ssec-s3-substituter-authenticated-writes"/>, and
+ that the <literal>root</literal> user's default AWS profile can
+ upload to the bucket.
+ </para>
+</section>
+
+<section>
+ <title>Set up a Signing Key</title>
+ <para>Use <command>nix-store --generate-binary-cache-key</command> to
+ create our public and private signing keys. We will sign paths
+ with the private key, and distribute the public key for verifying
+ the authenticity of the paths.</para>
+
+ <screen>
+# nix-store --generate-binary-cache-key example-nix-cache-1 /etc/nix/key.private /etc/nix/key.public
+# cat /etc/nix/key.public
+example-nix-cache-1:1/cKDz3QCCOmwcztD2eV6Coggp6rqc9DGjWv7C0G+rM=
+</screen>
+
+<para>Then, add the public key and the cache URL to your
+<filename>nix.conf</filename>'s <xref linkend="conf-trusted-public-keys"/>
+and <xref linkend="conf-substituters"/> like:</para>
+
+<programlisting>
+substituters = https://cache.nixos.org/ s3://example-nix-cache
+trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= example-nix-cache-1:1/cKDz3QCCOmwcztD2eV6Coggp6rqc9DGjWv7C0G+rM=
+</programlisting>
+
+<para>We will restart the Nix daemon in a later step.</para>
+</section>
+
+<section>
+ <title>Implementing the build hook</title>
+ <para>Write the following script to
+ <filename>/etc/nix/upload-to-cache.sh</filename>:
+ </para>
+
+ <programlisting>
+#!/bin/sh
+
+set -eu
+set -f # disable globbing
+export IFS=' '
+
+echo "Signing paths" $OUT_PATHS
+nix sign-paths --key-file /etc/nix/key.private $OUT_PATHS
+echo "Uploading paths" $OUT_PATHS
+exec nix copy --to 's3://example-nix-cache' $OUT_PATHS
+</programlisting>
+
+ <note>
+ <title>Should <literal>$OUT_PATHS</literal> be quoted?</title>
+ <para>
+ The <literal>$OUT_PATHS</literal> variable is a space-separated
+ list of Nix store paths. In this case, we expect and want the
+ shell to perform word splitting to make each output path its
+ own argument to <command>nix sign-paths</command>. Nix guarantees
+ the paths will not contain any spaces, however a store path
+ might contain glob characters. The <command>set -f</command>
+ disables globbing in the shell.
+ </para>
+ </note>
+ <para>
+ Then make sure the hook program is executable by the <literal>root</literal> user:
+ <screen>
+# chmod +x /etc/nix/upload-to-cache.sh
+</screen></para>
+</section>
+
+<section>
+ <title>Updating Nix Configuration</title>
+
+ <para>Edit <filename>/etc/nix/nix.conf</filename> to run our hook,
+ by adding the following configuration snippet at the end:</para>
+
+ <programlisting>
+post-build-hook = /etc/nix/upload-to-cache.sh
+</programlisting>
+
+<para>Then, restart the <command>nix-daemon</command>.</para>
+</section>
+
+<section>
+ <title>Testing</title>
+
+ <para>Build any derivation, for example:</para>
+
+ <screen>
+$ nix-build -E '(import <nixpkgs> {}).writeText "example" (builtins.toString builtins.currentTime)'
+this derivation will be built:
+ /nix/store/s4pnfbkalzy5qz57qs6yybna8wylkig6-example.drv
+building '/nix/store/s4pnfbkalzy5qz57qs6yybna8wylkig6-example.drv'...
+running post-build-hook '/home/grahamc/projects/github.com/NixOS/nix/post-hook.sh'...
+post-build-hook: Signing paths /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
+post-build-hook: Uploading paths /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
+/nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
+</screen>
+
+ <para>Then delete the path from the store, and try substituting it from the binary cache:</para>
+ <screen>
+$ rm ./result
+$ nix-store --delete /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
+</screen>
+
+<para>Now, copy the path back from the cache:</para>
+<screen>
+$ nix-store --realise /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
+copying path '/nix/store/m8bmqwrch6l3h8s0k3d673xpmipcdpsa-example from 's3://example-nix-cache'...
+warning: you did not specify '--add-root'; the result might be removed by the garbage collector
+/nix/store/m8bmqwrch6l3h8s0k3d673xpmipcdpsa-example
+</screen>
+</section>
+<section>
+ <title>Conclusion</title>
+ <para>
+ We now have a Nix installation configured to automatically sign and
+ upload every local build to a remote binary cache.
+ </para>
+
+ <para>
+ Before deploying this to production, be sure to consider the
+ implementation caveats in <xref linkend="chap-post-build-hook-caveats"/>.
+ </para>
+</section>
+</chapter>
+
+</part>
+ <part xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="part-command-ref" xml:base="command-ref/command-ref.xml">
+
+<title>Command Reference</title>
+
+<partintro>
+<para>This section lists commands and options that you can use when you
+work with Nix.</para>
+</partintro>
+
+<chapter xmlns="http://docbook.org/ns/docbook" xml:id="sec-common-options">
+
+<title>Common Options</title>
+
+
+<para>Most Nix commands accept the following command-line options:</para>
+
+<variablelist xml:id="opt-common">
+
+<varlistentry><term><option>--help</option></term>
+
+ <listitem><para>Prints out a summary of the command syntax and
+ exits.</para></listitem>
+
+</varlistentry>
+
+
+<varlistentry><term><option>--version</option></term>
+
+ <listitem><para>Prints out the Nix version number on standard output
+ and exits.</para></listitem>
+</varlistentry>
+
+
+<varlistentry><term><option>--verbose</option> / <option>-v</option></term>
+
+ <listitem>
+
+ <para>Increases the level of verbosity of diagnostic messages
+ printed on standard error. For each Nix operation, the information
+ printed on standard output is well-defined; any diagnostic
+ information is printed on standard error, never on standard
+ output.</para>
+
+ <para>This option may be specified repeatedly. Currently, the
+ following verbosity levels exist:</para>
+
+ <variablelist>
+
+ <varlistentry><term>0</term>
+ <listitem><para>“Errors only”: only print messages
+ explaining why the Nix invocation failed.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>1</term>
+ <listitem><para>“Informational”: print
+ <emphasis>useful</emphasis> messages about what Nix is doing.
+ This is the default.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>2</term>
+ <listitem><para>“Talkative”: print more informational
+ messages.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>3</term>
+ <listitem><para>“Chatty”: print even more
+ informational messages.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>4</term>
+ <listitem><para>“Debug”: print debug
+ information.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>5</term>
+ <listitem><para>“Vomit”: print vast amounts of debug
+ information.</para></listitem>
+ </varlistentry>
+
+ </variablelist>
+
+ </listitem>
+
+</varlistentry>
+
+
+<varlistentry><term><option>--quiet</option></term>
+
+ <listitem>
+
+ <para>Decreases the level of verbosity of diagnostic messages
+ printed on standard error. This is the inverse option to
+ <option>-v</option> / <option>--verbose</option>.
+ </para>
+
+ <para>This option may be specified repeatedly. See the previous
+ verbosity levels list.</para>
+
+ </listitem>
+
+</varlistentry>
+
+
+<varlistentry xml:id="opt-log-format"><term><option>--log-format</option> <replaceable>format</replaceable></term>
+
+ <listitem>
+
+ <para>This option can be used to change the output of the log format, with
+ <replaceable>format</replaceable> being one of:</para>
+
+ <variablelist>
+
+ <varlistentry><term>raw</term>
+ <listitem><para>This is the raw format, as outputted by nix-build.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>internal-json</term>
+ <listitem><para>Outputs the logs in a structured manner. NOTE: the json schema is not guarantees to be stable between releases.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>bar</term>
+ <listitem><para>Only display a progress bar during the builds.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>bar-with-logs</term>
+ <listitem><para>Display the raw logs, with the progress bar at the bottom.</para></listitem>
+ </varlistentry>
+
+ </variablelist>
+
+ </listitem>
+
+</varlistentry>
+
+<varlistentry><term><option>--no-build-output</option> / <option>-Q</option></term>
+
+ <listitem><para>By default, output written by builders to standard
+ output and standard error is echoed to the Nix command's standard
+ error. This option suppresses this behaviour. Note that the
+ builder's standard output and error are always written to a log file
+ in
+ <filename><replaceable>prefix</replaceable>/nix/var/log/nix</filename>.</para></listitem>
+
+</varlistentry>
+
+
+<varlistentry xml:id="opt-max-jobs"><term><option>--max-jobs</option> / <option>-j</option>
+<replaceable>number</replaceable></term>
+
+ <listitem>
+
+ <para>Sets the maximum number of build jobs that Nix will
+ perform in parallel to the specified number. Specify
+ <literal>auto</literal> to use the number of CPUs in the system.
+ The default is specified by the <link linkend="conf-max-jobs"><literal>max-jobs</literal></link>
+ configuration setting, which itself defaults to
+ <literal>1</literal>. A higher value is useful on SMP systems or to
+ exploit I/O latency.</para>
+
+ <para> Setting it to <literal>0</literal> disallows building on the local
+ machine, which is useful when you want builds to happen only on remote
+ builders.</para>
+
+ </listitem>
+
+</varlistentry>
+
+
+<varlistentry xml:id="opt-cores"><term><option>--cores</option></term>
+
+ <listitem><para>Sets the value of the <envar>NIX_BUILD_CORES</envar>
+ environment variable in the invocation of builders. Builders can
+ use this variable at their discretion to control the maximum amount
+ of parallelism. For instance, in Nixpkgs, if the derivation
+ attribute <varname>enableParallelBuilding</varname> is set to
+ <literal>true</literal>, the builder passes the
+ <option>-j<replaceable>N</replaceable></option> flag to GNU Make.
+ It defaults to the value of the <link linkend="conf-cores"><literal>cores</literal></link>
+ configuration setting, if set, or <literal>1</literal> otherwise.
+ The value <literal>0</literal> means that the builder should use all
+ available CPU cores in the system.</para></listitem>
+
+</varlistentry>
+
+
+<varlistentry xml:id="opt-max-silent-time"><term><option>--max-silent-time</option></term>
+
+ <listitem><para>Sets the maximum number of seconds that a builder
+ can go without producing any data on standard output or standard
+ error. The default is specified by the <link linkend="conf-max-silent-time"><literal>max-silent-time</literal></link>
+ configuration setting. <literal>0</literal> means no
+ time-out.</para></listitem>
+
+</varlistentry>
+
+<varlistentry xml:id="opt-timeout"><term><option>--timeout</option></term>
+
+ <listitem><para>Sets the maximum number of seconds that a builder
+ can run. The default is specified by the <link linkend="conf-timeout"><literal>timeout</literal></link>
+ configuration setting. <literal>0</literal> means no
+ timeout.</para></listitem>
+
+</varlistentry>
+
+<varlistentry><term><option>--keep-going</option> / <option>-k</option></term>
+
+ <listitem><para>Keep going in case of failed builds, to the
+ greatest extent possible. That is, if building an input of some
+ derivation fails, Nix will still build the other inputs, but not the
+ derivation itself. Without this option, Nix stops if any build
+ fails (except for builds of substitutes), possibly killing builds in
+ progress (in case of parallel or distributed builds).</para></listitem>
+
+</varlistentry>
+
+
+<varlistentry><term><option>--keep-failed</option> / <option>-K</option></term>
+
+ <listitem><para>Specifies that in case of a build failure, the
+ temporary directory (usually in <filename>/tmp</filename>) in which
+ the build takes place should not be deleted. The path of the build
+ directory is printed as an informational message.
+ </para>
+ </listitem>
+</varlistentry>
+
+
+<varlistentry><term><option>--fallback</option></term>
+
+ <listitem>
+
+ <para>Whenever Nix attempts to build a derivation for which
+ substitutes are known for each output path, but realising the output
+ paths through the substitutes fails, fall back on building the
+ derivation.</para>
+
+ <para>The most common scenario in which this is useful is when we
+ have registered substitutes in order to perform binary distribution
+ from, say, a network repository. If the repository is down, the
+ realisation of the derivation will fail. When this option is
+ specified, Nix will build the derivation instead. Thus,
+ installation from binaries falls back on installation from source.
+ This option is not the default since it is generally not desirable
+ for a transient failure in obtaining the substitutes to lead to a
+ full build from source (with the related consumption of
+ resources).</para>
+
+ </listitem>
+
+</varlistentry>
+
+<varlistentry><term><option>--no-build-hook</option></term>
+
+ <listitem>
+
+ <para>Disables the build hook mechanism. This allows to ignore remote
+ builders if they are setup on the machine.</para>
+
+ <para>It's useful in cases where the bandwidth between the client and the
+ remote builder is too low. In that case it can take more time to upload the
+ sources to the remote builder and fetch back the result than to do the
+ computation locally.</para>
+
+ </listitem>
+
+</varlistentry>
+
+
+
+<varlistentry><term><option>--readonly-mode</option></term>
+
+ <listitem><para>When this option is used, no attempt is made to open
+ the Nix database. Most Nix operations do need database access, so
+ those operations will fail.</para></listitem>
+
+</varlistentry>
+
+
+<varlistentry><term><option>--arg</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
+
+ <listitem><para>This option is accepted by
+ <command>nix-env</command>, <command>nix-instantiate</command>,
+ <command>nix-shell</command> and <command>nix-build</command>.
+ When evaluating Nix expressions, the expression evaluator will
+ automatically try to call functions that
+ it encounters. It can automatically call functions for which every
+ argument has a <link linkend="ss-functions">default value</link>
+ (e.g., <literal>{ <replaceable>argName</replaceable> ?
+ <replaceable>defaultValue</replaceable> }:
+ <replaceable>...</replaceable></literal>). With
+ <option>--arg</option>, you can also call functions that have
+ arguments without a default value (or override a default value).
+ That is, if the evaluator encounters a function with an argument
+ named <replaceable>name</replaceable>, it will call it with value
+ <replaceable>value</replaceable>.</para>
+
+ <para>For instance, the top-level <literal>default.nix</literal> in
+ Nixpkgs is actually a function:
+
+<programlisting>
+{ # The system (e.g., `i686-linux') for which to build the packages.
+ system ? builtins.currentSystem
+ <replaceable>...</replaceable>
+}: <replaceable>...</replaceable></programlisting>
+
+ So if you call this Nix expression (e.g., when you do
+ <literal>nix-env -i <replaceable>pkgname</replaceable></literal>),
+ the function will be called automatically using the value <link linkend="builtin-currentSystem"><literal>builtins.currentSystem</literal></link>
+ for the <literal>system</literal> argument. You can override this
+ using <option>--arg</option>, e.g., <literal>nix-env -i
+ <replaceable>pkgname</replaceable> --arg system
+ \"i686-freebsd\"</literal>. (Note that since the argument is a Nix
+ string literal, you have to escape the quotes.)</para></listitem>
+
+</varlistentry>
+
+
+<varlistentry><term><option>--argstr</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
+
+ <listitem><para>This option is like <option>--arg</option>, only the
+ value is not a Nix expression but a string. So instead of
+ <literal>--arg system \"i686-linux\"</literal> (the outer quotes are
+ to keep the shell happy) you can say <literal>--argstr system
+ i686-linux</literal>.</para></listitem>
+
+</varlistentry>
+
+
+<varlistentry xml:id="opt-attr"><term><option>--attr</option> / <option>-A</option>
+<replaceable>attrPath</replaceable></term>
+
+ <listitem><para>Select an attribute from the top-level Nix
+ expression being evaluated. (<command>nix-env</command>,
+ <command>nix-instantiate</command>, <command>nix-build</command> and
+ <command>nix-shell</command> only.) The <emphasis>attribute
+ path</emphasis> <replaceable>attrPath</replaceable> is a sequence of
+ attribute names separated by dots. For instance, given a top-level
+ Nix expression <replaceable>e</replaceable>, the attribute path
+ <literal>xorg.xorgserver</literal> would cause the expression
+ <literal><replaceable>e</replaceable>.xorg.xorgserver</literal> to
+ be used. See <link linkend="refsec-nix-env-install-examples"><command>nix-env
+ --install</command></link> for some concrete examples.</para>
+
+ <para>In addition to attribute names, you can also specify array
+ indices. For instance, the attribute path
+ <literal>foo.3.bar</literal> selects the <literal>bar</literal>
+ attribute of the fourth element of the array in the
+ <literal>foo</literal> attribute of the top-level
+ expression.</para></listitem>
+
+</varlistentry>
+
+
+<varlistentry><term><option>--expr</option> / <option>-E</option></term>
+
+ <listitem><para>Interpret the command line arguments as a list of
+ Nix expressions to be parsed and evaluated, rather than as a list
+ of file names of Nix expressions.
+ (<command>nix-instantiate</command>, <command>nix-build</command>
+ and <command>nix-shell</command> only.)</para>
+
+ <para>For <command>nix-shell</command>, this option is commonly used
+ to give you a shell in which you can build the packages returned
+ by the expression. If you want to get a shell which contain the
+ <emphasis>built</emphasis> packages ready for use, give your
+ expression to the <command>nix-shell -p</command> convenience flag
+ instead.</para></listitem>
+
+</varlistentry>
+
+
+<varlistentry xml:id="opt-I"><term><option>-I</option> <replaceable>path</replaceable></term>
+
+ <listitem><para>Add a path to the Nix expression search path. This
+ option may be given multiple times. See the <envar linkend="env-NIX_PATH">NIX_PATH</envar> environment variable for
+ information on the semantics of the Nix search path. Paths added
+ through <option>-I</option> take precedence over
+ <envar>NIX_PATH</envar>.</para></listitem>
+
+</varlistentry>
+
+
+<varlistentry><term><option>--option</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
+
+ <listitem><para>Set the Nix configuration option
+ <replaceable>name</replaceable> to <replaceable>value</replaceable>.
+ This overrides settings in the Nix configuration file (see
+ <citerefentry><refentrytitle>nix.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</para></listitem>
+
+</varlistentry>
+
+
+<varlistentry><term><option>--repair</option></term>
+
+ <listitem><para>Fix corrupted or missing store paths by
+ redownloading or rebuilding them. Note that this is slow because it
+ requires computing a cryptographic hash of the contents of every
+ path in the closure of the build. Also note the warning under
+ <command>nix-store --repair-path</command>.</para></listitem>
+
+</varlistentry>
+
+
+</variablelist>
+
+
+</chapter>
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-common-env">
+
+<title>Common Environment Variables</title>
+
+
+<para>Most Nix commands interpret the following environment variables:</para>
+
+<variablelist xml:id="env-common">
+
+<varlistentry><term><envar>IN_NIX_SHELL</envar></term>
+
+ <listitem><para>Indicator that tells if the current environment was set up by
+ <command>nix-shell</command>. Since Nix 2.0 the values are
+ <literal>"pure"</literal> and <literal>"impure"</literal></para></listitem>
+
+</varlistentry>
+
+<varlistentry xml:id="env-NIX_PATH"><term><envar>NIX_PATH</envar></term>
+
+ <listitem>
+
+ <para>A colon-separated list of directories used to look up Nix
+ expressions enclosed in angle brackets (i.e.,
+ <literal><<replaceable>path</replaceable>></literal>). For
+ instance, the value
+
+ <screen>
+/home/eelco/Dev:/etc/nixos</screen>
+
+ will cause Nix to look for paths relative to
+ <filename>/home/eelco/Dev</filename> and
+ <filename>/etc/nixos</filename>, in this order. It is also
+ possible to match paths against a prefix. For example, the value
+
+ <screen>
+nixpkgs=/home/eelco/Dev/nixpkgs-branch:/etc/nixos</screen>
+
+ will cause Nix to search for
+ <literal><nixpkgs/<replaceable>path</replaceable>></literal> in
+ <filename>/home/eelco/Dev/nixpkgs-branch/<replaceable>path</replaceable></filename>
+ and
+ <filename>/etc/nixos/nixpkgs/<replaceable>path</replaceable></filename>.</para>
+
+ <para>If a path in the Nix search path starts with
+ <literal>http://</literal> or <literal>https://</literal>, it is
+ interpreted as the URL of a tarball that will be downloaded and
+ unpacked to a temporary location. The tarball must consist of a
+ single top-level directory. For example, setting
+ <envar>NIX_PATH</envar> to
+
+ <screen>
+nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-15.09.tar.gz</screen>
+
+ tells Nix to download the latest revision in the Nixpkgs/NixOS
+ 15.09 channel.</para>
+
+ <para>A following shorthand can be used to refer to the official channels:
+
+ <screen>nixpkgs=channel:nixos-15.09</screen>
+ </para>
+
+ <para>The search path can be extended using the <option linkend="opt-I">-I</option> option, which takes precedence over
+ <envar>NIX_PATH</envar>.</para></listitem>
+
+</varlistentry>
+
+
+<varlistentry><term><envar>NIX_IGNORE_SYMLINK_STORE</envar></term>
+
+ <listitem>
+
+ <para>Normally, the Nix store directory (typically
+ <filename>/nix/store</filename>) is not allowed to contain any
+ symlink components. This is to prevent “impure” builds. Builders
+ sometimes “canonicalise” paths by resolving all symlink components.
+ Thus, builds on different machines (with
+ <filename>/nix/store</filename> resolving to different locations)
+ could yield different results. This is generally not a problem,
+ except when builds are deployed to machines where
+ <filename>/nix/store</filename> resolves differently. If you are
+ sure that you’re not going to do that, you can set
+ <envar>NIX_IGNORE_SYMLINK_STORE</envar> to <envar>1</envar>.</para>
+
+ <para>Note that if you’re symlinking the Nix store so that you can
+ put it on another file system than the root file system, on Linux
+ you’re better off using <literal>bind</literal> mount points, e.g.,
+
+ <screen>
+$ mkdir /nix
+$ mount -o bind /mnt/otherdisk/nix /nix</screen>
+
+ Consult the <citerefentry><refentrytitle>mount</refentrytitle>
+ <manvolnum>8</manvolnum></citerefentry> manual page for details.</para>
+
+ </listitem>
+
+</varlistentry>
+
+
+<varlistentry><term><envar>NIX_STORE_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix store (default
+ <filename><replaceable>prefix</replaceable>/store</filename>).</para></listitem>
+
+</varlistentry>
+
+
+<varlistentry><term><envar>NIX_DATA_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix static data
+ directory (default
+ <filename><replaceable>prefix</replaceable>/share</filename>).</para></listitem>
+
+</varlistentry>
+
+
+<varlistentry><term><envar>NIX_LOG_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix log directory
+ (default <filename><replaceable>prefix</replaceable>/var/log/nix</filename>).</para></listitem>
+
+</varlistentry>
+
+
+<varlistentry><term><envar>NIX_STATE_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix state directory
+ (default <filename><replaceable>prefix</replaceable>/var/nix</filename>).</para></listitem>
+
+</varlistentry>
+
+
+<varlistentry><term><envar>NIX_CONF_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the system Nix configuration
+ directory (default
+ <filename><replaceable>prefix</replaceable>/etc/nix</filename>).</para></listitem>
+
+</varlistentry>
+
+<varlistentry><term><envar>NIX_USER_CONF_FILES</envar></term>
+
+ <listitem><para>Overrides the location of the user Nix configuration files
+ to load from (defaults to the XDG spec locations). The variable is treated
+ as a list separated by the <literal>:</literal> token.</para></listitem>
+
+</varlistentry>
+
+<varlistentry><term><envar>TMPDIR</envar></term>
+
+ <listitem><para>Use the specified directory to store temporary
+ files. In particular, this includes temporary build directories;
+ these can take up substantial amounts of disk space. The default is
+ <filename>/tmp</filename>.</para></listitem>
+
+</varlistentry>
+
+
+<varlistentry xml:id="envar-remote"><term><envar>NIX_REMOTE</envar></term>
+
+ <listitem><para>This variable should be set to
+ <literal>daemon</literal> if you want to use the Nix daemon to
+ execute Nix operations. This is necessary in <link linkend="ssec-multi-user">multi-user Nix installations</link>.
+ If the Nix daemon's Unix socket is at some non-standard path,
+ this variable should be set to <literal>unix://path/to/socket</literal>.
+ Otherwise, it should be left unset.</para></listitem>
+
+</varlistentry>
+
+
+<varlistentry><term><envar>NIX_SHOW_STATS</envar></term>
+
+ <listitem><para>If set to <literal>1</literal>, Nix will print some
+ evaluation statistics, such as the number of values
+ allocated.</para></listitem>
+
+</varlistentry>
+
+
+<varlistentry><term><envar>NIX_COUNT_CALLS</envar></term>
+
+ <listitem><para>If set to <literal>1</literal>, Nix will print how
+ often functions were called during Nix expression evaluation. This
+ is useful for profiling your Nix expressions.</para></listitem>
+
+</varlistentry>
+
+
+<varlistentry><term><envar>GC_INITIAL_HEAP_SIZE</envar></term>
+
+ <listitem><para>If Nix has been configured to use the Boehm garbage
+ collector, this variable sets the initial size of the heap in bytes.
+ It defaults to 384 MiB. Setting it to a low value reduces memory
+ consumption, but will increase runtime due to the overhead of
+ garbage collection.</para></listitem>
+
+</varlistentry>
+
+
+</variablelist>
+
+
+</chapter>
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-main-commands">
+
+<title>Main Commands</title>
+
+<para>This section lists commands and options that you can use when you
+work with Nix.</para>
+
+<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-nix-env">
+
+<refmeta>
+ <refentrytitle>nix-env</refentrytitle>
+ <manvolnum>1</manvolnum>
+ <refmiscinfo class="source">Nix</refmiscinfo>
+ <refmiscinfo class="version">3.0</refmiscinfo>
+</refmeta>
+
+<refnamediv>
+ <refname>nix-env</refname>
+ <refpurpose>manipulate or query Nix user environments</refpurpose>
+</refnamediv>
+
+<refsynopsisdiv>
+ <cmdsynopsis>
+ <command>nix-env</command>
+ <arg xmlns="http://docbook.org/ns/docbook"><option>--help</option></arg><arg xmlns="http://docbook.org/ns/docbook"><option>--version</option></arg><arg xmlns="http://docbook.org/ns/docbook" rep="repeat">
+ <group choice="req">
+ <arg choice="plain"><option>--verbose</option></arg>
+ <arg choice="plain"><option>-v</option></arg>
+ </group>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <arg choice="plain"><option>--quiet</option></arg>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <option>--log-format</option>
+ <replaceable>format</replaceable>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <group choice="plain">
+ <arg choice="plain"><option>--no-build-output</option></arg>
+ <arg choice="plain"><option>-Q</option></arg>
+ </group>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <group choice="req">
+ <arg choice="plain"><option>--max-jobs</option></arg>
+ <arg choice="plain"><option>-j</option></arg>
+ </group>
+ <replaceable>number</replaceable>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <option>--cores</option>
+ <replaceable>number</replaceable>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <option>--max-silent-time</option>
+ <replaceable>number</replaceable>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <option>--timeout</option>
+ <replaceable>number</replaceable>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <group choice="plain">
+ <arg choice="plain"><option>--keep-going</option></arg>
+ <arg choice="plain"><option>-k</option></arg>
+ </group>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <group choice="plain">
+ <arg choice="plain"><option>--keep-failed</option></arg>
+ <arg choice="plain"><option>-K</option></arg>
+ </group>
+</arg><arg xmlns="http://docbook.org/ns/docbook"><option>--fallback</option></arg><arg xmlns="http://docbook.org/ns/docbook"><option>--readonly-mode</option></arg><arg xmlns="http://docbook.org/ns/docbook">
+ <option>-I</option>
+ <replaceable>path</replaceable>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <option>--option</option>
+ <replaceable>name</replaceable>
+ <replaceable>value</replaceable>
+</arg><sbr xmlns="http://docbook.org/ns/docbook"/>
+ <arg><option>--arg</option> <replaceable>name</replaceable> <replaceable>value</replaceable></arg>
+ <arg><option>--argstr</option> <replaceable>name</replaceable> <replaceable>value</replaceable></arg>
+ <arg>
+ <group choice="req">
+ <arg choice="plain"><option>--file</option></arg>
+ <arg choice="plain"><option>-f</option></arg>
+ </group>
+ <replaceable>path</replaceable>
+ </arg>
+ <arg>
+ <group choice="req">
+ <arg choice="plain"><option>--profile</option></arg>
+ <arg choice="plain"><option>-p</option></arg>
+ </group>
+ <replaceable>path</replaceable>
+ </arg>
+ <arg>
+ <arg choice="plain"><option>--system-filter</option></arg>
+ <replaceable>system</replaceable>
+ </arg>
+ <arg><option>--dry-run</option></arg>
+ <arg choice="plain"><replaceable>operation</replaceable></arg>
+ <arg rep="repeat"><replaceable>options</replaceable></arg>
+ <arg rep="repeat"><replaceable>arguments</replaceable></arg>
+ </cmdsynopsis>
+</refsynopsisdiv>
+
+
+<refsection><title>Description</title>
+
+<para>The command <command>nix-env</command> is used to manipulate Nix
+user environments. User environments are sets of software packages
+available to a user at some point in time. In other words, they are a
+synthesised view of the programs available in the Nix store. There
+may be many user environments: different users can have different
+environments, and individual users can switch between different
+environments.</para>
+
+<para><command>nix-env</command> takes exactly one
+<emphasis>operation</emphasis> flag which indicates the subcommand to
+be performed. These are documented below.</para>
+
+</refsection>
+
+
+
+<!--######################################################################-->
+
+<refsection><title>Selectors</title>
+
+<para>Several commands, such as <command>nix-env -q</command> and
+<command>nix-env -i</command>, take a list of arguments that specify
+the packages on which to operate. These are extended regular
+expressions that must match the entire name of the package. (For
+details on regular expressions, see
+<citerefentry><refentrytitle>regex</refentrytitle><manvolnum>7</manvolnum></citerefentry>.)
+The match is case-sensitive. The regular expression can optionally be
+followed by a dash and a version number; if omitted, any version of
+the package will match. Here are some examples:
+
+<variablelist>
+
+ <varlistentry>
+ <term><literal>firefox</literal></term>
+ <listitem><para>Matches the package name
+ <literal>firefox</literal> and any version.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>firefox-32.0</literal></term>
+ <listitem><para>Matches the package name
+ <literal>firefox</literal> and version
+ <literal>32.0</literal>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>gtk\\+</literal></term>
+ <listitem><para>Matches the package name
+ <literal>gtk+</literal>. The <literal>+</literal> character must
+ be escaped using a backslash to prevent it from being interpreted
+ as a quantifier, and the backslash must be escaped in turn with
+ another backslash to ensure that the shell passes it
+ on.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>.\*</literal></term>
+ <listitem><para>Matches any package name. This is the default for
+ most commands.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>'.*zip.*'</literal></term>
+ <listitem><para>Matches any package name containing the string
+ <literal>zip</literal>. Note the dots: <literal>'*zip*'</literal>
+ does not work, because in a regular expression, the character
+ <literal>*</literal> is interpreted as a
+ quantifier.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>'.*(firefox|chromium).*'</literal></term>
+ <listitem><para>Matches any package name containing the strings
+ <literal>firefox</literal> or
+ <literal>chromium</literal>.</para></listitem>
+ </varlistentry>
+
+</variablelist>
+
+</para>
+
+</refsection>
+
+
+
+<!--######################################################################-->
+
+<refsection><title>Common options</title>
+
+<para>This section lists the options that are common to all
+operations. These options are allowed for every subcommand, though
+they may not always have an effect. <phrase condition="manual">See
+also <xref linkend="sec-common-options"/>.</phrase></para>
+
+<variablelist>
+
+ <varlistentry><term><option>--file</option> / <option>-f</option> <replaceable>path</replaceable></term>
+
+ <listitem><para>Specifies the Nix expression (designated below as
+ the <emphasis>active Nix expression</emphasis>) used by the
+ <option>--install</option>, <option>--upgrade</option>, and
+ <option>--query --available</option> operations to obtain
+ derivations. The default is
+ <filename>~/.nix-defexpr</filename>.</para>
+
+ <para>If the argument starts with <literal>http://</literal> or
+ <literal>https://</literal>, it is interpreted as the URL of a
+ tarball that will be downloaded and unpacked to a temporary
+ location. The tarball must include a single top-level directory
+ containing at least a file named <filename>default.nix</filename>.</para>
+
+ </listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--profile</option> / <option>-p</option> <replaceable>path</replaceable></term>
+
+ <listitem><para>Specifies the profile to be used by those
+ operations that operate on a profile (designated below as the
+ <emphasis>active profile</emphasis>). A profile is a sequence of
+ user environments called <emphasis>generations</emphasis>, one of
+ which is the <emphasis>current
+ generation</emphasis>.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--dry-run</option></term>
+
+ <listitem><para>For the <option>--install</option>,
+ <option>--upgrade</option>, <option>--uninstall</option>,
+ <option>--switch-generation</option>,
+ <option>--delete-generations</option> and
+ <option>--rollback</option> operations, this flag will cause
+ <command>nix-env</command> to print what
+ <emphasis>would</emphasis> be done if this flag had not been
+ specified, without actually doing it.</para>
+
+ <para><option>--dry-run</option> also prints out which paths will
+ be <link linkend="gloss-substitute">substituted</link> (i.e.,
+ downloaded) and which paths will be built from source (because no
+ substitute is available).</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--system-filter</option> <replaceable>system</replaceable></term>
+
+ <listitem><para>By default, operations such as <option>--query
+ --available</option> show derivations matching any platform. This
+ option allows you to use derivations for the specified platform
+ <replaceable>system</replaceable>.</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+<variablelist condition="manpage">
+ <varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--help</option></term>
+
+ <listitem><para>Prints out a summary of the command syntax and
+ exits.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--version</option></term>
+
+ <listitem><para>Prints out the Nix version number on standard output
+ and exits.</para></listitem>
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--verbose</option> / <option>-v</option></term>
+
+ <listitem>
+
+ <para>Increases the level of verbosity of diagnostic messages
+ printed on standard error. For each Nix operation, the information
+ printed on standard output is well-defined; any diagnostic
+ information is printed on standard error, never on standard
+ output.</para>
+
+ <para>This option may be specified repeatedly. Currently, the
+ following verbosity levels exist:</para>
+
+ <variablelist>
+
+ <varlistentry><term>0</term>
+ <listitem><para>“Errors only”: only print messages
+ explaining why the Nix invocation failed.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>1</term>
+ <listitem><para>“Informational”: print
+ <emphasis>useful</emphasis> messages about what Nix is doing.
+ This is the default.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>2</term>
+ <listitem><para>“Talkative”: print more informational
+ messages.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>3</term>
+ <listitem><para>“Chatty”: print even more
+ informational messages.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>4</term>
+ <listitem><para>“Debug”: print debug
+ information.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>5</term>
+ <listitem><para>“Vomit”: print vast amounts of debug
+ information.</para></listitem>
+ </varlistentry>
+
+ </variablelist>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--quiet</option></term>
+
+ <listitem>
+
+ <para>Decreases the level of verbosity of diagnostic messages
+ printed on standard error. This is the inverse option to
+ <option>-v</option> / <option>--verbose</option>.
+ </para>
+
+ <para>This option may be specified repeatedly. See the previous
+ verbosity levels list.</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-log-format"><term><option>--log-format</option> <replaceable>format</replaceable></term>
+
+ <listitem>
+
+ <para>This option can be used to change the output of the log format, with
+ <replaceable>format</replaceable> being one of:</para>
+
+ <variablelist>
+
+ <varlistentry><term>raw</term>
+ <listitem><para>This is the raw format, as outputted by nix-build.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>internal-json</term>
+ <listitem><para>Outputs the logs in a structured manner. NOTE: the json schema is not guarantees to be stable between releases.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>bar</term>
+ <listitem><para>Only display a progress bar during the builds.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>bar-with-logs</term>
+ <listitem><para>Display the raw logs, with the progress bar at the bottom.</para></listitem>
+ </varlistentry>
+
+ </variablelist>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--no-build-output</option> / <option>-Q</option></term>
+
+ <listitem><para>By default, output written by builders to standard
+ output and standard error is echoed to the Nix command's standard
+ error. This option suppresses this behaviour. Note that the
+ builder's standard output and error are always written to a log file
+ in
+ <filename><replaceable>prefix</replaceable>/nix/var/log/nix</filename>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-max-jobs"><term><option>--max-jobs</option> / <option>-j</option>
+<replaceable>number</replaceable></term>
+
+ <listitem>
+
+ <para>Sets the maximum number of build jobs that Nix will
+ perform in parallel to the specified number. Specify
+ <literal>auto</literal> to use the number of CPUs in the system.
+ The default is specified by the <link linkend="conf-max-jobs"><literal>max-jobs</literal></link>
+ configuration setting, which itself defaults to
+ <literal>1</literal>. A higher value is useful on SMP systems or to
+ exploit I/O latency.</para>
+
+ <para> Setting it to <literal>0</literal> disallows building on the local
+ machine, which is useful when you want builds to happen only on remote
+ builders.</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-cores"><term><option>--cores</option></term>
+
+ <listitem><para>Sets the value of the <envar>NIX_BUILD_CORES</envar>
+ environment variable in the invocation of builders. Builders can
+ use this variable at their discretion to control the maximum amount
+ of parallelism. For instance, in Nixpkgs, if the derivation
+ attribute <varname>enableParallelBuilding</varname> is set to
+ <literal>true</literal>, the builder passes the
+ <option>-j<replaceable>N</replaceable></option> flag to GNU Make.
+ It defaults to the value of the <link linkend="conf-cores"><literal>cores</literal></link>
+ configuration setting, if set, or <literal>1</literal> otherwise.
+ The value <literal>0</literal> means that the builder should use all
+ available CPU cores in the system.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-max-silent-time"><term><option>--max-silent-time</option></term>
+
+ <listitem><para>Sets the maximum number of seconds that a builder
+ can go without producing any data on standard output or standard
+ error. The default is specified by the <link linkend="conf-max-silent-time"><literal>max-silent-time</literal></link>
+ configuration setting. <literal>0</literal> means no
+ time-out.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-timeout"><term><option>--timeout</option></term>
+
+ <listitem><para>Sets the maximum number of seconds that a builder
+ can run. The default is specified by the <link linkend="conf-timeout"><literal>timeout</literal></link>
+ configuration setting. <literal>0</literal> means no
+ timeout.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--keep-going</option> / <option>-k</option></term>
+
+ <listitem><para>Keep going in case of failed builds, to the
+ greatest extent possible. That is, if building an input of some
+ derivation fails, Nix will still build the other inputs, but not the
+ derivation itself. Without this option, Nix stops if any build
+ fails (except for builds of substitutes), possibly killing builds in
+ progress (in case of parallel or distributed builds).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--keep-failed</option> / <option>-K</option></term>
+
+ <listitem><para>Specifies that in case of a build failure, the
+ temporary directory (usually in <filename>/tmp</filename>) in which
+ the build takes place should not be deleted. The path of the build
+ directory is printed as an informational message.
+ </para>
+ </listitem>
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--fallback</option></term>
+
+ <listitem>
+
+ <para>Whenever Nix attempts to build a derivation for which
+ substitutes are known for each output path, but realising the output
+ paths through the substitutes fails, fall back on building the
+ derivation.</para>
+
+ <para>The most common scenario in which this is useful is when we
+ have registered substitutes in order to perform binary distribution
+ from, say, a network repository. If the repository is down, the
+ realisation of the derivation will fail. When this option is
+ specified, Nix will build the derivation instead. Thus,
+ installation from binaries falls back on installation from source.
+ This option is not the default since it is generally not desirable
+ for a transient failure in obtaining the substitutes to lead to a
+ full build from source (with the related consumption of
+ resources).</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--no-build-hook</option></term>
+
+ <listitem>
+
+ <para>Disables the build hook mechanism. This allows to ignore remote
+ builders if they are setup on the machine.</para>
+
+ <para>It's useful in cases where the bandwidth between the client and the
+ remote builder is too low. In that case it can take more time to upload the
+ sources to the remote builder and fetch back the result than to do the
+ computation locally.</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--readonly-mode</option></term>
+
+ <listitem><para>When this option is used, no attempt is made to open
+ the Nix database. Most Nix operations do need database access, so
+ those operations will fail.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--arg</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
+
+ <listitem><para>This option is accepted by
+ <command>nix-env</command>, <command>nix-instantiate</command>,
+ <command>nix-shell</command> and <command>nix-build</command>.
+ When evaluating Nix expressions, the expression evaluator will
+ automatically try to call functions that
+ it encounters. It can automatically call functions for which every
+ argument has a <link linkend="ss-functions">default value</link>
+ (e.g., <literal>{ <replaceable>argName</replaceable> ?
+ <replaceable>defaultValue</replaceable> }:
+ <replaceable>...</replaceable></literal>). With
+ <option>--arg</option>, you can also call functions that have
+ arguments without a default value (or override a default value).
+ That is, if the evaluator encounters a function with an argument
+ named <replaceable>name</replaceable>, it will call it with value
+ <replaceable>value</replaceable>.</para>
+
+ <para>For instance, the top-level <literal>default.nix</literal> in
+ Nixpkgs is actually a function:
+
+<programlisting>
+{ # The system (e.g., `i686-linux') for which to build the packages.
+ system ? builtins.currentSystem
+ <replaceable>...</replaceable>
+}: <replaceable>...</replaceable></programlisting>
+
+ So if you call this Nix expression (e.g., when you do
+ <literal>nix-env -i <replaceable>pkgname</replaceable></literal>),
+ the function will be called automatically using the value <link linkend="builtin-currentSystem"><literal>builtins.currentSystem</literal></link>
+ for the <literal>system</literal> argument. You can override this
+ using <option>--arg</option>, e.g., <literal>nix-env -i
+ <replaceable>pkgname</replaceable> --arg system
+ \"i686-freebsd\"</literal>. (Note that since the argument is a Nix
+ string literal, you have to escape the quotes.)</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--argstr</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
+
+ <listitem><para>This option is like <option>--arg</option>, only the
+ value is not a Nix expression but a string. So instead of
+ <literal>--arg system \"i686-linux\"</literal> (the outer quotes are
+ to keep the shell happy) you can say <literal>--argstr system
+ i686-linux</literal>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-attr"><term><option>--attr</option> / <option>-A</option>
+<replaceable>attrPath</replaceable></term>
+
+ <listitem><para>Select an attribute from the top-level Nix
+ expression being evaluated. (<command>nix-env</command>,
+ <command>nix-instantiate</command>, <command>nix-build</command> and
+ <command>nix-shell</command> only.) The <emphasis>attribute
+ path</emphasis> <replaceable>attrPath</replaceable> is a sequence of
+ attribute names separated by dots. For instance, given a top-level
+ Nix expression <replaceable>e</replaceable>, the attribute path
+ <literal>xorg.xorgserver</literal> would cause the expression
+ <literal><replaceable>e</replaceable>.xorg.xorgserver</literal> to
+ be used. See <link linkend="refsec-nix-env-install-examples"><command>nix-env
+ --install</command></link> for some concrete examples.</para>
+
+ <para>In addition to attribute names, you can also specify array
+ indices. For instance, the attribute path
+ <literal>foo.3.bar</literal> selects the <literal>bar</literal>
+ attribute of the fourth element of the array in the
+ <literal>foo</literal> attribute of the top-level
+ expression.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--expr</option> / <option>-E</option></term>
+
+ <listitem><para>Interpret the command line arguments as a list of
+ Nix expressions to be parsed and evaluated, rather than as a list
+ of file names of Nix expressions.
+ (<command>nix-instantiate</command>, <command>nix-build</command>
+ and <command>nix-shell</command> only.)</para>
+
+ <para>For <command>nix-shell</command>, this option is commonly used
+ to give you a shell in which you can build the packages returned
+ by the expression. If you want to get a shell which contain the
+ <emphasis>built</emphasis> packages ready for use, give your
+ expression to the <command>nix-shell -p</command> convenience flag
+ instead.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-I"><term><option>-I</option> <replaceable>path</replaceable></term>
+
+ <listitem><para>Add a path to the Nix expression search path. This
+ option may be given multiple times. See the <envar linkend="env-NIX_PATH">NIX_PATH</envar> environment variable for
+ information on the semantics of the Nix search path. Paths added
+ through <option>-I</option> take precedence over
+ <envar>NIX_PATH</envar>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--option</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
+
+ <listitem><para>Set the Nix configuration option
+ <replaceable>name</replaceable> to <replaceable>value</replaceable>.
+ This overrides settings in the Nix configuration file (see
+ <citerefentry><refentrytitle>nix.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--repair</option></term>
+
+ <listitem><para>Fix corrupted or missing store paths by
+ redownloading or rebuilding them. Note that this is slow because it
+ requires computing a cryptographic hash of the contents of every
+ path in the closure of the build. Also note the warning under
+ <command>nix-store --repair-path</command>.</para></listitem>
+
+</varlistentry>
+</variablelist>
+
+</refsection>
+
+
+
+<!--######################################################################-->
+
+<refsection><title>Files</title>
+
+<variablelist>
+
+ <varlistentry><term><filename>~/.nix-defexpr</filename></term>
+
+ <listitem><para>The source for the default Nix
+ expressions used by the <option>--install</option>,
+ <option>--upgrade</option>, and <option>--query
+ --available</option> operations to obtain derivations. The
+ <option>--file</option> option may be used to override this
+ default.</para>
+
+ <para>If <filename>~/.nix-defexpr</filename> is a file,
+ it is loaded as a Nix expression. If the expression
+ is a set, it is used as the default Nix expression.
+ If the expression is a function, an empty set is passed
+ as argument and the return value is used as
+ the default Nix expression.</para>
+
+ <para>If <filename>~/.nix-defexpr</filename> is a directory
+ containing a <filename>default.nix</filename> file, that file
+ is loaded as in the above paragraph.</para>
+
+ <para>If <filename>~/.nix-defexpr</filename> is a directory without
+ a <filename>default.nix</filename> file, then its contents
+ (both files and subdirectories) are loaded as Nix expressions.
+ The expressions are combined into a single set, each expression
+ under an attribute with the same name as the original file
+ or subdirectory.
+ </para>
+
+ <para>For example, if <filename>~/.nix-defexpr</filename> contains
+ two files, <filename>foo.nix</filename> and <filename>bar.nix</filename>,
+ then the default Nix expression will essentially be
+
+<programlisting>
+{
+ foo = import ~/.nix-defexpr/foo.nix;
+ bar = import ~/.nix-defexpr/bar.nix;
+}</programlisting>
+
+ </para>
+
+ <para>The file <filename>manifest.nix</filename> is always ignored.
+ Subdirectories without a <filename>default.nix</filename> file
+ are traversed recursively in search of more Nix expressions,
+ but the names of these intermediate directories are not
+ added to the attribute paths of the default Nix expression.</para>
+
+ <para>The command <command>nix-channel</command> places symlinks
+ to the downloaded Nix expressions from each subscribed channel in
+ this directory.</para>
+ </listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><filename>~/.nix-profile</filename></term>
+
+ <listitem><para>A symbolic link to the user's current profile. By
+ default, this symlink points to
+ <filename><replaceable>prefix</replaceable>/var/nix/profiles/default</filename>.
+ The <envar>PATH</envar> environment variable should include
+ <filename>~/.nix-profile/bin</filename> for the user environment
+ to be visible to the user.</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+</refsection>
+
+
+
+<!--######################################################################-->
+
+<refsection xml:id="rsec-nix-env-install"><title>Operation <option>--install</option></title>
+
+<refsection><title>Synopsis</title>
+
+<cmdsynopsis>
+ <command>nix-env</command>
+ <group choice="req">
+ <arg choice="plain"><option>--install</option></arg>
+ <arg choice="plain"><option>-i</option></arg>
+ </group>
+ <arg xmlns="http://docbook.org/ns/docbook">
+ <group choice="req">
+ <arg choice="plain"><option>--prebuilt-only</option></arg>
+ <arg choice="plain"><option>-b</option></arg>
+ </group>
+ </arg><arg xmlns="http://docbook.org/ns/docbook">
+ <group choice="req">
+ <arg choice="plain"><option>--attr</option></arg>
+ <arg choice="plain"><option>-A</option></arg>
+ </group>
+ </arg><arg xmlns="http://docbook.org/ns/docbook"><option>--from-expression</option></arg><arg xmlns="http://docbook.org/ns/docbook"><option>-E</option></arg><arg xmlns="http://docbook.org/ns/docbook"><option>--from-profile</option> <replaceable>path</replaceable></arg>
+ <group choice="opt">
+ <arg choice="plain"><option>--preserve-installed</option></arg>
+ <arg choice="plain"><option>-P</option></arg>
+ </group>
+ <group choice="opt">
+ <arg choice="plain"><option>--remove-all</option></arg>
+ <arg choice="plain"><option>-r</option></arg>
+ </group>
+ <arg choice="plain" rep="repeat"><replaceable>args</replaceable></arg>
+</cmdsynopsis>
+
+</refsection>
+
+
+<refsection><title>Description</title>
+
+<para>The install operation creates a new user environment, based on
+the current generation of the active profile, to which a set of store
+paths described by <replaceable>args</replaceable> is added. The
+arguments <replaceable>args</replaceable> map to store paths in a
+number of possible ways:
+
+<itemizedlist>
+
+ <listitem><para>By default, <replaceable>args</replaceable> is a set
+ of derivation names denoting derivations in the active Nix
+ expression. These are realised, and the resulting output paths are
+ installed. Currently installed derivations with a name equal to the
+ name of a derivation being added are removed unless the option
+ <option>--preserve-installed</option> is
+ specified.</para>
+
+ <para>If there are multiple derivations matching a name in
+ <replaceable>args</replaceable> that have the same name (e.g.,
+ <literal>gcc-3.3.6</literal> and <literal>gcc-4.1.1</literal>), then
+ the derivation with the highest <emphasis>priority</emphasis> is
+ used. A derivation can define a priority by declaring the
+ <varname>meta.priority</varname> attribute. This attribute should
+ be a number, with a higher value denoting a lower priority. The
+ default priority is <literal>0</literal>.</para>
+
+ <para>If there are multiple matching derivations with the same
+ priority, then the derivation with the highest version will be
+ installed.</para>
+
+ <para>You can force the installation of multiple derivations with
+ the same name by being specific about the versions. For instance,
+ <literal>nix-env -i gcc-3.3.6 gcc-4.1.1</literal> will install both
+ version of GCC (and will probably cause a user environment
+ conflict!).</para></listitem>
+
+ <listitem><para>If <link linkend="opt-attr"><option>--attr</option></link>
+ (<option>-A</option>) is specified, the arguments are
+ <emphasis>attribute paths</emphasis> that select attributes from the
+ top-level Nix expression. This is faster than using derivation
+ names and unambiguous. To find out the attribute paths of available
+ packages, use <literal>nix-env -qaP</literal>.</para></listitem>
+
+ <listitem><para>If <option>--from-profile</option>
+ <replaceable>path</replaceable> is given,
+ <replaceable>args</replaceable> is a set of names denoting installed
+ store paths in the profile <replaceable>path</replaceable>. This is
+ an easy way to copy user environment elements from one profile to
+ another.</para></listitem>
+
+ <listitem><para>If <option>--from-expression</option> is given,
+ <replaceable>args</replaceable> are Nix <link linkend="ss-functions">functions</link> that are called with the
+ active Nix expression as their single argument. The derivations
+ returned by those function calls are installed. This allows
+ derivations to be specified in an unambiguous way, which is necessary
+ if there are multiple derivations with the same
+ name.</para></listitem>
+
+ <listitem><para>If <replaceable>args</replaceable> are store
+ derivations, then these are <link linkend="rsec-nix-store-realise">realised</link>, and the resulting
+ output paths are installed.</para></listitem>
+
+ <listitem><para>If <replaceable>args</replaceable> are store paths
+ that are not store derivations, then these are <link linkend="rsec-nix-store-realise">realised</link> and
+ installed.</para></listitem>
+
+ <listitem><para>By default all outputs are installed for each derivation.
+ That can be reduced by setting <literal>meta.outputsToInstall</literal>.
+ </para></listitem> <!-- TODO: link nixpkgs docs on the ability to override those. -->
+
+</itemizedlist>
+
+</para>
+
+</refsection>
+
+
+<refsection><title>Flags</title>
+
+<variablelist>
+
+ <varlistentry><term><option>--prebuilt-only</option> / <option>-b</option></term>
+
+ <listitem><para>Use only derivations for which a substitute is
+ registered, i.e., there is a pre-built binary available that can
+ be downloaded in lieu of building the derivation. Thus, no
+ packages will be built from source.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--preserve-installed</option></term>
+ <term><option>-P</option></term>
+
+ <listitem><para>Do not remove derivations with a name matching one
+ of the derivations being installed. Usually, trying to have two
+ versions of the same package installed in the same generation of a
+ profile will lead to an error in building the generation, due to
+ file name clashes between the two versions. However, this is not
+ the case for all packages.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--remove-all</option></term>
+ <term><option>-r</option></term>
+
+ <listitem><para>Remove all previously installed packages first.
+ This is equivalent to running <literal>nix-env -e '.*'</literal>
+ first, except that everything happens in a single
+ transaction.</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+</refsection>
+
+
+<refsection xml:id="refsec-nix-env-install-examples"><title>Examples</title>
+
+<para>To install a specific version of <command>gcc</command> from the
+active Nix expression:
+
+<screen>
+$ nix-env --install gcc-3.3.2
+installing `gcc-3.3.2'
+uninstalling `gcc-3.1'</screen>
+
+Note the previously installed version is removed, since
+<option>--preserve-installed</option> was not specified.</para>
+
+<para>To install an arbitrary version:
+
+<screen>
+$ nix-env --install gcc
+installing `gcc-3.3.2'</screen>
+
+</para>
+
+<para>To install using a specific attribute:
+
+<screen>
+$ nix-env -i -A gcc40mips
+$ nix-env -i -A xorg.xorgserver</screen>
+
+</para>
+
+<para>To install all derivations in the Nix expression <filename>foo.nix</filename>:
+
+<screen>
+$ nix-env -f ~/foo.nix -i '.*'</screen>
+
+</para>
+
+<para>To copy the store path with symbolic name <literal>gcc</literal>
+from another profile:
+
+<screen>
+$ nix-env -i --from-profile /nix/var/nix/profiles/foo gcc</screen>
+
+</para>
+
+<para>To install a specific store derivation (typically created by
+<command>nix-instantiate</command>):
+
+<screen>
+$ nix-env -i /nix/store/fibjb1bfbpm5mrsxc4mh2d8n37sxh91i-gcc-3.4.3.drv</screen>
+
+</para>
+
+<para>To install a specific output path:
+
+<screen>
+$ nix-env -i /nix/store/y3cgx0xj1p4iv9x0pnnmdhr8iyg741vk-gcc-3.4.3</screen>
+
+</para>
+
+<para>To install from a Nix expression specified on the command-line:
+
+<screen>
+$ nix-env -f ./foo.nix -i -E \
+ 'f: (f {system = "i686-linux";}).subversionWithJava'</screen>
+
+I.e., this evaluates to <literal>(f: (f {system =
+"i686-linux";}).subversionWithJava) (import ./foo.nix)</literal>, thus
+selecting the <literal>subversionWithJava</literal> attribute from the
+set returned by calling the function defined in
+<filename>./foo.nix</filename>.</para>
+
+<para>A dry-run tells you which paths will be downloaded or built from
+source:
+
+<screen>
+$ nix-env -f '<nixpkgs>' -iA hello --dry-run
+(dry run; not doing anything)
+installing ‘hello-2.10’
+this path will be fetched (0.04 MiB download, 0.19 MiB unpacked):
+ /nix/store/wkhdf9jinag5750mqlax6z2zbwhqb76n-hello-2.10
+ <replaceable>...</replaceable></screen>
+
+</para>
+
+<para>To install Firefox from the latest revision in the Nixpkgs/NixOS
+14.12 channel:
+
+<screen>
+$ nix-env -f https://github.com/NixOS/nixpkgs/archive/nixos-14.12.tar.gz -iA firefox
+</screen>
+
+</para>
+
+</refsection>
+
+</refsection>
+
+
+
+<!--######################################################################-->
+
+<refsection xml:id="rsec-nix-env-upgrade"><title>Operation <option>--upgrade</option></title>
+
+<refsection><title>Synopsis</title>
+
+<cmdsynopsis>
+ <command>nix-env</command>
+ <group choice="req">
+ <arg choice="plain"><option>--upgrade</option></arg>
+ <arg choice="plain"><option>-u</option></arg>
+ </group>
+ <arg xmlns="http://docbook.org/ns/docbook">
+ <group choice="req">
+ <arg choice="plain"><option>--prebuilt-only</option></arg>
+ <arg choice="plain"><option>-b</option></arg>
+ </group>
+ </arg><arg xmlns="http://docbook.org/ns/docbook">
+ <group choice="req">
+ <arg choice="plain"><option>--attr</option></arg>
+ <arg choice="plain"><option>-A</option></arg>
+ </group>
+ </arg><arg xmlns="http://docbook.org/ns/docbook"><option>--from-expression</option></arg><arg xmlns="http://docbook.org/ns/docbook"><option>-E</option></arg><arg xmlns="http://docbook.org/ns/docbook"><option>--from-profile</option> <replaceable>path</replaceable></arg>
+ <group choice="opt">
+ <arg choice="plain"><option>--lt</option></arg>
+ <arg choice="plain"><option>--leq</option></arg>
+ <arg choice="plain"><option>--eq</option></arg>
+ <arg choice="plain"><option>--always</option></arg>
+ </group>
+ <arg choice="plain" rep="repeat"><replaceable>args</replaceable></arg>
+</cmdsynopsis>
+
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>The upgrade operation creates a new user environment, based on
+the current generation of the active profile, in which all store paths
+are replaced for which there are newer versions in the set of paths
+described by <replaceable>args</replaceable>. Paths for which there
+are no newer versions are left untouched; this is not an error. It is
+also not an error if an element of <replaceable>args</replaceable>
+matches no installed derivations.</para>
+
+<para>For a description of how <replaceable>args</replaceable> is
+mapped to a set of store paths, see <link linkend="rsec-nix-env-install"><option>--install</option></link>. If
+<replaceable>args</replaceable> describes multiple store paths with
+the same symbolic name, only the one with the highest version is
+installed.</para>
+
+</refsection>
+
+<refsection><title>Flags</title>
+
+<variablelist>
+
+ <varlistentry><term><option>--lt</option></term>
+
+ <listitem><para>Only upgrade a derivation to newer versions. This
+ is the default.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--leq</option></term>
+
+ <listitem><para>In addition to upgrading to newer versions, also
+ “upgrade” to derivations that have the same version. Version are
+ not a unique identification of a derivation, so there may be many
+ derivations that have the same version. This flag may be useful
+ to force “synchronisation” between the installed and available
+ derivations.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--eq</option></term>
+
+ <listitem><para><emphasis>Only</emphasis> “upgrade” to derivations
+ that have the same version. This may not seem very useful, but it
+ actually is, e.g., when there is a new release of Nixpkgs and you
+ want to replace installed applications with the same versions
+ built against newer dependencies (to reduce the number of
+ dependencies floating around on your system).</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--always</option></term>
+
+ <listitem><para>In addition to upgrading to newer versions, also
+ “upgrade” to derivations that have the same or a lower version.
+ I.e., derivations may actually be downgraded depending on what is
+ available in the active Nix expression.</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+<para>For the other flags, see <option linkend="rsec-nix-env-install">--install</option>.</para>
+
+</refsection>
+
+<refsection><title>Examples</title>
+
+<screen>
+$ nix-env --upgrade gcc
+upgrading `gcc-3.3.1' to `gcc-3.4'
+
+$ nix-env -u gcc-3.3.2 --always <lineannotation>(switch to a specific version)</lineannotation>
+upgrading `gcc-3.4' to `gcc-3.3.2'
+
+$ nix-env --upgrade pan
+<lineannotation>(no upgrades available, so nothing happens)</lineannotation>
+
+$ nix-env -u <lineannotation>(try to upgrade everything)</lineannotation>
+upgrading `hello-2.1.2' to `hello-2.1.3'
+upgrading `mozilla-1.2' to `mozilla-1.4'</screen>
+
+</refsection>
+
+<refsection xml:id="ssec-version-comparisons"><title>Versions</title>
+
+<para>The upgrade operation determines whether a derivation
+<varname>y</varname> is an upgrade of a derivation
+<varname>x</varname> by looking at their respective
+<literal>name</literal> attributes. The names (e.g.,
+<literal>gcc-3.3.1</literal> are split into two parts: the package
+name (<literal>gcc</literal>), and the version
+(<literal>3.3.1</literal>). The version part starts after the first
+dash not followed by a letter. <varname>x</varname> is considered an
+upgrade of <varname>y</varname> if their package names match, and the
+version of <varname>y</varname> is higher that that of
+<varname>x</varname>.</para>
+
+<para>The versions are compared by splitting them into contiguous
+components of numbers and letters. E.g., <literal>3.3.1pre5</literal>
+is split into <literal>[3, 3, 1, "pre", 5]</literal>. These lists are
+then compared lexicographically (from left to right). Corresponding
+components <varname>a</varname> and <varname>b</varname> are compared
+as follows. If they are both numbers, integer comparison is used. If
+<varname>a</varname> is an empty string and <varname>b</varname> is a
+number, <varname>a</varname> is considered less than
+<varname>b</varname>. The special string component
+<literal>pre</literal> (for <emphasis>pre-release</emphasis>) is
+considered to be less than other components. String components are
+considered less than number components. Otherwise, they are compared
+lexicographically (i.e., using case-sensitive string comparison).</para>
+
+<para>This is illustrated by the following examples:
+
+<screen>
+1.0 < 2.3
+2.1 < 2.3
+2.3 = 2.3
+2.5 > 2.3
+3.1 > 2.3
+2.3.1 > 2.3
+2.3.1 > 2.3a
+2.3pre1 < 2.3
+2.3pre3 < 2.3pre12
+2.3a < 2.3c
+2.3pre1 < 2.3c
+2.3pre1 < 2.3q</screen>
+
+</para>
+
+</refsection>
+
+</refsection>
+
+
+
+<!--######################################################################-->
+
+<refsection><title>Operation <option>--uninstall</option></title>
+
+<refsection><title>Synopsis</title>
+
+<cmdsynopsis>
+ <command>nix-env</command>
+ <group choice="req">
+ <arg choice="plain"><option>--uninstall</option></arg>
+ <arg choice="plain"><option>-e</option></arg>
+ </group>
+ <arg choice="plain" rep="repeat"><replaceable>drvnames</replaceable></arg>
+</cmdsynopsis>
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>The uninstall operation creates a new user environment, based on
+the current generation of the active profile, from which the store
+paths designated by the symbolic names
+<replaceable>names</replaceable> are removed.</para>
+
+</refsection>
+
+<refsection><title>Examples</title>
+
+<screen>
+$ nix-env --uninstall gcc
+$ nix-env -e '.*' <lineannotation>(remove everything)</lineannotation></screen>
+
+</refsection>
+
+</refsection>
+
+
+
+<!--######################################################################-->
+
+<refsection xml:id="rsec-nix-env-set"><title>Operation <option>--set</option></title>
+
+<refsection><title>Synopsis</title>
+
+<cmdsynopsis>
+ <command>nix-env</command>
+ <arg choice="plain"><option>--set</option></arg>
+ <arg choice="plain"><replaceable>drvname</replaceable></arg>
+</cmdsynopsis>
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>The <option>--set</option> operation modifies the current generation of a
+profile so that it contains exactly the specified derivation, and nothing else.
+</para>
+
+</refsection>
+
+<refsection><title>Examples</title>
+
+<para>
+The following updates a profile such that its current generation will contain
+just Firefox:
+
+<screen>
+$ nix-env -p /nix/var/nix/profiles/browser --set firefox</screen>
+
+</para>
+
+</refsection>
+
+</refsection>
+
+
+
+<!--######################################################################-->
+
+<refsection xml:id="rsec-nix-env-set-flag"><title>Operation <option>--set-flag</option></title>
+
+<refsection><title>Synopsis</title>
+
+<cmdsynopsis>
+ <command>nix-env</command>
+ <arg choice="plain"><option>--set-flag</option></arg>
+ <arg choice="plain"><replaceable>name</replaceable></arg>
+ <arg choice="plain"><replaceable>value</replaceable></arg>
+ <arg choice="plain" rep="repeat"><replaceable>drvnames</replaceable></arg>
+</cmdsynopsis>
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>The <option>--set-flag</option> operation allows meta attributes
+of installed packages to be modified. There are several attributes
+that can be usefully modified, because they affect the behaviour of
+<command>nix-env</command> or the user environment build
+script:
+
+<itemizedlist>
+
+ <listitem><para><varname>priority</varname> can be changed to
+ resolve filename clashes. The user environment build script uses
+ the <varname>meta.priority</varname> attribute of derivations to
+ resolve filename collisions between packages. Lower priority values
+ denote a higher priority. For instance, the GCC wrapper package and
+ the Binutils package in Nixpkgs both have a file
+ <filename>bin/ld</filename>, so previously if you tried to install
+ both you would get a collision. Now, on the other hand, the GCC
+ wrapper declares a higher priority than Binutils, so the former’s
+ <filename>bin/ld</filename> is symlinked in the user
+ environment.</para></listitem>
+
+ <listitem><para><varname>keep</varname> can be set to
+ <literal>true</literal> to prevent the package from being upgraded
+ or replaced. This is useful if you want to hang on to an older
+ version of a package.</para></listitem>
+
+ <listitem><para><varname>active</varname> can be set to
+ <literal>false</literal> to “disable” the package. That is, no
+ symlinks will be generated to the files of the package, but it
+ remains part of the profile (so it won’t be garbage-collected). It
+ can be set back to <literal>true</literal> to re-enable the
+ package.</para></listitem>
+
+</itemizedlist>
+
+</para>
+
+</refsection>
+
+<refsection><title>Examples</title>
+
+<para>To prevent the currently installed Firefox from being upgraded:
+
+<screen>
+$ nix-env --set-flag keep true firefox</screen>
+
+After this, <command>nix-env -u</command> will ignore Firefox.</para>
+
+<para>To disable the currently installed Firefox, then install a new
+Firefox while the old remains part of the profile:
+
+<screen>
+$ nix-env -q
+firefox-2.0.0.9 <lineannotation>(the current one)</lineannotation>
+
+$ nix-env --preserve-installed -i firefox-2.0.0.11
+installing `firefox-2.0.0.11'
+building path(s) `/nix/store/myy0y59q3ig70dgq37jqwg1j0rsapzsl-user-environment'
+collision between `/nix/store/<replaceable>...</replaceable>-firefox-2.0.0.11/bin/firefox'
+ and `/nix/store/<replaceable>...</replaceable>-firefox-2.0.0.9/bin/firefox'.
+<lineannotation>(i.e., can’t have two active at the same time)</lineannotation>
+
+$ nix-env --set-flag active false firefox
+setting flag on `firefox-2.0.0.9'
+
+$ nix-env --preserve-installed -i firefox-2.0.0.11
+installing `firefox-2.0.0.11'
+
+$ nix-env -q
+firefox-2.0.0.11 <lineannotation>(the enabled one)</lineannotation>
+firefox-2.0.0.9 <lineannotation>(the disabled one)</lineannotation></screen>
+
+</para>
+
+<para>To make files from <literal>binutils</literal> take precedence
+over files from <literal>gcc</literal>:
+
+<screen>
+$ nix-env --set-flag priority 5 binutils
+$ nix-env --set-flag priority 10 gcc</screen>
+
+</para>
+
+</refsection>
+
+</refsection>
+
+
+
+<!--######################################################################-->
+
+<refsection><title>Operation <option>--query</option></title>
+
+<refsection><title>Synopsis</title>
+
+<cmdsynopsis>
+ <command>nix-env</command>
+ <group choice="req">
+ <arg choice="plain"><option>--query</option></arg>
+ <arg choice="plain"><option>-q</option></arg>
+ </group>
+ <group choice="opt">
+ <arg choice="plain"><option>--installed</option></arg>
+ <arg choice="plain"><option>--available</option></arg>
+ <arg choice="plain"><option>-a</option></arg>
+ </group>
+
+ <sbr/>
+
+ <arg>
+ <group choice="req">
+ <arg choice="plain"><option>--status</option></arg>
+ <arg choice="plain"><option>-s</option></arg>
+ </group>
+ </arg>
+ <arg>
+ <group choice="req">
+ <arg choice="plain"><option>--attr-path</option></arg>
+ <arg choice="plain"><option>-P</option></arg>
+ </group>
+ </arg>
+ <arg><option>--no-name</option></arg>
+ <arg>
+ <group choice="req">
+ <arg choice="plain"><option>--compare-versions</option></arg>
+ <arg choice="plain"><option>-c</option></arg>
+ </group>
+ </arg>
+ <arg><option>--system</option></arg>
+ <arg><option>--drv-path</option></arg>
+ <arg><option>--out-path</option></arg>
+ <arg><option>--description</option></arg>
+ <arg><option>--meta</option></arg>
+
+ <sbr/>
+
+ <arg><option>--xml</option></arg>
+ <arg><option>--json</option></arg>
+ <arg>
+ <group choice="req">
+ <arg choice="plain"><option>--prebuilt-only</option></arg>
+ <arg choice="plain"><option>-b</option></arg>
+ </group>
+ </arg>
+
+ <arg>
+ <group choice="req">
+ <arg choice="plain"><option>--attr</option></arg>
+ <arg choice="plain"><option>-A</option></arg>
+ </group>
+ <replaceable>attribute-path</replaceable>
+ </arg>
+
+ <sbr/>
+
+ <arg choice="plain" rep="repeat"><replaceable>names</replaceable></arg>
+</cmdsynopsis>
+
+</refsection>
+
+
+<refsection><title>Description</title>
+
+<para>The query operation displays information about either the store
+paths that are installed in the current generation of the active
+profile (<option>--installed</option>), or the derivations that are
+available for installation in the active Nix expression
+(<option>--available</option>). It only prints information about
+derivations whose symbolic name matches one of
+<replaceable>names</replaceable>.</para>
+
+<para>The derivations are sorted by their <literal>name</literal>
+attributes.</para>
+
+</refsection>
+
+
+<refsection><title>Source selection</title>
+
+<para>The following flags specify the set of things on which the query
+operates.</para>
+
+<variablelist>
+
+ <varlistentry><term><option>--installed</option></term>
+
+ <listitem><para>The query operates on the store paths that are
+ installed in the current generation of the active profile. This
+ is the default.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--available</option></term>
+ <term><option>-a</option></term>
+
+ <listitem><para>The query operates on the derivations that are
+ available in the active Nix expression.</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+</refsection>
+
+
+<refsection><title>Queries</title>
+
+<para>The following flags specify what information to display about
+the selected derivations. Multiple flags may be specified, in which
+case the information is shown in the order given here. Note that the
+name of the derivation is shown unless <option>--no-name</option> is
+specified.</para>
+
+<!-- TODO: fix the terminology here; i.e., derivations, store paths,
+user environment elements, etc. -->
+
+<variablelist>
+
+ <varlistentry><term><option>--xml</option></term>
+
+ <listitem><para>Print the result in an XML representation suitable
+ for automatic processing by other tools. The root element is
+ called <literal>items</literal>, which contains a
+ <literal>item</literal> element for each available or installed
+ derivation. The fields discussed below are all stored in
+ attributes of the <literal>item</literal>
+ elements.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--json</option></term>
+
+ <listitem><para>Print the result in a JSON representation suitable
+ for automatic processing by other tools.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--prebuilt-only</option> / <option>-b</option></term>
+
+ <listitem><para>Show only derivations for which a substitute is
+ registered, i.e., there is a pre-built binary available that can
+ be downloaded in lieu of building the derivation. Thus, this
+ shows all packages that probably can be installed
+ quickly.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--status</option></term>
+ <term><option>-s</option></term>
+
+ <listitem><para>Print the <emphasis>status</emphasis> of the
+ derivation. The status consists of three characters. The first
+ is <literal>I</literal> or <literal>-</literal>, indicating
+ whether the derivation is currently installed in the current
+ generation of the active profile. This is by definition the case
+ for <option>--installed</option>, but not for
+ <option>--available</option>. The second is <literal>P</literal>
+ or <literal>-</literal>, indicating whether the derivation is
+ present on the system. This indicates whether installation of an
+ available derivation will require the derivation to be built. The
+ third is <literal>S</literal> or <literal>-</literal>, indicating
+ whether a substitute is available for the
+ derivation.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--attr-path</option></term>
+ <term><option>-P</option></term>
+
+ <listitem><para>Print the <emphasis>attribute path</emphasis> of
+ the derivation, which can be used to unambiguously select it using
+ the <link linkend="opt-attr"><option>--attr</option> option</link>
+ available in commands that install derivations like
+ <literal>nix-env --install</literal>. This option only works
+ together with <option>--available</option></para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--no-name</option></term>
+
+ <listitem><para>Suppress printing of the <literal>name</literal>
+ attribute of each derivation.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--compare-versions</option> /
+ <option>-c</option></term>
+
+ <listitem><para>Compare installed versions to available versions,
+ or vice versa (if <option>--available</option> is given). This is
+ useful for quickly seeing whether upgrades for installed
+ packages are available in a Nix expression. A column is added
+ with the following meaning:
+
+ <variablelist>
+
+ <varlistentry><term><literal><</literal> <replaceable>version</replaceable></term>
+
+ <listitem><para>A newer version of the package is available
+ or installed.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><literal>=</literal> <replaceable>version</replaceable></term>
+
+ <listitem><para>At most the same version of the package is
+ available or installed.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><literal>></literal> <replaceable>version</replaceable></term>
+
+ <listitem><para>Only older versions of the package are
+ available or installed.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><literal>- ?</literal></term>
+
+ <listitem><para>No version of the package is available or
+ installed.</para></listitem>
+
+ </varlistentry>
+
+ </variablelist>
+
+ </para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--system</option></term>
+
+ <listitem><para>Print the <literal>system</literal> attribute of
+ the derivation.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--drv-path</option></term>
+
+ <listitem><para>Print the path of the store
+ derivation.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--out-path</option></term>
+
+ <listitem><para>Print the output path of the
+ derivation.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--description</option></term>
+
+ <listitem><para>Print a short (one-line) description of the
+ derivation, if available. The description is taken from the
+ <literal>meta.description</literal> attribute of the
+ derivation.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--meta</option></term>
+
+ <listitem><para>Print all of the meta-attributes of the
+ derivation. This option is only available with
+ <option>--xml</option> or <option>--json</option>.</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+</refsection>
+
+
+<refsection><title>Examples</title>
+
+<para>To show installed packages:
+
+<screen>
+$ nix-env -q
+bison-1.875c
+docbook-xml-4.2
+firefox-1.0.4
+MPlayer-1.0pre7
+ORBit2-2.8.3
+<replaceable>…</replaceable>
+</screen>
+
+</para>
+
+<para>To show available packages:
+
+<screen>
+$ nix-env -qa
+firefox-1.0.7
+GConf-2.4.0.1
+MPlayer-1.0pre7
+ORBit2-2.8.3
+<replaceable>…</replaceable>
+</screen>
+
+</para>
+
+<para>To show the status of available packages:
+
+<screen>
+$ nix-env -qas
+-P- firefox-1.0.7 <lineannotation>(not installed but present)</lineannotation>
+--S GConf-2.4.0.1 <lineannotation>(not present, but there is a substitute for fast installation)</lineannotation>
+--S MPlayer-1.0pre3 <lineannotation>(i.e., this is not the installed MPlayer, even though the version is the same!)</lineannotation>
+IP- ORBit2-2.8.3 <lineannotation>(installed and by definition present)</lineannotation>
+<replaceable>…</replaceable>
+</screen>
+
+</para>
+
+<para>To show available packages in the Nix expression <filename>foo.nix</filename>:
+
+<screen>
+$ nix-env -f ./foo.nix -qa
+foo-1.2.3
+</screen>
+
+</para>
+
+<para>To compare installed versions to what’s available:
+
+<screen>
+$ nix-env -qc
+<replaceable>...</replaceable>
+acrobat-reader-7.0 - ? <lineannotation>(package is not available at all)</lineannotation>
+autoconf-2.59 = 2.59 <lineannotation>(same version)</lineannotation>
+firefox-1.0.4 < 1.0.7 <lineannotation>(a more recent version is available)</lineannotation>
+<replaceable>...</replaceable>
+</screen>
+
+</para>
+
+<para>To show all packages with “<literal>zip</literal>” in the name:
+
+<screen>
+$ nix-env -qa '.*zip.*'
+bzip2-1.0.6
+gzip-1.6
+zip-3.0
+<replaceable>…</replaceable>
+</screen>
+
+</para>
+
+<para>To show all packages with “<literal>firefox</literal>” or
+“<literal>chromium</literal>” in the name:
+
+<screen>
+$ nix-env -qa '.*(firefox|chromium).*'
+chromium-37.0.2062.94
+chromium-beta-38.0.2125.24
+firefox-32.0.3
+firefox-with-plugins-13.0.1
+<replaceable>…</replaceable>
+</screen>
+
+</para>
+
+<para>To show all packages in the latest revision of the Nixpkgs
+repository:
+
+<screen>
+$ nix-env -f https://github.com/NixOS/nixpkgs/archive/master.tar.gz -qa
+</screen>
+
+</para>
+
+</refsection>
+
+</refsection>
+
+
+
+<!--######################################################################-->
+
+<refsection><title>Operation <option>--switch-profile</option></title>
+
+<refsection><title>Synopsis</title>
+
+<cmdsynopsis>
+ <command>nix-env</command>
+ <group choice="req">
+ <arg choice="plain"><option>--switch-profile</option></arg>
+ <arg choice="plain"><option>-S</option></arg>
+ </group>
+ <arg choice="req"><replaceable>path</replaceable></arg>
+</cmdsynopsis>
+
+</refsection>
+
+
+<refsection><title>Description</title>
+
+<para>This operation makes <replaceable>path</replaceable> the current
+profile for the user. That is, the symlink
+<filename>~/.nix-profile</filename> is made to point to
+<replaceable>path</replaceable>.</para>
+
+</refsection>
+
+<refsection><title>Examples</title>
+
+<screen>
+$ nix-env -S ~/my-profile</screen>
+
+</refsection>
+
+</refsection>
+
+
+
+<!--######################################################################-->
+
+<refsection><title>Operation <option>--list-generations</option></title>
+
+<refsection><title>Synopsis</title>
+
+<cmdsynopsis>
+ <command>nix-env</command>
+ <arg choice="plain"><option>--list-generations</option></arg>
+</cmdsynopsis>
+
+</refsection>
+
+
+<refsection><title>Description</title>
+
+<para>This operation print a list of all the currently existing
+generations for the active profile. These may be switched to using
+the <option>--switch-generation</option> operation. It also prints
+the creation date of the generation, and indicates the current
+generation.</para>
+
+</refsection>
+
+
+<refsection><title>Examples</title>
+
+<screen>
+$ nix-env --list-generations
+ 95 2004-02-06 11:48:24
+ 96 2004-02-06 11:49:01
+ 97 2004-02-06 16:22:45
+ 98 2004-02-06 16:24:33 (current)</screen>
+
+</refsection>
+
+</refsection>
+
+
+
+<!--######################################################################-->
+
+<refsection><title>Operation <option>--delete-generations</option></title>
+
+<refsection><title>Synopsis</title>
+
+<cmdsynopsis>
+ <command>nix-env</command>
+ <arg choice="plain"><option>--delete-generations</option></arg>
+ <arg choice="plain" rep="repeat"><replaceable>generations</replaceable></arg>
+</cmdsynopsis>
+
+</refsection>
+
+
+<refsection><title>Description</title>
+
+<para>This operation deletes the specified generations of the current
+profile. The generations can be a list of generation numbers, the
+special value <literal>old</literal> to delete all non-current
+generations, a value such as <literal>30d</literal> to delete all
+generations older than the specified number of days (except for the
+generation that was active at that point in time), or a value such as
+<literal>+5</literal> to keep the last <literal>5</literal> generations
+ignoring any newer than current, e.g., if <literal>30</literal> is the current
+generation <literal>+5</literal> will delete generation <literal>25</literal>
+and all older generations.
+Periodically deleting old generations is important to make garbage collection
+effective.</para>
+
+</refsection>
+
+<refsection><title>Examples</title>
+
+<screen>
+$ nix-env --delete-generations 3 4 8
+
+$ nix-env --delete-generations +5
+
+$ nix-env --delete-generations 30d
+
+$ nix-env -p other_profile --delete-generations old</screen>
+
+</refsection>
+
+</refsection>
+
+
+
+<!--######################################################################-->
+
+<refsection><title>Operation <option>--switch-generation</option></title>
+
+<refsection><title>Synopsis</title>
+
+<cmdsynopsis>
+ <command>nix-env</command>
+ <group choice="req">
+ <arg choice="plain"><option>--switch-generation</option></arg>
+ <arg choice="plain"><option>-G</option></arg>
+ </group>
+ <arg choice="req"><replaceable>generation</replaceable></arg>
+</cmdsynopsis>
+
+</refsection>
+
+
+<refsection><title>Description</title>
+
+<para>This operation makes generation number
+<replaceable>generation</replaceable> the current generation of the
+active profile. That is, if the
+<filename><replaceable>profile</replaceable></filename> is the path to
+the active profile, then the symlink
+<filename><replaceable>profile</replaceable></filename> is made to
+point to
+<filename><replaceable>profile</replaceable>-<replaceable>generation</replaceable>-link</filename>,
+which is in turn a symlink to the actual user environment in the Nix
+store.</para>
+
+<para>Switching will fail if the specified generation does not exist.</para>
+
+</refsection>
+
+
+<refsection><title>Examples</title>
+
+<screen>
+$ nix-env -G 42
+switching from generation 50 to 42</screen>
+
+</refsection>
+
+</refsection>
+
+
+
+<!--######################################################################-->
+
+<refsection><title>Operation <option>--rollback</option></title>
+
+<refsection><title>Synopsis</title>
+
+<cmdsynopsis>
+ <command>nix-env</command>
+ <arg choice="plain"><option>--rollback</option></arg>
+</cmdsynopsis>
+
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>This operation switches to the “previous” generation of the
+active profile, that is, the highest numbered generation lower than
+the current generation, if it exists. It is just a convenience
+wrapper around <option>--list-generations</option> and
+<option>--switch-generation</option>.</para>
+
+</refsection>
+
+
+<refsection><title>Examples</title>
+
+<screen>
+$ nix-env --rollback
+switching from generation 92 to 91
+
+$ nix-env --rollback
+error: no generation older than the current (91) exists</screen>
+
+</refsection>
+
+</refsection>
+
+
+<refsection condition="manpage"><title>Environment variables</title>
+
+<variablelist>
+
+ <varlistentry><term><envar>NIX_PROFILE</envar></term>
+
+ <listitem><para>Location of the Nix profile. Defaults to the
+ target of the symlink <filename>~/.nix-profile</filename>, if it
+ exists, or <filename>/nix/var/nix/profiles/default</filename>
+ otherwise.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>IN_NIX_SHELL</envar></term>
+
+ <listitem><para>Indicator that tells if the current environment was set up by
+ <command>nix-shell</command>. Since Nix 2.0 the values are
+ <literal>"pure"</literal> and <literal>"impure"</literal></para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="env-NIX_PATH"><term><envar>NIX_PATH</envar></term>
+
+ <listitem>
+
+ <para>A colon-separated list of directories used to look up Nix
+ expressions enclosed in angle brackets (i.e.,
+ <literal><<replaceable>path</replaceable>></literal>). For
+ instance, the value
+
+ <screen>
+/home/eelco/Dev:/etc/nixos</screen>
+
+ will cause Nix to look for paths relative to
+ <filename>/home/eelco/Dev</filename> and
+ <filename>/etc/nixos</filename>, in this order. It is also
+ possible to match paths against a prefix. For example, the value
+
+ <screen>
+nixpkgs=/home/eelco/Dev/nixpkgs-branch:/etc/nixos</screen>
+
+ will cause Nix to search for
+ <literal><nixpkgs/<replaceable>path</replaceable>></literal> in
+ <filename>/home/eelco/Dev/nixpkgs-branch/<replaceable>path</replaceable></filename>
+ and
+ <filename>/etc/nixos/nixpkgs/<replaceable>path</replaceable></filename>.</para>
+
+ <para>If a path in the Nix search path starts with
+ <literal>http://</literal> or <literal>https://</literal>, it is
+ interpreted as the URL of a tarball that will be downloaded and
+ unpacked to a temporary location. The tarball must consist of a
+ single top-level directory. For example, setting
+ <envar>NIX_PATH</envar> to
+
+ <screen>
+nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-15.09.tar.gz</screen>
+
+ tells Nix to download the latest revision in the Nixpkgs/NixOS
+ 15.09 channel.</para>
+
+ <para>A following shorthand can be used to refer to the official channels:
+
+ <screen>nixpkgs=channel:nixos-15.09</screen>
+ </para>
+
+ <para>The search path can be extended using the <option linkend="opt-I">-I</option> option, which takes precedence over
+ <envar>NIX_PATH</envar>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_IGNORE_SYMLINK_STORE</envar></term>
+
+ <listitem>
+
+ <para>Normally, the Nix store directory (typically
+ <filename>/nix/store</filename>) is not allowed to contain any
+ symlink components. This is to prevent “impure” builds. Builders
+ sometimes “canonicalise” paths by resolving all symlink components.
+ Thus, builds on different machines (with
+ <filename>/nix/store</filename> resolving to different locations)
+ could yield different results. This is generally not a problem,
+ except when builds are deployed to machines where
+ <filename>/nix/store</filename> resolves differently. If you are
+ sure that you’re not going to do that, you can set
+ <envar>NIX_IGNORE_SYMLINK_STORE</envar> to <envar>1</envar>.</para>
+
+ <para>Note that if you’re symlinking the Nix store so that you can
+ put it on another file system than the root file system, on Linux
+ you’re better off using <literal>bind</literal> mount points, e.g.,
+
+ <screen>
+$ mkdir /nix
+$ mount -o bind /mnt/otherdisk/nix /nix</screen>
+
+ Consult the <citerefentry><refentrytitle>mount</refentrytitle>
+ <manvolnum>8</manvolnum></citerefentry> manual page for details.</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_STORE_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix store (default
+ <filename><replaceable>prefix</replaceable>/store</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_DATA_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix static data
+ directory (default
+ <filename><replaceable>prefix</replaceable>/share</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_LOG_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix log directory
+ (default <filename><replaceable>prefix</replaceable>/var/log/nix</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_STATE_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix state directory
+ (default <filename><replaceable>prefix</replaceable>/var/nix</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_CONF_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the system Nix configuration
+ directory (default
+ <filename><replaceable>prefix</replaceable>/etc/nix</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_USER_CONF_FILES</envar></term>
+
+ <listitem><para>Overrides the location of the user Nix configuration files
+ to load from (defaults to the XDG spec locations). The variable is treated
+ as a list separated by the <literal>:</literal> token.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>TMPDIR</envar></term>
+
+ <listitem><para>Use the specified directory to store temporary
+ files. In particular, this includes temporary build directories;
+ these can take up substantial amounts of disk space. The default is
+ <filename>/tmp</filename>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="envar-remote"><term><envar>NIX_REMOTE</envar></term>
+
+ <listitem><para>This variable should be set to
+ <literal>daemon</literal> if you want to use the Nix daemon to
+ execute Nix operations. This is necessary in <link linkend="ssec-multi-user">multi-user Nix installations</link>.
+ If the Nix daemon's Unix socket is at some non-standard path,
+ this variable should be set to <literal>unix://path/to/socket</literal>.
+ Otherwise, it should be left unset.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_SHOW_STATS</envar></term>
+
+ <listitem><para>If set to <literal>1</literal>, Nix will print some
+ evaluation statistics, such as the number of values
+ allocated.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_COUNT_CALLS</envar></term>
+
+ <listitem><para>If set to <literal>1</literal>, Nix will print how
+ often functions were called during Nix expression evaluation. This
+ is useful for profiling your Nix expressions.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>GC_INITIAL_HEAP_SIZE</envar></term>
+
+ <listitem><para>If Nix has been configured to use the Boehm garbage
+ collector, this variable sets the initial size of the heap in bytes.
+ It defaults to 384 MiB. Setting it to a low value reduces memory
+ consumption, but will increase runtime due to the overhead of
+ garbage collection.</para></listitem>
+
+</varlistentry>
+</variablelist>
+
+</refsection>
+
+
+</refentry>
+<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-nix-build">
+
+<refmeta>
+ <refentrytitle>nix-build</refentrytitle>
+ <manvolnum>1</manvolnum>
+ <refmiscinfo class="source">Nix</refmiscinfo>
+ <refmiscinfo class="version">3.0</refmiscinfo>
+</refmeta>
+
+<refnamediv>
+ <refname>nix-build</refname>
+ <refpurpose>build a Nix expression</refpurpose>
+</refnamediv>
+
+<refsynopsisdiv>
+ <cmdsynopsis>
+ <command>nix-build</command>
+ <arg xmlns="http://docbook.org/ns/docbook"><option>--help</option></arg><arg xmlns="http://docbook.org/ns/docbook"><option>--version</option></arg><arg xmlns="http://docbook.org/ns/docbook" rep="repeat">
+ <group choice="req">
+ <arg choice="plain"><option>--verbose</option></arg>
+ <arg choice="plain"><option>-v</option></arg>
+ </group>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <arg choice="plain"><option>--quiet</option></arg>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <option>--log-format</option>
+ <replaceable>format</replaceable>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <group choice="plain">
+ <arg choice="plain"><option>--no-build-output</option></arg>
+ <arg choice="plain"><option>-Q</option></arg>
+ </group>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <group choice="req">
+ <arg choice="plain"><option>--max-jobs</option></arg>
+ <arg choice="plain"><option>-j</option></arg>
+ </group>
+ <replaceable>number</replaceable>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <option>--cores</option>
+ <replaceable>number</replaceable>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <option>--max-silent-time</option>
+ <replaceable>number</replaceable>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <option>--timeout</option>
+ <replaceable>number</replaceable>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <group choice="plain">
+ <arg choice="plain"><option>--keep-going</option></arg>
+ <arg choice="plain"><option>-k</option></arg>
+ </group>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <group choice="plain">
+ <arg choice="plain"><option>--keep-failed</option></arg>
+ <arg choice="plain"><option>-K</option></arg>
+ </group>
+</arg><arg xmlns="http://docbook.org/ns/docbook"><option>--fallback</option></arg><arg xmlns="http://docbook.org/ns/docbook"><option>--readonly-mode</option></arg><arg xmlns="http://docbook.org/ns/docbook">
+ <option>-I</option>
+ <replaceable>path</replaceable>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <option>--option</option>
+ <replaceable>name</replaceable>
+ <replaceable>value</replaceable>
+</arg><sbr xmlns="http://docbook.org/ns/docbook"/>
+ <arg><option>--arg</option> <replaceable>name</replaceable> <replaceable>value</replaceable></arg>
+ <arg><option>--argstr</option> <replaceable>name</replaceable> <replaceable>value</replaceable></arg>
+ <arg>
+ <group choice="req">
+ <arg choice="plain"><option>--attr</option></arg>
+ <arg choice="plain"><option>-A</option></arg>
+ </group>
+ <replaceable>attrPath</replaceable>
+ </arg>
+ <arg><option>--no-out-link</option></arg>
+ <arg><option>--dry-run</option></arg>
+ <arg>
+ <group choice="req">
+ <arg choice="plain"><option>--out-link</option></arg>
+ <arg choice="plain"><option>-o</option></arg>
+ </group>
+ <replaceable>outlink</replaceable>
+ </arg>
+ <arg choice="plain" rep="repeat"><replaceable>paths</replaceable></arg>
+ </cmdsynopsis>
+</refsynopsisdiv>
+
+<refsection><title>Description</title>
+
+<para>The <command>nix-build</command> command builds the derivations
+described by the Nix expressions in <replaceable>paths</replaceable>.
+If the build succeeds, it places a symlink to the result in the
+current directory. The symlink is called <filename>result</filename>.
+If there are multiple Nix expressions, or the Nix expressions evaluate
+to multiple derivations, multiple sequentially numbered symlinks are
+created (<filename>result</filename>, <filename>result-2</filename>,
+and so on).</para>
+
+<para>If no <replaceable>paths</replaceable> are specified, then
+<command>nix-build</command> will use <filename>default.nix</filename>
+in the current directory, if it exists.</para>
+
+<para>If an element of <replaceable>paths</replaceable> starts with
+<literal>http://</literal> or <literal>https://</literal>, it is
+interpreted as the URL of a tarball that will be downloaded and
+unpacked to a temporary location. The tarball must include a single
+top-level directory containing at least a file named
+<filename>default.nix</filename>.</para>
+
+<para><command>nix-build</command> is essentially a wrapper around
+<link linkend="sec-nix-instantiate"><command>nix-instantiate</command></link>
+(to translate a high-level Nix expression to a low-level store
+derivation) and <link linkend="rsec-nix-store-realise"><command>nix-store
+--realise</command></link> (to build the store derivation).</para>
+
+<warning><para>The result of the build is automatically registered as
+a root of the Nix garbage collector. This root disappears
+automatically when the <filename>result</filename> symlink is deleted
+or renamed. So don’t rename the symlink.</para></warning>
+
+</refsection>
+
+
+<refsection><title>Options</title>
+
+<para>All options not listed here are passed to <command>nix-store
+--realise</command>, except for <option>--arg</option> and
+<option>--attr</option> / <option>-A</option> which are passed to
+<command>nix-instantiate</command>. <phrase condition="manual">See
+also <xref linkend="sec-common-options"/>.</phrase></para>
+
+<variablelist>
+
+ <varlistentry><term><option>--no-out-link</option></term>
+
+ <listitem><para>Do not create a symlink to the output path. Note
+ that as a result the output does not become a root of the garbage
+ collector, and so might be deleted by <command>nix-store
+ --gc</command>.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--dry-run</option></term>
+ <listitem><para>Show what store paths would be built or downloaded.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="opt-out-link"><term><option>--out-link</option> /
+ <option>-o</option> <replaceable>outlink</replaceable></term>
+
+ <listitem><para>Change the name of the symlink to the output path
+ created from <filename>result</filename> to
+ <replaceable>outlink</replaceable>.</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+<para>The following common options are supported:</para>
+
+<variablelist condition="manpage">
+ <varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--help</option></term>
+
+ <listitem><para>Prints out a summary of the command syntax and
+ exits.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--version</option></term>
+
+ <listitem><para>Prints out the Nix version number on standard output
+ and exits.</para></listitem>
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--verbose</option> / <option>-v</option></term>
+
+ <listitem>
+
+ <para>Increases the level of verbosity of diagnostic messages
+ printed on standard error. For each Nix operation, the information
+ printed on standard output is well-defined; any diagnostic
+ information is printed on standard error, never on standard
+ output.</para>
+
+ <para>This option may be specified repeatedly. Currently, the
+ following verbosity levels exist:</para>
+
+ <variablelist>
+
+ <varlistentry><term>0</term>
+ <listitem><para>“Errors only”: only print messages
+ explaining why the Nix invocation failed.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>1</term>
+ <listitem><para>“Informational”: print
+ <emphasis>useful</emphasis> messages about what Nix is doing.
+ This is the default.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>2</term>
+ <listitem><para>“Talkative”: print more informational
+ messages.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>3</term>
+ <listitem><para>“Chatty”: print even more
+ informational messages.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>4</term>
+ <listitem><para>“Debug”: print debug
+ information.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>5</term>
+ <listitem><para>“Vomit”: print vast amounts of debug
+ information.</para></listitem>
+ </varlistentry>
+
+ </variablelist>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--quiet</option></term>
+
+ <listitem>
+
+ <para>Decreases the level of verbosity of diagnostic messages
+ printed on standard error. This is the inverse option to
+ <option>-v</option> / <option>--verbose</option>.
+ </para>
+
+ <para>This option may be specified repeatedly. See the previous
+ verbosity levels list.</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-log-format"><term><option>--log-format</option> <replaceable>format</replaceable></term>
+
+ <listitem>
+
+ <para>This option can be used to change the output of the log format, with
+ <replaceable>format</replaceable> being one of:</para>
+
+ <variablelist>
+
+ <varlistentry><term>raw</term>
+ <listitem><para>This is the raw format, as outputted by nix-build.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>internal-json</term>
+ <listitem><para>Outputs the logs in a structured manner. NOTE: the json schema is not guarantees to be stable between releases.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>bar</term>
+ <listitem><para>Only display a progress bar during the builds.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>bar-with-logs</term>
+ <listitem><para>Display the raw logs, with the progress bar at the bottom.</para></listitem>
+ </varlistentry>
+
+ </variablelist>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--no-build-output</option> / <option>-Q</option></term>
+
+ <listitem><para>By default, output written by builders to standard
+ output and standard error is echoed to the Nix command's standard
+ error. This option suppresses this behaviour. Note that the
+ builder's standard output and error are always written to a log file
+ in
+ <filename><replaceable>prefix</replaceable>/nix/var/log/nix</filename>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-max-jobs"><term><option>--max-jobs</option> / <option>-j</option>
+<replaceable>number</replaceable></term>
+
+ <listitem>
+
+ <para>Sets the maximum number of build jobs that Nix will
+ perform in parallel to the specified number. Specify
+ <literal>auto</literal> to use the number of CPUs in the system.
+ The default is specified by the <link linkend="conf-max-jobs"><literal>max-jobs</literal></link>
+ configuration setting, which itself defaults to
+ <literal>1</literal>. A higher value is useful on SMP systems or to
+ exploit I/O latency.</para>
+
+ <para> Setting it to <literal>0</literal> disallows building on the local
+ machine, which is useful when you want builds to happen only on remote
+ builders.</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-cores"><term><option>--cores</option></term>
+
+ <listitem><para>Sets the value of the <envar>NIX_BUILD_CORES</envar>
+ environment variable in the invocation of builders. Builders can
+ use this variable at their discretion to control the maximum amount
+ of parallelism. For instance, in Nixpkgs, if the derivation
+ attribute <varname>enableParallelBuilding</varname> is set to
+ <literal>true</literal>, the builder passes the
+ <option>-j<replaceable>N</replaceable></option> flag to GNU Make.
+ It defaults to the value of the <link linkend="conf-cores"><literal>cores</literal></link>
+ configuration setting, if set, or <literal>1</literal> otherwise.
+ The value <literal>0</literal> means that the builder should use all
+ available CPU cores in the system.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-max-silent-time"><term><option>--max-silent-time</option></term>
+
+ <listitem><para>Sets the maximum number of seconds that a builder
+ can go without producing any data on standard output or standard
+ error. The default is specified by the <link linkend="conf-max-silent-time"><literal>max-silent-time</literal></link>
+ configuration setting. <literal>0</literal> means no
+ time-out.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-timeout"><term><option>--timeout</option></term>
+
+ <listitem><para>Sets the maximum number of seconds that a builder
+ can run. The default is specified by the <link linkend="conf-timeout"><literal>timeout</literal></link>
+ configuration setting. <literal>0</literal> means no
+ timeout.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--keep-going</option> / <option>-k</option></term>
+
+ <listitem><para>Keep going in case of failed builds, to the
+ greatest extent possible. That is, if building an input of some
+ derivation fails, Nix will still build the other inputs, but not the
+ derivation itself. Without this option, Nix stops if any build
+ fails (except for builds of substitutes), possibly killing builds in
+ progress (in case of parallel or distributed builds).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--keep-failed</option> / <option>-K</option></term>
+
+ <listitem><para>Specifies that in case of a build failure, the
+ temporary directory (usually in <filename>/tmp</filename>) in which
+ the build takes place should not be deleted. The path of the build
+ directory is printed as an informational message.
+ </para>
+ </listitem>
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--fallback</option></term>
+
+ <listitem>
+
+ <para>Whenever Nix attempts to build a derivation for which
+ substitutes are known for each output path, but realising the output
+ paths through the substitutes fails, fall back on building the
+ derivation.</para>
+
+ <para>The most common scenario in which this is useful is when we
+ have registered substitutes in order to perform binary distribution
+ from, say, a network repository. If the repository is down, the
+ realisation of the derivation will fail. When this option is
+ specified, Nix will build the derivation instead. Thus,
+ installation from binaries falls back on installation from source.
+ This option is not the default since it is generally not desirable
+ for a transient failure in obtaining the substitutes to lead to a
+ full build from source (with the related consumption of
+ resources).</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--no-build-hook</option></term>
+
+ <listitem>
+
+ <para>Disables the build hook mechanism. This allows to ignore remote
+ builders if they are setup on the machine.</para>
+
+ <para>It's useful in cases where the bandwidth between the client and the
+ remote builder is too low. In that case it can take more time to upload the
+ sources to the remote builder and fetch back the result than to do the
+ computation locally.</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--readonly-mode</option></term>
+
+ <listitem><para>When this option is used, no attempt is made to open
+ the Nix database. Most Nix operations do need database access, so
+ those operations will fail.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--arg</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
+
+ <listitem><para>This option is accepted by
+ <command>nix-env</command>, <command>nix-instantiate</command>,
+ <command>nix-shell</command> and <command>nix-build</command>.
+ When evaluating Nix expressions, the expression evaluator will
+ automatically try to call functions that
+ it encounters. It can automatically call functions for which every
+ argument has a <link linkend="ss-functions">default value</link>
+ (e.g., <literal>{ <replaceable>argName</replaceable> ?
+ <replaceable>defaultValue</replaceable> }:
+ <replaceable>...</replaceable></literal>). With
+ <option>--arg</option>, you can also call functions that have
+ arguments without a default value (or override a default value).
+ That is, if the evaluator encounters a function with an argument
+ named <replaceable>name</replaceable>, it will call it with value
+ <replaceable>value</replaceable>.</para>
+
+ <para>For instance, the top-level <literal>default.nix</literal> in
+ Nixpkgs is actually a function:
+
+<programlisting>
+{ # The system (e.g., `i686-linux') for which to build the packages.
+ system ? builtins.currentSystem
+ <replaceable>...</replaceable>
+}: <replaceable>...</replaceable></programlisting>
+
+ So if you call this Nix expression (e.g., when you do
+ <literal>nix-env -i <replaceable>pkgname</replaceable></literal>),
+ the function will be called automatically using the value <link linkend="builtin-currentSystem"><literal>builtins.currentSystem</literal></link>
+ for the <literal>system</literal> argument. You can override this
+ using <option>--arg</option>, e.g., <literal>nix-env -i
+ <replaceable>pkgname</replaceable> --arg system
+ \"i686-freebsd\"</literal>. (Note that since the argument is a Nix
+ string literal, you have to escape the quotes.)</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--argstr</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
+
+ <listitem><para>This option is like <option>--arg</option>, only the
+ value is not a Nix expression but a string. So instead of
+ <literal>--arg system \"i686-linux\"</literal> (the outer quotes are
+ to keep the shell happy) you can say <literal>--argstr system
+ i686-linux</literal>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-attr"><term><option>--attr</option> / <option>-A</option>
+<replaceable>attrPath</replaceable></term>
+
+ <listitem><para>Select an attribute from the top-level Nix
+ expression being evaluated. (<command>nix-env</command>,
+ <command>nix-instantiate</command>, <command>nix-build</command> and
+ <command>nix-shell</command> only.) The <emphasis>attribute
+ path</emphasis> <replaceable>attrPath</replaceable> is a sequence of
+ attribute names separated by dots. For instance, given a top-level
+ Nix expression <replaceable>e</replaceable>, the attribute path
+ <literal>xorg.xorgserver</literal> would cause the expression
+ <literal><replaceable>e</replaceable>.xorg.xorgserver</literal> to
+ be used. See <link linkend="refsec-nix-env-install-examples"><command>nix-env
+ --install</command></link> for some concrete examples.</para>
+
+ <para>In addition to attribute names, you can also specify array
+ indices. For instance, the attribute path
+ <literal>foo.3.bar</literal> selects the <literal>bar</literal>
+ attribute of the fourth element of the array in the
+ <literal>foo</literal> attribute of the top-level
+ expression.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--expr</option> / <option>-E</option></term>
+
+ <listitem><para>Interpret the command line arguments as a list of
+ Nix expressions to be parsed and evaluated, rather than as a list
+ of file names of Nix expressions.
+ (<command>nix-instantiate</command>, <command>nix-build</command>
+ and <command>nix-shell</command> only.)</para>
+
+ <para>For <command>nix-shell</command>, this option is commonly used
+ to give you a shell in which you can build the packages returned
+ by the expression. If you want to get a shell which contain the
+ <emphasis>built</emphasis> packages ready for use, give your
+ expression to the <command>nix-shell -p</command> convenience flag
+ instead.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-I"><term><option>-I</option> <replaceable>path</replaceable></term>
+
+ <listitem><para>Add a path to the Nix expression search path. This
+ option may be given multiple times. See the <envar linkend="env-NIX_PATH">NIX_PATH</envar> environment variable for
+ information on the semantics of the Nix search path. Paths added
+ through <option>-I</option> take precedence over
+ <envar>NIX_PATH</envar>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--option</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
+
+ <listitem><para>Set the Nix configuration option
+ <replaceable>name</replaceable> to <replaceable>value</replaceable>.
+ This overrides settings in the Nix configuration file (see
+ <citerefentry><refentrytitle>nix.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--repair</option></term>
+
+ <listitem><para>Fix corrupted or missing store paths by
+ redownloading or rebuilding them. Note that this is slow because it
+ requires computing a cryptographic hash of the contents of every
+ path in the closure of the build. Also note the warning under
+ <command>nix-store --repair-path</command>.</para></listitem>
+
+</varlistentry>
+</variablelist>
+
+</refsection>
+
+
+<refsection><title>Examples</title>
+
+<screen>
+$ nix-build '<nixpkgs>' -A firefox
+store derivation is /nix/store/qybprl8sz2lc...-firefox-1.5.0.7.drv
+/nix/store/d18hyl92g30l...-firefox-1.5.0.7
+
+$ ls -l result
+lrwxrwxrwx <replaceable>...</replaceable> result -> /nix/store/d18hyl92g30l...-firefox-1.5.0.7
+
+$ ls ./result/bin/
+firefox firefox-config</screen>
+
+<para>If a derivation has multiple outputs,
+<command>nix-build</command> will build the default (first) output.
+You can also build all outputs:
+<screen>
+$ nix-build '<nixpkgs>' -A openssl.all
+</screen>
+This will create a symlink for each output named
+<filename>result-<replaceable>outputname</replaceable></filename>.
+The suffix is omitted if the output name is <literal>out</literal>.
+So if <literal>openssl</literal> has outputs <literal>out</literal>,
+<literal>bin</literal> and <literal>man</literal>,
+<command>nix-build</command> will create symlinks
+<literal>result</literal>, <literal>result-bin</literal> and
+<literal>result-man</literal>. It’s also possible to build a specific
+output:
+<screen>
+$ nix-build '<nixpkgs>' -A openssl.man
+</screen>
+This will create a symlink <literal>result-man</literal>.</para>
+
+<para>Build a Nix expression given on the command line:
+
+<screen>
+$ nix-build -E 'with import <nixpkgs> { }; runCommand "foo" { } "echo bar > $out"'
+$ cat ./result
+bar
+</screen>
+
+</para>
+
+<para>Build the GNU Hello package from the latest revision of the
+master branch of Nixpkgs:
+
+<screen>
+$ nix-build https://github.com/NixOS/nixpkgs/archive/master.tar.gz -A hello
+</screen>
+
+</para>
+
+</refsection>
+
+
+<refsection condition="manpage"><title>Environment variables</title>
+
+<variablelist>
+ <varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>IN_NIX_SHELL</envar></term>
+
+ <listitem><para>Indicator that tells if the current environment was set up by
+ <command>nix-shell</command>. Since Nix 2.0 the values are
+ <literal>"pure"</literal> and <literal>"impure"</literal></para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="env-NIX_PATH"><term><envar>NIX_PATH</envar></term>
+
+ <listitem>
+
+ <para>A colon-separated list of directories used to look up Nix
+ expressions enclosed in angle brackets (i.e.,
+ <literal><<replaceable>path</replaceable>></literal>). For
+ instance, the value
+
+ <screen>
+/home/eelco/Dev:/etc/nixos</screen>
+
+ will cause Nix to look for paths relative to
+ <filename>/home/eelco/Dev</filename> and
+ <filename>/etc/nixos</filename>, in this order. It is also
+ possible to match paths against a prefix. For example, the value
+
+ <screen>
+nixpkgs=/home/eelco/Dev/nixpkgs-branch:/etc/nixos</screen>
+
+ will cause Nix to search for
+ <literal><nixpkgs/<replaceable>path</replaceable>></literal> in
+ <filename>/home/eelco/Dev/nixpkgs-branch/<replaceable>path</replaceable></filename>
+ and
+ <filename>/etc/nixos/nixpkgs/<replaceable>path</replaceable></filename>.</para>
+
+ <para>If a path in the Nix search path starts with
+ <literal>http://</literal> or <literal>https://</literal>, it is
+ interpreted as the URL of a tarball that will be downloaded and
+ unpacked to a temporary location. The tarball must consist of a
+ single top-level directory. For example, setting
+ <envar>NIX_PATH</envar> to
+
+ <screen>
+nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-15.09.tar.gz</screen>
+
+ tells Nix to download the latest revision in the Nixpkgs/NixOS
+ 15.09 channel.</para>
+
+ <para>A following shorthand can be used to refer to the official channels:
+
+ <screen>nixpkgs=channel:nixos-15.09</screen>
+ </para>
+
+ <para>The search path can be extended using the <option linkend="opt-I">-I</option> option, which takes precedence over
+ <envar>NIX_PATH</envar>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_IGNORE_SYMLINK_STORE</envar></term>
+
+ <listitem>
+
+ <para>Normally, the Nix store directory (typically
+ <filename>/nix/store</filename>) is not allowed to contain any
+ symlink components. This is to prevent “impure” builds. Builders
+ sometimes “canonicalise” paths by resolving all symlink components.
+ Thus, builds on different machines (with
+ <filename>/nix/store</filename> resolving to different locations)
+ could yield different results. This is generally not a problem,
+ except when builds are deployed to machines where
+ <filename>/nix/store</filename> resolves differently. If you are
+ sure that you’re not going to do that, you can set
+ <envar>NIX_IGNORE_SYMLINK_STORE</envar> to <envar>1</envar>.</para>
+
+ <para>Note that if you’re symlinking the Nix store so that you can
+ put it on another file system than the root file system, on Linux
+ you’re better off using <literal>bind</literal> mount points, e.g.,
+
+ <screen>
+$ mkdir /nix
+$ mount -o bind /mnt/otherdisk/nix /nix</screen>
+
+ Consult the <citerefentry><refentrytitle>mount</refentrytitle>
+ <manvolnum>8</manvolnum></citerefentry> manual page for details.</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_STORE_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix store (default
+ <filename><replaceable>prefix</replaceable>/store</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_DATA_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix static data
+ directory (default
+ <filename><replaceable>prefix</replaceable>/share</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_LOG_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix log directory
+ (default <filename><replaceable>prefix</replaceable>/var/log/nix</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_STATE_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix state directory
+ (default <filename><replaceable>prefix</replaceable>/var/nix</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_CONF_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the system Nix configuration
+ directory (default
+ <filename><replaceable>prefix</replaceable>/etc/nix</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_USER_CONF_FILES</envar></term>
+
+ <listitem><para>Overrides the location of the user Nix configuration files
+ to load from (defaults to the XDG spec locations). The variable is treated
+ as a list separated by the <literal>:</literal> token.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>TMPDIR</envar></term>
+
+ <listitem><para>Use the specified directory to store temporary
+ files. In particular, this includes temporary build directories;
+ these can take up substantial amounts of disk space. The default is
+ <filename>/tmp</filename>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="envar-remote"><term><envar>NIX_REMOTE</envar></term>
+
+ <listitem><para>This variable should be set to
+ <literal>daemon</literal> if you want to use the Nix daemon to
+ execute Nix operations. This is necessary in <link linkend="ssec-multi-user">multi-user Nix installations</link>.
+ If the Nix daemon's Unix socket is at some non-standard path,
+ this variable should be set to <literal>unix://path/to/socket</literal>.
+ Otherwise, it should be left unset.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_SHOW_STATS</envar></term>
+
+ <listitem><para>If set to <literal>1</literal>, Nix will print some
+ evaluation statistics, such as the number of values
+ allocated.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_COUNT_CALLS</envar></term>
+
+ <listitem><para>If set to <literal>1</literal>, Nix will print how
+ often functions were called during Nix expression evaluation. This
+ is useful for profiling your Nix expressions.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>GC_INITIAL_HEAP_SIZE</envar></term>
+
+ <listitem><para>If Nix has been configured to use the Boehm garbage
+ collector, this variable sets the initial size of the heap in bytes.
+ It defaults to 384 MiB. Setting it to a low value reduces memory
+ consumption, but will increase runtime due to the overhead of
+ garbage collection.</para></listitem>
+
+</varlistentry>
+</variablelist>
+
+</refsection>
+
+
+</refentry>
+<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-nix-shell">
+
+<refmeta>
+ <refentrytitle>nix-shell</refentrytitle>
+ <manvolnum>1</manvolnum>
+ <refmiscinfo class="source">Nix</refmiscinfo>
+ <refmiscinfo class="version">3.0</refmiscinfo>
+</refmeta>
+
+<refnamediv>
+ <refname>nix-shell</refname>
+ <refpurpose>start an interactive shell based on a Nix expression</refpurpose>
+</refnamediv>
+
+<refsynopsisdiv>
+ <cmdsynopsis>
+ <command>nix-shell</command>
+ <arg><option>--arg</option> <replaceable>name</replaceable> <replaceable>value</replaceable></arg>
+ <arg><option>--argstr</option> <replaceable>name</replaceable> <replaceable>value</replaceable></arg>
+ <arg>
+ <group choice="req">
+ <arg choice="plain"><option>--attr</option></arg>
+ <arg choice="plain"><option>-A</option></arg>
+ </group>
+ <replaceable>attrPath</replaceable>
+ </arg>
+ <arg><option>--command</option> <replaceable>cmd</replaceable></arg>
+ <arg><option>--run</option> <replaceable>cmd</replaceable></arg>
+ <arg><option>--exclude</option> <replaceable>regexp</replaceable></arg>
+ <arg><option>--pure</option></arg>
+ <arg><option>--keep</option> <replaceable>name</replaceable></arg>
+ <group choice="req">
+ <arg choice="plain">
+ <group choice="req">
+ <arg choice="plain"><option>--packages</option></arg>
+ <arg choice="plain"><option>-p</option></arg>
+ </group>
+ <arg choice="plain" rep="repeat">
+ <group choice="req">
+ <arg choice="plain"><replaceable>packages</replaceable></arg>
+ <arg choice="plain"><replaceable>expressions</replaceable></arg>
+ </group>
+ </arg>
+ </arg>
+ <arg><replaceable>path</replaceable></arg>
+ </group>
+ </cmdsynopsis>
+</refsynopsisdiv>
+
+<refsection><title>Description</title>
+
+<para>The command <command>nix-shell</command> will build the
+dependencies of the specified derivation, but not the derivation
+itself. It will then start an interactive shell in which all
+environment variables defined by the derivation
+<replaceable>path</replaceable> have been set to their corresponding
+values, and the script <literal>$stdenv/setup</literal> has been
+sourced. This is useful for reproducing the environment of a
+derivation for development.</para>
+
+<para>If <replaceable>path</replaceable> is not given,
+<command>nix-shell</command> defaults to
+<filename>shell.nix</filename> if it exists, and
+<filename>default.nix</filename> otherwise.</para>
+
+<para>If <replaceable>path</replaceable> starts with
+<literal>http://</literal> or <literal>https://</literal>, it is
+interpreted as the URL of a tarball that will be downloaded and
+unpacked to a temporary location. The tarball must include a single
+top-level directory containing at least a file named
+<filename>default.nix</filename>.</para>
+
+<para>If the derivation defines the variable
+<varname>shellHook</varname>, it will be evaluated after
+<literal>$stdenv/setup</literal> has been sourced. Since this hook is
+not executed by regular Nix builds, it allows you to perform
+initialisation specific to <command>nix-shell</command>. For example,
+the derivation attribute
+
+<programlisting>
+shellHook =
+ ''
+ echo "Hello shell"
+ '';
+</programlisting>
+
+will cause <command>nix-shell</command> to print <literal>Hello shell</literal>.</para>
+
+</refsection>
+
+
+<refsection><title>Options</title>
+
+<para>All options not listed here are passed to <command>nix-store
+--realise</command>, except for <option>--arg</option> and
+<option>--attr</option> / <option>-A</option> which are passed to
+<command>nix-instantiate</command>. <phrase condition="manual">See
+also <xref linkend="sec-common-options"/>.</phrase></para>
+
+<variablelist>
+
+ <varlistentry><term><option>--command</option> <replaceable>cmd</replaceable></term>
+
+ <listitem><para>In the environment of the derivation, run the
+ shell command <replaceable>cmd</replaceable>. This command is
+ executed in an interactive shell. (Use <option>--run</option> to
+ use a non-interactive shell instead.) However, a call to
+ <literal>exit</literal> is implicitly added to the command, so the
+ shell will exit after running the command. To prevent this, add
+ <literal>return</literal> at the end; e.g. <literal>--command
+ "echo Hello; return"</literal> will print <literal>Hello</literal>
+ and then drop you into the interactive shell. This can be useful
+ for doing any additional initialisation.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--run</option> <replaceable>cmd</replaceable></term>
+
+ <listitem><para>Like <option>--command</option>, but executes the
+ command in a non-interactive shell. This means (among other
+ things) that if you hit Ctrl-C while the command is running, the
+ shell exits.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--exclude</option> <replaceable>regexp</replaceable></term>
+
+ <listitem><para>Do not build any dependencies whose store path
+ matches the regular expression <replaceable>regexp</replaceable>.
+ This option may be specified multiple times.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--pure</option></term>
+
+ <listitem><para>If this flag is specified, the environment is
+ almost entirely cleared before the interactive shell is started,
+ so you get an environment that more closely corresponds to the
+ “real” Nix build. A few variables, in particular
+ <envar>HOME</envar>, <envar>USER</envar> and
+ <envar>DISPLAY</envar>, are retained. Note that
+ <filename>~/.bashrc</filename> and (depending on your Bash
+ installation) <filename>/etc/bashrc</filename> are still sourced,
+ so any variables set there will affect the interactive
+ shell.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--packages</option> / <option>-p</option> <replaceable>packages</replaceable>…</term>
+
+ <listitem><para>Set up an environment in which the specified
+ packages are present. The command line arguments are interpreted
+ as attribute names inside the Nix Packages collection. Thus,
+ <literal>nix-shell -p libjpeg openjdk</literal> will start a shell
+ in which the packages denoted by the attribute names
+ <varname>libjpeg</varname> and <varname>openjdk</varname> are
+ present.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>-i</option> <replaceable>interpreter</replaceable></term>
+
+ <listitem><para>The chained script interpreter to be invoked by
+ <command>nix-shell</command>. Only applicable in
+ <literal>#!</literal>-scripts (described <link linkend="ssec-nix-shell-shebang">below</link>).</para>
+
+ </listitem></varlistentry>
+
+ <varlistentry><term><option>--keep</option> <replaceable>name</replaceable></term>
+
+ <listitem><para>When a <option>--pure</option> shell is started,
+ keep the listed environment variables.</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+<para>The following common options are supported:</para>
+
+<variablelist condition="manpage">
+ <varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--help</option></term>
+
+ <listitem><para>Prints out a summary of the command syntax and
+ exits.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--version</option></term>
+
+ <listitem><para>Prints out the Nix version number on standard output
+ and exits.</para></listitem>
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--verbose</option> / <option>-v</option></term>
+
+ <listitem>
+
+ <para>Increases the level of verbosity of diagnostic messages
+ printed on standard error. For each Nix operation, the information
+ printed on standard output is well-defined; any diagnostic
+ information is printed on standard error, never on standard
+ output.</para>
+
+ <para>This option may be specified repeatedly. Currently, the
+ following verbosity levels exist:</para>
+
+ <variablelist>
+
+ <varlistentry><term>0</term>
+ <listitem><para>“Errors only”: only print messages
+ explaining why the Nix invocation failed.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>1</term>
+ <listitem><para>“Informational”: print
+ <emphasis>useful</emphasis> messages about what Nix is doing.
+ This is the default.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>2</term>
+ <listitem><para>“Talkative”: print more informational
+ messages.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>3</term>
+ <listitem><para>“Chatty”: print even more
+ informational messages.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>4</term>
+ <listitem><para>“Debug”: print debug
+ information.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>5</term>
+ <listitem><para>“Vomit”: print vast amounts of debug
+ information.</para></listitem>
+ </varlistentry>
+
+ </variablelist>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--quiet</option></term>
+
+ <listitem>
+
+ <para>Decreases the level of verbosity of diagnostic messages
+ printed on standard error. This is the inverse option to
+ <option>-v</option> / <option>--verbose</option>.
+ </para>
+
+ <para>This option may be specified repeatedly. See the previous
+ verbosity levels list.</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-log-format"><term><option>--log-format</option> <replaceable>format</replaceable></term>
+
+ <listitem>
+
+ <para>This option can be used to change the output of the log format, with
+ <replaceable>format</replaceable> being one of:</para>
+
+ <variablelist>
+
+ <varlistentry><term>raw</term>
+ <listitem><para>This is the raw format, as outputted by nix-build.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>internal-json</term>
+ <listitem><para>Outputs the logs in a structured manner. NOTE: the json schema is not guarantees to be stable between releases.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>bar</term>
+ <listitem><para>Only display a progress bar during the builds.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>bar-with-logs</term>
+ <listitem><para>Display the raw logs, with the progress bar at the bottom.</para></listitem>
+ </varlistentry>
+
+ </variablelist>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--no-build-output</option> / <option>-Q</option></term>
+
+ <listitem><para>By default, output written by builders to standard
+ output and standard error is echoed to the Nix command's standard
+ error. This option suppresses this behaviour. Note that the
+ builder's standard output and error are always written to a log file
+ in
+ <filename><replaceable>prefix</replaceable>/nix/var/log/nix</filename>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-max-jobs"><term><option>--max-jobs</option> / <option>-j</option>
+<replaceable>number</replaceable></term>
+
+ <listitem>
+
+ <para>Sets the maximum number of build jobs that Nix will
+ perform in parallel to the specified number. Specify
+ <literal>auto</literal> to use the number of CPUs in the system.
+ The default is specified by the <link linkend="conf-max-jobs"><literal>max-jobs</literal></link>
+ configuration setting, which itself defaults to
+ <literal>1</literal>. A higher value is useful on SMP systems or to
+ exploit I/O latency.</para>
+
+ <para> Setting it to <literal>0</literal> disallows building on the local
+ machine, which is useful when you want builds to happen only on remote
+ builders.</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-cores"><term><option>--cores</option></term>
+
+ <listitem><para>Sets the value of the <envar>NIX_BUILD_CORES</envar>
+ environment variable in the invocation of builders. Builders can
+ use this variable at their discretion to control the maximum amount
+ of parallelism. For instance, in Nixpkgs, if the derivation
+ attribute <varname>enableParallelBuilding</varname> is set to
+ <literal>true</literal>, the builder passes the
+ <option>-j<replaceable>N</replaceable></option> flag to GNU Make.
+ It defaults to the value of the <link linkend="conf-cores"><literal>cores</literal></link>
+ configuration setting, if set, or <literal>1</literal> otherwise.
+ The value <literal>0</literal> means that the builder should use all
+ available CPU cores in the system.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-max-silent-time"><term><option>--max-silent-time</option></term>
+
+ <listitem><para>Sets the maximum number of seconds that a builder
+ can go without producing any data on standard output or standard
+ error. The default is specified by the <link linkend="conf-max-silent-time"><literal>max-silent-time</literal></link>
+ configuration setting. <literal>0</literal> means no
+ time-out.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-timeout"><term><option>--timeout</option></term>
+
+ <listitem><para>Sets the maximum number of seconds that a builder
+ can run. The default is specified by the <link linkend="conf-timeout"><literal>timeout</literal></link>
+ configuration setting. <literal>0</literal> means no
+ timeout.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--keep-going</option> / <option>-k</option></term>
+
+ <listitem><para>Keep going in case of failed builds, to the
+ greatest extent possible. That is, if building an input of some
+ derivation fails, Nix will still build the other inputs, but not the
+ derivation itself. Without this option, Nix stops if any build
+ fails (except for builds of substitutes), possibly killing builds in
+ progress (in case of parallel or distributed builds).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--keep-failed</option> / <option>-K</option></term>
+
+ <listitem><para>Specifies that in case of a build failure, the
+ temporary directory (usually in <filename>/tmp</filename>) in which
+ the build takes place should not be deleted. The path of the build
+ directory is printed as an informational message.
+ </para>
+ </listitem>
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--fallback</option></term>
+
+ <listitem>
+
+ <para>Whenever Nix attempts to build a derivation for which
+ substitutes are known for each output path, but realising the output
+ paths through the substitutes fails, fall back on building the
+ derivation.</para>
+
+ <para>The most common scenario in which this is useful is when we
+ have registered substitutes in order to perform binary distribution
+ from, say, a network repository. If the repository is down, the
+ realisation of the derivation will fail. When this option is
+ specified, Nix will build the derivation instead. Thus,
+ installation from binaries falls back on installation from source.
+ This option is not the default since it is generally not desirable
+ for a transient failure in obtaining the substitutes to lead to a
+ full build from source (with the related consumption of
+ resources).</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--no-build-hook</option></term>
+
+ <listitem>
+
+ <para>Disables the build hook mechanism. This allows to ignore remote
+ builders if they are setup on the machine.</para>
+
+ <para>It's useful in cases where the bandwidth between the client and the
+ remote builder is too low. In that case it can take more time to upload the
+ sources to the remote builder and fetch back the result than to do the
+ computation locally.</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--readonly-mode</option></term>
+
+ <listitem><para>When this option is used, no attempt is made to open
+ the Nix database. Most Nix operations do need database access, so
+ those operations will fail.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--arg</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
+
+ <listitem><para>This option is accepted by
+ <command>nix-env</command>, <command>nix-instantiate</command>,
+ <command>nix-shell</command> and <command>nix-build</command>.
+ When evaluating Nix expressions, the expression evaluator will
+ automatically try to call functions that
+ it encounters. It can automatically call functions for which every
+ argument has a <link linkend="ss-functions">default value</link>
+ (e.g., <literal>{ <replaceable>argName</replaceable> ?
+ <replaceable>defaultValue</replaceable> }:
+ <replaceable>...</replaceable></literal>). With
+ <option>--arg</option>, you can also call functions that have
+ arguments without a default value (or override a default value).
+ That is, if the evaluator encounters a function with an argument
+ named <replaceable>name</replaceable>, it will call it with value
+ <replaceable>value</replaceable>.</para>
+
+ <para>For instance, the top-level <literal>default.nix</literal> in
+ Nixpkgs is actually a function:
+
+<programlisting>
+{ # The system (e.g., `i686-linux') for which to build the packages.
+ system ? builtins.currentSystem
+ <replaceable>...</replaceable>
+}: <replaceable>...</replaceable></programlisting>
+
+ So if you call this Nix expression (e.g., when you do
+ <literal>nix-env -i <replaceable>pkgname</replaceable></literal>),
+ the function will be called automatically using the value <link linkend="builtin-currentSystem"><literal>builtins.currentSystem</literal></link>
+ for the <literal>system</literal> argument. You can override this
+ using <option>--arg</option>, e.g., <literal>nix-env -i
+ <replaceable>pkgname</replaceable> --arg system
+ \"i686-freebsd\"</literal>. (Note that since the argument is a Nix
+ string literal, you have to escape the quotes.)</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--argstr</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
+
+ <listitem><para>This option is like <option>--arg</option>, only the
+ value is not a Nix expression but a string. So instead of
+ <literal>--arg system \"i686-linux\"</literal> (the outer quotes are
+ to keep the shell happy) you can say <literal>--argstr system
+ i686-linux</literal>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-attr"><term><option>--attr</option> / <option>-A</option>
+<replaceable>attrPath</replaceable></term>
+
+ <listitem><para>Select an attribute from the top-level Nix
+ expression being evaluated. (<command>nix-env</command>,
+ <command>nix-instantiate</command>, <command>nix-build</command> and
+ <command>nix-shell</command> only.) The <emphasis>attribute
+ path</emphasis> <replaceable>attrPath</replaceable> is a sequence of
+ attribute names separated by dots. For instance, given a top-level
+ Nix expression <replaceable>e</replaceable>, the attribute path
+ <literal>xorg.xorgserver</literal> would cause the expression
+ <literal><replaceable>e</replaceable>.xorg.xorgserver</literal> to
+ be used. See <link linkend="refsec-nix-env-install-examples"><command>nix-env
+ --install</command></link> for some concrete examples.</para>
+
+ <para>In addition to attribute names, you can also specify array
+ indices. For instance, the attribute path
+ <literal>foo.3.bar</literal> selects the <literal>bar</literal>
+ attribute of the fourth element of the array in the
+ <literal>foo</literal> attribute of the top-level
+ expression.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--expr</option> / <option>-E</option></term>
+
+ <listitem><para>Interpret the command line arguments as a list of
+ Nix expressions to be parsed and evaluated, rather than as a list
+ of file names of Nix expressions.
+ (<command>nix-instantiate</command>, <command>nix-build</command>
+ and <command>nix-shell</command> only.)</para>
+
+ <para>For <command>nix-shell</command>, this option is commonly used
+ to give you a shell in which you can build the packages returned
+ by the expression. If you want to get a shell which contain the
+ <emphasis>built</emphasis> packages ready for use, give your
+ expression to the <command>nix-shell -p</command> convenience flag
+ instead.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-I"><term><option>-I</option> <replaceable>path</replaceable></term>
+
+ <listitem><para>Add a path to the Nix expression search path. This
+ option may be given multiple times. See the <envar linkend="env-NIX_PATH">NIX_PATH</envar> environment variable for
+ information on the semantics of the Nix search path. Paths added
+ through <option>-I</option> take precedence over
+ <envar>NIX_PATH</envar>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--option</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
+
+ <listitem><para>Set the Nix configuration option
+ <replaceable>name</replaceable> to <replaceable>value</replaceable>.
+ This overrides settings in the Nix configuration file (see
+ <citerefentry><refentrytitle>nix.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--repair</option></term>
+
+ <listitem><para>Fix corrupted or missing store paths by
+ redownloading or rebuilding them. Note that this is slow because it
+ requires computing a cryptographic hash of the contents of every
+ path in the closure of the build. Also note the warning under
+ <command>nix-store --repair-path</command>.</para></listitem>
+
+</varlistentry>
+</variablelist>
+
+</refsection>
+
+
+<refsection><title>Environment variables</title>
+
+<variablelist>
+
+ <varlistentry><term><envar>NIX_BUILD_SHELL</envar></term>
+
+ <listitem><para>Shell used to start the interactive environment.
+ Defaults to the <command>bash</command> found in <envar>PATH</envar>.</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+</refsection>
+
+
+<refsection><title>Examples</title>
+
+<para>To build the dependencies of the package Pan, and start an
+interactive shell in which to build it:
+
+<screen>
+$ nix-shell '<nixpkgs>' -A pan
+[nix-shell]$ unpackPhase
+[nix-shell]$ cd pan-*
+[nix-shell]$ configurePhase
+[nix-shell]$ buildPhase
+[nix-shell]$ ./pan/gui/pan
+</screen>
+
+To clear the environment first, and do some additional automatic
+initialisation of the interactive shell:
+
+<screen>
+$ nix-shell '<nixpkgs>' -A pan --pure \
+ --command 'export NIX_DEBUG=1; export NIX_CORES=8; return'
+</screen>
+
+Nix expressions can also be given on the command line using the
+<command>-E</command> and <command>-p</command> flags.
+For instance, the following starts a shell containing the packages
+<literal>sqlite</literal> and <literal>libX11</literal>:
+
+<screen>
+$ nix-shell -E 'with import <nixpkgs> { }; runCommand "dummy" { buildInputs = [ sqlite xorg.libX11 ]; } ""'
+</screen>
+
+A shorter way to do the same is:
+
+<screen>
+$ nix-shell -p sqlite xorg.libX11
+[nix-shell]$ echo $NIX_LDFLAGS
+… -L/nix/store/j1zg5v…-sqlite-3.8.0.2/lib -L/nix/store/0gmcz9…-libX11-1.6.1/lib …
+</screen>
+
+Note that <command>-p</command> accepts multiple full nix expressions that
+are valid in the <literal>buildInputs = [ ... ]</literal> shown above,
+not only package names. So the following is also legal:
+
+<screen>
+$ nix-shell -p sqlite 'git.override { withManual = false; }'
+</screen>
+
+The <command>-p</command> flag looks up Nixpkgs in the Nix search
+path. You can override it by passing <option>-I</option> or setting
+<envar>NIX_PATH</envar>. For example, the following gives you a shell
+containing the Pan package from a specific revision of Nixpkgs:
+
+<screen>
+$ nix-shell -p pan -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/8a3eea054838b55aca962c3fbde9c83c102b8bf2.tar.gz
+
+[nix-shell:~]$ pan --version
+Pan 0.139
+</screen>
+
+</para>
+
+</refsection>
+
+
+<refsection xml:id="ssec-nix-shell-shebang"><title>Use as a <literal>#!</literal>-interpreter</title>
+
+<para>You can use <command>nix-shell</command> as a script interpreter
+to allow scripts written in arbitrary languages to obtain their own
+dependencies via Nix. This is done by starting the script with the
+following lines:
+
+<programlisting>
+#! /usr/bin/env nix-shell
+#! nix-shell -i <replaceable>real-interpreter</replaceable> -p <replaceable>packages</replaceable>
+</programlisting>
+
+where <replaceable>real-interpreter</replaceable> is the “real” script
+interpreter that will be invoked by <command>nix-shell</command> after
+it has obtained the dependencies and initialised the environment, and
+<replaceable>packages</replaceable> are the attribute names of the
+dependencies in Nixpkgs.</para>
+
+<para>The lines starting with <literal>#! nix-shell</literal> specify
+<command>nix-shell</command> options (see above). Note that you cannot
+write <literal>#! /usr/bin/env nix-shell -i ...</literal> because
+many operating systems only allow one argument in
+<literal>#!</literal> lines.</para>
+
+<para>For example, here is a Python script that depends on Python and
+the <literal>prettytable</literal> package:
+
+<programlisting>
+#! /usr/bin/env nix-shell
+#! nix-shell -i python -p python pythonPackages.prettytable
+
+import prettytable
+
+# Print a simple table.
+t = prettytable.PrettyTable(["N", "N^2"])
+for n in range(1, 10): t.add_row([n, n * n])
+print t
+</programlisting>
+
+</para>
+
+<para>Similarly, the following is a Perl script that specifies that it
+requires Perl and the <literal>HTML::TokeParser::Simple</literal> and
+<literal>LWP</literal> packages:
+
+<programlisting>
+#! /usr/bin/env nix-shell
+#! nix-shell -i perl -p perl perlPackages.HTMLTokeParserSimple perlPackages.LWP
+
+use HTML::TokeParser::Simple;
+
+# Fetch nixos.org and print all hrefs.
+my $p = HTML::TokeParser::Simple->new(url => 'http://nixos.org/');
+
+while (my $token = $p->get_tag("a")) {
+ my $href = $token->get_attr("href");
+ print "$href\n" if $href;
+}
+</programlisting>
+
+</para>
+
+<para>Sometimes you need to pass a simple Nix expression to customize
+a package like Terraform:
+
+<programlisting><![CDATA[
+#! /usr/bin/env nix-shell
+#! nix-shell -i bash -p "terraform.withPlugins (plugins: [ plugins.openstack ])"
+
+terraform apply
+]]></programlisting>
+
+<note><para>You must use double quotes (<literal>"</literal>) when
+passing a simple Nix expression in a nix-shell shebang.</para></note>
+</para>
+
+<para>Finally, using the merging of multiple nix-shell shebangs the
+following Haskell script uses a specific branch of Nixpkgs/NixOS (the
+18.03 stable branch):
+
+<programlisting><![CDATA[
+#! /usr/bin/env nix-shell
+#! nix-shell -i runghc -p "haskellPackages.ghcWithPackages (ps: [ps.HTTP ps.tagsoup])"
+#! nix-shell -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-18.03.tar.gz
+
+import Network.HTTP
+import Text.HTML.TagSoup
+
+-- Fetch nixos.org and print all hrefs.
+main = do
+ resp <- Network.HTTP.simpleHTTP (getRequest "http://nixos.org/")
+ body <- getResponseBody resp
+ let tags = filter (isTagOpenName "a") $ parseTags body
+ let tags' = map (fromAttrib "href") tags
+ mapM_ putStrLn $ filter (/= "") tags'
+]]></programlisting>
+
+If you want to be even more precise, you can specify a specific
+revision of Nixpkgs:
+
+<programlisting>
+#! nix-shell -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/0672315759b3e15e2121365f067c1c8c56bb4722.tar.gz
+</programlisting>
+
+</para>
+
+<para>The examples above all used <option>-p</option> to get
+dependencies from Nixpkgs. You can also use a Nix expression to build
+your own dependencies. For example, the Python example could have been
+written as:
+
+<programlisting>
+#! /usr/bin/env nix-shell
+#! nix-shell deps.nix -i python
+</programlisting>
+
+where the file <filename>deps.nix</filename> in the same directory
+as the <literal>#!</literal>-script contains:
+
+<programlisting>
+with import <nixpkgs> {};
+
+runCommand "dummy" { buildInputs = [ python pythonPackages.prettytable ]; } ""
+</programlisting>
+
+</para>
+
+</refsection>
+
+
+<refsection condition="manpage"><title>Environment variables</title>
+
+<variablelist>
+ <varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>IN_NIX_SHELL</envar></term>
+
+ <listitem><para>Indicator that tells if the current environment was set up by
+ <command>nix-shell</command>. Since Nix 2.0 the values are
+ <literal>"pure"</literal> and <literal>"impure"</literal></para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="env-NIX_PATH"><term><envar>NIX_PATH</envar></term>
+
+ <listitem>
+
+ <para>A colon-separated list of directories used to look up Nix
+ expressions enclosed in angle brackets (i.e.,
+ <literal><<replaceable>path</replaceable>></literal>). For
+ instance, the value
+
+ <screen>
+/home/eelco/Dev:/etc/nixos</screen>
+
+ will cause Nix to look for paths relative to
+ <filename>/home/eelco/Dev</filename> and
+ <filename>/etc/nixos</filename>, in this order. It is also
+ possible to match paths against a prefix. For example, the value
+
+ <screen>
+nixpkgs=/home/eelco/Dev/nixpkgs-branch:/etc/nixos</screen>
+
+ will cause Nix to search for
+ <literal><nixpkgs/<replaceable>path</replaceable>></literal> in
+ <filename>/home/eelco/Dev/nixpkgs-branch/<replaceable>path</replaceable></filename>
+ and
+ <filename>/etc/nixos/nixpkgs/<replaceable>path</replaceable></filename>.</para>
+
+ <para>If a path in the Nix search path starts with
+ <literal>http://</literal> or <literal>https://</literal>, it is
+ interpreted as the URL of a tarball that will be downloaded and
+ unpacked to a temporary location. The tarball must consist of a
+ single top-level directory. For example, setting
+ <envar>NIX_PATH</envar> to
+
+ <screen>
+nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-15.09.tar.gz</screen>
+
+ tells Nix to download the latest revision in the Nixpkgs/NixOS
+ 15.09 channel.</para>
+
+ <para>A following shorthand can be used to refer to the official channels:
+
+ <screen>nixpkgs=channel:nixos-15.09</screen>
+ </para>
+
+ <para>The search path can be extended using the <option linkend="opt-I">-I</option> option, which takes precedence over
+ <envar>NIX_PATH</envar>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_IGNORE_SYMLINK_STORE</envar></term>
+
+ <listitem>
+
+ <para>Normally, the Nix store directory (typically
+ <filename>/nix/store</filename>) is not allowed to contain any
+ symlink components. This is to prevent “impure” builds. Builders
+ sometimes “canonicalise” paths by resolving all symlink components.
+ Thus, builds on different machines (with
+ <filename>/nix/store</filename> resolving to different locations)
+ could yield different results. This is generally not a problem,
+ except when builds are deployed to machines where
+ <filename>/nix/store</filename> resolves differently. If you are
+ sure that you’re not going to do that, you can set
+ <envar>NIX_IGNORE_SYMLINK_STORE</envar> to <envar>1</envar>.</para>
+
+ <para>Note that if you’re symlinking the Nix store so that you can
+ put it on another file system than the root file system, on Linux
+ you’re better off using <literal>bind</literal> mount points, e.g.,
+
+ <screen>
+$ mkdir /nix
+$ mount -o bind /mnt/otherdisk/nix /nix</screen>
+
+ Consult the <citerefentry><refentrytitle>mount</refentrytitle>
+ <manvolnum>8</manvolnum></citerefentry> manual page for details.</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_STORE_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix store (default
+ <filename><replaceable>prefix</replaceable>/store</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_DATA_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix static data
+ directory (default
+ <filename><replaceable>prefix</replaceable>/share</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_LOG_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix log directory
+ (default <filename><replaceable>prefix</replaceable>/var/log/nix</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_STATE_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix state directory
+ (default <filename><replaceable>prefix</replaceable>/var/nix</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_CONF_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the system Nix configuration
+ directory (default
+ <filename><replaceable>prefix</replaceable>/etc/nix</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_USER_CONF_FILES</envar></term>
+
+ <listitem><para>Overrides the location of the user Nix configuration files
+ to load from (defaults to the XDG spec locations). The variable is treated
+ as a list separated by the <literal>:</literal> token.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>TMPDIR</envar></term>
+
+ <listitem><para>Use the specified directory to store temporary
+ files. In particular, this includes temporary build directories;
+ these can take up substantial amounts of disk space. The default is
+ <filename>/tmp</filename>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="envar-remote"><term><envar>NIX_REMOTE</envar></term>
+
+ <listitem><para>This variable should be set to
+ <literal>daemon</literal> if you want to use the Nix daemon to
+ execute Nix operations. This is necessary in <link linkend="ssec-multi-user">multi-user Nix installations</link>.
+ If the Nix daemon's Unix socket is at some non-standard path,
+ this variable should be set to <literal>unix://path/to/socket</literal>.
+ Otherwise, it should be left unset.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_SHOW_STATS</envar></term>
+
+ <listitem><para>If set to <literal>1</literal>, Nix will print some
+ evaluation statistics, such as the number of values
+ allocated.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_COUNT_CALLS</envar></term>
+
+ <listitem><para>If set to <literal>1</literal>, Nix will print how
+ often functions were called during Nix expression evaluation. This
+ is useful for profiling your Nix expressions.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>GC_INITIAL_HEAP_SIZE</envar></term>
+
+ <listitem><para>If Nix has been configured to use the Boehm garbage
+ collector, this variable sets the initial size of the heap in bytes.
+ It defaults to 384 MiB. Setting it to a low value reduces memory
+ consumption, but will increase runtime due to the overhead of
+ garbage collection.</para></listitem>
+
+</varlistentry>
+</variablelist>
+
+</refsection>
+
+
+</refentry>
+<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-nix-store">
+
+<refmeta>
+ <refentrytitle>nix-store</refentrytitle>
+ <manvolnum>1</manvolnum>
+ <refmiscinfo class="source">Nix</refmiscinfo>
+ <refmiscinfo class="version">3.0</refmiscinfo>
+</refmeta>
+
+<refnamediv>
+ <refname>nix-store</refname>
+ <refpurpose>manipulate or query the Nix store</refpurpose>
+</refnamediv>
+
+<refsynopsisdiv>
+ <cmdsynopsis>
+ <command>nix-store</command>
+ <arg xmlns="http://docbook.org/ns/docbook"><option>--help</option></arg><arg xmlns="http://docbook.org/ns/docbook"><option>--version</option></arg><arg xmlns="http://docbook.org/ns/docbook" rep="repeat">
+ <group choice="req">
+ <arg choice="plain"><option>--verbose</option></arg>
+ <arg choice="plain"><option>-v</option></arg>
+ </group>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <arg choice="plain"><option>--quiet</option></arg>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <option>--log-format</option>
+ <replaceable>format</replaceable>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <group choice="plain">
+ <arg choice="plain"><option>--no-build-output</option></arg>
+ <arg choice="plain"><option>-Q</option></arg>
+ </group>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <group choice="req">
+ <arg choice="plain"><option>--max-jobs</option></arg>
+ <arg choice="plain"><option>-j</option></arg>
+ </group>
+ <replaceable>number</replaceable>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <option>--cores</option>
+ <replaceable>number</replaceable>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <option>--max-silent-time</option>
+ <replaceable>number</replaceable>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <option>--timeout</option>
+ <replaceable>number</replaceable>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <group choice="plain">
+ <arg choice="plain"><option>--keep-going</option></arg>
+ <arg choice="plain"><option>-k</option></arg>
+ </group>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <group choice="plain">
+ <arg choice="plain"><option>--keep-failed</option></arg>
+ <arg choice="plain"><option>-K</option></arg>
+ </group>
+</arg><arg xmlns="http://docbook.org/ns/docbook"><option>--fallback</option></arg><arg xmlns="http://docbook.org/ns/docbook"><option>--readonly-mode</option></arg><arg xmlns="http://docbook.org/ns/docbook">
+ <option>-I</option>
+ <replaceable>path</replaceable>
+</arg><arg xmlns="http://docbook.org/ns/docbook">
+ <option>--option</option>
+ <replaceable>name</replaceable>
+ <replaceable>value</replaceable>
+</arg><sbr xmlns="http://docbook.org/ns/docbook"/>
+ <arg><option>--add-root</option> <replaceable>path</replaceable></arg>
+ <arg><option>--indirect</option></arg>
+ <arg choice="plain"><replaceable>operation</replaceable></arg>
+ <arg rep="repeat"><replaceable>options</replaceable></arg>
+ <arg rep="repeat"><replaceable>arguments</replaceable></arg>
+ </cmdsynopsis>
+</refsynopsisdiv>
+
+
+<refsection><title>Description</title>
+
+<para>The command <command>nix-store</command> performs primitive
+operations on the Nix store. You generally do not need to run this
+command manually.</para>
+
+<para><command>nix-store</command> takes exactly one
+<emphasis>operation</emphasis> flag which indicates the subcommand to
+be performed. These are documented below.</para>
+
+</refsection>
+
+
+
+<!--######################################################################-->
+
+<refsection><title>Common options</title>
+
+<para>This section lists the options that are common to all
+operations. These options are allowed for every subcommand, though
+they may not always have an effect. <phrase condition="manual">See
+also <xref linkend="sec-common-options"/> for a list of common
+options.</phrase></para>
+
+<variablelist>
+
+ <varlistentry xml:id="opt-add-root"><term><option>--add-root</option> <replaceable>path</replaceable></term>
+
+ <listitem><para>Causes the result of a realisation
+ (<option>--realise</option> and <option>--force-realise</option>)
+ to be registered as a root of the garbage collector<phrase condition="manual"> (see <xref linkend="ssec-gc-roots"/>)</phrase>. The root is stored in
+ <replaceable>path</replaceable>, which must be inside a directory
+ that is scanned for roots by the garbage collector (i.e.,
+ typically in a subdirectory of
+ <filename>/nix/var/nix/gcroots/</filename>)
+ <emphasis>unless</emphasis> the <option>--indirect</option> flag
+ is used.</para>
+
+ <para>If there are multiple results, then multiple symlinks will
+ be created by sequentially numbering symlinks beyond the first one
+ (e.g., <filename>foo</filename>, <filename>foo-2</filename>,
+ <filename>foo-3</filename>, and so on).</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--indirect</option></term>
+
+ <listitem>
+
+ <para>In conjunction with <option>--add-root</option>, this option
+ allows roots to be stored <emphasis>outside</emphasis> of the GC
+ roots directory. This is useful for commands such as
+ <command>nix-build</command> that place a symlink to the build
+ result in the current directory; such a build result should not be
+ garbage-collected unless the symlink is removed.</para>
+
+ <para>The <option>--indirect</option> flag causes a uniquely named
+ symlink to <replaceable>path</replaceable> to be stored in
+ <filename>/nix/var/nix/gcroots/auto/</filename>. For instance,
+
+ <screen>
+$ nix-store --add-root /home/eelco/bla/result --indirect -r <replaceable>...</replaceable>
+
+$ ls -l /nix/var/nix/gcroots/auto
+lrwxrwxrwx 1 ... 2005-03-13 21:10 dn54lcypm8f8... -> /home/eelco/bla/result
+
+$ ls -l /home/eelco/bla/result
+lrwxrwxrwx 1 ... 2005-03-13 21:10 /home/eelco/bla/result -> /nix/store/1r11343n6qd4...-f-spot-0.0.10</screen>
+
+ Thus, when <filename>/home/eelco/bla/result</filename> is removed,
+ the GC root in the <filename>auto</filename> directory becomes a
+ dangling symlink and will be ignored by the collector.</para>
+
+ <warning><para>Note that it is not possible to move or rename
+ indirect GC roots, since the symlink in the
+ <filename>auto</filename> directory will still point to the old
+ location.</para></warning>
+
+ </listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+<variablelist condition="manpage">
+ <varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--help</option></term>
+
+ <listitem><para>Prints out a summary of the command syntax and
+ exits.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--version</option></term>
+
+ <listitem><para>Prints out the Nix version number on standard output
+ and exits.</para></listitem>
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--verbose</option> / <option>-v</option></term>
+
+ <listitem>
+
+ <para>Increases the level of verbosity of diagnostic messages
+ printed on standard error. For each Nix operation, the information
+ printed on standard output is well-defined; any diagnostic
+ information is printed on standard error, never on standard
+ output.</para>
+
+ <para>This option may be specified repeatedly. Currently, the
+ following verbosity levels exist:</para>
+
+ <variablelist>
+
+ <varlistentry><term>0</term>
+ <listitem><para>“Errors only”: only print messages
+ explaining why the Nix invocation failed.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>1</term>
+ <listitem><para>“Informational”: print
+ <emphasis>useful</emphasis> messages about what Nix is doing.
+ This is the default.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>2</term>
+ <listitem><para>“Talkative”: print more informational
+ messages.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>3</term>
+ <listitem><para>“Chatty”: print even more
+ informational messages.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>4</term>
+ <listitem><para>“Debug”: print debug
+ information.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>5</term>
+ <listitem><para>“Vomit”: print vast amounts of debug
+ information.</para></listitem>
+ </varlistentry>
+
+ </variablelist>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--quiet</option></term>
+
+ <listitem>
+
+ <para>Decreases the level of verbosity of diagnostic messages
+ printed on standard error. This is the inverse option to
+ <option>-v</option> / <option>--verbose</option>.
+ </para>
+
+ <para>This option may be specified repeatedly. See the previous
+ verbosity levels list.</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-log-format"><term><option>--log-format</option> <replaceable>format</replaceable></term>
+
+ <listitem>
+
+ <para>This option can be used to change the output of the log format, with
+ <replaceable>format</replaceable> being one of:</para>
+
+ <variablelist>
+
+ <varlistentry><term>raw</term>
+ <listitem><para>This is the raw format, as outputted by nix-build.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>internal-json</term>
+ <listitem><para>Outputs the logs in a structured manner. NOTE: the json schema is not guarantees to be stable between releases.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>bar</term>
+ <listitem><para>Only display a progress bar during the builds.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>bar-with-logs</term>
+ <listitem><para>Display the raw logs, with the progress bar at the bottom.</para></listitem>
+ </varlistentry>
+
+ </variablelist>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--no-build-output</option> / <option>-Q</option></term>
+
+ <listitem><para>By default, output written by builders to standard
+ output and standard error is echoed to the Nix command's standard
+ error. This option suppresses this behaviour. Note that the
+ builder's standard output and error are always written to a log file
+ in
+ <filename><replaceable>prefix</replaceable>/nix/var/log/nix</filename>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-max-jobs"><term><option>--max-jobs</option> / <option>-j</option>
+<replaceable>number</replaceable></term>
+
+ <listitem>
+
+ <para>Sets the maximum number of build jobs that Nix will
+ perform in parallel to the specified number. Specify
+ <literal>auto</literal> to use the number of CPUs in the system.
+ The default is specified by the <link linkend="conf-max-jobs"><literal>max-jobs</literal></link>
+ configuration setting, which itself defaults to
+ <literal>1</literal>. A higher value is useful on SMP systems or to
+ exploit I/O latency.</para>
+
+ <para> Setting it to <literal>0</literal> disallows building on the local
+ machine, which is useful when you want builds to happen only on remote
+ builders.</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-cores"><term><option>--cores</option></term>
+
+ <listitem><para>Sets the value of the <envar>NIX_BUILD_CORES</envar>
+ environment variable in the invocation of builders. Builders can
+ use this variable at their discretion to control the maximum amount
+ of parallelism. For instance, in Nixpkgs, if the derivation
+ attribute <varname>enableParallelBuilding</varname> is set to
+ <literal>true</literal>, the builder passes the
+ <option>-j<replaceable>N</replaceable></option> flag to GNU Make.
+ It defaults to the value of the <link linkend="conf-cores"><literal>cores</literal></link>
+ configuration setting, if set, or <literal>1</literal> otherwise.
+ The value <literal>0</literal> means that the builder should use all
+ available CPU cores in the system.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-max-silent-time"><term><option>--max-silent-time</option></term>
+
+ <listitem><para>Sets the maximum number of seconds that a builder
+ can go without producing any data on standard output or standard
+ error. The default is specified by the <link linkend="conf-max-silent-time"><literal>max-silent-time</literal></link>
+ configuration setting. <literal>0</literal> means no
+ time-out.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-timeout"><term><option>--timeout</option></term>
+
+ <listitem><para>Sets the maximum number of seconds that a builder
+ can run. The default is specified by the <link linkend="conf-timeout"><literal>timeout</literal></link>
+ configuration setting. <literal>0</literal> means no
+ timeout.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--keep-going</option> / <option>-k</option></term>
+
+ <listitem><para>Keep going in case of failed builds, to the
+ greatest extent possible. That is, if building an input of some
+ derivation fails, Nix will still build the other inputs, but not the
+ derivation itself. Without this option, Nix stops if any build
+ fails (except for builds of substitutes), possibly killing builds in
+ progress (in case of parallel or distributed builds).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--keep-failed</option> / <option>-K</option></term>
+
+ <listitem><para>Specifies that in case of a build failure, the
+ temporary directory (usually in <filename>/tmp</filename>) in which
+ the build takes place should not be deleted. The path of the build
+ directory is printed as an informational message.
+ </para>
+ </listitem>
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--fallback</option></term>
+
+ <listitem>
+
+ <para>Whenever Nix attempts to build a derivation for which
+ substitutes are known for each output path, but realising the output
+ paths through the substitutes fails, fall back on building the
+ derivation.</para>
+
+ <para>The most common scenario in which this is useful is when we
+ have registered substitutes in order to perform binary distribution
+ from, say, a network repository. If the repository is down, the
+ realisation of the derivation will fail. When this option is
+ specified, Nix will build the derivation instead. Thus,
+ installation from binaries falls back on installation from source.
+ This option is not the default since it is generally not desirable
+ for a transient failure in obtaining the substitutes to lead to a
+ full build from source (with the related consumption of
+ resources).</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--no-build-hook</option></term>
+
+ <listitem>
+
+ <para>Disables the build hook mechanism. This allows to ignore remote
+ builders if they are setup on the machine.</para>
+
+ <para>It's useful in cases where the bandwidth between the client and the
+ remote builder is too low. In that case it can take more time to upload the
+ sources to the remote builder and fetch back the result than to do the
+ computation locally.</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--readonly-mode</option></term>
+
+ <listitem><para>When this option is used, no attempt is made to open
+ the Nix database. Most Nix operations do need database access, so
+ those operations will fail.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--arg</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
+
+ <listitem><para>This option is accepted by
+ <command>nix-env</command>, <command>nix-instantiate</command>,
+ <command>nix-shell</command> and <command>nix-build</command>.
+ When evaluating Nix expressions, the expression evaluator will
+ automatically try to call functions that
+ it encounters. It can automatically call functions for which every
+ argument has a <link linkend="ss-functions">default value</link>
+ (e.g., <literal>{ <replaceable>argName</replaceable> ?
+ <replaceable>defaultValue</replaceable> }:
+ <replaceable>...</replaceable></literal>). With
+ <option>--arg</option>, you can also call functions that have
+ arguments without a default value (or override a default value).
+ That is, if the evaluator encounters a function with an argument
+ named <replaceable>name</replaceable>, it will call it with value
+ <replaceable>value</replaceable>.</para>
+
+ <para>For instance, the top-level <literal>default.nix</literal> in
+ Nixpkgs is actually a function:
+
+<programlisting>
+{ # The system (e.g., `i686-linux') for which to build the packages.
+ system ? builtins.currentSystem
+ <replaceable>...</replaceable>
+}: <replaceable>...</replaceable></programlisting>
+
+ So if you call this Nix expression (e.g., when you do
+ <literal>nix-env -i <replaceable>pkgname</replaceable></literal>),
+ the function will be called automatically using the value <link linkend="builtin-currentSystem"><literal>builtins.currentSystem</literal></link>
+ for the <literal>system</literal> argument. You can override this
+ using <option>--arg</option>, e.g., <literal>nix-env -i
+ <replaceable>pkgname</replaceable> --arg system
+ \"i686-freebsd\"</literal>. (Note that since the argument is a Nix
+ string literal, you have to escape the quotes.)</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--argstr</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
+
+ <listitem><para>This option is like <option>--arg</option>, only the
+ value is not a Nix expression but a string. So instead of
+ <literal>--arg system \"i686-linux\"</literal> (the outer quotes are
+ to keep the shell happy) you can say <literal>--argstr system
+ i686-linux</literal>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-attr"><term><option>--attr</option> / <option>-A</option>
+<replaceable>attrPath</replaceable></term>
+
+ <listitem><para>Select an attribute from the top-level Nix
+ expression being evaluated. (<command>nix-env</command>,
+ <command>nix-instantiate</command>, <command>nix-build</command> and
+ <command>nix-shell</command> only.) The <emphasis>attribute
+ path</emphasis> <replaceable>attrPath</replaceable> is a sequence of
+ attribute names separated by dots. For instance, given a top-level
+ Nix expression <replaceable>e</replaceable>, the attribute path
+ <literal>xorg.xorgserver</literal> would cause the expression
+ <literal><replaceable>e</replaceable>.xorg.xorgserver</literal> to
+ be used. See <link linkend="refsec-nix-env-install-examples"><command>nix-env
+ --install</command></link> for some concrete examples.</para>
+
+ <para>In addition to attribute names, you can also specify array
+ indices. For instance, the attribute path
+ <literal>foo.3.bar</literal> selects the <literal>bar</literal>
+ attribute of the fourth element of the array in the
+ <literal>foo</literal> attribute of the top-level
+ expression.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--expr</option> / <option>-E</option></term>
+
+ <listitem><para>Interpret the command line arguments as a list of
+ Nix expressions to be parsed and evaluated, rather than as a list
+ of file names of Nix expressions.
+ (<command>nix-instantiate</command>, <command>nix-build</command>
+ and <command>nix-shell</command> only.)</para>
+
+ <para>For <command>nix-shell</command>, this option is commonly used
+ to give you a shell in which you can build the packages returned
+ by the expression. If you want to get a shell which contain the
+ <emphasis>built</emphasis> packages ready for use, give your
+ expression to the <command>nix-shell -p</command> convenience flag
+ instead.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-I"><term><option>-I</option> <replaceable>path</replaceable></term>
+
+ <listitem><para>Add a path to the Nix expression search path. This
+ option may be given multiple times. See the <envar linkend="env-NIX_PATH">NIX_PATH</envar> environment variable for
+ information on the semantics of the Nix search path. Paths added
+ through <option>-I</option> take precedence over
+ <envar>NIX_PATH</envar>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--option</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
+
+ <listitem><para>Set the Nix configuration option
+ <replaceable>name</replaceable> to <replaceable>value</replaceable>.
+ This overrides settings in the Nix configuration file (see
+ <citerefentry><refentrytitle>nix.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--repair</option></term>
+
+ <listitem><para>Fix corrupted or missing store paths by
+ redownloading or rebuilding them. Note that this is slow because it
+ requires computing a cryptographic hash of the contents of every
+ path in the closure of the build. Also note the warning under
+ <command>nix-store --repair-path</command>.</para></listitem>
+
+</varlistentry>
+</variablelist>
+
+</refsection>
+
+
+
+<!--######################################################################-->
+
+<refsection xml:id="rsec-nix-store-realise"><title>Operation <option>--realise</option></title>
+
+<refsection><title>Synopsis</title>
+
+<cmdsynopsis>
+ <command>nix-store</command>
+ <group choice="req">
+ <arg choice="plain"><option>--realise</option></arg>
+ <arg choice="plain"><option>-r</option></arg>
+ </group>
+ <arg choice="plain" rep="repeat"><replaceable>paths</replaceable></arg>
+ <arg><option>--dry-run</option></arg>
+</cmdsynopsis>
+
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>The operation <option>--realise</option> essentially “builds”
+the specified store paths. Realisation is a somewhat overloaded term:
+
+<itemizedlist>
+
+ <listitem><para>If the store path is a
+ <emphasis>derivation</emphasis>, realisation ensures that the output
+ paths of the derivation are <link linkend="gloss-validity">valid</link> (i.e., the output path and its
+ closure exist in the file system). This can be done in several
+ ways. First, it is possible that the outputs are already valid, in
+ which case we are done immediately. Otherwise, there may be <link linkend="gloss-substitute">substitutes</link> that produce the
+ outputs (e.g., by downloading them). Finally, the outputs can be
+ produced by performing the build action described by the
+ derivation.</para></listitem>
+
+ <listitem><para>If the store path is not a derivation, realisation
+ ensures that the specified path is valid (i.e., it and its closure
+ exist in the file system). If the path is already valid, we are
+ done immediately. Otherwise, the path and any missing paths in its
+ closure may be produced through substitutes. If there are no
+ (successful) subsitutes, realisation fails.</para></listitem>
+
+</itemizedlist>
+
+</para>
+
+<para>The output path of each derivation is printed on standard
+output. (For non-derivations argument, the argument itself is
+printed.)</para>
+
+<para>The following flags are available:</para>
+
+<variablelist>
+
+ <varlistentry><term><option>--dry-run</option></term>
+
+ <listitem><para>Print on standard error a description of what
+ packages would be built or downloaded, without actually performing
+ the operation.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--ignore-unknown</option></term>
+
+ <listitem><para>If a non-derivation path does not have a
+ substitute, then silently ignore it.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--check</option></term>
+
+ <listitem><para>This option allows you to check whether a
+ derivation is deterministic. It rebuilds the specified derivation
+ and checks whether the result is bitwise-identical with the
+ existing outputs, printing an error if that’s not the case. The
+ outputs of the specified derivation must already exist. When used
+ with <option>-K</option>, if an output path is not identical to
+ the corresponding output from the previous build, the new output
+ path is left in
+ <filename>/nix/store/<replaceable>name</replaceable>.check.</filename></para>
+
+ <para>See also the <option>build-repeat</option> configuration
+ option, which repeats a derivation a number of times and prevents
+ its outputs from being registered as “valid” in the Nix store
+ unless they are identical.</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+<para>Special exit codes:</para>
+
+<variablelist>
+
+ <varlistentry><term><literal>100</literal></term>
+ <listitem><para>Generic build failure, the builder process
+ returned with a non-zero exit code.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><literal>101</literal></term>
+ <listitem><para>Build timeout, the build was aborted because it
+ did not complete within the specified <link linkend="conf-timeout"><literal>timeout</literal></link>.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><literal>102</literal></term>
+ <listitem><para>Hash mismatch, the build output was rejected
+ because it does not match the specified <link linkend="fixed-output-drvs"><varname>outputHash</varname></link>.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry><term><literal>104</literal></term>
+ <listitem><para>Not deterministic, the build succeeded in check
+ mode but the resulting output is not binary reproducable.</para>
+ </listitem>
+ </varlistentry>
+
+</variablelist>
+
+<para>With the <option>--keep-going</option> flag it's possible for
+multiple failures to occur, in this case the 1xx status codes are or combined
+using binary or. <screen>
+1100100
+ ^^^^
+ |||`- timeout
+ ||`-- output hash mismatch
+ |`--- build failure
+ `---- not deterministic
+</screen></para>
+
+</refsection>
+
+
+<refsection><title>Examples</title>
+
+<para>This operation is typically used to build store derivations
+produced by <link linkend="sec-nix-instantiate"><command>nix-instantiate</command></link>:
+
+<screen>
+$ nix-store -r $(nix-instantiate ./test.nix)
+/nix/store/31axcgrlbfsxzmfff1gyj1bf62hvkby2-aterm-2.3.1</screen>
+
+This is essentially what <link linkend="sec-nix-build"><command>nix-build</command></link> does.</para>
+
+<para>To test whether a previously-built derivation is deterministic:
+
+<screen>
+$ nix-build '<nixpkgs>' -A hello --check -K
+</screen>
+
+</para>
+
+</refsection>
+
+
+</refsection>
+
+
+
+<!--######################################################################-->
+
+<refsection xml:id="rsec-nix-store-serve"><title>Operation <option>--serve</option></title>
+
+<refsection><title>Synopsis</title>
+
+<cmdsynopsis>
+ <command>nix-store</command>
+ <arg choice="plain"><option>--serve</option></arg>
+ <arg><option>--write</option></arg>
+</cmdsynopsis>
+
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>The operation <option>--serve</option> provides access to
+the Nix store over stdin and stdout, and is intended to be used
+as a means of providing Nix store access to a restricted ssh user.
+</para>
+
+<para>The following flags are available:</para>
+
+<variablelist>
+
+ <varlistentry><term><option>--write</option></term>
+
+ <listitem><para>Allow the connected client to request the realization
+ of derivations. In effect, this can be used to make the host act
+ as a remote builder.</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+</refsection>
+
+
+<refsection><title>Examples</title>
+
+<para>To turn a host into a build server, the
+<filename>authorized_keys</filename> file can be used to provide build
+access to a given SSH public key:
+
+<screen>
+$ cat <<EOF >>/root/.ssh/authorized_keys
+command="nice -n20 nix-store --serve --write" ssh-rsa AAAAB3NzaC1yc2EAAAA...
+EOF
+</screen>
+
+</para>
+
+</refsection>
+
+
+</refsection>
+
+
+
+<!--######################################################################-->
+
+<refsection xml:id="rsec-nix-store-gc"><title>Operation <option>--gc</option></title>
+
+<refsection><title>Synopsis</title>
+
+<cmdsynopsis>
+ <command>nix-store</command>
+ <arg choice="plain"><option>--gc</option></arg>
+ <group>
+ <arg choice="plain"><option>--print-roots</option></arg>
+ <arg choice="plain"><option>--print-live</option></arg>
+ <arg choice="plain"><option>--print-dead</option></arg>
+ </group>
+ <arg><option>--max-freed</option> <replaceable>bytes</replaceable></arg>
+</cmdsynopsis>
+
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>Without additional flags, the operation <option>--gc</option>
+performs a garbage collection on the Nix store. That is, all paths in
+the Nix store not reachable via file system references from a set of
+“roots”, are deleted.</para>
+
+<para>The following suboperations may be specified:</para>
+
+<variablelist>
+
+ <varlistentry><term><option>--print-roots</option></term>
+
+ <listitem><para>This operation prints on standard output the set
+ of roots used by the garbage collector. What constitutes a root
+ is described in <xref linkend="ssec-gc-roots"/>.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--print-live</option></term>
+
+ <listitem><para>This operation prints on standard output the set
+ of “live” store paths, which are all the store paths reachable
+ from the roots. Live paths should never be deleted, since that
+ would break consistency — it would become possible that
+ applications are installed that reference things that are no
+ longer present in the store.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--print-dead</option></term>
+
+ <listitem><para>This operation prints out on standard output the
+ set of “dead” store paths, which is just the opposite of the set
+ of live paths: any path in the store that is not live (with
+ respect to the roots) is dead.</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+<para>By default, all unreachable paths are deleted. The following
+options control what gets deleted and in what order:
+
+<variablelist>
+
+ <varlistentry><term><option>--max-freed</option> <replaceable>bytes</replaceable></term>
+
+ <listitem><para>Keep deleting paths until at least
+ <replaceable>bytes</replaceable> bytes have been deleted, then
+ stop. The argument <replaceable>bytes</replaceable> can be
+ followed by the multiplicative suffix <literal>K</literal>,
+ <literal>M</literal>, <literal>G</literal> or
+ <literal>T</literal>, denoting KiB, MiB, GiB or TiB
+ units.</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+</para>
+
+<para>The behaviour of the collector is also influenced by the <link linkend="conf-keep-outputs"><literal>keep-outputs</literal></link>
+and <link linkend="conf-keep-derivations"><literal>keep-derivations</literal></link>
+variables in the Nix configuration file.</para>
+
+<para>By default, the collector prints the total number of freed bytes
+when it finishes (or when it is interrupted). With
+<option>--print-dead</option>, it prints the number of bytes that would
+be freed.</para>
+
+</refsection>
+
+
+<refsection><title>Examples</title>
+
+<para>To delete all unreachable paths, just do:
+
+<screen>
+$ nix-store --gc
+deleting `/nix/store/kq82idx6g0nyzsp2s14gfsc38npai7lf-cairo-1.0.4.tar.gz.drv'
+<replaceable>...</replaceable>
+8825586 bytes freed (8.42 MiB)</screen>
+
+</para>
+
+<para>To delete at least 100 MiBs of unreachable paths:
+
+<screen>
+$ nix-store --gc --max-freed $((100 * 1024 * 1024))</screen>
+
+</para>
+
+</refsection>
+
+
+</refsection>
+
+
+
+<!--######################################################################-->
+
+<refsection><title>Operation <option>--delete</option></title>
+
+<refsection><title>Synopsis</title>
+
+<cmdsynopsis>
+ <command>nix-store</command>
+ <arg choice="plain"><option>--delete</option></arg>
+ <arg><option>--ignore-liveness</option></arg>
+ <arg choice="plain" rep="repeat"><replaceable>paths</replaceable></arg>
+</cmdsynopsis>
+
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>The operation <option>--delete</option> deletes the store paths
+<replaceable>paths</replaceable> from the Nix store, but only if it is
+safe to do so; that is, when the path is not reachable from a root of
+the garbage collector. This means that you can only delete paths that
+would also be deleted by <literal>nix-store --gc</literal>. Thus,
+<literal>--delete</literal> is a more targeted version of
+<literal>--gc</literal>.</para>
+
+<para>With the option <option>--ignore-liveness</option>, reachability
+from the roots is ignored. However, the path still won’t be deleted
+if there are other paths in the store that refer to it (i.e., depend
+on it).</para>
+
+</refsection>
+
+<refsection><title>Example</title>
+
+<screen>
+$ nix-store --delete /nix/store/zq0h41l75vlb4z45kzgjjmsjxvcv1qk7-mesa-6.4
+0 bytes freed (0.00 MiB)
+error: cannot delete path `/nix/store/zq0h41l75vlb4z45kzgjjmsjxvcv1qk7-mesa-6.4' since it is still alive</screen>
+
+</refsection>
+
+</refsection>
+
+
+
+<!--######################################################################-->
+
+<refsection xml:id="refsec-nix-store-query"><title>Operation <option>--query</option></title>
+
+<refsection><title>Synopsis</title>
+
+<cmdsynopsis>
+ <command>nix-store</command>
+ <group choice="req">
+ <arg choice="plain"><option>--query</option></arg>
+ <arg choice="plain"><option>-q</option></arg>
+ </group>
+ <group choice="req">
+ <arg choice="plain"><option>--outputs</option></arg>
+ <arg choice="plain"><option>--requisites</option></arg>
+ <arg choice="plain"><option>-R</option></arg>
+ <arg choice="plain"><option>--references</option></arg>
+ <arg choice="plain"><option>--referrers</option></arg>
+ <arg choice="plain"><option>--referrers-closure</option></arg>
+ <arg choice="plain"><option>--deriver</option></arg>
+ <arg choice="plain"><option>-d</option></arg>
+ <arg choice="plain"><option>--graph</option></arg>
+ <arg choice="plain"><option>--tree</option></arg>
+ <arg choice="plain"><option>--binding</option> <replaceable>name</replaceable></arg>
+ <arg choice="plain"><option>-b</option> <replaceable>name</replaceable></arg>
+ <arg choice="plain"><option>--hash</option></arg>
+ <arg choice="plain"><option>--size</option></arg>
+ <arg choice="plain"><option>--roots</option></arg>
+ </group>
+ <arg><option>--use-output</option></arg>
+ <arg><option>-u</option></arg>
+ <arg><option>--force-realise</option></arg>
+ <arg><option>-f</option></arg>
+ <arg choice="plain" rep="repeat"><replaceable>paths</replaceable></arg>
+</cmdsynopsis>
+
+</refsection>
+
+
+<refsection><title>Description</title>
+
+<para>The operation <option>--query</option> displays various bits of
+information about the store paths . The queries are described below. At
+most one query can be specified. The default query is
+<option>--outputs</option>.</para>
+
+<para>The paths <replaceable>paths</replaceable> may also be symlinks
+from outside of the Nix store, to the Nix store. In that case, the
+query is applied to the target of the symlink.</para>
+
+
+</refsection>
+
+
+<refsection><title>Common query options</title>
+
+<variablelist>
+
+ <varlistentry><term><option>--use-output</option></term>
+ <term><option>-u</option></term>
+
+ <listitem><para>For each argument to the query that is a store
+ derivation, apply the query to the output path of the derivation
+ instead.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--force-realise</option></term>
+ <term><option>-f</option></term>
+
+ <listitem><para>Realise each argument to the query first (see
+ <link linkend="rsec-nix-store-realise"><command>nix-store
+ --realise</command></link>).</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+</refsection>
+
+
+<refsection xml:id="nixref-queries"><title>Queries</title>
+
+<variablelist>
+
+ <varlistentry><term><option>--outputs</option></term>
+
+ <listitem><para>Prints out the <link linkend="gloss-output-path">output paths</link> of the store
+ derivations <replaceable>paths</replaceable>. These are the paths
+ that will be produced when the derivation is
+ built.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--requisites</option></term>
+ <term><option>-R</option></term>
+
+ <listitem><para>Prints out the <link linkend="gloss-closure">closure</link> of the store path
+ <replaceable>paths</replaceable>.</para>
+
+ <para>This query has one option:</para>
+
+ <variablelist>
+
+ <varlistentry><term><option>--include-outputs</option></term>
+
+ <listitem><para>Also include the output path of store
+ derivations, and their closures.</para></listitem>
+
+ </varlistentry>
+
+ </variablelist>
+
+ <para>This query can be used to implement various kinds of
+ deployment. A <emphasis>source deployment</emphasis> is obtained
+ by distributing the closure of a store derivation. A
+ <emphasis>binary deployment</emphasis> is obtained by distributing
+ the closure of an output path. A <emphasis>cache
+ deployment</emphasis> (combined source/binary deployment,
+ including binaries of build-time-only dependencies) is obtained by
+ distributing the closure of a store derivation and specifying the
+ option <option>--include-outputs</option>.</para>
+
+ </listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--references</option></term>
+
+ <listitem><para>Prints the set of <link linkend="gloss-reference">references</link> of the store paths
+ <replaceable>paths</replaceable>, that is, their immediate
+ dependencies. (For <emphasis>all</emphasis> dependencies, use
+ <option>--requisites</option>.)</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--referrers</option></term>
+
+ <listitem><para>Prints the set of <emphasis>referrers</emphasis> of
+ the store paths <replaceable>paths</replaceable>, that is, the
+ store paths currently existing in the Nix store that refer to one
+ of <replaceable>paths</replaceable>. Note that contrary to the
+ references, the set of referrers is not constant; it can change as
+ store paths are added or removed.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--referrers-closure</option></term>
+
+ <listitem><para>Prints the closure of the set of store paths
+ <replaceable>paths</replaceable> under the referrers relation; that
+ is, all store paths that directly or indirectly refer to one of
+ <replaceable>paths</replaceable>. These are all the path currently
+ in the Nix store that are dependent on
+ <replaceable>paths</replaceable>.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--deriver</option></term>
+ <term><option>-d</option></term>
+
+ <listitem><para>Prints the <link linkend="gloss-deriver">deriver</link> of the store paths
+ <replaceable>paths</replaceable>. If the path has no deriver
+ (e.g., if it is a source file), or if the deriver is not known
+ (e.g., in the case of a binary-only deployment), the string
+ <literal>unknown-deriver</literal> is printed.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--graph</option></term>
+
+ <listitem><para>Prints the references graph of the store paths
+ <replaceable>paths</replaceable> in the format of the
+ <command>dot</command> tool of AT&T's <link xlink:href="http://www.graphviz.org/">Graphviz package</link>.
+ This can be used to visualise dependency graphs. To obtain a
+ build-time dependency graph, apply this to a store derivation. To
+ obtain a runtime dependency graph, apply it to an output
+ path.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--tree</option></term>
+
+ <listitem><para>Prints the references graph of the store paths
+ <replaceable>paths</replaceable> as a nested ASCII tree.
+ References are ordered by descending closure size; this tends to
+ flatten the tree, making it more readable. The query only
+ recurses into a store path when it is first encountered; this
+ prevents a blowup of the tree representation of the
+ graph.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--graphml</option></term>
+
+ <listitem><para>Prints the references graph of the store paths
+ <replaceable>paths</replaceable> in the <link xlink:href="http://graphml.graphdrawing.org/">GraphML</link> file format.
+ This can be used to visualise dependency graphs. To obtain a
+ build-time dependency graph, apply this to a store derivation. To
+ obtain a runtime dependency graph, apply it to an output
+ path.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--binding</option> <replaceable>name</replaceable></term>
+ <term><option>-b</option> <replaceable>name</replaceable></term>
+
+ <listitem><para>Prints the value of the attribute
+ <replaceable>name</replaceable> (i.e., environment variable) of
+ the store derivations <replaceable>paths</replaceable>. It is an
+ error for a derivation to not have the specified
+ attribute.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--hash</option></term>
+
+ <listitem><para>Prints the SHA-256 hash of the contents of the
+ store paths <replaceable>paths</replaceable> (that is, the hash of
+ the output of <command>nix-store --dump</command> on the given
+ paths). Since the hash is stored in the Nix database, this is a
+ fast operation.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--size</option></term>
+
+ <listitem><para>Prints the size in bytes of the contents of the
+ store paths <replaceable>paths</replaceable> — to be precise, the
+ size of the output of <command>nix-store --dump</command> on the
+ given paths. Note that the actual disk space required by the
+ store paths may be higher, especially on filesystems with large
+ cluster sizes.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--roots</option></term>
+
+ <listitem><para>Prints the garbage collector roots that point,
+ directly or indirectly, at the store paths
+ <replaceable>paths</replaceable>.</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+</refsection>
+
+
+<refsection><title>Examples</title>
+
+<para>Print the closure (runtime dependencies) of the
+<command>svn</command> program in the current user environment:
+
+<screen>
+$ nix-store -qR $(which svn)
+/nix/store/5mbglq5ldqld8sj57273aljwkfvj22mc-subversion-1.1.4
+/nix/store/9lz9yc6zgmc0vlqmn2ipcpkjlmbi51vv-glibc-2.3.4
+<replaceable>...</replaceable></screen>
+
+</para>
+
+<para>Print the build-time dependencies of <command>svn</command>:
+
+<screen>
+$ nix-store -qR $(nix-store -qd $(which svn))
+/nix/store/02iizgn86m42q905rddvg4ja975bk2i4-grep-2.5.1.tar.bz2.drv
+/nix/store/07a2bzxmzwz5hp58nf03pahrv2ygwgs3-gcc-wrapper.sh
+/nix/store/0ma7c9wsbaxahwwl04gbw3fcd806ski4-glibc-2.3.4.drv
+<replaceable>... lots of other paths ...</replaceable></screen>
+
+The difference with the previous example is that we ask the closure of
+the derivation (<option>-qd</option>), not the closure of the output
+path that contains <command>svn</command>.</para>
+
+<para>Show the build-time dependencies as a tree:
+
+<screen>
+$ nix-store -q --tree $(nix-store -qd $(which svn))
+/nix/store/7i5082kfb6yjbqdbiwdhhza0am2xvh6c-subversion-1.1.4.drv
++---/nix/store/d8afh10z72n8l1cr5w42366abiblgn54-builder.sh
++---/nix/store/fmzxmpjx2lh849ph0l36snfj9zdibw67-bash-3.0.drv
+| +---/nix/store/570hmhmx3v57605cqg9yfvvyh0nnb8k8-bash
+| +---/nix/store/p3srsbd8dx44v2pg6nbnszab5mcwx03v-builder.sh
+<replaceable>...</replaceable></screen>
+
+</para>
+
+<para>Show all paths that depend on the same OpenSSL library as
+<command>svn</command>:
+
+<screen>
+$ nix-store -q --referrers $(nix-store -q --binding openssl $(nix-store -qd $(which svn)))
+/nix/store/23ny9l9wixx21632y2wi4p585qhva1q8-sylpheed-1.0.0
+/nix/store/5mbglq5ldqld8sj57273aljwkfvj22mc-subversion-1.1.4
+/nix/store/dpmvp969yhdqs7lm2r1a3gng7pyq6vy4-subversion-1.1.3
+/nix/store/l51240xqsgg8a7yrbqdx1rfzyv6l26fx-lynx-2.8.5</screen>
+
+</para>
+
+<para>Show all paths that directly or indirectly depend on the Glibc
+(C library) used by <command>svn</command>:
+
+<screen>
+$ nix-store -q --referrers-closure $(ldd $(which svn) | grep /libc.so | awk '{print $3}')
+/nix/store/034a6h4vpz9kds5r6kzb9lhh81mscw43-libgnomeprintui-2.8.2
+/nix/store/15l3yi0d45prm7a82pcrknxdh6nzmxza-gawk-3.1.4
+<replaceable>...</replaceable></screen>
+
+Note that <command>ldd</command> is a command that prints out the
+dynamic libraries used by an ELF executable.</para>
+
+<para>Make a picture of the runtime dependency graph of the current
+user environment:
+
+<screen>
+$ nix-store -q --graph ~/.nix-profile | dot -Tps > graph.ps
+$ gv graph.ps</screen>
+
+</para>
+
+<para>Show every garbage collector root that points to a store path
+that depends on <command>svn</command>:
+
+<screen>
+$ nix-store -q --roots $(which svn)
+/nix/var/nix/profiles/default-81-link
+/nix/var/nix/profiles/default-82-link
+/nix/var/nix/profiles/per-user/eelco/profile-97-link
+</screen>
+
+</para>
+
+</refsection>
+
+
+</refsection>
+
+
+
+<!--######################################################################-->
+
+<!--
+<refsection xml:id="rsec-nix-store-reg-val"><title>Operation <option>-XXX-register-validity</option></title>
+
+<refsection><title>Synopsis</title>
+
+<cmdsynopsis>
+ <command>nix-store</command>
+ <arg choice='plain'><option>-XXX-register-validity</option></arg>
+</cmdsynopsis>
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>TODO</para>
+
+</refsection>
+
+</refsection>
+-->
+
+
+
+<!--######################################################################-->
+
+<refsection><title>Operation <option>--add</option></title>
+
+<refsection><title>Synopsis</title>
+
+<cmdsynopsis>
+ <command>nix-store</command>
+ <arg choice="plain"><option>--add</option></arg>
+ <arg choice="plain" rep="repeat"><replaceable>paths</replaceable></arg>
+</cmdsynopsis>
+
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>The operation <option>--add</option> adds the specified paths to
+the Nix store. It prints the resulting paths in the Nix store on
+standard output.</para>
+
+</refsection>
+
+<refsection><title>Example</title>
+
+<screen>
+$ nix-store --add ./foo.c
+/nix/store/m7lrha58ph6rcnv109yzx1nk1cj7k7zf-foo.c</screen>
+
+</refsection>
+
+</refsection>
+
+<!--######################################################################-->
+
+<refsection><title>Operation <option>--add-fixed</option></title>
+
+<refsection><title>Synopsis</title>
+
+<cmdsynopsis>
+ <command>nix-store</command>
+ <arg><option>--recursive</option></arg>
+ <arg choice="plain"><option>--add-fixed</option></arg>
+ <arg choice="plain"><replaceable>algorithm</replaceable></arg>
+ <arg choice="plain" rep="repeat"><replaceable>paths</replaceable></arg>
+</cmdsynopsis>
+
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>The operation <option>--add-fixed</option> adds the specified paths to
+the Nix store. Unlike <option>--add</option> paths are registered using the
+specified hashing algorithm, resulting in the same output path as a fixed-output
+derivation. This can be used for sources that are not available from a public
+url or broke since the download expression was written.
+</para>
+
+<para>This operation has the following options:
+
+<variablelist>
+
+ <varlistentry><term><option>--recursive</option></term>
+
+ <listitem><para>
+ Use recursive instead of flat hashing mode, used when adding directories
+ to the store.
+ </para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+</para>
+
+</refsection>
+
+<refsection><title>Example</title>
+
+<screen>
+$ nix-store --add-fixed sha256 ./hello-2.10.tar.gz
+/nix/store/3x7dwzq014bblazs7kq20p9hyzz0qh8g-hello-2.10.tar.gz</screen>
+
+</refsection>
+
+</refsection>
+
+
+
+<!--######################################################################-->
+
+<refsection xml:id="refsec-nix-store-verify"><title>Operation <option>--verify</option></title>
+
+<refsection>
+ <title>Synopsis</title>
+ <cmdsynopsis>
+ <command>nix-store</command>
+ <arg choice="plain"><option>--verify</option></arg>
+ <arg><option>--check-contents</option></arg>
+ <arg><option>--repair</option></arg>
+ </cmdsynopsis>
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>The operation <option>--verify</option> verifies the internal
+consistency of the Nix database, and the consistency between the Nix
+database and the Nix store. Any inconsistencies encountered are
+automatically repaired. Inconsistencies are generally the result of
+the Nix store or database being modified by non-Nix tools, or of bugs
+in Nix itself.</para>
+
+<para>This operation has the following options:
+
+<variablelist>
+
+ <varlistentry><term><option>--check-contents</option></term>
+
+ <listitem><para>Checks that the contents of every valid store path
+ has not been altered by computing a SHA-256 hash of the contents
+ and comparing it with the hash stored in the Nix database at build
+ time. Paths that have been modified are printed out. For large
+ stores, <option>--check-contents</option> is obviously quite
+ slow.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--repair</option></term>
+
+ <listitem><para>If any valid path is missing from the store, or
+ (if <option>--check-contents</option> is given) the contents of a
+ valid path has been modified, then try to repair the path by
+ redownloading it. See <command>nix-store --repair-path</command>
+ for details.</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+</para>
+
+</refsection>
+
+
+</refsection>
+
+
+<!--######################################################################-->
+
+<refsection><title>Operation <option>--verify-path</option></title>
+
+<refsection>
+ <title>Synopsis</title>
+ <cmdsynopsis>
+ <command>nix-store</command>
+ <arg choice="plain"><option>--verify-path</option></arg>
+ <arg choice="plain" rep="repeat"><replaceable>paths</replaceable></arg>
+ </cmdsynopsis>
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>The operation <option>--verify-path</option> compares the
+contents of the given store paths to their cryptographic hashes stored
+in Nix’s database. For every changed path, it prints a warning
+message. The exit status is 0 if no path has changed, and 1
+otherwise.</para>
+
+</refsection>
+
+<refsection><title>Example</title>
+
+<para>To verify the integrity of the <command>svn</command> command and all its dependencies:
+
+<screen>
+$ nix-store --verify-path $(nix-store -qR $(which svn))
+</screen>
+
+</para>
+
+</refsection>
+
+</refsection>
+
+
+<!--######################################################################-->
+
+<refsection><title>Operation <option>--repair-path</option></title>
+
+<refsection>
+ <title>Synopsis</title>
+ <cmdsynopsis>
+ <command>nix-store</command>
+ <arg choice="plain"><option>--repair-path</option></arg>
+ <arg choice="plain" rep="repeat"><replaceable>paths</replaceable></arg>
+ </cmdsynopsis>
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>The operation <option>--repair-path</option> attempts to
+“repair” the specified paths by redownloading them using the available
+substituters. If no substitutes are available, then repair is not
+possible.</para>
+
+<warning><para>During repair, there is a very small time window during
+which the old path (if it exists) is moved out of the way and replaced
+with the new path. If repair is interrupted in between, then the
+system may be left in a broken state (e.g., if the path contains a
+critical system component like the GNU C Library).</para></warning>
+
+</refsection>
+
+<refsection><title>Example</title>
+
+<screen>
+$ nix-store --verify-path /nix/store/dj7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13
+path `/nix/store/dj7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13' was modified!
+ expected hash `2db57715ae90b7e31ff1f2ecb8c12ec1cc43da920efcbe3b22763f36a1861588',
+ got `481c5aa5483ebc97c20457bb8bca24deea56550d3985cda0027f67fe54b808e4'
+
+$ nix-store --repair-path /nix/store/dj7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13
+fetching path `/nix/store/d7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13'...
+…
+</screen>
+
+</refsection>
+
+</refsection>
+
+
+<!--######################################################################-->
+
+<refsection xml:id="refsec-nix-store-dump"><title>Operation <option>--dump</option></title>
+
+<refsection>
+ <title>Synopsis</title>
+ <cmdsynopsis>
+ <command>nix-store</command>
+ <arg choice="plain"><option>--dump</option></arg>
+ <arg choice="plain"><replaceable>path</replaceable></arg>
+ </cmdsynopsis>
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>The operation <option>--dump</option> produces a NAR (Nix
+ARchive) file containing the contents of the file system tree rooted
+at <replaceable>path</replaceable>. The archive is written to
+standard output.</para>
+
+<para>A NAR archive is like a TAR or Zip archive, but it contains only
+the information that Nix considers important. For instance,
+timestamps are elided because all files in the Nix store have their
+timestamp set to 0 anyway. Likewise, all permissions are left out
+except for the execute bit, because all files in the Nix store have
+444 or 555 permission.</para>
+
+<para>Also, a NAR archive is <emphasis>canonical</emphasis>, meaning
+that “equal” paths always produce the same NAR archive. For instance,
+directory entries are always sorted so that the actual on-disk order
+doesn’t influence the result. This means that the cryptographic hash
+of a NAR dump of a path is usable as a fingerprint of the contents of
+the path. Indeed, the hashes of store paths stored in Nix’s database
+(see <link linkend="refsec-nix-store-query"><literal>nix-store -q
+--hash</literal></link>) are SHA-256 hashes of the NAR dump of each
+store path.</para>
+
+<para>NAR archives support filenames of unlimited length and 64-bit
+file sizes. They can contain regular files, directories, and symbolic
+links, but not other types of files (such as device nodes).</para>
+
+<para>A Nix archive can be unpacked using <literal>nix-store
+--restore</literal>.</para>
+
+</refsection>
+
+
+</refsection>
+
+
+<!--######################################################################-->
+
+<refsection><title>Operation <option>--restore</option></title>
+
+<refsection>
+ <title>Synopsis</title>
+ <cmdsynopsis>
+ <command>nix-store</command>
+ <arg choice="plain"><option>--restore</option></arg>
+ <arg choice="plain"><replaceable>path</replaceable></arg>
+ </cmdsynopsis>
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>The operation <option>--restore</option> unpacks a NAR archive
+to <replaceable>path</replaceable>, which must not already exist. The
+archive is read from standard input.</para>
+
+</refsection>
+
+
+</refsection>
+
+
+<!--######################################################################-->
+
+<refsection xml:id="refsec-nix-store-export"><title>Operation <option>--export</option></title>
+
+<refsection>
+ <title>Synopsis</title>
+ <cmdsynopsis>
+ <command>nix-store</command>
+ <arg choice="plain"><option>--export</option></arg>
+ <arg choice="plain" rep="repeat"><replaceable>paths</replaceable></arg>
+ </cmdsynopsis>
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>The operation <option>--export</option> writes a serialisation
+of the specified store paths to standard output in a format that can
+be imported into another Nix store with <command linkend="refsec-nix-store-import">nix-store --import</command>. This
+is like <command linkend="refsec-nix-store-dump">nix-store
+--dump</command>, except that the NAR archive produced by that command
+doesn’t contain the necessary meta-information to allow it to be
+imported into another Nix store (namely, the set of references of the
+path).</para>
+
+<para>This command does not produce a <emphasis>closure</emphasis> of
+the specified paths, so if a store path references other store paths
+that are missing in the target Nix store, the import will fail. To
+copy a whole closure, do something like:
+
+<screen>
+$ nix-store --export $(nix-store -qR <replaceable>paths</replaceable>) > out</screen>
+
+To import the whole closure again, run:
+
+<screen>
+$ nix-store --import < out</screen>
+
+</para>
+
+</refsection>
+
+
+</refsection>
+
+
+<!--######################################################################-->
+
+<refsection xml:id="refsec-nix-store-import"><title>Operation <option>--import</option></title>
+
+<refsection>
+ <title>Synopsis</title>
+ <cmdsynopsis>
+ <command>nix-store</command>
+ <arg choice="plain"><option>--import</option></arg>
+ </cmdsynopsis>
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>The operation <option>--import</option> reads a serialisation of
+a set of store paths produced by <command linkend="refsec-nix-store-export">nix-store --export</command> from
+standard input and adds those store paths to the Nix store. Paths
+that already exist in the Nix store are ignored. If a path refers to
+another path that doesn’t exist in the Nix store, the import
+fails.</para>
+
+</refsection>
+
+
+</refsection>
+
+
+<!--######################################################################-->
+
+<refsection><title>Operation <option>--optimise</option></title>
+
+<refsection>
+ <title>Synopsis</title>
+ <cmdsynopsis>
+ <command>nix-store</command>
+ <arg choice="plain"><option>--optimise</option></arg>
+ </cmdsynopsis>
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>The operation <option>--optimise</option> reduces Nix store disk
+space usage by finding identical files in the store and hard-linking
+them to each other. It typically reduces the size of the store by
+something like 25-35%. Only regular files and symlinks are
+hard-linked in this manner. Files are considered identical when they
+have the same NAR archive serialisation: that is, regular files must
+have the same contents and permission (executable or non-executable),
+and symlinks must have the same contents.</para>
+
+<para>After completion, or when the command is interrupted, a report
+on the achieved savings is printed on standard error.</para>
+
+<para>Use <option>-vv</option> or <option>-vvv</option> to get some
+progress indication.</para>
+
+</refsection>
+
+<refsection><title>Example</title>
+
+<screen>
+$ nix-store --optimise
+hashing files in `/nix/store/qhqx7l2f1kmwihc9bnxs7rc159hsxnf3-gcc-4.1.1'
+<replaceable>...</replaceable>
+541838819 bytes (516.74 MiB) freed by hard-linking 54143 files;
+there are 114486 files with equal contents out of 215894 files in total
+</screen>
+
+</refsection>
+
+
+</refsection>
+
+
+<!--######################################################################-->
+
+<refsection><title>Operation <option>--read-log</option></title>
+
+<refsection>
+ <title>Synopsis</title>
+ <cmdsynopsis>
+ <command>nix-store</command>
+ <group choice="req">
+ <arg choice="plain"><option>--read-log</option></arg>
+ <arg choice="plain"><option>-l</option></arg>
+ </group>
+ <arg choice="plain" rep="repeat"><replaceable>paths</replaceable></arg>
+ </cmdsynopsis>
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>The operation <option>--read-log</option> prints the build log
+of the specified store paths on standard output. The build log is
+whatever the builder of a derivation wrote to standard output and
+standard error. If a store path is not a derivation, the deriver of
+the store path is used.</para>
+
+<para>Build logs are kept in
+<filename>/nix/var/log/nix/drvs</filename>. However, there is no
+guarantee that a build log is available for any particular store path.
+For instance, if the path was downloaded as a pre-built binary through
+a substitute, then the log is unavailable.</para>
+
+</refsection>
+
+<refsection><title>Example</title>
+
+<screen>
+$ nix-store -l $(which ktorrent)
+building /nix/store/dhc73pvzpnzxhdgpimsd9sw39di66ph1-ktorrent-2.2.1
+unpacking sources
+unpacking source archive /nix/store/p8n1jpqs27mgkjw07pb5269717nzf5f8-ktorrent-2.2.1.tar.gz
+ktorrent-2.2.1/
+ktorrent-2.2.1/NEWS
+<replaceable>...</replaceable>
+</screen>
+
+</refsection>
+
+
+</refsection>
+
+
+<!--######################################################################-->
+
+<refsection><title>Operation <option>--dump-db</option></title>
+
+<refsection>
+ <title>Synopsis</title>
+ <cmdsynopsis>
+ <command>nix-store</command>
+ <arg choice="plain"><option>--dump-db</option></arg>
+ <arg rep="repeat"><replaceable>paths</replaceable></arg>
+ </cmdsynopsis>
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>The operation <option>--dump-db</option> writes a dump of the
+Nix database to standard output. It can be loaded into an empty Nix
+store using <option>--load-db</option>. This is useful for making
+backups and when migrating to different database schemas.</para>
+
+<para>By default, <option>--dump-db</option> will dump the entire Nix
+database. When one or more store paths is passed, only the subset of
+the Nix database for those store paths is dumped. As with
+<option>--export</option>, the user is responsible for passing all the
+store paths for a closure. See <option>--export</option> for an
+example.</para>
+
+</refsection>
+
+</refsection>
+
+
+<!--######################################################################-->
+
+<refsection><title>Operation <option>--load-db</option></title>
+
+<refsection>
+ <title>Synopsis</title>
+ <cmdsynopsis>
+ <command>nix-store</command>
+ <arg choice="plain"><option>--load-db</option></arg>
+ </cmdsynopsis>
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>The operation <option>--load-db</option> reads a dump of the Nix
+database created by <option>--dump-db</option> from standard input and
+loads it into the Nix database.</para>
+
+</refsection>
+
+</refsection>
+
+
+<!--######################################################################-->
+
+<refsection><title>Operation <option>--print-env</option></title>
+
+<refsection>
+ <title>Synopsis</title>
+ <cmdsynopsis>
+ <command>nix-store</command>
+ <arg choice="plain"><option>--print-env</option></arg>
+ <arg choice="plain"><replaceable>drvpath</replaceable></arg>
+ </cmdsynopsis>
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>The operation <option>--print-env</option> prints out the
+environment of a derivation in a format that can be evaluated by a
+shell. The command line arguments of the builder are placed in the
+variable <envar>_args</envar>.</para>
+
+</refsection>
+
+<refsection><title>Example</title>
+
+<screen>
+$ nix-store --print-env $(nix-instantiate '<nixpkgs>' -A firefox)
+<replaceable>…</replaceable>
+export src; src='/nix/store/plpj7qrwcz94z2psh6fchsi7s8yihc7k-firefox-12.0.source.tar.bz2'
+export stdenv; stdenv='/nix/store/7c8asx3yfrg5dg1gzhzyq2236zfgibnn-stdenv'
+export system; system='x86_64-linux'
+export _args; _args='-e /nix/store/9krlzvny65gdc8s7kpb6lkx8cd02c25c-default-builder.sh'
+</screen>
+
+</refsection>
+
+</refsection>
+
+
+<!--######################################################################-->
+
+<refsection xml:id="rsec-nix-store-generate-binary-cache-key"><title>Operation <option>--generate-binary-cache-key</option></title>
+
+<refsection>
+ <title>Synopsis</title>
+ <cmdsynopsis>
+ <command>nix-store</command>
+ <arg choice="plain">
+ <option>--generate-binary-cache-key</option>
+ <option>key-name</option>
+ <option>secret-key-file</option>
+ <option>public-key-file</option>
+ </arg>
+ </cmdsynopsis>
+</refsection>
+
+<refsection><title>Description</title>
+
+<para>This command generates an <link xlink:href="http://ed25519.cr.yp.to/">Ed25519 key pair</link> that can
+be used to create a signed binary cache. It takes three mandatory
+parameters:
+
+<orderedlist>
+
+ <listitem><para>A key name, such as
+ <literal>cache.example.org-1</literal>, that is used to look up keys
+ on the client when it verifies signatures. It can be anything, but
+ it’s suggested to use the host name of your cache
+ (e.g. <literal>cache.example.org</literal>) with a suffix denoting
+ the number of the key (to be incremented every time you need to
+ revoke a key).</para></listitem>
+
+ <listitem><para>The file name where the secret key is to be
+ stored.</para></listitem>
+
+ <listitem><para>The file name where the public key is to be
+ stored.</para></listitem>
+
+</orderedlist>
+
+</para>
+
+</refsection>
+
+</refsection>
+
+
+<!--######################################################################-->
+
+<refsection condition="manpage"><title>Environment variables</title>
+
+<variablelist>
+ <varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>IN_NIX_SHELL</envar></term>
+
+ <listitem><para>Indicator that tells if the current environment was set up by
+ <command>nix-shell</command>. Since Nix 2.0 the values are
+ <literal>"pure"</literal> and <literal>"impure"</literal></para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="env-NIX_PATH"><term><envar>NIX_PATH</envar></term>
+
+ <listitem>
+
+ <para>A colon-separated list of directories used to look up Nix
+ expressions enclosed in angle brackets (i.e.,
+ <literal><<replaceable>path</replaceable>></literal>). For
+ instance, the value
+
+ <screen>
+/home/eelco/Dev:/etc/nixos</screen>
+
+ will cause Nix to look for paths relative to
+ <filename>/home/eelco/Dev</filename> and
+ <filename>/etc/nixos</filename>, in this order. It is also
+ possible to match paths against a prefix. For example, the value
+
+ <screen>
+nixpkgs=/home/eelco/Dev/nixpkgs-branch:/etc/nixos</screen>
+
+ will cause Nix to search for
+ <literal><nixpkgs/<replaceable>path</replaceable>></literal> in
+ <filename>/home/eelco/Dev/nixpkgs-branch/<replaceable>path</replaceable></filename>
+ and
+ <filename>/etc/nixos/nixpkgs/<replaceable>path</replaceable></filename>.</para>
+
+ <para>If a path in the Nix search path starts with
+ <literal>http://</literal> or <literal>https://</literal>, it is
+ interpreted as the URL of a tarball that will be downloaded and
+ unpacked to a temporary location. The tarball must consist of a
+ single top-level directory. For example, setting
+ <envar>NIX_PATH</envar> to
+
+ <screen>
+nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-15.09.tar.gz</screen>
+
+ tells Nix to download the latest revision in the Nixpkgs/NixOS
+ 15.09 channel.</para>
+
+ <para>A following shorthand can be used to refer to the official channels:
+
+ <screen>nixpkgs=channel:nixos-15.09</screen>
+ </para>
+
+ <para>The search path can be extended using the <option linkend="opt-I">-I</option> option, which takes precedence over
+ <envar>NIX_PATH</envar>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_IGNORE_SYMLINK_STORE</envar></term>
+
+ <listitem>
+
+ <para>Normally, the Nix store directory (typically
+ <filename>/nix/store</filename>) is not allowed to contain any
+ symlink components. This is to prevent “impure” builds. Builders
+ sometimes “canonicalise” paths by resolving all symlink components.
+ Thus, builds on different machines (with
+ <filename>/nix/store</filename> resolving to different locations)
+ could yield different results. This is generally not a problem,
+ except when builds are deployed to machines where
+ <filename>/nix/store</filename> resolves differently. If you are
+ sure that you’re not going to do that, you can set
+ <envar>NIX_IGNORE_SYMLINK_STORE</envar> to <envar>1</envar>.</para>
+
+ <para>Note that if you’re symlinking the Nix store so that you can
+ put it on another file system than the root file system, on Linux
+ you’re better off using <literal>bind</literal> mount points, e.g.,
+
+ <screen>
+$ mkdir /nix
+$ mount -o bind /mnt/otherdisk/nix /nix</screen>
+
+ Consult the <citerefentry><refentrytitle>mount</refentrytitle>
+ <manvolnum>8</manvolnum></citerefentry> manual page for details.</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_STORE_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix store (default
+ <filename><replaceable>prefix</replaceable>/store</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_DATA_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix static data
+ directory (default
+ <filename><replaceable>prefix</replaceable>/share</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_LOG_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix log directory
+ (default <filename><replaceable>prefix</replaceable>/var/log/nix</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_STATE_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix state directory
+ (default <filename><replaceable>prefix</replaceable>/var/nix</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_CONF_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the system Nix configuration
+ directory (default
+ <filename><replaceable>prefix</replaceable>/etc/nix</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_USER_CONF_FILES</envar></term>
+
+ <listitem><para>Overrides the location of the user Nix configuration files
+ to load from (defaults to the XDG spec locations). The variable is treated
+ as a list separated by the <literal>:</literal> token.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>TMPDIR</envar></term>
+
+ <listitem><para>Use the specified directory to store temporary
+ files. In particular, this includes temporary build directories;
+ these can take up substantial amounts of disk space. The default is
+ <filename>/tmp</filename>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="envar-remote"><term><envar>NIX_REMOTE</envar></term>
+
+ <listitem><para>This variable should be set to
+ <literal>daemon</literal> if you want to use the Nix daemon to
+ execute Nix operations. This is necessary in <link linkend="ssec-multi-user">multi-user Nix installations</link>.
+ If the Nix daemon's Unix socket is at some non-standard path,
+ this variable should be set to <literal>unix://path/to/socket</literal>.
+ Otherwise, it should be left unset.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_SHOW_STATS</envar></term>
+
+ <listitem><para>If set to <literal>1</literal>, Nix will print some
+ evaluation statistics, such as the number of values
+ allocated.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_COUNT_CALLS</envar></term>
+
+ <listitem><para>If set to <literal>1</literal>, Nix will print how
+ often functions were called during Nix expression evaluation. This
+ is useful for profiling your Nix expressions.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>GC_INITIAL_HEAP_SIZE</envar></term>
+
+ <listitem><para>If Nix has been configured to use the Boehm garbage
+ collector, this variable sets the initial size of the heap in bytes.
+ It defaults to 384 MiB. Setting it to a low value reduces memory
+ consumption, but will increase runtime due to the overhead of
+ garbage collection.</para></listitem>
+
+</varlistentry>
+</variablelist>
+
+</refsection>
+
+
+</refentry>
+
+</chapter>
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-utilities">
+
+<title>Utilities</title>
+
+<para>This section lists utilities that you can use when you
+work with Nix.</para>
+
+<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-nix-channel">
+
+<refmeta>
+ <refentrytitle>nix-channel</refentrytitle>
+ <manvolnum>1</manvolnum>
+ <refmiscinfo class="source">Nix</refmiscinfo>
+ <refmiscinfo class="version">3.0</refmiscinfo>
+</refmeta>
+
+<refnamediv>
+ <refname>nix-channel</refname>
+ <refpurpose>manage Nix channels</refpurpose>
+</refnamediv>
+
+<refsynopsisdiv>
+ <cmdsynopsis>
+ <command>nix-channel</command>
+ <group choice="req">
+ <arg choice="plain"><option>--add</option> <replaceable>url</replaceable> <arg choice="opt"><replaceable>name</replaceable></arg></arg>
+ <arg choice="plain"><option>--remove</option> <replaceable>name</replaceable></arg>
+ <arg choice="plain"><option>--list</option></arg>
+ <arg choice="plain"><option>--update</option> <arg rep="repeat"><replaceable>names</replaceable></arg></arg>
+ <arg choice="plain"><option>--rollback</option> <arg choice="opt"><replaceable>generation</replaceable></arg></arg>
+ </group>
+ </cmdsynopsis>
+</refsynopsisdiv>
+
+<refsection><title>Description</title>
+
+<para>A Nix channel is a mechanism that allows you to automatically
+stay up-to-date with a set of pre-built Nix expressions. A Nix
+channel is just a URL that points to a place containing a set of Nix
+expressions. <phrase condition="manual">See also <xref linkend="sec-channels"/>.</phrase></para>
+
+<para>To see the list of official NixOS channels, visit <link xlink:href="https://nixos.org/channels"/>.</para>
+
+<para>This command has the following operations:
+
+<variablelist>
+
+ <varlistentry><term><option>--add</option> <replaceable>url</replaceable> [<replaceable>name</replaceable>]</term>
+
+ <listitem><para>Adds a channel named
+ <replaceable>name</replaceable> with URL
+ <replaceable>url</replaceable> to the list of subscribed channels.
+ If <replaceable>name</replaceable> is omitted, it defaults to the
+ last component of <replaceable>url</replaceable>, with the
+ suffixes <literal>-stable</literal> or
+ <literal>-unstable</literal> removed.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--remove</option> <replaceable>name</replaceable></term>
+
+ <listitem><para>Removes the channel named
+ <replaceable>name</replaceable> from the list of subscribed
+ channels.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--list</option></term>
+
+ <listitem><para>Prints the names and URLs of all subscribed
+ channels on standard output.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--update</option> [<replaceable>names</replaceable>…]</term>
+
+ <listitem><para>Downloads the Nix expressions of all subscribed
+ channels (or only those included in
+ <replaceable>names</replaceable> if specified) and makes them the
+ default for <command>nix-env</command> operations (by symlinking
+ them from the directory
+ <filename>~/.nix-defexpr</filename>).</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--rollback</option> [<replaceable>generation</replaceable>]</term>
+
+ <listitem><para>Reverts the previous call to <command>nix-channel
+ --update</command>. Optionally, you can specify a specific channel
+ generation number to restore.</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+</para>
+
+<para>Note that <option>--add</option> does not automatically perform
+an update.</para>
+
+<para>The list of subscribed channels is stored in
+<filename>~/.nix-channels</filename>.</para>
+
+</refsection>
+
+<refsection><title>Examples</title>
+
+<para>To subscribe to the Nixpkgs channel and install the GNU Hello package:</para>
+
+<screen>
+$ nix-channel --add https://nixos.org/channels/nixpkgs-unstable
+$ nix-channel --update
+$ nix-env -iA nixpkgs.hello</screen>
+
+<para>You can revert channel updates using <option>--rollback</option>:</para>
+
+<screen>
+$ nix-instantiate --eval -E '(import <nixpkgs> {}).lib.version'
+"14.04.527.0e935f1"
+
+$ nix-channel --rollback
+switching from generation 483 to 482
+
+$ nix-instantiate --eval -E '(import <nixpkgs> {}).lib.version'
+"14.04.526.dbadfad"
+</screen>
+
+</refsection>
+
+<refsection><title>Files</title>
+
+<variablelist>
+
+ <varlistentry><term><filename>/nix/var/nix/profiles/per-user/<replaceable>username</replaceable>/channels</filename></term>
+
+ <listitem><para><command>nix-channel</command> uses a
+ <command>nix-env</command> profile to keep track of previous
+ versions of the subscribed channels. Every time you run
+ <command>nix-channel --update</command>, a new channel generation
+ (that is, a symlink to the channel Nix expressions in the Nix store)
+ is created. This enables <command>nix-channel --rollback</command>
+ to revert to previous versions.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><filename>~/.nix-defexpr/channels</filename></term>
+
+ <listitem><para>This is a symlink to
+ <filename>/nix/var/nix/profiles/per-user/<replaceable>username</replaceable>/channels</filename>. It
+ ensures that <command>nix-env</command> can find your channels. In
+ a multi-user installation, you may also have
+ <filename>~/.nix-defexpr/channels_root</filename>, which links to
+ the channels of the root user.</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+</refsection>
+
+<refsection><title>Channel format</title>
+
+<para>A channel URL should point to a directory containing the
+following files:</para>
+
+<variablelist>
+
+ <varlistentry><term><filename>nixexprs.tar.xz</filename></term>
+
+ <listitem><para>A tarball containing Nix expressions and files
+ referenced by them (such as build scripts and patches). At the
+ top level, the tarball should contain a single directory. That
+ directory must contain a file <filename>default.nix</filename>
+ that serves as the channel’s “entry point”.</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+</refsection>
+
+</refentry>
+<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-nix-collect-garbage">
+
+<refmeta>
+ <refentrytitle>nix-collect-garbage</refentrytitle>
+ <manvolnum>1</manvolnum>
+ <refmiscinfo class="source">Nix</refmiscinfo>
+ <refmiscinfo class="version">3.0</refmiscinfo>
+</refmeta>
+
+<refnamediv>
+ <refname>nix-collect-garbage</refname>
+ <refpurpose>delete unreachable store paths</refpurpose>
+</refnamediv>
+
+<refsynopsisdiv>
+ <cmdsynopsis>
+ <command>nix-collect-garbage</command>
+ <arg><option>--delete-old</option></arg>
+ <arg><option>-d</option></arg>
+ <arg><option>--delete-older-than</option> <replaceable>period</replaceable></arg>
+ <arg><option>--max-freed</option> <replaceable>bytes</replaceable></arg>
+ <arg><option>--dry-run</option></arg>
+ </cmdsynopsis>
+</refsynopsisdiv>
+
+<refsection><title>Description</title>
+
+<para>The command <command>nix-collect-garbage</command> is mostly an
+alias of <link linkend="rsec-nix-store-gc"><command>nix-store
+--gc</command></link>, that is, it deletes all unreachable paths in
+the Nix store to clean up your system. However, it provides two
+additional options: <option>-d</option> (<option>--delete-old</option>),
+which deletes all old generations of all profiles in
+<filename>/nix/var/nix/profiles</filename> by invoking
+<literal>nix-env --delete-generations old</literal> on all profiles
+(of course, this makes rollbacks to previous configurations
+impossible); and
+<option>--delete-older-than</option> <replaceable>period</replaceable>,
+where period is a value such as <literal>30d</literal>, which deletes
+all generations older than the specified number of days in all profiles
+in <filename>/nix/var/nix/profiles</filename> (except for the generations
+that were active at that point in time).
+</para>
+
+</refsection>
+
+<refsection><title>Example</title>
+
+<para>To delete from the Nix store everything that is not used by the
+current generations of each profile, do
+
+<screen>
+$ nix-collect-garbage -d</screen>
+
+</para>
+
+</refsection>
+
+</refentry>
+<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" xml:id="sec-nix-copy-closure">
+
+<refmeta>
+ <refentrytitle>nix-copy-closure</refentrytitle>
+ <manvolnum>1</manvolnum>
+ <refmiscinfo class="source">Nix</refmiscinfo>
+ <refmiscinfo class="version">3.0</refmiscinfo>
+</refmeta>
+
+<refnamediv>
+ <refname>nix-copy-closure</refname>
+ <refpurpose>copy a closure to or from a remote machine via SSH</refpurpose>
+</refnamediv>
+
+<refsynopsisdiv>
+ <cmdsynopsis>
+ <command>nix-copy-closure</command>
+ <group>
+ <arg choice="plain"><option>--to</option></arg>
+ <arg choice="plain"><option>--from</option></arg>
+ </group>
+ <arg><option>--gzip</option></arg>
+ <!--
+ <arg><option>- -show-progress</option></arg>
+ -->
+ <arg><option>--include-outputs</option></arg>
+ <group>
+ <arg choice="plain"><option>--use-substitutes</option></arg>
+ <arg choice="plain"><option>-s</option></arg>
+ </group>
+ <arg><option>-v</option></arg>
+ <arg choice="plain">
+ <replaceable>user@</replaceable><replaceable>machine</replaceable>
+ </arg>
+ <arg choice="plain"><replaceable>paths</replaceable></arg>
+ </cmdsynopsis>
+</refsynopsisdiv>
+
+
+<refsection><title>Description</title>
+
+<para><command>nix-copy-closure</command> gives you an easy and
+efficient way to exchange software between machines. Given one or
+more Nix store <replaceable>paths</replaceable> on the local
+machine, <command>nix-copy-closure</command> computes the closure of
+those paths (i.e. all their dependencies in the Nix store), and copies
+all paths in the closure to the remote machine via the
+<command>ssh</command> (Secure Shell) command. With the
+<option>--from</option>, the direction is reversed:
+the closure of <replaceable>paths</replaceable> on a remote machine is
+copied to the Nix store on the local machine.</para>
+
+<para>This command is efficient because it only sends the store paths
+that are missing on the target machine.</para>
+
+<para>Since <command>nix-copy-closure</command> calls
+<command>ssh</command>, you may be asked to type in the appropriate
+password or passphrase. In fact, you may be asked
+<emphasis>twice</emphasis> because <command>nix-copy-closure</command>
+currently connects twice to the remote machine, first to get the set
+of paths missing on the target machine, and second to send the dump of
+those paths. If this bothers you, use
+<command>ssh-agent</command>.</para>
+
+
+<refsection><title>Options</title>
+
+<variablelist>
+
+ <varlistentry><term><option>--to</option></term>
+
+ <listitem><para>Copy the closure of
+ <replaceable>paths</replaceable> from the local Nix store to the
+ Nix store on <replaceable>machine</replaceable>. This is the
+ default.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--from</option></term>
+
+ <listitem><para>Copy the closure of
+ <replaceable>paths</replaceable> from the Nix store on
+ <replaceable>machine</replaceable> to the local Nix
+ store.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--gzip</option></term>
+
+ <listitem><para>Enable compression of the SSH
+ connection.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--include-outputs</option></term>
+
+ <listitem><para>Also copy the outputs of store derivations
+ included in the closure.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--use-substitutes</option> / <option>-s</option></term>
+
+ <listitem><para>Attempt to download missing paths on the target
+ machine using Nix’s substitute mechanism. Any paths that cannot
+ be substituted on the target are still copied normally from the
+ source. This is useful, for instance, if the connection between
+ the source and target machine is slow, but the connection between
+ the target machine and <literal>nixos.org</literal> (the default
+ binary cache server) is fast.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>-v</option></term>
+
+ <listitem><para>Show verbose output.</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+</refsection>
+
+
+<refsection><title>Environment variables</title>
+
+<variablelist>
+
+ <varlistentry><term><envar>NIX_SSHOPTS</envar></term>
+
+ <listitem><para>Additional options to be passed to
+ <command>ssh</command> on the command line.</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+</refsection>
+
+
+<refsection><title>Examples</title>
+
+<para>Copy Firefox with all its dependencies to a remote machine:
+
+<screen>
+$ nix-copy-closure --to alice@itchy.labs $(type -tP firefox)</screen>
+
+</para>
+
+<para>Copy Subversion from a remote machine and then install it into a
+user environment:
+
+<screen>
+$ nix-copy-closure --from alice@itchy.labs \
+ /nix/store/0dj0503hjxy5mbwlafv1rsbdiyx1gkdy-subversion-1.4.4
+$ nix-env -i /nix/store/0dj0503hjxy5mbwlafv1rsbdiyx1gkdy-subversion-1.4.4
+</screen>
+
+</para>
+
+</refsection>
+
+
+</refsection>
+
+</refentry>
+<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-nix-daemon">
+
+<refmeta>
+ <refentrytitle>nix-daemon</refentrytitle>
+ <manvolnum>8</manvolnum>
+ <refmiscinfo class="source">Nix</refmiscinfo>
+ <refmiscinfo class="version">3.0</refmiscinfo>
+</refmeta>
+
+<refnamediv>
+ <refname>nix-daemon</refname>
+ <refpurpose>Nix multi-user support daemon</refpurpose>
+</refnamediv>
+
+<refsynopsisdiv>
+ <cmdsynopsis>
+ <command>nix-daemon</command>
+ </cmdsynopsis>
+</refsynopsisdiv>
+
+
+<refsection><title>Description</title>
+
+<para>The Nix daemon is necessary in multi-user Nix installations. It
+performs build actions and other operations on the Nix store on behalf
+of unprivileged users.</para>
+
+
+</refsection>
+
+</refentry>
+<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-nix-hash">
+
+<refmeta>
+ <refentrytitle>nix-hash</refentrytitle>
+ <manvolnum>1</manvolnum>
+ <refmiscinfo class="source">Nix</refmiscinfo>
+ <refmiscinfo class="version">3.0</refmiscinfo>
+</refmeta>
+
+<refnamediv>
+ <refname>nix-hash</refname>
+ <refpurpose>compute the cryptographic hash of a path</refpurpose>
+</refnamediv>
+
+<refsynopsisdiv>
+ <cmdsynopsis>
+ <command>nix-hash</command>
+ <arg><option>--flat</option></arg>
+ <arg><option>--base32</option></arg>
+ <arg><option>--truncate</option></arg>
+ <arg><option>--type</option> <replaceable>hashAlgo</replaceable></arg>
+ <arg choice="plain" rep="repeat"><replaceable>path</replaceable></arg>
+ </cmdsynopsis>
+ <cmdsynopsis>
+ <command>nix-hash</command>
+ <arg choice="plain"><option>--to-base16</option></arg>
+ <arg choice="plain" rep="repeat"><replaceable>hash</replaceable></arg>
+ </cmdsynopsis>
+ <cmdsynopsis>
+ <command>nix-hash</command>
+ <arg choice="plain"><option>--to-base32</option></arg>
+ <arg choice="plain" rep="repeat"><replaceable>hash</replaceable></arg>
+ </cmdsynopsis>
+</refsynopsisdiv>
+
+
+<refsection><title>Description</title>
+
+<para>The command <command>nix-hash</command> computes the
+cryptographic hash of the contents of each
+<replaceable>path</replaceable> and prints it on standard output. By
+default, it computes an MD5 hash, but other hash algorithms are
+available as well. The hash is printed in hexadecimal. To generate
+the same hash as <command>nix-prefetch-url</command> you have to
+specify multiple arguments, see below for an example.</para>
+
+<para>The hash is computed over a <emphasis>serialisation</emphasis>
+of each path: a dump of the file system tree rooted at the path. This
+allows directories and symlinks to be hashed as well as regular files.
+The dump is in the <emphasis>NAR format</emphasis> produced by <link linkend="refsec-nix-store-dump"><command>nix-store</command>
+<option>--dump</option></link>. Thus, <literal>nix-hash
+<replaceable>path</replaceable></literal> yields the same
+cryptographic hash as <literal>nix-store --dump
+<replaceable>path</replaceable> | md5sum</literal>.</para>
+
+</refsection>
+
+
+<refsection><title>Options</title>
+
+<variablelist>
+
+ <varlistentry><term><option>--flat</option></term>
+
+ <listitem><para>Print the cryptographic hash of the contents of
+ each regular file <replaceable>path</replaceable>. That is, do
+ not compute the hash over the dump of
+ <replaceable>path</replaceable>. The result is identical to that
+ produced by the GNU commands <command>md5sum</command> and
+ <command>sha1sum</command>.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--base32</option></term>
+
+ <listitem><para>Print the hash in a base-32 representation rather
+ than hexadecimal. This base-32 representation is more compact and
+ can be used in Nix expressions (such as in calls to
+ <function>fetchurl</function>).</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--truncate</option></term>
+
+ <listitem><para>Truncate hashes longer than 160 bits (such as
+ SHA-256) to 160 bits.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--type</option> <replaceable>hashAlgo</replaceable></term>
+
+ <listitem><para>Use the specified cryptographic hash algorithm,
+ which can be one of <literal>md5</literal>,
+ <literal>sha1</literal>, and
+ <literal>sha256</literal>.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--to-base16</option></term>
+
+ <listitem><para>Don’t hash anything, but convert the base-32 hash
+ representation <replaceable>hash</replaceable> to
+ hexadecimal.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--to-base32</option></term>
+
+ <listitem><para>Don’t hash anything, but convert the hexadecimal
+ hash representation <replaceable>hash</replaceable> to
+ base-32.</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+</refsection>
+
+
+<refsection><title>Examples</title>
+
+<para>Computing the same hash as <command>nix-prefetch-url</command>:
+<screen>
+$ nix-prefetch-url file://<(echo test)
+1lkgqb6fclns49861dwk9rzb6xnfkxbpws74mxnx01z9qyv1pjpj
+$ nix-hash --type sha256 --flat --base32 <(echo test)
+1lkgqb6fclns49861dwk9rzb6xnfkxbpws74mxnx01z9qyv1pjpj
+</screen>
+</para>
+
+<para>Computing hashes:
+
+<screen>
+$ mkdir test
+$ echo "hello" > test/world
+
+$ nix-hash test/ <lineannotation>(MD5 hash; default)</lineannotation>
+8179d3caeff1869b5ba1744e5a245c04
+
+$ nix-store --dump test/ | md5sum <lineannotation>(for comparison)</lineannotation>
+8179d3caeff1869b5ba1744e5a245c04 -
+
+$ nix-hash --type sha1 test/
+e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
+
+$ nix-hash --type sha1 --base32 test/
+nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
+
+$ nix-hash --type sha256 --flat test/
+error: reading file `test/': Is a directory
+
+$ nix-hash --type sha256 --flat test/world
+5891b5b522d5df086d0ff0b110fbd9d21bb4fc7163af34d08286a2e846f6be03</screen>
+
+</para>
+
+<para>Converting between hexadecimal and base-32:
+
+<screen>
+$ nix-hash --type sha1 --to-base32 e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
+nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
+
+$ nix-hash --type sha1 --to-base16 nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
+e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6</screen>
+
+</para>
+
+</refsection>
+
+
+</refentry>
+<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-nix-instantiate">
+
+<refmeta>
+ <refentrytitle>nix-instantiate</refentrytitle>
+ <manvolnum>1</manvolnum>
+ <refmiscinfo class="source">Nix</refmiscinfo>
+ <refmiscinfo class="version">3.0</refmiscinfo>
+</refmeta>
+
+<refnamediv>
+ <refname>nix-instantiate</refname>
+ <refpurpose>instantiate store derivations from Nix expressions</refpurpose>
+</refnamediv>
+
+<refsynopsisdiv>
+ <cmdsynopsis>
+ <command>nix-instantiate</command>
+ <group>
+ <arg choice="plain"><option>--parse</option></arg>
+ <arg choice="plain">
+ <option>--eval</option>
+ <arg><option>--strict</option></arg>
+ <arg><option>--json</option></arg>
+ <arg><option>--xml</option></arg>
+ </arg>
+ </group>
+ <arg><option>--read-write-mode</option></arg>
+ <arg><option>--arg</option> <replaceable>name</replaceable> <replaceable>value</replaceable></arg>
+ <arg>
+ <group choice="req">
+ <arg choice="plain"><option>--attr</option></arg>
+ <arg choice="plain"><option>-A</option></arg>
+ </group>
+ <replaceable>attrPath</replaceable>
+ </arg>
+ <arg><option>--add-root</option> <replaceable>path</replaceable></arg>
+ <arg><option>--indirect</option></arg>
+ <group>
+ <arg choice="plain"><option>--expr</option></arg>
+ <arg choice="plain"><option>-E</option></arg>
+ </group>
+ <arg choice="plain" rep="repeat"><replaceable>files</replaceable></arg>
+ </cmdsynopsis>
+ <cmdsynopsis>
+ <command>nix-instantiate</command>
+ <arg choice="plain"><option>--find-file</option></arg>
+ <arg choice="plain" rep="repeat"><replaceable>files</replaceable></arg>
+ </cmdsynopsis>
+</refsynopsisdiv>
+
+
+<refsection><title>Description</title>
+
+<para>The command <command>nix-instantiate</command> generates <link linkend="gloss-derivation">store derivations</link> from (high-level)
+Nix expressions. It evaluates the Nix expressions in each of
+<replaceable>files</replaceable> (which defaults to
+<replaceable>./default.nix</replaceable>). Each top-level expression
+should evaluate to a derivation, a list of derivations, or a set of
+derivations. The paths of the resulting store derivations are printed
+on standard output.</para>
+
+<para>If <replaceable>files</replaceable> is the character
+<literal>-</literal>, then a Nix expression will be read from standard
+input.</para>
+
+<para condition="manual">See also <xref linkend="sec-common-options"/> for a list of common options.</para>
+
+</refsection>
+
+
+<refsection><title>Options</title>
+
+<variablelist>
+
+ <varlistentry>
+ <term><option>--add-root</option> <replaceable>path</replaceable></term>
+ <term><option>--indirect</option></term>
+
+ <listitem><para>See the <link linkend="opt-add-root">corresponding
+ options</link> in <command>nix-store</command>.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--parse</option></term>
+
+ <listitem><para>Just parse the input files, and print their
+ abstract syntax trees on standard output in ATerm
+ format.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--eval</option></term>
+
+ <listitem><para>Just parse and evaluate the input files, and print
+ the resulting values on standard output. No instantiation of
+ store derivations takes place.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--find-file</option></term>
+
+ <listitem><para>Look up the given files in Nix’s search path (as
+ specified by the <envar linkend="env-NIX_PATH">NIX_PATH</envar>
+ environment variable). If found, print the corresponding absolute
+ paths on standard output. For instance, if
+ <envar>NIX_PATH</envar> is
+ <literal>nixpkgs=/home/alice/nixpkgs</literal>, then
+ <literal>nix-instantiate --find-file nixpkgs/default.nix</literal>
+ will print
+ <literal>/home/alice/nixpkgs/default.nix</literal>.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--strict</option></term>
+
+ <listitem><para>When used with <option>--eval</option>,
+ recursively evaluate list elements and attributes. Normally, such
+ sub-expressions are left unevaluated (since the Nix expression
+ language is lazy).</para>
+
+ <warning><para>This option can cause non-termination, because lazy
+ data structures can be infinitely large.</para></warning>
+
+ </listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--json</option></term>
+
+ <listitem><para>When used with <option>--eval</option>, print the resulting
+ value as an JSON representation of the abstract syntax tree rather
+ than as an ATerm.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--xml</option></term>
+
+ <listitem><para>When used with <option>--eval</option>, print the resulting
+ value as an XML representation of the abstract syntax tree rather than as
+ an ATerm. The schema is the same as that used by the <link linkend="builtin-toXML"><function>toXML</function> built-in</link>.
+ </para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--read-write-mode</option></term>
+
+ <listitem><para>When used with <option>--eval</option>, perform
+ evaluation in read/write mode so nix language features that
+ require it will still work (at the cost of needing to do
+ instantiation of every evaluated derivation). If this option is
+ not enabled, there may be uninstantiated store paths in the final
+ output.</para>
+
+ </listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+<variablelist condition="manpage">
+ <varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--help</option></term>
+
+ <listitem><para>Prints out a summary of the command syntax and
+ exits.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--version</option></term>
+
+ <listitem><para>Prints out the Nix version number on standard output
+ and exits.</para></listitem>
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--verbose</option> / <option>-v</option></term>
+
+ <listitem>
+
+ <para>Increases the level of verbosity of diagnostic messages
+ printed on standard error. For each Nix operation, the information
+ printed on standard output is well-defined; any diagnostic
+ information is printed on standard error, never on standard
+ output.</para>
+
+ <para>This option may be specified repeatedly. Currently, the
+ following verbosity levels exist:</para>
+
+ <variablelist>
+
+ <varlistentry><term>0</term>
+ <listitem><para>“Errors only”: only print messages
+ explaining why the Nix invocation failed.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>1</term>
+ <listitem><para>“Informational”: print
+ <emphasis>useful</emphasis> messages about what Nix is doing.
+ This is the default.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>2</term>
+ <listitem><para>“Talkative”: print more informational
+ messages.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>3</term>
+ <listitem><para>“Chatty”: print even more
+ informational messages.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>4</term>
+ <listitem><para>“Debug”: print debug
+ information.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>5</term>
+ <listitem><para>“Vomit”: print vast amounts of debug
+ information.</para></listitem>
+ </varlistentry>
+
+ </variablelist>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--quiet</option></term>
+
+ <listitem>
+
+ <para>Decreases the level of verbosity of diagnostic messages
+ printed on standard error. This is the inverse option to
+ <option>-v</option> / <option>--verbose</option>.
+ </para>
+
+ <para>This option may be specified repeatedly. See the previous
+ verbosity levels list.</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-log-format"><term><option>--log-format</option> <replaceable>format</replaceable></term>
+
+ <listitem>
+
+ <para>This option can be used to change the output of the log format, with
+ <replaceable>format</replaceable> being one of:</para>
+
+ <variablelist>
+
+ <varlistentry><term>raw</term>
+ <listitem><para>This is the raw format, as outputted by nix-build.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>internal-json</term>
+ <listitem><para>Outputs the logs in a structured manner. NOTE: the json schema is not guarantees to be stable between releases.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>bar</term>
+ <listitem><para>Only display a progress bar during the builds.</para></listitem>
+ </varlistentry>
+
+ <varlistentry><term>bar-with-logs</term>
+ <listitem><para>Display the raw logs, with the progress bar at the bottom.</para></listitem>
+ </varlistentry>
+
+ </variablelist>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--no-build-output</option> / <option>-Q</option></term>
+
+ <listitem><para>By default, output written by builders to standard
+ output and standard error is echoed to the Nix command's standard
+ error. This option suppresses this behaviour. Note that the
+ builder's standard output and error are always written to a log file
+ in
+ <filename><replaceable>prefix</replaceable>/nix/var/log/nix</filename>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-max-jobs"><term><option>--max-jobs</option> / <option>-j</option>
+<replaceable>number</replaceable></term>
+
+ <listitem>
+
+ <para>Sets the maximum number of build jobs that Nix will
+ perform in parallel to the specified number. Specify
+ <literal>auto</literal> to use the number of CPUs in the system.
+ The default is specified by the <link linkend="conf-max-jobs"><literal>max-jobs</literal></link>
+ configuration setting, which itself defaults to
+ <literal>1</literal>. A higher value is useful on SMP systems or to
+ exploit I/O latency.</para>
+
+ <para> Setting it to <literal>0</literal> disallows building on the local
+ machine, which is useful when you want builds to happen only on remote
+ builders.</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-cores"><term><option>--cores</option></term>
+
+ <listitem><para>Sets the value of the <envar>NIX_BUILD_CORES</envar>
+ environment variable in the invocation of builders. Builders can
+ use this variable at their discretion to control the maximum amount
+ of parallelism. For instance, in Nixpkgs, if the derivation
+ attribute <varname>enableParallelBuilding</varname> is set to
+ <literal>true</literal>, the builder passes the
+ <option>-j<replaceable>N</replaceable></option> flag to GNU Make.
+ It defaults to the value of the <link linkend="conf-cores"><literal>cores</literal></link>
+ configuration setting, if set, or <literal>1</literal> otherwise.
+ The value <literal>0</literal> means that the builder should use all
+ available CPU cores in the system.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-max-silent-time"><term><option>--max-silent-time</option></term>
+
+ <listitem><para>Sets the maximum number of seconds that a builder
+ can go without producing any data on standard output or standard
+ error. The default is specified by the <link linkend="conf-max-silent-time"><literal>max-silent-time</literal></link>
+ configuration setting. <literal>0</literal> means no
+ time-out.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-timeout"><term><option>--timeout</option></term>
+
+ <listitem><para>Sets the maximum number of seconds that a builder
+ can run. The default is specified by the <link linkend="conf-timeout"><literal>timeout</literal></link>
+ configuration setting. <literal>0</literal> means no
+ timeout.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--keep-going</option> / <option>-k</option></term>
+
+ <listitem><para>Keep going in case of failed builds, to the
+ greatest extent possible. That is, if building an input of some
+ derivation fails, Nix will still build the other inputs, but not the
+ derivation itself. Without this option, Nix stops if any build
+ fails (except for builds of substitutes), possibly killing builds in
+ progress (in case of parallel or distributed builds).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--keep-failed</option> / <option>-K</option></term>
+
+ <listitem><para>Specifies that in case of a build failure, the
+ temporary directory (usually in <filename>/tmp</filename>) in which
+ the build takes place should not be deleted. The path of the build
+ directory is printed as an informational message.
+ </para>
+ </listitem>
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--fallback</option></term>
+
+ <listitem>
+
+ <para>Whenever Nix attempts to build a derivation for which
+ substitutes are known for each output path, but realising the output
+ paths through the substitutes fails, fall back on building the
+ derivation.</para>
+
+ <para>The most common scenario in which this is useful is when we
+ have registered substitutes in order to perform binary distribution
+ from, say, a network repository. If the repository is down, the
+ realisation of the derivation will fail. When this option is
+ specified, Nix will build the derivation instead. Thus,
+ installation from binaries falls back on installation from source.
+ This option is not the default since it is generally not desirable
+ for a transient failure in obtaining the substitutes to lead to a
+ full build from source (with the related consumption of
+ resources).</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--no-build-hook</option></term>
+
+ <listitem>
+
+ <para>Disables the build hook mechanism. This allows to ignore remote
+ builders if they are setup on the machine.</para>
+
+ <para>It's useful in cases where the bandwidth between the client and the
+ remote builder is too low. In that case it can take more time to upload the
+ sources to the remote builder and fetch back the result than to do the
+ computation locally.</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--readonly-mode</option></term>
+
+ <listitem><para>When this option is used, no attempt is made to open
+ the Nix database. Most Nix operations do need database access, so
+ those operations will fail.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--arg</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
+
+ <listitem><para>This option is accepted by
+ <command>nix-env</command>, <command>nix-instantiate</command>,
+ <command>nix-shell</command> and <command>nix-build</command>.
+ When evaluating Nix expressions, the expression evaluator will
+ automatically try to call functions that
+ it encounters. It can automatically call functions for which every
+ argument has a <link linkend="ss-functions">default value</link>
+ (e.g., <literal>{ <replaceable>argName</replaceable> ?
+ <replaceable>defaultValue</replaceable> }:
+ <replaceable>...</replaceable></literal>). With
+ <option>--arg</option>, you can also call functions that have
+ arguments without a default value (or override a default value).
+ That is, if the evaluator encounters a function with an argument
+ named <replaceable>name</replaceable>, it will call it with value
+ <replaceable>value</replaceable>.</para>
+
+ <para>For instance, the top-level <literal>default.nix</literal> in
+ Nixpkgs is actually a function:
+
+<programlisting>
+{ # The system (e.g., `i686-linux') for which to build the packages.
+ system ? builtins.currentSystem
+ <replaceable>...</replaceable>
+}: <replaceable>...</replaceable></programlisting>
+
+ So if you call this Nix expression (e.g., when you do
+ <literal>nix-env -i <replaceable>pkgname</replaceable></literal>),
+ the function will be called automatically using the value <link linkend="builtin-currentSystem"><literal>builtins.currentSystem</literal></link>
+ for the <literal>system</literal> argument. You can override this
+ using <option>--arg</option>, e.g., <literal>nix-env -i
+ <replaceable>pkgname</replaceable> --arg system
+ \"i686-freebsd\"</literal>. (Note that since the argument is a Nix
+ string literal, you have to escape the quotes.)</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--argstr</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
+
+ <listitem><para>This option is like <option>--arg</option>, only the
+ value is not a Nix expression but a string. So instead of
+ <literal>--arg system \"i686-linux\"</literal> (the outer quotes are
+ to keep the shell happy) you can say <literal>--argstr system
+ i686-linux</literal>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-attr"><term><option>--attr</option> / <option>-A</option>
+<replaceable>attrPath</replaceable></term>
+
+ <listitem><para>Select an attribute from the top-level Nix
+ expression being evaluated. (<command>nix-env</command>,
+ <command>nix-instantiate</command>, <command>nix-build</command> and
+ <command>nix-shell</command> only.) The <emphasis>attribute
+ path</emphasis> <replaceable>attrPath</replaceable> is a sequence of
+ attribute names separated by dots. For instance, given a top-level
+ Nix expression <replaceable>e</replaceable>, the attribute path
+ <literal>xorg.xorgserver</literal> would cause the expression
+ <literal><replaceable>e</replaceable>.xorg.xorgserver</literal> to
+ be used. See <link linkend="refsec-nix-env-install-examples"><command>nix-env
+ --install</command></link> for some concrete examples.</para>
+
+ <para>In addition to attribute names, you can also specify array
+ indices. For instance, the attribute path
+ <literal>foo.3.bar</literal> selects the <literal>bar</literal>
+ attribute of the fourth element of the array in the
+ <literal>foo</literal> attribute of the top-level
+ expression.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--expr</option> / <option>-E</option></term>
+
+ <listitem><para>Interpret the command line arguments as a list of
+ Nix expressions to be parsed and evaluated, rather than as a list
+ of file names of Nix expressions.
+ (<command>nix-instantiate</command>, <command>nix-build</command>
+ and <command>nix-shell</command> only.)</para>
+
+ <para>For <command>nix-shell</command>, this option is commonly used
+ to give you a shell in which you can build the packages returned
+ by the expression. If you want to get a shell which contain the
+ <emphasis>built</emphasis> packages ready for use, give your
+ expression to the <command>nix-shell -p</command> convenience flag
+ instead.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-I"><term><option>-I</option> <replaceable>path</replaceable></term>
+
+ <listitem><para>Add a path to the Nix expression search path. This
+ option may be given multiple times. See the <envar linkend="env-NIX_PATH">NIX_PATH</envar> environment variable for
+ information on the semantics of the Nix search path. Paths added
+ through <option>-I</option> take precedence over
+ <envar>NIX_PATH</envar>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--option</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
+
+ <listitem><para>Set the Nix configuration option
+ <replaceable>name</replaceable> to <replaceable>value</replaceable>.
+ This overrides settings in the Nix configuration file (see
+ <citerefentry><refentrytitle>nix.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--repair</option></term>
+
+ <listitem><para>Fix corrupted or missing store paths by
+ redownloading or rebuilding them. Note that this is slow because it
+ requires computing a cryptographic hash of the contents of every
+ path in the closure of the build. Also note the warning under
+ <command>nix-store --repair-path</command>.</para></listitem>
+
+</varlistentry>
+</variablelist>
+
+</refsection>
+
+
+<refsection><title>Examples</title>
+
+<para>Instantiating store derivations from a Nix expression, and
+building them using <command>nix-store</command>:
+
+<screen>
+$ nix-instantiate test.nix <lineannotation>(instantiate)</lineannotation>
+/nix/store/cigxbmvy6dzix98dxxh9b6shg7ar5bvs-perl-BerkeleyDB-0.26.drv
+
+$ nix-store -r $(nix-instantiate test.nix) <lineannotation>(build)</lineannotation>
+<replaceable>...</replaceable>
+/nix/store/qhqk4n8ci095g3sdp93x7rgwyh9rdvgk-perl-BerkeleyDB-0.26 <lineannotation>(output path)</lineannotation>
+
+$ ls -l /nix/store/qhqk4n8ci095g3sdp93x7rgwyh9rdvgk-perl-BerkeleyDB-0.26
+dr-xr-xr-x 2 eelco users 4096 1970-01-01 01:00 lib
+...</screen>
+
+</para>
+
+<para>You can also give a Nix expression on the command line:
+
+<screen>
+$ nix-instantiate -E 'with import <nixpkgs> { }; hello'
+/nix/store/j8s4zyv75a724q38cb0r87rlczaiag4y-hello-2.8.drv
+</screen>
+
+This is equivalent to:
+
+<screen>
+$ nix-instantiate '<nixpkgs>' -A hello
+</screen>
+
+</para>
+
+<para>Parsing and evaluating Nix expressions:
+
+<screen>
+$ nix-instantiate --parse -E '1 + 2'
+1 + 2
+
+$ nix-instantiate --eval -E '1 + 2'
+3
+
+$ nix-instantiate --eval --xml -E '1 + 2'
+<![CDATA[<?xml version='1.0' encoding='utf-8'?>
+<expr>
+ <int value="3" />
+</expr>]]></screen>
+
+</para>
+
+<para>The difference between non-strict and strict evaluation:
+
+<screen>
+$ nix-instantiate --eval --xml -E 'rec { x = "foo"; y = x; }'
+<replaceable>...</replaceable><![CDATA[
+ <attr name="x">
+ <string value="foo" />
+ </attr>
+ <attr name="y">
+ <unevaluated />
+ </attr>]]>
+<replaceable>...</replaceable></screen>
+
+Note that <varname>y</varname> is left unevaluated (the XML
+representation doesn’t attempt to show non-normal forms).
+
+<screen>
+$ nix-instantiate --eval --xml --strict -E 'rec { x = "foo"; y = x; }'
+<replaceable>...</replaceable><![CDATA[
+ <attr name="x">
+ <string value="foo" />
+ </attr>
+ <attr name="y">
+ <string value="foo" />
+ </attr>]]>
+<replaceable>...</replaceable></screen>
+
+</para>
+
+</refsection>
+
+
+<refsection condition="manpage"><title>Environment variables</title>
+
+<variablelist>
+ <varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>IN_NIX_SHELL</envar></term>
+
+ <listitem><para>Indicator that tells if the current environment was set up by
+ <command>nix-shell</command>. Since Nix 2.0 the values are
+ <literal>"pure"</literal> and <literal>"impure"</literal></para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="env-NIX_PATH"><term><envar>NIX_PATH</envar></term>
+
+ <listitem>
+
+ <para>A colon-separated list of directories used to look up Nix
+ expressions enclosed in angle brackets (i.e.,
+ <literal><<replaceable>path</replaceable>></literal>). For
+ instance, the value
+
+ <screen>
+/home/eelco/Dev:/etc/nixos</screen>
+
+ will cause Nix to look for paths relative to
+ <filename>/home/eelco/Dev</filename> and
+ <filename>/etc/nixos</filename>, in this order. It is also
+ possible to match paths against a prefix. For example, the value
+
+ <screen>
+nixpkgs=/home/eelco/Dev/nixpkgs-branch:/etc/nixos</screen>
+
+ will cause Nix to search for
+ <literal><nixpkgs/<replaceable>path</replaceable>></literal> in
+ <filename>/home/eelco/Dev/nixpkgs-branch/<replaceable>path</replaceable></filename>
+ and
+ <filename>/etc/nixos/nixpkgs/<replaceable>path</replaceable></filename>.</para>
+
+ <para>If a path in the Nix search path starts with
+ <literal>http://</literal> or <literal>https://</literal>, it is
+ interpreted as the URL of a tarball that will be downloaded and
+ unpacked to a temporary location. The tarball must consist of a
+ single top-level directory. For example, setting
+ <envar>NIX_PATH</envar> to
+
+ <screen>
+nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-15.09.tar.gz</screen>
+
+ tells Nix to download the latest revision in the Nixpkgs/NixOS
+ 15.09 channel.</para>
+
+ <para>A following shorthand can be used to refer to the official channels:
+
+ <screen>nixpkgs=channel:nixos-15.09</screen>
+ </para>
+
+ <para>The search path can be extended using the <option linkend="opt-I">-I</option> option, which takes precedence over
+ <envar>NIX_PATH</envar>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_IGNORE_SYMLINK_STORE</envar></term>
+
+ <listitem>
+
+ <para>Normally, the Nix store directory (typically
+ <filename>/nix/store</filename>) is not allowed to contain any
+ symlink components. This is to prevent “impure” builds. Builders
+ sometimes “canonicalise” paths by resolving all symlink components.
+ Thus, builds on different machines (with
+ <filename>/nix/store</filename> resolving to different locations)
+ could yield different results. This is generally not a problem,
+ except when builds are deployed to machines where
+ <filename>/nix/store</filename> resolves differently. If you are
+ sure that you’re not going to do that, you can set
+ <envar>NIX_IGNORE_SYMLINK_STORE</envar> to <envar>1</envar>.</para>
+
+ <para>Note that if you’re symlinking the Nix store so that you can
+ put it on another file system than the root file system, on Linux
+ you’re better off using <literal>bind</literal> mount points, e.g.,
+
+ <screen>
+$ mkdir /nix
+$ mount -o bind /mnt/otherdisk/nix /nix</screen>
+
+ Consult the <citerefentry><refentrytitle>mount</refentrytitle>
+ <manvolnum>8</manvolnum></citerefentry> manual page for details.</para>
+
+ </listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_STORE_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix store (default
+ <filename><replaceable>prefix</replaceable>/store</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_DATA_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix static data
+ directory (default
+ <filename><replaceable>prefix</replaceable>/share</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_LOG_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix log directory
+ (default <filename><replaceable>prefix</replaceable>/var/log/nix</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_STATE_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the Nix state directory
+ (default <filename><replaceable>prefix</replaceable>/var/nix</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_CONF_DIR</envar></term>
+
+ <listitem><para>Overrides the location of the system Nix configuration
+ directory (default
+ <filename><replaceable>prefix</replaceable>/etc/nix</filename>).</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_USER_CONF_FILES</envar></term>
+
+ <listitem><para>Overrides the location of the user Nix configuration files
+ to load from (defaults to the XDG spec locations). The variable is treated
+ as a list separated by the <literal>:</literal> token.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>TMPDIR</envar></term>
+
+ <listitem><para>Use the specified directory to store temporary
+ files. In particular, this includes temporary build directories;
+ these can take up substantial amounts of disk space. The default is
+ <filename>/tmp</filename>.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="envar-remote"><term><envar>NIX_REMOTE</envar></term>
+
+ <listitem><para>This variable should be set to
+ <literal>daemon</literal> if you want to use the Nix daemon to
+ execute Nix operations. This is necessary in <link linkend="ssec-multi-user">multi-user Nix installations</link>.
+ If the Nix daemon's Unix socket is at some non-standard path,
+ this variable should be set to <literal>unix://path/to/socket</literal>.
+ Otherwise, it should be left unset.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_SHOW_STATS</envar></term>
+
+ <listitem><para>If set to <literal>1</literal>, Nix will print some
+ evaluation statistics, such as the number of values
+ allocated.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_COUNT_CALLS</envar></term>
+
+ <listitem><para>If set to <literal>1</literal>, Nix will print how
+ often functions were called during Nix expression evaluation. This
+ is useful for profiling your Nix expressions.</para></listitem>
+
+</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>GC_INITIAL_HEAP_SIZE</envar></term>
+
+ <listitem><para>If Nix has been configured to use the Boehm garbage
+ collector, this variable sets the initial size of the heap in bytes.
+ It defaults to 384 MiB. Setting it to a low value reduces memory
+ consumption, but will increase runtime due to the overhead of
+ garbage collection.</para></listitem>
+
+</varlistentry>
+</variablelist>
+
+</refsection>
+
+
+</refentry>
+<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-nix-prefetch-url">
+
+<refmeta>
+ <refentrytitle>nix-prefetch-url</refentrytitle>
+ <manvolnum>1</manvolnum>
+ <refmiscinfo class="source">Nix</refmiscinfo>
+ <refmiscinfo class="version">3.0</refmiscinfo>
+</refmeta>
+
+<refnamediv>
+ <refname>nix-prefetch-url</refname>
+ <refpurpose>copy a file from a URL into the store and print its hash</refpurpose>
+</refnamediv>
+
+<refsynopsisdiv>
+ <cmdsynopsis>
+ <command>nix-prefetch-url</command>
+ <arg><option>--version</option></arg>
+ <arg><option>--type</option> <replaceable>hashAlgo</replaceable></arg>
+ <arg><option>--print-path</option></arg>
+ <arg><option>--unpack</option></arg>
+ <arg><option>--name</option> <replaceable>name</replaceable></arg>
+ <arg choice="plain"><replaceable>url</replaceable></arg>
+ <arg><replaceable>hash</replaceable></arg>
+ </cmdsynopsis>
+</refsynopsisdiv>
+
+<refsection><title>Description</title>
+
+<para>The command <command>nix-prefetch-url</command> downloads the
+file referenced by the URL <replaceable>url</replaceable>, prints its
+cryptographic hash, and copies it into the Nix store. The file name
+in the store is
+<filename><replaceable>hash</replaceable>-<replaceable>baseName</replaceable></filename>,
+where <replaceable>baseName</replaceable> is everything following the
+final slash in <replaceable>url</replaceable>.</para>
+
+<para>This command is just a convenience for Nix expression writers.
+Often a Nix expression fetches some source distribution from the
+network using the <literal>fetchurl</literal> expression contained in
+Nixpkgs. However, <literal>fetchurl</literal> requires a
+cryptographic hash. If you don't know the hash, you would have to
+download the file first, and then <literal>fetchurl</literal> would
+download it again when you build your Nix expression. Since
+<literal>fetchurl</literal> uses the same name for the downloaded file
+as <command>nix-prefetch-url</command>, the redundant download can be
+avoided.</para>
+
+<para>If <replaceable>hash</replaceable> is specified, then a download
+is not performed if the Nix store already contains a file with the
+same hash and base name. Otherwise, the file is downloaded, and an
+error is signaled if the actual hash of the file does not match the
+specified hash.</para>
+
+<para>This command prints the hash on standard output. Additionally,
+if the option <option>--print-path</option> is used, the path of the
+downloaded file in the Nix store is also printed.</para>
+
+</refsection>
+
+
+<refsection><title>Options</title>
+
+<variablelist>
+
+ <varlistentry><term><option>--type</option> <replaceable>hashAlgo</replaceable></term>
+
+ <listitem><para>Use the specified cryptographic hash algorithm,
+ which can be one of <literal>md5</literal>,
+ <literal>sha1</literal>, and
+ <literal>sha256</literal>.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--print-path</option></term>
+
+ <listitem><para>Print the store path of the downloaded file on
+ standard output.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--unpack</option></term>
+
+ <listitem><para>Unpack the archive (which must be a tarball or zip
+ file) and add the result to the Nix store. The resulting hash can
+ be used with functions such as Nixpkgs’s
+ <varname>fetchzip</varname> or
+ <varname>fetchFromGitHub</varname>.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry><term><option>--name</option> <replaceable>name</replaceable></term>
+
+ <listitem><para>Override the name of the file in the Nix store. By
+ default, this is
+ <literal><replaceable>hash</replaceable>-<replaceable>basename</replaceable></literal>,
+ where <replaceable>basename</replaceable> is the last component of
+ <replaceable>url</replaceable>. Overriding the name is necessary
+ when <replaceable>basename</replaceable> contains characters that
+ are not allowed in Nix store paths.</para></listitem>
+
+ </varlistentry>
+
+</variablelist>
+
+</refsection>
+
+
+<refsection><title>Examples</title>
+
+<screen>
+$ nix-prefetch-url ftp://ftp.gnu.org/pub/gnu/hello/hello-2.10.tar.gz
+0ssi1wpaf7plaswqqjwigppsg5fyh99vdlb9kzl7c9lng89ndq1i
+
+$ nix-prefetch-url --print-path mirror://gnu/hello/hello-2.10.tar.gz
+0ssi1wpaf7plaswqqjwigppsg5fyh99vdlb9kzl7c9lng89ndq1i
+/nix/store/3x7dwzq014bblazs7kq20p9hyzz0qh8g-hello-2.10.tar.gz
+
+$ nix-prefetch-url --unpack --print-path https://github.com/NixOS/patchelf/archive/0.8.tar.gz
+079agjlv0hrv7fxnx9ngipx14gyncbkllxrp9cccnh3a50fxcmy7
+/nix/store/19zrmhm3m40xxaw81c8cqm6aljgrnwj2-0.8.tar.gz
+</screen>
+
+</refsection>
+
+
+</refentry>
+
+</chapter>
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-files">
+
+<title>Files</title>
+
+<para>This section lists configuration files that you can use when you
+work with Nix.</para>
+
+<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" xml:id="sec-conf-file" version="5">
+
+<refmeta>
+ <refentrytitle>nix.conf</refentrytitle>
+ <manvolnum>5</manvolnum>
+ <refmiscinfo class="source">Nix</refmiscinfo>
+ <refmiscinfo class="version">3.0</refmiscinfo>
+</refmeta>
+
+<refnamediv>
+ <refname>nix.conf</refname>
+ <refpurpose>Nix configuration file</refpurpose>
+</refnamediv>
+
+<refsection><title>Description</title>
+
+<para>By default Nix reads settings from the following places:</para>
+
+<para>The system-wide configuration file
+<filename><replaceable>sysconfdir</replaceable>/nix/nix.conf</filename>
+(i.e. <filename>/etc/nix/nix.conf</filename> on most systems), or
+<filename>$NIX_CONF_DIR/nix.conf</filename> if
+<envar>NIX_CONF_DIR</envar> is set. Values loaded in this file are not forwarded to the Nix daemon. The
+client assumes that the daemon has already loaded them.
+</para>
+
+<para>User-specific configuration files:</para>
+
+<para>
+ If <envar>NIX_USER_CONF_FILES</envar> is set, then each path separated by
+ <literal>:</literal> will be loaded in reverse order.
+</para>
+
+<para>
+ Otherwise it will look for <filename>nix/nix.conf</filename> files in
+ <envar>XDG_CONFIG_DIRS</envar> and <envar>XDG_CONFIG_HOME</envar>.
+
+ The default location is <filename>$HOME/.config/nix.conf</filename> if
+ those environment variables are unset.
+</para>
+
+<para>The configuration files consist of
+<literal><replaceable>name</replaceable> =
+<replaceable>value</replaceable></literal> pairs, one per line. Other
+files can be included with a line like <literal>include
+<replaceable>path</replaceable></literal>, where
+<replaceable>path</replaceable> is interpreted relative to the current
+conf file and a missing file is an error unless
+<literal>!include</literal> is used instead.
+Comments start with a <literal>#</literal> character. Here is an
+example configuration file:</para>
+
+<programlisting>
+keep-outputs = true # Nice for developers
+keep-derivations = true # Idem
+</programlisting>
+
+<para>You can override settings on the command line using the
+<option>--option</option> flag, e.g. <literal>--option keep-outputs
+false</literal>.</para>
+
+<para>The following settings are currently available:
+
+<variablelist>
+
+
+ <varlistentry xml:id="conf-allowed-uris"><term><literal>allowed-uris</literal></term>
+
+ <listitem>
+
+ <para>A list of URI prefixes to which access is allowed in
+ restricted evaluation mode. For example, when set to
+ <literal>https://github.com/NixOS</literal>, builtin functions
+ such as <function>fetchGit</function> are allowed to access
+ <literal>https://github.com/NixOS/patchelf.git</literal>.</para>
+
+ </listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="conf-allow-import-from-derivation"><term><literal>allow-import-from-derivation</literal></term>
+
+ <listitem><para>By default, Nix allows you to <function>import</function> from a derivation,
+ allowing building at evaluation time. With this option set to false, Nix will throw an error
+ when evaluating an expression that uses this feature, allowing users to ensure their evaluation
+ will not require any builds to take place.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="conf-allow-new-privileges"><term><literal>allow-new-privileges</literal></term>
+
+ <listitem><para>(Linux-specific.) By default, builders on Linux
+ cannot acquire new privileges by calling setuid/setgid programs or
+ programs that have file capabilities. For example, programs such
+ as <command>sudo</command> or <command>ping</command> will
+ fail. (Note that in sandbox builds, no such programs are available
+ unless you bind-mount them into the sandbox via the
+ <option>sandbox-paths</option> option.) You can allow the
+ use of such programs by enabling this option. This is impure and
+ usually undesirable, but may be useful in certain scenarios
+ (e.g. to spin up containers or set up userspace network interfaces
+ in tests).</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="conf-allowed-users"><term><literal>allowed-users</literal></term>
+
+ <listitem>
+
+ <para>A list of names of users (separated by whitespace) that
+ are allowed to connect to the Nix daemon. As with the
+ <option>trusted-users</option> option, you can specify groups by
+ prefixing them with <literal>@</literal>. Also, you can allow
+ all users by specifying <literal>*</literal>. The default is
+ <literal>*</literal>.</para>
+
+ <para>Note that trusted users are always allowed to connect.</para>
+
+ </listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="conf-auto-optimise-store"><term><literal>auto-optimise-store</literal></term>
+
+ <listitem><para>If set to <literal>true</literal>, Nix
+ automatically detects files in the store that have identical
+ contents, and replaces them with hard links to a single copy.
+ This saves disk space. If set to <literal>false</literal> (the
+ default), you can still run <command>nix-store
+ --optimise</command> to get rid of duplicate
+ files.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-builders">
+ <term><literal>builders</literal></term>
+ <listitem>
+ <para>A list of machines on which to perform builds. <phrase condition="manual">See <xref linkend="chap-distributed-builds"/> for details.</phrase></para>
+ </listitem>
+ </varlistentry>
+
+
+ <varlistentry xml:id="conf-builders-use-substitutes"><term><literal>builders-use-substitutes</literal></term>
+
+ <listitem><para>If set to <literal>true</literal>, Nix will instruct
+ remote build machines to use their own binary substitutes if available. In
+ practical terms, this means that remote hosts will fetch as many build
+ dependencies as possible from their own substitutes (e.g, from
+ <literal>cache.nixos.org</literal>), instead of waiting for this host to
+ upload them all. This can drastically reduce build times if the network
+ connection between this computer and the remote build host is slow. Defaults
+ to <literal>false</literal>.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-build-users-group"><term><literal>build-users-group</literal></term>
+
+ <listitem><para>This options specifies the Unix group containing
+ the Nix build user accounts. In multi-user Nix installations,
+ builds should not be performed by the Nix account since that would
+ allow users to arbitrarily modify the Nix store and database by
+ supplying specially crafted builders; and they cannot be performed
+ by the calling user since that would allow him/her to influence
+ the build result.</para>
+
+ <para>Therefore, if this option is non-empty and specifies a valid
+ group, builds will be performed under the user accounts that are a
+ member of the group specified here (as listed in
+ <filename>/etc/group</filename>). Those user accounts should not
+ be used for any other purpose!</para>
+
+ <para>Nix will never run two builds under the same user account at
+ the same time. This is to prevent an obvious security hole: a
+ malicious user writing a Nix expression that modifies the build
+ result of a legitimate Nix expression being built by another user.
+ Therefore it is good to have as many Nix build user accounts as
+ you can spare. (Remember: uids are cheap.)</para>
+
+ <para>The build users should have permission to create files in
+ the Nix store, but not delete them. Therefore,
+ <filename>/nix/store</filename> should be owned by the Nix
+ account, its group should be the group specified here, and its
+ mode should be <literal>1775</literal>.</para>
+
+ <para>If the build users group is empty, builds will be performed
+ under the uid of the Nix process (that is, the uid of the caller
+ if <envar>NIX_REMOTE</envar> is empty, the uid under which the Nix
+ daemon runs if <envar>NIX_REMOTE</envar> is
+ <literal>daemon</literal>). Obviously, this should not be used in
+ multi-user settings with untrusted users.</para>
+
+ </listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="conf-compress-build-log"><term><literal>compress-build-log</literal></term>
+
+ <listitem><para>If set to <literal>true</literal> (the default),
+ build logs written to <filename>/nix/var/log/nix/drvs</filename>
+ will be compressed on the fly using bzip2. Otherwise, they will
+ not be compressed.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-connect-timeout"><term><literal>connect-timeout</literal></term>
+
+ <listitem>
+
+ <para>The timeout (in seconds) for establishing connections in
+ the binary cache substituter. It corresponds to
+ <command>curl</command>’s <option>--connect-timeout</option>
+ option.</para>
+
+ </listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="conf-cores"><term><literal>cores</literal></term>
+
+ <listitem><para>Sets the value of the
+ <envar>NIX_BUILD_CORES</envar> environment variable in the
+ invocation of builders. Builders can use this variable at their
+ discretion to control the maximum amount of parallelism. For
+ instance, in Nixpkgs, if the derivation attribute
+ <varname>enableParallelBuilding</varname> is set to
+ <literal>true</literal>, the builder passes the
+ <option>-j<replaceable>N</replaceable></option> flag to GNU Make.
+ It can be overridden using the <option linkend="opt-cores">--cores</option> command line switch and
+ defaults to <literal>1</literal>. The value <literal>0</literal>
+ means that the builder should use all available CPU cores in the
+ system.</para>
+
+ <para>See also <xref linkend="chap-tuning-cores-and-jobs"/>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-diff-hook"><term><literal>diff-hook</literal></term>
+ <listitem>
+ <para>
+ Absolute path to an executable capable of diffing build results.
+ The hook executes if <xref linkend="conf-run-diff-hook"/> is
+ true, and the output of a build is known to not be the same.
+ This program is not executed to determine if two results are the
+ same.
+ </para>
+
+ <para>
+ The diff hook is executed by the same user and group who ran the
+ build. However, the diff hook does not have write access to the
+ store path just built.
+ </para>
+
+ <para>The diff hook program receives three parameters:</para>
+
+ <orderedlist>
+ <listitem>
+ <para>
+ A path to the previous build's results
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ A path to the current build's results
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ The path to the build's derivation
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ The path to the build's scratch directory. This directory
+ will exist only if the build was run with
+ <option>--keep-failed</option>.
+ </para>
+ </listitem>
+ </orderedlist>
+
+ <para>
+ The stderr and stdout output from the diff hook will not be
+ displayed to the user. Instead, it will print to the nix-daemon's
+ log.
+ </para>
+
+ <para>When using the Nix daemon, <literal>diff-hook</literal> must
+ be set in the <filename>nix.conf</filename> configuration file, and
+ cannot be passed at the command line.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-enforce-determinism">
+ <term><literal>enforce-determinism</literal></term>
+
+ <listitem><para>See <xref linkend="conf-repeat"/>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-extra-sandbox-paths">
+ <term><literal>extra-sandbox-paths</literal></term>
+
+ <listitem><para>A list of additional paths appended to
+ <option>sandbox-paths</option>. Useful if you want to extend
+ its default value.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="conf-extra-platforms"><term><literal>extra-platforms</literal></term>
+
+ <listitem><para>Platforms other than the native one which
+ this machine is capable of building for. This can be useful for
+ supporting additional architectures on compatible machines:
+ i686-linux can be built on x86_64-linux machines (and the default
+ for this setting reflects this); armv7 is backwards-compatible with
+ armv6 and armv5tel; some aarch64 machines can also natively run
+ 32-bit ARM code; and qemu-user may be used to support non-native
+ platforms (though this may be slow and buggy). Most values for this
+ are not enabled by default because build systems will often
+ misdetect the target platform and generate incompatible code, so you
+ may wish to cross-check the results of using this option against
+ proper natively-built versions of your
+ derivations.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="conf-extra-substituters"><term><literal>extra-substituters</literal></term>
+
+ <listitem><para>Additional binary caches appended to those
+ specified in <option>substituters</option>. When used by
+ unprivileged users, untrusted substituters (i.e. those not listed
+ in <option>trusted-substituters</option>) are silently
+ ignored.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-fallback"><term><literal>fallback</literal></term>
+
+ <listitem><para>If set to <literal>true</literal>, Nix will fall
+ back to building from source if a binary substitute fails. This
+ is equivalent to the <option>--fallback</option> flag. The
+ default is <literal>false</literal>.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-fsync-metadata"><term><literal>fsync-metadata</literal></term>
+
+ <listitem><para>If set to <literal>true</literal>, changes to the
+ Nix store metadata (in <filename>/nix/var/nix/db</filename>) are
+ synchronously flushed to disk. This improves robustness in case
+ of system crashes, but reduces performance. The default is
+ <literal>true</literal>.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-hashed-mirrors"><term><literal>hashed-mirrors</literal></term>
+
+ <listitem><para>A list of web servers used by
+ <function>builtins.fetchurl</function> to obtain files by hash.
+ Given a hash type <replaceable>ht</replaceable> and a base-16 hash
+ <replaceable>h</replaceable>, Nix will try to download the file
+ from
+ <literal>hashed-mirror/<replaceable>ht</replaceable>/<replaceable>h</replaceable></literal>.
+ This allows files to be downloaded even if they have disappeared
+ from their original URI. For example, given the hashed mirror
+ <literal>http://tarballs.example.com/</literal>, when building the
+ derivation
+
+<programlisting>
+builtins.fetchurl {
+ url = "https://example.org/foo-1.2.3.tar.xz";
+ sha256 = "2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae";
+}
+</programlisting>
+
+ Nix will attempt to download this file from
+ <literal>http://tarballs.example.com/sha256/2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae</literal>
+ first. If it is not available there, if will try the original URI.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="conf-http-connections"><term><literal>http-connections</literal></term>
+
+ <listitem><para>The maximum number of parallel TCP connections
+ used to fetch files from binary caches and by other downloads. It
+ defaults to 25. 0 means no limit.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="conf-keep-build-log"><term><literal>keep-build-log</literal></term>
+
+ <listitem><para>If set to <literal>true</literal> (the default),
+ Nix will write the build log of a derivation (i.e. the standard
+ output and error of its builder) to the directory
+ <filename>/nix/var/log/nix/drvs</filename>. The build log can be
+ retrieved using the command <command>nix-store -l
+ <replaceable>path</replaceable></command>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="conf-keep-derivations"><term><literal>keep-derivations</literal></term>
+
+ <listitem><para>If <literal>true</literal> (default), the garbage
+ collector will keep the derivations from which non-garbage store
+ paths were built. If <literal>false</literal>, they will be
+ deleted unless explicitly registered as a root (or reachable from
+ other roots).</para>
+
+ <para>Keeping derivation around is useful for querying and
+ traceability (e.g., it allows you to ask with what dependencies or
+ options a store path was built), so by default this option is on.
+ Turn it off to save a bit of disk space (or a lot if
+ <literal>keep-outputs</literal> is also turned on).</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-keep-env-derivations"><term><literal>keep-env-derivations</literal></term>
+
+ <listitem><para>If <literal>false</literal> (default), derivations
+ are not stored in Nix user environments. That is, the derivations of
+ any build-time-only dependencies may be garbage-collected.</para>
+
+ <para>If <literal>true</literal>, when you add a Nix derivation to
+ a user environment, the path of the derivation is stored in the
+ user environment. Thus, the derivation will not be
+ garbage-collected until the user environment generation is deleted
+ (<command>nix-env --delete-generations</command>). To prevent
+ build-time-only dependencies from being collected, you should also
+ turn on <literal>keep-outputs</literal>.</para>
+
+ <para>The difference between this option and
+ <literal>keep-derivations</literal> is that this one is
+ “sticky”: it applies to any user environment created while this
+ option was enabled, while <literal>keep-derivations</literal>
+ only applies at the moment the garbage collector is
+ run.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-keep-outputs"><term><literal>keep-outputs</literal></term>
+
+ <listitem><para>If <literal>true</literal>, the garbage collector
+ will keep the outputs of non-garbage derivations. If
+ <literal>false</literal> (default), outputs will be deleted unless
+ they are GC roots themselves (or reachable from other roots).</para>
+
+ <para>In general, outputs must be registered as roots separately.
+ However, even if the output of a derivation is registered as a
+ root, the collector will still delete store paths that are used
+ only at build time (e.g., the C compiler, or source tarballs
+ downloaded from the network). To prevent it from doing so, set
+ this option to <literal>true</literal>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-max-build-log-size"><term><literal>max-build-log-size</literal></term>
+
+ <listitem>
+
+ <para>This option defines the maximum number of bytes that a
+ builder can write to its stdout/stderr. If the builder exceeds
+ this limit, it’s killed. A value of <literal>0</literal> (the
+ default) means that there is no limit.</para>
+
+ </listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-max-free"><term><literal>max-free</literal></term>
+
+ <listitem><para>When a garbage collection is triggered by the
+ <literal>min-free</literal> option, it stops as soon as
+ <literal>max-free</literal> bytes are available. The default is
+ infinity (i.e. delete all garbage).</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-max-jobs"><term><literal>max-jobs</literal></term>
+
+ <listitem><para>This option defines the maximum number of jobs
+ that Nix will try to build in parallel. The default is
+ <literal>1</literal>. The special value <literal>auto</literal>
+ causes Nix to use the number of CPUs in your system. <literal>0</literal>
+ is useful when using remote builders to prevent any local builds (except for
+ <literal>preferLocalBuild</literal> derivation attribute which executes locally
+ regardless). It can be
+ overridden using the <option linkend="opt-max-jobs">--max-jobs</option> (<option>-j</option>)
+ command line switch.</para>
+
+ <para>See also <xref linkend="chap-tuning-cores-and-jobs"/>.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-max-silent-time"><term><literal>max-silent-time</literal></term>
+
+ <listitem>
+
+ <para>This option defines the maximum number of seconds that a
+ builder can go without producing any data on standard output or
+ standard error. This is useful (for instance in an automated
+ build system) to catch builds that are stuck in an infinite
+ loop, or to catch remote builds that are hanging due to network
+ problems. It can be overridden using the <option linkend="opt-max-silent-time">--max-silent-time</option> command
+ line switch.</para>
+
+ <para>The value <literal>0</literal> means that there is no
+ timeout. This is also the default.</para>
+
+ </listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-min-free"><term><literal>min-free</literal></term>
+
+ <listitem>
+ <para>When free disk space in <filename>/nix/store</filename>
+ drops below <literal>min-free</literal> during a build, Nix
+ performs a garbage-collection until <literal>max-free</literal>
+ bytes are available or there is no more garbage. A value of
+ <literal>0</literal> (the default) disables this feature.</para>
+ </listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-narinfo-cache-negative-ttl"><term><literal>narinfo-cache-negative-ttl</literal></term>
+
+ <listitem>
+
+ <para>The TTL in seconds for negative lookups. If a store path is
+ queried from a substituter but was not found, there will be a
+ negative lookup cached in the local disk cache database for the
+ specified duration.</para>
+
+ </listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-narinfo-cache-positive-ttl"><term><literal>narinfo-cache-positive-ttl</literal></term>
+
+ <listitem>
+
+ <para>The TTL in seconds for positive lookups. If a store path is
+ queried from a substituter, the result of the query will be cached
+ in the local disk cache database including some of the NAR
+ metadata. The default TTL is a month, setting a shorter TTL for
+ positive lookups can be useful for binary caches that have
+ frequent garbage collection, in which case having a more frequent
+ cache invalidation would prevent trying to pull the path again and
+ failing with a hash mismatch if the build isn't reproducible.
+ </para>
+
+ </listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-netrc-file"><term><literal>netrc-file</literal></term>
+
+ <listitem><para>If set to an absolute path to a <filename>netrc</filename>
+ file, Nix will use the HTTP authentication credentials in this file when
+ trying to download from a remote host through HTTP or HTTPS. Defaults to
+ <filename>$NIX_CONF_DIR/netrc</filename>.</para>
+
+ <para>The <filename>netrc</filename> file consists of a list of
+ accounts in the following format:
+
+<screen>
+machine <replaceable>my-machine</replaceable>
+login <replaceable>my-username</replaceable>
+password <replaceable>my-password</replaceable>
+</screen>
+
+ For the exact syntax, see <link xlink:href="https://ec.haxx.se/usingcurl-netrc.html">the
+ <literal>curl</literal> documentation.</link></para>
+
+ <note><para>This must be an absolute path, and <literal>~</literal>
+ is not resolved. For example, <filename>~/.netrc</filename> won't
+ resolve to your home directory's <filename>.netrc</filename>.</para></note>
+ </listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="conf-plugin-files">
+ <term><literal>plugin-files</literal></term>
+ <listitem>
+ <para>
+ A list of plugin files to be loaded by Nix. Each of these
+ files will be dlopened by Nix, allowing them to affect
+ execution through static initialization. In particular, these
+ plugins may construct static instances of RegisterPrimOp to
+ add new primops or constants to the expression language,
+ RegisterStoreImplementation to add new store implementations,
+ RegisterCommand to add new subcommands to the
+ <literal>nix</literal> command, and RegisterSetting to add new
+ nix config settings. See the constructors for those types for
+ more details.
+ </para>
+ <para>
+ Since these files are loaded into the same address space as
+ Nix itself, they must be DSOs compatible with the instance of
+ Nix running at the time (i.e. compiled against the same
+ headers, not linked to any incompatible libraries). They
+ should not be linked to any Nix libs directly, as those will
+ be available already at load time.
+ </para>
+ <para>
+ If an entry in the list is a directory, all files in the
+ directory are loaded as plugins (non-recursively).
+ </para>
+ </listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-pre-build-hook"><term><literal>pre-build-hook</literal></term>
+
+ <listitem>
+
+
+ <para>If set, the path to a program that can set extra
+ derivation-specific settings for this system. This is used for settings
+ that can't be captured by the derivation model itself and are too variable
+ between different versions of the same system to be hard-coded into nix.
+ </para>
+
+ <para>The hook is passed the derivation path and, if sandboxes are enabled,
+ the sandbox directory. It can then modify the sandbox and send a series of
+ commands to modify various settings to stdout. The currently recognized
+ commands are:</para>
+
+ <variablelist>
+ <varlistentry xml:id="extra-sandbox-paths">
+ <term><literal>extra-sandbox-paths</literal></term>
+
+ <listitem>
+
+ <para>Pass a list of files and directories to be included in the
+ sandbox for this build. One entry per line, terminated by an empty
+ line. Entries have the same format as
+ <literal>sandbox-paths</literal>.</para>
+
+ </listitem>
+
+ </varlistentry>
+ </variablelist>
+ </listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-post-build-hook">
+ <term><literal>post-build-hook</literal></term>
+ <listitem>
+ <para>Optional. The path to a program to execute after each build.</para>
+
+ <para>This option is only settable in the global
+ <filename>nix.conf</filename>, or on the command line by trusted
+ users.</para>
+
+ <para>When using the nix-daemon, the daemon executes the hook as
+ <literal>root</literal>. If the nix-daemon is not involved, the
+ hook runs as the user executing the nix-build.</para>
+
+ <itemizedlist>
+ <listitem><para>The hook executes after an evaluation-time build.</para></listitem>
+ <listitem><para>The hook does not execute on substituted paths.</para></listitem>
+ <listitem><para>The hook's output always goes to the user's terminal.</para></listitem>
+ <listitem><para>If the hook fails, the build succeeds but no further builds execute.</para></listitem>
+ <listitem><para>The hook executes synchronously, and blocks other builds from progressing while it runs.</para></listitem>
+ </itemizedlist>
+
+ <para>The program executes with no arguments. The program's environment
+ contains the following environment variables:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><envar>DRV_PATH</envar></term>
+ <listitem>
+ <para>The derivation for the built paths.</para>
+ <para>Example:
+ <literal>/nix/store/5nihn1a7pa8b25l9zafqaqibznlvvp3f-bash-4.4-p23.drv</literal>
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><envar>OUT_PATHS</envar></term>
+ <listitem>
+ <para>Output paths of the built derivation, separated by a space character.</para>
+ <para>Example:
+ <literal>/nix/store/zf5lbh336mnzf1nlswdn11g4n2m8zh3g-bash-4.4-p23-dev
+ /nix/store/rjxwxwv1fpn9wa2x5ssk5phzwlcv4mna-bash-4.4-p23-doc
+ /nix/store/6bqvbzjkcp9695dq0dpl5y43nvy37pq1-bash-4.4-p23-info
+ /nix/store/r7fng3kk3vlpdlh2idnrbn37vh4imlj2-bash-4.4-p23-man
+ /nix/store/xfghy8ixrhz3kyy6p724iv3cxji088dx-bash-4.4-p23</literal>.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ <para>See <xref linkend="chap-post-build-hook"/> for an example
+ implementation.</para>
+
+ </listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-repeat"><term><literal>repeat</literal></term>
+
+ <listitem><para>How many times to repeat builds to check whether
+ they are deterministic. The default value is 0. If the value is
+ non-zero, every build is repeated the specified number of
+ times. If the contents of any of the runs differs from the
+ previous ones and <xref linkend="conf-enforce-determinism"/> is
+ true, the build is rejected and the resulting store paths are not
+ registered as “valid” in Nix’s database.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-require-sigs"><term><literal>require-sigs</literal></term>
+
+ <listitem><para>If set to <literal>true</literal> (the default),
+ any non-content-addressed path added or copied to the Nix store
+ (e.g. when substituting from a binary cache) must have a valid
+ signature, that is, be signed using one of the keys listed in
+ <option>trusted-public-keys</option> or
+ <option>secret-key-files</option>. Set to <literal>false</literal>
+ to disable signature checking.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="conf-restrict-eval"><term><literal>restrict-eval</literal></term>
+
+ <listitem>
+
+ <para>If set to <literal>true</literal>, the Nix evaluator will
+ not allow access to any files outside of the Nix search path (as
+ set via the <envar>NIX_PATH</envar> environment variable or the
+ <option>-I</option> option), or to URIs outside of
+ <option>allowed-uri</option>. The default is
+ <literal>false</literal>.</para>
+
+ </listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-run-diff-hook"><term><literal>run-diff-hook</literal></term>
+ <listitem>
+ <para>
+ If true, enable the execution of <xref linkend="conf-diff-hook"/>.
+ </para>
+
+ <para>
+ When using the Nix daemon, <literal>run-diff-hook</literal> must
+ be set in the <filename>nix.conf</filename> configuration file,
+ and cannot be passed at the command line.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-sandbox"><term><literal>sandbox</literal></term>
+
+ <listitem><para>If set to <literal>true</literal>, builds will be
+ performed in a <emphasis>sandboxed environment</emphasis>, i.e.,
+ they’re isolated from the normal file system hierarchy and will
+ only see their dependencies in the Nix store, the temporary build
+ directory, private versions of <filename>/proc</filename>,
+ <filename>/dev</filename>, <filename>/dev/shm</filename> and
+ <filename>/dev/pts</filename> (on Linux), and the paths configured with the
+ <link linkend="conf-sandbox-paths"><literal>sandbox-paths</literal>
+ option</link>. This is useful to prevent undeclared dependencies
+ on files in directories such as <filename>/usr/bin</filename>. In
+ addition, on Linux, builds run in private PID, mount, network, IPC
+ and UTS namespaces to isolate them from other processes in the
+ system (except that fixed-output derivations do not run in private
+ network namespace to ensure they can access the network).</para>
+
+ <para>Currently, sandboxing only work on Linux and macOS. The use
+ of a sandbox requires that Nix is run as root (so you should use
+ the <link linkend="conf-build-users-group">“build users”
+ feature</link> to perform the actual builds under different users
+ than root).</para>
+
+ <para>If this option is set to <literal>relaxed</literal>, then
+ fixed-output derivations and derivations that have the
+ <varname>__noChroot</varname> attribute set to
+ <literal>true</literal> do not run in sandboxes.</para>
+
+ <para>The default is <literal>true</literal> on Linux and
+ <literal>false</literal> on all other platforms.</para>
+
+ </listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-sandbox-dev-shm-size"><term><literal>sandbox-dev-shm-size</literal></term>
+
+ <listitem><para>This option determines the maximum size of the
+ <literal>tmpfs</literal> filesystem mounted on
+ <filename>/dev/shm</filename> in Linux sandboxes. For the format,
+ see the description of the <option>size</option> option of
+ <literal>tmpfs</literal> in
+ <citerefentry><refentrytitle>mount</refentrytitle><manvolnum>8</manvolnum></citerefentry>. The
+ default is <literal>50%</literal>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="conf-sandbox-paths">
+ <term><literal>sandbox-paths</literal></term>
+
+ <listitem><para>A list of paths bind-mounted into Nix sandbox
+ environments. You can use the syntax
+ <literal><replaceable>target</replaceable>=<replaceable>source</replaceable></literal>
+ to mount a path in a different location in the sandbox; for
+ instance, <literal>/bin=/nix-bin</literal> will mount the path
+ <literal>/nix-bin</literal> as <literal>/bin</literal> inside the
+ sandbox. If <replaceable>source</replaceable> is followed by
+ <literal>?</literal>, then it is not an error if
+ <replaceable>source</replaceable> does not exist; for example,
+ <literal>/dev/nvidiactl?</literal> specifies that
+ <filename>/dev/nvidiactl</filename> will only be mounted in the
+ sandbox if it exists in the host filesystem.</para>
+
+ <para>Depending on how Nix was built, the default value for this option
+ may be empty or provide <filename>/bin/sh</filename> as a
+ bind-mount of <command>bash</command>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="conf-secret-key-files"><term><literal>secret-key-files</literal></term>
+
+ <listitem><para>A whitespace-separated list of files containing
+ secret (private) keys. These are used to sign locally-built
+ paths. They can be generated using <command>nix-store
+ --generate-binary-cache-key</command>. The corresponding public
+ key can be distributed to other users, who can add it to
+ <option>trusted-public-keys</option> in their
+ <filename>nix.conf</filename>.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="conf-show-trace"><term><literal>show-trace</literal></term>
+
+ <listitem><para>Causes Nix to print out a stack trace in case of Nix
+ expression evaluation errors.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="conf-substitute"><term><literal>substitute</literal></term>
+
+ <listitem><para>If set to <literal>true</literal> (default), Nix
+ will use binary substitutes if available. This option can be
+ disabled to force building from source.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-stalled-download-timeout"><term><literal>stalled-download-timeout</literal></term>
+ <listitem>
+ <para>The timeout (in seconds) for receiving data from servers
+ during download. Nix cancels idle downloads after this timeout's
+ duration.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-substituters"><term><literal>substituters</literal></term>
+
+ <listitem><para>A list of URLs of substituters, separated by
+ whitespace. The default is
+ <literal>https://cache.nixos.org</literal>.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-system"><term><literal>system</literal></term>
+
+ <listitem><para>This option specifies the canonical Nix system
+ name of the current installation, such as
+ <literal>i686-linux</literal> or
+ <literal>x86_64-darwin</literal>. Nix can only build derivations
+ whose <literal>system</literal> attribute equals the value
+ specified here. In general, it never makes sense to modify this
+ value from its default, since you can use it to ‘lie’ about the
+ platform you are building on (e.g., perform a Mac OS build on a
+ Linux machine; the result would obviously be wrong). It only
+ makes sense if the Nix binaries can run on multiple platforms,
+ e.g., ‘universal binaries’ that run on <literal>x86_64-linux</literal> and
+ <literal>i686-linux</literal>.</para>
+
+ <para>It defaults to the canonical Nix system name detected by
+ <filename>configure</filename> at build time.</para></listitem>
+
+ </varlistentry>
+
+
+ <varlistentry xml:id="conf-system-features"><term><literal>system-features</literal></term>
+
+ <listitem><para>A set of system “features” supported by this
+ machine, e.g. <literal>kvm</literal>. Derivations can express a
+ dependency on such features through the derivation attribute
+ <varname>requiredSystemFeatures</varname>. For example, the
+ attribute
+
+<programlisting>
+requiredSystemFeatures = [ "kvm" ];
+</programlisting>
+
+ ensures that the derivation can only be built on a machine with
+ the <literal>kvm</literal> feature.</para>
+
+ <para>This setting by default includes <literal>kvm</literal> if
+ <filename>/dev/kvm</filename> is accessible, and the
+ pseudo-features <literal>nixos-test</literal>,
+ <literal>benchmark</literal> and <literal>big-parallel</literal>
+ that are used in Nixpkgs to route builds to specific
+ machines.</para>
+
+ </listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-tarball-ttl"><term><literal>tarball-ttl</literal></term>
+
+ <listitem>
+ <para>Default: <literal>3600</literal> seconds.</para>
+
+ <para>The number of seconds a downloaded tarball is considered
+ fresh. If the cached tarball is stale, Nix will check whether
+ it is still up to date using the ETag header. Nix will download
+ a new version if the ETag header is unsupported, or the
+ cached ETag doesn't match.
+ </para>
+
+ <para>Setting the TTL to <literal>0</literal> forces Nix to always
+ check if the tarball is up to date.</para>
+
+ <para>Nix caches tarballs in
+ <filename>$XDG_CACHE_HOME/nix/tarballs</filename>.</para>
+
+ <para>Files fetched via <envar>NIX_PATH</envar>,
+ <function>fetchGit</function>, <function>fetchMercurial</function>,
+ <function>fetchTarball</function>, and <function>fetchurl</function>
+ respect this TTL.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-timeout"><term><literal>timeout</literal></term>
+
+ <listitem>
+
+ <para>This option defines the maximum number of seconds that a
+ builder can run. This is useful (for instance in an automated
+ build system) to catch builds that are stuck in an infinite loop
+ but keep writing to their standard output or standard error. It
+ can be overridden using the <option linkend="opt-timeout">--timeout</option> command line
+ switch.</para>
+
+ <para>The value <literal>0</literal> means that there is no
+ timeout. This is also the default.</para>
+
+ </listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-trace-function-calls"><term><literal>trace-function-calls</literal></term>
+
+ <listitem>
+
+ <para>Default: <literal>false</literal>.</para>
+
+ <para>If set to <literal>true</literal>, the Nix evaluator will
+ trace every function call. Nix will print a log message at the
+ "vomit" level for every function entrance and function exit.</para>
+
+ <informalexample><screen>
+function-trace entered undefined position at 1565795816999559622
+function-trace exited undefined position at 1565795816999581277
+function-trace entered /nix/store/.../example.nix:226:41 at 1565795253249935150
+function-trace exited /nix/store/.../example.nix:226:41 at 1565795253249941684
+</screen></informalexample>
+
+ <para>The <literal>undefined position</literal> means the function
+ call is a builtin.</para>
+
+ <para>Use the <literal>contrib/stack-collapse.py</literal> script
+ distributed with the Nix source code to convert the trace logs
+ in to a format suitable for <command>flamegraph.pl</command>.</para>
+
+ </listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-trusted-public-keys"><term><literal>trusted-public-keys</literal></term>
+
+ <listitem><para>A whitespace-separated list of public keys. When
+ paths are copied from another Nix store (such as a binary cache),
+ they must be signed with one of these keys. For example:
+ <literal>cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
+ hydra.nixos.org-1:CNHJZBh9K4tP3EKF6FkkgeVYsS3ohTl+oS0Qa8bezVs=</literal>.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-trusted-substituters"><term><literal>trusted-substituters</literal></term>
+
+ <listitem><para>A list of URLs of substituters, separated by
+ whitespace. These are not used by default, but can be enabled by
+ users of the Nix daemon by specifying <literal>--option
+ substituters <replaceable>urls</replaceable></literal> on the
+ command line. Unprivileged users are only allowed to pass a
+ subset of the URLs listed in <literal>substituters</literal> and
+ <literal>trusted-substituters</literal>.</para></listitem>
+
+ </varlistentry>
+
+ <varlistentry xml:id="conf-trusted-users"><term><literal>trusted-users</literal></term>
+
+ <listitem>
+
+ <para>A list of names of users (separated by whitespace) that
+ have additional rights when connecting to the Nix daemon, such
+ as the ability to specify additional binary caches, or to import
+ unsigned NARs. You can also specify groups by prefixing them
+ with <literal>@</literal>; for instance,
+ <literal>@wheel</literal> means all users in the
+ <literal>wheel</literal> group. The default is
+ <literal>root</literal>.</para>
+
+ <warning><para>Adding a user to <option>trusted-users</option>
+ is essentially equivalent to giving that user root access to the
+ system. For example, the user can set
+ <option>sandbox-paths</option> and thereby obtain read access to
+ directories that are otherwise inacessible to
+ them.</para></warning>
+
+ </listitem>
+
+ </varlistentry>
+
+</variablelist>
+</para>
+
+<refsection>
+ <title>Deprecated Settings</title>
+
+<para>
+
+<variablelist>
+
+ <varlistentry xml:id="conf-binary-caches">
+ <term><literal>binary-caches</literal></term>
+
+ <listitem><para><emphasis>Deprecated:</emphasis>
+ <literal>binary-caches</literal> is now an alias to
+ <xref linkend="conf-substituters"/>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-binary-cache-public-keys">
+ <term><literal>binary-cache-public-keys</literal></term>
+
+ <listitem><para><emphasis>Deprecated:</emphasis>
+ <literal>binary-cache-public-keys</literal> is now an alias to
+ <xref linkend="conf-trusted-public-keys"/>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-build-compress-log">
+ <term><literal>build-compress-log</literal></term>
+
+ <listitem><para><emphasis>Deprecated:</emphasis>
+ <literal>build-compress-log</literal> is now an alias to
+ <xref linkend="conf-compress-build-log"/>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-build-cores">
+ <term><literal>build-cores</literal></term>
+
+ <listitem><para><emphasis>Deprecated:</emphasis>
+ <literal>build-cores</literal> is now an alias to
+ <xref linkend="conf-cores"/>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-build-extra-chroot-dirs">
+ <term><literal>build-extra-chroot-dirs</literal></term>
+
+ <listitem><para><emphasis>Deprecated:</emphasis>
+ <literal>build-extra-chroot-dirs</literal> is now an alias to
+ <xref linkend="conf-extra-sandbox-paths"/>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-build-extra-sandbox-paths">
+ <term><literal>build-extra-sandbox-paths</literal></term>
+
+ <listitem><para><emphasis>Deprecated:</emphasis>
+ <literal>build-extra-sandbox-paths</literal> is now an alias to
+ <xref linkend="conf-extra-sandbox-paths"/>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-build-fallback">
+ <term><literal>build-fallback</literal></term>
+
+ <listitem><para><emphasis>Deprecated:</emphasis>
+ <literal>build-fallback</literal> is now an alias to
+ <xref linkend="conf-fallback"/>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-build-max-jobs">
+ <term><literal>build-max-jobs</literal></term>
+
+ <listitem><para><emphasis>Deprecated:</emphasis>
+ <literal>build-max-jobs</literal> is now an alias to
+ <xref linkend="conf-max-jobs"/>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-build-max-log-size">
+ <term><literal>build-max-log-size</literal></term>
+
+ <listitem><para><emphasis>Deprecated:</emphasis>
+ <literal>build-max-log-size</literal> is now an alias to
+ <xref linkend="conf-max-build-log-size"/>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-build-max-silent-time">
+ <term><literal>build-max-silent-time</literal></term>
+
+ <listitem><para><emphasis>Deprecated:</emphasis>
+ <literal>build-max-silent-time</literal> is now an alias to
+ <xref linkend="conf-max-silent-time"/>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-build-repeat">
+ <term><literal>build-repeat</literal></term>
+
+ <listitem><para><emphasis>Deprecated:</emphasis>
+ <literal>build-repeat</literal> is now an alias to
+ <xref linkend="conf-repeat"/>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-build-timeout">
+ <term><literal>build-timeout</literal></term>
+
+ <listitem><para><emphasis>Deprecated:</emphasis>
+ <literal>build-timeout</literal> is now an alias to
+ <xref linkend="conf-timeout"/>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-build-use-chroot">
+ <term><literal>build-use-chroot</literal></term>
+
+ <listitem><para><emphasis>Deprecated:</emphasis>
+ <literal>build-use-chroot</literal> is now an alias to
+ <xref linkend="conf-sandbox"/>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-build-use-sandbox">
+ <term><literal>build-use-sandbox</literal></term>
+
+ <listitem><para><emphasis>Deprecated:</emphasis>
+ <literal>build-use-sandbox</literal> is now an alias to
+ <xref linkend="conf-sandbox"/>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-build-use-substitutes">
+ <term><literal>build-use-substitutes</literal></term>
+
+ <listitem><para><emphasis>Deprecated:</emphasis>
+ <literal>build-use-substitutes</literal> is now an alias to
+ <xref linkend="conf-substitute"/>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-gc-keep-derivations">
+ <term><literal>gc-keep-derivations</literal></term>
+
+ <listitem><para><emphasis>Deprecated:</emphasis>
+ <literal>gc-keep-derivations</literal> is now an alias to
+ <xref linkend="conf-keep-derivations"/>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-gc-keep-outputs">
+ <term><literal>gc-keep-outputs</literal></term>
+
+ <listitem><para><emphasis>Deprecated:</emphasis>
+ <literal>gc-keep-outputs</literal> is now an alias to
+ <xref linkend="conf-keep-outputs"/>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-env-keep-derivations">
+ <term><literal>env-keep-derivations</literal></term>
+
+ <listitem><para><emphasis>Deprecated:</emphasis>
+ <literal>env-keep-derivations</literal> is now an alias to
+ <xref linkend="conf-keep-env-derivations"/>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-extra-binary-caches">
+ <term><literal>extra-binary-caches</literal></term>
+
+ <listitem><para><emphasis>Deprecated:</emphasis>
+ <literal>extra-binary-caches</literal> is now an alias to
+ <xref linkend="conf-extra-substituters"/>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry xml:id="conf-trusted-binary-caches">
+ <term><literal>trusted-binary-caches</literal></term>
+
+ <listitem><para><emphasis>Deprecated:</emphasis>
+ <literal>trusted-binary-caches</literal> is now an alias to
+ <xref linkend="conf-trusted-substituters"/>.</para></listitem>
+ </varlistentry>
+</variablelist>
+</para>
+</refsection>
+
+</refsection>
+
+</refentry>
+
+</chapter>
+
+</part>
+ <appendix xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="part-glossary" xml:base="glossary/glossary.xml">
+
+<title>Glossary</title>
+
+
+<glosslist>
+
+
+<glossentry xml:id="gloss-derivation"><glossterm>derivation</glossterm>
+
+ <glossdef><para>A description of a build action. The result of a
+ derivation is a store object. Derivations are typically specified
+ in Nix expressions using the <link linkend="ssec-derivation"><function>derivation</function>
+ primitive</link>. These are translated into low-level
+ <emphasis>store derivations</emphasis> (implicitly by
+ <command>nix-env</command> and <command>nix-build</command>, or
+ explicitly by <command>nix-instantiate</command>).</para></glossdef>
+
+</glossentry>
+
+
+<glossentry><glossterm>store</glossterm>
+
+ <glossdef><para>The location in the file system where store objects
+ live. Typically <filename>/nix/store</filename>.</para></glossdef>
+
+</glossentry>
+
+
+<glossentry><glossterm>store path</glossterm>
+
+ <glossdef><para>The location in the file system of a store object,
+ i.e., an immediate child of the Nix store
+ directory.</para></glossdef>
+
+</glossentry>
+
+
+<glossentry><glossterm>store object</glossterm>
+
+ <glossdef><para>A file that is an immediate child of the Nix store
+ directory. These can be regular files, but also entire directory
+ trees. Store objects can be sources (objects copied from outside of
+ the store), derivation outputs (objects produced by running a build
+ action), or derivations (files describing a build
+ action).</para></glossdef>
+
+</glossentry>
+
+
+<glossentry xml:id="gloss-substitute"><glossterm>substitute</glossterm>
+
+ <glossdef><para>A substitute is a command invocation stored in the
+ Nix database that describes how to build a store object, bypassing
+ the normal build mechanism (i.e., derivations). Typically, the
+ substitute builds the store object by downloading a pre-built
+ version of the store object from some server.</para></glossdef>
+
+</glossentry>
+
+
+<glossentry><glossterm>purity</glossterm>
+
+ <glossdef><para>The assumption that equal Nix derivations when run
+ always produce the same output. This cannot be guaranteed in
+ general (e.g., a builder can rely on external inputs such as the
+ network or the system time) but the Nix model assumes
+ it.</para></glossdef>
+
+</glossentry>
+
+
+<glossentry><glossterm>Nix expression</glossterm>
+
+ <glossdef><para>A high-level description of software packages and
+ compositions thereof. Deploying software using Nix entails writing
+ Nix expressions for your packages. Nix expressions are translated
+ to derivations that are stored in the Nix store. These derivations
+ can then be built.</para></glossdef>
+
+</glossentry>
+
+
+<glossentry xml:id="gloss-reference"><glossterm>reference</glossterm>
+
+ <glossdef>
+ <para>A store path <varname>P</varname> is said to have a
+ reference to a store path <varname>Q</varname> if the store object
+ at <varname>P</varname> contains the path <varname>Q</varname>
+ somewhere. The <emphasis>references</emphasis> of a store path are
+ the set of store paths to which it has a reference.
+ </para>
+ <para>A derivation can reference other derivations and sources
+ (but not output paths), whereas an output path only references other
+ output paths.
+ </para>
+ </glossdef>
+
+</glossentry>
+
+<glossentry xml:id="gloss-reachable"><glossterm>reachable</glossterm>
+
+ <glossdef><para>A store path <varname>Q</varname> is reachable from
+ another store path <varname>P</varname> if <varname>Q</varname> is in the
+ <link linkend="gloss-closure">closure</link> of the
+ <link linkend="gloss-reference">references</link> relation.
+ </para></glossdef>
+</glossentry>
+
+<glossentry xml:id="gloss-closure"><glossterm>closure</glossterm>
+
+ <glossdef><para>The closure of a store path is the set of store
+ paths that are directly or indirectly “reachable” from that store
+ path; that is, it’s the closure of the path under the <link linkend="gloss-reference">references</link> relation. For a package, the
+ closure of its derivation is equivalent to the build-time
+ dependencies, while the closure of its output path is equivalent to its
+ runtime dependencies. For correct deployment it is necessary to deploy whole
+ closures, since otherwise at runtime files could be missing. The command
+ <command>nix-store -qR</command> prints out closures of store paths.
+ </para>
+ <para>As an example, if the store object at path <varname>P</varname> contains
+ a reference to path <varname>Q</varname>, then <varname>Q</varname> is
+ in the closure of <varname>P</varname>. Further, if <varname>Q</varname>
+ references <varname>R</varname> then <varname>R</varname> is also in
+ the closure of <varname>P</varname>.
+ </para></glossdef>
+
+</glossentry>
+
+
+<glossentry xml:id="gloss-output-path"><glossterm>output path</glossterm>
+
+ <glossdef><para>A store path produced by a derivation.</para></glossdef>
+
+</glossentry>
+
+
+<glossentry xml:id="gloss-deriver"><glossterm>deriver</glossterm>
+
+ <glossdef><para>The deriver of an <link linkend="gloss-output-path">output path</link> is the store
+ derivation that built it.</para></glossdef>
+
+</glossentry>
+
+
+<glossentry xml:id="gloss-validity"><glossterm>validity</glossterm>
+
+ <glossdef><para>A store path is considered
+ <emphasis>valid</emphasis> if it exists in the file system, is
+ listed in the Nix database as being valid, and if all paths in its
+ closure are also valid.</para></glossdef>
+
+</glossentry>
+
+
+<glossentry xml:id="gloss-user-env"><glossterm>user environment</glossterm>
+
+ <glossdef><para>An automatically generated store object that
+ consists of a set of symlinks to “active” applications, i.e., other
+ store paths. These are generated automatically by <link linkend="sec-nix-env"><command>nix-env</command></link>. See <xref linkend="sec-profiles"/>.</para>
+
+ </glossdef>
+
+</glossentry>
+
+
+<glossentry xml:id="gloss-profile"><glossterm>profile</glossterm>
+
+ <glossdef><para>A symlink to the current <link linkend="gloss-user-env">user environment</link> of a user, e.g.,
+ <filename>/nix/var/nix/profiles/default</filename>.</para></glossdef>
+
+</glossentry>
+
+
+<glossentry xml:id="gloss-nar"><glossterm>NAR</glossterm>
+
+ <glossdef><para>A <emphasis>N</emphasis>ix
+ <emphasis>AR</emphasis>chive. This is a serialisation of a path in
+ the Nix store. It can contain regular files, directories and
+ symbolic links. NARs are generated and unpacked using
+ <command>nix-store --dump</command> and <command>nix-store
+ --restore</command>.</para></glossdef>
+
+</glossentry>
+
+
+
+</glosslist>
+
+
+</appendix>
+ <appendix xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="chap-hacking">
+
+<title>Hacking</title>
+
+<para>This section provides some notes on how to hack on Nix. To get
+the latest version of Nix from GitHub:
+<screen>
+$ git clone https://github.com/NixOS/nix.git
+$ cd nix
+</screen>
+</para>
+
+<para>To build Nix for the current operating system/architecture use
+
+<screen>
+$ nix-build
+</screen>
+
+or if you have a flakes-enabled nix:
+
+<screen>
+$ nix build
+</screen>
+
+This will build <literal>defaultPackage</literal> attribute defined in the <literal>flake.nix</literal> file.
+
+To build for other platforms add one of the following suffixes to it: aarch64-linux,
+i686-linux, x86_64-darwin, x86_64-linux.
+
+i.e.
+
+<screen>
+nix-build -A defaultPackage.x86_64-linux
+</screen>
+
+</para>
+
+<para>To build all dependencies and start a shell in which all
+environment variables are set up so that those dependencies can be
+found:
+<screen>
+$ nix-shell
+</screen>
+To build Nix itself in this shell:
+<screen>
+[nix-shell]$ ./bootstrap.sh
+[nix-shell]$ ./configure $configureFlags
+[nix-shell]$ make -j $NIX_BUILD_CORES
+</screen>
+To install it in <literal>$(pwd)/inst</literal> and test it:
+<screen>
+[nix-shell]$ make install
+[nix-shell]$ make installcheck
+[nix-shell]$ ./inst/bin/nix --version
+nix (Nix) 2.4
+</screen>
+
+If you have a flakes-enabled nix you can replace:
+
+<screen>
+$ nix-shell
+</screen>
+
+by:
+
+<screen>
+$ nix develop
+</screen>
+
+</para>
+
+</appendix>
+ <appendix xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-relnotes" xml:base="release-notes/release-notes.xml">
+
+<title>Nix Release Notes</title>
+
+<!--
+<partintro>
+<para>This section lists the release notes for each stable version of Nix.</para>
+</partintro>
+-->
+
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-2.3">
+
+<title>Release 2.3 (2019-09-04)</title>
+
+<para>This is primarily a bug fix release. However, it makes some
+incompatible changes:</para>
+
+<itemizedlist>
+
+ <listitem>
+ <para>Nix now uses BSD file locks instead of POSIX file
+ locks. Because of this, you should not use Nix 2.3 and previous
+ releases at the same time on a Nix store.</para>
+ </listitem>
+
+</itemizedlist>
+
+<para>It also has the following changes:</para>
+
+<itemizedlist>
+
+ <listitem>
+ <para><function>builtins.fetchGit</function>'s <varname>ref</varname>
+ argument now allows specifying an absolute remote ref.
+ Nix will automatically prefix <varname>ref</varname> with
+ <literal>refs/heads</literal> only if <varname>ref</varname> doesn't
+ already begin with <literal>refs/</literal>.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>The installer now enables sandboxing by default on Linux when the
+ system has the necessary kernel support.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>The <literal>max-jobs</literal> setting now defaults to 1.</para>
+ </listitem>
+
+ <listitem>
+ <para>New builtin functions:
+ <literal>builtins.isPath</literal>,
+ <literal>builtins.hashFile</literal>.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>The <command>nix</command> command has a new
+ <option>--print-build-logs</option> (<option>-L</option>) flag to
+ print build log output to stderr, rather than showing the last log
+ line in the progress bar. To distinguish between concurrent
+ builds, log lines are prefixed by the name of the package.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>Builds are now executed in a pseudo-terminal, and the
+ <envar>TERM</envar> environment variable is set to
+ <literal>xterm-256color</literal>. This allows many programs
+ (e.g. <command>gcc</command>, <command>clang</command>,
+ <command>cmake</command>) to print colorized log output.</para>
+ </listitem>
+
+ <listitem>
+ <para>Add <option>--no-net</option> convenience flag. This flag
+ disables substituters; sets the <literal>tarball-ttl</literal>
+ setting to infinity (ensuring that any previously downloaded files
+ are considered current); and disables retrying downloads and sets
+ the connection timeout to the minimum. This flag is enabled
+ automatically if there are no configured non-loopback network
+ interfaces.</para>
+ </listitem>
+
+ <listitem>
+ <para>Add a <literal>post-build-hook</literal> setting to run a
+ program after a build has succeeded.</para>
+ </listitem>
+
+ <listitem>
+ <para>Add a <literal>trace-function-calls</literal> setting to log
+ the duration of Nix function calls to stderr.</para>
+ </listitem>
+
+</itemizedlist>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-2.2">
+
+<title>Release 2.2 (2019-01-11)</title>
+
+<para>This is primarily a bug fix release. It also has the following
+changes:</para>
+
+<itemizedlist>
+
+ <listitem>
+ <para>In derivations that use structured attributes (i.e. that
+ specify set the <varname>__structuredAttrs</varname> attribute to
+ <literal>true</literal> to cause all attributes to be passed to
+ the builder in JSON format), you can now specify closure checks
+ per output, e.g.:
+
+<programlisting>
+outputChecks."out" = {
+ # The closure of 'out' must not be larger than 256 MiB.
+ maxClosureSize = 256 * 1024 * 1024;
+
+ # It must not refer to C compiler or to the 'dev' output.
+ disallowedRequisites = [ stdenv.cc "dev" ];
+};
+
+outputChecks."dev" = {
+ # The 'dev' output must not be larger than 128 KiB.
+ maxSize = 128 * 1024;
+};
+</programlisting>
+
+ </para>
+ </listitem>
+
+
+ <listitem>
+ <para>The derivation attribute
+ <varname>requiredSystemFeatures</varname> is now enforced for
+ local builds, and not just to route builds to remote builders.
+ The supported features of a machine can be specified through the
+ configuration setting <varname>system-features</varname>.</para>
+
+ <para>By default, <varname>system-features</varname> includes
+ <literal>kvm</literal> if <filename>/dev/kvm</filename>
+ exists. For compatibility, it also includes the pseudo-features
+ <literal>nixos-test</literal>, <literal>benchmark</literal> and
+ <literal>big-parallel</literal> which are used by Nixpkgs to route
+ builds to particular Hydra build machines.</para>
+
+ </listitem>
+
+ <listitem>
+ <para>Sandbox builds are now enabled by default on Linux.</para>
+ </listitem>
+
+ <listitem>
+ <para>The new command <command>nix doctor</command> shows
+ potential issues with your Nix installation.</para>
+ </listitem>
+
+ <listitem>
+ <para>The <literal>fetchGit</literal> builtin function now uses a
+ caching scheme that puts different remote repositories in distinct
+ local repositories, rather than a single shared repository. This
+ may require more disk space but is faster.</para>
+ </listitem>
+
+ <listitem>
+ <para>The <literal>dirOf</literal> builtin function now works on
+ relative paths.</para>
+ </listitem>
+
+ <listitem>
+ <para>Nix now supports <link xlink:href="https://www.w3.org/TR/SRI/">SRI hashes</link>,
+ allowing the hash algorithm and hash to be specified in a single
+ string. For example, you can write:
+
+<programlisting>
+import <nix/fetchurl.nix> {
+ url = https://nixos.org/releases/nix/nix-2.1.3/nix-2.1.3.tar.xz;
+ hash = "sha256-XSLa0FjVyADWWhFfkZ2iKTjFDda6mMXjoYMXLRSYQKQ=";
+};
+</programlisting>
+
+ instead of
+
+<programlisting>
+import <nix/fetchurl.nix> {
+ url = https://nixos.org/releases/nix/nix-2.1.3/nix-2.1.3.tar.xz;
+ sha256 = "5d22dad058d5c800d65a115f919da22938c50dd6ba98c5e3a183172d149840a4";
+};
+</programlisting>
+
+ </para>
+
+ <para>In fixed-output derivations, the
+ <varname>outputHashAlgo</varname> attribute is no longer mandatory
+ if <varname>outputHash</varname> specifies the hash.</para>
+
+ <para><command>nix hash-file</command> and <command>nix
+ hash-path</command> now print hashes in SRI format by
+ default. They also use SHA-256 by default instead of SHA-512
+ because that's what we use most of the time in Nixpkgs.</para>
+ </listitem>
+
+ <listitem>
+ <para>Integers are now 64 bits on all platforms.</para>
+ </listitem>
+
+ <listitem>
+ <para>The evaluator now prints profiling statistics (enabled via
+ the <envar>NIX_SHOW_STATS</envar> and
+ <envar>NIX_COUNT_CALLS</envar> environment variables) in JSON
+ format.</para>
+ </listitem>
+
+ <listitem>
+ <para>The option <option>--xml</option> in <command>nix-store
+ --query</command> has been removed. Instead, there now is an
+ option <option>--graphml</option> to output the dependency graph
+ in GraphML format.</para>
+ </listitem>
+
+ <listitem>
+ <para>All <filename>nix-*</filename> commands are now symlinks to
+ <filename>nix</filename>. This saves a bit of disk space.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix repl</command> now uses
+ <literal>libeditline</literal> or
+ <literal>libreadline</literal>.</para>
+ </listitem>
+
+</itemizedlist>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-2.1">
+
+<title>Release 2.1 (2018-09-02)</title>
+
+<para>This is primarily a bug fix release. It also reduces memory
+consumption in certain situations. In addition, it has the following
+new features:</para>
+
+<itemizedlist>
+
+ <listitem>
+ <para>The Nix installer will no longer default to the Multi-User
+ installation for macOS. You can still <link linkend="sect-multi-user-installation">instruct the installer to
+ run in multi-user mode</link>.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>The Nix installer now supports performing a Multi-User
+ installation for Linux computers which are running systemd. You
+ can <link linkend="sect-multi-user-installation">select a Multi-User installation</link> by passing the
+ <option>--daemon</option> flag to the installer: <command>sh <(curl
+ https://nixos.org/nix/install) --daemon</command>.
+ </para>
+
+ <para>The multi-user installer cannot handle systems with SELinux.
+ If your system has SELinux enabled, you can <link linkend="sect-single-user-installation">force the installer to run
+ in single-user mode</link>.</para>
+ </listitem>
+
+ <listitem>
+ <para>New builtin functions:
+ <literal>builtins.bitAnd</literal>,
+ <literal>builtins.bitOr</literal>,
+ <literal>builtins.bitXor</literal>,
+ <literal>builtins.fromTOML</literal>,
+ <literal>builtins.concatMap</literal>,
+ <literal>builtins.mapAttrs</literal>.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>The S3 binary cache store now supports uploading NARs larger
+ than 5 GiB.</para>
+ </listitem>
+
+ <listitem>
+ <para>The S3 binary cache store now supports uploading to
+ S3-compatible services with the <literal>endpoint</literal>
+ option.</para>
+ </listitem>
+
+ <listitem>
+ <para>The flag <option>--fallback</option> is no longer required
+ to recover from disappeared NARs in binary caches.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix-daemon</command> now respects
+ <option>--store</option>.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix run</command> now respects
+ <varname>nix-support/propagated-user-env-packages</varname>.</para>
+ </listitem>
+
+</itemizedlist>
+
+<para>This release has contributions from
+
+Adrien Devresse,
+Aleksandr Pashkov,
+Alexandre Esteves,
+Amine Chikhaoui,
+Andrew Dunham,
+Asad Saeeduddin,
+aszlig,
+Ben Challenor,
+Ben Gamari,
+Benjamin Hipple,
+Bogdan Seniuc,
+Corey O'Connor,
+Daiderd Jordan,
+Daniel Peebles,
+Daniel Poelzleithner,
+Danylo Hlynskyi,
+Dmitry Kalinkin,
+Domen Kožar,
+Doug Beardsley,
+Eelco Dolstra,
+Erik Arvstedt,
+Félix Baylac-Jacqué,
+Gleb Peregud,
+Graham Christensen,
+Guillaume Maudoux,
+Ivan Kozik,
+John Arnold,
+Justin Humm,
+Linus Heckemann,
+Lorenzo Manacorda,
+Matthew Justin Bauer,
+Matthew O'Gorman,
+Maximilian Bosch,
+Michael Bishop,
+Michael Fiano,
+Michael Mercier,
+Michael Raskin,
+Michael Weiss,
+Nicolas Dudebout,
+Peter Simons,
+Ryan Trinkle,
+Samuel Dionne-Riel,
+Sean Seefried,
+Shea Levy,
+Symphorien Gibol,
+Tim Engler,
+Tim Sears,
+Tuomas Tynkkynen,
+volth,
+Will Dietz,
+Yorick van Pelt and
+zimbatm.
+</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-2.0">
+
+<title>Release 2.0 (2018-02-22)</title>
+
+<para>The following incompatible changes have been made:</para>
+
+<itemizedlist>
+
+ <listitem>
+ <para>The manifest-based substituter mechanism
+ (<command>download-using-manifests</command>) has been <link xlink:href="https://github.com/NixOS/nix/commit/867967265b80946dfe1db72d40324b4f9af988ed">removed</link>. It
+ has been superseded by the binary cache substituter mechanism
+ since several years. As a result, the following programs have been
+ removed:
+
+ <itemizedlist>
+ <listitem><para><command>nix-pull</command></para></listitem>
+ <listitem><para><command>nix-generate-patches</command></para></listitem>
+ <listitem><para><command>bsdiff</command></para></listitem>
+ <listitem><para><command>bspatch</command></para></listitem>
+ </itemizedlist>
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>The “copy from other stores” substituter mechanism
+ (<command>copy-from-other-stores</command> and the
+ <envar>NIX_OTHER_STORES</envar> environment variable) has been
+ removed. It was primarily used by the NixOS installer to copy
+ available paths from the installation medium. The replacement is
+ to use a chroot store as a substituter
+ (e.g. <literal>--substituters /mnt</literal>), or to build into a
+ chroot store (e.g. <literal>--store /mnt --substituters /</literal>).</para>
+ </listitem>
+
+ <listitem>
+ <para>The command <command>nix-push</command> has been removed as
+ part of the effort to eliminate Nix's dependency on Perl. You can
+ use <command>nix copy</command> instead, e.g. <literal>nix copy
+ --to file:///tmp/my-binary-cache <replaceable>paths…</replaceable></literal></para>
+ </listitem>
+
+ <listitem>
+ <para>The “nested” log output feature (<option>--log-type
+ pretty</option>) has been removed. As a result,
+ <command>nix-log2xml</command> was also removed.</para>
+ </listitem>
+
+ <listitem>
+ <para>OpenSSL-based signing has been <link xlink:href="https://github.com/NixOS/nix/commit/f435f8247553656774dd1b2c88e9de5d59cab203">removed</link>. This
+ feature was never well-supported. A better alternative is provided
+ by the <option>secret-key-files</option> and
+ <option>trusted-public-keys</option> options.</para>
+ </listitem>
+
+ <listitem>
+ <para>Failed build caching has been <link xlink:href="https://github.com/NixOS/nix/commit/8cffec84859cec8b610a2a22ab0c4d462a9351ff">removed</link>. This
+ feature was introduced to support the Hydra continuous build
+ system, but Hydra no longer uses it.</para>
+ </listitem>
+
+ <listitem>
+ <para><filename>nix-mode.el</filename> has been removed from
+ Nix. It is now <link xlink:href="https://github.com/NixOS/nix-mode">a separate
+ repository</link> and can be installed through the MELPA package
+ repository.</para>
+ </listitem>
+
+</itemizedlist>
+
+<para>This release has the following new features:</para>
+
+<itemizedlist>
+
+ <listitem>
+ <para>It introduces a new command named <command>nix</command>,
+ which is intended to eventually replace all
+ <command>nix-*</command> commands with a more consistent and
+ better designed user interface. It currently provides replacements
+ for some (but not all) of the functionality provided by
+ <command>nix-store</command>, <command>nix-build</command>,
+ <command>nix-shell -p</command>, <command>nix-env -qa</command>,
+ <command>nix-instantiate --eval</command>,
+ <command>nix-push</command> and
+ <command>nix-copy-closure</command>. It has the following major
+ features:</para>
+
+ <itemizedlist>
+
+ <listitem>
+ <para>Unlike the legacy commands, it has a consistent way to
+ refer to packages and package-like arguments (like store
+ paths). For example, the following commands all copy the GNU
+ Hello package to a remote machine:
+
+ <screen>nix copy --to ssh://machine nixpkgs.hello</screen>
+ <screen>nix copy --to ssh://machine /nix/store/0i2jd68mp5g6h2sa5k9c85rb80sn8hi9-hello-2.10</screen>
+ <screen>nix copy --to ssh://machine '(with import <nixpkgs> {}; hello)'</screen>
+
+ By contrast, <command>nix-copy-closure</command> only accepted
+ store paths as arguments.</para>
+ </listitem>
+
+ <listitem>
+ <para>It is self-documenting: <option>--help</option> shows
+ all available command-line arguments. If
+ <option>--help</option> is given after a subcommand, it shows
+ examples for that subcommand. <command>nix
+ --help-config</command> shows all configuration
+ options.</para>
+ </listitem>
+
+ <listitem>
+ <para>It is much less verbose. By default, it displays a
+ single-line progress indicator that shows how many packages
+ are left to be built or downloaded, and (if there are running
+ builds) the most recent line of builder output. If a build
+ fails, it shows the last few lines of builder output. The full
+ build log can be retrieved using <command>nix
+ log</command>.</para>
+ </listitem>
+
+ <listitem>
+ <para>It <link xlink:href="https://github.com/NixOS/nix/commit/b8283773bd64d7da6859ed520ee19867742a03ba">provides</link>
+ all <filename>nix.conf</filename> configuration options as
+ command line flags. For example, instead of <literal>--option
+ http-connections 100</literal> you can write
+ <literal>--http-connections 100</literal>. Boolean options can
+ be written as
+ <literal>--<replaceable>foo</replaceable></literal> or
+ <literal>--no-<replaceable>foo</replaceable></literal>
+ (e.g. <option>--no-auto-optimise-store</option>).</para>
+ </listitem>
+
+ <listitem>
+ <para>Many subcommands have a <option>--json</option> flag to
+ write results to stdout in JSON format.</para>
+ </listitem>
+
+ </itemizedlist>
+
+ <warning><para>Please note that the <command>nix</command> command
+ is a work in progress and the interface is subject to
+ change.</para></warning>
+
+ <para>It provides the following high-level (“porcelain”)
+ subcommands:</para>
+
+ <itemizedlist>
+
+ <listitem>
+ <para><command>nix build</command> is a replacement for
+ <command>nix-build</command>.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix run</command> executes a command in an
+ environment in which the specified packages are available. It
+ is (roughly) a replacement for <command>nix-shell
+ -p</command>. Unlike that command, it does not execute the
+ command in a shell, and has a flag (<command>-c</command>)
+ that specifies the unquoted command line to be
+ executed.</para>
+
+ <para>It is particularly useful in conjunction with chroot
+ stores, allowing Linux users who do not have permission to
+ install Nix in <command>/nix/store</command> to still use
+ binary substitutes that assume
+ <command>/nix/store</command>. For example,
+
+ <screen>nix run --store ~/my-nix nixpkgs.hello -c hello --greeting 'Hi everybody!'</screen>
+
+ downloads (or if not substitutes are available, builds) the
+ GNU Hello package into
+ <filename>~/my-nix/nix/store</filename>, then runs
+ <command>hello</command> in a mount namespace where
+ <filename>~/my-nix/nix/store</filename> is mounted onto
+ <command>/nix/store</command>.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix search</command> replaces <command>nix-env
+ -qa</command>. It searches the available packages for
+ occurrences of a search string in the attribute name, package
+ name or description. Unlike <command>nix-env -qa</command>, it
+ has a cache to speed up subsequent searches.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix copy</command> copies paths between
+ arbitrary Nix stores, generalising
+ <command>nix-copy-closure</command> and
+ <command>nix-push</command>.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix repl</command> replaces the external
+ program <command>nix-repl</command>. It provides an
+ interactive environment for evaluating and building Nix
+ expressions. Note that it uses <literal>linenoise-ng</literal>
+ instead of GNU Readline.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix upgrade-nix</command> upgrades Nix to the
+ latest stable version. This requires that Nix is installed in
+ a profile. (Thus it won’t work on NixOS, or if it’s installed
+ outside of the Nix store.)</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix verify</command> checks whether store paths
+ are unmodified and/or “trusted” (see below). It replaces
+ <command>nix-store --verify</command> and <command>nix-store
+ --verify-path</command>.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix log</command> shows the build log of a
+ package or path. If the build log is not available locally, it
+ will try to obtain it from the configured substituters (such
+ as <uri>cache.nixos.org</uri>, which now provides build
+ logs).</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix edit</command> opens the source code of a
+ package in your editor.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix eval</command> replaces
+ <command>nix-instantiate --eval</command>.</para>
+ </listitem>
+
+ <listitem>
+ <para><command xlink:href="https://github.com/NixOS/nix/commit/d41c5eb13f4f3a37d80dbc6d3888644170c3b44a">nix
+ why-depends</command> shows why one store path has another in
+ its closure. This is primarily useful to finding the causes of
+ closure bloat. For example,
+
+ <screen>nix why-depends nixpkgs.vlc nixpkgs.libdrm.dev</screen>
+
+ shows a chain of files and fragments of file contents that
+ cause the VLC package to have the “dev” output of
+ <literal>libdrm</literal> in its closure — an undesirable
+ situation.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix path-info</command> shows information about
+ store paths, replacing <command>nix-store -q</command>. A
+ useful feature is the option <option>--closure-size</option>
+ (<option>-S</option>). For example, the following command show
+ the closure sizes of every path in the current NixOS system
+ closure, sorted by size:
+
+ <screen>nix path-info -rS /run/current-system | sort -nk2</screen>
+
+ </para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix optimise-store</command> replaces
+ <command>nix-store --optimise</command>. The main difference
+ is that it has a progress indicator.</para>
+ </listitem>
+
+ </itemizedlist>
+
+ <para>A number of low-level (“plumbing”) commands are also
+ available:</para>
+
+ <itemizedlist>
+
+ <listitem>
+ <para><command>nix ls-store</command> and <command>nix
+ ls-nar</command> list the contents of a store path or NAR
+ file. The former is primarily useful in conjunction with
+ remote stores, e.g.
+
+ <screen>nix ls-store --store https://cache.nixos.org/ -lR /nix/store/0i2jd68mp5g6h2sa5k9c85rb80sn8hi9-hello-2.10</screen>
+
+ lists the contents of path in a binary cache.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix cat-store</command> and <command>nix
+ cat-nar</command> allow extracting a file from a store path or
+ NAR file.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix dump-path</command> writes the contents of
+ a store path to stdout in NAR format. This replaces
+ <command>nix-store --dump</command>.</para>
+ </listitem>
+
+ <listitem>
+ <para><command xlink:href="https://github.com/NixOS/nix/commit/e8d6ee7c1b90a2fe6d824f1a875acc56799ae6e2">nix
+ show-derivation</command> displays a store derivation in JSON
+ format. This is an alternative to
+ <command>pp-aterm</command>.</para>
+ </listitem>
+
+ <listitem>
+ <para><command xlink:href="https://github.com/NixOS/nix/commit/970366266b8df712f5f9cedb45af183ef5a8357f">nix
+ add-to-store</command> replaces <command>nix-store
+ --add</command>.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix sign-paths</command> signs store
+ paths.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix copy-sigs</command> copies signatures from
+ one store to another.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix show-config</command> shows all
+ configuration options and their current values.</para>
+ </listitem>
+
+ </itemizedlist>
+
+ </listitem>
+
+ <listitem>
+ <para>The store abstraction that Nix has had for a long time to
+ support store access via the Nix daemon has been extended
+ significantly. In particular, substituters (which used to be
+ external programs such as
+ <command>download-from-binary-cache</command>) are now subclasses
+ of the abstract <classname>Store</classname> class. This allows
+ many Nix commands to operate on such store types. For example,
+ <command>nix path-info</command> shows information about paths in
+ your local Nix store, while <command>nix path-info --store
+ https://cache.nixos.org/</command> shows information about paths
+ in the specified binary cache. Similarly,
+ <command>nix-copy-closure</command>, <command>nix-push</command>
+ and substitution are all instances of the general notion of
+ copying paths between different kinds of Nix stores.</para>
+
+ <para>Stores are specified using an URI-like syntax,
+ e.g. <uri>https://cache.nixos.org/</uri> or
+ <uri>ssh://machine</uri>. The following store types are supported:
+
+ <itemizedlist>
+
+ <listitem>
+
+ <para><classname>LocalStore</classname> (stori URI
+ <literal>local</literal> or an absolute path) and the misnamed
+ <classname>RemoteStore</classname> (<literal>daemon</literal>)
+ provide access to a local Nix store, the latter via the Nix
+ daemon. You can use <literal>auto</literal> or the empty
+ string to auto-select a local or daemon store depending on
+ whether you have write permission to the Nix store. It is no
+ longer necessary to set the <envar>NIX_REMOTE</envar>
+ environment variable to use the Nix daemon.</para>
+
+ <para>As noted above, <classname>LocalStore</classname> now
+ supports chroot builds, allowing the “physical” location of
+ the Nix store
+ (e.g. <filename>/home/alice/nix/store</filename>) to differ
+ from its “logical” location (typically
+ <filename>/nix/store</filename>). This allows non-root users
+ to use Nix while still getting the benefits from prebuilt
+ binaries from <uri>cache.nixos.org</uri>.</para>
+
+ </listitem>
+
+ <listitem>
+
+ <para><classname>BinaryCacheStore</classname> is the abstract
+ superclass of all binary cache stores. It supports writing
+ build logs and NAR content listings in JSON format.</para>
+
+ </listitem>
+
+ <listitem>
+
+ <para><classname>HttpBinaryCacheStore</classname>
+ (<literal>http://</literal>, <literal>https://</literal>)
+ supports binary caches via HTTP or HTTPS. If the server
+ supports <literal>PUT</literal> requests, it supports
+ uploading store paths via commands such as <command>nix
+ copy</command>.</para>
+
+ </listitem>
+
+ <listitem>
+
+ <para><classname>LocalBinaryCacheStore</classname>
+ (<literal>file://</literal>) supports binary caches in the
+ local filesystem.</para>
+
+ </listitem>
+
+ <listitem>
+
+ <para><classname>S3BinaryCacheStore</classname>
+ (<literal>s3://</literal>) supports binary caches stored in
+ Amazon S3, if enabled at compile time.</para>
+
+ </listitem>
+
+ <listitem>
+
+ <para><classname>LegacySSHStore</classname> (<literal>ssh://</literal>)
+ is used to implement remote builds and
+ <command>nix-copy-closure</command>.</para>
+
+ </listitem>
+
+ <listitem>
+
+ <para><classname>SSHStore</classname>
+ (<literal>ssh-ng://</literal>) supports arbitrary Nix
+ operations on a remote machine via the same protocol used by
+ <command>nix-daemon</command>.</para>
+
+ </listitem>
+
+ </itemizedlist>
+
+ </para>
+
+ </listitem>
+
+ <listitem>
+
+ <para>Security has been improved in various ways:
+
+ <itemizedlist>
+
+ <listitem>
+ <para>Nix now stores signatures for local store
+ paths. When paths are copied between stores (e.g., copied from
+ a binary cache to a local store), signatures are
+ propagated.</para>
+
+ <para>Locally-built paths are signed automatically using the
+ secret keys specified by the <option>secret-key-files</option>
+ store option. Secret/public key pairs can be generated using
+ <command>nix-store
+ --generate-binary-cache-key</command>.</para>
+
+ <para>In addition, locally-built store paths are marked as
+ “ultimately trusted”, but this bit is not propagated when
+ paths are copied between stores.</para>
+ </listitem>
+
+ <listitem>
+ <para>Content-addressable store paths no longer require
+ signatures — they can be imported into a store by unprivileged
+ users even if they lack signatures.</para>
+ </listitem>
+
+ <listitem>
+ <para>The command <command>nix verify</command> checks whether
+ the specified paths are trusted, i.e., have a certain number
+ of trusted signatures, are ultimately trusted, or are
+ content-addressed.</para>
+ </listitem>
+
+ <listitem>
+ <para>Substitutions from binary caches <link xlink:href="https://github.com/NixOS/nix/commit/ecbc3fedd3d5bdc5a0e1a0a51b29062f2874ac8b">now</link>
+ require signatures by default. This was already the case on
+ NixOS.</para>
+ </listitem>
+
+ <listitem>
+ <para>In Linux sandbox builds, we <link xlink:href="https://github.com/NixOS/nix/commit/eba840c8a13b465ace90172ff76a0db2899ab11b">now</link>
+ use <filename>/build</filename> instead of
+ <filename>/tmp</filename> as the temporary build
+ directory. This fixes potential security problems when a build
+ accidentally stores its <envar>TMPDIR</envar> in some
+ security-sensitive place, such as an RPATH.</para>
+ </listitem>
+
+ </itemizedlist>
+
+ </para>
+
+ </listitem>
+
+ <listitem>
+ <para><emphasis>Pure evaluation mode</emphasis>. With the
+ <literal>--pure-eval</literal> flag, Nix enables a variant of the existing
+ restricted evaluation mode that forbids access to anything that could cause
+ different evaluations of the same command line arguments to produce a
+ different result. This includes builtin functions such as
+ <function>builtins.getEnv</function>, but more importantly,
+ <emphasis>all</emphasis> filesystem or network access unless a content hash
+ or commit hash is specified. For example, calls to
+ <function>builtins.fetchGit</function> are only allowed if a
+ <varname>rev</varname> attribute is specified.</para>
+
+ <para>The goal of this feature is to enable true reproducibility
+ and traceability of builds (including NixOS system configurations)
+ at the evaluation level. For example, in the future,
+ <command>nixos-rebuild</command> might build configurations from a
+ Nix expression in a Git repository in pure mode. That expression
+ might fetch other repositories such as Nixpkgs via
+ <function>builtins.fetchGit</function>. The commit hash of the
+ top-level repository then uniquely identifies a running system,
+ and, in conjunction with that repository, allows it to be
+ reproduced or modified.</para>
+
+ </listitem>
+
+ <listitem>
+ <para>There are several new features to support binary
+ reproducibility (i.e. to help ensure that multiple builds of the
+ same derivation produce exactly the same output). When
+ <option>enforce-determinism</option> is set to
+ <literal>false</literal>, it’s <link xlink:href="https://github.com/NixOS/nix/commit/8bdf83f936adae6f2c907a6d2541e80d4120f051">no
+ longer</link> a fatal error if build rounds produce different
+ output. Also, a hook named <option>diff-hook</option> is <link xlink:href="https://github.com/NixOS/nix/commit/9a313469a4bdea2d1e8df24d16289dc2a172a169">provided</link>
+ to allow you to run tools such as <command>diffoscope</command>
+ when build rounds produce different output.</para>
+ </listitem>
+
+ <listitem>
+ <para>Configuring remote builds is a lot easier now. Provided you
+ are not using the Nix daemon, you can now just specify a remote
+ build machine on the command line, e.g. <literal>--option builders
+ 'ssh://my-mac x86_64-darwin'</literal>. The environment variable
+ <envar>NIX_BUILD_HOOK</envar> has been removed and is no longer
+ needed. The environment variable <envar>NIX_REMOTE_SYSTEMS</envar>
+ is still supported for compatibility, but it is also possible to
+ specify builders in <command>nix.conf</command> by setting the
+ option <literal>builders =
+ @<replaceable>path</replaceable></literal>.</para>
+ </listitem>
+
+ <listitem>
+ <para>If a fixed-output derivation produces a result with an
+ incorrect hash, the output path is moved to the location
+ corresponding to the actual hash and registered as valid. Thus, a
+ subsequent build of the fixed-output derivation with the correct
+ hash is unnecessary.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix-shell</command> <link xlink:href="https://github.com/NixOS/nix/commit/ea59f39326c8e9dc42dfed4bcbf597fbce58797c">now</link>
+ sets the <varname>IN_NIX_SHELL</varname> environment variable
+ during evaluation and in the shell itself. This can be used to
+ perform different actions depending on whether you’re in a Nix
+ shell or in a regular build. Nixpkgs provides
+ <varname>lib.inNixShell</varname> to check this variable during
+ evaluation.</para>
+ </listitem>
+
+ <listitem>
+ <para><envar>NIX_PATH</envar> is now lazy, so URIs in the path are
+ only downloaded if they are needed for evaluation.</para>
+ </listitem>
+
+ <listitem>
+ <para>You can now use
+ <uri>channel:<replaceable>channel-name</replaceable></uri> as a
+ short-hand for
+ <uri>https://nixos.org/channels/<replaceable>channel-name</replaceable>/nixexprs.tar.xz</uri>. For
+ example, <literal>nix-build channel:nixos-15.09 -A hello</literal>
+ will build the GNU Hello package from the
+ <literal>nixos-15.09</literal> channel. In the future, this may
+ use Git to fetch updates more efficiently.</para>
+ </listitem>
+
+ <listitem>
+ <para>When <option>--no-build-output</option> is given, the last
+ 10 lines of the build log will be shown if a build
+ fails.</para>
+ </listitem>
+
+ <listitem>
+ <para>Networking has been improved:
+
+ <itemizedlist>
+
+ <listitem>
+ <para>HTTP/2 is now supported. This makes binary cache lookups
+ <link xlink:href="https://github.com/NixOS/nix/commit/90ad02bf626b885a5dd8967894e2eafc953bdf92">much
+ more efficient</link>.</para>
+ </listitem>
+
+ <listitem>
+ <para>We now retry downloads on many HTTP errors, making
+ binary caches substituters more resilient to temporary
+ failures.</para>
+ </listitem>
+
+ <listitem>
+ <para>HTTP credentials can now be configured via the standard
+ <filename>netrc</filename> mechanism.</para>
+ </listitem>
+
+ <listitem>
+ <para>If S3 support is enabled at compile time,
+ <uri>s3://</uri> URIs are <link xlink:href="https://github.com/NixOS/nix/commit/9ff9c3f2f80ba4108e9c945bbfda2c64735f987b">supported</link>
+ in all places where Nix allows URIs.</para>
+ </listitem>
+
+ <listitem>
+ <para>Brotli compression is now supported. In particular,
+ <uri>cache.nixos.org</uri> build logs are now compressed using
+ Brotli.</para>
+ </listitem>
+
+ </itemizedlist>
+
+ </para>
+
+ </listitem>
+
+ <listitem>
+ <para><command>nix-env</command> <link xlink:href="https://github.com/NixOS/nix/commit/b0cb11722626e906a73f10dd9a0c9eea29faf43a">now</link>
+ ignores packages with bad derivation names (in particular those
+ starting with a digit or containing a dot).</para>
+ </listitem>
+
+ <listitem>
+ <para>Many configuration options have been renamed, either because
+ they were unnecessarily verbose
+ (e.g. <option>build-use-sandbox</option> is now just
+ <option>sandbox</option>) or to reflect generalised behaviour
+ (e.g. <option>binary-caches</option> is now
+ <option>substituters</option> because it allows arbitrary store
+ URIs). The old names are still supported for compatibility.</para>
+ </listitem>
+
+ <listitem>
+ <para>The <option>max-jobs</option> option can <link xlink:href="https://github.com/NixOS/nix/commit/7251d048fa812d2551b7003bc9f13a8f5d4c95a5">now</link>
+ be set to <literal>auto</literal> to use the number of CPUs in the
+ system.</para>
+ </listitem>
+
+ <listitem>
+ <para>Hashes can <link xlink:href="https://github.com/NixOS/nix/commit/c0015e87af70f539f24d2aa2bc224a9d8b84276b">now</link>
+ be specified in base-64 format, in addition to base-16 and the
+ non-standard base-32.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix-shell</command> now uses
+ <varname>bashInteractive</varname> from Nixpkgs, rather than the
+ <command>bash</command> command that happens to be in the caller’s
+ <envar>PATH</envar>. This is especially important on macOS where
+ the <command>bash</command> provided by the system is seriously
+ outdated and cannot execute <literal>stdenv</literal>’s setup
+ script.</para>
+ </listitem>
+
+ <listitem>
+ <para>Nix can now automatically trigger a garbage collection if
+ free disk space drops below a certain level during a build. This
+ is configured using the <option>min-free</option> and
+ <option>max-free</option> options.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix-store -q --roots</command> and
+ <command>nix-store --gc --print-roots</command> now show temporary
+ and in-memory roots.</para>
+ </listitem>
+
+ <listitem>
+ <para>
+ Nix can now be extended with plugins. See the documentation of
+ the <option>plugin-files</option> option for more details.
+ </para>
+ </listitem>
+
+</itemizedlist>
+
+<para>The Nix language has the following new features:
+
+<itemizedlist>
+
+ <listitem>
+ <para>It supports floating point numbers. They are based on the
+ C++ <literal>float</literal> type and are supported by the
+ existing numerical operators. Export and import to and from JSON
+ and XML works, too.</para>
+ </listitem>
+
+ <listitem>
+ <para>Derivation attributes can now reference the outputs of the
+ derivation using the <function>placeholder</function> builtin
+ function. For example, the attribute
+
+<programlisting>
+configureFlags = "--prefix=${placeholder "out"} --includedir=${placeholder "dev"}";
+</programlisting>
+
+ will cause the <envar>configureFlags</envar> environment variable
+ to contain the actual store paths corresponding to the
+ <literal>out</literal> and <literal>dev</literal> outputs.</para>
+ </listitem>
+
+</itemizedlist>
+
+</para>
+
+<para>The following builtin functions are new or extended:
+
+<itemizedlist>
+
+ <listitem>
+ <para><function xlink:href="https://github.com/NixOS/nix/commit/38539b943a060d9cdfc24d6e5d997c0885b8aa2f">builtins.fetchGit</function>
+ allows Git repositories to be fetched at evaluation time. Thus it
+ differs from the <function>fetchgit</function> function in
+ Nixpkgs, which fetches at build time and cannot be used to fetch
+ Nix expressions during evaluation. A typical use case is to import
+ external NixOS modules from your configuration, e.g.
+
+ <programlisting>imports = [ (builtins.fetchGit https://github.com/edolstra/dwarffs + "/module.nix") ];</programlisting>
+
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>Similarly, <function>builtins.fetchMercurial</function>
+ allows you to fetch Mercurial repositories.</para>
+ </listitem>
+
+ <listitem>
+ <para><function>builtins.path</function> generalises
+ <function>builtins.filterSource</function> and path literals
+ (e.g. <literal>./foo</literal>). It allows specifying a store path
+ name that differs from the source path name
+ (e.g. <literal>builtins.path { path = ./foo; name = "bar";
+ }</literal>) and also supports filtering out unwanted
+ files.</para>
+ </listitem>
+
+ <listitem>
+ <para><function>builtins.fetchurl</function> and
+ <function>builtins.fetchTarball</function> now support
+ <varname>sha256</varname> and <varname>name</varname>
+ attributes.</para>
+ </listitem>
+
+ <listitem>
+ <para><function xlink:href="https://github.com/NixOS/nix/commit/b8867a0239b1930a16f9ef3f7f3e864b01416dff">builtins.split</function>
+ splits a string using a POSIX extended regular expression as the
+ separator.</para>
+ </listitem>
+
+ <listitem>
+ <para><function xlink:href="https://github.com/NixOS/nix/commit/26d92017d3b36cff940dcb7d1611c42232edb81a">builtins.partition</function>
+ partitions the elements of a list into two lists, depending on a
+ Boolean predicate.</para>
+ </listitem>
+
+ <listitem>
+ <para><literal><nix/fetchurl.nix></literal> now uses the
+ content-addressable tarball cache at
+ <uri>http://tarballs.nixos.org/</uri>, just like
+ <function>fetchurl</function> in
+ Nixpkgs. (f2682e6e18a76ecbfb8a12c17e3a0ca15c084197)</para>
+ </listitem>
+
+ <listitem>
+ <para>In restricted and pure evaluation mode, builtin functions
+ that download from the network (such as
+ <function>fetchGit</function>) are permitted to fetch underneath a
+ list of URI prefixes specified in the option
+ <option>allowed-uris</option>.</para>
+ </listitem>
+
+</itemizedlist>
+
+</para>
+
+<para>The Nix build environment has the following changes:
+
+<itemizedlist>
+
+ <listitem>
+ <para>Values such as Booleans, integers, (nested) lists and
+ attribute sets can <link xlink:href="https://github.com/NixOS/nix/commit/6de33a9c675b187437a2e1abbcb290981a89ecb1">now</link>
+ be passed to builders in a non-lossy way. If the special attribute
+ <varname>__structuredAttrs</varname> is set to
+ <literal>true</literal>, the other derivation attributes are
+ serialised in JSON format and made available to the builder via
+ the file <envar>.attrs.json</envar> in the builder’s temporary
+ directory. This obviates the need for
+ <varname>passAsFile</varname> since JSON files have no size
+ restrictions, unlike process environments.</para>
+
+ <para><link xlink:href="https://github.com/NixOS/nix/commit/2d5b1b24bf70a498e4c0b378704cfdb6471cc699">As
+ a convenience to Bash builders</link>, Nix writes a script named
+ <envar>.attrs.sh</envar> to the builder’s directory that
+ initialises shell variables corresponding to all attributes that
+ are representable in Bash. This includes non-nested (associative)
+ arrays. For example, the attribute <literal>hardening.format =
+ true</literal> ends up as the Bash associative array element
+ <literal>${hardening[format]}</literal>.</para>
+ </listitem>
+
+ <listitem>
+ <para>Builders can <link xlink:href="https://github.com/NixOS/nix/commit/88e6bb76de5564b3217be9688677d1c89101b2a3">now</link>
+ communicate what build phase they are in by writing messages to
+ the file descriptor specified in <envar>NIX_LOG_FD</envar>. The
+ current phase is shown by the <command>nix</command> progress
+ indicator.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>In Linux sandbox builds, we <link xlink:href="https://github.com/NixOS/nix/commit/a2d92bb20e82a0957067ede60e91fab256948b41">now</link>
+ provide a default <filename>/bin/sh</filename> (namely
+ <filename>ash</filename> from BusyBox).</para>
+ </listitem>
+
+ <listitem>
+ <para>In structured attribute mode,
+ <varname>exportReferencesGraph</varname> <link xlink:href="https://github.com/NixOS/nix/commit/c2b0d8749f7e77afc1c4b3e8dd36b7ee9720af4a">exports</link>
+ extended information about closures in JSON format. In particular,
+ it includes the sizes and hashes of paths. This is primarily
+ useful for NixOS image builders.</para>
+ </listitem>
+
+ <listitem>
+ <para>Builds are <link xlink:href="https://github.com/NixOS/nix/commit/21948deed99a3295e4d5666e027a6ca42dc00b40">now</link>
+ killed as soon as Nix receives EOF on the builder’s stdout or
+ stderr. This fixes a bug that allowed builds to hang Nix
+ indefinitely, regardless of
+ timeouts.</para>
+ </listitem>
+
+ <listitem>
+ <para>The <option>sandbox-paths</option> configuration
+ option can now specify optional paths by appending a
+ <literal>?</literal>, e.g. <literal>/dev/nvidiactl?</literal> will
+ bind-mount <varname>/dev/nvidiactl</varname> only if it
+ exists.</para>
+ </listitem>
+
+ <listitem>
+ <para>On Linux, builds are now executed in a user
+ namespace with UID 1000 and GID 100.</para>
+ </listitem>
+
+</itemizedlist>
+
+</para>
+
+<para>A number of significant internal changes were made:
+
+<itemizedlist>
+
+ <listitem>
+ <para>Nix no longer depends on Perl and all Perl components have
+ been rewritten in C++ or removed. The Perl bindings that used to
+ be part of Nix have been moved to a separate package,
+ <literal>nix-perl</literal>.</para>
+ </listitem>
+
+ <listitem>
+ <para>All <classname>Store</classname> classes are now
+ thread-safe. <classname>RemoteStore</classname> supports multiple
+ concurrent connections to the daemon. This is primarily useful in
+ multi-threaded programs such as
+ <command>hydra-queue-runner</command>.</para>
+ </listitem>
+
+</itemizedlist>
+
+</para>
+
+<para>This release has contributions from
+
+Adrien Devresse,
+Alexander Ried,
+Alex Cruice,
+Alexey Shmalko,
+AmineChikhaoui,
+Andy Wingo,
+Aneesh Agrawal,
+Anthony Cowley,
+Armijn Hemel,
+aszlig,
+Ben Gamari,
+Benjamin Hipple,
+Benjamin Staffin,
+Benno Fünfstück,
+Bjørn Forsman,
+Brian McKenna,
+Charles Strahan,
+Chase Adams,
+Chris Martin,
+Christian Theune,
+Chris Warburton,
+Daiderd Jordan,
+Dan Connolly,
+Daniel Peebles,
+Dan Peebles,
+davidak,
+David McFarland,
+Dmitry Kalinkin,
+Domen Kožar,
+Eelco Dolstra,
+Emery Hemingway,
+Eric Litak,
+Eric Wolf,
+Fabian Schmitthenner,
+Frederik Rietdijk,
+Gabriel Gonzalez,
+Giorgio Gallo,
+Graham Christensen,
+Guillaume Maudoux,
+Harmen,
+Iavael,
+James Broadhead,
+James Earl Douglas,
+Janus Troelsen,
+Jeremy Shaw,
+Joachim Schiele,
+Joe Hermaszewski,
+Joel Moberg,
+Johannes 'fish' Ziemke,
+Jörg Thalheim,
+Jude Taylor,
+kballou,
+Keshav Kini,
+Kjetil Orbekk,
+Langston Barrett,
+Linus Heckemann,
+Ludovic Courtès,
+Manav Rathi,
+Marc Scholten,
+Markus Hauck,
+Matt Audesse,
+Matthew Bauer,
+Matthias Beyer,
+Matthieu Coudron,
+N1X,
+Nathan Zadoks,
+Neil Mayhew,
+Nicolas B. Pierron,
+Niklas Hambüchen,
+Nikolay Amiantov,
+Ole Jørgen Brønner,
+Orivej Desh,
+Peter Simons,
+Peter Stuart,
+Pyry Jahkola,
+regnat,
+Renzo Carbonara,
+Rhys,
+Robert Vollmert,
+Scott Olson,
+Scott R. Parish,
+Sergei Trofimovich,
+Shea Levy,
+Sheena Artrip,
+Spencer Baugh,
+Stefan Junker,
+Susan Potter,
+Thomas Tuegel,
+Timothy Allen,
+Tristan Hume,
+Tuomas Tynkkynen,
+tv,
+Tyson Whitehead,
+Vladimír Čunát,
+Will Dietz,
+wmertens,
+Wout Mertens,
+zimbatm and
+Zoran Plesivčak.
+</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.11.10">
+
+<title>Release 1.11.10 (2017-06-12)</title>
+
+<para>This release fixes a security bug in Nix’s “build user” build
+isolation mechanism. Previously, Nix builders had the ability to
+create setuid binaries owned by a <literal>nixbld</literal>
+user. Such a binary could then be used by an attacker to assume a
+<literal>nixbld</literal> identity and interfere with subsequent
+builds running under the same UID.</para>
+
+<para>To prevent this issue, Nix now disallows builders to create
+setuid and setgid binaries. On Linux, this is done using a seccomp BPF
+filter. Note that this imposes a small performance penalty (e.g. 1%
+when building GNU Hello). Using seccomp, we now also prevent the
+creation of extended attributes and POSIX ACLs since these cannot be
+represented in the NAR format and (in the case of POSIX ACLs) allow
+bypassing regular Nix store permissions. On macOS, the restriction is
+implemented using the existing sandbox mechanism, which now uses a
+minimal “allow all except the creation of setuid/setgid binaries”
+profile when regular sandboxing is disabled. On other platforms, the
+“build user” mechanism is now disabled.</para>
+
+<para>Thanks go to Linus Heckemann for discovering and reporting this
+bug.</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.11">
+
+<title>Release 1.11 (2016-01-19)</title>
+
+<para>This is primarily a bug fix release. It also has a number of new
+features:</para>
+
+<itemizedlist>
+
+ <listitem>
+ <para><command>nix-prefetch-url</command> can now download URLs
+ specified in a Nix expression. For example,
+
+<screen>
+$ nix-prefetch-url -A hello.src
+</screen>
+
+ will prefetch the file specified by the
+ <function>fetchurl</function> call in the attribute
+ <literal>hello.src</literal> from the Nix expression in the
+ current directory, and print the cryptographic hash of the
+ resulting file on stdout. This differs from <literal>nix-build -A
+ hello.src</literal> in that it doesn't verify the hash, and is
+ thus useful when you’re updating a Nix expression.</para>
+
+ <para>You can also prefetch the result of functions that unpack a
+ tarball, such as <function>fetchFromGitHub</function>. For example:
+
+<screen>
+$ nix-prefetch-url --unpack https://github.com/NixOS/patchelf/archive/0.8.tar.gz
+</screen>
+
+ or from a Nix expression:
+
+<screen>
+$ nix-prefetch-url -A nix-repl.src
+</screen>
+
+ </para>
+
+ </listitem>
+
+ <listitem>
+ <para>The builtin function
+ <function><nix/fetchurl.nix></function> now supports
+ downloading and unpacking NARs. This removes the need to have
+ multiple downloads in the Nixpkgs stdenv bootstrap process (like a
+ separate busybox binary for Linux, or curl/mkdir/sh/bzip2 for
+ Darwin). Now all those files can be combined into a single NAR,
+ optionally compressed using <command>xz</command>.</para>
+ </listitem>
+
+ <listitem>
+ <para>Nix now supports SHA-512 hashes for verifying fixed-output
+ derivations, and in <function>builtins.hashString</function>.</para>
+ </listitem>
+
+ <listitem>
+ <para>
+ The new flag <option>--option build-repeat
+ <replaceable>N</replaceable></option> will cause every build to
+ be executed <replaceable>N</replaceable>+1 times. If the build
+ output differs between any round, the build is rejected, and the
+ output paths are not registered as valid. This is primarily
+ useful to verify build determinism. (We already had a
+ <option>--check</option> option to repeat a previously succeeded
+ build. However, with <option>--check</option>, non-deterministic
+ builds are registered in the DB. Preventing that is useful for
+ Hydra to ensure that non-deterministic builds don't end up
+ getting published to the binary cache.)
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ The options <option>--check</option> and <option>--option
+ build-repeat <replaceable>N</replaceable></option>, if they
+ detect a difference between two runs of the same derivation and
+ <option>-K</option> is given, will make the output of the other
+ run available under
+ <filename><replaceable>store-path</replaceable>-check</filename>. This
+ makes it easier to investigate the non-determinism using tools
+ like <command>diffoscope</command>, e.g.,
+
+<screen>
+$ nix-build pkgs/stdenv/linux -A stage1.pkgs.zlib --check -K
+error: derivation ‘/nix/store/l54i8wlw2265…-zlib-1.2.8.drv’ may not
+be deterministic: output ‘/nix/store/11a27shh6n2i…-zlib-1.2.8’
+differs from ‘/nix/store/11a27shh6n2i…-zlib-1.2.8-check’
+
+$ diffoscope /nix/store/11a27shh6n2i…-zlib-1.2.8 /nix/store/11a27shh6n2i…-zlib-1.2.8-check
+…
+├── lib/libz.a
+│ ├── metadata
+│ │ @@ -1,15 +1,15 @@
+│ │ -rw-r--r-- 30001/30000 3096 Jan 12 15:20 2016 adler32.o
+…
+│ │ +rw-r--r-- 30001/30000 3096 Jan 12 15:28 2016 adler32.o
+…
+</screen>
+
+ </para></listitem>
+
+ <listitem>
+ <para>Improved FreeBSD support.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix-env -qa --xml --meta</command> now prints
+ license information.</para>
+ </listitem>
+
+ <listitem>
+ <para>The maximum number of parallel TCP connections that the
+ binary cache substituter will use has been decreased from 150 to
+ 25. This should prevent upsetting some broken NAT routers, and
+ also improves performance.</para>
+ </listitem>
+
+ <listitem>
+ <para>All "chroot"-containing strings got renamed to "sandbox".
+ In particular, some Nix options got renamed, but the old names
+ are still accepted as lower-priority aliases.
+ </para>
+ </listitem>
+
+</itemizedlist>
+
+<para>This release has contributions from Anders Claesson, Anthony
+Cowley, Bjørn Forsman, Brian McKenna, Danny Wilson, davidak, Eelco Dolstra,
+Fabian Schmitthenner, FrankHB, Ilya Novoselov, janus, Jim Garrison, John
+Ericson, Jude Taylor, Ludovic Courtès, Manuel Jacob, Mathnerd314,
+Pascal Wittmann, Peter Simons, Philip Potter, Preston Bennes, Rommel
+M. Martinez, Sander van der Burg, Shea Levy, Tim Cuthbertson, Tuomas
+Tynkkynen, Utku Demir and Vladimír Čunát.</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.10">
+
+<title>Release 1.10 (2015-09-03)</title>
+
+<para>This is primarily a bug fix release. It also has a number of new
+features:</para>
+
+<itemizedlist>
+
+ <listitem>
+ <para>A number of builtin functions have been added to reduce
+ Nixpkgs/NixOS evaluation time and memory consumption:
+ <function>all</function>,
+ <function>any</function>,
+ <function>concatStringsSep</function>,
+ <function>foldl’</function>,
+ <function>genList</function>,
+ <function>replaceStrings</function>,
+ <function>sort</function>.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>The garbage collector is more robust when the disk is full.</para>
+ </listitem>
+
+ <listitem>
+ <para>Nix supports a new API for building derivations that doesn’t
+ require a <literal>.drv</literal> file to be present on disk; it
+ only requires an in-memory representation of the derivation. This
+ is used by the Hydra continuous build system to make remote builds
+ more efficient.</para>
+ </listitem>
+
+ <listitem>
+ <para>The function <literal><nix/fetchurl.nix></literal> now
+ uses a <emphasis>builtin</emphasis> builder (i.e. it doesn’t
+ require starting an external process; the download is performed by
+ Nix itself). This ensures that derivation paths don’t change when
+ Nix is upgraded, and obviates the need for ugly hacks to support
+ chroot execution.</para>
+ </listitem>
+
+ <listitem>
+ <para><option>--version -v</option> now prints some configuration
+ information, in particular what compile-time optional features are
+ enabled, and the paths of various directories.</para>
+ </listitem>
+
+ <listitem>
+ <para>Build users have their supplementary groups set correctly.</para>
+ </listitem>
+
+</itemizedlist>
+
+<para>This release has contributions from Eelco Dolstra, Guillaume
+Maudoux, Iwan Aucamp, Jaka Hudoklin, Kirill Elagin, Ludovic Courtès,
+Manolis Ragkousis, Nicolas B. Pierron and Shea Levy.</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.9">
+
+<title>Release 1.9 (2015-06-12)</title>
+
+<para>In addition to the usual bug fixes, this release has the
+following new features:</para>
+
+<itemizedlist>
+
+ <listitem>
+ <para>Signed binary cache support. You can enable signature
+ checking by adding the following to <filename>nix.conf</filename>:
+
+<programlisting>
+signed-binary-caches = *
+binary-cache-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
+</programlisting>
+
+ This will prevent Nix from downloading any binary from the cache
+ that is not signed by one of the keys listed in
+ <option>binary-cache-public-keys</option>.</para>
+
+ <para>Signature checking is only supported if you built Nix with
+ the <literal>libsodium</literal> package.</para>
+
+ <para>Note that while Nix has had experimental support for signed
+ binary caches since version 1.7, this release changes the
+ signature format in a backwards-incompatible way.</para>
+
+ </listitem>
+
+ <listitem>
+
+ <para>Automatic downloading of Nix expression tarballs. In various
+ places, you can now specify the URL of a tarball containing Nix
+ expressions (such as Nixpkgs), which will be downloaded and
+ unpacked automatically. For example:</para>
+
+ <itemizedlist>
+
+ <listitem><para>In <command>nix-env</command>:
+
+<screen>
+$ nix-env -f https://github.com/NixOS/nixpkgs-channels/archive/nixos-14.12.tar.gz -iA firefox
+</screen>
+
+ This installs Firefox from the latest tested and built revision
+ of the NixOS 14.12 channel.</para></listitem>
+
+ <listitem><para>In <command>nix-build</command> and
+ <command>nix-shell</command>:
+
+<screen>
+$ nix-build https://github.com/NixOS/nixpkgs/archive/master.tar.gz -A hello
+</screen>
+
+ This builds GNU Hello from the latest revision of the Nixpkgs
+ master branch.</para></listitem>
+
+ <listitem><para>In the Nix search path (as specified via
+ <envar>NIX_PATH</envar> or <option>-I</option>). For example, to
+ start a shell containing the Pan package from a specific version
+ of Nixpkgs:
+
+<screen>
+$ nix-shell -p pan -I nixpkgs=https://github.com/NixOS/nixpkgs-channels/archive/8a3eea054838b55aca962c3fbde9c83c102b8bf2.tar.gz
+</screen>
+
+ </para></listitem>
+
+ <listitem><para>In <command>nixos-rebuild</command> (on NixOS):
+
+<screen>
+$ nixos-rebuild test -I nixpkgs=https://github.com/NixOS/nixpkgs-channels/archive/nixos-unstable.tar.gz
+</screen>
+
+ </para></listitem>
+
+ <listitem><para>In Nix expressions, via the new builtin function <function>fetchTarball</function>:
+
+<programlisting>
+with import (fetchTarball https://github.com/NixOS/nixpkgs-channels/archive/nixos-14.12.tar.gz) {}; …
+</programlisting>
+
+ (This is not allowed in restricted mode.)</para></listitem>
+
+ </itemizedlist>
+
+ </listitem>
+
+ <listitem>
+
+ <para><command>nix-shell</command> improvements:</para>
+
+ <itemizedlist>
+
+ <listitem><para><command>nix-shell</command> now has a flag
+ <option>--run</option> to execute a command in the
+ <command>nix-shell</command> environment,
+ e.g. <literal>nix-shell --run make</literal>. This is like
+ the existing <option>--command</option> flag, except that it
+ uses a non-interactive shell (ensuring that hitting Ctrl-C won’t
+ drop you into the child shell).</para></listitem>
+
+ <listitem><para><command>nix-shell</command> can now be used as
+ a <literal>#!</literal>-interpreter. This allows you to write
+ scripts that dynamically fetch their own dependencies. For
+ example, here is a Haskell script that, when invoked, first
+ downloads GHC and the Haskell packages on which it depends:
+
+<programlisting>
+#! /usr/bin/env nix-shell
+#! nix-shell -i runghc -p haskellPackages.ghc haskellPackages.HTTP
+
+import Network.HTTP
+
+main = do
+ resp <- Network.HTTP.simpleHTTP (getRequest "http://nixos.org/")
+ body <- getResponseBody resp
+ print (take 100 body)
+</programlisting>
+
+ Of course, the dependencies are cached in the Nix store, so the
+ second invocation of this script will be much
+ faster.</para></listitem>
+
+ </itemizedlist>
+
+ </listitem>
+
+ <listitem>
+
+ <para>Chroot improvements:</para>
+
+ <itemizedlist>
+
+ <listitem><para>Chroot builds are now supported on Mac OS X
+ (using its sandbox mechanism).</para></listitem>
+
+ <listitem><para>If chroots are enabled, they are now used for
+ all derivations, including fixed-output derivations (such as
+ <function>fetchurl</function>). The latter do have network
+ access, but can no longer access the host filesystem. If you
+ need the old behaviour, you can set the option
+ <option>build-use-chroot</option> to
+ <literal>relaxed</literal>.</para></listitem>
+
+ <listitem><para>On Linux, if chroots are enabled, builds are
+ performed in a private PID namespace once again. (This
+ functionality was lost in Nix 1.8.)</para></listitem>
+
+ <listitem><para>Store paths listed in
+ <option>build-chroot-dirs</option> are now automatically
+ expanded to their closure. For instance, if you want
+ <filename>/nix/store/…-bash/bin/sh</filename> mounted in your
+ chroot as <filename>/bin/sh</filename>, you only need to say
+ <literal>build-chroot-dirs =
+ /bin/sh=/nix/store/…-bash/bin/sh</literal>; it is no longer
+ necessary to specify the dependencies of Bash.</para></listitem>
+
+ </itemizedlist>
+
+ </listitem>
+
+ <listitem><para>The new derivation attribute
+ <varname>passAsFile</varname> allows you to specify that the
+ contents of derivation attributes should be passed via files rather
+ than environment variables. This is useful if you need to pass very
+ long strings that exceed the size limit of the environment. The
+ Nixpkgs function <function>writeTextFile</function> uses
+ this.</para></listitem>
+
+ <listitem><para>You can now use <literal>~</literal> in Nix file
+ names to refer to your home directory, e.g. <literal>import
+ ~/.nixpkgs/config.nix</literal>.</para></listitem>
+
+ <listitem><para>Nix has a new option <option>restrict-eval</option>
+ that allows limiting what paths the Nix evaluator has access to. By
+ passing <literal>--option restrict-eval true</literal> to Nix, the
+ evaluator will throw an exception if an attempt is made to access
+ any file outside of the Nix search path. This is primarily intended
+ for Hydra to ensure that a Hydra jobset only refers to its declared
+ inputs (and is therefore reproducible).</para></listitem>
+
+ <listitem><para><command>nix-env</command> now only creates a new
+ “generation” symlink in <filename>/nix/var/nix/profiles</filename>
+ if something actually changed.</para></listitem>
+
+ <listitem><para>The environment variable <envar>NIX_PAGER</envar>
+ can now be set to override <envar>PAGER</envar>. You can set it to
+ <literal>cat</literal> to disable paging for Nix commands
+ only.</para></listitem>
+
+ <listitem><para>Failing <literal><...></literal>
+ lookups now show position information.</para></listitem>
+
+ <listitem><para>Improved Boehm GC use: we disabled scanning for
+ interior pointers, which should reduce the “<literal>Repeated
+ allocation of very large block</literal>” warnings and associated
+ retention of memory.</para></listitem>
+
+</itemizedlist>
+
+<para>This release has contributions from aszlig, Benjamin Staffin,
+Charles Strahan, Christian Theune, Daniel Hahler, Danylo Hlynskyi
+Daniel Peebles, Dan Peebles, Domen Kožar, Eelco Dolstra, Harald van
+Dijk, Hoang Xuan Phu, Jaka Hudoklin, Jeff Ramnani, j-keck, Linquize,
+Luca Bruno, Michael Merickel, Oliver Dunkl, Rob Vermaas, Rok Garbas,
+Shea Levy, Tobias Geerinckx-Rice and William A. Kennington III.</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.8">
+
+<title>Release 1.8 (2014-12-14)</title>
+
+<itemizedlist>
+
+ <listitem><para>Breaking change: to address a race condition, the
+ remote build hook mechanism now uses <command>nix-store
+ --serve</command> on the remote machine. This requires build slaves
+ to be updated to Nix 1.8.</para></listitem>
+
+ <listitem><para>Nix now uses HTTPS instead of HTTP to access the
+ default binary cache,
+ <literal>cache.nixos.org</literal>.</para></listitem>
+
+ <listitem><para><command>nix-env</command> selectors are now regular
+ expressions. For instance, you can do
+
+<screen>
+$ nix-env -qa '.*zip.*'
+</screen>
+
+ to query all packages with a name containing
+ <literal>zip</literal>.</para></listitem>
+
+ <listitem><para><command>nix-store --read-log</command> can now
+ fetch remote build logs. If a build log is not available locally,
+ then ‘nix-store -l’ will now try to download it from the servers
+ listed in the ‘log-servers’ option in nix.conf. For instance, if you
+ have the configuration option
+
+<programlisting>
+log-servers = http://hydra.nixos.org/log
+</programlisting>
+
+then it will try to get logs from
+<literal>http://hydra.nixos.org/log/<replaceable>base name of the
+store path</replaceable></literal>. This allows you to do things like:
+
+<screen>
+$ nix-store -l $(which xterm)
+</screen>
+
+ and get a log even if <command>xterm</command> wasn't built
+ locally.</para></listitem>
+
+ <listitem><para>New builtin functions:
+ <function>attrValues</function>, <function>deepSeq</function>,
+ <function>fromJSON</function>, <function>readDir</function>,
+ <function>seq</function>.</para></listitem>
+
+ <listitem><para><command>nix-instantiate --eval</command> now has a
+ <option>--json</option> flag to print the resulting value in JSON
+ format.</para></listitem>
+
+ <listitem><para><command>nix-copy-closure</command> now uses
+ <command>nix-store --serve</command> on the remote side to send or
+ receive closures. This fixes a race condition between
+ <command>nix-copy-closure</command> and the garbage
+ collector.</para></listitem>
+
+ <listitem><para>Derivations can specify the new special attribute
+ <varname>allowedRequisites</varname>, which has a similar meaning to
+ <varname>allowedReferences</varname>. But instead of only enforcing
+ to explicitly specify the immediate references, it requires the
+ derivation to specify all the dependencies recursively (hence the
+ name, requisites) that are used by the resulting
+ output.</para></listitem>
+
+ <listitem><para>On Mac OS X, Nix now handles case collisions when
+ importing closures from case-sensitive file systems. This is mostly
+ useful for running NixOps on Mac OS X.</para></listitem>
+
+ <listitem><para>The Nix daemon has new configuration options
+ <option>allowed-users</option> (specifying the users and groups that
+ are allowed to connect to the daemon) and
+ <option>trusted-users</option> (specifying the users and groups that
+ can perform privileged operations like specifying untrusted binary
+ caches).</para></listitem>
+
+ <listitem><para>The configuration option
+ <option>build-cores</option> now defaults to the number of available
+ CPU cores.</para></listitem>
+
+ <listitem><para>Build users are now used by default when Nix is
+ invoked as root. This prevents builds from accidentally running as
+ root.</para></listitem>
+
+ <listitem><para>Nix now includes systemd units and Upstart
+ jobs.</para></listitem>
+
+ <listitem><para>Speed improvements to <command>nix-store
+ --optimise</command>.</para></listitem>
+
+ <listitem><para>Language change: the <literal>==</literal> operator
+ now ignores string contexts (the “dependencies” of a
+ string).</para></listitem>
+
+ <listitem><para>Nix now filters out Nix-specific ANSI escape
+ sequences on standard error. They are supposed to be invisible, but
+ some terminals show them anyway.</para></listitem>
+
+ <listitem><para>Various commands now automatically pipe their output
+ into the pager as specified by the <envar>PAGER</envar> environment
+ variable.</para></listitem>
+
+ <listitem><para>Several improvements to reduce memory consumption in
+ the evaluator.</para></listitem>
+
+</itemizedlist>
+
+<para>This release has contributions from Adam Szkoda, Aristid
+Breitkreuz, Bob van der Linden, Charles Strahan, darealshinji, Eelco
+Dolstra, Gergely Risko, Joel Taylor, Ludovic Courtès, Marko Durkovic,
+Mikey Ariel, Paul Colomiets, Ricardo M. Correia, Ricky Elrod, Robert
+Helgesson, Rob Vermaas, Russell O'Connor, Shea Levy, Shell Turner,
+Sönke Hahn, Steve Purcell, Vladimír Čunát and Wout Mertens.</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.7">
+
+<title>Release 1.7 (2014-04-11)</title>
+
+<para>In addition to the usual bug fixes, this release has the
+following new features:</para>
+
+<itemizedlist>
+
+ <listitem>
+ <para>Antiquotation is now allowed inside of quoted attribute
+ names (e.g. <literal>set."${foo}"</literal>). In the case where
+ the attribute name is just a single antiquotation, the quotes can
+ be dropped (e.g. the above example can be written
+ <literal>set.${foo}</literal>). If an attribute name inside of a
+ set declaration evaluates to <literal>null</literal> (e.g.
+ <literal>{ ${null} = false; }</literal>), then that attribute is
+ not added to the set.</para>
+ </listitem>
+
+ <listitem>
+ <para>Experimental support for cryptographically signed binary
+ caches. See <link xlink:href="https://github.com/NixOS/nix/commit/0fdf4da0e979f992db75cc17376e455ddc5a96d8">the
+ commit for details</link>.</para>
+ </listitem>
+
+ <listitem>
+ <para>An experimental new substituter,
+ <command>download-via-ssh</command>, that fetches binaries from
+ remote machines via SSH. Specifying the flags <literal>--option
+ use-ssh-substituter true --option ssh-substituter-hosts
+ <replaceable>user@hostname</replaceable></literal> will cause Nix
+ to download binaries from the specified machine, if it has
+ them.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix-store -r</command> and
+ <command>nix-build</command> have a new flag,
+ <option>--check</option>, that builds a previously built
+ derivation again, and prints an error message if the output is not
+ exactly the same. This helps to verify whether a derivation is
+ truly deterministic. For example:
+
+<screen>
+$ nix-build '<nixpkgs>' -A patchelf
+<replaceable>…</replaceable>
+$ nix-build '<nixpkgs>' -A patchelf --check
+<replaceable>…</replaceable>
+error: derivation `/nix/store/1ipvxs…-patchelf-0.6' may not be deterministic:
+ hash mismatch in output `/nix/store/4pc1dm…-patchelf-0.6.drv'
+</screen>
+
+ </para>
+
+ </listitem>
+
+ <listitem>
+ <para>The <command>nix-instantiate</command> flags
+ <option>--eval-only</option> and <option>--parse-only</option>
+ have been renamed to <option>--eval</option> and
+ <option>--parse</option>, respectively.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix-instantiate</command>,
+ <command>nix-build</command> and <command>nix-shell</command> now
+ have a flag <option>--expr</option> (or <option>-E</option>) that
+ allows you to specify the expression to be evaluated as a command
+ line argument. For instance, <literal>nix-instantiate --eval -E
+ '1 + 2'</literal> will print <literal>3</literal>.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix-shell</command> improvements:</para>
+
+ <itemizedlist>
+
+ <listitem>
+ <para>It has a new flag, <option>--packages</option> (or
+ <option>-p</option>), that sets up a build environment
+ containing the specified packages from Nixpkgs. For example,
+ the command
+
+<screen>
+$ nix-shell -p sqlite xorg.libX11 hello
+</screen>
+
+ will start a shell in which the given packages are
+ present.</para>
+ </listitem>
+
+ <listitem>
+ <para>It now uses <filename>shell.nix</filename> as the
+ default expression, falling back to
+ <filename>default.nix</filename> if the former doesn’t
+ exist. This makes it convenient to have a
+ <filename>shell.nix</filename> in your project to set up a
+ nice development environment.</para>
+ </listitem>
+
+ <listitem>
+ <para>It evaluates the derivation attribute
+ <varname>shellHook</varname>, if set. Since
+ <literal>stdenv</literal> does not normally execute this hook,
+ it allows you to do <command>nix-shell</command>-specific
+ setup.</para>
+ </listitem>
+
+ <listitem>
+ <para>It preserves the user’s timezone setting.</para>
+ </listitem>
+
+ </itemizedlist>
+
+ </listitem>
+
+ <listitem>
+ <para>In chroots, Nix now sets up a <filename>/dev</filename>
+ containing only a minimal set of devices (such as
+ <filename>/dev/null</filename>). Note that it only does this if
+ you <emphasis>don’t</emphasis> have <filename>/dev</filename>
+ listed in your <option>build-chroot-dirs</option> setting;
+ otherwise, it will bind-mount the <literal>/dev</literal> from
+ outside the chroot.</para>
+
+ <para>Similarly, if you don’t have <filename>/dev/pts</filename> listed
+ in <option>build-chroot-dirs</option>, Nix will mount a private
+ <literal>devpts</literal> filesystem on the chroot’s
+ <filename>/dev/pts</filename>.</para>
+
+ </listitem>
+
+ <listitem>
+ <para>New built-in function: <function>builtins.toJSON</function>,
+ which returns a JSON representation of a value.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix-env -q</command> has a new flag
+ <option>--json</option> to print a JSON representation of the
+ installed or available packages.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix-env</command> now supports meta attributes with
+ more complex values, such as attribute sets.</para>
+ </listitem>
+
+ <listitem>
+ <para>The <option>-A</option> flag now allows attribute names with
+ dots in them, e.g.
+
+<screen>
+$ nix-instantiate --eval '<nixos>' -A 'config.systemd.units."nscd.service".text'
+</screen>
+
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>The <option>--max-freed</option> option to
+ <command>nix-store --gc</command> now accepts a unit
+ specifier. For example, <literal>nix-store --gc --max-freed
+ 1G</literal> will free up to 1 gigabyte of disk space.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix-collect-garbage</command> has a new flag
+ <option>--delete-older-than</option>
+ <replaceable>N</replaceable><literal>d</literal>, which deletes
+ all user environment generations older than
+ <replaceable>N</replaceable> days. Likewise, <command>nix-env
+ --delete-generations</command> accepts a
+ <replaceable>N</replaceable><literal>d</literal> age limit.</para>
+ </listitem>
+
+ <listitem>
+ <para>Nix now heuristically detects whether a build failure was
+ due to a disk-full condition. In that case, the build is not
+ flagged as “permanently failed”. This is mostly useful for Hydra,
+ which needs to distinguish between permanent and transient build
+ failures.</para>
+ </listitem>
+
+ <listitem>
+ <para>There is a new symbol <literal>__curPos</literal> that
+ expands to an attribute set containing its file name and line and
+ column numbers, e.g. <literal>{ file = "foo.nix"; line = 10;
+ column = 5; }</literal>. There also is a new builtin function,
+ <varname>unsafeGetAttrPos</varname>, that returns the position of
+ an attribute. This is used by Nixpkgs to provide location
+ information in error messages, e.g.
+
+<screen>
+$ nix-build '<nixpkgs>' -A libreoffice --argstr system x86_64-darwin
+error: the package ‘libreoffice-4.0.5.2’ in ‘.../applications/office/libreoffice/default.nix:263’
+ is not supported on ‘x86_64-darwin’
+</screen>
+
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>The garbage collector is now more concurrent with other Nix
+ processes because it releases certain locks earlier.</para>
+ </listitem>
+
+ <listitem>
+ <para>The binary tarball installer has been improved. You can now
+ install Nix by running:
+
+<screen>
+$ bash <(curl https://nixos.org/nix/install)
+</screen>
+
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>More evaluation errors include position information. For
+ instance, selecting a missing attribute will print something like
+
+<screen>
+error: attribute `nixUnstabl' missing, at /etc/nixos/configurations/misc/eelco/mandark.nix:216:15
+</screen>
+
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>The command <command>nix-setuid-helper</command> is
+ gone.</para>
+ </listitem>
+
+ <listitem>
+ <para>Nix no longer uses Automake, but instead has a
+ non-recursive, GNU Make-based build system.</para>
+ </listitem>
+
+ <listitem>
+ <para>All installed libraries now have the prefix
+ <literal>libnix</literal>. In particular, this gets rid of
+ <literal>libutil</literal>, which could clash with libraries with
+ the same name from other packages.</para>
+ </listitem>
+
+ <listitem>
+ <para>Nix now requires a compiler that supports C++11.</para>
+ </listitem>
+
+</itemizedlist>
+
+<para>This release has contributions from Danny Wilson, Domen Kožar,
+Eelco Dolstra, Ian-Woo Kim, Ludovic Courtès, Maxim Ivanov, Petr
+Rockai, Ricardo M. Correia and Shea Levy.</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.6.1">
+
+<title>Release 1.6.1 (2013-10-28)</title>
+
+<para>This is primarily a bug fix release. Changes of interest
+are:</para>
+
+<itemizedlist>
+
+ <listitem>
+ <para>Nix 1.6 accidentally changed the semantics of antiquoted
+ paths in strings, such as <literal>"${/foo}/bar"</literal>. This
+ release reverts to the Nix 1.5.3 behaviour.</para>
+ </listitem>
+
+ <listitem>
+ <para>Previously, Nix optimised expressions such as
+ <literal>"${<replaceable>expr</replaceable>}"</literal> to
+ <replaceable>expr</replaceable>. Thus it neither checked whether
+ <replaceable>expr</replaceable> could be coerced to a string, nor
+ applied such coercions. This meant that
+ <literal>"${123}"</literal> evaluatued to <literal>123</literal>,
+ and <literal>"${./foo}"</literal> evaluated to
+ <literal>./foo</literal> (even though
+ <literal>"${./foo} "</literal> evaluates to
+ <literal>"/nix/store/<replaceable>hash</replaceable>-foo "</literal>).
+ Nix now checks the type of antiquoted expressions and
+ applies coercions.</para>
+ </listitem>
+
+ <listitem>
+ <para>Nix now shows the exact position of undefined variables. In
+ particular, undefined variable errors in a <literal>with</literal>
+ previously didn't show <emphasis>any</emphasis> position
+ information, so this makes it a lot easier to fix such
+ errors.</para>
+ </listitem>
+
+ <listitem>
+ <para>Undefined variables are now treated consistently.
+ Previously, the <function>tryEval</function> function would catch
+ undefined variables inside a <literal>with</literal> but not
+ outside. Now <function>tryEval</function> never catches undefined
+ variables.</para>
+ </listitem>
+
+ <listitem>
+ <para>Bash completion in <command>nix-shell</command> now works
+ correctly.</para>
+ </listitem>
+
+ <listitem>
+ <para>Stack traces are less verbose: they no longer show calls to
+ builtin functions and only show a single line for each derivation
+ on the call stack.</para>
+ </listitem>
+
+ <listitem>
+ <para>New built-in function: <function>builtins.typeOf</function>,
+ which returns the type of its argument as a string.</para>
+ </listitem>
+
+</itemizedlist>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.6.0">
+
+<title>Release 1.6 (2013-09-10)</title>
+
+<para>In addition to the usual bug fixes, this release has several new
+features:</para>
+
+<itemizedlist>
+
+ <listitem>
+ <para>The command <command>nix-build --run-env</command> has been
+ renamed to <command>nix-shell</command>.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix-shell</command> now sources
+ <filename>$stdenv/setup</filename> <emphasis>inside</emphasis> the
+ interactive shell, rather than in a parent shell. This ensures
+ that shell functions defined by <literal>stdenv</literal> can be
+ used in the interactive shell.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix-shell</command> has a new flag
+ <option>--pure</option> to clear the environment, so you get an
+ environment that more closely corresponds to the “real” Nix build.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix-shell</command> now sets the shell prompt
+ (<envar>PS1</envar>) to ensure that Nix shells are distinguishable
+ from your regular shells.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix-env</command> no longer requires a
+ <literal>*</literal> argument to match all packages, so
+ <literal>nix-env -qa</literal> is equivalent to <literal>nix-env
+ -qa '*'</literal>.</para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix-env -i</command> has a new flag
+ <option>--remove-all</option> (<option>-r</option>) to remove all
+ previous packages from the profile. This makes it easier to do
+ declarative package management similar to NixOS’s
+ <option>environment.systemPackages</option>. For instance, if you
+ have a specification <filename>my-packages.nix</filename> like this:
+
+<programlisting>
+with import <nixpkgs> {};
+[ thunderbird
+ geeqie
+ ...
+]
+</programlisting>
+
+ then after any change to this file, you can run:
+
+<screen>
+$ nix-env -f my-packages.nix -ir
+</screen>
+
+ to update your profile to match the specification.</para>
+ </listitem>
+
+ <listitem>
+ <para>The ‘<literal>with</literal>’ language construct is now more
+ lazy. It only evaluates its argument if a variable might actually
+ refer to an attribute in the argument. For instance, this now
+ works:
+
+<programlisting>
+let
+ pkgs = with pkgs; { foo = "old"; bar = foo; } // overrides;
+ overrides = { foo = "new"; };
+in pkgs.bar
+</programlisting>
+
+ This evaluates to <literal>"new"</literal>, while previously it
+ gave an “infinite recursion” error.</para>
+ </listitem>
+
+ <listitem>
+ <para>Nix now has proper integer arithmetic operators. For
+ instance, you can write <literal>x + y</literal> instead of
+ <literal>builtins.add x y</literal>, or <literal>x <
+ y</literal> instead of <literal>builtins.lessThan x y</literal>.
+ The comparison operators also work on strings.</para>
+ </listitem>
+
+ <listitem>
+ <para>On 64-bit systems, Nix integers are now 64 bits rather than
+ 32 bits.</para>
+ </listitem>
+
+ <listitem>
+ <para>When using the Nix daemon, the <command>nix-daemon</command>
+ worker process now runs on the same CPU as the client, on systems
+ that support setting CPU affinity. This gives a significant speedup
+ on some systems.</para>
+ </listitem>
+
+ <listitem>
+ <para>If a stack overflow occurs in the Nix evaluator, you now get
+ a proper error message (rather than “Segmentation fault”) on some
+ systems.</para>
+ </listitem>
+
+ <listitem>
+ <para>In addition to directories, you can now bind-mount regular
+ files in chroots through the (now misnamed) option
+ <option>build-chroot-dirs</option>.</para>
+ </listitem>
+
+</itemizedlist>
+
+<para>This release has contributions from Domen Kožar, Eelco Dolstra,
+Florian Friesdorf, Gergely Risko, Ivan Kozik, Ludovic Courtès and Shea
+Levy.</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.5.2">
+
+<title>Release 1.5.2 (2013-05-13)</title>
+
+<para>This is primarily a bug fix release. It has contributions from
+Eelco Dolstra, Lluís Batlle i Rossell and Shea Levy.</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.5">
+
+<title>Release 1.5 (2013-02-27)</title>
+
+<para>This is a brown paper bag release to fix a regression introduced
+by the hard link security fix in 1.4.</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.4">
+
+<title>Release 1.4 (2013-02-26)</title>
+
+<para>This release fixes a security bug in multi-user operation. It
+was possible for derivations to cause the mode of files outside of the
+Nix store to be changed to 444 (read-only but world-readable) by
+creating hard links to those files (<link xlink:href="https://github.com/NixOS/nix/commit/5526a282b5b44e9296e61e07d7d2626a79141ac4">details</link>).</para>
+
+<para>There are also the following improvements:</para>
+
+<itemizedlist>
+
+ <listitem><para>New built-in function:
+ <function>builtins.hashString</function>.</para></listitem>
+
+ <listitem><para>Build logs are now stored in
+ <filename>/nix/var/log/nix/drvs/<replaceable>XX</replaceable>/</filename>,
+ where <replaceable>XX</replaceable> is the first two characters of
+ the derivation. This is useful on machines that keep a lot of build
+ logs (such as Hydra servers).</para></listitem>
+
+ <listitem><para>The function <function>corepkgs/fetchurl</function>
+ can now make the downloaded file executable. This will allow
+ getting rid of all bootstrap binaries in the Nixpkgs source
+ tree.</para></listitem>
+
+ <listitem><para>Language change: The expression <literal>"${./path}
+ ..."</literal> now evaluates to a string instead of a
+ path.</para></listitem>
+
+</itemizedlist>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.3">
+
+<title>Release 1.3 (2013-01-04)</title>
+
+<para>This is primarily a bug fix release. When this version is first
+run on Linux, it removes any immutable bits from the Nix store and
+increases the schema version of the Nix store. (The previous release
+removed support for setting the immutable bit; this release clears any
+remaining immutable bits to make certain operations more
+efficient.)</para>
+
+<para>This release has contributions from Eelco Dolstra and Stuart
+Pernsteiner.</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.2">
+
+<title>Release 1.2 (2012-12-06)</title>
+
+<para>This release has the following improvements and changes:</para>
+
+<itemizedlist>
+
+ <listitem>
+ <para>Nix has a new binary substituter mechanism: the
+ <emphasis>binary cache</emphasis>. A binary cache contains
+ pre-built binaries of Nix packages. Whenever Nix wants to build a
+ missing Nix store path, it will check a set of binary caches to
+ see if any of them has a pre-built binary of that path. The
+ configuration setting <option>binary-caches</option> contains a
+ list of URLs of binary caches. For instance, doing
+<screen>
+$ nix-env -i thunderbird --option binary-caches http://cache.nixos.org
+</screen>
+ will install Thunderbird and its dependencies, using the available
+ pre-built binaries in <uri>http://cache.nixos.org</uri>.
+ The main advantage over the old “manifest”-based method of getting
+ pre-built binaries is that you don’t have to worry about your
+ manifest being in sync with the Nix expressions you’re installing
+ from; i.e., you don’t need to run <command>nix-pull</command> to
+ update your manifest. It’s also more scalable because you don’t
+ need to redownload a giant manifest file every time.
+ </para>
+
+ <para>A Nix channel can provide a binary cache URL that will be
+ used automatically if you subscribe to that channel. If you use
+ the Nixpkgs or NixOS channels
+ (<uri>http://nixos.org/channels</uri>) you automatically get the
+ cache <uri>http://cache.nixos.org</uri>.</para>
+
+ <para>Binary caches are created using <command>nix-push</command>.
+ For details on the operation and format of binary caches, see the
+ <command>nix-push</command> manpage. More details are provided in
+ <link xlink:href="https://nixos.org/nix-dev/2012-September/009826.html">this
+ nix-dev posting</link>.</para>
+ </listitem>
+
+ <listitem>
+ <para>Multiple output support should now be usable. A derivation
+ can declare that it wants to produce multiple store paths by
+ saying something like
+<programlisting>
+outputs = [ "lib" "headers" "doc" ];
+</programlisting>
+ This will cause Nix to pass the intended store path of each output
+ to the builder through the environment variables
+ <literal>lib</literal>, <literal>headers</literal> and
+ <literal>doc</literal>. Other packages can refer to a specific
+ output by referring to
+ <literal><replaceable>pkg</replaceable>.<replaceable>output</replaceable></literal>,
+ e.g.
+<programlisting>
+buildInputs = [ pkg.lib pkg.headers ];
+</programlisting>
+ If you install a package with multiple outputs using
+ <command>nix-env</command>, each output path will be symlinked
+ into the user environment.</para>
+ </listitem>
+
+ <listitem>
+ <para>Dashes are now valid as part of identifiers and attribute
+ names.</para>
+ </listitem>
+
+ <listitem>
+ <para>The new operation <command>nix-store --repair-path</command>
+ allows corrupted or missing store paths to be repaired by
+ redownloading them. <command>nix-store --verify --check-contents
+ --repair</command> will scan and repair all paths in the Nix
+ store. Similarly, <command>nix-env</command>,
+ <command>nix-build</command>, <command>nix-instantiate</command>
+ and <command>nix-store --realise</command> have a
+ <option>--repair</option> flag to detect and fix bad paths by
+ rebuilding or redownloading them.</para>
+ </listitem>
+
+ <listitem>
+ <para>Nix no longer sets the immutable bit on files in the Nix
+ store. Instead, the recommended way to guard the Nix store
+ against accidental modification on Linux is to make it a read-only
+ bind mount, like this:
+
+<screen>
+$ mount --bind /nix/store /nix/store
+$ mount -o remount,ro,bind /nix/store
+</screen>
+
+ Nix will automatically make <filename>/nix/store</filename>
+ writable as needed (using a private mount namespace) to allow
+ modifications.</para>
+ </listitem>
+
+ <listitem>
+ <para>Store optimisation (replacing identical files in the store
+ with hard links) can now be done automatically every time a path
+ is added to the store. This is enabled by setting the
+ configuration option <literal>auto-optimise-store</literal> to
+ <literal>true</literal> (disabled by default).</para>
+ </listitem>
+
+ <listitem>
+ <para>Nix now supports <command>xz</command> compression for NARs
+ in addition to <command>bzip2</command>. It compresses about 30%
+ better on typical archives and decompresses about twice as
+ fast.</para>
+ </listitem>
+
+ <listitem>
+ <para>Basic Nix expression evaluation profiling: setting the
+ environment variable <envar>NIX_COUNT_CALLS</envar> to
+ <literal>1</literal> will cause Nix to print how many times each
+ primop or function was executed.</para>
+ </listitem>
+
+ <listitem>
+ <para>New primops: <varname>concatLists</varname>,
+ <varname>elem</varname>, <varname>elemAt</varname> and
+ <varname>filter</varname>.</para>
+ </listitem>
+
+ <listitem>
+ <para>The command <command>nix-copy-closure</command> has a new
+ flag <option>--use-substitutes</option> (<option>-s</option>) to
+ download missing paths on the target machine using the substitute
+ mechanism.</para>
+ </listitem>
+
+ <listitem>
+ <para>The command <command>nix-worker</command> has been renamed
+ to <command>nix-daemon</command>. Support for running the Nix
+ worker in “slave” mode has been removed.</para>
+ </listitem>
+
+ <listitem>
+ <para>The <option>--help</option> flag of every Nix command now
+ invokes <command>man</command>.</para>
+ </listitem>
+
+ <listitem>
+ <para>Chroot builds are now supported on systemd machines.</para>
+ </listitem>
+
+</itemizedlist>
+
+<para>This release has contributions from Eelco Dolstra, Florian
+Friesdorf, Mats Erik Andersson and Shea Levy.</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.1">
+
+<title>Release 1.1 (2012-07-18)</title>
+
+<para>This release has the following improvements:</para>
+
+<itemizedlist>
+
+ <listitem>
+ <para>On Linux, when doing a chroot build, Nix now uses various
+ namespace features provided by the Linux kernel to improve
+ build isolation. Namely:
+ <itemizedlist>
+ <listitem><para>The private network namespace ensures that
+ builders cannot talk to the outside world (or vice versa): each
+ build only sees a private loopback interface. This also means
+ that two concurrent builds can listen on the same port (e.g. as
+ part of a test) without conflicting with each
+ other.</para></listitem>
+ <listitem><para>The PID namespace causes each build to start as
+ PID 1. Processes outside of the chroot are not visible to those
+ on the inside. On the other hand, processes inside the chroot
+ <emphasis>are</emphasis> visible from the outside (though with
+ different PIDs).</para></listitem>
+ <listitem><para>The IPC namespace prevents the builder from
+ communicating with outside processes using SysV IPC mechanisms
+ (shared memory, message queues, semaphores). It also ensures
+ that all IPC objects are destroyed when the builder
+ exits.</para></listitem>
+ <listitem><para>The UTS namespace ensures that builders see a
+ hostname of <literal>localhost</literal> rather than the actual
+ hostname.</para></listitem>
+ <listitem><para>The private mount namespace was already used by
+ Nix to ensure that the bind-mounts used to set up the chroot are
+ cleaned up automatically.</para></listitem>
+ </itemizedlist>
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>Build logs are now compressed using
+ <command>bzip2</command>. The command <command>nix-store
+ -l</command> decompresses them on the fly. This can be disabled
+ by setting the option <literal>build-compress-log</literal> to
+ <literal>false</literal>.</para>
+ </listitem>
+
+ <listitem>
+ <para>The creation of build logs in
+ <filename>/nix/var/log/nix/drvs</filename> can be disabled by
+ setting the new option <literal>build-keep-log</literal> to
+ <literal>false</literal>. This is useful, for instance, for Hydra
+ build machines.</para>
+ </listitem>
+
+ <listitem>
+ <para>Nix now reserves some space in
+ <filename>/nix/var/nix/db/reserved</filename> to ensure that the
+ garbage collector can run successfully if the disk is full. This
+ is necessary because SQLite transactions fail if the disk is
+ full.</para>
+ </listitem>
+
+ <listitem>
+ <para>Added a basic <function>fetchurl</function> function. This
+ is not intended to replace the <function>fetchurl</function> in
+ Nixpkgs, but is useful for bootstrapping; e.g., it will allow us
+ to get rid of the bootstrap binaries in the Nixpkgs source tree
+ and download them instead. You can use it by doing
+ <literal>import <nix/fetchurl.nix> { url =
+ <replaceable>url</replaceable>; sha256 =
+ "<replaceable>hash</replaceable>"; }</literal>. (Shea Levy)</para>
+ </listitem>
+
+ <listitem>
+ <para>Improved RPM spec file. (Michel Alexandre Salim)</para>
+ </listitem>
+
+ <listitem>
+ <para>Support for on-demand socket-based activation in the Nix
+ daemon with <command>systemd</command>.</para>
+ </listitem>
+
+ <listitem>
+ <para>Added a manpage for
+ <citerefentry><refentrytitle>nix.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
+ </listitem>
+
+ <listitem>
+ <para>When using the Nix daemon, the <option>-s</option> flag in
+ <command>nix-env -qa</command> is now much faster.</para>
+ </listitem>
+
+</itemizedlist>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.0">
+
+<title>Release 1.0 (2012-05-11)</title>
+
+<para>There have been numerous improvements and bug fixes since the
+previous release. Here are the most significant:</para>
+
+<itemizedlist>
+
+ <listitem>
+ <para>Nix can now optionally use the Boehm garbage collector.
+ This significantly reduces the Nix evaluator’s memory footprint,
+ especially when evaluating large NixOS system configurations. It
+ can be enabled using the <option>--enable-gc</option> configure
+ option.</para>
+ </listitem>
+
+ <listitem>
+ <para>Nix now uses SQLite for its database. This is faster and
+ more flexible than the old <emphasis>ad hoc</emphasis> format.
+ SQLite is also used to cache the manifests in
+ <filename>/nix/var/nix/manifests</filename>, resulting in a
+ significant speedup.</para>
+ </listitem>
+
+ <listitem>
+ <para>Nix now has an search path for expressions. The search path
+ is set using the environment variable <envar>NIX_PATH</envar> and
+ the <option>-I</option> command line option. In Nix expressions,
+ paths between angle brackets are used to specify files that must
+ be looked up in the search path. For instance, the expression
+ <literal><nixpkgs/default.nix></literal> looks for a file
+ <filename>nixpkgs/default.nix</filename> relative to every element
+ in the search path.</para>
+ </listitem>
+
+ <listitem>
+ <para>The new command <command>nix-build --run-env</command>
+ builds all dependencies of a derivation, then starts a shell in an
+ environment containing all variables from the derivation. This is
+ useful for reproducing the environment of a derivation for
+ development.</para>
+ </listitem>
+
+ <listitem>
+ <para>The new command <command>nix-store --verify-path</command>
+ verifies that the contents of a store path have not
+ changed.</para>
+ </listitem>
+
+ <listitem>
+ <para>The new command <command>nix-store --print-env</command>
+ prints out the environment of a derivation in a format that can be
+ evaluated by a shell.</para>
+ </listitem>
+
+ <listitem>
+ <para>Attribute names can now be arbitrary strings. For instance,
+ you can write <literal>{ "foo-1.2" = …; "bla bla" = …; }."bla
+ bla"</literal>.</para>
+ </listitem>
+
+ <listitem>
+ <para>Attribute selection can now provide a default value using
+ the <literal>or</literal> operator. For instance, the expression
+ <literal>x.y.z or e</literal> evaluates to the attribute
+ <literal>x.y.z</literal> if it exists, and <literal>e</literal>
+ otherwise.</para>
+ </listitem>
+
+ <listitem>
+ <para>The right-hand side of the <literal>?</literal> operator can
+ now be an attribute path, e.g., <literal>attrs ?
+ a.b.c</literal>.</para>
+ </listitem>
+
+ <listitem>
+ <para>On Linux, Nix will now make files in the Nix store immutable
+ on filesystems that support it. This prevents accidental
+ modification of files in the store by the root user.</para>
+ </listitem>
+
+ <listitem>
+ <para>Nix has preliminary support for derivations with multiple
+ outputs. This is useful because it allows parts of a package to
+ be deployed and garbage-collected separately. For instance,
+ development parts of a package such as header files or static
+ libraries would typically not be part of the closure of an
+ application, resulting in reduced disk usage and installation
+ time.</para>
+ </listitem>
+
+ <listitem>
+ <para>The Nix store garbage collector is faster and holds the
+ global lock for a shorter amount of time.</para>
+ </listitem>
+
+ <listitem>
+ <para>The option <option>--timeout</option> (corresponding to the
+ configuration setting <literal>build-timeout</literal>) allows you
+ to set an absolute timeout on builds — if a build runs for more than
+ the given number of seconds, it is terminated. This is useful for
+ recovering automatically from builds that are stuck in an infinite
+ loop but keep producing output, and for which
+ <literal>--max-silent-time</literal> is ineffective.</para>
+ </listitem>
+
+ <listitem>
+ <para>Nix development has moved to GitHub (<link xlink:href="https://github.com/NixOS/nix"/>).</para>
+ </listitem>
+
+</itemizedlist>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-0.16">
+
+<title>Release 0.16 (2010-08-17)</title>
+
+<para>This release has the following improvements:</para>
+
+<itemizedlist>
+
+ <listitem>
+ <para>The Nix expression evaluator is now much faster in most
+ cases: typically, <link xlink:href="http://www.mail-archive.com/nix-dev@cs.uu.nl/msg04113.html">3
+ to 8 times compared to the old implementation</link>. It also
+ uses less memory. It no longer depends on the ATerm
+ library.</para>
+ </listitem>
+
+ <listitem>
+ <para>
+ Support for configurable parallelism inside builders. Build
+ scripts have always had the ability to perform multiple build
+ actions in parallel (for instance, by running <command>make -j
+ 2</command>), but this was not desirable because the number of
+ actions to be performed in parallel was not configurable. Nix
+ now has an option <option>--cores
+ <replaceable>N</replaceable></option> as well as a configuration
+ setting <varname>build-cores =
+ <replaceable>N</replaceable></varname> that causes the
+ environment variable <envar>NIX_BUILD_CORES</envar> to be set to
+ <replaceable>N</replaceable> when the builder is invoked. The
+ builder can use this at its discretion to perform a parallel
+ build, e.g., by calling <command>make -j
+ <replaceable>N</replaceable></command>. In Nixpkgs, this can be
+ enabled on a per-package basis by setting the derivation
+ attribute <varname>enableParallelBuilding</varname> to
+ <literal>true</literal>.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para><command>nix-store -q</command> now supports XML output
+ through the <option>--xml</option> flag.</para>
+ </listitem>
+
+ <listitem>
+ <para>Several bug fixes.</para>
+ </listitem>
+
+</itemizedlist>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-0.15">
+
+<title>Release 0.15 (2010-03-17)</title>
+
+<para>This is a bug-fix release. Among other things, it fixes
+building on Mac OS X (Snow Leopard), and improves the contents of
+<filename>/etc/passwd</filename> and <filename>/etc/group</filename>
+in <literal>chroot</literal> builds.</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-0.14">
+
+<title>Release 0.14 (2010-02-04)</title>
+
+<para>This release has the following improvements:</para>
+
+<itemizedlist>
+
+ <listitem>
+ <para>The garbage collector now starts deleting garbage much
+ faster than before. It no longer determines liveness of all paths
+ in the store, but does so on demand.</para>
+ </listitem>
+
+ <listitem>
+ <para>Added a new operation, <command>nix-store --query
+ --roots</command>, that shows the garbage collector roots that
+ directly or indirectly point to the given store paths.</para>
+ </listitem>
+
+ <listitem>
+ <para>Removed support for converting Berkeley DB-based Nix
+ databases to the new schema.</para>
+ </listitem>
+
+ <listitem>
+ <para>Removed the <option>--use-atime</option> and
+ <option>--max-atime</option> garbage collector options. They were
+ not very useful in practice.</para>
+ </listitem>
+
+ <listitem>
+ <para>On Windows, Nix now requires Cygwin 1.7.x.</para>
+ </listitem>
+
+ <listitem>
+ <para>A few bug fixes.</para>
+ </listitem>
+
+</itemizedlist>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-0.13">
+
+<title>Release 0.13 (2009-11-05)</title>
+
+<para>This is primarily a bug fix release. It has some new
+features:</para>
+
+<itemizedlist>
+
+ <listitem>
+ <para>Syntactic sugar for writing nested attribute sets. Instead of
+
+<programlisting>
+{
+ foo = {
+ bar = 123;
+ xyzzy = true;
+ };
+ a = { b = { c = "d"; }; };
+}
+</programlisting>
+
+ you can write
+
+<programlisting>
+{
+ foo.bar = 123;
+ foo.xyzzy = true;
+ a.b.c = "d";
+}
+</programlisting>
+
+ This is useful, for instance, in NixOS configuration files.</para>
+
+ </listitem>
+
+ <listitem>
+ <para>Support for Nix channels generated by Hydra, the Nix-based
+ continuous build system. (Hydra generates NAR archives on the
+ fly, so the size and hash of these archives isn’t known in
+ advance.)</para>
+ </listitem>
+
+ <listitem>
+ <para>Support <literal>i686-linux</literal> builds directly on
+ <literal>x86_64-linux</literal> Nix installations. This is
+ implemented using the <function>personality()</function> syscall,
+ which causes <command>uname</command> to return
+ <literal>i686</literal> in child processes.</para>
+ </listitem>
+
+ <listitem>
+ <para>Various improvements to the <literal>chroot</literal>
+ support. Building in a <literal>chroot</literal> works quite well
+ now.</para>
+ </listitem>
+
+ <listitem>
+ <para>Nix no longer blocks if it tries to build a path and another
+ process is already building the same path. Instead it tries to
+ build another buildable path first. This improves
+ parallelism.</para>
+ </listitem>
+
+ <listitem>
+ <para>Support for large (> 4 GiB) files in NAR archives.</para>
+ </listitem>
+
+ <listitem>
+ <para>Various (performance) improvements to the remote build
+ mechanism.</para>
+ </listitem>
+
+ <listitem>
+ <para>New primops: <varname>builtins.addErrorContext</varname> (to
+ add a string to stack traces — useful for debugging),
+ <varname>builtins.isBool</varname>,
+ <varname>builtins.isString</varname>,
+ <varname>builtins.isInt</varname>,
+ <varname>builtins.intersectAttrs</varname>.</para>
+ </listitem>
+
+ <listitem>
+ <para>OpenSolaris support (Sander van der Burg).</para>
+ </listitem>
+
+ <listitem>
+ <para>Stack traces are no longer displayed unless the
+ <option>--show-trace</option> option is used.</para>
+ </listitem>
+
+ <listitem>
+ <para>The scoping rules for <literal>inherit
+ (<replaceable>e</replaceable>) ...</literal> in recursive
+ attribute sets have changed. The expression
+ <replaceable>e</replaceable> can now refer to the attributes
+ defined in the containing set.</para>
+ </listitem>
+
+</itemizedlist>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-0.12">
+
+<title>Release 0.12 (2008-11-20)</title>
+
+<itemizedlist>
+
+ <listitem>
+ <para>Nix no longer uses Berkeley DB to store Nix store metadata.
+ The principal advantages of the new storage scheme are: it works
+ properly over decent implementations of NFS (allowing Nix stores
+ to be shared between multiple machines); no recovery is needed
+ when a Nix process crashes; no write access is needed for
+ read-only operations; no more running out of Berkeley DB locks on
+ certain operations.</para>
+
+ <para>You still need to compile Nix with Berkeley DB support if
+ you want Nix to automatically convert your old Nix store to the
+ new schema. If you don’t need this, you can build Nix with the
+ <filename>configure</filename> option
+ <option>--disable-old-db-compat</option>.</para>
+
+ <para>After the automatic conversion to the new schema, you can
+ delete the old Berkeley DB files:
+
+ <screen>
+$ cd /nix/var/nix/db
+$ rm __db* log.* derivers references referrers reserved validpaths DB_CONFIG</screen>
+
+ The new metadata is stored in the directories
+ <filename>/nix/var/nix/db/info</filename> and
+ <filename>/nix/var/nix/db/referrer</filename>. Though the
+ metadata is stored in human-readable plain-text files, they are
+ not intended to be human-editable, as Nix is rather strict about
+ the format.</para>
+
+ <para>The new storage schema may or may not require less disk
+ space than the Berkeley DB environment, mostly depending on the
+ cluster size of your file system. With 1 KiB clusters (which
+ seems to be the <literal>ext3</literal> default nowadays) it
+ usually takes up much less space.</para>
+ </listitem>
+
+ <listitem><para>There is a new substituter that copies paths
+ directly from other (remote) Nix stores mounted somewhere in the
+ filesystem. For instance, you can speed up an installation by
+ mounting some remote Nix store that already has the packages in
+ question via NFS or <literal>sshfs</literal>. The environment
+ variable <envar>NIX_OTHER_STORES</envar> specifies the locations of
+ the remote Nix directories,
+ e.g. <literal>/mnt/remote-fs/nix</literal>.</para></listitem>
+
+ <listitem><para>New <command>nix-store</command> operations
+ <option>--dump-db</option> and <option>--load-db</option> to dump
+ and reload the Nix database.</para></listitem>
+
+ <listitem><para>The garbage collector has a number of new options to
+ allow only some of the garbage to be deleted. The option
+ <option>--max-freed <replaceable>N</replaceable></option> tells the
+ collector to stop after at least <replaceable>N</replaceable> bytes
+ have been deleted. The option <option>--max-links
+ <replaceable>N</replaceable></option> tells it to stop after the
+ link count on <filename>/nix/store</filename> has dropped below
+ <replaceable>N</replaceable>. This is useful for very large Nix
+ stores on filesystems with a 32000 subdirectories limit (like
+ <literal>ext3</literal>). The option <option>--use-atime</option>
+ causes store paths to be deleted in order of ascending last access
+ time. This allows non-recently used stuff to be deleted. The
+ option <option>--max-atime <replaceable>time</replaceable></option>
+ specifies an upper limit to the last accessed time of paths that may
+ be deleted. For instance,
+
+ <screen>
+ $ nix-store --gc -v --max-atime $(date +%s -d "2 months ago")</screen>
+
+ deletes everything that hasn’t been accessed in two months.</para></listitem>
+
+ <listitem><para><command>nix-env</command> now uses optimistic
+ profile locking when performing an operation like installing or
+ upgrading, instead of setting an exclusive lock on the profile.
+ This allows multiple <command>nix-env -i / -u / -e</command>
+ operations on the same profile in parallel. If a
+ <command>nix-env</command> operation sees at the end that the profile
+ was changed in the meantime by another process, it will just
+ restart. This is generally cheap because the build results are
+ still in the Nix store.</para></listitem>
+
+ <listitem><para>The option <option>--dry-run</option> is now
+ supported by <command>nix-store -r</command> and
+ <command>nix-build</command>.</para></listitem>
+
+ <listitem><para>The information previously shown by
+ <option>--dry-run</option> (i.e., which derivations will be built
+ and which paths will be substituted) is now always shown by
+ <command>nix-env</command>, <command>nix-store -r</command> and
+ <command>nix-build</command>. The total download size of
+ substitutable paths is now also shown. For instance, a build will
+ show something like
+
+ <screen>
+the following derivations will be built:
+ /nix/store/129sbxnk5n466zg6r1qmq1xjv9zymyy7-activate-configuration.sh.drv
+ /nix/store/7mzy971rdm8l566ch8hgxaf89x7lr7ik-upstart-jobs.drv
+ ...
+the following paths will be downloaded/copied (30.02 MiB):
+ /nix/store/4m8pvgy2dcjgppf5b4cj5l6wyshjhalj-samba-3.2.4
+ /nix/store/7h1kwcj29ip8vk26rhmx6bfjraxp0g4l-libunwind-0.98.6
+ ...</screen>
+
+ </para></listitem>
+
+ <listitem><para>Language features:
+
+ <itemizedlist>
+
+ <listitem><para>@-patterns as in Haskell. For instance, in a
+ function definition
+
+ <programlisting>f = args @ {x, y, z}: <replaceable>...</replaceable>;</programlisting>
+
+ <varname>args</varname> refers to the argument as a whole, which
+ is further pattern-matched against the attribute set pattern
+ <literal>{x, y, z}</literal>.</para></listitem>
+
+ <listitem><para>“<literal>...</literal>” (ellipsis) patterns.
+ An attribute set pattern can now say <literal>...</literal> at
+ the end of the attribute name list to specify that the function
+ takes <emphasis>at least</emphasis> the listed attributes, while
+ ignoring additional attributes. For instance,
+
+ <programlisting>{stdenv, fetchurl, fuse, ...}: <replaceable>...</replaceable></programlisting>
+
+ defines a function that accepts any attribute set that includes
+ at least the three listed attributes.</para></listitem>
+
+ <listitem><para>New primops:
+ <varname>builtins.parseDrvName</varname> (split a package name
+ string like <literal>"nix-0.12pre12876"</literal> into its name
+ and version components, e.g. <literal>"nix"</literal> and
+ <literal>"0.12pre12876"</literal>),
+ <varname>builtins.compareVersions</varname> (compare two version
+ strings using the same algorithm that <command>nix-env</command>
+ uses), <varname>builtins.length</varname> (efficiently compute
+ the length of a list), <varname>builtins.mul</varname> (integer
+ multiplication), <varname>builtins.div</varname> (integer
+ division).
+ <!-- <varname>builtins.genericClosure</varname> -->
+ </para></listitem>
+
+ </itemizedlist>
+
+ </para></listitem>
+
+ <listitem><para><command>nix-prefetch-url</command> now supports
+ <literal>mirror://</literal> URLs, provided that the environment
+ variable <envar>NIXPKGS_ALL</envar> points at a Nixpkgs
+ tree.</para></listitem>
+
+ <listitem><para>Removed the commands
+ <command>nix-pack-closure</command> and
+ <command>nix-unpack-closure</command>. You can do almost the same
+ thing but much more efficiently by doing <literal>nix-store --export
+ $(nix-store -qR <replaceable>paths</replaceable>) > closure</literal> and
+ <literal>nix-store --import <
+ closure</literal>.</para></listitem>
+
+ <listitem><para>Lots of bug fixes, including a big performance bug in
+ the handling of <literal>with</literal>-expressions.</para></listitem>
+
+</itemizedlist>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-0.11">
+
+<title>Release 0.11 (2007-12-31)</title>
+
+<para>Nix 0.11 has many improvements over the previous stable release.
+The most important improvement is secure multi-user support. It also
+features many usability enhancements and language extensions, many of
+them prompted by NixOS, the purely functional Linux distribution based
+on Nix. Here is an (incomplete) list:</para>
+
+
+<itemizedlist>
+
+
+ <listitem><para>Secure multi-user support. A single Nix store can
+ now be shared between multiple (possible untrusted) users. This is
+ an important feature for NixOS, where it allows non-root users to
+ install software. The old setuid method for sharing a store between
+ multiple users has been removed. Details for setting up a
+ multi-user store can be found in the manual.</para></listitem>
+
+
+ <listitem><para>The new command <command>nix-copy-closure</command>
+ gives you an easy and efficient way to exchange software between
+ machines. It copies the missing parts of the closure of a set of
+ store path to or from a remote machine via
+ <command>ssh</command>.</para></listitem>
+
+
+ <listitem><para>A new kind of string literal: strings between double
+ single-quotes (<literal>''</literal>) have indentation
+ “intelligently” removed. This allows large strings (such as shell
+ scripts or configuration file fragments in NixOS) to cleanly follow
+ the indentation of the surrounding expression. It also requires
+ much less escaping, since <literal>''</literal> is less common in
+ most languages than <literal>"</literal>.</para></listitem>
+
+
+ <listitem><para><command>nix-env</command> <option>--set</option>
+ modifies the current generation of a profile so that it contains
+ exactly the specified derivation, and nothing else. For example,
+ <literal>nix-env -p /nix/var/nix/profiles/browser --set
+ firefox</literal> lets the profile named
+ <filename>browser</filename> contain just Firefox.</para></listitem>
+
+
+ <listitem><para><command>nix-env</command> now maintains
+ meta-information about installed packages in profiles. The
+ meta-information is the contents of the <varname>meta</varname>
+ attribute of derivations, such as <varname>description</varname> or
+ <varname>homepage</varname>. The command <literal>nix-env -q --xml
+ --meta</literal> shows all meta-information.</para></listitem>
+
+
+ <listitem><para><command>nix-env</command> now uses the
+ <varname>meta.priority</varname> attribute of derivations to resolve
+ filename collisions between packages. Lower priority values denote
+ a higher priority. For instance, the GCC wrapper package and the
+ Binutils package in Nixpkgs both have a file
+ <filename>bin/ld</filename>, so previously if you tried to install
+ both you would get a collision. Now, on the other hand, the GCC
+ wrapper declares a higher priority than Binutils, so the former’s
+ <filename>bin/ld</filename> is symlinked in the user
+ environment.</para></listitem>
+
+
+ <listitem><para><command>nix-env -i / -u</command>: instead of
+ breaking package ties by version, break them by priority and version
+ number. That is, if there are multiple packages with the same name,
+ then pick the package with the highest priority, and only use the
+ version if there are multiple packages with the same
+ priority.</para>
+
+ <para>This makes it possible to mark specific versions/variant in
+ Nixpkgs more or less desirable than others. A typical example would
+ be a beta version of some package (e.g.,
+ <literal>gcc-4.2.0rc1</literal>) which should not be installed even
+ though it is the highest version, except when it is explicitly
+ selected (e.g., <literal>nix-env -i
+ gcc-4.2.0rc1</literal>).</para></listitem>
+
+
+ <listitem><para><command>nix-env --set-flag</command> allows meta
+ attributes of installed packages to be modified. There are several
+ attributes that can be usefully modified, because they affect the
+ behaviour of <command>nix-env</command> or the user environment
+ build script:
+
+ <itemizedlist>
+
+ <listitem><para><varname>meta.priority</varname> can be changed
+ to resolve filename clashes (see above).</para></listitem>
+
+ <listitem><para><varname>meta.keep</varname> can be set to
+ <literal>true</literal> to prevent the package from being
+ upgraded or replaced. Useful if you want to hang on to an older
+ version of a package.</para></listitem>
+
+ <listitem><para><varname>meta.active</varname> can be set to
+ <literal>false</literal> to “disable” the package. That is, no
+ symlinks will be generated to the files of the package, but it
+ remains part of the profile (so it won’t be garbage-collected).
+ Set it back to <literal>true</literal> to re-enable the
+ package.</para></listitem>
+
+ </itemizedlist>
+
+ </para></listitem>
+
+
+ <listitem><para><command>nix-env -q</command> now has a flag
+ <option>--prebuilt-only</option> (<option>-b</option>) that causes
+ <command>nix-env</command> to show only those derivations whose
+ output is already in the Nix store or that can be substituted (i.e.,
+ downloaded from somewhere). In other words, it shows the packages
+ that can be installed “quickly”, i.e., don’t need to be built from
+ source. The <option>-b</option> flag is also available in
+ <command>nix-env -i</command> and <command>nix-env -u</command> to
+ filter out derivations for which no pre-built binary is
+ available.</para></listitem>
+
+
+ <listitem><para>The new option <option>--argstr</option> (in
+ <command>nix-env</command>, <command>nix-instantiate</command> and
+ <command>nix-build</command>) is like <option>--arg</option>, except
+ that the value is a string. For example, <literal>--argstr system
+ i686-linux</literal> is equivalent to <literal>--arg system
+ \"i686-linux\"</literal> (note that <option>--argstr</option>
+ prevents annoying quoting around shell arguments).</para></listitem>
+
+
+ <listitem><para><command>nix-store</command> has a new operation
+ <option>--read-log</option> (<option>-l</option>)
+ <parameter>paths</parameter> that shows the build log of the given
+ paths.</para></listitem>
+
+
+ <!--
+ <listitem><para>TODO: semantic cleanups of string concatenation
+ etc. (mostly in r6740).</para></listitem>
+ -->
+
+
+ <listitem><para>Nix now uses Berkeley DB 4.5. The database is
+ upgraded automatically, but you should be careful not to use old
+ versions of Nix that still use Berkeley DB 4.4.</para></listitem>
+
+
+ <!-- foo
+ <listitem><para>TODO: option <option>- -reregister</option> in
+ <command>nix-store - -register-validity</command>.</para></listitem>
+ -->
+
+
+ <listitem><para>The option <option>--max-silent-time</option>
+ (corresponding to the configuration setting
+ <literal>build-max-silent-time</literal>) allows you to set a
+ timeout on builds — if a build produces no output on
+ <literal>stdout</literal> or <literal>stderr</literal> for the given
+ number of seconds, it is terminated. This is useful for recovering
+ automatically from builds that are stuck in an infinite
+ loop.</para></listitem>
+
+
+ <listitem><para><command>nix-channel</command>: each subscribed
+ channel is its own attribute in the top-level expression generated
+ for the channel. This allows disambiguation (e.g. <literal>nix-env
+ -i -A nixpkgs_unstable.firefox</literal>).</para></listitem>
+
+
+ <listitem><para>The substitutes table has been removed from the
+ database. This makes operations such as <command>nix-pull</command>
+ and <command>nix-channel --update</command> much, much
+ faster.</para></listitem>
+
+
+ <listitem><para><command>nix-pull</command> now supports
+ bzip2-compressed manifests. This speeds up
+ channels.</para></listitem>
+
+
+ <listitem><para><command>nix-prefetch-url</command> now has a
+ limited form of caching. This is used by
+ <command>nix-channel</command> to prevent unnecessary downloads when
+ the channel hasn’t changed.</para></listitem>
+
+
+ <listitem><para><command>nix-prefetch-url</command> now by default
+ computes the SHA-256 hash of the file instead of the MD5 hash. In
+ calls to <function>fetchurl</function> you should pass the
+ <literal>sha256</literal> attribute instead of
+ <literal>md5</literal>. You can pass either a hexadecimal or a
+ base-32 encoding of the hash.</para></listitem>
+
+
+ <listitem><para>Nix can now perform builds in an automatically
+ generated “chroot”. This prevents a builder from accessing stuff
+ outside of the Nix store, and thus helps ensure purity. This is an
+ experimental feature.</para></listitem>
+
+
+ <listitem><para>The new command <command>nix-store
+ --optimise</command> reduces Nix store disk space usage by finding
+ identical files in the store and hard-linking them to each other.
+ It typically reduces the size of the store by something like
+ 25-35%.</para></listitem>
+
+
+ <listitem><para><filename>~/.nix-defexpr</filename> can now be a
+ directory, in which case the Nix expressions in that directory are
+ combined into an attribute set, with the file names used as the
+ names of the attributes. The command <command>nix-env
+ --import</command> (which set the
+ <filename>~/.nix-defexpr</filename> symlink) is
+ removed.</para></listitem>
+
+
+ <listitem><para>Derivations can specify the new special attribute
+ <varname>allowedReferences</varname> to enforce that the references
+ in the output of a derivation are a subset of a declared set of
+ paths. For example, if <varname>allowedReferences</varname> is an
+ empty list, then the output must not have any references. This is
+ used in NixOS to check that generated files such as initial ramdisks
+ for booting Linux don’t have any dependencies.</para></listitem>
+
+
+ <listitem><para>The new attribute
+ <varname>exportReferencesGraph</varname> allows builders access to
+ the references graph of their inputs. This is used in NixOS for
+ tasks such as generating ISO-9660 images that contain a Nix store
+ populated with the closure of certain paths.</para></listitem>
+
+
+ <listitem><para>Fixed-output derivations (like
+ <function>fetchurl</function>) can define the attribute
+ <varname>impureEnvVars</varname> to allow external environment
+ variables to be passed to builders. This is used in Nixpkgs to
+ support proxy configuration, among other things.</para></listitem>
+
+
+ <listitem><para>Several new built-in functions:
+ <function>builtins.attrNames</function>,
+ <function>builtins.filterSource</function>,
+ <function>builtins.isAttrs</function>,
+ <function>builtins.isFunction</function>,
+ <function>builtins.listToAttrs</function>,
+ <function>builtins.stringLength</function>,
+ <function>builtins.sub</function>,
+ <function>builtins.substring</function>,
+ <function>throw</function>,
+ <function>builtins.trace</function>,
+ <function>builtins.readFile</function>.</para></listitem>
+
+
+</itemizedlist>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-relnotes-0.10.1">
+
+<title>Release 0.10.1 (2006-10-11)</title>
+
+<para>This release fixes two somewhat obscure bugs that occur when
+evaluating Nix expressions that are stored inside the Nix store
+(<literal>NIX-67</literal>). These do not affect most users.</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-relnotes-0.10">
+
+<title>Release 0.10 (2006-10-06)</title>
+
+<note><para>This version of Nix uses Berkeley DB 4.4 instead of 4.3.
+The database is upgraded automatically, but you should be careful not
+to use old versions of Nix that still use Berkeley DB 4.3. In
+particular, if you use a Nix installed through Nix, you should run
+
+<screen>
+$ nix-store --clear-substitutes</screen>
+
+first.</para></note>
+
+<warning><para>Also, the database schema has changed slighted to fix a
+performance issue (see below). When you run any Nix 0.10 command for
+the first time, the database will be upgraded automatically. This is
+irreversible.</para></warning>
+
+<itemizedlist>
+
+
+ <!-- Usability / features -->
+
+
+ <listitem><para><command>nix-env</command> usability improvements:
+
+ <itemizedlist>
+
+ <listitem><para>An option <option>--compare-versions</option>
+ (or <option>-c</option>) has been added to <command>nix-env
+ --query</command> to allow you to compare installed versions of
+ packages to available versions, or vice versa. An easy way to
+ see if you are up to date with what’s in your subscribed
+ channels is <literal>nix-env -qc \*</literal>.</para></listitem>
+
+ <listitem><para><literal>nix-env --query</literal> now takes as
+ arguments a list of package names about which to show
+ information, just like <option>--install</option>, etc.: for
+ example, <literal>nix-env -q gcc</literal>. Note that to show
+ all derivations, you need to specify
+ <literal>\*</literal>.</para></listitem>
+
+ <listitem><para><literal>nix-env -i
+ <replaceable>pkgname</replaceable></literal> will now install
+ the highest available version of
+ <replaceable>pkgname</replaceable>, rather than installing all
+ available versions (which would probably give collisions)
+ (<literal>NIX-31</literal>).</para></listitem>
+
+ <listitem><para><literal>nix-env (-i|-u) --dry-run</literal> now
+ shows exactly which missing paths will be built or
+ substituted.</para></listitem>
+
+ <listitem><para><literal>nix-env -qa --description</literal>
+ shows human-readable descriptions of packages, provided that
+ they have a <literal>meta.description</literal> attribute (which
+ most packages in Nixpkgs don’t have yet).</para></listitem>
+
+ </itemizedlist>
+
+ </para></listitem>
+
+
+ <listitem><para>New language features:
+
+ <itemizedlist>
+
+ <listitem><para>Reference scanning (which happens after each
+ build) is much faster and takes a constant amount of
+ memory.</para></listitem>
+
+ <listitem><para>String interpolation. Expressions like
+
+<programlisting>
+"--with-freetype2-library=" + freetype + "/lib"</programlisting>
+
+ can now be written as
+
+<programlisting>
+"--with-freetype2-library=${freetype}/lib"</programlisting>
+
+ You can write arbitrary expressions within
+ <literal>${<replaceable>...</replaceable>}</literal>, not just
+ identifiers.</para></listitem>
+
+ <listitem><para>Multi-line string literals.</para></listitem>
+
+ <listitem><para>String concatenations can now involve
+ derivations, as in the example <code>"--with-freetype2-library="
+ + freetype + "/lib"</code>. This was not previously possible
+ because we need to register that a derivation that uses such a
+ string is dependent on <literal>freetype</literal>. The
+ evaluator now properly propagates this information.
+ Consequently, the subpath operator (<literal>~</literal>) has
+ been deprecated.</para></listitem>
+
+ <listitem><para>Default values of function arguments can now
+ refer to other function arguments; that is, all arguments are in
+ scope in the default values
+ (<literal>NIX-45</literal>).</para></listitem>
+
+ <!--
+ <listitem><para>TODO: domain checks (r5895).</para></listitem>
+ -->
+
+ <listitem><para>Lots of new built-in primitives, such as
+ functions for list manipulation and integer arithmetic. See the
+ manual for a complete list. All primops are now available in
+ the set <varname>builtins</varname>, allowing one to test for
+ the availability of primop in a backwards-compatible
+ way.</para></listitem>
+
+ <listitem><para>Real let-expressions: <literal>let x = ...;
+ ... z = ...; in ...</literal>.</para></listitem>
+
+ </itemizedlist>
+
+ </para></listitem>
+
+
+ <listitem><para>New commands <command>nix-pack-closure</command> and
+ <command>nix-unpack-closure</command> than can be used to easily
+ transfer a store path with all its dependencies to another machine.
+ Very convenient whenever you have some package on your machine and
+ you want to copy it somewhere else.</para></listitem>
+
+
+ <listitem><para>XML support:
+
+ <itemizedlist>
+
+ <listitem><para><literal>nix-env -q --xml</literal> prints the
+ installed or available packages in an XML representation for
+ easy processing by other tools.</para></listitem>
+
+ <listitem><para><literal>nix-instantiate --eval-only
+ --xml</literal> prints an XML representation of the resulting
+ term. (The new flag <option>--strict</option> forces ‘deep’
+ evaluation of the result, i.e., list elements and attributes are
+ evaluated recursively.)</para></listitem>
+
+ <listitem><para>In Nix expressions, the primop
+ <function>builtins.toXML</function> converts a term to an XML
+ representation. This is primarily useful for passing structured
+ information to builders.</para></listitem>
+
+ </itemizedlist>
+
+ </para></listitem>
+
+
+ <listitem><para>You can now unambiguously specify which derivation to
+ build or install in <command>nix-env</command>,
+ <command>nix-instantiate</command> and <command>nix-build</command>
+ using the <option>--attr</option> / <option>-A</option> flags, which
+ takes an attribute name as argument. (Unlike symbolic package names
+ such as <literal>subversion-1.4.0</literal>, attribute names in an
+ attribute set are unique.) For instance, a quick way to perform a
+ test build of a package in Nixpkgs is <literal>nix-build
+ pkgs/top-level/all-packages.nix -A
+ <replaceable>foo</replaceable></literal>. <literal>nix-env -q
+ --attr</literal> shows the attribute names corresponding to each
+ derivation.</para></listitem>
+
+
+ <listitem><para>If the top-level Nix expression used by
+ <command>nix-env</command>, <command>nix-instantiate</command> or
+ <command>nix-build</command> evaluates to a function whose arguments
+ all have default values, the function will be called automatically.
+ Also, the new command-line switch <option>--arg
+ <replaceable>name</replaceable>
+ <replaceable>value</replaceable></option> can be used to specify
+ function arguments on the command line.</para></listitem>
+
+
+ <listitem><para><literal>nix-install-package --url
+ <replaceable>URL</replaceable></literal> allows a package to be
+ installed directly from the given URL.</para></listitem>
+
+
+ <listitem><para>Nix now works behind an HTTP proxy server; just set
+ the standard environment variables <envar>http_proxy</envar>,
+ <envar>https_proxy</envar>, <envar>ftp_proxy</envar> or
+ <envar>all_proxy</envar> appropriately. Functions such as
+ <function>fetchurl</function> in Nixpkgs also respect these
+ variables.</para></listitem>
+
+
+ <listitem><para><literal>nix-build -o
+ <replaceable>symlink</replaceable></literal> allows the symlink to
+ the build result to be named something other than
+ <literal>result</literal>.</para></listitem>
+
+
+ <!-- Stability / performance / etc. -->
+
+
+ <listitem><para>Platform support:
+
+ <itemizedlist>
+
+ <listitem><para>Support for 64-bit platforms, provided a <link xlink:href="http://bugzilla.sen.cwi.nl:8080/show_bug.cgi?id=606">suitably
+ patched ATerm library</link> is used. Also, files larger than 2
+ GiB are now supported.</para></listitem>
+
+ <listitem><para>Added support for Cygwin (Windows,
+ <literal>i686-cygwin</literal>), Mac OS X on Intel
+ (<literal>i686-darwin</literal>) and Linux on PowerPC
+ (<literal>powerpc-linux</literal>).</para></listitem>
+
+ <listitem><para>Users of SMP and multicore machines will
+ appreciate that the number of builds to be performed in parallel
+ can now be specified in the configuration file in the
+ <literal>build-max-jobs</literal> setting.</para></listitem>
+
+ </itemizedlist>
+
+ </para></listitem>
+
+
+ <listitem><para>Garbage collector improvements:
+
+ <itemizedlist>
+
+ <listitem><para>Open files (such as running programs) are now
+ used as roots of the garbage collector. This prevents programs
+ that have been uninstalled from being garbage collected while
+ they are still running. The script that detects these
+ additional runtime roots
+ (<filename>find-runtime-roots.pl</filename>) is inherently
+ system-specific, but it should work on Linux and on all
+ platforms that have the <command>lsof</command>
+ utility.</para></listitem>
+
+ <listitem><para><literal>nix-store --gc</literal>
+ (a.k.a. <command>nix-collect-garbage</command>) prints out the
+ number of bytes freed on standard output. <literal>nix-store
+ --gc --print-dead</literal> shows how many bytes would be freed
+ by an actual garbage collection.</para></listitem>
+
+ <listitem><para><literal>nix-collect-garbage -d</literal>
+ removes all old generations of <emphasis>all</emphasis> profiles
+ before calling the actual garbage collector (<literal>nix-store
+ --gc</literal>). This is an easy way to get rid of all old
+ packages in the Nix store.</para></listitem>
+
+ <listitem><para><command>nix-store</command> now has an
+ operation <option>--delete</option> to delete specific paths
+ from the Nix store. It won’t delete reachable (non-garbage)
+ paths unless <option>--ignore-liveness</option> is
+ specified.</para></listitem>
+
+ </itemizedlist>
+
+ </para></listitem>
+
+
+ <listitem><para>Berkeley DB 4.4’s process registry feature is used
+ to recover from crashed Nix processes.</para></listitem>
+
+ <!-- <listitem><para>TODO: shared stores.</para></listitem> -->
+
+ <listitem><para>A performance issue has been fixed with the
+ <literal>referer</literal> table, which stores the inverse of the
+ <literal>references</literal> table (i.e., it tells you what store
+ paths refer to a given path). Maintaining this table could take a
+ quadratic amount of time, as well as a quadratic amount of Berkeley
+ DB log file space (in particular when running the garbage collector)
+ (<literal>NIX-23</literal>).</para></listitem>
+
+ <listitem><para>Nix now catches the <literal>TERM</literal> and
+ <literal>HUP</literal> signals in addition to the
+ <literal>INT</literal> signal. So you can now do a <literal>killall
+ nix-store</literal> without triggering a database
+ recovery.</para></listitem>
+
+ <listitem><para><command>bsdiff</command> updated to version
+ 4.3.</para></listitem>
+
+ <listitem><para>Substantial performance improvements in expression
+ evaluation and <literal>nix-env -qa</literal>, all thanks to <link xlink:href="http://valgrind.org/">Valgrind</link>. Memory use has
+ been reduced by a factor 8 or so. Big speedup by memoisation of
+ path hashing.</para></listitem>
+
+ <listitem><para>Lots of bug fixes, notably:
+
+ <itemizedlist>
+
+ <listitem><para>Make sure that the garbage collector can run
+ successfully when the disk is full
+ (<literal>NIX-18</literal>).</para></listitem>
+
+ <listitem><para><command>nix-env</command> now locks the profile
+ to prevent races between concurrent <command>nix-env</command>
+ operations on the same profile
+ (<literal>NIX-7</literal>).</para></listitem>
+
+ <listitem><para>Removed misleading messages from
+ <literal>nix-env -i</literal> (e.g., <literal>installing
+ `foo'</literal> followed by <literal>uninstalling
+ `foo'</literal>) (<literal>NIX-17</literal>).</para></listitem>
+
+ </itemizedlist>
+
+ </para></listitem>
+
+ <listitem><para>Nix source distributions are a lot smaller now since
+ we no longer include a full copy of the Berkeley DB source
+ distribution (but only the bits we need).</para></listitem>
+
+ <listitem><para>Header files are now installed so that external
+ programs can use the Nix libraries.</para></listitem>
+
+</itemizedlist>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-relnotes-0.9.2">
+
+<title>Release 0.9.2 (2005-09-21)</title>
+
+<para>This bug fix release fixes two problems on Mac OS X:
+
+<itemizedlist>
+
+ <listitem><para>If Nix was linked against statically linked versions
+ of the ATerm or Berkeley DB library, there would be dynamic link
+ errors at runtime.</para></listitem>
+
+ <listitem><para><command>nix-pull</command> and
+ <command>nix-push</command> intermittently failed due to race
+ conditions involving pipes and child processes with error messages
+ such as <literal>open2: open(GLOB(0x180b2e4), >&=9) failed: Bad
+ file descriptor at /nix/bin/nix-pull line 77</literal> (issue
+ <literal>NIX-14</literal>).</para></listitem>
+
+</itemizedlist>
+
+</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-relnotes-0.9.1">
+
+<title>Release 0.9.1 (2005-09-20)</title>
+
+<para>This bug fix release addresses a problem with the ATerm library
+when the <option>--with-aterm</option> flag in
+<command>configure</command> was <emphasis>not</emphasis> used.</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-relnotes-0.9">
+
+<title>Release 0.9 (2005-09-16)</title>
+
+<para>NOTE: this version of Nix uses Berkeley DB 4.3 instead of 4.2.
+The database is upgraded automatically, but you should be careful not
+to use old versions of Nix that still use Berkeley DB 4.2. In
+particular, if you use a Nix installed through Nix, you should run
+
+<screen>
+$ nix-store --clear-substitutes</screen>
+
+first.</para>
+
+
+<itemizedlist>
+
+ <listitem><para>Unpacking of patch sequences is much faster now
+ since we no longer do redundant unpacking and repacking of
+ intermediate paths.</para></listitem>
+
+ <listitem><para>Nix now uses Berkeley DB 4.3.</para></listitem>
+
+ <listitem><para>The <function>derivation</function> primitive is
+ lazier. Attributes of dependent derivations can mutually refer to
+ each other (as long as there are no data dependencies on the
+ <varname>outPath</varname> and <varname>drvPath</varname> attributes
+ computed by <function>derivation</function>).</para>
+
+ <para>For example, the expression <literal>derivation
+ attrs</literal> now evaluates to (essentially)
+
+ <programlisting>
+attrs // {
+ type = "derivation";
+ outPath = derivation! attrs;
+ drvPath = derivation! attrs;
+}</programlisting>
+
+ where <function>derivation!</function> is a primop that does the
+ actual derivation instantiation (i.e., it does what
+ <function>derivation</function> used to do). The advantage is that
+ it allows commands such as <command>nix-env -qa</command> and
+ <command>nix-env -i</command> to be much faster since they no longer
+ need to instantiate all derivations, just the
+ <varname>name</varname> attribute.</para>
+
+ <para>Also, it allows derivations to cyclically reference each
+ other, for example,
+
+ <programlisting>
+webServer = derivation {
+ ...
+ hostName = "svn.cs.uu.nl";
+ services = [svnService];
+};
+
+svnService = derivation {
+ ...
+ hostName = webServer.hostName;
+};</programlisting>
+
+ Previously, this would yield a black hole (infinite recursion).</para>
+
+ </listitem>
+
+ <listitem><para><command>nix-build</command> now defaults to using
+ <filename>./default.nix</filename> if no Nix expression is
+ specified.</para></listitem>
+
+ <listitem><para><command>nix-instantiate</command>, when applied to
+ a Nix expression that evaluates to a function, will call the
+ function automatically if all its arguments have
+ defaults.</para></listitem>
+
+ <listitem><para>Nix now uses libtool to build dynamic libraries.
+ This reduces the size of executables.</para></listitem>
+
+ <listitem><para>A new list concatenation operator
+ <literal>++</literal>. For example, <literal>[1 2 3] ++ [4 5
+ 6]</literal> evaluates to <literal>[1 2 3 4 5
+ 6]</literal>.</para></listitem>
+
+ <listitem><para>Some currently undocumented primops to support
+ low-level build management using Nix (i.e., using Nix as a Make
+ replacement). See the commit messages for <literal>r3578</literal>
+ and <literal>r3580</literal>.</para></listitem>
+
+ <listitem><para>Various bug fixes and performance
+ improvements.</para></listitem>
+
+</itemizedlist>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-relnotes-0.8.1">
+
+<title>Release 0.8.1 (2005-04-13)</title>
+
+<para>This is a bug fix release.</para>
+
+<itemizedlist>
+
+ <listitem><para>Patch downloading was broken.</para></listitem>
+
+ <listitem><para>The garbage collector would not delete paths that
+ had references from invalid (but substitutable)
+ paths.</para></listitem>
+
+</itemizedlist>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-relnotes-0.8">
+
+<title>Release 0.8 (2005-04-11)</title>
+
+<para>NOTE: the hashing scheme in Nix 0.8 changed (as detailed below).
+As a result, <command>nix-pull</command> manifests and channels built
+for Nix 0.7 and below will not work anymore. However, the Nix
+expression language has not changed, so you can still build from
+source. Also, existing user environments continue to work. Nix 0.8
+will automatically upgrade the database schema of previous
+installations when it is first run.</para>
+
+<para>If you get the error message
+
+<screen>
+you have an old-style manifest `/nix/var/nix/manifests/[...]'; please
+delete it</screen>
+
+you should delete previously downloaded manifests:
+
+<screen>
+$ rm /nix/var/nix/manifests/*</screen>
+
+If <command>nix-channel</command> gives the error message
+
+<screen>
+manifest `http://catamaran.labs.cs.uu.nl/dist/nix/channels/[channel]/MANIFEST'
+is too old (i.e., for Nix <= 0.7)</screen>
+
+then you should unsubscribe from the offending channel
+(<command>nix-channel --remove
+<replaceable>URL</replaceable></command>; leave out
+<literal>/MANIFEST</literal>), and subscribe to the same URL, with
+<literal>channels</literal> replaced by <literal>channels-v3</literal>
+(e.g., <link xlink:href="http://catamaran.labs.cs.uu.nl/dist/nix/channels-v3/nixpkgs-unstable"/>).</para>
+
+<para>Nix 0.8 has the following improvements:
+
+<itemizedlist>
+
+ <listitem><para>The cryptographic hashes used in store paths are now
+ 160 bits long, but encoded in base-32 so that they are still only 32
+ characters long (e.g.,
+ <filename>/nix/store/csw87wag8bqlqk7ipllbwypb14xainap-atk-1.9.0</filename>).
+ (This is actually a 160 bit truncation of a SHA-256
+ hash.)</para></listitem>
+
+ <listitem><para>Big cleanups and simplifications of the basic store
+ semantics. The notion of “closure store expressions” is gone (and
+ so is the notion of “successors”); the file system references of a
+ store path are now just stored in the database.</para>
+
+ <para>For instance, given any store path, you can query its closure:
+
+ <screen>
+$ nix-store -qR $(which firefox)
+... lots of paths ...</screen>
+
+ Also, Nix now remembers for each store path the derivation that
+ built it (the “deriver”):
+
+ <screen>
+$ nix-store -qR $(which firefox)
+/nix/store/4b0jx7vq80l9aqcnkszxhymsf1ffa5jd-firefox-1.0.1.drv</screen>
+
+ So to see the build-time dependencies, you can do
+
+ <screen>
+$ nix-store -qR $(nix-store -qd $(which firefox))</screen>
+
+ or, in a nicer format:
+
+ <screen>
+$ nix-store -q --tree $(nix-store -qd $(which firefox))</screen>
+
+ </para>
+
+ <para>File system references are also stored in reverse. For
+ instance, you can query all paths that directly or indirectly use a
+ certain Glibc:
+
+ <screen>
+$ nix-store -q --referrers-closure \
+ /nix/store/8lz9yc6zgmc0vlqmn2ipcpkjlmbi51vv-glibc-2.3.4</screen>
+
+ </para>
+
+ </listitem>
+
+ <listitem><para>The concept of fixed-output derivations has been
+ formalised. Previously, functions such as
+ <function>fetchurl</function> in Nixpkgs used a hack (namely,
+ explicitly specifying a store path hash) to prevent changes to, say,
+ the URL of the file from propagating upwards through the dependency
+ graph, causing rebuilds of everything. This can now be done cleanly
+ by specifying the <varname>outputHash</varname> and
+ <varname>outputHashAlgo</varname> attributes. Nix itself checks
+ that the content of the output has the specified hash. (This is
+ important for maintaining certain invariants necessary for future
+ work on secure shared stores.)</para></listitem>
+
+ <listitem><para>One-click installation :-) It is now possible to
+ install any top-level component in Nixpkgs directly, through the web
+ — see, e.g., <link xlink:href="http://catamaran.labs.cs.uu.nl/dist/nixpkgs-0.8/"/>.
+ All you have to do is associate
+ <filename>/nix/bin/nix-install-package</filename> with the MIME type
+ <literal>application/nix-package</literal> (or the extension
+ <filename>.nixpkg</filename>), and clicking on a package link will
+ cause it to be installed, with all appropriate dependencies. If you
+ just want to install some specific application, this is easier than
+ subscribing to a channel.</para></listitem>
+
+ <listitem><para><command>nix-store -r
+ <replaceable>PATHS</replaceable></command> now builds all the
+ derivations PATHS in parallel. Previously it did them sequentially
+ (though exploiting possible parallelism between subderivations).
+ This is nice for build farms.</para></listitem>
+
+ <listitem><para><command>nix-channel</command> has new operations
+ <option>--list</option> and
+ <option>--remove</option>.</para></listitem>
+
+ <listitem><para>New ways of installing components into user
+ environments:
+
+ <itemizedlist>
+
+ <listitem><para>Copy from another user environment:
+
+ <screen>
+$ nix-env -i --from-profile .../other-profile firefox</screen>
+
+ </para></listitem>
+
+ <listitem><para>Install a store derivation directly (bypassing the
+ Nix expression language entirely):
+
+ <screen>
+$ nix-env -i /nix/store/z58v41v21xd3...-aterm-2.3.1.drv</screen>
+
+ (This is used to implement <command>nix-install-package</command>,
+ which is therefore immune to evolution in the Nix expression
+ language.)</para></listitem>
+
+ <listitem><para>Install an already built store path directly:
+
+ <screen>
+$ nix-env -i /nix/store/hsyj5pbn0d9i...-aterm-2.3.1</screen>
+
+ </para></listitem>
+
+ <listitem><para>Install the result of a Nix expression specified
+ as a command-line argument:
+
+ <screen>
+$ nix-env -f .../i686-linux.nix -i -E 'x: x.firefoxWrapper'</screen>
+
+ The difference with the normal installation mode is that
+ <option>-E</option> does not use the <varname>name</varname>
+ attributes of derivations. Therefore, this can be used to
+ disambiguate multiple derivations with the same
+ name.</para></listitem>
+
+ </itemizedlist></para></listitem>
+
+ <listitem><para>A hash of the contents of a store path is now stored
+ in the database after a successful build. This allows you to check
+ whether store paths have been tampered with: <command>nix-store
+ --verify --check-contents</command>.</para></listitem>
+
+ <listitem>
+
+ <para>Implemented a concurrent garbage collector. It is now
+ always safe to run the garbage collector, even if other Nix
+ operations are happening simultaneously.</para>
+
+ <para>However, there can still be GC races if you use
+ <command>nix-instantiate</command> and <command>nix-store
+ --realise</command> directly to build things. To prevent races,
+ use the <option>--add-root</option> flag of those commands.</para>
+
+ </listitem>
+
+ <listitem><para>The garbage collector now finally deletes paths in
+ the right order (i.e., topologically sorted under the “references”
+ relation), thus making it safe to interrupt the collector without
+ risking a store that violates the closure
+ invariant.</para></listitem>
+
+ <listitem><para>Likewise, the substitute mechanism now downloads
+ files in the right order, thus preserving the closure invariant at
+ all times.</para></listitem>
+
+ <listitem><para>The result of <command>nix-build</command> is now
+ registered as a root of the garbage collector. If the
+ <filename>./result</filename> link is deleted, the GC root
+ disappears automatically.</para></listitem>
+
+ <listitem>
+
+ <para>The behaviour of the garbage collector can be changed
+ globally by setting options in
+ <filename>/nix/etc/nix/nix.conf</filename>.
+
+ <itemizedlist>
+
+ <listitem><para><literal>gc-keep-derivations</literal> specifies
+ whether deriver links should be followed when searching for live
+ paths.</para></listitem>
+
+ <listitem><para><literal>gc-keep-outputs</literal> specifies
+ whether outputs of derivations should be followed when searching
+ for live paths.</para></listitem>
+
+ <listitem><para><literal>env-keep-derivations</literal>
+ specifies whether user environments should store the paths of
+ derivations when they are added (thus keeping the derivations
+ alive).</para></listitem>
+
+ </itemizedlist>
+
+ </para></listitem>
+
+ <listitem><para>New <command>nix-env</command> query flags
+ <option>--drv-path</option> and
+ <option>--out-path</option>.</para></listitem>
+
+ <listitem><para><command>fetchurl</command> allows SHA-1 and SHA-256
+ in addition to MD5. Just specify the attribute
+ <varname>sha1</varname> or <varname>sha256</varname> instead of
+ <varname>md5</varname>.</para></listitem>
+
+ <listitem><para>Manual updates.</para></listitem>
+
+</itemizedlist>
+
+</para>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-relnotes-0.7">
+
+<title>Release 0.7 (2005-01-12)</title>
+
+<itemizedlist>
+
+ <listitem><para>Binary patching. When upgrading components using
+ pre-built binaries (through nix-pull / nix-channel), Nix can
+ automatically download and apply binary patches to already installed
+ components instead of full downloads. Patching is “smart”: if there
+ is a <emphasis>sequence</emphasis> of patches to an installed
+ component, Nix will use it. Patches are currently generated
+ automatically between Nixpkgs (pre-)releases.</para></listitem>
+
+ <listitem><para>Simplifications to the substitute
+ mechanism.</para></listitem>
+
+ <listitem><para>Nix-pull now stores downloaded manifests in
+ <filename>/nix/var/nix/manifests</filename>.</para></listitem>
+
+ <listitem><para>Metadata on files in the Nix store is canonicalised
+ after builds: the last-modified timestamp is set to 0 (00:00:00
+ 1/1/1970), the mode is set to 0444 or 0555 (readable and possibly
+ executable by all; setuid/setgid bits are dropped), and the group is
+ set to the default. This ensures that the result of a build and an
+ installation through a substitute is the same; and that timestamp
+ dependencies are revealed.</para></listitem>
+
+</itemizedlist>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-relnotes-0.6">
+
+<title>Release 0.6 (2004-11-14)</title>
+
+<itemizedlist>
+
+ <listitem>
+ <para>Rewrite of the normalisation engine.
+
+ <itemizedlist>
+
+ <listitem><para>Multiple builds can now be performed in parallel
+ (option <option>-j</option>).</para></listitem>
+
+ <listitem><para>Distributed builds. Nix can now call a shell
+ script to forward builds to Nix installations on remote
+ machines, which may or may not be of the same platform
+ type.</para></listitem>
+
+ <listitem><para>Option <option>--fallback</option> allows
+ recovery from broken substitutes.</para></listitem>
+
+ <listitem><para>Option <option>--keep-going</option> causes
+ building of other (unaffected) derivations to continue if one
+ failed.</para></listitem>
+
+ </itemizedlist>
+
+ </para>
+
+ </listitem>
+
+ <listitem><para>Improvements to the garbage collector (i.e., it
+ should actually work now).</para></listitem>
+
+ <listitem><para>Setuid Nix installations allow a Nix store to be
+ shared among multiple users.</para></listitem>
+
+ <listitem><para>Substitute registration is much faster
+ now.</para></listitem>
+
+ <listitem><para>A utility <command>nix-build</command> to build a
+ Nix expression and create a symlink to the result int the current
+ directory; useful for testing Nix derivations.</para></listitem>
+
+ <listitem><para>Manual updates.</para></listitem>
+
+ <listitem>
+
+ <para><command>nix-env</command> changes:
+
+ <itemizedlist>
+
+ <listitem><para>Derivations for other platforms are filtered out
+ (which can be overridden using
+ <option>--system-filter</option>).</para></listitem>
+
+ <listitem><para><option>--install</option> by default now
+ uninstall previous derivations with the same
+ name.</para></listitem>
+
+ <listitem><para><option>--upgrade</option> allows upgrading to a
+ specific version.</para></listitem>
+
+ <listitem><para>New operation
+ <option>--delete-generations</option> to remove profile
+ generations (necessary for effective garbage
+ collection).</para></listitem>
+
+ <listitem><para>Nicer output (sorted,
+ columnised).</para></listitem>
+
+ </itemizedlist>
+
+ </para>
+
+ </listitem>
+
+ <listitem><para>More sensible verbosity levels all around (builder
+ output is now shown always, unless <option>-Q</option> is
+ given).</para></listitem>
+
+ <listitem>
+
+ <para>Nix expression language changes:
+
+ <itemizedlist>
+
+ <listitem><para>New language construct: <literal>with
+ <replaceable>E1</replaceable>;
+ <replaceable>E2</replaceable></literal> brings all attributes
+ defined in the attribute set <replaceable>E1</replaceable> in
+ scope in <replaceable>E2</replaceable>.</para></listitem>
+
+ <listitem><para>Added a <function>map</function>
+ function.</para></listitem>
+
+ <listitem><para>Various new operators (e.g., string
+ concatenation).</para></listitem>
+
+ </itemizedlist>
+
+ </para>
+
+ </listitem>
+
+ <listitem><para>Expression evaluation is much
+ faster.</para></listitem>
+
+ <listitem><para>An Emacs mode for editing Nix expressions (with
+ syntax highlighting and indentation) has been
+ added.</para></listitem>
+
+ <listitem><para>Many bug fixes.</para></listitem>
+
+</itemizedlist>
+
+</section>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-relnotes-0.5">
+
+<title>Release 0.5 and earlier</title>
+
+<para>Please refer to the Subversion commit log messages.</para>
+
+</section>
+
+</appendix>
+
+<!--
+<appendix>
+ <title>Nix Release Notes</title>
+ <xi:include href="release-notes/release-notes.xml"
+ xpointer="xmlns(x=http://docbook.org/ns/docbook)xpointer(x:article/x:section)" />
+ </appendix>
+-->
+
+</book>
diff --git a/doc/manual/src/command-ref/conf-file.md.tmp b/doc/manual/src/command-ref/conf-file.md.tmp
new file mode 100644
index 000000000..93d52069b
--- /dev/null
+++ b/doc/manual/src/command-ref/conf-file.md.tmp
@@ -0,0 +1,52 @@
+# Name
+
+`nix.conf` - Nix configuration file
+
+# Description
+
+By default Nix reads settings from the following places:
+
+ - The system-wide configuration file `sysconfdir/nix/nix.conf` (i.e.
+ `/etc/nix/nix.conf` on most systems), or `$NIX_CONF_DIR/nix.conf` if
+ `NIX_CONF_DIR` is set. Values loaded in this file are not forwarded
+ to the Nix daemon. The client assumes that the daemon has already
+ loaded them.
+
+ - If `NIX_USER_CONF_FILES` is set, then each path separated by `:`
+ will be loaded in reverse order.
+
+ Otherwise it will look for `nix/nix.conf` files in `XDG_CONFIG_DIRS`
+ and `XDG_CONFIG_HOME`. If these are unset, it will look in
+ `$HOME/.config/nix.conf`.
+
+ - If `NIX_CONFIG` is set, its contents is treated as the contents of
+ a configuration file.
+
+The configuration files consist of `name = value` pairs, one per
+line. Other files can be included with a line like `include path`,
+where *path* is interpreted relative to the current conf file and a
+missing file is an error unless `!include` is used instead. Comments
+start with a `#` character. Here is an example configuration file:
+
+ keep-outputs = true # Nice for developers
+ keep-derivations = true # Idem
+
+You can override settings on the command line using the `--option`
+flag, e.g. `--option keep-outputs false`. Every configuration setting
+also has a corresponding command line flag, e.g. `--max-jobs 16`; for
+Boolean settings, there are two flags to enable or disable the setting
+(e.g. `--keep-failed` and `--no-keep-failed`).
+
+A configuration setting usually overrides any previous value. However,
+you can prefix the name of the setting by `extra-` to *append* to the
+previous value. For instance,
+
+ substituters = a b
+ extra-substituters = c d
+
+defines the `substituters` setting to be `a b c d`. This is also
+available as a command line flag (e.g. `--extra-substituters`).
+
+The following settings are currently available:
+
+EvalCommand::getEvalState()0
diff --git a/doc/manual/src/command-ref/nix.md b/doc/manual/src/command-ref/nix.md
new file mode 100644
index 000000000..acc7da3a6
--- /dev/null
+++ b/doc/manual/src/command-ref/nix.md
@@ -0,0 +1,3021 @@
+# Name
+
+`nix` - a tool for reproducible and declarative configuration management
+
+# Synopsis
+
+`nix` [*flags*...] *subcommand*
+
+# Flags
+
+ - `--debug`
+ enable debug output
+
+ - `--help`
+ show usage information
+
+ - `--help-config`
+ show configuration options
+
+ - `--log-format` *format*
+ format of log output; `raw`, `internal-json`, `bar` or `bar-with-logs`
+
+ - `--no-net`
+ disable substituters and consider all previously downloaded files up-to-date
+
+ - `--option` *name* *value*
+ set a Nix configuration option (overriding `nix.conf`)
+
+ - `--print-build-logs` / `L`
+ print full build logs on stderr
+
+ - `--quiet`
+ decrease verbosity level
+
+ - `--refresh`
+ consider all previously downloaded files out-of-date
+
+ - `--verbose` / `v`
+ increase verbosity level
+
+ - `--version`
+ show version information
+
+# Subcommand `nix add-to-store`
+
+## Name
+
+`nix add-to-store` - add a path to the Nix store
+
+## Synopsis
+
+`nix add-to-store` [*flags*...] *path*
+
+## Description
+
+
+Copy the file or directory *path* to the Nix store, and
+print the resulting store path on standard output.
+
+
+
+## Flags
+
+ - `--dry-run`
+ show what this command would do without doing it
+
+ - `--flat`
+ add flat file to the Nix store
+
+ - `--name` / `n` *name*
+ name component of the store path
+
+# Subcommand `nix build`
+
+## Name
+
+`nix build` - build a derivation or fetch a store path
+
+## Synopsis
+
+`nix build` [*flags*...] *installables*...
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--derivation`
+ operate on the store derivation rather than its outputs
+
+ - `--dry-run`
+ show what this command would do without doing it
+
+ - `--expr` *expr*
+ evaluate attributes from *expr*
+
+ - `--file` / `f` *file*
+ evaluate *file* rather than the default
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--no-link`
+ do not create a symlink to the build result
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--out-link` / `o` *path*
+ path of the symlink to the build result
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--profile` *path*
+ profile to update
+
+ - `--rebuild`
+ rebuild an already built package and compare the result to the existing store paths
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+## Examples
+
+To build and run GNU Hello from NixOS 17.03:
+
+```console
+nix build -f channel:nixos-17.03 hello; ./result/bin/hello
+```
+
+To build the build.x86_64-linux attribute from release.nix:
+
+```console
+nix build -f release.nix build.x86_64-linux
+```
+
+To make a profile point at GNU Hello:
+
+```console
+nix build --profile /tmp/profile nixpkgs#hello
+```
+
+# Subcommand `nix bundle`
+
+## Name
+
+`nix bundle` - bundle an application so that it works outside of the Nix store
+
+## Synopsis
+
+`nix bundle` [*flags*...] *installable*
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--bundler` *flake-url*
+ use custom bundler
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--derivation`
+ operate on the store derivation rather than its outputs
+
+ - `--expr` *expr*
+ evaluate attributes from *expr*
+
+ - `--file` / `f` *file*
+ evaluate *file* rather than the default
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--out-link` / `o` *path*
+ path of the symlink to the build result
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+## Examples
+
+To bundle Hello:
+
+```console
+nix bundle hello
+```
+
+# Subcommand `nix cat-nar`
+
+## Name
+
+`nix cat-nar` - print the contents of a file inside a NAR file on stdout
+
+## Synopsis
+
+`nix cat-nar` [*flags*...] *nar* *path*
+
+# Subcommand `nix cat-store`
+
+## Name
+
+`nix cat-store` - print the contents of a file in the Nix store on stdout
+
+## Synopsis
+
+`nix cat-store` [*flags*...] *path*
+
+# Subcommand `nix copy`
+
+## Name
+
+`nix copy` - copy paths between Nix stores
+
+## Synopsis
+
+`nix copy` [*flags*...] *installables*...
+
+## Flags
+
+ - `--all`
+ apply operation to the entire store
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--derivation`
+ operate on the store derivation rather than its outputs
+
+ - `--expr` *expr*
+ evaluate attributes from *expr*
+
+ - `--file` / `f` *file*
+ evaluate *file* rather than the default
+
+ - `--from` *store-uri*
+ URI of the source Nix store
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--no-check-sigs`
+ do not require that paths are signed by trusted keys
+
+ - `--no-recursive`
+ apply operation to specified paths only
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--substitute-on-destination` / `s`
+ whether to try substitutes on the destination store (only supported by SSH)
+
+ - `--to` *store-uri*
+ URI of the destination Nix store
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+## Examples
+
+To copy Firefox from the local store to a binary cache in file:///tmp/cache:
+
+```console
+nix copy --to file:///tmp/cache $(type -p firefox)
+```
+
+To copy the entire current NixOS system closure to another machine via SSH:
+
+```console
+nix copy --to ssh://server /run/current-system
+```
+
+To copy a closure from another machine via SSH:
+
+```console
+nix copy --from ssh://server /nix/store/a6cnl93nk1wxnq84brbbwr6hxw9gp2w9-blender-2.79-rc2
+```
+
+To copy Hello to an S3 binary cache:
+
+```console
+nix copy --to s3://my-bucket?region=eu-west-1 nixpkgs#hello
+```
+
+To copy Hello to an S3-compatible binary cache:
+
+```console
+nix copy --to s3://my-bucket?region=eu-west-1&endpoint=example.com nixpkgs#hello
+```
+
+# Subcommand `nix copy-sigs`
+
+## Name
+
+`nix copy-sigs` - copy path signatures from substituters (like binary caches)
+
+## Synopsis
+
+`nix copy-sigs` [*flags*...] *installables*...
+
+## Flags
+
+ - `--all`
+ apply operation to the entire store
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--derivation`
+ operate on the store derivation rather than its outputs
+
+ - `--expr` *expr*
+ evaluate attributes from *expr*
+
+ - `--file` / `f` *file*
+ evaluate *file* rather than the default
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--recursive` / `r`
+ apply operation to closure of the specified paths
+
+ - `--substituter` / `s` *store-uri*
+ use signatures from specified store
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+# Subcommand `nix describe-stores`
+
+## Name
+
+`nix describe-stores` - show registered store types and their available options
+
+## Synopsis
+
+`nix describe-stores` [*flags*...]
+
+## Flags
+
+ - `--json`
+ produce JSON output
+
+# Subcommand `nix develop`
+
+## Name
+
+`nix develop` - run a bash shell that provides the build environment of a derivation
+
+## Synopsis
+
+`nix develop` [*flags*...] *installable*
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--build`
+ run the build phase
+
+ - `--check`
+ run the check phase
+
+ - `--command` / `c` *command* *args*
+ command and arguments to be executed instead of an interactive shell
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--configure`
+ run the configure phase
+
+ - `--derivation`
+ operate on the store derivation rather than its outputs
+
+ - `--expr` *expr*
+ evaluate attributes from *expr*
+
+ - `--file` / `f` *file*
+ evaluate *file* rather than the default
+
+ - `--ignore-environment` / `i`
+ clear the entire environment (except those specified with --keep)
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--install`
+ run the install phase
+
+ - `--installcheck`
+ run the installcheck phase
+
+ - `--keep` / `k` *name*
+ keep specified environment variable
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--phase` *phase-name*
+ phase to run (e.g. `build` or `configure`)
+
+ - `--profile` *path*
+ profile to update
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--redirect` *installable* *outputs-dir*
+ redirect a store path to a mutable location
+
+ - `--unset` / `u` *name*
+ unset specified environment variable
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+## Examples
+
+To get the build environment of GNU hello:
+
+```console
+nix develop nixpkgs#hello
+```
+
+To get the build environment of the default package of flake in the current directory:
+
+```console
+nix develop
+```
+
+To store the build environment in a profile:
+
+```console
+nix develop --profile /tmp/my-shell nixpkgs#hello
+```
+
+To use a build environment previously recorded in a profile:
+
+```console
+nix develop /tmp/my-shell
+```
+
+To replace all occurences of a store path with a writable directory:
+
+```console
+nix develop --redirect nixpkgs#glibc.dev ~/my-glibc/outputs/dev
+```
+
+# Subcommand `nix diff-closures`
+
+## Name
+
+`nix diff-closures` - show what packages and versions were added and removed between two closures
+
+## Synopsis
+
+`nix diff-closures` [*flags*...] *before* *after*
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--derivation`
+ operate on the store derivation rather than its outputs
+
+ - `--expr` *expr*
+ evaluate attributes from *expr*
+
+ - `--file` / `f` *file*
+ evaluate *file* rather than the default
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+## Examples
+
+To show what got added and removed between two versions of the NixOS system profile:
+
+```console
+nix diff-closures /nix/var/nix/profiles/system-655-link /nix/var/nix/profiles/system-658-link
+```
+
+# Subcommand `nix doctor`
+
+## Name
+
+`nix doctor` - check your system for potential problems and print a PASS or FAIL for each check
+
+## Synopsis
+
+`nix doctor` [*flags*...]
+
+# Subcommand `nix dump-path`
+
+## Name
+
+`nix dump-path` - dump a store path to stdout (in NAR format)
+
+## Synopsis
+
+`nix dump-path` [*flags*...] *installables*...
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--derivation`
+ operate on the store derivation rather than its outputs
+
+ - `--expr` *expr*
+ evaluate attributes from *expr*
+
+ - `--file` / `f` *file*
+ evaluate *file* rather than the default
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+## Examples
+
+To get a NAR from the binary cache https://cache.nixos.org/:
+
+```console
+nix dump-path --store https://cache.nixos.org/ /nix/store/7crrmih8c52r8fbnqb933dxrsp44md93-glibc-2.25
+```
+
+# Subcommand `nix edit`
+
+## Name
+
+`nix edit` - open the Nix expression of a Nix package in $EDITOR
+
+## Synopsis
+
+`nix edit` [*flags*...] *installable*
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--derivation`
+ operate on the store derivation rather than its outputs
+
+ - `--expr` *expr*
+ evaluate attributes from *expr*
+
+ - `--file` / `f` *file*
+ evaluate *file* rather than the default
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+## Examples
+
+To open the Nix expression of the GNU Hello package:
+
+```console
+nix edit nixpkgs#hello
+```
+
+# Subcommand `nix eval`
+
+## Name
+
+`nix eval` - evaluate a Nix expression
+
+## Synopsis
+
+`nix eval` [*flags*...] *installable*
+
+## Flags
+
+ - `--apply` *expr*
+ apply a function to each argument
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--derivation`
+ operate on the store derivation rather than its outputs
+
+ - `--expr` *expr*
+ evaluate attributes from *expr*
+
+ - `--file` / `f` *file*
+ evaluate *file* rather than the default
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--json`
+ produce JSON output
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--raw`
+ print strings unquoted
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+## Examples
+
+To evaluate a Nix expression given on the command line:
+
+```console
+nix eval --expr '1 + 2'
+```
+
+To evaluate a Nix expression from a file or URI:
+
+```console
+nix eval -f ./my-nixpkgs hello.name
+```
+
+To get the current version of Nixpkgs:
+
+```console
+nix eval --raw nixpkgs#lib.version
+```
+
+To print the store path of the Hello package:
+
+```console
+nix eval --raw nixpkgs#hello
+```
+
+To get a list of checks in the 'nix' flake:
+
+```console
+nix eval nix#checks.x86_64-linux --apply builtins.attrNames
+```
+
+# Subcommand `nix flake`
+
+## Name
+
+`nix flake` - manage Nix flakes
+
+## Synopsis
+
+`nix flake` [*flags*...] *subcommand*
+
+# Subcommand `nix flake archive`
+
+## Name
+
+`nix flake archive` - copy a flake and all its inputs to a store
+
+## Synopsis
+
+`nix flake archive` [*flags*...] *flake-url*
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--dry-run`
+ show what this command would do without doing it
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--json`
+ produce JSON output
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--to` *store-uri*
+ URI of the destination Nix store
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+## Examples
+
+To copy the dwarffs flake and its dependencies to a binary cache:
+
+```console
+nix flake archive --to file:///tmp/my-cache dwarffs
+```
+
+To fetch the dwarffs flake and its dependencies to the local Nix store:
+
+```console
+nix flake archive dwarffs
+```
+
+To print the store paths of the flake sources of NixOps without fetching them:
+
+```console
+nix flake archive --json --dry-run nixops
+```
+
+# Subcommand `nix flake check`
+
+## Name
+
+`nix flake check` - check whether the flake evaluates and run its tests
+
+## Synopsis
+
+`nix flake check` [*flags*...] *flake-url*
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--no-build`
+ do not build checks
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+# Subcommand `nix flake clone`
+
+## Name
+
+`nix flake clone` - clone flake repository
+
+## Synopsis
+
+`nix flake clone` [*flags*...] *flake-url*
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--dest` / `f` *path*
+ destination path
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+# Subcommand `nix flake info`
+
+## Name
+
+`nix flake info` - list info about a given flake
+
+## Synopsis
+
+`nix flake info` [*flags*...] *flake-url*
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--json`
+ produce JSON output
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+# Subcommand `nix flake init`
+
+## Name
+
+`nix flake init` - create a flake in the current directory from a template
+
+## Synopsis
+
+`nix flake init` [*flags*...]
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--template` / `t` *template*
+ the template to use
+
+## Examples
+
+To create a flake using the default template:
+
+```console
+nix flake init
+```
+
+To see available templates:
+
+```console
+nix flake show templates
+```
+
+To create a flake from a specific template:
+
+```console
+nix flake init -t templates#nixos-container
+```
+
+# Subcommand `nix flake list-inputs`
+
+## Name
+
+`nix flake list-inputs` - list flake inputs
+
+## Synopsis
+
+`nix flake list-inputs` [*flags*...] *flake-url*
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--json`
+ produce JSON output
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+# Subcommand `nix flake new`
+
+## Name
+
+`nix flake new` - create a flake in the specified directory from a template
+
+## Synopsis
+
+`nix flake new` [*flags*...] *dest-dir*
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--template` / `t` *template*
+ the template to use
+
+# Subcommand `nix flake show`
+
+## Name
+
+`nix flake show` - show the outputs provided by a flake
+
+## Synopsis
+
+`nix flake show` [*flags*...] *flake-url*
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--legacy`
+ show the contents of the 'legacyPackages' output
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+# Subcommand `nix flake update`
+
+## Name
+
+`nix flake update` - update flake lock file
+
+## Synopsis
+
+`nix flake update` [*flags*...] *flake-url*
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+# Subcommand `nix hash-file`
+
+## Name
+
+`nix hash-file` - print cryptographic hash of a regular file
+
+## Synopsis
+
+`nix hash-file` [*flags*...] *paths*...
+
+## Flags
+
+ - `--base16`
+ print hash in base-16
+
+ - `--base32`
+ print hash in base-32 (Nix-specific)
+
+ - `--base64`
+ print hash in base-64
+
+ - `--sri`
+ print hash in SRI format
+
+ - `--type` *hash-algo*
+ hash algorithm ('md5', 'sha1', 'sha256', or 'sha512')
+
+# Subcommand `nix hash-path`
+
+## Name
+
+`nix hash-path` - print cryptographic hash of the NAR serialisation of a path
+
+## Synopsis
+
+`nix hash-path` [*flags*...] *paths*...
+
+## Flags
+
+ - `--base16`
+ print hash in base-16
+
+ - `--base32`
+ print hash in base-32 (Nix-specific)
+
+ - `--base64`
+ print hash in base-64
+
+ - `--sri`
+ print hash in SRI format
+
+ - `--type` *hash-algo*
+ hash algorithm ('md5', 'sha1', 'sha256', or 'sha512')
+
+# Subcommand `nix log`
+
+## Name
+
+`nix log` - show the build log of the specified packages or paths, if available
+
+## Synopsis
+
+`nix log` [*flags*...] *installable*
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--derivation`
+ operate on the store derivation rather than its outputs
+
+ - `--expr` *expr*
+ evaluate attributes from *expr*
+
+ - `--file` / `f` *file*
+ evaluate *file* rather than the default
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+## Examples
+
+To get the build log of GNU Hello:
+
+```console
+nix log nixpkgs#hello
+```
+
+To get the build log of a specific path:
+
+```console
+nix log /nix/store/lmngj4wcm9rkv3w4dfhzhcyij3195hiq-thunderbird-52.2.1
+```
+
+To get a build log from a specific binary cache:
+
+```console
+nix log --store https://cache.nixos.org nixpkgs#hello
+```
+
+# Subcommand `nix ls-nar`
+
+## Name
+
+`nix ls-nar` - show information about a path inside a NAR file
+
+## Synopsis
+
+`nix ls-nar` [*flags*...] *nar* *path*
+
+## Flags
+
+ - `--directory` / `d`
+ show directories rather than their contents
+
+ - `--json`
+ produce JSON output
+
+ - `--long` / `l`
+ show more file information
+
+ - `--recursive` / `R`
+ list subdirectories recursively
+
+## Examples
+
+To list a specific file in a NAR:
+
+```console
+nix ls-nar -l hello.nar /bin/hello
+```
+
+# Subcommand `nix ls-store`
+
+## Name
+
+`nix ls-store` - show information about a path in the Nix store
+
+## Synopsis
+
+`nix ls-store` [*flags*...] *path*
+
+## Flags
+
+ - `--directory` / `d`
+ show directories rather than their contents
+
+ - `--json`
+ produce JSON output
+
+ - `--long` / `l`
+ show more file information
+
+ - `--recursive` / `R`
+ list subdirectories recursively
+
+## Examples
+
+To list the contents of a store path in a binary cache:
+
+```console
+nix ls-store --store https://cache.nixos.org/ -lR /nix/store/0i2jd68mp5g6h2sa5k9c85rb80sn8hi9-hello-2.10
+```
+
+# Subcommand `nix make-content-addressable`
+
+## Name
+
+`nix make-content-addressable` - rewrite a path or closure to content-addressable form
+
+## Synopsis
+
+`nix make-content-addressable` [*flags*...] *installables*...
+
+## Flags
+
+ - `--all`
+ apply operation to the entire store
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--derivation`
+ operate on the store derivation rather than its outputs
+
+ - `--expr` *expr*
+ evaluate attributes from *expr*
+
+ - `--file` / `f` *file*
+ evaluate *file* rather than the default
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--json`
+ produce JSON output
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--recursive` / `r`
+ apply operation to closure of the specified paths
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+## Examples
+
+To create a content-addressable representation of GNU Hello (but not its dependencies):
+
+```console
+nix make-content-addressable nixpkgs#hello
+```
+
+To compute a content-addressable representation of the current NixOS system closure:
+
+```console
+nix make-content-addressable -r /run/current-system
+```
+
+# Subcommand `nix optimise-store`
+
+## Name
+
+`nix optimise-store` - replace identical files in the store by hard links
+
+## Synopsis
+
+`nix optimise-store` [*flags*...]
+
+## Examples
+
+To optimise the Nix store:
+
+```console
+nix optimise-store
+```
+
+# Subcommand `nix path-info`
+
+## Name
+
+`nix path-info` - query information about store paths
+
+## Synopsis
+
+`nix path-info` [*flags*...] *installables*...
+
+## Flags
+
+ - `--all`
+ apply operation to the entire store
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--closure-size` / `S`
+ print sum size of the NAR dumps of the closure of each path
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--derivation`
+ operate on the store derivation rather than its outputs
+
+ - `--expr` *expr*
+ evaluate attributes from *expr*
+
+ - `--file` / `f` *file*
+ evaluate *file* rather than the default
+
+ - `--human-readable` / `h`
+ with -s and -S, print sizes like 1K 234M 5.67G etc.
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--json`
+ produce JSON output
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--recursive` / `r`
+ apply operation to closure of the specified paths
+
+ - `--sigs`
+ show signatures
+
+ - `--size` / `s`
+ print size of the NAR dump of each path
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+## Examples
+
+To show the closure sizes of every path in the current NixOS system closure, sorted by size:
+
+```console
+nix path-info -rS /run/current-system | sort -nk2
+```
+
+To show a package's closure size and all its dependencies with human readable sizes:
+
+```console
+nix path-info -rsSh nixpkgs#rust
+```
+
+To check the existence of a path in a binary cache:
+
+```console
+nix path-info -r /nix/store/7qvk5c91...-geeqie-1.1 --store https://cache.nixos.org/
+```
+
+To print the 10 most recently added paths (using --json and the jq(1) command):
+
+```console
+nix path-info --json --all | jq -r 'sort_by(.registrationTime)[-11:-1][].path'
+```
+
+To show the size of the entire Nix store:
+
+```console
+nix path-info --json --all | jq 'map(.narSize) | add'
+```
+
+To show every path whose closure is bigger than 1 GB, sorted by closure size:
+
+```console
+nix path-info --json --all -S | jq 'map(select(.closureSize > 1e9)) | sort_by(.closureSize) | map([.path, .closureSize])'
+```
+
+# Subcommand `nix ping-store`
+
+## Name
+
+`nix ping-store` - test whether a store can be opened
+
+## Synopsis
+
+`nix ping-store` [*flags*...]
+
+## Examples
+
+To test whether connecting to a remote Nix store via SSH works:
+
+```console
+nix ping-store --store ssh://mac1
+```
+
+# Subcommand `nix print-dev-env`
+
+## Name
+
+`nix print-dev-env` - print shell code that can be sourced by bash to reproduce the build environment of a derivation
+
+## Synopsis
+
+`nix print-dev-env` [*flags*...] *installable*
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--derivation`
+ operate on the store derivation rather than its outputs
+
+ - `--expr` *expr*
+ evaluate attributes from *expr*
+
+ - `--file` / `f` *file*
+ evaluate *file* rather than the default
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--profile` *path*
+ profile to update
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--redirect` *installable* *outputs-dir*
+ redirect a store path to a mutable location
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+## Examples
+
+To apply the build environment of GNU hello to the current shell:
+
+```console
+. <(nix print-dev-env nixpkgs#hello)
+```
+
+# Subcommand `nix profile`
+
+## Name
+
+`nix profile` - manage Nix profiles
+
+## Synopsis
+
+`nix profile` [*flags*...] *subcommand*
+
+# Subcommand `nix profile diff-closures`
+
+## Name
+
+`nix profile diff-closures` - show the closure difference between each generation of a profile
+
+## Synopsis
+
+`nix profile diff-closures` [*flags*...]
+
+## Flags
+
+ - `--profile` *path*
+ profile to update
+
+## Examples
+
+To show what changed between each generation of the NixOS system profile:
+
+```console
+nix profile diff-closure --profile /nix/var/nix/profiles/system
+```
+
+# Subcommand `nix profile info`
+
+## Name
+
+`nix profile info` - list installed packages
+
+## Synopsis
+
+`nix profile info` [*flags*...]
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--profile` *path*
+ profile to update
+
+## Examples
+
+To show what packages are installed in the default profile:
+
+```console
+nix profile info
+```
+
+# Subcommand `nix profile install`
+
+## Name
+
+`nix profile install` - install a package into a profile
+
+## Synopsis
+
+`nix profile install` [*flags*...] *installables*...
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--derivation`
+ operate on the store derivation rather than its outputs
+
+ - `--expr` *expr*
+ evaluate attributes from *expr*
+
+ - `--file` / `f` *file*
+ evaluate *file* rather than the default
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--profile` *path*
+ profile to update
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+## Examples
+
+To install a package from Nixpkgs:
+
+```console
+nix profile install nixpkgs#hello
+```
+
+To install a package from a specific branch of Nixpkgs:
+
+```console
+nix profile install nixpkgs/release-19.09#hello
+```
+
+To install a package from a specific revision of Nixpkgs:
+
+```console
+nix profile install nixpkgs/1028bb33859f8dfad7f98e1c8d185f3d1aaa7340#hello
+```
+
+# Subcommand `nix profile remove`
+
+## Name
+
+`nix profile remove` - remove packages from a profile
+
+## Synopsis
+
+`nix profile remove` [*flags*...] *elements*...
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--profile` *path*
+ profile to update
+
+## Examples
+
+To remove a package by attribute path:
+
+```console
+nix profile remove packages.x86_64-linux.hello
+```
+
+To remove all packages:
+
+```console
+nix profile remove '.*'
+```
+
+To remove a package by store path:
+
+```console
+nix profile remove /nix/store/rr3y0c6zyk7kjjl8y19s4lsrhn4aiq1z-hello-2.10
+```
+
+To remove a package by position:
+
+```console
+nix profile remove 3
+```
+
+# Subcommand `nix profile upgrade`
+
+## Name
+
+`nix profile upgrade` - upgrade packages using their most recent flake
+
+## Synopsis
+
+`nix profile upgrade` [*flags*...] *elements*...
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--derivation`
+ operate on the store derivation rather than its outputs
+
+ - `--expr` *expr*
+ evaluate attributes from *expr*
+
+ - `--file` / `f` *file*
+ evaluate *file* rather than the default
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--profile` *path*
+ profile to update
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+## Examples
+
+To upgrade all packages that were installed using a mutable flake reference:
+
+```console
+nix profile upgrade '.*'
+```
+
+To upgrade a specific package:
+
+```console
+nix profile upgrade packages.x86_64-linux.hello
+```
+
+# Subcommand `nix registry`
+
+## Name
+
+`nix registry` - manage the flake registry
+
+## Synopsis
+
+`nix registry` [*flags*...] *subcommand*
+
+# Subcommand `nix registry add`
+
+## Name
+
+`nix registry add` - add/replace flake in user flake registry
+
+## Synopsis
+
+`nix registry add` [*flags*...] *from-url* *to-url*
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+# Subcommand `nix registry list`
+
+## Name
+
+`nix registry list` - list available Nix flakes
+
+## Synopsis
+
+`nix registry list` [*flags*...]
+
+# Subcommand `nix registry pin`
+
+## Name
+
+`nix registry pin` - pin a flake to its current version in user flake registry
+
+## Synopsis
+
+`nix registry pin` [*flags*...] *url*
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+# Subcommand `nix registry remove`
+
+## Name
+
+`nix registry remove` - remove flake from user flake registry
+
+## Synopsis
+
+`nix registry remove` [*flags*...] *url*
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+# Subcommand `nix repl`
+
+## Name
+
+`nix repl` - start an interactive environment for evaluating Nix expressions
+
+## Synopsis
+
+`nix repl` [*flags*...] *files*...
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+## Examples
+
+Display all special commands within the REPL:
+
+```console
+nix repl
+nix-repl> :?
+```
+
+# Subcommand `nix run`
+
+## Name
+
+`nix run` - run a Nix application
+
+## Synopsis
+
+`nix run` [*flags*...] *installable* *args*...
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--derivation`
+ operate on the store derivation rather than its outputs
+
+ - `--expr` *expr*
+ evaluate attributes from *expr*
+
+ - `--file` / `f` *file*
+ evaluate *file* rather than the default
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+## Examples
+
+To run Blender:
+
+```console
+nix run blender-bin
+```
+
+To run vim from nixpkgs:
+
+```console
+nix run nixpkgs#vim
+```
+
+To run vim from nixpkgs with arguments:
+
+```console
+nix run nixpkgs#vim -- --help
+```
+
+# Subcommand `nix search`
+
+## Name
+
+`nix search` - query available packages
+
+## Synopsis
+
+`nix search` [*flags*...] *installable* *regex*...
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--derivation`
+ operate on the store derivation rather than its outputs
+
+ - `--expr` *expr*
+ evaluate attributes from *expr*
+
+ - `--file` / `f` *file*
+ evaluate *file* rather than the default
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--json`
+ produce JSON output
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+## Examples
+
+To show all packages in the flake in the current directory:
+
+```console
+nix search
+```
+
+To show packages in the 'nixpkgs' flake containing 'blender' in its name or description:
+
+```console
+nix search nixpkgs blender
+```
+
+To search for Firefox or Chromium:
+
+```console
+nix search nixpkgs 'firefox|chromium'
+```
+
+To search for packages containing 'git' and either 'frontend' or 'gui':
+
+```console
+nix search nixpkgs git 'frontend|gui'
+```
+
+# Subcommand `nix shell`
+
+## Name
+
+`nix shell` - run a shell in which the specified packages are available
+
+## Synopsis
+
+`nix shell` [*flags*...] *installables*...
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--command` / `c` *command* *args*
+ command and arguments to be executed; defaults to '$SHELL'
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--derivation`
+ operate on the store derivation rather than its outputs
+
+ - `--expr` *expr*
+ evaluate attributes from *expr*
+
+ - `--file` / `f` *file*
+ evaluate *file* rather than the default
+
+ - `--ignore-environment` / `i`
+ clear the entire environment (except those specified with --keep)
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--keep` / `k` *name*
+ keep specified environment variable
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--unset` / `u` *name*
+ unset specified environment variable
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+## Examples
+
+To start a shell providing GNU Hello from NixOS 20.03:
+
+```console
+nix shell nixpkgs/nixos-20.03#hello
+```
+
+To start a shell providing youtube-dl from your 'nixpkgs' channel:
+
+```console
+nix shell nixpkgs#youtube-dl
+```
+
+To run GNU Hello:
+
+```console
+nix shell nixpkgs#hello -c hello --greeting 'Hi everybody!'
+```
+
+To run GNU Hello in a chroot store:
+
+```console
+nix shell --store ~/my-nix nixpkgs#hello -c hello
+```
+
+# Subcommand `nix show-config`
+
+## Name
+
+`nix show-config` - show the Nix configuration
+
+## Synopsis
+
+`nix show-config` [*flags*...]
+
+## Flags
+
+ - `--json`
+ produce JSON output
+
+# Subcommand `nix show-derivation`
+
+## Name
+
+`nix show-derivation` - show the contents of a store derivation
+
+## Synopsis
+
+`nix show-derivation` [*flags*...] *installables*...
+
+## Flags
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--derivation`
+ operate on the store derivation rather than its outputs
+
+ - `--expr` *expr*
+ evaluate attributes from *expr*
+
+ - `--file` / `f` *file*
+ evaluate *file* rather than the default
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--recursive` / `r`
+ include the dependencies of the specified derivations
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+## Examples
+
+To show the store derivation that results from evaluating the Hello package:
+
+```console
+nix show-derivation nixpkgs#hello
+```
+
+To show the full derivation graph (if available) that produced your NixOS system:
+
+```console
+nix show-derivation -r /run/current-system
+```
+
+# Subcommand `nix sign-paths`
+
+## Name
+
+`nix sign-paths` - sign the specified paths
+
+## Synopsis
+
+`nix sign-paths` [*flags*...] *installables*...
+
+## Flags
+
+ - `--all`
+ apply operation to the entire store
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--derivation`
+ operate on the store derivation rather than its outputs
+
+ - `--expr` *expr*
+ evaluate attributes from *expr*
+
+ - `--file` / `f` *file*
+ evaluate *file* rather than the default
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--key-file` / `k` *file*
+ file containing the secret signing key
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--recursive` / `r`
+ apply operation to closure of the specified paths
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+# Subcommand `nix to-base16`
+
+## Name
+
+`nix to-base16` - convert a hash to base-16 representation
+
+## Synopsis
+
+`nix to-base16` [*flags*...] *strings*...
+
+## Flags
+
+ - `--type` *hash-algo*
+ hash algorithm ('md5', 'sha1', 'sha256', or 'sha512'). Optional as can also be gotten from SRI hash itself.
+
+# Subcommand `nix to-base32`
+
+## Name
+
+`nix to-base32` - convert a hash to base-32 representation
+
+## Synopsis
+
+`nix to-base32` [*flags*...] *strings*...
+
+## Flags
+
+ - `--type` *hash-algo*
+ hash algorithm ('md5', 'sha1', 'sha256', or 'sha512'). Optional as can also be gotten from SRI hash itself.
+
+# Subcommand `nix to-base64`
+
+## Name
+
+`nix to-base64` - convert a hash to base-64 representation
+
+## Synopsis
+
+`nix to-base64` [*flags*...] *strings*...
+
+## Flags
+
+ - `--type` *hash-algo*
+ hash algorithm ('md5', 'sha1', 'sha256', or 'sha512'). Optional as can also be gotten from SRI hash itself.
+
+# Subcommand `nix to-sri`
+
+## Name
+
+`nix to-sri` - convert a hash to SRI representation
+
+## Synopsis
+
+`nix to-sri` [*flags*...] *strings*...
+
+## Flags
+
+ - `--type` *hash-algo*
+ hash algorithm ('md5', 'sha1', 'sha256', or 'sha512'). Optional as can also be gotten from SRI hash itself.
+
+# Subcommand `nix upgrade-nix`
+
+## Name
+
+`nix upgrade-nix` - upgrade Nix to the latest stable version
+
+## Synopsis
+
+`nix upgrade-nix` [*flags*...]
+
+## Flags
+
+ - `--dry-run`
+ show what this command would do without doing it
+
+ - `--nix-store-paths-url` *url*
+ URL of the file that contains the store paths of the latest Nix release
+
+ - `--profile` / `p` *profile-dir*
+ the Nix profile to upgrade
+
+## Examples
+
+To upgrade Nix to the latest stable version:
+
+```console
+nix upgrade-nix
+```
+
+To upgrade Nix in a specific profile:
+
+```console
+nix upgrade-nix -p /nix/var/nix/profiles/per-user/alice/profile
+```
+
+# Subcommand `nix verify`
+
+## Name
+
+`nix verify` - verify the integrity of store paths
+
+## Synopsis
+
+`nix verify` [*flags*...] *installables*...
+
+## Flags
+
+ - `--all`
+ apply operation to the entire store
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--derivation`
+ operate on the store derivation rather than its outputs
+
+ - `--expr` *expr*
+ evaluate attributes from *expr*
+
+ - `--file` / `f` *file*
+ evaluate *file* rather than the default
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--no-contents`
+ do not verify the contents of each store path
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-trust`
+ do not verify whether each store path is trusted
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--recursive` / `r`
+ apply operation to closure of the specified paths
+
+ - `--sigs-needed` / `n` *N*
+ require that each path has at least N valid signatures
+
+ - `--substituter` / `s` *store-uri*
+ use signatures from specified store
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+## Examples
+
+To verify the entire Nix store:
+
+```console
+nix verify --all
+```
+
+To check whether each path in the closure of Firefox has at least 2 signatures:
+
+```console
+nix verify -r -n2 --no-contents $(type -p firefox)
+```
+
+# Subcommand `nix why-depends`
+
+## Name
+
+`nix why-depends` - show why a package has another package in its closure
+
+## Synopsis
+
+`nix why-depends` [*flags*...] *package* *dependency*
+
+## Flags
+
+ - `--all` / `a`
+ show all edges in the dependency graph leading from 'package' to 'dependency', rather than just a shortest path
+
+ - `--arg` *name* *expr*
+ argument to be passed to Nix functions
+
+ - `--argstr` *name* *string*
+ string-valued argument to be passed to Nix functions
+
+ - `--commit-lock-file`
+ commit changes to the lock file
+
+ - `--derivation`
+ operate on the store derivation rather than its outputs
+
+ - `--expr` *expr*
+ evaluate attributes from *expr*
+
+ - `--file` / `f` *file*
+ evaluate *file* rather than the default
+
+ - `--impure`
+ allow access to mutable paths and repositories
+
+ - `--include` / `I` *path*
+ add a path to the list of locations used to look up `<...>` file names
+
+ - `--inputs-from` *flake-url*
+ use the inputs of the specified flake as registry entries
+
+ - `--no-registries`
+ don't use flake registries
+
+ - `--no-update-lock-file`
+ do not allow any updates to the lock file
+
+ - `--no-write-lock-file`
+ do not write the newly generated lock file
+
+ - `--override-flake` *original-ref* *resolved-ref*
+ override a flake registry value
+
+ - `--override-input` *input-path* *flake-url*
+ override a specific flake input (e.g. `dwarffs/nixpkgs`)
+
+ - `--recreate-lock-file`
+ recreate lock file from scratch
+
+ - `--update-input` *input-path*
+ update a specific flake input
+
+## Examples
+
+To show one path through the dependency graph leading from Hello to Glibc:
+
+```console
+nix why-depends nixpkgs#hello nixpkgs#glibc
+```
+
+To show all files and paths in the dependency graph leading from Thunderbird to libX11:
+
+```console
+nix why-depends --all nixpkgs#thunderbird nixpkgs#xorg.libX11
+```
+
+To show why Glibc depends on itself:
+
+```console
+nix why-depends nixpkgs#glibc nixpkgs#glibc
+```
+
diff --git a/doc/manual/src/expressions/builtins.md.tmp b/doc/manual/src/expressions/builtins.md.tmp
new file mode 100644
index 000000000..95a73709e
--- /dev/null
+++ b/doc/manual/src/expressions/builtins.md.tmp
@@ -0,0 +1,16 @@
+# Built-in Functions
+
+This section lists the functions built into the Nix expression
+evaluator. (The built-in function `derivation` is discussed above.)
+Some built-ins, such as `derivation`, are always in scope of every Nix
+expression; you can just access them right away. But to prevent
+polluting the namespace too much, most built-ins are not in
+scope. Instead, you can access them through the `builtins` built-in
+value, which is a set that contains all built-in functions and values.
+For instance, `derivation` is also available as `builtins.derivation`.
+
+ - `derivation` *attrs*; `builtins.derivation` *attrs*\
+
+ `derivation` is described in [its own section](derivations.md).
+
+EvalCommand::getEvalState()0
diff --git a/doc/manual/version.txt b/doc/manual/version.txt
new file mode 100644
index 000000000..f398a2061
--- /dev/null
+++ b/doc/manual/version.txt
@@ -0,0 +1 @@
+3.0
\ No newline at end of file
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 45665b555..07f4208da 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -109,6 +109,7 @@ ref<EvalState> EvalCommand::getEvalState()
if (startReplOnEvalErrors)
debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error & error, const Env & env) {
printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error.what());
+ // printEnvPosChain(env);
printEnvBindings(env);
auto vm = mapEnvBindings(env);
runRepl(evalState, *vm);
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index c6fb052f4..19379b876 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -648,13 +648,11 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
// LocalNoInline(valmap * mapBindings(Bindings &b))
// {
// auto map = new valmap();
-
// for (auto i = b.begin(); i != b.end(); ++i)
// {
// std::string s = i->name;
// (*map)[s] = i->value;
// }
-
// return map;
// }
@@ -668,12 +666,13 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
// }
// }
-
void printEnvBindings(const Env &env, int lv )
{
+ std::cout << "env " << lv << " type: " << env.type << std::endl;
if (env.values[0]->type() == nAttrs) {
Bindings::iterator j = env.values[0]->attrs->begin();
+
while (j != env.values[0]->attrs->end()) {
std::cout << lv << " env binding: " << j->name << std::endl;
// if (countCalls && j->pos) attrSelects[*j->pos]++;
@@ -690,6 +689,33 @@ void printEnvBindings(const Env &env, int lv )
}
}
+void printEnvPosChain(const Env &env, int lv )
+{
+ std::cout << "printEnvPosChain " << lv << std::endl;
+
+ std::cout << "env" << env.values[0] << std::endl;
+
+ if (env.values[0] && env.values[0]->type() == nAttrs) {
+ std::cout << "im in the loop" << std::endl;
+ std::cout << "pos " << env.values[0]->attrs->pos << std::endl;
+ if (env.values[0]->attrs->pos) {
+ ErrPos ep(*env.values[0]->attrs->pos);
+ auto loc = getCodeLines(ep);
+ if (loc)
+ printCodeLines(std::cout,
+ std::__cxx11::to_string(lv),
+ ep,
+ *loc);
+ }
+ }
+
+ std::cout << "next env : " << env.up << std::endl;
+
+ if (env.up) {
+ printEnvPosChain(*env.up, ++lv);
+ }
+}
+
void mapEnvBindings(const Env &env, valmap & vm)
{
// add bindings for the next level up first.
@@ -699,7 +725,7 @@ void mapEnvBindings(const Env &env, valmap & vm)
// merge - and write over - higher level bindings.
// note; skipping HasWithExpr that haven't been evaled yet.
- if (env.values[0]->type() == nAttrs) {
+ if (env.values[0] && env.values[0]->type() == nAttrs) {
auto map = valmap();
Bindings::iterator j = env.values[0]->attrs->begin();
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index ca3a7b742..c96e2c726 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -45,6 +45,7 @@ struct Env
void printEnvBindings(const Env &env, int lv = 0);
valmap * mapEnvBindings(const Env &env);
+void printEnvPosChain(const Env &env, int lv = 0);
Value & mkString(Value & v, std::string_view s, const PathSet & context = PathSet());
diff --git a/src/libutil/error.hh b/src/libutil/error.hh
index ff58d3e00..b6670c8b2 100644
--- a/src/libutil/error.hh
+++ b/src/libutil/error.hh
@@ -100,6 +100,12 @@ struct ErrPos {
}
};
+std::optional<LinesOfCode> getCodeLines(const ErrPos & errPos);
+void printCodeLines(std::ostream & out,
+ const string & prefix,
+ const ErrPos & errPos,
+ const LinesOfCode & loc);
+
struct Trace {
std::optional<ErrPos> pos;
hintformat hint;
From 21071bfdeb0a5bc2b75018c91a4c2f138f233e33 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Tue, 14 Sep 2021 10:49:22 -0600
Subject: [PATCH 034/188] shared_ptr for StaticEnv
---
doc/manual/src/expressions/builtins.md.tmp | 16 ------
src/libcmd/repl.cc | 11 ++--
src/libexpr/eval.cc | 8 +--
src/libexpr/eval.hh | 9 +--
src/libexpr/nixexpr.cc | 64 +++++++++++-----------
src/libexpr/nixexpr.hh | 8 ++-
src/libexpr/parser.y | 6 +-
src/libexpr/primops.cc | 4 +-
8 files changed, 57 insertions(+), 69 deletions(-)
delete mode 100644 doc/manual/src/expressions/builtins.md.tmp
diff --git a/doc/manual/src/expressions/builtins.md.tmp b/doc/manual/src/expressions/builtins.md.tmp
deleted file mode 100644
index 95a73709e..000000000
--- a/doc/manual/src/expressions/builtins.md.tmp
+++ /dev/null
@@ -1,16 +0,0 @@
-# Built-in Functions
-
-This section lists the functions built into the Nix expression
-evaluator. (The built-in function `derivation` is discussed above.)
-Some built-ins, such as `derivation`, are always in scope of every Nix
-expression; you can just access them right away. But to prevent
-polluting the namespace too much, most built-ins are not in
-scope. Instead, you can access them through the `builtins` built-in
-value, which is a set that contains all built-in functions and values.
-For instance, `derivation` is also available as `builtins.derivation`.
-
- - `derivation` *attrs*; `builtins.derivation` *attrs*\
-
- `derivation` is described in [its own section](derivations.md).
-
-EvalCommand::getEvalState()0
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 57174bf0e..e1b58cc76 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -53,7 +53,8 @@ struct NixRepl
Strings loadedFiles;
const static int envSize = 32768;
- StaticEnv staticEnv;
+ std::shared_ptr<StaticEnv> staticEnv;
+ // StaticEnv staticEnv;
Env * env;
int displ;
StringSet varNames;
@@ -92,7 +93,7 @@ string removeWhitespace(string s)
NixRepl::NixRepl(ref<EvalState> state)
: state(state)
- , staticEnv(false, &state->staticBaseEnv)
+ , staticEnv(new StaticEnv(false, state->staticBaseEnv.get()))
, historyFile(getDataDir() + "/nix/repl-history")
{
curDir = absPath(".");
@@ -567,10 +568,10 @@ void NixRepl::initEnv()
env = &state->allocEnv(envSize);
env->up = &state->baseEnv;
displ = 0;
- staticEnv.vars.clear();
+ staticEnv->vars.clear();
varNames.clear();
- for (auto & i : state->staticBaseEnv.vars)
+ for (auto & i : state->staticBaseEnv->vars)
varNames.insert(i.first);
}
@@ -605,7 +606,7 @@ void NixRepl::addVarToScope(const Symbol & name, Value * v)
{
if (displ >= envSize)
throw Error("environment full; cannot add more variables");
- staticEnv.vars[name] = displ;
+ staticEnv->vars[name] = displ;
env->values[displ++] = v;
varNames.insert((string) name);
}
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 19379b876..69e3a4107 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -401,7 +401,7 @@ EvalState::EvalState(const Strings & _searchPath, ref<Store> store)
, store(store)
, regexCache(makeRegexCache())
, baseEnv(allocEnv(128))
- , staticBaseEnv(false, 0)
+ , staticBaseEnv(new StaticEnv(false, 0))
{
countCalls = getEnv("NIX_COUNT_CALLS").value_or("0") != "0";
@@ -538,7 +538,7 @@ Value * EvalState::addConstant(const string & name, Value & v)
{
Value * v2 = allocValue();
*v2 = v;
- staticBaseEnv.vars[symbols.create(name)] = baseEnvDispl;
+ staticBaseEnv->vars[symbols.create(name)] = baseEnvDispl;
baseEnv.values[baseEnvDispl++] = v2;
string name2 = string(name, 0, 2) == "__" ? string(name, 2) : name;
baseEnv.values[0]->attrs->push_back(Attr(symbols.create(name2), v2));
@@ -564,7 +564,7 @@ Value * EvalState::addPrimOp(const string & name,
Value * v = allocValue();
v->mkPrimOp(new PrimOp { .fun = primOp, .arity = arity, .name = sym });
- staticBaseEnv.vars[symbols.create(name)] = baseEnvDispl;
+ staticBaseEnv->vars[symbols.create(name)] = baseEnvDispl;
baseEnv.values[baseEnvDispl++] = v;
baseEnv.values[0]->attrs->push_back(Attr(sym, v));
return v;
@@ -590,7 +590,7 @@ Value * EvalState::addPrimOp(PrimOp && primOp)
Value * v = allocValue();
v->mkPrimOp(new PrimOp(std::move(primOp)));
- staticBaseEnv.vars[envName] = baseEnvDispl;
+ staticBaseEnv->vars[envName] = baseEnvDispl;
baseEnv.values[baseEnvDispl++] = v;
baseEnv.values[0]->attrs->push_back(Attr(primOp.name, v));
return v;
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index c96e2c726..8edc17789 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -23,6 +23,7 @@ enum RepairFlag : bool;
typedef void (* PrimOpFun) (EvalState & state, const Pos & pos, Value * * args, Value & v);
+extern std::function<void(const Error & error, const Env & env)> debuggerHook;
struct PrimOp
{
@@ -154,10 +155,10 @@ public:
/* Parse a Nix expression from the specified file. */
Expr * parseExprFromFile(const Path & path);
- Expr * parseExprFromFile(const Path & path, StaticEnv & staticEnv);
+ Expr * parseExprFromFile(const Path & path, std::shared_ptr<StaticEnv> & staticEnv);
/* Parse a Nix expression from the specified string. */
- Expr * parseExprFromString(std::string_view s, const Path & basePath, StaticEnv & staticEnv);
+ Expr * parseExprFromString(std::string_view s, const Path & basePath, std::shared_ptr<StaticEnv> & staticEnv);
Expr * parseExprFromString(std::string_view s, const Path & basePath);
Expr * parseStdin();
@@ -238,7 +239,7 @@ public:
Env & baseEnv;
/* The same, but used during parsing to resolve variables. */
- StaticEnv staticBaseEnv; // !!! should be private
+ std::shared_ptr<StaticEnv> staticBaseEnv; // !!! should be private
private:
@@ -277,7 +278,7 @@ private:
friend struct ExprLet;
Expr * parse(const char * text, FileOrigin origin, const Path & path,
- const Path & basePath, StaticEnv & staticEnv);
+ const Path & basePath, std::shared_ptr<StaticEnv> & staticEnv);
public:
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index 492b819e7..218e35f33 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -237,35 +237,35 @@ Pos noPos;
/* Computing levels/displacements for variables. */
-void Expr::bindVars(const StaticEnv & env)
+void Expr::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
abort();
}
-void ExprInt::bindVars(const StaticEnv & env)
+void ExprInt::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
}
-void ExprFloat::bindVars(const StaticEnv & env)
+void ExprFloat::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
}
-void ExprString::bindVars(const StaticEnv & env)
+void ExprString::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
}
-void ExprPath::bindVars(const StaticEnv & env)
+void ExprPath::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
}
-void ExprVar::bindVars(const StaticEnv & env)
+void ExprVar::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
/* Check whether the variable appears in the environment. If so,
set its level and displacement. */
const StaticEnv * curEnv;
unsigned int level;
int withLevel = -1;
- for (curEnv = &env, level = 0; curEnv; curEnv = curEnv->up, level++) {
+ for (curEnv = env.get(), level = 0; curEnv; curEnv = curEnv->up, level++) {
if (curEnv->isWith) {
if (withLevel == -1) withLevel = level;
} else {
@@ -291,7 +291,7 @@ void ExprVar::bindVars(const StaticEnv & env)
this->level = withLevel;
}
-void ExprSelect::bindVars(const StaticEnv & env)
+void ExprSelect::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
e->bindVars(env);
if (def) def->bindVars(env);
@@ -300,7 +300,7 @@ void ExprSelect::bindVars(const StaticEnv & env)
i.expr->bindVars(env);
}
-void ExprOpHasAttr::bindVars(const StaticEnv & env)
+void ExprOpHasAttr::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
e->bindVars(env);
for (auto & i : attrPath)
@@ -308,17 +308,17 @@ void ExprOpHasAttr::bindVars(const StaticEnv & env)
i.expr->bindVars(env);
}
-void ExprAttrs::bindVars(const StaticEnv & env)
+void ExprAttrs::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
- const StaticEnv * dynamicEnv = &env;
- StaticEnv newEnv(false, &env);
+ const StaticEnv * dynamicEnv = env.get();
+ auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, env.get())); // also make shared_ptr?
if (recursive) {
- dynamicEnv = &newEnv;
+ dynamicEnv = newEnv.get();
unsigned int displ = 0;
for (auto & i : attrs)
- newEnv.vars[i.first] = i.second.displ = displ++;
+ newEnv->vars[i.first] = i.second.displ = displ++;
for (auto & i : attrs)
i.second.e->bindVars(i.second.inherited ? env : newEnv);
@@ -329,28 +329,28 @@ void ExprAttrs::bindVars(const StaticEnv & env)
i.second.e->bindVars(env);
for (auto & i : dynamicAttrs) {
- i.nameExpr->bindVars(*dynamicEnv);
- i.valueExpr->bindVars(*dynamicEnv);
+ i.nameExpr->bindVars(newEnv);
+ i.valueExpr->bindVars(newEnv);
}
}
-void ExprList::bindVars(const StaticEnv & env)
+void ExprList::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
for (auto & i : elems)
i->bindVars(env);
}
-void ExprLambda::bindVars(const StaticEnv & env)
+void ExprLambda::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
- StaticEnv newEnv(false, &env);
+ auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, env.get())); // also make shared_ptr?
unsigned int displ = 0;
- if (!arg.empty()) newEnv.vars[arg] = displ++;
+ if (!arg.empty()) newEnv->vars[arg] = displ++;
if (matchAttrs) {
for (auto & i : formals->formals)
- newEnv.vars[i.name] = displ++;
+ newEnv->vars[i.name] = displ++;
for (auto & i : formals->formals)
if (i.def) i.def->bindVars(newEnv);
@@ -359,13 +359,13 @@ void ExprLambda::bindVars(const StaticEnv & env)
body->bindVars(newEnv);
}
-void ExprLet::bindVars(const StaticEnv & env)
+void ExprLet::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
- StaticEnv newEnv(false, &env);
+ auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, env.get())); // also make shared_ptr?
unsigned int displ = 0;
for (auto & i : attrs->attrs)
- newEnv.vars[i.first] = i.second.displ = displ++;
+ newEnv->vars[i.first] = i.second.displ = displ++;
for (auto & i : attrs->attrs)
i.second.e->bindVars(i.second.inherited ? env : newEnv);
@@ -373,7 +373,7 @@ void ExprLet::bindVars(const StaticEnv & env)
body->bindVars(newEnv);
}
-void ExprWith::bindVars(const StaticEnv & env)
+void ExprWith::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
/* Does this `with' have an enclosing `with'? If so, record its
level so that `lookupVar' can look up variables in the previous
@@ -381,42 +381,42 @@ void ExprWith::bindVars(const StaticEnv & env)
const StaticEnv * curEnv;
unsigned int level;
prevWith = 0;
- for (curEnv = &env, level = 1; curEnv; curEnv = curEnv->up, level++)
+ for (curEnv = env.get(), level = 1; curEnv; curEnv = curEnv->up, level++)
if (curEnv->isWith) {
prevWith = level;
break;
}
attrs->bindVars(env);
- StaticEnv newEnv(true, &env);
+ auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, env.get())); // also make shared_ptr?
body->bindVars(newEnv);
}
-void ExprIf::bindVars(const StaticEnv & env)
+void ExprIf::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
cond->bindVars(env);
then->bindVars(env);
else_->bindVars(env);
}
-void ExprAssert::bindVars(const StaticEnv & env)
+void ExprAssert::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
cond->bindVars(env);
body->bindVars(env);
}
-void ExprOpNot::bindVars(const StaticEnv & env)
+void ExprOpNot::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
e->bindVars(env);
}
-void ExprConcatStrings::bindVars(const StaticEnv & env)
+void ExprConcatStrings::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
for (auto & i : *es)
i->bindVars(env);
}
-void ExprPos::bindVars(const StaticEnv & env)
+void ExprPos::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
}
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index 51a14cd59..4c55cb64b 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -79,10 +79,12 @@ struct Expr
{
virtual ~Expr() { };
virtual void show(std::ostream & str) const;
- virtual void bindVars(const StaticEnv & env);
+ virtual void bindVars(const std::shared_ptr<const StaticEnv> & env);
virtual void eval(EvalState & state, Env & env, Value & v);
virtual Value * maybeThunk(EvalState & state, Env & env);
virtual void setName(Symbol & name);
+
+ std::shared_ptr<StaticEnv> staticenv;
};
std::ostream & operator << (std::ostream & str, const Expr & e);
@@ -90,7 +92,7 @@ std::ostream & operator << (std::ostream & str, const Expr & e);
#define COMMON_METHODS \
void show(std::ostream & str) const; \
void eval(EvalState & state, Env & env, Value & v); \
- void bindVars(const StaticEnv & env);
+ void bindVars(const std::shared_ptr<const StaticEnv> & env);
struct ExprInt : Expr
{
@@ -301,7 +303,7 @@ struct ExprOpNot : Expr
{ \
str << "(" << *e1 << " " s " " << *e2 << ")"; \
} \
- void bindVars(const StaticEnv & env) \
+ void bindVars(const std::shared_ptr<const StaticEnv> & env) \
{ \
e1->bindVars(env); e2->bindVars(env); \
} \
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index f948dde47..d1e898677 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -570,7 +570,7 @@ namespace nix {
Expr * EvalState::parse(const char * text, FileOrigin origin,
- const Path & path, const Path & basePath, StaticEnv & staticEnv)
+ const Path & path, const Path & basePath, std::shared_ptr<StaticEnv> & staticEnv)
{
yyscan_t scanner;
ParseData data(*this);
@@ -633,13 +633,13 @@ Expr * EvalState::parseExprFromFile(const Path & path)
}
-Expr * EvalState::parseExprFromFile(const Path & path, StaticEnv & staticEnv)
+Expr * EvalState::parseExprFromFile(const Path & path, std::shared_ptr<StaticEnv> & staticEnv)
{
return parse(readFile(path).c_str(), foFile, path, dirOf(path), staticEnv);
}
-Expr * EvalState::parseExprFromString(std::string_view s, const Path & basePath, StaticEnv & staticEnv)
+Expr * EvalState::parseExprFromString(std::string_view s, const Path & basePath, std::shared_ptr<StaticEnv> & staticEnv)
{
return parse(s.data(), foString, "", basePath, staticEnv);
}
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index fc4afaab8..0400c8942 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -186,11 +186,11 @@ static void import(EvalState & state, const Pos & pos, Value & vPath, Value * vS
Env * env = &state.allocEnv(vScope->attrs->size());
env->up = &state.baseEnv;
- StaticEnv staticEnv(false, &state.staticBaseEnv);
+ auto staticEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, state.staticBaseEnv.get()));
unsigned int displ = 0;
for (auto & attr : *vScope->attrs) {
- staticEnv.vars[attr.name] = displ;
+ staticEnv->vars[attr.name] = displ;
env->values[displ++] = attr.value;
}
From 2f90d92763f3af607fa1b609785d05a145f9a4ed Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Tue, 14 Sep 2021 10:51:14 -0600
Subject: [PATCH 035/188] remove docs accidentally added to version control
---
doc/manual/manual.html | 8926 --------
doc/manual/manual.xmli | 20139 ------------------
doc/manual/src/command-ref/conf-file.md.tmp | 52 -
doc/manual/src/command-ref/nix.md | 3021 ---
4 files changed, 32138 deletions(-)
delete mode 100644 doc/manual/manual.html
delete mode 100644 doc/manual/manual.xmli
delete mode 100644 doc/manual/src/command-ref/conf-file.md.tmp
delete mode 100644 doc/manual/src/command-ref/nix.md
diff --git a/doc/manual/manual.html b/doc/manual/manual.html
deleted file mode 100644
index 2396756ef..000000000
--- a/doc/manual/manual.html
+++ /dev/null
@@ -1,8926 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Nix Package Manager Guide</title><meta name="generator" content="DocBook XSL Stylesheets V1.79.2" /></head><body><div class="book"><div class="titlepage"><div><div><h1 class="title"><a id="idm139733328760992"></a>Nix Package Manager Guide</h1></div><div><h2 class="subtitle">Version 3.0</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Eelco</span> <span class="surname">Dolstra</span></h3></div></div><div><p class="copyright">Copyright © 2004-2018 Eelco Dolstra</p></div></div><hr /></div><div class="toc"><dl class="toc"><dt><span class="part"><a href="#chap-introduction">I. Introduction</a></span></dt><dd><dl><dt><span class="chapter"><a href="#ch-about-nix">1. About Nix</a></span></dt><dt><span class="chapter"><a href="#chap-quick-start">2. Quick Start</a></span></dt></dl></dd><dt><span class="part"><a href="#chap-installation">II. Installation</a></span></dt><dd><dl><dt><span class="chapter"><a href="#ch-supported-platforms">3. Supported Platforms</a></span></dt><dt><span class="chapter"><a href="#ch-installing-binary">4. Installing a Binary Distribution</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-single-user-installation">4.1. Single User Installation</a></span></dt><dt><span class="section"><a href="#sect-multi-user-installation">4.2. Multi User Installation</a></span></dt><dt><span class="section"><a href="#sect-macos-installation">4.3. macOS Installation</a></span></dt><dd><dl><dt><span class="section"><a href="#sect-macos-installation-change-store-prefix">4.3.1. Change the Nix store path prefix</a></span></dt><dt><span class="section"><a href="#sect-macos-installation-encrypted-volume">4.3.2. Use a separate encrypted volume</a></span></dt><dt><span class="section"><a href="#sect-macos-installation-symlink">4.3.3. Symlink the Nix store to a custom location</a></span></dt><dt><span class="section"><a href="#sect-macos-installation-recommended-notes">4.3.4. Notes on the recommended approach</a></span></dt></dl></dd><dt><span class="section"><a href="#sect-nix-install-pinned-version-url">4.4. Installing a pinned Nix version from a URL</a></span></dt><dt><span class="section"><a href="#sect-nix-install-binary-tarball">4.5. Installing from a binary tarball</a></span></dt></dl></dd><dt><span class="chapter"><a href="#ch-installing-source">5. Installing Nix from Source</a></span></dt><dd><dl><dt><span class="section"><a href="#sec-prerequisites-source">5.1. Prerequisites</a></span></dt><dt><span class="section"><a href="#sec-obtaining-source">5.2. Obtaining a Source Distribution</a></span></dt><dt><span class="section"><a href="#sec-building-source">5.3. Building Nix from Source</a></span></dt></dl></dd><dt><span class="chapter"><a href="#ch-nix-security">6. Security</a></span></dt><dd><dl><dt><span class="section"><a href="#sec-single-user">6.1. Single-User Mode</a></span></dt><dt><span class="section"><a href="#ssec-multi-user">6.2. Multi-User Mode</a></span></dt></dl></dd><dt><span class="chapter"><a href="#ch-env-variables">7. Environment Variables</a></span></dt><dd><dl><dt><span class="section"><a href="#sec-nix-ssl-cert-file">7.1. <code class="envar">NIX_SSL_CERT_FILE</code></a></span></dt><dd><dl><dt><span class="section"><a href="#sec-nix-ssl-cert-file-with-nix-daemon-and-macos">7.1.1. <code class="envar">NIX_SSL_CERT_FILE</code> with macOS and the Nix daemon</a></span></dt><dt><span class="section"><a href="#sec-installer-proxy-settings">7.1.2. Proxy Environment Variables</a></span></dt></dl></dd></dl></dd></dl></dd><dt><span class="chapter"><a href="#ch-upgrading-nix">8. Upgrading Nix</a></span></dt><dt><span class="part"><a href="#chap-package-management">III. Package Management</a></span></dt><dd><dl><dt><span class="chapter"><a href="#ch-basic-package-mgmt">9. Basic Package Management</a></span></dt><dt><span class="chapter"><a href="#sec-profiles">10. Profiles</a></span></dt><dt><span class="chapter"><a href="#sec-garbage-collection">11. Garbage Collection</a></span></dt><dd><dl><dt><span class="section"><a href="#ssec-gc-roots">11.1. Garbage Collector Roots</a></span></dt></dl></dd><dt><span class="chapter"><a href="#sec-channels">12. Channels</a></span></dt><dt><span class="chapter"><a href="#sec-sharing-packages">13. Sharing Packages Between Machines</a></span></dt><dd><dl><dt><span class="section"><a href="#ssec-binary-cache-substituter">13.1. Serving a Nix store via HTTP</a></span></dt><dt><span class="section"><a href="#ssec-copy-closure">13.2. Copying Closures Via SSH</a></span></dt><dt><span class="section"><a href="#ssec-ssh-substituter">13.3. Serving a Nix store via SSH</a></span></dt><dt><span class="section"><a href="#ssec-s3-substituter">13.4. Serving a Nix store via AWS S3 or S3-compatible Service</a></span></dt><dd><dl><dt><span class="section"><a href="#ssec-s3-substituter-anonymous-reads">13.4.1. Anonymous Reads to your S3-compatible binary cache</a></span></dt><dt><span class="section"><a href="#ssec-s3-substituter-authenticated-reads">13.4.2. Authenticated Reads to your S3 binary cache</a></span></dt><dt><span class="section"><a href="#ssec-s3-substituter-authenticated-writes">13.4.3. Authenticated Writes to your S3-compatible binary cache</a></span></dt></dl></dd></dl></dd></dl></dd><dt><span class="part"><a href="#chap-writing-nix-expressions">IV. Writing Nix Expressions</a></span></dt><dd><dl><dt><span class="chapter"><a href="#ch-simple-expression">14. A Simple Nix Expression</a></span></dt><dd><dl><dt><span class="section"><a href="#sec-expression-syntax">14.1. Expression Syntax</a></span></dt><dt><span class="section"><a href="#sec-build-script">14.2. Build Script</a></span></dt><dt><span class="section"><a href="#sec-arguments">14.3. Arguments and Variables</a></span></dt><dt><span class="section"><a href="#sec-building-simple">14.4. Building and Testing</a></span></dt><dt><span class="section"><a href="#sec-generic-builder">14.5. Generic Builder Syntax</a></span></dt></dl></dd><dt><span class="chapter"><a href="#ch-expression-language">15. Nix Expression Language</a></span></dt><dd><dl><dt><span class="section"><a href="#ssec-values">15.1. Values</a></span></dt><dt><span class="section"><a href="#sec-constructs">15.2. Language Constructs</a></span></dt><dt><span class="section"><a href="#sec-language-operators">15.3. Operators</a></span></dt><dt><span class="section"><a href="#ssec-derivation">15.4. Derivations</a></span></dt><dd><dl><dt><span class="section"><a href="#sec-advanced-attributes">15.4.1. Advanced Attributes</a></span></dt></dl></dd><dt><span class="section"><a href="#ssec-builtins">15.5. Built-in Functions</a></span></dt></dl></dd></dl></dd><dt><span class="part"><a href="#part-advanced-topics">V. Advanced Topics</a></span></dt><dd><dl><dt><span class="chapter"><a href="#chap-distributed-builds">16. Remote Builds</a></span></dt><dt><span class="chapter"><a href="#chap-tuning-cores-and-jobs">17. Tuning Cores and Jobs</a></span></dt><dt><span class="chapter"><a href="#chap-diff-hook">18. Verifying Build Reproducibility with <code class="option"><a class="option" href="#conf-diff-hook">diff-hook</a></code></a></span></dt><dd><dl><dt><span class="section"><a href="#idm139733300510624">18.1.
- Spot-Checking Build Determinism
- </a></span></dt><dt><span class="section"><a href="#idm139733300495744">18.2.
- Automatic and Optionally Enforced Determinism Verification
- </a></span></dt></dl></dd><dt><span class="chapter"><a href="#chap-post-build-hook">19. Using the <code class="option"><a class="option" href="#conf-post-build-hook">post-build-hook</a></code></a></span></dt><dd><dl><dt><span class="section"><a href="#chap-post-build-hook-caveats">19.1. Implementation Caveats</a></span></dt><dt><span class="section"><a href="#idm139733300481840">19.2. Prerequisites</a></span></dt><dt><span class="section"><a href="#idm139733300479440">19.3. Set up a Signing Key</a></span></dt><dt><span class="section"><a href="#idm139733300473952">19.4. Implementing the build hook</a></span></dt><dt><span class="section"><a href="#idm139733300467040">19.5. Updating Nix Configuration</a></span></dt><dt><span class="section"><a href="#idm139733300464016">19.6. Testing</a></span></dt><dt><span class="section"><a href="#idm139733300459088">19.7. Conclusion</a></span></dt></dl></dd></dl></dd><dt><span class="part"><a href="#part-command-ref">VI. Command Reference</a></span></dt><dd><dl><dt><span class="chapter"><a href="#sec-common-options">20. Common Options</a></span></dt><dt><span class="chapter"><a href="#sec-common-env">21. Common Environment Variables</a></span></dt><dt><span class="chapter"><a href="#ch-main-commands">22. Main Commands</a></span></dt><dd><dl><dt><span class="refentrytitle"><a href="#sec-nix-env">nix-env</a></span><span class="refpurpose"> — manipulate or query Nix user environments</span></dt><dt><span class="refentrytitle"><a href="#sec-nix-build">nix-build</a></span><span class="refpurpose"> — build a Nix expression</span></dt><dt><span class="refentrytitle"><a href="#sec-nix-shell">nix-shell</a></span><span class="refpurpose"> — start an interactive shell based on a Nix expression</span></dt><dt><span class="refentrytitle"><a href="#sec-nix-store">nix-store</a></span><span class="refpurpose"> — manipulate or query the Nix store</span></dt></dl></dd><dt><span class="chapter"><a href="#ch-utilities">23. Utilities</a></span></dt><dd><dl><dt><span class="refentrytitle"><a href="#sec-nix-channel">nix-channel</a></span><span class="refpurpose"> — manage Nix channels</span></dt><dt><span class="refentrytitle"><a href="#sec-nix-collect-garbage">nix-collect-garbage</a></span><span class="refpurpose"> — delete unreachable store paths</span></dt><dt><span class="refentrytitle"><a href="#sec-nix-copy-closure">nix-copy-closure</a></span><span class="refpurpose"> — copy a closure to or from a remote machine via SSH</span></dt><dt><span class="refentrytitle"><a href="#sec-nix-daemon">nix-daemon</a></span><span class="refpurpose"> — Nix multi-user support daemon</span></dt><dt><span class="refentrytitle"><a href="#sec-nix-hash">nix-hash</a></span><span class="refpurpose"> — compute the cryptographic hash of a path</span></dt><dt><span class="refentrytitle"><a href="#sec-nix-instantiate">nix-instantiate</a></span><span class="refpurpose"> — instantiate store derivations from Nix expressions</span></dt><dt><span class="refentrytitle"><a href="#sec-nix-prefetch-url">nix-prefetch-url</a></span><span class="refpurpose"> — copy a file from a URL into the store and print its hash</span></dt></dl></dd><dt><span class="chapter"><a href="#ch-files">24. Files</a></span></dt><dd><dl><dt><span class="refentrytitle"><a href="#sec-conf-file">nix.conf</a></span><span class="refpurpose"> — Nix configuration file</span></dt></dl></dd></dl></dd><dt><span class="appendix"><a href="#part-glossary">A. Glossary</a></span></dt><dt><span class="appendix"><a href="#chap-hacking">B. Hacking</a></span></dt><dt><span class="appendix"><a href="#sec-relnotes">C. Nix Release Notes</a></span></dt><dd><dl><dt><span class="section"><a href="#ssec-relnotes-2.3">C.1. Release 2.3 (2019-09-04)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-2.2">C.2. Release 2.2 (2019-01-11)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-2.1">C.3. Release 2.1 (2018-09-02)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-2.0">C.4. Release 2.0 (2018-02-22)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.11.10">C.5. Release 1.11.10 (2017-06-12)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.11">C.6. Release 1.11 (2016-01-19)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.10">C.7. Release 1.10 (2015-09-03)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.9">C.8. Release 1.9 (2015-06-12)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.8">C.9. Release 1.8 (2014-12-14)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.7">C.10. Release 1.7 (2014-04-11)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.6.1">C.11. Release 1.6.1 (2013-10-28)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.6.0">C.12. Release 1.6 (2013-09-10)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.5.2">C.13. Release 1.5.2 (2013-05-13)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.5">C.14. Release 1.5 (2013-02-27)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.4">C.15. Release 1.4 (2013-02-26)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.3">C.16. Release 1.3 (2013-01-04)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.2">C.17. Release 1.2 (2012-12-06)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.1">C.18. Release 1.1 (2012-07-18)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-1.0">C.19. Release 1.0 (2012-05-11)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-0.16">C.20. Release 0.16 (2010-08-17)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-0.15">C.21. Release 0.15 (2010-03-17)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-0.14">C.22. Release 0.14 (2010-02-04)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-0.13">C.23. Release 0.13 (2009-11-05)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-0.12">C.24. Release 0.12 (2008-11-20)</a></span></dt><dt><span class="section"><a href="#ssec-relnotes-0.11">C.25. Release 0.11 (2007-12-31)</a></span></dt><dt><span class="section"><a href="#ch-relnotes-0.10.1">C.26. Release 0.10.1 (2006-10-11)</a></span></dt><dt><span class="section"><a href="#ch-relnotes-0.10">C.27. Release 0.10 (2006-10-06)</a></span></dt><dt><span class="section"><a href="#ch-relnotes-0.9.2">C.28. Release 0.9.2 (2005-09-21)</a></span></dt><dt><span class="section"><a href="#ch-relnotes-0.9.1">C.29. Release 0.9.1 (2005-09-20)</a></span></dt><dt><span class="section"><a href="#ch-relnotes-0.9">C.30. Release 0.9 (2005-09-16)</a></span></dt><dt><span class="section"><a href="#ch-relnotes-0.8.1">C.31. Release 0.8.1 (2005-04-13)</a></span></dt><dt><span class="section"><a href="#ch-relnotes-0.8">C.32. Release 0.8 (2005-04-11)</a></span></dt><dt><span class="section"><a href="#ch-relnotes-0.7">C.33. Release 0.7 (2005-01-12)</a></span></dt><dt><span class="section"><a href="#ch-relnotes-0.6">C.34. Release 0.6 (2004-11-14)</a></span></dt><dt><span class="section"><a href="#ch-relnotes-0.5">C.35. Release 0.5 and earlier</a></span></dt></dl></dd></dl></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a id="chap-introduction"></a>Part I. Introduction</h1></div></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-about-nix"></a>Chapter 1. About Nix</h2></div></div></div><p>Nix is a <span class="emphasis"><em>purely functional package manager</em></span>.
-This means that it treats packages like values in purely functional
-programming languages such as Haskell — they are built by functions
-that don’t have side-effects, and they never change after they have
-been built. Nix stores packages in the <span class="emphasis"><em>Nix
-store</em></span>, usually the directory
-<code class="filename">/nix/store</code>, where each package has its own unique
-subdirectory such as
-
-</p><pre class="programlisting">
-/nix/store/b6gvzjyb2pg0kjfwrjmg1vfhh54ad73z-firefox-33.1/
-</pre><p>
-
-where <code class="literal">b6gvzjyb2pg0…</code> is a unique identifier for the
-package that captures all its dependencies (it’s a cryptographic hash
-of the package’s build dependency graph). This enables many powerful
-features.</p><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733302010000"></a>Multiple versions</h2></div></div></div><p>You can have multiple versions or variants of a package
-installed at the same time. This is especially important when
-different applications have dependencies on different versions of the
-same package — it prevents the “DLL hell”. Because of the hashing
-scheme, different versions of a package end up in different paths in
-the Nix store, so they don’t interfere with each other.</p><p>An important consequence is that operations like upgrading or
-uninstalling an application cannot break other applications, since
-these operations never “destructively” update or delete files that are
-used by other packages.</p></div><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733302007296"></a>Complete dependencies</h2></div></div></div><p>Nix helps you make sure that package dependency specifications
-are complete. In general, when you’re making a package for a package
-management system like RPM, you have to specify for each package what
-its dependencies are, but there are no guarantees that this
-specification is complete. If you forget a dependency, then the
-package will build and work correctly on <span class="emphasis"><em>your</em></span>
-machine if you have the dependency installed, but not on the end
-user's machine if it's not there.</p><p>Since Nix on the other hand doesn’t install packages in “global”
-locations like <code class="filename">/usr/bin</code> but in package-specific
-directories, the risk of incomplete dependencies is greatly reduced.
-This is because tools such as compilers don’t search in per-packages
-directories such as
-<code class="filename">/nix/store/5lbfaxb722zp…-openssl-0.9.8d/include</code>,
-so if a package builds correctly on your system, this is because you
-specified the dependency explicitly. This takes care of the build-time
-dependencies.</p><p>Once a package is built, runtime dependencies are found by
-scanning binaries for the hash parts of Nix store paths (such as
-<code class="literal">r8vvq9kq…</code>). This sounds risky, but it works
-extremely well.</p></div><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733302002080"></a>Multi-user support</h2></div></div></div><p>Nix has multi-user support. This means that non-privileged
-users can securely install software. Each user can have a different
-<span class="emphasis"><em>profile</em></span>, a set of packages in the Nix store that
-appear in the user’s <code class="envar">PATH</code>. If a user installs a
-package that another user has already installed previously, the
-package won’t be built or downloaded a second time. At the same time,
-it is not possible for one user to inject a Trojan horse into a
-package that might be used by another user.</p></div><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733301999344"></a>Atomic upgrades and rollbacks</h2></div></div></div><p>Since package management operations never overwrite packages in
-the Nix store but just add new versions in different paths, they are
-<span class="emphasis"><em>atomic</em></span>. So during a package upgrade, there is no
-time window in which the package has some files from the old version
-and some files from the new version — which would be bad because a
-program might well crash if it’s started during that period.</p><p>And since packages aren’t overwritten, the old versions are still
-there after an upgrade. This means that you can <span class="emphasis"><em>roll
-back</em></span> to the old version:</p><pre class="screen">
-$ nix-env --upgrade <em class="replaceable"><code>some-packages</code></em>
-$ nix-env --rollback
-</pre></div><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733301995248"></a>Garbage collection</h2></div></div></div><p>When you uninstall a package like this…
-
-</p><pre class="screen">
-$ nix-env --uninstall firefox
-</pre><p>
-
-the package isn’t deleted from the system right away (after all, you
-might want to do a rollback, or it might be in the profiles of other
-users). Instead, unused packages can be deleted safely by running the
-<span class="emphasis"><em>garbage collector</em></span>:
-
-</p><pre class="screen">
-$ nix-collect-garbage
-</pre><p>
-
-This deletes all packages that aren’t in use by any user profile or by
-a currently running program.</p></div><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733301992112"></a>Functional package language</h2></div></div></div><p>Packages are built from <span class="emphasis"><em>Nix expressions</em></span>,
-which is a simple functional language. A Nix expression describes
-everything that goes into a package build action (a “derivation”):
-other packages, sources, the build script, environment variables for
-the build script, etc. Nix tries very hard to ensure that Nix
-expressions are <span class="emphasis"><em>deterministic</em></span>: building a Nix
-expression twice should yield the same result.</p><p>Because it’s a functional language, it’s easy to support
-building variants of a package: turn the Nix expression into a
-function and call it any number of times with the appropriate
-arguments. Due to the hashing scheme, variants don’t conflict with
-each other in the Nix store.</p></div><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733301988512"></a>Transparent source/binary deployment</h2></div></div></div><p>Nix expressions generally describe how to build a package from
-source, so an installation action like
-
-</p><pre class="screen">
-$ nix-env --install firefox
-</pre><p>
-
-<span class="emphasis"><em>could</em></span> cause quite a bit of build activity, as not
-only Firefox but also all its dependencies (all the way up to the C
-library and the compiler) would have to built, at least if they are
-not already in the Nix store. This is a <span class="emphasis"><em>source deployment
-model</em></span>. For most users, building from source is not very
-pleasant as it takes far too long. However, Nix can automatically
-skip building from source and instead use a <span class="emphasis"><em>binary
-cache</em></span>, a web server that provides pre-built binaries. For
-instance, when asked to build
-<code class="literal">/nix/store/b6gvzjyb2pg0…-firefox-33.1</code> from source,
-Nix would first check if the file
-<code class="uri">https://cache.nixos.org/b6gvzjyb2pg0….narinfo</code> exists, and
-if so, fetch the pre-built binary referenced from there; otherwise, it
-would fall back to building from source.</p></div><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733301983504"></a>Nix Packages collection</h2></div></div></div><p>We provide a large set of Nix expressions containing hundreds of
-existing Unix packages, the <span class="emphasis"><em>Nix Packages
-collection</em></span> (Nixpkgs).</p></div><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733301981888"></a>Managing build environments</h2></div></div></div><p>Nix is extremely useful for developers as it makes it easy to
-automatically set up the build environment for a package. Given a
-Nix expression that describes the dependencies of your package, the
-command <span class="command"><strong>nix-shell</strong></span> will build or download those
-dependencies if they’re not already in your Nix store, and then start
-a Bash shell in which all necessary environment variables (such as
-compiler search paths) are set.</p><p>For example, the following command gets all dependencies of the
-Pan newsreader, as described by <a class="link" href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/networking/newsreaders/pan/default.nix" target="_top">its
-Nix expression</a>:</p><pre class="screen">
-$ nix-shell '<nixpkgs>' -A pan
-</pre><p>You’re then dropped into a shell where you can edit, build and test
-the package:</p><pre class="screen">
-[nix-shell]$ tar xf $src
-[nix-shell]$ cd pan-*
-[nix-shell]$ ./configure
-[nix-shell]$ make
-[nix-shell]$ ./pan/gui/pan
-</pre></div><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733301976352"></a>Portability</h2></div></div></div><p>Nix runs on Linux and macOS.</p></div><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733301975296"></a>NixOS</h2></div></div></div><p>NixOS is a Linux distribution based on Nix. It uses Nix not
-just for package management but also to manage the system
-configuration (e.g., to build configuration files in
-<code class="filename">/etc</code>). This means, among other things, that it
-is easy to roll back the entire configuration of the system to an
-earlier state. Also, users can install software without root
-privileges. For more information and downloads, see the <a class="link" href="http://nixos.org/" target="_top">NixOS homepage</a>.</p></div><div class="simplesect"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733301972848"></a>License</h2></div></div></div><p>Nix is released under the terms of the <a class="link" href="http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html" target="_top">GNU
-LGPLv2.1 or (at your option) any later version</a>.</p></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="chap-quick-start"></a>Chapter 2. Quick Start</h2></div></div></div><p>This chapter is for impatient people who don't like reading
-documentation. For more in-depth information you are kindly referred
-to subsequent chapters.</p><div class="procedure"><ol class="procedure" type="1"><li class="step"><p>Install single-user Nix by running the following:
-
-</p><pre class="screen">
-$ bash <(curl -L https://nixos.org/nix/install)
-</pre><p>
-
-This will install Nix in <code class="filename">/nix</code>. The install script
-will create <code class="filename">/nix</code> using <span class="command"><strong>sudo</strong></span>,
-so make sure you have sufficient rights. (For other installation
-methods, see <a class="xref" href="#chap-installation" title="Part II. Installation">Part II, “Installation”</a>.)</p></li><li class="step"><p>See what installable packages are currently available
-in the channel:
-
-</p><pre class="screen">
-$ nix-env -qa
-docbook-xml-4.3
-docbook-xml-4.5
-firefox-33.0.2
-hello-2.9
-libxslt-1.1.28
-<em class="replaceable"><code>...</code></em></pre><p>
-
-</p></li><li class="step"><p>Install some packages from the channel:
-
-</p><pre class="screen">
-$ nix-env -i hello</pre><p>
-
-This should download pre-built packages; it should not build them
-locally (if it does, something went wrong).</p></li><li class="step"><p>Test that they work:
-
-</p><pre class="screen">
-$ which hello
-/home/eelco/.nix-profile/bin/hello
-$ hello
-Hello, world!
-</pre><p>
-
-</p></li><li class="step"><p>Uninstall a package:
-
-</p><pre class="screen">
-$ nix-env -e hello</pre><p>
-
-</p></li><li class="step"><p>You can also test a package without installing it:
-
-</p><pre class="screen">
-$ nix-shell -p hello
-</pre><p>
-
-This builds or downloads GNU Hello and its dependencies, then drops
-you into a Bash shell where the <span class="command"><strong>hello</strong></span> command is
-present, all without affecting your normal environment:
-
-</p><pre class="screen">
-[nix-shell:~]$ hello
-Hello, world!
-
-[nix-shell:~]$ exit
-
-$ hello
-hello: command not found
-</pre><p>
-
-</p></li><li class="step"><p>To keep up-to-date with the channel, do:
-
-</p><pre class="screen">
-$ nix-channel --update nixpkgs
-$ nix-env -u '*'</pre><p>
-
-The latter command will upgrade each installed package for which there
-is a “newer” version (as determined by comparing the version
-numbers).</p></li><li class="step"><p>If you're unhappy with the result of a
-<span class="command"><strong>nix-env</strong></span> action (e.g., an upgraded package turned
-out not to work properly), you can go back:
-
-</p><pre class="screen">
-$ nix-env --rollback</pre><p>
-
-</p></li><li class="step"><p>You should periodically run the Nix garbage collector
-to get rid of unused packages, since uninstalls or upgrades don't
-actually delete them:
-
-</p><pre class="screen">
-$ nix-collect-garbage -d</pre><p>
-
-
-
-</p></li></ol></div></div></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a id="chap-installation"></a>Part II. Installation</h1></div></div></div><div class="partintro"><div></div><p>This section describes how to install and configure Nix for first-time use.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-supported-platforms"></a>Chapter 3. Supported Platforms</h2></div></div></div><p>Nix is currently supported on the following platforms:
-
-</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Linux (i686, x86_64, aarch64).</p></li><li class="listitem"><p>macOS (x86_64).</p></li></ul></div><p>
-
-</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-installing-binary"></a>Chapter 4. Installing a Binary Distribution</h2></div></div></div><p>
- If you are using Linux or macOS versions up to 10.14 (Mojave), the
- easiest way to install Nix is to run the following command:
-</p><pre class="screen">
- $ sh <(curl -L https://nixos.org/nix/install)
-</pre><p>
- If you're using macOS 10.15 (Catalina) or newer, consult
- <a class="link" href="#sect-macos-installation" title="4.3. macOS Installation">the macOS installation instructions</a>
- before installing.
-</p><p>
- As of Nix 2.1.0, the Nix installer will always default to creating a
- single-user installation, however opting in to the multi-user
- installation is highly recommended.
-
-</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sect-single-user-installation"></a>4.1. Single User Installation</h2></div></div></div><p>
- To explicitly select a single-user installation on your system:
-
- </p><pre class="screen">
- sh <(curl -L https://nixos.org/nix/install) --no-daemon
-</pre><p>
- </p><p>
-This will perform a single-user installation of Nix, meaning that
-<code class="filename">/nix</code> is owned by the invoking user. You should
-run this under your usual user account, <span class="emphasis"><em>not</em></span> as
-root. The script will invoke <span class="command"><strong>sudo</strong></span> to create
-<code class="filename">/nix</code> if it doesn’t already exist. If you don’t
-have <span class="command"><strong>sudo</strong></span>, you should manually create
-<code class="filename">/nix</code> first as root, e.g.:
-
-</p><pre class="screen">
-$ mkdir /nix
-$ chown alice /nix
-</pre><p>
-
-The install script will modify the first writable file from amongst
-<code class="filename">.bash_profile</code>, <code class="filename">.bash_login</code>
-and <code class="filename">.profile</code> to source
-<code class="filename">~/.nix-profile/etc/profile.d/nix.sh</code>. You can set
-the <code class="envar">NIX_INSTALLER_NO_MODIFY_PROFILE</code> environment
-variable before executing the install script to disable this
-behaviour.
-</p><p>You can uninstall Nix simply by running:
-
-</p><pre class="screen">
-$ rm -rf /nix
-</pre><p>
-
-</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sect-multi-user-installation"></a>4.2. Multi User Installation</h2></div></div></div><p>
- The multi-user Nix installation creates system users, and a system
- service for the Nix daemon.
- </p><div class="itemizedlist"><p class="title"><strong>Supported Systems</strong></p><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Linux running systemd, with SELinux disabled</p></li><li class="listitem"><p>macOS</p></li></ul></div><p>
- You can instruct the installer to perform a multi-user
- installation on your system:
- </p><pre class="screen">sh <(curl -L https://nixos.org/nix/install) --daemon</pre><p>
- The multi-user installation of Nix will create build users between
- the user IDs 30001 and 30032, and a group with the group ID 30000.
-
- You should run this under your usual user account,
- <span class="emphasis"><em>not</em></span> as root. The script will invoke
- <span class="command"><strong>sudo</strong></span> as needed.
- </p><div class="note"><h3 class="title">Note</h3><p>
- If you need Nix to use a different group ID or user ID set, you
- will have to download the tarball manually and <a class="link" href="#sect-nix-install-binary-tarball" title="4.5. Installing from a binary tarball">edit the install
- script</a>.
- </p></div><p>
- The installer will modify <code class="filename">/etc/bashrc</code>, and
- <code class="filename">/etc/zshrc</code> if they exist. The installer will
- first back up these files with a
- <code class="literal">.backup-before-nix</code> extension. The installer
- will also create <code class="filename">/etc/profile.d/nix.sh</code>.
- </p><p>You can uninstall Nix with the following commands:
-
-</p><pre class="screen">
-sudo rm -rf /etc/profile/nix.sh /etc/nix /nix ~root/.nix-profile ~root/.nix-defexpr ~root/.nix-channels ~/.nix-profile ~/.nix-defexpr ~/.nix-channels
-
-# If you are on Linux with systemd, you will need to run:
-sudo systemctl stop nix-daemon.socket
-sudo systemctl stop nix-daemon.service
-sudo systemctl disable nix-daemon.socket
-sudo systemctl disable nix-daemon.service
-sudo systemctl daemon-reload
-
-# If you are on macOS, you will need to run:
-sudo launchctl unload /Library/LaunchDaemons/org.nixos.nix-daemon.plist
-sudo rm /Library/LaunchDaemons/org.nixos.nix-daemon.plist
-</pre><p>
-
- There may also be references to Nix in
- <code class="filename">/etc/profile</code>,
- <code class="filename">/etc/bashrc</code>, and
- <code class="filename">/etc/zshrc</code> which you may remove.
- </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sect-macos-installation"></a>4.3. macOS Installation</h2></div></div></div><p>
- Starting with macOS 10.15 (Catalina), the root filesystem is read-only.
- This means <code class="filename">/nix</code> can no longer live on your system
- volume, and that you'll need a workaround to install Nix.
- </p><p>
- The recommended approach, which creates an unencrypted APFS volume
- for your Nix store and a "synthetic" empty directory to mount it
- over at <code class="filename">/nix</code>, is least likely to impair Nix
- or your system.
- </p><div class="note"><h3 class="title">Note</h3><p>
- With all separate-volume approaches, it's possible something on
- your system (particularly daemons/services and restored apps) may
- need access to your Nix store before the volume is mounted. Adding
- additional encryption makes this more likely.
- </p></div><p>
- If you're using a recent Mac with a
- <a class="link" href="https://www.apple.com/euro/mac/shared/docs/Apple_T2_Security_Chip_Overview.pdf" target="_top">T2 chip</a>,
- your drive will still be encrypted at rest (in which case "unencrypted"
- is a bit of a misnomer). To use this approach, just install Nix with:
- </p><pre class="screen">$ sh <(curl -L https://nixos.org/nix/install) --darwin-use-unencrypted-nix-store-volume</pre><p>
- If you don't like the sound of this, you'll want to weigh the
- other approaches and tradeoffs detailed in this section.
- </p><div class="note"><h3 class="title">Eventual solutions?</h3><p>
- All of the known workarounds have drawbacks, but we hope
- better solutions will be available in the future. Some that
- we have our eye on are:
- </p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
- A true firmlink would enable the Nix store to live on the
- primary data volume without the build problems caused by
- the symlink approach. End users cannot currently
- create true firmlinks.
- </p></li><li class="listitem"><p>
- If the Nix store volume shared FileVault encryption
- with the primary data volume (probably by using the same
- volume group and role), FileVault encryption could be
- easily supported by the installer without requiring
- manual setup by each user.
- </p></li></ol></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="sect-macos-installation-change-store-prefix"></a>4.3.1. Change the Nix store path prefix</h3></div></div></div><p>
- Changing the default prefix for the Nix store is a simple
- approach which enables you to leave it on your root volume,
- where it can take full advantage of FileVault encryption if
- enabled. Unfortunately, this approach also opts your device out
- of some benefits that are enabled by using the same prefix
- across systems:
-
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
- Your system won't be able to take advantage of the binary
- cache (unless someone is able to stand up and support
- duplicate caching infrastructure), which means you'll
- spend more time waiting for builds.
- </p></li><li class="listitem"><p>
- It's harder to build and deploy packages to Linux systems.
- </p></li></ul></div><p>
-
-
-
- It would also possible (and often requested) to just apply this
- change ecosystem-wide, but it's an intrusive process that has
- side effects we want to avoid for now.
-
- </p><p>
- </p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="sect-macos-installation-encrypted-volume"></a>4.3.2. Use a separate encrypted volume</h3></div></div></div><p>
- If you like, you can also add encryption to the recommended
- approach taken by the installer. You can do this by pre-creating
- an encrypted volume before you run the installer--or you can
- run the installer and encrypt the volume it creates later.
-
- </p><p>
- In either case, adding encryption to a second volume isn't quite
- as simple as enabling FileVault for your boot volume. Before you
- dive in, there are a few things to weigh:
- </p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
- The additional volume won't be encrypted with your existing
- FileVault key, so you'll need another mechanism to decrypt
- the volume.
- </p></li><li class="listitem"><p>
- You can store the password in Keychain to automatically
- decrypt the volume on boot--but it'll have to wait on Keychain
- and may not mount before your GUI apps restore. If any of
- your launchd agents or apps depend on Nix-installed software
- (for example, if you use a Nix-installed login shell), the
- restore may fail or break.
- </p><p>
- On a case-by-case basis, you may be able to work around this
- problem by using <span class="command"><strong>wait4path</strong></span> to block
- execution until your executable is available.
- </p><p>
- It's also possible to decrypt and mount the volume earlier
- with a login hook--but this mechanism appears to be
- deprecated and its future is unclear.
- </p></li><li class="listitem"><p>
- You can hard-code the password in the clear, so that your
- store volume can be decrypted before Keychain is available.
- </p></li></ol></div><p>
- If you are comfortable navigating these tradeoffs, you can encrypt the volume with
- something along the lines of:
-
- </p><pre class="screen">alice$ diskutil apfs enableFileVault /nix -user disk</pre></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="sect-macos-installation-symlink"></a>4.3.3. Symlink the Nix store to a custom location</h3></div></div></div><p>
- Another simple approach is using <code class="filename">/etc/synthetic.conf</code>
- to symlink the Nix store to the data volume. This option also
- enables your store to share any configured FileVault encryption.
- Unfortunately, builds that resolve the symlink may leak the
- canonical path or even fail.
- </p><p>
- Because of these downsides, we can't recommend this approach.
- </p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="sect-macos-installation-recommended-notes"></a>4.3.4. Notes on the recommended approach</h3></div></div></div><p>
- This section goes into a little more detail on the recommended
- approach. You don't need to understand it to run the installer,
- but it can serve as a helpful reference if you run into trouble.
- </p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
- In order to compose user-writable locations into the new
- read-only system root, Apple introduced a new concept called
- <code class="literal">firmlinks</code>, which it describes as a
- "bi-directional wormhole" between two filesystems. You can
- see the current firmlinks in <code class="filename">/usr/share/firmlinks</code>.
- Unfortunately, firmlinks aren't (currently?) user-configurable.
- </p><p>
- For special cases like NFS mount points or package manager roots,
- <a class="link" href="https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man5/synthetic.conf.5.html" target="_top">synthetic.conf(5)</a>
- supports limited user-controlled file-creation (of symlinks,
- and synthetic empty directories) at <code class="filename">/</code>.
- To create a synthetic empty directory for mounting at <code class="filename">/nix</code>,
- add the following line to <code class="filename">/etc/synthetic.conf</code>
- (create it if necessary):
- </p><pre class="screen">nix</pre></li><li class="listitem"><p>
- This configuration is applied at boot time, but you can use
- <span class="command"><strong>apfs.util</strong></span> to trigger creation (not deletion)
- of new entries without a reboot:
- </p><pre class="screen">alice$ /System/Library/Filesystems/apfs.fs/Contents/Resources/apfs.util -B</pre></li><li class="listitem"><p>
- Create the new APFS volume with diskutil:
- </p><pre class="screen">alice$ sudo diskutil apfs addVolume diskX APFS 'Nix Store' -mountpoint /nix</pre></li><li class="listitem"><p>
- Using <span class="command"><strong>vifs</strong></span>, add the new mount to
- <code class="filename">/etc/fstab</code>. If it doesn't already have
- other entries, it should look something like:
- </p><pre class="screen">
-#
-# Warning - this file should only be modified with vifs(8)
-#
-# Failure to do so is unsupported and may be destructive.
-#
-LABEL=Nix\040Store /nix apfs rw,nobrowse
-</pre><p>
- The nobrowse setting will keep Spotlight from indexing this
- volume, and keep it from showing up on your desktop.
- </p></li></ol></div></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sect-nix-install-pinned-version-url"></a>4.4. Installing a pinned Nix version from a URL</h2></div></div></div><p>
- NixOS.org hosts version-specific installation URLs for all Nix
- versions since 1.11.16, at
- <code class="literal">https://releases.nixos.org/nix/nix-<em class="replaceable"><code>version</code></em>/install</code>.
- </p><p>
- These install scripts can be used the same as the main
- NixOS.org installation script:
-
- </p><pre class="screen">
- sh <(curl -L https://nixos.org/nix/install)
-</pre><p>
- </p><p>
- In the same directory of the install script are sha256 sums, and
- gpg signature files.
- </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sect-nix-install-binary-tarball"></a>4.5. Installing from a binary tarball</h2></div></div></div><p>
- You can also download a binary tarball that contains Nix and all
- its dependencies. (This is what the install script at
- <code class="uri">https://nixos.org/nix/install</code> does automatically.) You
- should unpack it somewhere (e.g. in <code class="filename">/tmp</code>),
- and then run the script named <span class="command"><strong>install</strong></span> inside
- the binary tarball:
-
-
-</p><pre class="screen">
-alice$ cd /tmp
-alice$ tar xfj nix-1.8-x86_64-darwin.tar.bz2
-alice$ cd nix-1.8-x86_64-darwin
-alice$ ./install
-</pre><p>
- </p><p>
- If you need to edit the multi-user installation script to use
- different group ID or a different user ID range, modify the
- variables set in the file named
- <code class="filename">install-multi-user</code>.
- </p></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-installing-source"></a>Chapter 5. Installing Nix from Source</h2></div></div></div><p>If no binary package is available, you can download and compile
-a source distribution.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-prerequisites-source"></a>5.1. Prerequisites</h2></div></div></div><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>GNU Autoconf
- (<a class="link" href="https://www.gnu.org/software/autoconf/" target="_top">https://www.gnu.org/software/autoconf/</a>)
- and the autoconf-archive macro collection
- (<a class="link" href="https://www.gnu.org/software/autoconf-archive/" target="_top">https://www.gnu.org/software/autoconf-archive/</a>).
- These are only needed to run the bootstrap script, and are not necessary
- if your source distribution came with a pre-built
- <code class="literal">./configure</code> script.</p></li><li class="listitem"><p>GNU Make.</p></li><li class="listitem"><p>Bash Shell. The <code class="literal">./configure</code> script
- relies on bashisms, so Bash is required.</p></li><li class="listitem"><p>A version of GCC or Clang that supports C++17.</p></li><li class="listitem"><p><span class="command"><strong>pkg-config</strong></span> to locate
- dependencies. If your distribution does not provide it, you can get
- it from <a class="link" href="http://www.freedesktop.org/wiki/Software/pkg-config" target="_top">http://www.freedesktop.org/wiki/Software/pkg-config</a>.</p></li><li class="listitem"><p>The OpenSSL library to calculate cryptographic hashes.
- If your distribution does not provide it, you can get it from <a class="link" href="https://www.openssl.org" target="_top">https://www.openssl.org</a>.</p></li><li class="listitem"><p>The <code class="literal">libbrotlienc</code> and
- <code class="literal">libbrotlidec</code> libraries to provide implementation
- of the Brotli compression algorithm. They are available for download
- from the official repository <a class="link" href="https://github.com/google/brotli" target="_top">https://github.com/google/brotli</a>.</p></li><li class="listitem"><p>The bzip2 compressor program and the
- <code class="literal">libbz2</code> library. Thus you must have bzip2
- installed, including development headers and libraries. If your
- distribution does not provide these, you can obtain bzip2 from <a class="link" href="https://web.archive.org/web/20180624184756/http://www.bzip.org/" target="_top">https://web.archive.org/web/20180624184756/http://www.bzip.org/</a>.</p></li><li class="listitem"><p><code class="literal">liblzma</code>, which is provided by
- XZ Utils. If your distribution does not provide this, you can
- get it from <a class="link" href="https://tukaani.org/xz/" target="_top">https://tukaani.org/xz/</a>.</p></li><li class="listitem"><p>cURL and its library. If your distribution does not
- provide it, you can get it from <a class="link" href="https://curl.haxx.se/" target="_top">https://curl.haxx.se/</a>.</p></li><li class="listitem"><p>The SQLite embedded database library, version 3.6.19
- or higher. If your distribution does not provide it, please install
- it from <a class="link" href="http://www.sqlite.org/" target="_top">http://www.sqlite.org/</a>.</p></li><li class="listitem"><p>The <a class="link" href="http://www.hboehm.info/gc/" target="_top">Boehm
- garbage collector</a> to reduce the evaluator’s memory
- consumption (optional). To enable it, install
- <code class="literal">pkgconfig</code> and the Boehm garbage collector, and
- pass the flag <code class="option">--enable-gc</code> to
- <span class="command"><strong>configure</strong></span>.</p></li><li class="listitem"><p>The <code class="literal">boost</code> library of version
- 1.66.0 or higher. It can be obtained from the official web site
- <a class="link" href="https://www.boost.org/" target="_top">https://www.boost.org/</a>.</p></li><li class="listitem"><p>The <code class="literal">editline</code> library of version
- 1.14.0 or higher. It can be obtained from the its repository
- <a class="link" href="https://github.com/troglobit/editline" target="_top">https://github.com/troglobit/editline</a>.</p></li><li class="listitem"><p>The <span class="command"><strong>xmllint</strong></span> and
- <span class="command"><strong>xsltproc</strong></span> programs to build this manual and the
- man-pages. These are part of the <code class="literal">libxml2</code> and
- <code class="literal">libxslt</code> packages, respectively. You also need
- the <a class="link" href="http://docbook.sourceforge.net/projects/xsl/" target="_top">DocBook
- XSL stylesheets</a> and optionally the <a class="link" href="http://www.docbook.org/schemas/5x" target="_top"> DocBook 5.0 RELAX NG
- schemas</a>. Note that these are only required if you modify the
- manual sources or when you are building from the Git
- repository.</p></li><li class="listitem"><p>Recent versions of Bison and Flex to build the
- parser. (This is because Nix needs GLR support in Bison and
- reentrancy support in Flex.) For Bison, you need version 2.6, which
- can be obtained from the <a class="link" href="ftp://alpha.gnu.org/pub/gnu/bison" target="_top">GNU FTP
- server</a>. For Flex, you need version 2.5.35, which is
- available on <a class="link" href="http://lex.sourceforge.net/" target="_top">SourceForge</a>.
- Slightly older versions may also work, but ancient versions like the
- ubiquitous 2.5.4a won't. Note that these are only required if you
- modify the parser or when you are building from the Git
- repository.</p></li><li class="listitem"><p>The <code class="literal">libseccomp</code> is used to provide
- syscall filtering on Linux. This is an optional dependency and can
- be disabled passing a <code class="option">--disable-seccomp-sandboxing</code>
- option to the <span class="command"><strong>configure</strong></span> script (Not recommended
- unless your system doesn't support
- <code class="literal">libseccomp</code>). To get the library, visit <a class="link" href="https://github.com/seccomp/libseccomp" target="_top">https://github.com/seccomp/libseccomp</a>.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-obtaining-source"></a>5.2. Obtaining a Source Distribution</h2></div></div></div><p>The source tarball of the most recent stable release can be
-downloaded from the <a class="link" href="http://nixos.org/nix/download.html" target="_top">Nix homepage</a>.
-You can also grab the <a class="link" href="http://hydra.nixos.org/job/nix/master/release/latest-finished#tabs-constituents" target="_top">most
-recent development release</a>.</p><p>Alternatively, the most recent sources of Nix can be obtained
-from its <a class="link" href="https://github.com/NixOS/nix" target="_top">Git
-repository</a>. For example, the following command will check out
-the latest revision into a directory called
-<code class="filename">nix</code>:</p><pre class="screen">
-$ git clone https://github.com/NixOS/nix</pre><p>Likewise, specific releases can be obtained from the <a class="link" href="https://github.com/NixOS/nix/tags" target="_top">tags</a> of the
-repository.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-building-source"></a>5.3. Building Nix from Source</h2></div></div></div><p>After unpacking or checking out the Nix sources, issue the
-following commands:
-
-</p><pre class="screen">
-$ ./configure <em class="replaceable"><code>options...</code></em>
-$ make
-$ make install</pre><p>
-
-Nix requires GNU Make so you may need to invoke
-<span class="command"><strong>gmake</strong></span> instead.</p><p>When building from the Git repository, these should be preceded
-by the command:
-
-</p><pre class="screen">
-$ ./bootstrap.sh</pre><p>
-
-</p><p>The installation path can be specified by passing the
-<code class="option">--prefix=<em class="replaceable"><code>prefix</code></em></code> to
-<span class="command"><strong>configure</strong></span>. The default installation directory is
-<code class="filename">/usr/local</code>. You can change this to any location
-you like. You must have write permission to the
-<em class="replaceable"><code>prefix</code></em> path.</p><p>Nix keeps its <span class="emphasis"><em>store</em></span> (the place where
-packages are stored) in <code class="filename">/nix/store</code> by default.
-This can be changed using
-<code class="option">--with-store-dir=<em class="replaceable"><code>path</code></em></code>.</p><div class="warning"><h3 class="title">Warning</h3><p>It is best <span class="emphasis"><em>not</em></span> to change the Nix
-store from its default, since doing so makes it impossible to use
-pre-built binaries from the standard Nixpkgs channels — that is, all
-packages will need to be built from source.</p></div><p>Nix keeps state (such as its database and log files) in
-<code class="filename">/nix/var</code> by default. This can be changed using
-<code class="option">--localstatedir=<em class="replaceable"><code>path</code></em></code>.</p></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-nix-security"></a>Chapter 6. Security</h2></div></div></div><p>Nix has two basic security models. First, it can be used in
-“single-user mode”, which is similar to what most other package
-management tools do: there is a single user (typically <code class="systemitem">root</code>) who performs all package
-management operations. All other users can then use the installed
-packages, but they cannot perform package management operations
-themselves.</p><p>Alternatively, you can configure Nix in “multi-user mode”. In
-this model, all users can perform package management operations — for
-instance, every user can install software without requiring root
-privileges. Nix ensures that this is secure. For instance, it’s not
-possible for one user to overwrite a package used by another user with
-a Trojan horse.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-single-user"></a>6.1. Single-User Mode</h2></div></div></div><p>In single-user mode, all Nix operations that access the database
-in <code class="filename"><em class="replaceable"><code>prefix</code></em>/var/nix/db</code>
-or modify the Nix store in
-<code class="filename"><em class="replaceable"><code>prefix</code></em>/store</code> must be
-performed under the user ID that owns those directories. This is
-typically <code class="systemitem">root</code>. (If you
-install from RPM packages, that’s in fact the default ownership.)
-However, on single-user machines, it is often convenient to
-<span class="command"><strong>chown</strong></span> those directories to your normal user account
-so that you don’t have to <span class="command"><strong>su</strong></span> to <code class="systemitem">root</code> all the time.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-multi-user"></a>6.2. Multi-User Mode</h2></div></div></div><p>To allow a Nix store to be shared safely among multiple users,
-it is important that users are not able to run builders that modify
-the Nix store or database in arbitrary ways, or that interfere with
-builds started by other users. If they could do so, they could
-install a Trojan horse in some package and compromise the accounts of
-other users.</p><p>To prevent this, the Nix store and database are owned by some
-privileged user (usually <code class="literal">root</code>) and builders are
-executed under special user accounts (usually named
-<code class="literal">nixbld1</code>, <code class="literal">nixbld2</code>, etc.). When a
-unprivileged user runs a Nix command, actions that operate on the Nix
-store (such as builds) are forwarded to a <span class="emphasis"><em>Nix
-daemon</em></span> running under the owner of the Nix store/database
-that performs the operation.</p><div class="note"><h3 class="title">Note</h3><p>Multi-user mode has one important limitation: only
-<code class="systemitem">root</code> and a set of trusted
-users specified in <code class="filename">nix.conf</code> can specify arbitrary
-binary caches. So while unprivileged users may install packages from
-arbitrary Nix expressions, they may not get pre-built
-binaries.</p></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301775792"></a>Setting up the build users</h3></div></div></div><p>The <span class="emphasis"><em>build users</em></span> are the special UIDs under
-which builds are performed. They should all be members of the
-<span class="emphasis"><em>build users group</em></span> <code class="literal">nixbld</code>.
-This group should have no other members. The build users should not
-be members of any other group. On Linux, you can create the group and
-users as follows:
-
-</p><pre class="screen">
-$ groupadd -r nixbld
-$ for n in $(seq 1 10); do useradd -c "Nix build user $n" \
- -d /var/empty -g nixbld -G nixbld -M -N -r -s "$(which nologin)" \
- nixbld$n; done
-</pre><p>
-
-This creates 10 build users. There can never be more concurrent builds
-than the number of build users, so you may want to increase this if
-you expect to do many builds at the same time.</p></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301772240"></a>Running the daemon</h3></div></div></div><p>The <a class="link" href="#sec-nix-daemon" title="nix-daemon">Nix daemon</a> should be
-started as follows (as <code class="literal">root</code>):
-
-</p><pre class="screen">
-$ nix-daemon</pre><p>
-
-You’ll want to put that line somewhere in your system’s boot
-scripts.</p><p>To let unprivileged users use the daemon, they should set the
-<a class="link" href="#envar-remote"><code class="envar">NIX_REMOTE</code> environment
-variable</a> to <code class="literal">daemon</code>. So you should put a
-line like
-
-</p><pre class="programlisting">
-export NIX_REMOTE=daemon</pre><p>
-
-into the users’ login scripts.</p></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301766816"></a>Restricting access</h3></div></div></div><p>To limit which users can perform Nix operations, you can use the
-permissions on the directory
-<code class="filename">/nix/var/nix/daemon-socket</code>. For instance, if you
-want to restrict the use of Nix to the members of a group called
-<code class="literal">nix-users</code>, do
-
-</p><pre class="screen">
-$ chgrp nix-users /nix/var/nix/daemon-socket
-$ chmod ug=rwx,o= /nix/var/nix/daemon-socket
-</pre><p>
-
-This way, users who are not in the <code class="literal">nix-users</code> group
-cannot connect to the Unix domain socket
-<code class="filename">/nix/var/nix/daemon-socket/socket</code>, so they cannot
-perform Nix operations.</p></div></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-env-variables"></a>Chapter 7. Environment Variables</h2></div></div></div><p>To use Nix, some environment variables should be set. In
-particular, <code class="envar">PATH</code> should contain the directories
-<code class="filename"><em class="replaceable"><code>prefix</code></em>/bin</code> and
-<code class="filename">~/.nix-profile/bin</code>. The first directory contains
-the Nix tools themselves, while <code class="filename">~/.nix-profile</code> is
-a symbolic link to the current <span class="emphasis"><em>user environment</em></span>
-(an automatically generated package consisting of symlinks to
-installed packages). The simplest way to set the required environment
-variables is to include the file
-<code class="filename"><em class="replaceable"><code>prefix</code></em>/etc/profile.d/nix.sh</code>
-in your <code class="filename">~/.profile</code> (or similar), like this:</p><pre class="screen">
-source <em class="replaceable"><code>prefix</code></em>/etc/profile.d/nix.sh</pre><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-nix-ssl-cert-file"></a>7.1. <code class="envar">NIX_SSL_CERT_FILE</code></h2></div></div></div><p>If you need to specify a custom certificate bundle to account
-for an HTTPS-intercepting man in the middle proxy, you must specify
-the path to the certificate bundle in the environment variable
-<code class="envar">NIX_SSL_CERT_FILE</code>.</p><p>If you don't specify a <code class="envar">NIX_SSL_CERT_FILE</code>
-manually, Nix will install and use its own certificate
-bundle.</p><div class="procedure"><ol class="procedure" type="1"><li class="step"><p>Set the environment variable and install Nix</p><pre class="screen">
-$ export NIX_SSL_CERT_FILE=/etc/ssl/my-certificate-bundle.crt
-$ sh <(curl -L https://nixos.org/nix/install)
-</pre></li><li class="step"><p>In the shell profile and rc files (for example,
- <code class="filename">/etc/bashrc</code>, <code class="filename">/etc/zshrc</code>),
- add the following line:</p><pre class="programlisting">
-export NIX_SSL_CERT_FILE=/etc/ssl/my-certificate-bundle.crt
-</pre></li></ol></div><div class="note"><h3 class="title">Note</h3><p>You must not add the export and then do the install, as
-the Nix installer will detect the presense of Nix configuration, and
-abort.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="sec-nix-ssl-cert-file-with-nix-daemon-and-macos"></a>7.1.1. <code class="envar">NIX_SSL_CERT_FILE</code> with macOS and the Nix daemon</h3></div></div></div><p>On macOS you must specify the environment variable for the Nix
-daemon service, then restart it:</p><pre class="screen">
-$ sudo launchctl setenv NIX_SSL_CERT_FILE /etc/ssl/my-certificate-bundle.crt
-$ sudo launchctl kickstart -k system/org.nixos.nix-daemon
-</pre></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="sec-installer-proxy-settings"></a>7.1.2. Proxy Environment Variables</h3></div></div></div><p>The Nix installer has special handling for these proxy-related
-environment variables:
-<code class="varname">http_proxy</code>, <code class="varname">https_proxy</code>,
-<code class="varname">ftp_proxy</code>, <code class="varname">no_proxy</code>,
-<code class="varname">HTTP_PROXY</code>, <code class="varname">HTTPS_PROXY</code>,
-<code class="varname">FTP_PROXY</code>, <code class="varname">NO_PROXY</code>.
-</p><p>If any of these variables are set when running the Nix installer,
-then the installer will create an override file at
-<code class="filename">/etc/systemd/system/nix-daemon.service.d/override.conf</code>
-so <span class="command"><strong>nix-daemon</strong></span> will use them.
-</p></div></div></div></div><div class="chapter"><div class="titlepage"><div><div><h1 class="title"><a id="ch-upgrading-nix"></a>Chapter 8. Upgrading Nix</h1></div></div></div><p>
- Multi-user Nix users on macOS can upgrade Nix by running:
- <span class="command"><strong>sudo -i sh -c 'nix-channel --update &&
- nix-env -iA nixpkgs.nix &&
- launchctl remove org.nixos.nix-daemon &&
- launchctl load /Library/LaunchDaemons/org.nixos.nix-daemon.plist'</strong></span>
- </p><p>
- Single-user installations of Nix should run this:
- <span class="command"><strong>nix-channel --update; nix-env -iA nixpkgs.nix nixpkgs.cacert</strong></span>
- </p><p>
- Multi-user Nix users on Linux should run this with sudo:
- <span class="command"><strong>nix-channel --update; nix-env -iA nixpkgs.nix nixpkgs.cacert; systemctl daemon-reload; systemctl restart nix-daemon</strong></span>
- </p></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a id="chap-package-management"></a>Part III. Package Management</h1></div></div></div><div class="partintro"><div></div><p>This chapter discusses how to do package management with Nix,
-i.e., how to obtain, install, upgrade, and erase packages. This is
-the “user’s” perspective of the Nix system — people
-who want to <span class="emphasis"><em>create</em></span> packages should consult
-<a class="xref" href="#chap-writing-nix-expressions" title="Part IV. Writing Nix Expressions">Part IV, “Writing Nix Expressions”</a>.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-basic-package-mgmt"></a>Chapter 9. Basic Package Management</h2></div></div></div><p>The main command for package management is <a class="link" href="#sec-nix-env" title="nix-env"><span class="command"><strong>nix-env</strong></span></a>. You can use
-it to install, upgrade, and erase packages, and to query what
-packages are installed or are available for installation.</p><p>In Nix, different users can have different “views”
-on the set of installed applications. That is, there might be lots of
-applications present on the system (possibly in many different
-versions), but users can have a specific selection of those active —
-where “active” just means that it appears in a directory
-in the user’s <code class="envar">PATH</code>. Such a view on the set of
-installed applications is called a <span class="emphasis"><em>user
-environment</em></span>, which is just a directory tree consisting of
-symlinks to the files of the active applications. </p><p>Components are installed from a set of <span class="emphasis"><em>Nix
-expressions</em></span> that tell Nix how to build those packages,
-including, if necessary, their dependencies. There is a collection of
-Nix expressions called the Nixpkgs package collection that contains
-packages ranging from basic development stuff such as GCC and Glibc,
-to end-user applications like Mozilla Firefox. (Nix is however not
-tied to the Nixpkgs package collection; you could write your own Nix
-expressions based on Nixpkgs, or completely new ones.)</p><p>You can manually download the latest version of Nixpkgs from
-<a class="link" href="http://nixos.org/nixpkgs/download.html" target="_top">http://nixos.org/nixpkgs/download.html</a>. However,
-it’s much more convenient to use the Nixpkgs
-<span class="emphasis"><em>channel</em></span>, since it makes it easy to stay up to
-date with new versions of Nixpkgs. (Channels are described in more
-detail in <a class="xref" href="#sec-channels" title="Chapter 12. Channels">Chapter 12, <em>Channels</em></a>.) Nixpkgs is automatically
-added to your list of “subscribed” channels when you install
-Nix. If this is not the case for some reason, you can add it as
-follows:
-
-</p><pre class="screen">
-$ nix-channel --add https://nixos.org/channels/nixpkgs-unstable
-$ nix-channel --update
-</pre><p>
-
-</p><div class="note"><h3 class="title">Note</h3><p>On NixOS, you’re automatically subscribed to a NixOS
-channel corresponding to your NixOS major release
-(e.g. <code class="uri">http://nixos.org/channels/nixos-14.12</code>). A NixOS
-channel is identical to the Nixpkgs channel, except that it contains
-only Linux binaries and is updated only if a set of regression tests
-succeed.</p></div><p>You can view the set of available packages in Nixpkgs:
-
-</p><pre class="screen">
-$ nix-env -qa
-aterm-2.2
-bash-3.0
-binutils-2.15
-bison-1.875d
-blackdown-1.4.2
-bzip2-1.0.2
-…</pre><p>
-
-The flag <code class="option">-q</code> specifies a query operation, and
-<code class="option">-a</code> means that you want to show the “available” (i.e.,
-installable) packages, as opposed to the installed packages. If you
-downloaded Nixpkgs yourself, or if you checked it out from GitHub,
-then you need to pass the path to your Nixpkgs tree using the
-<code class="option">-f</code> flag:
-
-</p><pre class="screen">
-$ nix-env -qaf <em class="replaceable"><code>/path/to/nixpkgs</code></em>
-</pre><p>
-
-where <em class="replaceable"><code>/path/to/nixpkgs</code></em> is where you’ve
-unpacked or checked out Nixpkgs.</p><p>You can select specific packages by name:
-
-</p><pre class="screen">
-$ nix-env -qa firefox
-firefox-34.0.5
-firefox-with-plugins-34.0.5
-</pre><p>
-
-and using regular expressions:
-
-</p><pre class="screen">
-$ nix-env -qa 'firefox.*'
-</pre><p>
-
-</p><p>It is also possible to see the <span class="emphasis"><em>status</em></span> of
-available packages, i.e., whether they are installed into the user
-environment and/or present in the system:
-
-</p><pre class="screen">
-$ nix-env -qas
-…
--PS bash-3.0
---S binutils-2.15
-IPS bison-1.875d
-…</pre><p>
-
-The first character (<code class="literal">I</code>) indicates whether the
-package is installed in your current user environment. The second
-(<code class="literal">P</code>) indicates whether it is present on your system
-(in which case installing it into your user environment would be a
-very quick operation). The last one (<code class="literal">S</code>) indicates
-whether there is a so-called <span class="emphasis"><em>substitute</em></span> for the
-package, which is Nix’s mechanism for doing binary deployment. It
-just means that Nix knows that it can fetch a pre-built package from
-somewhere (typically a network server) instead of building it
-locally.</p><p>You can install a package using <code class="literal">nix-env -i</code>.
-For instance,
-
-</p><pre class="screen">
-$ nix-env -i subversion</pre><p>
-
-will install the package called <code class="literal">subversion</code> (which
-is, of course, the <a class="link" href="http://subversion.tigris.org/" target="_top">Subversion version
-management system</a>).</p><div class="note"><h3 class="title">Note</h3><p>When you ask Nix to install a package, it will first try
-to get it in pre-compiled form from a <span class="emphasis"><em>binary
-cache</em></span>. By default, Nix will use the binary cache
-<code class="uri">https://cache.nixos.org</code>; it contains binaries for most
-packages in Nixpkgs. Only if no binary is available in the binary
-cache, Nix will build the package from source. So if <code class="literal">nix-env
--i subversion</code> results in Nix building stuff from source,
-then either the package is not built for your platform by the Nixpkgs
-build servers, or your version of Nixpkgs is too old or too new. For
-instance, if you have a very recent checkout of Nixpkgs, then the
-Nixpkgs build servers may not have had a chance to build everything
-and upload the resulting binaries to
-<code class="uri">https://cache.nixos.org</code>. The Nixpkgs channel is only
-updated after all binaries have been uploaded to the cache, so if you
-stick to the Nixpkgs channel (rather than using a Git checkout of the
-Nixpkgs tree), you will get binaries for most packages.</p></div><p>Naturally, packages can also be uninstalled:
-
-</p><pre class="screen">
-$ nix-env -e subversion</pre><p>
-
-</p><p>Upgrading to a new version is just as easy. If you have a new
-release of Nix Packages, you can do:
-
-</p><pre class="screen">
-$ nix-env -u subversion</pre><p>
-
-This will <span class="emphasis"><em>only</em></span> upgrade Subversion if there is a
-“newer” version in the new set of Nix expressions, as
-defined by some pretty arbitrary rules regarding ordering of version
-numbers (which generally do what you’d expect of them). To just
-unconditionally replace Subversion with whatever version is in the Nix
-expressions, use <em class="parameter"><code>-i</code></em> instead of
-<em class="parameter"><code>-u</code></em>; <em class="parameter"><code>-i</code></em> will remove
-whatever version is already installed.</p><p>You can also upgrade all packages for which there are newer
-versions:
-
-</p><pre class="screen">
-$ nix-env -u</pre><p>
-
-</p><p>Sometimes it’s useful to be able to ask what
-<span class="command"><strong>nix-env</strong></span> would do, without actually doing it. For
-instance, to find out what packages would be upgraded by
-<code class="literal">nix-env -u</code>, you can do
-
-</p><pre class="screen">
-$ nix-env -u --dry-run
-(dry run; not doing anything)
-upgrading `libxslt-1.1.0' to `libxslt-1.1.10'
-upgrading `graphviz-1.10' to `graphviz-1.12'
-upgrading `coreutils-5.0' to `coreutils-5.2.1'</pre><p>
-
-</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="sec-profiles"></a>Chapter 10. Profiles</h2></div></div></div><p>Profiles and user environments are Nix’s mechanism for
-implementing the ability to allow different users to have different
-configurations, and to do atomic upgrades and rollbacks. To
-understand how they work, it’s useful to know a bit about how Nix
-works. In Nix, packages are stored in unique locations in the
-<span class="emphasis"><em>Nix store</em></span> (typically,
-<code class="filename">/nix/store</code>). For instance, a particular version
-of the Subversion package might be stored in a directory
-<code class="filename">/nix/store/dpmvp969yhdqs7lm2r1a3gng7pyq6vy4-subversion-1.1.3/</code>,
-while another version might be stored in
-<code class="filename">/nix/store/5mq2jcn36ldlmh93yj1n8s9c95pj7c5s-subversion-1.1.2</code>.
-The long strings prefixed to the directory names are cryptographic
-hashes<a href="#ftn.idm139733301692864" class="footnote" id="idm139733301692864"><sup class="footnote">[1]</sup></a> of
-<span class="emphasis"><em>all</em></span> inputs involved in building the package —
-sources, dependencies, compiler flags, and so on. So if two
-packages differ in any way, they end up in different locations in
-the file system, so they don’t interfere with each other. <a class="xref" href="#fig-user-environments" title="Figure 10.1. User environments">Figure 10.1, “User environments”</a> shows a part of a typical Nix
-store.</p><div class="figure"><a id="fig-user-environments"></a><p class="title"><strong>Figure 10.1. User environments</strong></p><div class="figure-contents"><div class="mediaobject"><img src="figures/user-environments.png" alt="User environments" /></div></div></div><br class="figure-break" /><p>Of course, you wouldn’t want to type
-
-</p><pre class="screen">
-$ /nix/store/dpmvp969yhdq...-subversion-1.1.3/bin/svn</pre><p>
-
-every time you want to run Subversion. Of course we could set up the
-<code class="envar">PATH</code> environment variable to include the
-<code class="filename">bin</code> directory of every package we want to use,
-but this is not very convenient since changing <code class="envar">PATH</code>
-doesn’t take effect for already existing processes. The solution Nix
-uses is to create directory trees of symlinks to
-<span class="emphasis"><em>activated</em></span> packages. These are called
-<span class="emphasis"><em>user environments</em></span> and they are packages
-themselves (though automatically generated by
-<span class="command"><strong>nix-env</strong></span>), so they too reside in the Nix store. For
-instance, in <a class="xref" href="#fig-user-environments" title="Figure 10.1. User environments">Figure 10.1, “User environments”</a> the user
-environment <code class="filename">/nix/store/0c1p5z4kda11...-user-env</code>
-contains a symlink to just Subversion 1.1.2 (arrows in the figure
-indicate symlinks). This would be what we would obtain if we had done
-
-</p><pre class="screen">
-$ nix-env -i subversion</pre><p>
-
-on a set of Nix expressions that contained Subversion 1.1.2.</p><p>This doesn’t in itself solve the problem, of course; you
-wouldn’t want to type
-<code class="filename">/nix/store/0c1p5z4kda11...-user-env/bin/svn</code>
-either. That’s why there are symlinks outside of the store that point
-to the user environments in the store; for instance, the symlinks
-<code class="filename">default-42-link</code> and
-<code class="filename">default-43-link</code> in the example. These are called
-<span class="emphasis"><em>generations</em></span> since every time you perform a
-<span class="command"><strong>nix-env</strong></span> operation, a new user environment is
-generated based on the current one. For instance, generation 43 was
-created from generation 42 when we did
-
-</p><pre class="screen">
-$ nix-env -i subversion firefox</pre><p>
-
-on a set of Nix expressions that contained Firefox and a new version
-of Subversion.</p><p>Generations are grouped together into
-<span class="emphasis"><em>profiles</em></span> so that different users don’t interfere
-with each other if they don’t want to. For example:
-
-</p><pre class="screen">
-$ ls -l /nix/var/nix/profiles/
-...
-lrwxrwxrwx 1 eelco ... default-42-link -> /nix/store/0c1p5z4kda11...-user-env
-lrwxrwxrwx 1 eelco ... default-43-link -> /nix/store/3aw2pdyx2jfc...-user-env
-lrwxrwxrwx 1 eelco ... default -> default-43-link</pre><p>
-
-This shows a profile called <code class="filename">default</code>. The file
-<code class="filename">default</code> itself is actually a symlink that points
-to the current generation. When we do a <span class="command"><strong>nix-env</strong></span>
-operation, a new user environment and generation link are created
-based on the current one, and finally the <code class="filename">default</code>
-symlink is made to point at the new generation. This last step is
-atomic on Unix, which explains how we can do atomic upgrades. (Note
-that the building/installing of new packages doesn’t interfere in
-any way with old packages, since they are stored in different
-locations in the Nix store.)</p><p>If you find that you want to undo a <span class="command"><strong>nix-env</strong></span>
-operation, you can just do
-
-</p><pre class="screen">
-$ nix-env --rollback</pre><p>
-
-which will just make the current generation link point at the previous
-link. E.g., <code class="filename">default</code> would be made to point at
-<code class="filename">default-42-link</code>. You can also switch to a
-specific generation:
-
-</p><pre class="screen">
-$ nix-env --switch-generation 43</pre><p>
-
-which in this example would roll forward to generation 43 again. You
-can also see all available generations:
-
-</p><pre class="screen">
-$ nix-env --list-generations</pre><p>You generally wouldn’t have
-<code class="filename">/nix/var/nix/profiles/<em class="replaceable"><code>some-profile</code></em>/bin</code>
-in your <code class="envar">PATH</code>. Rather, there is a symlink
-<code class="filename">~/.nix-profile</code> that points to your current
-profile. This means that you should put
-<code class="filename">~/.nix-profile/bin</code> in your <code class="envar">PATH</code>
-(and indeed, that’s what the initialisation script
-<code class="filename">/nix/etc/profile.d/nix.sh</code> does). This makes it
-easier to switch to a different profile. You can do that using the
-command <span class="command"><strong>nix-env --switch-profile</strong></span>:
-
-</p><pre class="screen">
-$ nix-env --switch-profile /nix/var/nix/profiles/my-profile
-
-$ nix-env --switch-profile /nix/var/nix/profiles/default</pre><p>
-
-These commands switch to the <code class="filename">my-profile</code> and
-default profile, respectively. If the profile doesn’t exist, it will
-be created automatically. You should be careful about storing a
-profile in another location than the <code class="filename">profiles</code>
-directory, since otherwise it might not be used as a root of the
-garbage collector (see <a class="xref" href="#sec-garbage-collection" title="Chapter 11. Garbage Collection">Chapter 11, <em>Garbage Collection</em></a>).</p><p>All <span class="command"><strong>nix-env</strong></span> operations work on the profile
-pointed to by <span class="command"><strong>~/.nix-profile</strong></span>, but you can override
-this using the <code class="option">--profile</code> option (abbreviation
-<code class="option">-p</code>):
-
-</p><pre class="screen">
-$ nix-env -p /nix/var/nix/profiles/other-profile -i subversion</pre><p>
-
-This will <span class="emphasis"><em>not</em></span> change the
-<span class="command"><strong>~/.nix-profile</strong></span> symlink.</p><div class="footnotes"><br /><hr style="width:100; text-align:left;margin-left: 0" /><div id="ftn.idm139733301692864" class="footnote"><p><a href="#idm139733301692864" class="para"><sup class="para">[1] </sup></a>160-bit truncations of SHA-256 hashes encoded in
-a base-32 notation, to be precise.</p></div></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="sec-garbage-collection"></a>Chapter 11. Garbage Collection</h2></div></div></div><p><span class="command"><strong>nix-env</strong></span> operations such as upgrades
-(<code class="option">-u</code>) and uninstall (<code class="option">-e</code>) never
-actually delete packages from the system. All they do (as shown
-above) is to create a new user environment that no longer contains
-symlinks to the “deleted” packages.</p><p>Of course, since disk space is not infinite, unused packages
-should be removed at some point. You can do this by running the Nix
-garbage collector. It will remove from the Nix store any package
-not used (directly or indirectly) by any generation of any
-profile.</p><p>Note however that as long as old generations reference a
-package, it will not be deleted. After all, we wouldn’t be able to
-do a rollback otherwise. So in order for garbage collection to be
-effective, you should also delete (some) old generations. Of course,
-this should only be done if you are certain that you will not need to
-roll back.</p><p>To delete all old (non-current) generations of your current
-profile:
-
-</p><pre class="screen">
-$ nix-env --delete-generations old</pre><p>
-
-Instead of <code class="literal">old</code> you can also specify a list of
-generations, e.g.,
-
-</p><pre class="screen">
-$ nix-env --delete-generations 10 11 14</pre><p>
-
-To delete all generations older than a specified number of days
-(except the current generation), use the <code class="literal">d</code>
-suffix. For example,
-
-</p><pre class="screen">
-$ nix-env --delete-generations 14d</pre><p>
-
-deletes all generations older than two weeks.</p><p>After removing appropriate old generations you can run the
-garbage collector as follows:
-
-</p><pre class="screen">
-$ nix-store --gc</pre><p>
-
-The behaviour of the gargage collector is affected by the
-<code class="literal">keep-derivations</code> (default: true) and <code class="literal">keep-outputs</code>
-(default: false) options in the Nix configuration file. The defaults will ensure
-that all derivations that are build-time dependencies of garbage collector roots
-will be kept and that all output paths that are runtime dependencies
-will be kept as well. All other derivations or paths will be collected.
-(This is usually what you want, but while you are developing
-it may make sense to keep outputs to ensure that rebuild times are quick.)
-
-If you are feeling uncertain, you can also first view what files would
-be deleted:
-
-</p><pre class="screen">
-$ nix-store --gc --print-dead</pre><p>
-
-Likewise, the option <code class="option">--print-live</code> will show the paths
-that <span class="emphasis"><em>won’t</em></span> be deleted.</p><p>There is also a convenient little utility
-<span class="command"><strong>nix-collect-garbage</strong></span>, which when invoked with the
-<code class="option">-d</code> (<code class="option">--delete-old</code>) switch deletes all
-old generations of all profiles in
-<code class="filename">/nix/var/nix/profiles</code>. So
-
-</p><pre class="screen">
-$ nix-collect-garbage -d</pre><p>
-
-is a quick and easy way to clean up your system.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-gc-roots"></a>11.1. Garbage Collector Roots</h2></div></div></div><p>The roots of the garbage collector are all store paths to which
-there are symlinks in the directory
-<code class="filename"><em class="replaceable"><code>prefix</code></em>/nix/var/nix/gcroots</code>.
-For instance, the following command makes the path
-<code class="filename">/nix/store/d718ef...-foo</code> a root of the collector:
-
-</p><pre class="screen">
-$ ln -s /nix/store/d718ef...-foo /nix/var/nix/gcroots/bar</pre><p>
-
-That is, after this command, the garbage collector will not remove
-<code class="filename">/nix/store/d718ef...-foo</code> or any of its
-dependencies.</p><p>Subdirectories of
-<code class="filename"><em class="replaceable"><code>prefix</code></em>/nix/var/nix/gcroots</code>
-are also searched for symlinks. Symlinks to non-store paths are
-followed and searched for roots, but symlinks to non-store paths
-<span class="emphasis"><em>inside</em></span> the paths reached in that way are not
-followed to prevent infinite recursion.</p></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="sec-channels"></a>Chapter 12. Channels</h2></div></div></div><p>If you want to stay up to date with a set of packages, it’s not
-very convenient to manually download the latest set of Nix expressions
-for those packages and upgrade using <span class="command"><strong>nix-env</strong></span>.
-Fortunately, there’s a better way: <span class="emphasis"><em>Nix
-channels</em></span>.</p><p>A Nix channel is just a URL that points to a place that contains
-a set of Nix expressions and a manifest. Using the command <a class="link" href="#sec-nix-channel" title="nix-channel"><span class="command"><strong>nix-channel</strong></span></a> you
-can automatically stay up to date with whatever is available at that
-URL.</p><p>To see the list of official NixOS channels, visit <a class="link" href="https://nixos.org/channels" target="_top">https://nixos.org/channels</a>.</p><p>You can “subscribe” to a channel using
-<span class="command"><strong>nix-channel --add</strong></span>, e.g.,
-
-</p><pre class="screen">
-$ nix-channel --add https://nixos.org/channels/nixpkgs-unstable</pre><p>
-
-subscribes you to a channel that always contains that latest version
-of the Nix Packages collection. (Subscribing really just means that
-the URL is added to the file <code class="filename">~/.nix-channels</code>,
-where it is read by subsequent calls to <span class="command"><strong>nix-channel
---update</strong></span>.) You can “unsubscribe” using <span class="command"><strong>nix-channel
---remove</strong></span>:
-
-</p><pre class="screen">
-$ nix-channel --remove nixpkgs
-</pre><p>
-</p><p>To obtain the latest Nix expressions available in a channel, do
-
-</p><pre class="screen">
-$ nix-channel --update</pre><p>
-
-This downloads and unpacks the Nix expressions in every channel
-(downloaded from <code class="literal"><em class="replaceable"><code>url</code></em>/nixexprs.tar.bz2</code>).
-It also makes the union of each channel’s Nix expressions available by
-default to <span class="command"><strong>nix-env</strong></span> operations (via the symlink
-<code class="filename">~/.nix-defexpr/channels</code>). Consequently, you can
-then say
-
-</p><pre class="screen">
-$ nix-env -u</pre><p>
-
-to upgrade all packages in your profile to the latest versions
-available in the subscribed channels.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="sec-sharing-packages"></a>Chapter 13. Sharing Packages Between Machines</h2></div></div></div><p>Sometimes you want to copy a package from one machine to
-another. Or, you want to install some packages and you know that
-another machine already has some or all of those packages or their
-dependencies. In that case there are mechanisms to quickly copy
-packages between machines.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-binary-cache-substituter"></a>13.1. Serving a Nix store via HTTP</h2></div></div></div><p>You can easily share the Nix store of a machine via HTTP. This
-allows other machines to fetch store paths from that machine to speed
-up installations. It uses the same <span class="emphasis"><em>binary cache</em></span>
-mechanism that Nix usually uses to fetch pre-built binaries from
-<code class="uri">https://cache.nixos.org</code>.</p><p>The daemon that handles binary cache requests via HTTP,
-<span class="command"><strong>nix-serve</strong></span>, is not part of the Nix distribution, but
-you can install it from Nixpkgs:
-
-</p><pre class="screen">
-$ nix-env -i nix-serve
-</pre><p>
-
-You can then start the server, listening for HTTP connections on
-whatever port you like:
-
-</p><pre class="screen">
-$ nix-serve -p 8080
-</pre><p>
-
-To check whether it works, try the following on the client:
-
-</p><pre class="screen">
-$ curl http://avalon:8080/nix-cache-info
-</pre><p>
-
-which should print something like:
-
-</p><pre class="screen">
-StoreDir: /nix/store
-WantMassQuery: 1
-Priority: 30
-</pre><p>
-
-</p><p>On the client side, you can tell Nix to use your binary cache
-using <code class="option">--option extra-binary-caches</code>, e.g.:
-
-</p><pre class="screen">
-$ nix-env -i firefox --option extra-binary-caches http://avalon:8080/
-</pre><p>
-
-The option <code class="option">extra-binary-caches</code> tells Nix to use this
-binary cache in addition to your default caches, such as
-<code class="uri">https://cache.nixos.org</code>. Thus, for any path in the closure
-of Firefox, Nix will first check if the path is available on the
-server <code class="literal">avalon</code> or another binary caches. If not, it
-will fall back to building from source.</p><p>You can also tell Nix to always use your binary cache by adding
-a line to the <code class="filename"><a class="filename" href="#sec-conf-file" title="nix.conf">nix.conf</a></code>
-configuration file like this:
-
-</p><pre class="programlisting">
-binary-caches = http://avalon:8080/ https://cache.nixos.org/
-</pre><p>
-
-</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-copy-closure"></a>13.2. Copying Closures Via SSH</h2></div></div></div><p>The command <span class="command"><strong><a class="command" href="#sec-nix-copy-closure" title="nix-copy-closure">nix-copy-closure</a></strong></span> copies a Nix
-store path along with all its dependencies to or from another machine
-via the SSH protocol. It doesn’t copy store paths that are already
-present on the target machine. For example, the following command
-copies Firefox with all its dependencies:
-
-</p><pre class="screen">
-$ nix-copy-closure --to alice@itchy.example.org $(type -p firefox)</pre><p>
-
-See <a class="xref" href="#sec-nix-copy-closure" title="nix-copy-closure"><span class="refentrytitle">nix-copy-closure</span>(1)</a> for details.</p><p>With <span class="command"><strong><a class="command" href="#refsec-nix-store-export" title="Operation --export">nix-store
---export</a></strong></span> and <span class="command"><strong><a class="command" href="#refsec-nix-store-import" title="Operation --import">nix-store --import</a></strong></span> you can
-write the closure of a store path (that is, the path and all its
-dependencies) to a file, and then unpack that file into another Nix
-store. For example,
-
-</p><pre class="screen">
-$ nix-store --export $(nix-store -qR $(type -p firefox)) > firefox.closure</pre><p>
-
-writes the closure of Firefox to a file. You can then copy this file
-to another machine and install the closure:
-
-</p><pre class="screen">
-$ nix-store --import < firefox.closure</pre><p>
-
-Any store paths in the closure that are already present in the target
-store are ignored. It is also possible to pipe the export into
-another command, e.g. to copy and install a closure directly to/on
-another machine:
-
-</p><pre class="screen">
-$ nix-store --export $(nix-store -qR $(type -p firefox)) | bzip2 | \
- ssh alice@itchy.example.org "bunzip2 | nix-store --import"</pre><p>
-
-However, <span class="command"><strong>nix-copy-closure</strong></span> is generally more
-efficient because it only copies paths that are not already present in
-the target Nix store.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-ssh-substituter"></a>13.3. Serving a Nix store via SSH</h2></div></div></div><p>You can tell Nix to automatically fetch needed binaries from a
-remote Nix store via SSH. For example, the following installs Firefox,
-automatically fetching any store paths in Firefox’s closure if they
-are available on the server <code class="literal">avalon</code>:
-
-</p><pre class="screen">
-$ nix-env -i firefox --substituters ssh://alice@avalon
-</pre><p>
-
-This works similar to the binary cache substituter that Nix usually
-uses, only using SSH instead of HTTP: if a store path
-<code class="literal">P</code> is needed, Nix will first check if it’s available
-in the Nix store on <code class="literal">avalon</code>. If not, it will fall
-back to using the binary cache substituter, and then to building from
-source.</p><div class="note"><h3 class="title">Note</h3><p>The SSH substituter currently does not allow you to enter
-an SSH passphrase interactively. Therefore, you should use
-<span class="command"><strong>ssh-add</strong></span> to load the decrypted private key into
-<span class="command"><strong>ssh-agent</strong></span>.</p></div><p>You can also copy the closure of some store path, without
-installing it into your profile, e.g.
-
-</p><pre class="screen">
-$ nix-store -r /nix/store/m85bxg…-firefox-34.0.5 --substituters ssh://alice@avalon
-</pre><p>
-
-This is essentially equivalent to doing
-
-</p><pre class="screen">
-$ nix-copy-closure --from alice@avalon /nix/store/m85bxg…-firefox-34.0.5
-</pre><p>
-
-</p><p>You can use SSH’s <span class="emphasis"><em>forced command</em></span> feature to
-set up a restricted user account for SSH substituter access, allowing
-read-only access to the local Nix store, but nothing more. For
-example, add the following lines to <code class="filename">sshd_config</code>
-to restrict the user <code class="literal">nix-ssh</code>:
-
-</p><pre class="programlisting">
-Match User nix-ssh
- AllowAgentForwarding no
- AllowTcpForwarding no
- PermitTTY no
- PermitTunnel no
- X11Forwarding no
- ForceCommand nix-store --serve
-Match All
-</pre><p>
-
-On NixOS, you can accomplish the same by adding the following to your
-<code class="filename">configuration.nix</code>:
-
-</p><pre class="programlisting">
-nix.sshServe.enable = true;
-nix.sshServe.keys = [ "ssh-dss AAAAB3NzaC1k... bob@example.org" ];
-</pre><p>
-
-where the latter line lists the public keys of users that are allowed
-to connect.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-s3-substituter"></a>13.4. Serving a Nix store via AWS S3 or S3-compatible Service</h2></div></div></div><p>Nix has built-in support for storing and fetching store paths
-from Amazon S3 and S3 compatible services. This uses the same
-<span class="emphasis"><em>binary</em></span> cache mechanism that Nix usually uses to
-fetch prebuilt binaries from <code class="uri">cache.nixos.org</code>.</p><p>The following options can be specified as URL parameters to
-the S3 URL:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">profile</code></span></dt><dd><p>
- The name of the AWS configuration profile to use. By default
- Nix will use the <code class="literal">default</code> profile.
- </p></dd><dt><span class="term"><code class="literal">region</code></span></dt><dd><p>
- The region of the S3 bucket. <code class="literal">us–east-1</code> by
- default.
- </p><p>
- If your bucket is not in <code class="literal">us–east-1</code>, you
- should always explicitly specify the region parameter.
- </p></dd><dt><span class="term"><code class="literal">endpoint</code></span></dt><dd><p>
- The URL to your S3-compatible service, for when not using
- Amazon S3. Do not specify this value if you're using Amazon
- S3.
- </p><div class="note"><h3 class="title">Note</h3><p>This endpoint must support HTTPS and will use
- path-based addressing instead of virtual host based
- addressing.</p></div></dd><dt><span class="term"><code class="literal">scheme</code></span></dt><dd><p>
- The scheme used for S3 requests, <code class="literal">https</code>
- (default) or <code class="literal">http</code>. This option allows you to
- disable HTTPS for binary caches which don't support it.
- </p><div class="note"><h3 class="title">Note</h3><p>HTTPS should be used if the cache might contain
- sensitive information.</p></div></dd></dl></div><p>In this example we will use the bucket named
-<code class="literal">example-nix-cache</code>.</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="ssec-s3-substituter-anonymous-reads"></a>13.4.1. Anonymous Reads to your S3-compatible binary cache</h3></div></div></div><p>If your binary cache is publicly accessible and does not
- require authentication, the simplest and easiest way to use Nix with
- your S3 compatible binary cache is to use the HTTP URL for that
- cache.</p><p>For AWS S3 the binary cache URL for example bucket will be
- exactly <code class="uri">https://example-nix-cache.s3.amazonaws.com</code> or
- <code class="uri">s3://example-nix-cache</code>. For S3 compatible binary caches,
- consult that cache's documentation.</p><p>Your bucket will need the following bucket policy:</p><pre class="programlisting">
-{
- "Id": "DirectReads",
- "Version": "2012-10-17",
- "Statement": [
- {
- "Sid": "AllowDirectReads",
- "Action": [
- "s3:GetObject",
- "s3:GetBucketLocation"
- ],
- "Effect": "Allow",
- "Resource": [
- "arn:aws:s3:::example-nix-cache",
- "arn:aws:s3:::example-nix-cache/*"
- ],
- "Principal": "*"
- }
- ]
-}
-</pre></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="ssec-s3-substituter-authenticated-reads"></a>13.4.2. Authenticated Reads to your S3 binary cache</h3></div></div></div><p>For AWS S3 the binary cache URL for example bucket will be
- exactly <code class="uri">s3://example-nix-cache</code>.</p><p>Nix will use the <a class="link" href="https://docs.aws.amazon.com/sdk-for-cpp/v1/developer-guide/credentials.html" target="_top">default
- credential provider chain</a> for authenticating requests to
- Amazon S3.</p><p>Nix supports authenticated reads from Amazon S3 and S3
- compatible binary caches.</p><p>Your bucket will need a bucket policy allowing the desired
- users to perform the <code class="literal">s3:GetObject</code> and
- <code class="literal">s3:GetBucketLocation</code> action on all objects in the
- bucket. The anonymous policy in <a class="xref" href="#ssec-s3-substituter-anonymous-reads" title="13.4.1. Anonymous Reads to your S3-compatible binary cache">Section 13.4.1, “Anonymous Reads to your S3-compatible binary cache”</a> can be updated to
- have a restricted <code class="literal">Principal</code> to support
- this.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="ssec-s3-substituter-authenticated-writes"></a>13.4.3. Authenticated Writes to your S3-compatible binary cache</h3></div></div></div><p>Nix support fully supports writing to Amazon S3 and S3
- compatible buckets. The binary cache URL for our example bucket will
- be <code class="uri">s3://example-nix-cache</code>.</p><p>Nix will use the <a class="link" href="https://docs.aws.amazon.com/sdk-for-cpp/v1/developer-guide/credentials.html" target="_top">default
- credential provider chain</a> for authenticating requests to
- Amazon S3.</p><p>Your account will need the following IAM policy to
- upload to the cache:</p><pre class="programlisting">
-{
- "Version": "2012-10-17",
- "Statement": [
- {
- "Sid": "UploadToCache",
- "Effect": "Allow",
- "Action": [
- "s3:AbortMultipartUpload",
- "s3:GetBucketLocation",
- "s3:GetObject",
- "s3:ListBucket",
- "s3:ListBucketMultipartUploads",
- "s3:ListMultipartUploadParts",
- "s3:PutObject"
- ],
- "Resource": [
- "arn:aws:s3:::example-nix-cache",
- "arn:aws:s3:::example-nix-cache/*"
- ]
- }
- ]
-}
-</pre><div class="example"><a id="idm139733301558256"></a><p class="title"><strong>Example 13.1. Uploading with a specific credential profile for Amazon S3</strong></p><div class="example-contents"><p><span class="command"><strong>nix copy --to 's3://example-nix-cache?profile=cache-upload&region=eu-west-2' nixpkgs.hello</strong></span></p></div></div><br class="example-break" /><div class="example"><a id="idm139733301556896"></a><p class="title"><strong>Example 13.2. Uploading to an S3-Compatible Binary Cache</strong></p><div class="example-contents"><p><span class="command"><strong>nix copy --to 's3://example-nix-cache?profile=cache-upload&scheme=https&endpoint=minio.example.com' nixpkgs.hello</strong></span></p></div></div><br class="example-break" /></div></div></div></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a id="chap-writing-nix-expressions"></a>Part IV. Writing Nix Expressions</h1></div></div></div><div class="partintro"><div></div><p>This chapter shows you how to write Nix expressions, which
-instruct Nix how to build packages. It starts with a
-simple example (a Nix expression for GNU Hello), and then moves
-on to a more in-depth look at the Nix expression language.</p><div class="note"><h3 class="title">Note</h3><p>This chapter is mostly about the Nix expression language.
-For more extensive information on adding packages to the Nix Packages
-collection (such as functions in the standard environment and coding
-conventions), please consult <a class="link" href="http://nixos.org/nixpkgs/manual/" target="_top">its
-manual</a>.</p></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-simple-expression"></a>Chapter 14. A Simple Nix Expression</h2></div></div></div><p>This section shows how to add and test the <a class="link" href="http://www.gnu.org/software/hello/hello.html" target="_top">GNU Hello
-package</a> to the Nix Packages collection. Hello is a program
-that prints out the text <span class="quote">“<span class="quote">Hello, world!</span>”</span>.</p><p>To add a package to the Nix Packages collection, you generally
-need to do three things:
-
-</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>Write a Nix expression for the package. This is a
- file that describes all the inputs involved in building the package,
- such as dependencies, sources, and so on.</p></li><li class="listitem"><p>Write a <span class="emphasis"><em>builder</em></span>. This is a
- shell script<a href="#ftn.idm139733301545648" class="footnote" id="idm139733301545648"><sup class="footnote">[2]</sup></a> that actually builds the package from
- the inputs.</p></li><li class="listitem"><p>Add the package to the file
- <code class="filename">pkgs/top-level/all-packages.nix</code>. The Nix
- expression written in the first step is a
- <span class="emphasis"><em>function</em></span>; it requires other packages in order
- to build it. In this step you put it all together, i.e., you call
- the function with the right arguments to build the actual
- package.</p></li></ol></div><p>
-
-</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-expression-syntax"></a>14.1. Expression Syntax</h2></div></div></div><div class="example"><a id="ex-hello-nix"></a><p class="title"><strong>Example 14.1. Nix expression for GNU Hello
-(<code class="filename">default.nix</code>)</strong></p><div class="example-contents"><pre class="programlisting">
-{ stdenv, fetchurl, perl }: <a id="ex-hello-nix-co-1"></a>(1)
-
-stdenv.mkDerivation { <a id="ex-hello-nix-co-2"></a>(2)
- name = "hello-2.1.1"; <a id="ex-hello-nix-co-3"></a>(3)
- builder = ./builder.sh; <a id="ex-hello-nix-co-4"></a>(4)
- src = fetchurl { <a id="ex-hello-nix-co-5"></a>(5)
- url = "ftp://ftp.nluug.nl/pub/gnu/hello/hello-2.1.1.tar.gz";
- sha256 = "1md7jsfd8pa45z73bz1kszpp01yw6x5ljkjk2hx7wl800any6465";
- };
- inherit perl; <a id="ex-hello-nix-co-6"></a>(6)
-}</pre></div></div><br class="example-break" /><p><a class="xref" href="#ex-hello-nix" title="Example 14.1. Nix expression for GNU Hello (default.nix)">Example 14.1, “Nix expression for GNU Hello
-(<code class="filename">default.nix</code>)”</a> shows a Nix expression for GNU
-Hello. It's actually already in the Nix Packages collection in
-<code class="filename">pkgs/applications/misc/hello/ex-1/default.nix</code>.
-It is customary to place each package in a separate directory and call
-the single Nix expression in that directory
-<code class="filename">default.nix</code>. The file has the following elements
-(referenced from the figure by number):
-
-</p><div class="calloutlist"><table border="0" summary="Callout list"><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-nix-co-1">(1)</a> </p></td><td valign="top" align="left"><p>This states that the expression is a
- <span class="emphasis"><em>function</em></span> that expects to be called with three
- arguments: <code class="varname">stdenv</code>, <code class="varname">fetchurl</code>,
- and <code class="varname">perl</code>. They are needed to build Hello, but
- we don't know how to build them here; that's why they are function
- arguments. <code class="varname">stdenv</code> is a package that is used
- by almost all Nix Packages packages; it provides a
- <span class="quote">“<span class="quote">standard</span>”</span> environment consisting of the things you
- would expect in a basic Unix environment: a C/C++ compiler (GCC,
- to be precise), the Bash shell, fundamental Unix tools such as
- <span class="command"><strong>cp</strong></span>, <span class="command"><strong>grep</strong></span>,
- <span class="command"><strong>tar</strong></span>, etc. <code class="varname">fetchurl</code> is a
- function that downloads files. <code class="varname">perl</code> is the
- Perl interpreter.</p><p>Nix functions generally have the form <code class="literal">{ x, y, ...,
- z }: e</code> where <code class="varname">x</code>, <code class="varname">y</code>,
- etc. are the names of the expected arguments, and where
- <em class="replaceable"><code>e</code></em> is the body of the function. So
- here, the entire remainder of the file is the body of the
- function; when given the required arguments, the body should
- describe how to build an instance of the Hello package.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-nix-co-2">(2)</a> </p></td><td valign="top" align="left"><p>So we have to build a package. Building something from
- other stuff is called a <span class="emphasis"><em>derivation</em></span> in Nix (as
- opposed to sources, which are built by humans instead of
- computers). We perform a derivation by calling
- <code class="varname">stdenv.mkDerivation</code>.
- <code class="varname">mkDerivation</code> is a function provided by
- <code class="varname">stdenv</code> that builds a package from a set of
- <span class="emphasis"><em>attributes</em></span>. A set is just a list of
- key/value pairs where each key is a string and each value is an
- arbitrary Nix expression. They take the general form <code class="literal">{
- <em class="replaceable"><code>name1</code></em> =
- <em class="replaceable"><code>expr1</code></em>; <em class="replaceable"><code>...</code></em>
- <em class="replaceable"><code>nameN</code></em> =
- <em class="replaceable"><code>exprN</code></em>; }</code>.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-nix-co-3">(3)</a> </p></td><td valign="top" align="left"><p>The attribute <code class="varname">name</code> specifies the symbolic
- name and version of the package. Nix doesn't really care about
- these things, but they are used by for instance <span class="command"><strong>nix-env
- -q</strong></span> to show a <span class="quote">“<span class="quote">human-readable</span>”</span> name for
- packages. This attribute is required by
- <code class="varname">mkDerivation</code>.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-nix-co-4">(4)</a> </p></td><td valign="top" align="left"><p>The attribute <code class="varname">builder</code> specifies the
- builder. This attribute can sometimes be omitted, in which case
- <code class="varname">mkDerivation</code> will fill in a default builder
- (which does a <code class="literal">configure; make; make install</code>, in
- essence). Hello is sufficiently simple that the default builder
- would suffice, but in this case, we will show an actual builder
- for educational purposes. The value
- <span class="command"><strong>./builder.sh</strong></span> refers to the shell script shown
- in <a class="xref" href="#ex-hello-builder" title="Example 14.2. Build script for GNU Hello (builder.sh)">Example 14.2, “Build script for GNU Hello
-(<code class="filename">builder.sh</code>)”</a>, discussed below.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-nix-co-5">(5)</a> </p></td><td valign="top" align="left"><p>The builder has to know what the sources of the package
- are. Here, the attribute <code class="varname">src</code> is bound to the
- result of a call to the <span class="command"><strong>fetchurl</strong></span> function.
- Given a URL and a SHA-256 hash of the expected contents of the file
- at that URL, this function builds a derivation that downloads the
- file and checks its hash. So the sources are a dependency that
- like all other dependencies is built before Hello itself is
- built.</p><p>Instead of <code class="varname">src</code> any other name could have
- been used, and in fact there can be any number of sources (bound
- to different attributes). However, <code class="varname">src</code> is
- customary, and it's also expected by the default builder (which we
- don't use in this example).</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-nix-co-6">(6)</a> </p></td><td valign="top" align="left"><p>Since the derivation requires Perl, we have to pass the
- value of the <code class="varname">perl</code> function argument to the
- builder. All attributes in the set are actually passed as
- environment variables to the builder, so declaring an attribute
-
- </p><pre class="programlisting">
-perl = perl;</pre><p>
-
- will do the trick: it binds an attribute <code class="varname">perl</code>
- to the function argument which also happens to be called
- <code class="varname">perl</code>. However, it looks a bit silly, so there
- is a shorter syntax. The <code class="literal">inherit</code> keyword
- causes the specified attributes to be bound to whatever variables
- with the same name happen to be in scope.</p></td></tr></table></div><p>
-
-</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-build-script"></a>14.2. Build Script</h2></div></div></div><div class="example"><a id="ex-hello-builder"></a><p class="title"><strong>Example 14.2. Build script for GNU Hello
-(<code class="filename">builder.sh</code>)</strong></p><div class="example-contents"><pre class="programlisting">
-source $stdenv/setup <a id="ex-hello-builder-co-1"></a>(1)
-
-PATH=$perl/bin:$PATH <a id="ex-hello-builder-co-2"></a>(2)
-
-tar xvfz $src <a id="ex-hello-builder-co-3"></a>(3)
-cd hello-*
-./configure --prefix=$out <a id="ex-hello-builder-co-4"></a>(4)
-make <a id="ex-hello-builder-co-5"></a>(5)
-make install</pre></div></div><br class="example-break" /><p><a class="xref" href="#ex-hello-builder" title="Example 14.2. Build script for GNU Hello (builder.sh)">Example 14.2, “Build script for GNU Hello
-(<code class="filename">builder.sh</code>)”</a> shows the builder referenced
-from Hello's Nix expression (stored in
-<code class="filename">pkgs/applications/misc/hello/ex-1/builder.sh</code>).
-The builder can actually be made a lot shorter by using the
-<span class="emphasis"><em>generic builder</em></span> functions provided by
-<code class="varname">stdenv</code>, but here we write out the build steps to
-elucidate what a builder does. It performs the following
-steps:</p><div class="calloutlist"><table border="0" summary="Callout list"><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-builder-co-1">(1)</a> </p></td><td valign="top" align="left"><p>When Nix runs a builder, it initially completely clears the
- environment (except for the attributes declared in the
- derivation). For instance, the <code class="envar">PATH</code> variable is
- empty<a href="#ftn.idm139733301492640" class="footnote" id="idm139733301492640"><sup class="footnote">[3]</sup></a>. This is done to prevent
- undeclared inputs from being used in the build process. If for
- example the <code class="envar">PATH</code> contained
- <code class="filename">/usr/bin</code>, then you might accidentally use
- <code class="filename">/usr/bin/gcc</code>.</p><p>So the first step is to set up the environment. This is
- done by calling the <code class="filename">setup</code> script of the
- standard environment. The environment variable
- <code class="envar">stdenv</code> points to the location of the standard
- environment being used. (It wasn't specified explicitly as an
- attribute in <a class="xref" href="#ex-hello-nix" title="Example 14.1. Nix expression for GNU Hello (default.nix)">Example 14.1, “Nix expression for GNU Hello
-(<code class="filename">default.nix</code>)”</a>, but
- <code class="varname">mkDerivation</code> adds it automatically.)</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-builder-co-2">(2)</a> </p></td><td valign="top" align="left"><p>Since Hello needs Perl, we have to make sure that Perl is in
- the <code class="envar">PATH</code>. The <code class="envar">perl</code> environment
- variable points to the location of the Perl package (since it
- was passed in as an attribute to the derivation), so
- <code class="filename"><em class="replaceable"><code>$perl</code></em>/bin</code> is the
- directory containing the Perl interpreter.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-builder-co-3">(3)</a> </p></td><td valign="top" align="left"><p>Now we have to unpack the sources. The
- <code class="varname">src</code> attribute was bound to the result of
- fetching the Hello source tarball from the network, so the
- <code class="envar">src</code> environment variable points to the location in
- the Nix store to which the tarball was downloaded. After
- unpacking, we <span class="command"><strong>cd</strong></span> to the resulting source
- directory.</p><p>The whole build is performed in a temporary directory
- created in <code class="varname">/tmp</code>, by the way. This directory is
- removed after the builder finishes, so there is no need to clean
- up the sources afterwards. Also, the temporary directory is
- always newly created, so you don't have to worry about files from
- previous builds interfering with the current build.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-builder-co-4">(4)</a> </p></td><td valign="top" align="left"><p>GNU Hello is a typical Autoconf-based package, so we first
- have to run its <code class="filename">configure</code> script. In Nix
- every package is stored in a separate location in the Nix store,
- for instance
- <code class="filename">/nix/store/9a54ba97fb71b65fda531012d0443ce2-hello-2.1.1</code>.
- Nix computes this path by cryptographically hashing all attributes
- of the derivation. The path is passed to the builder through the
- <code class="envar">out</code> environment variable. So here we give
- <code class="filename">configure</code> the parameter
- <code class="literal">--prefix=$out</code> to cause Hello to be installed in
- the expected location.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-builder-co-5">(5)</a> </p></td><td valign="top" align="left"><p>Finally we build Hello (<code class="literal">make</code>) and install
- it into the location specified by <code class="envar">out</code>
- (<code class="literal">make install</code>).</p></td></tr></table></div><p>If you are wondering about the absence of error checking on the
-result of various commands called in the builder: this is because the
-shell script is evaluated with Bash's <code class="option">-e</code> option,
-which causes the script to be aborted if any command fails without an
-error check.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-arguments"></a>14.3. Arguments and Variables</h2></div></div></div><div class="example"><a id="ex-hello-composition"></a><p class="title"><strong>Example 14.3. Composing GNU Hello
-(<code class="filename">all-packages.nix</code>)</strong></p><div class="example-contents"><pre class="programlisting">
-...
-
-rec { <a id="ex-hello-composition-co-1"></a>(1)
-
- hello = import ../applications/misc/hello/ex-1 <a id="ex-hello-composition-co-2"></a>(2) { <a id="ex-hello-composition-co-3"></a>(3)
- inherit fetchurl stdenv perl;
- };
-
- perl = import ../development/interpreters/perl { <a id="ex-hello-composition-co-4"></a>(4)
- inherit fetchurl stdenv;
- };
-
- fetchurl = import ../build-support/fetchurl {
- inherit stdenv; ...
- };
-
- stdenv = ...;
-
-}
-</pre></div></div><br class="example-break" /><p>The Nix expression in <a class="xref" href="#ex-hello-nix" title="Example 14.1. Nix expression for GNU Hello (default.nix)">Example 14.1, “Nix expression for GNU Hello
-(<code class="filename">default.nix</code>)”</a> is a
-function; it is missing some arguments that have to be filled in
-somewhere. In the Nix Packages collection this is done in the file
-<code class="filename">pkgs/top-level/all-packages.nix</code>, where all
-Nix expressions for packages are imported and called with the
-appropriate arguments. <a class="xref" href="#ex-hello-composition" title="Example 14.3. Composing GNU Hello (all-packages.nix)">Example 14.3, “Composing GNU Hello
-(<code class="filename">all-packages.nix</code>)”</a> shows
-some fragments of
-<code class="filename">all-packages.nix</code>.</p><div class="calloutlist"><table border="0" summary="Callout list"><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-composition-co-1">(1)</a> </p></td><td valign="top" align="left"><p>This file defines a set of attributes, all of which are
- concrete derivations (i.e., not functions). In fact, we define a
- <span class="emphasis"><em>mutually recursive</em></span> set of attributes. That
- is, the attributes can refer to each other. This is precisely
- what we want since we want to <span class="quote">“<span class="quote">plug</span>”</span> the
- various packages into each other.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-composition-co-2">(2)</a> </p></td><td valign="top" align="left"><p>Here we <span class="emphasis"><em>import</em></span> the Nix expression for
- GNU Hello. The import operation just loads and returns the
- specified Nix expression. In fact, we could just have put the
- contents of <a class="xref" href="#ex-hello-nix" title="Example 14.1. Nix expression for GNU Hello (default.nix)">Example 14.1, “Nix expression for GNU Hello
-(<code class="filename">default.nix</code>)”</a> in
- <code class="filename">all-packages.nix</code> at this point. That
- would be completely equivalent, but it would make the file rather
- bulky.</p><p>Note that we refer to
- <code class="filename">../applications/misc/hello/ex-1</code>, not
- <code class="filename">../applications/misc/hello/ex-1/default.nix</code>.
- When you try to import a directory, Nix automatically appends
- <code class="filename">/default.nix</code> to the file name.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-composition-co-3">(3)</a> </p></td><td valign="top" align="left"><p>This is where the actual composition takes place. Here we
- <span class="emphasis"><em>call</em></span> the function imported from
- <code class="filename">../applications/misc/hello/ex-1</code> with a set
- containing the things that the function expects, namely
- <code class="varname">fetchurl</code>, <code class="varname">stdenv</code>, and
- <code class="varname">perl</code>. We use inherit again to use the
- attributes defined in the surrounding scope (we could also have
- written <code class="literal">fetchurl = fetchurl;</code>, etc.).</p><p>The result of this function call is an actual derivation
- that can be built by Nix (since when we fill in the arguments of
- the function, what we get is its body, which is the call to
- <code class="varname">stdenv.mkDerivation</code> in <a class="xref" href="#ex-hello-nix" title="Example 14.1. Nix expression for GNU Hello (default.nix)">Example 14.1, “Nix expression for GNU Hello
-(<code class="filename">default.nix</code>)”</a>).</p><div class="note"><h3 class="title">Note</h3><p>Nixpkgs has a convenience function
- <code class="function">callPackage</code> that imports and calls a
- function, filling in any missing arguments by passing the
- corresponding attribute from the Nixpkgs set, like this:
-
-</p><pre class="programlisting">
-hello = callPackage ../applications/misc/hello/ex-1 { };
-</pre><p>
-
- If necessary, you can set or override arguments:
-
-</p><pre class="programlisting">
-hello = callPackage ../applications/misc/hello/ex-1 { stdenv = myStdenv; };
-</pre><p>
-
- </p></div></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-composition-co-4">(4)</a> </p></td><td valign="top" align="left"><p>Likewise, we have to instantiate Perl,
- <code class="varname">fetchurl</code>, and the standard environment.</p></td></tr></table></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-building-simple"></a>14.4. Building and Testing</h2></div></div></div><p>You can now try to build Hello. Of course, you could do
-<code class="literal">nix-env -i hello</code>, but you may not want to install a
-possibly broken package just yet. The best way to test the package is by
-using the command <span class="command"><strong><a class="command" href="#sec-nix-build" title="nix-build">nix-build</a></strong></span>,
-which builds a Nix expression and creates a symlink named
-<code class="filename">result</code> in the current directory:
-
-</p><pre class="screen">
-$ nix-build -A hello
-building path `/nix/store/632d2b22514d...-hello-2.1.1'
-hello-2.1.1/
-hello-2.1.1/intl/
-hello-2.1.1/intl/ChangeLog
-<em class="replaceable"><code>...</code></em>
-
-$ ls -l result
-lrwxrwxrwx ... 2006-09-29 10:43 result -> /nix/store/632d2b22514d...-hello-2.1.1
-
-$ ./result/bin/hello
-Hello, world!</pre><p>
-
-The <a class="link" href="#opt-attr"><code class="option">-A</code></a> option selects
-the <code class="literal">hello</code> attribute. This is faster than using the
-symbolic package name specified by the <code class="literal">name</code>
-attribute (which also happens to be <code class="literal">hello</code>) and is
-unambiguous (there can be multiple packages with the symbolic name
-<code class="literal">hello</code>, but there can be only one attribute in a set
-named <code class="literal">hello</code>).</p><p><span class="command"><strong>nix-build</strong></span> registers the
-<code class="filename">./result</code> symlink as a garbage collection root, so
-unless and until you delete the <code class="filename">./result</code> symlink,
-the output of the build will be safely kept on your system. You can
-use <span class="command"><strong>nix-build</strong></span>’s <code class="option"><a class="option" href="#opt-out-link">-o</a></code> switch to give the symlink another
-name.</p><p>Nix has transactional semantics. Once a build finishes
-successfully, Nix makes a note of this in its database: it registers
-that the path denoted by <code class="envar">out</code> is now
-<span class="quote">“<span class="quote">valid</span>”</span>. If you try to build the derivation again, Nix
-will see that the path is already valid and finish immediately. If a
-build fails, either because it returns a non-zero exit code, because
-Nix or the builder are killed, or because the machine crashes, then
-the output paths will not be registered as valid. If you try to build
-the derivation again, Nix will remove the output paths if they exist
-(e.g., because the builder died half-way through <code class="literal">make
-install</code>) and try again. Note that there is no
-<span class="quote">“<span class="quote">negative caching</span>”</span>: Nix doesn't remember that a build
-failed, and so a failed build can always be repeated. This is because
-Nix cannot distinguish between permanent failures (e.g., a compiler
-error due to a syntax error in the source) and transient failures
-(e.g., a disk full condition).</p><p>Nix also performs locking. If you run multiple Nix builds
-simultaneously, and they try to build the same derivation, the first
-Nix instance that gets there will perform the build, while the others
-block (or perform other derivations if available) until the build
-finishes:
-
-</p><pre class="screen">
-$ nix-build -A hello
-waiting for lock on `/nix/store/0h5b7hp8d4hqfrw8igvx97x1xawrjnac-hello-2.1.1x'</pre><p>
-
-So it is always safe to run multiple instances of Nix in parallel
-(which isn’t the case with, say, <span class="command"><strong>make</strong></span>).</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-generic-builder"></a>14.5. Generic Builder Syntax</h2></div></div></div><p>Recall from <a class="xref" href="#ex-hello-builder" title="Example 14.2. Build script for GNU Hello (builder.sh)">Example 14.2, “Build script for GNU Hello
-(<code class="filename">builder.sh</code>)”</a> that the builder
-looked something like this:
-
-</p><pre class="programlisting">
-PATH=$perl/bin:$PATH
-tar xvfz $src
-cd hello-*
-./configure --prefix=$out
-make
-make install</pre><p>
-
-The builders for almost all Unix packages look like this — set up some
-environment variables, unpack the sources, configure, build, and
-install. For this reason the standard environment provides some Bash
-functions that automate the build process. A builder using the
-generic build facilities in shown in <a class="xref" href="#ex-hello-builder2" title="Example 14.4. Build script using the generic build functions">Example 14.4, “Build script using the generic
-build functions”</a>.</p><div class="example"><a id="ex-hello-builder2"></a><p class="title"><strong>Example 14.4. Build script using the generic
-build functions</strong></p><div class="example-contents"><pre class="programlisting">
-buildInputs="$perl" <a id="ex-hello-builder2-co-1"></a>(1)
-
-source $stdenv/setup <a id="ex-hello-builder2-co-2"></a>(2)
-
-genericBuild <a id="ex-hello-builder2-co-3"></a>(3)</pre></div></div><br class="example-break" /><div class="calloutlist"><table border="0" summary="Callout list"><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-builder2-co-1">(1)</a> </p></td><td valign="top" align="left"><p>The <code class="envar">buildInputs</code> variable tells
- <code class="filename">setup</code> to use the indicated packages as
- <span class="quote">“<span class="quote">inputs</span>”</span>. This means that if a package provides a
- <code class="filename">bin</code> subdirectory, it's added to
- <code class="envar">PATH</code>; if it has a <code class="filename">include</code>
- subdirectory, it's added to GCC's header search path; and so
- on.<a href="#ftn.idm139733301420112" class="footnote" id="idm139733301420112"><sup class="footnote">[4]</sup></a>
- </p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-builder2-co-2">(2)</a> </p></td><td valign="top" align="left"><p>The function <code class="function">genericBuild</code> is defined in
- the file <code class="literal">$stdenv/setup</code>.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-hello-builder2-co-3">(3)</a> </p></td><td valign="top" align="left"><p>The final step calls the shell function
- <code class="function">genericBuild</code>, which performs the steps that
- were done explicitly in <a class="xref" href="#ex-hello-builder" title="Example 14.2. Build script for GNU Hello (builder.sh)">Example 14.2, “Build script for GNU Hello
-(<code class="filename">builder.sh</code>)”</a>. The
- generic builder is smart enough to figure out whether to unpack
- the sources using <span class="command"><strong>gzip</strong></span>,
- <span class="command"><strong>bzip2</strong></span>, etc. It can be customised in many ways;
- see the Nixpkgs manual for details.</p></td></tr></table></div><p>Discerning readers will note that the
-<code class="envar">buildInputs</code> could just as well have been set in the Nix
-expression, like this:
-
-</p><pre class="programlisting">
- buildInputs = [ perl ];</pre><p>
-
-The <code class="varname">perl</code> attribute can then be removed, and the
-builder becomes even shorter:
-
-</p><pre class="programlisting">
-source $stdenv/setup
-genericBuild</pre><p>
-
-In fact, <code class="varname">mkDerivation</code> provides a default builder
-that looks exactly like that, so it is actually possible to omit the
-builder for Hello entirely.</p></div><div class="footnotes"><br /><hr style="width:100; text-align:left;margin-left: 0" /><div id="ftn.idm139733301545648" class="footnote"><p><a href="#idm139733301545648" class="para"><sup class="para">[2] </sup></a>In fact, it can be written in any
- language, but typically it's a <span class="command"><strong>bash</strong></span> shell
- script.</p></div><div id="ftn.idm139733301492640" class="footnote"><p><a href="#idm139733301492640" class="para"><sup class="para">[3] </sup></a>Actually, it's initialised to
- <code class="filename">/path-not-set</code> to prevent Bash from setting it
- to a default value.</p></div><div id="ftn.idm139733301420112" class="footnote"><p><a href="#idm139733301420112" class="para"><sup class="para">[4] </sup></a>How does it work? <code class="filename">setup</code>
- tries to source the file
- <code class="filename"><em class="replaceable"><code>pkg</code></em>/nix-support/setup-hook</code>
- of all dependencies. These “setup hooks” can then set up whatever
- environment variables they want; for instance, the setup hook for
- Perl sets the <code class="envar">PERL5LIB</code> environment variable to
- contain the <code class="filename">lib/site_perl</code> directories of all
- inputs.</p></div></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-expression-language"></a>Chapter 15. Nix Expression Language</h2></div></div></div><p>The Nix expression language is a pure, lazy, functional
-language. Purity means that operations in the language don't have
-side-effects (for instance, there is no variable assignment).
-Laziness means that arguments to functions are evaluated only when
-they are needed. Functional means that functions are
-<span class="quote">“<span class="quote">normal</span>”</span> values that can be passed around and manipulated
-in interesting ways. The language is not a full-featured, general
-purpose language. Its main job is to describe packages,
-compositions of packages, and the variability within
-packages.</p><p>This section presents the various features of the
-language.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-values"></a>15.1. Values</h2></div></div></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301403360"></a>Simple Values</h3></div></div></div><p>Nix has the following basic data types:
-
-</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><span class="emphasis"><em>Strings</em></span> can be written in three
- ways.</p><p>The most common way is to enclose the string between double
- quotes, e.g., <code class="literal">"foo bar"</code>. Strings can span
- multiple lines. The special characters <code class="literal">"</code> and
- <code class="literal">\</code> and the character sequence
- <code class="literal">${</code> must be escaped by prefixing them with a
- backslash (<code class="literal">\</code>). Newlines, carriage returns and
- tabs can be written as <code class="literal">\n</code>,
- <code class="literal">\r</code> and <code class="literal">\t</code>,
- respectively.</p><p>You can include the result of an expression into a string by
- enclosing it in
- <code class="literal">${<em class="replaceable"><code>...</code></em>}</code>, a feature
- known as <span class="emphasis"><em>antiquotation</em></span>. The enclosed
- expression must evaluate to something that can be coerced into a
- string (meaning that it must be a string, a path, or a
- derivation). For instance, rather than writing
-
-</p><pre class="programlisting">
-"--with-freetype2-library=" + freetype + "/lib"</pre><p>
-
- (where <code class="varname">freetype</code> is a derivation), you can
- instead write the more natural
-
-</p><pre class="programlisting">
-"--with-freetype2-library=${freetype}/lib"</pre><p>
-
- The latter is automatically translated to the former. A more
- complicated example (from the Nix expression for <a class="link" href="http://www.trolltech.com/products/qt" target="_top">Qt</a>):
-
-</p><pre class="programlisting">
-configureFlags = "
- -system-zlib -system-libpng -system-libjpeg
- ${if openglSupport then "-dlopen-opengl
- -L${mesa}/lib -I${mesa}/include
- -L${libXmu}/lib -I${libXmu}/include" else ""}
- ${if threadSupport then "-thread" else "-no-thread"}
-";</pre><p>
-
- Note that Nix expressions and strings can be arbitrarily nested;
- in this case the outer string contains various antiquotations that
- themselves contain strings (e.g., <code class="literal">"-thread"</code>),
- some of which in turn contain expressions (e.g.,
- <code class="literal">${mesa}</code>).</p><p>The second way to write string literals is as an
- <span class="emphasis"><em>indented string</em></span>, which is enclosed between
- pairs of <span class="emphasis"><em>double single-quotes</em></span>, like so:
-
-</p><pre class="programlisting">
-''
- This is the first line.
- This is the second line.
- This is the third line.
-''</pre><p>
-
- This kind of string literal intelligently strips indentation from
- the start of each line. To be precise, it strips from each line a
- number of spaces equal to the minimal indentation of the string as
- a whole (disregarding the indentation of empty lines). For
- instance, the first and second line are indented two space, while
- the third line is indented four spaces. Thus, two spaces are
- stripped from each line, so the resulting string is
-
-</p><pre class="programlisting">
-"This is the first line.\nThis is the second line.\n This is the third line.\n"</pre><p>
-
- </p><p>Note that the whitespace and newline following the opening
- <code class="literal">''</code> is ignored if there is no non-whitespace
- text on the initial line.</p><p>Antiquotation
- (<code class="literal">${<em class="replaceable"><code>expr</code></em>}</code>) is
- supported in indented strings.</p><p>Since <code class="literal">${</code> and <code class="literal">''</code> have
- special meaning in indented strings, you need a way to quote them.
- <code class="literal">$</code> can be escaped by prefixing it with
- <code class="literal">''</code> (that is, two single quotes), i.e.,
- <code class="literal">''$</code>. <code class="literal">''</code> can be escaped by
- prefixing it with <code class="literal">'</code>, i.e.,
- <code class="literal">'''</code>. <code class="literal">$</code> removes any special meaning
- from the following <code class="literal">$</code>. Linefeed, carriage-return and tab
- characters can be written as <code class="literal">''\n</code>,
- <code class="literal">''\r</code>, <code class="literal">''\t</code>, and <code class="literal">''\</code>
- escapes any other character.
-
- </p><p>Indented strings are primarily useful in that they allow
- multi-line string literals to follow the indentation of the
- enclosing Nix expression, and that less escaping is typically
- necessary for strings representing languages such as shell scripts
- and configuration files because <code class="literal">''</code> is much less
- common than <code class="literal">"</code>. Example:
-
-</p><pre class="programlisting">
-stdenv.mkDerivation {
- <em class="replaceable"><code>...</code></em>
- postInstall =
- ''
- mkdir $out/bin $out/etc
- cp foo $out/bin
- echo "Hello World" > $out/etc/foo.conf
- ${if enableBar then "cp bar $out/bin" else ""}
- '';
- <em class="replaceable"><code>...</code></em>
-}
-</pre><p>
-
- </p><p>Finally, as a convenience, <span class="emphasis"><em>URIs</em></span> as
- defined in appendix B of <a class="link" href="http://www.ietf.org/rfc/rfc2396.txt" target="_top">RFC 2396</a>
- can be written <span class="emphasis"><em>as is</em></span>, without quotes. For
- instance, the string
- <code class="literal">"http://example.org/foo.tar.bz2"</code>
- can also be written as
- <code class="literal">http://example.org/foo.tar.bz2</code>.</p></li><li class="listitem"><p>Numbers, which can be <span class="emphasis"><em>integers</em></span> (like
- <code class="literal">123</code>) or <span class="emphasis"><em>floating point</em></span> (like
- <code class="literal">123.43</code> or <code class="literal">.27e13</code>).</p><p>Numbers are type-compatible: pure integer operations will always
- return integers, whereas any operation involving at least one floating point
- number will have a floating point number as a result.</p></li><li class="listitem"><p><span class="emphasis"><em>Paths</em></span>, e.g.,
- <code class="filename">/bin/sh</code> or <code class="filename">./builder.sh</code>.
- A path must contain at least one slash to be recognised as such; for
- instance, <code class="filename">builder.sh</code> is not a
- path<a href="#ftn.idm139733301368560" class="footnote" id="idm139733301368560"><sup class="footnote">[5]</sup></a>. If the file name is
- relative, i.e., if it does not begin with a slash, it is made
- absolute at parse time relative to the directory of the Nix
- expression that contained it. For instance, if a Nix expression in
- <code class="filename">/foo/bar/bla.nix</code> refers to
- <code class="filename">../xyzzy/fnord.nix</code>, the absolute path is
- <code class="filename">/foo/xyzzy/fnord.nix</code>.</p><p>If the first component of a path is a <code class="literal">~</code>,
- it is interpreted as if the rest of the path were relative to the
- user's home directory. e.g. <code class="filename">~/foo</code> would be
- equivalent to <code class="filename">/home/edolstra/foo</code> for a user
- whose home directory is <code class="filename">/home/edolstra</code>.
- </p><p>Paths can also be specified between angle brackets, e.g.
- <code class="literal"><nixpkgs></code>. This means that the directories
- listed in the environment variable
- <code class="envar"><a class="envar" href="#env-NIX_PATH">NIX_PATH</a></code> will be searched
- for the given file or directory name.
- </p></li><li class="listitem"><p><span class="emphasis"><em>Booleans</em></span> with values
- <code class="literal">true</code> and
- <code class="literal">false</code>.</p></li><li class="listitem"><p>The null value, denoted as
- <code class="literal">null</code>.</p></li></ul></div><p>
-
-</p></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301358208"></a>Lists</h3></div></div></div><p>Lists are formed by enclosing a whitespace-separated list of
-values between square brackets. For example,
-
-</p><pre class="programlisting">
-[ 123 ./foo.nix "abc" (f { x = y; }) ]</pre><p>
-
-defines a list of four elements, the last being the result of a call
-to the function <code class="varname">f</code>. Note that function calls have
-to be enclosed in parentheses. If they had been omitted, e.g.,
-
-</p><pre class="programlisting">
-[ 123 ./foo.nix "abc" f { x = y; } ]</pre><p>
-
-the result would be a list of five elements, the fourth one being a
-function and the fifth being a set.</p><p>Note that lists are only lazy in values, and they are strict in length.
-</p></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301354960"></a>Sets</h3></div></div></div><p>Sets are really the core of the language, since ultimately the
-Nix language is all about creating derivations, which are really just
-sets of attributes to be passed to build scripts.</p><p>Sets are just a list of name/value pairs (called
-<span class="emphasis"><em>attributes</em></span>) enclosed in curly brackets, where
-each value is an arbitrary expression terminated by a semicolon. For
-example:
-
-</p><pre class="programlisting">
-{ x = 123;
- text = "Hello";
- y = f { bla = 456; };
-}</pre><p>
-
-This defines a set with attributes named <code class="varname">x</code>,
-<code class="varname">text</code>, <code class="varname">y</code>. The order of the
-attributes is irrelevant. An attribute name may only occur
-once.</p><p>Attributes can be selected from a set using the
-<code class="literal">.</code> operator. For instance,
-
-</p><pre class="programlisting">
-{ a = "Foo"; b = "Bar"; }.a</pre><p>
-
-evaluates to <code class="literal">"Foo"</code>. It is possible to provide a
-default value in an attribute selection using the
-<code class="literal">or</code> keyword. For example,
-
-</p><pre class="programlisting">
-{ a = "Foo"; b = "Bar"; }.c or "Xyzzy"</pre><p>
-
-will evaluate to <code class="literal">"Xyzzy"</code> because there is no
-<code class="varname">c</code> attribute in the set.</p><p>You can use arbitrary double-quoted strings as attribute
-names:
-
-</p><pre class="programlisting">
-{ "foo ${bar}" = 123; "nix-1.0" = 456; }."foo ${bar}"
-</pre><p>
-
-This will evaluate to <code class="literal">123</code> (Assuming
-<code class="literal">bar</code> is antiquotable). In the case where an
-attribute name is just a single antiquotation, the quotes can be
-dropped:
-
-</p><pre class="programlisting">
-{ foo = 123; }.${bar} or 456 </pre><p>
-
-This will evaluate to <code class="literal">123</code> if
-<code class="literal">bar</code> evaluates to <code class="literal">"foo"</code> when
-coerced to a string and <code class="literal">456</code> otherwise (again
-assuming <code class="literal">bar</code> is antiquotable).</p><p>In the special case where an attribute name inside of a set declaration
-evaluates to <code class="literal">null</code> (which is normally an error, as
-<code class="literal">null</code> is not antiquotable), that attribute is simply not
-added to the set:
-
-</p><pre class="programlisting">
-{ ${if foo then "bar" else null} = true; }</pre><p>
-
-This will evaluate to <code class="literal">{}</code> if <code class="literal">foo</code>
-evaluates to <code class="literal">false</code>.</p><p>A set that has a <code class="literal">__functor</code> attribute whose value
-is callable (i.e. is itself a function or a set with a
-<code class="literal">__functor</code> attribute whose value is callable) can be
-applied as if it were a function, with the set itself passed in first
-, e.g.,
-
-</p><pre class="programlisting">
-let add = { __functor = self: x: x + self.x; };
- inc = add // { x = 1; };
-in inc 1
-</pre><p>
-
-evaluates to <code class="literal">2</code>. This can be used to attach metadata to a
-function without the caller needing to treat it specially, or to implement
-a form of object-oriented programming, for example.
-
-</p></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-constructs"></a>15.2. Language Constructs</h2></div></div></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301335376"></a>Recursive sets</h3></div></div></div><p>Recursive sets are just normal sets, but the attributes can
-refer to each other. For example,
-
-</p><pre class="programlisting">
-rec {
- x = y;
- y = 123;
-}.x
-</pre><p>
-
-evaluates to <code class="literal">123</code>. Note that without
-<code class="literal">rec</code> the binding <code class="literal">x = y;</code> would
-refer to the variable <code class="varname">y</code> in the surrounding scope,
-if one exists, and would be invalid if no such variable exists. That
-is, in a normal (non-recursive) set, attributes are not added to the
-lexical scope; in a recursive set, they are.</p><p>Recursive sets of course introduce the danger of infinite
-recursion. For example,
-
-</p><pre class="programlisting">
-rec {
- x = y;
- y = x;
-}.x</pre><p>
-
-does not terminate<a href="#ftn.idm139733301331328" class="footnote" id="idm139733301331328"><sup class="footnote">[6]</sup></a>.</p></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="sect-let-expressions"></a>Let-expressions</h3></div></div></div><p>A let-expression allows you to define local variables for an
-expression. For instance,
-
-</p><pre class="programlisting">
-let
- x = "foo";
- y = "bar";
-in x + y</pre><p>
-
-evaluates to <code class="literal">"foobar"</code>.
-
-</p></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301327568"></a>Inheriting attributes</h3></div></div></div><p>When defining a set or in a let-expression it is often convenient to copy variables
-from the surrounding lexical scope (e.g., when you want to propagate
-attributes). This can be shortened using the
-<code class="literal">inherit</code> keyword. For instance,
-
-</p><pre class="programlisting">
-let x = 123; in
-{ inherit x;
- y = 456;
-}</pre><p>
-
-is equivalent to
-
-</p><pre class="programlisting">
-let x = 123; in
-{ x = x;
- y = 456;
-}</pre><p>
-
-and both evaluate to <code class="literal">{ x = 123; y = 456; }</code>. (Note that
-this works because <code class="varname">x</code> is added to the lexical scope
-by the <code class="literal">let</code> construct.) It is also possible to
-inherit attributes from another set. For instance, in this fragment
-from <code class="filename">all-packages.nix</code>,
-
-</p><pre class="programlisting">
- graphviz = (import ../tools/graphics/graphviz) {
- inherit fetchurl stdenv libpng libjpeg expat x11 yacc;
- inherit (xlibs) libXaw;
- };
-
- xlibs = {
- libX11 = ...;
- libXaw = ...;
- ...
- }
-
- libpng = ...;
- libjpg = ...;
- ...</pre><p>
-
-the set used in the function call to the function defined in
-<code class="filename">../tools/graphics/graphviz</code> inherits a number of
-variables from the surrounding scope (<code class="varname">fetchurl</code>
-... <code class="varname">yacc</code>), but also inherits
-<code class="varname">libXaw</code> (the X Athena Widgets) from the
-<code class="varname">xlibs</code> (X11 client-side libraries) set.</p><p>
-Summarizing the fragment
-
-</p><pre class="programlisting">
-...
-inherit x y z;
-inherit (src-set) a b c;
-...</pre><p>
-
-is equivalent to
-
-</p><pre class="programlisting">
-...
-x = x; y = y; z = z;
-a = src-set.a; b = src-set.b; c = src-set.c;
-...</pre><p>
-
-when used while defining local variables in a let-expression or
-while defining a set.</p></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="ss-functions"></a>Functions</h3></div></div></div><p>Functions have the following form:
-
-</p><pre class="programlisting">
-<em class="replaceable"><code>pattern</code></em>: <em class="replaceable"><code>body</code></em></pre><p>
-
-The pattern specifies what the argument of the function must look
-like, and binds variables in the body to (parts of) the
-argument. There are three kinds of patterns:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>If a pattern is a single identifier, then the
- function matches any argument. Example:
-
- </p><pre class="programlisting">
-let negate = x: !x;
- concat = x: y: x + y;
-in if negate true then concat "foo" "bar" else ""</pre><p>
-
- Note that <code class="function">concat</code> is a function that takes one
- argument and returns a function that takes another argument. This
- allows partial parameterisation (i.e., only filling some of the
- arguments of a function); e.g.,
-
- </p><pre class="programlisting">
-map (concat "foo") [ "bar" "bla" "abc" ]</pre><p>
-
- evaluates to <code class="literal">[ "foobar" "foobla"
- "fooabc" ]</code>.</p></li><li class="listitem"><p>A <span class="emphasis"><em>set pattern</em></span> of the form
- <code class="literal">{ name1, name2, …, nameN }</code> matches a set
- containing the listed attributes, and binds the values of those
- attributes to variables in the function body. For example, the
- function
-
-</p><pre class="programlisting">
-{ x, y, z }: z + y + x</pre><p>
-
- can only be called with a set containing exactly the attributes
- <code class="varname">x</code>, <code class="varname">y</code> and
- <code class="varname">z</code>. No other attributes are allowed. If you want
- to allow additional arguments, you can use an ellipsis
- (<code class="literal">...</code>):
-
-</p><pre class="programlisting">
-{ x, y, z, ... }: z + y + x</pre><p>
-
- This works on any set that contains at least the three named
- attributes.</p><p>It is possible to provide <span class="emphasis"><em>default values</em></span>
- for attributes, in which case they are allowed to be missing. A
- default value is specified by writing
- <code class="literal"><em class="replaceable"><code>name</code></em> ?
- <em class="replaceable"><code>e</code></em></code>, where
- <em class="replaceable"><code>e</code></em> is an arbitrary expression. For example,
-
-</p><pre class="programlisting">
-{ x, y ? "foo", z ? "bar" }: z + y + x</pre><p>
-
- specifies a function that only requires an attribute named
- <code class="varname">x</code>, but optionally accepts <code class="varname">y</code>
- and <code class="varname">z</code>.</p></li><li class="listitem"><p>An <code class="literal">@</code>-pattern provides a means of referring
- to the whole value being matched:
-
-</p><pre class="programlisting"> args@{ x, y, z, ... }: z + y + x + args.a</pre><p>
-
-but can also be written as:
-
-</p><pre class="programlisting"> { x, y, z, ... } @ args: z + y + x + args.a</pre><p>
-
- Here <code class="varname">args</code> is bound to the entire argument, which
- is further matched against the pattern <code class="literal">{ x, y, z,
- ... }</code>. <code class="literal">@</code>-pattern makes mainly sense with an
- ellipsis(<code class="literal">...</code>) as you can access attribute names as
- <code class="literal">a</code>, using <code class="literal">args.a</code>, which was given as an
- additional attribute to the function.
- </p><div class="warning"><h3 class="title">Warning</h3><p>
- The <code class="literal">args@</code> expression is bound to the argument passed to the function which
- means that attributes with defaults that aren't explicitly specified in the function call
- won't cause an evaluation error, but won't exist in <code class="literal">args</code>.
- </p><p>
- For instance
-</p><pre class="programlisting">
-let
- function = args@{ a ? 23, ... }: args;
-in
- function {}
-</pre><p>
- will evaluate to an empty attribute set.
- </p></div></li></ul></div><p>Note that functions do not have names. If you want to give them
-a name, you can bind them to an attribute, e.g.,
-
-</p><pre class="programlisting">
-let concat = { x, y }: x + y;
-in concat { x = "foo"; y = "bar"; }</pre><p>
-
-</p></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301295536"></a>Conditionals</h3></div></div></div><p>Conditionals look like this:
-
-</p><pre class="programlisting">
-if <em class="replaceable"><code>e1</code></em> then <em class="replaceable"><code>e2</code></em> else <em class="replaceable"><code>e3</code></em></pre><p>
-
-where <em class="replaceable"><code>e1</code></em> is an expression that should
-evaluate to a Boolean value (<code class="literal">true</code> or
-<code class="literal">false</code>).</p></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301291568"></a>Assertions</h3></div></div></div><p>Assertions are generally used to check that certain requirements
-on or between features and dependencies hold. They look like this:
-
-</p><pre class="programlisting">
-assert <em class="replaceable"><code>e1</code></em>; <em class="replaceable"><code>e2</code></em></pre><p>
-
-where <em class="replaceable"><code>e1</code></em> is an expression that should
-evaluate to a Boolean value. If it evaluates to
-<code class="literal">true</code>, <em class="replaceable"><code>e2</code></em> is returned;
-otherwise expression evaluation is aborted and a backtrace is printed.</p><div class="example"><a id="ex-subversion-nix"></a><p class="title"><strong>Example 15.1. Nix expression for Subversion</strong></p><div class="example-contents"><pre class="programlisting">
-{ localServer ? false
-, httpServer ? false
-, sslSupport ? false
-, pythonBindings ? false
-, javaSwigBindings ? false
-, javahlBindings ? false
-, stdenv, fetchurl
-, openssl ? null, httpd ? null, db4 ? null, expat, swig ? null, j2sdk ? null
-}:
-
-assert localServer -> db4 != null; <a id="ex-subversion-nix-co-1"></a>(1)
-assert httpServer -> httpd != null && httpd.expat == expat; <a id="ex-subversion-nix-co-2"></a>(2)
-assert sslSupport -> openssl != null && (httpServer -> httpd.openssl == openssl); <a id="ex-subversion-nix-co-3"></a>(3)
-assert pythonBindings -> swig != null && swig.pythonSupport;
-assert javaSwigBindings -> swig != null && swig.javaSupport;
-assert javahlBindings -> j2sdk != null;
-
-stdenv.mkDerivation {
- name = "subversion-1.1.1";
- ...
- openssl = if sslSupport then openssl else null; <a id="ex-subversion-nix-co-4"></a>(4)
- ...
-}</pre></div></div><br class="example-break" /><p><a class="xref" href="#ex-subversion-nix" title="Example 15.1. Nix expression for Subversion">Example 15.1, “Nix expression for Subversion”</a> show how assertions are
-used in the Nix expression for Subversion.</p><div class="calloutlist"><table border="0" summary="Callout list"><tr><td width="5%" valign="top" align="left"><p><a href="#ex-subversion-nix-co-1">(1)</a> </p></td><td valign="top" align="left"><p>This assertion states that if Subversion is to have support
- for local repositories, then Berkeley DB is needed. So if the
- Subversion function is called with the
- <code class="varname">localServer</code> argument set to
- <code class="literal">true</code> but the <code class="varname">db4</code> argument
- set to <code class="literal">null</code>, then the evaluation fails.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-subversion-nix-co-2">(2)</a> </p></td><td valign="top" align="left"><p>This is a more subtle condition: if Subversion is built with
- Apache (<code class="literal">httpServer</code>) support, then the Expat
- library (an XML library) used by Subversion should be same as the
- one used by Apache. This is because in this configuration
- Subversion code ends up being linked with Apache code, and if the
- Expat libraries do not match, a build- or runtime link error or
- incompatibility might occur.</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-subversion-nix-co-3">(3)</a> </p></td><td valign="top" align="left"><p>This assertion says that in order for Subversion to have SSL
- support (so that it can access <code class="literal">https</code> URLs), an
- OpenSSL library must be passed. Additionally, it says that
- <span class="emphasis"><em>if</em></span> Apache support is enabled, then Apache's
- OpenSSL should match Subversion's. (Note that if Apache support
- is not enabled, we don't care about Apache's OpenSSL.)</p></td></tr><tr><td width="5%" valign="top" align="left"><p><a href="#ex-subversion-nix-co-4">(4)</a> </p></td><td valign="top" align="left"><p>The conditional here is not really related to assertions,
- but is worth pointing out: it ensures that if SSL support is
- disabled, then the Subversion derivation is not dependent on
- OpenSSL, even if a non-<code class="literal">null</code> value was passed.
- This prevents an unnecessary rebuild of Subversion if OpenSSL
- changes.</p></td></tr></table></div></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301272384"></a>With-expressions</h3></div></div></div><p>A <span class="emphasis"><em>with-expression</em></span>,
-
-</p><pre class="programlisting">
-with <em class="replaceable"><code>e1</code></em>; <em class="replaceable"><code>e2</code></em></pre><p>
-
-introduces the set <em class="replaceable"><code>e1</code></em> into the lexical
-scope of the expression <em class="replaceable"><code>e2</code></em>. For instance,
-
-</p><pre class="programlisting">
-let as = { x = "foo"; y = "bar"; };
-in with as; x + y</pre><p>
-
-evaluates to <code class="literal">"foobar"</code> since the
-<code class="literal">with</code> adds the <code class="varname">x</code> and
-<code class="varname">y</code> attributes of <code class="varname">as</code> to the
-lexical scope in the expression <code class="literal">x + y</code>. The most
-common use of <code class="literal">with</code> is in conjunction with the
-<code class="function">import</code> function. E.g.,
-
-</p><pre class="programlisting">
-with (import ./definitions.nix); ...</pre><p>
-
-makes all attributes defined in the file
-<code class="filename">definitions.nix</code> available as if they were defined
-locally in a <code class="literal">let</code>-expression.</p><p>The bindings introduced by <code class="literal">with</code> do not shadow bindings
-introduced by other means, e.g.
-
-</p><pre class="programlisting">
-let a = 3; in with { a = 1; }; let a = 4; in with { a = 2; }; ...</pre><p>
-
-establishes the same scope as
-
-</p><pre class="programlisting">
-let a = 1; in let a = 2; in let a = 3; in let a = 4; in ...</pre><p>
-
-</p></div><div class="simplesect"><div class="titlepage"><div><div><h3 class="title"><a id="idm139733301261632"></a>Comments</h3></div></div></div><p>Comments can be single-line, started with a <code class="literal">#</code>
-character, or inline/multi-line, enclosed within <code class="literal">/*
-... */</code>.</p></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="sec-language-operators"></a>15.3. Operators</h2></div></div></div><p><a class="xref" href="#table-operators" title="Table 15.1. Operators">Table 15.1, “Operators”</a> lists the operators in the
-Nix expression language, in order of precedence (from strongest to
-weakest binding).</p><div class="table"><a id="table-operators"></a><p class="title"><strong>Table 15.1. Operators</strong></p><div class="table-contents"><table class="table" summary="Operators" border="1"><colgroup><col /><col /><col /></colgroup><thead><tr><th>Name</th><th>Syntax</th><th>Associativity</th><th>Description</th><th>Precedence</th></tr></thead><tbody><tr><td>Select</td><td><em class="replaceable"><code>e</code></em> <code class="literal">.</code>
- <em class="replaceable"><code>attrpath</code></em>
- [ <code class="literal">or</code> <em class="replaceable"><code>def</code></em> ]
- </td><td>none</td><td>Select attribute denoted by the attribute path
- <em class="replaceable"><code>attrpath</code></em> from set
- <em class="replaceable"><code>e</code></em>. (An attribute path is a
- dot-separated list of attribute names.) If the attribute
- doesn’t exist, return <em class="replaceable"><code>def</code></em> if
- provided, otherwise abort evaluation.</td><td>1</td></tr><tr><td>Application</td><td><em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></td><td>left</td><td>Call function <em class="replaceable"><code>e1</code></em> with
- argument <em class="replaceable"><code>e2</code></em>.</td><td>2</td></tr><tr><td>Arithmetic Negation</td><td><code class="literal">-</code> <em class="replaceable"><code>e</code></em></td><td>none</td><td>Arithmetic negation.</td><td>3</td></tr><tr><td>Has Attribute</td><td><em class="replaceable"><code>e</code></em> <code class="literal">?</code>
- <em class="replaceable"><code>attrpath</code></em></td><td>none</td><td>Test whether set <em class="replaceable"><code>e</code></em> contains
- the attribute denoted by <em class="replaceable"><code>attrpath</code></em>;
- return <code class="literal">true</code> or
- <code class="literal">false</code>.</td><td>4</td></tr><tr><td>List Concatenation</td><td><em class="replaceable"><code>e1</code></em> <code class="literal">++</code> <em class="replaceable"><code>e2</code></em></td><td>right</td><td>List concatenation.</td><td>5</td></tr><tr><td>Multiplication</td><td>
- <em class="replaceable"><code>e1</code></em> <code class="literal">*</code> <em class="replaceable"><code>e2</code></em>,
- </td><td>left</td><td>Arithmetic multiplication.</td><td>6</td></tr><tr><td>Division</td><td>
- <em class="replaceable"><code>e1</code></em> <code class="literal">/</code> <em class="replaceable"><code>e2</code></em>
- </td><td>left</td><td>Arithmetic division.</td><td>6</td></tr><tr><td>Addition</td><td>
- <em class="replaceable"><code>e1</code></em> <code class="literal">+</code> <em class="replaceable"><code>e2</code></em>
- </td><td>left</td><td>Arithmetic addition.</td><td>7</td></tr><tr><td>Subtraction</td><td>
- <em class="replaceable"><code>e1</code></em> <code class="literal">-</code> <em class="replaceable"><code>e2</code></em>
- </td><td>left</td><td>Arithmetic subtraction.</td><td>7</td></tr><tr><td>String Concatenation</td><td>
- <em class="replaceable"><code>string1</code></em> <code class="literal">+</code> <em class="replaceable"><code>string2</code></em>
- </td><td>left</td><td>String concatenation.</td><td>7</td></tr><tr><td>Not</td><td><code class="literal">!</code> <em class="replaceable"><code>e</code></em></td><td>none</td><td>Boolean negation.</td><td>8</td></tr><tr><td>Update</td><td><em class="replaceable"><code>e1</code></em> <code class="literal">//</code>
- <em class="replaceable"><code>e2</code></em></td><td>right</td><td>Return a set consisting of the attributes in
- <em class="replaceable"><code>e1</code></em> and
- <em class="replaceable"><code>e2</code></em> (with the latter taking
- precedence over the former in case of equally named
- attributes).</td><td>9</td></tr><tr><td>Less Than</td><td>
- <em class="replaceable"><code>e1</code></em> <code class="literal"><</code> <em class="replaceable"><code>e2</code></em>,
- </td><td>none</td><td>Arithmetic comparison.</td><td>10</td></tr><tr><td>Less Than or Equal To</td><td>
- <em class="replaceable"><code>e1</code></em> <code class="literal"><=</code> <em class="replaceable"><code>e2</code></em>
- </td><td>none</td><td>Arithmetic comparison.</td><td>10</td></tr><tr><td>Greater Than</td><td>
- <em class="replaceable"><code>e1</code></em> <code class="literal">></code> <em class="replaceable"><code>e2</code></em>
- </td><td>none</td><td>Arithmetic comparison.</td><td>10</td></tr><tr><td>Greater Than or Equal To</td><td>
- <em class="replaceable"><code>e1</code></em> <code class="literal">>=</code> <em class="replaceable"><code>e2</code></em>
- </td><td>none</td><td>Arithmetic comparison.</td><td>10</td></tr><tr><td>Equality</td><td>
- <em class="replaceable"><code>e1</code></em> <code class="literal">==</code> <em class="replaceable"><code>e2</code></em>
- </td><td>none</td><td>Equality.</td><td>11</td></tr><tr><td>Inequality</td><td>
- <em class="replaceable"><code>e1</code></em> <code class="literal">!=</code> <em class="replaceable"><code>e2</code></em>
- </td><td>none</td><td>Inequality.</td><td>11</td></tr><tr><td>Logical AND</td><td><em class="replaceable"><code>e1</code></em> <code class="literal">&&</code>
- <em class="replaceable"><code>e2</code></em></td><td>left</td><td>Logical AND.</td><td>12</td></tr><tr><td>Logical OR</td><td><em class="replaceable"><code>e1</code></em> <code class="literal">||</code>
- <em class="replaceable"><code>e2</code></em></td><td>left</td><td>Logical OR.</td><td>13</td></tr><tr><td>Logical Implication</td><td><em class="replaceable"><code>e1</code></em> <code class="literal">-></code>
- <em class="replaceable"><code>e2</code></em></td><td>none</td><td>Logical implication (equivalent to
- <code class="literal">!<em class="replaceable"><code>e1</code></em> ||
- <em class="replaceable"><code>e2</code></em></code>).</td><td>14</td></tr></tbody></table></div></div><br class="table-break" /></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-derivation"></a>15.4. Derivations</h2></div></div></div><p>The most important built-in function is
-<code class="function">derivation</code>, which is used to describe a single
-derivation (a build action). It takes as input a set, the attributes
-of which specify the inputs of the build.</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><a id="attr-system"></a>There must be an attribute named
- <code class="varname">system</code> whose value must be a string specifying a
- Nix platform identifier, such as <code class="literal">"i686-linux"</code> or
- <code class="literal">"x86_64-darwin"</code><a href="#ftn.idm139733301168656" class="footnote" id="idm139733301168656"><sup class="footnote">[7]</sup></a> The build
- can only be performed on a machine and operating system matching the
- platform identifier. (Nix can automatically forward builds for
- other platforms by forwarding them to other machines; see <a class="xref" href="#chap-distributed-builds" title="Chapter 16. Remote Builds">Chapter 16, <em>Remote Builds</em></a>.)</p></li><li class="listitem"><p>There must be an attribute named
- <code class="varname">name</code> whose value must be a string. This is used
- as a symbolic name for the package by <span class="command"><strong>nix-env</strong></span>,
- and it is appended to the output paths of the
- derivation.</p></li><li class="listitem"><p>There must be an attribute named
- <code class="varname">builder</code> that identifies the program that is
- executed to perform the build. It can be either a derivation or a
- source (a local file reference, e.g.,
- <code class="filename">./builder.sh</code>).</p></li><li class="listitem"><p>Every attribute is passed as an environment variable
- to the builder. Attribute values are translated to environment
- variables as follows:
-
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Strings and numbers are just passed
- verbatim.</p></li><li class="listitem"><p>A <span class="emphasis"><em>path</em></span> (e.g.,
- <code class="filename">../foo/sources.tar</code>) causes the referenced
- file to be copied to the store; its location in the store is put
- in the environment variable. The idea is that all sources
- should reside in the Nix store, since all inputs to a derivation
- should reside in the Nix store.</p></li><li class="listitem"><p>A <span class="emphasis"><em>derivation</em></span> causes that
- derivation to be built prior to the present derivation; its
- default output path is put in the environment
- variable.</p></li><li class="listitem"><p>Lists of the previous types are also allowed.
- They are simply concatenated, separated by
- spaces.</p></li><li class="listitem"><p><code class="literal">true</code> is passed as the string
- <code class="literal">1</code>, <code class="literal">false</code> and
- <code class="literal">null</code> are passed as an empty string.
- </p></li></ul></div><p>
-
- </p></li><li class="listitem"><p>The optional attribute <code class="varname">args</code>
- specifies command-line arguments to be passed to the builder. It
- should be a list.</p></li><li class="listitem"><p>The optional attribute <code class="varname">outputs</code>
- specifies a list of symbolic outputs of the derivation. By default,
- a derivation produces a single output path, denoted as
- <code class="literal">out</code>. However, derivations can produce multiple
- output paths. This is useful because it allows outputs to be
- downloaded or garbage-collected separately. For instance, imagine a
- library package that provides a dynamic library, header files, and
- documentation. A program that links against the library doesn’t
- need the header files and documentation at runtime, and it doesn’t
- need the documentation at build time. Thus, the library package
- could specify:
-</p><pre class="programlisting">
-outputs = [ "lib" "headers" "doc" ];
-</pre><p>
- This will cause Nix to pass environment variables
- <code class="literal">lib</code>, <code class="literal">headers</code> and
- <code class="literal">doc</code> to the builder containing the intended store
- paths of each output. The builder would typically do something like
-</p><pre class="programlisting">
-./configure --libdir=$lib/lib --includedir=$headers/include --docdir=$doc/share/doc
-</pre><p>
- for an Autoconf-style package. You can refer to each output of a
- derivation by selecting it as an attribute, e.g.
-</p><pre class="programlisting">
-buildInputs = [ pkg.lib pkg.headers ];
-</pre><p>
- The first element of <code class="varname">outputs</code> determines the
- <span class="emphasis"><em>default output</em></span>. Thus, you could also write
-</p><pre class="programlisting">
-buildInputs = [ pkg pkg.headers ];
-</pre><p>
- since <code class="literal">pkg</code> is equivalent to
- <code class="literal">pkg.lib</code>.</p></li></ul></div><p>The function <code class="function">mkDerivation</code> in the Nixpkgs
-standard environment is a wrapper around
-<code class="function">derivation</code> that adds a default value for
-<code class="varname">system</code> and always uses Bash as the builder, to
-which the supplied builder is passed as a command-line argument. See
-the Nixpkgs manual for details.</p><p>The builder is executed as follows:
-
-</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>A temporary directory is created under the directory
- specified by <code class="envar">TMPDIR</code> (default
- <code class="filename">/tmp</code>) where the build will take place. The
- current directory is changed to this directory.</p></li><li class="listitem"><p>The environment is cleared and set to the derivation
- attributes, as specified above.</p></li><li class="listitem"><p>In addition, the following variables are set:
-
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p><code class="envar">NIX_BUILD_TOP</code> contains the path of
- the temporary directory for this build.</p></li><li class="listitem"><p>Also, <code class="envar">TMPDIR</code>,
- <code class="envar">TEMPDIR</code>, <code class="envar">TMP</code>, <code class="envar">TEMP</code>
- are set to point to the temporary directory. This is to prevent
- the builder from accidentally writing temporary files anywhere
- else. Doing so might cause interference by other
- processes.</p></li><li class="listitem"><p><code class="envar">PATH</code> is set to
- <code class="filename">/path-not-set</code> to prevent shells from
- initialising it to their built-in default value.</p></li><li class="listitem"><p><code class="envar">HOME</code> is set to
- <code class="filename">/homeless-shelter</code> to prevent programs from
- using <code class="filename">/etc/passwd</code> or the like to find the
- user's home directory, which could cause impurity. Usually, when
- <code class="envar">HOME</code> is set, it is used as the location of the home
- directory, even if it points to a non-existent
- path.</p></li><li class="listitem"><p><code class="envar">NIX_STORE</code> is set to the path of the
- top-level Nix store directory (typically,
- <code class="filename">/nix/store</code>).</p></li><li class="listitem"><p>For each output declared in
- <code class="varname">outputs</code>, the corresponding environment variable
- is set to point to the intended path in the Nix store for that
- output. Each output path is a concatenation of the cryptographic
- hash of all build inputs, the <code class="varname">name</code> attribute
- and the output name. (The output name is omitted if it’s
- <code class="literal">out</code>.)</p></li></ul></div><p>
-
- </p></li><li class="listitem"><p>If an output path already exists, it is removed.
- Also, locks are acquired to prevent multiple Nix instances from
- performing the same build at the same time.</p></li><li class="listitem"><p>A log of the combined standard output and error is
- written to <code class="filename">/nix/var/log/nix</code>.</p></li><li class="listitem"><p>The builder is executed with the arguments specified
- by the attribute <code class="varname">args</code>. If it exits with exit
- code 0, it is considered to have succeeded.</p></li><li class="listitem"><p>The temporary directory is removed (unless the
- <code class="option">-K</code> option was specified).</p></li><li class="listitem"><p>If the build was successful, Nix scans each output
- path for references to input paths by looking for the hash parts of
- the input paths. Since these are potential runtime dependencies,
- Nix registers them as dependencies of the output
- paths.</p></li><li class="listitem"><p>After the build, Nix sets the last-modified
- timestamp on all files in the build result to 1 (00:00:01 1/1/1970
- UTC), sets the group to the default group, and sets the mode of the
- file to 0444 or 0555 (i.e., read-only, with execute permission
- enabled if the file was originally executable). Note that possible
- <code class="literal">setuid</code> and <code class="literal">setgid</code> bits are
- cleared. Setuid and setgid programs are not currently supported by
- Nix. This is because the Nix archives used in deployment have no
- concept of ownership information, and because it makes the build
- result dependent on the user performing the build.</p></li></ul></div><p>
-
-</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="sec-advanced-attributes"></a>15.4.1. Advanced Attributes</h3></div></div></div><p>Derivations can declare some infrequently used optional
-attributes.</p><div class="variablelist"><dl class="variablelist"><dt><a id="adv-attr-allowedReferences"></a><span class="term"><code class="varname">allowedReferences</code></span></dt><dd><p>The optional attribute
- <code class="varname">allowedReferences</code> specifies a list of legal
- references (dependencies) of the output of the builder. For
- example,
-
-</p><pre class="programlisting">
-allowedReferences = [];
-</pre><p>
-
- enforces that the output of a derivation cannot have any runtime
- dependencies on its inputs. To allow an output to have a runtime
- dependency on itself, use <code class="literal">"out"</code> as a list item.
- This is used in NixOS to check that generated files such as
- initial ramdisks for booting Linux don’t have accidental
- dependencies on other paths in the Nix store.</p></dd><dt><a id="adv-attr-allowedRequisites"></a><span class="term"><code class="varname">allowedRequisites</code></span></dt><dd><p>This attribute is similar to
- <code class="varname">allowedReferences</code>, but it specifies the legal
- requisites of the whole closure, so all the dependencies
- recursively. For example,
-
-</p><pre class="programlisting">
-allowedRequisites = [ foobar ];
-</pre><p>
-
- enforces that the output of a derivation cannot have any other
- runtime dependency than <code class="varname">foobar</code>, and in addition
- it enforces that <code class="varname">foobar</code> itself doesn't
- introduce any other dependency itself.</p></dd><dt><a id="adv-attr-disallowedReferences"></a><span class="term"><code class="varname">disallowedReferences</code></span></dt><dd><p>The optional attribute
- <code class="varname">disallowedReferences</code> specifies a list of illegal
- references (dependencies) of the output of the builder. For
- example,
-
-</p><pre class="programlisting">
-disallowedReferences = [ foo ];
-</pre><p>
-
- enforces that the output of a derivation cannot have a direct runtime
- dependencies on the derivation <code class="varname">foo</code>.</p></dd><dt><a id="adv-attr-disallowedRequisites"></a><span class="term"><code class="varname">disallowedRequisites</code></span></dt><dd><p>This attribute is similar to
- <code class="varname">disallowedReferences</code>, but it specifies illegal
- requisites for the whole closure, so all the dependencies
- recursively. For example,
-
-</p><pre class="programlisting">
-disallowedRequisites = [ foobar ];
-</pre><p>
-
- enforces that the output of a derivation cannot have any
- runtime dependency on <code class="varname">foobar</code> or any other derivation
- depending recursively on <code class="varname">foobar</code>.</p></dd><dt><a id="adv-attr-exportReferencesGraph"></a><span class="term"><code class="varname">exportReferencesGraph</code></span></dt><dd><p>This attribute allows builders access to the
- references graph of their inputs. The attribute is a list of
- inputs in the Nix store whose references graph the builder needs
- to know. The value of this attribute should be a list of pairs
- <code class="literal">[ <em class="replaceable"><code>name1</code></em>
- <em class="replaceable"><code>path1</code></em> <em class="replaceable"><code>name2</code></em>
- <em class="replaceable"><code>path2</code></em> <em class="replaceable"><code>...</code></em>
- ]</code>. The references graph of each
- <em class="replaceable"><code>pathN</code></em> will be stored in a text file
- <em class="replaceable"><code>nameN</code></em> in the temporary build directory.
- The text files have the format used by <span class="command"><strong>nix-store
- --register-validity</strong></span> (with the deriver fields left
- empty). For example, when the following derivation is built:
-
-</p><pre class="programlisting">
-derivation {
- ...
- exportReferencesGraph = [ "libfoo-graph" libfoo ];
-};
-</pre><p>
-
- the references graph of <code class="literal">libfoo</code> is placed in the
- file <code class="filename">libfoo-graph</code> in the temporary build
- directory.</p><p><code class="varname">exportReferencesGraph</code> is useful for
- builders that want to do something with the closure of a store
- path. Examples include the builders in NixOS that generate the
- initial ramdisk for booting Linux (a <span class="command"><strong>cpio</strong></span>
- archive containing the closure of the boot script) and the
- ISO-9660 image for the installation CD (which is populated with a
- Nix store containing the closure of a bootable NixOS
- configuration).</p></dd><dt><a id="adv-attr-impureEnvVars"></a><span class="term"><code class="varname">impureEnvVars</code></span></dt><dd><p>This attribute allows you to specify a list of
- environment variables that should be passed from the environment
- of the calling user to the builder. Usually, the environment is
- cleared completely when the builder is executed, but with this
- attribute you can allow specific environment variables to be
- passed unmodified. For example, <code class="function">fetchurl</code> in
- Nixpkgs has the line
-
-</p><pre class="programlisting">
-impureEnvVars = [ "http_proxy" "https_proxy" <em class="replaceable"><code>...</code></em> ];
-</pre><p>
-
- to make it use the proxy server configuration specified by the
- user in the environment variables <code class="envar">http_proxy</code> and
- friends.</p><p>This attribute is only allowed in <a class="link" href="#fixed-output-drvs">fixed-output derivations</a>, where
- impurities such as these are okay since (the hash of) the output
- is known in advance. It is ignored for all other
- derivations.</p><div class="warning"><h3 class="title">Warning</h3><p><code class="varname">impureEnvVars</code> implementation takes
- environment variables from the current builder process. When a daemon is
- building its environmental variables are used. Without the daemon, the
- environmental variables come from the environment of the
- <span class="command"><strong>nix-build</strong></span>.</p></div></dd><dt><a id="fixed-output-drvs"></a><span class="term"><a id="adv-attr-outputHash"></a><code class="varname">outputHash</code>, </span><span class="term"><a id="adv-attr-outputHashAlgo"></a><code class="varname">outputHashAlgo</code>, </span><span class="term"><a id="adv-attr-outputHashMode"></a><code class="varname">outputHashMode</code></span></dt><dd><p>These attributes declare that the derivation is a
- so-called <span class="emphasis"><em>fixed-output derivation</em></span>, which
- means that a cryptographic hash of the output is already known in
- advance. When the build of a fixed-output derivation finishes,
- Nix computes the cryptographic hash of the output and compares it
- to the hash declared with these attributes. If there is a
- mismatch, the build fails.</p><p>The rationale for fixed-output derivations is derivations
- such as those produced by the <code class="function">fetchurl</code>
- function. This function downloads a file from a given URL. To
- ensure that the downloaded file has not been modified, the caller
- must also specify a cryptographic hash of the file. For example,
-
-</p><pre class="programlisting">
-fetchurl {
- url = "http://ftp.gnu.org/pub/gnu/hello/hello-2.1.1.tar.gz";
- sha256 = "1md7jsfd8pa45z73bz1kszpp01yw6x5ljkjk2hx7wl800any6465";
-}
-</pre><p>
-
- It sometimes happens that the URL of the file changes, e.g.,
- because servers are reorganised or no longer available. We then
- must update the call to <code class="function">fetchurl</code>, e.g.,
-
-</p><pre class="programlisting">
-fetchurl {
- url = "ftp://ftp.nluug.nl/pub/gnu/hello/hello-2.1.1.tar.gz";
- sha256 = "1md7jsfd8pa45z73bz1kszpp01yw6x5ljkjk2hx7wl800any6465";
-}
-</pre><p>
-
- If a <code class="function">fetchurl</code> derivation was treated like a
- normal derivation, the output paths of the derivation and
- <span class="emphasis"><em>all derivations depending on it</em></span> would change.
- For instance, if we were to change the URL of the Glibc source
- distribution in Nixpkgs (a package on which almost all other
- packages depend) massive rebuilds would be needed. This is
- unfortunate for a change which we know cannot have a real effect
- as it propagates upwards through the dependency graph.</p><p>For fixed-output derivations, on the other hand, the name of
- the output path only depends on the <code class="varname">outputHash*</code>
- and <code class="varname">name</code> attributes, while all other attributes
- are ignored for the purpose of computing the output path. (The
- <code class="varname">name</code> attribute is included because it is part
- of the path.)</p><p>As an example, here is the (simplified) Nix expression for
- <code class="varname">fetchurl</code>:
-
-</p><pre class="programlisting">
-{ stdenv, curl }: # The <span class="command"><strong>curl</strong></span> program is used for downloading.
-
-{ url, sha256 }:
-
-stdenv.mkDerivation {
- name = baseNameOf (toString url);
- builder = ./builder.sh;
- buildInputs = [ curl ];
-
- # This is a fixed-output derivation; the output must be a regular
- # file with SHA256 hash <code class="varname">sha256</code>.
- outputHashMode = "flat";
- outputHashAlgo = "sha256";
- outputHash = sha256;
-
- inherit url;
-}
-</pre><p>
-
- </p><p>The <code class="varname">outputHashAlgo</code> attribute specifies
- the hash algorithm used to compute the hash. It can currently be
- <code class="literal">"sha1"</code>, <code class="literal">"sha256"</code> or
- <code class="literal">"sha512"</code>.</p><p>The <code class="varname">outputHashMode</code> attribute determines
- how the hash is computed. It must be one of the following two
- values:
-
- </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">"flat"</code></span></dt><dd><p>The output must be a non-executable regular
- file. If it isn’t, the build fails. The hash is simply
- computed over the contents of that file (so it’s equal to what
- Unix commands like <span class="command"><strong>sha256sum</strong></span> or
- <span class="command"><strong>sha1sum</strong></span> produce).</p><p>This is the default.</p></dd><dt><span class="term"><code class="literal">"recursive"</code></span></dt><dd><p>The hash is computed over the NAR archive dump
- of the output (i.e., the result of <a class="link" href="#refsec-nix-store-dump" title="Operation --dump"><span class="command"><strong>nix-store
- --dump</strong></span></a>). In this case, the output can be
- anything, including a directory tree.</p></dd></dl></div><p>
-
- </p><p>The <code class="varname">outputHash</code> attribute, finally, must
- be a string containing the hash in either hexadecimal or base-32
- notation. (See the <a class="link" href="#sec-nix-hash" title="nix-hash"><span class="command"><strong>nix-hash</strong></span> command</a>
- for information about converting to and from base-32
- notation.)</p></dd><dt><a id="adv-attr-passAsFile"></a><span class="term"><code class="varname">passAsFile</code></span></dt><dd><p>A list of names of attributes that should be
- passed via files rather than environment variables. For example,
- if you have
-
- </p><pre class="programlisting">
-passAsFile = ["big"];
-big = "a very long string";
- </pre><p>
-
- then when the builder runs, the environment variable
- <code class="envar">bigPath</code> will contain the absolute path to a
- temporary file containing <code class="literal">a very long
- string</code>. That is, for any attribute
- <em class="replaceable"><code>x</code></em> listed in
- <code class="varname">passAsFile</code>, Nix will pass an environment
- variable <code class="envar"><em class="replaceable"><code>x</code></em>Path</code> holding
- the path of the file containing the value of attribute
- <em class="replaceable"><code>x</code></em>. This is useful when you need to pass
- large strings to a builder, since most operating systems impose a
- limit on the size of the environment (typically, a few hundred
- kilobyte).</p></dd><dt><a id="adv-attr-preferLocalBuild"></a><span class="term"><code class="varname">preferLocalBuild</code></span></dt><dd><p>If this attribute is set to
- <code class="literal">true</code> and <a class="link" href="#chap-distributed-builds" title="Chapter 16. Remote Builds">distributed building is
- enabled</a>, then, if possible, the derivaton will be built
- locally instead of forwarded to a remote machine. This is
- appropriate for trivial builders where the cost of doing a
- download or remote build would exceed the cost of building
- locally.</p></dd><dt><a id="adv-attr-allowSubstitutes"></a><span class="term"><code class="varname">allowSubstitutes</code></span></dt><dd><p>If this attribute is set to
- <code class="literal">false</code>, then Nix will always build this
- derivation; it will not try to substitute its outputs. This is
- useful for very trivial derivations (such as
- <code class="function">writeText</code> in Nixpkgs) that are cheaper to
- build than to substitute from a binary cache.</p><div class="note"><h3 class="title">Note</h3><p>You need to have a builder configured which satisfies
- the derivation’s <code class="literal">system</code> attribute, since the
- derivation cannot be substituted. Thus it is usually a good idea
- to align <code class="literal">system</code> with
- <code class="literal">builtins.currentSystem</code> when setting
- <code class="literal">allowSubstitutes</code> to <code class="literal">false</code>.
- For most trivial derivations this should be the case.
- </p></div></dd></dl></div></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-builtins"></a>15.5. Built-in Functions</h2></div></div></div><p>This section lists the functions and constants built into the
-Nix expression evaluator. (The built-in function
-<code class="function">derivation</code> is discussed above.) Some built-ins,
-such as <code class="function">derivation</code>, are always in scope of every
-Nix expression; you can just access them right away. But to prevent
-polluting the namespace too much, most built-ins are not in scope.
-Instead, you can access them through the <code class="varname">builtins</code>
-built-in value, which is a set that contains all built-in functions
-and values. For instance, <code class="function">derivation</code> is also
-available as <code class="function">builtins.derivation</code>.</p><div class="variablelist"><dl class="variablelist"><dt><a id="builtin-abort"></a><span class="term"><code class="function">abort</code> <em class="replaceable"><code>s</code></em>, </span><span class="term"><code class="function">builtins.abort</code> <em class="replaceable"><code>s</code></em></span></dt><dd><p>Abort Nix expression evaluation, print error
- message <em class="replaceable"><code>s</code></em>.</p></dd><dt><a id="builtin-add"></a><span class="term"><code class="function">builtins.add</code>
- <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em>
- </span></dt><dd><p>Return the sum of the numbers
- <em class="replaceable"><code>e1</code></em> and
- <em class="replaceable"><code>e2</code></em>.</p></dd><dt><a id="builtin-all"></a><span class="term"><code class="function">builtins.all</code>
- <em class="replaceable"><code>pred</code></em> <em class="replaceable"><code>list</code></em></span></dt><dd><p>Return <code class="literal">true</code> if the function
- <em class="replaceable"><code>pred</code></em> returns <code class="literal">true</code>
- for all elements of <em class="replaceable"><code>list</code></em>,
- and <code class="literal">false</code> otherwise.</p></dd><dt><a id="builtin-any"></a><span class="term"><code class="function">builtins.any</code>
- <em class="replaceable"><code>pred</code></em> <em class="replaceable"><code>list</code></em></span></dt><dd><p>Return <code class="literal">true</code> if the function
- <em class="replaceable"><code>pred</code></em> returns <code class="literal">true</code>
- for at least one element of <em class="replaceable"><code>list</code></em>,
- and <code class="literal">false</code> otherwise.</p></dd><dt><a id="builtin-attrNames"></a><span class="term"><code class="function">builtins.attrNames</code>
- <em class="replaceable"><code>set</code></em></span></dt><dd><p>Return the names of the attributes in the set
- <em class="replaceable"><code>set</code></em> in an alphabetically sorted list. For instance,
- <code class="literal">builtins.attrNames { y = 1; x = "foo"; }</code>
- evaluates to <code class="literal">[ "x" "y" ]</code>.</p></dd><dt><a id="builtin-attrValues"></a><span class="term"><code class="function">builtins.attrValues</code>
- <em class="replaceable"><code>set</code></em></span></dt><dd><p>Return the values of the attributes in the set
- <em class="replaceable"><code>set</code></em> in the order corresponding to the
- sorted attribute names.</p></dd><dt><a id="builtin-baseNameOf"></a><span class="term"><code class="function">baseNameOf</code> <em class="replaceable"><code>s</code></em></span></dt><dd><p>Return the <span class="emphasis"><em>base name</em></span> of the
- string <em class="replaceable"><code>s</code></em>, that is, everything following
- the final slash in the string. This is similar to the GNU
- <span class="command"><strong>basename</strong></span> command.</p></dd><dt><a id="builtin-bitAnd"></a><span class="term"><code class="function">builtins.bitAnd</code>
- <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>Return the bitwise AND of the integers
- <em class="replaceable"><code>e1</code></em> and
- <em class="replaceable"><code>e2</code></em>.</p></dd><dt><a id="builtin-bitOr"></a><span class="term"><code class="function">builtins.bitOr</code>
- <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>Return the bitwise OR of the integers
- <em class="replaceable"><code>e1</code></em> and
- <em class="replaceable"><code>e2</code></em>.</p></dd><dt><a id="builtin-bitXor"></a><span class="term"><code class="function">builtins.bitXor</code>
- <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>Return the bitwise XOR of the integers
- <em class="replaceable"><code>e1</code></em> and
- <em class="replaceable"><code>e2</code></em>.</p></dd><dt><a id="builtin-builtins"></a><span class="term"><code class="varname">builtins</code></span></dt><dd><p>The set <code class="varname">builtins</code> contains all
- the built-in functions and values. You can use
- <code class="varname">builtins</code> to test for the availability of
- features in the Nix installation, e.g.,
-
-</p><pre class="programlisting">
-if builtins ? getEnv then builtins.getEnv "PATH" else ""</pre><p>
-
- This allows a Nix expression to fall back gracefully on older Nix
- installations that don’t have the desired built-in
- function.</p></dd><dt><a id="builtin-compareVersions"></a><span class="term"><code class="function">builtins.compareVersions</code>
- <em class="replaceable"><code>s1</code></em> <em class="replaceable"><code>s2</code></em></span></dt><dd><p>Compare two strings representing versions and
- return <code class="literal">-1</code> if version
- <em class="replaceable"><code>s1</code></em> is older than version
- <em class="replaceable"><code>s2</code></em>, <code class="literal">0</code> if they are
- the same, and <code class="literal">1</code> if
- <em class="replaceable"><code>s1</code></em> is newer than
- <em class="replaceable"><code>s2</code></em>. The version comparison algorithm
- is the same as the one used by <a class="link" href="#ssec-version-comparisons" title="Versions"><span class="command"><strong>nix-env
- -u</strong></span></a>.</p></dd><dt><a id="builtin-concatLists"></a><span class="term"><code class="function">builtins.concatLists</code>
- <em class="replaceable"><code>lists</code></em></span></dt><dd><p>Concatenate a list of lists into a single
- list.</p></dd><dt><a id="builtin-concatStringsSep"></a><span class="term"><code class="function">builtins.concatStringsSep</code>
- <em class="replaceable"><code>separator</code></em> <em class="replaceable"><code>list</code></em></span></dt><dd><p>Concatenate a list of strings with a separator
- between each element, e.g. <code class="literal">concatStringsSep "/"
- ["usr" "local" "bin"] == "usr/local/bin"</code></p></dd><dt><a id="builtin-currentSystem"></a><span class="term"><code class="varname">builtins.currentSystem</code></span></dt><dd><p>The built-in value <code class="varname">currentSystem</code>
- evaluates to the Nix platform identifier for the Nix installation
- on which the expression is being evaluated, such as
- <code class="literal">"i686-linux"</code> or
- <code class="literal">"x86_64-darwin"</code>.</p></dd><dt><a id="builtin-deepSeq"></a><span class="term"><code class="function">builtins.deepSeq</code>
- <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>This is like <code class="literal">seq
- <em class="replaceable"><code>e1</code></em>
- <em class="replaceable"><code>e2</code></em></code>, except that
- <em class="replaceable"><code>e1</code></em> is evaluated
- <span class="emphasis"><em>deeply</em></span>: if it’s a list or set, its elements
- or attributes are also evaluated recursively.</p></dd><dt><a id="builtin-derivation"></a><span class="term"><code class="function">derivation</code>
- <em class="replaceable"><code>attrs</code></em>, </span><span class="term"><code class="function">builtins.derivation</code>
- <em class="replaceable"><code>attrs</code></em></span></dt><dd><p><code class="function">derivation</code> is described in
- <a class="xref" href="#ssec-derivation" title="15.4. Derivations">Section 15.4, “Derivations”</a>.</p></dd><dt><a id="builtin-dirOf"></a><span class="term"><code class="function">dirOf</code> <em class="replaceable"><code>s</code></em>, </span><span class="term"><code class="function">builtins.dirOf</code> <em class="replaceable"><code>s</code></em></span></dt><dd><p>Return the directory part of the string
- <em class="replaceable"><code>s</code></em>, that is, everything before the final
- slash in the string. This is similar to the GNU
- <span class="command"><strong>dirname</strong></span> command.</p></dd><dt><a id="builtin-div"></a><span class="term"><code class="function">builtins.div</code>
- <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>Return the quotient of the numbers
- <em class="replaceable"><code>e1</code></em> and
- <em class="replaceable"><code>e2</code></em>.</p></dd><dt><a id="builtin-elem"></a><span class="term"><code class="function">builtins.elem</code>
- <em class="replaceable"><code>x</code></em> <em class="replaceable"><code>xs</code></em></span></dt><dd><p>Return <code class="literal">true</code> if a value equal to
- <em class="replaceable"><code>x</code></em> occurs in the list
- <em class="replaceable"><code>xs</code></em>, and <code class="literal">false</code>
- otherwise.</p></dd><dt><a id="builtin-elemAt"></a><span class="term"><code class="function">builtins.elemAt</code>
- <em class="replaceable"><code>xs</code></em> <em class="replaceable"><code>n</code></em></span></dt><dd><p>Return element <em class="replaceable"><code>n</code></em> from
- the list <em class="replaceable"><code>xs</code></em>. Elements are counted
- starting from 0. A fatal error occurs if the index is out of
- bounds.</p></dd><dt><a id="builtin-fetchurl"></a><span class="term"><code class="function">builtins.fetchurl</code>
- <em class="replaceable"><code>url</code></em></span></dt><dd><p>Download the specified URL and return the path of
- the downloaded file. This function is not available if <a class="link" href="#conf-restrict-eval">restricted evaluation mode</a> is
- enabled.</p></dd><dt><a id="builtin-fetchTarball"></a><span class="term"><code class="function">fetchTarball</code>
- <em class="replaceable"><code>url</code></em>, </span><span class="term"><code class="function">builtins.fetchTarball</code>
- <em class="replaceable"><code>url</code></em></span></dt><dd><p>Download the specified URL, unpack it and return
- the path of the unpacked tree. The file must be a tape archive
- (<code class="filename">.tar</code>) compressed with
- <code class="literal">gzip</code>, <code class="literal">bzip2</code> or
- <code class="literal">xz</code>. The top-level path component of the files
- in the tarball is removed, so it is best if the tarball contains a
- single directory at top level. The typical use of the function is
- to obtain external Nix expression dependencies, such as a
- particular version of Nixpkgs, e.g.
-
-</p><pre class="programlisting">
-with import (fetchTarball https://github.com/NixOS/nixpkgs/archive/nixos-14.12.tar.gz) {};
-
-stdenv.mkDerivation { … }
-</pre><p>
- </p><p>The fetched tarball is cached for a certain amount of time
- (1 hour by default) in <code class="filename">~/.cache/nix/tarballs/</code>.
- You can change the cache timeout either on the command line with
- <code class="option">--option tarball-ttl <em class="replaceable"><code>number of seconds</code></em></code> or
- in the Nix configuration file with this option:
- <code class="literal"><a class="xref" href="#conf-tarball-ttl"><code class="literal">tarball-ttl</code></a> <em class="replaceable"><code>number of seconds to cache</code></em></code>.
- </p><p>Note that when obtaining the hash with <code class="varname">nix-prefetch-url
- </code> the option <code class="varname">--unpack</code> is required.
- </p><p>This function can also verify the contents against a hash.
- In that case, the function takes a set instead of a URL. The set
- requires the attribute <code class="varname">url</code> and the attribute
- <code class="varname">sha256</code>, e.g.
-
-</p><pre class="programlisting">
-with import (fetchTarball {
- url = "https://github.com/NixOS/nixpkgs/archive/nixos-14.12.tar.gz";
- sha256 = "1jppksrfvbk5ypiqdz4cddxdl8z6zyzdb2srq8fcffr327ld5jj2";
-}) {};
-
-stdenv.mkDerivation { … }
-</pre><p>
-
- </p><p>This function is not available if <a class="link" href="#conf-restrict-eval">restricted evaluation mode</a> is
- enabled.</p></dd><dt><a id="builtin-fetchGit"></a><span class="term">
- <code class="function">builtins.fetchGit</code>
- <em class="replaceable"><code>args</code></em>
- </span></dt><dd><p>
- Fetch a path from git. <em class="replaceable"><code>args</code></em> can be
- a URL, in which case the HEAD of the repo at that URL is
- fetched. Otherwise, it can be an attribute with the following
- attributes (all except <code class="varname">url</code> optional):
- </p><div class="variablelist"><dl class="variablelist"><dt><span class="term">url</span></dt><dd><p>
- The URL of the repo.
- </p></dd><dt><span class="term">name</span></dt><dd><p>
- The name of the directory the repo should be exported to
- in the store. Defaults to the basename of the URL.
- </p></dd><dt><span class="term">rev</span></dt><dd><p>
- The git revision to fetch. Defaults to the tip of
- <code class="varname">ref</code>.
- </p></dd><dt><span class="term">ref</span></dt><dd><p>
- The git ref to look for the requested revision under.
- This is often a branch or tag name. Defaults to
- <code class="literal">HEAD</code>.
- </p><p>
- By default, the <code class="varname">ref</code> value is prefixed
- with <code class="literal">refs/heads/</code>. As of Nix 2.3.0
- Nix will not prefix <code class="literal">refs/heads/</code> if
- <code class="varname">ref</code> starts with <code class="literal">refs/</code>.
- </p></dd><dt><span class="term">submodules</span></dt><dd><p>
- A Boolean parameter that specifies whether submodules
- should be checked out. Defaults to
- <code class="literal">false</code>.
- </p></dd></dl></div><div class="example"><a id="idm139733300931888"></a><p class="title"><strong>Example 15.2. Fetching a private repository over SSH</strong></p><div class="example-contents"><pre class="programlisting">builtins.fetchGit {
- url = "git@github.com:my-secret/repository.git";
- ref = "master";
- rev = "adab8b916a45068c044658c4158d81878f9ed1c3";
-}</pre></div></div><br class="example-break" /><div class="example"><a id="idm139733300930528"></a><p class="title"><strong>Example 15.3. Fetching an arbitrary ref</strong></p><div class="example-contents"><pre class="programlisting">builtins.fetchGit {
- url = "https://github.com/NixOS/nix.git";
- ref = "refs/heads/0.5-release";
-}</pre></div></div><br class="example-break" /><div class="example"><a id="idm139733300929216"></a><p class="title"><strong>Example 15.4. Fetching a repository's specific commit on an arbitrary branch</strong></p><div class="example-contents"><p>
- If the revision you're looking for is in the default branch
- of the git repository you don't strictly need to specify
- the branch name in the <code class="varname">ref</code> attribute.
- </p><p>
- However, if the revision you're looking for is in a future
- branch for the non-default branch you will need to specify
- the the <code class="varname">ref</code> attribute as well.
- </p><pre class="programlisting">builtins.fetchGit {
- url = "https://github.com/nixos/nix.git";
- rev = "841fcbd04755c7a2865c51c1e2d3b045976b7452";
- ref = "1.11-maintenance";
-}</pre><div class="note"><h3 class="title">Note</h3><p>
- It is nice to always specify the branch which a revision
- belongs to. Without the branch being specified, the
- fetcher might fail if the default branch changes.
- Additionally, it can be confusing to try a commit from a
- non-default branch and see the fetch fail. If the branch
- is specified the fault is much more obvious.
- </p></div></div></div><br class="example-break" /><div class="example"><a id="idm139733300924656"></a><p class="title"><strong>Example 15.5. Fetching a repository's specific commit on the default branch</strong></p><div class="example-contents"><p>
- If the revision you're looking for is in the default branch
- of the git repository you may omit the
- <code class="varname">ref</code> attribute.
- </p><pre class="programlisting">builtins.fetchGit {
- url = "https://github.com/nixos/nix.git";
- rev = "841fcbd04755c7a2865c51c1e2d3b045976b7452";
-}</pre></div></div><br class="example-break" /><div class="example"><a id="idm139733300922352"></a><p class="title"><strong>Example 15.6. Fetching a tag</strong></p><div class="example-contents"><pre class="programlisting">builtins.fetchGit {
- url = "https://github.com/nixos/nix.git";
- ref = "refs/tags/1.9";
-}</pre></div></div><br class="example-break" /><div class="example"><a id="idm139733300921056"></a><p class="title"><strong>Example 15.7. Fetching the latest version of a remote branch</strong></p><div class="example-contents"><p>
- <code class="function">builtins.fetchGit</code> can behave impurely
- fetch the latest version of a remote branch.
- </p><div class="note"><h3 class="title">Note</h3><p>Nix will refetch the branch in accordance to
- <a class="xref" href="#conf-tarball-ttl"><code class="literal">tarball-ttl</code></a>.</p></div><div class="note"><h3 class="title">Note</h3><p>This behavior is disabled in
- <span class="emphasis"><em>Pure evaluation mode</em></span>.</p></div><pre class="programlisting">builtins.fetchGit {
- url = "ssh://git@github.com/nixos/nix.git";
- ref = "master";
-}</pre></div></div><br class="example-break" /></dd><dt><span class="term"><code class="function">builtins.filter</code>
- <em class="replaceable"><code>f</code></em> <em class="replaceable"><code>xs</code></em></span></dt><dd><p>Return a list consisting of the elements of
- <em class="replaceable"><code>xs</code></em> for which the function
- <em class="replaceable"><code>f</code></em> returns
- <code class="literal">true</code>.</p></dd><dt><a id="builtin-filterSource"></a><span class="term"><code class="function">builtins.filterSource</code>
- <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>This function allows you to copy sources into the Nix
- store while filtering certain files. For instance, suppose that
- you want to use the directory <code class="filename">source-dir</code> as
- an input to a Nix expression, e.g.
-
-</p><pre class="programlisting">
-stdenv.mkDerivation {
- ...
- src = ./source-dir;
-}
-</pre><p>
-
- However, if <code class="filename">source-dir</code> is a Subversion
- working copy, then all those annoying <code class="filename">.svn</code>
- subdirectories will also be copied to the store. Worse, the
- contents of those directories may change a lot, causing lots of
- spurious rebuilds. With <code class="function">filterSource</code> you
- can filter out the <code class="filename">.svn</code> directories:
-
-</p><pre class="programlisting">
- src = builtins.filterSource
- (path: type: type != "directory" || baseNameOf path != ".svn")
- ./source-dir;
-</pre><p>
-
- </p><p>Thus, the first argument <em class="replaceable"><code>e1</code></em>
- must be a predicate function that is called for each regular
- file, directory or symlink in the source tree
- <em class="replaceable"><code>e2</code></em>. If the function returns
- <code class="literal">true</code>, the file is copied to the Nix store,
- otherwise it is omitted. The function is called with two
- arguments. The first is the full path of the file. The second
- is a string that identifies the type of the file, which is
- either <code class="literal">"regular"</code>,
- <code class="literal">"directory"</code>, <code class="literal">"symlink"</code> or
- <code class="literal">"unknown"</code> (for other kinds of files such as
- device nodes or fifos — but note that those cannot be copied to
- the Nix store, so if the predicate returns
- <code class="literal">true</code> for them, the copy will fail). If you
- exclude a directory, the entire corresponding subtree of
- <em class="replaceable"><code>e2</code></em> will be excluded.</p></dd><dt><a id="builtin-foldl-prime"></a><span class="term"><code class="function">builtins.foldl’</code>
- <em class="replaceable"><code>op</code></em> <em class="replaceable"><code>nul</code></em> <em class="replaceable"><code>list</code></em></span></dt><dd><p>Reduce a list by applying a binary operator, from
- left to right, e.g. <code class="literal">foldl’ op nul [x0 x1 x2 ...] = op (op
- (op nul x0) x1) x2) ...</code>. The operator is applied
- strictly, i.e., its arguments are evaluated first. For example,
- <code class="literal">foldl’ (x: y: x + y) 0 [1 2 3]</code> evaluates to
- 6.</p></dd><dt><a id="builtin-functionArgs"></a><span class="term"><code class="function">builtins.functionArgs</code>
- <em class="replaceable"><code>f</code></em></span></dt><dd><p>
- Return a set containing the names of the formal arguments expected
- by the function <em class="replaceable"><code>f</code></em>.
- The value of each attribute is a Boolean denoting whether the corresponding
- argument has a default value. For instance,
- <code class="literal">functionArgs ({ x, y ? 123}: ...) = { x = false; y = true; }</code>.
- </p><p>"Formal argument" here refers to the attributes pattern-matched by
- the function. Plain lambdas are not included, e.g.
- <code class="literal">functionArgs (x: ...) = { }</code>.
- </p></dd><dt><a id="builtin-fromJSON"></a><span class="term"><code class="function">builtins.fromJSON</code> <em class="replaceable"><code>e</code></em></span></dt><dd><p>Convert a JSON string to a Nix
- value. For example,
-
-</p><pre class="programlisting">
-builtins.fromJSON ''{"x": [1, 2, 3], "y": null}''
-</pre><p>
-
- returns the value <code class="literal">{ x = [ 1 2 3 ]; y = null;
- }</code>.</p></dd><dt><a id="builtin-genList"></a><span class="term"><code class="function">builtins.genList</code>
- <em class="replaceable"><code>generator</code></em> <em class="replaceable"><code>length</code></em></span></dt><dd><p>Generate list of size
- <em class="replaceable"><code>length</code></em>, with each element
- <em class="replaceable"><code>i</code></em> equal to the value returned by
- <em class="replaceable"><code>generator</code></em> <code class="literal">i</code>. For
- example,
-
-</p><pre class="programlisting">
-builtins.genList (x: x * x) 5
-</pre><p>
-
- returns the list <code class="literal">[ 0 1 4 9 16 ]</code>.</p></dd><dt><a id="builtin-getAttr"></a><span class="term"><code class="function">builtins.getAttr</code>
- <em class="replaceable"><code>s</code></em> <em class="replaceable"><code>set</code></em></span></dt><dd><p><code class="function">getAttr</code> returns the attribute
- named <em class="replaceable"><code>s</code></em> from
- <em class="replaceable"><code>set</code></em>. Evaluation aborts if the
- attribute doesn’t exist. This is a dynamic version of the
- <code class="literal">.</code> operator, since <em class="replaceable"><code>s</code></em>
- is an expression rather than an identifier.</p></dd><dt><a id="builtin-getEnv"></a><span class="term"><code class="function">builtins.getEnv</code>
- <em class="replaceable"><code>s</code></em></span></dt><dd><p><code class="function">getEnv</code> returns the value of
- the environment variable <em class="replaceable"><code>s</code></em>, or an empty
- string if the variable doesn’t exist. This function should be
- used with care, as it can introduce all sorts of nasty environment
- dependencies in your Nix expression.</p><p><code class="function">getEnv</code> is used in Nix Packages to
- locate the file <code class="filename">~/.nixpkgs/config.nix</code>, which
- contains user-local settings for Nix Packages. (That is, it does
- a <code class="literal">getEnv "HOME"</code> to locate the user’s home
- directory.)</p></dd><dt><a id="builtin-hasAttr"></a><span class="term"><code class="function">builtins.hasAttr</code>
- <em class="replaceable"><code>s</code></em> <em class="replaceable"><code>set</code></em></span></dt><dd><p><code class="function">hasAttr</code> returns
- <code class="literal">true</code> if <em class="replaceable"><code>set</code></em> has an
- attribute named <em class="replaceable"><code>s</code></em>, and
- <code class="literal">false</code> otherwise. This is a dynamic version of
- the <code class="literal">?</code> operator, since
- <em class="replaceable"><code>s</code></em> is an expression rather than an
- identifier.</p></dd><dt><a id="builtin-hashString"></a><span class="term"><code class="function">builtins.hashString</code>
- <em class="replaceable"><code>type</code></em> <em class="replaceable"><code>s</code></em></span></dt><dd><p>Return a base-16 representation of the
- cryptographic hash of string <em class="replaceable"><code>s</code></em>. The
- hash algorithm specified by <em class="replaceable"><code>type</code></em> must
- be one of <code class="literal">"md5"</code>, <code class="literal">"sha1"</code>,
- <code class="literal">"sha256"</code> or <code class="literal">"sha512"</code>.</p></dd><dt><a id="builtin-hashFile"></a><span class="term"><code class="function">builtins.hashFile</code>
- <em class="replaceable"><code>type</code></em> <em class="replaceable"><code>p</code></em></span></dt><dd><p>Return a base-16 representation of the
- cryptographic hash of the file at path <em class="replaceable"><code>p</code></em>. The
- hash algorithm specified by <em class="replaceable"><code>type</code></em> must
- be one of <code class="literal">"md5"</code>, <code class="literal">"sha1"</code>,
- <code class="literal">"sha256"</code> or <code class="literal">"sha512"</code>.</p></dd><dt><a id="builtin-head"></a><span class="term"><code class="function">builtins.head</code>
- <em class="replaceable"><code>list</code></em></span></dt><dd><p>Return the first element of a list; abort
- evaluation if the argument isn’t a list or is an empty list. You
- can test whether a list is empty by comparing it with
- <code class="literal">[]</code>.</p></dd><dt><a id="builtin-import"></a><span class="term"><code class="function">import</code>
- <em class="replaceable"><code>path</code></em>, </span><span class="term"><code class="function">builtins.import</code>
- <em class="replaceable"><code>path</code></em></span></dt><dd><p>Load, parse and return the Nix expression in the
- file <em class="replaceable"><code>path</code></em>. If <em class="replaceable"><code>path
- </code></em> is a directory, the file <code class="filename">default.nix
- </code> in that directory is loaded. Evaluation aborts if the
- file doesn’t exist or contains an incorrect Nix expression.
- <code class="function">import</code> implements Nix’s module system: you
- can put any Nix expression (such as a set or a function) in a
- separate file, and use it from Nix expressions in other
- files.</p><div class="note"><h3 class="title">Note</h3><p>Unlike some languages, <code class="function">import</code> is a regular
- function in Nix. Paths using the angle bracket syntax (e.g., <code class="function">
- import</code> <em class="replaceable"><code><foo></code></em>) are normal path
- values (see <a class="xref" href="#ssec-values" title="15.1. Values">Section 15.1, “Values”</a>).</p></div><p>A Nix expression loaded by <code class="function">import</code> must
- not contain any <span class="emphasis"><em>free variables</em></span> (identifiers
- that are not defined in the Nix expression itself and are not
- built-in). Therefore, it cannot refer to variables that are in
- scope at the call site. For instance, if you have a calling
- expression
-
-</p><pre class="programlisting">
-rec {
- x = 123;
- y = import ./foo.nix;
-}</pre><p>
-
- then the following <code class="filename">foo.nix</code> will give an
- error:
-
-</p><pre class="programlisting">
-x + 456</pre><p>
-
- since <code class="varname">x</code> is not in scope in
- <code class="filename">foo.nix</code>. If you want <code class="varname">x</code>
- to be available in <code class="filename">foo.nix</code>, you should pass
- it as a function argument:
-
-</p><pre class="programlisting">
-rec {
- x = 123;
- y = import ./foo.nix x;
-}</pre><p>
-
- and
-
-</p><pre class="programlisting">
-x: x + 456</pre><p>
-
- (The function argument doesn’t have to be called
- <code class="varname">x</code> in <code class="filename">foo.nix</code>; any name
- would work.)</p></dd><dt><a id="builtin-intersectAttrs"></a><span class="term"><code class="function">builtins.intersectAttrs</code>
- <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>Return a set consisting of the attributes in the
- set <em class="replaceable"><code>e2</code></em> that also exist in the set
- <em class="replaceable"><code>e1</code></em>.</p></dd><dt><a id="builtin-isAttrs"></a><span class="term"><code class="function">builtins.isAttrs</code>
- <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return <code class="literal">true</code> if
- <em class="replaceable"><code>e</code></em> evaluates to a set, and
- <code class="literal">false</code> otherwise.</p></dd><dt><a id="builtin-isList"></a><span class="term"><code class="function">builtins.isList</code>
- <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return <code class="literal">true</code> if
- <em class="replaceable"><code>e</code></em> evaluates to a list, and
- <code class="literal">false</code> otherwise.</p></dd><dt><a id="builtin-isFunction"></a><span class="term"><code class="function">builtins.isFunction</code>
- <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return <code class="literal">true</code> if
- <em class="replaceable"><code>e</code></em> evaluates to a function, and
- <code class="literal">false</code> otherwise.</p></dd><dt><a id="builtin-isString"></a><span class="term"><code class="function">builtins.isString</code>
- <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return <code class="literal">true</code> if
- <em class="replaceable"><code>e</code></em> evaluates to a string, and
- <code class="literal">false</code> otherwise.</p></dd><dt><a id="builtin-isInt"></a><span class="term"><code class="function">builtins.isInt</code>
- <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return <code class="literal">true</code> if
- <em class="replaceable"><code>e</code></em> evaluates to an int, and
- <code class="literal">false</code> otherwise.</p></dd><dt><a id="builtin-isFloat"></a><span class="term"><code class="function">builtins.isFloat</code>
- <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return <code class="literal">true</code> if
- <em class="replaceable"><code>e</code></em> evaluates to a float, and
- <code class="literal">false</code> otherwise.</p></dd><dt><a id="builtin-isBool"></a><span class="term"><code class="function">builtins.isBool</code>
- <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return <code class="literal">true</code> if
- <em class="replaceable"><code>e</code></em> evaluates to a bool, and
- <code class="literal">false</code> otherwise.</p></dd><dt><span class="term"><code class="function">builtins.isPath</code>
- <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return <code class="literal">true</code> if
- <em class="replaceable"><code>e</code></em> evaluates to a path, and
- <code class="literal">false</code> otherwise.</p></dd><dt><a id="builtin-isNull"></a><span class="term"><code class="function">isNull</code>
- <em class="replaceable"><code>e</code></em>, </span><span class="term"><code class="function">builtins.isNull</code>
- <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return <code class="literal">true</code> if
- <em class="replaceable"><code>e</code></em> evaluates to <code class="literal">null</code>,
- and <code class="literal">false</code> otherwise.</p><div class="warning"><h3 class="title">Warning</h3><p>This function is <span class="emphasis"><em>deprecated</em></span>;
- just write <code class="literal">e == null</code> instead.</p></div></dd><dt><a id="builtin-length"></a><span class="term"><code class="function">builtins.length</code>
- <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return the length of the list
- <em class="replaceable"><code>e</code></em>.</p></dd><dt><a id="builtin-lessThan"></a><span class="term"><code class="function">builtins.lessThan</code>
- <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>Return <code class="literal">true</code> if the number
- <em class="replaceable"><code>e1</code></em> is less than the number
- <em class="replaceable"><code>e2</code></em>, and <code class="literal">false</code>
- otherwise. Evaluation aborts if either
- <em class="replaceable"><code>e1</code></em> or <em class="replaceable"><code>e2</code></em>
- does not evaluate to a number.</p></dd><dt><a id="builtin-listToAttrs"></a><span class="term"><code class="function">builtins.listToAttrs</code>
- <em class="replaceable"><code>e</code></em></span></dt><dd><p>Construct a set from a list specifying the names
- and values of each attribute. Each element of the list should be
- a set consisting of a string-valued attribute
- <code class="varname">name</code> specifying the name of the attribute, and
- an attribute <code class="varname">value</code> specifying its value.
- Example:
-
-</p><pre class="programlisting">
-builtins.listToAttrs
- [ { name = "foo"; value = 123; }
- { name = "bar"; value = 456; }
- ]
-</pre><p>
-
- evaluates to
-
-</p><pre class="programlisting">
-{ foo = 123; bar = 456; }
-</pre><p>
-
- </p></dd><dt><a id="builtin-map"></a><span class="term"><code class="function">map</code>
- <em class="replaceable"><code>f</code></em> <em class="replaceable"><code>list</code></em>, </span><span class="term"><code class="function">builtins.map</code>
- <em class="replaceable"><code>f</code></em> <em class="replaceable"><code>list</code></em></span></dt><dd><p>Apply the function <em class="replaceable"><code>f</code></em> to
- each element in the list <em class="replaceable"><code>list</code></em>. For
- example,
-
-</p><pre class="programlisting">
-map (x: "foo" + x) [ "bar" "bla" "abc" ]</pre><p>
-
- evaluates to <code class="literal">[ "foobar" "foobla" "fooabc"
- ]</code>.</p></dd><dt><a id="builtin-match"></a><span class="term"><code class="function">builtins.match</code>
- <em class="replaceable"><code>regex</code></em> <em class="replaceable"><code>str</code></em></span></dt><dd><p>Returns a list if the <a class="link" href="http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_04" target="_top">extended
- POSIX regular expression</a> <em class="replaceable"><code>regex</code></em>
- matches <em class="replaceable"><code>str</code></em> precisely, otherwise returns
- <code class="literal">null</code>. Each item in the list is a regex group.
-
-</p><pre class="programlisting">
-builtins.match "ab" "abc"
-</pre><p>
-
-Evaluates to <code class="literal">null</code>.
-
-</p><pre class="programlisting">
-builtins.match "abc" "abc"
-</pre><p>
-
-Evaluates to <code class="literal">[ ]</code>.
-
-</p><pre class="programlisting">
-builtins.match "a(b)(c)" "abc"
-</pre><p>
-
-Evaluates to <code class="literal">[ "b" "c" ]</code>.
-
-</p><pre class="programlisting">
-builtins.match "[[:space:]]+([[:upper:]]+)[[:space:]]+" " FOO "
-</pre><p>
-
-Evaluates to <code class="literal">[ "foo" ]</code>.
-
- </p></dd><dt><a id="builtin-mul"></a><span class="term"><code class="function">builtins.mul</code>
- <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>Return the product of the numbers
- <em class="replaceable"><code>e1</code></em> and
- <em class="replaceable"><code>e2</code></em>.</p></dd><dt><a id="builtin-parseDrvName"></a><span class="term"><code class="function">builtins.parseDrvName</code>
- <em class="replaceable"><code>s</code></em></span></dt><dd><p>Split the string <em class="replaceable"><code>s</code></em> into
- a package name and version. The package name is everything up to
- but not including the first dash followed by a digit, and the
- version is everything following that dash. The result is returned
- in a set <code class="literal">{ name, version }</code>. Thus,
- <code class="literal">builtins.parseDrvName "nix-0.12pre12876"</code>
- returns <code class="literal">{ name = "nix"; version = "0.12pre12876";
- }</code>.</p></dd><dt><a id="builtin-path"></a><span class="term">
- <code class="function">builtins.path</code>
- <em class="replaceable"><code>args</code></em>
- </span></dt><dd><p>
- An enrichment of the built-in path type, based on the attributes
- present in <em class="replaceable"><code>args</code></em>. All are optional
- except <code class="varname">path</code>:
- </p><div class="variablelist"><dl class="variablelist"><dt><span class="term">path</span></dt><dd><p>The underlying path.</p></dd><dt><span class="term">name</span></dt><dd><p>
- The name of the path when added to the store. This can
- used to reference paths that have nix-illegal characters
- in their names, like <code class="literal">@</code>.
- </p></dd><dt><span class="term">filter</span></dt><dd><p>
- A function of the type expected by
- <a class="link" href="#builtin-filterSource">builtins.filterSource</a>,
- with the same semantics.
- </p></dd><dt><span class="term">recursive</span></dt><dd><p>
- When <code class="literal">false</code>, when
- <code class="varname">path</code> is added to the store it is with a
- flat hash, rather than a hash of the NAR serialization of
- the file. Thus, <code class="varname">path</code> must refer to a
- regular file, not a directory. This allows similar
- behavior to <code class="literal">fetchurl</code>. Defaults to
- <code class="literal">true</code>.
- </p></dd><dt><span class="term">sha256</span></dt><dd><p>
- When provided, this is the expected hash of the file at
- the path. Evaluation will fail if the hash is incorrect,
- and providing a hash allows
- <code class="literal">builtins.path</code> to be used even when the
- <code class="literal">pure-eval</code> nix config option is on.
- </p></dd></dl></div></dd><dt><a id="builtin-pathExists"></a><span class="term"><code class="function">builtins.pathExists</code>
- <em class="replaceable"><code>path</code></em></span></dt><dd><p>Return <code class="literal">true</code> if the path
- <em class="replaceable"><code>path</code></em> exists at evaluation time, and
- <code class="literal">false</code> otherwise.</p></dd><dt><a id="builtin-placeholder"></a><span class="term"><code class="function">builtins.placeholder</code>
- <em class="replaceable"><code>output</code></em></span></dt><dd><p>Return a placeholder string for the specified
- <em class="replaceable"><code>output</code></em> that will be substituted by the
- corresponding output path at build time. Typical outputs would be
- <code class="literal">"out"</code>, <code class="literal">"bin"</code> or
- <code class="literal">"dev"</code>.</p></dd><dt><a id="builtin-readDir"></a><span class="term"><code class="function">builtins.readDir</code>
- <em class="replaceable"><code>path</code></em></span></dt><dd><p>Return the contents of the directory
- <em class="replaceable"><code>path</code></em> as a set mapping directory entries
- to the corresponding file type. For instance, if directory
- <code class="filename">A</code> contains a regular file
- <code class="filename">B</code> and another directory
- <code class="filename">C</code>, then <code class="literal">builtins.readDir
- ./A</code> will return the set
-
-</p><pre class="programlisting">
-{ B = "regular"; C = "directory"; }</pre><p>
-
- The possible values for the file type are
- <code class="literal">"regular"</code>, <code class="literal">"directory"</code>,
- <code class="literal">"symlink"</code> and
- <code class="literal">"unknown"</code>.</p></dd><dt><a id="builtin-readFile"></a><span class="term"><code class="function">builtins.readFile</code>
- <em class="replaceable"><code>path</code></em></span></dt><dd><p>Return the contents of the file
- <em class="replaceable"><code>path</code></em> as a string.</p></dd><dt><a id="builtin-removeAttrs"></a><span class="term"><code class="function">removeAttrs</code>
- <em class="replaceable"><code>set</code></em> <em class="replaceable"><code>list</code></em>, </span><span class="term"><code class="function">builtins.removeAttrs</code>
- <em class="replaceable"><code>set</code></em> <em class="replaceable"><code>list</code></em></span></dt><dd><p>Remove the attributes listed in
- <em class="replaceable"><code>list</code></em> from
- <em class="replaceable"><code>set</code></em>. The attributes don’t have to
- exist in <em class="replaceable"><code>set</code></em>. For instance,
-
-</p><pre class="programlisting">
-removeAttrs { x = 1; y = 2; z = 3; } [ "a" "x" "z" ]</pre><p>
-
- evaluates to <code class="literal">{ y = 2; }</code>.</p></dd><dt><a id="builtin-replaceStrings"></a><span class="term"><code class="function">builtins.replaceStrings</code>
- <em class="replaceable"><code>from</code></em> <em class="replaceable"><code>to</code></em> <em class="replaceable"><code>s</code></em></span></dt><dd><p>Given string <em class="replaceable"><code>s</code></em>, replace
- every occurrence of the strings in <em class="replaceable"><code>from</code></em>
- with the corresponding string in
- <em class="replaceable"><code>to</code></em>. For example,
-
-</p><pre class="programlisting">
-builtins.replaceStrings ["oo" "a"] ["a" "i"] "foobar"
-</pre><p>
-
- evaluates to <code class="literal">"fabir"</code>.</p></dd><dt><a id="builtin-seq"></a><span class="term"><code class="function">builtins.seq</code>
- <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>Evaluate <em class="replaceable"><code>e1</code></em>, then
- evaluate and return <em class="replaceable"><code>e2</code></em>. This ensures
- that a computation is strict in the value of
- <em class="replaceable"><code>e1</code></em>.</p></dd><dt><a id="builtin-sort"></a><span class="term"><code class="function">builtins.sort</code>
- <em class="replaceable"><code>comparator</code></em> <em class="replaceable"><code>list</code></em></span></dt><dd><p>Return <em class="replaceable"><code>list</code></em> in sorted
- order. It repeatedly calls the function
- <em class="replaceable"><code>comparator</code></em> with two elements. The
- comparator should return <code class="literal">true</code> if the first
- element is less than the second, and <code class="literal">false</code>
- otherwise. For example,
-
-</p><pre class="programlisting">
-builtins.sort builtins.lessThan [ 483 249 526 147 42 77 ]
-</pre><p>
-
- produces the list <code class="literal">[ 42 77 147 249 483 526
- ]</code>.</p><p>This is a stable sort: it preserves the relative order of
- elements deemed equal by the comparator.</p></dd><dt><a id="builtin-split"></a><span class="term"><code class="function">builtins.split</code>
- <em class="replaceable"><code>regex</code></em> <em class="replaceable"><code>str</code></em></span></dt><dd><p>Returns a list composed of non matched strings interleaved
- with the lists of the <a class="link" href="http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_04" target="_top">extended
- POSIX regular expression</a> <em class="replaceable"><code>regex</code></em> matches
- of <em class="replaceable"><code>str</code></em>. Each item in the lists of matched
- sequences is a regex group.
-
-</p><pre class="programlisting">
-builtins.split "(a)b" "abc"
-</pre><p>
-
-Evaluates to <code class="literal">[ "" [ "a" ] "c" ]</code>.
-
-</p><pre class="programlisting">
-builtins.split "([ac])" "abc"
-</pre><p>
-
-Evaluates to <code class="literal">[ "" [ "a" ] "b" [ "c" ] "" ]</code>.
-
-</p><pre class="programlisting">
-builtins.split "(a)|(c)" "abc"
-</pre><p>
-
-Evaluates to <code class="literal">[ "" [ "a" null ] "b" [ null "c" ] "" ]</code>.
-
-</p><pre class="programlisting">
-builtins.split "([[:upper:]]+)" " FOO "
-</pre><p>
-
-Evaluates to <code class="literal">[ " " [ "FOO" ] " " ]</code>.
-
- </p></dd><dt><a id="builtin-splitVersion"></a><span class="term"><code class="function">builtins.splitVersion</code>
- <em class="replaceable"><code>s</code></em></span></dt><dd><p>Split a string representing a version into its
- components, by the same version splitting logic underlying the
- version comparison in <a class="link" href="#ssec-version-comparisons" title="Versions">
- <span class="command"><strong>nix-env -u</strong></span></a>.</p></dd><dt><a id="builtin-stringLength"></a><span class="term"><code class="function">builtins.stringLength</code>
- <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return the length of the string
- <em class="replaceable"><code>e</code></em>. If <em class="replaceable"><code>e</code></em> is
- not a string, evaluation is aborted.</p></dd><dt><a id="builtin-sub"></a><span class="term"><code class="function">builtins.sub</code>
- <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>Return the difference between the numbers
- <em class="replaceable"><code>e1</code></em> and
- <em class="replaceable"><code>e2</code></em>.</p></dd><dt><a id="builtin-substring"></a><span class="term"><code class="function">builtins.substring</code>
- <em class="replaceable"><code>start</code></em> <em class="replaceable"><code>len</code></em>
- <em class="replaceable"><code>s</code></em></span></dt><dd><p>Return the substring of
- <em class="replaceable"><code>s</code></em> from character position
- <em class="replaceable"><code>start</code></em> (zero-based) up to but not
- including <em class="replaceable"><code>start + len</code></em>. If
- <em class="replaceable"><code>start</code></em> is greater than the length of the
- string, an empty string is returned, and if <em class="replaceable"><code>start +
- len</code></em> lies beyond the end of the string, only the
- substring up to the end of the string is returned.
- <em class="replaceable"><code>start</code></em> must be
- non-negative. For example,
-
-</p><pre class="programlisting">
-builtins.substring 0 3 "nixos"
-</pre><p>
-
- evaluates to <code class="literal">"nix"</code>.
- </p></dd><dt><a id="builtin-tail"></a><span class="term"><code class="function">builtins.tail</code>
- <em class="replaceable"><code>list</code></em></span></dt><dd><p>Return the second to last elements of a list;
- abort evaluation if the argument isn’t a list or is an empty
- list.</p></dd><dt><a id="builtin-throw"></a><span class="term"><code class="function">throw</code>
- <em class="replaceable"><code>s</code></em>, </span><span class="term"><code class="function">builtins.throw</code>
- <em class="replaceable"><code>s</code></em></span></dt><dd><p>Throw an error message
- <em class="replaceable"><code>s</code></em>. This usually aborts Nix expression
- evaluation, but in <span class="command"><strong>nix-env -qa</strong></span> and other
- commands that try to evaluate a set of derivations to get
- information about those derivations, a derivation that throws an
- error is silently skipped (which is not the case for
- <code class="function">abort</code>).</p></dd><dt><a id="builtin-toFile"></a><span class="term"><code class="function">builtins.toFile</code>
- <em class="replaceable"><code>name</code></em>
- <em class="replaceable"><code>s</code></em></span></dt><dd><p>Store the string <em class="replaceable"><code>s</code></em> in a
- file in the Nix store and return its path. The file has suffix
- <em class="replaceable"><code>name</code></em>. This file can be used as an
- input to derivations. One application is to write builders
- “inline”. For instance, the following Nix expression combines
- <a class="xref" href="#ex-hello-nix" title="Example 14.1. Nix expression for GNU Hello (default.nix)">Example 14.1, “Nix expression for GNU Hello
-(<code class="filename">default.nix</code>)”</a> and <a class="xref" href="#ex-hello-builder" title="Example 14.2. Build script for GNU Hello (builder.sh)">Example 14.2, “Build script for GNU Hello
-(<code class="filename">builder.sh</code>)”</a> into one file:
-
-</p><pre class="programlisting">
-{ stdenv, fetchurl, perl }:
-
-stdenv.mkDerivation {
- name = "hello-2.1.1";
-
- builder = builtins.toFile "builder.sh" "
- source $stdenv/setup
-
- PATH=$perl/bin:$PATH
-
- tar xvfz $src
- cd hello-*
- ./configure --prefix=$out
- make
- make install
- ";
-
- src = fetchurl {
- url = "http://ftp.nluug.nl/pub/gnu/hello/hello-2.1.1.tar.gz";
- sha256 = "1md7jsfd8pa45z73bz1kszpp01yw6x5ljkjk2hx7wl800any6465";
- };
- inherit perl;
-}</pre><p>
-
- </p><p>It is even possible for one file to refer to another, e.g.,
-
-</p><pre class="programlisting">
- builder = let
- configFile = builtins.toFile "foo.conf" "
- # This is some dummy configuration file.
- <em class="replaceable"><code>...</code></em>
- ";
- in builtins.toFile "builder.sh" "
- source $stdenv/setup
- <em class="replaceable"><code>...</code></em>
- cp ${configFile} $out/etc/foo.conf
- ";</pre><p>
-
- Note that <code class="literal">${configFile}</code> is an antiquotation
- (see <a class="xref" href="#ssec-values" title="15.1. Values">Section 15.1, “Values”</a>), so the result of the
- expression <code class="literal">configFile</code> (i.e., a path like
- <code class="filename">/nix/store/m7p7jfny445k...-foo.conf</code>) will be
- spliced into the resulting string.</p><p>It is however <span class="emphasis"><em>not</em></span> allowed to have files
- mutually referring to each other, like so:
-
-</p><pre class="programlisting">
-let
- foo = builtins.toFile "foo" "...${bar}...";
- bar = builtins.toFile "bar" "...${foo}...";
-in foo</pre><p>
-
- This is not allowed because it would cause a cyclic dependency in
- the computation of the cryptographic hashes for
- <code class="varname">foo</code> and <code class="varname">bar</code>.</p><p>It is also not possible to reference the result of a derivation.
- If you are using Nixpkgs, the <code class="literal">writeTextFile</code> function is able to
- do that.</p></dd><dt><a id="builtin-toJSON"></a><span class="term"><code class="function">builtins.toJSON</code> <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return a string containing a JSON representation
- of <em class="replaceable"><code>e</code></em>. Strings, integers, floats, booleans,
- nulls and lists are mapped to their JSON equivalents. Sets
- (except derivations) are represented as objects. Derivations are
- translated to a JSON string containing the derivation’s output
- path. Paths are copied to the store and represented as a JSON
- string of the resulting store path.</p></dd><dt><a id="builtin-toPath"></a><span class="term"><code class="function">builtins.toPath</code> <em class="replaceable"><code>s</code></em></span></dt><dd><p> DEPRECATED. Use <code class="literal">/. + "/path"</code>
- to convert a string into an absolute path. For relative paths,
- use <code class="literal">./. + "/path"</code>.
- </p></dd><dt><a id="builtin-toString"></a><span class="term"><code class="function">toString</code> <em class="replaceable"><code>e</code></em>, </span><span class="term"><code class="function">builtins.toString</code> <em class="replaceable"><code>e</code></em></span></dt><dd><p>Convert the expression
- <em class="replaceable"><code>e</code></em> to a string.
- <em class="replaceable"><code>e</code></em> can be:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>A string (in which case the string is returned unmodified).</p></li><li class="listitem"><p>A path (e.g., <code class="literal">toString /foo/bar</code> yields <code class="literal">"/foo/bar"</code>.</p></li><li class="listitem"><p>A set containing <code class="literal">{ __toString = self: ...; }</code>.</p></li><li class="listitem"><p>An integer.</p></li><li class="listitem"><p>A list, in which case the string representations of its elements are joined with spaces.</p></li><li class="listitem"><p>A Boolean (<code class="literal">false</code> yields <code class="literal">""</code>, <code class="literal">true</code> yields <code class="literal">"1"</code>).</p></li><li class="listitem"><p><code class="literal">null</code>, which yields the empty string.</p></li></ul></div></dd><dt><a id="builtin-toXML"></a><span class="term"><code class="function">builtins.toXML</code> <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return a string containing an XML representation
- of <em class="replaceable"><code>e</code></em>. The main application for
- <code class="function">toXML</code> is to communicate information with the
- builder in a more structured format than plain environment
- variables.</p><p><a class="xref" href="#ex-toxml" title="Example 15.8. Passing information to a builder using toXML">Example 15.8, “Passing information to a builder
- using <code class="function">toXML</code>”</a> shows an example where this is
- the case. The builder is supposed to generate the configuration
- file for a <a class="link" href="http://jetty.mortbay.org/" target="_top">Jetty
- servlet container</a>. A servlet container contains a number
- of servlets (<code class="filename">*.war</code> files) each exported under
- a specific URI prefix. So the servlet configuration is a list of
- sets containing the <code class="varname">path</code> and
- <code class="varname">war</code> of the servlet (<a class="xref" href="#ex-toxml-co-servlets">(3)</a>). This kind of information is
- difficult to communicate with the normal method of passing
- information through an environment variable, which just
- concatenates everything together into a string (which might just
- work in this case, but wouldn’t work if fields are optional or
- contain lists themselves). Instead the Nix expression is
- converted to an XML representation with
- <code class="function">toXML</code>, which is unambiguous and can easily be
- processed with the appropriate tools. For instance, in the
- example an XSLT stylesheet (<a class="xref" href="#ex-toxml-co-stylesheet">(2)</a>) is applied to it (<a class="xref" href="#ex-toxml-co-apply">(1)</a>) to
- generate the XML configuration file for the Jetty server. The XML
- representation produced from <a class="xref" href="#ex-toxml-co-servlets">(3)</a> by <code class="function">toXML</code> is shown in <a class="xref" href="#ex-toxml-result" title="Example 15.9. XML representation produced by toXML">Example 15.9, “XML representation produced by
- <code class="function">toXML</code>”</a>.</p><p>Note that <a class="xref" href="#ex-toxml" title="Example 15.8. Passing information to a builder using toXML">Example 15.8, “Passing information to a builder
- using <code class="function">toXML</code>”</a> uses the <code class="function"><a class="function" href="#builtin-toFile">toFile</a></code> built-in to write the
- builder and the stylesheet “inline” in the Nix expression. The
- path of the stylesheet is spliced into the builder at
- <code class="literal">xsltproc ${stylesheet}
- <em class="replaceable"><code>...</code></em></code>.</p><div class="example"><a id="ex-toxml"></a><p class="title"><strong>Example 15.8. Passing information to a builder
- using <code class="function">toXML</code></strong></p><div class="example-contents"><pre class="programlisting">
-{ stdenv, fetchurl, libxslt, jira, uberwiki }:
-
-stdenv.mkDerivation (rec {
- name = "web-server";
-
- buildInputs = [ libxslt ];
-
- builder = builtins.toFile "builder.sh" "
- source $stdenv/setup
- mkdir $out
- echo "$servlets" | xsltproc ${stylesheet} - > $out/server-conf.xml <a id="ex-toxml-co-apply"></a>(1)
- ";
-
- stylesheet = builtins.toFile "stylesheet.xsl" <a id="ex-toxml-co-stylesheet"></a>(2)
- "<?xml version='1.0' encoding='UTF-8'?>
- <xsl:stylesheet xmlns:xsl='http://www.w3.org/1999/XSL/Transform' version='1.0'>
- <xsl:template match='/'>
- <Configure>
- <xsl:for-each select='/expr/list/attrs'>
- <Call name='addWebApplication'>
- <Arg><xsl:value-of select=\"attr[@name = 'path']/string/@value\" /></Arg>
- <Arg><xsl:value-of select=\"attr[@name = 'war']/path/@value\" /></Arg>
- </Call>
- </xsl:for-each>
- </Configure>
- </xsl:template>
- </xsl:stylesheet>
- ";
-
- servlets = builtins.toXML [ <a id="ex-toxml-co-servlets"></a>(3)
- { path = "/bugtracker"; war = jira + "/lib/atlassian-jira.war"; }
- { path = "/wiki"; war = uberwiki + "/uberwiki.war"; }
- ];
-})</pre></div></div><br class="example-break" /><div class="example"><a id="ex-toxml-result"></a><p class="title"><strong>Example 15.9. XML representation produced by
- <code class="function">toXML</code></strong></p><div class="example-contents"><pre class="programlisting"><?xml version='1.0' encoding='utf-8'?>
-<expr>
- <list>
- <attrs>
- <attr name="path">
- <string value="/bugtracker" />
- </attr>
- <attr name="war">
- <path value="/nix/store/d1jh9pasa7k2...-jira/lib/atlassian-jira.war" />
- </attr>
- </attrs>
- <attrs>
- <attr name="path">
- <string value="/wiki" />
- </attr>
- <attr name="war">
- <path value="/nix/store/y6423b1yi4sx...-uberwiki/uberwiki.war" />
- </attr>
- </attrs>
- </list>
-</expr></pre></div></div><br class="example-break" /></dd><dt><a id="builtin-trace"></a><span class="term"><code class="function">builtins.trace</code>
- <em class="replaceable"><code>e1</code></em> <em class="replaceable"><code>e2</code></em></span></dt><dd><p>Evaluate <em class="replaceable"><code>e1</code></em> and print its
- abstract syntax representation on standard error. Then return
- <em class="replaceable"><code>e2</code></em>. This function is useful for
- debugging.</p></dd><dt><a id="builtin-tryEval"></a><span class="term"><code class="function">builtins.tryEval</code>
- <em class="replaceable"><code>e</code></em></span></dt><dd><p>Try to shallowly evaluate <em class="replaceable"><code>e</code></em>.
- Return a set containing the attributes <code class="literal">success</code>
- (<code class="literal">true</code> if <em class="replaceable"><code>e</code></em> evaluated
- successfully, <code class="literal">false</code> if an error was thrown) and
- <code class="literal">value</code>, equalling <em class="replaceable"><code>e</code></em>
- if successful and <code class="literal">false</code> otherwise. Note that this
- doesn't evaluate <em class="replaceable"><code>e</code></em> deeply, so
- <code class="literal">let e = { x = throw ""; }; in (builtins.tryEval e).success
- </code> will be <code class="literal">true</code>. Using <code class="literal">builtins.deepSeq
- </code> one can get the expected result: <code class="literal">let e = { x = throw "";
- }; in (builtins.tryEval (builtins.deepSeq e e)).success</code> will be
- <code class="literal">false</code>.
- </p></dd><dt><a id="builtin-typeOf"></a><span class="term"><code class="function">builtins.typeOf</code>
- <em class="replaceable"><code>e</code></em></span></dt><dd><p>Return a string representing the type of the value
- <em class="replaceable"><code>e</code></em>, namely <code class="literal">"int"</code>,
- <code class="literal">"bool"</code>, <code class="literal">"string"</code>,
- <code class="literal">"path"</code>, <code class="literal">"null"</code>,
- <code class="literal">"set"</code>, <code class="literal">"list"</code>,
- <code class="literal">"lambda"</code> or
- <code class="literal">"float"</code>.</p></dd></dl></div></div><div class="footnotes"><br /><hr style="width:100; text-align:left;margin-left: 0" /><div id="ftn.idm139733301368560" class="footnote"><p><a href="#idm139733301368560" class="para"><sup class="para">[5] </sup></a>It's parsed as an expression that selects the
- attribute <code class="varname">sh</code> from the variable
- <code class="varname">builder</code>.</p></div><div id="ftn.idm139733301331328" class="footnote"><p><a href="#idm139733301331328" class="para"><sup class="para">[6] </sup></a>Actually, Nix detects infinite
-recursion in this case and aborts (<span class="quote">“<span class="quote">infinite recursion
-encountered</span>”</span>).</p></div><div id="ftn.idm139733301168656" class="footnote"><p><a href="#idm139733301168656" class="para"><sup class="para">[7] </sup></a>To figure out
- your platform identifier, look at the line <span class="quote">“<span class="quote">Checking for the
- canonical Nix system name</span>”</span> in the output of Nix's
- <code class="filename">configure</code> script.</p></div></div></div></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a id="part-advanced-topics"></a>Part V. Advanced Topics</h1></div></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="chap-distributed-builds"></a>Chapter 16. Remote Builds</h2></div></div></div><p>Nix supports remote builds, where a local Nix installation can
-forward Nix builds to other machines. This allows multiple builds to
-be performed in parallel and allows Nix to perform multi-platform
-builds in a semi-transparent way. For instance, if you perform a
-build for a <code class="literal">x86_64-darwin</code> on an
-<code class="literal">i686-linux</code> machine, Nix can automatically forward
-the build to a <code class="literal">x86_64-darwin</code> machine, if
-available.</p><p>To forward a build to a remote machine, it’s required that the
-remote machine is accessible via SSH and that it has Nix
-installed. You can test whether connecting to the remote Nix instance
-works, e.g.
-
-</p><pre class="screen">
-$ nix ping-store --store ssh://mac
-</pre><p>
-
-will try to connect to the machine named <code class="literal">mac</code>. It is
-possible to specify an SSH identity file as part of the remote store
-URI, e.g.
-
-</p><pre class="screen">
-$ nix ping-store --store ssh://mac?ssh-key=/home/alice/my-key
-</pre><p>
-
-Since builds should be non-interactive, the key should not have a
-passphrase. Alternatively, you can load identities ahead of time into
-<span class="command"><strong>ssh-agent</strong></span> or <span class="command"><strong>gpg-agent</strong></span>.</p><p>If you get the error
-
-</p><pre class="screen">
-bash: nix-store: command not found
-error: cannot connect to 'mac'
-</pre><p>
-
-then you need to ensure that the <code class="envar">PATH</code> of
-non-interactive login shells contains Nix.</p><div class="warning"><h3 class="title">Warning</h3><p>If you are building via the Nix daemon, it is the Nix
-daemon user account (that is, <code class="literal">root</code>) that should
-have SSH access to the remote machine. If you can’t or don’t want to
-configure <code class="literal">root</code> to be able to access to remote
-machine, you can use a private Nix store instead by passing
-e.g. <code class="literal">--store ~/my-nix</code>.</p></div><p>The list of remote machines can be specified on the command line
-or in the Nix configuration file. The former is convenient for
-testing. For example, the following command allows you to build a
-derivation for <code class="literal">x86_64-darwin</code> on a Linux machine:
-
-</p><pre class="screen">
-$ uname
-Linux
-
-$ nix build \
- '(with import <nixpkgs> { system = "x86_64-darwin"; }; runCommand "foo" {} "uname > $out")' \
- --builders 'ssh://mac x86_64-darwin'
-[1/0/1 built, 0.0 MiB DL] building foo on ssh://mac
-
-$ cat ./result
-Darwin
-</pre><p>
-
-It is possible to specify multiple builders separated by a semicolon
-or a newline, e.g.
-
-</p><pre class="screen">
- --builders 'ssh://mac x86_64-darwin ; ssh://beastie x86_64-freebsd'
-</pre><p>
-</p><p>Each machine specification consists of the following elements,
-separated by spaces. Only the first element is required.
-To leave a field at its default, set it to <code class="literal">-</code>.
-
-</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>The URI of the remote store in the format
- <code class="literal">ssh://[<em class="replaceable"><code>username</code></em>@]<em class="replaceable"><code>hostname</code></em></code>,
- e.g. <code class="literal">ssh://nix@mac</code> or
- <code class="literal">ssh://mac</code>. For backward compatibility,
- <code class="literal">ssh://</code> may be omitted. The hostname may be an
- alias defined in your
- <code class="filename">~/.ssh/config</code>.</p></li><li class="listitem"><p>A comma-separated list of Nix platform type
- identifiers, such as <code class="literal">x86_64-darwin</code>. It is
- possible for a machine to support multiple platform types, e.g.,
- <code class="literal">i686-linux,x86_64-linux</code>. If omitted, this
- defaults to the local platform type.</p></li><li class="listitem"><p>The SSH identity file to be used to log in to the
- remote machine. If omitted, SSH will use its regular
- identities.</p></li><li class="listitem"><p>The maximum number of builds that Nix will execute
- in parallel on the machine. Typically this should be equal to the
- number of CPU cores. For instance, the machine
- <code class="literal">itchy</code> in the example will execute up to 8 builds
- in parallel.</p></li><li class="listitem"><p>The “speed factor”, indicating the relative speed of
- the machine. If there are multiple machines of the right type, Nix
- will prefer the fastest, taking load into account.</p></li><li class="listitem"><p>A comma-separated list of <span class="emphasis"><em>supported
- features</em></span>. If a derivation has the
- <code class="varname">requiredSystemFeatures</code> attribute, then Nix will
- only perform the derivation on a machine that has the specified
- features. For instance, the attribute
-
-</p><pre class="programlisting">
-requiredSystemFeatures = [ "kvm" ];
-</pre><p>
-
- will cause the build to be performed on a machine that has the
- <code class="literal">kvm</code> feature.</p></li><li class="listitem"><p>A comma-separated list of <span class="emphasis"><em>mandatory
- features</em></span>. A machine will only be used to build a
- derivation if all of the machine’s mandatory features appear in the
- derivation’s <code class="varname">requiredSystemFeatures</code>
- attribute..</p></li></ol></div><p>
-
-For example, the machine specification
-
-</p><pre class="programlisting">
-nix@scratchy.labs.cs.uu.nl i686-linux /home/nix/.ssh/id_scratchy_auto 8 1 kvm
-nix@itchy.labs.cs.uu.nl i686-linux /home/nix/.ssh/id_scratchy_auto 8 2
-nix@poochie.labs.cs.uu.nl i686-linux /home/nix/.ssh/id_scratchy_auto 1 2 kvm benchmark
-</pre><p>
-
-specifies several machines that can perform
-<code class="literal">i686-linux</code> builds. However,
-<code class="literal">poochie</code> will only do builds that have the attribute
-
-</p><pre class="programlisting">
-requiredSystemFeatures = [ "benchmark" ];
-</pre><p>
-
-or
-
-</p><pre class="programlisting">
-requiredSystemFeatures = [ "benchmark" "kvm" ];
-</pre><p>
-
-<code class="literal">itchy</code> cannot do builds that require
-<code class="literal">kvm</code>, but <code class="literal">scratchy</code> does support
-such builds. For regular builds, <code class="literal">itchy</code> will be
-preferred over <code class="literal">scratchy</code> because it has a higher
-speed factor.</p><p>Remote builders can also be configured in
-<code class="filename">nix.conf</code>, e.g.
-
-</p><pre class="programlisting">
-builders = ssh://mac x86_64-darwin ; ssh://beastie x86_64-freebsd
-</pre><p>
-
-Finally, remote builders can be configured in a separate configuration
-file included in <code class="option">builders</code> via the syntax
-<code class="literal">@<em class="replaceable"><code>file</code></em></code>. For example,
-
-</p><pre class="programlisting">
-builders = @/etc/nix/machines
-</pre><p>
-
-causes the list of machines in <code class="filename">/etc/nix/machines</code>
-to be included. (This is the default.)</p><p>If you want the builders to use caches, you likely want to set
-the option <a class="link" href="#conf-builders-use-substitutes"><code class="literal">builders-use-substitutes</code></a>
-in your local <code class="filename">nix.conf</code>.</p><p>To build only on remote builders and disable building on the local machine,
-you can use the option <code class="option">--max-jobs 0</code>.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="chap-tuning-cores-and-jobs"></a>Chapter 17. Tuning Cores and Jobs</h2></div></div></div><p>Nix has two relevant settings with regards to how your CPU cores
-will be utilized: <a class="xref" href="#conf-cores"><code class="literal">cores</code></a> and
-<a class="xref" href="#conf-max-jobs"><code class="literal">max-jobs</code></a>. This chapter will talk about what
-they are, how they interact, and their configuration trade-offs.</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><a class="xref" href="#conf-max-jobs"><code class="literal">max-jobs</code></a></span></dt><dd><p>
- Dictates how many separate derivations will be built at the same
- time. If you set this to zero, the local machine will do no
- builds. Nix will still substitute from binary caches, and build
- remotely if remote builders are configured.
- </p></dd><dt><span class="term"><a class="xref" href="#conf-cores"><code class="literal">cores</code></a></span></dt><dd><p>
- Suggests how many cores each derivation should use. Similar to
- <span class="command"><strong>make -j</strong></span>.
- </p></dd></dl></div><p>The <a class="xref" href="#conf-cores"><code class="literal">cores</code></a> setting determines the value of
-<code class="envar">NIX_BUILD_CORES</code>. <code class="envar">NIX_BUILD_CORES</code> is equal
-to <a class="xref" href="#conf-cores"><code class="literal">cores</code></a>, unless <a class="xref" href="#conf-cores"><code class="literal">cores</code></a>
-equals <code class="literal">0</code>, in which case <code class="envar">NIX_BUILD_CORES</code>
-will be the total number of cores in the system.</p><p>The maximum number of consumed cores is a simple multiplication,
-<a class="xref" href="#conf-max-jobs"><code class="literal">max-jobs</code></a> * <code class="envar">NIX_BUILD_CORES</code>.</p><p>The balance on how to set these two independent variables depends
-upon each builder's workload and hardware. Here are a few example
-scenarios on a machine with 24 cores:</p><div class="table"><a id="idm139733300537552"></a><p class="title"><strong>Table 17.1. Balancing 24 Build Cores</strong></p><div class="table-contents"><table><thead><tr>
- <th><a class="xref" href="#conf-max-jobs"><code class="literal">max-jobs</code></a></th>
- <th><a class="xref" href="#conf-cores"><code class="literal">cores</code></a></th>
- <th><code class="envar">NIX_BUILD_CORES</code></th>
- <th>Maximum Processes</th>
- <th>Result</th>
- </tr></thead><tbody><tr>
- <td>1</td>
- <td>24</td>
- <td>24</td>
- <td>24</td>
- <td>
- One derivation will be built at a time, each one can use 24
- cores. Undersold if a job can’t use 24 cores.
- </td>
- </tr><tr>
- <td>4</td>
- <td>6</td>
- <td>6</td>
- <td>24</td>
- <td>
- Four derivations will be built at once, each given access to
- six cores.
- </td>
- </tr><tr>
- <td>12</td>
- <td>6</td>
- <td>6</td>
- <td>72</td>
- <td>
- 12 derivations will be built at once, each given access to six
- cores. This configuration is over-sold. If all 12 derivations
- being built simultaneously try to use all six cores, the
- machine's performance will be degraded due to extensive context
- switching between the 12 builds.
- </td>
- </tr><tr>
- <td>24</td>
- <td>1</td>
- <td>1</td>
- <td>24</td>
- <td>
- 24 derivations can build at the same time, each using a single
- core. Never oversold, but derivations which require many cores
- will be very slow to compile.
- </td>
- </tr><tr>
- <td>24</td>
- <td>0</td>
- <td>24</td>
- <td>576</td>
- <td>
- 24 derivations can build at the same time, each using all the
- available cores of the machine. Very likely to be oversold,
- and very likely to suffer context switches.
- </td>
- </tr></tbody></table></div></div><br class="table-break" /><p>It is up to the derivations' build script to respect
-host's requested cores-per-build by following the value of the
-<code class="envar">NIX_BUILD_CORES</code> environment variable.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="chap-diff-hook"></a>Chapter 18. Verifying Build Reproducibility with <code class="option"><a class="option" href="#conf-diff-hook">diff-hook</a></code></h2></div><div><h3 class="subtitle"><em>Check build reproducibility by running builds multiple times
-and comparing their results.</em></h3></div></div></div><p>Specify a program with Nix's <a class="xref" href="#conf-diff-hook"><code class="literal">diff-hook</code></a> to
-compare build results when two builds produce different results. Note:
-this hook is only executed if the results are not the same, this hook
-is not used for determining if the results are the same.</p><p>For purposes of demonstration, we'll use the following Nix file,
-<code class="filename">deterministic.nix</code> for testing:</p><pre class="programlisting">
-let
- inherit (import <nixpkgs> {}) runCommand;
-in {
- stable = runCommand "stable" {} ''
- touch $out
- '';
-
- unstable = runCommand "unstable" {} ''
- echo $RANDOM > $out
- '';
-}
-</pre><p>Additionally, <code class="filename">nix.conf</code> contains:
-
-</p><pre class="programlisting">
-diff-hook = /etc/nix/my-diff-hook
-run-diff-hook = true
-</pre><p>
-
-where <code class="filename">/etc/nix/my-diff-hook</code> is an executable
-file containing:
-
-</p><pre class="programlisting">
-#!/bin/sh
-exec >&2
-echo "For derivation $3:"
-/run/current-system/sw/bin/diff -r "$1" "$2"
-</pre><p>
-
-</p><p>The diff hook is executed by the same user and group who ran the
-build. However, the diff hook does not have write access to the store
-path just built.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733300510624"></a>18.1.
- Spot-Checking Build Determinism
- </h2></div></div></div><p>
- Verify a path which already exists in the Nix store by passing
- <code class="option">--check</code> to the build command.
- </p><p>If the build passes and is deterministic, Nix will exit with a
- status code of 0:</p><pre class="screen">
-$ nix-build ./deterministic.nix -A stable
-this derivation will be built:
- /nix/store/z98fasz2jqy9gs0xbvdj939p27jwda38-stable.drv
-building '/nix/store/z98fasz2jqy9gs0xbvdj939p27jwda38-stable.drv'...
-/nix/store/yyxlzw3vqaas7wfp04g0b1xg51f2czgq-stable
-
-$ nix-build ./deterministic.nix -A stable --check
-checking outputs of '/nix/store/z98fasz2jqy9gs0xbvdj939p27jwda38-stable.drv'...
-/nix/store/yyxlzw3vqaas7wfp04g0b1xg51f2czgq-stable
-</pre><p>If the build is not deterministic, Nix will exit with a status
- code of 1:</p><pre class="screen">
-$ nix-build ./deterministic.nix -A unstable
-this derivation will be built:
- /nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv
-building '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv'...
-/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable
-
-$ nix-build ./deterministic.nix -A unstable --check
-checking outputs of '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv'...
-error: derivation '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv' may not be deterministic: output '/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable' differs
-</pre><p>In the Nix daemon's log, we will now see:
-</p><pre class="screen">
-For derivation /nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv:
-1c1
-< 8108
----
-> 30204
-</pre><p>
-</p><p>Using <code class="option">--check</code> with <code class="option">--keep-failed</code>
- will cause Nix to keep the second build's output in a special,
- <code class="literal">.check</code> path:</p><pre class="screen">
-$ nix-build ./deterministic.nix -A unstable --check --keep-failed
-checking outputs of '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv'...
-note: keeping build directory '/tmp/nix-build-unstable.drv-0'
-error: derivation '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv' may not be deterministic: output '/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable' differs from '/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable.check'
-</pre><p>In particular, notice the
- <code class="literal">/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable.check</code>
- output. Nix has copied the build results to that directory where you
- can examine it.</p><div class="note"><h3 class="title"><a id="check-dirs-are-unregistered"></a><code class="literal">.check</code> paths are not registered store paths</h3><p>Check paths are not protected against garbage collection,
- and this path will be deleted on the next garbage collection.</p><p>The path is guaranteed to be alive for the duration of
- <a class="xref" href="#conf-diff-hook"><code class="literal">diff-hook</code></a>'s execution, but may be deleted
- any time after.</p><p>If the comparison is performed as part of automated tooling,
- please use the diff-hook or author your tooling to handle the case
- where the build was not deterministic and also a check path does
- not exist.</p></div><p>
- <code class="option">--check</code> is only usable if the derivation has
- been built on the system already. If the derivation has not been
- built Nix will fail with the error:
- </p><pre class="screen">
-error: some outputs of '/nix/store/hzi1h60z2qf0nb85iwnpvrai3j2w7rr6-unstable.drv' are not valid, so checking is not possible
-</pre><p>
-
- Run the build without <code class="option">--check</code>, and then try with
- <code class="option">--check</code> again.
- </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733300495744"></a>18.2.
- Automatic and Optionally Enforced Determinism Verification
- </h2></div></div></div><p>
- Automatically verify every build at build time by executing the
- build multiple times.
- </p><p>
- Setting <a class="xref" href="#conf-repeat"><code class="literal">repeat</code></a> and
- <a class="xref" href="#conf-enforce-determinism"><code class="literal">enforce-determinism</code></a> in your
- <code class="filename">nix.conf</code> permits the automated verification
- of every build Nix performs.
- </p><p>
- The following configuration will run each build three times, and
- will require the build to be deterministic:
-
- </p><pre class="programlisting">
-enforce-determinism = true
-repeat = 2
-</pre><p>
- </p><p>
- Setting <a class="xref" href="#conf-enforce-determinism"><code class="literal">enforce-determinism</code></a> to false as in
- the following configuration will run the build multiple times,
- execute the build hook, but will allow the build to succeed even
- if it does not build reproducibly:
-
- </p><pre class="programlisting">
-enforce-determinism = false
-repeat = 1
-</pre><p>
- </p><p>
- An example output of this configuration:
- </p><pre class="screen">
-$ nix-build ./test.nix -A unstable
-this derivation will be built:
- /nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv
-building '/nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv' (round 1/2)...
-building '/nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv' (round 2/2)...
-output '/nix/store/6xg356v9gl03hpbbg8gws77n19qanh02-unstable' of '/nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv' differs from '/nix/store/6xg356v9gl03hpbbg8gws77n19qanh02-unstable.check' from previous round
-/nix/store/6xg356v9gl03hpbbg8gws77n19qanh02-unstable
-</pre><p>
- </p></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="chap-post-build-hook"></a>Chapter 19. Using the <code class="option"><a class="option" href="#conf-post-build-hook">post-build-hook</a></code></h2></div><div><h3 class="subtitle"><em>Uploading to an S3-compatible binary cache after each build</em></h3></div></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="chap-post-build-hook-caveats"></a>19.1. Implementation Caveats</h2></div></div></div><p>Here we use the post-build hook to upload to a binary cache.
- This is a simple and working example, but it is not suitable for all
- use cases.</p><p>The post build hook program runs after each executed build,
- and blocks the build loop. The build loop exits if the hook program
- fails.</p><p>Concretely, this implementation will make Nix slow or unusable
- when the internet is slow or unreliable.</p><p>A more advanced implementation might pass the store paths to a
- user-supplied daemon or queue for processing the store paths outside
- of the build loop.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733300481840"></a>19.2. Prerequisites</h2></div></div></div><p>
- This tutorial assumes you have configured an S3-compatible binary cache
- according to the instructions at
- <a class="xref" href="#ssec-s3-substituter-authenticated-writes" title="13.4.3. Authenticated Writes to your S3-compatible binary cache">Section 13.4.3, “Authenticated Writes to your S3-compatible binary cache”</a>, and
- that the <code class="literal">root</code> user's default AWS profile can
- upload to the bucket.
- </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733300479440"></a>19.3. Set up a Signing Key</h2></div></div></div><p>Use <span class="command"><strong>nix-store --generate-binary-cache-key</strong></span> to
- create our public and private signing keys. We will sign paths
- with the private key, and distribute the public key for verifying
- the authenticity of the paths.</p><pre class="screen">
-# nix-store --generate-binary-cache-key example-nix-cache-1 /etc/nix/key.private /etc/nix/key.public
-# cat /etc/nix/key.public
-example-nix-cache-1:1/cKDz3QCCOmwcztD2eV6Coggp6rqc9DGjWv7C0G+rM=
-</pre><p>Then, add the public key and the cache URL to your
-<code class="filename">nix.conf</code>'s <a class="xref" href="#conf-trusted-public-keys"><code class="literal">trusted-public-keys</code></a>
-and <a class="xref" href="#conf-substituters"><code class="literal">substituters</code></a> like:</p><pre class="programlisting">
-substituters = https://cache.nixos.org/ s3://example-nix-cache
-trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= example-nix-cache-1:1/cKDz3QCCOmwcztD2eV6Coggp6rqc9DGjWv7C0G+rM=
-</pre><p>We will restart the Nix daemon in a later step.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733300473952"></a>19.4. Implementing the build hook</h2></div></div></div><p>Write the following script to
- <code class="filename">/etc/nix/upload-to-cache.sh</code>:
- </p><pre class="programlisting">
-#!/bin/sh
-
-set -eu
-set -f # disable globbing
-export IFS=' '
-
-echo "Signing paths" $OUT_PATHS
-nix sign-paths --key-file /etc/nix/key.private $OUT_PATHS
-echo "Uploading paths" $OUT_PATHS
-exec nix copy --to 's3://example-nix-cache' $OUT_PATHS
-</pre><div class="note"><h3 class="title">Should <code class="literal">$OUT_PATHS</code> be quoted?</h3><p>
- The <code class="literal">$OUT_PATHS</code> variable is a space-separated
- list of Nix store paths. In this case, we expect and want the
- shell to perform word splitting to make each output path its
- own argument to <span class="command"><strong>nix sign-paths</strong></span>. Nix guarantees
- the paths will not contain any spaces, however a store path
- might contain glob characters. The <span class="command"><strong>set -f</strong></span>
- disables globbing in the shell.
- </p></div><p>
- Then make sure the hook program is executable by the <code class="literal">root</code> user:
- </p><pre class="screen">
-# chmod +x /etc/nix/upload-to-cache.sh
-</pre></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733300467040"></a>19.5. Updating Nix Configuration</h2></div></div></div><p>Edit <code class="filename">/etc/nix/nix.conf</code> to run our hook,
- by adding the following configuration snippet at the end:</p><pre class="programlisting">
-post-build-hook = /etc/nix/upload-to-cache.sh
-</pre><p>Then, restart the <span class="command"><strong>nix-daemon</strong></span>.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733300464016"></a>19.6. Testing</h2></div></div></div><p>Build any derivation, for example:</p><pre class="screen">
-$ nix-build -E '(import <nixpkgs> {}).writeText "example" (builtins.toString builtins.currentTime)'
-this derivation will be built:
- /nix/store/s4pnfbkalzy5qz57qs6yybna8wylkig6-example.drv
-building '/nix/store/s4pnfbkalzy5qz57qs6yybna8wylkig6-example.drv'...
-running post-build-hook '/home/grahamc/projects/github.com/NixOS/nix/post-hook.sh'...
-post-build-hook: Signing paths /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
-post-build-hook: Uploading paths /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
-/nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
-</pre><p>Then delete the path from the store, and try substituting it from the binary cache:</p><pre class="screen">
-$ rm ./result
-$ nix-store --delete /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
-</pre><p>Now, copy the path back from the cache:</p><pre class="screen">
-$ nix-store --realise /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
-copying path '/nix/store/m8bmqwrch6l3h8s0k3d673xpmipcdpsa-example from 's3://example-nix-cache'...
-warning: you did not specify '--add-root'; the result might be removed by the garbage collector
-/nix/store/m8bmqwrch6l3h8s0k3d673xpmipcdpsa-example
-</pre></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="idm139733300459088"></a>19.7. Conclusion</h2></div></div></div><p>
- We now have a Nix installation configured to automatically sign and
- upload every local build to a remote binary cache.
- </p><p>
- Before deploying this to production, be sure to consider the
- implementation caveats in <a class="xref" href="#chap-post-build-hook-caveats" title="19.1. Implementation Caveats">Section 19.1, “Implementation Caveats”</a>.
- </p></div></div></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a id="part-command-ref"></a>Part VI. Command Reference</h1></div></div></div><div class="partintro"><div></div><p>This section lists commands and options that you can use when you
-work with Nix.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="sec-common-options"></a>Chapter 20. Common Options</h2></div></div></div><p>Most Nix commands accept the following command-line options:</p><div class="variablelist"><a id="opt-common"></a><dl class="variablelist"><dt><span class="term"><code class="option">--help</code></span></dt><dd><p>Prints out a summary of the command syntax and
- exits.</p></dd><dt><span class="term"><code class="option">--version</code></span></dt><dd><p>Prints out the Nix version number on standard output
- and exits.</p></dd><dt><span class="term"><code class="option">--verbose</code> / <code class="option">-v</code></span></dt><dd><p>Increases the level of verbosity of diagnostic messages
- printed on standard error. For each Nix operation, the information
- printed on standard output is well-defined; any diagnostic
- information is printed on standard error, never on standard
- output.</p><p>This option may be specified repeatedly. Currently, the
- following verbosity levels exist:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term">0</span></dt><dd><p>“Errors only”: only print messages
- explaining why the Nix invocation failed.</p></dd><dt><span class="term">1</span></dt><dd><p>“Informational”: print
- <span class="emphasis"><em>useful</em></span> messages about what Nix is doing.
- This is the default.</p></dd><dt><span class="term">2</span></dt><dd><p>“Talkative”: print more informational
- messages.</p></dd><dt><span class="term">3</span></dt><dd><p>“Chatty”: print even more
- informational messages.</p></dd><dt><span class="term">4</span></dt><dd><p>“Debug”: print debug
- information.</p></dd><dt><span class="term">5</span></dt><dd><p>“Vomit”: print vast amounts of debug
- information.</p></dd></dl></div></dd><dt><span class="term"><code class="option">--quiet</code></span></dt><dd><p>Decreases the level of verbosity of diagnostic messages
- printed on standard error. This is the inverse option to
- <code class="option">-v</code> / <code class="option">--verbose</code>.
- </p><p>This option may be specified repeatedly. See the previous
- verbosity levels list.</p></dd><dt><a id="opt-log-format"></a><span class="term"><code class="option">--log-format</code> <em class="replaceable"><code>format</code></em></span></dt><dd><p>This option can be used to change the output of the log format, with
- <em class="replaceable"><code>format</code></em> being one of:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term">raw</span></dt><dd><p>This is the raw format, as outputted by nix-build.</p></dd><dt><span class="term">internal-json</span></dt><dd><p>Outputs the logs in a structured manner. NOTE: the json schema is not guarantees to be stable between releases.</p></dd><dt><span class="term">bar</span></dt><dd><p>Only display a progress bar during the builds.</p></dd><dt><span class="term">bar-with-logs</span></dt><dd><p>Display the raw logs, with the progress bar at the bottom.</p></dd></dl></div></dd><dt><span class="term"><code class="option">--no-build-output</code> / <code class="option">-Q</code></span></dt><dd><p>By default, output written by builders to standard
- output and standard error is echoed to the Nix command's standard
- error. This option suppresses this behaviour. Note that the
- builder's standard output and error are always written to a log file
- in
- <code class="filename"><em class="replaceable"><code>prefix</code></em>/nix/var/log/nix</code>.</p></dd><dt><a id="opt-max-jobs"></a><span class="term"><code class="option">--max-jobs</code> / <code class="option">-j</code>
-<em class="replaceable"><code>number</code></em></span></dt><dd><p>Sets the maximum number of build jobs that Nix will
- perform in parallel to the specified number. Specify
- <code class="literal">auto</code> to use the number of CPUs in the system.
- The default is specified by the <a class="link" href="#conf-max-jobs"><code class="literal">max-jobs</code></a>
- configuration setting, which itself defaults to
- <code class="literal">1</code>. A higher value is useful on SMP systems or to
- exploit I/O latency.</p><p> Setting it to <code class="literal">0</code> disallows building on the local
- machine, which is useful when you want builds to happen only on remote
- builders.</p></dd><dt><a id="opt-cores"></a><span class="term"><code class="option">--cores</code></span></dt><dd><p>Sets the value of the <code class="envar">NIX_BUILD_CORES</code>
- environment variable in the invocation of builders. Builders can
- use this variable at their discretion to control the maximum amount
- of parallelism. For instance, in Nixpkgs, if the derivation
- attribute <code class="varname">enableParallelBuilding</code> is set to
- <code class="literal">true</code>, the builder passes the
- <code class="option">-j<em class="replaceable"><code>N</code></em></code> flag to GNU Make.
- It defaults to the value of the <a class="link" href="#conf-cores"><code class="literal">cores</code></a>
- configuration setting, if set, or <code class="literal">1</code> otherwise.
- The value <code class="literal">0</code> means that the builder should use all
- available CPU cores in the system.</p></dd><dt><a id="opt-max-silent-time"></a><span class="term"><code class="option">--max-silent-time</code></span></dt><dd><p>Sets the maximum number of seconds that a builder
- can go without producing any data on standard output or standard
- error. The default is specified by the <a class="link" href="#conf-max-silent-time"><code class="literal">max-silent-time</code></a>
- configuration setting. <code class="literal">0</code> means no
- time-out.</p></dd><dt><a id="opt-timeout"></a><span class="term"><code class="option">--timeout</code></span></dt><dd><p>Sets the maximum number of seconds that a builder
- can run. The default is specified by the <a class="link" href="#conf-timeout"><code class="literal">timeout</code></a>
- configuration setting. <code class="literal">0</code> means no
- timeout.</p></dd><dt><span class="term"><code class="option">--keep-going</code> / <code class="option">-k</code></span></dt><dd><p>Keep going in case of failed builds, to the
- greatest extent possible. That is, if building an input of some
- derivation fails, Nix will still build the other inputs, but not the
- derivation itself. Without this option, Nix stops if any build
- fails (except for builds of substitutes), possibly killing builds in
- progress (in case of parallel or distributed builds).</p></dd><dt><span class="term"><code class="option">--keep-failed</code> / <code class="option">-K</code></span></dt><dd><p>Specifies that in case of a build failure, the
- temporary directory (usually in <code class="filename">/tmp</code>) in which
- the build takes place should not be deleted. The path of the build
- directory is printed as an informational message.
- </p></dd><dt><span class="term"><code class="option">--fallback</code></span></dt><dd><p>Whenever Nix attempts to build a derivation for which
- substitutes are known for each output path, but realising the output
- paths through the substitutes fails, fall back on building the
- derivation.</p><p>The most common scenario in which this is useful is when we
- have registered substitutes in order to perform binary distribution
- from, say, a network repository. If the repository is down, the
- realisation of the derivation will fail. When this option is
- specified, Nix will build the derivation instead. Thus,
- installation from binaries falls back on installation from source.
- This option is not the default since it is generally not desirable
- for a transient failure in obtaining the substitutes to lead to a
- full build from source (with the related consumption of
- resources).</p></dd><dt><span class="term"><code class="option">--no-build-hook</code></span></dt><dd><p>Disables the build hook mechanism. This allows to ignore remote
- builders if they are setup on the machine.</p><p>It's useful in cases where the bandwidth between the client and the
- remote builder is too low. In that case it can take more time to upload the
- sources to the remote builder and fetch back the result than to do the
- computation locally.</p></dd><dt><span class="term"><code class="option">--readonly-mode</code></span></dt><dd><p>When this option is used, no attempt is made to open
- the Nix database. Most Nix operations do need database access, so
- those operations will fail.</p></dd><dt><span class="term"><code class="option">--arg</code> <em class="replaceable"><code>name</code></em> <em class="replaceable"><code>value</code></em></span></dt><dd><p>This option is accepted by
- <span class="command"><strong>nix-env</strong></span>, <span class="command"><strong>nix-instantiate</strong></span>,
- <span class="command"><strong>nix-shell</strong></span> and <span class="command"><strong>nix-build</strong></span>.
- When evaluating Nix expressions, the expression evaluator will
- automatically try to call functions that
- it encounters. It can automatically call functions for which every
- argument has a <a class="link" href="#ss-functions" title="Functions">default value</a>
- (e.g., <code class="literal">{ <em class="replaceable"><code>argName</code></em> ?
- <em class="replaceable"><code>defaultValue</code></em> }:
- <em class="replaceable"><code>...</code></em></code>). With
- <code class="option">--arg</code>, you can also call functions that have
- arguments without a default value (or override a default value).
- That is, if the evaluator encounters a function with an argument
- named <em class="replaceable"><code>name</code></em>, it will call it with value
- <em class="replaceable"><code>value</code></em>.</p><p>For instance, the top-level <code class="literal">default.nix</code> in
- Nixpkgs is actually a function:
-
-</p><pre class="programlisting">
-{ # The system (e.g., `i686-linux') for which to build the packages.
- system ? builtins.currentSystem
- <em class="replaceable"><code>...</code></em>
-}: <em class="replaceable"><code>...</code></em></pre><p>
-
- So if you call this Nix expression (e.g., when you do
- <code class="literal">nix-env -i <em class="replaceable"><code>pkgname</code></em></code>),
- the function will be called automatically using the value <a class="link" href="#builtin-currentSystem"><code class="literal">builtins.currentSystem</code></a>
- for the <code class="literal">system</code> argument. You can override this
- using <code class="option">--arg</code>, e.g., <code class="literal">nix-env -i
- <em class="replaceable"><code>pkgname</code></em> --arg system
- \"i686-freebsd\"</code>. (Note that since the argument is a Nix
- string literal, you have to escape the quotes.)</p></dd><dt><span class="term"><code class="option">--argstr</code> <em class="replaceable"><code>name</code></em> <em class="replaceable"><code>value</code></em></span></dt><dd><p>This option is like <code class="option">--arg</code>, only the
- value is not a Nix expression but a string. So instead of
- <code class="literal">--arg system \"i686-linux\"</code> (the outer quotes are
- to keep the shell happy) you can say <code class="literal">--argstr system
- i686-linux</code>.</p></dd><dt><a id="opt-attr"></a><span class="term"><code class="option">--attr</code> / <code class="option">-A</code>
-<em class="replaceable"><code>attrPath</code></em></span></dt><dd><p>Select an attribute from the top-level Nix
- expression being evaluated. (<span class="command"><strong>nix-env</strong></span>,
- <span class="command"><strong>nix-instantiate</strong></span>, <span class="command"><strong>nix-build</strong></span> and
- <span class="command"><strong>nix-shell</strong></span> only.) The <span class="emphasis"><em>attribute
- path</em></span> <em class="replaceable"><code>attrPath</code></em> is a sequence of
- attribute names separated by dots. For instance, given a top-level
- Nix expression <em class="replaceable"><code>e</code></em>, the attribute path
- <code class="literal">xorg.xorgserver</code> would cause the expression
- <code class="literal"><em class="replaceable"><code>e</code></em>.xorg.xorgserver</code> to
- be used. See <a class="link" href="#refsec-nix-env-install-examples" title="Examples"><span class="command"><strong>nix-env
- --install</strong></span></a> for some concrete examples.</p><p>In addition to attribute names, you can also specify array
- indices. For instance, the attribute path
- <code class="literal">foo.3.bar</code> selects the <code class="literal">bar</code>
- attribute of the fourth element of the array in the
- <code class="literal">foo</code> attribute of the top-level
- expression.</p></dd><dt><span class="term"><code class="option">--expr</code> / <code class="option">-E</code></span></dt><dd><p>Interpret the command line arguments as a list of
- Nix expressions to be parsed and evaluated, rather than as a list
- of file names of Nix expressions.
- (<span class="command"><strong>nix-instantiate</strong></span>, <span class="command"><strong>nix-build</strong></span>
- and <span class="command"><strong>nix-shell</strong></span> only.)</p><p>For <span class="command"><strong>nix-shell</strong></span>, this option is commonly used
- to give you a shell in which you can build the packages returned
- by the expression. If you want to get a shell which contain the
- <span class="emphasis"><em>built</em></span> packages ready for use, give your
- expression to the <span class="command"><strong>nix-shell -p</strong></span> convenience flag
- instead.</p></dd><dt><a id="opt-I"></a><span class="term"><code class="option">-I</code> <em class="replaceable"><code>path</code></em></span></dt><dd><p>Add a path to the Nix expression search path. This
- option may be given multiple times. See the <code class="envar"><a class="envar" href="#env-NIX_PATH">NIX_PATH</a></code> environment variable for
- information on the semantics of the Nix search path. Paths added
- through <code class="option">-I</code> take precedence over
- <code class="envar">NIX_PATH</code>.</p></dd><dt><span class="term"><code class="option">--option</code> <em class="replaceable"><code>name</code></em> <em class="replaceable"><code>value</code></em></span></dt><dd><p>Set the Nix configuration option
- <em class="replaceable"><code>name</code></em> to <em class="replaceable"><code>value</code></em>.
- This overrides settings in the Nix configuration file (see
- <span class="citerefentry"><span class="refentrytitle">nix.conf</span>(5)</span>).</p></dd><dt><span class="term"><code class="option">--repair</code></span></dt><dd><p>Fix corrupted or missing store paths by
- redownloading or rebuilding them. Note that this is slow because it
- requires computing a cryptographic hash of the contents of every
- path in the closure of the build. Also note the warning under
- <span class="command"><strong>nix-store --repair-path</strong></span>.</p></dd></dl></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="sec-common-env"></a>Chapter 21. Common Environment Variables</h2></div></div></div><p>Most Nix commands interpret the following environment variables:</p><div class="variablelist"><a id="env-common"></a><dl class="variablelist"><dt><span class="term"><code class="envar">IN_NIX_SHELL</code></span></dt><dd><p>Indicator that tells if the current environment was set up by
- <span class="command"><strong>nix-shell</strong></span>. Since Nix 2.0 the values are
- <code class="literal">"pure"</code> and <code class="literal">"impure"</code></p></dd><dt><a id="env-NIX_PATH"></a><span class="term"><code class="envar">NIX_PATH</code></span></dt><dd><p>A colon-separated list of directories used to look up Nix
- expressions enclosed in angle brackets (i.e.,
- <code class="literal"><<em class="replaceable"><code>path</code></em>></code>). For
- instance, the value
-
- </p><pre class="screen">
-/home/eelco/Dev:/etc/nixos</pre><p>
-
- will cause Nix to look for paths relative to
- <code class="filename">/home/eelco/Dev</code> and
- <code class="filename">/etc/nixos</code>, in this order. It is also
- possible to match paths against a prefix. For example, the value
-
- </p><pre class="screen">
-nixpkgs=/home/eelco/Dev/nixpkgs-branch:/etc/nixos</pre><p>
-
- will cause Nix to search for
- <code class="literal"><nixpkgs/<em class="replaceable"><code>path</code></em>></code> in
- <code class="filename">/home/eelco/Dev/nixpkgs-branch/<em class="replaceable"><code>path</code></em></code>
- and
- <code class="filename">/etc/nixos/nixpkgs/<em class="replaceable"><code>path</code></em></code>.</p><p>If a path in the Nix search path starts with
- <code class="literal">http://</code> or <code class="literal">https://</code>, it is
- interpreted as the URL of a tarball that will be downloaded and
- unpacked to a temporary location. The tarball must consist of a
- single top-level directory. For example, setting
- <code class="envar">NIX_PATH</code> to
-
- </p><pre class="screen">
-nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-15.09.tar.gz</pre><p>
-
- tells Nix to download the latest revision in the Nixpkgs/NixOS
- 15.09 channel.</p><p>A following shorthand can be used to refer to the official channels:
-
- </p><pre class="screen">nixpkgs=channel:nixos-15.09</pre><p>
- </p><p>The search path can be extended using the <code class="option"><a class="option" href="#opt-I">-I</a></code> option, which takes precedence over
- <code class="envar">NIX_PATH</code>.</p></dd><dt><span class="term"><code class="envar">NIX_IGNORE_SYMLINK_STORE</code></span></dt><dd><p>Normally, the Nix store directory (typically
- <code class="filename">/nix/store</code>) is not allowed to contain any
- symlink components. This is to prevent “impure” builds. Builders
- sometimes “canonicalise” paths by resolving all symlink components.
- Thus, builds on different machines (with
- <code class="filename">/nix/store</code> resolving to different locations)
- could yield different results. This is generally not a problem,
- except when builds are deployed to machines where
- <code class="filename">/nix/store</code> resolves differently. If you are
- sure that you’re not going to do that, you can set
- <code class="envar">NIX_IGNORE_SYMLINK_STORE</code> to <code class="envar">1</code>.</p><p>Note that if you’re symlinking the Nix store so that you can
- put it on another file system than the root file system, on Linux
- you’re better off using <code class="literal">bind</code> mount points, e.g.,
-
- </p><pre class="screen">
-$ mkdir /nix
-$ mount -o bind /mnt/otherdisk/nix /nix</pre><p>
-
- Consult the <span class="citerefentry"><span class="refentrytitle">mount</span>(8)</span> manual page for details.</p></dd><dt><span class="term"><code class="envar">NIX_STORE_DIR</code></span></dt><dd><p>Overrides the location of the Nix store (default
- <code class="filename"><em class="replaceable"><code>prefix</code></em>/store</code>).</p></dd><dt><span class="term"><code class="envar">NIX_DATA_DIR</code></span></dt><dd><p>Overrides the location of the Nix static data
- directory (default
- <code class="filename"><em class="replaceable"><code>prefix</code></em>/share</code>).</p></dd><dt><span class="term"><code class="envar">NIX_LOG_DIR</code></span></dt><dd><p>Overrides the location of the Nix log directory
- (default <code class="filename"><em class="replaceable"><code>prefix</code></em>/var/log/nix</code>).</p></dd><dt><span class="term"><code class="envar">NIX_STATE_DIR</code></span></dt><dd><p>Overrides the location of the Nix state directory
- (default <code class="filename"><em class="replaceable"><code>prefix</code></em>/var/nix</code>).</p></dd><dt><span class="term"><code class="envar">NIX_CONF_DIR</code></span></dt><dd><p>Overrides the location of the system Nix configuration
- directory (default
- <code class="filename"><em class="replaceable"><code>prefix</code></em>/etc/nix</code>).</p></dd><dt><span class="term"><code class="envar">NIX_USER_CONF_FILES</code></span></dt><dd><p>Overrides the location of the user Nix configuration files
- to load from (defaults to the XDG spec locations). The variable is treated
- as a list separated by the <code class="literal">:</code> token.</p></dd><dt><span class="term"><code class="envar">TMPDIR</code></span></dt><dd><p>Use the specified directory to store temporary
- files. In particular, this includes temporary build directories;
- these can take up substantial amounts of disk space. The default is
- <code class="filename">/tmp</code>.</p></dd><dt><a id="envar-remote"></a><span class="term"><code class="envar">NIX_REMOTE</code></span></dt><dd><p>This variable should be set to
- <code class="literal">daemon</code> if you want to use the Nix daemon to
- execute Nix operations. This is necessary in <a class="link" href="#ssec-multi-user" title="6.2. Multi-User Mode">multi-user Nix installations</a>.
- If the Nix daemon's Unix socket is at some non-standard path,
- this variable should be set to <code class="literal">unix://path/to/socket</code>.
- Otherwise, it should be left unset.</p></dd><dt><span class="term"><code class="envar">NIX_SHOW_STATS</code></span></dt><dd><p>If set to <code class="literal">1</code>, Nix will print some
- evaluation statistics, such as the number of values
- allocated.</p></dd><dt><span class="term"><code class="envar">NIX_COUNT_CALLS</code></span></dt><dd><p>If set to <code class="literal">1</code>, Nix will print how
- often functions were called during Nix expression evaluation. This
- is useful for profiling your Nix expressions.</p></dd><dt><span class="term"><code class="envar">GC_INITIAL_HEAP_SIZE</code></span></dt><dd><p>If Nix has been configured to use the Boehm garbage
- collector, this variable sets the initial size of the heap in bytes.
- It defaults to 384 MiB. Setting it to a low value reduces memory
- consumption, but will increase runtime due to the overhead of
- garbage collection.</p></dd></dl></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-main-commands"></a>Chapter 22. Main Commands</h2></div></div></div><p>This section lists commands and options that you can use when you
-work with Nix.</p><div class="refentry"><a id="sec-nix-env"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix-env — manipulate or query Nix user environments</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">nix-env</code> [<code class="option">--help</code>] [<code class="option">--version</code>] [
- { <code class="option">--verbose</code> | <code class="option">-v</code> }
-...] [
- <code class="option">--quiet</code>
-] [
- <code class="option">--log-format</code>
- <em class="replaceable"><code>format</code></em>
-] [
- <code class="option">--no-build-output</code> | <code class="option">-Q</code>
-] [
- { <code class="option">--max-jobs</code> | <code class="option">-j</code> }
- <em class="replaceable"><code>number</code></em>
-] [
- <code class="option">--cores</code>
- <em class="replaceable"><code>number</code></em>
-] [
- <code class="option">--max-silent-time</code>
- <em class="replaceable"><code>number</code></em>
-] [
- <code class="option">--timeout</code>
- <em class="replaceable"><code>number</code></em>
-] [
- <code class="option">--keep-going</code> | <code class="option">-k</code>
-] [
- <code class="option">--keep-failed</code> | <code class="option">-K</code>
-] [<code class="option">--fallback</code>] [<code class="option">--readonly-mode</code>] [
- <code class="option">-I</code>
- <em class="replaceable"><code>path</code></em>
-] [
- <code class="option">--option</code>
- <em class="replaceable"><code>name</code></em>
- <em class="replaceable"><code>value</code></em>
-]<br /> [<code class="option">--arg</code> <em class="replaceable"><code>name</code></em> <em class="replaceable"><code>value</code></em>] [<code class="option">--argstr</code> <em class="replaceable"><code>name</code></em> <em class="replaceable"><code>value</code></em>] [
- { <code class="option">--file</code> | <code class="option">-f</code> }
- <em class="replaceable"><code>path</code></em>
- ] [
- { <code class="option">--profile</code> | <code class="option">-p</code> }
- <em class="replaceable"><code>path</code></em>
- ] [
- <code class="option">--system-filter</code>
- <em class="replaceable"><code>system</code></em>
- ] [<code class="option">--dry-run</code>] <em class="replaceable"><code>operation</code></em> [<em class="replaceable"><code>options</code></em>...] [<em class="replaceable"><code>arguments</code></em>...]</p></div></div><div class="refsection"><a id="idm139733300260096"></a><h2>Description</h2><p>The command <span class="command"><strong>nix-env</strong></span> is used to manipulate Nix
-user environments. User environments are sets of software packages
-available to a user at some point in time. In other words, they are a
-synthesised view of the programs available in the Nix store. There
-may be many user environments: different users can have different
-environments, and individual users can switch between different
-environments.</p><p><span class="command"><strong>nix-env</strong></span> takes exactly one
-<span class="emphasis"><em>operation</em></span> flag which indicates the subcommand to
-be performed. These are documented below.</p></div><div class="refsection"><a id="idm139733300256528"></a><h2>Selectors</h2><p>Several commands, such as <span class="command"><strong>nix-env -q</strong></span> and
-<span class="command"><strong>nix-env -i</strong></span>, take a list of arguments that specify
-the packages on which to operate. These are extended regular
-expressions that must match the entire name of the package. (For
-details on regular expressions, see
-<span class="citerefentry"><span class="refentrytitle">regex</span>(7)</span>.)
-The match is case-sensitive. The regular expression can optionally be
-followed by a dash and a version number; if omitted, any version of
-the package will match. Here are some examples:
-
-</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">firefox</code></span></dt><dd><p>Matches the package name
- <code class="literal">firefox</code> and any version.</p></dd><dt><span class="term"><code class="literal">firefox-32.0</code></span></dt><dd><p>Matches the package name
- <code class="literal">firefox</code> and version
- <code class="literal">32.0</code>.</p></dd><dt><span class="term"><code class="literal">gtk\\+</code></span></dt><dd><p>Matches the package name
- <code class="literal">gtk+</code>. The <code class="literal">+</code> character must
- be escaped using a backslash to prevent it from being interpreted
- as a quantifier, and the backslash must be escaped in turn with
- another backslash to ensure that the shell passes it
- on.</p></dd><dt><span class="term"><code class="literal">.\*</code></span></dt><dd><p>Matches any package name. This is the default for
- most commands.</p></dd><dt><span class="term"><code class="literal">'.*zip.*'</code></span></dt><dd><p>Matches any package name containing the string
- <code class="literal">zip</code>. Note the dots: <code class="literal">'*zip*'</code>
- does not work, because in a regular expression, the character
- <code class="literal">*</code> is interpreted as a
- quantifier.</p></dd><dt><span class="term"><code class="literal">'.*(firefox|chromium).*'</code></span></dt><dd><p>Matches any package name containing the strings
- <code class="literal">firefox</code> or
- <code class="literal">chromium</code>.</p></dd></dl></div><p>
-
-</p></div><div class="refsection"><a id="idm139733300238960"></a><h2>Common options</h2><p>This section lists the options that are common to all
-operations. These options are allowed for every subcommand, though
-they may not always have an effect. <span class="phrase">See
-also <a class="xref" href="#sec-common-options" title="Chapter 20. Common Options">Chapter 20, <em>Common Options</em></a>.</span></p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--file</code> / <code class="option">-f</code> <em class="replaceable"><code>path</code></em></span></dt><dd><p>Specifies the Nix expression (designated below as
- the <span class="emphasis"><em>active Nix expression</em></span>) used by the
- <code class="option">--install</code>, <code class="option">--upgrade</code>, and
- <code class="option">--query --available</code> operations to obtain
- derivations. The default is
- <code class="filename">~/.nix-defexpr</code>.</p><p>If the argument starts with <code class="literal">http://</code> or
- <code class="literal">https://</code>, it is interpreted as the URL of a
- tarball that will be downloaded and unpacked to a temporary
- location. The tarball must include a single top-level directory
- containing at least a file named <code class="filename">default.nix</code>.</p></dd><dt><span class="term"><code class="option">--profile</code> / <code class="option">-p</code> <em class="replaceable"><code>path</code></em></span></dt><dd><p>Specifies the profile to be used by those
- operations that operate on a profile (designated below as the
- <span class="emphasis"><em>active profile</em></span>). A profile is a sequence of
- user environments called <span class="emphasis"><em>generations</em></span>, one of
- which is the <span class="emphasis"><em>current
- generation</em></span>.</p></dd><dt><span class="term"><code class="option">--dry-run</code></span></dt><dd><p>For the <code class="option">--install</code>,
- <code class="option">--upgrade</code>, <code class="option">--uninstall</code>,
- <code class="option">--switch-generation</code>,
- <code class="option">--delete-generations</code> and
- <code class="option">--rollback</code> operations, this flag will cause
- <span class="command"><strong>nix-env</strong></span> to print what
- <span class="emphasis"><em>would</em></span> be done if this flag had not been
- specified, without actually doing it.</p><p><code class="option">--dry-run</code> also prints out which paths will
- be <a class="link" href="#gloss-substitute" title="substitute">substituted</a> (i.e.,
- downloaded) and which paths will be built from source (because no
- substitute is available).</p></dd><dt><span class="term"><code class="option">--system-filter</code> <em class="replaceable"><code>system</code></em></span></dt><dd><p>By default, operations such as <code class="option">--query
- --available</code> show derivations matching any platform. This
- option allows you to use derivations for the specified platform
- <em class="replaceable"><code>system</code></em>.</p></dd></dl></div></div><div class="refsection"><a id="idm139733300216432"></a><h2>Files</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="filename">~/.nix-defexpr</code></span></dt><dd><p>The source for the default Nix
- expressions used by the <code class="option">--install</code>,
- <code class="option">--upgrade</code>, and <code class="option">--query
- --available</code> operations to obtain derivations. The
- <code class="option">--file</code> option may be used to override this
- default.</p><p>If <code class="filename">~/.nix-defexpr</code> is a file,
- it is loaded as a Nix expression. If the expression
- is a set, it is used as the default Nix expression.
- If the expression is a function, an empty set is passed
- as argument and the return value is used as
- the default Nix expression.</p><p>If <code class="filename">~/.nix-defexpr</code> is a directory
- containing a <code class="filename">default.nix</code> file, that file
- is loaded as in the above paragraph.</p><p>If <code class="filename">~/.nix-defexpr</code> is a directory without
- a <code class="filename">default.nix</code> file, then its contents
- (both files and subdirectories) are loaded as Nix expressions.
- The expressions are combined into a single set, each expression
- under an attribute with the same name as the original file
- or subdirectory.
- </p><p>For example, if <code class="filename">~/.nix-defexpr</code> contains
- two files, <code class="filename">foo.nix</code> and <code class="filename">bar.nix</code>,
- then the default Nix expression will essentially be
-
-</p><pre class="programlisting">
-{
- foo = import ~/.nix-defexpr/foo.nix;
- bar = import ~/.nix-defexpr/bar.nix;
-}</pre><p>
-
- </p><p>The file <code class="filename">manifest.nix</code> is always ignored.
- Subdirectories without a <code class="filename">default.nix</code> file
- are traversed recursively in search of more Nix expressions,
- but the names of these intermediate directories are not
- added to the attribute paths of the default Nix expression.</p><p>The command <span class="command"><strong>nix-channel</strong></span> places symlinks
- to the downloaded Nix expressions from each subscribed channel in
- this directory.</p></dd><dt><span class="term"><code class="filename">~/.nix-profile</code></span></dt><dd><p>A symbolic link to the user's current profile. By
- default, this symlink points to
- <code class="filename"><em class="replaceable"><code>prefix</code></em>/var/nix/profiles/default</code>.
- The <code class="envar">PATH</code> environment variable should include
- <code class="filename">~/.nix-profile/bin</code> for the user environment
- to be visible to the user.</p></dd></dl></div></div><div class="refsection"><a id="rsec-nix-env-install"></a><h2>Operation <code class="option">--install</code></h2><div class="refsection"><a id="idm139733300198432"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-env</code> { <code class="option">--install</code> | <code class="option">-i</code> } [
- { <code class="option">--prebuilt-only</code> | <code class="option">-b</code> }
- ] [
- { <code class="option">--attr</code> | <code class="option">-A</code> }
- ] [<code class="option">--from-expression</code>] [<code class="option">-E</code>] [<code class="option">--from-profile</code> <em class="replaceable"><code>path</code></em>] [ <code class="option">--preserve-installed</code> | <code class="option">-P</code> ] [ <code class="option">--remove-all</code> | <code class="option">-r</code> ] <em class="replaceable"><code>args</code></em>... </p></div></div><div class="refsection"><a id="idm139733300182432"></a><h3>Description</h3><p>The install operation creates a new user environment, based on
-the current generation of the active profile, to which a set of store
-paths described by <em class="replaceable"><code>args</code></em> is added. The
-arguments <em class="replaceable"><code>args</code></em> map to store paths in a
-number of possible ways:
-
-</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>By default, <em class="replaceable"><code>args</code></em> is a set
- of derivation names denoting derivations in the active Nix
- expression. These are realised, and the resulting output paths are
- installed. Currently installed derivations with a name equal to the
- name of a derivation being added are removed unless the option
- <code class="option">--preserve-installed</code> is
- specified.</p><p>If there are multiple derivations matching a name in
- <em class="replaceable"><code>args</code></em> that have the same name (e.g.,
- <code class="literal">gcc-3.3.6</code> and <code class="literal">gcc-4.1.1</code>), then
- the derivation with the highest <span class="emphasis"><em>priority</em></span> is
- used. A derivation can define a priority by declaring the
- <code class="varname">meta.priority</code> attribute. This attribute should
- be a number, with a higher value denoting a lower priority. The
- default priority is <code class="literal">0</code>.</p><p>If there are multiple matching derivations with the same
- priority, then the derivation with the highest version will be
- installed.</p><p>You can force the installation of multiple derivations with
- the same name by being specific about the versions. For instance,
- <code class="literal">nix-env -i gcc-3.3.6 gcc-4.1.1</code> will install both
- version of GCC (and will probably cause a user environment
- conflict!).</p></li><li class="listitem"><p>If <a class="link" href="#opt-attr"><code class="option">--attr</code></a>
- (<code class="option">-A</code>) is specified, the arguments are
- <span class="emphasis"><em>attribute paths</em></span> that select attributes from the
- top-level Nix expression. This is faster than using derivation
- names and unambiguous. To find out the attribute paths of available
- packages, use <code class="literal">nix-env -qaP</code>.</p></li><li class="listitem"><p>If <code class="option">--from-profile</code>
- <em class="replaceable"><code>path</code></em> is given,
- <em class="replaceable"><code>args</code></em> is a set of names denoting installed
- store paths in the profile <em class="replaceable"><code>path</code></em>. This is
- an easy way to copy user environment elements from one profile to
- another.</p></li><li class="listitem"><p>If <code class="option">--from-expression</code> is given,
- <em class="replaceable"><code>args</code></em> are Nix <a class="link" href="#ss-functions" title="Functions">functions</a> that are called with the
- active Nix expression as their single argument. The derivations
- returned by those function calls are installed. This allows
- derivations to be specified in an unambiguous way, which is necessary
- if there are multiple derivations with the same
- name.</p></li><li class="listitem"><p>If <em class="replaceable"><code>args</code></em> are store
- derivations, then these are <a class="link" href="#rsec-nix-store-realise" title="Operation --realise">realised</a>, and the resulting
- output paths are installed.</p></li><li class="listitem"><p>If <em class="replaceable"><code>args</code></em> are store paths
- that are not store derivations, then these are <a class="link" href="#rsec-nix-store-realise" title="Operation --realise">realised</a> and
- installed.</p></li><li class="listitem"><p>By default all outputs are installed for each derivation.
- That can be reduced by setting <code class="literal">meta.outputsToInstall</code>.
- </p></li></ul></div><p>
-
-</p></div><div class="refsection"><a id="idm139733300160752"></a><h3>Flags</h3><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--prebuilt-only</code> / <code class="option">-b</code></span></dt><dd><p>Use only derivations for which a substitute is
- registered, i.e., there is a pre-built binary available that can
- be downloaded in lieu of building the derivation. Thus, no
- packages will be built from source.</p></dd><dt><span class="term"><code class="option">--preserve-installed</code>, </span><span class="term"><code class="option">-P</code></span></dt><dd><p>Do not remove derivations with a name matching one
- of the derivations being installed. Usually, trying to have two
- versions of the same package installed in the same generation of a
- profile will lead to an error in building the generation, due to
- file name clashes between the two versions. However, this is not
- the case for all packages.</p></dd><dt><span class="term"><code class="option">--remove-all</code>, </span><span class="term"><code class="option">-r</code></span></dt><dd><p>Remove all previously installed packages first.
- This is equivalent to running <code class="literal">nix-env -e '.*'</code>
- first, except that everything happens in a single
- transaction.</p></dd></dl></div></div><div class="refsection"><a id="refsec-nix-env-install-examples"></a><h3>Examples</h3><p>To install a specific version of <span class="command"><strong>gcc</strong></span> from the
-active Nix expression:
-
-</p><pre class="screen">
-$ nix-env --install gcc-3.3.2
-installing `gcc-3.3.2'
-uninstalling `gcc-3.1'</pre><p>
-
-Note the previously installed version is removed, since
-<code class="option">--preserve-installed</code> was not specified.</p><p>To install an arbitrary version:
-
-</p><pre class="screen">
-$ nix-env --install gcc
-installing `gcc-3.3.2'</pre><p>
-
-</p><p>To install using a specific attribute:
-
-</p><pre class="screen">
-$ nix-env -i -A gcc40mips
-$ nix-env -i -A xorg.xorgserver</pre><p>
-
-</p><p>To install all derivations in the Nix expression <code class="filename">foo.nix</code>:
-
-</p><pre class="screen">
-$ nix-env -f ~/foo.nix -i '.*'</pre><p>
-
-</p><p>To copy the store path with symbolic name <code class="literal">gcc</code>
-from another profile:
-
-</p><pre class="screen">
-$ nix-env -i --from-profile /nix/var/nix/profiles/foo gcc</pre><p>
-
-</p><p>To install a specific store derivation (typically created by
-<span class="command"><strong>nix-instantiate</strong></span>):
-
-</p><pre class="screen">
-$ nix-env -i /nix/store/fibjb1bfbpm5mrsxc4mh2d8n37sxh91i-gcc-3.4.3.drv</pre><p>
-
-</p><p>To install a specific output path:
-
-</p><pre class="screen">
-$ nix-env -i /nix/store/y3cgx0xj1p4iv9x0pnnmdhr8iyg741vk-gcc-3.4.3</pre><p>
-
-</p><p>To install from a Nix expression specified on the command-line:
-
-</p><pre class="screen">
-$ nix-env -f ./foo.nix -i -E \
- 'f: (f {system = "i686-linux";}).subversionWithJava'</pre><p>
-
-I.e., this evaluates to <code class="literal">(f: (f {system =
-"i686-linux";}).subversionWithJava) (import ./foo.nix)</code>, thus
-selecting the <code class="literal">subversionWithJava</code> attribute from the
-set returned by calling the function defined in
-<code class="filename">./foo.nix</code>.</p><p>A dry-run tells you which paths will be downloaded or built from
-source:
-
-</p><pre class="screen">
-$ nix-env -f '<nixpkgs>' -iA hello --dry-run
-(dry run; not doing anything)
-installing ‘hello-2.10’
-this path will be fetched (0.04 MiB download, 0.19 MiB unpacked):
- /nix/store/wkhdf9jinag5750mqlax6z2zbwhqb76n-hello-2.10
- <em class="replaceable"><code>...</code></em></pre><p>
-
-</p><p>To install Firefox from the latest revision in the Nixpkgs/NixOS
-14.12 channel:
-
-</p><pre class="screen">
-$ nix-env -f https://github.com/NixOS/nixpkgs/archive/nixos-14.12.tar.gz -iA firefox
-</pre><p>
-
-</p></div></div><div class="refsection"><a id="rsec-nix-env-upgrade"></a><h2>Operation <code class="option">--upgrade</code></h2><div class="refsection"><a id="idm139733300136496"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-env</code> { <code class="option">--upgrade</code> | <code class="option">-u</code> } [
- { <code class="option">--prebuilt-only</code> | <code class="option">-b</code> }
- ] [
- { <code class="option">--attr</code> | <code class="option">-A</code> }
- ] [<code class="option">--from-expression</code>] [<code class="option">-E</code>] [<code class="option">--from-profile</code> <em class="replaceable"><code>path</code></em>] [ <code class="option">--lt</code> | <code class="option">--leq</code> | <code class="option">--eq</code> | <code class="option">--always</code> ] <em class="replaceable"><code>args</code></em>... </p></div></div><div class="refsection"><a id="idm139733300121104"></a><h3>Description</h3><p>The upgrade operation creates a new user environment, based on
-the current generation of the active profile, in which all store paths
-are replaced for which there are newer versions in the set of paths
-described by <em class="replaceable"><code>args</code></em>. Paths for which there
-are no newer versions are left untouched; this is not an error. It is
-also not an error if an element of <em class="replaceable"><code>args</code></em>
-matches no installed derivations.</p><p>For a description of how <em class="replaceable"><code>args</code></em> is
-mapped to a set of store paths, see <a class="link" href="#rsec-nix-env-install" title="Operation --install"><code class="option">--install</code></a>. If
-<em class="replaceable"><code>args</code></em> describes multiple store paths with
-the same symbolic name, only the one with the highest version is
-installed.</p></div><div class="refsection"><a id="idm139733300116496"></a><h3>Flags</h3><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--lt</code></span></dt><dd><p>Only upgrade a derivation to newer versions. This
- is the default.</p></dd><dt><span class="term"><code class="option">--leq</code></span></dt><dd><p>In addition to upgrading to newer versions, also
- “upgrade” to derivations that have the same version. Version are
- not a unique identification of a derivation, so there may be many
- derivations that have the same version. This flag may be useful
- to force “synchronisation” between the installed and available
- derivations.</p></dd><dt><span class="term"><code class="option">--eq</code></span></dt><dd><p><span class="emphasis"><em>Only</em></span> “upgrade” to derivations
- that have the same version. This may not seem very useful, but it
- actually is, e.g., when there is a new release of Nixpkgs and you
- want to replace installed applications with the same versions
- built against newer dependencies (to reduce the number of
- dependencies floating around on your system).</p></dd><dt><span class="term"><code class="option">--always</code></span></dt><dd><p>In addition to upgrading to newer versions, also
- “upgrade” to derivations that have the same or a lower version.
- I.e., derivations may actually be downgraded depending on what is
- available in the active Nix expression.</p></dd></dl></div><p>For the other flags, see <code class="option"><a class="option" href="#rsec-nix-env-install" title="Operation --install">--install</a></code>.</p></div><div class="refsection"><a id="idm139733300106960"></a><h3>Examples</h3><pre class="screen">
-$ nix-env --upgrade gcc
-upgrading `gcc-3.3.1' to `gcc-3.4'
-
-$ nix-env -u gcc-3.3.2 --always <em class="lineannotation"><span class="lineannotation">(switch to a specific version)</span></em>
-upgrading `gcc-3.4' to `gcc-3.3.2'
-
-$ nix-env --upgrade pan
-<em class="lineannotation"><span class="lineannotation">(no upgrades available, so nothing happens)</span></em>
-
-$ nix-env -u <em class="lineannotation"><span class="lineannotation">(try to upgrade everything)</span></em>
-upgrading `hello-2.1.2' to `hello-2.1.3'
-upgrading `mozilla-1.2' to `mozilla-1.4'</pre></div><div class="refsection"><a id="ssec-version-comparisons"></a><h3>Versions</h3><p>The upgrade operation determines whether a derivation
-<code class="varname">y</code> is an upgrade of a derivation
-<code class="varname">x</code> by looking at their respective
-<code class="literal">name</code> attributes. The names (e.g.,
-<code class="literal">gcc-3.3.1</code> are split into two parts: the package
-name (<code class="literal">gcc</code>), and the version
-(<code class="literal">3.3.1</code>). The version part starts after the first
-dash not followed by a letter. <code class="varname">x</code> is considered an
-upgrade of <code class="varname">y</code> if their package names match, and the
-version of <code class="varname">y</code> is higher that that of
-<code class="varname">x</code>.</p><p>The versions are compared by splitting them into contiguous
-components of numbers and letters. E.g., <code class="literal">3.3.1pre5</code>
-is split into <code class="literal">[3, 3, 1, "pre", 5]</code>. These lists are
-then compared lexicographically (from left to right). Corresponding
-components <code class="varname">a</code> and <code class="varname">b</code> are compared
-as follows. If they are both numbers, integer comparison is used. If
-<code class="varname">a</code> is an empty string and <code class="varname">b</code> is a
-number, <code class="varname">a</code> is considered less than
-<code class="varname">b</code>. The special string component
-<code class="literal">pre</code> (for <span class="emphasis"><em>pre-release</em></span>) is
-considered to be less than other components. String components are
-considered less than number components. Otherwise, they are compared
-lexicographically (i.e., using case-sensitive string comparison).</p><p>This is illustrated by the following examples:
-
-</p><pre class="screen">
-1.0 < 2.3
-2.1 < 2.3
-2.3 = 2.3
-2.5 > 2.3
-3.1 > 2.3
-2.3.1 > 2.3
-2.3.1 > 2.3a
-2.3pre1 < 2.3
-2.3pre3 < 2.3pre12
-2.3a < 2.3c
-2.3pre1 < 2.3c
-2.3pre1 < 2.3q</pre><p>
-
-</p></div></div><div class="refsection"><a id="idm139733300091392"></a><h2>Operation <code class="option">--uninstall</code></h2><div class="refsection"><a id="idm139733300090560"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-env</code> { <code class="option">--uninstall</code> | <code class="option">-e</code> } <em class="replaceable"><code>drvnames</code></em>... </p></div></div><div class="refsection"><a id="idm139733300085776"></a><h3>Description</h3><p>The uninstall operation creates a new user environment, based on
-the current generation of the active profile, from which the store
-paths designated by the symbolic names
-<em class="replaceable"><code>names</code></em> are removed.</p></div><div class="refsection"><a id="idm139733300084080"></a><h3>Examples</h3><pre class="screen">
-$ nix-env --uninstall gcc
-$ nix-env -e '.*' <em class="lineannotation"><span class="lineannotation">(remove everything)</span></em></pre></div></div><div class="refsection"><a id="rsec-nix-env-set"></a><h2>Operation <code class="option">--set</code></h2><div class="refsection"><a id="idm139733300080928"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-env</code> <code class="option">--set</code> <em class="replaceable"><code>drvname</code></em> </p></div></div><div class="refsection"><a id="idm139733300077824"></a><h3>Description</h3><p>The <code class="option">--set</code> operation modifies the current generation of a
-profile so that it contains exactly the specified derivation, and nothing else.
-</p></div><div class="refsection"><a id="idm139733300076176"></a><h3>Examples</h3><p>
-The following updates a profile such that its current generation will contain
-just Firefox:
-
-</p><pre class="screen">
-$ nix-env -p /nix/var/nix/profiles/browser --set firefox</pre><p>
-
-</p></div></div><div class="refsection"><a id="rsec-nix-env-set-flag"></a><h2>Operation <code class="option">--set-flag</code></h2><div class="refsection"><a id="idm139733300072736"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-env</code> <code class="option">--set-flag</code> <em class="replaceable"><code>name</code></em> <em class="replaceable"><code>value</code></em> <em class="replaceable"><code>drvnames</code></em>... </p></div></div><div class="refsection"><a id="idm139733300067728"></a><h3>Description</h3><p>The <code class="option">--set-flag</code> operation allows meta attributes
-of installed packages to be modified. There are several attributes
-that can be usefully modified, because they affect the behaviour of
-<span class="command"><strong>nix-env</strong></span> or the user environment build
-script:
-
-</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><code class="varname">priority</code> can be changed to
- resolve filename clashes. The user environment build script uses
- the <code class="varname">meta.priority</code> attribute of derivations to
- resolve filename collisions between packages. Lower priority values
- denote a higher priority. For instance, the GCC wrapper package and
- the Binutils package in Nixpkgs both have a file
- <code class="filename">bin/ld</code>, so previously if you tried to install
- both you would get a collision. Now, on the other hand, the GCC
- wrapper declares a higher priority than Binutils, so the former’s
- <code class="filename">bin/ld</code> is symlinked in the user
- environment.</p></li><li class="listitem"><p><code class="varname">keep</code> can be set to
- <code class="literal">true</code> to prevent the package from being upgraded
- or replaced. This is useful if you want to hang on to an older
- version of a package.</p></li><li class="listitem"><p><code class="varname">active</code> can be set to
- <code class="literal">false</code> to “disable” the package. That is, no
- symlinks will be generated to the files of the package, but it
- remains part of the profile (so it won’t be garbage-collected). It
- can be set back to <code class="literal">true</code> to re-enable the
- package.</p></li></ul></div><p>
-
-</p></div><div class="refsection"><a id="idm139733300058816"></a><h3>Examples</h3><p>To prevent the currently installed Firefox from being upgraded:
-
-</p><pre class="screen">
-$ nix-env --set-flag keep true firefox</pre><p>
-
-After this, <span class="command"><strong>nix-env -u</strong></span> will ignore Firefox.</p><p>To disable the currently installed Firefox, then install a new
-Firefox while the old remains part of the profile:
-
-</p><pre class="screen">
-$ nix-env -q
-firefox-2.0.0.9 <em class="lineannotation"><span class="lineannotation">(the current one)</span></em>
-
-$ nix-env --preserve-installed -i firefox-2.0.0.11
-installing `firefox-2.0.0.11'
-building path(s) `/nix/store/myy0y59q3ig70dgq37jqwg1j0rsapzsl-user-environment'
-collision between `/nix/store/<em class="replaceable"><code>...</code></em>-firefox-2.0.0.11/bin/firefox'
- and `/nix/store/<em class="replaceable"><code>...</code></em>-firefox-2.0.0.9/bin/firefox'.
-<em class="lineannotation"><span class="lineannotation">(i.e., can’t have two active at the same time)</span></em>
-
-$ nix-env --set-flag active false firefox
-setting flag on `firefox-2.0.0.9'
-
-$ nix-env --preserve-installed -i firefox-2.0.0.11
-installing `firefox-2.0.0.11'
-
-$ nix-env -q
-firefox-2.0.0.11 <em class="lineannotation"><span class="lineannotation">(the enabled one)</span></em>
-firefox-2.0.0.9 <em class="lineannotation"><span class="lineannotation">(the disabled one)</span></em></pre><p>
-
-</p><p>To make files from <code class="literal">binutils</code> take precedence
-over files from <code class="literal">gcc</code>:
-
-</p><pre class="screen">
-$ nix-env --set-flag priority 5 binutils
-$ nix-env --set-flag priority 10 gcc</pre><p>
-
-</p></div></div><div class="refsection"><a id="idm139733300050640"></a><h2>Operation <code class="option">--query</code></h2><div class="refsection"><a id="idm139733300049808"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-env</code> { <code class="option">--query</code> | <code class="option">-q</code> } [ <code class="option">--installed</code> | <code class="option">--available</code> | <code class="option">-a</code> ]<br /> [
- { <code class="option">--status</code> | <code class="option">-s</code> }
- ] [
- { <code class="option">--attr-path</code> | <code class="option">-P</code> }
- ] [<code class="option">--no-name</code>] [
- { <code class="option">--compare-versions</code> | <code class="option">-c</code> }
- ] [<code class="option">--system</code>] [<code class="option">--drv-path</code>] [<code class="option">--out-path</code>] [<code class="option">--description</code>] [<code class="option">--meta</code>]<br /> [<code class="option">--xml</code>] [<code class="option">--json</code>] [
- { <code class="option">--prebuilt-only</code> | <code class="option">-b</code> }
- ] [
- { <code class="option">--attr</code> | <code class="option">-A</code> }
- <em class="replaceable"><code>attribute-path</code></em>
- ]<br /> <em class="replaceable"><code>names</code></em>... </p></div></div><div class="refsection"><a id="idm139733300023312"></a><h3>Description</h3><p>The query operation displays information about either the store
-paths that are installed in the current generation of the active
-profile (<code class="option">--installed</code>), or the derivations that are
-available for installation in the active Nix expression
-(<code class="option">--available</code>). It only prints information about
-derivations whose symbolic name matches one of
-<em class="replaceable"><code>names</code></em>.</p><p>The derivations are sorted by their <code class="literal">name</code>
-attributes.</p></div><div class="refsection"><a id="idm139733300019760"></a><h3>Source selection</h3><p>The following flags specify the set of things on which the query
-operates.</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--installed</code></span></dt><dd><p>The query operates on the store paths that are
- installed in the current generation of the active profile. This
- is the default.</p></dd><dt><span class="term"><code class="option">--available</code>, </span><span class="term"><code class="option">-a</code></span></dt><dd><p>The query operates on the derivations that are
- available in the active Nix expression.</p></dd></dl></div></div><div class="refsection"><a id="idm139733300014832"></a><h3>Queries</h3><p>The following flags specify what information to display about
-the selected derivations. Multiple flags may be specified, in which
-case the information is shown in the order given here. Note that the
-name of the derivation is shown unless <code class="option">--no-name</code> is
-specified.</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--xml</code></span></dt><dd><p>Print the result in an XML representation suitable
- for automatic processing by other tools. The root element is
- called <code class="literal">items</code>, which contains a
- <code class="literal">item</code> element for each available or installed
- derivation. The fields discussed below are all stored in
- attributes of the <code class="literal">item</code>
- elements.</p></dd><dt><span class="term"><code class="option">--json</code></span></dt><dd><p>Print the result in a JSON representation suitable
- for automatic processing by other tools.</p></dd><dt><span class="term"><code class="option">--prebuilt-only</code> / <code class="option">-b</code></span></dt><dd><p>Show only derivations for which a substitute is
- registered, i.e., there is a pre-built binary available that can
- be downloaded in lieu of building the derivation. Thus, this
- shows all packages that probably can be installed
- quickly.</p></dd><dt><span class="term"><code class="option">--status</code>, </span><span class="term"><code class="option">-s</code></span></dt><dd><p>Print the <span class="emphasis"><em>status</em></span> of the
- derivation. The status consists of three characters. The first
- is <code class="literal">I</code> or <code class="literal">-</code>, indicating
- whether the derivation is currently installed in the current
- generation of the active profile. This is by definition the case
- for <code class="option">--installed</code>, but not for
- <code class="option">--available</code>. The second is <code class="literal">P</code>
- or <code class="literal">-</code>, indicating whether the derivation is
- present on the system. This indicates whether installation of an
- available derivation will require the derivation to be built. The
- third is <code class="literal">S</code> or <code class="literal">-</code>, indicating
- whether a substitute is available for the
- derivation.</p></dd><dt><span class="term"><code class="option">--attr-path</code>, </span><span class="term"><code class="option">-P</code></span></dt><dd><p>Print the <span class="emphasis"><em>attribute path</em></span> of
- the derivation, which can be used to unambiguously select it using
- the <a class="link" href="#opt-attr"><code class="option">--attr</code> option</a>
- available in commands that install derivations like
- <code class="literal">nix-env --install</code>. This option only works
- together with <code class="option">--available</code></p></dd><dt><span class="term"><code class="option">--no-name</code></span></dt><dd><p>Suppress printing of the <code class="literal">name</code>
- attribute of each derivation.</p></dd><dt><span class="term"><code class="option">--compare-versions</code> /
- <code class="option">-c</code></span></dt><dd><p>Compare installed versions to available versions,
- or vice versa (if <code class="option">--available</code> is given). This is
- useful for quickly seeing whether upgrades for installed
- packages are available in a Nix expression. A column is added
- with the following meaning:
-
- </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal"><</code> <em class="replaceable"><code>version</code></em></span></dt><dd><p>A newer version of the package is available
- or installed.</p></dd><dt><span class="term"><code class="literal">=</code> <em class="replaceable"><code>version</code></em></span></dt><dd><p>At most the same version of the package is
- available or installed.</p></dd><dt><span class="term"><code class="literal">></code> <em class="replaceable"><code>version</code></em></span></dt><dd><p>Only older versions of the package are
- available or installed.</p></dd><dt><span class="term"><code class="literal">- ?</code></span></dt><dd><p>No version of the package is available or
- installed.</p></dd></dl></div><p>
-
- </p></dd><dt><span class="term"><code class="option">--system</code></span></dt><dd><p>Print the <code class="literal">system</code> attribute of
- the derivation.</p></dd><dt><span class="term"><code class="option">--drv-path</code></span></dt><dd><p>Print the path of the store
- derivation.</p></dd><dt><span class="term"><code class="option">--out-path</code></span></dt><dd><p>Print the output path of the
- derivation.</p></dd><dt><span class="term"><code class="option">--description</code></span></dt><dd><p>Print a short (one-line) description of the
- derivation, if available. The description is taken from the
- <code class="literal">meta.description</code> attribute of the
- derivation.</p></dd><dt><span class="term"><code class="option">--meta</code></span></dt><dd><p>Print all of the meta-attributes of the
- derivation. This option is only available with
- <code class="option">--xml</code> or <code class="option">--json</code>.</p></dd></dl></div></div><div class="refsection"><a id="idm139733299975552"></a><h3>Examples</h3><p>To show installed packages:
-
-</p><pre class="screen">
-$ nix-env -q
-bison-1.875c
-docbook-xml-4.2
-firefox-1.0.4
-MPlayer-1.0pre7
-ORBit2-2.8.3
-<em class="replaceable"><code>…</code></em>
-</pre><p>
-
-</p><p>To show available packages:
-
-</p><pre class="screen">
-$ nix-env -qa
-firefox-1.0.7
-GConf-2.4.0.1
-MPlayer-1.0pre7
-ORBit2-2.8.3
-<em class="replaceable"><code>…</code></em>
-</pre><p>
-
-</p><p>To show the status of available packages:
-
-</p><pre class="screen">
-$ nix-env -qas
--P- firefox-1.0.7 <em class="lineannotation"><span class="lineannotation">(not installed but present)</span></em>
---S GConf-2.4.0.1 <em class="lineannotation"><span class="lineannotation">(not present, but there is a substitute for fast installation)</span></em>
---S MPlayer-1.0pre3 <em class="lineannotation"><span class="lineannotation">(i.e., this is not the installed MPlayer, even though the version is the same!)</span></em>
-IP- ORBit2-2.8.3 <em class="lineannotation"><span class="lineannotation">(installed and by definition present)</span></em>
-<em class="replaceable"><code>…</code></em>
-</pre><p>
-
-</p><p>To show available packages in the Nix expression <code class="filename">foo.nix</code>:
-
-</p><pre class="screen">
-$ nix-env -f ./foo.nix -qa
-foo-1.2.3
-</pre><p>
-
-</p><p>To compare installed versions to what’s available:
-
-</p><pre class="screen">
-$ nix-env -qc
-<em class="replaceable"><code>...</code></em>
-acrobat-reader-7.0 - ? <em class="lineannotation"><span class="lineannotation">(package is not available at all)</span></em>
-autoconf-2.59 = 2.59 <em class="lineannotation"><span class="lineannotation">(same version)</span></em>
-firefox-1.0.4 < 1.0.7 <em class="lineannotation"><span class="lineannotation">(a more recent version is available)</span></em>
-<em class="replaceable"><code>...</code></em>
-</pre><p>
-
-</p><p>To show all packages with “<code class="literal">zip</code>” in the name:
-
-</p><pre class="screen">
-$ nix-env -qa '.*zip.*'
-bzip2-1.0.6
-gzip-1.6
-zip-3.0
-<em class="replaceable"><code>…</code></em>
-</pre><p>
-
-</p><p>To show all packages with “<code class="literal">firefox</code>” or
-“<code class="literal">chromium</code>” in the name:
-
-</p><pre class="screen">
-$ nix-env -qa '.*(firefox|chromium).*'
-chromium-37.0.2062.94
-chromium-beta-38.0.2125.24
-firefox-32.0.3
-firefox-with-plugins-13.0.1
-<em class="replaceable"><code>…</code></em>
-</pre><p>
-
-</p><p>To show all packages in the latest revision of the Nixpkgs
-repository:
-
-</p><pre class="screen">
-$ nix-env -f https://github.com/NixOS/nixpkgs/archive/master.tar.gz -qa
-</pre><p>
-
-</p></div></div><div class="refsection"><a id="idm139733299959008"></a><h2>Operation <code class="option">--switch-profile</code></h2><div class="refsection"><a id="idm139733299958176"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-env</code> { <code class="option">--switch-profile</code> | <code class="option">-S</code> } {<em class="replaceable"><code>path</code></em>}</p></div></div><div class="refsection"><a id="idm139733299953696"></a><h3>Description</h3><p>This operation makes <em class="replaceable"><code>path</code></em> the current
-profile for the user. That is, the symlink
-<code class="filename">~/.nix-profile</code> is made to point to
-<em class="replaceable"><code>path</code></em>.</p></div><div class="refsection"><a id="idm139733299951328"></a><h3>Examples</h3><pre class="screen">
-$ nix-env -S ~/my-profile</pre></div></div><div class="refsection"><a id="idm139733299949648"></a><h2>Operation <code class="option">--list-generations</code></h2><div class="refsection"><a id="idm139733299948816"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-env</code> <code class="option">--list-generations</code> </p></div></div><div class="refsection"><a id="idm139733299946528"></a><h3>Description</h3><p>This operation print a list of all the currently existing
-generations for the active profile. These may be switched to using
-the <code class="option">--switch-generation</code> operation. It also prints
-the creation date of the generation, and indicates the current
-generation.</p></div><div class="refsection"><a id="idm139733299944800"></a><h3>Examples</h3><pre class="screen">
-$ nix-env --list-generations
- 95 2004-02-06 11:48:24
- 96 2004-02-06 11:49:01
- 97 2004-02-06 16:22:45
- 98 2004-02-06 16:24:33 (current)</pre></div></div><div class="refsection"><a id="idm139733299943088"></a><h2>Operation <code class="option">--delete-generations</code></h2><div class="refsection"><a id="idm139733299942256"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-env</code> <code class="option">--delete-generations</code> <em class="replaceable"><code>generations</code></em>... </p></div></div><div class="refsection"><a id="idm139733299938880"></a><h3>Description</h3><p>This operation deletes the specified generations of the current
-profile. The generations can be a list of generation numbers, the
-special value <code class="literal">old</code> to delete all non-current
-generations, a value such as <code class="literal">30d</code> to delete all
-generations older than the specified number of days (except for the
-generation that was active at that point in time), or a value such as
-<code class="literal">+5</code> to keep the last <code class="literal">5</code> generations
-ignoring any newer than current, e.g., if <code class="literal">30</code> is the current
-generation <code class="literal">+5</code> will delete generation <code class="literal">25</code>
-and all older generations.
-Periodically deleting old generations is important to make garbage collection
-effective.</p></div><div class="refsection"><a id="idm139733299934384"></a><h3>Examples</h3><pre class="screen">
-$ nix-env --delete-generations 3 4 8
-
-$ nix-env --delete-generations +5
-
-$ nix-env --delete-generations 30d
-
-$ nix-env -p other_profile --delete-generations old</pre></div></div><div class="refsection"><a id="idm139733299932576"></a><h2>Operation <code class="option">--switch-generation</code></h2><div class="refsection"><a id="idm139733299931744"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-env</code> { <code class="option">--switch-generation</code> | <code class="option">-G</code> } {<em class="replaceable"><code>generation</code></em>}</p></div></div><div class="refsection"><a id="idm139733299927264"></a><h3>Description</h3><p>This operation makes generation number
-<em class="replaceable"><code>generation</code></em> the current generation of the
-active profile. That is, if the
-<code class="filename"><em class="replaceable"><code>profile</code></em></code> is the path to
-the active profile, then the symlink
-<code class="filename"><em class="replaceable"><code>profile</code></em></code> is made to
-point to
-<code class="filename"><em class="replaceable"><code>profile</code></em>-<em class="replaceable"><code>generation</code></em>-link</code>,
-which is in turn a symlink to the actual user environment in the Nix
-store.</p><p>Switching will fail if the specified generation does not exist.</p></div><div class="refsection"><a id="idm139733299922880"></a><h3>Examples</h3><pre class="screen">
-$ nix-env -G 42
-switching from generation 50 to 42</pre></div></div><div class="refsection"><a id="idm139733299921184"></a><h2>Operation <code class="option">--rollback</code></h2><div class="refsection"><a id="idm139733299920352"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-env</code> <code class="option">--rollback</code> </p></div></div><div class="refsection"><a id="idm139733299918064"></a><h3>Description</h3><p>This operation switches to the “previous” generation of the
-active profile, that is, the highest numbered generation lower than
-the current generation, if it exists. It is just a convenience
-wrapper around <code class="option">--list-generations</code> and
-<code class="option">--switch-generation</code>.</p></div><div class="refsection"><a id="idm139733299915712"></a><h3>Examples</h3><pre class="screen">
-$ nix-env --rollback
-switching from generation 92 to 91
-
-$ nix-env --rollback
-error: no generation older than the current (91) exists</pre></div></div></div><div class="refentry"><div class="refentry.separator"><hr /></div><a id="sec-nix-build"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix-build — build a Nix expression</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">nix-build</code> [<code class="option">--help</code>] [<code class="option">--version</code>] [
- { <code class="option">--verbose</code> | <code class="option">-v</code> }
-...] [
- <code class="option">--quiet</code>
-] [
- <code class="option">--log-format</code>
- <em class="replaceable"><code>format</code></em>
-] [
- <code class="option">--no-build-output</code> | <code class="option">-Q</code>
-] [
- { <code class="option">--max-jobs</code> | <code class="option">-j</code> }
- <em class="replaceable"><code>number</code></em>
-] [
- <code class="option">--cores</code>
- <em class="replaceable"><code>number</code></em>
-] [
- <code class="option">--max-silent-time</code>
- <em class="replaceable"><code>number</code></em>
-] [
- <code class="option">--timeout</code>
- <em class="replaceable"><code>number</code></em>
-] [
- <code class="option">--keep-going</code> | <code class="option">-k</code>
-] [
- <code class="option">--keep-failed</code> | <code class="option">-K</code>
-] [<code class="option">--fallback</code>] [<code class="option">--readonly-mode</code>] [
- <code class="option">-I</code>
- <em class="replaceable"><code>path</code></em>
-] [
- <code class="option">--option</code>
- <em class="replaceable"><code>name</code></em>
- <em class="replaceable"><code>value</code></em>
-]<br /> [<code class="option">--arg</code> <em class="replaceable"><code>name</code></em> <em class="replaceable"><code>value</code></em>] [<code class="option">--argstr</code> <em class="replaceable"><code>name</code></em> <em class="replaceable"><code>value</code></em>] [
- { <code class="option">--attr</code> | <code class="option">-A</code> }
- <em class="replaceable"><code>attrPath</code></em>
- ] [<code class="option">--no-out-link</code>] [<code class="option">--dry-run</code>] [
- { <code class="option">--out-link</code> | <code class="option">-o</code> }
- <em class="replaceable"><code>outlink</code></em>
- ] <em class="replaceable"><code>paths</code></em>... </p></div></div><div class="refsection"><a id="idm139733299874432"></a><h2>Description</h2><p>The <span class="command"><strong>nix-build</strong></span> command builds the derivations
-described by the Nix expressions in <em class="replaceable"><code>paths</code></em>.
-If the build succeeds, it places a symlink to the result in the
-current directory. The symlink is called <code class="filename">result</code>.
-If there are multiple Nix expressions, or the Nix expressions evaluate
-to multiple derivations, multiple sequentially numbered symlinks are
-created (<code class="filename">result</code>, <code class="filename">result-2</code>,
-and so on).</p><p>If no <em class="replaceable"><code>paths</code></em> are specified, then
-<span class="command"><strong>nix-build</strong></span> will use <code class="filename">default.nix</code>
-in the current directory, if it exists.</p><p>If an element of <em class="replaceable"><code>paths</code></em> starts with
-<code class="literal">http://</code> or <code class="literal">https://</code>, it is
-interpreted as the URL of a tarball that will be downloaded and
-unpacked to a temporary location. The tarball must include a single
-top-level directory containing at least a file named
-<code class="filename">default.nix</code>.</p><p><span class="command"><strong>nix-build</strong></span> is essentially a wrapper around
-<a class="link" href="#sec-nix-instantiate" title="nix-instantiate"><span class="command"><strong>nix-instantiate</strong></span></a>
-(to translate a high-level Nix expression to a low-level store
-derivation) and <a class="link" href="#rsec-nix-store-realise" title="Operation --realise"><span class="command"><strong>nix-store
---realise</strong></span></a> (to build the store derivation).</p><div class="warning"><h3 class="title">Warning</h3><p>The result of the build is automatically registered as
-a root of the Nix garbage collector. This root disappears
-automatically when the <code class="filename">result</code> symlink is deleted
-or renamed. So don’t rename the symlink.</p></div></div><div class="refsection"><a id="idm139733299863072"></a><h2>Options</h2><p>All options not listed here are passed to <span class="command"><strong>nix-store
---realise</strong></span>, except for <code class="option">--arg</code> and
-<code class="option">--attr</code> / <code class="option">-A</code> which are passed to
-<span class="command"><strong>nix-instantiate</strong></span>. <span class="phrase">See
-also <a class="xref" href="#sec-common-options" title="Chapter 20. Common Options">Chapter 20, <em>Common Options</em></a>.</span></p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--no-out-link</code></span></dt><dd><p>Do not create a symlink to the output path. Note
- that as a result the output does not become a root of the garbage
- collector, and so might be deleted by <span class="command"><strong>nix-store
- --gc</strong></span>.</p></dd><dt><span class="term"><code class="option">--dry-run</code></span></dt><dd><p>Show what store paths would be built or downloaded.</p></dd><dt><a id="opt-out-link"></a><span class="term"><code class="option">--out-link</code> /
- <code class="option">-o</code> <em class="replaceable"><code>outlink</code></em></span></dt><dd><p>Change the name of the symlink to the output path
- created from <code class="filename">result</code> to
- <em class="replaceable"><code>outlink</code></em>.</p></dd></dl></div><p>The following common options are supported:</p></div><div class="refsection"><a id="idm139733299851056"></a><h2>Examples</h2><pre class="screen">
-$ nix-build '<nixpkgs>' -A firefox
-store derivation is /nix/store/qybprl8sz2lc...-firefox-1.5.0.7.drv
-/nix/store/d18hyl92g30l...-firefox-1.5.0.7
-
-$ ls -l result
-lrwxrwxrwx <em class="replaceable"><code>...</code></em> result -> /nix/store/d18hyl92g30l...-firefox-1.5.0.7
-
-$ ls ./result/bin/
-firefox firefox-config</pre><p>If a derivation has multiple outputs,
-<span class="command"><strong>nix-build</strong></span> will build the default (first) output.
-You can also build all outputs:
-</p><pre class="screen">
-$ nix-build '<nixpkgs>' -A openssl.all
-</pre><p>
-This will create a symlink for each output named
-<code class="filename">result-<em class="replaceable"><code>outputname</code></em></code>.
-The suffix is omitted if the output name is <code class="literal">out</code>.
-So if <code class="literal">openssl</code> has outputs <code class="literal">out</code>,
-<code class="literal">bin</code> and <code class="literal">man</code>,
-<span class="command"><strong>nix-build</strong></span> will create symlinks
-<code class="literal">result</code>, <code class="literal">result-bin</code> and
-<code class="literal">result-man</code>. It’s also possible to build a specific
-output:
-</p><pre class="screen">
-$ nix-build '<nixpkgs>' -A openssl.man
-</pre><p>
-This will create a symlink <code class="literal">result-man</code>.</p><p>Build a Nix expression given on the command line:
-
-</p><pre class="screen">
-$ nix-build -E 'with import <nixpkgs> { }; runCommand "foo" { } "echo bar > $out"'
-$ cat ./result
-bar
-</pre><p>
-
-</p><p>Build the GNU Hello package from the latest revision of the
-master branch of Nixpkgs:
-
-</p><pre class="screen">
-$ nix-build https://github.com/NixOS/nixpkgs/archive/master.tar.gz -A hello
-</pre><p>
-
-</p></div></div><div class="refentry"><div class="refentry.separator"><hr /></div><a id="sec-nix-shell"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix-shell — start an interactive shell based on a Nix expression</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">nix-shell</code> [<code class="option">--arg</code> <em class="replaceable"><code>name</code></em> <em class="replaceable"><code>value</code></em>] [<code class="option">--argstr</code> <em class="replaceable"><code>name</code></em> <em class="replaceable"><code>value</code></em>] [
- { <code class="option">--attr</code> | <code class="option">-A</code> }
- <em class="replaceable"><code>attrPath</code></em>
- ] [<code class="option">--command</code> <em class="replaceable"><code>cmd</code></em>] [<code class="option">--run</code> <em class="replaceable"><code>cmd</code></em>] [<code class="option">--exclude</code> <em class="replaceable"><code>regexp</code></em>] [<code class="option">--pure</code>] [<code class="option">--keep</code> <em class="replaceable"><code>name</code></em>] {
- { <code class="option">--packages</code> | <code class="option">-p</code> }
-
- { <em class="replaceable"><code>packages</code></em> | <em class="replaceable"><code>expressions</code></em> }
- ...
- | [<em class="replaceable"><code>path</code></em>]}</p></div></div><div class="refsection"><a id="idm139733299816608"></a><h2>Description</h2><p>The command <span class="command"><strong>nix-shell</strong></span> will build the
-dependencies of the specified derivation, but not the derivation
-itself. It will then start an interactive shell in which all
-environment variables defined by the derivation
-<em class="replaceable"><code>path</code></em> have been set to their corresponding
-values, and the script <code class="literal">$stdenv/setup</code> has been
-sourced. This is useful for reproducing the environment of a
-derivation for development.</p><p>If <em class="replaceable"><code>path</code></em> is not given,
-<span class="command"><strong>nix-shell</strong></span> defaults to
-<code class="filename">shell.nix</code> if it exists, and
-<code class="filename">default.nix</code> otherwise.</p><p>If <em class="replaceable"><code>path</code></em> starts with
-<code class="literal">http://</code> or <code class="literal">https://</code>, it is
-interpreted as the URL of a tarball that will be downloaded and
-unpacked to a temporary location. The tarball must include a single
-top-level directory containing at least a file named
-<code class="filename">default.nix</code>.</p><p>If the derivation defines the variable
-<code class="varname">shellHook</code>, it will be evaluated after
-<code class="literal">$stdenv/setup</code> has been sourced. Since this hook is
-not executed by regular Nix builds, it allows you to perform
-initialisation specific to <span class="command"><strong>nix-shell</strong></span>. For example,
-the derivation attribute
-
-</p><pre class="programlisting">
-shellHook =
- ''
- echo "Hello shell"
- '';
-</pre><p>
-
-will cause <span class="command"><strong>nix-shell</strong></span> to print <code class="literal">Hello shell</code>.</p></div><div class="refsection"><a id="idm139733299806096"></a><h2>Options</h2><p>All options not listed here are passed to <span class="command"><strong>nix-store
---realise</strong></span>, except for <code class="option">--arg</code> and
-<code class="option">--attr</code> / <code class="option">-A</code> which are passed to
-<span class="command"><strong>nix-instantiate</strong></span>. <span class="phrase">See
-also <a class="xref" href="#sec-common-options" title="Chapter 20. Common Options">Chapter 20, <em>Common Options</em></a>.</span></p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--command</code> <em class="replaceable"><code>cmd</code></em></span></dt><dd><p>In the environment of the derivation, run the
- shell command <em class="replaceable"><code>cmd</code></em>. This command is
- executed in an interactive shell. (Use <code class="option">--run</code> to
- use a non-interactive shell instead.) However, a call to
- <code class="literal">exit</code> is implicitly added to the command, so the
- shell will exit after running the command. To prevent this, add
- <code class="literal">return</code> at the end; e.g. <code class="literal">--command
- "echo Hello; return"</code> will print <code class="literal">Hello</code>
- and then drop you into the interactive shell. This can be useful
- for doing any additional initialisation.</p></dd><dt><span class="term"><code class="option">--run</code> <em class="replaceable"><code>cmd</code></em></span></dt><dd><p>Like <code class="option">--command</code>, but executes the
- command in a non-interactive shell. This means (among other
- things) that if you hit Ctrl-C while the command is running, the
- shell exits.</p></dd><dt><span class="term"><code class="option">--exclude</code> <em class="replaceable"><code>regexp</code></em></span></dt><dd><p>Do not build any dependencies whose store path
- matches the regular expression <em class="replaceable"><code>regexp</code></em>.
- This option may be specified multiple times.</p></dd><dt><span class="term"><code class="option">--pure</code></span></dt><dd><p>If this flag is specified, the environment is
- almost entirely cleared before the interactive shell is started,
- so you get an environment that more closely corresponds to the
- “real” Nix build. A few variables, in particular
- <code class="envar">HOME</code>, <code class="envar">USER</code> and
- <code class="envar">DISPLAY</code>, are retained. Note that
- <code class="filename">~/.bashrc</code> and (depending on your Bash
- installation) <code class="filename">/etc/bashrc</code> are still sourced,
- so any variables set there will affect the interactive
- shell.</p></dd><dt><span class="term"><code class="option">--packages</code> / <code class="option">-p</code> <em class="replaceable"><code>packages</code></em>…</span></dt><dd><p>Set up an environment in which the specified
- packages are present. The command line arguments are interpreted
- as attribute names inside the Nix Packages collection. Thus,
- <code class="literal">nix-shell -p libjpeg openjdk</code> will start a shell
- in which the packages denoted by the attribute names
- <code class="varname">libjpeg</code> and <code class="varname">openjdk</code> are
- present.</p></dd><dt><span class="term"><code class="option">-i</code> <em class="replaceable"><code>interpreter</code></em></span></dt><dd><p>The chained script interpreter to be invoked by
- <span class="command"><strong>nix-shell</strong></span>. Only applicable in
- <code class="literal">#!</code>-scripts (described <a class="link" href="#ssec-nix-shell-shebang" title="Use as a #!-interpreter">below</a>).</p></dd><dt><span class="term"><code class="option">--keep</code> <em class="replaceable"><code>name</code></em></span></dt><dd><p>When a <code class="option">--pure</code> shell is started,
- keep the listed environment variables.</p></dd></dl></div><p>The following common options are supported:</p></div><div class="refsection"><a id="idm139733299777888"></a><h2>Environment variables</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="envar">NIX_BUILD_SHELL</code></span></dt><dd><p>Shell used to start the interactive environment.
- Defaults to the <span class="command"><strong>bash</strong></span> found in <code class="envar">PATH</code>.</p></dd></dl></div></div><div class="refsection"><a id="idm139733299774576"></a><h2>Examples</h2><p>To build the dependencies of the package Pan, and start an
-interactive shell in which to build it:
-
-</p><pre class="screen">
-$ nix-shell '<nixpkgs>' -A pan
-[nix-shell]$ unpackPhase
-[nix-shell]$ cd pan-*
-[nix-shell]$ configurePhase
-[nix-shell]$ buildPhase
-[nix-shell]$ ./pan/gui/pan
-</pre><p>
-
-To clear the environment first, and do some additional automatic
-initialisation of the interactive shell:
-
-</p><pre class="screen">
-$ nix-shell '<nixpkgs>' -A pan --pure \
- --command 'export NIX_DEBUG=1; export NIX_CORES=8; return'
-</pre><p>
-
-Nix expressions can also be given on the command line using the
-<span class="command"><strong>-E</strong></span> and <span class="command"><strong>-p</strong></span> flags.
-For instance, the following starts a shell containing the packages
-<code class="literal">sqlite</code> and <code class="literal">libX11</code>:
-
-</p><pre class="screen">
-$ nix-shell -E 'with import <nixpkgs> { }; runCommand "dummy" { buildInputs = [ sqlite xorg.libX11 ]; } ""'
-</pre><p>
-
-A shorter way to do the same is:
-
-</p><pre class="screen">
-$ nix-shell -p sqlite xorg.libX11
-[nix-shell]$ echo $NIX_LDFLAGS
-… -L/nix/store/j1zg5v…-sqlite-3.8.0.2/lib -L/nix/store/0gmcz9…-libX11-1.6.1/lib …
-</pre><p>
-
-Note that <span class="command"><strong>-p</strong></span> accepts multiple full nix expressions that
-are valid in the <code class="literal">buildInputs = [ ... ]</code> shown above,
-not only package names. So the following is also legal:
-
-</p><pre class="screen">
-$ nix-shell -p sqlite 'git.override { withManual = false; }'
-</pre><p>
-
-The <span class="command"><strong>-p</strong></span> flag looks up Nixpkgs in the Nix search
-path. You can override it by passing <code class="option">-I</code> or setting
-<code class="envar">NIX_PATH</code>. For example, the following gives you a shell
-containing the Pan package from a specific revision of Nixpkgs:
-
-</p><pre class="screen">
-$ nix-shell -p pan -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/8a3eea054838b55aca962c3fbde9c83c102b8bf2.tar.gz
-
-[nix-shell:~]$ pan --version
-Pan 0.139
-</pre><p>
-
-</p></div><div class="refsection"><a id="ssec-nix-shell-shebang"></a><h2>Use as a <code class="literal">#!</code>-interpreter</h2><p>You can use <span class="command"><strong>nix-shell</strong></span> as a script interpreter
-to allow scripts written in arbitrary languages to obtain their own
-dependencies via Nix. This is done by starting the script with the
-following lines:
-
-</p><pre class="programlisting">
-#! /usr/bin/env nix-shell
-#! nix-shell -i <em class="replaceable"><code>real-interpreter</code></em> -p <em class="replaceable"><code>packages</code></em>
-</pre><p>
-
-where <em class="replaceable"><code>real-interpreter</code></em> is the “real” script
-interpreter that will be invoked by <span class="command"><strong>nix-shell</strong></span> after
-it has obtained the dependencies and initialised the environment, and
-<em class="replaceable"><code>packages</code></em> are the attribute names of the
-dependencies in Nixpkgs.</p><p>The lines starting with <code class="literal">#! nix-shell</code> specify
-<span class="command"><strong>nix-shell</strong></span> options (see above). Note that you cannot
-write <code class="literal">#! /usr/bin/env nix-shell -i ...</code> because
-many operating systems only allow one argument in
-<code class="literal">#!</code> lines.</p><p>For example, here is a Python script that depends on Python and
-the <code class="literal">prettytable</code> package:
-
-</p><pre class="programlisting">
-#! /usr/bin/env nix-shell
-#! nix-shell -i python -p python pythonPackages.prettytable
-
-import prettytable
-
-# Print a simple table.
-t = prettytable.PrettyTable(["N", "N^2"])
-for n in range(1, 10): t.add_row([n, n * n])
-print t
-</pre><p>
-
-</p><p>Similarly, the following is a Perl script that specifies that it
-requires Perl and the <code class="literal">HTML::TokeParser::Simple</code> and
-<code class="literal">LWP</code> packages:
-
-</p><pre class="programlisting">
-#! /usr/bin/env nix-shell
-#! nix-shell -i perl -p perl perlPackages.HTMLTokeParserSimple perlPackages.LWP
-
-use HTML::TokeParser::Simple;
-
-# Fetch nixos.org and print all hrefs.
-my $p = HTML::TokeParser::Simple->new(url => 'http://nixos.org/');
-
-while (my $token = $p->get_tag("a")) {
- my $href = $token->get_attr("href");
- print "$href\n" if $href;
-}
-</pre><p>
-
-</p><p>Sometimes you need to pass a simple Nix expression to customize
-a package like Terraform:
-
-</p><pre class="programlisting">
-#! /usr/bin/env nix-shell
-#! nix-shell -i bash -p "terraform.withPlugins (plugins: [ plugins.openstack ])"
-
-terraform apply
-</pre><p>
-
-</p><div class="note"><h3 class="title">Note</h3><p>You must use double quotes (<code class="literal">"</code>) when
-passing a simple Nix expression in a nix-shell shebang.</p></div><p>
-</p><p>Finally, using the merging of multiple nix-shell shebangs the
-following Haskell script uses a specific branch of Nixpkgs/NixOS (the
-18.03 stable branch):
-
-</p><pre class="programlisting">
-#! /usr/bin/env nix-shell
-#! nix-shell -i runghc -p "haskellPackages.ghcWithPackages (ps: [ps.HTTP ps.tagsoup])"
-#! nix-shell -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-18.03.tar.gz
-
-import Network.HTTP
-import Text.HTML.TagSoup
-
--- Fetch nixos.org and print all hrefs.
-main = do
- resp <- Network.HTTP.simpleHTTP (getRequest "http://nixos.org/")
- body <- getResponseBody resp
- let tags = filter (isTagOpenName "a") $ parseTags body
- let tags' = map (fromAttrib "href") tags
- mapM_ putStrLn $ filter (/= "") tags'
-</pre><p>
-
-If you want to be even more precise, you can specify a specific
-revision of Nixpkgs:
-
-</p><pre class="programlisting">
-#! nix-shell -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/0672315759b3e15e2121365f067c1c8c56bb4722.tar.gz
-</pre><p>
-
-</p><p>The examples above all used <code class="option">-p</code> to get
-dependencies from Nixpkgs. You can also use a Nix expression to build
-your own dependencies. For example, the Python example could have been
-written as:
-
-</p><pre class="programlisting">
-#! /usr/bin/env nix-shell
-#! nix-shell deps.nix -i python
-</pre><p>
-
-where the file <code class="filename">deps.nix</code> in the same directory
-as the <code class="literal">#!</code>-script contains:
-
-</p><pre class="programlisting">
-with import <nixpkgs> {};
-
-runCommand "dummy" { buildInputs = [ python pythonPackages.prettytable ]; } ""
-</pre><p>
-
-</p></div></div><div class="refentry"><div class="refentry.separator"><hr /></div><a id="sec-nix-store"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix-store — manipulate or query the Nix store</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">nix-store</code> [<code class="option">--help</code>] [<code class="option">--version</code>] [
- { <code class="option">--verbose</code> | <code class="option">-v</code> }
-...] [
- <code class="option">--quiet</code>
-] [
- <code class="option">--log-format</code>
- <em class="replaceable"><code>format</code></em>
-] [
- <code class="option">--no-build-output</code> | <code class="option">-Q</code>
-] [
- { <code class="option">--max-jobs</code> | <code class="option">-j</code> }
- <em class="replaceable"><code>number</code></em>
-] [
- <code class="option">--cores</code>
- <em class="replaceable"><code>number</code></em>
-] [
- <code class="option">--max-silent-time</code>
- <em class="replaceable"><code>number</code></em>
-] [
- <code class="option">--timeout</code>
- <em class="replaceable"><code>number</code></em>
-] [
- <code class="option">--keep-going</code> | <code class="option">-k</code>
-] [
- <code class="option">--keep-failed</code> | <code class="option">-K</code>
-] [<code class="option">--fallback</code>] [<code class="option">--readonly-mode</code>] [
- <code class="option">-I</code>
- <em class="replaceable"><code>path</code></em>
-] [
- <code class="option">--option</code>
- <em class="replaceable"><code>name</code></em>
- <em class="replaceable"><code>value</code></em>
-]<br /> [<code class="option">--add-root</code> <em class="replaceable"><code>path</code></em>] [<code class="option">--indirect</code>] <em class="replaceable"><code>operation</code></em> [<em class="replaceable"><code>options</code></em>...] [<em class="replaceable"><code>arguments</code></em>...]</p></div></div><div class="refsection"><a id="idm139733299713504"></a><h2>Description</h2><p>The command <span class="command"><strong>nix-store</strong></span> performs primitive
-operations on the Nix store. You generally do not need to run this
-command manually.</p><p><span class="command"><strong>nix-store</strong></span> takes exactly one
-<span class="emphasis"><em>operation</em></span> flag which indicates the subcommand to
-be performed. These are documented below.</p></div><div class="refsection"><a id="idm139733299710208"></a><h2>Common options</h2><p>This section lists the options that are common to all
-operations. These options are allowed for every subcommand, though
-they may not always have an effect. <span class="phrase">See
-also <a class="xref" href="#sec-common-options" title="Chapter 20. Common Options">Chapter 20, <em>Common Options</em></a> for a list of common
-options.</span></p><div class="variablelist"><dl class="variablelist"><dt><a id="opt-add-root"></a><span class="term"><code class="option">--add-root</code> <em class="replaceable"><code>path</code></em></span></dt><dd><p>Causes the result of a realisation
- (<code class="option">--realise</code> and <code class="option">--force-realise</code>)
- to be registered as a root of the garbage collector<span class="phrase"> (see <a class="xref" href="#ssec-gc-roots" title="11.1. Garbage Collector Roots">Section 11.1, “Garbage Collector Roots”</a>)</span>. The root is stored in
- <em class="replaceable"><code>path</code></em>, which must be inside a directory
- that is scanned for roots by the garbage collector (i.e.,
- typically in a subdirectory of
- <code class="filename">/nix/var/nix/gcroots/</code>)
- <span class="emphasis"><em>unless</em></span> the <code class="option">--indirect</code> flag
- is used.</p><p>If there are multiple results, then multiple symlinks will
- be created by sequentially numbering symlinks beyond the first one
- (e.g., <code class="filename">foo</code>, <code class="filename">foo-2</code>,
- <code class="filename">foo-3</code>, and so on).</p></dd><dt><span class="term"><code class="option">--indirect</code></span></dt><dd><p>In conjunction with <code class="option">--add-root</code>, this option
- allows roots to be stored <span class="emphasis"><em>outside</em></span> of the GC
- roots directory. This is useful for commands such as
- <span class="command"><strong>nix-build</strong></span> that place a symlink to the build
- result in the current directory; such a build result should not be
- garbage-collected unless the symlink is removed.</p><p>The <code class="option">--indirect</code> flag causes a uniquely named
- symlink to <em class="replaceable"><code>path</code></em> to be stored in
- <code class="filename">/nix/var/nix/gcroots/auto/</code>. For instance,
-
- </p><pre class="screen">
-$ nix-store --add-root /home/eelco/bla/result --indirect -r <em class="replaceable"><code>...</code></em>
-
-$ ls -l /nix/var/nix/gcroots/auto
-lrwxrwxrwx 1 ... 2005-03-13 21:10 dn54lcypm8f8... -> /home/eelco/bla/result
-
-$ ls -l /home/eelco/bla/result
-lrwxrwxrwx 1 ... 2005-03-13 21:10 /home/eelco/bla/result -> /nix/store/1r11343n6qd4...-f-spot-0.0.10</pre><p>
-
- Thus, when <code class="filename">/home/eelco/bla/result</code> is removed,
- the GC root in the <code class="filename">auto</code> directory becomes a
- dangling symlink and will be ignored by the collector.</p><div class="warning"><h3 class="title">Warning</h3><p>Note that it is not possible to move or rename
- indirect GC roots, since the symlink in the
- <code class="filename">auto</code> directory will still point to the old
- location.</p></div></dd></dl></div></div><div class="refsection"><a id="rsec-nix-store-realise"></a><h2>Operation <code class="option">--realise</code></h2><div class="refsection"><a id="idm139733299689136"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> { <code class="option">--realise</code> | <code class="option">-r</code> } <em class="replaceable"><code>paths</code></em>... [<code class="option">--dry-run</code>]</p></div></div><div class="refsection"><a id="idm139733299683808"></a><h3>Description</h3><p>The operation <code class="option">--realise</code> essentially “builds”
-the specified store paths. Realisation is a somewhat overloaded term:
-
-</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>If the store path is a
- <span class="emphasis"><em>derivation</em></span>, realisation ensures that the output
- paths of the derivation are <a class="link" href="#gloss-validity" title="validity">valid</a> (i.e., the output path and its
- closure exist in the file system). This can be done in several
- ways. First, it is possible that the outputs are already valid, in
- which case we are done immediately. Otherwise, there may be <a class="link" href="#gloss-substitute" title="substitute">substitutes</a> that produce the
- outputs (e.g., by downloading them). Finally, the outputs can be
- produced by performing the build action described by the
- derivation.</p></li><li class="listitem"><p>If the store path is not a derivation, realisation
- ensures that the specified path is valid (i.e., it and its closure
- exist in the file system). If the path is already valid, we are
- done immediately. Otherwise, the path and any missing paths in its
- closure may be produced through substitutes. If there are no
- (successful) subsitutes, realisation fails.</p></li></ul></div><p>
-
-</p><p>The output path of each derivation is printed on standard
-output. (For non-derivations argument, the argument itself is
-printed.)</p><p>The following flags are available:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--dry-run</code></span></dt><dd><p>Print on standard error a description of what
- packages would be built or downloaded, without actually performing
- the operation.</p></dd><dt><span class="term"><code class="option">--ignore-unknown</code></span></dt><dd><p>If a non-derivation path does not have a
- substitute, then silently ignore it.</p></dd><dt><span class="term"><code class="option">--check</code></span></dt><dd><p>This option allows you to check whether a
- derivation is deterministic. It rebuilds the specified derivation
- and checks whether the result is bitwise-identical with the
- existing outputs, printing an error if that’s not the case. The
- outputs of the specified derivation must already exist. When used
- with <code class="option">-K</code>, if an output path is not identical to
- the corresponding output from the previous build, the new output
- path is left in
- <code class="filename">/nix/store/<em class="replaceable"><code>name</code></em>.check.</code></p><p>See also the <code class="option">build-repeat</code> configuration
- option, which repeats a derivation a number of times and prevents
- its outputs from being registered as “valid” in the Nix store
- unless they are identical.</p></dd></dl></div><p>Special exit codes:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">100</code></span></dt><dd><p>Generic build failure, the builder process
- returned with a non-zero exit code.</p></dd><dt><span class="term"><code class="literal">101</code></span></dt><dd><p>Build timeout, the build was aborted because it
- did not complete within the specified <a class="link" href="#conf-timeout"><code class="literal">timeout</code></a>.
- </p></dd><dt><span class="term"><code class="literal">102</code></span></dt><dd><p>Hash mismatch, the build output was rejected
- because it does not match the specified <a class="link" href="#fixed-output-drvs"><code class="varname">outputHash</code></a>.
- </p></dd><dt><span class="term"><code class="literal">104</code></span></dt><dd><p>Not deterministic, the build succeeded in check
- mode but the resulting output is not binary reproducable.</p></dd></dl></div><p>With the <code class="option">--keep-going</code> flag it's possible for
-multiple failures to occur, in this case the 1xx status codes are or combined
-using binary or. </p><pre class="screen">
-1100100
- ^^^^
- |||`- timeout
- ||`-- output hash mismatch
- |`--- build failure
- `---- not deterministic
-</pre></div><div class="refsection"><a id="idm139733299659648"></a><h3>Examples</h3><p>This operation is typically used to build store derivations
-produced by <a class="link" href="#sec-nix-instantiate" title="nix-instantiate"><span class="command"><strong>nix-instantiate</strong></span></a>:
-
-</p><pre class="screen">
-$ nix-store -r $(nix-instantiate ./test.nix)
-/nix/store/31axcgrlbfsxzmfff1gyj1bf62hvkby2-aterm-2.3.1</pre><p>
-
-This is essentially what <a class="link" href="#sec-nix-build" title="nix-build"><span class="command"><strong>nix-build</strong></span></a> does.</p><p>To test whether a previously-built derivation is deterministic:
-
-</p><pre class="screen">
-$ nix-build '<nixpkgs>' -A hello --check -K
-</pre><p>
-
-</p></div></div><div class="refsection"><a id="rsec-nix-store-serve"></a><h2>Operation <code class="option">--serve</code></h2><div class="refsection"><a id="idm139733299653424"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--serve</code> [<code class="option">--write</code>]</p></div></div><div class="refsection"><a id="idm139733299650592"></a><h3>Description</h3><p>The operation <code class="option">--serve</code> provides access to
-the Nix store over stdin and stdout, and is intended to be used
-as a means of providing Nix store access to a restricted ssh user.
-</p><p>The following flags are available:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--write</code></span></dt><dd><p>Allow the connected client to request the realization
- of derivations. In effect, this can be used to make the host act
- as a remote builder.</p></dd></dl></div></div><div class="refsection"><a id="idm139733299646640"></a><h3>Examples</h3><p>To turn a host into a build server, the
-<code class="filename">authorized_keys</code> file can be used to provide build
-access to a given SSH public key:
-
-</p><pre class="screen">
-$ cat <<EOF >>/root/.ssh/authorized_keys
-command="nice -n20 nix-store --serve --write" ssh-rsa AAAAB3NzaC1yc2EAAAA...
-EOF
-</pre><p>
-
-</p></div></div><div class="refsection"><a id="rsec-nix-store-gc"></a><h2>Operation <code class="option">--gc</code></h2><div class="refsection"><a id="idm139733299642624"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--gc</code> [ <code class="option">--print-roots</code> | <code class="option">--print-live</code> | <code class="option">--print-dead</code> ] [<code class="option">--max-freed</code> <em class="replaceable"><code>bytes</code></em>]</p></div></div><div class="refsection"><a id="idm139733299636544"></a><h3>Description</h3><p>Without additional flags, the operation <code class="option">--gc</code>
-performs a garbage collection on the Nix store. That is, all paths in
-the Nix store not reachable via file system references from a set of
-“roots”, are deleted.</p><p>The following suboperations may be specified:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--print-roots</code></span></dt><dd><p>This operation prints on standard output the set
- of roots used by the garbage collector. What constitutes a root
- is described in <a class="xref" href="#ssec-gc-roots" title="11.1. Garbage Collector Roots">Section 11.1, “Garbage Collector Roots”</a>.</p></dd><dt><span class="term"><code class="option">--print-live</code></span></dt><dd><p>This operation prints on standard output the set
- of “live” store paths, which are all the store paths reachable
- from the roots. Live paths should never be deleted, since that
- would break consistency — it would become possible that
- applications are installed that reference things that are no
- longer present in the store.</p></dd><dt><span class="term"><code class="option">--print-dead</code></span></dt><dd><p>This operation prints out on standard output the
- set of “dead” store paths, which is just the opposite of the set
- of live paths: any path in the store that is not live (with
- respect to the roots) is dead.</p></dd></dl></div><p>By default, all unreachable paths are deleted. The following
-options control what gets deleted and in what order:
-
-</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--max-freed</code> <em class="replaceable"><code>bytes</code></em></span></dt><dd><p>Keep deleting paths until at least
- <em class="replaceable"><code>bytes</code></em> bytes have been deleted, then
- stop. The argument <em class="replaceable"><code>bytes</code></em> can be
- followed by the multiplicative suffix <code class="literal">K</code>,
- <code class="literal">M</code>, <code class="literal">G</code> or
- <code class="literal">T</code>, denoting KiB, MiB, GiB or TiB
- units.</p></dd></dl></div><p>
-
-</p><p>The behaviour of the collector is also influenced by the <a class="link" href="#conf-keep-outputs"><code class="literal">keep-outputs</code></a>
-and <a class="link" href="#conf-keep-derivations"><code class="literal">keep-derivations</code></a>
-variables in the Nix configuration file.</p><p>By default, the collector prints the total number of freed bytes
-when it finishes (or when it is interrupted). With
-<code class="option">--print-dead</code>, it prints the number of bytes that would
-be freed.</p></div><div class="refsection"><a id="idm139733299619488"></a><h3>Examples</h3><p>To delete all unreachable paths, just do:
-
-</p><pre class="screen">
-$ nix-store --gc
-deleting `/nix/store/kq82idx6g0nyzsp2s14gfsc38npai7lf-cairo-1.0.4.tar.gz.drv'
-<em class="replaceable"><code>...</code></em>
-8825586 bytes freed (8.42 MiB)</pre><p>
-
-</p><p>To delete at least 100 MiBs of unreachable paths:
-
-</p><pre class="screen">
-$ nix-store --gc --max-freed $((100 * 1024 * 1024))</pre><p>
-
-</p></div></div><div class="refsection"><a id="idm139733299615968"></a><h2>Operation <code class="option">--delete</code></h2><div class="refsection"><a id="idm139733299615136"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--delete</code> [<code class="option">--ignore-liveness</code>] <em class="replaceable"><code>paths</code></em>... </p></div></div><div class="refsection"><a id="idm139733299611216"></a><h3>Description</h3><p>The operation <code class="option">--delete</code> deletes the store paths
-<em class="replaceable"><code>paths</code></em> from the Nix store, but only if it is
-safe to do so; that is, when the path is not reachable from a root of
-the garbage collector. This means that you can only delete paths that
-would also be deleted by <code class="literal">nix-store --gc</code>. Thus,
-<code class="literal">--delete</code> is a more targeted version of
-<code class="literal">--gc</code>.</p><p>With the option <code class="option">--ignore-liveness</code>, reachability
-from the roots is ignored. However, the path still won’t be deleted
-if there are other paths in the store that refer to it (i.e., depend
-on it).</p></div><div class="refsection"><a id="idm139733299606528"></a><h3>Example</h3><pre class="screen">
-$ nix-store --delete /nix/store/zq0h41l75vlb4z45kzgjjmsjxvcv1qk7-mesa-6.4
-0 bytes freed (0.00 MiB)
-error: cannot delete path `/nix/store/zq0h41l75vlb4z45kzgjjmsjxvcv1qk7-mesa-6.4' since it is still alive</pre></div></div><div class="refsection"><a id="refsec-nix-store-query"></a><h2>Operation <code class="option">--query</code></h2><div class="refsection"><a id="idm139733299603504"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> { <code class="option">--query</code> | <code class="option">-q</code> } { <code class="option">--outputs</code> | <code class="option">--requisites</code> | <code class="option">-R</code> | <code class="option">--references</code> | <code class="option">--referrers</code> | <code class="option">--referrers-closure</code> | <code class="option">--deriver</code> | <code class="option">-d</code> | <code class="option">--graph</code> | <code class="option">--tree</code> | <code class="option">--binding</code> <em class="replaceable"><code>name</code></em> | <code class="option">-b</code> <em class="replaceable"><code>name</code></em> | <code class="option">--hash</code> | <code class="option">--size</code> | <code class="option">--roots</code> } [<code class="option">--use-output</code>] [<code class="option">-u</code>] [<code class="option">--force-realise</code>] [<code class="option">-f</code>] <em class="replaceable"><code>paths</code></em>... </p></div></div><div class="refsection"><a id="idm139733299583008"></a><h3>Description</h3><p>The operation <code class="option">--query</code> displays various bits of
-information about the store paths . The queries are described below. At
-most one query can be specified. The default query is
-<code class="option">--outputs</code>.</p><p>The paths <em class="replaceable"><code>paths</code></em> may also be symlinks
-from outside of the Nix store, to the Nix store. In that case, the
-query is applied to the target of the symlink.</p></div><div class="refsection"><a id="idm139733299579920"></a><h3>Common query options</h3><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--use-output</code>, </span><span class="term"><code class="option">-u</code></span></dt><dd><p>For each argument to the query that is a store
- derivation, apply the query to the output path of the derivation
- instead.</p></dd><dt><span class="term"><code class="option">--force-realise</code>, </span><span class="term"><code class="option">-f</code></span></dt><dd><p>Realise each argument to the query first (see
- <a class="link" href="#rsec-nix-store-realise" title="Operation --realise"><span class="command"><strong>nix-store
- --realise</strong></span></a>).</p></dd></dl></div></div><div class="refsection"><a id="nixref-queries"></a><h3>Queries</h3><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--outputs</code></span></dt><dd><p>Prints out the <a class="link" href="#gloss-output-path" title="output path">output paths</a> of the store
- derivations <em class="replaceable"><code>paths</code></em>. These are the paths
- that will be produced when the derivation is
- built.</p></dd><dt><span class="term"><code class="option">--requisites</code>, </span><span class="term"><code class="option">-R</code></span></dt><dd><p>Prints out the <a class="link" href="#gloss-closure" title="closure">closure</a> of the store path
- <em class="replaceable"><code>paths</code></em>.</p><p>This query has one option:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--include-outputs</code></span></dt><dd><p>Also include the output path of store
- derivations, and their closures.</p></dd></dl></div><p>This query can be used to implement various kinds of
- deployment. A <span class="emphasis"><em>source deployment</em></span> is obtained
- by distributing the closure of a store derivation. A
- <span class="emphasis"><em>binary deployment</em></span> is obtained by distributing
- the closure of an output path. A <span class="emphasis"><em>cache
- deployment</em></span> (combined source/binary deployment,
- including binaries of build-time-only dependencies) is obtained by
- distributing the closure of a store derivation and specifying the
- option <code class="option">--include-outputs</code>.</p></dd><dt><span class="term"><code class="option">--references</code></span></dt><dd><p>Prints the set of <a class="link" href="#gloss-reference" title="reference">references</a> of the store paths
- <em class="replaceable"><code>paths</code></em>, that is, their immediate
- dependencies. (For <span class="emphasis"><em>all</em></span> dependencies, use
- <code class="option">--requisites</code>.)</p></dd><dt><span class="term"><code class="option">--referrers</code></span></dt><dd><p>Prints the set of <span class="emphasis"><em>referrers</em></span> of
- the store paths <em class="replaceable"><code>paths</code></em>, that is, the
- store paths currently existing in the Nix store that refer to one
- of <em class="replaceable"><code>paths</code></em>. Note that contrary to the
- references, the set of referrers is not constant; it can change as
- store paths are added or removed.</p></dd><dt><span class="term"><code class="option">--referrers-closure</code></span></dt><dd><p>Prints the closure of the set of store paths
- <em class="replaceable"><code>paths</code></em> under the referrers relation; that
- is, all store paths that directly or indirectly refer to one of
- <em class="replaceable"><code>paths</code></em>. These are all the path currently
- in the Nix store that are dependent on
- <em class="replaceable"><code>paths</code></em>.</p></dd><dt><span class="term"><code class="option">--deriver</code>, </span><span class="term"><code class="option">-d</code></span></dt><dd><p>Prints the <a class="link" href="#gloss-deriver" title="deriver">deriver</a> of the store paths
- <em class="replaceable"><code>paths</code></em>. If the path has no deriver
- (e.g., if it is a source file), or if the deriver is not known
- (e.g., in the case of a binary-only deployment), the string
- <code class="literal">unknown-deriver</code> is printed.</p></dd><dt><span class="term"><code class="option">--graph</code></span></dt><dd><p>Prints the references graph of the store paths
- <em class="replaceable"><code>paths</code></em> in the format of the
- <span class="command"><strong>dot</strong></span> tool of AT&T's <a class="link" href="http://www.graphviz.org/" target="_top">Graphviz package</a>.
- This can be used to visualise dependency graphs. To obtain a
- build-time dependency graph, apply this to a store derivation. To
- obtain a runtime dependency graph, apply it to an output
- path.</p></dd><dt><span class="term"><code class="option">--tree</code></span></dt><dd><p>Prints the references graph of the store paths
- <em class="replaceable"><code>paths</code></em> as a nested ASCII tree.
- References are ordered by descending closure size; this tends to
- flatten the tree, making it more readable. The query only
- recurses into a store path when it is first encountered; this
- prevents a blowup of the tree representation of the
- graph.</p></dd><dt><span class="term"><code class="option">--graphml</code></span></dt><dd><p>Prints the references graph of the store paths
- <em class="replaceable"><code>paths</code></em> in the <a class="link" href="http://graphml.graphdrawing.org/" target="_top">GraphML</a> file format.
- This can be used to visualise dependency graphs. To obtain a
- build-time dependency graph, apply this to a store derivation. To
- obtain a runtime dependency graph, apply it to an output
- path.</p></dd><dt><span class="term"><code class="option">--binding</code> <em class="replaceable"><code>name</code></em>, </span><span class="term"><code class="option">-b</code> <em class="replaceable"><code>name</code></em></span></dt><dd><p>Prints the value of the attribute
- <em class="replaceable"><code>name</code></em> (i.e., environment variable) of
- the store derivations <em class="replaceable"><code>paths</code></em>. It is an
- error for a derivation to not have the specified
- attribute.</p></dd><dt><span class="term"><code class="option">--hash</code></span></dt><dd><p>Prints the SHA-256 hash of the contents of the
- store paths <em class="replaceable"><code>paths</code></em> (that is, the hash of
- the output of <span class="command"><strong>nix-store --dump</strong></span> on the given
- paths). Since the hash is stored in the Nix database, this is a
- fast operation.</p></dd><dt><span class="term"><code class="option">--size</code></span></dt><dd><p>Prints the size in bytes of the contents of the
- store paths <em class="replaceable"><code>paths</code></em> — to be precise, the
- size of the output of <span class="command"><strong>nix-store --dump</strong></span> on the
- given paths. Note that the actual disk space required by the
- store paths may be higher, especially on filesystems with large
- cluster sizes.</p></dd><dt><span class="term"><code class="option">--roots</code></span></dt><dd><p>Prints the garbage collector roots that point,
- directly or indirectly, at the store paths
- <em class="replaceable"><code>paths</code></em>.</p></dd></dl></div></div><div class="refsection"><a id="idm139733299531008"></a><h3>Examples</h3><p>Print the closure (runtime dependencies) of the
-<span class="command"><strong>svn</strong></span> program in the current user environment:
-
-</p><pre class="screen">
-$ nix-store -qR $(which svn)
-/nix/store/5mbglq5ldqld8sj57273aljwkfvj22mc-subversion-1.1.4
-/nix/store/9lz9yc6zgmc0vlqmn2ipcpkjlmbi51vv-glibc-2.3.4
-<em class="replaceable"><code>...</code></em></pre><p>
-
-</p><p>Print the build-time dependencies of <span class="command"><strong>svn</strong></span>:
-
-</p><pre class="screen">
-$ nix-store -qR $(nix-store -qd $(which svn))
-/nix/store/02iizgn86m42q905rddvg4ja975bk2i4-grep-2.5.1.tar.bz2.drv
-/nix/store/07a2bzxmzwz5hp58nf03pahrv2ygwgs3-gcc-wrapper.sh
-/nix/store/0ma7c9wsbaxahwwl04gbw3fcd806ski4-glibc-2.3.4.drv
-<em class="replaceable"><code>... lots of other paths ...</code></em></pre><p>
-
-The difference with the previous example is that we ask the closure of
-the derivation (<code class="option">-qd</code>), not the closure of the output
-path that contains <span class="command"><strong>svn</strong></span>.</p><p>Show the build-time dependencies as a tree:
-
-</p><pre class="screen">
-$ nix-store -q --tree $(nix-store -qd $(which svn))
-/nix/store/7i5082kfb6yjbqdbiwdhhza0am2xvh6c-subversion-1.1.4.drv
-+---/nix/store/d8afh10z72n8l1cr5w42366abiblgn54-builder.sh
-+---/nix/store/fmzxmpjx2lh849ph0l36snfj9zdibw67-bash-3.0.drv
-| +---/nix/store/570hmhmx3v57605cqg9yfvvyh0nnb8k8-bash
-| +---/nix/store/p3srsbd8dx44v2pg6nbnszab5mcwx03v-builder.sh
-<em class="replaceable"><code>...</code></em></pre><p>
-
-</p><p>Show all paths that depend on the same OpenSSL library as
-<span class="command"><strong>svn</strong></span>:
-
-</p><pre class="screen">
-$ nix-store -q --referrers $(nix-store -q --binding openssl $(nix-store -qd $(which svn)))
-/nix/store/23ny9l9wixx21632y2wi4p585qhva1q8-sylpheed-1.0.0
-/nix/store/5mbglq5ldqld8sj57273aljwkfvj22mc-subversion-1.1.4
-/nix/store/dpmvp969yhdqs7lm2r1a3gng7pyq6vy4-subversion-1.1.3
-/nix/store/l51240xqsgg8a7yrbqdx1rfzyv6l26fx-lynx-2.8.5</pre><p>
-
-</p><p>Show all paths that directly or indirectly depend on the Glibc
-(C library) used by <span class="command"><strong>svn</strong></span>:
-
-</p><pre class="screen">
-$ nix-store -q --referrers-closure $(ldd $(which svn) | grep /libc.so | awk '{print $3}')
-/nix/store/034a6h4vpz9kds5r6kzb9lhh81mscw43-libgnomeprintui-2.8.2
-/nix/store/15l3yi0d45prm7a82pcrknxdh6nzmxza-gawk-3.1.4
-<em class="replaceable"><code>...</code></em></pre><p>
-
-Note that <span class="command"><strong>ldd</strong></span> is a command that prints out the
-dynamic libraries used by an ELF executable.</p><p>Make a picture of the runtime dependency graph of the current
-user environment:
-
-</p><pre class="screen">
-$ nix-store -q --graph ~/.nix-profile | dot -Tps > graph.ps
-$ gv graph.ps</pre><p>
-
-</p><p>Show every garbage collector root that points to a store path
-that depends on <span class="command"><strong>svn</strong></span>:
-
-</p><pre class="screen">
-$ nix-store -q --roots $(which svn)
-/nix/var/nix/profiles/default-81-link
-/nix/var/nix/profiles/default-82-link
-/nix/var/nix/profiles/per-user/eelco/profile-97-link
-</pre><p>
-
-</p></div></div><div class="refsection"><a id="idm139733299516176"></a><h2>Operation <code class="option">--add</code></h2><div class="refsection"><a id="idm139733299515344"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--add</code> <em class="replaceable"><code>paths</code></em>... </p></div></div><div class="refsection"><a id="idm139733299511968"></a><h3>Description</h3><p>The operation <code class="option">--add</code> adds the specified paths to
-the Nix store. It prints the resulting paths in the Nix store on
-standard output.</p></div><div class="refsection"><a id="idm139733299510336"></a><h3>Example</h3><pre class="screen">
-$ nix-store --add ./foo.c
-/nix/store/m7lrha58ph6rcnv109yzx1nk1cj7k7zf-foo.c</pre></div></div><div class="refsection"><a id="idm139733299508688"></a><h2>Operation <code class="option">--add-fixed</code></h2><div class="refsection"><a id="idm139733299507856"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> [<code class="option">--recursive</code>] <code class="option">--add-fixed</code> <em class="replaceable"><code>algorithm</code></em> <em class="replaceable"><code>paths</code></em>... </p></div></div><div class="refsection"><a id="idm139733299503120"></a><h3>Description</h3><p>The operation <code class="option">--add-fixed</code> adds the specified paths to
-the Nix store. Unlike <code class="option">--add</code> paths are registered using the
-specified hashing algorithm, resulting in the same output path as a fixed-output
-derivation. This can be used for sources that are not available from a public
-url or broke since the download expression was written.
-</p><p>This operation has the following options:
-
-</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--recursive</code></span></dt><dd><p>
- Use recursive instead of flat hashing mode, used when adding directories
- to the store.
- </p></dd></dl></div><p>
-
-</p></div><div class="refsection"><a id="idm139733299498592"></a><h3>Example</h3><pre class="screen">
-$ nix-store --add-fixed sha256 ./hello-2.10.tar.gz
-/nix/store/3x7dwzq014bblazs7kq20p9hyzz0qh8g-hello-2.10.tar.gz</pre></div></div><div class="refsection"><a id="refsec-nix-store-verify"></a><h2>Operation <code class="option">--verify</code></h2><div class="refsection"><a id="idm139733299495712"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--verify</code> [<code class="option">--check-contents</code>] [<code class="option">--repair</code>]</p></div></div><div class="refsection"><a id="idm139733299492208"></a><h3>Description</h3><p>The operation <code class="option">--verify</code> verifies the internal
-consistency of the Nix database, and the consistency between the Nix
-database and the Nix store. Any inconsistencies encountered are
-automatically repaired. Inconsistencies are generally the result of
-the Nix store or database being modified by non-Nix tools, or of bugs
-in Nix itself.</p><p>This operation has the following options:
-
-</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--check-contents</code></span></dt><dd><p>Checks that the contents of every valid store path
- has not been altered by computing a SHA-256 hash of the contents
- and comparing it with the hash stored in the Nix database at build
- time. Paths that have been modified are printed out. For large
- stores, <code class="option">--check-contents</code> is obviously quite
- slow.</p></dd><dt><span class="term"><code class="option">--repair</code></span></dt><dd><p>If any valid path is missing from the store, or
- (if <code class="option">--check-contents</code> is given) the contents of a
- valid path has been modified, then try to repair the path by
- redownloading it. See <span class="command"><strong>nix-store --repair-path</strong></span>
- for details.</p></dd></dl></div><p>
-
-</p></div></div><div class="refsection"><a id="idm139733299484592"></a><h2>Operation <code class="option">--verify-path</code></h2><div class="refsection"><a id="idm139733299483760"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--verify-path</code> <em class="replaceable"><code>paths</code></em>... </p></div></div><div class="refsection"><a id="idm139733299480256"></a><h3>Description</h3><p>The operation <code class="option">--verify-path</code> compares the
-contents of the given store paths to their cryptographic hashes stored
-in Nix’s database. For every changed path, it prints a warning
-message. The exit status is 0 if no path has changed, and 1
-otherwise.</p></div><div class="refsection"><a id="idm139733299478288"></a><h3>Example</h3><p>To verify the integrity of the <span class="command"><strong>svn</strong></span> command and all its dependencies:
-
-</p><pre class="screen">
-$ nix-store --verify-path $(nix-store -qR $(which svn))
-</pre><p>
-
-</p></div></div><div class="refsection"><a id="idm139733299475792"></a><h2>Operation <code class="option">--repair-path</code></h2><div class="refsection"><a id="idm139733299474960"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--repair-path</code> <em class="replaceable"><code>paths</code></em>... </p></div></div><div class="refsection"><a id="idm139733299471456"></a><h3>Description</h3><p>The operation <code class="option">--repair-path</code> attempts to
-“repair” the specified paths by redownloading them using the available
-substituters. If no substitutes are available, then repair is not
-possible.</p><div class="warning"><h3 class="title">Warning</h3><p>During repair, there is a very small time window during
-which the old path (if it exists) is moved out of the way and replaced
-with the new path. If repair is interrupted in between, then the
-system may be left in a broken state (e.g., if the path contains a
-critical system component like the GNU C Library).</p></div></div><div class="refsection"><a id="idm139733299468768"></a><h3>Example</h3><pre class="screen">
-$ nix-store --verify-path /nix/store/dj7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13
-path `/nix/store/dj7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13' was modified!
- expected hash `2db57715ae90b7e31ff1f2ecb8c12ec1cc43da920efcbe3b22763f36a1861588',
- got `481c5aa5483ebc97c20457bb8bca24deea56550d3985cda0027f67fe54b808e4'
-
-$ nix-store --repair-path /nix/store/dj7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13
-fetching path `/nix/store/d7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13'...
-…
-</pre></div></div><div class="refsection"><a id="refsec-nix-store-dump"></a><h2>Operation <code class="option">--dump</code></h2><div class="refsection"><a id="idm139733299465056"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--dump</code> <em class="replaceable"><code>path</code></em> </p></div></div><div class="refsection"><a id="idm139733299461824"></a><h3>Description</h3><p>The operation <code class="option">--dump</code> produces a NAR (Nix
-ARchive) file containing the contents of the file system tree rooted
-at <em class="replaceable"><code>path</code></em>. The archive is written to
-standard output.</p><p>A NAR archive is like a TAR or Zip archive, but it contains only
-the information that Nix considers important. For instance,
-timestamps are elided because all files in the Nix store have their
-timestamp set to 0 anyway. Likewise, all permissions are left out
-except for the execute bit, because all files in the Nix store have
-444 or 555 permission.</p><p>Also, a NAR archive is <span class="emphasis"><em>canonical</em></span>, meaning
-that “equal” paths always produce the same NAR archive. For instance,
-directory entries are always sorted so that the actual on-disk order
-doesn’t influence the result. This means that the cryptographic hash
-of a NAR dump of a path is usable as a fingerprint of the contents of
-the path. Indeed, the hashes of store paths stored in Nix’s database
-(see <a class="link" href="#refsec-nix-store-query" title="Operation --query"><code class="literal">nix-store -q
---hash</code></a>) are SHA-256 hashes of the NAR dump of each
-store path.</p><p>NAR archives support filenames of unlimited length and 64-bit
-file sizes. They can contain regular files, directories, and symbolic
-links, but not other types of files (such as device nodes).</p><p>A Nix archive can be unpacked using <code class="literal">nix-store
---restore</code>.</p></div></div><div class="refsection"><a id="idm139733299454672"></a><h2>Operation <code class="option">--restore</code></h2><div class="refsection"><a id="idm139733299453840"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--restore</code> <em class="replaceable"><code>path</code></em> </p></div></div><div class="refsection"><a id="idm139733299450608"></a><h3>Description</h3><p>The operation <code class="option">--restore</code> unpacks a NAR archive
-to <em class="replaceable"><code>path</code></em>, which must not already exist. The
-archive is read from standard input.</p></div></div><div class="refsection"><a id="refsec-nix-store-export"></a><h2>Operation <code class="option">--export</code></h2><div class="refsection"><a id="idm139733299446736"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--export</code> <em class="replaceable"><code>paths</code></em>... </p></div></div><div class="refsection"><a id="idm139733299443232"></a><h3>Description</h3><p>The operation <code class="option">--export</code> writes a serialisation
-of the specified store paths to standard output in a format that can
-be imported into another Nix store with <span class="command"><strong><a class="command" href="#refsec-nix-store-import" title="Operation --import">nix-store --import</a></strong></span>. This
-is like <span class="command"><strong><a class="command" href="#refsec-nix-store-dump" title="Operation --dump">nix-store
---dump</a></strong></span>, except that the NAR archive produced by that command
-doesn’t contain the necessary meta-information to allow it to be
-imported into another Nix store (namely, the set of references of the
-path).</p><p>This command does not produce a <span class="emphasis"><em>closure</em></span> of
-the specified paths, so if a store path references other store paths
-that are missing in the target Nix store, the import will fail. To
-copy a whole closure, do something like:
-
-</p><pre class="screen">
-$ nix-store --export $(nix-store -qR <em class="replaceable"><code>paths</code></em>) > out</pre><p>
-
-To import the whole closure again, run:
-
-</p><pre class="screen">
-$ nix-store --import < out</pre><p>
-
-</p></div></div><div class="refsection"><a id="refsec-nix-store-import"></a><h2>Operation <code class="option">--import</code></h2><div class="refsection"><a id="idm139733299435520"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--import</code> </p></div></div><div class="refsection"><a id="idm139733299433104"></a><h3>Description</h3><p>The operation <code class="option">--import</code> reads a serialisation of
-a set of store paths produced by <span class="command"><strong><a class="command" href="#refsec-nix-store-export" title="Operation --export">nix-store --export</a></strong></span> from
-standard input and adds those store paths to the Nix store. Paths
-that already exist in the Nix store are ignored. If a path refers to
-another path that doesn’t exist in the Nix store, the import
-fails.</p></div></div><div class="refsection"><a id="idm139733299429888"></a><h2>Operation <code class="option">--optimise</code></h2><div class="refsection"><a id="idm139733299429056"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--optimise</code> </p></div></div><div class="refsection"><a id="idm139733299426640"></a><h3>Description</h3><p>The operation <code class="option">--optimise</code> reduces Nix store disk
-space usage by finding identical files in the store and hard-linking
-them to each other. It typically reduces the size of the store by
-something like 25-35%. Only regular files and symlinks are
-hard-linked in this manner. Files are considered identical when they
-have the same NAR archive serialisation: that is, regular files must
-have the same contents and permission (executable or non-executable),
-and symlinks must have the same contents.</p><p>After completion, or when the command is interrupted, a report
-on the achieved savings is printed on standard error.</p><p>Use <code class="option">-vv</code> or <code class="option">-vvv</code> to get some
-progress indication.</p></div><div class="refsection"><a id="idm139733299423328"></a><h3>Example</h3><pre class="screen">
-$ nix-store --optimise
-hashing files in `/nix/store/qhqx7l2f1kmwihc9bnxs7rc159hsxnf3-gcc-4.1.1'
-<em class="replaceable"><code>...</code></em>
-541838819 bytes (516.74 MiB) freed by hard-linking 54143 files;
-there are 114486 files with equal contents out of 215894 files in total
-</pre></div></div><div class="refsection"><a id="idm139733299421120"></a><h2>Operation <code class="option">--read-log</code></h2><div class="refsection"><a id="idm139733299420288"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> { <code class="option">--read-log</code> | <code class="option">-l</code> } <em class="replaceable"><code>paths</code></em>... </p></div></div><div class="refsection"><a id="idm139733299415376"></a><h3>Description</h3><p>The operation <code class="option">--read-log</code> prints the build log
-of the specified store paths on standard output. The build log is
-whatever the builder of a derivation wrote to standard output and
-standard error. If a store path is not a derivation, the deriver of
-the store path is used.</p><p>Build logs are kept in
-<code class="filename">/nix/var/log/nix/drvs</code>. However, there is no
-guarantee that a build log is available for any particular store path.
-For instance, if the path was downloaded as a pre-built binary through
-a substitute, then the log is unavailable.</p></div><div class="refsection"><a id="idm139733299412560"></a><h3>Example</h3><pre class="screen">
-$ nix-store -l $(which ktorrent)
-building /nix/store/dhc73pvzpnzxhdgpimsd9sw39di66ph1-ktorrent-2.2.1
-unpacking sources
-unpacking source archive /nix/store/p8n1jpqs27mgkjw07pb5269717nzf5f8-ktorrent-2.2.1.tar.gz
-ktorrent-2.2.1/
-ktorrent-2.2.1/NEWS
-<em class="replaceable"><code>...</code></em>
-</pre></div></div><div class="refsection"><a id="idm139733299410368"></a><h2>Operation <code class="option">--dump-db</code></h2><div class="refsection"><a id="idm139733299409536"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--dump-db</code> [<em class="replaceable"><code>paths</code></em>...]</p></div></div><div class="refsection"><a id="idm139733299406304"></a><h3>Description</h3><p>The operation <code class="option">--dump-db</code> writes a dump of the
-Nix database to standard output. It can be loaded into an empty Nix
-store using <code class="option">--load-db</code>. This is useful for making
-backups and when migrating to different database schemas.</p><p>By default, <code class="option">--dump-db</code> will dump the entire Nix
-database. When one or more store paths is passed, only the subset of
-the Nix database for those store paths is dumped. As with
-<code class="option">--export</code>, the user is responsible for passing all the
-store paths for a closure. See <code class="option">--export</code> for an
-example.</p></div></div><div class="refsection"><a id="idm139733299401712"></a><h2>Operation <code class="option">--load-db</code></h2><div class="refsection"><a id="idm139733299400880"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--load-db</code> </p></div></div><div class="refsection"><a id="idm139733299398464"></a><h3>Description</h3><p>The operation <code class="option">--load-db</code> reads a dump of the Nix
-database created by <code class="option">--dump-db</code> from standard input and
-loads it into the Nix database.</p></div></div><div class="refsection"><a id="idm139733299395904"></a><h2>Operation <code class="option">--print-env</code></h2><div class="refsection"><a id="idm139733299395072"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code> <code class="option">--print-env</code> <em class="replaceable"><code>drvpath</code></em> </p></div></div><div class="refsection"><a id="idm139733299391840"></a><h3>Description</h3><p>The operation <code class="option">--print-env</code> prints out the
-environment of a derivation in a format that can be evaluated by a
-shell. The command line arguments of the builder are placed in the
-variable <code class="envar">_args</code>.</p></div><div class="refsection"><a id="idm139733299389744"></a><h3>Example</h3><pre class="screen">
-$ nix-store --print-env $(nix-instantiate '<nixpkgs>' -A firefox)
-<em class="replaceable"><code>…</code></em>
-export src; src='/nix/store/plpj7qrwcz94z2psh6fchsi7s8yihc7k-firefox-12.0.source.tar.bz2'
-export stdenv; stdenv='/nix/store/7c8asx3yfrg5dg1gzhzyq2236zfgibnn-stdenv'
-export system; system='x86_64-linux'
-export _args; _args='-e /nix/store/9krlzvny65gdc8s7kpb6lkx8cd02c25c-default-builder.sh'
-</pre></div></div><div class="refsection"><a id="rsec-nix-store-generate-binary-cache-key"></a><h2>Operation <code class="option">--generate-binary-cache-key</code></h2><div class="refsection"><a id="idm139733299386016"></a><h3>Synopsis</h3><div class="cmdsynopsis"><p><code class="command">nix-store</code>
- <code class="option">--generate-binary-cache-key</code>
- <code class="option">key-name</code>
- <code class="option">secret-key-file</code>
- <code class="option">public-key-file</code>
- </p></div></div><div class="refsection"><a id="idm139733299382080"></a><h3>Description</h3><p>This command generates an <a class="link" href="http://ed25519.cr.yp.to/" target="_top">Ed25519 key pair</a> that can
-be used to create a signed binary cache. It takes three mandatory
-parameters:
-
-</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>A key name, such as
- <code class="literal">cache.example.org-1</code>, that is used to look up keys
- on the client when it verifies signatures. It can be anything, but
- it’s suggested to use the host name of your cache
- (e.g. <code class="literal">cache.example.org</code>) with a suffix denoting
- the number of the key (to be incremented every time you need to
- revoke a key).</p></li><li class="listitem"><p>The file name where the secret key is to be
- stored.</p></li><li class="listitem"><p>The file name where the public key is to be
- stored.</p></li></ol></div><p>
-
-</p></div></div></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-utilities"></a>Chapter 23. Utilities</h2></div></div></div><p>This section lists utilities that you can use when you
-work with Nix.</p><div class="refentry"><a id="sec-nix-channel"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix-channel — manage Nix channels</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">nix-channel</code> { <code class="option">--add</code> <em class="replaceable"><code>url</code></em> [<em class="replaceable"><code>name</code></em>] | <code class="option">--remove</code> <em class="replaceable"><code>name</code></em> | <code class="option">--list</code> | <code class="option">--update</code> [<em class="replaceable"><code>names</code></em>...] | <code class="option">--rollback</code> [<em class="replaceable"><code>generation</code></em>] }</p></div></div><div class="refsection"><a id="idm139733299360672"></a><h2>Description</h2><p>A Nix channel is a mechanism that allows you to automatically
-stay up-to-date with a set of pre-built Nix expressions. A Nix
-channel is just a URL that points to a place containing a set of Nix
-expressions. <span class="phrase">See also <a class="xref" href="#sec-channels" title="Chapter 12. Channels">Chapter 12, <em>Channels</em></a>.</span></p><p>To see the list of official NixOS channels, visit <a class="link" href="https://nixos.org/channels" target="_top">https://nixos.org/channels</a>.</p><p>This command has the following operations:
-
-</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--add</code> <em class="replaceable"><code>url</code></em> [<em class="replaceable"><code>name</code></em>]</span></dt><dd><p>Adds a channel named
- <em class="replaceable"><code>name</code></em> with URL
- <em class="replaceable"><code>url</code></em> to the list of subscribed channels.
- If <em class="replaceable"><code>name</code></em> is omitted, it defaults to the
- last component of <em class="replaceable"><code>url</code></em>, with the
- suffixes <code class="literal">-stable</code> or
- <code class="literal">-unstable</code> removed.</p></dd><dt><span class="term"><code class="option">--remove</code> <em class="replaceable"><code>name</code></em></span></dt><dd><p>Removes the channel named
- <em class="replaceable"><code>name</code></em> from the list of subscribed
- channels.</p></dd><dt><span class="term"><code class="option">--list</code></span></dt><dd><p>Prints the names and URLs of all subscribed
- channels on standard output.</p></dd><dt><span class="term"><code class="option">--update</code> [<em class="replaceable"><code>names</code></em>…]</span></dt><dd><p>Downloads the Nix expressions of all subscribed
- channels (or only those included in
- <em class="replaceable"><code>names</code></em> if specified) and makes them the
- default for <span class="command"><strong>nix-env</strong></span> operations (by symlinking
- them from the directory
- <code class="filename">~/.nix-defexpr</code>).</p></dd><dt><span class="term"><code class="option">--rollback</code> [<em class="replaceable"><code>generation</code></em>]</span></dt><dd><p>Reverts the previous call to <span class="command"><strong>nix-channel
- --update</strong></span>. Optionally, you can specify a specific channel
- generation number to restore.</p></dd></dl></div><p>
-
-</p><p>Note that <code class="option">--add</code> does not automatically perform
-an update.</p><p>The list of subscribed channels is stored in
-<code class="filename">~/.nix-channels</code>.</p></div><div class="refsection"><a id="idm139733299340240"></a><h2>Examples</h2><p>To subscribe to the Nixpkgs channel and install the GNU Hello package:</p><pre class="screen">
-$ nix-channel --add https://nixos.org/channels/nixpkgs-unstable
-$ nix-channel --update
-$ nix-env -iA nixpkgs.hello</pre><p>You can revert channel updates using <code class="option">--rollback</code>:</p><pre class="screen">
-$ nix-instantiate --eval -E '(import <nixpkgs> {}).lib.version'
-"14.04.527.0e935f1"
-
-$ nix-channel --rollback
-switching from generation 483 to 482
-
-$ nix-instantiate --eval -E '(import <nixpkgs> {}).lib.version'
-"14.04.526.dbadfad"
-</pre></div><div class="refsection"><a id="idm139733299336912"></a><h2>Files</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="filename">/nix/var/nix/profiles/per-user/<em class="replaceable"><code>username</code></em>/channels</code></span></dt><dd><p><span class="command"><strong>nix-channel</strong></span> uses a
- <span class="command"><strong>nix-env</strong></span> profile to keep track of previous
- versions of the subscribed channels. Every time you run
- <span class="command"><strong>nix-channel --update</strong></span>, a new channel generation
- (that is, a symlink to the channel Nix expressions in the Nix store)
- is created. This enables <span class="command"><strong>nix-channel --rollback</strong></span>
- to revert to previous versions.</p></dd><dt><span class="term"><code class="filename">~/.nix-defexpr/channels</code></span></dt><dd><p>This is a symlink to
- <code class="filename">/nix/var/nix/profiles/per-user/<em class="replaceable"><code>username</code></em>/channels</code>. It
- ensures that <span class="command"><strong>nix-env</strong></span> can find your channels. In
- a multi-user installation, you may also have
- <code class="filename">~/.nix-defexpr/channels_root</code>, which links to
- the channels of the root user.</p></dd></dl></div></div><div class="refsection"><a id="idm139733299328928"></a><h2>Channel format</h2><p>A channel URL should point to a directory containing the
-following files:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="filename">nixexprs.tar.xz</code></span></dt><dd><p>A tarball containing Nix expressions and files
- referenced by them (such as build scripts and patches). At the
- top level, the tarball should contain a single directory. That
- directory must contain a file <code class="filename">default.nix</code>
- that serves as the channel’s “entry point”.</p></dd></dl></div></div></div><div class="refentry"><div class="refentry.separator"><hr /></div><a id="sec-nix-collect-garbage"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix-collect-garbage — delete unreachable store paths</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">nix-collect-garbage</code> [<code class="option">--delete-old</code>] [<code class="option">-d</code>] [<code class="option">--delete-older-than</code> <em class="replaceable"><code>period</code></em>] [<code class="option">--max-freed</code> <em class="replaceable"><code>bytes</code></em>] [<code class="option">--dry-run</code>]</p></div></div><div class="refsection"><a id="idm139733299315776"></a><h2>Description</h2><p>The command <span class="command"><strong>nix-collect-garbage</strong></span> is mostly an
-alias of <a class="link" href="#rsec-nix-store-gc" title="Operation --gc"><span class="command"><strong>nix-store
---gc</strong></span></a>, that is, it deletes all unreachable paths in
-the Nix store to clean up your system. However, it provides two
-additional options: <code class="option">-d</code> (<code class="option">--delete-old</code>),
-which deletes all old generations of all profiles in
-<code class="filename">/nix/var/nix/profiles</code> by invoking
-<code class="literal">nix-env --delete-generations old</code> on all profiles
-(of course, this makes rollbacks to previous configurations
-impossible); and
-<code class="option">--delete-older-than</code> <em class="replaceable"><code>period</code></em>,
-where period is a value such as <code class="literal">30d</code>, which deletes
-all generations older than the specified number of days in all profiles
-in <code class="filename">/nix/var/nix/profiles</code> (except for the generations
-that were active at that point in time).
-</p></div><div class="refsection"><a id="idm139733299309536"></a><h2>Example</h2><p>To delete from the Nix store everything that is not used by the
-current generations of each profile, do
-
-</p><pre class="screen">
-$ nix-collect-garbage -d</pre><p>
-
-</p></div></div><div class="refentry"><div class="refentry.separator"><hr /></div><a id="sec-nix-copy-closure"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix-copy-closure — copy a closure to or from a remote machine via SSH</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">nix-copy-closure</code> [ <code class="option">--to</code> | <code class="option">--from</code> ] [<code class="option">--gzip</code>] [<code class="option">--include-outputs</code>] [ <code class="option">--use-substitutes</code> | <code class="option">-s</code> ] [<code class="option">-v</code>]
- <em class="replaceable"><code>user@</code></em><em class="replaceable"><code>machine</code></em>
- <em class="replaceable"><code>paths</code></em> </p></div></div><div class="refsection"><a id="idm139733299294048"></a><h2>Description</h2><p><span class="command"><strong>nix-copy-closure</strong></span> gives you an easy and
-efficient way to exchange software between machines. Given one or
-more Nix store <em class="replaceable"><code>paths</code></em> on the local
-machine, <span class="command"><strong>nix-copy-closure</strong></span> computes the closure of
-those paths (i.e. all their dependencies in the Nix store), and copies
-all paths in the closure to the remote machine via the
-<span class="command"><strong>ssh</strong></span> (Secure Shell) command. With the
-<code class="option">--from</code>, the direction is reversed:
-the closure of <em class="replaceable"><code>paths</code></em> on a remote machine is
-copied to the Nix store on the local machine.</p><p>This command is efficient because it only sends the store paths
-that are missing on the target machine.</p><p>Since <span class="command"><strong>nix-copy-closure</strong></span> calls
-<span class="command"><strong>ssh</strong></span>, you may be asked to type in the appropriate
-password or passphrase. In fact, you may be asked
-<span class="emphasis"><em>twice</em></span> because <span class="command"><strong>nix-copy-closure</strong></span>
-currently connects twice to the remote machine, first to get the set
-of paths missing on the target machine, and second to send the dump of
-those paths. If this bothers you, use
-<span class="command"><strong>ssh-agent</strong></span>.</p><div class="refsection"><a id="idm139733299286896"></a><h3>Options</h3><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--to</code></span></dt><dd><p>Copy the closure of
- <em class="replaceable"><code>paths</code></em> from the local Nix store to the
- Nix store on <em class="replaceable"><code>machine</code></em>. This is the
- default.</p></dd><dt><span class="term"><code class="option">--from</code></span></dt><dd><p>Copy the closure of
- <em class="replaceable"><code>paths</code></em> from the Nix store on
- <em class="replaceable"><code>machine</code></em> to the local Nix
- store.</p></dd><dt><span class="term"><code class="option">--gzip</code></span></dt><dd><p>Enable compression of the SSH
- connection.</p></dd><dt><span class="term"><code class="option">--include-outputs</code></span></dt><dd><p>Also copy the outputs of store derivations
- included in the closure.</p></dd><dt><span class="term"><code class="option">--use-substitutes</code> / <code class="option">-s</code></span></dt><dd><p>Attempt to download missing paths on the target
- machine using Nix’s substitute mechanism. Any paths that cannot
- be substituted on the target are still copied normally from the
- source. This is useful, for instance, if the connection between
- the source and target machine is slow, but the connection between
- the target machine and <code class="literal">nixos.org</code> (the default
- binary cache server) is fast.</p></dd><dt><span class="term"><code class="option">-v</code></span></dt><dd><p>Show verbose output.</p></dd></dl></div></div><div class="refsection"><a id="idm139733299274272"></a><h3>Environment variables</h3><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="envar">NIX_SSHOPTS</code></span></dt><dd><p>Additional options to be passed to
- <span class="command"><strong>ssh</strong></span> on the command line.</p></dd></dl></div></div><div class="refsection"><a id="idm139733299271440"></a><h3>Examples</h3><p>Copy Firefox with all its dependencies to a remote machine:
-
-</p><pre class="screen">
-$ nix-copy-closure --to alice@itchy.labs $(type -tP firefox)</pre><p>
-
-</p><p>Copy Subversion from a remote machine and then install it into a
-user environment:
-
-</p><pre class="screen">
-$ nix-copy-closure --from alice@itchy.labs \
- /nix/store/0dj0503hjxy5mbwlafv1rsbdiyx1gkdy-subversion-1.4.4
-$ nix-env -i /nix/store/0dj0503hjxy5mbwlafv1rsbdiyx1gkdy-subversion-1.4.4
-</pre><p>
-
-</p></div></div></div><div class="refentry"><div class="refentry.separator"><hr /></div><a id="sec-nix-daemon"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix-daemon — Nix multi-user support daemon</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">nix-daemon</code> </p></div></div><div class="refsection"><a id="idm139733299262736"></a><h2>Description</h2><p>The Nix daemon is necessary in multi-user Nix installations. It
-performs build actions and other operations on the Nix store on behalf
-of unprivileged users.</p></div></div><div class="refentry"><div class="refentry.separator"><hr /></div><a id="sec-nix-hash"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix-hash — compute the cryptographic hash of a path</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">nix-hash</code> [<code class="option">--flat</code>] [<code class="option">--base32</code>] [<code class="option">--truncate</code>] [<code class="option">--type</code> <em class="replaceable"><code>hashAlgo</code></em>] <em class="replaceable"><code>path</code></em>... </p></div><div class="cmdsynopsis"><p><code class="command">nix-hash</code> <code class="option">--to-base16</code> <em class="replaceable"><code>hash</code></em>... </p></div><div class="cmdsynopsis"><p><code class="command">nix-hash</code> <code class="option">--to-base32</code> <em class="replaceable"><code>hash</code></em>... </p></div></div><div class="refsection"><a id="idm139733299246496"></a><h2>Description</h2><p>The command <span class="command"><strong>nix-hash</strong></span> computes the
-cryptographic hash of the contents of each
-<em class="replaceable"><code>path</code></em> and prints it on standard output. By
-default, it computes an MD5 hash, but other hash algorithms are
-available as well. The hash is printed in hexadecimal. To generate
-the same hash as <span class="command"><strong>nix-prefetch-url</strong></span> you have to
-specify multiple arguments, see below for an example.</p><p>The hash is computed over a <span class="emphasis"><em>serialisation</em></span>
-of each path: a dump of the file system tree rooted at the path. This
-allows directories and symlinks to be hashed as well as regular files.
-The dump is in the <span class="emphasis"><em>NAR format</em></span> produced by <a class="link" href="#refsec-nix-store-dump" title="Operation --dump"><span class="command"><strong>nix-store</strong></span>
-<code class="option">--dump</code></a>. Thus, <code class="literal">nix-hash
-<em class="replaceable"><code>path</code></em></code> yields the same
-cryptographic hash as <code class="literal">nix-store --dump
-<em class="replaceable"><code>path</code></em> | md5sum</code>.</p></div><div class="refsection"><a id="idm139733299239440"></a><h2>Options</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--flat</code></span></dt><dd><p>Print the cryptographic hash of the contents of
- each regular file <em class="replaceable"><code>path</code></em>. That is, do
- not compute the hash over the dump of
- <em class="replaceable"><code>path</code></em>. The result is identical to that
- produced by the GNU commands <span class="command"><strong>md5sum</strong></span> and
- <span class="command"><strong>sha1sum</strong></span>.</p></dd><dt><span class="term"><code class="option">--base32</code></span></dt><dd><p>Print the hash in a base-32 representation rather
- than hexadecimal. This base-32 representation is more compact and
- can be used in Nix expressions (such as in calls to
- <code class="function">fetchurl</code>).</p></dd><dt><span class="term"><code class="option">--truncate</code></span></dt><dd><p>Truncate hashes longer than 160 bits (such as
- SHA-256) to 160 bits.</p></dd><dt><span class="term"><code class="option">--type</code> <em class="replaceable"><code>hashAlgo</code></em></span></dt><dd><p>Use the specified cryptographic hash algorithm,
- which can be one of <code class="literal">md5</code>,
- <code class="literal">sha1</code>, and
- <code class="literal">sha256</code>.</p></dd><dt><span class="term"><code class="option">--to-base16</code></span></dt><dd><p>Don’t hash anything, but convert the base-32 hash
- representation <em class="replaceable"><code>hash</code></em> to
- hexadecimal.</p></dd><dt><span class="term"><code class="option">--to-base32</code></span></dt><dd><p>Don’t hash anything, but convert the hexadecimal
- hash representation <em class="replaceable"><code>hash</code></em> to
- base-32.</p></dd></dl></div></div><div class="refsection"><a id="idm139733299224832"></a><h2>Examples</h2><p>Computing the same hash as <span class="command"><strong>nix-prefetch-url</strong></span>:
-</p><pre class="screen">
-$ nix-prefetch-url file://<(echo test)
-1lkgqb6fclns49861dwk9rzb6xnfkxbpws74mxnx01z9qyv1pjpj
-$ nix-hash --type sha256 --flat --base32 <(echo test)
-1lkgqb6fclns49861dwk9rzb6xnfkxbpws74mxnx01z9qyv1pjpj
-</pre><p>
-</p><p>Computing hashes:
-
-</p><pre class="screen">
-$ mkdir test
-$ echo "hello" > test/world
-
-$ nix-hash test/ <em class="lineannotation"><span class="lineannotation">(MD5 hash; default)</span></em>
-8179d3caeff1869b5ba1744e5a245c04
-
-$ nix-store --dump test/ | md5sum <em class="lineannotation"><span class="lineannotation">(for comparison)</span></em>
-8179d3caeff1869b5ba1744e5a245c04 -
-
-$ nix-hash --type sha1 test/
-e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
-
-$ nix-hash --type sha1 --base32 test/
-nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
-
-$ nix-hash --type sha256 --flat test/
-error: reading file `test/': Is a directory
-
-$ nix-hash --type sha256 --flat test/world
-5891b5b522d5df086d0ff0b110fbd9d21bb4fc7163af34d08286a2e846f6be03</pre><p>
-
-</p><p>Converting between hexadecimal and base-32:
-
-</p><pre class="screen">
-$ nix-hash --type sha1 --to-base32 e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
-nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
-
-$ nix-hash --type sha1 --to-base16 nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
-e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6</pre><p>
-
-</p></div></div><div class="refentry"><div class="refentry.separator"><hr /></div><a id="sec-nix-instantiate"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix-instantiate — instantiate store derivations from Nix expressions</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">nix-instantiate</code> [ <code class="option">--parse</code> |
- <code class="option">--eval</code>
- [<code class="option">--strict</code>]
- [<code class="option">--json</code>]
- [<code class="option">--xml</code>]
- ] [<code class="option">--read-write-mode</code>] [<code class="option">--arg</code> <em class="replaceable"><code>name</code></em> <em class="replaceable"><code>value</code></em>] [
- { <code class="option">--attr</code> | <code class="option">-A</code> }
- <em class="replaceable"><code>attrPath</code></em>
- ] [<code class="option">--add-root</code> <em class="replaceable"><code>path</code></em>] [<code class="option">--indirect</code>] [ <code class="option">--expr</code> | <code class="option">-E</code> ] <em class="replaceable"><code>files</code></em>... </p></div><div class="cmdsynopsis"><p><code class="command">nix-instantiate</code> <code class="option">--find-file</code> <em class="replaceable"><code>files</code></em>... </p></div></div><div class="refsection"><a id="idm139733299196816"></a><h2>Description</h2><p>The command <span class="command"><strong>nix-instantiate</strong></span> generates <a class="link" href="#gloss-derivation" title="derivation">store derivations</a> from (high-level)
-Nix expressions. It evaluates the Nix expressions in each of
-<em class="replaceable"><code>files</code></em> (which defaults to
-<em class="replaceable"><code>./default.nix</code></em>). Each top-level expression
-should evaluate to a derivation, a list of derivations, or a set of
-derivations. The paths of the resulting store derivations are printed
-on standard output.</p><p>If <em class="replaceable"><code>files</code></em> is the character
-<code class="literal">-</code>, then a Nix expression will be read from standard
-input.</p><p>See also <a class="xref" href="#sec-common-options" title="Chapter 20. Common Options">Chapter 20, <em>Common Options</em></a> for a list of common options.</p></div><div class="refsection"><a id="idm139733299190864"></a><h2>Options</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--add-root</code> <em class="replaceable"><code>path</code></em>, </span><span class="term"><code class="option">--indirect</code></span></dt><dd><p>See the <a class="link" href="#opt-add-root">corresponding
- options</a> in <span class="command"><strong>nix-store</strong></span>.</p></dd><dt><span class="term"><code class="option">--parse</code></span></dt><dd><p>Just parse the input files, and print their
- abstract syntax trees on standard output in ATerm
- format.</p></dd><dt><span class="term"><code class="option">--eval</code></span></dt><dd><p>Just parse and evaluate the input files, and print
- the resulting values on standard output. No instantiation of
- store derivations takes place.</p></dd><dt><span class="term"><code class="option">--find-file</code></span></dt><dd><p>Look up the given files in Nix’s search path (as
- specified by the <code class="envar"><a class="envar" href="#env-NIX_PATH">NIX_PATH</a></code>
- environment variable). If found, print the corresponding absolute
- paths on standard output. For instance, if
- <code class="envar">NIX_PATH</code> is
- <code class="literal">nixpkgs=/home/alice/nixpkgs</code>, then
- <code class="literal">nix-instantiate --find-file nixpkgs/default.nix</code>
- will print
- <code class="literal">/home/alice/nixpkgs/default.nix</code>.</p></dd><dt><span class="term"><code class="option">--strict</code></span></dt><dd><p>When used with <code class="option">--eval</code>,
- recursively evaluate list elements and attributes. Normally, such
- sub-expressions are left unevaluated (since the Nix expression
- language is lazy).</p><div class="warning"><h3 class="title">Warning</h3><p>This option can cause non-termination, because lazy
- data structures can be infinitely large.</p></div></dd><dt><span class="term"><code class="option">--json</code></span></dt><dd><p>When used with <code class="option">--eval</code>, print the resulting
- value as an JSON representation of the abstract syntax tree rather
- than as an ATerm.</p></dd><dt><span class="term"><code class="option">--xml</code></span></dt><dd><p>When used with <code class="option">--eval</code>, print the resulting
- value as an XML representation of the abstract syntax tree rather than as
- an ATerm. The schema is the same as that used by the <a class="link" href="#builtin-toXML"><code class="function">toXML</code> built-in</a>.
- </p></dd><dt><span class="term"><code class="option">--read-write-mode</code></span></dt><dd><p>When used with <code class="option">--eval</code>, perform
- evaluation in read/write mode so nix language features that
- require it will still work (at the cost of needing to do
- instantiation of every evaluated derivation). If this option is
- not enabled, there may be uninstantiated store paths in the final
- output.</p></dd></dl></div></div><div class="refsection"><a id="idm139733299169472"></a><h2>Examples</h2><p>Instantiating store derivations from a Nix expression, and
-building them using <span class="command"><strong>nix-store</strong></span>:
-
-</p><pre class="screen">
-$ nix-instantiate test.nix <em class="lineannotation"><span class="lineannotation">(instantiate)</span></em>
-/nix/store/cigxbmvy6dzix98dxxh9b6shg7ar5bvs-perl-BerkeleyDB-0.26.drv
-
-$ nix-store -r $(nix-instantiate test.nix) <em class="lineannotation"><span class="lineannotation">(build)</span></em>
-<em class="replaceable"><code>...</code></em>
-/nix/store/qhqk4n8ci095g3sdp93x7rgwyh9rdvgk-perl-BerkeleyDB-0.26 <em class="lineannotation"><span class="lineannotation">(output path)</span></em>
-
-$ ls -l /nix/store/qhqk4n8ci095g3sdp93x7rgwyh9rdvgk-perl-BerkeleyDB-0.26
-dr-xr-xr-x 2 eelco users 4096 1970-01-01 01:00 lib
-...</pre><p>
-
-</p><p>You can also give a Nix expression on the command line:
-
-</p><pre class="screen">
-$ nix-instantiate -E 'with import <nixpkgs> { }; hello'
-/nix/store/j8s4zyv75a724q38cb0r87rlczaiag4y-hello-2.8.drv
-</pre><p>
-
-This is equivalent to:
-
-</p><pre class="screen">
-$ nix-instantiate '<nixpkgs>' -A hello
-</pre><p>
-
-</p><p>Parsing and evaluating Nix expressions:
-
-</p><pre class="screen">
-$ nix-instantiate --parse -E '1 + 2'
-1 + 2
-
-$ nix-instantiate --eval -E '1 + 2'
-3
-
-$ nix-instantiate --eval --xml -E '1 + 2'
-<?xml version='1.0' encoding='utf-8'?>
-<expr>
- <int value="3" />
-</expr></pre><p>
-
-</p><p>The difference between non-strict and strict evaluation:
-
-</p><pre class="screen">
-$ nix-instantiate --eval --xml -E 'rec { x = "foo"; y = x; }'
-<em class="replaceable"><code>...</code></em>
- <attr name="x">
- <string value="foo" />
- </attr>
- <attr name="y">
- <unevaluated />
- </attr>
-<em class="replaceable"><code>...</code></em></pre><p>
-
-Note that <code class="varname">y</code> is left unevaluated (the XML
-representation doesn’t attempt to show non-normal forms).
-
-</p><pre class="screen">
-$ nix-instantiate --eval --xml --strict -E 'rec { x = "foo"; y = x; }'
-<em class="replaceable"><code>...</code></em>
- <attr name="x">
- <string value="foo" />
- </attr>
- <attr name="y">
- <string value="foo" />
- </attr>
-<em class="replaceable"><code>...</code></em></pre><p>
-
-</p></div></div><div class="refentry"><div class="refentry.separator"><hr /></div><a id="sec-nix-prefetch-url"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix-prefetch-url — copy a file from a URL into the store and print its hash</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p><code class="command">nix-prefetch-url</code> [<code class="option">--version</code>] [<code class="option">--type</code> <em class="replaceable"><code>hashAlgo</code></em>] [<code class="option">--print-path</code>] [<code class="option">--unpack</code>] [<code class="option">--name</code> <em class="replaceable"><code>name</code></em>] <em class="replaceable"><code>url</code></em> [<em class="replaceable"><code>hash</code></em>]</p></div></div><div class="refsection"><a id="idm139733299148080"></a><h2>Description</h2><p>The command <span class="command"><strong>nix-prefetch-url</strong></span> downloads the
-file referenced by the URL <em class="replaceable"><code>url</code></em>, prints its
-cryptographic hash, and copies it into the Nix store. The file name
-in the store is
-<code class="filename"><em class="replaceable"><code>hash</code></em>-<em class="replaceable"><code>baseName</code></em></code>,
-where <em class="replaceable"><code>baseName</code></em> is everything following the
-final slash in <em class="replaceable"><code>url</code></em>.</p><p>This command is just a convenience for Nix expression writers.
-Often a Nix expression fetches some source distribution from the
-network using the <code class="literal">fetchurl</code> expression contained in
-Nixpkgs. However, <code class="literal">fetchurl</code> requires a
-cryptographic hash. If you don't know the hash, you would have to
-download the file first, and then <code class="literal">fetchurl</code> would
-download it again when you build your Nix expression. Since
-<code class="literal">fetchurl</code> uses the same name for the downloaded file
-as <span class="command"><strong>nix-prefetch-url</strong></span>, the redundant download can be
-avoided.</p><p>If <em class="replaceable"><code>hash</code></em> is specified, then a download
-is not performed if the Nix store already contains a file with the
-same hash and base name. Otherwise, the file is downloaded, and an
-error is signaled if the actual hash of the file does not match the
-specified hash.</p><p>This command prints the hash on standard output. Additionally,
-if the option <code class="option">--print-path</code> is used, the path of the
-downloaded file in the Nix store is also printed.</p></div><div class="refsection"><a id="idm139733299139072"></a><h2>Options</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--type</code> <em class="replaceable"><code>hashAlgo</code></em></span></dt><dd><p>Use the specified cryptographic hash algorithm,
- which can be one of <code class="literal">md5</code>,
- <code class="literal">sha1</code>, and
- <code class="literal">sha256</code>.</p></dd><dt><span class="term"><code class="option">--print-path</code></span></dt><dd><p>Print the store path of the downloaded file on
- standard output.</p></dd><dt><span class="term"><code class="option">--unpack</code></span></dt><dd><p>Unpack the archive (which must be a tarball or zip
- file) and add the result to the Nix store. The resulting hash can
- be used with functions such as Nixpkgs’s
- <code class="varname">fetchzip</code> or
- <code class="varname">fetchFromGitHub</code>.</p></dd><dt><span class="term"><code class="option">--name</code> <em class="replaceable"><code>name</code></em></span></dt><dd><p>Override the name of the file in the Nix store. By
- default, this is
- <code class="literal"><em class="replaceable"><code>hash</code></em>-<em class="replaceable"><code>basename</code></em></code>,
- where <em class="replaceable"><code>basename</code></em> is the last component of
- <em class="replaceable"><code>url</code></em>. Overriding the name is necessary
- when <em class="replaceable"><code>basename</code></em> contains characters that
- are not allowed in Nix store paths.</p></dd></dl></div></div><div class="refsection"><a id="idm139733299126752"></a><h2>Examples</h2><pre class="screen">
-$ nix-prefetch-url ftp://ftp.gnu.org/pub/gnu/hello/hello-2.10.tar.gz
-0ssi1wpaf7plaswqqjwigppsg5fyh99vdlb9kzl7c9lng89ndq1i
-
-$ nix-prefetch-url --print-path mirror://gnu/hello/hello-2.10.tar.gz
-0ssi1wpaf7plaswqqjwigppsg5fyh99vdlb9kzl7c9lng89ndq1i
-/nix/store/3x7dwzq014bblazs7kq20p9hyzz0qh8g-hello-2.10.tar.gz
-
-$ nix-prefetch-url --unpack --print-path https://github.com/NixOS/patchelf/archive/0.8.tar.gz
-079agjlv0hrv7fxnx9ngipx14gyncbkllxrp9cccnh3a50fxcmy7
-/nix/store/19zrmhm3m40xxaw81c8cqm6aljgrnwj2-0.8.tar.gz
-</pre></div></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a id="ch-files"></a>Chapter 24. Files</h2></div></div></div><p>This section lists configuration files that you can use when you
-work with Nix.</p><div class="refentry"><a id="sec-conf-file"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>nix.conf — Nix configuration file</p></div><div class="refsection"><a id="idm139733299118992"></a><h2>Description</h2><p>By default Nix reads settings from the following places:</p><p>The system-wide configuration file
-<code class="filename"><em class="replaceable"><code>sysconfdir</code></em>/nix/nix.conf</code>
-(i.e. <code class="filename">/etc/nix/nix.conf</code> on most systems), or
-<code class="filename">$NIX_CONF_DIR/nix.conf</code> if
-<code class="envar">NIX_CONF_DIR</code> is set. Values loaded in this file are not forwarded to the Nix daemon. The
-client assumes that the daemon has already loaded them.
-</p><p>User-specific configuration files:</p><p>
- If <code class="envar">NIX_USER_CONF_FILES</code> is set, then each path separated by
- <code class="literal">:</code> will be loaded in reverse order.
-</p><p>
- Otherwise it will look for <code class="filename">nix/nix.conf</code> files in
- <code class="envar">XDG_CONFIG_DIRS</code> and <code class="envar">XDG_CONFIG_HOME</code>.
-
- The default location is <code class="filename">$HOME/.config/nix.conf</code> if
- those environment variables are unset.
-</p><p>The configuration files consist of
-<code class="literal"><em class="replaceable"><code>name</code></em> =
-<em class="replaceable"><code>value</code></em></code> pairs, one per line. Other
-files can be included with a line like <code class="literal">include
-<em class="replaceable"><code>path</code></em></code>, where
-<em class="replaceable"><code>path</code></em> is interpreted relative to the current
-conf file and a missing file is an error unless
-<code class="literal">!include</code> is used instead.
-Comments start with a <code class="literal">#</code> character. Here is an
-example configuration file:</p><pre class="programlisting">
-keep-outputs = true # Nice for developers
-keep-derivations = true # Idem
-</pre><p>You can override settings on the command line using the
-<code class="option">--option</code> flag, e.g. <code class="literal">--option keep-outputs
-false</code>.</p><p>The following settings are currently available:
-
-</p><div class="variablelist"><dl class="variablelist"><dt><a id="conf-allowed-uris"></a><span class="term"><code class="literal">allowed-uris</code></span></dt><dd><p>A list of URI prefixes to which access is allowed in
- restricted evaluation mode. For example, when set to
- <code class="literal">https://github.com/NixOS</code>, builtin functions
- such as <code class="function">fetchGit</code> are allowed to access
- <code class="literal">https://github.com/NixOS/patchelf.git</code>.</p></dd><dt><a id="conf-allow-import-from-derivation"></a><span class="term"><code class="literal">allow-import-from-derivation</code></span></dt><dd><p>By default, Nix allows you to <code class="function">import</code> from a derivation,
- allowing building at evaluation time. With this option set to false, Nix will throw an error
- when evaluating an expression that uses this feature, allowing users to ensure their evaluation
- will not require any builds to take place.</p></dd><dt><a id="conf-allow-new-privileges"></a><span class="term"><code class="literal">allow-new-privileges</code></span></dt><dd><p>(Linux-specific.) By default, builders on Linux
- cannot acquire new privileges by calling setuid/setgid programs or
- programs that have file capabilities. For example, programs such
- as <span class="command"><strong>sudo</strong></span> or <span class="command"><strong>ping</strong></span> will
- fail. (Note that in sandbox builds, no such programs are available
- unless you bind-mount them into the sandbox via the
- <code class="option">sandbox-paths</code> option.) You can allow the
- use of such programs by enabling this option. This is impure and
- usually undesirable, but may be useful in certain scenarios
- (e.g. to spin up containers or set up userspace network interfaces
- in tests).</p></dd><dt><a id="conf-allowed-users"></a><span class="term"><code class="literal">allowed-users</code></span></dt><dd><p>A list of names of users (separated by whitespace) that
- are allowed to connect to the Nix daemon. As with the
- <code class="option">trusted-users</code> option, you can specify groups by
- prefixing them with <code class="literal">@</code>. Also, you can allow
- all users by specifying <code class="literal">*</code>. The default is
- <code class="literal">*</code>.</p><p>Note that trusted users are always allowed to connect.</p></dd><dt><a id="conf-auto-optimise-store"></a><span class="term"><code class="literal">auto-optimise-store</code></span></dt><dd><p>If set to <code class="literal">true</code>, Nix
- automatically detects files in the store that have identical
- contents, and replaces them with hard links to a single copy.
- This saves disk space. If set to <code class="literal">false</code> (the
- default), you can still run <span class="command"><strong>nix-store
- --optimise</strong></span> to get rid of duplicate
- files.</p></dd><dt><a id="conf-builders"></a><span class="term"><code class="literal">builders</code></span></dt><dd><p>A list of machines on which to perform builds. <span class="phrase">See <a class="xref" href="#chap-distributed-builds" title="Chapter 16. Remote Builds">Chapter 16, <em>Remote Builds</em></a> for details.</span></p></dd><dt><a id="conf-builders-use-substitutes"></a><span class="term"><code class="literal">builders-use-substitutes</code></span></dt><dd><p>If set to <code class="literal">true</code>, Nix will instruct
- remote build machines to use their own binary substitutes if available. In
- practical terms, this means that remote hosts will fetch as many build
- dependencies as possible from their own substitutes (e.g, from
- <code class="literal">cache.nixos.org</code>), instead of waiting for this host to
- upload them all. This can drastically reduce build times if the network
- connection between this computer and the remote build host is slow. Defaults
- to <code class="literal">false</code>.</p></dd><dt><a id="conf-build-users-group"></a><span class="term"><code class="literal">build-users-group</code></span></dt><dd><p>This options specifies the Unix group containing
- the Nix build user accounts. In multi-user Nix installations,
- builds should not be performed by the Nix account since that would
- allow users to arbitrarily modify the Nix store and database by
- supplying specially crafted builders; and they cannot be performed
- by the calling user since that would allow him/her to influence
- the build result.</p><p>Therefore, if this option is non-empty and specifies a valid
- group, builds will be performed under the user accounts that are a
- member of the group specified here (as listed in
- <code class="filename">/etc/group</code>). Those user accounts should not
- be used for any other purpose!</p><p>Nix will never run two builds under the same user account at
- the same time. This is to prevent an obvious security hole: a
- malicious user writing a Nix expression that modifies the build
- result of a legitimate Nix expression being built by another user.
- Therefore it is good to have as many Nix build user accounts as
- you can spare. (Remember: uids are cheap.)</p><p>The build users should have permission to create files in
- the Nix store, but not delete them. Therefore,
- <code class="filename">/nix/store</code> should be owned by the Nix
- account, its group should be the group specified here, and its
- mode should be <code class="literal">1775</code>.</p><p>If the build users group is empty, builds will be performed
- under the uid of the Nix process (that is, the uid of the caller
- if <code class="envar">NIX_REMOTE</code> is empty, the uid under which the Nix
- daemon runs if <code class="envar">NIX_REMOTE</code> is
- <code class="literal">daemon</code>). Obviously, this should not be used in
- multi-user settings with untrusted users.</p></dd><dt><a id="conf-compress-build-log"></a><span class="term"><code class="literal">compress-build-log</code></span></dt><dd><p>If set to <code class="literal">true</code> (the default),
- build logs written to <code class="filename">/nix/var/log/nix/drvs</code>
- will be compressed on the fly using bzip2. Otherwise, they will
- not be compressed.</p></dd><dt><a id="conf-connect-timeout"></a><span class="term"><code class="literal">connect-timeout</code></span></dt><dd><p>The timeout (in seconds) for establishing connections in
- the binary cache substituter. It corresponds to
- <span class="command"><strong>curl</strong></span>’s <code class="option">--connect-timeout</code>
- option.</p></dd><dt><a id="conf-cores"></a><span class="term"><code class="literal">cores</code></span></dt><dd><p>Sets the value of the
- <code class="envar">NIX_BUILD_CORES</code> environment variable in the
- invocation of builders. Builders can use this variable at their
- discretion to control the maximum amount of parallelism. For
- instance, in Nixpkgs, if the derivation attribute
- <code class="varname">enableParallelBuilding</code> is set to
- <code class="literal">true</code>, the builder passes the
- <code class="option">-j<em class="replaceable"><code>N</code></em></code> flag to GNU Make.
- It can be overridden using the <code class="option"><a class="option" href="#opt-cores">--cores</a></code> command line switch and
- defaults to <code class="literal">1</code>. The value <code class="literal">0</code>
- means that the builder should use all available CPU cores in the
- system.</p><p>See also <a class="xref" href="#chap-tuning-cores-and-jobs" title="Chapter 17. Tuning Cores and Jobs">Chapter 17, <em>Tuning Cores and Jobs</em></a>.</p></dd><dt><a id="conf-diff-hook"></a><span class="term"><code class="literal">diff-hook</code></span></dt><dd><p>
- Absolute path to an executable capable of diffing build results.
- The hook executes if <a class="xref" href="#conf-run-diff-hook"><code class="literal">run-diff-hook</code></a> is
- true, and the output of a build is known to not be the same.
- This program is not executed to determine if two results are the
- same.
- </p><p>
- The diff hook is executed by the same user and group who ran the
- build. However, the diff hook does not have write access to the
- store path just built.
- </p><p>The diff hook program receives three parameters:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
- A path to the previous build's results
- </p></li><li class="listitem"><p>
- A path to the current build's results
- </p></li><li class="listitem"><p>
- The path to the build's derivation
- </p></li><li class="listitem"><p>
- The path to the build's scratch directory. This directory
- will exist only if the build was run with
- <code class="option">--keep-failed</code>.
- </p></li></ol></div><p>
- The stderr and stdout output from the diff hook will not be
- displayed to the user. Instead, it will print to the nix-daemon's
- log.
- </p><p>When using the Nix daemon, <code class="literal">diff-hook</code> must
- be set in the <code class="filename">nix.conf</code> configuration file, and
- cannot be passed at the command line.
- </p></dd><dt><a id="conf-enforce-determinism"></a><span class="term"><code class="literal">enforce-determinism</code></span></dt><dd><p>See <a class="xref" href="#conf-repeat"><code class="literal">repeat</code></a>.</p></dd><dt><a id="conf-extra-sandbox-paths"></a><span class="term"><code class="literal">extra-sandbox-paths</code></span></dt><dd><p>A list of additional paths appended to
- <code class="option">sandbox-paths</code>. Useful if you want to extend
- its default value.</p></dd><dt><a id="conf-extra-platforms"></a><span class="term"><code class="literal">extra-platforms</code></span></dt><dd><p>Platforms other than the native one which
- this machine is capable of building for. This can be useful for
- supporting additional architectures on compatible machines:
- i686-linux can be built on x86_64-linux machines (and the default
- for this setting reflects this); armv7 is backwards-compatible with
- armv6 and armv5tel; some aarch64 machines can also natively run
- 32-bit ARM code; and qemu-user may be used to support non-native
- platforms (though this may be slow and buggy). Most values for this
- are not enabled by default because build systems will often
- misdetect the target platform and generate incompatible code, so you
- may wish to cross-check the results of using this option against
- proper natively-built versions of your
- derivations.</p></dd><dt><a id="conf-extra-substituters"></a><span class="term"><code class="literal">extra-substituters</code></span></dt><dd><p>Additional binary caches appended to those
- specified in <code class="option">substituters</code>. When used by
- unprivileged users, untrusted substituters (i.e. those not listed
- in <code class="option">trusted-substituters</code>) are silently
- ignored.</p></dd><dt><a id="conf-fallback"></a><span class="term"><code class="literal">fallback</code></span></dt><dd><p>If set to <code class="literal">true</code>, Nix will fall
- back to building from source if a binary substitute fails. This
- is equivalent to the <code class="option">--fallback</code> flag. The
- default is <code class="literal">false</code>.</p></dd><dt><a id="conf-fsync-metadata"></a><span class="term"><code class="literal">fsync-metadata</code></span></dt><dd><p>If set to <code class="literal">true</code>, changes to the
- Nix store metadata (in <code class="filename">/nix/var/nix/db</code>) are
- synchronously flushed to disk. This improves robustness in case
- of system crashes, but reduces performance. The default is
- <code class="literal">true</code>.</p></dd><dt><a id="conf-hashed-mirrors"></a><span class="term"><code class="literal">hashed-mirrors</code></span></dt><dd><p>A list of web servers used by
- <code class="function">builtins.fetchurl</code> to obtain files by hash.
- Given a hash type <em class="replaceable"><code>ht</code></em> and a base-16 hash
- <em class="replaceable"><code>h</code></em>, Nix will try to download the file
- from
- <code class="literal">hashed-mirror/<em class="replaceable"><code>ht</code></em>/<em class="replaceable"><code>h</code></em></code>.
- This allows files to be downloaded even if they have disappeared
- from their original URI. For example, given the hashed mirror
- <code class="literal">http://tarballs.example.com/</code>, when building the
- derivation
-
-</p><pre class="programlisting">
-builtins.fetchurl {
- url = "https://example.org/foo-1.2.3.tar.xz";
- sha256 = "2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae";
-}
-</pre><p>
-
- Nix will attempt to download this file from
- <code class="literal">http://tarballs.example.com/sha256/2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae</code>
- first. If it is not available there, if will try the original URI.</p></dd><dt><a id="conf-http-connections"></a><span class="term"><code class="literal">http-connections</code></span></dt><dd><p>The maximum number of parallel TCP connections
- used to fetch files from binary caches and by other downloads. It
- defaults to 25. 0 means no limit.</p></dd><dt><a id="conf-keep-build-log"></a><span class="term"><code class="literal">keep-build-log</code></span></dt><dd><p>If set to <code class="literal">true</code> (the default),
- Nix will write the build log of a derivation (i.e. the standard
- output and error of its builder) to the directory
- <code class="filename">/nix/var/log/nix/drvs</code>. The build log can be
- retrieved using the command <span class="command"><strong>nix-store -l
- <em class="replaceable"><code>path</code></em></strong></span>.</p></dd><dt><a id="conf-keep-derivations"></a><span class="term"><code class="literal">keep-derivations</code></span></dt><dd><p>If <code class="literal">true</code> (default), the garbage
- collector will keep the derivations from which non-garbage store
- paths were built. If <code class="literal">false</code>, they will be
- deleted unless explicitly registered as a root (or reachable from
- other roots).</p><p>Keeping derivation around is useful for querying and
- traceability (e.g., it allows you to ask with what dependencies or
- options a store path was built), so by default this option is on.
- Turn it off to save a bit of disk space (or a lot if
- <code class="literal">keep-outputs</code> is also turned on).</p></dd><dt><a id="conf-keep-env-derivations"></a><span class="term"><code class="literal">keep-env-derivations</code></span></dt><dd><p>If <code class="literal">false</code> (default), derivations
- are not stored in Nix user environments. That is, the derivations of
- any build-time-only dependencies may be garbage-collected.</p><p>If <code class="literal">true</code>, when you add a Nix derivation to
- a user environment, the path of the derivation is stored in the
- user environment. Thus, the derivation will not be
- garbage-collected until the user environment generation is deleted
- (<span class="command"><strong>nix-env --delete-generations</strong></span>). To prevent
- build-time-only dependencies from being collected, you should also
- turn on <code class="literal">keep-outputs</code>.</p><p>The difference between this option and
- <code class="literal">keep-derivations</code> is that this one is
- “sticky”: it applies to any user environment created while this
- option was enabled, while <code class="literal">keep-derivations</code>
- only applies at the moment the garbage collector is
- run.</p></dd><dt><a id="conf-keep-outputs"></a><span class="term"><code class="literal">keep-outputs</code></span></dt><dd><p>If <code class="literal">true</code>, the garbage collector
- will keep the outputs of non-garbage derivations. If
- <code class="literal">false</code> (default), outputs will be deleted unless
- they are GC roots themselves (or reachable from other roots).</p><p>In general, outputs must be registered as roots separately.
- However, even if the output of a derivation is registered as a
- root, the collector will still delete store paths that are used
- only at build time (e.g., the C compiler, or source tarballs
- downloaded from the network). To prevent it from doing so, set
- this option to <code class="literal">true</code>.</p></dd><dt><a id="conf-max-build-log-size"></a><span class="term"><code class="literal">max-build-log-size</code></span></dt><dd><p>This option defines the maximum number of bytes that a
- builder can write to its stdout/stderr. If the builder exceeds
- this limit, it’s killed. A value of <code class="literal">0</code> (the
- default) means that there is no limit.</p></dd><dt><a id="conf-max-free"></a><span class="term"><code class="literal">max-free</code></span></dt><dd><p>When a garbage collection is triggered by the
- <code class="literal">min-free</code> option, it stops as soon as
- <code class="literal">max-free</code> bytes are available. The default is
- infinity (i.e. delete all garbage).</p></dd><dt><a id="conf-max-jobs"></a><span class="term"><code class="literal">max-jobs</code></span></dt><dd><p>This option defines the maximum number of jobs
- that Nix will try to build in parallel. The default is
- <code class="literal">1</code>. The special value <code class="literal">auto</code>
- causes Nix to use the number of CPUs in your system. <code class="literal">0</code>
- is useful when using remote builders to prevent any local builds (except for
- <code class="literal">preferLocalBuild</code> derivation attribute which executes locally
- regardless). It can be
- overridden using the <code class="option"><a class="option" href="#opt-max-jobs">--max-jobs</a></code> (<code class="option">-j</code>)
- command line switch.</p><p>See also <a class="xref" href="#chap-tuning-cores-and-jobs" title="Chapter 17. Tuning Cores and Jobs">Chapter 17, <em>Tuning Cores and Jobs</em></a>.</p></dd><dt><a id="conf-max-silent-time"></a><span class="term"><code class="literal">max-silent-time</code></span></dt><dd><p>This option defines the maximum number of seconds that a
- builder can go without producing any data on standard output or
- standard error. This is useful (for instance in an automated
- build system) to catch builds that are stuck in an infinite
- loop, or to catch remote builds that are hanging due to network
- problems. It can be overridden using the <code class="option"><a class="option" href="#opt-max-silent-time">--max-silent-time</a></code> command
- line switch.</p><p>The value <code class="literal">0</code> means that there is no
- timeout. This is also the default.</p></dd><dt><a id="conf-min-free"></a><span class="term"><code class="literal">min-free</code></span></dt><dd><p>When free disk space in <code class="filename">/nix/store</code>
- drops below <code class="literal">min-free</code> during a build, Nix
- performs a garbage-collection until <code class="literal">max-free</code>
- bytes are available or there is no more garbage. A value of
- <code class="literal">0</code> (the default) disables this feature.</p></dd><dt><a id="conf-narinfo-cache-negative-ttl"></a><span class="term"><code class="literal">narinfo-cache-negative-ttl</code></span></dt><dd><p>The TTL in seconds for negative lookups. If a store path is
- queried from a substituter but was not found, there will be a
- negative lookup cached in the local disk cache database for the
- specified duration.</p></dd><dt><a id="conf-narinfo-cache-positive-ttl"></a><span class="term"><code class="literal">narinfo-cache-positive-ttl</code></span></dt><dd><p>The TTL in seconds for positive lookups. If a store path is
- queried from a substituter, the result of the query will be cached
- in the local disk cache database including some of the NAR
- metadata. The default TTL is a month, setting a shorter TTL for
- positive lookups can be useful for binary caches that have
- frequent garbage collection, in which case having a more frequent
- cache invalidation would prevent trying to pull the path again and
- failing with a hash mismatch if the build isn't reproducible.
- </p></dd><dt><a id="conf-netrc-file"></a><span class="term"><code class="literal">netrc-file</code></span></dt><dd><p>If set to an absolute path to a <code class="filename">netrc</code>
- file, Nix will use the HTTP authentication credentials in this file when
- trying to download from a remote host through HTTP or HTTPS. Defaults to
- <code class="filename">$NIX_CONF_DIR/netrc</code>.</p><p>The <code class="filename">netrc</code> file consists of a list of
- accounts in the following format:
-
-</p><pre class="screen">
-machine <em class="replaceable"><code>my-machine</code></em>
-login <em class="replaceable"><code>my-username</code></em>
-password <em class="replaceable"><code>my-password</code></em>
-</pre><p>
-
- For the exact syntax, see <a class="link" href="https://ec.haxx.se/usingcurl-netrc.html" target="_top">the
- <code class="literal">curl</code> documentation.</a></p><div class="note"><h3 class="title">Note</h3><p>This must be an absolute path, and <code class="literal">~</code>
- is not resolved. For example, <code class="filename">~/.netrc</code> won't
- resolve to your home directory's <code class="filename">.netrc</code>.</p></div></dd><dt><a id="conf-plugin-files"></a><span class="term"><code class="literal">plugin-files</code></span></dt><dd><p>
- A list of plugin files to be loaded by Nix. Each of these
- files will be dlopened by Nix, allowing them to affect
- execution through static initialization. In particular, these
- plugins may construct static instances of RegisterPrimOp to
- add new primops or constants to the expression language,
- RegisterStoreImplementation to add new store implementations,
- RegisterCommand to add new subcommands to the
- <code class="literal">nix</code> command, and RegisterSetting to add new
- nix config settings. See the constructors for those types for
- more details.
- </p><p>
- Since these files are loaded into the same address space as
- Nix itself, they must be DSOs compatible with the instance of
- Nix running at the time (i.e. compiled against the same
- headers, not linked to any incompatible libraries). They
- should not be linked to any Nix libs directly, as those will
- be available already at load time.
- </p><p>
- If an entry in the list is a directory, all files in the
- directory are loaded as plugins (non-recursively).
- </p></dd><dt><a id="conf-pre-build-hook"></a><span class="term"><code class="literal">pre-build-hook</code></span></dt><dd><p>If set, the path to a program that can set extra
- derivation-specific settings for this system. This is used for settings
- that can't be captured by the derivation model itself and are too variable
- between different versions of the same system to be hard-coded into nix.
- </p><p>The hook is passed the derivation path and, if sandboxes are enabled,
- the sandbox directory. It can then modify the sandbox and send a series of
- commands to modify various settings to stdout. The currently recognized
- commands are:</p><div class="variablelist"><dl class="variablelist"><dt><a id="extra-sandbox-paths"></a><span class="term"><code class="literal">extra-sandbox-paths</code></span></dt><dd><p>Pass a list of files and directories to be included in the
- sandbox for this build. One entry per line, terminated by an empty
- line. Entries have the same format as
- <code class="literal">sandbox-paths</code>.</p></dd></dl></div></dd><dt><a id="conf-post-build-hook"></a><span class="term"><code class="literal">post-build-hook</code></span></dt><dd><p>Optional. The path to a program to execute after each build.</p><p>This option is only settable in the global
- <code class="filename">nix.conf</code>, or on the command line by trusted
- users.</p><p>When using the nix-daemon, the daemon executes the hook as
- <code class="literal">root</code>. If the nix-daemon is not involved, the
- hook runs as the user executing the nix-build.</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>The hook executes after an evaluation-time build.</p></li><li class="listitem"><p>The hook does not execute on substituted paths.</p></li><li class="listitem"><p>The hook's output always goes to the user's terminal.</p></li><li class="listitem"><p>If the hook fails, the build succeeds but no further builds execute.</p></li><li class="listitem"><p>The hook executes synchronously, and blocks other builds from progressing while it runs.</p></li></ul></div><p>The program executes with no arguments. The program's environment
- contains the following environment variables:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="envar">DRV_PATH</code></span></dt><dd><p>The derivation for the built paths.</p><p>Example:
- <code class="literal">/nix/store/5nihn1a7pa8b25l9zafqaqibznlvvp3f-bash-4.4-p23.drv</code>
- </p></dd><dt><span class="term"><code class="envar">OUT_PATHS</code></span></dt><dd><p>Output paths of the built derivation, separated by a space character.</p><p>Example:
- <code class="literal">/nix/store/zf5lbh336mnzf1nlswdn11g4n2m8zh3g-bash-4.4-p23-dev
- /nix/store/rjxwxwv1fpn9wa2x5ssk5phzwlcv4mna-bash-4.4-p23-doc
- /nix/store/6bqvbzjkcp9695dq0dpl5y43nvy37pq1-bash-4.4-p23-info
- /nix/store/r7fng3kk3vlpdlh2idnrbn37vh4imlj2-bash-4.4-p23-man
- /nix/store/xfghy8ixrhz3kyy6p724iv3cxji088dx-bash-4.4-p23</code>.
- </p></dd></dl></div><p>See <a class="xref" href="#chap-post-build-hook" title="Chapter 19. Using the post-build-hook">Chapter 19, <em>Using the <code class="option"><a class="option" href="#conf-post-build-hook">post-build-hook</a></code></em></a> for an example
- implementation.</p></dd><dt><a id="conf-repeat"></a><span class="term"><code class="literal">repeat</code></span></dt><dd><p>How many times to repeat builds to check whether
- they are deterministic. The default value is 0. If the value is
- non-zero, every build is repeated the specified number of
- times. If the contents of any of the runs differs from the
- previous ones and <a class="xref" href="#conf-enforce-determinism"><code class="literal">enforce-determinism</code></a> is
- true, the build is rejected and the resulting store paths are not
- registered as “valid” in Nix’s database.</p></dd><dt><a id="conf-require-sigs"></a><span class="term"><code class="literal">require-sigs</code></span></dt><dd><p>If set to <code class="literal">true</code> (the default),
- any non-content-addressed path added or copied to the Nix store
- (e.g. when substituting from a binary cache) must have a valid
- signature, that is, be signed using one of the keys listed in
- <code class="option">trusted-public-keys</code> or
- <code class="option">secret-key-files</code>. Set to <code class="literal">false</code>
- to disable signature checking.</p></dd><dt><a id="conf-restrict-eval"></a><span class="term"><code class="literal">restrict-eval</code></span></dt><dd><p>If set to <code class="literal">true</code>, the Nix evaluator will
- not allow access to any files outside of the Nix search path (as
- set via the <code class="envar">NIX_PATH</code> environment variable or the
- <code class="option">-I</code> option), or to URIs outside of
- <code class="option">allowed-uri</code>. The default is
- <code class="literal">false</code>.</p></dd><dt><a id="conf-run-diff-hook"></a><span class="term"><code class="literal">run-diff-hook</code></span></dt><dd><p>
- If true, enable the execution of <a class="xref" href="#conf-diff-hook"><code class="literal">diff-hook</code></a>.
- </p><p>
- When using the Nix daemon, <code class="literal">run-diff-hook</code> must
- be set in the <code class="filename">nix.conf</code> configuration file,
- and cannot be passed at the command line.
- </p></dd><dt><a id="conf-sandbox"></a><span class="term"><code class="literal">sandbox</code></span></dt><dd><p>If set to <code class="literal">true</code>, builds will be
- performed in a <span class="emphasis"><em>sandboxed environment</em></span>, i.e.,
- they’re isolated from the normal file system hierarchy and will
- only see their dependencies in the Nix store, the temporary build
- directory, private versions of <code class="filename">/proc</code>,
- <code class="filename">/dev</code>, <code class="filename">/dev/shm</code> and
- <code class="filename">/dev/pts</code> (on Linux), and the paths configured with the
- <a class="link" href="#conf-sandbox-paths"><code class="literal">sandbox-paths</code>
- option</a>. This is useful to prevent undeclared dependencies
- on files in directories such as <code class="filename">/usr/bin</code>. In
- addition, on Linux, builds run in private PID, mount, network, IPC
- and UTS namespaces to isolate them from other processes in the
- system (except that fixed-output derivations do not run in private
- network namespace to ensure they can access the network).</p><p>Currently, sandboxing only work on Linux and macOS. The use
- of a sandbox requires that Nix is run as root (so you should use
- the <a class="link" href="#conf-build-users-group">“build users”
- feature</a> to perform the actual builds under different users
- than root).</p><p>If this option is set to <code class="literal">relaxed</code>, then
- fixed-output derivations and derivations that have the
- <code class="varname">__noChroot</code> attribute set to
- <code class="literal">true</code> do not run in sandboxes.</p><p>The default is <code class="literal">true</code> on Linux and
- <code class="literal">false</code> on all other platforms.</p></dd><dt><a id="conf-sandbox-dev-shm-size"></a><span class="term"><code class="literal">sandbox-dev-shm-size</code></span></dt><dd><p>This option determines the maximum size of the
- <code class="literal">tmpfs</code> filesystem mounted on
- <code class="filename">/dev/shm</code> in Linux sandboxes. For the format,
- see the description of the <code class="option">size</code> option of
- <code class="literal">tmpfs</code> in
- <span class="citerefentry"><span class="refentrytitle">mount</span>(8)</span>. The
- default is <code class="literal">50%</code>.</p></dd><dt><a id="conf-sandbox-paths"></a><span class="term"><code class="literal">sandbox-paths</code></span></dt><dd><p>A list of paths bind-mounted into Nix sandbox
- environments. You can use the syntax
- <code class="literal"><em class="replaceable"><code>target</code></em>=<em class="replaceable"><code>source</code></em></code>
- to mount a path in a different location in the sandbox; for
- instance, <code class="literal">/bin=/nix-bin</code> will mount the path
- <code class="literal">/nix-bin</code> as <code class="literal">/bin</code> inside the
- sandbox. If <em class="replaceable"><code>source</code></em> is followed by
- <code class="literal">?</code>, then it is not an error if
- <em class="replaceable"><code>source</code></em> does not exist; for example,
- <code class="literal">/dev/nvidiactl?</code> specifies that
- <code class="filename">/dev/nvidiactl</code> will only be mounted in the
- sandbox if it exists in the host filesystem.</p><p>Depending on how Nix was built, the default value for this option
- may be empty or provide <code class="filename">/bin/sh</code> as a
- bind-mount of <span class="command"><strong>bash</strong></span>.</p></dd><dt><a id="conf-secret-key-files"></a><span class="term"><code class="literal">secret-key-files</code></span></dt><dd><p>A whitespace-separated list of files containing
- secret (private) keys. These are used to sign locally-built
- paths. They can be generated using <span class="command"><strong>nix-store
- --generate-binary-cache-key</strong></span>. The corresponding public
- key can be distributed to other users, who can add it to
- <code class="option">trusted-public-keys</code> in their
- <code class="filename">nix.conf</code>.</p></dd><dt><a id="conf-show-trace"></a><span class="term"><code class="literal">show-trace</code></span></dt><dd><p>Causes Nix to print out a stack trace in case of Nix
- expression evaluation errors.</p></dd><dt><a id="conf-substitute"></a><span class="term"><code class="literal">substitute</code></span></dt><dd><p>If set to <code class="literal">true</code> (default), Nix
- will use binary substitutes if available. This option can be
- disabled to force building from source.</p></dd><dt><a id="conf-stalled-download-timeout"></a><span class="term"><code class="literal">stalled-download-timeout</code></span></dt><dd><p>The timeout (in seconds) for receiving data from servers
- during download. Nix cancels idle downloads after this timeout's
- duration.</p></dd><dt><a id="conf-substituters"></a><span class="term"><code class="literal">substituters</code></span></dt><dd><p>A list of URLs of substituters, separated by
- whitespace. The default is
- <code class="literal">https://cache.nixos.org</code>.</p></dd><dt><a id="conf-system"></a><span class="term"><code class="literal">system</code></span></dt><dd><p>This option specifies the canonical Nix system
- name of the current installation, such as
- <code class="literal">i686-linux</code> or
- <code class="literal">x86_64-darwin</code>. Nix can only build derivations
- whose <code class="literal">system</code> attribute equals the value
- specified here. In general, it never makes sense to modify this
- value from its default, since you can use it to ‘lie’ about the
- platform you are building on (e.g., perform a Mac OS build on a
- Linux machine; the result would obviously be wrong). It only
- makes sense if the Nix binaries can run on multiple platforms,
- e.g., ‘universal binaries’ that run on <code class="literal">x86_64-linux</code> and
- <code class="literal">i686-linux</code>.</p><p>It defaults to the canonical Nix system name detected by
- <code class="filename">configure</code> at build time.</p></dd><dt><a id="conf-system-features"></a><span class="term"><code class="literal">system-features</code></span></dt><dd><p>A set of system “features” supported by this
- machine, e.g. <code class="literal">kvm</code>. Derivations can express a
- dependency on such features through the derivation attribute
- <code class="varname">requiredSystemFeatures</code>. For example, the
- attribute
-
-</p><pre class="programlisting">
-requiredSystemFeatures = [ "kvm" ];
-</pre><p>
-
- ensures that the derivation can only be built on a machine with
- the <code class="literal">kvm</code> feature.</p><p>This setting by default includes <code class="literal">kvm</code> if
- <code class="filename">/dev/kvm</code> is accessible, and the
- pseudo-features <code class="literal">nixos-test</code>,
- <code class="literal">benchmark</code> and <code class="literal">big-parallel</code>
- that are used in Nixpkgs to route builds to specific
- machines.</p></dd><dt><a id="conf-tarball-ttl"></a><span class="term"><code class="literal">tarball-ttl</code></span></dt><dd><p>Default: <code class="literal">3600</code> seconds.</p><p>The number of seconds a downloaded tarball is considered
- fresh. If the cached tarball is stale, Nix will check whether
- it is still up to date using the ETag header. Nix will download
- a new version if the ETag header is unsupported, or the
- cached ETag doesn't match.
- </p><p>Setting the TTL to <code class="literal">0</code> forces Nix to always
- check if the tarball is up to date.</p><p>Nix caches tarballs in
- <code class="filename">$XDG_CACHE_HOME/nix/tarballs</code>.</p><p>Files fetched via <code class="envar">NIX_PATH</code>,
- <code class="function">fetchGit</code>, <code class="function">fetchMercurial</code>,
- <code class="function">fetchTarball</code>, and <code class="function">fetchurl</code>
- respect this TTL.
- </p></dd><dt><a id="conf-timeout"></a><span class="term"><code class="literal">timeout</code></span></dt><dd><p>This option defines the maximum number of seconds that a
- builder can run. This is useful (for instance in an automated
- build system) to catch builds that are stuck in an infinite loop
- but keep writing to their standard output or standard error. It
- can be overridden using the <code class="option"><a class="option" href="#opt-timeout">--timeout</a></code> command line
- switch.</p><p>The value <code class="literal">0</code> means that there is no
- timeout. This is also the default.</p></dd><dt><a id="conf-trace-function-calls"></a><span class="term"><code class="literal">trace-function-calls</code></span></dt><dd><p>Default: <code class="literal">false</code>.</p><p>If set to <code class="literal">true</code>, the Nix evaluator will
- trace every function call. Nix will print a log message at the
- "vomit" level for every function entrance and function exit.</p><div class="informalexample"><pre class="screen">
-function-trace entered undefined position at 1565795816999559622
-function-trace exited undefined position at 1565795816999581277
-function-trace entered /nix/store/.../example.nix:226:41 at 1565795253249935150
-function-trace exited /nix/store/.../example.nix:226:41 at 1565795253249941684
-</pre></div><p>The <code class="literal">undefined position</code> means the function
- call is a builtin.</p><p>Use the <code class="literal">contrib/stack-collapse.py</code> script
- distributed with the Nix source code to convert the trace logs
- in to a format suitable for <span class="command"><strong>flamegraph.pl</strong></span>.</p></dd><dt><a id="conf-trusted-public-keys"></a><span class="term"><code class="literal">trusted-public-keys</code></span></dt><dd><p>A whitespace-separated list of public keys. When
- paths are copied from another Nix store (such as a binary cache),
- they must be signed with one of these keys. For example:
- <code class="literal">cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
- hydra.nixos.org-1:CNHJZBh9K4tP3EKF6FkkgeVYsS3ohTl+oS0Qa8bezVs=</code>.</p></dd><dt><a id="conf-trusted-substituters"></a><span class="term"><code class="literal">trusted-substituters</code></span></dt><dd><p>A list of URLs of substituters, separated by
- whitespace. These are not used by default, but can be enabled by
- users of the Nix daemon by specifying <code class="literal">--option
- substituters <em class="replaceable"><code>urls</code></em></code> on the
- command line. Unprivileged users are only allowed to pass a
- subset of the URLs listed in <code class="literal">substituters</code> and
- <code class="literal">trusted-substituters</code>.</p></dd><dt><a id="conf-trusted-users"></a><span class="term"><code class="literal">trusted-users</code></span></dt><dd><p>A list of names of users (separated by whitespace) that
- have additional rights when connecting to the Nix daemon, such
- as the ability to specify additional binary caches, or to import
- unsigned NARs. You can also specify groups by prefixing them
- with <code class="literal">@</code>; for instance,
- <code class="literal">@wheel</code> means all users in the
- <code class="literal">wheel</code> group. The default is
- <code class="literal">root</code>.</p><div class="warning"><h3 class="title">Warning</h3><p>Adding a user to <code class="option">trusted-users</code>
- is essentially equivalent to giving that user root access to the
- system. For example, the user can set
- <code class="option">sandbox-paths</code> and thereby obtain read access to
- directories that are otherwise inacessible to
- them.</p></div></dd></dl></div><p>
-</p><div class="refsection"><a id="idm139733298856336"></a><h3>Deprecated Settings</h3><p>
-
-</p><div class="variablelist"><dl class="variablelist"><dt><a id="conf-binary-caches"></a><span class="term"><code class="literal">binary-caches</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
- <code class="literal">binary-caches</code> is now an alias to
- <a class="xref" href="#conf-substituters"><code class="literal">substituters</code></a>.</p></dd><dt><a id="conf-binary-cache-public-keys"></a><span class="term"><code class="literal">binary-cache-public-keys</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
- <code class="literal">binary-cache-public-keys</code> is now an alias to
- <a class="xref" href="#conf-trusted-public-keys"><code class="literal">trusted-public-keys</code></a>.</p></dd><dt><a id="conf-build-compress-log"></a><span class="term"><code class="literal">build-compress-log</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
- <code class="literal">build-compress-log</code> is now an alias to
- <a class="xref" href="#conf-compress-build-log"><code class="literal">compress-build-log</code></a>.</p></dd><dt><a id="conf-build-cores"></a><span class="term"><code class="literal">build-cores</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
- <code class="literal">build-cores</code> is now an alias to
- <a class="xref" href="#conf-cores"><code class="literal">cores</code></a>.</p></dd><dt><a id="conf-build-extra-chroot-dirs"></a><span class="term"><code class="literal">build-extra-chroot-dirs</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
- <code class="literal">build-extra-chroot-dirs</code> is now an alias to
- <a class="xref" href="#conf-extra-sandbox-paths"><code class="literal">extra-sandbox-paths</code></a>.</p></dd><dt><a id="conf-build-extra-sandbox-paths"></a><span class="term"><code class="literal">build-extra-sandbox-paths</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
- <code class="literal">build-extra-sandbox-paths</code> is now an alias to
- <a class="xref" href="#conf-extra-sandbox-paths"><code class="literal">extra-sandbox-paths</code></a>.</p></dd><dt><a id="conf-build-fallback"></a><span class="term"><code class="literal">build-fallback</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
- <code class="literal">build-fallback</code> is now an alias to
- <a class="xref" href="#conf-fallback"><code class="literal">fallback</code></a>.</p></dd><dt><a id="conf-build-max-jobs"></a><span class="term"><code class="literal">build-max-jobs</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
- <code class="literal">build-max-jobs</code> is now an alias to
- <a class="xref" href="#conf-max-jobs"><code class="literal">max-jobs</code></a>.</p></dd><dt><a id="conf-build-max-log-size"></a><span class="term"><code class="literal">build-max-log-size</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
- <code class="literal">build-max-log-size</code> is now an alias to
- <a class="xref" href="#conf-max-build-log-size"><code class="literal">max-build-log-size</code></a>.</p></dd><dt><a id="conf-build-max-silent-time"></a><span class="term"><code class="literal">build-max-silent-time</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
- <code class="literal">build-max-silent-time</code> is now an alias to
- <a class="xref" href="#conf-max-silent-time"><code class="literal">max-silent-time</code></a>.</p></dd><dt><a id="conf-build-repeat"></a><span class="term"><code class="literal">build-repeat</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
- <code class="literal">build-repeat</code> is now an alias to
- <a class="xref" href="#conf-repeat"><code class="literal">repeat</code></a>.</p></dd><dt><a id="conf-build-timeout"></a><span class="term"><code class="literal">build-timeout</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
- <code class="literal">build-timeout</code> is now an alias to
- <a class="xref" href="#conf-timeout"><code class="literal">timeout</code></a>.</p></dd><dt><a id="conf-build-use-chroot"></a><span class="term"><code class="literal">build-use-chroot</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
- <code class="literal">build-use-chroot</code> is now an alias to
- <a class="xref" href="#conf-sandbox"><code class="literal">sandbox</code></a>.</p></dd><dt><a id="conf-build-use-sandbox"></a><span class="term"><code class="literal">build-use-sandbox</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
- <code class="literal">build-use-sandbox</code> is now an alias to
- <a class="xref" href="#conf-sandbox"><code class="literal">sandbox</code></a>.</p></dd><dt><a id="conf-build-use-substitutes"></a><span class="term"><code class="literal">build-use-substitutes</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
- <code class="literal">build-use-substitutes</code> is now an alias to
- <a class="xref" href="#conf-substitute"><code class="literal">substitute</code></a>.</p></dd><dt><a id="conf-gc-keep-derivations"></a><span class="term"><code class="literal">gc-keep-derivations</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
- <code class="literal">gc-keep-derivations</code> is now an alias to
- <a class="xref" href="#conf-keep-derivations"><code class="literal">keep-derivations</code></a>.</p></dd><dt><a id="conf-gc-keep-outputs"></a><span class="term"><code class="literal">gc-keep-outputs</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
- <code class="literal">gc-keep-outputs</code> is now an alias to
- <a class="xref" href="#conf-keep-outputs"><code class="literal">keep-outputs</code></a>.</p></dd><dt><a id="conf-env-keep-derivations"></a><span class="term"><code class="literal">env-keep-derivations</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
- <code class="literal">env-keep-derivations</code> is now an alias to
- <a class="xref" href="#conf-keep-env-derivations"><code class="literal">keep-env-derivations</code></a>.</p></dd><dt><a id="conf-extra-binary-caches"></a><span class="term"><code class="literal">extra-binary-caches</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
- <code class="literal">extra-binary-caches</code> is now an alias to
- <a class="xref" href="#conf-extra-substituters"><code class="literal">extra-substituters</code></a>.</p></dd><dt><a id="conf-trusted-binary-caches"></a><span class="term"><code class="literal">trusted-binary-caches</code></span></dt><dd><p><span class="emphasis"><em>Deprecated:</em></span>
- <code class="literal">trusted-binary-caches</code> is now an alias to
- <a class="xref" href="#conf-trusted-substituters"><code class="literal">trusted-substituters</code></a>.</p></dd></dl></div><p>
-</p></div></div></div></div></div><div class="appendix"><div class="titlepage"><div><div><h1 class="title"><a id="part-glossary"></a>Appendix A. Glossary</h1></div></div></div><div class="glosslist"><dl><dt><a id="gloss-derivation"></a><span class="glossterm">derivation</span></dt><dd class="glossdef"><p>A description of a build action. The result of a
- derivation is a store object. Derivations are typically specified
- in Nix expressions using the <a class="link" href="#ssec-derivation" title="15.4. Derivations"><code class="function">derivation</code>
- primitive</a>. These are translated into low-level
- <span class="emphasis"><em>store derivations</em></span> (implicitly by
- <span class="command"><strong>nix-env</strong></span> and <span class="command"><strong>nix-build</strong></span>, or
- explicitly by <span class="command"><strong>nix-instantiate</strong></span>).</p></dd><dt><span class="glossterm">store</span></dt><dd class="glossdef"><p>The location in the file system where store objects
- live. Typically <code class="filename">/nix/store</code>.</p></dd><dt><span class="glossterm">store path</span></dt><dd class="glossdef"><p>The location in the file system of a store object,
- i.e., an immediate child of the Nix store
- directory.</p></dd><dt><span class="glossterm">store object</span></dt><dd class="glossdef"><p>A file that is an immediate child of the Nix store
- directory. These can be regular files, but also entire directory
- trees. Store objects can be sources (objects copied from outside of
- the store), derivation outputs (objects produced by running a build
- action), or derivations (files describing a build
- action).</p></dd><dt><a id="gloss-substitute"></a><span class="glossterm">substitute</span></dt><dd class="glossdef"><p>A substitute is a command invocation stored in the
- Nix database that describes how to build a store object, bypassing
- the normal build mechanism (i.e., derivations). Typically, the
- substitute builds the store object by downloading a pre-built
- version of the store object from some server.</p></dd><dt><span class="glossterm">purity</span></dt><dd class="glossdef"><p>The assumption that equal Nix derivations when run
- always produce the same output. This cannot be guaranteed in
- general (e.g., a builder can rely on external inputs such as the
- network or the system time) but the Nix model assumes
- it.</p></dd><dt><span class="glossterm">Nix expression</span></dt><dd class="glossdef"><p>A high-level description of software packages and
- compositions thereof. Deploying software using Nix entails writing
- Nix expressions for your packages. Nix expressions are translated
- to derivations that are stored in the Nix store. These derivations
- can then be built.</p></dd><dt><a id="gloss-reference"></a><span class="glossterm">reference</span></dt><dd class="glossdef"><p>A store path <code class="varname">P</code> is said to have a
- reference to a store path <code class="varname">Q</code> if the store object
- at <code class="varname">P</code> contains the path <code class="varname">Q</code>
- somewhere. The <span class="emphasis"><em>references</em></span> of a store path are
- the set of store paths to which it has a reference.
- </p><p>A derivation can reference other derivations and sources
- (but not output paths), whereas an output path only references other
- output paths.
- </p></dd><dt><a id="gloss-reachable"></a><span class="glossterm">reachable</span></dt><dd class="glossdef"><p>A store path <code class="varname">Q</code> is reachable from
- another store path <code class="varname">P</code> if <code class="varname">Q</code> is in the
- <a class="link" href="#gloss-closure" title="closure">closure</a> of the
- <a class="link" href="#gloss-reference" title="reference">references</a> relation.
- </p></dd><dt><a id="gloss-closure"></a><span class="glossterm">closure</span></dt><dd class="glossdef"><p>The closure of a store path is the set of store
- paths that are directly or indirectly “reachable” from that store
- path; that is, it’s the closure of the path under the <a class="link" href="#gloss-reference" title="reference">references</a> relation. For a package, the
- closure of its derivation is equivalent to the build-time
- dependencies, while the closure of its output path is equivalent to its
- runtime dependencies. For correct deployment it is necessary to deploy whole
- closures, since otherwise at runtime files could be missing. The command
- <span class="command"><strong>nix-store -qR</strong></span> prints out closures of store paths.
- </p><p>As an example, if the store object at path <code class="varname">P</code> contains
- a reference to path <code class="varname">Q</code>, then <code class="varname">Q</code> is
- in the closure of <code class="varname">P</code>. Further, if <code class="varname">Q</code>
- references <code class="varname">R</code> then <code class="varname">R</code> is also in
- the closure of <code class="varname">P</code>.
- </p></dd><dt><a id="gloss-output-path"></a><span class="glossterm">output path</span></dt><dd class="glossdef"><p>A store path produced by a derivation.</p></dd><dt><a id="gloss-deriver"></a><span class="glossterm">deriver</span></dt><dd class="glossdef"><p>The deriver of an <a class="link" href="#gloss-output-path" title="output path">output path</a> is the store
- derivation that built it.</p></dd><dt><a id="gloss-validity"></a><span class="glossterm">validity</span></dt><dd class="glossdef"><p>A store path is considered
- <span class="emphasis"><em>valid</em></span> if it exists in the file system, is
- listed in the Nix database as being valid, and if all paths in its
- closure are also valid.</p></dd><dt><a id="gloss-user-env"></a><span class="glossterm">user environment</span></dt><dd class="glossdef"><p>An automatically generated store object that
- consists of a set of symlinks to “active” applications, i.e., other
- store paths. These are generated automatically by <a class="link" href="#sec-nix-env" title="nix-env"><span class="command"><strong>nix-env</strong></span></a>. See <a class="xref" href="#sec-profiles" title="Chapter 10. Profiles">Chapter 10, <em>Profiles</em></a>.</p></dd><dt><a id="gloss-profile"></a><span class="glossterm">profile</span></dt><dd class="glossdef"><p>A symlink to the current <a class="link" href="#gloss-user-env" title="user environment">user environment</a> of a user, e.g.,
- <code class="filename">/nix/var/nix/profiles/default</code>.</p></dd><dt><a id="gloss-nar"></a><span class="glossterm">NAR</span></dt><dd class="glossdef"><p>A <span class="emphasis"><em>N</em></span>ix
- <span class="emphasis"><em>AR</em></span>chive. This is a serialisation of a path in
- the Nix store. It can contain regular files, directories and
- symbolic links. NARs are generated and unpacked using
- <span class="command"><strong>nix-store --dump</strong></span> and <span class="command"><strong>nix-store
- --restore</strong></span>.</p></dd></dl></div></div><div class="appendix"><div class="titlepage"><div><div><h1 class="title"><a id="chap-hacking"></a>Appendix B. Hacking</h1></div></div></div><p>This section provides some notes on how to hack on Nix. To get
-the latest version of Nix from GitHub:
-</p><pre class="screen">
-$ git clone https://github.com/NixOS/nix.git
-$ cd nix
-</pre><p>
-</p><p>To build Nix for the current operating system/architecture use
-
-</p><pre class="screen">
-$ nix-build
-</pre><p>
-
-or if you have a flakes-enabled nix:
-
-</p><pre class="screen">
-$ nix build
-</pre><p>
-
-This will build <code class="literal">defaultPackage</code> attribute defined in the <code class="literal">flake.nix</code> file.
-
-To build for other platforms add one of the following suffixes to it: aarch64-linux,
-i686-linux, x86_64-darwin, x86_64-linux.
-
-i.e.
-
-</p><pre class="screen">
-nix-build -A defaultPackage.x86_64-linux
-</pre><p>
-
-</p><p>To build all dependencies and start a shell in which all
-environment variables are set up so that those dependencies can be
-found:
-</p><pre class="screen">
-$ nix-shell
-</pre><p>
-To build Nix itself in this shell:
-</p><pre class="screen">
-[nix-shell]$ ./bootstrap.sh
-[nix-shell]$ ./configure $configureFlags
-[nix-shell]$ make -j $NIX_BUILD_CORES
-</pre><p>
-To install it in <code class="literal">$(pwd)/inst</code> and test it:
-</p><pre class="screen">
-[nix-shell]$ make install
-[nix-shell]$ make installcheck
-[nix-shell]$ ./inst/bin/nix --version
-nix (Nix) 2.4
-</pre><p>
-
-If you have a flakes-enabled nix you can replace:
-
-</p><pre class="screen">
-$ nix-shell
-</pre><p>
-
-by:
-
-</p><pre class="screen">
-$ nix develop
-</pre><p>
-
-</p></div><div class="appendix"><div class="titlepage"><div><div><h1 class="title"><a id="sec-relnotes"></a>Appendix C. Nix Release Notes</h1></div></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-2.3"></a>C.1. Release 2.3 (2019-09-04)</h2></div></div></div><p>This is primarily a bug fix release. However, it makes some
-incompatible changes:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Nix now uses BSD file locks instead of POSIX file
- locks. Because of this, you should not use Nix 2.3 and previous
- releases at the same time on a Nix store.</p></li></ul></div><p>It also has the following changes:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><code class="function">builtins.fetchGit</code>'s <code class="varname">ref</code>
- argument now allows specifying an absolute remote ref.
- Nix will automatically prefix <code class="varname">ref</code> with
- <code class="literal">refs/heads</code> only if <code class="varname">ref</code> doesn't
- already begin with <code class="literal">refs/</code>.
- </p></li><li class="listitem"><p>The installer now enables sandboxing by default on Linux when the
- system has the necessary kernel support.
- </p></li><li class="listitem"><p>The <code class="literal">max-jobs</code> setting now defaults to 1.</p></li><li class="listitem"><p>New builtin functions:
- <code class="literal">builtins.isPath</code>,
- <code class="literal">builtins.hashFile</code>.
- </p></li><li class="listitem"><p>The <span class="command"><strong>nix</strong></span> command has a new
- <code class="option">--print-build-logs</code> (<code class="option">-L</code>) flag to
- print build log output to stderr, rather than showing the last log
- line in the progress bar. To distinguish between concurrent
- builds, log lines are prefixed by the name of the package.
- </p></li><li class="listitem"><p>Builds are now executed in a pseudo-terminal, and the
- <code class="envar">TERM</code> environment variable is set to
- <code class="literal">xterm-256color</code>. This allows many programs
- (e.g. <span class="command"><strong>gcc</strong></span>, <span class="command"><strong>clang</strong></span>,
- <span class="command"><strong>cmake</strong></span>) to print colorized log output.</p></li><li class="listitem"><p>Add <code class="option">--no-net</code> convenience flag. This flag
- disables substituters; sets the <code class="literal">tarball-ttl</code>
- setting to infinity (ensuring that any previously downloaded files
- are considered current); and disables retrying downloads and sets
- the connection timeout to the minimum. This flag is enabled
- automatically if there are no configured non-loopback network
- interfaces.</p></li><li class="listitem"><p>Add a <code class="literal">post-build-hook</code> setting to run a
- program after a build has succeeded.</p></li><li class="listitem"><p>Add a <code class="literal">trace-function-calls</code> setting to log
- the duration of Nix function calls to stderr.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-2.2"></a>C.2. Release 2.2 (2019-01-11)</h2></div></div></div><p>This is primarily a bug fix release. It also has the following
-changes:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>In derivations that use structured attributes (i.e. that
- specify set the <code class="varname">__structuredAttrs</code> attribute to
- <code class="literal">true</code> to cause all attributes to be passed to
- the builder in JSON format), you can now specify closure checks
- per output, e.g.:
-
-</p><pre class="programlisting">
-outputChecks."out" = {
- # The closure of 'out' must not be larger than 256 MiB.
- maxClosureSize = 256 * 1024 * 1024;
-
- # It must not refer to C compiler or to the 'dev' output.
- disallowedRequisites = [ stdenv.cc "dev" ];
-};
-
-outputChecks."dev" = {
- # The 'dev' output must not be larger than 128 KiB.
- maxSize = 128 * 1024;
-};
-</pre><p>
-
- </p></li><li class="listitem"><p>The derivation attribute
- <code class="varname">requiredSystemFeatures</code> is now enforced for
- local builds, and not just to route builds to remote builders.
- The supported features of a machine can be specified through the
- configuration setting <code class="varname">system-features</code>.</p><p>By default, <code class="varname">system-features</code> includes
- <code class="literal">kvm</code> if <code class="filename">/dev/kvm</code>
- exists. For compatibility, it also includes the pseudo-features
- <code class="literal">nixos-test</code>, <code class="literal">benchmark</code> and
- <code class="literal">big-parallel</code> which are used by Nixpkgs to route
- builds to particular Hydra build machines.</p></li><li class="listitem"><p>Sandbox builds are now enabled by default on Linux.</p></li><li class="listitem"><p>The new command <span class="command"><strong>nix doctor</strong></span> shows
- potential issues with your Nix installation.</p></li><li class="listitem"><p>The <code class="literal">fetchGit</code> builtin function now uses a
- caching scheme that puts different remote repositories in distinct
- local repositories, rather than a single shared repository. This
- may require more disk space but is faster.</p></li><li class="listitem"><p>The <code class="literal">dirOf</code> builtin function now works on
- relative paths.</p></li><li class="listitem"><p>Nix now supports <a class="link" href="https://www.w3.org/TR/SRI/" target="_top">SRI hashes</a>,
- allowing the hash algorithm and hash to be specified in a single
- string. For example, you can write:
-
-</p><pre class="programlisting">
-import <nix/fetchurl.nix> {
- url = https://nixos.org/releases/nix/nix-2.1.3/nix-2.1.3.tar.xz;
- hash = "sha256-XSLa0FjVyADWWhFfkZ2iKTjFDda6mMXjoYMXLRSYQKQ=";
-};
-</pre><p>
-
- instead of
-
-</p><pre class="programlisting">
-import <nix/fetchurl.nix> {
- url = https://nixos.org/releases/nix/nix-2.1.3/nix-2.1.3.tar.xz;
- sha256 = "5d22dad058d5c800d65a115f919da22938c50dd6ba98c5e3a183172d149840a4";
-};
-</pre><p>
-
- </p><p>In fixed-output derivations, the
- <code class="varname">outputHashAlgo</code> attribute is no longer mandatory
- if <code class="varname">outputHash</code> specifies the hash.</p><p><span class="command"><strong>nix hash-file</strong></span> and <span class="command"><strong>nix
- hash-path</strong></span> now print hashes in SRI format by
- default. They also use SHA-256 by default instead of SHA-512
- because that's what we use most of the time in Nixpkgs.</p></li><li class="listitem"><p>Integers are now 64 bits on all platforms.</p></li><li class="listitem"><p>The evaluator now prints profiling statistics (enabled via
- the <code class="envar">NIX_SHOW_STATS</code> and
- <code class="envar">NIX_COUNT_CALLS</code> environment variables) in JSON
- format.</p></li><li class="listitem"><p>The option <code class="option">--xml</code> in <span class="command"><strong>nix-store
- --query</strong></span> has been removed. Instead, there now is an
- option <code class="option">--graphml</code> to output the dependency graph
- in GraphML format.</p></li><li class="listitem"><p>All <code class="filename">nix-*</code> commands are now symlinks to
- <code class="filename">nix</code>. This saves a bit of disk space.</p></li><li class="listitem"><p><span class="command"><strong>nix repl</strong></span> now uses
- <code class="literal">libeditline</code> or
- <code class="literal">libreadline</code>.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-2.1"></a>C.3. Release 2.1 (2018-09-02)</h2></div></div></div><p>This is primarily a bug fix release. It also reduces memory
-consumption in certain situations. In addition, it has the following
-new features:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>The Nix installer will no longer default to the Multi-User
- installation for macOS. You can still <a class="link" href="#sect-multi-user-installation" title="4.2. Multi User Installation">instruct the installer to
- run in multi-user mode</a>.
- </p></li><li class="listitem"><p>The Nix installer now supports performing a Multi-User
- installation for Linux computers which are running systemd. You
- can <a class="link" href="#sect-multi-user-installation" title="4.2. Multi User Installation">select a Multi-User installation</a> by passing the
- <code class="option">--daemon</code> flag to the installer: <span class="command"><strong>sh <(curl
- https://nixos.org/nix/install) --daemon</strong></span>.
- </p><p>The multi-user installer cannot handle systems with SELinux.
- If your system has SELinux enabled, you can <a class="link" href="#sect-single-user-installation" title="4.1. Single User Installation">force the installer to run
- in single-user mode</a>.</p></li><li class="listitem"><p>New builtin functions:
- <code class="literal">builtins.bitAnd</code>,
- <code class="literal">builtins.bitOr</code>,
- <code class="literal">builtins.bitXor</code>,
- <code class="literal">builtins.fromTOML</code>,
- <code class="literal">builtins.concatMap</code>,
- <code class="literal">builtins.mapAttrs</code>.
- </p></li><li class="listitem"><p>The S3 binary cache store now supports uploading NARs larger
- than 5 GiB.</p></li><li class="listitem"><p>The S3 binary cache store now supports uploading to
- S3-compatible services with the <code class="literal">endpoint</code>
- option.</p></li><li class="listitem"><p>The flag <code class="option">--fallback</code> is no longer required
- to recover from disappeared NARs in binary caches.</p></li><li class="listitem"><p><span class="command"><strong>nix-daemon</strong></span> now respects
- <code class="option">--store</code>.</p></li><li class="listitem"><p><span class="command"><strong>nix run</strong></span> now respects
- <code class="varname">nix-support/propagated-user-env-packages</code>.</p></li></ul></div><p>This release has contributions from
-
-Adrien Devresse,
-Aleksandr Pashkov,
-Alexandre Esteves,
-Amine Chikhaoui,
-Andrew Dunham,
-Asad Saeeduddin,
-aszlig,
-Ben Challenor,
-Ben Gamari,
-Benjamin Hipple,
-Bogdan Seniuc,
-Corey O'Connor,
-Daiderd Jordan,
-Daniel Peebles,
-Daniel Poelzleithner,
-Danylo Hlynskyi,
-Dmitry Kalinkin,
-Domen Kožar,
-Doug Beardsley,
-Eelco Dolstra,
-Erik Arvstedt,
-Félix Baylac-Jacqué,
-Gleb Peregud,
-Graham Christensen,
-Guillaume Maudoux,
-Ivan Kozik,
-John Arnold,
-Justin Humm,
-Linus Heckemann,
-Lorenzo Manacorda,
-Matthew Justin Bauer,
-Matthew O'Gorman,
-Maximilian Bosch,
-Michael Bishop,
-Michael Fiano,
-Michael Mercier,
-Michael Raskin,
-Michael Weiss,
-Nicolas Dudebout,
-Peter Simons,
-Ryan Trinkle,
-Samuel Dionne-Riel,
-Sean Seefried,
-Shea Levy,
-Symphorien Gibol,
-Tim Engler,
-Tim Sears,
-Tuomas Tynkkynen,
-volth,
-Will Dietz,
-Yorick van Pelt and
-zimbatm.
-</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-2.0"></a>C.4. Release 2.0 (2018-02-22)</h2></div></div></div><p>The following incompatible changes have been made:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>The manifest-based substituter mechanism
- (<span class="command"><strong>download-using-manifests</strong></span>) has been <a class="link" href="https://github.com/NixOS/nix/commit/867967265b80946dfe1db72d40324b4f9af988ed" target="_top">removed</a>. It
- has been superseded by the binary cache substituter mechanism
- since several years. As a result, the following programs have been
- removed:
-
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p><span class="command"><strong>nix-pull</strong></span></p></li><li class="listitem"><p><span class="command"><strong>nix-generate-patches</strong></span></p></li><li class="listitem"><p><span class="command"><strong>bsdiff</strong></span></p></li><li class="listitem"><p><span class="command"><strong>bspatch</strong></span></p></li></ul></div><p>
- </p></li><li class="listitem"><p>The “copy from other stores” substituter mechanism
- (<span class="command"><strong>copy-from-other-stores</strong></span> and the
- <code class="envar">NIX_OTHER_STORES</code> environment variable) has been
- removed. It was primarily used by the NixOS installer to copy
- available paths from the installation medium. The replacement is
- to use a chroot store as a substituter
- (e.g. <code class="literal">--substituters /mnt</code>), or to build into a
- chroot store (e.g. <code class="literal">--store /mnt --substituters /</code>).</p></li><li class="listitem"><p>The command <span class="command"><strong>nix-push</strong></span> has been removed as
- part of the effort to eliminate Nix's dependency on Perl. You can
- use <span class="command"><strong>nix copy</strong></span> instead, e.g. <code class="literal">nix copy
- --to file:///tmp/my-binary-cache <em class="replaceable"><code>paths…</code></em></code></p></li><li class="listitem"><p>The “nested” log output feature (<code class="option">--log-type
- pretty</code>) has been removed. As a result,
- <span class="command"><strong>nix-log2xml</strong></span> was also removed.</p></li><li class="listitem"><p>OpenSSL-based signing has been <a class="link" href="https://github.com/NixOS/nix/commit/f435f8247553656774dd1b2c88e9de5d59cab203" target="_top">removed</a>. This
- feature was never well-supported. A better alternative is provided
- by the <code class="option">secret-key-files</code> and
- <code class="option">trusted-public-keys</code> options.</p></li><li class="listitem"><p>Failed build caching has been <a class="link" href="https://github.com/NixOS/nix/commit/8cffec84859cec8b610a2a22ab0c4d462a9351ff" target="_top">removed</a>. This
- feature was introduced to support the Hydra continuous build
- system, but Hydra no longer uses it.</p></li><li class="listitem"><p><code class="filename">nix-mode.el</code> has been removed from
- Nix. It is now <a class="link" href="https://github.com/NixOS/nix-mode" target="_top">a separate
- repository</a> and can be installed through the MELPA package
- repository.</p></li></ul></div><p>This release has the following new features:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>It introduces a new command named <span class="command"><strong>nix</strong></span>,
- which is intended to eventually replace all
- <span class="command"><strong>nix-*</strong></span> commands with a more consistent and
- better designed user interface. It currently provides replacements
- for some (but not all) of the functionality provided by
- <span class="command"><strong>nix-store</strong></span>, <span class="command"><strong>nix-build</strong></span>,
- <span class="command"><strong>nix-shell -p</strong></span>, <span class="command"><strong>nix-env -qa</strong></span>,
- <span class="command"><strong>nix-instantiate --eval</strong></span>,
- <span class="command"><strong>nix-push</strong></span> and
- <span class="command"><strong>nix-copy-closure</strong></span>. It has the following major
- features:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Unlike the legacy commands, it has a consistent way to
- refer to packages and package-like arguments (like store
- paths). For example, the following commands all copy the GNU
- Hello package to a remote machine:
-
- </p><pre class="screen">nix copy --to ssh://machine nixpkgs.hello</pre><p>
- </p><pre class="screen">nix copy --to ssh://machine /nix/store/0i2jd68mp5g6h2sa5k9c85rb80sn8hi9-hello-2.10</pre><p>
- </p><pre class="screen">nix copy --to ssh://machine '(with import <nixpkgs> {}; hello)'</pre><p>
-
- By contrast, <span class="command"><strong>nix-copy-closure</strong></span> only accepted
- store paths as arguments.</p></li><li class="listitem"><p>It is self-documenting: <code class="option">--help</code> shows
- all available command-line arguments. If
- <code class="option">--help</code> is given after a subcommand, it shows
- examples for that subcommand. <span class="command"><strong>nix
- --help-config</strong></span> shows all configuration
- options.</p></li><li class="listitem"><p>It is much less verbose. By default, it displays a
- single-line progress indicator that shows how many packages
- are left to be built or downloaded, and (if there are running
- builds) the most recent line of builder output. If a build
- fails, it shows the last few lines of builder output. The full
- build log can be retrieved using <span class="command"><strong>nix
- log</strong></span>.</p></li><li class="listitem"><p>It <a class="link" href="https://github.com/NixOS/nix/commit/b8283773bd64d7da6859ed520ee19867742a03ba" target="_top">provides</a>
- all <code class="filename">nix.conf</code> configuration options as
- command line flags. For example, instead of <code class="literal">--option
- http-connections 100</code> you can write
- <code class="literal">--http-connections 100</code>. Boolean options can
- be written as
- <code class="literal">--<em class="replaceable"><code>foo</code></em></code> or
- <code class="literal">--no-<em class="replaceable"><code>foo</code></em></code>
- (e.g. <code class="option">--no-auto-optimise-store</code>).</p></li><li class="listitem"><p>Many subcommands have a <code class="option">--json</code> flag to
- write results to stdout in JSON format.</p></li></ul></div><div class="warning"><h3 class="title">Warning</h3><p>Please note that the <span class="command"><strong>nix</strong></span> command
- is a work in progress and the interface is subject to
- change.</p></div><p>It provides the following high-level (“porcelain”)
- subcommands:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p><span class="command"><strong>nix build</strong></span> is a replacement for
- <span class="command"><strong>nix-build</strong></span>.</p></li><li class="listitem"><p><span class="command"><strong>nix run</strong></span> executes a command in an
- environment in which the specified packages are available. It
- is (roughly) a replacement for <span class="command"><strong>nix-shell
- -p</strong></span>. Unlike that command, it does not execute the
- command in a shell, and has a flag (<span class="command"><strong>-c</strong></span>)
- that specifies the unquoted command line to be
- executed.</p><p>It is particularly useful in conjunction with chroot
- stores, allowing Linux users who do not have permission to
- install Nix in <span class="command"><strong>/nix/store</strong></span> to still use
- binary substitutes that assume
- <span class="command"><strong>/nix/store</strong></span>. For example,
-
- </p><pre class="screen">nix run --store ~/my-nix nixpkgs.hello -c hello --greeting 'Hi everybody!'</pre><p>
-
- downloads (or if not substitutes are available, builds) the
- GNU Hello package into
- <code class="filename">~/my-nix/nix/store</code>, then runs
- <span class="command"><strong>hello</strong></span> in a mount namespace where
- <code class="filename">~/my-nix/nix/store</code> is mounted onto
- <span class="command"><strong>/nix/store</strong></span>.</p></li><li class="listitem"><p><span class="command"><strong>nix search</strong></span> replaces <span class="command"><strong>nix-env
- -qa</strong></span>. It searches the available packages for
- occurrences of a search string in the attribute name, package
- name or description. Unlike <span class="command"><strong>nix-env -qa</strong></span>, it
- has a cache to speed up subsequent searches.</p></li><li class="listitem"><p><span class="command"><strong>nix copy</strong></span> copies paths between
- arbitrary Nix stores, generalising
- <span class="command"><strong>nix-copy-closure</strong></span> and
- <span class="command"><strong>nix-push</strong></span>.</p></li><li class="listitem"><p><span class="command"><strong>nix repl</strong></span> replaces the external
- program <span class="command"><strong>nix-repl</strong></span>. It provides an
- interactive environment for evaluating and building Nix
- expressions. Note that it uses <code class="literal">linenoise-ng</code>
- instead of GNU Readline.</p></li><li class="listitem"><p><span class="command"><strong>nix upgrade-nix</strong></span> upgrades Nix to the
- latest stable version. This requires that Nix is installed in
- a profile. (Thus it won’t work on NixOS, or if it’s installed
- outside of the Nix store.)</p></li><li class="listitem"><p><span class="command"><strong>nix verify</strong></span> checks whether store paths
- are unmodified and/or “trusted” (see below). It replaces
- <span class="command"><strong>nix-store --verify</strong></span> and <span class="command"><strong>nix-store
- --verify-path</strong></span>.</p></li><li class="listitem"><p><span class="command"><strong>nix log</strong></span> shows the build log of a
- package or path. If the build log is not available locally, it
- will try to obtain it from the configured substituters (such
- as <code class="uri">cache.nixos.org</code>, which now provides build
- logs).</p></li><li class="listitem"><p><span class="command"><strong>nix edit</strong></span> opens the source code of a
- package in your editor.</p></li><li class="listitem"><p><span class="command"><strong>nix eval</strong></span> replaces
- <span class="command"><strong>nix-instantiate --eval</strong></span>.</p></li><li class="listitem"><p><span class="command"><strong><a class="command" href="https://github.com/NixOS/nix/commit/d41c5eb13f4f3a37d80dbc6d3888644170c3b44a" target="_top">nix
- why-depends</a></strong></span> shows why one store path has another in
- its closure. This is primarily useful to finding the causes of
- closure bloat. For example,
-
- </p><pre class="screen">nix why-depends nixpkgs.vlc nixpkgs.libdrm.dev</pre><p>
-
- shows a chain of files and fragments of file contents that
- cause the VLC package to have the “dev” output of
- <code class="literal">libdrm</code> in its closure — an undesirable
- situation.</p></li><li class="listitem"><p><span class="command"><strong>nix path-info</strong></span> shows information about
- store paths, replacing <span class="command"><strong>nix-store -q</strong></span>. A
- useful feature is the option <code class="option">--closure-size</code>
- (<code class="option">-S</code>). For example, the following command show
- the closure sizes of every path in the current NixOS system
- closure, sorted by size:
-
- </p><pre class="screen">nix path-info -rS /run/current-system | sort -nk2</pre><p>
-
- </p></li><li class="listitem"><p><span class="command"><strong>nix optimise-store</strong></span> replaces
- <span class="command"><strong>nix-store --optimise</strong></span>. The main difference
- is that it has a progress indicator.</p></li></ul></div><p>A number of low-level (“plumbing”) commands are also
- available:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p><span class="command"><strong>nix ls-store</strong></span> and <span class="command"><strong>nix
- ls-nar</strong></span> list the contents of a store path or NAR
- file. The former is primarily useful in conjunction with
- remote stores, e.g.
-
- </p><pre class="screen">nix ls-store --store https://cache.nixos.org/ -lR /nix/store/0i2jd68mp5g6h2sa5k9c85rb80sn8hi9-hello-2.10</pre><p>
-
- lists the contents of path in a binary cache.</p></li><li class="listitem"><p><span class="command"><strong>nix cat-store</strong></span> and <span class="command"><strong>nix
- cat-nar</strong></span> allow extracting a file from a store path or
- NAR file.</p></li><li class="listitem"><p><span class="command"><strong>nix dump-path</strong></span> writes the contents of
- a store path to stdout in NAR format. This replaces
- <span class="command"><strong>nix-store --dump</strong></span>.</p></li><li class="listitem"><p><span class="command"><strong><a class="command" href="https://github.com/NixOS/nix/commit/e8d6ee7c1b90a2fe6d824f1a875acc56799ae6e2" target="_top">nix
- show-derivation</a></strong></span> displays a store derivation in JSON
- format. This is an alternative to
- <span class="command"><strong>pp-aterm</strong></span>.</p></li><li class="listitem"><p><span class="command"><strong><a class="command" href="https://github.com/NixOS/nix/commit/970366266b8df712f5f9cedb45af183ef5a8357f" target="_top">nix
- add-to-store</a></strong></span> replaces <span class="command"><strong>nix-store
- --add</strong></span>.</p></li><li class="listitem"><p><span class="command"><strong>nix sign-paths</strong></span> signs store
- paths.</p></li><li class="listitem"><p><span class="command"><strong>nix copy-sigs</strong></span> copies signatures from
- one store to another.</p></li><li class="listitem"><p><span class="command"><strong>nix show-config</strong></span> shows all
- configuration options and their current values.</p></li></ul></div></li><li class="listitem"><p>The store abstraction that Nix has had for a long time to
- support store access via the Nix daemon has been extended
- significantly. In particular, substituters (which used to be
- external programs such as
- <span class="command"><strong>download-from-binary-cache</strong></span>) are now subclasses
- of the abstract <code class="classname">Store</code> class. This allows
- many Nix commands to operate on such store types. For example,
- <span class="command"><strong>nix path-info</strong></span> shows information about paths in
- your local Nix store, while <span class="command"><strong>nix path-info --store
- https://cache.nixos.org/</strong></span> shows information about paths
- in the specified binary cache. Similarly,
- <span class="command"><strong>nix-copy-closure</strong></span>, <span class="command"><strong>nix-push</strong></span>
- and substitution are all instances of the general notion of
- copying paths between different kinds of Nix stores.</p><p>Stores are specified using an URI-like syntax,
- e.g. <code class="uri">https://cache.nixos.org/</code> or
- <code class="uri">ssh://machine</code>. The following store types are supported:
-
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p><code class="classname">LocalStore</code> (stori URI
- <code class="literal">local</code> or an absolute path) and the misnamed
- <code class="classname">RemoteStore</code> (<code class="literal">daemon</code>)
- provide access to a local Nix store, the latter via the Nix
- daemon. You can use <code class="literal">auto</code> or the empty
- string to auto-select a local or daemon store depending on
- whether you have write permission to the Nix store. It is no
- longer necessary to set the <code class="envar">NIX_REMOTE</code>
- environment variable to use the Nix daemon.</p><p>As noted above, <code class="classname">LocalStore</code> now
- supports chroot builds, allowing the “physical” location of
- the Nix store
- (e.g. <code class="filename">/home/alice/nix/store</code>) to differ
- from its “logical” location (typically
- <code class="filename">/nix/store</code>). This allows non-root users
- to use Nix while still getting the benefits from prebuilt
- binaries from <code class="uri">cache.nixos.org</code>.</p></li><li class="listitem"><p><code class="classname">BinaryCacheStore</code> is the abstract
- superclass of all binary cache stores. It supports writing
- build logs and NAR content listings in JSON format.</p></li><li class="listitem"><p><code class="classname">HttpBinaryCacheStore</code>
- (<code class="literal">http://</code>, <code class="literal">https://</code>)
- supports binary caches via HTTP or HTTPS. If the server
- supports <code class="literal">PUT</code> requests, it supports
- uploading store paths via commands such as <span class="command"><strong>nix
- copy</strong></span>.</p></li><li class="listitem"><p><code class="classname">LocalBinaryCacheStore</code>
- (<code class="literal">file://</code>) supports binary caches in the
- local filesystem.</p></li><li class="listitem"><p><code class="classname">S3BinaryCacheStore</code>
- (<code class="literal">s3://</code>) supports binary caches stored in
- Amazon S3, if enabled at compile time.</p></li><li class="listitem"><p><code class="classname">LegacySSHStore</code> (<code class="literal">ssh://</code>)
- is used to implement remote builds and
- <span class="command"><strong>nix-copy-closure</strong></span>.</p></li><li class="listitem"><p><code class="classname">SSHStore</code>
- (<code class="literal">ssh-ng://</code>) supports arbitrary Nix
- operations on a remote machine via the same protocol used by
- <span class="command"><strong>nix-daemon</strong></span>.</p></li></ul></div><p>
-
- </p></li><li class="listitem"><p>Security has been improved in various ways:
-
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Nix now stores signatures for local store
- paths. When paths are copied between stores (e.g., copied from
- a binary cache to a local store), signatures are
- propagated.</p><p>Locally-built paths are signed automatically using the
- secret keys specified by the <code class="option">secret-key-files</code>
- store option. Secret/public key pairs can be generated using
- <span class="command"><strong>nix-store
- --generate-binary-cache-key</strong></span>.</p><p>In addition, locally-built store paths are marked as
- “ultimately trusted”, but this bit is not propagated when
- paths are copied between stores.</p></li><li class="listitem"><p>Content-addressable store paths no longer require
- signatures — they can be imported into a store by unprivileged
- users even if they lack signatures.</p></li><li class="listitem"><p>The command <span class="command"><strong>nix verify</strong></span> checks whether
- the specified paths are trusted, i.e., have a certain number
- of trusted signatures, are ultimately trusted, or are
- content-addressed.</p></li><li class="listitem"><p>Substitutions from binary caches <a class="link" href="https://github.com/NixOS/nix/commit/ecbc3fedd3d5bdc5a0e1a0a51b29062f2874ac8b" target="_top">now</a>
- require signatures by default. This was already the case on
- NixOS.</p></li><li class="listitem"><p>In Linux sandbox builds, we <a class="link" href="https://github.com/NixOS/nix/commit/eba840c8a13b465ace90172ff76a0db2899ab11b" target="_top">now</a>
- use <code class="filename">/build</code> instead of
- <code class="filename">/tmp</code> as the temporary build
- directory. This fixes potential security problems when a build
- accidentally stores its <code class="envar">TMPDIR</code> in some
- security-sensitive place, such as an RPATH.</p></li></ul></div><p>
-
- </p></li><li class="listitem"><p><span class="emphasis"><em>Pure evaluation mode</em></span>. With the
- <code class="literal">--pure-eval</code> flag, Nix enables a variant of the existing
- restricted evaluation mode that forbids access to anything that could cause
- different evaluations of the same command line arguments to produce a
- different result. This includes builtin functions such as
- <code class="function">builtins.getEnv</code>, but more importantly,
- <span class="emphasis"><em>all</em></span> filesystem or network access unless a content hash
- or commit hash is specified. For example, calls to
- <code class="function">builtins.fetchGit</code> are only allowed if a
- <code class="varname">rev</code> attribute is specified.</p><p>The goal of this feature is to enable true reproducibility
- and traceability of builds (including NixOS system configurations)
- at the evaluation level. For example, in the future,
- <span class="command"><strong>nixos-rebuild</strong></span> might build configurations from a
- Nix expression in a Git repository in pure mode. That expression
- might fetch other repositories such as Nixpkgs via
- <code class="function">builtins.fetchGit</code>. The commit hash of the
- top-level repository then uniquely identifies a running system,
- and, in conjunction with that repository, allows it to be
- reproduced or modified.</p></li><li class="listitem"><p>There are several new features to support binary
- reproducibility (i.e. to help ensure that multiple builds of the
- same derivation produce exactly the same output). When
- <code class="option">enforce-determinism</code> is set to
- <code class="literal">false</code>, it’s <a class="link" href="https://github.com/NixOS/nix/commit/8bdf83f936adae6f2c907a6d2541e80d4120f051" target="_top">no
- longer</a> a fatal error if build rounds produce different
- output. Also, a hook named <code class="option">diff-hook</code> is <a class="link" href="https://github.com/NixOS/nix/commit/9a313469a4bdea2d1e8df24d16289dc2a172a169" target="_top">provided</a>
- to allow you to run tools such as <span class="command"><strong>diffoscope</strong></span>
- when build rounds produce different output.</p></li><li class="listitem"><p>Configuring remote builds is a lot easier now. Provided you
- are not using the Nix daemon, you can now just specify a remote
- build machine on the command line, e.g. <code class="literal">--option builders
- 'ssh://my-mac x86_64-darwin'</code>. The environment variable
- <code class="envar">NIX_BUILD_HOOK</code> has been removed and is no longer
- needed. The environment variable <code class="envar">NIX_REMOTE_SYSTEMS</code>
- is still supported for compatibility, but it is also possible to
- specify builders in <span class="command"><strong>nix.conf</strong></span> by setting the
- option <code class="literal">builders =
- @<em class="replaceable"><code>path</code></em></code>.</p></li><li class="listitem"><p>If a fixed-output derivation produces a result with an
- incorrect hash, the output path is moved to the location
- corresponding to the actual hash and registered as valid. Thus, a
- subsequent build of the fixed-output derivation with the correct
- hash is unnecessary.</p></li><li class="listitem"><p><span class="command"><strong>nix-shell</strong></span> <a class="link" href="https://github.com/NixOS/nix/commit/ea59f39326c8e9dc42dfed4bcbf597fbce58797c" target="_top">now</a>
- sets the <code class="varname">IN_NIX_SHELL</code> environment variable
- during evaluation and in the shell itself. This can be used to
- perform different actions depending on whether you’re in a Nix
- shell or in a regular build. Nixpkgs provides
- <code class="varname">lib.inNixShell</code> to check this variable during
- evaluation.</p></li><li class="listitem"><p><code class="envar">NIX_PATH</code> is now lazy, so URIs in the path are
- only downloaded if they are needed for evaluation.</p></li><li class="listitem"><p>You can now use
- <code class="uri">channel:<em class="replaceable"><code>channel-name</code></em></code> as a
- short-hand for
- <code class="uri">https://nixos.org/channels/<em class="replaceable"><code>channel-name</code></em>/nixexprs.tar.xz</code>. For
- example, <code class="literal">nix-build channel:nixos-15.09 -A hello</code>
- will build the GNU Hello package from the
- <code class="literal">nixos-15.09</code> channel. In the future, this may
- use Git to fetch updates more efficiently.</p></li><li class="listitem"><p>When <code class="option">--no-build-output</code> is given, the last
- 10 lines of the build log will be shown if a build
- fails.</p></li><li class="listitem"><p>Networking has been improved:
-
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>HTTP/2 is now supported. This makes binary cache lookups
- <a class="link" href="https://github.com/NixOS/nix/commit/90ad02bf626b885a5dd8967894e2eafc953bdf92" target="_top">much
- more efficient</a>.</p></li><li class="listitem"><p>We now retry downloads on many HTTP errors, making
- binary caches substituters more resilient to temporary
- failures.</p></li><li class="listitem"><p>HTTP credentials can now be configured via the standard
- <code class="filename">netrc</code> mechanism.</p></li><li class="listitem"><p>If S3 support is enabled at compile time,
- <code class="uri">s3://</code> URIs are <a class="link" href="https://github.com/NixOS/nix/commit/9ff9c3f2f80ba4108e9c945bbfda2c64735f987b" target="_top">supported</a>
- in all places where Nix allows URIs.</p></li><li class="listitem"><p>Brotli compression is now supported. In particular,
- <code class="uri">cache.nixos.org</code> build logs are now compressed using
- Brotli.</p></li></ul></div><p>
-
- </p></li><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> <a class="link" href="https://github.com/NixOS/nix/commit/b0cb11722626e906a73f10dd9a0c9eea29faf43a" target="_top">now</a>
- ignores packages with bad derivation names (in particular those
- starting with a digit or containing a dot).</p></li><li class="listitem"><p>Many configuration options have been renamed, either because
- they were unnecessarily verbose
- (e.g. <code class="option">build-use-sandbox</code> is now just
- <code class="option">sandbox</code>) or to reflect generalised behaviour
- (e.g. <code class="option">binary-caches</code> is now
- <code class="option">substituters</code> because it allows arbitrary store
- URIs). The old names are still supported for compatibility.</p></li><li class="listitem"><p>The <code class="option">max-jobs</code> option can <a class="link" href="https://github.com/NixOS/nix/commit/7251d048fa812d2551b7003bc9f13a8f5d4c95a5" target="_top">now</a>
- be set to <code class="literal">auto</code> to use the number of CPUs in the
- system.</p></li><li class="listitem"><p>Hashes can <a class="link" href="https://github.com/NixOS/nix/commit/c0015e87af70f539f24d2aa2bc224a9d8b84276b" target="_top">now</a>
- be specified in base-64 format, in addition to base-16 and the
- non-standard base-32.</p></li><li class="listitem"><p><span class="command"><strong>nix-shell</strong></span> now uses
- <code class="varname">bashInteractive</code> from Nixpkgs, rather than the
- <span class="command"><strong>bash</strong></span> command that happens to be in the caller’s
- <code class="envar">PATH</code>. This is especially important on macOS where
- the <span class="command"><strong>bash</strong></span> provided by the system is seriously
- outdated and cannot execute <code class="literal">stdenv</code>’s setup
- script.</p></li><li class="listitem"><p>Nix can now automatically trigger a garbage collection if
- free disk space drops below a certain level during a build. This
- is configured using the <code class="option">min-free</code> and
- <code class="option">max-free</code> options.</p></li><li class="listitem"><p><span class="command"><strong>nix-store -q --roots</strong></span> and
- <span class="command"><strong>nix-store --gc --print-roots</strong></span> now show temporary
- and in-memory roots.</p></li><li class="listitem"><p>
- Nix can now be extended with plugins. See the documentation of
- the <code class="option">plugin-files</code> option for more details.
- </p></li></ul></div><p>The Nix language has the following new features:
-
-</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>It supports floating point numbers. They are based on the
- C++ <code class="literal">float</code> type and are supported by the
- existing numerical operators. Export and import to and from JSON
- and XML works, too.</p></li><li class="listitem"><p>Derivation attributes can now reference the outputs of the
- derivation using the <code class="function">placeholder</code> builtin
- function. For example, the attribute
-
-</p><pre class="programlisting">
-configureFlags = "--prefix=${placeholder "out"} --includedir=${placeholder "dev"}";
-</pre><p>
-
- will cause the <code class="envar">configureFlags</code> environment variable
- to contain the actual store paths corresponding to the
- <code class="literal">out</code> and <code class="literal">dev</code> outputs.</p></li></ul></div><p>
-
-</p><p>The following builtin functions are new or extended:
-
-</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><code class="function"><a class="function" href="https://github.com/NixOS/nix/commit/38539b943a060d9cdfc24d6e5d997c0885b8aa2f" target="_top">builtins.fetchGit</a></code>
- allows Git repositories to be fetched at evaluation time. Thus it
- differs from the <code class="function">fetchgit</code> function in
- Nixpkgs, which fetches at build time and cannot be used to fetch
- Nix expressions during evaluation. A typical use case is to import
- external NixOS modules from your configuration, e.g.
-
- </p><pre class="programlisting">imports = [ (builtins.fetchGit https://github.com/edolstra/dwarffs + "/module.nix") ];</pre><p>
-
- </p></li><li class="listitem"><p>Similarly, <code class="function">builtins.fetchMercurial</code>
- allows you to fetch Mercurial repositories.</p></li><li class="listitem"><p><code class="function">builtins.path</code> generalises
- <code class="function">builtins.filterSource</code> and path literals
- (e.g. <code class="literal">./foo</code>). It allows specifying a store path
- name that differs from the source path name
- (e.g. <code class="literal">builtins.path { path = ./foo; name = "bar";
- }</code>) and also supports filtering out unwanted
- files.</p></li><li class="listitem"><p><code class="function">builtins.fetchurl</code> and
- <code class="function">builtins.fetchTarball</code> now support
- <code class="varname">sha256</code> and <code class="varname">name</code>
- attributes.</p></li><li class="listitem"><p><code class="function"><a class="function" href="https://github.com/NixOS/nix/commit/b8867a0239b1930a16f9ef3f7f3e864b01416dff" target="_top">builtins.split</a></code>
- splits a string using a POSIX extended regular expression as the
- separator.</p></li><li class="listitem"><p><code class="function"><a class="function" href="https://github.com/NixOS/nix/commit/26d92017d3b36cff940dcb7d1611c42232edb81a" target="_top">builtins.partition</a></code>
- partitions the elements of a list into two lists, depending on a
- Boolean predicate.</p></li><li class="listitem"><p><code class="literal"><nix/fetchurl.nix></code> now uses the
- content-addressable tarball cache at
- <code class="uri">http://tarballs.nixos.org/</code>, just like
- <code class="function">fetchurl</code> in
- Nixpkgs. (f2682e6e18a76ecbfb8a12c17e3a0ca15c084197)</p></li><li class="listitem"><p>In restricted and pure evaluation mode, builtin functions
- that download from the network (such as
- <code class="function">fetchGit</code>) are permitted to fetch underneath a
- list of URI prefixes specified in the option
- <code class="option">allowed-uris</code>.</p></li></ul></div><p>
-
-</p><p>The Nix build environment has the following changes:
-
-</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Values such as Booleans, integers, (nested) lists and
- attribute sets can <a class="link" href="https://github.com/NixOS/nix/commit/6de33a9c675b187437a2e1abbcb290981a89ecb1" target="_top">now</a>
- be passed to builders in a non-lossy way. If the special attribute
- <code class="varname">__structuredAttrs</code> is set to
- <code class="literal">true</code>, the other derivation attributes are
- serialised in JSON format and made available to the builder via
- the file <code class="envar">.attrs.json</code> in the builder’s temporary
- directory. This obviates the need for
- <code class="varname">passAsFile</code> since JSON files have no size
- restrictions, unlike process environments.</p><p><a class="link" href="https://github.com/NixOS/nix/commit/2d5b1b24bf70a498e4c0b378704cfdb6471cc699" target="_top">As
- a convenience to Bash builders</a>, Nix writes a script named
- <code class="envar">.attrs.sh</code> to the builder’s directory that
- initialises shell variables corresponding to all attributes that
- are representable in Bash. This includes non-nested (associative)
- arrays. For example, the attribute <code class="literal">hardening.format =
- true</code> ends up as the Bash associative array element
- <code class="literal">${hardening[format]}</code>.</p></li><li class="listitem"><p>Builders can <a class="link" href="https://github.com/NixOS/nix/commit/88e6bb76de5564b3217be9688677d1c89101b2a3" target="_top">now</a>
- communicate what build phase they are in by writing messages to
- the file descriptor specified in <code class="envar">NIX_LOG_FD</code>. The
- current phase is shown by the <span class="command"><strong>nix</strong></span> progress
- indicator.
- </p></li><li class="listitem"><p>In Linux sandbox builds, we <a class="link" href="https://github.com/NixOS/nix/commit/a2d92bb20e82a0957067ede60e91fab256948b41" target="_top">now</a>
- provide a default <code class="filename">/bin/sh</code> (namely
- <code class="filename">ash</code> from BusyBox).</p></li><li class="listitem"><p>In structured attribute mode,
- <code class="varname">exportReferencesGraph</code> <a class="link" href="https://github.com/NixOS/nix/commit/c2b0d8749f7e77afc1c4b3e8dd36b7ee9720af4a" target="_top">exports</a>
- extended information about closures in JSON format. In particular,
- it includes the sizes and hashes of paths. This is primarily
- useful for NixOS image builders.</p></li><li class="listitem"><p>Builds are <a class="link" href="https://github.com/NixOS/nix/commit/21948deed99a3295e4d5666e027a6ca42dc00b40" target="_top">now</a>
- killed as soon as Nix receives EOF on the builder’s stdout or
- stderr. This fixes a bug that allowed builds to hang Nix
- indefinitely, regardless of
- timeouts.</p></li><li class="listitem"><p>The <code class="option">sandbox-paths</code> configuration
- option can now specify optional paths by appending a
- <code class="literal">?</code>, e.g. <code class="literal">/dev/nvidiactl?</code> will
- bind-mount <code class="varname">/dev/nvidiactl</code> only if it
- exists.</p></li><li class="listitem"><p>On Linux, builds are now executed in a user
- namespace with UID 1000 and GID 100.</p></li></ul></div><p>
-
-</p><p>A number of significant internal changes were made:
-
-</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Nix no longer depends on Perl and all Perl components have
- been rewritten in C++ or removed. The Perl bindings that used to
- be part of Nix have been moved to a separate package,
- <code class="literal">nix-perl</code>.</p></li><li class="listitem"><p>All <code class="classname">Store</code> classes are now
- thread-safe. <code class="classname">RemoteStore</code> supports multiple
- concurrent connections to the daemon. This is primarily useful in
- multi-threaded programs such as
- <span class="command"><strong>hydra-queue-runner</strong></span>.</p></li></ul></div><p>
-
-</p><p>This release has contributions from
-
-Adrien Devresse,
-Alexander Ried,
-Alex Cruice,
-Alexey Shmalko,
-AmineChikhaoui,
-Andy Wingo,
-Aneesh Agrawal,
-Anthony Cowley,
-Armijn Hemel,
-aszlig,
-Ben Gamari,
-Benjamin Hipple,
-Benjamin Staffin,
-Benno Fünfstück,
-Bjørn Forsman,
-Brian McKenna,
-Charles Strahan,
-Chase Adams,
-Chris Martin,
-Christian Theune,
-Chris Warburton,
-Daiderd Jordan,
-Dan Connolly,
-Daniel Peebles,
-Dan Peebles,
-davidak,
-David McFarland,
-Dmitry Kalinkin,
-Domen Kožar,
-Eelco Dolstra,
-Emery Hemingway,
-Eric Litak,
-Eric Wolf,
-Fabian Schmitthenner,
-Frederik Rietdijk,
-Gabriel Gonzalez,
-Giorgio Gallo,
-Graham Christensen,
-Guillaume Maudoux,
-Harmen,
-Iavael,
-James Broadhead,
-James Earl Douglas,
-Janus Troelsen,
-Jeremy Shaw,
-Joachim Schiele,
-Joe Hermaszewski,
-Joel Moberg,
-Johannes 'fish' Ziemke,
-Jörg Thalheim,
-Jude Taylor,
-kballou,
-Keshav Kini,
-Kjetil Orbekk,
-Langston Barrett,
-Linus Heckemann,
-Ludovic Courtès,
-Manav Rathi,
-Marc Scholten,
-Markus Hauck,
-Matt Audesse,
-Matthew Bauer,
-Matthias Beyer,
-Matthieu Coudron,
-N1X,
-Nathan Zadoks,
-Neil Mayhew,
-Nicolas B. Pierron,
-Niklas Hambüchen,
-Nikolay Amiantov,
-Ole Jørgen Brønner,
-Orivej Desh,
-Peter Simons,
-Peter Stuart,
-Pyry Jahkola,
-regnat,
-Renzo Carbonara,
-Rhys,
-Robert Vollmert,
-Scott Olson,
-Scott R. Parish,
-Sergei Trofimovich,
-Shea Levy,
-Sheena Artrip,
-Spencer Baugh,
-Stefan Junker,
-Susan Potter,
-Thomas Tuegel,
-Timothy Allen,
-Tristan Hume,
-Tuomas Tynkkynen,
-tv,
-Tyson Whitehead,
-Vladimír Čunát,
-Will Dietz,
-wmertens,
-Wout Mertens,
-zimbatm and
-Zoran Plesivčak.
-</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.11.10"></a>C.5. Release 1.11.10 (2017-06-12)</h2></div></div></div><p>This release fixes a security bug in Nix’s “build user” build
-isolation mechanism. Previously, Nix builders had the ability to
-create setuid binaries owned by a <code class="literal">nixbld</code>
-user. Such a binary could then be used by an attacker to assume a
-<code class="literal">nixbld</code> identity and interfere with subsequent
-builds running under the same UID.</p><p>To prevent this issue, Nix now disallows builders to create
-setuid and setgid binaries. On Linux, this is done using a seccomp BPF
-filter. Note that this imposes a small performance penalty (e.g. 1%
-when building GNU Hello). Using seccomp, we now also prevent the
-creation of extended attributes and POSIX ACLs since these cannot be
-represented in the NAR format and (in the case of POSIX ACLs) allow
-bypassing regular Nix store permissions. On macOS, the restriction is
-implemented using the existing sandbox mechanism, which now uses a
-minimal “allow all except the creation of setuid/setgid binaries”
-profile when regular sandboxing is disabled. On other platforms, the
-“build user” mechanism is now disabled.</p><p>Thanks go to Linus Heckemann for discovering and reporting this
-bug.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.11"></a>C.6. Release 1.11 (2016-01-19)</h2></div></div></div><p>This is primarily a bug fix release. It also has a number of new
-features:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><span class="command"><strong>nix-prefetch-url</strong></span> can now download URLs
- specified in a Nix expression. For example,
-
-</p><pre class="screen">
-$ nix-prefetch-url -A hello.src
-</pre><p>
-
- will prefetch the file specified by the
- <code class="function">fetchurl</code> call in the attribute
- <code class="literal">hello.src</code> from the Nix expression in the
- current directory, and print the cryptographic hash of the
- resulting file on stdout. This differs from <code class="literal">nix-build -A
- hello.src</code> in that it doesn't verify the hash, and is
- thus useful when you’re updating a Nix expression.</p><p>You can also prefetch the result of functions that unpack a
- tarball, such as <code class="function">fetchFromGitHub</code>. For example:
-
-</p><pre class="screen">
-$ nix-prefetch-url --unpack https://github.com/NixOS/patchelf/archive/0.8.tar.gz
-</pre><p>
-
- or from a Nix expression:
-
-</p><pre class="screen">
-$ nix-prefetch-url -A nix-repl.src
-</pre><p>
-
- </p></li><li class="listitem"><p>The builtin function
- <code class="function"><nix/fetchurl.nix></code> now supports
- downloading and unpacking NARs. This removes the need to have
- multiple downloads in the Nixpkgs stdenv bootstrap process (like a
- separate busybox binary for Linux, or curl/mkdir/sh/bzip2 for
- Darwin). Now all those files can be combined into a single NAR,
- optionally compressed using <span class="command"><strong>xz</strong></span>.</p></li><li class="listitem"><p>Nix now supports SHA-512 hashes for verifying fixed-output
- derivations, and in <code class="function">builtins.hashString</code>.</p></li><li class="listitem"><p>
- The new flag <code class="option">--option build-repeat
- <em class="replaceable"><code>N</code></em></code> will cause every build to
- be executed <em class="replaceable"><code>N</code></em>+1 times. If the build
- output differs between any round, the build is rejected, and the
- output paths are not registered as valid. This is primarily
- useful to verify build determinism. (We already had a
- <code class="option">--check</code> option to repeat a previously succeeded
- build. However, with <code class="option">--check</code>, non-deterministic
- builds are registered in the DB. Preventing that is useful for
- Hydra to ensure that non-deterministic builds don't end up
- getting published to the binary cache.)
- </p></li><li class="listitem"><p>
- The options <code class="option">--check</code> and <code class="option">--option
- build-repeat <em class="replaceable"><code>N</code></em></code>, if they
- detect a difference between two runs of the same derivation and
- <code class="option">-K</code> is given, will make the output of the other
- run available under
- <code class="filename"><em class="replaceable"><code>store-path</code></em>-check</code>. This
- makes it easier to investigate the non-determinism using tools
- like <span class="command"><strong>diffoscope</strong></span>, e.g.,
-
-</p><pre class="screen">
-$ nix-build pkgs/stdenv/linux -A stage1.pkgs.zlib --check -K
-error: derivation ‘/nix/store/l54i8wlw2265…-zlib-1.2.8.drv’ may not
-be deterministic: output ‘/nix/store/11a27shh6n2i…-zlib-1.2.8’
-differs from ‘/nix/store/11a27shh6n2i…-zlib-1.2.8-check’
-
-$ diffoscope /nix/store/11a27shh6n2i…-zlib-1.2.8 /nix/store/11a27shh6n2i…-zlib-1.2.8-check
-…
-├── lib/libz.a
-│ ├── metadata
-│ │ @@ -1,15 +1,15 @@
-│ │ -rw-r--r-- 30001/30000 3096 Jan 12 15:20 2016 adler32.o
-…
-│ │ +rw-r--r-- 30001/30000 3096 Jan 12 15:28 2016 adler32.o
-…
-</pre><p>
-
- </p></li><li class="listitem"><p>Improved FreeBSD support.</p></li><li class="listitem"><p><span class="command"><strong>nix-env -qa --xml --meta</strong></span> now prints
- license information.</p></li><li class="listitem"><p>The maximum number of parallel TCP connections that the
- binary cache substituter will use has been decreased from 150 to
- 25. This should prevent upsetting some broken NAT routers, and
- also improves performance.</p></li><li class="listitem"><p>All "chroot"-containing strings got renamed to "sandbox".
- In particular, some Nix options got renamed, but the old names
- are still accepted as lower-priority aliases.
- </p></li></ul></div><p>This release has contributions from Anders Claesson, Anthony
-Cowley, Bjørn Forsman, Brian McKenna, Danny Wilson, davidak, Eelco Dolstra,
-Fabian Schmitthenner, FrankHB, Ilya Novoselov, janus, Jim Garrison, John
-Ericson, Jude Taylor, Ludovic Courtès, Manuel Jacob, Mathnerd314,
-Pascal Wittmann, Peter Simons, Philip Potter, Preston Bennes, Rommel
-M. Martinez, Sander van der Burg, Shea Levy, Tim Cuthbertson, Tuomas
-Tynkkynen, Utku Demir and Vladimír Čunát.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.10"></a>C.7. Release 1.10 (2015-09-03)</h2></div></div></div><p>This is primarily a bug fix release. It also has a number of new
-features:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>A number of builtin functions have been added to reduce
- Nixpkgs/NixOS evaluation time and memory consumption:
- <code class="function">all</code>,
- <code class="function">any</code>,
- <code class="function">concatStringsSep</code>,
- <code class="function">foldl’</code>,
- <code class="function">genList</code>,
- <code class="function">replaceStrings</code>,
- <code class="function">sort</code>.
- </p></li><li class="listitem"><p>The garbage collector is more robust when the disk is full.</p></li><li class="listitem"><p>Nix supports a new API for building derivations that doesn’t
- require a <code class="literal">.drv</code> file to be present on disk; it
- only requires an in-memory representation of the derivation. This
- is used by the Hydra continuous build system to make remote builds
- more efficient.</p></li><li class="listitem"><p>The function <code class="literal"><nix/fetchurl.nix></code> now
- uses a <span class="emphasis"><em>builtin</em></span> builder (i.e. it doesn’t
- require starting an external process; the download is performed by
- Nix itself). This ensures that derivation paths don’t change when
- Nix is upgraded, and obviates the need for ugly hacks to support
- chroot execution.</p></li><li class="listitem"><p><code class="option">--version -v</code> now prints some configuration
- information, in particular what compile-time optional features are
- enabled, and the paths of various directories.</p></li><li class="listitem"><p>Build users have their supplementary groups set correctly.</p></li></ul></div><p>This release has contributions from Eelco Dolstra, Guillaume
-Maudoux, Iwan Aucamp, Jaka Hudoklin, Kirill Elagin, Ludovic Courtès,
-Manolis Ragkousis, Nicolas B. Pierron and Shea Levy.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.9"></a>C.8. Release 1.9 (2015-06-12)</h2></div></div></div><p>In addition to the usual bug fixes, this release has the
-following new features:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Signed binary cache support. You can enable signature
- checking by adding the following to <code class="filename">nix.conf</code>:
-
-</p><pre class="programlisting">
-signed-binary-caches = *
-binary-cache-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
-</pre><p>
-
- This will prevent Nix from downloading any binary from the cache
- that is not signed by one of the keys listed in
- <code class="option">binary-cache-public-keys</code>.</p><p>Signature checking is only supported if you built Nix with
- the <code class="literal">libsodium</code> package.</p><p>Note that while Nix has had experimental support for signed
- binary caches since version 1.7, this release changes the
- signature format in a backwards-incompatible way.</p></li><li class="listitem"><p>Automatic downloading of Nix expression tarballs. In various
- places, you can now specify the URL of a tarball containing Nix
- expressions (such as Nixpkgs), which will be downloaded and
- unpacked automatically. For example:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>In <span class="command"><strong>nix-env</strong></span>:
-
-</p><pre class="screen">
-$ nix-env -f https://github.com/NixOS/nixpkgs-channels/archive/nixos-14.12.tar.gz -iA firefox
-</pre><p>
-
- This installs Firefox from the latest tested and built revision
- of the NixOS 14.12 channel.</p></li><li class="listitem"><p>In <span class="command"><strong>nix-build</strong></span> and
- <span class="command"><strong>nix-shell</strong></span>:
-
-</p><pre class="screen">
-$ nix-build https://github.com/NixOS/nixpkgs/archive/master.tar.gz -A hello
-</pre><p>
-
- This builds GNU Hello from the latest revision of the Nixpkgs
- master branch.</p></li><li class="listitem"><p>In the Nix search path (as specified via
- <code class="envar">NIX_PATH</code> or <code class="option">-I</code>). For example, to
- start a shell containing the Pan package from a specific version
- of Nixpkgs:
-
-</p><pre class="screen">
-$ nix-shell -p pan -I nixpkgs=https://github.com/NixOS/nixpkgs-channels/archive/8a3eea054838b55aca962c3fbde9c83c102b8bf2.tar.gz
-</pre><p>
-
- </p></li><li class="listitem"><p>In <span class="command"><strong>nixos-rebuild</strong></span> (on NixOS):
-
-</p><pre class="screen">
-$ nixos-rebuild test -I nixpkgs=https://github.com/NixOS/nixpkgs-channels/archive/nixos-unstable.tar.gz
-</pre><p>
-
- </p></li><li class="listitem"><p>In Nix expressions, via the new builtin function <code class="function">fetchTarball</code>:
-
-</p><pre class="programlisting">
-with import (fetchTarball https://github.com/NixOS/nixpkgs-channels/archive/nixos-14.12.tar.gz) {}; …
-</pre><p>
-
- (This is not allowed in restricted mode.)</p></li></ul></div></li><li class="listitem"><p><span class="command"><strong>nix-shell</strong></span> improvements:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p><span class="command"><strong>nix-shell</strong></span> now has a flag
- <code class="option">--run</code> to execute a command in the
- <span class="command"><strong>nix-shell</strong></span> environment,
- e.g. <code class="literal">nix-shell --run make</code>. This is like
- the existing <code class="option">--command</code> flag, except that it
- uses a non-interactive shell (ensuring that hitting Ctrl-C won’t
- drop you into the child shell).</p></li><li class="listitem"><p><span class="command"><strong>nix-shell</strong></span> can now be used as
- a <code class="literal">#!</code>-interpreter. This allows you to write
- scripts that dynamically fetch their own dependencies. For
- example, here is a Haskell script that, when invoked, first
- downloads GHC and the Haskell packages on which it depends:
-
-</p><pre class="programlisting">
-#! /usr/bin/env nix-shell
-#! nix-shell -i runghc -p haskellPackages.ghc haskellPackages.HTTP
-
-import Network.HTTP
-
-main = do
- resp <- Network.HTTP.simpleHTTP (getRequest "http://nixos.org/")
- body <- getResponseBody resp
- print (take 100 body)
-</pre><p>
-
- Of course, the dependencies are cached in the Nix store, so the
- second invocation of this script will be much
- faster.</p></li></ul></div></li><li class="listitem"><p>Chroot improvements:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Chroot builds are now supported on Mac OS X
- (using its sandbox mechanism).</p></li><li class="listitem"><p>If chroots are enabled, they are now used for
- all derivations, including fixed-output derivations (such as
- <code class="function">fetchurl</code>). The latter do have network
- access, but can no longer access the host filesystem. If you
- need the old behaviour, you can set the option
- <code class="option">build-use-chroot</code> to
- <code class="literal">relaxed</code>.</p></li><li class="listitem"><p>On Linux, if chroots are enabled, builds are
- performed in a private PID namespace once again. (This
- functionality was lost in Nix 1.8.)</p></li><li class="listitem"><p>Store paths listed in
- <code class="option">build-chroot-dirs</code> are now automatically
- expanded to their closure. For instance, if you want
- <code class="filename">/nix/store/…-bash/bin/sh</code> mounted in your
- chroot as <code class="filename">/bin/sh</code>, you only need to say
- <code class="literal">build-chroot-dirs =
- /bin/sh=/nix/store/…-bash/bin/sh</code>; it is no longer
- necessary to specify the dependencies of Bash.</p></li></ul></div></li><li class="listitem"><p>The new derivation attribute
- <code class="varname">passAsFile</code> allows you to specify that the
- contents of derivation attributes should be passed via files rather
- than environment variables. This is useful if you need to pass very
- long strings that exceed the size limit of the environment. The
- Nixpkgs function <code class="function">writeTextFile</code> uses
- this.</p></li><li class="listitem"><p>You can now use <code class="literal">~</code> in Nix file
- names to refer to your home directory, e.g. <code class="literal">import
- ~/.nixpkgs/config.nix</code>.</p></li><li class="listitem"><p>Nix has a new option <code class="option">restrict-eval</code>
- that allows limiting what paths the Nix evaluator has access to. By
- passing <code class="literal">--option restrict-eval true</code> to Nix, the
- evaluator will throw an exception if an attempt is made to access
- any file outside of the Nix search path. This is primarily intended
- for Hydra to ensure that a Hydra jobset only refers to its declared
- inputs (and is therefore reproducible).</p></li><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> now only creates a new
- “generation” symlink in <code class="filename">/nix/var/nix/profiles</code>
- if something actually changed.</p></li><li class="listitem"><p>The environment variable <code class="envar">NIX_PAGER</code>
- can now be set to override <code class="envar">PAGER</code>. You can set it to
- <code class="literal">cat</code> to disable paging for Nix commands
- only.</p></li><li class="listitem"><p>Failing <code class="literal"><...></code>
- lookups now show position information.</p></li><li class="listitem"><p>Improved Boehm GC use: we disabled scanning for
- interior pointers, which should reduce the “<code class="literal">Repeated
- allocation of very large block</code>” warnings and associated
- retention of memory.</p></li></ul></div><p>This release has contributions from aszlig, Benjamin Staffin,
-Charles Strahan, Christian Theune, Daniel Hahler, Danylo Hlynskyi
-Daniel Peebles, Dan Peebles, Domen Kožar, Eelco Dolstra, Harald van
-Dijk, Hoang Xuan Phu, Jaka Hudoklin, Jeff Ramnani, j-keck, Linquize,
-Luca Bruno, Michael Merickel, Oliver Dunkl, Rob Vermaas, Rok Garbas,
-Shea Levy, Tobias Geerinckx-Rice and William A. Kennington III.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.8"></a>C.9. Release 1.8 (2014-12-14)</h2></div></div></div><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Breaking change: to address a race condition, the
- remote build hook mechanism now uses <span class="command"><strong>nix-store
- --serve</strong></span> on the remote machine. This requires build slaves
- to be updated to Nix 1.8.</p></li><li class="listitem"><p>Nix now uses HTTPS instead of HTTP to access the
- default binary cache,
- <code class="literal">cache.nixos.org</code>.</p></li><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> selectors are now regular
- expressions. For instance, you can do
-
-</p><pre class="screen">
-$ nix-env -qa '.*zip.*'
-</pre><p>
-
- to query all packages with a name containing
- <code class="literal">zip</code>.</p></li><li class="listitem"><p><span class="command"><strong>nix-store --read-log</strong></span> can now
- fetch remote build logs. If a build log is not available locally,
- then ‘nix-store -l’ will now try to download it from the servers
- listed in the ‘log-servers’ option in nix.conf. For instance, if you
- have the configuration option
-
-</p><pre class="programlisting">
-log-servers = http://hydra.nixos.org/log
-</pre><p>
-
-then it will try to get logs from
-<code class="literal">http://hydra.nixos.org/log/<em class="replaceable"><code>base name of the
-store path</code></em></code>. This allows you to do things like:
-
-</p><pre class="screen">
-$ nix-store -l $(which xterm)
-</pre><p>
-
- and get a log even if <span class="command"><strong>xterm</strong></span> wasn't built
- locally.</p></li><li class="listitem"><p>New builtin functions:
- <code class="function">attrValues</code>, <code class="function">deepSeq</code>,
- <code class="function">fromJSON</code>, <code class="function">readDir</code>,
- <code class="function">seq</code>.</p></li><li class="listitem"><p><span class="command"><strong>nix-instantiate --eval</strong></span> now has a
- <code class="option">--json</code> flag to print the resulting value in JSON
- format.</p></li><li class="listitem"><p><span class="command"><strong>nix-copy-closure</strong></span> now uses
- <span class="command"><strong>nix-store --serve</strong></span> on the remote side to send or
- receive closures. This fixes a race condition between
- <span class="command"><strong>nix-copy-closure</strong></span> and the garbage
- collector.</p></li><li class="listitem"><p>Derivations can specify the new special attribute
- <code class="varname">allowedRequisites</code>, which has a similar meaning to
- <code class="varname">allowedReferences</code>. But instead of only enforcing
- to explicitly specify the immediate references, it requires the
- derivation to specify all the dependencies recursively (hence the
- name, requisites) that are used by the resulting
- output.</p></li><li class="listitem"><p>On Mac OS X, Nix now handles case collisions when
- importing closures from case-sensitive file systems. This is mostly
- useful for running NixOps on Mac OS X.</p></li><li class="listitem"><p>The Nix daemon has new configuration options
- <code class="option">allowed-users</code> (specifying the users and groups that
- are allowed to connect to the daemon) and
- <code class="option">trusted-users</code> (specifying the users and groups that
- can perform privileged operations like specifying untrusted binary
- caches).</p></li><li class="listitem"><p>The configuration option
- <code class="option">build-cores</code> now defaults to the number of available
- CPU cores.</p></li><li class="listitem"><p>Build users are now used by default when Nix is
- invoked as root. This prevents builds from accidentally running as
- root.</p></li><li class="listitem"><p>Nix now includes systemd units and Upstart
- jobs.</p></li><li class="listitem"><p>Speed improvements to <span class="command"><strong>nix-store
- --optimise</strong></span>.</p></li><li class="listitem"><p>Language change: the <code class="literal">==</code> operator
- now ignores string contexts (the “dependencies” of a
- string).</p></li><li class="listitem"><p>Nix now filters out Nix-specific ANSI escape
- sequences on standard error. They are supposed to be invisible, but
- some terminals show them anyway.</p></li><li class="listitem"><p>Various commands now automatically pipe their output
- into the pager as specified by the <code class="envar">PAGER</code> environment
- variable.</p></li><li class="listitem"><p>Several improvements to reduce memory consumption in
- the evaluator.</p></li></ul></div><p>This release has contributions from Adam Szkoda, Aristid
-Breitkreuz, Bob van der Linden, Charles Strahan, darealshinji, Eelco
-Dolstra, Gergely Risko, Joel Taylor, Ludovic Courtès, Marko Durkovic,
-Mikey Ariel, Paul Colomiets, Ricardo M. Correia, Ricky Elrod, Robert
-Helgesson, Rob Vermaas, Russell O'Connor, Shea Levy, Shell Turner,
-Sönke Hahn, Steve Purcell, Vladimír Čunát and Wout Mertens.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.7"></a>C.10. Release 1.7 (2014-04-11)</h2></div></div></div><p>In addition to the usual bug fixes, this release has the
-following new features:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Antiquotation is now allowed inside of quoted attribute
- names (e.g. <code class="literal">set."${foo}"</code>). In the case where
- the attribute name is just a single antiquotation, the quotes can
- be dropped (e.g. the above example can be written
- <code class="literal">set.${foo}</code>). If an attribute name inside of a
- set declaration evaluates to <code class="literal">null</code> (e.g.
- <code class="literal">{ ${null} = false; }</code>), then that attribute is
- not added to the set.</p></li><li class="listitem"><p>Experimental support for cryptographically signed binary
- caches. See <a class="link" href="https://github.com/NixOS/nix/commit/0fdf4da0e979f992db75cc17376e455ddc5a96d8" target="_top">the
- commit for details</a>.</p></li><li class="listitem"><p>An experimental new substituter,
- <span class="command"><strong>download-via-ssh</strong></span>, that fetches binaries from
- remote machines via SSH. Specifying the flags <code class="literal">--option
- use-ssh-substituter true --option ssh-substituter-hosts
- <em class="replaceable"><code>user@hostname</code></em></code> will cause Nix
- to download binaries from the specified machine, if it has
- them.</p></li><li class="listitem"><p><span class="command"><strong>nix-store -r</strong></span> and
- <span class="command"><strong>nix-build</strong></span> have a new flag,
- <code class="option">--check</code>, that builds a previously built
- derivation again, and prints an error message if the output is not
- exactly the same. This helps to verify whether a derivation is
- truly deterministic. For example:
-
-</p><pre class="screen">
-$ nix-build '<nixpkgs>' -A patchelf
-<em class="replaceable"><code>…</code></em>
-$ nix-build '<nixpkgs>' -A patchelf --check
-<em class="replaceable"><code>…</code></em>
-error: derivation `/nix/store/1ipvxs…-patchelf-0.6' may not be deterministic:
- hash mismatch in output `/nix/store/4pc1dm…-patchelf-0.6.drv'
-</pre><p>
-
- </p></li><li class="listitem"><p>The <span class="command"><strong>nix-instantiate</strong></span> flags
- <code class="option">--eval-only</code> and <code class="option">--parse-only</code>
- have been renamed to <code class="option">--eval</code> and
- <code class="option">--parse</code>, respectively.</p></li><li class="listitem"><p><span class="command"><strong>nix-instantiate</strong></span>,
- <span class="command"><strong>nix-build</strong></span> and <span class="command"><strong>nix-shell</strong></span> now
- have a flag <code class="option">--expr</code> (or <code class="option">-E</code>) that
- allows you to specify the expression to be evaluated as a command
- line argument. For instance, <code class="literal">nix-instantiate --eval -E
- '1 + 2'</code> will print <code class="literal">3</code>.</p></li><li class="listitem"><p><span class="command"><strong>nix-shell</strong></span> improvements:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>It has a new flag, <code class="option">--packages</code> (or
- <code class="option">-p</code>), that sets up a build environment
- containing the specified packages from Nixpkgs. For example,
- the command
-
-</p><pre class="screen">
-$ nix-shell -p sqlite xorg.libX11 hello
-</pre><p>
-
- will start a shell in which the given packages are
- present.</p></li><li class="listitem"><p>It now uses <code class="filename">shell.nix</code> as the
- default expression, falling back to
- <code class="filename">default.nix</code> if the former doesn’t
- exist. This makes it convenient to have a
- <code class="filename">shell.nix</code> in your project to set up a
- nice development environment.</p></li><li class="listitem"><p>It evaluates the derivation attribute
- <code class="varname">shellHook</code>, if set. Since
- <code class="literal">stdenv</code> does not normally execute this hook,
- it allows you to do <span class="command"><strong>nix-shell</strong></span>-specific
- setup.</p></li><li class="listitem"><p>It preserves the user’s timezone setting.</p></li></ul></div></li><li class="listitem"><p>In chroots, Nix now sets up a <code class="filename">/dev</code>
- containing only a minimal set of devices (such as
- <code class="filename">/dev/null</code>). Note that it only does this if
- you <span class="emphasis"><em>don’t</em></span> have <code class="filename">/dev</code>
- listed in your <code class="option">build-chroot-dirs</code> setting;
- otherwise, it will bind-mount the <code class="literal">/dev</code> from
- outside the chroot.</p><p>Similarly, if you don’t have <code class="filename">/dev/pts</code> listed
- in <code class="option">build-chroot-dirs</code>, Nix will mount a private
- <code class="literal">devpts</code> filesystem on the chroot’s
- <code class="filename">/dev/pts</code>.</p></li><li class="listitem"><p>New built-in function: <code class="function">builtins.toJSON</code>,
- which returns a JSON representation of a value.</p></li><li class="listitem"><p><span class="command"><strong>nix-env -q</strong></span> has a new flag
- <code class="option">--json</code> to print a JSON representation of the
- installed or available packages.</p></li><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> now supports meta attributes with
- more complex values, such as attribute sets.</p></li><li class="listitem"><p>The <code class="option">-A</code> flag now allows attribute names with
- dots in them, e.g.
-
-</p><pre class="screen">
-$ nix-instantiate --eval '<nixos>' -A 'config.systemd.units."nscd.service".text'
-</pre><p>
-
- </p></li><li class="listitem"><p>The <code class="option">--max-freed</code> option to
- <span class="command"><strong>nix-store --gc</strong></span> now accepts a unit
- specifier. For example, <code class="literal">nix-store --gc --max-freed
- 1G</code> will free up to 1 gigabyte of disk space.</p></li><li class="listitem"><p><span class="command"><strong>nix-collect-garbage</strong></span> has a new flag
- <code class="option">--delete-older-than</code>
- <em class="replaceable"><code>N</code></em><code class="literal">d</code>, which deletes
- all user environment generations older than
- <em class="replaceable"><code>N</code></em> days. Likewise, <span class="command"><strong>nix-env
- --delete-generations</strong></span> accepts a
- <em class="replaceable"><code>N</code></em><code class="literal">d</code> age limit.</p></li><li class="listitem"><p>Nix now heuristically detects whether a build failure was
- due to a disk-full condition. In that case, the build is not
- flagged as “permanently failed”. This is mostly useful for Hydra,
- which needs to distinguish between permanent and transient build
- failures.</p></li><li class="listitem"><p>There is a new symbol <code class="literal">__curPos</code> that
- expands to an attribute set containing its file name and line and
- column numbers, e.g. <code class="literal">{ file = "foo.nix"; line = 10;
- column = 5; }</code>. There also is a new builtin function,
- <code class="varname">unsafeGetAttrPos</code>, that returns the position of
- an attribute. This is used by Nixpkgs to provide location
- information in error messages, e.g.
-
-</p><pre class="screen">
-$ nix-build '<nixpkgs>' -A libreoffice --argstr system x86_64-darwin
-error: the package ‘libreoffice-4.0.5.2’ in ‘.../applications/office/libreoffice/default.nix:263’
- is not supported on ‘x86_64-darwin’
-</pre><p>
-
- </p></li><li class="listitem"><p>The garbage collector is now more concurrent with other Nix
- processes because it releases certain locks earlier.</p></li><li class="listitem"><p>The binary tarball installer has been improved. You can now
- install Nix by running:
-
-</p><pre class="screen">
-$ bash <(curl https://nixos.org/nix/install)
-</pre><p>
-
- </p></li><li class="listitem"><p>More evaluation errors include position information. For
- instance, selecting a missing attribute will print something like
-
-</p><pre class="screen">
-error: attribute `nixUnstabl' missing, at /etc/nixos/configurations/misc/eelco/mandark.nix:216:15
-</pre><p>
-
- </p></li><li class="listitem"><p>The command <span class="command"><strong>nix-setuid-helper</strong></span> is
- gone.</p></li><li class="listitem"><p>Nix no longer uses Automake, but instead has a
- non-recursive, GNU Make-based build system.</p></li><li class="listitem"><p>All installed libraries now have the prefix
- <code class="literal">libnix</code>. In particular, this gets rid of
- <code class="literal">libutil</code>, which could clash with libraries with
- the same name from other packages.</p></li><li class="listitem"><p>Nix now requires a compiler that supports C++11.</p></li></ul></div><p>This release has contributions from Danny Wilson, Domen Kožar,
-Eelco Dolstra, Ian-Woo Kim, Ludovic Courtès, Maxim Ivanov, Petr
-Rockai, Ricardo M. Correia and Shea Levy.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.6.1"></a>C.11. Release 1.6.1 (2013-10-28)</h2></div></div></div><p>This is primarily a bug fix release. Changes of interest
-are:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Nix 1.6 accidentally changed the semantics of antiquoted
- paths in strings, such as <code class="literal">"${/foo}/bar"</code>. This
- release reverts to the Nix 1.5.3 behaviour.</p></li><li class="listitem"><p>Previously, Nix optimised expressions such as
- <code class="literal">"${<em class="replaceable"><code>expr</code></em>}"</code> to
- <em class="replaceable"><code>expr</code></em>. Thus it neither checked whether
- <em class="replaceable"><code>expr</code></em> could be coerced to a string, nor
- applied such coercions. This meant that
- <code class="literal">"${123}"</code> evaluatued to <code class="literal">123</code>,
- and <code class="literal">"${./foo}"</code> evaluated to
- <code class="literal">./foo</code> (even though
- <code class="literal">"${./foo} "</code> evaluates to
- <code class="literal">"/nix/store/<em class="replaceable"><code>hash</code></em>-foo "</code>).
- Nix now checks the type of antiquoted expressions and
- applies coercions.</p></li><li class="listitem"><p>Nix now shows the exact position of undefined variables. In
- particular, undefined variable errors in a <code class="literal">with</code>
- previously didn't show <span class="emphasis"><em>any</em></span> position
- information, so this makes it a lot easier to fix such
- errors.</p></li><li class="listitem"><p>Undefined variables are now treated consistently.
- Previously, the <code class="function">tryEval</code> function would catch
- undefined variables inside a <code class="literal">with</code> but not
- outside. Now <code class="function">tryEval</code> never catches undefined
- variables.</p></li><li class="listitem"><p>Bash completion in <span class="command"><strong>nix-shell</strong></span> now works
- correctly.</p></li><li class="listitem"><p>Stack traces are less verbose: they no longer show calls to
- builtin functions and only show a single line for each derivation
- on the call stack.</p></li><li class="listitem"><p>New built-in function: <code class="function">builtins.typeOf</code>,
- which returns the type of its argument as a string.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.6.0"></a>C.12. Release 1.6 (2013-09-10)</h2></div></div></div><p>In addition to the usual bug fixes, this release has several new
-features:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>The command <span class="command"><strong>nix-build --run-env</strong></span> has been
- renamed to <span class="command"><strong>nix-shell</strong></span>.</p></li><li class="listitem"><p><span class="command"><strong>nix-shell</strong></span> now sources
- <code class="filename">$stdenv/setup</code> <span class="emphasis"><em>inside</em></span> the
- interactive shell, rather than in a parent shell. This ensures
- that shell functions defined by <code class="literal">stdenv</code> can be
- used in the interactive shell.</p></li><li class="listitem"><p><span class="command"><strong>nix-shell</strong></span> has a new flag
- <code class="option">--pure</code> to clear the environment, so you get an
- environment that more closely corresponds to the “real” Nix build.
- </p></li><li class="listitem"><p><span class="command"><strong>nix-shell</strong></span> now sets the shell prompt
- (<code class="envar">PS1</code>) to ensure that Nix shells are distinguishable
- from your regular shells.</p></li><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> no longer requires a
- <code class="literal">*</code> argument to match all packages, so
- <code class="literal">nix-env -qa</code> is equivalent to <code class="literal">nix-env
- -qa '*'</code>.</p></li><li class="listitem"><p><span class="command"><strong>nix-env -i</strong></span> has a new flag
- <code class="option">--remove-all</code> (<code class="option">-r</code>) to remove all
- previous packages from the profile. This makes it easier to do
- declarative package management similar to NixOS’s
- <code class="option">environment.systemPackages</code>. For instance, if you
- have a specification <code class="filename">my-packages.nix</code> like this:
-
-</p><pre class="programlisting">
-with import <nixpkgs> {};
-[ thunderbird
- geeqie
- ...
-]
-</pre><p>
-
- then after any change to this file, you can run:
-
-</p><pre class="screen">
-$ nix-env -f my-packages.nix -ir
-</pre><p>
-
- to update your profile to match the specification.</p></li><li class="listitem"><p>The ‘<code class="literal">with</code>’ language construct is now more
- lazy. It only evaluates its argument if a variable might actually
- refer to an attribute in the argument. For instance, this now
- works:
-
-</p><pre class="programlisting">
-let
- pkgs = with pkgs; { foo = "old"; bar = foo; } // overrides;
- overrides = { foo = "new"; };
-in pkgs.bar
-</pre><p>
-
- This evaluates to <code class="literal">"new"</code>, while previously it
- gave an “infinite recursion” error.</p></li><li class="listitem"><p>Nix now has proper integer arithmetic operators. For
- instance, you can write <code class="literal">x + y</code> instead of
- <code class="literal">builtins.add x y</code>, or <code class="literal">x <
- y</code> instead of <code class="literal">builtins.lessThan x y</code>.
- The comparison operators also work on strings.</p></li><li class="listitem"><p>On 64-bit systems, Nix integers are now 64 bits rather than
- 32 bits.</p></li><li class="listitem"><p>When using the Nix daemon, the <span class="command"><strong>nix-daemon</strong></span>
- worker process now runs on the same CPU as the client, on systems
- that support setting CPU affinity. This gives a significant speedup
- on some systems.</p></li><li class="listitem"><p>If a stack overflow occurs in the Nix evaluator, you now get
- a proper error message (rather than “Segmentation fault”) on some
- systems.</p></li><li class="listitem"><p>In addition to directories, you can now bind-mount regular
- files in chroots through the (now misnamed) option
- <code class="option">build-chroot-dirs</code>.</p></li></ul></div><p>This release has contributions from Domen Kožar, Eelco Dolstra,
-Florian Friesdorf, Gergely Risko, Ivan Kozik, Ludovic Courtès and Shea
-Levy.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.5.2"></a>C.13. Release 1.5.2 (2013-05-13)</h2></div></div></div><p>This is primarily a bug fix release. It has contributions from
-Eelco Dolstra, Lluís Batlle i Rossell and Shea Levy.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.5"></a>C.14. Release 1.5 (2013-02-27)</h2></div></div></div><p>This is a brown paper bag release to fix a regression introduced
-by the hard link security fix in 1.4.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.4"></a>C.15. Release 1.4 (2013-02-26)</h2></div></div></div><p>This release fixes a security bug in multi-user operation. It
-was possible for derivations to cause the mode of files outside of the
-Nix store to be changed to 444 (read-only but world-readable) by
-creating hard links to those files (<a class="link" href="https://github.com/NixOS/nix/commit/5526a282b5b44e9296e61e07d7d2626a79141ac4" target="_top">details</a>).</p><p>There are also the following improvements:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>New built-in function:
- <code class="function">builtins.hashString</code>.</p></li><li class="listitem"><p>Build logs are now stored in
- <code class="filename">/nix/var/log/nix/drvs/<em class="replaceable"><code>XX</code></em>/</code>,
- where <em class="replaceable"><code>XX</code></em> is the first two characters of
- the derivation. This is useful on machines that keep a lot of build
- logs (such as Hydra servers).</p></li><li class="listitem"><p>The function <code class="function">corepkgs/fetchurl</code>
- can now make the downloaded file executable. This will allow
- getting rid of all bootstrap binaries in the Nixpkgs source
- tree.</p></li><li class="listitem"><p>Language change: The expression <code class="literal">"${./path}
- ..."</code> now evaluates to a string instead of a
- path.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.3"></a>C.16. Release 1.3 (2013-01-04)</h2></div></div></div><p>This is primarily a bug fix release. When this version is first
-run on Linux, it removes any immutable bits from the Nix store and
-increases the schema version of the Nix store. (The previous release
-removed support for setting the immutable bit; this release clears any
-remaining immutable bits to make certain operations more
-efficient.)</p><p>This release has contributions from Eelco Dolstra and Stuart
-Pernsteiner.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.2"></a>C.17. Release 1.2 (2012-12-06)</h2></div></div></div><p>This release has the following improvements and changes:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Nix has a new binary substituter mechanism: the
- <span class="emphasis"><em>binary cache</em></span>. A binary cache contains
- pre-built binaries of Nix packages. Whenever Nix wants to build a
- missing Nix store path, it will check a set of binary caches to
- see if any of them has a pre-built binary of that path. The
- configuration setting <code class="option">binary-caches</code> contains a
- list of URLs of binary caches. For instance, doing
-</p><pre class="screen">
-$ nix-env -i thunderbird --option binary-caches http://cache.nixos.org
-</pre><p>
- will install Thunderbird and its dependencies, using the available
- pre-built binaries in <code class="uri">http://cache.nixos.org</code>.
- The main advantage over the old “manifest”-based method of getting
- pre-built binaries is that you don’t have to worry about your
- manifest being in sync with the Nix expressions you’re installing
- from; i.e., you don’t need to run <span class="command"><strong>nix-pull</strong></span> to
- update your manifest. It’s also more scalable because you don’t
- need to redownload a giant manifest file every time.
- </p><p>A Nix channel can provide a binary cache URL that will be
- used automatically if you subscribe to that channel. If you use
- the Nixpkgs or NixOS channels
- (<code class="uri">http://nixos.org/channels</code>) you automatically get the
- cache <code class="uri">http://cache.nixos.org</code>.</p><p>Binary caches are created using <span class="command"><strong>nix-push</strong></span>.
- For details on the operation and format of binary caches, see the
- <span class="command"><strong>nix-push</strong></span> manpage. More details are provided in
- <a class="link" href="https://nixos.org/nix-dev/2012-September/009826.html" target="_top">this
- nix-dev posting</a>.</p></li><li class="listitem"><p>Multiple output support should now be usable. A derivation
- can declare that it wants to produce multiple store paths by
- saying something like
-</p><pre class="programlisting">
-outputs = [ "lib" "headers" "doc" ];
-</pre><p>
- This will cause Nix to pass the intended store path of each output
- to the builder through the environment variables
- <code class="literal">lib</code>, <code class="literal">headers</code> and
- <code class="literal">doc</code>. Other packages can refer to a specific
- output by referring to
- <code class="literal"><em class="replaceable"><code>pkg</code></em>.<em class="replaceable"><code>output</code></em></code>,
- e.g.
-</p><pre class="programlisting">
-buildInputs = [ pkg.lib pkg.headers ];
-</pre><p>
- If you install a package with multiple outputs using
- <span class="command"><strong>nix-env</strong></span>, each output path will be symlinked
- into the user environment.</p></li><li class="listitem"><p>Dashes are now valid as part of identifiers and attribute
- names.</p></li><li class="listitem"><p>The new operation <span class="command"><strong>nix-store --repair-path</strong></span>
- allows corrupted or missing store paths to be repaired by
- redownloading them. <span class="command"><strong>nix-store --verify --check-contents
- --repair</strong></span> will scan and repair all paths in the Nix
- store. Similarly, <span class="command"><strong>nix-env</strong></span>,
- <span class="command"><strong>nix-build</strong></span>, <span class="command"><strong>nix-instantiate</strong></span>
- and <span class="command"><strong>nix-store --realise</strong></span> have a
- <code class="option">--repair</code> flag to detect and fix bad paths by
- rebuilding or redownloading them.</p></li><li class="listitem"><p>Nix no longer sets the immutable bit on files in the Nix
- store. Instead, the recommended way to guard the Nix store
- against accidental modification on Linux is to make it a read-only
- bind mount, like this:
-
-</p><pre class="screen">
-$ mount --bind /nix/store /nix/store
-$ mount -o remount,ro,bind /nix/store
-</pre><p>
-
- Nix will automatically make <code class="filename">/nix/store</code>
- writable as needed (using a private mount namespace) to allow
- modifications.</p></li><li class="listitem"><p>Store optimisation (replacing identical files in the store
- with hard links) can now be done automatically every time a path
- is added to the store. This is enabled by setting the
- configuration option <code class="literal">auto-optimise-store</code> to
- <code class="literal">true</code> (disabled by default).</p></li><li class="listitem"><p>Nix now supports <span class="command"><strong>xz</strong></span> compression for NARs
- in addition to <span class="command"><strong>bzip2</strong></span>. It compresses about 30%
- better on typical archives and decompresses about twice as
- fast.</p></li><li class="listitem"><p>Basic Nix expression evaluation profiling: setting the
- environment variable <code class="envar">NIX_COUNT_CALLS</code> to
- <code class="literal">1</code> will cause Nix to print how many times each
- primop or function was executed.</p></li><li class="listitem"><p>New primops: <code class="varname">concatLists</code>,
- <code class="varname">elem</code>, <code class="varname">elemAt</code> and
- <code class="varname">filter</code>.</p></li><li class="listitem"><p>The command <span class="command"><strong>nix-copy-closure</strong></span> has a new
- flag <code class="option">--use-substitutes</code> (<code class="option">-s</code>) to
- download missing paths on the target machine using the substitute
- mechanism.</p></li><li class="listitem"><p>The command <span class="command"><strong>nix-worker</strong></span> has been renamed
- to <span class="command"><strong>nix-daemon</strong></span>. Support for running the Nix
- worker in “slave” mode has been removed.</p></li><li class="listitem"><p>The <code class="option">--help</code> flag of every Nix command now
- invokes <span class="command"><strong>man</strong></span>.</p></li><li class="listitem"><p>Chroot builds are now supported on systemd machines.</p></li></ul></div><p>This release has contributions from Eelco Dolstra, Florian
-Friesdorf, Mats Erik Andersson and Shea Levy.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.1"></a>C.18. Release 1.1 (2012-07-18)</h2></div></div></div><p>This release has the following improvements:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>On Linux, when doing a chroot build, Nix now uses various
- namespace features provided by the Linux kernel to improve
- build isolation. Namely:
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>The private network namespace ensures that
- builders cannot talk to the outside world (or vice versa): each
- build only sees a private loopback interface. This also means
- that two concurrent builds can listen on the same port (e.g. as
- part of a test) without conflicting with each
- other.</p></li><li class="listitem"><p>The PID namespace causes each build to start as
- PID 1. Processes outside of the chroot are not visible to those
- on the inside. On the other hand, processes inside the chroot
- <span class="emphasis"><em>are</em></span> visible from the outside (though with
- different PIDs).</p></li><li class="listitem"><p>The IPC namespace prevents the builder from
- communicating with outside processes using SysV IPC mechanisms
- (shared memory, message queues, semaphores). It also ensures
- that all IPC objects are destroyed when the builder
- exits.</p></li><li class="listitem"><p>The UTS namespace ensures that builders see a
- hostname of <code class="literal">localhost</code> rather than the actual
- hostname.</p></li><li class="listitem"><p>The private mount namespace was already used by
- Nix to ensure that the bind-mounts used to set up the chroot are
- cleaned up automatically.</p></li></ul></div><p>
- </p></li><li class="listitem"><p>Build logs are now compressed using
- <span class="command"><strong>bzip2</strong></span>. The command <span class="command"><strong>nix-store
- -l</strong></span> decompresses them on the fly. This can be disabled
- by setting the option <code class="literal">build-compress-log</code> to
- <code class="literal">false</code>.</p></li><li class="listitem"><p>The creation of build logs in
- <code class="filename">/nix/var/log/nix/drvs</code> can be disabled by
- setting the new option <code class="literal">build-keep-log</code> to
- <code class="literal">false</code>. This is useful, for instance, for Hydra
- build machines.</p></li><li class="listitem"><p>Nix now reserves some space in
- <code class="filename">/nix/var/nix/db/reserved</code> to ensure that the
- garbage collector can run successfully if the disk is full. This
- is necessary because SQLite transactions fail if the disk is
- full.</p></li><li class="listitem"><p>Added a basic <code class="function">fetchurl</code> function. This
- is not intended to replace the <code class="function">fetchurl</code> in
- Nixpkgs, but is useful for bootstrapping; e.g., it will allow us
- to get rid of the bootstrap binaries in the Nixpkgs source tree
- and download them instead. You can use it by doing
- <code class="literal">import <nix/fetchurl.nix> { url =
- <em class="replaceable"><code>url</code></em>; sha256 =
- "<em class="replaceable"><code>hash</code></em>"; }</code>. (Shea Levy)</p></li><li class="listitem"><p>Improved RPM spec file. (Michel Alexandre Salim)</p></li><li class="listitem"><p>Support for on-demand socket-based activation in the Nix
- daemon with <span class="command"><strong>systemd</strong></span>.</p></li><li class="listitem"><p>Added a manpage for
- <span class="citerefentry"><span class="refentrytitle">nix.conf</span>(5)</span>.</p></li><li class="listitem"><p>When using the Nix daemon, the <code class="option">-s</code> flag in
- <span class="command"><strong>nix-env -qa</strong></span> is now much faster.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-1.0"></a>C.19. Release 1.0 (2012-05-11)</h2></div></div></div><p>There have been numerous improvements and bug fixes since the
-previous release. Here are the most significant:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Nix can now optionally use the Boehm garbage collector.
- This significantly reduces the Nix evaluator’s memory footprint,
- especially when evaluating large NixOS system configurations. It
- can be enabled using the <code class="option">--enable-gc</code> configure
- option.</p></li><li class="listitem"><p>Nix now uses SQLite for its database. This is faster and
- more flexible than the old <span class="emphasis"><em>ad hoc</em></span> format.
- SQLite is also used to cache the manifests in
- <code class="filename">/nix/var/nix/manifests</code>, resulting in a
- significant speedup.</p></li><li class="listitem"><p>Nix now has an search path for expressions. The search path
- is set using the environment variable <code class="envar">NIX_PATH</code> and
- the <code class="option">-I</code> command line option. In Nix expressions,
- paths between angle brackets are used to specify files that must
- be looked up in the search path. For instance, the expression
- <code class="literal"><nixpkgs/default.nix></code> looks for a file
- <code class="filename">nixpkgs/default.nix</code> relative to every element
- in the search path.</p></li><li class="listitem"><p>The new command <span class="command"><strong>nix-build --run-env</strong></span>
- builds all dependencies of a derivation, then starts a shell in an
- environment containing all variables from the derivation. This is
- useful for reproducing the environment of a derivation for
- development.</p></li><li class="listitem"><p>The new command <span class="command"><strong>nix-store --verify-path</strong></span>
- verifies that the contents of a store path have not
- changed.</p></li><li class="listitem"><p>The new command <span class="command"><strong>nix-store --print-env</strong></span>
- prints out the environment of a derivation in a format that can be
- evaluated by a shell.</p></li><li class="listitem"><p>Attribute names can now be arbitrary strings. For instance,
- you can write <code class="literal">{ "foo-1.2" = …; "bla bla" = …; }."bla
- bla"</code>.</p></li><li class="listitem"><p>Attribute selection can now provide a default value using
- the <code class="literal">or</code> operator. For instance, the expression
- <code class="literal">x.y.z or e</code> evaluates to the attribute
- <code class="literal">x.y.z</code> if it exists, and <code class="literal">e</code>
- otherwise.</p></li><li class="listitem"><p>The right-hand side of the <code class="literal">?</code> operator can
- now be an attribute path, e.g., <code class="literal">attrs ?
- a.b.c</code>.</p></li><li class="listitem"><p>On Linux, Nix will now make files in the Nix store immutable
- on filesystems that support it. This prevents accidental
- modification of files in the store by the root user.</p></li><li class="listitem"><p>Nix has preliminary support for derivations with multiple
- outputs. This is useful because it allows parts of a package to
- be deployed and garbage-collected separately. For instance,
- development parts of a package such as header files or static
- libraries would typically not be part of the closure of an
- application, resulting in reduced disk usage and installation
- time.</p></li><li class="listitem"><p>The Nix store garbage collector is faster and holds the
- global lock for a shorter amount of time.</p></li><li class="listitem"><p>The option <code class="option">--timeout</code> (corresponding to the
- configuration setting <code class="literal">build-timeout</code>) allows you
- to set an absolute timeout on builds — if a build runs for more than
- the given number of seconds, it is terminated. This is useful for
- recovering automatically from builds that are stuck in an infinite
- loop but keep producing output, and for which
- <code class="literal">--max-silent-time</code> is ineffective.</p></li><li class="listitem"><p>Nix development has moved to GitHub (<a class="link" href="https://github.com/NixOS/nix" target="_top">https://github.com/NixOS/nix</a>).</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-0.16"></a>C.20. Release 0.16 (2010-08-17)</h2></div></div></div><p>This release has the following improvements:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>The Nix expression evaluator is now much faster in most
- cases: typically, <a class="link" href="http://www.mail-archive.com/nix-dev@cs.uu.nl/msg04113.html" target="_top">3
- to 8 times compared to the old implementation</a>. It also
- uses less memory. It no longer depends on the ATerm
- library.</p></li><li class="listitem"><p>
- Support for configurable parallelism inside builders. Build
- scripts have always had the ability to perform multiple build
- actions in parallel (for instance, by running <span class="command"><strong>make -j
- 2</strong></span>), but this was not desirable because the number of
- actions to be performed in parallel was not configurable. Nix
- now has an option <code class="option">--cores
- <em class="replaceable"><code>N</code></em></code> as well as a configuration
- setting <code class="varname">build-cores =
- <em class="replaceable"><code>N</code></em></code> that causes the
- environment variable <code class="envar">NIX_BUILD_CORES</code> to be set to
- <em class="replaceable"><code>N</code></em> when the builder is invoked. The
- builder can use this at its discretion to perform a parallel
- build, e.g., by calling <span class="command"><strong>make -j
- <em class="replaceable"><code>N</code></em></strong></span>. In Nixpkgs, this can be
- enabled on a per-package basis by setting the derivation
- attribute <code class="varname">enableParallelBuilding</code> to
- <code class="literal">true</code>.
- </p></li><li class="listitem"><p><span class="command"><strong>nix-store -q</strong></span> now supports XML output
- through the <code class="option">--xml</code> flag.</p></li><li class="listitem"><p>Several bug fixes.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-0.15"></a>C.21. Release 0.15 (2010-03-17)</h2></div></div></div><p>This is a bug-fix release. Among other things, it fixes
-building on Mac OS X (Snow Leopard), and improves the contents of
-<code class="filename">/etc/passwd</code> and <code class="filename">/etc/group</code>
-in <code class="literal">chroot</code> builds.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-0.14"></a>C.22. Release 0.14 (2010-02-04)</h2></div></div></div><p>This release has the following improvements:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>The garbage collector now starts deleting garbage much
- faster than before. It no longer determines liveness of all paths
- in the store, but does so on demand.</p></li><li class="listitem"><p>Added a new operation, <span class="command"><strong>nix-store --query
- --roots</strong></span>, that shows the garbage collector roots that
- directly or indirectly point to the given store paths.</p></li><li class="listitem"><p>Removed support for converting Berkeley DB-based Nix
- databases to the new schema.</p></li><li class="listitem"><p>Removed the <code class="option">--use-atime</code> and
- <code class="option">--max-atime</code> garbage collector options. They were
- not very useful in practice.</p></li><li class="listitem"><p>On Windows, Nix now requires Cygwin 1.7.x.</p></li><li class="listitem"><p>A few bug fixes.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-0.13"></a>C.23. Release 0.13 (2009-11-05)</h2></div></div></div><p>This is primarily a bug fix release. It has some new
-features:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Syntactic sugar for writing nested attribute sets. Instead of
-
-</p><pre class="programlisting">
-{
- foo = {
- bar = 123;
- xyzzy = true;
- };
- a = { b = { c = "d"; }; };
-}
-</pre><p>
-
- you can write
-
-</p><pre class="programlisting">
-{
- foo.bar = 123;
- foo.xyzzy = true;
- a.b.c = "d";
-}
-</pre><p>
-
- This is useful, for instance, in NixOS configuration files.</p></li><li class="listitem"><p>Support for Nix channels generated by Hydra, the Nix-based
- continuous build system. (Hydra generates NAR archives on the
- fly, so the size and hash of these archives isn’t known in
- advance.)</p></li><li class="listitem"><p>Support <code class="literal">i686-linux</code> builds directly on
- <code class="literal">x86_64-linux</code> Nix installations. This is
- implemented using the <code class="function">personality()</code> syscall,
- which causes <span class="command"><strong>uname</strong></span> to return
- <code class="literal">i686</code> in child processes.</p></li><li class="listitem"><p>Various improvements to the <code class="literal">chroot</code>
- support. Building in a <code class="literal">chroot</code> works quite well
- now.</p></li><li class="listitem"><p>Nix no longer blocks if it tries to build a path and another
- process is already building the same path. Instead it tries to
- build another buildable path first. This improves
- parallelism.</p></li><li class="listitem"><p>Support for large (> 4 GiB) files in NAR archives.</p></li><li class="listitem"><p>Various (performance) improvements to the remote build
- mechanism.</p></li><li class="listitem"><p>New primops: <code class="varname">builtins.addErrorContext</code> (to
- add a string to stack traces — useful for debugging),
- <code class="varname">builtins.isBool</code>,
- <code class="varname">builtins.isString</code>,
- <code class="varname">builtins.isInt</code>,
- <code class="varname">builtins.intersectAttrs</code>.</p></li><li class="listitem"><p>OpenSolaris support (Sander van der Burg).</p></li><li class="listitem"><p>Stack traces are no longer displayed unless the
- <code class="option">--show-trace</code> option is used.</p></li><li class="listitem"><p>The scoping rules for <code class="literal">inherit
- (<em class="replaceable"><code>e</code></em>) ...</code> in recursive
- attribute sets have changed. The expression
- <em class="replaceable"><code>e</code></em> can now refer to the attributes
- defined in the containing set.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-0.12"></a>C.24. Release 0.12 (2008-11-20)</h2></div></div></div><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Nix no longer uses Berkeley DB to store Nix store metadata.
- The principal advantages of the new storage scheme are: it works
- properly over decent implementations of NFS (allowing Nix stores
- to be shared between multiple machines); no recovery is needed
- when a Nix process crashes; no write access is needed for
- read-only operations; no more running out of Berkeley DB locks on
- certain operations.</p><p>You still need to compile Nix with Berkeley DB support if
- you want Nix to automatically convert your old Nix store to the
- new schema. If you don’t need this, you can build Nix with the
- <code class="filename">configure</code> option
- <code class="option">--disable-old-db-compat</code>.</p><p>After the automatic conversion to the new schema, you can
- delete the old Berkeley DB files:
-
- </p><pre class="screen">
-$ cd /nix/var/nix/db
-$ rm __db* log.* derivers references referrers reserved validpaths DB_CONFIG</pre><p>
-
- The new metadata is stored in the directories
- <code class="filename">/nix/var/nix/db/info</code> and
- <code class="filename">/nix/var/nix/db/referrer</code>. Though the
- metadata is stored in human-readable plain-text files, they are
- not intended to be human-editable, as Nix is rather strict about
- the format.</p><p>The new storage schema may or may not require less disk
- space than the Berkeley DB environment, mostly depending on the
- cluster size of your file system. With 1 KiB clusters (which
- seems to be the <code class="literal">ext3</code> default nowadays) it
- usually takes up much less space.</p></li><li class="listitem"><p>There is a new substituter that copies paths
- directly from other (remote) Nix stores mounted somewhere in the
- filesystem. For instance, you can speed up an installation by
- mounting some remote Nix store that already has the packages in
- question via NFS or <code class="literal">sshfs</code>. The environment
- variable <code class="envar">NIX_OTHER_STORES</code> specifies the locations of
- the remote Nix directories,
- e.g. <code class="literal">/mnt/remote-fs/nix</code>.</p></li><li class="listitem"><p>New <span class="command"><strong>nix-store</strong></span> operations
- <code class="option">--dump-db</code> and <code class="option">--load-db</code> to dump
- and reload the Nix database.</p></li><li class="listitem"><p>The garbage collector has a number of new options to
- allow only some of the garbage to be deleted. The option
- <code class="option">--max-freed <em class="replaceable"><code>N</code></em></code> tells the
- collector to stop after at least <em class="replaceable"><code>N</code></em> bytes
- have been deleted. The option <code class="option">--max-links
- <em class="replaceable"><code>N</code></em></code> tells it to stop after the
- link count on <code class="filename">/nix/store</code> has dropped below
- <em class="replaceable"><code>N</code></em>. This is useful for very large Nix
- stores on filesystems with a 32000 subdirectories limit (like
- <code class="literal">ext3</code>). The option <code class="option">--use-atime</code>
- causes store paths to be deleted in order of ascending last access
- time. This allows non-recently used stuff to be deleted. The
- option <code class="option">--max-atime <em class="replaceable"><code>time</code></em></code>
- specifies an upper limit to the last accessed time of paths that may
- be deleted. For instance,
-
- </p><pre class="screen">
- $ nix-store --gc -v --max-atime $(date +%s -d "2 months ago")</pre><p>
-
- deletes everything that hasn’t been accessed in two months.</p></li><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> now uses optimistic
- profile locking when performing an operation like installing or
- upgrading, instead of setting an exclusive lock on the profile.
- This allows multiple <span class="command"><strong>nix-env -i / -u / -e</strong></span>
- operations on the same profile in parallel. If a
- <span class="command"><strong>nix-env</strong></span> operation sees at the end that the profile
- was changed in the meantime by another process, it will just
- restart. This is generally cheap because the build results are
- still in the Nix store.</p></li><li class="listitem"><p>The option <code class="option">--dry-run</code> is now
- supported by <span class="command"><strong>nix-store -r</strong></span> and
- <span class="command"><strong>nix-build</strong></span>.</p></li><li class="listitem"><p>The information previously shown by
- <code class="option">--dry-run</code> (i.e., which derivations will be built
- and which paths will be substituted) is now always shown by
- <span class="command"><strong>nix-env</strong></span>, <span class="command"><strong>nix-store -r</strong></span> and
- <span class="command"><strong>nix-build</strong></span>. The total download size of
- substitutable paths is now also shown. For instance, a build will
- show something like
-
- </p><pre class="screen">
-the following derivations will be built:
- /nix/store/129sbxnk5n466zg6r1qmq1xjv9zymyy7-activate-configuration.sh.drv
- /nix/store/7mzy971rdm8l566ch8hgxaf89x7lr7ik-upstart-jobs.drv
- ...
-the following paths will be downloaded/copied (30.02 MiB):
- /nix/store/4m8pvgy2dcjgppf5b4cj5l6wyshjhalj-samba-3.2.4
- /nix/store/7h1kwcj29ip8vk26rhmx6bfjraxp0g4l-libunwind-0.98.6
- ...</pre><p>
-
- </p></li><li class="listitem"><p>Language features:
-
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>@-patterns as in Haskell. For instance, in a
- function definition
-
- </p><pre class="programlisting">f = args @ {x, y, z}: <em class="replaceable"><code>...</code></em>;</pre><p>
-
- <code class="varname">args</code> refers to the argument as a whole, which
- is further pattern-matched against the attribute set pattern
- <code class="literal">{x, y, z}</code>.</p></li><li class="listitem"><p>“<code class="literal">...</code>” (ellipsis) patterns.
- An attribute set pattern can now say <code class="literal">...</code> at
- the end of the attribute name list to specify that the function
- takes <span class="emphasis"><em>at least</em></span> the listed attributes, while
- ignoring additional attributes. For instance,
-
- </p><pre class="programlisting">{stdenv, fetchurl, fuse, ...}: <em class="replaceable"><code>...</code></em></pre><p>
-
- defines a function that accepts any attribute set that includes
- at least the three listed attributes.</p></li><li class="listitem"><p>New primops:
- <code class="varname">builtins.parseDrvName</code> (split a package name
- string like <code class="literal">"nix-0.12pre12876"</code> into its name
- and version components, e.g. <code class="literal">"nix"</code> and
- <code class="literal">"0.12pre12876"</code>),
- <code class="varname">builtins.compareVersions</code> (compare two version
- strings using the same algorithm that <span class="command"><strong>nix-env</strong></span>
- uses), <code class="varname">builtins.length</code> (efficiently compute
- the length of a list), <code class="varname">builtins.mul</code> (integer
- multiplication), <code class="varname">builtins.div</code> (integer
- division).
-
- </p></li></ul></div><p>
-
- </p></li><li class="listitem"><p><span class="command"><strong>nix-prefetch-url</strong></span> now supports
- <code class="literal">mirror://</code> URLs, provided that the environment
- variable <code class="envar">NIXPKGS_ALL</code> points at a Nixpkgs
- tree.</p></li><li class="listitem"><p>Removed the commands
- <span class="command"><strong>nix-pack-closure</strong></span> and
- <span class="command"><strong>nix-unpack-closure</strong></span>. You can do almost the same
- thing but much more efficiently by doing <code class="literal">nix-store --export
- $(nix-store -qR <em class="replaceable"><code>paths</code></em>) > closure</code> and
- <code class="literal">nix-store --import <
- closure</code>.</p></li><li class="listitem"><p>Lots of bug fixes, including a big performance bug in
- the handling of <code class="literal">with</code>-expressions.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ssec-relnotes-0.11"></a>C.25. Release 0.11 (2007-12-31)</h2></div></div></div><p>Nix 0.11 has many improvements over the previous stable release.
-The most important improvement is secure multi-user support. It also
-features many usability enhancements and language extensions, many of
-them prompted by NixOS, the purely functional Linux distribution based
-on Nix. Here is an (incomplete) list:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Secure multi-user support. A single Nix store can
- now be shared between multiple (possible untrusted) users. This is
- an important feature for NixOS, where it allows non-root users to
- install software. The old setuid method for sharing a store between
- multiple users has been removed. Details for setting up a
- multi-user store can be found in the manual.</p></li><li class="listitem"><p>The new command <span class="command"><strong>nix-copy-closure</strong></span>
- gives you an easy and efficient way to exchange software between
- machines. It copies the missing parts of the closure of a set of
- store path to or from a remote machine via
- <span class="command"><strong>ssh</strong></span>.</p></li><li class="listitem"><p>A new kind of string literal: strings between double
- single-quotes (<code class="literal">''</code>) have indentation
- “intelligently” removed. This allows large strings (such as shell
- scripts or configuration file fragments in NixOS) to cleanly follow
- the indentation of the surrounding expression. It also requires
- much less escaping, since <code class="literal">''</code> is less common in
- most languages than <code class="literal">"</code>.</p></li><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> <code class="option">--set</code>
- modifies the current generation of a profile so that it contains
- exactly the specified derivation, and nothing else. For example,
- <code class="literal">nix-env -p /nix/var/nix/profiles/browser --set
- firefox</code> lets the profile named
- <code class="filename">browser</code> contain just Firefox.</p></li><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> now maintains
- meta-information about installed packages in profiles. The
- meta-information is the contents of the <code class="varname">meta</code>
- attribute of derivations, such as <code class="varname">description</code> or
- <code class="varname">homepage</code>. The command <code class="literal">nix-env -q --xml
- --meta</code> shows all meta-information.</p></li><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> now uses the
- <code class="varname">meta.priority</code> attribute of derivations to resolve
- filename collisions between packages. Lower priority values denote
- a higher priority. For instance, the GCC wrapper package and the
- Binutils package in Nixpkgs both have a file
- <code class="filename">bin/ld</code>, so previously if you tried to install
- both you would get a collision. Now, on the other hand, the GCC
- wrapper declares a higher priority than Binutils, so the former’s
- <code class="filename">bin/ld</code> is symlinked in the user
- environment.</p></li><li class="listitem"><p><span class="command"><strong>nix-env -i / -u</strong></span>: instead of
- breaking package ties by version, break them by priority and version
- number. That is, if there are multiple packages with the same name,
- then pick the package with the highest priority, and only use the
- version if there are multiple packages with the same
- priority.</p><p>This makes it possible to mark specific versions/variant in
- Nixpkgs more or less desirable than others. A typical example would
- be a beta version of some package (e.g.,
- <code class="literal">gcc-4.2.0rc1</code>) which should not be installed even
- though it is the highest version, except when it is explicitly
- selected (e.g., <code class="literal">nix-env -i
- gcc-4.2.0rc1</code>).</p></li><li class="listitem"><p><span class="command"><strong>nix-env --set-flag</strong></span> allows meta
- attributes of installed packages to be modified. There are several
- attributes that can be usefully modified, because they affect the
- behaviour of <span class="command"><strong>nix-env</strong></span> or the user environment
- build script:
-
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p><code class="varname">meta.priority</code> can be changed
- to resolve filename clashes (see above).</p></li><li class="listitem"><p><code class="varname">meta.keep</code> can be set to
- <code class="literal">true</code> to prevent the package from being
- upgraded or replaced. Useful if you want to hang on to an older
- version of a package.</p></li><li class="listitem"><p><code class="varname">meta.active</code> can be set to
- <code class="literal">false</code> to “disable” the package. That is, no
- symlinks will be generated to the files of the package, but it
- remains part of the profile (so it won’t be garbage-collected).
- Set it back to <code class="literal">true</code> to re-enable the
- package.</p></li></ul></div><p>
-
- </p></li><li class="listitem"><p><span class="command"><strong>nix-env -q</strong></span> now has a flag
- <code class="option">--prebuilt-only</code> (<code class="option">-b</code>) that causes
- <span class="command"><strong>nix-env</strong></span> to show only those derivations whose
- output is already in the Nix store or that can be substituted (i.e.,
- downloaded from somewhere). In other words, it shows the packages
- that can be installed “quickly”, i.e., don’t need to be built from
- source. The <code class="option">-b</code> flag is also available in
- <span class="command"><strong>nix-env -i</strong></span> and <span class="command"><strong>nix-env -u</strong></span> to
- filter out derivations for which no pre-built binary is
- available.</p></li><li class="listitem"><p>The new option <code class="option">--argstr</code> (in
- <span class="command"><strong>nix-env</strong></span>, <span class="command"><strong>nix-instantiate</strong></span> and
- <span class="command"><strong>nix-build</strong></span>) is like <code class="option">--arg</code>, except
- that the value is a string. For example, <code class="literal">--argstr system
- i686-linux</code> is equivalent to <code class="literal">--arg system
- \"i686-linux\"</code> (note that <code class="option">--argstr</code>
- prevents annoying quoting around shell arguments).</p></li><li class="listitem"><p><span class="command"><strong>nix-store</strong></span> has a new operation
- <code class="option">--read-log</code> (<code class="option">-l</code>)
- <em class="parameter"><code>paths</code></em> that shows the build log of the given
- paths.</p></li><li class="listitem"><p>Nix now uses Berkeley DB 4.5. The database is
- upgraded automatically, but you should be careful not to use old
- versions of Nix that still use Berkeley DB 4.4.</p></li><li class="listitem"><p>The option <code class="option">--max-silent-time</code>
- (corresponding to the configuration setting
- <code class="literal">build-max-silent-time</code>) allows you to set a
- timeout on builds — if a build produces no output on
- <code class="literal">stdout</code> or <code class="literal">stderr</code> for the given
- number of seconds, it is terminated. This is useful for recovering
- automatically from builds that are stuck in an infinite
- loop.</p></li><li class="listitem"><p><span class="command"><strong>nix-channel</strong></span>: each subscribed
- channel is its own attribute in the top-level expression generated
- for the channel. This allows disambiguation (e.g. <code class="literal">nix-env
- -i -A nixpkgs_unstable.firefox</code>).</p></li><li class="listitem"><p>The substitutes table has been removed from the
- database. This makes operations such as <span class="command"><strong>nix-pull</strong></span>
- and <span class="command"><strong>nix-channel --update</strong></span> much, much
- faster.</p></li><li class="listitem"><p><span class="command"><strong>nix-pull</strong></span> now supports
- bzip2-compressed manifests. This speeds up
- channels.</p></li><li class="listitem"><p><span class="command"><strong>nix-prefetch-url</strong></span> now has a
- limited form of caching. This is used by
- <span class="command"><strong>nix-channel</strong></span> to prevent unnecessary downloads when
- the channel hasn’t changed.</p></li><li class="listitem"><p><span class="command"><strong>nix-prefetch-url</strong></span> now by default
- computes the SHA-256 hash of the file instead of the MD5 hash. In
- calls to <code class="function">fetchurl</code> you should pass the
- <code class="literal">sha256</code> attribute instead of
- <code class="literal">md5</code>. You can pass either a hexadecimal or a
- base-32 encoding of the hash.</p></li><li class="listitem"><p>Nix can now perform builds in an automatically
- generated “chroot”. This prevents a builder from accessing stuff
- outside of the Nix store, and thus helps ensure purity. This is an
- experimental feature.</p></li><li class="listitem"><p>The new command <span class="command"><strong>nix-store
- --optimise</strong></span> reduces Nix store disk space usage by finding
- identical files in the store and hard-linking them to each other.
- It typically reduces the size of the store by something like
- 25-35%.</p></li><li class="listitem"><p><code class="filename">~/.nix-defexpr</code> can now be a
- directory, in which case the Nix expressions in that directory are
- combined into an attribute set, with the file names used as the
- names of the attributes. The command <span class="command"><strong>nix-env
- --import</strong></span> (which set the
- <code class="filename">~/.nix-defexpr</code> symlink) is
- removed.</p></li><li class="listitem"><p>Derivations can specify the new special attribute
- <code class="varname">allowedReferences</code> to enforce that the references
- in the output of a derivation are a subset of a declared set of
- paths. For example, if <code class="varname">allowedReferences</code> is an
- empty list, then the output must not have any references. This is
- used in NixOS to check that generated files such as initial ramdisks
- for booting Linux don’t have any dependencies.</p></li><li class="listitem"><p>The new attribute
- <code class="varname">exportReferencesGraph</code> allows builders access to
- the references graph of their inputs. This is used in NixOS for
- tasks such as generating ISO-9660 images that contain a Nix store
- populated with the closure of certain paths.</p></li><li class="listitem"><p>Fixed-output derivations (like
- <code class="function">fetchurl</code>) can define the attribute
- <code class="varname">impureEnvVars</code> to allow external environment
- variables to be passed to builders. This is used in Nixpkgs to
- support proxy configuration, among other things.</p></li><li class="listitem"><p>Several new built-in functions:
- <code class="function">builtins.attrNames</code>,
- <code class="function">builtins.filterSource</code>,
- <code class="function">builtins.isAttrs</code>,
- <code class="function">builtins.isFunction</code>,
- <code class="function">builtins.listToAttrs</code>,
- <code class="function">builtins.stringLength</code>,
- <code class="function">builtins.sub</code>,
- <code class="function">builtins.substring</code>,
- <code class="function">throw</code>,
- <code class="function">builtins.trace</code>,
- <code class="function">builtins.readFile</code>.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ch-relnotes-0.10.1"></a>C.26. Release 0.10.1 (2006-10-11)</h2></div></div></div><p>This release fixes two somewhat obscure bugs that occur when
-evaluating Nix expressions that are stored inside the Nix store
-(<code class="literal">NIX-67</code>). These do not affect most users.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ch-relnotes-0.10"></a>C.27. Release 0.10 (2006-10-06)</h2></div></div></div><div class="note"><h3 class="title">Note</h3><p>This version of Nix uses Berkeley DB 4.4 instead of 4.3.
-The database is upgraded automatically, but you should be careful not
-to use old versions of Nix that still use Berkeley DB 4.3. In
-particular, if you use a Nix installed through Nix, you should run
-
-</p><pre class="screen">
-$ nix-store --clear-substitutes</pre><p>
-
-first.</p></div><div class="warning"><h3 class="title">Warning</h3><p>Also, the database schema has changed slighted to fix a
-performance issue (see below). When you run any Nix 0.10 command for
-the first time, the database will be upgraded automatically. This is
-irreversible.</p></div><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> usability improvements:
-
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>An option <code class="option">--compare-versions</code>
- (or <code class="option">-c</code>) has been added to <span class="command"><strong>nix-env
- --query</strong></span> to allow you to compare installed versions of
- packages to available versions, or vice versa. An easy way to
- see if you are up to date with what’s in your subscribed
- channels is <code class="literal">nix-env -qc \*</code>.</p></li><li class="listitem"><p><code class="literal">nix-env --query</code> now takes as
- arguments a list of package names about which to show
- information, just like <code class="option">--install</code>, etc.: for
- example, <code class="literal">nix-env -q gcc</code>. Note that to show
- all derivations, you need to specify
- <code class="literal">\*</code>.</p></li><li class="listitem"><p><code class="literal">nix-env -i
- <em class="replaceable"><code>pkgname</code></em></code> will now install
- the highest available version of
- <em class="replaceable"><code>pkgname</code></em>, rather than installing all
- available versions (which would probably give collisions)
- (<code class="literal">NIX-31</code>).</p></li><li class="listitem"><p><code class="literal">nix-env (-i|-u) --dry-run</code> now
- shows exactly which missing paths will be built or
- substituted.</p></li><li class="listitem"><p><code class="literal">nix-env -qa --description</code>
- shows human-readable descriptions of packages, provided that
- they have a <code class="literal">meta.description</code> attribute (which
- most packages in Nixpkgs don’t have yet).</p></li></ul></div><p>
-
- </p></li><li class="listitem"><p>New language features:
-
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Reference scanning (which happens after each
- build) is much faster and takes a constant amount of
- memory.</p></li><li class="listitem"><p>String interpolation. Expressions like
-
-</p><pre class="programlisting">
-"--with-freetype2-library=" + freetype + "/lib"</pre><p>
-
- can now be written as
-
-</p><pre class="programlisting">
-"--with-freetype2-library=${freetype}/lib"</pre><p>
-
- You can write arbitrary expressions within
- <code class="literal">${<em class="replaceable"><code>...</code></em>}</code>, not just
- identifiers.</p></li><li class="listitem"><p>Multi-line string literals.</p></li><li class="listitem"><p>String concatenations can now involve
- derivations, as in the example <code class="code">"--with-freetype2-library="
- + freetype + "/lib"</code>. This was not previously possible
- because we need to register that a derivation that uses such a
- string is dependent on <code class="literal">freetype</code>. The
- evaluator now properly propagates this information.
- Consequently, the subpath operator (<code class="literal">~</code>) has
- been deprecated.</p></li><li class="listitem"><p>Default values of function arguments can now
- refer to other function arguments; that is, all arguments are in
- scope in the default values
- (<code class="literal">NIX-45</code>).</p></li><li class="listitem"><p>Lots of new built-in primitives, such as
- functions for list manipulation and integer arithmetic. See the
- manual for a complete list. All primops are now available in
- the set <code class="varname">builtins</code>, allowing one to test for
- the availability of primop in a backwards-compatible
- way.</p></li><li class="listitem"><p>Real let-expressions: <code class="literal">let x = ...;
- ... z = ...; in ...</code>.</p></li></ul></div><p>
-
- </p></li><li class="listitem"><p>New commands <span class="command"><strong>nix-pack-closure</strong></span> and
- <span class="command"><strong>nix-unpack-closure</strong></span> than can be used to easily
- transfer a store path with all its dependencies to another machine.
- Very convenient whenever you have some package on your machine and
- you want to copy it somewhere else.</p></li><li class="listitem"><p>XML support:
-
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p><code class="literal">nix-env -q --xml</code> prints the
- installed or available packages in an XML representation for
- easy processing by other tools.</p></li><li class="listitem"><p><code class="literal">nix-instantiate --eval-only
- --xml</code> prints an XML representation of the resulting
- term. (The new flag <code class="option">--strict</code> forces ‘deep’
- evaluation of the result, i.e., list elements and attributes are
- evaluated recursively.)</p></li><li class="listitem"><p>In Nix expressions, the primop
- <code class="function">builtins.toXML</code> converts a term to an XML
- representation. This is primarily useful for passing structured
- information to builders.</p></li></ul></div><p>
-
- </p></li><li class="listitem"><p>You can now unambiguously specify which derivation to
- build or install in <span class="command"><strong>nix-env</strong></span>,
- <span class="command"><strong>nix-instantiate</strong></span> and <span class="command"><strong>nix-build</strong></span>
- using the <code class="option">--attr</code> / <code class="option">-A</code> flags, which
- takes an attribute name as argument. (Unlike symbolic package names
- such as <code class="literal">subversion-1.4.0</code>, attribute names in an
- attribute set are unique.) For instance, a quick way to perform a
- test build of a package in Nixpkgs is <code class="literal">nix-build
- pkgs/top-level/all-packages.nix -A
- <em class="replaceable"><code>foo</code></em></code>. <code class="literal">nix-env -q
- --attr</code> shows the attribute names corresponding to each
- derivation.</p></li><li class="listitem"><p>If the top-level Nix expression used by
- <span class="command"><strong>nix-env</strong></span>, <span class="command"><strong>nix-instantiate</strong></span> or
- <span class="command"><strong>nix-build</strong></span> evaluates to a function whose arguments
- all have default values, the function will be called automatically.
- Also, the new command-line switch <code class="option">--arg
- <em class="replaceable"><code>name</code></em>
- <em class="replaceable"><code>value</code></em></code> can be used to specify
- function arguments on the command line.</p></li><li class="listitem"><p><code class="literal">nix-install-package --url
- <em class="replaceable"><code>URL</code></em></code> allows a package to be
- installed directly from the given URL.</p></li><li class="listitem"><p>Nix now works behind an HTTP proxy server; just set
- the standard environment variables <code class="envar">http_proxy</code>,
- <code class="envar">https_proxy</code>, <code class="envar">ftp_proxy</code> or
- <code class="envar">all_proxy</code> appropriately. Functions such as
- <code class="function">fetchurl</code> in Nixpkgs also respect these
- variables.</p></li><li class="listitem"><p><code class="literal">nix-build -o
- <em class="replaceable"><code>symlink</code></em></code> allows the symlink to
- the build result to be named something other than
- <code class="literal">result</code>.</p></li><li class="listitem"><p>Platform support:
-
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Support for 64-bit platforms, provided a <a class="link" href="http://bugzilla.sen.cwi.nl:8080/show_bug.cgi?id=606" target="_top">suitably
- patched ATerm library</a> is used. Also, files larger than 2
- GiB are now supported.</p></li><li class="listitem"><p>Added support for Cygwin (Windows,
- <code class="literal">i686-cygwin</code>), Mac OS X on Intel
- (<code class="literal">i686-darwin</code>) and Linux on PowerPC
- (<code class="literal">powerpc-linux</code>).</p></li><li class="listitem"><p>Users of SMP and multicore machines will
- appreciate that the number of builds to be performed in parallel
- can now be specified in the configuration file in the
- <code class="literal">build-max-jobs</code> setting.</p></li></ul></div><p>
-
- </p></li><li class="listitem"><p>Garbage collector improvements:
-
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Open files (such as running programs) are now
- used as roots of the garbage collector. This prevents programs
- that have been uninstalled from being garbage collected while
- they are still running. The script that detects these
- additional runtime roots
- (<code class="filename">find-runtime-roots.pl</code>) is inherently
- system-specific, but it should work on Linux and on all
- platforms that have the <span class="command"><strong>lsof</strong></span>
- utility.</p></li><li class="listitem"><p><code class="literal">nix-store --gc</code>
- (a.k.a. <span class="command"><strong>nix-collect-garbage</strong></span>) prints out the
- number of bytes freed on standard output. <code class="literal">nix-store
- --gc --print-dead</code> shows how many bytes would be freed
- by an actual garbage collection.</p></li><li class="listitem"><p><code class="literal">nix-collect-garbage -d</code>
- removes all old generations of <span class="emphasis"><em>all</em></span> profiles
- before calling the actual garbage collector (<code class="literal">nix-store
- --gc</code>). This is an easy way to get rid of all old
- packages in the Nix store.</p></li><li class="listitem"><p><span class="command"><strong>nix-store</strong></span> now has an
- operation <code class="option">--delete</code> to delete specific paths
- from the Nix store. It won’t delete reachable (non-garbage)
- paths unless <code class="option">--ignore-liveness</code> is
- specified.</p></li></ul></div><p>
-
- </p></li><li class="listitem"><p>Berkeley DB 4.4’s process registry feature is used
- to recover from crashed Nix processes.</p></li><li class="listitem"><p>A performance issue has been fixed with the
- <code class="literal">referer</code> table, which stores the inverse of the
- <code class="literal">references</code> table (i.e., it tells you what store
- paths refer to a given path). Maintaining this table could take a
- quadratic amount of time, as well as a quadratic amount of Berkeley
- DB log file space (in particular when running the garbage collector)
- (<code class="literal">NIX-23</code>).</p></li><li class="listitem"><p>Nix now catches the <code class="literal">TERM</code> and
- <code class="literal">HUP</code> signals in addition to the
- <code class="literal">INT</code> signal. So you can now do a <code class="literal">killall
- nix-store</code> without triggering a database
- recovery.</p></li><li class="listitem"><p><span class="command"><strong>bsdiff</strong></span> updated to version
- 4.3.</p></li><li class="listitem"><p>Substantial performance improvements in expression
- evaluation and <code class="literal">nix-env -qa</code>, all thanks to <a class="link" href="http://valgrind.org/" target="_top">Valgrind</a>. Memory use has
- been reduced by a factor 8 or so. Big speedup by memoisation of
- path hashing.</p></li><li class="listitem"><p>Lots of bug fixes, notably:
-
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Make sure that the garbage collector can run
- successfully when the disk is full
- (<code class="literal">NIX-18</code>).</p></li><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> now locks the profile
- to prevent races between concurrent <span class="command"><strong>nix-env</strong></span>
- operations on the same profile
- (<code class="literal">NIX-7</code>).</p></li><li class="listitem"><p>Removed misleading messages from
- <code class="literal">nix-env -i</code> (e.g., <code class="literal">installing
- `foo'</code> followed by <code class="literal">uninstalling
- `foo'</code>) (<code class="literal">NIX-17</code>).</p></li></ul></div><p>
-
- </p></li><li class="listitem"><p>Nix source distributions are a lot smaller now since
- we no longer include a full copy of the Berkeley DB source
- distribution (but only the bits we need).</p></li><li class="listitem"><p>Header files are now installed so that external
- programs can use the Nix libraries.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ch-relnotes-0.9.2"></a>C.28. Release 0.9.2 (2005-09-21)</h2></div></div></div><p>This bug fix release fixes two problems on Mac OS X:
-
-</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>If Nix was linked against statically linked versions
- of the ATerm or Berkeley DB library, there would be dynamic link
- errors at runtime.</p></li><li class="listitem"><p><span class="command"><strong>nix-pull</strong></span> and
- <span class="command"><strong>nix-push</strong></span> intermittently failed due to race
- conditions involving pipes and child processes with error messages
- such as <code class="literal">open2: open(GLOB(0x180b2e4), >&=9) failed: Bad
- file descriptor at /nix/bin/nix-pull line 77</code> (issue
- <code class="literal">NIX-14</code>).</p></li></ul></div><p>
-
-</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ch-relnotes-0.9.1"></a>C.29. Release 0.9.1 (2005-09-20)</h2></div></div></div><p>This bug fix release addresses a problem with the ATerm library
-when the <code class="option">--with-aterm</code> flag in
-<span class="command"><strong>configure</strong></span> was <span class="emphasis"><em>not</em></span> used.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ch-relnotes-0.9"></a>C.30. Release 0.9 (2005-09-16)</h2></div></div></div><p>NOTE: this version of Nix uses Berkeley DB 4.3 instead of 4.2.
-The database is upgraded automatically, but you should be careful not
-to use old versions of Nix that still use Berkeley DB 4.2. In
-particular, if you use a Nix installed through Nix, you should run
-
-</p><pre class="screen">
-$ nix-store --clear-substitutes</pre><p>
-
-first.</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Unpacking of patch sequences is much faster now
- since we no longer do redundant unpacking and repacking of
- intermediate paths.</p></li><li class="listitem"><p>Nix now uses Berkeley DB 4.3.</p></li><li class="listitem"><p>The <code class="function">derivation</code> primitive is
- lazier. Attributes of dependent derivations can mutually refer to
- each other (as long as there are no data dependencies on the
- <code class="varname">outPath</code> and <code class="varname">drvPath</code> attributes
- computed by <code class="function">derivation</code>).</p><p>For example, the expression <code class="literal">derivation
- attrs</code> now evaluates to (essentially)
-
- </p><pre class="programlisting">
-attrs // {
- type = "derivation";
- outPath = derivation! attrs;
- drvPath = derivation! attrs;
-}</pre><p>
-
- where <code class="function">derivation!</code> is a primop that does the
- actual derivation instantiation (i.e., it does what
- <code class="function">derivation</code> used to do). The advantage is that
- it allows commands such as <span class="command"><strong>nix-env -qa</strong></span> and
- <span class="command"><strong>nix-env -i</strong></span> to be much faster since they no longer
- need to instantiate all derivations, just the
- <code class="varname">name</code> attribute.</p><p>Also, it allows derivations to cyclically reference each
- other, for example,
-
- </p><pre class="programlisting">
-webServer = derivation {
- ...
- hostName = "svn.cs.uu.nl";
- services = [svnService];
-};
-
-svnService = derivation {
- ...
- hostName = webServer.hostName;
-};</pre><p>
-
- Previously, this would yield a black hole (infinite recursion).</p></li><li class="listitem"><p><span class="command"><strong>nix-build</strong></span> now defaults to using
- <code class="filename">./default.nix</code> if no Nix expression is
- specified.</p></li><li class="listitem"><p><span class="command"><strong>nix-instantiate</strong></span>, when applied to
- a Nix expression that evaluates to a function, will call the
- function automatically if all its arguments have
- defaults.</p></li><li class="listitem"><p>Nix now uses libtool to build dynamic libraries.
- This reduces the size of executables.</p></li><li class="listitem"><p>A new list concatenation operator
- <code class="literal">++</code>. For example, <code class="literal">[1 2 3] ++ [4 5
- 6]</code> evaluates to <code class="literal">[1 2 3 4 5
- 6]</code>.</p></li><li class="listitem"><p>Some currently undocumented primops to support
- low-level build management using Nix (i.e., using Nix as a Make
- replacement). See the commit messages for <code class="literal">r3578</code>
- and <code class="literal">r3580</code>.</p></li><li class="listitem"><p>Various bug fixes and performance
- improvements.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ch-relnotes-0.8.1"></a>C.31. Release 0.8.1 (2005-04-13)</h2></div></div></div><p>This is a bug fix release.</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Patch downloading was broken.</p></li><li class="listitem"><p>The garbage collector would not delete paths that
- had references from invalid (but substitutable)
- paths.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ch-relnotes-0.8"></a>C.32. Release 0.8 (2005-04-11)</h2></div></div></div><p>NOTE: the hashing scheme in Nix 0.8 changed (as detailed below).
-As a result, <span class="command"><strong>nix-pull</strong></span> manifests and channels built
-for Nix 0.7 and below will not work anymore. However, the Nix
-expression language has not changed, so you can still build from
-source. Also, existing user environments continue to work. Nix 0.8
-will automatically upgrade the database schema of previous
-installations when it is first run.</p><p>If you get the error message
-
-</p><pre class="screen">
-you have an old-style manifest `/nix/var/nix/manifests/[...]'; please
-delete it</pre><p>
-
-you should delete previously downloaded manifests:
-
-</p><pre class="screen">
-$ rm /nix/var/nix/manifests/*</pre><p>
-
-If <span class="command"><strong>nix-channel</strong></span> gives the error message
-
-</p><pre class="screen">
-manifest `http://catamaran.labs.cs.uu.nl/dist/nix/channels/[channel]/MANIFEST'
-is too old (i.e., for Nix <= 0.7)</pre><p>
-
-then you should unsubscribe from the offending channel
-(<span class="command"><strong>nix-channel --remove
-<em class="replaceable"><code>URL</code></em></strong></span>; leave out
-<code class="literal">/MANIFEST</code>), and subscribe to the same URL, with
-<code class="literal">channels</code> replaced by <code class="literal">channels-v3</code>
-(e.g., <a class="link" href="http://catamaran.labs.cs.uu.nl/dist/nix/channels-v3/nixpkgs-unstable" target="_top">http://catamaran.labs.cs.uu.nl/dist/nix/channels-v3/nixpkgs-unstable</a>).</p><p>Nix 0.8 has the following improvements:
-
-</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>The cryptographic hashes used in store paths are now
- 160 bits long, but encoded in base-32 so that they are still only 32
- characters long (e.g.,
- <code class="filename">/nix/store/csw87wag8bqlqk7ipllbwypb14xainap-atk-1.9.0</code>).
- (This is actually a 160 bit truncation of a SHA-256
- hash.)</p></li><li class="listitem"><p>Big cleanups and simplifications of the basic store
- semantics. The notion of “closure store expressions” is gone (and
- so is the notion of “successors”); the file system references of a
- store path are now just stored in the database.</p><p>For instance, given any store path, you can query its closure:
-
- </p><pre class="screen">
-$ nix-store -qR $(which firefox)
-... lots of paths ...</pre><p>
-
- Also, Nix now remembers for each store path the derivation that
- built it (the “deriver”):
-
- </p><pre class="screen">
-$ nix-store -qR $(which firefox)
-/nix/store/4b0jx7vq80l9aqcnkszxhymsf1ffa5jd-firefox-1.0.1.drv</pre><p>
-
- So to see the build-time dependencies, you can do
-
- </p><pre class="screen">
-$ nix-store -qR $(nix-store -qd $(which firefox))</pre><p>
-
- or, in a nicer format:
-
- </p><pre class="screen">
-$ nix-store -q --tree $(nix-store -qd $(which firefox))</pre><p>
-
- </p><p>File system references are also stored in reverse. For
- instance, you can query all paths that directly or indirectly use a
- certain Glibc:
-
- </p><pre class="screen">
-$ nix-store -q --referrers-closure \
- /nix/store/8lz9yc6zgmc0vlqmn2ipcpkjlmbi51vv-glibc-2.3.4</pre><p>
-
- </p></li><li class="listitem"><p>The concept of fixed-output derivations has been
- formalised. Previously, functions such as
- <code class="function">fetchurl</code> in Nixpkgs used a hack (namely,
- explicitly specifying a store path hash) to prevent changes to, say,
- the URL of the file from propagating upwards through the dependency
- graph, causing rebuilds of everything. This can now be done cleanly
- by specifying the <code class="varname">outputHash</code> and
- <code class="varname">outputHashAlgo</code> attributes. Nix itself checks
- that the content of the output has the specified hash. (This is
- important for maintaining certain invariants necessary for future
- work on secure shared stores.)</p></li><li class="listitem"><p>One-click installation :-) It is now possible to
- install any top-level component in Nixpkgs directly, through the web
- — see, e.g., <a class="link" href="http://catamaran.labs.cs.uu.nl/dist/nixpkgs-0.8/" target="_top">http://catamaran.labs.cs.uu.nl/dist/nixpkgs-0.8/</a>.
- All you have to do is associate
- <code class="filename">/nix/bin/nix-install-package</code> with the MIME type
- <code class="literal">application/nix-package</code> (or the extension
- <code class="filename">.nixpkg</code>), and clicking on a package link will
- cause it to be installed, with all appropriate dependencies. If you
- just want to install some specific application, this is easier than
- subscribing to a channel.</p></li><li class="listitem"><p><span class="command"><strong>nix-store -r
- <em class="replaceable"><code>PATHS</code></em></strong></span> now builds all the
- derivations PATHS in parallel. Previously it did them sequentially
- (though exploiting possible parallelism between subderivations).
- This is nice for build farms.</p></li><li class="listitem"><p><span class="command"><strong>nix-channel</strong></span> has new operations
- <code class="option">--list</code> and
- <code class="option">--remove</code>.</p></li><li class="listitem"><p>New ways of installing components into user
- environments:
-
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Copy from another user environment:
-
- </p><pre class="screen">
-$ nix-env -i --from-profile .../other-profile firefox</pre><p>
-
- </p></li><li class="listitem"><p>Install a store derivation directly (bypassing the
- Nix expression language entirely):
-
- </p><pre class="screen">
-$ nix-env -i /nix/store/z58v41v21xd3...-aterm-2.3.1.drv</pre><p>
-
- (This is used to implement <span class="command"><strong>nix-install-package</strong></span>,
- which is therefore immune to evolution in the Nix expression
- language.)</p></li><li class="listitem"><p>Install an already built store path directly:
-
- </p><pre class="screen">
-$ nix-env -i /nix/store/hsyj5pbn0d9i...-aterm-2.3.1</pre><p>
-
- </p></li><li class="listitem"><p>Install the result of a Nix expression specified
- as a command-line argument:
-
- </p><pre class="screen">
-$ nix-env -f .../i686-linux.nix -i -E 'x: x.firefoxWrapper'</pre><p>
-
- The difference with the normal installation mode is that
- <code class="option">-E</code> does not use the <code class="varname">name</code>
- attributes of derivations. Therefore, this can be used to
- disambiguate multiple derivations with the same
- name.</p></li></ul></div></li><li class="listitem"><p>A hash of the contents of a store path is now stored
- in the database after a successful build. This allows you to check
- whether store paths have been tampered with: <span class="command"><strong>nix-store
- --verify --check-contents</strong></span>.</p></li><li class="listitem"><p>Implemented a concurrent garbage collector. It is now
- always safe to run the garbage collector, even if other Nix
- operations are happening simultaneously.</p><p>However, there can still be GC races if you use
- <span class="command"><strong>nix-instantiate</strong></span> and <span class="command"><strong>nix-store
- --realise</strong></span> directly to build things. To prevent races,
- use the <code class="option">--add-root</code> flag of those commands.</p></li><li class="listitem"><p>The garbage collector now finally deletes paths in
- the right order (i.e., topologically sorted under the “references”
- relation), thus making it safe to interrupt the collector without
- risking a store that violates the closure
- invariant.</p></li><li class="listitem"><p>Likewise, the substitute mechanism now downloads
- files in the right order, thus preserving the closure invariant at
- all times.</p></li><li class="listitem"><p>The result of <span class="command"><strong>nix-build</strong></span> is now
- registered as a root of the garbage collector. If the
- <code class="filename">./result</code> link is deleted, the GC root
- disappears automatically.</p></li><li class="listitem"><p>The behaviour of the garbage collector can be changed
- globally by setting options in
- <code class="filename">/nix/etc/nix/nix.conf</code>.
-
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p><code class="literal">gc-keep-derivations</code> specifies
- whether deriver links should be followed when searching for live
- paths.</p></li><li class="listitem"><p><code class="literal">gc-keep-outputs</code> specifies
- whether outputs of derivations should be followed when searching
- for live paths.</p></li><li class="listitem"><p><code class="literal">env-keep-derivations</code>
- specifies whether user environments should store the paths of
- derivations when they are added (thus keeping the derivations
- alive).</p></li></ul></div><p>
-
- </p></li><li class="listitem"><p>New <span class="command"><strong>nix-env</strong></span> query flags
- <code class="option">--drv-path</code> and
- <code class="option">--out-path</code>.</p></li><li class="listitem"><p><span class="command"><strong>fetchurl</strong></span> allows SHA-1 and SHA-256
- in addition to MD5. Just specify the attribute
- <code class="varname">sha1</code> or <code class="varname">sha256</code> instead of
- <code class="varname">md5</code>.</p></li><li class="listitem"><p>Manual updates.</p></li></ul></div><p>
-
-</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ch-relnotes-0.7"></a>C.33. Release 0.7 (2005-01-12)</h2></div></div></div><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Binary patching. When upgrading components using
- pre-built binaries (through nix-pull / nix-channel), Nix can
- automatically download and apply binary patches to already installed
- components instead of full downloads. Patching is “smart”: if there
- is a <span class="emphasis"><em>sequence</em></span> of patches to an installed
- component, Nix will use it. Patches are currently generated
- automatically between Nixpkgs (pre-)releases.</p></li><li class="listitem"><p>Simplifications to the substitute
- mechanism.</p></li><li class="listitem"><p>Nix-pull now stores downloaded manifests in
- <code class="filename">/nix/var/nix/manifests</code>.</p></li><li class="listitem"><p>Metadata on files in the Nix store is canonicalised
- after builds: the last-modified timestamp is set to 0 (00:00:00
- 1/1/1970), the mode is set to 0444 or 0555 (readable and possibly
- executable by all; setuid/setgid bits are dropped), and the group is
- set to the default. This ensures that the result of a build and an
- installation through a substitute is the same; and that timestamp
- dependencies are revealed.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ch-relnotes-0.6"></a>C.34. Release 0.6 (2004-11-14)</h2></div></div></div><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Rewrite of the normalisation engine.
-
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Multiple builds can now be performed in parallel
- (option <code class="option">-j</code>).</p></li><li class="listitem"><p>Distributed builds. Nix can now call a shell
- script to forward builds to Nix installations on remote
- machines, which may or may not be of the same platform
- type.</p></li><li class="listitem"><p>Option <code class="option">--fallback</code> allows
- recovery from broken substitutes.</p></li><li class="listitem"><p>Option <code class="option">--keep-going</code> causes
- building of other (unaffected) derivations to continue if one
- failed.</p></li></ul></div><p>
-
- </p></li><li class="listitem"><p>Improvements to the garbage collector (i.e., it
- should actually work now).</p></li><li class="listitem"><p>Setuid Nix installations allow a Nix store to be
- shared among multiple users.</p></li><li class="listitem"><p>Substitute registration is much faster
- now.</p></li><li class="listitem"><p>A utility <span class="command"><strong>nix-build</strong></span> to build a
- Nix expression and create a symlink to the result int the current
- directory; useful for testing Nix derivations.</p></li><li class="listitem"><p>Manual updates.</p></li><li class="listitem"><p><span class="command"><strong>nix-env</strong></span> changes:
-
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>Derivations for other platforms are filtered out
- (which can be overridden using
- <code class="option">--system-filter</code>).</p></li><li class="listitem"><p><code class="option">--install</code> by default now
- uninstall previous derivations with the same
- name.</p></li><li class="listitem"><p><code class="option">--upgrade</code> allows upgrading to a
- specific version.</p></li><li class="listitem"><p>New operation
- <code class="option">--delete-generations</code> to remove profile
- generations (necessary for effective garbage
- collection).</p></li><li class="listitem"><p>Nicer output (sorted,
- columnised).</p></li></ul></div><p>
-
- </p></li><li class="listitem"><p>More sensible verbosity levels all around (builder
- output is now shown always, unless <code class="option">-Q</code> is
- given).</p></li><li class="listitem"><p>Nix expression language changes:
-
- </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>New language construct: <code class="literal">with
- <em class="replaceable"><code>E1</code></em>;
- <em class="replaceable"><code>E2</code></em></code> brings all attributes
- defined in the attribute set <em class="replaceable"><code>E1</code></em> in
- scope in <em class="replaceable"><code>E2</code></em>.</p></li><li class="listitem"><p>Added a <code class="function">map</code>
- function.</p></li><li class="listitem"><p>Various new operators (e.g., string
- concatenation).</p></li></ul></div><p>
-
- </p></li><li class="listitem"><p>Expression evaluation is much
- faster.</p></li><li class="listitem"><p>An Emacs mode for editing Nix expressions (with
- syntax highlighting and indentation) has been
- added.</p></li><li class="listitem"><p>Many bug fixes.</p></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ch-relnotes-0.5"></a>C.35. Release 0.5 and earlier</h2></div></div></div><p>Please refer to the Subversion commit log messages.</p></div></div></div></body></html>
\ No newline at end of file
diff --git a/doc/manual/manual.xmli b/doc/manual/manual.xmli
deleted file mode 100644
index 241eef2cc..000000000
--- a/doc/manual/manual.xmli
+++ /dev/null
@@ -1,20139 +0,0 @@
-<?xml version="1.0"?>
-<book xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0">
-
- <info>
- <title>Nix Package Manager Guide</title>
- <subtitle>Version 3.0</subtitle>
-
- <author>
- <personname>
- <firstname>Eelco</firstname>
- <surname>Dolstra</surname>
- </personname>
- <contrib>Author</contrib>
- </author>
-
- <copyright>
- <year>2004-2018</year>
- <holder>Eelco Dolstra</holder>
- </copyright>
-
- </info>
-
- <!--
- <preface>
- <title>Preface</title>
- <para>This manual describes how to set up and use the Nix package
- manager.</para>
- </preface>
- -->
-
- <part xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="chap-introduction" xml:base="introduction/introduction.xml">
-
-<title>Introduction</title>
-
-<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-about-nix">
-
-<title>About Nix</title>
-
-<para>Nix is a <emphasis>purely functional package manager</emphasis>.
-This means that it treats packages like values in purely functional
-programming languages such as Haskell — they are built by functions
-that don’t have side-effects, and they never change after they have
-been built. Nix stores packages in the <emphasis>Nix
-store</emphasis>, usually the directory
-<filename>/nix/store</filename>, where each package has its own unique
-subdirectory such as
-
-<programlisting>
-/nix/store/b6gvzjyb2pg0kjfwrjmg1vfhh54ad73z-firefox-33.1/
-</programlisting>
-
-where <literal>b6gvzjyb2pg0…</literal> is a unique identifier for the
-package that captures all its dependencies (it’s a cryptographic hash
-of the package’s build dependency graph). This enables many powerful
-features.</para>
-
-
-<simplesect><title>Multiple versions</title>
-
-<para>You can have multiple versions or variants of a package
-installed at the same time. This is especially important when
-different applications have dependencies on different versions of the
-same package — it prevents the “DLL hell”. Because of the hashing
-scheme, different versions of a package end up in different paths in
-the Nix store, so they don’t interfere with each other.</para>
-
-<para>An important consequence is that operations like upgrading or
-uninstalling an application cannot break other applications, since
-these operations never “destructively” update or delete files that are
-used by other packages.</para>
-
-</simplesect>
-
-
-<simplesect><title>Complete dependencies</title>
-
-<para>Nix helps you make sure that package dependency specifications
-are complete. In general, when you’re making a package for a package
-management system like RPM, you have to specify for each package what
-its dependencies are, but there are no guarantees that this
-specification is complete. If you forget a dependency, then the
-package will build and work correctly on <emphasis>your</emphasis>
-machine if you have the dependency installed, but not on the end
-user's machine if it's not there.</para>
-
-<para>Since Nix on the other hand doesn’t install packages in “global”
-locations like <filename>/usr/bin</filename> but in package-specific
-directories, the risk of incomplete dependencies is greatly reduced.
-This is because tools such as compilers don’t search in per-packages
-directories such as
-<filename>/nix/store/5lbfaxb722zp…-openssl-0.9.8d/include</filename>,
-so if a package builds correctly on your system, this is because you
-specified the dependency explicitly. This takes care of the build-time
-dependencies.</para>
-
-<para>Once a package is built, runtime dependencies are found by
-scanning binaries for the hash parts of Nix store paths (such as
-<literal>r8vvq9kq…</literal>). This sounds risky, but it works
-extremely well.</para>
-
-</simplesect>
-
-
-<simplesect><title>Multi-user support</title>
-
-<para>Nix has multi-user support. This means that non-privileged
-users can securely install software. Each user can have a different
-<emphasis>profile</emphasis>, a set of packages in the Nix store that
-appear in the user’s <envar>PATH</envar>. If a user installs a
-package that another user has already installed previously, the
-package won’t be built or downloaded a second time. At the same time,
-it is not possible for one user to inject a Trojan horse into a
-package that might be used by another user.</para>
-
-</simplesect>
-
-
-<simplesect><title>Atomic upgrades and rollbacks</title>
-
-<para>Since package management operations never overwrite packages in
-the Nix store but just add new versions in different paths, they are
-<emphasis>atomic</emphasis>. So during a package upgrade, there is no
-time window in which the package has some files from the old version
-and some files from the new version — which would be bad because a
-program might well crash if it’s started during that period.</para>
-
-<para>And since packages aren’t overwritten, the old versions are still
-there after an upgrade. This means that you can <emphasis>roll
-back</emphasis> to the old version:</para>
-
-<screen>
-$ nix-env --upgrade <replaceable>some-packages</replaceable>
-$ nix-env --rollback
-</screen>
-
-</simplesect>
-
-
-<simplesect><title>Garbage collection</title>
-
-<para>When you uninstall a package like this…
-
-<screen>
-$ nix-env --uninstall firefox
-</screen>
-
-the package isn’t deleted from the system right away (after all, you
-might want to do a rollback, or it might be in the profiles of other
-users). Instead, unused packages can be deleted safely by running the
-<emphasis>garbage collector</emphasis>:
-
-<screen>
-$ nix-collect-garbage
-</screen>
-
-This deletes all packages that aren’t in use by any user profile or by
-a currently running program.</para>
-
-</simplesect>
-
-
-<simplesect><title>Functional package language</title>
-
-<para>Packages are built from <emphasis>Nix expressions</emphasis>,
-which is a simple functional language. A Nix expression describes
-everything that goes into a package build action (a “derivation”):
-other packages, sources, the build script, environment variables for
-the build script, etc. Nix tries very hard to ensure that Nix
-expressions are <emphasis>deterministic</emphasis>: building a Nix
-expression twice should yield the same result.</para>
-
-<para>Because it’s a functional language, it’s easy to support
-building variants of a package: turn the Nix expression into a
-function and call it any number of times with the appropriate
-arguments. Due to the hashing scheme, variants don’t conflict with
-each other in the Nix store.</para>
-
-</simplesect>
-
-
-<simplesect><title>Transparent source/binary deployment</title>
-
-<para>Nix expressions generally describe how to build a package from
-source, so an installation action like
-
-<screen>
-$ nix-env --install firefox
-</screen>
-
-<emphasis>could</emphasis> cause quite a bit of build activity, as not
-only Firefox but also all its dependencies (all the way up to the C
-library and the compiler) would have to built, at least if they are
-not already in the Nix store. This is a <emphasis>source deployment
-model</emphasis>. For most users, building from source is not very
-pleasant as it takes far too long. However, Nix can automatically
-skip building from source and instead use a <emphasis>binary
-cache</emphasis>, a web server that provides pre-built binaries. For
-instance, when asked to build
-<literal>/nix/store/b6gvzjyb2pg0…-firefox-33.1</literal> from source,
-Nix would first check if the file
-<uri>https://cache.nixos.org/b6gvzjyb2pg0….narinfo</uri> exists, and
-if so, fetch the pre-built binary referenced from there; otherwise, it
-would fall back to building from source.</para>
-
-</simplesect>
-
-
-<!--
-<simplesect><title>Binary patching</title>
-
-<para>In addition to downloading binaries automatically if they’re
-available, Nix can download binary deltas that patch an existing
-package in the Nix store into a new version. This speeds up
-upgrades.</para>
-
-</simplesect>
--->
-
-
-<simplesect><title>Nix Packages collection</title>
-
-<para>We provide a large set of Nix expressions containing hundreds of
-existing Unix packages, the <emphasis>Nix Packages
-collection</emphasis> (Nixpkgs).</para>
-
-</simplesect>
-
-
-<simplesect><title>Managing build environments</title>
-
-<para>Nix is extremely useful for developers as it makes it easy to
-automatically set up the build environment for a package. Given a
-Nix expression that describes the dependencies of your package, the
-command <command>nix-shell</command> will build or download those
-dependencies if they’re not already in your Nix store, and then start
-a Bash shell in which all necessary environment variables (such as
-compiler search paths) are set.</para>
-
-<para>For example, the following command gets all dependencies of the
-Pan newsreader, as described by <link xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/networking/newsreaders/pan/default.nix">its
-Nix expression</link>:</para>
-
-<screen>
-$ nix-shell '<nixpkgs>' -A pan
-</screen>
-
-<para>You’re then dropped into a shell where you can edit, build and test
-the package:</para>
-
-<screen>
-[nix-shell]$ tar xf $src
-[nix-shell]$ cd pan-*
-[nix-shell]$ ./configure
-[nix-shell]$ make
-[nix-shell]$ ./pan/gui/pan
-</screen>
-
-<!--
-<para>Since Nix packages are reproducible and have complete dependency
-specifications, Nix makes an excellent basis for <a
-href="[%root%]hydra">a continuous build system</a>.</para>
--->
-
-</simplesect>
-
-
-<simplesect><title>Portability</title>
-
-<para>Nix runs on Linux and macOS.</para>
-
-</simplesect>
-
-
-<simplesect><title>NixOS</title>
-
-<para>NixOS is a Linux distribution based on Nix. It uses Nix not
-just for package management but also to manage the system
-configuration (e.g., to build configuration files in
-<filename>/etc</filename>). This means, among other things, that it
-is easy to roll back the entire configuration of the system to an
-earlier state. Also, users can install software without root
-privileges. For more information and downloads, see the <link xlink:href="http://nixos.org/">NixOS homepage</link>.</para>
-
-</simplesect>
-
-
-<simplesect><title>License</title>
-
-<para>Nix is released under the terms of the <link xlink:href="http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html">GNU
-LGPLv2.1 or (at your option) any later version</link>.</para>
-
-</simplesect>
-
-
-</chapter>
-<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="chap-quick-start">
-
-<title>Quick Start</title>
-
-<para>This chapter is for impatient people who don't like reading
-documentation. For more in-depth information you are kindly referred
-to subsequent chapters.</para>
-
-<procedure>
-
-<step><para>Install single-user Nix by running the following:
-
-<screen>
-$ bash <(curl -L https://nixos.org/nix/install)
-</screen>
-
-This will install Nix in <filename>/nix</filename>. The install script
-will create <filename>/nix</filename> using <command>sudo</command>,
-so make sure you have sufficient rights. (For other installation
-methods, see <xref linkend="chap-installation"/>.)</para></step>
-
-<step><para>See what installable packages are currently available
-in the channel:
-
-<screen>
-$ nix-env -qa
-docbook-xml-4.3
-docbook-xml-4.5
-firefox-33.0.2
-hello-2.9
-libxslt-1.1.28
-<replaceable>...</replaceable></screen>
-
-</para></step>
-
-<step><para>Install some packages from the channel:
-
-<screen>
-$ nix-env -i hello</screen>
-
-This should download pre-built packages; it should not build them
-locally (if it does, something went wrong).</para></step>
-
-<step><para>Test that they work:
-
-<screen>
-$ which hello
-/home/eelco/.nix-profile/bin/hello
-$ hello
-Hello, world!
-</screen>
-
-</para></step>
-
-<step><para>Uninstall a package:
-
-<screen>
-$ nix-env -e hello</screen>
-
-</para></step>
-
-<step><para>You can also test a package without installing it:
-
-<screen>
-$ nix-shell -p hello
-</screen>
-
-This builds or downloads GNU Hello and its dependencies, then drops
-you into a Bash shell where the <command>hello</command> command is
-present, all without affecting your normal environment:
-
-<screen>
-[nix-shell:~]$ hello
-Hello, world!
-
-[nix-shell:~]$ exit
-
-$ hello
-hello: command not found
-</screen>
-
-</para></step>
-
-<step><para>To keep up-to-date with the channel, do:
-
-<screen>
-$ nix-channel --update nixpkgs
-$ nix-env -u '*'</screen>
-
-The latter command will upgrade each installed package for which there
-is a “newer” version (as determined by comparing the version
-numbers).</para></step>
-
-<step><para>If you're unhappy with the result of a
-<command>nix-env</command> action (e.g., an upgraded package turned
-out not to work properly), you can go back:
-
-<screen>
-$ nix-env --rollback</screen>
-
-</para></step>
-
-<step><para>You should periodically run the Nix garbage collector
-to get rid of unused packages, since uninstalls or upgrades don't
-actually delete them:
-
-<screen>
-$ nix-collect-garbage -d</screen>
-
-<!--
-The first command deletes old “generations” of your profile (making
-rollbacks impossible, but also making the packages in those old
-generations available for garbage collection), while the second
-command actually deletes them.-->
-
-</para></step>
-
-</procedure>
-
-</chapter>
-
-</part>
- <part xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="chap-installation" xml:base="installation/installation.xml">
-
-<title>Installation</title>
-
-<partintro>
-<para>This section describes how to install and configure Nix for first-time use.</para>
-</partintro>
-
-<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-supported-platforms">
-
-<title>Supported Platforms</title>
-
-<para>Nix is currently supported on the following platforms:
-
-<itemizedlist>
-
- <listitem><para>Linux (i686, x86_64, aarch64).</para></listitem>
-
- <listitem><para>macOS (x86_64).</para></listitem>
-
- <!--
- <listitem><para>FreeBSD (only tested on Intel).</para></listitem>
- -->
-
- <!--
- <listitem><para>Windows through <link
- xlink:href="http://www.cygwin.com/">Cygwin</link>.</para>
-
- <warning><para>On Cygwin, Nix <emphasis>must</emphasis> be installed
- on an NTFS partition. It will not work correctly on a FAT
- partition.</para></warning>
-
- </listitem>
- -->
-
-</itemizedlist>
-
-</para>
-
-</chapter>
-<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-installing-binary">
-
-<title>Installing a Binary Distribution</title>
-
-<para>
- If you are using Linux or macOS versions up to 10.14 (Mojave), the
- easiest way to install Nix is to run the following command:
-</para>
-
-<screen>
- $ sh <(curl -L https://nixos.org/nix/install)
-</screen>
-
-<para>
- If you're using macOS 10.15 (Catalina) or newer, consult
- <link linkend="sect-macos-installation">the macOS installation instructions</link>
- before installing.
-</para>
-
-<para>
- As of Nix 2.1.0, the Nix installer will always default to creating a
- single-user installation, however opting in to the multi-user
- installation is highly recommended.
- <!-- TODO: this explains *neither* why the default version is
- single-user, nor why we'd recommend multi-user over the default.
- True prospective users don't have much basis for evaluating this.
- What's it to me? Who should pick which? Why? What if I pick wrong?
- -->
-</para>
-
-<section xml:id="sect-single-user-installation">
- <title>Single User Installation</title>
-
- <para>
- To explicitly select a single-user installation on your system:
-
- <screen>
- sh <(curl -L https://nixos.org/nix/install) --no-daemon
-</screen>
- </para>
-
-<para>
-This will perform a single-user installation of Nix, meaning that
-<filename>/nix</filename> is owned by the invoking user. You should
-run this under your usual user account, <emphasis>not</emphasis> as
-root. The script will invoke <command>sudo</command> to create
-<filename>/nix</filename> if it doesn’t already exist. If you don’t
-have <command>sudo</command>, you should manually create
-<filename>/nix</filename> first as root, e.g.:
-
-<screen>
-$ mkdir /nix
-$ chown alice /nix
-</screen>
-
-The install script will modify the first writable file from amongst
-<filename>.bash_profile</filename>, <filename>.bash_login</filename>
-and <filename>.profile</filename> to source
-<filename>~/.nix-profile/etc/profile.d/nix.sh</filename>. You can set
-the <envar>NIX_INSTALLER_NO_MODIFY_PROFILE</envar> environment
-variable before executing the install script to disable this
-behaviour.
-</para>
-
-
-<para>You can uninstall Nix simply by running:
-
-<screen>
-$ rm -rf /nix
-</screen>
-
-</para>
-</section>
-
-<section xml:id="sect-multi-user-installation">
- <title>Multi User Installation</title>
- <para>
- The multi-user Nix installation creates system users, and a system
- service for the Nix daemon.
- </para>
-
- <itemizedlist>
- <title>Supported Systems</title>
-
- <listitem>
- <para>Linux running systemd, with SELinux disabled</para>
- </listitem>
- <listitem><para>macOS</para></listitem>
- </itemizedlist>
-
- <para>
- You can instruct the installer to perform a multi-user
- installation on your system:
- </para>
-
- <screen>sh <(curl -L https://nixos.org/nix/install) --daemon</screen>
-
- <para>
- The multi-user installation of Nix will create build users between
- the user IDs 30001 and 30032, and a group with the group ID 30000.
-
- You should run this under your usual user account,
- <emphasis>not</emphasis> as root. The script will invoke
- <command>sudo</command> as needed.
- </para>
-
- <note><para>
- If you need Nix to use a different group ID or user ID set, you
- will have to download the tarball manually and <link linkend="sect-nix-install-binary-tarball">edit the install
- script</link>.
- </para></note>
-
- <para>
- The installer will modify <filename>/etc/bashrc</filename>, and
- <filename>/etc/zshrc</filename> if they exist. The installer will
- first back up these files with a
- <literal>.backup-before-nix</literal> extension. The installer
- will also create <filename>/etc/profile.d/nix.sh</filename>.
- </para>
-
- <para>You can uninstall Nix with the following commands:
-
-<screen>
-sudo rm -rf /etc/profile/nix.sh /etc/nix /nix ~root/.nix-profile ~root/.nix-defexpr ~root/.nix-channels ~/.nix-profile ~/.nix-defexpr ~/.nix-channels
-
-# If you are on Linux with systemd, you will need to run:
-sudo systemctl stop nix-daemon.socket
-sudo systemctl stop nix-daemon.service
-sudo systemctl disable nix-daemon.socket
-sudo systemctl disable nix-daemon.service
-sudo systemctl daemon-reload
-
-# If you are on macOS, you will need to run:
-sudo launchctl unload /Library/LaunchDaemons/org.nixos.nix-daemon.plist
-sudo rm /Library/LaunchDaemons/org.nixos.nix-daemon.plist
-</screen>
-
- There may also be references to Nix in
- <filename>/etc/profile</filename>,
- <filename>/etc/bashrc</filename>, and
- <filename>/etc/zshrc</filename> which you may remove.
- </para>
-
-</section>
-
-<section xml:id="sect-macos-installation">
- <title>macOS Installation</title>
-
- <para>
- Starting with macOS 10.15 (Catalina), the root filesystem is read-only.
- This means <filename>/nix</filename> can no longer live on your system
- volume, and that you'll need a workaround to install Nix.
- </para>
-
- <para>
- The recommended approach, which creates an unencrypted APFS volume
- for your Nix store and a "synthetic" empty directory to mount it
- over at <filename>/nix</filename>, is least likely to impair Nix
- or your system.
- </para>
-
- <note><para>
- With all separate-volume approaches, it's possible something on
- your system (particularly daemons/services and restored apps) may
- need access to your Nix store before the volume is mounted. Adding
- additional encryption makes this more likely.
- </para></note>
-
- <para>
- If you're using a recent Mac with a
- <link xlink:href="https://www.apple.com/euro/mac/shared/docs/Apple_T2_Security_Chip_Overview.pdf">T2 chip</link>,
- your drive will still be encrypted at rest (in which case "unencrypted"
- is a bit of a misnomer). To use this approach, just install Nix with:
- </para>
-
- <screen>$ sh <(curl -L https://nixos.org/nix/install) --darwin-use-unencrypted-nix-store-volume</screen>
-
- <para>
- If you don't like the sound of this, you'll want to weigh the
- other approaches and tradeoffs detailed in this section.
- </para>
-
- <note>
- <title>Eventual solutions?</title>
- <para>
- All of the known workarounds have drawbacks, but we hope
- better solutions will be available in the future. Some that
- we have our eye on are:
- </para>
- <orderedlist>
- <listitem>
- <para>
- A true firmlink would enable the Nix store to live on the
- primary data volume without the build problems caused by
- the symlink approach. End users cannot currently
- create true firmlinks.
- </para>
- </listitem>
- <listitem>
- <para>
- If the Nix store volume shared FileVault encryption
- with the primary data volume (probably by using the same
- volume group and role), FileVault encryption could be
- easily supported by the installer without requiring
- manual setup by each user.
- </para>
- </listitem>
- </orderedlist>
- </note>
-
- <section xml:id="sect-macos-installation-change-store-prefix">
- <title>Change the Nix store path prefix</title>
- <para>
- Changing the default prefix for the Nix store is a simple
- approach which enables you to leave it on your root volume,
- where it can take full advantage of FileVault encryption if
- enabled. Unfortunately, this approach also opts your device out
- of some benefits that are enabled by using the same prefix
- across systems:
-
- <itemizedlist>
- <listitem>
- <para>
- Your system won't be able to take advantage of the binary
- cache (unless someone is able to stand up and support
- duplicate caching infrastructure), which means you'll
- spend more time waiting for builds.
- </para>
- </listitem>
- <listitem>
- <para>
- It's harder to build and deploy packages to Linux systems.
- </para>
- </listitem>
- <!-- TODO: may be more here -->
- </itemizedlist>
-
- <!-- TODO: Yes, but how?! -->
-
- It would also possible (and often requested) to just apply this
- change ecosystem-wide, but it's an intrusive process that has
- side effects we want to avoid for now.
- <!-- magnificent hand-wavy gesture -->
- </para>
- <para>
- </para>
- </section>
-
- <section xml:id="sect-macos-installation-encrypted-volume">
- <title>Use a separate encrypted volume</title>
- <para>
- If you like, you can also add encryption to the recommended
- approach taken by the installer. You can do this by pre-creating
- an encrypted volume before you run the installer--or you can
- run the installer and encrypt the volume it creates later.
- <!-- TODO: see later note about whether this needs both add-encryption and from-scratch directions -->
- </para>
- <para>
- In either case, adding encryption to a second volume isn't quite
- as simple as enabling FileVault for your boot volume. Before you
- dive in, there are a few things to weigh:
- </para>
- <orderedlist>
- <listitem>
- <para>
- The additional volume won't be encrypted with your existing
- FileVault key, so you'll need another mechanism to decrypt
- the volume.
- </para>
- </listitem>
- <listitem>
- <para>
- You can store the password in Keychain to automatically
- decrypt the volume on boot--but it'll have to wait on Keychain
- and may not mount before your GUI apps restore. If any of
- your launchd agents or apps depend on Nix-installed software
- (for example, if you use a Nix-installed login shell), the
- restore may fail or break.
- </para>
- <para>
- On a case-by-case basis, you may be able to work around this
- problem by using <command>wait4path</command> to block
- execution until your executable is available.
- </para>
- <para>
- It's also possible to decrypt and mount the volume earlier
- with a login hook--but this mechanism appears to be
- deprecated and its future is unclear.
- </para>
- </listitem>
- <listitem>
- <para>
- You can hard-code the password in the clear, so that your
- store volume can be decrypted before Keychain is available.
- </para>
- </listitem>
- </orderedlist>
- <para>
- If you are comfortable navigating these tradeoffs, you can encrypt the volume with
- something along the lines of:
- <!-- TODO:
- I don't know if this also needs from-scratch instructions?
- can we just recommend use-the-installer-and-then-encrypt?
- -->
- </para>
- <!--
- TODO: it looks like this option can be encryptVolume|encrypt|enableFileVault
-
- It may be more clear to use encryptVolume, here? FileVault seems
- heavily associated with the boot-volume behavior; I worry
- a little that it can mislead here, especially as it gets
- copied around minus doc context...?
- -->
- <screen>alice$ diskutil apfs enableFileVault /nix -user disk</screen>
-
- <!-- TODO: and then go into detail on the mount/decrypt approaches? -->
- </section>
-
- <section xml:id="sect-macos-installation-symlink">
- <!--
- Maybe a good razor is: if we'd hate having to support someone who
- installed Nix this way, it shouldn't even be detailed?
- -->
- <title>Symlink the Nix store to a custom location</title>
- <para>
- Another simple approach is using <filename>/etc/synthetic.conf</filename>
- to symlink the Nix store to the data volume. This option also
- enables your store to share any configured FileVault encryption.
- Unfortunately, builds that resolve the symlink may leak the
- canonical path or even fail.
- </para>
- <para>
- Because of these downsides, we can't recommend this approach.
- </para>
- <!-- Leaving out instructions for this one. -->
- </section>
-
- <section xml:id="sect-macos-installation-recommended-notes">
- <title>Notes on the recommended approach</title>
- <para>
- This section goes into a little more detail on the recommended
- approach. You don't need to understand it to run the installer,
- but it can serve as a helpful reference if you run into trouble.
- </para>
- <orderedlist>
- <listitem>
- <para>
- In order to compose user-writable locations into the new
- read-only system root, Apple introduced a new concept called
- <literal>firmlinks</literal>, which it describes as a
- "bi-directional wormhole" between two filesystems. You can
- see the current firmlinks in <filename>/usr/share/firmlinks</filename>.
- Unfortunately, firmlinks aren't (currently?) user-configurable.
- </para>
-
- <para>
- For special cases like NFS mount points or package manager roots,
- <link xlink:href="https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man5/synthetic.conf.5.html">synthetic.conf(5)</link>
- supports limited user-controlled file-creation (of symlinks,
- and synthetic empty directories) at <filename>/</filename>.
- To create a synthetic empty directory for mounting at <filename>/nix</filename>,
- add the following line to <filename>/etc/synthetic.conf</filename>
- (create it if necessary):
- </para>
-
- <screen>nix</screen>
- </listitem>
-
- <listitem>
- <para>
- This configuration is applied at boot time, but you can use
- <command>apfs.util</command> to trigger creation (not deletion)
- of new entries without a reboot:
- </para>
-
- <screen>alice$ /System/Library/Filesystems/apfs.fs/Contents/Resources/apfs.util -B</screen>
- </listitem>
-
- <listitem>
- <para>
- Create the new APFS volume with diskutil:
- </para>
-
- <screen>alice$ sudo diskutil apfs addVolume diskX APFS 'Nix Store' -mountpoint /nix</screen>
- </listitem>
-
- <listitem>
- <para>
- Using <command>vifs</command>, add the new mount to
- <filename>/etc/fstab</filename>. If it doesn't already have
- other entries, it should look something like:
- </para>
-
-<screen>
-#
-# Warning - this file should only be modified with vifs(8)
-#
-# Failure to do so is unsupported and may be destructive.
-#
-LABEL=Nix\040Store /nix apfs rw,nobrowse
-</screen>
-
- <para>
- The nobrowse setting will keep Spotlight from indexing this
- volume, and keep it from showing up on your desktop.
- </para>
- </listitem>
- </orderedlist>
- </section>
-
-</section>
-
-<section xml:id="sect-nix-install-pinned-version-url">
- <title>Installing a pinned Nix version from a URL</title>
-
- <para>
- NixOS.org hosts version-specific installation URLs for all Nix
- versions since 1.11.16, at
- <literal>https://releases.nixos.org/nix/nix-<replaceable>version</replaceable>/install</literal>.
- </para>
-
- <para>
- These install scripts can be used the same as the main
- NixOS.org installation script:
-
- <screen>
- sh <(curl -L https://nixos.org/nix/install)
-</screen>
- </para>
-
- <para>
- In the same directory of the install script are sha256 sums, and
- gpg signature files.
- </para>
-</section>
-
-<section xml:id="sect-nix-install-binary-tarball">
- <title>Installing from a binary tarball</title>
-
- <para>
- You can also download a binary tarball that contains Nix and all
- its dependencies. (This is what the install script at
- <uri>https://nixos.org/nix/install</uri> does automatically.) You
- should unpack it somewhere (e.g. in <filename>/tmp</filename>),
- and then run the script named <command>install</command> inside
- the binary tarball:
-
-
-<screen>
-alice$ cd /tmp
-alice$ tar xfj nix-1.8-x86_64-darwin.tar.bz2
-alice$ cd nix-1.8-x86_64-darwin
-alice$ ./install
-</screen>
- </para>
-
- <para>
- If you need to edit the multi-user installation script to use
- different group ID or a different user ID range, modify the
- variables set in the file named
- <filename>install-multi-user</filename>.
- </para>
-</section>
-</chapter>
-<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-installing-source">
-
-<title>Installing Nix from Source</title>
-
-<para>If no binary package is available, you can download and compile
-a source distribution.</para>
-
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-prerequisites-source">
-
-<title>Prerequisites</title>
-
-<itemizedlist>
-
- <listitem><para>GNU Autoconf
- (<link xlink:href="https://www.gnu.org/software/autoconf/"/>)
- and the autoconf-archive macro collection
- (<link xlink:href="https://www.gnu.org/software/autoconf-archive/"/>).
- These are only needed to run the bootstrap script, and are not necessary
- if your source distribution came with a pre-built
- <literal>./configure</literal> script.</para></listitem>
-
- <listitem><para>GNU Make.</para></listitem>
-
- <listitem><para>Bash Shell. The <literal>./configure</literal> script
- relies on bashisms, so Bash is required.</para></listitem>
-
- <listitem><para>A version of GCC or Clang that supports C++17.</para></listitem>
-
- <listitem><para><command>pkg-config</command> to locate
- dependencies. If your distribution does not provide it, you can get
- it from <link xlink:href="http://www.freedesktop.org/wiki/Software/pkg-config"/>.</para></listitem>
-
- <listitem><para>The OpenSSL library to calculate cryptographic hashes.
- If your distribution does not provide it, you can get it from <link xlink:href="https://www.openssl.org"/>.</para></listitem>
-
- <listitem><para>The <literal>libbrotlienc</literal> and
- <literal>libbrotlidec</literal> libraries to provide implementation
- of the Brotli compression algorithm. They are available for download
- from the official repository <link xlink:href="https://github.com/google/brotli"/>.</para></listitem>
-
- <listitem><para>The bzip2 compressor program and the
- <literal>libbz2</literal> library. Thus you must have bzip2
- installed, including development headers and libraries. If your
- distribution does not provide these, you can obtain bzip2 from <link xlink:href="https://web.archive.org/web/20180624184756/http://www.bzip.org/"/>.</para></listitem>
-
- <listitem><para><literal>liblzma</literal>, which is provided by
- XZ Utils. If your distribution does not provide this, you can
- get it from <link xlink:href="https://tukaani.org/xz/"/>.</para></listitem>
-
- <listitem><para>cURL and its library. If your distribution does not
- provide it, you can get it from <link xlink:href="https://curl.haxx.se/"/>.</para></listitem>
-
- <listitem><para>The SQLite embedded database library, version 3.6.19
- or higher. If your distribution does not provide it, please install
- it from <link xlink:href="http://www.sqlite.org/"/>.</para></listitem>
-
- <listitem><para>The <link xlink:href="http://www.hboehm.info/gc/">Boehm
- garbage collector</link> to reduce the evaluator’s memory
- consumption (optional). To enable it, install
- <literal>pkgconfig</literal> and the Boehm garbage collector, and
- pass the flag <option>--enable-gc</option> to
- <command>configure</command>.</para></listitem>
-
- <listitem><para>The <literal>boost</literal> library of version
- 1.66.0 or higher. It can be obtained from the official web site
- <link xlink:href="https://www.boost.org/"/>.</para></listitem>
-
- <listitem><para>The <literal>editline</literal> library of version
- 1.14.0 or higher. It can be obtained from the its repository
- <link xlink:href="https://github.com/troglobit/editline"/>.</para></listitem>
-
- <listitem><para>The <command>xmllint</command> and
- <command>xsltproc</command> programs to build this manual and the
- man-pages. These are part of the <literal>libxml2</literal> and
- <literal>libxslt</literal> packages, respectively. You also need
- the <link xlink:href="http://docbook.sourceforge.net/projects/xsl/">DocBook
- XSL stylesheets</link> and optionally the <link xlink:href="http://www.docbook.org/schemas/5x"> DocBook 5.0 RELAX NG
- schemas</link>. Note that these are only required if you modify the
- manual sources or when you are building from the Git
- repository.</para></listitem>
-
- <listitem><para>Recent versions of Bison and Flex to build the
- parser. (This is because Nix needs GLR support in Bison and
- reentrancy support in Flex.) For Bison, you need version 2.6, which
- can be obtained from the <link xlink:href="ftp://alpha.gnu.org/pub/gnu/bison">GNU FTP
- server</link>. For Flex, you need version 2.5.35, which is
- available on <link xlink:href="http://lex.sourceforge.net/">SourceForge</link>.
- Slightly older versions may also work, but ancient versions like the
- ubiquitous 2.5.4a won't. Note that these are only required if you
- modify the parser or when you are building from the Git
- repository.</para></listitem>
-
- <listitem><para>The <literal>libseccomp</literal> is used to provide
- syscall filtering on Linux. This is an optional dependency and can
- be disabled passing a <option>--disable-seccomp-sandboxing</option>
- option to the <command>configure</command> script (Not recommended
- unless your system doesn't support
- <literal>libseccomp</literal>). To get the library, visit <link xlink:href="https://github.com/seccomp/libseccomp"/>.</para></listitem>
-
-</itemizedlist>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-obtaining-source">
-
-<title>Obtaining a Source Distribution</title>
-
-<para>The source tarball of the most recent stable release can be
-downloaded from the <link xlink:href="http://nixos.org/nix/download.html">Nix homepage</link>.
-You can also grab the <link xlink:href="http://hydra.nixos.org/job/nix/master/release/latest-finished#tabs-constituents">most
-recent development release</link>.</para>
-
-<para>Alternatively, the most recent sources of Nix can be obtained
-from its <link xlink:href="https://github.com/NixOS/nix">Git
-repository</link>. For example, the following command will check out
-the latest revision into a directory called
-<filename>nix</filename>:</para>
-
-<screen>
-$ git clone https://github.com/NixOS/nix</screen>
-
-<para>Likewise, specific releases can be obtained from the <link xlink:href="https://github.com/NixOS/nix/tags">tags</link> of the
-repository.</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-building-source">
-
-<title>Building Nix from Source</title>
-
-<para>After unpacking or checking out the Nix sources, issue the
-following commands:
-
-<screen>
-$ ./configure <replaceable>options...</replaceable>
-$ make
-$ make install</screen>
-
-Nix requires GNU Make so you may need to invoke
-<command>gmake</command> instead.</para>
-
-<para>When building from the Git repository, these should be preceded
-by the command:
-
-<screen>
-$ ./bootstrap.sh</screen>
-
-</para>
-
-<para>The installation path can be specified by passing the
-<option>--prefix=<replaceable>prefix</replaceable></option> to
-<command>configure</command>. The default installation directory is
-<filename>/usr/local</filename>. You can change this to any location
-you like. You must have write permission to the
-<replaceable>prefix</replaceable> path.</para>
-
-<para>Nix keeps its <emphasis>store</emphasis> (the place where
-packages are stored) in <filename>/nix/store</filename> by default.
-This can be changed using
-<option>--with-store-dir=<replaceable>path</replaceable></option>.</para>
-
-<warning><para>It is best <emphasis>not</emphasis> to change the Nix
-store from its default, since doing so makes it impossible to use
-pre-built binaries from the standard Nixpkgs channels — that is, all
-packages will need to be built from source.</para></warning>
-
-<para>Nix keeps state (such as its database and log files) in
-<filename>/nix/var</filename> by default. This can be changed using
-<option>--localstatedir=<replaceable>path</replaceable></option>.</para>
-
-</section>
-
-</chapter>
-<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-nix-security">
-
-<title>Security</title>
-
-<para>Nix has two basic security models. First, it can be used in
-“single-user mode”, which is similar to what most other package
-management tools do: there is a single user (typically <systemitem class="username">root</systemitem>) who performs all package
-management operations. All other users can then use the installed
-packages, but they cannot perform package management operations
-themselves.</para>
-
-<para>Alternatively, you can configure Nix in “multi-user mode”. In
-this model, all users can perform package management operations — for
-instance, every user can install software without requiring root
-privileges. Nix ensures that this is secure. For instance, it’s not
-possible for one user to overwrite a package used by another user with
-a Trojan horse.</para>
-
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-single-user">
-
-<title>Single-User Mode</title>
-
-<para>In single-user mode, all Nix operations that access the database
-in <filename><replaceable>prefix</replaceable>/var/nix/db</filename>
-or modify the Nix store in
-<filename><replaceable>prefix</replaceable>/store</filename> must be
-performed under the user ID that owns those directories. This is
-typically <systemitem class="username">root</systemitem>. (If you
-install from RPM packages, that’s in fact the default ownership.)
-However, on single-user machines, it is often convenient to
-<command>chown</command> those directories to your normal user account
-so that you don’t have to <command>su</command> to <systemitem class="username">root</systemitem> all the time.</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-multi-user">
-
-<title>Multi-User Mode</title>
-
-<para>To allow a Nix store to be shared safely among multiple users,
-it is important that users are not able to run builders that modify
-the Nix store or database in arbitrary ways, or that interfere with
-builds started by other users. If they could do so, they could
-install a Trojan horse in some package and compromise the accounts of
-other users.</para>
-
-<para>To prevent this, the Nix store and database are owned by some
-privileged user (usually <literal>root</literal>) and builders are
-executed under special user accounts (usually named
-<literal>nixbld1</literal>, <literal>nixbld2</literal>, etc.). When a
-unprivileged user runs a Nix command, actions that operate on the Nix
-store (such as builds) are forwarded to a <emphasis>Nix
-daemon</emphasis> running under the owner of the Nix store/database
-that performs the operation.</para>
-
-<note><para>Multi-user mode has one important limitation: only
-<systemitem class="username">root</systemitem> and a set of trusted
-users specified in <filename>nix.conf</filename> can specify arbitrary
-binary caches. So while unprivileged users may install packages from
-arbitrary Nix expressions, they may not get pre-built
-binaries.</para></note>
-
-
-<simplesect>
-
-<title>Setting up the build users</title>
-
-<para>The <emphasis>build users</emphasis> are the special UIDs under
-which builds are performed. They should all be members of the
-<emphasis>build users group</emphasis> <literal>nixbld</literal>.
-This group should have no other members. The build users should not
-be members of any other group. On Linux, you can create the group and
-users as follows:
-
-<screen>
-$ groupadd -r nixbld
-$ for n in $(seq 1 10); do useradd -c "Nix build user $n" \
- -d /var/empty -g nixbld -G nixbld -M -N -r -s "$(which nologin)" \
- nixbld$n; done
-</screen>
-
-This creates 10 build users. There can never be more concurrent builds
-than the number of build users, so you may want to increase this if
-you expect to do many builds at the same time.</para>
-
-</simplesect>
-
-
-<simplesect>
-
-<title>Running the daemon</title>
-
-<para>The <link linkend="sec-nix-daemon">Nix daemon</link> should be
-started as follows (as <literal>root</literal>):
-
-<screen>
-$ nix-daemon</screen>
-
-You’ll want to put that line somewhere in your system’s boot
-scripts.</para>
-
-<para>To let unprivileged users use the daemon, they should set the
-<link linkend="envar-remote"><envar>NIX_REMOTE</envar> environment
-variable</link> to <literal>daemon</literal>. So you should put a
-line like
-
-<programlisting>
-export NIX_REMOTE=daemon</programlisting>
-
-into the users’ login scripts.</para>
-
-</simplesect>
-
-
-<simplesect>
-
-<title>Restricting access</title>
-
-<para>To limit which users can perform Nix operations, you can use the
-permissions on the directory
-<filename>/nix/var/nix/daemon-socket</filename>. For instance, if you
-want to restrict the use of Nix to the members of a group called
-<literal>nix-users</literal>, do
-
-<screen>
-$ chgrp nix-users /nix/var/nix/daemon-socket
-$ chmod ug=rwx,o= /nix/var/nix/daemon-socket
-</screen>
-
-This way, users who are not in the <literal>nix-users</literal> group
-cannot connect to the Unix domain socket
-<filename>/nix/var/nix/daemon-socket/socket</filename>, so they cannot
-perform Nix operations.</para>
-
-</simplesect>
-
-
-</section>
-
-</chapter>
-<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-env-variables">
-
-<title>Environment Variables</title>
-
-<para>To use Nix, some environment variables should be set. In
-particular, <envar>PATH</envar> should contain the directories
-<filename><replaceable>prefix</replaceable>/bin</filename> and
-<filename>~/.nix-profile/bin</filename>. The first directory contains
-the Nix tools themselves, while <filename>~/.nix-profile</filename> is
-a symbolic link to the current <emphasis>user environment</emphasis>
-(an automatically generated package consisting of symlinks to
-installed packages). The simplest way to set the required environment
-variables is to include the file
-<filename><replaceable>prefix</replaceable>/etc/profile.d/nix.sh</filename>
-in your <filename>~/.profile</filename> (or similar), like this:</para>
-
-<screen>
-source <replaceable>prefix</replaceable>/etc/profile.d/nix.sh</screen>
-
-<section xml:id="sec-nix-ssl-cert-file">
-
-<title><envar>NIX_SSL_CERT_FILE</envar></title>
-
-<para>If you need to specify a custom certificate bundle to account
-for an HTTPS-intercepting man in the middle proxy, you must specify
-the path to the certificate bundle in the environment variable
-<envar>NIX_SSL_CERT_FILE</envar>.</para>
-
-
-<para>If you don't specify a <envar>NIX_SSL_CERT_FILE</envar>
-manually, Nix will install and use its own certificate
-bundle.</para>
-
-<procedure>
- <step><para>Set the environment variable and install Nix</para>
- <screen>
-$ export NIX_SSL_CERT_FILE=/etc/ssl/my-certificate-bundle.crt
-$ sh <(curl -L https://nixos.org/nix/install)
-</screen></step>
-
- <step><para>In the shell profile and rc files (for example,
- <filename>/etc/bashrc</filename>, <filename>/etc/zshrc</filename>),
- add the following line:</para>
-<programlisting>
-export NIX_SSL_CERT_FILE=/etc/ssl/my-certificate-bundle.crt
-</programlisting>
-</step>
-</procedure>
-
-<note><para>You must not add the export and then do the install, as
-the Nix installer will detect the presense of Nix configuration, and
-abort.</para></note>
-
-<section xml:id="sec-nix-ssl-cert-file-with-nix-daemon-and-macos">
-<title><envar>NIX_SSL_CERT_FILE</envar> with macOS and the Nix daemon</title>
-
-<para>On macOS you must specify the environment variable for the Nix
-daemon service, then restart it:</para>
-
-<screen>
-$ sudo launchctl setenv NIX_SSL_CERT_FILE /etc/ssl/my-certificate-bundle.crt
-$ sudo launchctl kickstart -k system/org.nixos.nix-daemon
-</screen>
-</section>
-
-<section xml:id="sec-installer-proxy-settings">
-
-<title>Proxy Environment Variables</title>
-
-<para>The Nix installer has special handling for these proxy-related
-environment variables:
-<varname>http_proxy</varname>, <varname>https_proxy</varname>,
-<varname>ftp_proxy</varname>, <varname>no_proxy</varname>,
-<varname>HTTP_PROXY</varname>, <varname>HTTPS_PROXY</varname>,
-<varname>FTP_PROXY</varname>, <varname>NO_PROXY</varname>.
-</para>
-<para>If any of these variables are set when running the Nix installer,
-then the installer will create an override file at
-<filename>/etc/systemd/system/nix-daemon.service.d/override.conf</filename>
-so <command>nix-daemon</command> will use them.
-</para>
-</section>
-
-</section>
-</chapter>
-
-<!-- TODO: should be updated
-<section><title>Upgrading Nix through Nix</title>
-
-<para>You can install the latest stable version of Nix through Nix
-itself by subscribing to the channel <link
-xlink:href="http://nixos.org/releases/nix/channels/nix-stable" />,
-or the latest unstable version by subscribing to the channel <link
-xlink:href="http://nixos.org/releases/nix/channels/nix-unstable" />.
-You can also do a <link linkend="sec-one-click">one-click
-installation</link> by clicking on the package links at <link
-xlink:href="http://nixos.org/releases/full-index-nix.html" />.</para>
-
-</section>
--->
-
-</part>
- <chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-upgrading-nix" xml:base="installation/upgrading.xml">
-
- <title>Upgrading Nix</title>
-
- <para>
- Multi-user Nix users on macOS can upgrade Nix by running:
- <command>sudo -i sh -c 'nix-channel --update &&
- nix-env -iA nixpkgs.nix &&
- launchctl remove org.nixos.nix-daemon &&
- launchctl load /Library/LaunchDaemons/org.nixos.nix-daemon.plist'</command>
- </para>
-
-
- <para>
- Single-user installations of Nix should run this:
- <command>nix-channel --update; nix-env -iA nixpkgs.nix nixpkgs.cacert</command>
- </para>
-
- <para>
- Multi-user Nix users on Linux should run this with sudo:
- <command>nix-channel --update; nix-env -iA nixpkgs.nix nixpkgs.cacert; systemctl daemon-reload; systemctl restart nix-daemon</command>
- </para>
-</chapter>
- <part xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="chap-package-management" xml:base="packages/package-management.xml">
-
-<title>Package Management</title>
-
-<partintro>
-<para>This chapter discusses how to do package management with Nix,
-i.e., how to obtain, install, upgrade, and erase packages. This is
-the “user’s” perspective of the Nix system — people
-who want to <emphasis>create</emphasis> packages should consult
-<xref linkend="chap-writing-nix-expressions"/>.</para>
-</partintro>
-
-<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-basic-package-mgmt">
-
-<title>Basic Package Management</title>
-
-<para>The main command for package management is <link linkend="sec-nix-env"><command>nix-env</command></link>. You can use
-it to install, upgrade, and erase packages, and to query what
-packages are installed or are available for installation.</para>
-
-<para>In Nix, different users can have different “views”
-on the set of installed applications. That is, there might be lots of
-applications present on the system (possibly in many different
-versions), but users can have a specific selection of those active —
-where “active” just means that it appears in a directory
-in the user’s <envar>PATH</envar>. Such a view on the set of
-installed applications is called a <emphasis>user
-environment</emphasis>, which is just a directory tree consisting of
-symlinks to the files of the active applications. </para>
-
-<para>Components are installed from a set of <emphasis>Nix
-expressions</emphasis> that tell Nix how to build those packages,
-including, if necessary, their dependencies. There is a collection of
-Nix expressions called the Nixpkgs package collection that contains
-packages ranging from basic development stuff such as GCC and Glibc,
-to end-user applications like Mozilla Firefox. (Nix is however not
-tied to the Nixpkgs package collection; you could write your own Nix
-expressions based on Nixpkgs, or completely new ones.)</para>
-
-<para>You can manually download the latest version of Nixpkgs from
-<link xlink:href="http://nixos.org/nixpkgs/download.html"/>. However,
-it’s much more convenient to use the Nixpkgs
-<emphasis>channel</emphasis>, since it makes it easy to stay up to
-date with new versions of Nixpkgs. (Channels are described in more
-detail in <xref linkend="sec-channels"/>.) Nixpkgs is automatically
-added to your list of “subscribed” channels when you install
-Nix. If this is not the case for some reason, you can add it as
-follows:
-
-<screen>
-$ nix-channel --add https://nixos.org/channels/nixpkgs-unstable
-$ nix-channel --update
-</screen>
-
-</para>
-
-<note><para>On NixOS, you’re automatically subscribed to a NixOS
-channel corresponding to your NixOS major release
-(e.g. <uri>http://nixos.org/channels/nixos-14.12</uri>). A NixOS
-channel is identical to the Nixpkgs channel, except that it contains
-only Linux binaries and is updated only if a set of regression tests
-succeed.</para></note>
-
-<para>You can view the set of available packages in Nixpkgs:
-
-<screen>
-$ nix-env -qa
-aterm-2.2
-bash-3.0
-binutils-2.15
-bison-1.875d
-blackdown-1.4.2
-bzip2-1.0.2
-…</screen>
-
-The flag <option>-q</option> specifies a query operation, and
-<option>-a</option> means that you want to show the “available” (i.e.,
-installable) packages, as opposed to the installed packages. If you
-downloaded Nixpkgs yourself, or if you checked it out from GitHub,
-then you need to pass the path to your Nixpkgs tree using the
-<option>-f</option> flag:
-
-<screen>
-$ nix-env -qaf <replaceable>/path/to/nixpkgs</replaceable>
-</screen>
-
-where <replaceable>/path/to/nixpkgs</replaceable> is where you’ve
-unpacked or checked out Nixpkgs.</para>
-
-<para>You can select specific packages by name:
-
-<screen>
-$ nix-env -qa firefox
-firefox-34.0.5
-firefox-with-plugins-34.0.5
-</screen>
-
-and using regular expressions:
-
-<screen>
-$ nix-env -qa 'firefox.*'
-</screen>
-
-</para>
-
-<para>It is also possible to see the <emphasis>status</emphasis> of
-available packages, i.e., whether they are installed into the user
-environment and/or present in the system:
-
-<screen>
-$ nix-env -qas
-…
--PS bash-3.0
---S binutils-2.15
-IPS bison-1.875d
-…</screen>
-
-The first character (<literal>I</literal>) indicates whether the
-package is installed in your current user environment. The second
-(<literal>P</literal>) indicates whether it is present on your system
-(in which case installing it into your user environment would be a
-very quick operation). The last one (<literal>S</literal>) indicates
-whether there is a so-called <emphasis>substitute</emphasis> for the
-package, which is Nix’s mechanism for doing binary deployment. It
-just means that Nix knows that it can fetch a pre-built package from
-somewhere (typically a network server) instead of building it
-locally.</para>
-
-<para>You can install a package using <literal>nix-env -i</literal>.
-For instance,
-
-<screen>
-$ nix-env -i subversion</screen>
-
-will install the package called <literal>subversion</literal> (which
-is, of course, the <link xlink:href="http://subversion.tigris.org/">Subversion version
-management system</link>).</para>
-
-<note><para>When you ask Nix to install a package, it will first try
-to get it in pre-compiled form from a <emphasis>binary
-cache</emphasis>. By default, Nix will use the binary cache
-<uri>https://cache.nixos.org</uri>; it contains binaries for most
-packages in Nixpkgs. Only if no binary is available in the binary
-cache, Nix will build the package from source. So if <literal>nix-env
--i subversion</literal> results in Nix building stuff from source,
-then either the package is not built for your platform by the Nixpkgs
-build servers, or your version of Nixpkgs is too old or too new. For
-instance, if you have a very recent checkout of Nixpkgs, then the
-Nixpkgs build servers may not have had a chance to build everything
-and upload the resulting binaries to
-<uri>https://cache.nixos.org</uri>. The Nixpkgs channel is only
-updated after all binaries have been uploaded to the cache, so if you
-stick to the Nixpkgs channel (rather than using a Git checkout of the
-Nixpkgs tree), you will get binaries for most packages.</para></note>
-
-<para>Naturally, packages can also be uninstalled:
-
-<screen>
-$ nix-env -e subversion</screen>
-
-</para>
-
-<para>Upgrading to a new version is just as easy. If you have a new
-release of Nix Packages, you can do:
-
-<screen>
-$ nix-env -u subversion</screen>
-
-This will <emphasis>only</emphasis> upgrade Subversion if there is a
-“newer” version in the new set of Nix expressions, as
-defined by some pretty arbitrary rules regarding ordering of version
-numbers (which generally do what you’d expect of them). To just
-unconditionally replace Subversion with whatever version is in the Nix
-expressions, use <parameter>-i</parameter> instead of
-<parameter>-u</parameter>; <parameter>-i</parameter> will remove
-whatever version is already installed.</para>
-
-<para>You can also upgrade all packages for which there are newer
-versions:
-
-<screen>
-$ nix-env -u</screen>
-
-</para>
-
-<para>Sometimes it’s useful to be able to ask what
-<command>nix-env</command> would do, without actually doing it. For
-instance, to find out what packages would be upgraded by
-<literal>nix-env -u</literal>, you can do
-
-<screen>
-$ nix-env -u --dry-run
-(dry run; not doing anything)
-upgrading `libxslt-1.1.0' to `libxslt-1.1.10'
-upgrading `graphviz-1.10' to `graphviz-1.12'
-upgrading `coreutils-5.0' to `coreutils-5.2.1'</screen>
-
-</para>
-
-</chapter>
-<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-profiles">
-
-<title>Profiles</title>
-
-<para>Profiles and user environments are Nix’s mechanism for
-implementing the ability to allow different users to have different
-configurations, and to do atomic upgrades and rollbacks. To
-understand how they work, it’s useful to know a bit about how Nix
-works. In Nix, packages are stored in unique locations in the
-<emphasis>Nix store</emphasis> (typically,
-<filename>/nix/store</filename>). For instance, a particular version
-of the Subversion package might be stored in a directory
-<filename>/nix/store/dpmvp969yhdqs7lm2r1a3gng7pyq6vy4-subversion-1.1.3/</filename>,
-while another version might be stored in
-<filename>/nix/store/5mq2jcn36ldlmh93yj1n8s9c95pj7c5s-subversion-1.1.2</filename>.
-The long strings prefixed to the directory names are cryptographic
-hashes<footnote><para>160-bit truncations of SHA-256 hashes encoded in
-a base-32 notation, to be precise.</para></footnote> of
-<emphasis>all</emphasis> inputs involved in building the package —
-sources, dependencies, compiler flags, and so on. So if two
-packages differ in any way, they end up in different locations in
-the file system, so they don’t interfere with each other. <xref linkend="fig-user-environments"/> shows a part of a typical Nix
-store.</para>
-
-<figure xml:id="fig-user-environments"><title>User environments</title>
- <mediaobject>
- <imageobject>
- <imagedata fileref="../figures/user-environments.png" format="PNG"/>
- </imageobject>
- </mediaobject>
-</figure>
-
-<para>Of course, you wouldn’t want to type
-
-<screen>
-$ /nix/store/dpmvp969yhdq...-subversion-1.1.3/bin/svn</screen>
-
-every time you want to run Subversion. Of course we could set up the
-<envar>PATH</envar> environment variable to include the
-<filename>bin</filename> directory of every package we want to use,
-but this is not very convenient since changing <envar>PATH</envar>
-doesn’t take effect for already existing processes. The solution Nix
-uses is to create directory trees of symlinks to
-<emphasis>activated</emphasis> packages. These are called
-<emphasis>user environments</emphasis> and they are packages
-themselves (though automatically generated by
-<command>nix-env</command>), so they too reside in the Nix store. For
-instance, in <xref linkend="fig-user-environments"/> the user
-environment <filename>/nix/store/0c1p5z4kda11...-user-env</filename>
-contains a symlink to just Subversion 1.1.2 (arrows in the figure
-indicate symlinks). This would be what we would obtain if we had done
-
-<screen>
-$ nix-env -i subversion</screen>
-
-on a set of Nix expressions that contained Subversion 1.1.2.</para>
-
-<para>This doesn’t in itself solve the problem, of course; you
-wouldn’t want to type
-<filename>/nix/store/0c1p5z4kda11...-user-env/bin/svn</filename>
-either. That’s why there are symlinks outside of the store that point
-to the user environments in the store; for instance, the symlinks
-<filename>default-42-link</filename> and
-<filename>default-43-link</filename> in the example. These are called
-<emphasis>generations</emphasis> since every time you perform a
-<command>nix-env</command> operation, a new user environment is
-generated based on the current one. For instance, generation 43 was
-created from generation 42 when we did
-
-<screen>
-$ nix-env -i subversion firefox</screen>
-
-on a set of Nix expressions that contained Firefox and a new version
-of Subversion.</para>
-
-<para>Generations are grouped together into
-<emphasis>profiles</emphasis> so that different users don’t interfere
-with each other if they don’t want to. For example:
-
-<screen>
-$ ls -l /nix/var/nix/profiles/
-...
-lrwxrwxrwx 1 eelco ... default-42-link -> /nix/store/0c1p5z4kda11...-user-env
-lrwxrwxrwx 1 eelco ... default-43-link -> /nix/store/3aw2pdyx2jfc...-user-env
-lrwxrwxrwx 1 eelco ... default -> default-43-link</screen>
-
-This shows a profile called <filename>default</filename>. The file
-<filename>default</filename> itself is actually a symlink that points
-to the current generation. When we do a <command>nix-env</command>
-operation, a new user environment and generation link are created
-based on the current one, and finally the <filename>default</filename>
-symlink is made to point at the new generation. This last step is
-atomic on Unix, which explains how we can do atomic upgrades. (Note
-that the building/installing of new packages doesn’t interfere in
-any way with old packages, since they are stored in different
-locations in the Nix store.)</para>
-
-<para>If you find that you want to undo a <command>nix-env</command>
-operation, you can just do
-
-<screen>
-$ nix-env --rollback</screen>
-
-which will just make the current generation link point at the previous
-link. E.g., <filename>default</filename> would be made to point at
-<filename>default-42-link</filename>. You can also switch to a
-specific generation:
-
-<screen>
-$ nix-env --switch-generation 43</screen>
-
-which in this example would roll forward to generation 43 again. You
-can also see all available generations:
-
-<screen>
-$ nix-env --list-generations</screen></para>
-
-<para>You generally wouldn’t have
-<filename>/nix/var/nix/profiles/<replaceable>some-profile</replaceable>/bin</filename>
-in your <envar>PATH</envar>. Rather, there is a symlink
-<filename>~/.nix-profile</filename> that points to your current
-profile. This means that you should put
-<filename>~/.nix-profile/bin</filename> in your <envar>PATH</envar>
-(and indeed, that’s what the initialisation script
-<filename>/nix/etc/profile.d/nix.sh</filename> does). This makes it
-easier to switch to a different profile. You can do that using the
-command <command>nix-env --switch-profile</command>:
-
-<screen>
-$ nix-env --switch-profile /nix/var/nix/profiles/my-profile
-
-$ nix-env --switch-profile /nix/var/nix/profiles/default</screen>
-
-These commands switch to the <filename>my-profile</filename> and
-default profile, respectively. If the profile doesn’t exist, it will
-be created automatically. You should be careful about storing a
-profile in another location than the <filename>profiles</filename>
-directory, since otherwise it might not be used as a root of the
-garbage collector (see <xref linkend="sec-garbage-collection"/>).</para>
-
-<para>All <command>nix-env</command> operations work on the profile
-pointed to by <command>~/.nix-profile</command>, but you can override
-this using the <option>--profile</option> option (abbreviation
-<option>-p</option>):
-
-<screen>
-$ nix-env -p /nix/var/nix/profiles/other-profile -i subversion</screen>
-
-This will <emphasis>not</emphasis> change the
-<command>~/.nix-profile</command> symlink.</para>
-
-</chapter>
-<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-garbage-collection">
-
-<title>Garbage Collection</title>
-
-<para><command>nix-env</command> operations such as upgrades
-(<option>-u</option>) and uninstall (<option>-e</option>) never
-actually delete packages from the system. All they do (as shown
-above) is to create a new user environment that no longer contains
-symlinks to the “deleted” packages.</para>
-
-<para>Of course, since disk space is not infinite, unused packages
-should be removed at some point. You can do this by running the Nix
-garbage collector. It will remove from the Nix store any package
-not used (directly or indirectly) by any generation of any
-profile.</para>
-
-<para>Note however that as long as old generations reference a
-package, it will not be deleted. After all, we wouldn’t be able to
-do a rollback otherwise. So in order for garbage collection to be
-effective, you should also delete (some) old generations. Of course,
-this should only be done if you are certain that you will not need to
-roll back.</para>
-
-<para>To delete all old (non-current) generations of your current
-profile:
-
-<screen>
-$ nix-env --delete-generations old</screen>
-
-Instead of <literal>old</literal> you can also specify a list of
-generations, e.g.,
-
-<screen>
-$ nix-env --delete-generations 10 11 14</screen>
-
-To delete all generations older than a specified number of days
-(except the current generation), use the <literal>d</literal>
-suffix. For example,
-
-<screen>
-$ nix-env --delete-generations 14d</screen>
-
-deletes all generations older than two weeks.</para>
-
-<para>After removing appropriate old generations you can run the
-garbage collector as follows:
-
-<screen>
-$ nix-store --gc</screen>
-
-The behaviour of the gargage collector is affected by the
-<literal>keep-derivations</literal> (default: true) and <literal>keep-outputs</literal>
-(default: false) options in the Nix configuration file. The defaults will ensure
-that all derivations that are build-time dependencies of garbage collector roots
-will be kept and that all output paths that are runtime dependencies
-will be kept as well. All other derivations or paths will be collected.
-(This is usually what you want, but while you are developing
-it may make sense to keep outputs to ensure that rebuild times are quick.)
-
-If you are feeling uncertain, you can also first view what files would
-be deleted:
-
-<screen>
-$ nix-store --gc --print-dead</screen>
-
-Likewise, the option <option>--print-live</option> will show the paths
-that <emphasis>won’t</emphasis> be deleted.</para>
-
-<para>There is also a convenient little utility
-<command>nix-collect-garbage</command>, which when invoked with the
-<option>-d</option> (<option>--delete-old</option>) switch deletes all
-old generations of all profiles in
-<filename>/nix/var/nix/profiles</filename>. So
-
-<screen>
-$ nix-collect-garbage -d</screen>
-
-is a quick and easy way to clean up your system.</para>
-
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-gc-roots">
-
-<title>Garbage Collector Roots</title>
-
-<para>The roots of the garbage collector are all store paths to which
-there are symlinks in the directory
-<filename><replaceable>prefix</replaceable>/nix/var/nix/gcroots</filename>.
-For instance, the following command makes the path
-<filename>/nix/store/d718ef...-foo</filename> a root of the collector:
-
-<screen>
-$ ln -s /nix/store/d718ef...-foo /nix/var/nix/gcroots/bar</screen>
-
-That is, after this command, the garbage collector will not remove
-<filename>/nix/store/d718ef...-foo</filename> or any of its
-dependencies.</para>
-
-<para>Subdirectories of
-<filename><replaceable>prefix</replaceable>/nix/var/nix/gcroots</filename>
-are also searched for symlinks. Symlinks to non-store paths are
-followed and searched for roots, but symlinks to non-store paths
-<emphasis>inside</emphasis> the paths reached in that way are not
-followed to prevent infinite recursion.</para>
-
-</section>
-
-</chapter>
-<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-channels">
-
-<title>Channels</title>
-
-<para>If you want to stay up to date with a set of packages, it’s not
-very convenient to manually download the latest set of Nix expressions
-for those packages and upgrade using <command>nix-env</command>.
-Fortunately, there’s a better way: <emphasis>Nix
-channels</emphasis>.</para>
-
-<para>A Nix channel is just a URL that points to a place that contains
-a set of Nix expressions and a manifest. Using the command <link linkend="sec-nix-channel"><command>nix-channel</command></link> you
-can automatically stay up to date with whatever is available at that
-URL.</para>
-
-<para>To see the list of official NixOS channels, visit <link xlink:href="https://nixos.org/channels"/>.</para>
-
-<para>You can “subscribe” to a channel using
-<command>nix-channel --add</command>, e.g.,
-
-<screen>
-$ nix-channel --add https://nixos.org/channels/nixpkgs-unstable</screen>
-
-subscribes you to a channel that always contains that latest version
-of the Nix Packages collection. (Subscribing really just means that
-the URL is added to the file <filename>~/.nix-channels</filename>,
-where it is read by subsequent calls to <command>nix-channel
---update</command>.) You can “unsubscribe” using <command>nix-channel
---remove</command>:
-
-<screen>
-$ nix-channel --remove nixpkgs
-</screen>
-</para>
-
-<para>To obtain the latest Nix expressions available in a channel, do
-
-<screen>
-$ nix-channel --update</screen>
-
-This downloads and unpacks the Nix expressions in every channel
-(downloaded from <literal><replaceable>url</replaceable>/nixexprs.tar.bz2</literal>).
-It also makes the union of each channel’s Nix expressions available by
-default to <command>nix-env</command> operations (via the symlink
-<filename>~/.nix-defexpr/channels</filename>). Consequently, you can
-then say
-
-<screen>
-$ nix-env -u</screen>
-
-to upgrade all packages in your profile to the latest versions
-available in the subscribed channels.</para>
-
-</chapter>
-<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-sharing-packages">
-
-<title>Sharing Packages Between Machines</title>
-
-<para>Sometimes you want to copy a package from one machine to
-another. Or, you want to install some packages and you know that
-another machine already has some or all of those packages or their
-dependencies. In that case there are mechanisms to quickly copy
-packages between machines.</para>
-
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-binary-cache-substituter">
-
-<title>Serving a Nix store via HTTP</title>
-
-<para>You can easily share the Nix store of a machine via HTTP. This
-allows other machines to fetch store paths from that machine to speed
-up installations. It uses the same <emphasis>binary cache</emphasis>
-mechanism that Nix usually uses to fetch pre-built binaries from
-<uri>https://cache.nixos.org</uri>.</para>
-
-<para>The daemon that handles binary cache requests via HTTP,
-<command>nix-serve</command>, is not part of the Nix distribution, but
-you can install it from Nixpkgs:
-
-<screen>
-$ nix-env -i nix-serve
-</screen>
-
-You can then start the server, listening for HTTP connections on
-whatever port you like:
-
-<screen>
-$ nix-serve -p 8080
-</screen>
-
-To check whether it works, try the following on the client:
-
-<screen>
-$ curl http://avalon:8080/nix-cache-info
-</screen>
-
-which should print something like:
-
-<screen>
-StoreDir: /nix/store
-WantMassQuery: 1
-Priority: 30
-</screen>
-
-</para>
-
-<para>On the client side, you can tell Nix to use your binary cache
-using <option>--option extra-binary-caches</option>, e.g.:
-
-<screen>
-$ nix-env -i firefox --option extra-binary-caches http://avalon:8080/
-</screen>
-
-The option <option>extra-binary-caches</option> tells Nix to use this
-binary cache in addition to your default caches, such as
-<uri>https://cache.nixos.org</uri>. Thus, for any path in the closure
-of Firefox, Nix will first check if the path is available on the
-server <literal>avalon</literal> or another binary caches. If not, it
-will fall back to building from source.</para>
-
-<para>You can also tell Nix to always use your binary cache by adding
-a line to the <filename linkend="sec-conf-file">nix.conf</filename>
-configuration file like this:
-
-<programlisting>
-binary-caches = http://avalon:8080/ https://cache.nixos.org/
-</programlisting>
-
-</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-copy-closure">
-
-<title>Copying Closures Via SSH</title>
-
-<para>The command <command linkend="sec-nix-copy-closure">nix-copy-closure</command> copies a Nix
-store path along with all its dependencies to or from another machine
-via the SSH protocol. It doesn’t copy store paths that are already
-present on the target machine. For example, the following command
-copies Firefox with all its dependencies:
-
-<screen>
-$ nix-copy-closure --to alice@itchy.example.org $(type -p firefox)</screen>
-
-See <xref linkend="sec-nix-copy-closure"/> for details.</para>
-
-<para>With <command linkend="refsec-nix-store-export">nix-store
---export</command> and <command linkend="refsec-nix-store-import">nix-store --import</command> you can
-write the closure of a store path (that is, the path and all its
-dependencies) to a file, and then unpack that file into another Nix
-store. For example,
-
-<screen>
-$ nix-store --export $(nix-store -qR $(type -p firefox)) > firefox.closure</screen>
-
-writes the closure of Firefox to a file. You can then copy this file
-to another machine and install the closure:
-
-<screen>
-$ nix-store --import < firefox.closure</screen>
-
-Any store paths in the closure that are already present in the target
-store are ignored. It is also possible to pipe the export into
-another command, e.g. to copy and install a closure directly to/on
-another machine:
-
-<screen>
-$ nix-store --export $(nix-store -qR $(type -p firefox)) | bzip2 | \
- ssh alice@itchy.example.org "bunzip2 | nix-store --import"</screen>
-
-However, <command>nix-copy-closure</command> is generally more
-efficient because it only copies paths that are not already present in
-the target Nix store.</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-ssh-substituter">
-
-<title>Serving a Nix store via SSH</title>
-
-<para>You can tell Nix to automatically fetch needed binaries from a
-remote Nix store via SSH. For example, the following installs Firefox,
-automatically fetching any store paths in Firefox’s closure if they
-are available on the server <literal>avalon</literal>:
-
-<screen>
-$ nix-env -i firefox --substituters ssh://alice@avalon
-</screen>
-
-This works similar to the binary cache substituter that Nix usually
-uses, only using SSH instead of HTTP: if a store path
-<literal>P</literal> is needed, Nix will first check if it’s available
-in the Nix store on <literal>avalon</literal>. If not, it will fall
-back to using the binary cache substituter, and then to building from
-source.</para>
-
-<note><para>The SSH substituter currently does not allow you to enter
-an SSH passphrase interactively. Therefore, you should use
-<command>ssh-add</command> to load the decrypted private key into
-<command>ssh-agent</command>.</para></note>
-
-<para>You can also copy the closure of some store path, without
-installing it into your profile, e.g.
-
-<screen>
-$ nix-store -r /nix/store/m85bxg…-firefox-34.0.5 --substituters ssh://alice@avalon
-</screen>
-
-This is essentially equivalent to doing
-
-<screen>
-$ nix-copy-closure --from alice@avalon /nix/store/m85bxg…-firefox-34.0.5
-</screen>
-
-</para>
-
-<para>You can use SSH’s <emphasis>forced command</emphasis> feature to
-set up a restricted user account for SSH substituter access, allowing
-read-only access to the local Nix store, but nothing more. For
-example, add the following lines to <filename>sshd_config</filename>
-to restrict the user <literal>nix-ssh</literal>:
-
-<programlisting>
-Match User nix-ssh
- AllowAgentForwarding no
- AllowTcpForwarding no
- PermitTTY no
- PermitTunnel no
- X11Forwarding no
- ForceCommand nix-store --serve
-Match All
-</programlisting>
-
-On NixOS, you can accomplish the same by adding the following to your
-<filename>configuration.nix</filename>:
-
-<programlisting>
-nix.sshServe.enable = true;
-nix.sshServe.keys = [ "ssh-dss AAAAB3NzaC1k... bob@example.org" ];
-</programlisting>
-
-where the latter line lists the public keys of users that are allowed
-to connect.</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-s3-substituter">
-
-<title>Serving a Nix store via AWS S3 or S3-compatible Service</title>
-
-<para>Nix has built-in support for storing and fetching store paths
-from Amazon S3 and S3 compatible services. This uses the same
-<emphasis>binary</emphasis> cache mechanism that Nix usually uses to
-fetch prebuilt binaries from <uri>cache.nixos.org</uri>.</para>
-
-<para>The following options can be specified as URL parameters to
-the S3 URL:</para>
-
-<variablelist>
- <varlistentry><term><literal>profile</literal></term>
- <listitem>
- <para>
- The name of the AWS configuration profile to use. By default
- Nix will use the <literal>default</literal> profile.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry><term><literal>region</literal></term>
- <listitem>
- <para>
- The region of the S3 bucket. <literal>us–east-1</literal> by
- default.
- </para>
-
- <para>
- If your bucket is not in <literal>us–east-1</literal>, you
- should always explicitly specify the region parameter.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry><term><literal>endpoint</literal></term>
- <listitem>
- <para>
- The URL to your S3-compatible service, for when not using
- Amazon S3. Do not specify this value if you're using Amazon
- S3.
- </para>
- <note><para>This endpoint must support HTTPS and will use
- path-based addressing instead of virtual host based
- addressing.</para></note>
- </listitem>
- </varlistentry>
-
- <varlistentry><term><literal>scheme</literal></term>
- <listitem>
- <para>
- The scheme used for S3 requests, <literal>https</literal>
- (default) or <literal>http</literal>. This option allows you to
- disable HTTPS for binary caches which don't support it.
- </para>
- <note><para>HTTPS should be used if the cache might contain
- sensitive information.</para></note>
- </listitem>
- </varlistentry>
-</variablelist>
-
-<para>In this example we will use the bucket named
-<literal>example-nix-cache</literal>.</para>
-
-<section xml:id="ssec-s3-substituter-anonymous-reads">
- <title>Anonymous Reads to your S3-compatible binary cache</title>
-
- <para>If your binary cache is publicly accessible and does not
- require authentication, the simplest and easiest way to use Nix with
- your S3 compatible binary cache is to use the HTTP URL for that
- cache.</para>
-
- <para>For AWS S3 the binary cache URL for example bucket will be
- exactly <uri>https://example-nix-cache.s3.amazonaws.com</uri> or
- <uri>s3://example-nix-cache</uri>. For S3 compatible binary caches,
- consult that cache's documentation.</para>
-
- <para>Your bucket will need the following bucket policy:</para>
-
- <programlisting><![CDATA[
-{
- "Id": "DirectReads",
- "Version": "2012-10-17",
- "Statement": [
- {
- "Sid": "AllowDirectReads",
- "Action": [
- "s3:GetObject",
- "s3:GetBucketLocation"
- ],
- "Effect": "Allow",
- "Resource": [
- "arn:aws:s3:::example-nix-cache",
- "arn:aws:s3:::example-nix-cache/*"
- ],
- "Principal": "*"
- }
- ]
-}
-]]></programlisting>
-</section>
-
-<section xml:id="ssec-s3-substituter-authenticated-reads">
- <title>Authenticated Reads to your S3 binary cache</title>
-
- <para>For AWS S3 the binary cache URL for example bucket will be
- exactly <uri>s3://example-nix-cache</uri>.</para>
-
- <para>Nix will use the <link xlink:href="https://docs.aws.amazon.com/sdk-for-cpp/v1/developer-guide/credentials.html">default
- credential provider chain</link> for authenticating requests to
- Amazon S3.</para>
-
- <para>Nix supports authenticated reads from Amazon S3 and S3
- compatible binary caches.</para>
-
- <para>Your bucket will need a bucket policy allowing the desired
- users to perform the <literal>s3:GetObject</literal> and
- <literal>s3:GetBucketLocation</literal> action on all objects in the
- bucket. The anonymous policy in <xref linkend="ssec-s3-substituter-anonymous-reads"/> can be updated to
- have a restricted <literal>Principal</literal> to support
- this.</para>
-</section>
-
-
-<section xml:id="ssec-s3-substituter-authenticated-writes">
- <title>Authenticated Writes to your S3-compatible binary cache</title>
-
- <para>Nix support fully supports writing to Amazon S3 and S3
- compatible buckets. The binary cache URL for our example bucket will
- be <uri>s3://example-nix-cache</uri>.</para>
-
- <para>Nix will use the <link xlink:href="https://docs.aws.amazon.com/sdk-for-cpp/v1/developer-guide/credentials.html">default
- credential provider chain</link> for authenticating requests to
- Amazon S3.</para>
-
- <para>Your account will need the following IAM policy to
- upload to the cache:</para>
-
- <programlisting><![CDATA[
-{
- "Version": "2012-10-17",
- "Statement": [
- {
- "Sid": "UploadToCache",
- "Effect": "Allow",
- "Action": [
- "s3:AbortMultipartUpload",
- "s3:GetBucketLocation",
- "s3:GetObject",
- "s3:ListBucket",
- "s3:ListBucketMultipartUploads",
- "s3:ListMultipartUploadParts",
- "s3:PutObject"
- ],
- "Resource": [
- "arn:aws:s3:::example-nix-cache",
- "arn:aws:s3:::example-nix-cache/*"
- ]
- }
- ]
-}
-]]></programlisting>
-
-
- <example><title>Uploading with a specific credential profile for Amazon S3</title>
- <para><command>nix copy --to 's3://example-nix-cache?profile=cache-upload&region=eu-west-2' nixpkgs.hello</command></para>
- </example>
-
- <example><title>Uploading to an S3-Compatible Binary Cache</title>
- <para><command>nix copy --to 's3://example-nix-cache?profile=cache-upload&scheme=https&endpoint=minio.example.com' nixpkgs.hello</command></para>
- </example>
-</section>
-</section>
-
-</chapter>
-
-</part>
- <part xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="chap-writing-nix-expressions" xml:base="expressions/writing-nix-expressions.xml">
-
-<title>Writing Nix Expressions</title>
-
-<partintro>
-<para>This chapter shows you how to write Nix expressions, which
-instruct Nix how to build packages. It starts with a
-simple example (a Nix expression for GNU Hello), and then moves
-on to a more in-depth look at the Nix expression language.</para>
-
-<note><para>This chapter is mostly about the Nix expression language.
-For more extensive information on adding packages to the Nix Packages
-collection (such as functions in the standard environment and coding
-conventions), please consult <link xlink:href="http://nixos.org/nixpkgs/manual/">its
-manual</link>.</para></note>
-</partintro>
-
-<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-simple-expression">
-
-<title>A Simple Nix Expression</title>
-
-<para>This section shows how to add and test the <link xlink:href="http://www.gnu.org/software/hello/hello.html">GNU Hello
-package</link> to the Nix Packages collection. Hello is a program
-that prints out the text <quote>Hello, world!</quote>.</para>
-
-<para>To add a package to the Nix Packages collection, you generally
-need to do three things:
-
-<orderedlist>
-
- <listitem><para>Write a Nix expression for the package. This is a
- file that describes all the inputs involved in building the package,
- such as dependencies, sources, and so on.</para></listitem>
-
- <listitem><para>Write a <emphasis>builder</emphasis>. This is a
- shell script<footnote><para>In fact, it can be written in any
- language, but typically it's a <command>bash</command> shell
- script.</para></footnote> that actually builds the package from
- the inputs.</para></listitem>
-
- <listitem><para>Add the package to the file
- <filename>pkgs/top-level/all-packages.nix</filename>. The Nix
- expression written in the first step is a
- <emphasis>function</emphasis>; it requires other packages in order
- to build it. In this step you put it all together, i.e., you call
- the function with the right arguments to build the actual
- package.</para></listitem>
-
-</orderedlist>
-
-</para>
-
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-expression-syntax">
-
-<title>Expression Syntax</title>
-
-<example xml:id="ex-hello-nix"><title>Nix expression for GNU Hello
-(<filename>default.nix</filename>)</title>
-<programlisting>
-{ stdenv, fetchurl, perl }: <co xml:id="ex-hello-nix-co-1"/>
-
-stdenv.mkDerivation { <co xml:id="ex-hello-nix-co-2"/>
- name = "hello-2.1.1"; <co xml:id="ex-hello-nix-co-3"/>
- builder = ./builder.sh; <co xml:id="ex-hello-nix-co-4"/>
- src = fetchurl { <co xml:id="ex-hello-nix-co-5"/>
- url = "ftp://ftp.nluug.nl/pub/gnu/hello/hello-2.1.1.tar.gz";
- sha256 = "1md7jsfd8pa45z73bz1kszpp01yw6x5ljkjk2hx7wl800any6465";
- };
- inherit perl; <co xml:id="ex-hello-nix-co-6"/>
-}</programlisting>
-</example>
-
-<para><xref linkend="ex-hello-nix"/> shows a Nix expression for GNU
-Hello. It's actually already in the Nix Packages collection in
-<filename>pkgs/applications/misc/hello/ex-1/default.nix</filename>.
-It is customary to place each package in a separate directory and call
-the single Nix expression in that directory
-<filename>default.nix</filename>. The file has the following elements
-(referenced from the figure by number):
-
-<calloutlist>
-
- <callout arearefs="ex-hello-nix-co-1">
-
- <para>This states that the expression is a
- <emphasis>function</emphasis> that expects to be called with three
- arguments: <varname>stdenv</varname>, <varname>fetchurl</varname>,
- and <varname>perl</varname>. They are needed to build Hello, but
- we don't know how to build them here; that's why they are function
- arguments. <varname>stdenv</varname> is a package that is used
- by almost all Nix Packages packages; it provides a
- <quote>standard</quote> environment consisting of the things you
- would expect in a basic Unix environment: a C/C++ compiler (GCC,
- to be precise), the Bash shell, fundamental Unix tools such as
- <command>cp</command>, <command>grep</command>,
- <command>tar</command>, etc. <varname>fetchurl</varname> is a
- function that downloads files. <varname>perl</varname> is the
- Perl interpreter.</para>
-
- <para>Nix functions generally have the form <literal>{ x, y, ...,
- z }: e</literal> where <varname>x</varname>, <varname>y</varname>,
- etc. are the names of the expected arguments, and where
- <replaceable>e</replaceable> is the body of the function. So
- here, the entire remainder of the file is the body of the
- function; when given the required arguments, the body should
- describe how to build an instance of the Hello package.</para>
-
- </callout>
-
- <callout arearefs="ex-hello-nix-co-2">
-
- <para>So we have to build a package. Building something from
- other stuff is called a <emphasis>derivation</emphasis> in Nix (as
- opposed to sources, which are built by humans instead of
- computers). We perform a derivation by calling
- <varname>stdenv.mkDerivation</varname>.
- <varname>mkDerivation</varname> is a function provided by
- <varname>stdenv</varname> that builds a package from a set of
- <emphasis>attributes</emphasis>. A set is just a list of
- key/value pairs where each key is a string and each value is an
- arbitrary Nix expression. They take the general form <literal>{
- <replaceable>name1</replaceable> =
- <replaceable>expr1</replaceable>; <replaceable>...</replaceable>
- <replaceable>nameN</replaceable> =
- <replaceable>exprN</replaceable>; }</literal>.</para>
-
- </callout>
-
- <callout arearefs="ex-hello-nix-co-3">
-
- <para>The attribute <varname>name</varname> specifies the symbolic
- name and version of the package. Nix doesn't really care about
- these things, but they are used by for instance <command>nix-env
- -q</command> to show a <quote>human-readable</quote> name for
- packages. This attribute is required by
- <varname>mkDerivation</varname>.</para>
-
- </callout>
-
- <callout arearefs="ex-hello-nix-co-4">
-
- <para>The attribute <varname>builder</varname> specifies the
- builder. This attribute can sometimes be omitted, in which case
- <varname>mkDerivation</varname> will fill in a default builder
- (which does a <literal>configure; make; make install</literal>, in
- essence). Hello is sufficiently simple that the default builder
- would suffice, but in this case, we will show an actual builder
- for educational purposes. The value
- <command>./builder.sh</command> refers to the shell script shown
- in <xref linkend="ex-hello-builder"/>, discussed below.</para>
-
- </callout>
-
- <callout arearefs="ex-hello-nix-co-5">
-
- <para>The builder has to know what the sources of the package
- are. Here, the attribute <varname>src</varname> is bound to the
- result of a call to the <command>fetchurl</command> function.
- Given a URL and a SHA-256 hash of the expected contents of the file
- at that URL, this function builds a derivation that downloads the
- file and checks its hash. So the sources are a dependency that
- like all other dependencies is built before Hello itself is
- built.</para>
-
- <para>Instead of <varname>src</varname> any other name could have
- been used, and in fact there can be any number of sources (bound
- to different attributes). However, <varname>src</varname> is
- customary, and it's also expected by the default builder (which we
- don't use in this example).</para>
-
- </callout>
-
- <callout arearefs="ex-hello-nix-co-6">
-
- <para>Since the derivation requires Perl, we have to pass the
- value of the <varname>perl</varname> function argument to the
- builder. All attributes in the set are actually passed as
- environment variables to the builder, so declaring an attribute
-
- <programlisting>
-perl = perl;</programlisting>
-
- will do the trick: it binds an attribute <varname>perl</varname>
- to the function argument which also happens to be called
- <varname>perl</varname>. However, it looks a bit silly, so there
- is a shorter syntax. The <literal>inherit</literal> keyword
- causes the specified attributes to be bound to whatever variables
- with the same name happen to be in scope.</para>
-
- </callout>
-
-</calloutlist>
-
-</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-build-script">
-
-<title>Build Script</title>
-
-<example xml:id="ex-hello-builder"><title>Build script for GNU Hello
-(<filename>builder.sh</filename>)</title>
-<programlisting>
-source $stdenv/setup <co xml:id="ex-hello-builder-co-1"/>
-
-PATH=$perl/bin:$PATH <co xml:id="ex-hello-builder-co-2"/>
-
-tar xvfz $src <co xml:id="ex-hello-builder-co-3"/>
-cd hello-*
-./configure --prefix=$out <co xml:id="ex-hello-builder-co-4"/>
-make <co xml:id="ex-hello-builder-co-5"/>
-make install</programlisting>
-</example>
-
-<para><xref linkend="ex-hello-builder"/> shows the builder referenced
-from Hello's Nix expression (stored in
-<filename>pkgs/applications/misc/hello/ex-1/builder.sh</filename>).
-The builder can actually be made a lot shorter by using the
-<emphasis>generic builder</emphasis> functions provided by
-<varname>stdenv</varname>, but here we write out the build steps to
-elucidate what a builder does. It performs the following
-steps:</para>
-
-<calloutlist>
-
- <callout arearefs="ex-hello-builder-co-1">
-
- <para>When Nix runs a builder, it initially completely clears the
- environment (except for the attributes declared in the
- derivation). For instance, the <envar>PATH</envar> variable is
- empty<footnote><para>Actually, it's initialised to
- <filename>/path-not-set</filename> to prevent Bash from setting it
- to a default value.</para></footnote>. This is done to prevent
- undeclared inputs from being used in the build process. If for
- example the <envar>PATH</envar> contained
- <filename>/usr/bin</filename>, then you might accidentally use
- <filename>/usr/bin/gcc</filename>.</para>
-
- <para>So the first step is to set up the environment. This is
- done by calling the <filename>setup</filename> script of the
- standard environment. The environment variable
- <envar>stdenv</envar> points to the location of the standard
- environment being used. (It wasn't specified explicitly as an
- attribute in <xref linkend="ex-hello-nix"/>, but
- <varname>mkDerivation</varname> adds it automatically.)</para>
-
- </callout>
-
- <callout arearefs="ex-hello-builder-co-2">
-
- <para>Since Hello needs Perl, we have to make sure that Perl is in
- the <envar>PATH</envar>. The <envar>perl</envar> environment
- variable points to the location of the Perl package (since it
- was passed in as an attribute to the derivation), so
- <filename><replaceable>$perl</replaceable>/bin</filename> is the
- directory containing the Perl interpreter.</para>
-
- </callout>
-
- <callout arearefs="ex-hello-builder-co-3">
-
- <para>Now we have to unpack the sources. The
- <varname>src</varname> attribute was bound to the result of
- fetching the Hello source tarball from the network, so the
- <envar>src</envar> environment variable points to the location in
- the Nix store to which the tarball was downloaded. After
- unpacking, we <command>cd</command> to the resulting source
- directory.</para>
-
- <para>The whole build is performed in a temporary directory
- created in <varname>/tmp</varname>, by the way. This directory is
- removed after the builder finishes, so there is no need to clean
- up the sources afterwards. Also, the temporary directory is
- always newly created, so you don't have to worry about files from
- previous builds interfering with the current build.</para>
-
- </callout>
-
- <callout arearefs="ex-hello-builder-co-4">
-
- <para>GNU Hello is a typical Autoconf-based package, so we first
- have to run its <filename>configure</filename> script. In Nix
- every package is stored in a separate location in the Nix store,
- for instance
- <filename>/nix/store/9a54ba97fb71b65fda531012d0443ce2-hello-2.1.1</filename>.
- Nix computes this path by cryptographically hashing all attributes
- of the derivation. The path is passed to the builder through the
- <envar>out</envar> environment variable. So here we give
- <filename>configure</filename> the parameter
- <literal>--prefix=$out</literal> to cause Hello to be installed in
- the expected location.</para>
-
- </callout>
-
- <callout arearefs="ex-hello-builder-co-5">
-
- <para>Finally we build Hello (<literal>make</literal>) and install
- it into the location specified by <envar>out</envar>
- (<literal>make install</literal>).</para>
-
- </callout>
-
-</calloutlist>
-
-<para>If you are wondering about the absence of error checking on the
-result of various commands called in the builder: this is because the
-shell script is evaluated with Bash's <option>-e</option> option,
-which causes the script to be aborted if any command fails without an
-error check.</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-arguments">
-
-<title>Arguments and Variables</title>
-
-<example xml:id="ex-hello-composition">
-
-<title>Composing GNU Hello
-(<filename>all-packages.nix</filename>)</title>
-<programlisting>
-...
-
-rec { <co xml:id="ex-hello-composition-co-1"/>
-
- hello = import ../applications/misc/hello/ex-1 <co xml:id="ex-hello-composition-co-2"/> { <co xml:id="ex-hello-composition-co-3"/>
- inherit fetchurl stdenv perl;
- };
-
- perl = import ../development/interpreters/perl { <co xml:id="ex-hello-composition-co-4"/>
- inherit fetchurl stdenv;
- };
-
- fetchurl = import ../build-support/fetchurl {
- inherit stdenv; ...
- };
-
- stdenv = ...;
-
-}
-</programlisting>
-</example>
-
-<para>The Nix expression in <xref linkend="ex-hello-nix"/> is a
-function; it is missing some arguments that have to be filled in
-somewhere. In the Nix Packages collection this is done in the file
-<filename>pkgs/top-level/all-packages.nix</filename>, where all
-Nix expressions for packages are imported and called with the
-appropriate arguments. <xref linkend="ex-hello-composition"/> shows
-some fragments of
-<filename>all-packages.nix</filename>.</para>
-
-<calloutlist>
-
- <callout arearefs="ex-hello-composition-co-1">
-
- <para>This file defines a set of attributes, all of which are
- concrete derivations (i.e., not functions). In fact, we define a
- <emphasis>mutually recursive</emphasis> set of attributes. That
- is, the attributes can refer to each other. This is precisely
- what we want since we want to <quote>plug</quote> the
- various packages into each other.</para>
-
- </callout>
-
- <callout arearefs="ex-hello-composition-co-2">
-
- <para>Here we <emphasis>import</emphasis> the Nix expression for
- GNU Hello. The import operation just loads and returns the
- specified Nix expression. In fact, we could just have put the
- contents of <xref linkend="ex-hello-nix"/> in
- <filename>all-packages.nix</filename> at this point. That
- would be completely equivalent, but it would make the file rather
- bulky.</para>
-
- <para>Note that we refer to
- <filename>../applications/misc/hello/ex-1</filename>, not
- <filename>../applications/misc/hello/ex-1/default.nix</filename>.
- When you try to import a directory, Nix automatically appends
- <filename>/default.nix</filename> to the file name.</para>
-
- </callout>
-
- <callout arearefs="ex-hello-composition-co-3">
-
- <para>This is where the actual composition takes place. Here we
- <emphasis>call</emphasis> the function imported from
- <filename>../applications/misc/hello/ex-1</filename> with a set
- containing the things that the function expects, namely
- <varname>fetchurl</varname>, <varname>stdenv</varname>, and
- <varname>perl</varname>. We use inherit again to use the
- attributes defined in the surrounding scope (we could also have
- written <literal>fetchurl = fetchurl;</literal>, etc.).</para>
-
- <para>The result of this function call is an actual derivation
- that can be built by Nix (since when we fill in the arguments of
- the function, what we get is its body, which is the call to
- <varname>stdenv.mkDerivation</varname> in <xref linkend="ex-hello-nix"/>).</para>
-
- <note><para>Nixpkgs has a convenience function
- <function>callPackage</function> that imports and calls a
- function, filling in any missing arguments by passing the
- corresponding attribute from the Nixpkgs set, like this:
-
-<programlisting>
-hello = callPackage ../applications/misc/hello/ex-1 { };
-</programlisting>
-
- If necessary, you can set or override arguments:
-
-<programlisting>
-hello = callPackage ../applications/misc/hello/ex-1 { stdenv = myStdenv; };
-</programlisting>
-
- </para></note>
-
- </callout>
-
- <callout arearefs="ex-hello-composition-co-4">
-
- <para>Likewise, we have to instantiate Perl,
- <varname>fetchurl</varname>, and the standard environment.</para>
-
- </callout>
-
-</calloutlist>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-building-simple">
-
-<title>Building and Testing</title>
-
-<para>You can now try to build Hello. Of course, you could do
-<literal>nix-env -i hello</literal>, but you may not want to install a
-possibly broken package just yet. The best way to test the package is by
-using the command <command linkend="sec-nix-build">nix-build</command>,
-which builds a Nix expression and creates a symlink named
-<filename>result</filename> in the current directory:
-
-<screen>
-$ nix-build -A hello
-building path `/nix/store/632d2b22514d...-hello-2.1.1'
-hello-2.1.1/
-hello-2.1.1/intl/
-hello-2.1.1/intl/ChangeLog
-<replaceable>...</replaceable>
-
-$ ls -l result
-lrwxrwxrwx ... 2006-09-29 10:43 result -> /nix/store/632d2b22514d...-hello-2.1.1
-
-$ ./result/bin/hello
-Hello, world!</screen>
-
-The <link linkend="opt-attr"><option>-A</option></link> option selects
-the <literal>hello</literal> attribute. This is faster than using the
-symbolic package name specified by the <literal>name</literal>
-attribute (which also happens to be <literal>hello</literal>) and is
-unambiguous (there can be multiple packages with the symbolic name
-<literal>hello</literal>, but there can be only one attribute in a set
-named <literal>hello</literal>).</para>
-
-<para><command>nix-build</command> registers the
-<filename>./result</filename> symlink as a garbage collection root, so
-unless and until you delete the <filename>./result</filename> symlink,
-the output of the build will be safely kept on your system. You can
-use <command>nix-build</command>’s <option linkend="opt-out-link">-o</option> switch to give the symlink another
-name.</para>
-
-<para>Nix has transactional semantics. Once a build finishes
-successfully, Nix makes a note of this in its database: it registers
-that the path denoted by <envar>out</envar> is now
-<quote>valid</quote>. If you try to build the derivation again, Nix
-will see that the path is already valid and finish immediately. If a
-build fails, either because it returns a non-zero exit code, because
-Nix or the builder are killed, or because the machine crashes, then
-the output paths will not be registered as valid. If you try to build
-the derivation again, Nix will remove the output paths if they exist
-(e.g., because the builder died half-way through <literal>make
-install</literal>) and try again. Note that there is no
-<quote>negative caching</quote>: Nix doesn't remember that a build
-failed, and so a failed build can always be repeated. This is because
-Nix cannot distinguish between permanent failures (e.g., a compiler
-error due to a syntax error in the source) and transient failures
-(e.g., a disk full condition).</para>
-
-<para>Nix also performs locking. If you run multiple Nix builds
-simultaneously, and they try to build the same derivation, the first
-Nix instance that gets there will perform the build, while the others
-block (or perform other derivations if available) until the build
-finishes:
-
-<screen>
-$ nix-build -A hello
-waiting for lock on `/nix/store/0h5b7hp8d4hqfrw8igvx97x1xawrjnac-hello-2.1.1x'</screen>
-
-So it is always safe to run multiple instances of Nix in parallel
-(which isn’t the case with, say, <command>make</command>).</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-generic-builder">
-
-<title>Generic Builder Syntax</title>
-
-<para>Recall from <xref linkend="ex-hello-builder"/> that the builder
-looked something like this:
-
-<programlisting>
-PATH=$perl/bin:$PATH
-tar xvfz $src
-cd hello-*
-./configure --prefix=$out
-make
-make install</programlisting>
-
-The builders for almost all Unix packages look like this — set up some
-environment variables, unpack the sources, configure, build, and
-install. For this reason the standard environment provides some Bash
-functions that automate the build process. A builder using the
-generic build facilities in shown in <xref linkend="ex-hello-builder2"/>.</para>
-
-<example xml:id="ex-hello-builder2"><title>Build script using the generic
-build functions</title>
-<programlisting>
-buildInputs="$perl" <co xml:id="ex-hello-builder2-co-1"/>
-
-source $stdenv/setup <co xml:id="ex-hello-builder2-co-2"/>
-
-genericBuild <co xml:id="ex-hello-builder2-co-3"/></programlisting>
-</example>
-
-<calloutlist>
-
- <callout arearefs="ex-hello-builder2-co-1">
-
- <para>The <envar>buildInputs</envar> variable tells
- <filename>setup</filename> to use the indicated packages as
- <quote>inputs</quote>. This means that if a package provides a
- <filename>bin</filename> subdirectory, it's added to
- <envar>PATH</envar>; if it has a <filename>include</filename>
- subdirectory, it's added to GCC's header search path; and so
- on.<footnote><para>How does it work? <filename>setup</filename>
- tries to source the file
- <filename><replaceable>pkg</replaceable>/nix-support/setup-hook</filename>
- of all dependencies. These “setup hooks” can then set up whatever
- environment variables they want; for instance, the setup hook for
- Perl sets the <envar>PERL5LIB</envar> environment variable to
- contain the <filename>lib/site_perl</filename> directories of all
- inputs.</para></footnote>
- </para>
-
- </callout>
-
- <callout arearefs="ex-hello-builder2-co-2">
-
- <para>The function <function>genericBuild</function> is defined in
- the file <literal>$stdenv/setup</literal>.</para>
-
- </callout>
-
- <callout arearefs="ex-hello-builder2-co-3">
-
- <para>The final step calls the shell function
- <function>genericBuild</function>, which performs the steps that
- were done explicitly in <xref linkend="ex-hello-builder"/>. The
- generic builder is smart enough to figure out whether to unpack
- the sources using <command>gzip</command>,
- <command>bzip2</command>, etc. It can be customised in many ways;
- see the Nixpkgs manual for details.</para>
-
- </callout>
-
-</calloutlist>
-
-<para>Discerning readers will note that the
-<envar>buildInputs</envar> could just as well have been set in the Nix
-expression, like this:
-
-<programlisting>
- buildInputs = [ perl ];</programlisting>
-
-The <varname>perl</varname> attribute can then be removed, and the
-builder becomes even shorter:
-
-<programlisting>
-source $stdenv/setup
-genericBuild</programlisting>
-
-In fact, <varname>mkDerivation</varname> provides a default builder
-that looks exactly like that, so it is actually possible to omit the
-builder for Hello entirely.</para>
-
-</section>
-
-</chapter>
-<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-expression-language">
-
-<title>Nix Expression Language</title>
-
-<para>The Nix expression language is a pure, lazy, functional
-language. Purity means that operations in the language don't have
-side-effects (for instance, there is no variable assignment).
-Laziness means that arguments to functions are evaluated only when
-they are needed. Functional means that functions are
-<quote>normal</quote> values that can be passed around and manipulated
-in interesting ways. The language is not a full-featured, general
-purpose language. Its main job is to describe packages,
-compositions of packages, and the variability within
-packages.</para>
-
-<para>This section presents the various features of the
-language.</para>
-
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-values">
-
-<title>Values</title>
-
-
-<simplesect><title>Simple Values</title>
-
-<para>Nix has the following basic data types:
-
-<itemizedlist>
-
- <listitem>
-
- <para><emphasis>Strings</emphasis> can be written in three
- ways.</para>
-
- <para>The most common way is to enclose the string between double
- quotes, e.g., <literal>"foo bar"</literal>. Strings can span
- multiple lines. The special characters <literal>"</literal> and
- <literal>\</literal> and the character sequence
- <literal>${</literal> must be escaped by prefixing them with a
- backslash (<literal>\</literal>). Newlines, carriage returns and
- tabs can be written as <literal>\n</literal>,
- <literal>\r</literal> and <literal>\t</literal>,
- respectively.</para>
-
- <para>You can include the result of an expression into a string by
- enclosing it in
- <literal>${<replaceable>...</replaceable>}</literal>, a feature
- known as <emphasis>antiquotation</emphasis>. The enclosed
- expression must evaluate to something that can be coerced into a
- string (meaning that it must be a string, a path, or a
- derivation). For instance, rather than writing
-
-<programlisting>
-"--with-freetype2-library=" + freetype + "/lib"</programlisting>
-
- (where <varname>freetype</varname> is a derivation), you can
- instead write the more natural
-
-<programlisting>
-"--with-freetype2-library=${freetype}/lib"</programlisting>
-
- The latter is automatically translated to the former. A more
- complicated example (from the Nix expression for <link xlink:href="http://www.trolltech.com/products/qt">Qt</link>):
-
-<programlisting>
-configureFlags = "
- -system-zlib -system-libpng -system-libjpeg
- ${if openglSupport then "-dlopen-opengl
- -L${mesa}/lib -I${mesa}/include
- -L${libXmu}/lib -I${libXmu}/include" else ""}
- ${if threadSupport then "-thread" else "-no-thread"}
-";</programlisting>
-
- Note that Nix expressions and strings can be arbitrarily nested;
- in this case the outer string contains various antiquotations that
- themselves contain strings (e.g., <literal>"-thread"</literal>),
- some of which in turn contain expressions (e.g.,
- <literal>${mesa}</literal>).</para>
-
- <para>The second way to write string literals is as an
- <emphasis>indented string</emphasis>, which is enclosed between
- pairs of <emphasis>double single-quotes</emphasis>, like so:
-
-<programlisting>
-''
- This is the first line.
- This is the second line.
- This is the third line.
-''</programlisting>
-
- This kind of string literal intelligently strips indentation from
- the start of each line. To be precise, it strips from each line a
- number of spaces equal to the minimal indentation of the string as
- a whole (disregarding the indentation of empty lines). For
- instance, the first and second line are indented two space, while
- the third line is indented four spaces. Thus, two spaces are
- stripped from each line, so the resulting string is
-
-<programlisting>
-"This is the first line.\nThis is the second line.\n This is the third line.\n"</programlisting>
-
- </para>
-
- <para>Note that the whitespace and newline following the opening
- <literal>''</literal> is ignored if there is no non-whitespace
- text on the initial line.</para>
-
- <para>Antiquotation
- (<literal>${<replaceable>expr</replaceable>}</literal>) is
- supported in indented strings.</para>
-
- <para>Since <literal>${</literal> and <literal>''</literal> have
- special meaning in indented strings, you need a way to quote them.
- <literal>$</literal> can be escaped by prefixing it with
- <literal>''</literal> (that is, two single quotes), i.e.,
- <literal>''$</literal>. <literal>''</literal> can be escaped by
- prefixing it with <literal>'</literal>, i.e.,
- <literal>'''</literal>. <literal>$</literal> removes any special meaning
- from the following <literal>$</literal>. Linefeed, carriage-return and tab
- characters can be written as <literal>''\n</literal>,
- <literal>''\r</literal>, <literal>''\t</literal>, and <literal>''\</literal>
- escapes any other character.
-
- </para>
-
- <para>Indented strings are primarily useful in that they allow
- multi-line string literals to follow the indentation of the
- enclosing Nix expression, and that less escaping is typically
- necessary for strings representing languages such as shell scripts
- and configuration files because <literal>''</literal> is much less
- common than <literal>"</literal>. Example:
-
-<programlisting>
-stdenv.mkDerivation {
- <replaceable>...</replaceable>
- postInstall =
- ''
- mkdir $out/bin $out/etc
- cp foo $out/bin
- echo "Hello World" > $out/etc/foo.conf
- ${if enableBar then "cp bar $out/bin" else ""}
- '';
- <replaceable>...</replaceable>
-}
-</programlisting>
-
- </para>
-
- <para>Finally, as a convenience, <emphasis>URIs</emphasis> as
- defined in appendix B of <link xlink:href="http://www.ietf.org/rfc/rfc2396.txt">RFC 2396</link>
- can be written <emphasis>as is</emphasis>, without quotes. For
- instance, the string
- <literal>"http://example.org/foo.tar.bz2"</literal>
- can also be written as
- <literal>http://example.org/foo.tar.bz2</literal>.</para>
-
- </listitem>
-
- <listitem><para>Numbers, which can be <emphasis>integers</emphasis> (like
- <literal>123</literal>) or <emphasis>floating point</emphasis> (like
- <literal>123.43</literal> or <literal>.27e13</literal>).</para>
-
- <para>Numbers are type-compatible: pure integer operations will always
- return integers, whereas any operation involving at least one floating point
- number will have a floating point number as a result.</para></listitem>
-
- <listitem><para><emphasis>Paths</emphasis>, e.g.,
- <filename>/bin/sh</filename> or <filename>./builder.sh</filename>.
- A path must contain at least one slash to be recognised as such; for
- instance, <filename>builder.sh</filename> is not a
- path<footnote><para>It's parsed as an expression that selects the
- attribute <varname>sh</varname> from the variable
- <varname>builder</varname>.</para></footnote>. If the file name is
- relative, i.e., if it does not begin with a slash, it is made
- absolute at parse time relative to the directory of the Nix
- expression that contained it. For instance, if a Nix expression in
- <filename>/foo/bar/bla.nix</filename> refers to
- <filename>../xyzzy/fnord.nix</filename>, the absolute path is
- <filename>/foo/xyzzy/fnord.nix</filename>.</para>
-
- <para>If the first component of a path is a <literal>~</literal>,
- it is interpreted as if the rest of the path were relative to the
- user's home directory. e.g. <filename>~/foo</filename> would be
- equivalent to <filename>/home/edolstra/foo</filename> for a user
- whose home directory is <filename>/home/edolstra</filename>.
- </para>
-
- <para>Paths can also be specified between angle brackets, e.g.
- <literal><nixpkgs></literal>. This means that the directories
- listed in the environment variable
- <envar linkend="env-NIX_PATH">NIX_PATH</envar> will be searched
- for the given file or directory name.
- </para>
-
- </listitem>
-
- <listitem><para><emphasis>Booleans</emphasis> with values
- <literal>true</literal> and
- <literal>false</literal>.</para></listitem>
-
- <listitem><para>The null value, denoted as
- <literal>null</literal>.</para></listitem>
-
-</itemizedlist>
-
-</para>
-
-</simplesect>
-
-
-<simplesect><title>Lists</title>
-
-<para>Lists are formed by enclosing a whitespace-separated list of
-values between square brackets. For example,
-
-<programlisting>
-[ 123 ./foo.nix "abc" (f { x = y; }) ]</programlisting>
-
-defines a list of four elements, the last being the result of a call
-to the function <varname>f</varname>. Note that function calls have
-to be enclosed in parentheses. If they had been omitted, e.g.,
-
-<programlisting>
-[ 123 ./foo.nix "abc" f { x = y; } ]</programlisting>
-
-the result would be a list of five elements, the fourth one being a
-function and the fifth being a set.</para>
-
-<para>Note that lists are only lazy in values, and they are strict in length.
-</para>
-
-</simplesect>
-
-
-<simplesect><title>Sets</title>
-
-<para>Sets are really the core of the language, since ultimately the
-Nix language is all about creating derivations, which are really just
-sets of attributes to be passed to build scripts.</para>
-
-<para>Sets are just a list of name/value pairs (called
-<emphasis>attributes</emphasis>) enclosed in curly brackets, where
-each value is an arbitrary expression terminated by a semicolon. For
-example:
-
-<programlisting>
-{ x = 123;
- text = "Hello";
- y = f { bla = 456; };
-}</programlisting>
-
-This defines a set with attributes named <varname>x</varname>,
-<varname>text</varname>, <varname>y</varname>. The order of the
-attributes is irrelevant. An attribute name may only occur
-once.</para>
-
-<para>Attributes can be selected from a set using the
-<literal>.</literal> operator. For instance,
-
-<programlisting>
-{ a = "Foo"; b = "Bar"; }.a</programlisting>
-
-evaluates to <literal>"Foo"</literal>. It is possible to provide a
-default value in an attribute selection using the
-<literal>or</literal> keyword. For example,
-
-<programlisting>
-{ a = "Foo"; b = "Bar"; }.c or "Xyzzy"</programlisting>
-
-will evaluate to <literal>"Xyzzy"</literal> because there is no
-<varname>c</varname> attribute in the set.</para>
-
-<para>You can use arbitrary double-quoted strings as attribute
-names:
-
-<programlisting>
-{ "foo ${bar}" = 123; "nix-1.0" = 456; }."foo ${bar}"
-</programlisting>
-
-This will evaluate to <literal>123</literal> (Assuming
-<literal>bar</literal> is antiquotable). In the case where an
-attribute name is just a single antiquotation, the quotes can be
-dropped:
-
-<programlisting>
-{ foo = 123; }.${bar} or 456 </programlisting>
-
-This will evaluate to <literal>123</literal> if
-<literal>bar</literal> evaluates to <literal>"foo"</literal> when
-coerced to a string and <literal>456</literal> otherwise (again
-assuming <literal>bar</literal> is antiquotable).</para>
-
-<para>In the special case where an attribute name inside of a set declaration
-evaluates to <literal>null</literal> (which is normally an error, as
-<literal>null</literal> is not antiquotable), that attribute is simply not
-added to the set:
-
-<programlisting>
-{ ${if foo then "bar" else null} = true; }</programlisting>
-
-This will evaluate to <literal>{}</literal> if <literal>foo</literal>
-evaluates to <literal>false</literal>.</para>
-
-<para>A set that has a <literal>__functor</literal> attribute whose value
-is callable (i.e. is itself a function or a set with a
-<literal>__functor</literal> attribute whose value is callable) can be
-applied as if it were a function, with the set itself passed in first
-, e.g.,
-
-<programlisting>
-let add = { __functor = self: x: x + self.x; };
- inc = add // { x = 1; };
-in inc 1
-</programlisting>
-
-evaluates to <literal>2</literal>. This can be used to attach metadata to a
-function without the caller needing to treat it specially, or to implement
-a form of object-oriented programming, for example.
-
-</para>
-
-</simplesect>
-
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-constructs">
-
-<title>Language Constructs</title>
-
-<simplesect><title>Recursive sets</title>
-
-<para>Recursive sets are just normal sets, but the attributes can
-refer to each other. For example,
-
-<programlisting>
-rec {
- x = y;
- y = 123;
-}.x
-</programlisting>
-
-evaluates to <literal>123</literal>. Note that without
-<literal>rec</literal> the binding <literal>x = y;</literal> would
-refer to the variable <varname>y</varname> in the surrounding scope,
-if one exists, and would be invalid if no such variable exists. That
-is, in a normal (non-recursive) set, attributes are not added to the
-lexical scope; in a recursive set, they are.</para>
-
-<para>Recursive sets of course introduce the danger of infinite
-recursion. For example,
-
-<programlisting>
-rec {
- x = y;
- y = x;
-}.x</programlisting>
-
-does not terminate<footnote><para>Actually, Nix detects infinite
-recursion in this case and aborts (<quote>infinite recursion
-encountered</quote>).</para></footnote>.</para>
-
-</simplesect>
-
-
-<simplesect xml:id="sect-let-expressions"><title>Let-expressions</title>
-
-<para>A let-expression allows you to define local variables for an
-expression. For instance,
-
-<programlisting>
-let
- x = "foo";
- y = "bar";
-in x + y</programlisting>
-
-evaluates to <literal>"foobar"</literal>.
-
-</para>
-
-</simplesect>
-
-
-<simplesect><title>Inheriting attributes</title>
-
-<para>When defining a set or in a let-expression it is often convenient to copy variables
-from the surrounding lexical scope (e.g., when you want to propagate
-attributes). This can be shortened using the
-<literal>inherit</literal> keyword. For instance,
-
-<programlisting>
-let x = 123; in
-{ inherit x;
- y = 456;
-}</programlisting>
-
-is equivalent to
-
-<programlisting>
-let x = 123; in
-{ x = x;
- y = 456;
-}</programlisting>
-
-and both evaluate to <literal>{ x = 123; y = 456; }</literal>. (Note that
-this works because <varname>x</varname> is added to the lexical scope
-by the <literal>let</literal> construct.) It is also possible to
-inherit attributes from another set. For instance, in this fragment
-from <filename>all-packages.nix</filename>,
-
-<programlisting>
- graphviz = (import ../tools/graphics/graphviz) {
- inherit fetchurl stdenv libpng libjpeg expat x11 yacc;
- inherit (xlibs) libXaw;
- };
-
- xlibs = {
- libX11 = ...;
- libXaw = ...;
- ...
- }
-
- libpng = ...;
- libjpg = ...;
- ...</programlisting>
-
-the set used in the function call to the function defined in
-<filename>../tools/graphics/graphviz</filename> inherits a number of
-variables from the surrounding scope (<varname>fetchurl</varname>
-... <varname>yacc</varname>), but also inherits
-<varname>libXaw</varname> (the X Athena Widgets) from the
-<varname>xlibs</varname> (X11 client-side libraries) set.</para>
-
-<para>
-Summarizing the fragment
-
-<programlisting>
-...
-inherit x y z;
-inherit (src-set) a b c;
-...</programlisting>
-
-is equivalent to
-
-<programlisting>
-...
-x = x; y = y; z = z;
-a = src-set.a; b = src-set.b; c = src-set.c;
-...</programlisting>
-
-when used while defining local variables in a let-expression or
-while defining a set.</para>
-
-</simplesect>
-
-
-<simplesect xml:id="ss-functions"><title>Functions</title>
-
-<para>Functions have the following form:
-
-<programlisting>
-<replaceable>pattern</replaceable>: <replaceable>body</replaceable></programlisting>
-
-The pattern specifies what the argument of the function must look
-like, and binds variables in the body to (parts of) the
-argument. There are three kinds of patterns:</para>
-
-<itemizedlist>
-
-
- <listitem><para>If a pattern is a single identifier, then the
- function matches any argument. Example:
-
- <programlisting>
-let negate = x: !x;
- concat = x: y: x + y;
-in if negate true then concat "foo" "bar" else ""</programlisting>
-
- Note that <function>concat</function> is a function that takes one
- argument and returns a function that takes another argument. This
- allows partial parameterisation (i.e., only filling some of the
- arguments of a function); e.g.,
-
- <programlisting>
-map (concat "foo") [ "bar" "bla" "abc" ]</programlisting>
-
- evaluates to <literal>[ "foobar" "foobla"
- "fooabc" ]</literal>.</para></listitem>
-
-
- <listitem><para>A <emphasis>set pattern</emphasis> of the form
- <literal>{ name1, name2, …, nameN }</literal> matches a set
- containing the listed attributes, and binds the values of those
- attributes to variables in the function body. For example, the
- function
-
-<programlisting>
-{ x, y, z }: z + y + x</programlisting>
-
- can only be called with a set containing exactly the attributes
- <varname>x</varname>, <varname>y</varname> and
- <varname>z</varname>. No other attributes are allowed. If you want
- to allow additional arguments, you can use an ellipsis
- (<literal>...</literal>):
-
-<programlisting>
-{ x, y, z, ... }: z + y + x</programlisting>
-
- This works on any set that contains at least the three named
- attributes.</para>
-
- <para>It is possible to provide <emphasis>default values</emphasis>
- for attributes, in which case they are allowed to be missing. A
- default value is specified by writing
- <literal><replaceable>name</replaceable> ?
- <replaceable>e</replaceable></literal>, where
- <replaceable>e</replaceable> is an arbitrary expression. For example,
-
-<programlisting>
-{ x, y ? "foo", z ? "bar" }: z + y + x</programlisting>
-
- specifies a function that only requires an attribute named
- <varname>x</varname>, but optionally accepts <varname>y</varname>
- and <varname>z</varname>.</para></listitem>
-
-
- <listitem><para>An <literal>@</literal>-pattern provides a means of referring
- to the whole value being matched:
-
-<programlisting> args@{ x, y, z, ... }: z + y + x + args.a</programlisting>
-
-but can also be written as:
-
-<programlisting> { x, y, z, ... } @ args: z + y + x + args.a</programlisting>
-
- Here <varname>args</varname> is bound to the entire argument, which
- is further matched against the pattern <literal>{ x, y, z,
- ... }</literal>. <literal>@</literal>-pattern makes mainly sense with an
- ellipsis(<literal>...</literal>) as you can access attribute names as
- <literal>a</literal>, using <literal>args.a</literal>, which was given as an
- additional attribute to the function.
- </para>
-
- <warning>
- <para>
- The <literal>args@</literal> expression is bound to the argument passed to the function which
- means that attributes with defaults that aren't explicitly specified in the function call
- won't cause an evaluation error, but won't exist in <literal>args</literal>.
- </para>
- <para>
- For instance
-<programlisting>
-let
- function = args@{ a ? 23, ... }: args;
-in
- function {}
-</programlisting>
- will evaluate to an empty attribute set.
- </para>
- </warning></listitem>
-
-</itemizedlist>
-
-<para>Note that functions do not have names. If you want to give them
-a name, you can bind them to an attribute, e.g.,
-
-<programlisting>
-let concat = { x, y }: x + y;
-in concat { x = "foo"; y = "bar"; }</programlisting>
-
-</para>
-
-</simplesect>
-
-
-<simplesect><title>Conditionals</title>
-
-<para>Conditionals look like this:
-
-<programlisting>
-if <replaceable>e1</replaceable> then <replaceable>e2</replaceable> else <replaceable>e3</replaceable></programlisting>
-
-where <replaceable>e1</replaceable> is an expression that should
-evaluate to a Boolean value (<literal>true</literal> or
-<literal>false</literal>).</para>
-
-</simplesect>
-
-
-<simplesect><title>Assertions</title>
-
-<para>Assertions are generally used to check that certain requirements
-on or between features and dependencies hold. They look like this:
-
-<programlisting>
-assert <replaceable>e1</replaceable>; <replaceable>e2</replaceable></programlisting>
-
-where <replaceable>e1</replaceable> is an expression that should
-evaluate to a Boolean value. If it evaluates to
-<literal>true</literal>, <replaceable>e2</replaceable> is returned;
-otherwise expression evaluation is aborted and a backtrace is printed.</para>
-
-<example xml:id="ex-subversion-nix"><title>Nix expression for Subversion</title>
-<programlisting>
-{ localServer ? false
-, httpServer ? false
-, sslSupport ? false
-, pythonBindings ? false
-, javaSwigBindings ? false
-, javahlBindings ? false
-, stdenv, fetchurl
-, openssl ? null, httpd ? null, db4 ? null, expat, swig ? null, j2sdk ? null
-}:
-
-assert localServer -> db4 != null; <co xml:id="ex-subversion-nix-co-1"/>
-assert httpServer -> httpd != null && httpd.expat == expat; <co xml:id="ex-subversion-nix-co-2"/>
-assert sslSupport -> openssl != null && (httpServer -> httpd.openssl == openssl); <co xml:id="ex-subversion-nix-co-3"/>
-assert pythonBindings -> swig != null && swig.pythonSupport;
-assert javaSwigBindings -> swig != null && swig.javaSupport;
-assert javahlBindings -> j2sdk != null;
-
-stdenv.mkDerivation {
- name = "subversion-1.1.1";
- ...
- openssl = if sslSupport then openssl else null; <co xml:id="ex-subversion-nix-co-4"/>
- ...
-}</programlisting>
-</example>
-
-<para><xref linkend="ex-subversion-nix"/> show how assertions are
-used in the Nix expression for Subversion.</para>
-
-<calloutlist>
-
- <callout arearefs="ex-subversion-nix-co-1">
- <para>This assertion states that if Subversion is to have support
- for local repositories, then Berkeley DB is needed. So if the
- Subversion function is called with the
- <varname>localServer</varname> argument set to
- <literal>true</literal> but the <varname>db4</varname> argument
- set to <literal>null</literal>, then the evaluation fails.</para>
- </callout>
-
- <callout arearefs="ex-subversion-nix-co-2">
- <para>This is a more subtle condition: if Subversion is built with
- Apache (<literal>httpServer</literal>) support, then the Expat
- library (an XML library) used by Subversion should be same as the
- one used by Apache. This is because in this configuration
- Subversion code ends up being linked with Apache code, and if the
- Expat libraries do not match, a build- or runtime link error or
- incompatibility might occur.</para>
- </callout>
-
- <callout arearefs="ex-subversion-nix-co-3">
- <para>This assertion says that in order for Subversion to have SSL
- support (so that it can access <literal>https</literal> URLs), an
- OpenSSL library must be passed. Additionally, it says that
- <emphasis>if</emphasis> Apache support is enabled, then Apache's
- OpenSSL should match Subversion's. (Note that if Apache support
- is not enabled, we don't care about Apache's OpenSSL.)</para>
- </callout>
-
- <callout arearefs="ex-subversion-nix-co-4">
- <para>The conditional here is not really related to assertions,
- but is worth pointing out: it ensures that if SSL support is
- disabled, then the Subversion derivation is not dependent on
- OpenSSL, even if a non-<literal>null</literal> value was passed.
- This prevents an unnecessary rebuild of Subversion if OpenSSL
- changes.</para>
- </callout>
-
-</calloutlist>
-
-</simplesect>
-
-
-
-<simplesect><title>With-expressions</title>
-
-<para>A <emphasis>with-expression</emphasis>,
-
-<programlisting>
-with <replaceable>e1</replaceable>; <replaceable>e2</replaceable></programlisting>
-
-introduces the set <replaceable>e1</replaceable> into the lexical
-scope of the expression <replaceable>e2</replaceable>. For instance,
-
-<programlisting>
-let as = { x = "foo"; y = "bar"; };
-in with as; x + y</programlisting>
-
-evaluates to <literal>"foobar"</literal> since the
-<literal>with</literal> adds the <varname>x</varname> and
-<varname>y</varname> attributes of <varname>as</varname> to the
-lexical scope in the expression <literal>x + y</literal>. The most
-common use of <literal>with</literal> is in conjunction with the
-<function>import</function> function. E.g.,
-
-<programlisting>
-with (import ./definitions.nix); ...</programlisting>
-
-makes all attributes defined in the file
-<filename>definitions.nix</filename> available as if they were defined
-locally in a <literal>let</literal>-expression.</para>
-
-<para>The bindings introduced by <literal>with</literal> do not shadow bindings
-introduced by other means, e.g.
-
-<programlisting>
-let a = 3; in with { a = 1; }; let a = 4; in with { a = 2; }; ...</programlisting>
-
-establishes the same scope as
-
-<programlisting>
-let a = 1; in let a = 2; in let a = 3; in let a = 4; in ...</programlisting>
-
-</para>
-
-</simplesect>
-
-
-<simplesect><title>Comments</title>
-
-<para>Comments can be single-line, started with a <literal>#</literal>
-character, or inline/multi-line, enclosed within <literal>/*
-... */</literal>.</para>
-
-</simplesect>
-
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-language-operators">
-
-<title>Operators</title>
-
-<para><xref linkend="table-operators"/> lists the operators in the
-Nix expression language, in order of precedence (from strongest to
-weakest binding).</para>
-
-<table xml:id="table-operators">
- <title>Operators</title>
- <tgroup cols="3">
- <thead>
- <row>
- <entry>Name</entry>
- <entry>Syntax</entry>
- <entry>Associativity</entry>
- <entry>Description</entry>
- <entry>Precedence</entry>
- </row>
- </thead>
- <tbody>
- <row>
- <entry>Select</entry>
- <entry><replaceable>e</replaceable> <literal>.</literal>
- <replaceable>attrpath</replaceable>
- [ <literal>or</literal> <replaceable>def</replaceable> ]
- </entry>
- <entry>none</entry>
- <entry>Select attribute denoted by the attribute path
- <replaceable>attrpath</replaceable> from set
- <replaceable>e</replaceable>. (An attribute path is a
- dot-separated list of attribute names.) If the attribute
- doesn’t exist, return <replaceable>def</replaceable> if
- provided, otherwise abort evaluation.</entry>
- <entry>1</entry>
- </row>
- <row>
- <entry>Application</entry>
- <entry><replaceable>e1</replaceable> <replaceable>e2</replaceable></entry>
- <entry>left</entry>
- <entry>Call function <replaceable>e1</replaceable> with
- argument <replaceable>e2</replaceable>.</entry>
- <entry>2</entry>
- </row>
- <row>
- <entry>Arithmetic Negation</entry>
- <entry><literal>-</literal> <replaceable>e</replaceable></entry>
- <entry>none</entry>
- <entry>Arithmetic negation.</entry>
- <entry>3</entry>
- </row>
- <row>
- <entry>Has Attribute</entry>
- <entry><replaceable>e</replaceable> <literal>?</literal>
- <replaceable>attrpath</replaceable></entry>
- <entry>none</entry>
- <entry>Test whether set <replaceable>e</replaceable> contains
- the attribute denoted by <replaceable>attrpath</replaceable>;
- return <literal>true</literal> or
- <literal>false</literal>.</entry>
- <entry>4</entry>
- </row>
- <row>
- <entry>List Concatenation</entry>
- <entry><replaceable>e1</replaceable> <literal>++</literal> <replaceable>e2</replaceable></entry>
- <entry>right</entry>
- <entry>List concatenation.</entry>
- <entry>5</entry>
- </row>
- <row>
- <entry>Multiplication</entry>
- <entry>
- <replaceable>e1</replaceable> <literal>*</literal> <replaceable>e2</replaceable>,
- </entry>
- <entry>left</entry>
- <entry>Arithmetic multiplication.</entry>
- <entry>6</entry>
- </row>
- <row>
- <entry>Division</entry>
- <entry>
- <replaceable>e1</replaceable> <literal>/</literal> <replaceable>e2</replaceable>
- </entry>
- <entry>left</entry>
- <entry>Arithmetic division.</entry>
- <entry>6</entry>
- </row>
- <row>
- <entry>Addition</entry>
- <entry>
- <replaceable>e1</replaceable> <literal>+</literal> <replaceable>e2</replaceable>
- </entry>
- <entry>left</entry>
- <entry>Arithmetic addition.</entry>
- <entry>7</entry>
- </row>
- <row>
- <entry>Subtraction</entry>
- <entry>
- <replaceable>e1</replaceable> <literal>-</literal> <replaceable>e2</replaceable>
- </entry>
- <entry>left</entry>
- <entry>Arithmetic subtraction.</entry>
- <entry>7</entry>
- </row>
- <row>
- <entry>String Concatenation</entry>
- <entry>
- <replaceable>string1</replaceable> <literal>+</literal> <replaceable>string2</replaceable>
- </entry>
- <entry>left</entry>
- <entry>String concatenation.</entry>
- <entry>7</entry>
- </row>
- <row>
- <entry>Not</entry>
- <entry><literal>!</literal> <replaceable>e</replaceable></entry>
- <entry>none</entry>
- <entry>Boolean negation.</entry>
- <entry>8</entry>
- </row>
- <row>
- <entry>Update</entry>
- <entry><replaceable>e1</replaceable> <literal>//</literal>
- <replaceable>e2</replaceable></entry>
- <entry>right</entry>
- <entry>Return a set consisting of the attributes in
- <replaceable>e1</replaceable> and
- <replaceable>e2</replaceable> (with the latter taking
- precedence over the former in case of equally named
- attributes).</entry>
- <entry>9</entry>
- </row>
- <row>
- <entry>Less Than</entry>
- <entry>
- <replaceable>e1</replaceable> <literal><</literal> <replaceable>e2</replaceable>,
- </entry>
- <entry>none</entry>
- <entry>Arithmetic comparison.</entry>
- <entry>10</entry>
- </row>
- <row>
- <entry>Less Than or Equal To</entry>
- <entry>
- <replaceable>e1</replaceable> <literal><=</literal> <replaceable>e2</replaceable>
- </entry>
- <entry>none</entry>
- <entry>Arithmetic comparison.</entry>
- <entry>10</entry>
- </row>
- <row>
- <entry>Greater Than</entry>
- <entry>
- <replaceable>e1</replaceable> <literal>></literal> <replaceable>e2</replaceable>
- </entry>
- <entry>none</entry>
- <entry>Arithmetic comparison.</entry>
- <entry>10</entry>
- </row>
- <row>
- <entry>Greater Than or Equal To</entry>
- <entry>
- <replaceable>e1</replaceable> <literal>>=</literal> <replaceable>e2</replaceable>
- </entry>
- <entry>none</entry>
- <entry>Arithmetic comparison.</entry>
- <entry>10</entry>
- </row>
- <row>
- <entry>Equality</entry>
- <entry>
- <replaceable>e1</replaceable> <literal>==</literal> <replaceable>e2</replaceable>
- </entry>
- <entry>none</entry>
- <entry>Equality.</entry>
- <entry>11</entry>
- </row>
- <row>
- <entry>Inequality</entry>
- <entry>
- <replaceable>e1</replaceable> <literal>!=</literal> <replaceable>e2</replaceable>
- </entry>
- <entry>none</entry>
- <entry>Inequality.</entry>
- <entry>11</entry>
- </row>
- <row>
- <entry>Logical AND</entry>
- <entry><replaceable>e1</replaceable> <literal>&&</literal>
- <replaceable>e2</replaceable></entry>
- <entry>left</entry>
- <entry>Logical AND.</entry>
- <entry>12</entry>
- </row>
- <row>
- <entry>Logical OR</entry>
- <entry><replaceable>e1</replaceable> <literal>||</literal>
- <replaceable>e2</replaceable></entry>
- <entry>left</entry>
- <entry>Logical OR.</entry>
- <entry>13</entry>
- </row>
- <row>
- <entry>Logical Implication</entry>
- <entry><replaceable>e1</replaceable> <literal>-></literal>
- <replaceable>e2</replaceable></entry>
- <entry>none</entry>
- <entry>Logical implication (equivalent to
- <literal>!<replaceable>e1</replaceable> ||
- <replaceable>e2</replaceable></literal>).</entry>
- <entry>14</entry>
- </row>
- </tbody>
- </tgroup>
-</table>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-derivation">
-
-<title>Derivations</title>
-
-<para>The most important built-in function is
-<function>derivation</function>, which is used to describe a single
-derivation (a build action). It takes as input a set, the attributes
-of which specify the inputs of the build.</para>
-
-<itemizedlist>
-
- <listitem xml:id="attr-system"><para>There must be an attribute named
- <varname>system</varname> whose value must be a string specifying a
- Nix platform identifier, such as <literal>"i686-linux"</literal> or
- <literal>"x86_64-darwin"</literal><footnote><para>To figure out
- your platform identifier, look at the line <quote>Checking for the
- canonical Nix system name</quote> in the output of Nix's
- <filename>configure</filename> script.</para></footnote> The build
- can only be performed on a machine and operating system matching the
- platform identifier. (Nix can automatically forward builds for
- other platforms by forwarding them to other machines; see <xref linkend="chap-distributed-builds"/>.)</para></listitem>
-
- <listitem><para>There must be an attribute named
- <varname>name</varname> whose value must be a string. This is used
- as a symbolic name for the package by <command>nix-env</command>,
- and it is appended to the output paths of the
- derivation.</para></listitem>
-
- <listitem><para>There must be an attribute named
- <varname>builder</varname> that identifies the program that is
- executed to perform the build. It can be either a derivation or a
- source (a local file reference, e.g.,
- <filename>./builder.sh</filename>).</para></listitem>
-
- <listitem><para>Every attribute is passed as an environment variable
- to the builder. Attribute values are translated to environment
- variables as follows:
-
- <itemizedlist>
-
- <listitem><para>Strings and numbers are just passed
- verbatim.</para></listitem>
-
- <listitem><para>A <emphasis>path</emphasis> (e.g.,
- <filename>../foo/sources.tar</filename>) causes the referenced
- file to be copied to the store; its location in the store is put
- in the environment variable. The idea is that all sources
- should reside in the Nix store, since all inputs to a derivation
- should reside in the Nix store.</para></listitem>
-
- <listitem><para>A <emphasis>derivation</emphasis> causes that
- derivation to be built prior to the present derivation; its
- default output path is put in the environment
- variable.</para></listitem>
-
- <listitem><para>Lists of the previous types are also allowed.
- They are simply concatenated, separated by
- spaces.</para></listitem>
-
- <listitem><para><literal>true</literal> is passed as the string
- <literal>1</literal>, <literal>false</literal> and
- <literal>null</literal> are passed as an empty string.
- </para></listitem>
- </itemizedlist>
-
- </para></listitem>
-
- <listitem><para>The optional attribute <varname>args</varname>
- specifies command-line arguments to be passed to the builder. It
- should be a list.</para></listitem>
-
- <listitem><para>The optional attribute <varname>outputs</varname>
- specifies a list of symbolic outputs of the derivation. By default,
- a derivation produces a single output path, denoted as
- <literal>out</literal>. However, derivations can produce multiple
- output paths. This is useful because it allows outputs to be
- downloaded or garbage-collected separately. For instance, imagine a
- library package that provides a dynamic library, header files, and
- documentation. A program that links against the library doesn’t
- need the header files and documentation at runtime, and it doesn’t
- need the documentation at build time. Thus, the library package
- could specify:
-<programlisting>
-outputs = [ "lib" "headers" "doc" ];
-</programlisting>
- This will cause Nix to pass environment variables
- <literal>lib</literal>, <literal>headers</literal> and
- <literal>doc</literal> to the builder containing the intended store
- paths of each output. The builder would typically do something like
-<programlisting>
-./configure --libdir=$lib/lib --includedir=$headers/include --docdir=$doc/share/doc
-</programlisting>
- for an Autoconf-style package. You can refer to each output of a
- derivation by selecting it as an attribute, e.g.
-<programlisting>
-buildInputs = [ pkg.lib pkg.headers ];
-</programlisting>
- The first element of <varname>outputs</varname> determines the
- <emphasis>default output</emphasis>. Thus, you could also write
-<programlisting>
-buildInputs = [ pkg pkg.headers ];
-</programlisting>
- since <literal>pkg</literal> is equivalent to
- <literal>pkg.lib</literal>.</para></listitem>
-
-</itemizedlist>
-
-<para>The function <function>mkDerivation</function> in the Nixpkgs
-standard environment is a wrapper around
-<function>derivation</function> that adds a default value for
-<varname>system</varname> and always uses Bash as the builder, to
-which the supplied builder is passed as a command-line argument. See
-the Nixpkgs manual for details.</para>
-
-<para>The builder is executed as follows:
-
-<itemizedlist>
-
- <listitem><para>A temporary directory is created under the directory
- specified by <envar>TMPDIR</envar> (default
- <filename>/tmp</filename>) where the build will take place. The
- current directory is changed to this directory.</para></listitem>
-
- <listitem><para>The environment is cleared and set to the derivation
- attributes, as specified above.</para></listitem>
-
- <listitem><para>In addition, the following variables are set:
-
- <itemizedlist>
-
- <listitem><para><envar>NIX_BUILD_TOP</envar> contains the path of
- the temporary directory for this build.</para></listitem>
-
- <listitem><para>Also, <envar>TMPDIR</envar>,
- <envar>TEMPDIR</envar>, <envar>TMP</envar>, <envar>TEMP</envar>
- are set to point to the temporary directory. This is to prevent
- the builder from accidentally writing temporary files anywhere
- else. Doing so might cause interference by other
- processes.</para></listitem>
-
- <listitem><para><envar>PATH</envar> is set to
- <filename>/path-not-set</filename> to prevent shells from
- initialising it to their built-in default value.</para></listitem>
-
- <listitem><para><envar>HOME</envar> is set to
- <filename>/homeless-shelter</filename> to prevent programs from
- using <filename>/etc/passwd</filename> or the like to find the
- user's home directory, which could cause impurity. Usually, when
- <envar>HOME</envar> is set, it is used as the location of the home
- directory, even if it points to a non-existent
- path.</para></listitem>
-
- <listitem><para><envar>NIX_STORE</envar> is set to the path of the
- top-level Nix store directory (typically,
- <filename>/nix/store</filename>).</para></listitem>
-
- <listitem><para>For each output declared in
- <varname>outputs</varname>, the corresponding environment variable
- is set to point to the intended path in the Nix store for that
- output. Each output path is a concatenation of the cryptographic
- hash of all build inputs, the <varname>name</varname> attribute
- and the output name. (The output name is omitted if it’s
- <literal>out</literal>.)</para></listitem>
-
- </itemizedlist>
-
- </para></listitem>
-
- <listitem><para>If an output path already exists, it is removed.
- Also, locks are acquired to prevent multiple Nix instances from
- performing the same build at the same time.</para></listitem>
-
- <listitem><para>A log of the combined standard output and error is
- written to <filename>/nix/var/log/nix</filename>.</para></listitem>
-
- <listitem><para>The builder is executed with the arguments specified
- by the attribute <varname>args</varname>. If it exits with exit
- code 0, it is considered to have succeeded.</para></listitem>
-
- <listitem><para>The temporary directory is removed (unless the
- <option>-K</option> option was specified).</para></listitem>
-
- <listitem><para>If the build was successful, Nix scans each output
- path for references to input paths by looking for the hash parts of
- the input paths. Since these are potential runtime dependencies,
- Nix registers them as dependencies of the output
- paths.</para></listitem>
-
- <listitem><para>After the build, Nix sets the last-modified
- timestamp on all files in the build result to 1 (00:00:01 1/1/1970
- UTC), sets the group to the default group, and sets the mode of the
- file to 0444 or 0555 (i.e., read-only, with execute permission
- enabled if the file was originally executable). Note that possible
- <literal>setuid</literal> and <literal>setgid</literal> bits are
- cleared. Setuid and setgid programs are not currently supported by
- Nix. This is because the Nix archives used in deployment have no
- concept of ownership information, and because it makes the build
- result dependent on the user performing the build.</para></listitem>
-
-</itemizedlist>
-
-</para>
-
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-advanced-attributes">
-
-<title>Advanced Attributes</title>
-
-<para>Derivations can declare some infrequently used optional
-attributes.</para>
-
-<variablelist>
-
- <varlistentry xml:id="adv-attr-allowedReferences"><term><varname>allowedReferences</varname></term>
-
- <listitem><para>The optional attribute
- <varname>allowedReferences</varname> specifies a list of legal
- references (dependencies) of the output of the builder. For
- example,
-
-<programlisting>
-allowedReferences = [];
-</programlisting>
-
- enforces that the output of a derivation cannot have any runtime
- dependencies on its inputs. To allow an output to have a runtime
- dependency on itself, use <literal>"out"</literal> as a list item.
- This is used in NixOS to check that generated files such as
- initial ramdisks for booting Linux don’t have accidental
- dependencies on other paths in the Nix store.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="adv-attr-allowedRequisites"><term><varname>allowedRequisites</varname></term>
-
- <listitem><para>This attribute is similar to
- <varname>allowedReferences</varname>, but it specifies the legal
- requisites of the whole closure, so all the dependencies
- recursively. For example,
-
-<programlisting>
-allowedRequisites = [ foobar ];
-</programlisting>
-
- enforces that the output of a derivation cannot have any other
- runtime dependency than <varname>foobar</varname>, and in addition
- it enforces that <varname>foobar</varname> itself doesn't
- introduce any other dependency itself.</para></listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="adv-attr-disallowedReferences"><term><varname>disallowedReferences</varname></term>
-
- <listitem><para>The optional attribute
- <varname>disallowedReferences</varname> specifies a list of illegal
- references (dependencies) of the output of the builder. For
- example,
-
-<programlisting>
-disallowedReferences = [ foo ];
-</programlisting>
-
- enforces that the output of a derivation cannot have a direct runtime
- dependencies on the derivation <varname>foo</varname>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="adv-attr-disallowedRequisites"><term><varname>disallowedRequisites</varname></term>
-
- <listitem><para>This attribute is similar to
- <varname>disallowedReferences</varname>, but it specifies illegal
- requisites for the whole closure, so all the dependencies
- recursively. For example,
-
-<programlisting>
-disallowedRequisites = [ foobar ];
-</programlisting>
-
- enforces that the output of a derivation cannot have any
- runtime dependency on <varname>foobar</varname> or any other derivation
- depending recursively on <varname>foobar</varname>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="adv-attr-exportReferencesGraph"><term><varname>exportReferencesGraph</varname></term>
-
- <listitem><para>This attribute allows builders access to the
- references graph of their inputs. The attribute is a list of
- inputs in the Nix store whose references graph the builder needs
- to know. The value of this attribute should be a list of pairs
- <literal>[ <replaceable>name1</replaceable>
- <replaceable>path1</replaceable> <replaceable>name2</replaceable>
- <replaceable>path2</replaceable> <replaceable>...</replaceable>
- ]</literal>. The references graph of each
- <replaceable>pathN</replaceable> will be stored in a text file
- <replaceable>nameN</replaceable> in the temporary build directory.
- The text files have the format used by <command>nix-store
- --register-validity</command> (with the deriver fields left
- empty). For example, when the following derivation is built:
-
-<programlisting>
-derivation {
- ...
- exportReferencesGraph = [ "libfoo-graph" libfoo ];
-};
-</programlisting>
-
- the references graph of <literal>libfoo</literal> is placed in the
- file <filename>libfoo-graph</filename> in the temporary build
- directory.</para>
-
- <para><varname>exportReferencesGraph</varname> is useful for
- builders that want to do something with the closure of a store
- path. Examples include the builders in NixOS that generate the
- initial ramdisk for booting Linux (a <command>cpio</command>
- archive containing the closure of the boot script) and the
- ISO-9660 image for the installation CD (which is populated with a
- Nix store containing the closure of a bootable NixOS
- configuration).</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="adv-attr-impureEnvVars"><term><varname>impureEnvVars</varname></term>
-
- <listitem><para>This attribute allows you to specify a list of
- environment variables that should be passed from the environment
- of the calling user to the builder. Usually, the environment is
- cleared completely when the builder is executed, but with this
- attribute you can allow specific environment variables to be
- passed unmodified. For example, <function>fetchurl</function> in
- Nixpkgs has the line
-
-<programlisting>
-impureEnvVars = [ "http_proxy" "https_proxy" <replaceable>...</replaceable> ];
-</programlisting>
-
- to make it use the proxy server configuration specified by the
- user in the environment variables <envar>http_proxy</envar> and
- friends.</para>
-
- <para>This attribute is only allowed in <link linkend="fixed-output-drvs">fixed-output derivations</link>, where
- impurities such as these are okay since (the hash of) the output
- is known in advance. It is ignored for all other
- derivations.</para>
-
- <warning><para><varname>impureEnvVars</varname> implementation takes
- environment variables from the current builder process. When a daemon is
- building its environmental variables are used. Without the daemon, the
- environmental variables come from the environment of the
- <command>nix-build</command>.</para></warning></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="fixed-output-drvs">
- <term xml:id="adv-attr-outputHash"><varname>outputHash</varname></term>
- <term xml:id="adv-attr-outputHashAlgo"><varname>outputHashAlgo</varname></term>
- <term xml:id="adv-attr-outputHashMode"><varname>outputHashMode</varname></term>
-
- <listitem><para>These attributes declare that the derivation is a
- so-called <emphasis>fixed-output derivation</emphasis>, which
- means that a cryptographic hash of the output is already known in
- advance. When the build of a fixed-output derivation finishes,
- Nix computes the cryptographic hash of the output and compares it
- to the hash declared with these attributes. If there is a
- mismatch, the build fails.</para>
-
- <para>The rationale for fixed-output derivations is derivations
- such as those produced by the <function>fetchurl</function>
- function. This function downloads a file from a given URL. To
- ensure that the downloaded file has not been modified, the caller
- must also specify a cryptographic hash of the file. For example,
-
-<programlisting>
-fetchurl {
- url = "http://ftp.gnu.org/pub/gnu/hello/hello-2.1.1.tar.gz";
- sha256 = "1md7jsfd8pa45z73bz1kszpp01yw6x5ljkjk2hx7wl800any6465";
-}
-</programlisting>
-
- It sometimes happens that the URL of the file changes, e.g.,
- because servers are reorganised or no longer available. We then
- must update the call to <function>fetchurl</function>, e.g.,
-
-<programlisting>
-fetchurl {
- url = "ftp://ftp.nluug.nl/pub/gnu/hello/hello-2.1.1.tar.gz";
- sha256 = "1md7jsfd8pa45z73bz1kszpp01yw6x5ljkjk2hx7wl800any6465";
-}
-</programlisting>
-
- If a <function>fetchurl</function> derivation was treated like a
- normal derivation, the output paths of the derivation and
- <emphasis>all derivations depending on it</emphasis> would change.
- For instance, if we were to change the URL of the Glibc source
- distribution in Nixpkgs (a package on which almost all other
- packages depend) massive rebuilds would be needed. This is
- unfortunate for a change which we know cannot have a real effect
- as it propagates upwards through the dependency graph.</para>
-
- <para>For fixed-output derivations, on the other hand, the name of
- the output path only depends on the <varname>outputHash*</varname>
- and <varname>name</varname> attributes, while all other attributes
- are ignored for the purpose of computing the output path. (The
- <varname>name</varname> attribute is included because it is part
- of the path.)</para>
-
- <para>As an example, here is the (simplified) Nix expression for
- <varname>fetchurl</varname>:
-
-<programlisting>
-{ stdenv, curl }: # The <command>curl</command> program is used for downloading.
-
-{ url, sha256 }:
-
-stdenv.mkDerivation {
- name = baseNameOf (toString url);
- builder = ./builder.sh;
- buildInputs = [ curl ];
-
- # This is a fixed-output derivation; the output must be a regular
- # file with SHA256 hash <varname>sha256</varname>.
- outputHashMode = "flat";
- outputHashAlgo = "sha256";
- outputHash = sha256;
-
- inherit url;
-}
-</programlisting>
-
- </para>
-
- <para>The <varname>outputHashAlgo</varname> attribute specifies
- the hash algorithm used to compute the hash. It can currently be
- <literal>"sha1"</literal>, <literal>"sha256"</literal> or
- <literal>"sha512"</literal>.</para>
-
- <para>The <varname>outputHashMode</varname> attribute determines
- how the hash is computed. It must be one of the following two
- values:
-
- <variablelist>
-
- <varlistentry><term><literal>"flat"</literal></term>
-
- <listitem><para>The output must be a non-executable regular
- file. If it isn’t, the build fails. The hash is simply
- computed over the contents of that file (so it’s equal to what
- Unix commands like <command>sha256sum</command> or
- <command>sha1sum</command> produce).</para>
-
- <para>This is the default.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><literal>"recursive"</literal></term>
-
- <listitem><para>The hash is computed over the NAR archive dump
- of the output (i.e., the result of <link linkend="refsec-nix-store-dump"><command>nix-store
- --dump</command></link>). In this case, the output can be
- anything, including a directory tree.</para></listitem>
-
- </varlistentry>
-
- </variablelist>
-
- </para>
-
- <para>The <varname>outputHash</varname> attribute, finally, must
- be a string containing the hash in either hexadecimal or base-32
- notation. (See the <link linkend="sec-nix-hash"><command>nix-hash</command> command</link>
- for information about converting to and from base-32
- notation.)</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="adv-attr-passAsFile"><term><varname>passAsFile</varname></term>
-
- <listitem><para>A list of names of attributes that should be
- passed via files rather than environment variables. For example,
- if you have
-
- <programlisting>
-passAsFile = ["big"];
-big = "a very long string";
- </programlisting>
-
- then when the builder runs, the environment variable
- <envar>bigPath</envar> will contain the absolute path to a
- temporary file containing <literal>a very long
- string</literal>. That is, for any attribute
- <replaceable>x</replaceable> listed in
- <varname>passAsFile</varname>, Nix will pass an environment
- variable <envar><replaceable>x</replaceable>Path</envar> holding
- the path of the file containing the value of attribute
- <replaceable>x</replaceable>. This is useful when you need to pass
- large strings to a builder, since most operating systems impose a
- limit on the size of the environment (typically, a few hundred
- kilobyte).</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="adv-attr-preferLocalBuild"><term><varname>preferLocalBuild</varname></term>
-
- <listitem><para>If this attribute is set to
- <literal>true</literal> and <link linkend="chap-distributed-builds">distributed building is
- enabled</link>, then, if possible, the derivaton will be built
- locally instead of forwarded to a remote machine. This is
- appropriate for trivial builders where the cost of doing a
- download or remote build would exceed the cost of building
- locally.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="adv-attr-allowSubstitutes"><term><varname>allowSubstitutes</varname></term>
-
- <listitem>
- <para>If this attribute is set to
- <literal>false</literal>, then Nix will always build this
- derivation; it will not try to substitute its outputs. This is
- useful for very trivial derivations (such as
- <function>writeText</function> in Nixpkgs) that are cheaper to
- build than to substitute from a binary cache.</para>
-
- <note><para>You need to have a builder configured which satisfies
- the derivation’s <literal>system</literal> attribute, since the
- derivation cannot be substituted. Thus it is usually a good idea
- to align <literal>system</literal> with
- <literal>builtins.currentSystem</literal> when setting
- <literal>allowSubstitutes</literal> to <literal>false</literal>.
- For most trivial derivations this should be the case.
- </para></note>
- </listitem>
-
- </varlistentry>
-
-
-</variablelist>
-
-</section>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-builtins">
-
-<title>Built-in Functions</title>
-
-<para>This section lists the functions and constants built into the
-Nix expression evaluator. (The built-in function
-<function>derivation</function> is discussed above.) Some built-ins,
-such as <function>derivation</function>, are always in scope of every
-Nix expression; you can just access them right away. But to prevent
-polluting the namespace too much, most built-ins are not in scope.
-Instead, you can access them through the <varname>builtins</varname>
-built-in value, which is a set that contains all built-in functions
-and values. For instance, <function>derivation</function> is also
-available as <function>builtins.derivation</function>.</para>
-
-
-<variablelist>
-
-
- <varlistentry xml:id="builtin-abort">
- <term><function>abort</function> <replaceable>s</replaceable></term>
- <term><function>builtins.abort</function> <replaceable>s</replaceable></term>
-
- <listitem><para>Abort Nix expression evaluation, print error
- message <replaceable>s</replaceable>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-add">
- <term><function>builtins.add</function>
- <replaceable>e1</replaceable> <replaceable>e2</replaceable>
- </term>
-
- <listitem><para>Return the sum of the numbers
- <replaceable>e1</replaceable> and
- <replaceable>e2</replaceable>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-all">
- <term><function>builtins.all</function>
- <replaceable>pred</replaceable> <replaceable>list</replaceable></term>
-
- <listitem><para>Return <literal>true</literal> if the function
- <replaceable>pred</replaceable> returns <literal>true</literal>
- for all elements of <replaceable>list</replaceable>,
- and <literal>false</literal> otherwise.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-any">
- <term><function>builtins.any</function>
- <replaceable>pred</replaceable> <replaceable>list</replaceable></term>
-
- <listitem><para>Return <literal>true</literal> if the function
- <replaceable>pred</replaceable> returns <literal>true</literal>
- for at least one element of <replaceable>list</replaceable>,
- and <literal>false</literal> otherwise.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-attrNames">
- <term><function>builtins.attrNames</function>
- <replaceable>set</replaceable></term>
-
- <listitem><para>Return the names of the attributes in the set
- <replaceable>set</replaceable> in an alphabetically sorted list. For instance,
- <literal>builtins.attrNames { y = 1; x = "foo"; }</literal>
- evaluates to <literal>[ "x" "y" ]</literal>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-attrValues">
- <term><function>builtins.attrValues</function>
- <replaceable>set</replaceable></term>
-
- <listitem><para>Return the values of the attributes in the set
- <replaceable>set</replaceable> in the order corresponding to the
- sorted attribute names.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-baseNameOf">
- <term><function>baseNameOf</function> <replaceable>s</replaceable></term>
-
- <listitem><para>Return the <emphasis>base name</emphasis> of the
- string <replaceable>s</replaceable>, that is, everything following
- the final slash in the string. This is similar to the GNU
- <command>basename</command> command.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-bitAnd">
- <term><function>builtins.bitAnd</function>
- <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
-
- <listitem><para>Return the bitwise AND of the integers
- <replaceable>e1</replaceable> and
- <replaceable>e2</replaceable>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-bitOr">
- <term><function>builtins.bitOr</function>
- <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
-
- <listitem><para>Return the bitwise OR of the integers
- <replaceable>e1</replaceable> and
- <replaceable>e2</replaceable>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-bitXor">
- <term><function>builtins.bitXor</function>
- <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
-
- <listitem><para>Return the bitwise XOR of the integers
- <replaceable>e1</replaceable> and
- <replaceable>e2</replaceable>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-builtins">
- <term><varname>builtins</varname></term>
-
- <listitem><para>The set <varname>builtins</varname> contains all
- the built-in functions and values. You can use
- <varname>builtins</varname> to test for the availability of
- features in the Nix installation, e.g.,
-
-<programlisting>
-if builtins ? getEnv then builtins.getEnv "PATH" else ""</programlisting>
-
- This allows a Nix expression to fall back gracefully on older Nix
- installations that don’t have the desired built-in
- function.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-compareVersions">
- <term><function>builtins.compareVersions</function>
- <replaceable>s1</replaceable> <replaceable>s2</replaceable></term>
-
- <listitem><para>Compare two strings representing versions and
- return <literal>-1</literal> if version
- <replaceable>s1</replaceable> is older than version
- <replaceable>s2</replaceable>, <literal>0</literal> if they are
- the same, and <literal>1</literal> if
- <replaceable>s1</replaceable> is newer than
- <replaceable>s2</replaceable>. The version comparison algorithm
- is the same as the one used by <link linkend="ssec-version-comparisons"><command>nix-env
- -u</command></link>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-concatLists">
- <term><function>builtins.concatLists</function>
- <replaceable>lists</replaceable></term>
-
- <listitem><para>Concatenate a list of lists into a single
- list.</para></listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="builtin-concatStringsSep">
- <term><function>builtins.concatStringsSep</function>
- <replaceable>separator</replaceable> <replaceable>list</replaceable></term>
-
- <listitem><para>Concatenate a list of strings with a separator
- between each element, e.g. <literal>concatStringsSep "/"
- ["usr" "local" "bin"] == "usr/local/bin"</literal></para></listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="builtin-currentSystem">
- <term><varname>builtins.currentSystem</varname></term>
-
- <listitem><para>The built-in value <varname>currentSystem</varname>
- evaluates to the Nix platform identifier for the Nix installation
- on which the expression is being evaluated, such as
- <literal>"i686-linux"</literal> or
- <literal>"x86_64-darwin"</literal>.</para></listitem>
-
- </varlistentry>
-
-
- <!--
- <varlistentry><term><function>currentTime</function></term>
-
- <listitem><para>The built-in value <varname>currentTime</varname>
- returns the current system time in seconds since 00:00:00 1/1/1970
- UTC. Due to the evaluation model of Nix expressions
- (<emphasis>maximal laziness</emphasis>), it always yields the same
- value within an execution of Nix.</para></listitem>
-
- </varlistentry>
- -->
-
-
- <!--
- <varlistentry><term><function>dependencyClosure</function></term>
-
- <listitem><para>TODO</para></listitem>
-
- </varlistentry>
- -->
-
-
- <varlistentry xml:id="builtin-deepSeq">
- <term><function>builtins.deepSeq</function>
- <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
-
- <listitem><para>This is like <literal>seq
- <replaceable>e1</replaceable>
- <replaceable>e2</replaceable></literal>, except that
- <replaceable>e1</replaceable> is evaluated
- <emphasis>deeply</emphasis>: if it’s a list or set, its elements
- or attributes are also evaluated recursively.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-derivation">
- <term><function>derivation</function>
- <replaceable>attrs</replaceable></term>
- <term><function>builtins.derivation</function>
- <replaceable>attrs</replaceable></term>
-
- <listitem><para><function>derivation</function> is described in
- <xref linkend="ssec-derivation"/>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-dirOf">
- <term><function>dirOf</function> <replaceable>s</replaceable></term>
- <term><function>builtins.dirOf</function> <replaceable>s</replaceable></term>
-
- <listitem><para>Return the directory part of the string
- <replaceable>s</replaceable>, that is, everything before the final
- slash in the string. This is similar to the GNU
- <command>dirname</command> command.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-div">
- <term><function>builtins.div</function>
- <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
-
- <listitem><para>Return the quotient of the numbers
- <replaceable>e1</replaceable> and
- <replaceable>e2</replaceable>.</para></listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="builtin-elem">
- <term><function>builtins.elem</function>
- <replaceable>x</replaceable> <replaceable>xs</replaceable></term>
-
- <listitem><para>Return <literal>true</literal> if a value equal to
- <replaceable>x</replaceable> occurs in the list
- <replaceable>xs</replaceable>, and <literal>false</literal>
- otherwise.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-elemAt">
- <term><function>builtins.elemAt</function>
- <replaceable>xs</replaceable> <replaceable>n</replaceable></term>
-
- <listitem><para>Return element <replaceable>n</replaceable> from
- the list <replaceable>xs</replaceable>. Elements are counted
- starting from 0. A fatal error occurs if the index is out of
- bounds.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-fetchurl">
- <term><function>builtins.fetchurl</function>
- <replaceable>url</replaceable></term>
-
- <listitem><para>Download the specified URL and return the path of
- the downloaded file. This function is not available if <link linkend="conf-restrict-eval">restricted evaluation mode</link> is
- enabled.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-fetchTarball">
- <term><function>fetchTarball</function>
- <replaceable>url</replaceable></term>
- <term><function>builtins.fetchTarball</function>
- <replaceable>url</replaceable></term>
-
- <listitem><para>Download the specified URL, unpack it and return
- the path of the unpacked tree. The file must be a tape archive
- (<filename>.tar</filename>) compressed with
- <literal>gzip</literal>, <literal>bzip2</literal> or
- <literal>xz</literal>. The top-level path component of the files
- in the tarball is removed, so it is best if the tarball contains a
- single directory at top level. The typical use of the function is
- to obtain external Nix expression dependencies, such as a
- particular version of Nixpkgs, e.g.
-
-<programlisting>
-with import (fetchTarball https://github.com/NixOS/nixpkgs/archive/nixos-14.12.tar.gz) {};
-
-stdenv.mkDerivation { … }
-</programlisting>
- </para>
-
- <para>The fetched tarball is cached for a certain amount of time
- (1 hour by default) in <filename>~/.cache/nix/tarballs/</filename>.
- You can change the cache timeout either on the command line with
- <option>--option tarball-ttl <replaceable>number of seconds</replaceable></option> or
- in the Nix configuration file with this option:
- <literal><xref linkend="conf-tarball-ttl"/> <replaceable>number of seconds to cache</replaceable></literal>.
- </para>
-
- <para>Note that when obtaining the hash with <varname>nix-prefetch-url
- </varname> the option <varname>--unpack</varname> is required.
- </para>
-
- <para>This function can also verify the contents against a hash.
- In that case, the function takes a set instead of a URL. The set
- requires the attribute <varname>url</varname> and the attribute
- <varname>sha256</varname>, e.g.
-
-<programlisting>
-with import (fetchTarball {
- url = "https://github.com/NixOS/nixpkgs/archive/nixos-14.12.tar.gz";
- sha256 = "1jppksrfvbk5ypiqdz4cddxdl8z6zyzdb2srq8fcffr327ld5jj2";
-}) {};
-
-stdenv.mkDerivation { … }
-</programlisting>
-
- </para>
-
- <para>This function is not available if <link linkend="conf-restrict-eval">restricted evaluation mode</link> is
- enabled.</para></listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="builtin-fetchGit">
- <term>
- <function>builtins.fetchGit</function>
- <replaceable>args</replaceable>
- </term>
-
- <listitem>
- <para>
- Fetch a path from git. <replaceable>args</replaceable> can be
- a URL, in which case the HEAD of the repo at that URL is
- fetched. Otherwise, it can be an attribute with the following
- attributes (all except <varname>url</varname> optional):
- </para>
-
- <variablelist>
- <varlistentry>
- <term>url</term>
- <listitem>
- <para>
- The URL of the repo.
- </para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>name</term>
- <listitem>
- <para>
- The name of the directory the repo should be exported to
- in the store. Defaults to the basename of the URL.
- </para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>rev</term>
- <listitem>
- <para>
- The git revision to fetch. Defaults to the tip of
- <varname>ref</varname>.
- </para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>ref</term>
- <listitem>
- <para>
- The git ref to look for the requested revision under.
- This is often a branch or tag name. Defaults to
- <literal>HEAD</literal>.
- </para>
-
- <para>
- By default, the <varname>ref</varname> value is prefixed
- with <literal>refs/heads/</literal>. As of Nix 2.3.0
- Nix will not prefix <literal>refs/heads/</literal> if
- <varname>ref</varname> starts with <literal>refs/</literal>.
- </para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>submodules</term>
- <listitem>
- <para>
- A Boolean parameter that specifies whether submodules
- should be checked out. Defaults to
- <literal>false</literal>.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
-
- <example>
- <title>Fetching a private repository over SSH</title>
- <programlisting>builtins.fetchGit {
- url = "git@github.com:my-secret/repository.git";
- ref = "master";
- rev = "adab8b916a45068c044658c4158d81878f9ed1c3";
-}</programlisting>
- </example>
-
- <example>
- <title>Fetching an arbitrary ref</title>
- <programlisting>builtins.fetchGit {
- url = "https://github.com/NixOS/nix.git";
- ref = "refs/heads/0.5-release";
-}</programlisting>
- </example>
-
- <example>
- <title>Fetching a repository's specific commit on an arbitrary branch</title>
- <para>
- If the revision you're looking for is in the default branch
- of the git repository you don't strictly need to specify
- the branch name in the <varname>ref</varname> attribute.
- </para>
- <para>
- However, if the revision you're looking for is in a future
- branch for the non-default branch you will need to specify
- the the <varname>ref</varname> attribute as well.
- </para>
- <programlisting>builtins.fetchGit {
- url = "https://github.com/nixos/nix.git";
- rev = "841fcbd04755c7a2865c51c1e2d3b045976b7452";
- ref = "1.11-maintenance";
-}</programlisting>
- <note>
- <para>
- It is nice to always specify the branch which a revision
- belongs to. Without the branch being specified, the
- fetcher might fail if the default branch changes.
- Additionally, it can be confusing to try a commit from a
- non-default branch and see the fetch fail. If the branch
- is specified the fault is much more obvious.
- </para>
- </note>
- </example>
-
- <example>
- <title>Fetching a repository's specific commit on the default branch</title>
- <para>
- If the revision you're looking for is in the default branch
- of the git repository you may omit the
- <varname>ref</varname> attribute.
- </para>
- <programlisting>builtins.fetchGit {
- url = "https://github.com/nixos/nix.git";
- rev = "841fcbd04755c7a2865c51c1e2d3b045976b7452";
-}</programlisting>
- </example>
-
- <example>
- <title>Fetching a tag</title>
- <programlisting>builtins.fetchGit {
- url = "https://github.com/nixos/nix.git";
- ref = "refs/tags/1.9";
-}</programlisting>
- </example>
-
- <example>
- <title>Fetching the latest version of a remote branch</title>
- <para>
- <function>builtins.fetchGit</function> can behave impurely
- fetch the latest version of a remote branch.
- </para>
- <note><para>Nix will refetch the branch in accordance to
- <xref linkend="conf-tarball-ttl"/>.</para></note>
- <note><para>This behavior is disabled in
- <emphasis>Pure evaluation mode</emphasis>.</para></note>
- <programlisting>builtins.fetchGit {
- url = "ssh://git@github.com/nixos/nix.git";
- ref = "master";
-}</programlisting>
- </example>
- </listitem>
- </varlistentry>
-
-
- <varlistentry><term><function>builtins.filter</function>
- <replaceable>f</replaceable> <replaceable>xs</replaceable></term>
-
- <listitem><para>Return a list consisting of the elements of
- <replaceable>xs</replaceable> for which the function
- <replaceable>f</replaceable> returns
- <literal>true</literal>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-filterSource">
- <term><function>builtins.filterSource</function>
- <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
-
- <listitem>
-
- <para>This function allows you to copy sources into the Nix
- store while filtering certain files. For instance, suppose that
- you want to use the directory <filename>source-dir</filename> as
- an input to a Nix expression, e.g.
-
-<programlisting>
-stdenv.mkDerivation {
- ...
- src = ./source-dir;
-}
-</programlisting>
-
- However, if <filename>source-dir</filename> is a Subversion
- working copy, then all those annoying <filename>.svn</filename>
- subdirectories will also be copied to the store. Worse, the
- contents of those directories may change a lot, causing lots of
- spurious rebuilds. With <function>filterSource</function> you
- can filter out the <filename>.svn</filename> directories:
-
-<programlisting>
- src = builtins.filterSource
- (path: type: type != "directory" || baseNameOf path != ".svn")
- ./source-dir;
-</programlisting>
-
- </para>
-
- <para>Thus, the first argument <replaceable>e1</replaceable>
- must be a predicate function that is called for each regular
- file, directory or symlink in the source tree
- <replaceable>e2</replaceable>. If the function returns
- <literal>true</literal>, the file is copied to the Nix store,
- otherwise it is omitted. The function is called with two
- arguments. The first is the full path of the file. The second
- is a string that identifies the type of the file, which is
- either <literal>"regular"</literal>,
- <literal>"directory"</literal>, <literal>"symlink"</literal> or
- <literal>"unknown"</literal> (for other kinds of files such as
- device nodes or fifos — but note that those cannot be copied to
- the Nix store, so if the predicate returns
- <literal>true</literal> for them, the copy will fail). If you
- exclude a directory, the entire corresponding subtree of
- <replaceable>e2</replaceable> will be excluded.</para>
-
- </listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-foldl-prime">
- <term><function>builtins.foldl’</function>
- <replaceable>op</replaceable> <replaceable>nul</replaceable> <replaceable>list</replaceable></term>
-
- <listitem><para>Reduce a list by applying a binary operator, from
- left to right, e.g. <literal>foldl’ op nul [x0 x1 x2 ...] = op (op
- (op nul x0) x1) x2) ...</literal>. The operator is applied
- strictly, i.e., its arguments are evaluated first. For example,
- <literal>foldl’ (x: y: x + y) 0 [1 2 3]</literal> evaluates to
- 6.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-functionArgs">
- <term><function>builtins.functionArgs</function>
- <replaceable>f</replaceable></term>
-
- <listitem><para>
- Return a set containing the names of the formal arguments expected
- by the function <replaceable>f</replaceable>.
- The value of each attribute is a Boolean denoting whether the corresponding
- argument has a default value. For instance,
- <literal>functionArgs ({ x, y ? 123}: ...) = { x = false; y = true; }</literal>.
- </para>
-
- <para>"Formal argument" here refers to the attributes pattern-matched by
- the function. Plain lambdas are not included, e.g.
- <literal>functionArgs (x: ...) = { }</literal>.
- </para></listitem>
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-fromJSON">
- <term><function>builtins.fromJSON</function> <replaceable>e</replaceable></term>
-
- <listitem><para>Convert a JSON string to a Nix
- value. For example,
-
-<programlisting>
-builtins.fromJSON ''{"x": [1, 2, 3], "y": null}''
-</programlisting>
-
- returns the value <literal>{ x = [ 1 2 3 ]; y = null;
- }</literal>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-genList">
- <term><function>builtins.genList</function>
- <replaceable>generator</replaceable> <replaceable>length</replaceable></term>
-
- <listitem><para>Generate list of size
- <replaceable>length</replaceable>, with each element
- <replaceable>i</replaceable> equal to the value returned by
- <replaceable>generator</replaceable> <literal>i</literal>. For
- example,
-
-<programlisting>
-builtins.genList (x: x * x) 5
-</programlisting>
-
- returns the list <literal>[ 0 1 4 9 16 ]</literal>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-getAttr">
- <term><function>builtins.getAttr</function>
- <replaceable>s</replaceable> <replaceable>set</replaceable></term>
-
- <listitem><para><function>getAttr</function> returns the attribute
- named <replaceable>s</replaceable> from
- <replaceable>set</replaceable>. Evaluation aborts if the
- attribute doesn’t exist. This is a dynamic version of the
- <literal>.</literal> operator, since <replaceable>s</replaceable>
- is an expression rather than an identifier.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-getEnv">
- <term><function>builtins.getEnv</function>
- <replaceable>s</replaceable></term>
-
- <listitem><para><function>getEnv</function> returns the value of
- the environment variable <replaceable>s</replaceable>, or an empty
- string if the variable doesn’t exist. This function should be
- used with care, as it can introduce all sorts of nasty environment
- dependencies in your Nix expression.</para>
-
- <para><function>getEnv</function> is used in Nix Packages to
- locate the file <filename>~/.nixpkgs/config.nix</filename>, which
- contains user-local settings for Nix Packages. (That is, it does
- a <literal>getEnv "HOME"</literal> to locate the user’s home
- directory.)</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-hasAttr">
- <term><function>builtins.hasAttr</function>
- <replaceable>s</replaceable> <replaceable>set</replaceable></term>
-
- <listitem><para><function>hasAttr</function> returns
- <literal>true</literal> if <replaceable>set</replaceable> has an
- attribute named <replaceable>s</replaceable>, and
- <literal>false</literal> otherwise. This is a dynamic version of
- the <literal>?</literal> operator, since
- <replaceable>s</replaceable> is an expression rather than an
- identifier.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-hashString">
- <term><function>builtins.hashString</function>
- <replaceable>type</replaceable> <replaceable>s</replaceable></term>
-
- <listitem><para>Return a base-16 representation of the
- cryptographic hash of string <replaceable>s</replaceable>. The
- hash algorithm specified by <replaceable>type</replaceable> must
- be one of <literal>"md5"</literal>, <literal>"sha1"</literal>,
- <literal>"sha256"</literal> or <literal>"sha512"</literal>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-hashFile">
- <term><function>builtins.hashFile</function>
- <replaceable>type</replaceable> <replaceable>p</replaceable></term>
-
- <listitem><para>Return a base-16 representation of the
- cryptographic hash of the file at path <replaceable>p</replaceable>. The
- hash algorithm specified by <replaceable>type</replaceable> must
- be one of <literal>"md5"</literal>, <literal>"sha1"</literal>,
- <literal>"sha256"</literal> or <literal>"sha512"</literal>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-head">
- <term><function>builtins.head</function>
- <replaceable>list</replaceable></term>
-
- <listitem><para>Return the first element of a list; abort
- evaluation if the argument isn’t a list or is an empty list. You
- can test whether a list is empty by comparing it with
- <literal>[]</literal>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-import">
- <term><function>import</function>
- <replaceable>path</replaceable></term>
- <term><function>builtins.import</function>
- <replaceable>path</replaceable></term>
-
- <listitem><para>Load, parse and return the Nix expression in the
- file <replaceable>path</replaceable>. If <replaceable>path
- </replaceable> is a directory, the file <filename>default.nix
- </filename> in that directory is loaded. Evaluation aborts if the
- file doesn’t exist or contains an incorrect Nix expression.
- <function>import</function> implements Nix’s module system: you
- can put any Nix expression (such as a set or a function) in a
- separate file, and use it from Nix expressions in other
- files.</para>
-
- <note><para>Unlike some languages, <function>import</function> is a regular
- function in Nix. Paths using the angle bracket syntax (e.g., <function>
- import</function> <replaceable><foo></replaceable>) are normal path
- values (see <xref linkend="ssec-values"/>).</para></note>
-
- <para>A Nix expression loaded by <function>import</function> must
- not contain any <emphasis>free variables</emphasis> (identifiers
- that are not defined in the Nix expression itself and are not
- built-in). Therefore, it cannot refer to variables that are in
- scope at the call site. For instance, if you have a calling
- expression
-
-<programlisting>
-rec {
- x = 123;
- y = import ./foo.nix;
-}</programlisting>
-
- then the following <filename>foo.nix</filename> will give an
- error:
-
-<programlisting>
-x + 456</programlisting>
-
- since <varname>x</varname> is not in scope in
- <filename>foo.nix</filename>. If you want <varname>x</varname>
- to be available in <filename>foo.nix</filename>, you should pass
- it as a function argument:
-
-<programlisting>
-rec {
- x = 123;
- y = import ./foo.nix x;
-}</programlisting>
-
- and
-
-<programlisting>
-x: x + 456</programlisting>
-
- (The function argument doesn’t have to be called
- <varname>x</varname> in <filename>foo.nix</filename>; any name
- would work.)</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-intersectAttrs">
- <term><function>builtins.intersectAttrs</function>
- <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
-
- <listitem><para>Return a set consisting of the attributes in the
- set <replaceable>e2</replaceable> that also exist in the set
- <replaceable>e1</replaceable>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-isAttrs">
- <term><function>builtins.isAttrs</function>
- <replaceable>e</replaceable></term>
-
- <listitem><para>Return <literal>true</literal> if
- <replaceable>e</replaceable> evaluates to a set, and
- <literal>false</literal> otherwise.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-isList">
- <term><function>builtins.isList</function>
- <replaceable>e</replaceable></term>
-
- <listitem><para>Return <literal>true</literal> if
- <replaceable>e</replaceable> evaluates to a list, and
- <literal>false</literal> otherwise.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-isFunction"><term><function>builtins.isFunction</function>
- <replaceable>e</replaceable></term>
-
- <listitem><para>Return <literal>true</literal> if
- <replaceable>e</replaceable> evaluates to a function, and
- <literal>false</literal> otherwise.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-isString">
- <term><function>builtins.isString</function>
- <replaceable>e</replaceable></term>
-
- <listitem><para>Return <literal>true</literal> if
- <replaceable>e</replaceable> evaluates to a string, and
- <literal>false</literal> otherwise.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-isInt">
- <term><function>builtins.isInt</function>
- <replaceable>e</replaceable></term>
-
- <listitem><para>Return <literal>true</literal> if
- <replaceable>e</replaceable> evaluates to an int, and
- <literal>false</literal> otherwise.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-isFloat">
- <term><function>builtins.isFloat</function>
- <replaceable>e</replaceable></term>
-
- <listitem><para>Return <literal>true</literal> if
- <replaceable>e</replaceable> evaluates to a float, and
- <literal>false</literal> otherwise.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-isBool">
- <term><function>builtins.isBool</function>
- <replaceable>e</replaceable></term>
-
- <listitem><para>Return <literal>true</literal> if
- <replaceable>e</replaceable> evaluates to a bool, and
- <literal>false</literal> otherwise.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><function>builtins.isPath</function>
- <replaceable>e</replaceable></term>
-
- <listitem><para>Return <literal>true</literal> if
- <replaceable>e</replaceable> evaluates to a path, and
- <literal>false</literal> otherwise.</para></listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="builtin-isNull">
- <term><function>isNull</function>
- <replaceable>e</replaceable></term>
- <term><function>builtins.isNull</function>
- <replaceable>e</replaceable></term>
-
- <listitem><para>Return <literal>true</literal> if
- <replaceable>e</replaceable> evaluates to <literal>null</literal>,
- and <literal>false</literal> otherwise.</para>
-
- <warning><para>This function is <emphasis>deprecated</emphasis>;
- just write <literal>e == null</literal> instead.</para></warning>
-
- </listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-length">
- <term><function>builtins.length</function>
- <replaceable>e</replaceable></term>
-
- <listitem><para>Return the length of the list
- <replaceable>e</replaceable>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-lessThan">
- <term><function>builtins.lessThan</function>
- <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
-
- <listitem><para>Return <literal>true</literal> if the number
- <replaceable>e1</replaceable> is less than the number
- <replaceable>e2</replaceable>, and <literal>false</literal>
- otherwise. Evaluation aborts if either
- <replaceable>e1</replaceable> or <replaceable>e2</replaceable>
- does not evaluate to a number.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-listToAttrs">
- <term><function>builtins.listToAttrs</function>
- <replaceable>e</replaceable></term>
-
- <listitem><para>Construct a set from a list specifying the names
- and values of each attribute. Each element of the list should be
- a set consisting of a string-valued attribute
- <varname>name</varname> specifying the name of the attribute, and
- an attribute <varname>value</varname> specifying its value.
- Example:
-
-<programlisting>
-builtins.listToAttrs
- [ { name = "foo"; value = 123; }
- { name = "bar"; value = 456; }
- ]
-</programlisting>
-
- evaluates to
-
-<programlisting>
-{ foo = 123; bar = 456; }
-</programlisting>
-
- </para></listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="builtin-map">
- <term><function>map</function>
- <replaceable>f</replaceable> <replaceable>list</replaceable></term>
- <term><function>builtins.map</function>
- <replaceable>f</replaceable> <replaceable>list</replaceable></term>
-
- <listitem><para>Apply the function <replaceable>f</replaceable> to
- each element in the list <replaceable>list</replaceable>. For
- example,
-
-<programlisting>
-map (x: "foo" + x) [ "bar" "bla" "abc" ]</programlisting>
-
- evaluates to <literal>[ "foobar" "foobla" "fooabc"
- ]</literal>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-match">
- <term><function>builtins.match</function>
- <replaceable>regex</replaceable> <replaceable>str</replaceable></term>
-
- <listitem><para>Returns a list if the <link xlink:href="http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_04">extended
- POSIX regular expression</link> <replaceable>regex</replaceable>
- matches <replaceable>str</replaceable> precisely, otherwise returns
- <literal>null</literal>. Each item in the list is a regex group.
-
-<programlisting>
-builtins.match "ab" "abc"
-</programlisting>
-
-Evaluates to <literal>null</literal>.
-
-<programlisting>
-builtins.match "abc" "abc"
-</programlisting>
-
-Evaluates to <literal>[ ]</literal>.
-
-<programlisting>
-builtins.match "a(b)(c)" "abc"
-</programlisting>
-
-Evaluates to <literal>[ "b" "c" ]</literal>.
-
-<programlisting>
-builtins.match "[[:space:]]+([[:upper:]]+)[[:space:]]+" " FOO "
-</programlisting>
-
-Evaluates to <literal>[ "foo" ]</literal>.
-
- </para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="builtin-mul">
- <term><function>builtins.mul</function>
- <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
-
- <listitem><para>Return the product of the numbers
- <replaceable>e1</replaceable> and
- <replaceable>e2</replaceable>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-parseDrvName">
- <term><function>builtins.parseDrvName</function>
- <replaceable>s</replaceable></term>
-
- <listitem><para>Split the string <replaceable>s</replaceable> into
- a package name and version. The package name is everything up to
- but not including the first dash followed by a digit, and the
- version is everything following that dash. The result is returned
- in a set <literal>{ name, version }</literal>. Thus,
- <literal>builtins.parseDrvName "nix-0.12pre12876"</literal>
- returns <literal>{ name = "nix"; version = "0.12pre12876";
- }</literal>.</para></listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="builtin-path">
- <term>
- <function>builtins.path</function>
- <replaceable>args</replaceable>
- </term>
-
- <listitem>
- <para>
- An enrichment of the built-in path type, based on the attributes
- present in <replaceable>args</replaceable>. All are optional
- except <varname>path</varname>:
- </para>
-
- <variablelist>
- <varlistentry>
- <term>path</term>
- <listitem>
- <para>The underlying path.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>name</term>
- <listitem>
- <para>
- The name of the path when added to the store. This can
- used to reference paths that have nix-illegal characters
- in their names, like <literal>@</literal>.
- </para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>filter</term>
- <listitem>
- <para>
- A function of the type expected by
- <link linkend="builtin-filterSource">builtins.filterSource</link>,
- with the same semantics.
- </para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>recursive</term>
- <listitem>
- <para>
- When <literal>false</literal>, when
- <varname>path</varname> is added to the store it is with a
- flat hash, rather than a hash of the NAR serialization of
- the file. Thus, <varname>path</varname> must refer to a
- regular file, not a directory. This allows similar
- behavior to <literal>fetchurl</literal>. Defaults to
- <literal>true</literal>.
- </para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>sha256</term>
- <listitem>
- <para>
- When provided, this is the expected hash of the file at
- the path. Evaluation will fail if the hash is incorrect,
- and providing a hash allows
- <literal>builtins.path</literal> to be used even when the
- <literal>pure-eval</literal> nix config option is on.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
- </listitem>
- </varlistentry>
-
- <varlistentry xml:id="builtin-pathExists">
- <term><function>builtins.pathExists</function>
- <replaceable>path</replaceable></term>
-
- <listitem><para>Return <literal>true</literal> if the path
- <replaceable>path</replaceable> exists at evaluation time, and
- <literal>false</literal> otherwise.</para></listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="builtin-placeholder">
- <term><function>builtins.placeholder</function>
- <replaceable>output</replaceable></term>
-
- <listitem><para>Return a placeholder string for the specified
- <replaceable>output</replaceable> that will be substituted by the
- corresponding output path at build time. Typical outputs would be
- <literal>"out"</literal>, <literal>"bin"</literal> or
- <literal>"dev"</literal>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="builtin-readDir">
- <term><function>builtins.readDir</function>
- <replaceable>path</replaceable></term>
-
- <listitem><para>Return the contents of the directory
- <replaceable>path</replaceable> as a set mapping directory entries
- to the corresponding file type. For instance, if directory
- <filename>A</filename> contains a regular file
- <filename>B</filename> and another directory
- <filename>C</filename>, then <literal>builtins.readDir
- ./A</literal> will return the set
-
-<programlisting>
-{ B = "regular"; C = "directory"; }</programlisting>
-
- The possible values for the file type are
- <literal>"regular"</literal>, <literal>"directory"</literal>,
- <literal>"symlink"</literal> and
- <literal>"unknown"</literal>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-readFile">
- <term><function>builtins.readFile</function>
- <replaceable>path</replaceable></term>
-
- <listitem><para>Return the contents of the file
- <replaceable>path</replaceable> as a string.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-removeAttrs">
- <term><function>removeAttrs</function>
- <replaceable>set</replaceable> <replaceable>list</replaceable></term>
- <term><function>builtins.removeAttrs</function>
- <replaceable>set</replaceable> <replaceable>list</replaceable></term>
-
- <listitem><para>Remove the attributes listed in
- <replaceable>list</replaceable> from
- <replaceable>set</replaceable>. The attributes don’t have to
- exist in <replaceable>set</replaceable>. For instance,
-
-<programlisting>
-removeAttrs { x = 1; y = 2; z = 3; } [ "a" "x" "z" ]</programlisting>
-
- evaluates to <literal>{ y = 2; }</literal>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-replaceStrings">
- <term><function>builtins.replaceStrings</function>
- <replaceable>from</replaceable> <replaceable>to</replaceable> <replaceable>s</replaceable></term>
-
- <listitem><para>Given string <replaceable>s</replaceable>, replace
- every occurrence of the strings in <replaceable>from</replaceable>
- with the corresponding string in
- <replaceable>to</replaceable>. For example,
-
-<programlisting>
-builtins.replaceStrings ["oo" "a"] ["a" "i"] "foobar"
-</programlisting>
-
- evaluates to <literal>"fabir"</literal>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-seq">
- <term><function>builtins.seq</function>
- <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
-
- <listitem><para>Evaluate <replaceable>e1</replaceable>, then
- evaluate and return <replaceable>e2</replaceable>. This ensures
- that a computation is strict in the value of
- <replaceable>e1</replaceable>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-sort">
- <term><function>builtins.sort</function>
- <replaceable>comparator</replaceable> <replaceable>list</replaceable></term>
-
- <listitem><para>Return <replaceable>list</replaceable> in sorted
- order. It repeatedly calls the function
- <replaceable>comparator</replaceable> with two elements. The
- comparator should return <literal>true</literal> if the first
- element is less than the second, and <literal>false</literal>
- otherwise. For example,
-
-<programlisting>
-builtins.sort builtins.lessThan [ 483 249 526 147 42 77 ]
-</programlisting>
-
- produces the list <literal>[ 42 77 147 249 483 526
- ]</literal>.</para>
-
- <para>This is a stable sort: it preserves the relative order of
- elements deemed equal by the comparator.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-split">
- <term><function>builtins.split</function>
- <replaceable>regex</replaceable> <replaceable>str</replaceable></term>
-
- <listitem><para>Returns a list composed of non matched strings interleaved
- with the lists of the <link xlink:href="http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_04">extended
- POSIX regular expression</link> <replaceable>regex</replaceable> matches
- of <replaceable>str</replaceable>. Each item in the lists of matched
- sequences is a regex group.
-
-<programlisting>
-builtins.split "(a)b" "abc"
-</programlisting>
-
-Evaluates to <literal>[ "" [ "a" ] "c" ]</literal>.
-
-<programlisting>
-builtins.split "([ac])" "abc"
-</programlisting>
-
-Evaluates to <literal>[ "" [ "a" ] "b" [ "c" ] "" ]</literal>.
-
-<programlisting>
-builtins.split "(a)|(c)" "abc"
-</programlisting>
-
-Evaluates to <literal>[ "" [ "a" null ] "b" [ null "c" ] "" ]</literal>.
-
-<programlisting>
-builtins.split "([[:upper:]]+)" " FOO "
-</programlisting>
-
-Evaluates to <literal>[ " " [ "FOO" ] " " ]</literal>.
-
- </para></listitem>
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-splitVersion">
- <term><function>builtins.splitVersion</function>
- <replaceable>s</replaceable></term>
-
- <listitem><para>Split a string representing a version into its
- components, by the same version splitting logic underlying the
- version comparison in <link linkend="ssec-version-comparisons">
- <command>nix-env -u</command></link>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-stringLength">
- <term><function>builtins.stringLength</function>
- <replaceable>e</replaceable></term>
-
- <listitem><para>Return the length of the string
- <replaceable>e</replaceable>. If <replaceable>e</replaceable> is
- not a string, evaluation is aborted.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-sub">
- <term><function>builtins.sub</function>
- <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
-
- <listitem><para>Return the difference between the numbers
- <replaceable>e1</replaceable> and
- <replaceable>e2</replaceable>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-substring">
- <term><function>builtins.substring</function>
- <replaceable>start</replaceable> <replaceable>len</replaceable>
- <replaceable>s</replaceable></term>
-
- <listitem><para>Return the substring of
- <replaceable>s</replaceable> from character position
- <replaceable>start</replaceable> (zero-based) up to but not
- including <replaceable>start + len</replaceable>. If
- <replaceable>start</replaceable> is greater than the length of the
- string, an empty string is returned, and if <replaceable>start +
- len</replaceable> lies beyond the end of the string, only the
- substring up to the end of the string is returned.
- <replaceable>start</replaceable> must be
- non-negative. For example,
-
-<programlisting>
-builtins.substring 0 3 "nixos"
-</programlisting>
-
- evaluates to <literal>"nix"</literal>.
- </para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-tail">
- <term><function>builtins.tail</function>
- <replaceable>list</replaceable></term>
-
- <listitem><para>Return the second to last elements of a list;
- abort evaluation if the argument isn’t a list or is an empty
- list.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-throw">
- <term><function>throw</function>
- <replaceable>s</replaceable></term>
- <term><function>builtins.throw</function>
- <replaceable>s</replaceable></term>
-
- <listitem><para>Throw an error message
- <replaceable>s</replaceable>. This usually aborts Nix expression
- evaluation, but in <command>nix-env -qa</command> and other
- commands that try to evaluate a set of derivations to get
- information about those derivations, a derivation that throws an
- error is silently skipped (which is not the case for
- <function>abort</function>).</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-toFile">
- <term><function>builtins.toFile</function>
- <replaceable>name</replaceable>
- <replaceable>s</replaceable></term>
-
- <listitem><para>Store the string <replaceable>s</replaceable> in a
- file in the Nix store and return its path. The file has suffix
- <replaceable>name</replaceable>. This file can be used as an
- input to derivations. One application is to write builders
- “inline”. For instance, the following Nix expression combines
- <xref linkend="ex-hello-nix"/> and <xref linkend="ex-hello-builder"/> into one file:
-
-<programlisting>
-{ stdenv, fetchurl, perl }:
-
-stdenv.mkDerivation {
- name = "hello-2.1.1";
-
- builder = builtins.toFile "builder.sh" "
- source $stdenv/setup
-
- PATH=$perl/bin:$PATH
-
- tar xvfz $src
- cd hello-*
- ./configure --prefix=$out
- make
- make install
- ";
-
- src = fetchurl {
- url = "http://ftp.nluug.nl/pub/gnu/hello/hello-2.1.1.tar.gz";
- sha256 = "1md7jsfd8pa45z73bz1kszpp01yw6x5ljkjk2hx7wl800any6465";
- };
- inherit perl;
-}</programlisting>
-
- </para>
-
- <para>It is even possible for one file to refer to another, e.g.,
-
-<programlisting>
- builder = let
- configFile = builtins.toFile "foo.conf" "
- # This is some dummy configuration file.
- <replaceable>...</replaceable>
- ";
- in builtins.toFile "builder.sh" "
- source $stdenv/setup
- <replaceable>...</replaceable>
- cp ${configFile} $out/etc/foo.conf
- ";</programlisting>
-
- Note that <literal>${configFile}</literal> is an antiquotation
- (see <xref linkend="ssec-values"/>), so the result of the
- expression <literal>configFile</literal> (i.e., a path like
- <filename>/nix/store/m7p7jfny445k...-foo.conf</filename>) will be
- spliced into the resulting string.</para>
-
- <para>It is however <emphasis>not</emphasis> allowed to have files
- mutually referring to each other, like so:
-
-<programlisting>
-let
- foo = builtins.toFile "foo" "...${bar}...";
- bar = builtins.toFile "bar" "...${foo}...";
-in foo</programlisting>
-
- This is not allowed because it would cause a cyclic dependency in
- the computation of the cryptographic hashes for
- <varname>foo</varname> and <varname>bar</varname>.</para>
- <para>It is also not possible to reference the result of a derivation.
- If you are using Nixpkgs, the <literal>writeTextFile</literal> function is able to
- do that.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-toJSON">
- <term><function>builtins.toJSON</function> <replaceable>e</replaceable></term>
-
- <listitem><para>Return a string containing a JSON representation
- of <replaceable>e</replaceable>. Strings, integers, floats, booleans,
- nulls and lists are mapped to their JSON equivalents. Sets
- (except derivations) are represented as objects. Derivations are
- translated to a JSON string containing the derivation’s output
- path. Paths are copied to the store and represented as a JSON
- string of the resulting store path.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-toPath">
- <term><function>builtins.toPath</function> <replaceable>s</replaceable></term>
-
- <listitem><para> DEPRECATED. Use <literal>/. + "/path"</literal>
- to convert a string into an absolute path. For relative paths,
- use <literal>./. + "/path"</literal>.
- </para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-toString">
- <term><function>toString</function> <replaceable>e</replaceable></term>
- <term><function>builtins.toString</function> <replaceable>e</replaceable></term>
-
- <listitem><para>Convert the expression
- <replaceable>e</replaceable> to a string.
- <replaceable>e</replaceable> can be:</para>
- <itemizedlist>
- <listitem><para>A string (in which case the string is returned unmodified).</para></listitem>
- <listitem><para>A path (e.g., <literal>toString /foo/bar</literal> yields <literal>"/foo/bar"</literal>.</para></listitem>
- <listitem><para>A set containing <literal>{ __toString = self: ...; }</literal>.</para></listitem>
- <listitem><para>An integer.</para></listitem>
- <listitem><para>A list, in which case the string representations of its elements are joined with spaces.</para></listitem>
- <listitem><para>A Boolean (<literal>false</literal> yields <literal>""</literal>, <literal>true</literal> yields <literal>"1"</literal>).</para></listitem>
- <listitem><para><literal>null</literal>, which yields the empty string.</para></listitem>
- </itemizedlist>
- </listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-toXML">
- <term><function>builtins.toXML</function> <replaceable>e</replaceable></term>
-
- <listitem><para>Return a string containing an XML representation
- of <replaceable>e</replaceable>. The main application for
- <function>toXML</function> is to communicate information with the
- builder in a more structured format than plain environment
- variables.</para>
-
- <!-- TODO: more formally describe the schema of the XML
- representation -->
-
- <para><xref linkend="ex-toxml"/> shows an example where this is
- the case. The builder is supposed to generate the configuration
- file for a <link xlink:href="http://jetty.mortbay.org/">Jetty
- servlet container</link>. A servlet container contains a number
- of servlets (<filename>*.war</filename> files) each exported under
- a specific URI prefix. So the servlet configuration is a list of
- sets containing the <varname>path</varname> and
- <varname>war</varname> of the servlet (<xref linkend="ex-toxml-co-servlets"/>). This kind of information is
- difficult to communicate with the normal method of passing
- information through an environment variable, which just
- concatenates everything together into a string (which might just
- work in this case, but wouldn’t work if fields are optional or
- contain lists themselves). Instead the Nix expression is
- converted to an XML representation with
- <function>toXML</function>, which is unambiguous and can easily be
- processed with the appropriate tools. For instance, in the
- example an XSLT stylesheet (<xref linkend="ex-toxml-co-stylesheet"/>) is applied to it (<xref linkend="ex-toxml-co-apply"/>) to
- generate the XML configuration file for the Jetty server. The XML
- representation produced from <xref linkend="ex-toxml-co-servlets"/> by <function>toXML</function> is shown in <xref linkend="ex-toxml-result"/>.</para>
-
- <para>Note that <xref linkend="ex-toxml"/> uses the <function linkend="builtin-toFile">toFile</function> built-in to write the
- builder and the stylesheet “inline” in the Nix expression. The
- path of the stylesheet is spliced into the builder at
- <literal>xsltproc ${stylesheet}
- <replaceable>...</replaceable></literal>.</para>
-
- <example xml:id="ex-toxml"><title>Passing information to a builder
- using <function>toXML</function></title>
-
-<programlisting><![CDATA[
-{ stdenv, fetchurl, libxslt, jira, uberwiki }:
-
-stdenv.mkDerivation (rec {
- name = "web-server";
-
- buildInputs = [ libxslt ];
-
- builder = builtins.toFile "builder.sh" "
- source $stdenv/setup
- mkdir $out
- echo "$servlets" | xsltproc ${stylesheet} - > $out/server-conf.xml]]> <co xml:id="ex-toxml-co-apply"/> <![CDATA[
- ";
-
- stylesheet = builtins.toFile "stylesheet.xsl"]]> <co xml:id="ex-toxml-co-stylesheet"/> <![CDATA[
- "<?xml version='1.0' encoding='UTF-8'?>
- <xsl:stylesheet xmlns:xsl='http://www.w3.org/1999/XSL/Transform' version='1.0'>
- <xsl:template match='/'>
- <Configure>
- <xsl:for-each select='/expr/list/attrs'>
- <Call name='addWebApplication'>
- <Arg><xsl:value-of select=\"attr[@name = 'path']/string/@value\" /></Arg>
- <Arg><xsl:value-of select=\"attr[@name = 'war']/path/@value\" /></Arg>
- </Call>
- </xsl:for-each>
- </Configure>
- </xsl:template>
- </xsl:stylesheet>
- ";
-
- servlets = builtins.toXML []]> <co xml:id="ex-toxml-co-servlets"/> <![CDATA[
- { path = "/bugtracker"; war = jira + "/lib/atlassian-jira.war"; }
- { path = "/wiki"; war = uberwiki + "/uberwiki.war"; }
- ];
-})]]></programlisting>
-
- </example>
-
- <example xml:id="ex-toxml-result"><title>XML representation produced by
- <function>toXML</function></title>
-
-<programlisting><![CDATA[<?xml version='1.0' encoding='utf-8'?>
-<expr>
- <list>
- <attrs>
- <attr name="path">
- <string value="/bugtracker" />
- </attr>
- <attr name="war">
- <path value="/nix/store/d1jh9pasa7k2...-jira/lib/atlassian-jira.war" />
- </attr>
- </attrs>
- <attrs>
- <attr name="path">
- <string value="/wiki" />
- </attr>
- <attr name="war">
- <path value="/nix/store/y6423b1yi4sx...-uberwiki/uberwiki.war" />
- </attr>
- </attrs>
- </list>
-</expr>]]></programlisting>
-
- </example>
-
- </listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-trace">
- <term><function>builtins.trace</function>
- <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
-
- <listitem><para>Evaluate <replaceable>e1</replaceable> and print its
- abstract syntax representation on standard error. Then return
- <replaceable>e2</replaceable>. This function is useful for
- debugging.</para></listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="builtin-tryEval">
- <term><function>builtins.tryEval</function>
- <replaceable>e</replaceable></term>
-
- <listitem><para>Try to shallowly evaluate <replaceable>e</replaceable>.
- Return a set containing the attributes <literal>success</literal>
- (<literal>true</literal> if <replaceable>e</replaceable> evaluated
- successfully, <literal>false</literal> if an error was thrown) and
- <literal>value</literal>, equalling <replaceable>e</replaceable>
- if successful and <literal>false</literal> otherwise. Note that this
- doesn't evaluate <replaceable>e</replaceable> deeply, so
- <literal>let e = { x = throw ""; }; in (builtins.tryEval e).success
- </literal> will be <literal>true</literal>. Using <literal>builtins.deepSeq
- </literal> one can get the expected result: <literal>let e = { x = throw "";
- }; in (builtins.tryEval (builtins.deepSeq e e)).success</literal> will be
- <literal>false</literal>.
- </para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="builtin-typeOf">
- <term><function>builtins.typeOf</function>
- <replaceable>e</replaceable></term>
-
- <listitem><para>Return a string representing the type of the value
- <replaceable>e</replaceable>, namely <literal>"int"</literal>,
- <literal>"bool"</literal>, <literal>"string"</literal>,
- <literal>"path"</literal>, <literal>"null"</literal>,
- <literal>"set"</literal>, <literal>"list"</literal>,
- <literal>"lambda"</literal> or
- <literal>"float"</literal>.</para></listitem>
-
- </varlistentry>
-
-
-</variablelist>
-
-
-</section>
-
-
-</chapter>
-
-</part>
- <part xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" xml:id="part-advanced-topics" version="5.0" xml:base="advanced-topics/advanced-topics.xml">
-
-<title>Advanced Topics</title>
-
-<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="chap-distributed-builds">
-
-<title>Remote Builds</title>
-
-<para>Nix supports remote builds, where a local Nix installation can
-forward Nix builds to other machines. This allows multiple builds to
-be performed in parallel and allows Nix to perform multi-platform
-builds in a semi-transparent way. For instance, if you perform a
-build for a <literal>x86_64-darwin</literal> on an
-<literal>i686-linux</literal> machine, Nix can automatically forward
-the build to a <literal>x86_64-darwin</literal> machine, if
-available.</para>
-
-<para>To forward a build to a remote machine, it’s required that the
-remote machine is accessible via SSH and that it has Nix
-installed. You can test whether connecting to the remote Nix instance
-works, e.g.
-
-<screen>
-$ nix ping-store --store ssh://mac
-</screen>
-
-will try to connect to the machine named <literal>mac</literal>. It is
-possible to specify an SSH identity file as part of the remote store
-URI, e.g.
-
-<screen>
-$ nix ping-store --store ssh://mac?ssh-key=/home/alice/my-key
-</screen>
-
-Since builds should be non-interactive, the key should not have a
-passphrase. Alternatively, you can load identities ahead of time into
-<command>ssh-agent</command> or <command>gpg-agent</command>.</para>
-
-<para>If you get the error
-
-<screen>
-bash: nix-store: command not found
-error: cannot connect to 'mac'
-</screen>
-
-then you need to ensure that the <envar>PATH</envar> of
-non-interactive login shells contains Nix.</para>
-
-<warning><para>If you are building via the Nix daemon, it is the Nix
-daemon user account (that is, <literal>root</literal>) that should
-have SSH access to the remote machine. If you can’t or don’t want to
-configure <literal>root</literal> to be able to access to remote
-machine, you can use a private Nix store instead by passing
-e.g. <literal>--store ~/my-nix</literal>.</para></warning>
-
-<para>The list of remote machines can be specified on the command line
-or in the Nix configuration file. The former is convenient for
-testing. For example, the following command allows you to build a
-derivation for <literal>x86_64-darwin</literal> on a Linux machine:
-
-<screen>
-$ uname
-Linux
-
-$ nix build \
- '(with import <nixpkgs> { system = "x86_64-darwin"; }; runCommand "foo" {} "uname > $out")' \
- --builders 'ssh://mac x86_64-darwin'
-[1/0/1 built, 0.0 MiB DL] building foo on ssh://mac
-
-$ cat ./result
-Darwin
-</screen>
-
-It is possible to specify multiple builders separated by a semicolon
-or a newline, e.g.
-
-<screen>
- --builders 'ssh://mac x86_64-darwin ; ssh://beastie x86_64-freebsd'
-</screen>
-</para>
-
-<para>Each machine specification consists of the following elements,
-separated by spaces. Only the first element is required.
-To leave a field at its default, set it to <literal>-</literal>.
-
-<orderedlist>
-
- <listitem><para>The URI of the remote store in the format
- <literal>ssh://[<replaceable>username</replaceable>@]<replaceable>hostname</replaceable></literal>,
- e.g. <literal>ssh://nix@mac</literal> or
- <literal>ssh://mac</literal>. For backward compatibility,
- <literal>ssh://</literal> may be omitted. The hostname may be an
- alias defined in your
- <filename>~/.ssh/config</filename>.</para></listitem>
-
- <listitem><para>A comma-separated list of Nix platform type
- identifiers, such as <literal>x86_64-darwin</literal>. It is
- possible for a machine to support multiple platform types, e.g.,
- <literal>i686-linux,x86_64-linux</literal>. If omitted, this
- defaults to the local platform type.</para></listitem>
-
- <listitem><para>The SSH identity file to be used to log in to the
- remote machine. If omitted, SSH will use its regular
- identities.</para></listitem>
-
- <listitem><para>The maximum number of builds that Nix will execute
- in parallel on the machine. Typically this should be equal to the
- number of CPU cores. For instance, the machine
- <literal>itchy</literal> in the example will execute up to 8 builds
- in parallel.</para></listitem>
-
- <listitem><para>The “speed factor”, indicating the relative speed of
- the machine. If there are multiple machines of the right type, Nix
- will prefer the fastest, taking load into account.</para></listitem>
-
- <listitem><para>A comma-separated list of <emphasis>supported
- features</emphasis>. If a derivation has the
- <varname>requiredSystemFeatures</varname> attribute, then Nix will
- only perform the derivation on a machine that has the specified
- features. For instance, the attribute
-
-<programlisting>
-requiredSystemFeatures = [ "kvm" ];
-</programlisting>
-
- will cause the build to be performed on a machine that has the
- <literal>kvm</literal> feature.</para></listitem>
-
- <listitem><para>A comma-separated list of <emphasis>mandatory
- features</emphasis>. A machine will only be used to build a
- derivation if all of the machine’s mandatory features appear in the
- derivation’s <varname>requiredSystemFeatures</varname>
- attribute..</para></listitem>
-
-</orderedlist>
-
-For example, the machine specification
-
-<programlisting>
-nix@scratchy.labs.cs.uu.nl i686-linux /home/nix/.ssh/id_scratchy_auto 8 1 kvm
-nix@itchy.labs.cs.uu.nl i686-linux /home/nix/.ssh/id_scratchy_auto 8 2
-nix@poochie.labs.cs.uu.nl i686-linux /home/nix/.ssh/id_scratchy_auto 1 2 kvm benchmark
-</programlisting>
-
-specifies several machines that can perform
-<literal>i686-linux</literal> builds. However,
-<literal>poochie</literal> will only do builds that have the attribute
-
-<programlisting>
-requiredSystemFeatures = [ "benchmark" ];
-</programlisting>
-
-or
-
-<programlisting>
-requiredSystemFeatures = [ "benchmark" "kvm" ];
-</programlisting>
-
-<literal>itchy</literal> cannot do builds that require
-<literal>kvm</literal>, but <literal>scratchy</literal> does support
-such builds. For regular builds, <literal>itchy</literal> will be
-preferred over <literal>scratchy</literal> because it has a higher
-speed factor.</para>
-
-<para>Remote builders can also be configured in
-<filename>nix.conf</filename>, e.g.
-
-<programlisting>
-builders = ssh://mac x86_64-darwin ; ssh://beastie x86_64-freebsd
-</programlisting>
-
-Finally, remote builders can be configured in a separate configuration
-file included in <option>builders</option> via the syntax
-<literal>@<replaceable>file</replaceable></literal>. For example,
-
-<programlisting>
-builders = @/etc/nix/machines
-</programlisting>
-
-causes the list of machines in <filename>/etc/nix/machines</filename>
-to be included. (This is the default.)</para>
-
-<para>If you want the builders to use caches, you likely want to set
-the option <link linkend="conf-builders-use-substitutes"><literal>builders-use-substitutes</literal></link>
-in your local <filename>nix.conf</filename>.</para>
-
-<para>To build only on remote builders and disable building on the local machine,
-you can use the option <option>--max-jobs 0</option>.</para>
-
-</chapter>
-<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="chap-tuning-cores-and-jobs">
-
-<title>Tuning Cores and Jobs</title>
-
-<para>Nix has two relevant settings with regards to how your CPU cores
-will be utilized: <xref linkend="conf-cores"/> and
-<xref linkend="conf-max-jobs"/>. This chapter will talk about what
-they are, how they interact, and their configuration trade-offs.</para>
-
-<variablelist>
- <varlistentry>
- <term><xref linkend="conf-max-jobs"/></term>
- <listitem><para>
- Dictates how many separate derivations will be built at the same
- time. If you set this to zero, the local machine will do no
- builds. Nix will still substitute from binary caches, and build
- remotely if remote builders are configured.
- </para></listitem>
- </varlistentry>
- <varlistentry>
- <term><xref linkend="conf-cores"/></term>
- <listitem><para>
- Suggests how many cores each derivation should use. Similar to
- <command>make -j</command>.
- </para></listitem>
- </varlistentry>
-</variablelist>
-
-<para>The <xref linkend="conf-cores"/> setting determines the value of
-<envar>NIX_BUILD_CORES</envar>. <envar>NIX_BUILD_CORES</envar> is equal
-to <xref linkend="conf-cores"/>, unless <xref linkend="conf-cores"/>
-equals <literal>0</literal>, in which case <envar>NIX_BUILD_CORES</envar>
-will be the total number of cores in the system.</para>
-
-<para>The maximum number of consumed cores is a simple multiplication,
-<xref linkend="conf-max-jobs"/> * <envar>NIX_BUILD_CORES</envar>.</para>
-
-<para>The balance on how to set these two independent variables depends
-upon each builder's workload and hardware. Here are a few example
-scenarios on a machine with 24 cores:</para>
-
-<table>
- <caption>Balancing 24 Build Cores</caption>
- <thead>
- <tr>
- <th><xref linkend="conf-max-jobs"/></th>
- <th><xref linkend="conf-cores"/></th>
- <th><envar>NIX_BUILD_CORES</envar></th>
- <th>Maximum Processes</th>
- <th>Result</th>
- </tr>
- </thead>
- <tbody>
- <tr>
- <td>1</td>
- <td>24</td>
- <td>24</td>
- <td>24</td>
- <td>
- One derivation will be built at a time, each one can use 24
- cores. Undersold if a job can’t use 24 cores.
- </td>
- </tr>
-
- <tr>
- <td>4</td>
- <td>6</td>
- <td>6</td>
- <td>24</td>
- <td>
- Four derivations will be built at once, each given access to
- six cores.
- </td>
- </tr>
- <tr>
- <td>12</td>
- <td>6</td>
- <td>6</td>
- <td>72</td>
- <td>
- 12 derivations will be built at once, each given access to six
- cores. This configuration is over-sold. If all 12 derivations
- being built simultaneously try to use all six cores, the
- machine's performance will be degraded due to extensive context
- switching between the 12 builds.
- </td>
- </tr>
- <tr>
- <td>24</td>
- <td>1</td>
- <td>1</td>
- <td>24</td>
- <td>
- 24 derivations can build at the same time, each using a single
- core. Never oversold, but derivations which require many cores
- will be very slow to compile.
- </td>
- </tr>
- <tr>
- <td>24</td>
- <td>0</td>
- <td>24</td>
- <td>576</td>
- <td>
- 24 derivations can build at the same time, each using all the
- available cores of the machine. Very likely to be oversold,
- and very likely to suffer context switches.
- </td>
- </tr>
- </tbody>
-</table>
-
-<para>It is up to the derivations' build script to respect
-host's requested cores-per-build by following the value of the
-<envar>NIX_BUILD_CORES</envar> environment variable.</para>
-
-</chapter>
-<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" xml:id="chap-diff-hook" version="5.0">
-
-<title>Verifying Build Reproducibility with <option linkend="conf-diff-hook">diff-hook</option></title>
-
-<subtitle>Check build reproducibility by running builds multiple times
-and comparing their results.</subtitle>
-
-<para>Specify a program with Nix's <xref linkend="conf-diff-hook"/> to
-compare build results when two builds produce different results. Note:
-this hook is only executed if the results are not the same, this hook
-is not used for determining if the results are the same.</para>
-
-<para>For purposes of demonstration, we'll use the following Nix file,
-<filename>deterministic.nix</filename> for testing:</para>
-
-<programlisting>
-let
- inherit (import <nixpkgs> {}) runCommand;
-in {
- stable = runCommand "stable" {} ''
- touch $out
- '';
-
- unstable = runCommand "unstable" {} ''
- echo $RANDOM > $out
- '';
-}
-</programlisting>
-
-<para>Additionally, <filename>nix.conf</filename> contains:
-
-<programlisting>
-diff-hook = /etc/nix/my-diff-hook
-run-diff-hook = true
-</programlisting>
-
-where <filename>/etc/nix/my-diff-hook</filename> is an executable
-file containing:
-
-<programlisting>
-#!/bin/sh
-exec >&2
-echo "For derivation $3:"
-/run/current-system/sw/bin/diff -r "$1" "$2"
-</programlisting>
-
-</para>
-
-<para>The diff hook is executed by the same user and group who ran the
-build. However, the diff hook does not have write access to the store
-path just built.</para>
-
-<section>
- <title>
- Spot-Checking Build Determinism
- </title>
-
- <para>
- Verify a path which already exists in the Nix store by passing
- <option>--check</option> to the build command.
- </para>
-
- <para>If the build passes and is deterministic, Nix will exit with a
- status code of 0:</para>
-
- <screen>
-$ nix-build ./deterministic.nix -A stable
-this derivation will be built:
- /nix/store/z98fasz2jqy9gs0xbvdj939p27jwda38-stable.drv
-building '/nix/store/z98fasz2jqy9gs0xbvdj939p27jwda38-stable.drv'...
-/nix/store/yyxlzw3vqaas7wfp04g0b1xg51f2czgq-stable
-
-$ nix-build ./deterministic.nix -A stable --check
-checking outputs of '/nix/store/z98fasz2jqy9gs0xbvdj939p27jwda38-stable.drv'...
-/nix/store/yyxlzw3vqaas7wfp04g0b1xg51f2czgq-stable
-</screen>
-
- <para>If the build is not deterministic, Nix will exit with a status
- code of 1:</para>
-
- <screen>
-$ nix-build ./deterministic.nix -A unstable
-this derivation will be built:
- /nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv
-building '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv'...
-/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable
-
-$ nix-build ./deterministic.nix -A unstable --check
-checking outputs of '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv'...
-error: derivation '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv' may not be deterministic: output '/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable' differs
-</screen>
-
-<para>In the Nix daemon's log, we will now see:
-<screen>
-For derivation /nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv:
-1c1
-< 8108
----
-> 30204
-</screen>
-</para>
-
- <para>Using <option>--check</option> with <option>--keep-failed</option>
- will cause Nix to keep the second build's output in a special,
- <literal>.check</literal> path:</para>
-
- <screen>
-$ nix-build ./deterministic.nix -A unstable --check --keep-failed
-checking outputs of '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv'...
-note: keeping build directory '/tmp/nix-build-unstable.drv-0'
-error: derivation '/nix/store/cgl13lbj1w368r5z8gywipl1ifli7dhk-unstable.drv' may not be deterministic: output '/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable' differs from '/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable.check'
-</screen>
-
- <para>In particular, notice the
- <literal>/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable.check</literal>
- output. Nix has copied the build results to that directory where you
- can examine it.</para>
-
- <note xml:id="check-dirs-are-unregistered">
- <title><literal>.check</literal> paths are not registered store paths</title>
-
- <para>Check paths are not protected against garbage collection,
- and this path will be deleted on the next garbage collection.</para>
-
- <para>The path is guaranteed to be alive for the duration of
- <xref linkend="conf-diff-hook"/>'s execution, but may be deleted
- any time after.</para>
-
- <para>If the comparison is performed as part of automated tooling,
- please use the diff-hook or author your tooling to handle the case
- where the build was not deterministic and also a check path does
- not exist.</para>
- </note>
-
- <para>
- <option>--check</option> is only usable if the derivation has
- been built on the system already. If the derivation has not been
- built Nix will fail with the error:
- <screen>
-error: some outputs of '/nix/store/hzi1h60z2qf0nb85iwnpvrai3j2w7rr6-unstable.drv' are not valid, so checking is not possible
-</screen>
-
- Run the build without <option>--check</option>, and then try with
- <option>--check</option> again.
- </para>
-</section>
-
-<section>
- <title>
- Automatic and Optionally Enforced Determinism Verification
- </title>
-
- <para>
- Automatically verify every build at build time by executing the
- build multiple times.
- </para>
-
- <para>
- Setting <xref linkend="conf-repeat"/> and
- <xref linkend="conf-enforce-determinism"/> in your
- <filename>nix.conf</filename> permits the automated verification
- of every build Nix performs.
- </para>
-
- <para>
- The following configuration will run each build three times, and
- will require the build to be deterministic:
-
- <programlisting>
-enforce-determinism = true
-repeat = 2
-</programlisting>
- </para>
-
- <para>
- Setting <xref linkend="conf-enforce-determinism"/> to false as in
- the following configuration will run the build multiple times,
- execute the build hook, but will allow the build to succeed even
- if it does not build reproducibly:
-
- <programlisting>
-enforce-determinism = false
-repeat = 1
-</programlisting>
- </para>
-
- <para>
- An example output of this configuration:
- <screen>
-$ nix-build ./test.nix -A unstable
-this derivation will be built:
- /nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv
-building '/nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv' (round 1/2)...
-building '/nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv' (round 2/2)...
-output '/nix/store/6xg356v9gl03hpbbg8gws77n19qanh02-unstable' of '/nix/store/ch6llwpr2h8c3jmnf3f2ghkhx59aa97f-unstable.drv' differs from '/nix/store/6xg356v9gl03hpbbg8gws77n19qanh02-unstable.check' from previous round
-/nix/store/6xg356v9gl03hpbbg8gws77n19qanh02-unstable
-</screen>
- </para>
-</section>
-</chapter>
-<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" xml:id="chap-post-build-hook" version="5.0">
-
-<title>Using the <option linkend="conf-post-build-hook">post-build-hook</option></title>
-<subtitle>Uploading to an S3-compatible binary cache after each build</subtitle>
-
-
-<section xml:id="chap-post-build-hook-caveats">
- <title>Implementation Caveats</title>
- <para>Here we use the post-build hook to upload to a binary cache.
- This is a simple and working example, but it is not suitable for all
- use cases.</para>
-
- <para>The post build hook program runs after each executed build,
- and blocks the build loop. The build loop exits if the hook program
- fails.</para>
-
- <para>Concretely, this implementation will make Nix slow or unusable
- when the internet is slow or unreliable.</para>
-
- <para>A more advanced implementation might pass the store paths to a
- user-supplied daemon or queue for processing the store paths outside
- of the build loop.</para>
-</section>
-
-<section>
- <title>Prerequisites</title>
-
- <para>
- This tutorial assumes you have configured an S3-compatible binary cache
- according to the instructions at
- <xref linkend="ssec-s3-substituter-authenticated-writes"/>, and
- that the <literal>root</literal> user's default AWS profile can
- upload to the bucket.
- </para>
-</section>
-
-<section>
- <title>Set up a Signing Key</title>
- <para>Use <command>nix-store --generate-binary-cache-key</command> to
- create our public and private signing keys. We will sign paths
- with the private key, and distribute the public key for verifying
- the authenticity of the paths.</para>
-
- <screen>
-# nix-store --generate-binary-cache-key example-nix-cache-1 /etc/nix/key.private /etc/nix/key.public
-# cat /etc/nix/key.public
-example-nix-cache-1:1/cKDz3QCCOmwcztD2eV6Coggp6rqc9DGjWv7C0G+rM=
-</screen>
-
-<para>Then, add the public key and the cache URL to your
-<filename>nix.conf</filename>'s <xref linkend="conf-trusted-public-keys"/>
-and <xref linkend="conf-substituters"/> like:</para>
-
-<programlisting>
-substituters = https://cache.nixos.org/ s3://example-nix-cache
-trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= example-nix-cache-1:1/cKDz3QCCOmwcztD2eV6Coggp6rqc9DGjWv7C0G+rM=
-</programlisting>
-
-<para>We will restart the Nix daemon in a later step.</para>
-</section>
-
-<section>
- <title>Implementing the build hook</title>
- <para>Write the following script to
- <filename>/etc/nix/upload-to-cache.sh</filename>:
- </para>
-
- <programlisting>
-#!/bin/sh
-
-set -eu
-set -f # disable globbing
-export IFS=' '
-
-echo "Signing paths" $OUT_PATHS
-nix sign-paths --key-file /etc/nix/key.private $OUT_PATHS
-echo "Uploading paths" $OUT_PATHS
-exec nix copy --to 's3://example-nix-cache' $OUT_PATHS
-</programlisting>
-
- <note>
- <title>Should <literal>$OUT_PATHS</literal> be quoted?</title>
- <para>
- The <literal>$OUT_PATHS</literal> variable is a space-separated
- list of Nix store paths. In this case, we expect and want the
- shell to perform word splitting to make each output path its
- own argument to <command>nix sign-paths</command>. Nix guarantees
- the paths will not contain any spaces, however a store path
- might contain glob characters. The <command>set -f</command>
- disables globbing in the shell.
- </para>
- </note>
- <para>
- Then make sure the hook program is executable by the <literal>root</literal> user:
- <screen>
-# chmod +x /etc/nix/upload-to-cache.sh
-</screen></para>
-</section>
-
-<section>
- <title>Updating Nix Configuration</title>
-
- <para>Edit <filename>/etc/nix/nix.conf</filename> to run our hook,
- by adding the following configuration snippet at the end:</para>
-
- <programlisting>
-post-build-hook = /etc/nix/upload-to-cache.sh
-</programlisting>
-
-<para>Then, restart the <command>nix-daemon</command>.</para>
-</section>
-
-<section>
- <title>Testing</title>
-
- <para>Build any derivation, for example:</para>
-
- <screen>
-$ nix-build -E '(import <nixpkgs> {}).writeText "example" (builtins.toString builtins.currentTime)'
-this derivation will be built:
- /nix/store/s4pnfbkalzy5qz57qs6yybna8wylkig6-example.drv
-building '/nix/store/s4pnfbkalzy5qz57qs6yybna8wylkig6-example.drv'...
-running post-build-hook '/home/grahamc/projects/github.com/NixOS/nix/post-hook.sh'...
-post-build-hook: Signing paths /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
-post-build-hook: Uploading paths /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
-/nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
-</screen>
-
- <para>Then delete the path from the store, and try substituting it from the binary cache:</para>
- <screen>
-$ rm ./result
-$ nix-store --delete /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
-</screen>
-
-<para>Now, copy the path back from the cache:</para>
-<screen>
-$ nix-store --realise /nix/store/ibcyipq5gf91838ldx40mjsp0b8w9n18-example
-copying path '/nix/store/m8bmqwrch6l3h8s0k3d673xpmipcdpsa-example from 's3://example-nix-cache'...
-warning: you did not specify '--add-root'; the result might be removed by the garbage collector
-/nix/store/m8bmqwrch6l3h8s0k3d673xpmipcdpsa-example
-</screen>
-</section>
-<section>
- <title>Conclusion</title>
- <para>
- We now have a Nix installation configured to automatically sign and
- upload every local build to a remote binary cache.
- </para>
-
- <para>
- Before deploying this to production, be sure to consider the
- implementation caveats in <xref linkend="chap-post-build-hook-caveats"/>.
- </para>
-</section>
-</chapter>
-
-</part>
- <part xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="part-command-ref" xml:base="command-ref/command-ref.xml">
-
-<title>Command Reference</title>
-
-<partintro>
-<para>This section lists commands and options that you can use when you
-work with Nix.</para>
-</partintro>
-
-<chapter xmlns="http://docbook.org/ns/docbook" xml:id="sec-common-options">
-
-<title>Common Options</title>
-
-
-<para>Most Nix commands accept the following command-line options:</para>
-
-<variablelist xml:id="opt-common">
-
-<varlistentry><term><option>--help</option></term>
-
- <listitem><para>Prints out a summary of the command syntax and
- exits.</para></listitem>
-
-</varlistentry>
-
-
-<varlistentry><term><option>--version</option></term>
-
- <listitem><para>Prints out the Nix version number on standard output
- and exits.</para></listitem>
-</varlistentry>
-
-
-<varlistentry><term><option>--verbose</option> / <option>-v</option></term>
-
- <listitem>
-
- <para>Increases the level of verbosity of diagnostic messages
- printed on standard error. For each Nix operation, the information
- printed on standard output is well-defined; any diagnostic
- information is printed on standard error, never on standard
- output.</para>
-
- <para>This option may be specified repeatedly. Currently, the
- following verbosity levels exist:</para>
-
- <variablelist>
-
- <varlistentry><term>0</term>
- <listitem><para>“Errors only”: only print messages
- explaining why the Nix invocation failed.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>1</term>
- <listitem><para>“Informational”: print
- <emphasis>useful</emphasis> messages about what Nix is doing.
- This is the default.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>2</term>
- <listitem><para>“Talkative”: print more informational
- messages.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>3</term>
- <listitem><para>“Chatty”: print even more
- informational messages.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>4</term>
- <listitem><para>“Debug”: print debug
- information.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>5</term>
- <listitem><para>“Vomit”: print vast amounts of debug
- information.</para></listitem>
- </varlistentry>
-
- </variablelist>
-
- </listitem>
-
-</varlistentry>
-
-
-<varlistentry><term><option>--quiet</option></term>
-
- <listitem>
-
- <para>Decreases the level of verbosity of diagnostic messages
- printed on standard error. This is the inverse option to
- <option>-v</option> / <option>--verbose</option>.
- </para>
-
- <para>This option may be specified repeatedly. See the previous
- verbosity levels list.</para>
-
- </listitem>
-
-</varlistentry>
-
-
-<varlistentry xml:id="opt-log-format"><term><option>--log-format</option> <replaceable>format</replaceable></term>
-
- <listitem>
-
- <para>This option can be used to change the output of the log format, with
- <replaceable>format</replaceable> being one of:</para>
-
- <variablelist>
-
- <varlistentry><term>raw</term>
- <listitem><para>This is the raw format, as outputted by nix-build.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>internal-json</term>
- <listitem><para>Outputs the logs in a structured manner. NOTE: the json schema is not guarantees to be stable between releases.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>bar</term>
- <listitem><para>Only display a progress bar during the builds.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>bar-with-logs</term>
- <listitem><para>Display the raw logs, with the progress bar at the bottom.</para></listitem>
- </varlistentry>
-
- </variablelist>
-
- </listitem>
-
-</varlistentry>
-
-<varlistentry><term><option>--no-build-output</option> / <option>-Q</option></term>
-
- <listitem><para>By default, output written by builders to standard
- output and standard error is echoed to the Nix command's standard
- error. This option suppresses this behaviour. Note that the
- builder's standard output and error are always written to a log file
- in
- <filename><replaceable>prefix</replaceable>/nix/var/log/nix</filename>.</para></listitem>
-
-</varlistentry>
-
-
-<varlistentry xml:id="opt-max-jobs"><term><option>--max-jobs</option> / <option>-j</option>
-<replaceable>number</replaceable></term>
-
- <listitem>
-
- <para>Sets the maximum number of build jobs that Nix will
- perform in parallel to the specified number. Specify
- <literal>auto</literal> to use the number of CPUs in the system.
- The default is specified by the <link linkend="conf-max-jobs"><literal>max-jobs</literal></link>
- configuration setting, which itself defaults to
- <literal>1</literal>. A higher value is useful on SMP systems or to
- exploit I/O latency.</para>
-
- <para> Setting it to <literal>0</literal> disallows building on the local
- machine, which is useful when you want builds to happen only on remote
- builders.</para>
-
- </listitem>
-
-</varlistentry>
-
-
-<varlistentry xml:id="opt-cores"><term><option>--cores</option></term>
-
- <listitem><para>Sets the value of the <envar>NIX_BUILD_CORES</envar>
- environment variable in the invocation of builders. Builders can
- use this variable at their discretion to control the maximum amount
- of parallelism. For instance, in Nixpkgs, if the derivation
- attribute <varname>enableParallelBuilding</varname> is set to
- <literal>true</literal>, the builder passes the
- <option>-j<replaceable>N</replaceable></option> flag to GNU Make.
- It defaults to the value of the <link linkend="conf-cores"><literal>cores</literal></link>
- configuration setting, if set, or <literal>1</literal> otherwise.
- The value <literal>0</literal> means that the builder should use all
- available CPU cores in the system.</para></listitem>
-
-</varlistentry>
-
-
-<varlistentry xml:id="opt-max-silent-time"><term><option>--max-silent-time</option></term>
-
- <listitem><para>Sets the maximum number of seconds that a builder
- can go without producing any data on standard output or standard
- error. The default is specified by the <link linkend="conf-max-silent-time"><literal>max-silent-time</literal></link>
- configuration setting. <literal>0</literal> means no
- time-out.</para></listitem>
-
-</varlistentry>
-
-<varlistentry xml:id="opt-timeout"><term><option>--timeout</option></term>
-
- <listitem><para>Sets the maximum number of seconds that a builder
- can run. The default is specified by the <link linkend="conf-timeout"><literal>timeout</literal></link>
- configuration setting. <literal>0</literal> means no
- timeout.</para></listitem>
-
-</varlistentry>
-
-<varlistentry><term><option>--keep-going</option> / <option>-k</option></term>
-
- <listitem><para>Keep going in case of failed builds, to the
- greatest extent possible. That is, if building an input of some
- derivation fails, Nix will still build the other inputs, but not the
- derivation itself. Without this option, Nix stops if any build
- fails (except for builds of substitutes), possibly killing builds in
- progress (in case of parallel or distributed builds).</para></listitem>
-
-</varlistentry>
-
-
-<varlistentry><term><option>--keep-failed</option> / <option>-K</option></term>
-
- <listitem><para>Specifies that in case of a build failure, the
- temporary directory (usually in <filename>/tmp</filename>) in which
- the build takes place should not be deleted. The path of the build
- directory is printed as an informational message.
- </para>
- </listitem>
-</varlistentry>
-
-
-<varlistentry><term><option>--fallback</option></term>
-
- <listitem>
-
- <para>Whenever Nix attempts to build a derivation for which
- substitutes are known for each output path, but realising the output
- paths through the substitutes fails, fall back on building the
- derivation.</para>
-
- <para>The most common scenario in which this is useful is when we
- have registered substitutes in order to perform binary distribution
- from, say, a network repository. If the repository is down, the
- realisation of the derivation will fail. When this option is
- specified, Nix will build the derivation instead. Thus,
- installation from binaries falls back on installation from source.
- This option is not the default since it is generally not desirable
- for a transient failure in obtaining the substitutes to lead to a
- full build from source (with the related consumption of
- resources).</para>
-
- </listitem>
-
-</varlistentry>
-
-<varlistentry><term><option>--no-build-hook</option></term>
-
- <listitem>
-
- <para>Disables the build hook mechanism. This allows to ignore remote
- builders if they are setup on the machine.</para>
-
- <para>It's useful in cases where the bandwidth between the client and the
- remote builder is too low. In that case it can take more time to upload the
- sources to the remote builder and fetch back the result than to do the
- computation locally.</para>
-
- </listitem>
-
-</varlistentry>
-
-
-
-<varlistentry><term><option>--readonly-mode</option></term>
-
- <listitem><para>When this option is used, no attempt is made to open
- the Nix database. Most Nix operations do need database access, so
- those operations will fail.</para></listitem>
-
-</varlistentry>
-
-
-<varlistentry><term><option>--arg</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
-
- <listitem><para>This option is accepted by
- <command>nix-env</command>, <command>nix-instantiate</command>,
- <command>nix-shell</command> and <command>nix-build</command>.
- When evaluating Nix expressions, the expression evaluator will
- automatically try to call functions that
- it encounters. It can automatically call functions for which every
- argument has a <link linkend="ss-functions">default value</link>
- (e.g., <literal>{ <replaceable>argName</replaceable> ?
- <replaceable>defaultValue</replaceable> }:
- <replaceable>...</replaceable></literal>). With
- <option>--arg</option>, you can also call functions that have
- arguments without a default value (or override a default value).
- That is, if the evaluator encounters a function with an argument
- named <replaceable>name</replaceable>, it will call it with value
- <replaceable>value</replaceable>.</para>
-
- <para>For instance, the top-level <literal>default.nix</literal> in
- Nixpkgs is actually a function:
-
-<programlisting>
-{ # The system (e.g., `i686-linux') for which to build the packages.
- system ? builtins.currentSystem
- <replaceable>...</replaceable>
-}: <replaceable>...</replaceable></programlisting>
-
- So if you call this Nix expression (e.g., when you do
- <literal>nix-env -i <replaceable>pkgname</replaceable></literal>),
- the function will be called automatically using the value <link linkend="builtin-currentSystem"><literal>builtins.currentSystem</literal></link>
- for the <literal>system</literal> argument. You can override this
- using <option>--arg</option>, e.g., <literal>nix-env -i
- <replaceable>pkgname</replaceable> --arg system
- \"i686-freebsd\"</literal>. (Note that since the argument is a Nix
- string literal, you have to escape the quotes.)</para></listitem>
-
-</varlistentry>
-
-
-<varlistentry><term><option>--argstr</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
-
- <listitem><para>This option is like <option>--arg</option>, only the
- value is not a Nix expression but a string. So instead of
- <literal>--arg system \"i686-linux\"</literal> (the outer quotes are
- to keep the shell happy) you can say <literal>--argstr system
- i686-linux</literal>.</para></listitem>
-
-</varlistentry>
-
-
-<varlistentry xml:id="opt-attr"><term><option>--attr</option> / <option>-A</option>
-<replaceable>attrPath</replaceable></term>
-
- <listitem><para>Select an attribute from the top-level Nix
- expression being evaluated. (<command>nix-env</command>,
- <command>nix-instantiate</command>, <command>nix-build</command> and
- <command>nix-shell</command> only.) The <emphasis>attribute
- path</emphasis> <replaceable>attrPath</replaceable> is a sequence of
- attribute names separated by dots. For instance, given a top-level
- Nix expression <replaceable>e</replaceable>, the attribute path
- <literal>xorg.xorgserver</literal> would cause the expression
- <literal><replaceable>e</replaceable>.xorg.xorgserver</literal> to
- be used. See <link linkend="refsec-nix-env-install-examples"><command>nix-env
- --install</command></link> for some concrete examples.</para>
-
- <para>In addition to attribute names, you can also specify array
- indices. For instance, the attribute path
- <literal>foo.3.bar</literal> selects the <literal>bar</literal>
- attribute of the fourth element of the array in the
- <literal>foo</literal> attribute of the top-level
- expression.</para></listitem>
-
-</varlistentry>
-
-
-<varlistentry><term><option>--expr</option> / <option>-E</option></term>
-
- <listitem><para>Interpret the command line arguments as a list of
- Nix expressions to be parsed and evaluated, rather than as a list
- of file names of Nix expressions.
- (<command>nix-instantiate</command>, <command>nix-build</command>
- and <command>nix-shell</command> only.)</para>
-
- <para>For <command>nix-shell</command>, this option is commonly used
- to give you a shell in which you can build the packages returned
- by the expression. If you want to get a shell which contain the
- <emphasis>built</emphasis> packages ready for use, give your
- expression to the <command>nix-shell -p</command> convenience flag
- instead.</para></listitem>
-
-</varlistentry>
-
-
-<varlistentry xml:id="opt-I"><term><option>-I</option> <replaceable>path</replaceable></term>
-
- <listitem><para>Add a path to the Nix expression search path. This
- option may be given multiple times. See the <envar linkend="env-NIX_PATH">NIX_PATH</envar> environment variable for
- information on the semantics of the Nix search path. Paths added
- through <option>-I</option> take precedence over
- <envar>NIX_PATH</envar>.</para></listitem>
-
-</varlistentry>
-
-
-<varlistentry><term><option>--option</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
-
- <listitem><para>Set the Nix configuration option
- <replaceable>name</replaceable> to <replaceable>value</replaceable>.
- This overrides settings in the Nix configuration file (see
- <citerefentry><refentrytitle>nix.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</para></listitem>
-
-</varlistentry>
-
-
-<varlistentry><term><option>--repair</option></term>
-
- <listitem><para>Fix corrupted or missing store paths by
- redownloading or rebuilding them. Note that this is slow because it
- requires computing a cryptographic hash of the contents of every
- path in the closure of the build. Also note the warning under
- <command>nix-store --repair-path</command>.</para></listitem>
-
-</varlistentry>
-
-
-</variablelist>
-
-
-</chapter>
-<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-common-env">
-
-<title>Common Environment Variables</title>
-
-
-<para>Most Nix commands interpret the following environment variables:</para>
-
-<variablelist xml:id="env-common">
-
-<varlistentry><term><envar>IN_NIX_SHELL</envar></term>
-
- <listitem><para>Indicator that tells if the current environment was set up by
- <command>nix-shell</command>. Since Nix 2.0 the values are
- <literal>"pure"</literal> and <literal>"impure"</literal></para></listitem>
-
-</varlistentry>
-
-<varlistentry xml:id="env-NIX_PATH"><term><envar>NIX_PATH</envar></term>
-
- <listitem>
-
- <para>A colon-separated list of directories used to look up Nix
- expressions enclosed in angle brackets (i.e.,
- <literal><<replaceable>path</replaceable>></literal>). For
- instance, the value
-
- <screen>
-/home/eelco/Dev:/etc/nixos</screen>
-
- will cause Nix to look for paths relative to
- <filename>/home/eelco/Dev</filename> and
- <filename>/etc/nixos</filename>, in this order. It is also
- possible to match paths against a prefix. For example, the value
-
- <screen>
-nixpkgs=/home/eelco/Dev/nixpkgs-branch:/etc/nixos</screen>
-
- will cause Nix to search for
- <literal><nixpkgs/<replaceable>path</replaceable>></literal> in
- <filename>/home/eelco/Dev/nixpkgs-branch/<replaceable>path</replaceable></filename>
- and
- <filename>/etc/nixos/nixpkgs/<replaceable>path</replaceable></filename>.</para>
-
- <para>If a path in the Nix search path starts with
- <literal>http://</literal> or <literal>https://</literal>, it is
- interpreted as the URL of a tarball that will be downloaded and
- unpacked to a temporary location. The tarball must consist of a
- single top-level directory. For example, setting
- <envar>NIX_PATH</envar> to
-
- <screen>
-nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-15.09.tar.gz</screen>
-
- tells Nix to download the latest revision in the Nixpkgs/NixOS
- 15.09 channel.</para>
-
- <para>A following shorthand can be used to refer to the official channels:
-
- <screen>nixpkgs=channel:nixos-15.09</screen>
- </para>
-
- <para>The search path can be extended using the <option linkend="opt-I">-I</option> option, which takes precedence over
- <envar>NIX_PATH</envar>.</para></listitem>
-
-</varlistentry>
-
-
-<varlistentry><term><envar>NIX_IGNORE_SYMLINK_STORE</envar></term>
-
- <listitem>
-
- <para>Normally, the Nix store directory (typically
- <filename>/nix/store</filename>) is not allowed to contain any
- symlink components. This is to prevent “impure” builds. Builders
- sometimes “canonicalise” paths by resolving all symlink components.
- Thus, builds on different machines (with
- <filename>/nix/store</filename> resolving to different locations)
- could yield different results. This is generally not a problem,
- except when builds are deployed to machines where
- <filename>/nix/store</filename> resolves differently. If you are
- sure that you’re not going to do that, you can set
- <envar>NIX_IGNORE_SYMLINK_STORE</envar> to <envar>1</envar>.</para>
-
- <para>Note that if you’re symlinking the Nix store so that you can
- put it on another file system than the root file system, on Linux
- you’re better off using <literal>bind</literal> mount points, e.g.,
-
- <screen>
-$ mkdir /nix
-$ mount -o bind /mnt/otherdisk/nix /nix</screen>
-
- Consult the <citerefentry><refentrytitle>mount</refentrytitle>
- <manvolnum>8</manvolnum></citerefentry> manual page for details.</para>
-
- </listitem>
-
-</varlistentry>
-
-
-<varlistentry><term><envar>NIX_STORE_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix store (default
- <filename><replaceable>prefix</replaceable>/store</filename>).</para></listitem>
-
-</varlistentry>
-
-
-<varlistentry><term><envar>NIX_DATA_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix static data
- directory (default
- <filename><replaceable>prefix</replaceable>/share</filename>).</para></listitem>
-
-</varlistentry>
-
-
-<varlistentry><term><envar>NIX_LOG_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix log directory
- (default <filename><replaceable>prefix</replaceable>/var/log/nix</filename>).</para></listitem>
-
-</varlistentry>
-
-
-<varlistentry><term><envar>NIX_STATE_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix state directory
- (default <filename><replaceable>prefix</replaceable>/var/nix</filename>).</para></listitem>
-
-</varlistentry>
-
-
-<varlistentry><term><envar>NIX_CONF_DIR</envar></term>
-
- <listitem><para>Overrides the location of the system Nix configuration
- directory (default
- <filename><replaceable>prefix</replaceable>/etc/nix</filename>).</para></listitem>
-
-</varlistentry>
-
-<varlistentry><term><envar>NIX_USER_CONF_FILES</envar></term>
-
- <listitem><para>Overrides the location of the user Nix configuration files
- to load from (defaults to the XDG spec locations). The variable is treated
- as a list separated by the <literal>:</literal> token.</para></listitem>
-
-</varlistentry>
-
-<varlistentry><term><envar>TMPDIR</envar></term>
-
- <listitem><para>Use the specified directory to store temporary
- files. In particular, this includes temporary build directories;
- these can take up substantial amounts of disk space. The default is
- <filename>/tmp</filename>.</para></listitem>
-
-</varlistentry>
-
-
-<varlistentry xml:id="envar-remote"><term><envar>NIX_REMOTE</envar></term>
-
- <listitem><para>This variable should be set to
- <literal>daemon</literal> if you want to use the Nix daemon to
- execute Nix operations. This is necessary in <link linkend="ssec-multi-user">multi-user Nix installations</link>.
- If the Nix daemon's Unix socket is at some non-standard path,
- this variable should be set to <literal>unix://path/to/socket</literal>.
- Otherwise, it should be left unset.</para></listitem>
-
-</varlistentry>
-
-
-<varlistentry><term><envar>NIX_SHOW_STATS</envar></term>
-
- <listitem><para>If set to <literal>1</literal>, Nix will print some
- evaluation statistics, such as the number of values
- allocated.</para></listitem>
-
-</varlistentry>
-
-
-<varlistentry><term><envar>NIX_COUNT_CALLS</envar></term>
-
- <listitem><para>If set to <literal>1</literal>, Nix will print how
- often functions were called during Nix expression evaluation. This
- is useful for profiling your Nix expressions.</para></listitem>
-
-</varlistentry>
-
-
-<varlistentry><term><envar>GC_INITIAL_HEAP_SIZE</envar></term>
-
- <listitem><para>If Nix has been configured to use the Boehm garbage
- collector, this variable sets the initial size of the heap in bytes.
- It defaults to 384 MiB. Setting it to a low value reduces memory
- consumption, but will increase runtime due to the overhead of
- garbage collection.</para></listitem>
-
-</varlistentry>
-
-
-</variablelist>
-
-
-</chapter>
-<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-main-commands">
-
-<title>Main Commands</title>
-
-<para>This section lists commands and options that you can use when you
-work with Nix.</para>
-
-<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-nix-env">
-
-<refmeta>
- <refentrytitle>nix-env</refentrytitle>
- <manvolnum>1</manvolnum>
- <refmiscinfo class="source">Nix</refmiscinfo>
- <refmiscinfo class="version">3.0</refmiscinfo>
-</refmeta>
-
-<refnamediv>
- <refname>nix-env</refname>
- <refpurpose>manipulate or query Nix user environments</refpurpose>
-</refnamediv>
-
-<refsynopsisdiv>
- <cmdsynopsis>
- <command>nix-env</command>
- <arg xmlns="http://docbook.org/ns/docbook"><option>--help</option></arg><arg xmlns="http://docbook.org/ns/docbook"><option>--version</option></arg><arg xmlns="http://docbook.org/ns/docbook" rep="repeat">
- <group choice="req">
- <arg choice="plain"><option>--verbose</option></arg>
- <arg choice="plain"><option>-v</option></arg>
- </group>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <arg choice="plain"><option>--quiet</option></arg>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <option>--log-format</option>
- <replaceable>format</replaceable>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <group choice="plain">
- <arg choice="plain"><option>--no-build-output</option></arg>
- <arg choice="plain"><option>-Q</option></arg>
- </group>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <group choice="req">
- <arg choice="plain"><option>--max-jobs</option></arg>
- <arg choice="plain"><option>-j</option></arg>
- </group>
- <replaceable>number</replaceable>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <option>--cores</option>
- <replaceable>number</replaceable>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <option>--max-silent-time</option>
- <replaceable>number</replaceable>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <option>--timeout</option>
- <replaceable>number</replaceable>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <group choice="plain">
- <arg choice="plain"><option>--keep-going</option></arg>
- <arg choice="plain"><option>-k</option></arg>
- </group>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <group choice="plain">
- <arg choice="plain"><option>--keep-failed</option></arg>
- <arg choice="plain"><option>-K</option></arg>
- </group>
-</arg><arg xmlns="http://docbook.org/ns/docbook"><option>--fallback</option></arg><arg xmlns="http://docbook.org/ns/docbook"><option>--readonly-mode</option></arg><arg xmlns="http://docbook.org/ns/docbook">
- <option>-I</option>
- <replaceable>path</replaceable>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <option>--option</option>
- <replaceable>name</replaceable>
- <replaceable>value</replaceable>
-</arg><sbr xmlns="http://docbook.org/ns/docbook"/>
- <arg><option>--arg</option> <replaceable>name</replaceable> <replaceable>value</replaceable></arg>
- <arg><option>--argstr</option> <replaceable>name</replaceable> <replaceable>value</replaceable></arg>
- <arg>
- <group choice="req">
- <arg choice="plain"><option>--file</option></arg>
- <arg choice="plain"><option>-f</option></arg>
- </group>
- <replaceable>path</replaceable>
- </arg>
- <arg>
- <group choice="req">
- <arg choice="plain"><option>--profile</option></arg>
- <arg choice="plain"><option>-p</option></arg>
- </group>
- <replaceable>path</replaceable>
- </arg>
- <arg>
- <arg choice="plain"><option>--system-filter</option></arg>
- <replaceable>system</replaceable>
- </arg>
- <arg><option>--dry-run</option></arg>
- <arg choice="plain"><replaceable>operation</replaceable></arg>
- <arg rep="repeat"><replaceable>options</replaceable></arg>
- <arg rep="repeat"><replaceable>arguments</replaceable></arg>
- </cmdsynopsis>
-</refsynopsisdiv>
-
-
-<refsection><title>Description</title>
-
-<para>The command <command>nix-env</command> is used to manipulate Nix
-user environments. User environments are sets of software packages
-available to a user at some point in time. In other words, they are a
-synthesised view of the programs available in the Nix store. There
-may be many user environments: different users can have different
-environments, and individual users can switch between different
-environments.</para>
-
-<para><command>nix-env</command> takes exactly one
-<emphasis>operation</emphasis> flag which indicates the subcommand to
-be performed. These are documented below.</para>
-
-</refsection>
-
-
-
-<!--######################################################################-->
-
-<refsection><title>Selectors</title>
-
-<para>Several commands, such as <command>nix-env -q</command> and
-<command>nix-env -i</command>, take a list of arguments that specify
-the packages on which to operate. These are extended regular
-expressions that must match the entire name of the package. (For
-details on regular expressions, see
-<citerefentry><refentrytitle>regex</refentrytitle><manvolnum>7</manvolnum></citerefentry>.)
-The match is case-sensitive. The regular expression can optionally be
-followed by a dash and a version number; if omitted, any version of
-the package will match. Here are some examples:
-
-<variablelist>
-
- <varlistentry>
- <term><literal>firefox</literal></term>
- <listitem><para>Matches the package name
- <literal>firefox</literal> and any version.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><literal>firefox-32.0</literal></term>
- <listitem><para>Matches the package name
- <literal>firefox</literal> and version
- <literal>32.0</literal>.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><literal>gtk\\+</literal></term>
- <listitem><para>Matches the package name
- <literal>gtk+</literal>. The <literal>+</literal> character must
- be escaped using a backslash to prevent it from being interpreted
- as a quantifier, and the backslash must be escaped in turn with
- another backslash to ensure that the shell passes it
- on.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><literal>.\*</literal></term>
- <listitem><para>Matches any package name. This is the default for
- most commands.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><literal>'.*zip.*'</literal></term>
- <listitem><para>Matches any package name containing the string
- <literal>zip</literal>. Note the dots: <literal>'*zip*'</literal>
- does not work, because in a regular expression, the character
- <literal>*</literal> is interpreted as a
- quantifier.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><literal>'.*(firefox|chromium).*'</literal></term>
- <listitem><para>Matches any package name containing the strings
- <literal>firefox</literal> or
- <literal>chromium</literal>.</para></listitem>
- </varlistentry>
-
-</variablelist>
-
-</para>
-
-</refsection>
-
-
-
-<!--######################################################################-->
-
-<refsection><title>Common options</title>
-
-<para>This section lists the options that are common to all
-operations. These options are allowed for every subcommand, though
-they may not always have an effect. <phrase condition="manual">See
-also <xref linkend="sec-common-options"/>.</phrase></para>
-
-<variablelist>
-
- <varlistentry><term><option>--file</option> / <option>-f</option> <replaceable>path</replaceable></term>
-
- <listitem><para>Specifies the Nix expression (designated below as
- the <emphasis>active Nix expression</emphasis>) used by the
- <option>--install</option>, <option>--upgrade</option>, and
- <option>--query --available</option> operations to obtain
- derivations. The default is
- <filename>~/.nix-defexpr</filename>.</para>
-
- <para>If the argument starts with <literal>http://</literal> or
- <literal>https://</literal>, it is interpreted as the URL of a
- tarball that will be downloaded and unpacked to a temporary
- location. The tarball must include a single top-level directory
- containing at least a file named <filename>default.nix</filename>.</para>
-
- </listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--profile</option> / <option>-p</option> <replaceable>path</replaceable></term>
-
- <listitem><para>Specifies the profile to be used by those
- operations that operate on a profile (designated below as the
- <emphasis>active profile</emphasis>). A profile is a sequence of
- user environments called <emphasis>generations</emphasis>, one of
- which is the <emphasis>current
- generation</emphasis>.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--dry-run</option></term>
-
- <listitem><para>For the <option>--install</option>,
- <option>--upgrade</option>, <option>--uninstall</option>,
- <option>--switch-generation</option>,
- <option>--delete-generations</option> and
- <option>--rollback</option> operations, this flag will cause
- <command>nix-env</command> to print what
- <emphasis>would</emphasis> be done if this flag had not been
- specified, without actually doing it.</para>
-
- <para><option>--dry-run</option> also prints out which paths will
- be <link linkend="gloss-substitute">substituted</link> (i.e.,
- downloaded) and which paths will be built from source (because no
- substitute is available).</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--system-filter</option> <replaceable>system</replaceable></term>
-
- <listitem><para>By default, operations such as <option>--query
- --available</option> show derivations matching any platform. This
- option allows you to use derivations for the specified platform
- <replaceable>system</replaceable>.</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-<variablelist condition="manpage">
- <varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--help</option></term>
-
- <listitem><para>Prints out a summary of the command syntax and
- exits.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--version</option></term>
-
- <listitem><para>Prints out the Nix version number on standard output
- and exits.</para></listitem>
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--verbose</option> / <option>-v</option></term>
-
- <listitem>
-
- <para>Increases the level of verbosity of diagnostic messages
- printed on standard error. For each Nix operation, the information
- printed on standard output is well-defined; any diagnostic
- information is printed on standard error, never on standard
- output.</para>
-
- <para>This option may be specified repeatedly. Currently, the
- following verbosity levels exist:</para>
-
- <variablelist>
-
- <varlistentry><term>0</term>
- <listitem><para>“Errors only”: only print messages
- explaining why the Nix invocation failed.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>1</term>
- <listitem><para>“Informational”: print
- <emphasis>useful</emphasis> messages about what Nix is doing.
- This is the default.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>2</term>
- <listitem><para>“Talkative”: print more informational
- messages.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>3</term>
- <listitem><para>“Chatty”: print even more
- informational messages.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>4</term>
- <listitem><para>“Debug”: print debug
- information.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>5</term>
- <listitem><para>“Vomit”: print vast amounts of debug
- information.</para></listitem>
- </varlistentry>
-
- </variablelist>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--quiet</option></term>
-
- <listitem>
-
- <para>Decreases the level of verbosity of diagnostic messages
- printed on standard error. This is the inverse option to
- <option>-v</option> / <option>--verbose</option>.
- </para>
-
- <para>This option may be specified repeatedly. See the previous
- verbosity levels list.</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-log-format"><term><option>--log-format</option> <replaceable>format</replaceable></term>
-
- <listitem>
-
- <para>This option can be used to change the output of the log format, with
- <replaceable>format</replaceable> being one of:</para>
-
- <variablelist>
-
- <varlistentry><term>raw</term>
- <listitem><para>This is the raw format, as outputted by nix-build.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>internal-json</term>
- <listitem><para>Outputs the logs in a structured manner. NOTE: the json schema is not guarantees to be stable between releases.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>bar</term>
- <listitem><para>Only display a progress bar during the builds.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>bar-with-logs</term>
- <listitem><para>Display the raw logs, with the progress bar at the bottom.</para></listitem>
- </varlistentry>
-
- </variablelist>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--no-build-output</option> / <option>-Q</option></term>
-
- <listitem><para>By default, output written by builders to standard
- output and standard error is echoed to the Nix command's standard
- error. This option suppresses this behaviour. Note that the
- builder's standard output and error are always written to a log file
- in
- <filename><replaceable>prefix</replaceable>/nix/var/log/nix</filename>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-max-jobs"><term><option>--max-jobs</option> / <option>-j</option>
-<replaceable>number</replaceable></term>
-
- <listitem>
-
- <para>Sets the maximum number of build jobs that Nix will
- perform in parallel to the specified number. Specify
- <literal>auto</literal> to use the number of CPUs in the system.
- The default is specified by the <link linkend="conf-max-jobs"><literal>max-jobs</literal></link>
- configuration setting, which itself defaults to
- <literal>1</literal>. A higher value is useful on SMP systems or to
- exploit I/O latency.</para>
-
- <para> Setting it to <literal>0</literal> disallows building on the local
- machine, which is useful when you want builds to happen only on remote
- builders.</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-cores"><term><option>--cores</option></term>
-
- <listitem><para>Sets the value of the <envar>NIX_BUILD_CORES</envar>
- environment variable in the invocation of builders. Builders can
- use this variable at their discretion to control the maximum amount
- of parallelism. For instance, in Nixpkgs, if the derivation
- attribute <varname>enableParallelBuilding</varname> is set to
- <literal>true</literal>, the builder passes the
- <option>-j<replaceable>N</replaceable></option> flag to GNU Make.
- It defaults to the value of the <link linkend="conf-cores"><literal>cores</literal></link>
- configuration setting, if set, or <literal>1</literal> otherwise.
- The value <literal>0</literal> means that the builder should use all
- available CPU cores in the system.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-max-silent-time"><term><option>--max-silent-time</option></term>
-
- <listitem><para>Sets the maximum number of seconds that a builder
- can go without producing any data on standard output or standard
- error. The default is specified by the <link linkend="conf-max-silent-time"><literal>max-silent-time</literal></link>
- configuration setting. <literal>0</literal> means no
- time-out.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-timeout"><term><option>--timeout</option></term>
-
- <listitem><para>Sets the maximum number of seconds that a builder
- can run. The default is specified by the <link linkend="conf-timeout"><literal>timeout</literal></link>
- configuration setting. <literal>0</literal> means no
- timeout.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--keep-going</option> / <option>-k</option></term>
-
- <listitem><para>Keep going in case of failed builds, to the
- greatest extent possible. That is, if building an input of some
- derivation fails, Nix will still build the other inputs, but not the
- derivation itself. Without this option, Nix stops if any build
- fails (except for builds of substitutes), possibly killing builds in
- progress (in case of parallel or distributed builds).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--keep-failed</option> / <option>-K</option></term>
-
- <listitem><para>Specifies that in case of a build failure, the
- temporary directory (usually in <filename>/tmp</filename>) in which
- the build takes place should not be deleted. The path of the build
- directory is printed as an informational message.
- </para>
- </listitem>
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--fallback</option></term>
-
- <listitem>
-
- <para>Whenever Nix attempts to build a derivation for which
- substitutes are known for each output path, but realising the output
- paths through the substitutes fails, fall back on building the
- derivation.</para>
-
- <para>The most common scenario in which this is useful is when we
- have registered substitutes in order to perform binary distribution
- from, say, a network repository. If the repository is down, the
- realisation of the derivation will fail. When this option is
- specified, Nix will build the derivation instead. Thus,
- installation from binaries falls back on installation from source.
- This option is not the default since it is generally not desirable
- for a transient failure in obtaining the substitutes to lead to a
- full build from source (with the related consumption of
- resources).</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--no-build-hook</option></term>
-
- <listitem>
-
- <para>Disables the build hook mechanism. This allows to ignore remote
- builders if they are setup on the machine.</para>
-
- <para>It's useful in cases where the bandwidth between the client and the
- remote builder is too low. In that case it can take more time to upload the
- sources to the remote builder and fetch back the result than to do the
- computation locally.</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--readonly-mode</option></term>
-
- <listitem><para>When this option is used, no attempt is made to open
- the Nix database. Most Nix operations do need database access, so
- those operations will fail.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--arg</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
-
- <listitem><para>This option is accepted by
- <command>nix-env</command>, <command>nix-instantiate</command>,
- <command>nix-shell</command> and <command>nix-build</command>.
- When evaluating Nix expressions, the expression evaluator will
- automatically try to call functions that
- it encounters. It can automatically call functions for which every
- argument has a <link linkend="ss-functions">default value</link>
- (e.g., <literal>{ <replaceable>argName</replaceable> ?
- <replaceable>defaultValue</replaceable> }:
- <replaceable>...</replaceable></literal>). With
- <option>--arg</option>, you can also call functions that have
- arguments without a default value (or override a default value).
- That is, if the evaluator encounters a function with an argument
- named <replaceable>name</replaceable>, it will call it with value
- <replaceable>value</replaceable>.</para>
-
- <para>For instance, the top-level <literal>default.nix</literal> in
- Nixpkgs is actually a function:
-
-<programlisting>
-{ # The system (e.g., `i686-linux') for which to build the packages.
- system ? builtins.currentSystem
- <replaceable>...</replaceable>
-}: <replaceable>...</replaceable></programlisting>
-
- So if you call this Nix expression (e.g., when you do
- <literal>nix-env -i <replaceable>pkgname</replaceable></literal>),
- the function will be called automatically using the value <link linkend="builtin-currentSystem"><literal>builtins.currentSystem</literal></link>
- for the <literal>system</literal> argument. You can override this
- using <option>--arg</option>, e.g., <literal>nix-env -i
- <replaceable>pkgname</replaceable> --arg system
- \"i686-freebsd\"</literal>. (Note that since the argument is a Nix
- string literal, you have to escape the quotes.)</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--argstr</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
-
- <listitem><para>This option is like <option>--arg</option>, only the
- value is not a Nix expression but a string. So instead of
- <literal>--arg system \"i686-linux\"</literal> (the outer quotes are
- to keep the shell happy) you can say <literal>--argstr system
- i686-linux</literal>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-attr"><term><option>--attr</option> / <option>-A</option>
-<replaceable>attrPath</replaceable></term>
-
- <listitem><para>Select an attribute from the top-level Nix
- expression being evaluated. (<command>nix-env</command>,
- <command>nix-instantiate</command>, <command>nix-build</command> and
- <command>nix-shell</command> only.) The <emphasis>attribute
- path</emphasis> <replaceable>attrPath</replaceable> is a sequence of
- attribute names separated by dots. For instance, given a top-level
- Nix expression <replaceable>e</replaceable>, the attribute path
- <literal>xorg.xorgserver</literal> would cause the expression
- <literal><replaceable>e</replaceable>.xorg.xorgserver</literal> to
- be used. See <link linkend="refsec-nix-env-install-examples"><command>nix-env
- --install</command></link> for some concrete examples.</para>
-
- <para>In addition to attribute names, you can also specify array
- indices. For instance, the attribute path
- <literal>foo.3.bar</literal> selects the <literal>bar</literal>
- attribute of the fourth element of the array in the
- <literal>foo</literal> attribute of the top-level
- expression.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--expr</option> / <option>-E</option></term>
-
- <listitem><para>Interpret the command line arguments as a list of
- Nix expressions to be parsed and evaluated, rather than as a list
- of file names of Nix expressions.
- (<command>nix-instantiate</command>, <command>nix-build</command>
- and <command>nix-shell</command> only.)</para>
-
- <para>For <command>nix-shell</command>, this option is commonly used
- to give you a shell in which you can build the packages returned
- by the expression. If you want to get a shell which contain the
- <emphasis>built</emphasis> packages ready for use, give your
- expression to the <command>nix-shell -p</command> convenience flag
- instead.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-I"><term><option>-I</option> <replaceable>path</replaceable></term>
-
- <listitem><para>Add a path to the Nix expression search path. This
- option may be given multiple times. See the <envar linkend="env-NIX_PATH">NIX_PATH</envar> environment variable for
- information on the semantics of the Nix search path. Paths added
- through <option>-I</option> take precedence over
- <envar>NIX_PATH</envar>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--option</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
-
- <listitem><para>Set the Nix configuration option
- <replaceable>name</replaceable> to <replaceable>value</replaceable>.
- This overrides settings in the Nix configuration file (see
- <citerefentry><refentrytitle>nix.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--repair</option></term>
-
- <listitem><para>Fix corrupted or missing store paths by
- redownloading or rebuilding them. Note that this is slow because it
- requires computing a cryptographic hash of the contents of every
- path in the closure of the build. Also note the warning under
- <command>nix-store --repair-path</command>.</para></listitem>
-
-</varlistentry>
-</variablelist>
-
-</refsection>
-
-
-
-<!--######################################################################-->
-
-<refsection><title>Files</title>
-
-<variablelist>
-
- <varlistentry><term><filename>~/.nix-defexpr</filename></term>
-
- <listitem><para>The source for the default Nix
- expressions used by the <option>--install</option>,
- <option>--upgrade</option>, and <option>--query
- --available</option> operations to obtain derivations. The
- <option>--file</option> option may be used to override this
- default.</para>
-
- <para>If <filename>~/.nix-defexpr</filename> is a file,
- it is loaded as a Nix expression. If the expression
- is a set, it is used as the default Nix expression.
- If the expression is a function, an empty set is passed
- as argument and the return value is used as
- the default Nix expression.</para>
-
- <para>If <filename>~/.nix-defexpr</filename> is a directory
- containing a <filename>default.nix</filename> file, that file
- is loaded as in the above paragraph.</para>
-
- <para>If <filename>~/.nix-defexpr</filename> is a directory without
- a <filename>default.nix</filename> file, then its contents
- (both files and subdirectories) are loaded as Nix expressions.
- The expressions are combined into a single set, each expression
- under an attribute with the same name as the original file
- or subdirectory.
- </para>
-
- <para>For example, if <filename>~/.nix-defexpr</filename> contains
- two files, <filename>foo.nix</filename> and <filename>bar.nix</filename>,
- then the default Nix expression will essentially be
-
-<programlisting>
-{
- foo = import ~/.nix-defexpr/foo.nix;
- bar = import ~/.nix-defexpr/bar.nix;
-}</programlisting>
-
- </para>
-
- <para>The file <filename>manifest.nix</filename> is always ignored.
- Subdirectories without a <filename>default.nix</filename> file
- are traversed recursively in search of more Nix expressions,
- but the names of these intermediate directories are not
- added to the attribute paths of the default Nix expression.</para>
-
- <para>The command <command>nix-channel</command> places symlinks
- to the downloaded Nix expressions from each subscribed channel in
- this directory.</para>
- </listitem>
-
- </varlistentry>
-
- <varlistentry><term><filename>~/.nix-profile</filename></term>
-
- <listitem><para>A symbolic link to the user's current profile. By
- default, this symlink points to
- <filename><replaceable>prefix</replaceable>/var/nix/profiles/default</filename>.
- The <envar>PATH</envar> environment variable should include
- <filename>~/.nix-profile/bin</filename> for the user environment
- to be visible to the user.</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-</refsection>
-
-
-
-<!--######################################################################-->
-
-<refsection xml:id="rsec-nix-env-install"><title>Operation <option>--install</option></title>
-
-<refsection><title>Synopsis</title>
-
-<cmdsynopsis>
- <command>nix-env</command>
- <group choice="req">
- <arg choice="plain"><option>--install</option></arg>
- <arg choice="plain"><option>-i</option></arg>
- </group>
- <arg xmlns="http://docbook.org/ns/docbook">
- <group choice="req">
- <arg choice="plain"><option>--prebuilt-only</option></arg>
- <arg choice="plain"><option>-b</option></arg>
- </group>
- </arg><arg xmlns="http://docbook.org/ns/docbook">
- <group choice="req">
- <arg choice="plain"><option>--attr</option></arg>
- <arg choice="plain"><option>-A</option></arg>
- </group>
- </arg><arg xmlns="http://docbook.org/ns/docbook"><option>--from-expression</option></arg><arg xmlns="http://docbook.org/ns/docbook"><option>-E</option></arg><arg xmlns="http://docbook.org/ns/docbook"><option>--from-profile</option> <replaceable>path</replaceable></arg>
- <group choice="opt">
- <arg choice="plain"><option>--preserve-installed</option></arg>
- <arg choice="plain"><option>-P</option></arg>
- </group>
- <group choice="opt">
- <arg choice="plain"><option>--remove-all</option></arg>
- <arg choice="plain"><option>-r</option></arg>
- </group>
- <arg choice="plain" rep="repeat"><replaceable>args</replaceable></arg>
-</cmdsynopsis>
-
-</refsection>
-
-
-<refsection><title>Description</title>
-
-<para>The install operation creates a new user environment, based on
-the current generation of the active profile, to which a set of store
-paths described by <replaceable>args</replaceable> is added. The
-arguments <replaceable>args</replaceable> map to store paths in a
-number of possible ways:
-
-<itemizedlist>
-
- <listitem><para>By default, <replaceable>args</replaceable> is a set
- of derivation names denoting derivations in the active Nix
- expression. These are realised, and the resulting output paths are
- installed. Currently installed derivations with a name equal to the
- name of a derivation being added are removed unless the option
- <option>--preserve-installed</option> is
- specified.</para>
-
- <para>If there are multiple derivations matching a name in
- <replaceable>args</replaceable> that have the same name (e.g.,
- <literal>gcc-3.3.6</literal> and <literal>gcc-4.1.1</literal>), then
- the derivation with the highest <emphasis>priority</emphasis> is
- used. A derivation can define a priority by declaring the
- <varname>meta.priority</varname> attribute. This attribute should
- be a number, with a higher value denoting a lower priority. The
- default priority is <literal>0</literal>.</para>
-
- <para>If there are multiple matching derivations with the same
- priority, then the derivation with the highest version will be
- installed.</para>
-
- <para>You can force the installation of multiple derivations with
- the same name by being specific about the versions. For instance,
- <literal>nix-env -i gcc-3.3.6 gcc-4.1.1</literal> will install both
- version of GCC (and will probably cause a user environment
- conflict!).</para></listitem>
-
- <listitem><para>If <link linkend="opt-attr"><option>--attr</option></link>
- (<option>-A</option>) is specified, the arguments are
- <emphasis>attribute paths</emphasis> that select attributes from the
- top-level Nix expression. This is faster than using derivation
- names and unambiguous. To find out the attribute paths of available
- packages, use <literal>nix-env -qaP</literal>.</para></listitem>
-
- <listitem><para>If <option>--from-profile</option>
- <replaceable>path</replaceable> is given,
- <replaceable>args</replaceable> is a set of names denoting installed
- store paths in the profile <replaceable>path</replaceable>. This is
- an easy way to copy user environment elements from one profile to
- another.</para></listitem>
-
- <listitem><para>If <option>--from-expression</option> is given,
- <replaceable>args</replaceable> are Nix <link linkend="ss-functions">functions</link> that are called with the
- active Nix expression as their single argument. The derivations
- returned by those function calls are installed. This allows
- derivations to be specified in an unambiguous way, which is necessary
- if there are multiple derivations with the same
- name.</para></listitem>
-
- <listitem><para>If <replaceable>args</replaceable> are store
- derivations, then these are <link linkend="rsec-nix-store-realise">realised</link>, and the resulting
- output paths are installed.</para></listitem>
-
- <listitem><para>If <replaceable>args</replaceable> are store paths
- that are not store derivations, then these are <link linkend="rsec-nix-store-realise">realised</link> and
- installed.</para></listitem>
-
- <listitem><para>By default all outputs are installed for each derivation.
- That can be reduced by setting <literal>meta.outputsToInstall</literal>.
- </para></listitem> <!-- TODO: link nixpkgs docs on the ability to override those. -->
-
-</itemizedlist>
-
-</para>
-
-</refsection>
-
-
-<refsection><title>Flags</title>
-
-<variablelist>
-
- <varlistentry><term><option>--prebuilt-only</option> / <option>-b</option></term>
-
- <listitem><para>Use only derivations for which a substitute is
- registered, i.e., there is a pre-built binary available that can
- be downloaded in lieu of building the derivation. Thus, no
- packages will be built from source.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--preserve-installed</option></term>
- <term><option>-P</option></term>
-
- <listitem><para>Do not remove derivations with a name matching one
- of the derivations being installed. Usually, trying to have two
- versions of the same package installed in the same generation of a
- profile will lead to an error in building the generation, due to
- file name clashes between the two versions. However, this is not
- the case for all packages.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--remove-all</option></term>
- <term><option>-r</option></term>
-
- <listitem><para>Remove all previously installed packages first.
- This is equivalent to running <literal>nix-env -e '.*'</literal>
- first, except that everything happens in a single
- transaction.</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-</refsection>
-
-
-<refsection xml:id="refsec-nix-env-install-examples"><title>Examples</title>
-
-<para>To install a specific version of <command>gcc</command> from the
-active Nix expression:
-
-<screen>
-$ nix-env --install gcc-3.3.2
-installing `gcc-3.3.2'
-uninstalling `gcc-3.1'</screen>
-
-Note the previously installed version is removed, since
-<option>--preserve-installed</option> was not specified.</para>
-
-<para>To install an arbitrary version:
-
-<screen>
-$ nix-env --install gcc
-installing `gcc-3.3.2'</screen>
-
-</para>
-
-<para>To install using a specific attribute:
-
-<screen>
-$ nix-env -i -A gcc40mips
-$ nix-env -i -A xorg.xorgserver</screen>
-
-</para>
-
-<para>To install all derivations in the Nix expression <filename>foo.nix</filename>:
-
-<screen>
-$ nix-env -f ~/foo.nix -i '.*'</screen>
-
-</para>
-
-<para>To copy the store path with symbolic name <literal>gcc</literal>
-from another profile:
-
-<screen>
-$ nix-env -i --from-profile /nix/var/nix/profiles/foo gcc</screen>
-
-</para>
-
-<para>To install a specific store derivation (typically created by
-<command>nix-instantiate</command>):
-
-<screen>
-$ nix-env -i /nix/store/fibjb1bfbpm5mrsxc4mh2d8n37sxh91i-gcc-3.4.3.drv</screen>
-
-</para>
-
-<para>To install a specific output path:
-
-<screen>
-$ nix-env -i /nix/store/y3cgx0xj1p4iv9x0pnnmdhr8iyg741vk-gcc-3.4.3</screen>
-
-</para>
-
-<para>To install from a Nix expression specified on the command-line:
-
-<screen>
-$ nix-env -f ./foo.nix -i -E \
- 'f: (f {system = "i686-linux";}).subversionWithJava'</screen>
-
-I.e., this evaluates to <literal>(f: (f {system =
-"i686-linux";}).subversionWithJava) (import ./foo.nix)</literal>, thus
-selecting the <literal>subversionWithJava</literal> attribute from the
-set returned by calling the function defined in
-<filename>./foo.nix</filename>.</para>
-
-<para>A dry-run tells you which paths will be downloaded or built from
-source:
-
-<screen>
-$ nix-env -f '<nixpkgs>' -iA hello --dry-run
-(dry run; not doing anything)
-installing ‘hello-2.10’
-this path will be fetched (0.04 MiB download, 0.19 MiB unpacked):
- /nix/store/wkhdf9jinag5750mqlax6z2zbwhqb76n-hello-2.10
- <replaceable>...</replaceable></screen>
-
-</para>
-
-<para>To install Firefox from the latest revision in the Nixpkgs/NixOS
-14.12 channel:
-
-<screen>
-$ nix-env -f https://github.com/NixOS/nixpkgs/archive/nixos-14.12.tar.gz -iA firefox
-</screen>
-
-</para>
-
-</refsection>
-
-</refsection>
-
-
-
-<!--######################################################################-->
-
-<refsection xml:id="rsec-nix-env-upgrade"><title>Operation <option>--upgrade</option></title>
-
-<refsection><title>Synopsis</title>
-
-<cmdsynopsis>
- <command>nix-env</command>
- <group choice="req">
- <arg choice="plain"><option>--upgrade</option></arg>
- <arg choice="plain"><option>-u</option></arg>
- </group>
- <arg xmlns="http://docbook.org/ns/docbook">
- <group choice="req">
- <arg choice="plain"><option>--prebuilt-only</option></arg>
- <arg choice="plain"><option>-b</option></arg>
- </group>
- </arg><arg xmlns="http://docbook.org/ns/docbook">
- <group choice="req">
- <arg choice="plain"><option>--attr</option></arg>
- <arg choice="plain"><option>-A</option></arg>
- </group>
- </arg><arg xmlns="http://docbook.org/ns/docbook"><option>--from-expression</option></arg><arg xmlns="http://docbook.org/ns/docbook"><option>-E</option></arg><arg xmlns="http://docbook.org/ns/docbook"><option>--from-profile</option> <replaceable>path</replaceable></arg>
- <group choice="opt">
- <arg choice="plain"><option>--lt</option></arg>
- <arg choice="plain"><option>--leq</option></arg>
- <arg choice="plain"><option>--eq</option></arg>
- <arg choice="plain"><option>--always</option></arg>
- </group>
- <arg choice="plain" rep="repeat"><replaceable>args</replaceable></arg>
-</cmdsynopsis>
-
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>The upgrade operation creates a new user environment, based on
-the current generation of the active profile, in which all store paths
-are replaced for which there are newer versions in the set of paths
-described by <replaceable>args</replaceable>. Paths for which there
-are no newer versions are left untouched; this is not an error. It is
-also not an error if an element of <replaceable>args</replaceable>
-matches no installed derivations.</para>
-
-<para>For a description of how <replaceable>args</replaceable> is
-mapped to a set of store paths, see <link linkend="rsec-nix-env-install"><option>--install</option></link>. If
-<replaceable>args</replaceable> describes multiple store paths with
-the same symbolic name, only the one with the highest version is
-installed.</para>
-
-</refsection>
-
-<refsection><title>Flags</title>
-
-<variablelist>
-
- <varlistentry><term><option>--lt</option></term>
-
- <listitem><para>Only upgrade a derivation to newer versions. This
- is the default.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--leq</option></term>
-
- <listitem><para>In addition to upgrading to newer versions, also
- “upgrade” to derivations that have the same version. Version are
- not a unique identification of a derivation, so there may be many
- derivations that have the same version. This flag may be useful
- to force “synchronisation” between the installed and available
- derivations.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--eq</option></term>
-
- <listitem><para><emphasis>Only</emphasis> “upgrade” to derivations
- that have the same version. This may not seem very useful, but it
- actually is, e.g., when there is a new release of Nixpkgs and you
- want to replace installed applications with the same versions
- built against newer dependencies (to reduce the number of
- dependencies floating around on your system).</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--always</option></term>
-
- <listitem><para>In addition to upgrading to newer versions, also
- “upgrade” to derivations that have the same or a lower version.
- I.e., derivations may actually be downgraded depending on what is
- available in the active Nix expression.</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-<para>For the other flags, see <option linkend="rsec-nix-env-install">--install</option>.</para>
-
-</refsection>
-
-<refsection><title>Examples</title>
-
-<screen>
-$ nix-env --upgrade gcc
-upgrading `gcc-3.3.1' to `gcc-3.4'
-
-$ nix-env -u gcc-3.3.2 --always <lineannotation>(switch to a specific version)</lineannotation>
-upgrading `gcc-3.4' to `gcc-3.3.2'
-
-$ nix-env --upgrade pan
-<lineannotation>(no upgrades available, so nothing happens)</lineannotation>
-
-$ nix-env -u <lineannotation>(try to upgrade everything)</lineannotation>
-upgrading `hello-2.1.2' to `hello-2.1.3'
-upgrading `mozilla-1.2' to `mozilla-1.4'</screen>
-
-</refsection>
-
-<refsection xml:id="ssec-version-comparisons"><title>Versions</title>
-
-<para>The upgrade operation determines whether a derivation
-<varname>y</varname> is an upgrade of a derivation
-<varname>x</varname> by looking at their respective
-<literal>name</literal> attributes. The names (e.g.,
-<literal>gcc-3.3.1</literal> are split into two parts: the package
-name (<literal>gcc</literal>), and the version
-(<literal>3.3.1</literal>). The version part starts after the first
-dash not followed by a letter. <varname>x</varname> is considered an
-upgrade of <varname>y</varname> if their package names match, and the
-version of <varname>y</varname> is higher that that of
-<varname>x</varname>.</para>
-
-<para>The versions are compared by splitting them into contiguous
-components of numbers and letters. E.g., <literal>3.3.1pre5</literal>
-is split into <literal>[3, 3, 1, "pre", 5]</literal>. These lists are
-then compared lexicographically (from left to right). Corresponding
-components <varname>a</varname> and <varname>b</varname> are compared
-as follows. If they are both numbers, integer comparison is used. If
-<varname>a</varname> is an empty string and <varname>b</varname> is a
-number, <varname>a</varname> is considered less than
-<varname>b</varname>. The special string component
-<literal>pre</literal> (for <emphasis>pre-release</emphasis>) is
-considered to be less than other components. String components are
-considered less than number components. Otherwise, they are compared
-lexicographically (i.e., using case-sensitive string comparison).</para>
-
-<para>This is illustrated by the following examples:
-
-<screen>
-1.0 < 2.3
-2.1 < 2.3
-2.3 = 2.3
-2.5 > 2.3
-3.1 > 2.3
-2.3.1 > 2.3
-2.3.1 > 2.3a
-2.3pre1 < 2.3
-2.3pre3 < 2.3pre12
-2.3a < 2.3c
-2.3pre1 < 2.3c
-2.3pre1 < 2.3q</screen>
-
-</para>
-
-</refsection>
-
-</refsection>
-
-
-
-<!--######################################################################-->
-
-<refsection><title>Operation <option>--uninstall</option></title>
-
-<refsection><title>Synopsis</title>
-
-<cmdsynopsis>
- <command>nix-env</command>
- <group choice="req">
- <arg choice="plain"><option>--uninstall</option></arg>
- <arg choice="plain"><option>-e</option></arg>
- </group>
- <arg choice="plain" rep="repeat"><replaceable>drvnames</replaceable></arg>
-</cmdsynopsis>
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>The uninstall operation creates a new user environment, based on
-the current generation of the active profile, from which the store
-paths designated by the symbolic names
-<replaceable>names</replaceable> are removed.</para>
-
-</refsection>
-
-<refsection><title>Examples</title>
-
-<screen>
-$ nix-env --uninstall gcc
-$ nix-env -e '.*' <lineannotation>(remove everything)</lineannotation></screen>
-
-</refsection>
-
-</refsection>
-
-
-
-<!--######################################################################-->
-
-<refsection xml:id="rsec-nix-env-set"><title>Operation <option>--set</option></title>
-
-<refsection><title>Synopsis</title>
-
-<cmdsynopsis>
- <command>nix-env</command>
- <arg choice="plain"><option>--set</option></arg>
- <arg choice="plain"><replaceable>drvname</replaceable></arg>
-</cmdsynopsis>
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>The <option>--set</option> operation modifies the current generation of a
-profile so that it contains exactly the specified derivation, and nothing else.
-</para>
-
-</refsection>
-
-<refsection><title>Examples</title>
-
-<para>
-The following updates a profile such that its current generation will contain
-just Firefox:
-
-<screen>
-$ nix-env -p /nix/var/nix/profiles/browser --set firefox</screen>
-
-</para>
-
-</refsection>
-
-</refsection>
-
-
-
-<!--######################################################################-->
-
-<refsection xml:id="rsec-nix-env-set-flag"><title>Operation <option>--set-flag</option></title>
-
-<refsection><title>Synopsis</title>
-
-<cmdsynopsis>
- <command>nix-env</command>
- <arg choice="plain"><option>--set-flag</option></arg>
- <arg choice="plain"><replaceable>name</replaceable></arg>
- <arg choice="plain"><replaceable>value</replaceable></arg>
- <arg choice="plain" rep="repeat"><replaceable>drvnames</replaceable></arg>
-</cmdsynopsis>
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>The <option>--set-flag</option> operation allows meta attributes
-of installed packages to be modified. There are several attributes
-that can be usefully modified, because they affect the behaviour of
-<command>nix-env</command> or the user environment build
-script:
-
-<itemizedlist>
-
- <listitem><para><varname>priority</varname> can be changed to
- resolve filename clashes. The user environment build script uses
- the <varname>meta.priority</varname> attribute of derivations to
- resolve filename collisions between packages. Lower priority values
- denote a higher priority. For instance, the GCC wrapper package and
- the Binutils package in Nixpkgs both have a file
- <filename>bin/ld</filename>, so previously if you tried to install
- both you would get a collision. Now, on the other hand, the GCC
- wrapper declares a higher priority than Binutils, so the former’s
- <filename>bin/ld</filename> is symlinked in the user
- environment.</para></listitem>
-
- <listitem><para><varname>keep</varname> can be set to
- <literal>true</literal> to prevent the package from being upgraded
- or replaced. This is useful if you want to hang on to an older
- version of a package.</para></listitem>
-
- <listitem><para><varname>active</varname> can be set to
- <literal>false</literal> to “disable” the package. That is, no
- symlinks will be generated to the files of the package, but it
- remains part of the profile (so it won’t be garbage-collected). It
- can be set back to <literal>true</literal> to re-enable the
- package.</para></listitem>
-
-</itemizedlist>
-
-</para>
-
-</refsection>
-
-<refsection><title>Examples</title>
-
-<para>To prevent the currently installed Firefox from being upgraded:
-
-<screen>
-$ nix-env --set-flag keep true firefox</screen>
-
-After this, <command>nix-env -u</command> will ignore Firefox.</para>
-
-<para>To disable the currently installed Firefox, then install a new
-Firefox while the old remains part of the profile:
-
-<screen>
-$ nix-env -q
-firefox-2.0.0.9 <lineannotation>(the current one)</lineannotation>
-
-$ nix-env --preserve-installed -i firefox-2.0.0.11
-installing `firefox-2.0.0.11'
-building path(s) `/nix/store/myy0y59q3ig70dgq37jqwg1j0rsapzsl-user-environment'
-collision between `/nix/store/<replaceable>...</replaceable>-firefox-2.0.0.11/bin/firefox'
- and `/nix/store/<replaceable>...</replaceable>-firefox-2.0.0.9/bin/firefox'.
-<lineannotation>(i.e., can’t have two active at the same time)</lineannotation>
-
-$ nix-env --set-flag active false firefox
-setting flag on `firefox-2.0.0.9'
-
-$ nix-env --preserve-installed -i firefox-2.0.0.11
-installing `firefox-2.0.0.11'
-
-$ nix-env -q
-firefox-2.0.0.11 <lineannotation>(the enabled one)</lineannotation>
-firefox-2.0.0.9 <lineannotation>(the disabled one)</lineannotation></screen>
-
-</para>
-
-<para>To make files from <literal>binutils</literal> take precedence
-over files from <literal>gcc</literal>:
-
-<screen>
-$ nix-env --set-flag priority 5 binutils
-$ nix-env --set-flag priority 10 gcc</screen>
-
-</para>
-
-</refsection>
-
-</refsection>
-
-
-
-<!--######################################################################-->
-
-<refsection><title>Operation <option>--query</option></title>
-
-<refsection><title>Synopsis</title>
-
-<cmdsynopsis>
- <command>nix-env</command>
- <group choice="req">
- <arg choice="plain"><option>--query</option></arg>
- <arg choice="plain"><option>-q</option></arg>
- </group>
- <group choice="opt">
- <arg choice="plain"><option>--installed</option></arg>
- <arg choice="plain"><option>--available</option></arg>
- <arg choice="plain"><option>-a</option></arg>
- </group>
-
- <sbr/>
-
- <arg>
- <group choice="req">
- <arg choice="plain"><option>--status</option></arg>
- <arg choice="plain"><option>-s</option></arg>
- </group>
- </arg>
- <arg>
- <group choice="req">
- <arg choice="plain"><option>--attr-path</option></arg>
- <arg choice="plain"><option>-P</option></arg>
- </group>
- </arg>
- <arg><option>--no-name</option></arg>
- <arg>
- <group choice="req">
- <arg choice="plain"><option>--compare-versions</option></arg>
- <arg choice="plain"><option>-c</option></arg>
- </group>
- </arg>
- <arg><option>--system</option></arg>
- <arg><option>--drv-path</option></arg>
- <arg><option>--out-path</option></arg>
- <arg><option>--description</option></arg>
- <arg><option>--meta</option></arg>
-
- <sbr/>
-
- <arg><option>--xml</option></arg>
- <arg><option>--json</option></arg>
- <arg>
- <group choice="req">
- <arg choice="plain"><option>--prebuilt-only</option></arg>
- <arg choice="plain"><option>-b</option></arg>
- </group>
- </arg>
-
- <arg>
- <group choice="req">
- <arg choice="plain"><option>--attr</option></arg>
- <arg choice="plain"><option>-A</option></arg>
- </group>
- <replaceable>attribute-path</replaceable>
- </arg>
-
- <sbr/>
-
- <arg choice="plain" rep="repeat"><replaceable>names</replaceable></arg>
-</cmdsynopsis>
-
-</refsection>
-
-
-<refsection><title>Description</title>
-
-<para>The query operation displays information about either the store
-paths that are installed in the current generation of the active
-profile (<option>--installed</option>), or the derivations that are
-available for installation in the active Nix expression
-(<option>--available</option>). It only prints information about
-derivations whose symbolic name matches one of
-<replaceable>names</replaceable>.</para>
-
-<para>The derivations are sorted by their <literal>name</literal>
-attributes.</para>
-
-</refsection>
-
-
-<refsection><title>Source selection</title>
-
-<para>The following flags specify the set of things on which the query
-operates.</para>
-
-<variablelist>
-
- <varlistentry><term><option>--installed</option></term>
-
- <listitem><para>The query operates on the store paths that are
- installed in the current generation of the active profile. This
- is the default.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--available</option></term>
- <term><option>-a</option></term>
-
- <listitem><para>The query operates on the derivations that are
- available in the active Nix expression.</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-</refsection>
-
-
-<refsection><title>Queries</title>
-
-<para>The following flags specify what information to display about
-the selected derivations. Multiple flags may be specified, in which
-case the information is shown in the order given here. Note that the
-name of the derivation is shown unless <option>--no-name</option> is
-specified.</para>
-
-<!-- TODO: fix the terminology here; i.e., derivations, store paths,
-user environment elements, etc. -->
-
-<variablelist>
-
- <varlistentry><term><option>--xml</option></term>
-
- <listitem><para>Print the result in an XML representation suitable
- for automatic processing by other tools. The root element is
- called <literal>items</literal>, which contains a
- <literal>item</literal> element for each available or installed
- derivation. The fields discussed below are all stored in
- attributes of the <literal>item</literal>
- elements.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--json</option></term>
-
- <listitem><para>Print the result in a JSON representation suitable
- for automatic processing by other tools.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--prebuilt-only</option> / <option>-b</option></term>
-
- <listitem><para>Show only derivations for which a substitute is
- registered, i.e., there is a pre-built binary available that can
- be downloaded in lieu of building the derivation. Thus, this
- shows all packages that probably can be installed
- quickly.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--status</option></term>
- <term><option>-s</option></term>
-
- <listitem><para>Print the <emphasis>status</emphasis> of the
- derivation. The status consists of three characters. The first
- is <literal>I</literal> or <literal>-</literal>, indicating
- whether the derivation is currently installed in the current
- generation of the active profile. This is by definition the case
- for <option>--installed</option>, but not for
- <option>--available</option>. The second is <literal>P</literal>
- or <literal>-</literal>, indicating whether the derivation is
- present on the system. This indicates whether installation of an
- available derivation will require the derivation to be built. The
- third is <literal>S</literal> or <literal>-</literal>, indicating
- whether a substitute is available for the
- derivation.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--attr-path</option></term>
- <term><option>-P</option></term>
-
- <listitem><para>Print the <emphasis>attribute path</emphasis> of
- the derivation, which can be used to unambiguously select it using
- the <link linkend="opt-attr"><option>--attr</option> option</link>
- available in commands that install derivations like
- <literal>nix-env --install</literal>. This option only works
- together with <option>--available</option></para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--no-name</option></term>
-
- <listitem><para>Suppress printing of the <literal>name</literal>
- attribute of each derivation.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--compare-versions</option> /
- <option>-c</option></term>
-
- <listitem><para>Compare installed versions to available versions,
- or vice versa (if <option>--available</option> is given). This is
- useful for quickly seeing whether upgrades for installed
- packages are available in a Nix expression. A column is added
- with the following meaning:
-
- <variablelist>
-
- <varlistentry><term><literal><</literal> <replaceable>version</replaceable></term>
-
- <listitem><para>A newer version of the package is available
- or installed.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><literal>=</literal> <replaceable>version</replaceable></term>
-
- <listitem><para>At most the same version of the package is
- available or installed.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><literal>></literal> <replaceable>version</replaceable></term>
-
- <listitem><para>Only older versions of the package are
- available or installed.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><literal>- ?</literal></term>
-
- <listitem><para>No version of the package is available or
- installed.</para></listitem>
-
- </varlistentry>
-
- </variablelist>
-
- </para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--system</option></term>
-
- <listitem><para>Print the <literal>system</literal> attribute of
- the derivation.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--drv-path</option></term>
-
- <listitem><para>Print the path of the store
- derivation.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--out-path</option></term>
-
- <listitem><para>Print the output path of the
- derivation.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--description</option></term>
-
- <listitem><para>Print a short (one-line) description of the
- derivation, if available. The description is taken from the
- <literal>meta.description</literal> attribute of the
- derivation.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--meta</option></term>
-
- <listitem><para>Print all of the meta-attributes of the
- derivation. This option is only available with
- <option>--xml</option> or <option>--json</option>.</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-</refsection>
-
-
-<refsection><title>Examples</title>
-
-<para>To show installed packages:
-
-<screen>
-$ nix-env -q
-bison-1.875c
-docbook-xml-4.2
-firefox-1.0.4
-MPlayer-1.0pre7
-ORBit2-2.8.3
-<replaceable>…</replaceable>
-</screen>
-
-</para>
-
-<para>To show available packages:
-
-<screen>
-$ nix-env -qa
-firefox-1.0.7
-GConf-2.4.0.1
-MPlayer-1.0pre7
-ORBit2-2.8.3
-<replaceable>…</replaceable>
-</screen>
-
-</para>
-
-<para>To show the status of available packages:
-
-<screen>
-$ nix-env -qas
--P- firefox-1.0.7 <lineannotation>(not installed but present)</lineannotation>
---S GConf-2.4.0.1 <lineannotation>(not present, but there is a substitute for fast installation)</lineannotation>
---S MPlayer-1.0pre3 <lineannotation>(i.e., this is not the installed MPlayer, even though the version is the same!)</lineannotation>
-IP- ORBit2-2.8.3 <lineannotation>(installed and by definition present)</lineannotation>
-<replaceable>…</replaceable>
-</screen>
-
-</para>
-
-<para>To show available packages in the Nix expression <filename>foo.nix</filename>:
-
-<screen>
-$ nix-env -f ./foo.nix -qa
-foo-1.2.3
-</screen>
-
-</para>
-
-<para>To compare installed versions to what’s available:
-
-<screen>
-$ nix-env -qc
-<replaceable>...</replaceable>
-acrobat-reader-7.0 - ? <lineannotation>(package is not available at all)</lineannotation>
-autoconf-2.59 = 2.59 <lineannotation>(same version)</lineannotation>
-firefox-1.0.4 < 1.0.7 <lineannotation>(a more recent version is available)</lineannotation>
-<replaceable>...</replaceable>
-</screen>
-
-</para>
-
-<para>To show all packages with “<literal>zip</literal>” in the name:
-
-<screen>
-$ nix-env -qa '.*zip.*'
-bzip2-1.0.6
-gzip-1.6
-zip-3.0
-<replaceable>…</replaceable>
-</screen>
-
-</para>
-
-<para>To show all packages with “<literal>firefox</literal>” or
-“<literal>chromium</literal>” in the name:
-
-<screen>
-$ nix-env -qa '.*(firefox|chromium).*'
-chromium-37.0.2062.94
-chromium-beta-38.0.2125.24
-firefox-32.0.3
-firefox-with-plugins-13.0.1
-<replaceable>…</replaceable>
-</screen>
-
-</para>
-
-<para>To show all packages in the latest revision of the Nixpkgs
-repository:
-
-<screen>
-$ nix-env -f https://github.com/NixOS/nixpkgs/archive/master.tar.gz -qa
-</screen>
-
-</para>
-
-</refsection>
-
-</refsection>
-
-
-
-<!--######################################################################-->
-
-<refsection><title>Operation <option>--switch-profile</option></title>
-
-<refsection><title>Synopsis</title>
-
-<cmdsynopsis>
- <command>nix-env</command>
- <group choice="req">
- <arg choice="plain"><option>--switch-profile</option></arg>
- <arg choice="plain"><option>-S</option></arg>
- </group>
- <arg choice="req"><replaceable>path</replaceable></arg>
-</cmdsynopsis>
-
-</refsection>
-
-
-<refsection><title>Description</title>
-
-<para>This operation makes <replaceable>path</replaceable> the current
-profile for the user. That is, the symlink
-<filename>~/.nix-profile</filename> is made to point to
-<replaceable>path</replaceable>.</para>
-
-</refsection>
-
-<refsection><title>Examples</title>
-
-<screen>
-$ nix-env -S ~/my-profile</screen>
-
-</refsection>
-
-</refsection>
-
-
-
-<!--######################################################################-->
-
-<refsection><title>Operation <option>--list-generations</option></title>
-
-<refsection><title>Synopsis</title>
-
-<cmdsynopsis>
- <command>nix-env</command>
- <arg choice="plain"><option>--list-generations</option></arg>
-</cmdsynopsis>
-
-</refsection>
-
-
-<refsection><title>Description</title>
-
-<para>This operation print a list of all the currently existing
-generations for the active profile. These may be switched to using
-the <option>--switch-generation</option> operation. It also prints
-the creation date of the generation, and indicates the current
-generation.</para>
-
-</refsection>
-
-
-<refsection><title>Examples</title>
-
-<screen>
-$ nix-env --list-generations
- 95 2004-02-06 11:48:24
- 96 2004-02-06 11:49:01
- 97 2004-02-06 16:22:45
- 98 2004-02-06 16:24:33 (current)</screen>
-
-</refsection>
-
-</refsection>
-
-
-
-<!--######################################################################-->
-
-<refsection><title>Operation <option>--delete-generations</option></title>
-
-<refsection><title>Synopsis</title>
-
-<cmdsynopsis>
- <command>nix-env</command>
- <arg choice="plain"><option>--delete-generations</option></arg>
- <arg choice="plain" rep="repeat"><replaceable>generations</replaceable></arg>
-</cmdsynopsis>
-
-</refsection>
-
-
-<refsection><title>Description</title>
-
-<para>This operation deletes the specified generations of the current
-profile. The generations can be a list of generation numbers, the
-special value <literal>old</literal> to delete all non-current
-generations, a value such as <literal>30d</literal> to delete all
-generations older than the specified number of days (except for the
-generation that was active at that point in time), or a value such as
-<literal>+5</literal> to keep the last <literal>5</literal> generations
-ignoring any newer than current, e.g., if <literal>30</literal> is the current
-generation <literal>+5</literal> will delete generation <literal>25</literal>
-and all older generations.
-Periodically deleting old generations is important to make garbage collection
-effective.</para>
-
-</refsection>
-
-<refsection><title>Examples</title>
-
-<screen>
-$ nix-env --delete-generations 3 4 8
-
-$ nix-env --delete-generations +5
-
-$ nix-env --delete-generations 30d
-
-$ nix-env -p other_profile --delete-generations old</screen>
-
-</refsection>
-
-</refsection>
-
-
-
-<!--######################################################################-->
-
-<refsection><title>Operation <option>--switch-generation</option></title>
-
-<refsection><title>Synopsis</title>
-
-<cmdsynopsis>
- <command>nix-env</command>
- <group choice="req">
- <arg choice="plain"><option>--switch-generation</option></arg>
- <arg choice="plain"><option>-G</option></arg>
- </group>
- <arg choice="req"><replaceable>generation</replaceable></arg>
-</cmdsynopsis>
-
-</refsection>
-
-
-<refsection><title>Description</title>
-
-<para>This operation makes generation number
-<replaceable>generation</replaceable> the current generation of the
-active profile. That is, if the
-<filename><replaceable>profile</replaceable></filename> is the path to
-the active profile, then the symlink
-<filename><replaceable>profile</replaceable></filename> is made to
-point to
-<filename><replaceable>profile</replaceable>-<replaceable>generation</replaceable>-link</filename>,
-which is in turn a symlink to the actual user environment in the Nix
-store.</para>
-
-<para>Switching will fail if the specified generation does not exist.</para>
-
-</refsection>
-
-
-<refsection><title>Examples</title>
-
-<screen>
-$ nix-env -G 42
-switching from generation 50 to 42</screen>
-
-</refsection>
-
-</refsection>
-
-
-
-<!--######################################################################-->
-
-<refsection><title>Operation <option>--rollback</option></title>
-
-<refsection><title>Synopsis</title>
-
-<cmdsynopsis>
- <command>nix-env</command>
- <arg choice="plain"><option>--rollback</option></arg>
-</cmdsynopsis>
-
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>This operation switches to the “previous” generation of the
-active profile, that is, the highest numbered generation lower than
-the current generation, if it exists. It is just a convenience
-wrapper around <option>--list-generations</option> and
-<option>--switch-generation</option>.</para>
-
-</refsection>
-
-
-<refsection><title>Examples</title>
-
-<screen>
-$ nix-env --rollback
-switching from generation 92 to 91
-
-$ nix-env --rollback
-error: no generation older than the current (91) exists</screen>
-
-</refsection>
-
-</refsection>
-
-
-<refsection condition="manpage"><title>Environment variables</title>
-
-<variablelist>
-
- <varlistentry><term><envar>NIX_PROFILE</envar></term>
-
- <listitem><para>Location of the Nix profile. Defaults to the
- target of the symlink <filename>~/.nix-profile</filename>, if it
- exists, or <filename>/nix/var/nix/profiles/default</filename>
- otherwise.</para></listitem>
-
- </varlistentry>
-
- <varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>IN_NIX_SHELL</envar></term>
-
- <listitem><para>Indicator that tells if the current environment was set up by
- <command>nix-shell</command>. Since Nix 2.0 the values are
- <literal>"pure"</literal> and <literal>"impure"</literal></para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="env-NIX_PATH"><term><envar>NIX_PATH</envar></term>
-
- <listitem>
-
- <para>A colon-separated list of directories used to look up Nix
- expressions enclosed in angle brackets (i.e.,
- <literal><<replaceable>path</replaceable>></literal>). For
- instance, the value
-
- <screen>
-/home/eelco/Dev:/etc/nixos</screen>
-
- will cause Nix to look for paths relative to
- <filename>/home/eelco/Dev</filename> and
- <filename>/etc/nixos</filename>, in this order. It is also
- possible to match paths against a prefix. For example, the value
-
- <screen>
-nixpkgs=/home/eelco/Dev/nixpkgs-branch:/etc/nixos</screen>
-
- will cause Nix to search for
- <literal><nixpkgs/<replaceable>path</replaceable>></literal> in
- <filename>/home/eelco/Dev/nixpkgs-branch/<replaceable>path</replaceable></filename>
- and
- <filename>/etc/nixos/nixpkgs/<replaceable>path</replaceable></filename>.</para>
-
- <para>If a path in the Nix search path starts with
- <literal>http://</literal> or <literal>https://</literal>, it is
- interpreted as the URL of a tarball that will be downloaded and
- unpacked to a temporary location. The tarball must consist of a
- single top-level directory. For example, setting
- <envar>NIX_PATH</envar> to
-
- <screen>
-nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-15.09.tar.gz</screen>
-
- tells Nix to download the latest revision in the Nixpkgs/NixOS
- 15.09 channel.</para>
-
- <para>A following shorthand can be used to refer to the official channels:
-
- <screen>nixpkgs=channel:nixos-15.09</screen>
- </para>
-
- <para>The search path can be extended using the <option linkend="opt-I">-I</option> option, which takes precedence over
- <envar>NIX_PATH</envar>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_IGNORE_SYMLINK_STORE</envar></term>
-
- <listitem>
-
- <para>Normally, the Nix store directory (typically
- <filename>/nix/store</filename>) is not allowed to contain any
- symlink components. This is to prevent “impure” builds. Builders
- sometimes “canonicalise” paths by resolving all symlink components.
- Thus, builds on different machines (with
- <filename>/nix/store</filename> resolving to different locations)
- could yield different results. This is generally not a problem,
- except when builds are deployed to machines where
- <filename>/nix/store</filename> resolves differently. If you are
- sure that you’re not going to do that, you can set
- <envar>NIX_IGNORE_SYMLINK_STORE</envar> to <envar>1</envar>.</para>
-
- <para>Note that if you’re symlinking the Nix store so that you can
- put it on another file system than the root file system, on Linux
- you’re better off using <literal>bind</literal> mount points, e.g.,
-
- <screen>
-$ mkdir /nix
-$ mount -o bind /mnt/otherdisk/nix /nix</screen>
-
- Consult the <citerefentry><refentrytitle>mount</refentrytitle>
- <manvolnum>8</manvolnum></citerefentry> manual page for details.</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_STORE_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix store (default
- <filename><replaceable>prefix</replaceable>/store</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_DATA_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix static data
- directory (default
- <filename><replaceable>prefix</replaceable>/share</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_LOG_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix log directory
- (default <filename><replaceable>prefix</replaceable>/var/log/nix</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_STATE_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix state directory
- (default <filename><replaceable>prefix</replaceable>/var/nix</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_CONF_DIR</envar></term>
-
- <listitem><para>Overrides the location of the system Nix configuration
- directory (default
- <filename><replaceable>prefix</replaceable>/etc/nix</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_USER_CONF_FILES</envar></term>
-
- <listitem><para>Overrides the location of the user Nix configuration files
- to load from (defaults to the XDG spec locations). The variable is treated
- as a list separated by the <literal>:</literal> token.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>TMPDIR</envar></term>
-
- <listitem><para>Use the specified directory to store temporary
- files. In particular, this includes temporary build directories;
- these can take up substantial amounts of disk space. The default is
- <filename>/tmp</filename>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="envar-remote"><term><envar>NIX_REMOTE</envar></term>
-
- <listitem><para>This variable should be set to
- <literal>daemon</literal> if you want to use the Nix daemon to
- execute Nix operations. This is necessary in <link linkend="ssec-multi-user">multi-user Nix installations</link>.
- If the Nix daemon's Unix socket is at some non-standard path,
- this variable should be set to <literal>unix://path/to/socket</literal>.
- Otherwise, it should be left unset.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_SHOW_STATS</envar></term>
-
- <listitem><para>If set to <literal>1</literal>, Nix will print some
- evaluation statistics, such as the number of values
- allocated.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_COUNT_CALLS</envar></term>
-
- <listitem><para>If set to <literal>1</literal>, Nix will print how
- often functions were called during Nix expression evaluation. This
- is useful for profiling your Nix expressions.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>GC_INITIAL_HEAP_SIZE</envar></term>
-
- <listitem><para>If Nix has been configured to use the Boehm garbage
- collector, this variable sets the initial size of the heap in bytes.
- It defaults to 384 MiB. Setting it to a low value reduces memory
- consumption, but will increase runtime due to the overhead of
- garbage collection.</para></listitem>
-
-</varlistentry>
-</variablelist>
-
-</refsection>
-
-
-</refentry>
-<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-nix-build">
-
-<refmeta>
- <refentrytitle>nix-build</refentrytitle>
- <manvolnum>1</manvolnum>
- <refmiscinfo class="source">Nix</refmiscinfo>
- <refmiscinfo class="version">3.0</refmiscinfo>
-</refmeta>
-
-<refnamediv>
- <refname>nix-build</refname>
- <refpurpose>build a Nix expression</refpurpose>
-</refnamediv>
-
-<refsynopsisdiv>
- <cmdsynopsis>
- <command>nix-build</command>
- <arg xmlns="http://docbook.org/ns/docbook"><option>--help</option></arg><arg xmlns="http://docbook.org/ns/docbook"><option>--version</option></arg><arg xmlns="http://docbook.org/ns/docbook" rep="repeat">
- <group choice="req">
- <arg choice="plain"><option>--verbose</option></arg>
- <arg choice="plain"><option>-v</option></arg>
- </group>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <arg choice="plain"><option>--quiet</option></arg>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <option>--log-format</option>
- <replaceable>format</replaceable>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <group choice="plain">
- <arg choice="plain"><option>--no-build-output</option></arg>
- <arg choice="plain"><option>-Q</option></arg>
- </group>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <group choice="req">
- <arg choice="plain"><option>--max-jobs</option></arg>
- <arg choice="plain"><option>-j</option></arg>
- </group>
- <replaceable>number</replaceable>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <option>--cores</option>
- <replaceable>number</replaceable>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <option>--max-silent-time</option>
- <replaceable>number</replaceable>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <option>--timeout</option>
- <replaceable>number</replaceable>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <group choice="plain">
- <arg choice="plain"><option>--keep-going</option></arg>
- <arg choice="plain"><option>-k</option></arg>
- </group>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <group choice="plain">
- <arg choice="plain"><option>--keep-failed</option></arg>
- <arg choice="plain"><option>-K</option></arg>
- </group>
-</arg><arg xmlns="http://docbook.org/ns/docbook"><option>--fallback</option></arg><arg xmlns="http://docbook.org/ns/docbook"><option>--readonly-mode</option></arg><arg xmlns="http://docbook.org/ns/docbook">
- <option>-I</option>
- <replaceable>path</replaceable>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <option>--option</option>
- <replaceable>name</replaceable>
- <replaceable>value</replaceable>
-</arg><sbr xmlns="http://docbook.org/ns/docbook"/>
- <arg><option>--arg</option> <replaceable>name</replaceable> <replaceable>value</replaceable></arg>
- <arg><option>--argstr</option> <replaceable>name</replaceable> <replaceable>value</replaceable></arg>
- <arg>
- <group choice="req">
- <arg choice="plain"><option>--attr</option></arg>
- <arg choice="plain"><option>-A</option></arg>
- </group>
- <replaceable>attrPath</replaceable>
- </arg>
- <arg><option>--no-out-link</option></arg>
- <arg><option>--dry-run</option></arg>
- <arg>
- <group choice="req">
- <arg choice="plain"><option>--out-link</option></arg>
- <arg choice="plain"><option>-o</option></arg>
- </group>
- <replaceable>outlink</replaceable>
- </arg>
- <arg choice="plain" rep="repeat"><replaceable>paths</replaceable></arg>
- </cmdsynopsis>
-</refsynopsisdiv>
-
-<refsection><title>Description</title>
-
-<para>The <command>nix-build</command> command builds the derivations
-described by the Nix expressions in <replaceable>paths</replaceable>.
-If the build succeeds, it places a symlink to the result in the
-current directory. The symlink is called <filename>result</filename>.
-If there are multiple Nix expressions, or the Nix expressions evaluate
-to multiple derivations, multiple sequentially numbered symlinks are
-created (<filename>result</filename>, <filename>result-2</filename>,
-and so on).</para>
-
-<para>If no <replaceable>paths</replaceable> are specified, then
-<command>nix-build</command> will use <filename>default.nix</filename>
-in the current directory, if it exists.</para>
-
-<para>If an element of <replaceable>paths</replaceable> starts with
-<literal>http://</literal> or <literal>https://</literal>, it is
-interpreted as the URL of a tarball that will be downloaded and
-unpacked to a temporary location. The tarball must include a single
-top-level directory containing at least a file named
-<filename>default.nix</filename>.</para>
-
-<para><command>nix-build</command> is essentially a wrapper around
-<link linkend="sec-nix-instantiate"><command>nix-instantiate</command></link>
-(to translate a high-level Nix expression to a low-level store
-derivation) and <link linkend="rsec-nix-store-realise"><command>nix-store
---realise</command></link> (to build the store derivation).</para>
-
-<warning><para>The result of the build is automatically registered as
-a root of the Nix garbage collector. This root disappears
-automatically when the <filename>result</filename> symlink is deleted
-or renamed. So don’t rename the symlink.</para></warning>
-
-</refsection>
-
-
-<refsection><title>Options</title>
-
-<para>All options not listed here are passed to <command>nix-store
---realise</command>, except for <option>--arg</option> and
-<option>--attr</option> / <option>-A</option> which are passed to
-<command>nix-instantiate</command>. <phrase condition="manual">See
-also <xref linkend="sec-common-options"/>.</phrase></para>
-
-<variablelist>
-
- <varlistentry><term><option>--no-out-link</option></term>
-
- <listitem><para>Do not create a symlink to the output path. Note
- that as a result the output does not become a root of the garbage
- collector, and so might be deleted by <command>nix-store
- --gc</command>.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--dry-run</option></term>
- <listitem><para>Show what store paths would be built or downloaded.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="opt-out-link"><term><option>--out-link</option> /
- <option>-o</option> <replaceable>outlink</replaceable></term>
-
- <listitem><para>Change the name of the symlink to the output path
- created from <filename>result</filename> to
- <replaceable>outlink</replaceable>.</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-<para>The following common options are supported:</para>
-
-<variablelist condition="manpage">
- <varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--help</option></term>
-
- <listitem><para>Prints out a summary of the command syntax and
- exits.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--version</option></term>
-
- <listitem><para>Prints out the Nix version number on standard output
- and exits.</para></listitem>
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--verbose</option> / <option>-v</option></term>
-
- <listitem>
-
- <para>Increases the level of verbosity of diagnostic messages
- printed on standard error. For each Nix operation, the information
- printed on standard output is well-defined; any diagnostic
- information is printed on standard error, never on standard
- output.</para>
-
- <para>This option may be specified repeatedly. Currently, the
- following verbosity levels exist:</para>
-
- <variablelist>
-
- <varlistentry><term>0</term>
- <listitem><para>“Errors only”: only print messages
- explaining why the Nix invocation failed.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>1</term>
- <listitem><para>“Informational”: print
- <emphasis>useful</emphasis> messages about what Nix is doing.
- This is the default.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>2</term>
- <listitem><para>“Talkative”: print more informational
- messages.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>3</term>
- <listitem><para>“Chatty”: print even more
- informational messages.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>4</term>
- <listitem><para>“Debug”: print debug
- information.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>5</term>
- <listitem><para>“Vomit”: print vast amounts of debug
- information.</para></listitem>
- </varlistentry>
-
- </variablelist>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--quiet</option></term>
-
- <listitem>
-
- <para>Decreases the level of verbosity of diagnostic messages
- printed on standard error. This is the inverse option to
- <option>-v</option> / <option>--verbose</option>.
- </para>
-
- <para>This option may be specified repeatedly. See the previous
- verbosity levels list.</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-log-format"><term><option>--log-format</option> <replaceable>format</replaceable></term>
-
- <listitem>
-
- <para>This option can be used to change the output of the log format, with
- <replaceable>format</replaceable> being one of:</para>
-
- <variablelist>
-
- <varlistentry><term>raw</term>
- <listitem><para>This is the raw format, as outputted by nix-build.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>internal-json</term>
- <listitem><para>Outputs the logs in a structured manner. NOTE: the json schema is not guarantees to be stable between releases.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>bar</term>
- <listitem><para>Only display a progress bar during the builds.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>bar-with-logs</term>
- <listitem><para>Display the raw logs, with the progress bar at the bottom.</para></listitem>
- </varlistentry>
-
- </variablelist>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--no-build-output</option> / <option>-Q</option></term>
-
- <listitem><para>By default, output written by builders to standard
- output and standard error is echoed to the Nix command's standard
- error. This option suppresses this behaviour. Note that the
- builder's standard output and error are always written to a log file
- in
- <filename><replaceable>prefix</replaceable>/nix/var/log/nix</filename>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-max-jobs"><term><option>--max-jobs</option> / <option>-j</option>
-<replaceable>number</replaceable></term>
-
- <listitem>
-
- <para>Sets the maximum number of build jobs that Nix will
- perform in parallel to the specified number. Specify
- <literal>auto</literal> to use the number of CPUs in the system.
- The default is specified by the <link linkend="conf-max-jobs"><literal>max-jobs</literal></link>
- configuration setting, which itself defaults to
- <literal>1</literal>. A higher value is useful on SMP systems or to
- exploit I/O latency.</para>
-
- <para> Setting it to <literal>0</literal> disallows building on the local
- machine, which is useful when you want builds to happen only on remote
- builders.</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-cores"><term><option>--cores</option></term>
-
- <listitem><para>Sets the value of the <envar>NIX_BUILD_CORES</envar>
- environment variable in the invocation of builders. Builders can
- use this variable at their discretion to control the maximum amount
- of parallelism. For instance, in Nixpkgs, if the derivation
- attribute <varname>enableParallelBuilding</varname> is set to
- <literal>true</literal>, the builder passes the
- <option>-j<replaceable>N</replaceable></option> flag to GNU Make.
- It defaults to the value of the <link linkend="conf-cores"><literal>cores</literal></link>
- configuration setting, if set, or <literal>1</literal> otherwise.
- The value <literal>0</literal> means that the builder should use all
- available CPU cores in the system.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-max-silent-time"><term><option>--max-silent-time</option></term>
-
- <listitem><para>Sets the maximum number of seconds that a builder
- can go without producing any data on standard output or standard
- error. The default is specified by the <link linkend="conf-max-silent-time"><literal>max-silent-time</literal></link>
- configuration setting. <literal>0</literal> means no
- time-out.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-timeout"><term><option>--timeout</option></term>
-
- <listitem><para>Sets the maximum number of seconds that a builder
- can run. The default is specified by the <link linkend="conf-timeout"><literal>timeout</literal></link>
- configuration setting. <literal>0</literal> means no
- timeout.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--keep-going</option> / <option>-k</option></term>
-
- <listitem><para>Keep going in case of failed builds, to the
- greatest extent possible. That is, if building an input of some
- derivation fails, Nix will still build the other inputs, but not the
- derivation itself. Without this option, Nix stops if any build
- fails (except for builds of substitutes), possibly killing builds in
- progress (in case of parallel or distributed builds).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--keep-failed</option> / <option>-K</option></term>
-
- <listitem><para>Specifies that in case of a build failure, the
- temporary directory (usually in <filename>/tmp</filename>) in which
- the build takes place should not be deleted. The path of the build
- directory is printed as an informational message.
- </para>
- </listitem>
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--fallback</option></term>
-
- <listitem>
-
- <para>Whenever Nix attempts to build a derivation for which
- substitutes are known for each output path, but realising the output
- paths through the substitutes fails, fall back on building the
- derivation.</para>
-
- <para>The most common scenario in which this is useful is when we
- have registered substitutes in order to perform binary distribution
- from, say, a network repository. If the repository is down, the
- realisation of the derivation will fail. When this option is
- specified, Nix will build the derivation instead. Thus,
- installation from binaries falls back on installation from source.
- This option is not the default since it is generally not desirable
- for a transient failure in obtaining the substitutes to lead to a
- full build from source (with the related consumption of
- resources).</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--no-build-hook</option></term>
-
- <listitem>
-
- <para>Disables the build hook mechanism. This allows to ignore remote
- builders if they are setup on the machine.</para>
-
- <para>It's useful in cases where the bandwidth between the client and the
- remote builder is too low. In that case it can take more time to upload the
- sources to the remote builder and fetch back the result than to do the
- computation locally.</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--readonly-mode</option></term>
-
- <listitem><para>When this option is used, no attempt is made to open
- the Nix database. Most Nix operations do need database access, so
- those operations will fail.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--arg</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
-
- <listitem><para>This option is accepted by
- <command>nix-env</command>, <command>nix-instantiate</command>,
- <command>nix-shell</command> and <command>nix-build</command>.
- When evaluating Nix expressions, the expression evaluator will
- automatically try to call functions that
- it encounters. It can automatically call functions for which every
- argument has a <link linkend="ss-functions">default value</link>
- (e.g., <literal>{ <replaceable>argName</replaceable> ?
- <replaceable>defaultValue</replaceable> }:
- <replaceable>...</replaceable></literal>). With
- <option>--arg</option>, you can also call functions that have
- arguments without a default value (or override a default value).
- That is, if the evaluator encounters a function with an argument
- named <replaceable>name</replaceable>, it will call it with value
- <replaceable>value</replaceable>.</para>
-
- <para>For instance, the top-level <literal>default.nix</literal> in
- Nixpkgs is actually a function:
-
-<programlisting>
-{ # The system (e.g., `i686-linux') for which to build the packages.
- system ? builtins.currentSystem
- <replaceable>...</replaceable>
-}: <replaceable>...</replaceable></programlisting>
-
- So if you call this Nix expression (e.g., when you do
- <literal>nix-env -i <replaceable>pkgname</replaceable></literal>),
- the function will be called automatically using the value <link linkend="builtin-currentSystem"><literal>builtins.currentSystem</literal></link>
- for the <literal>system</literal> argument. You can override this
- using <option>--arg</option>, e.g., <literal>nix-env -i
- <replaceable>pkgname</replaceable> --arg system
- \"i686-freebsd\"</literal>. (Note that since the argument is a Nix
- string literal, you have to escape the quotes.)</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--argstr</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
-
- <listitem><para>This option is like <option>--arg</option>, only the
- value is not a Nix expression but a string. So instead of
- <literal>--arg system \"i686-linux\"</literal> (the outer quotes are
- to keep the shell happy) you can say <literal>--argstr system
- i686-linux</literal>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-attr"><term><option>--attr</option> / <option>-A</option>
-<replaceable>attrPath</replaceable></term>
-
- <listitem><para>Select an attribute from the top-level Nix
- expression being evaluated. (<command>nix-env</command>,
- <command>nix-instantiate</command>, <command>nix-build</command> and
- <command>nix-shell</command> only.) The <emphasis>attribute
- path</emphasis> <replaceable>attrPath</replaceable> is a sequence of
- attribute names separated by dots. For instance, given a top-level
- Nix expression <replaceable>e</replaceable>, the attribute path
- <literal>xorg.xorgserver</literal> would cause the expression
- <literal><replaceable>e</replaceable>.xorg.xorgserver</literal> to
- be used. See <link linkend="refsec-nix-env-install-examples"><command>nix-env
- --install</command></link> for some concrete examples.</para>
-
- <para>In addition to attribute names, you can also specify array
- indices. For instance, the attribute path
- <literal>foo.3.bar</literal> selects the <literal>bar</literal>
- attribute of the fourth element of the array in the
- <literal>foo</literal> attribute of the top-level
- expression.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--expr</option> / <option>-E</option></term>
-
- <listitem><para>Interpret the command line arguments as a list of
- Nix expressions to be parsed and evaluated, rather than as a list
- of file names of Nix expressions.
- (<command>nix-instantiate</command>, <command>nix-build</command>
- and <command>nix-shell</command> only.)</para>
-
- <para>For <command>nix-shell</command>, this option is commonly used
- to give you a shell in which you can build the packages returned
- by the expression. If you want to get a shell which contain the
- <emphasis>built</emphasis> packages ready for use, give your
- expression to the <command>nix-shell -p</command> convenience flag
- instead.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-I"><term><option>-I</option> <replaceable>path</replaceable></term>
-
- <listitem><para>Add a path to the Nix expression search path. This
- option may be given multiple times. See the <envar linkend="env-NIX_PATH">NIX_PATH</envar> environment variable for
- information on the semantics of the Nix search path. Paths added
- through <option>-I</option> take precedence over
- <envar>NIX_PATH</envar>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--option</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
-
- <listitem><para>Set the Nix configuration option
- <replaceable>name</replaceable> to <replaceable>value</replaceable>.
- This overrides settings in the Nix configuration file (see
- <citerefentry><refentrytitle>nix.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--repair</option></term>
-
- <listitem><para>Fix corrupted or missing store paths by
- redownloading or rebuilding them. Note that this is slow because it
- requires computing a cryptographic hash of the contents of every
- path in the closure of the build. Also note the warning under
- <command>nix-store --repair-path</command>.</para></listitem>
-
-</varlistentry>
-</variablelist>
-
-</refsection>
-
-
-<refsection><title>Examples</title>
-
-<screen>
-$ nix-build '<nixpkgs>' -A firefox
-store derivation is /nix/store/qybprl8sz2lc...-firefox-1.5.0.7.drv
-/nix/store/d18hyl92g30l...-firefox-1.5.0.7
-
-$ ls -l result
-lrwxrwxrwx <replaceable>...</replaceable> result -> /nix/store/d18hyl92g30l...-firefox-1.5.0.7
-
-$ ls ./result/bin/
-firefox firefox-config</screen>
-
-<para>If a derivation has multiple outputs,
-<command>nix-build</command> will build the default (first) output.
-You can also build all outputs:
-<screen>
-$ nix-build '<nixpkgs>' -A openssl.all
-</screen>
-This will create a symlink for each output named
-<filename>result-<replaceable>outputname</replaceable></filename>.
-The suffix is omitted if the output name is <literal>out</literal>.
-So if <literal>openssl</literal> has outputs <literal>out</literal>,
-<literal>bin</literal> and <literal>man</literal>,
-<command>nix-build</command> will create symlinks
-<literal>result</literal>, <literal>result-bin</literal> and
-<literal>result-man</literal>. It’s also possible to build a specific
-output:
-<screen>
-$ nix-build '<nixpkgs>' -A openssl.man
-</screen>
-This will create a symlink <literal>result-man</literal>.</para>
-
-<para>Build a Nix expression given on the command line:
-
-<screen>
-$ nix-build -E 'with import <nixpkgs> { }; runCommand "foo" { } "echo bar > $out"'
-$ cat ./result
-bar
-</screen>
-
-</para>
-
-<para>Build the GNU Hello package from the latest revision of the
-master branch of Nixpkgs:
-
-<screen>
-$ nix-build https://github.com/NixOS/nixpkgs/archive/master.tar.gz -A hello
-</screen>
-
-</para>
-
-</refsection>
-
-
-<refsection condition="manpage"><title>Environment variables</title>
-
-<variablelist>
- <varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>IN_NIX_SHELL</envar></term>
-
- <listitem><para>Indicator that tells if the current environment was set up by
- <command>nix-shell</command>. Since Nix 2.0 the values are
- <literal>"pure"</literal> and <literal>"impure"</literal></para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="env-NIX_PATH"><term><envar>NIX_PATH</envar></term>
-
- <listitem>
-
- <para>A colon-separated list of directories used to look up Nix
- expressions enclosed in angle brackets (i.e.,
- <literal><<replaceable>path</replaceable>></literal>). For
- instance, the value
-
- <screen>
-/home/eelco/Dev:/etc/nixos</screen>
-
- will cause Nix to look for paths relative to
- <filename>/home/eelco/Dev</filename> and
- <filename>/etc/nixos</filename>, in this order. It is also
- possible to match paths against a prefix. For example, the value
-
- <screen>
-nixpkgs=/home/eelco/Dev/nixpkgs-branch:/etc/nixos</screen>
-
- will cause Nix to search for
- <literal><nixpkgs/<replaceable>path</replaceable>></literal> in
- <filename>/home/eelco/Dev/nixpkgs-branch/<replaceable>path</replaceable></filename>
- and
- <filename>/etc/nixos/nixpkgs/<replaceable>path</replaceable></filename>.</para>
-
- <para>If a path in the Nix search path starts with
- <literal>http://</literal> or <literal>https://</literal>, it is
- interpreted as the URL of a tarball that will be downloaded and
- unpacked to a temporary location. The tarball must consist of a
- single top-level directory. For example, setting
- <envar>NIX_PATH</envar> to
-
- <screen>
-nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-15.09.tar.gz</screen>
-
- tells Nix to download the latest revision in the Nixpkgs/NixOS
- 15.09 channel.</para>
-
- <para>A following shorthand can be used to refer to the official channels:
-
- <screen>nixpkgs=channel:nixos-15.09</screen>
- </para>
-
- <para>The search path can be extended using the <option linkend="opt-I">-I</option> option, which takes precedence over
- <envar>NIX_PATH</envar>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_IGNORE_SYMLINK_STORE</envar></term>
-
- <listitem>
-
- <para>Normally, the Nix store directory (typically
- <filename>/nix/store</filename>) is not allowed to contain any
- symlink components. This is to prevent “impure” builds. Builders
- sometimes “canonicalise” paths by resolving all symlink components.
- Thus, builds on different machines (with
- <filename>/nix/store</filename> resolving to different locations)
- could yield different results. This is generally not a problem,
- except when builds are deployed to machines where
- <filename>/nix/store</filename> resolves differently. If you are
- sure that you’re not going to do that, you can set
- <envar>NIX_IGNORE_SYMLINK_STORE</envar> to <envar>1</envar>.</para>
-
- <para>Note that if you’re symlinking the Nix store so that you can
- put it on another file system than the root file system, on Linux
- you’re better off using <literal>bind</literal> mount points, e.g.,
-
- <screen>
-$ mkdir /nix
-$ mount -o bind /mnt/otherdisk/nix /nix</screen>
-
- Consult the <citerefentry><refentrytitle>mount</refentrytitle>
- <manvolnum>8</manvolnum></citerefentry> manual page for details.</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_STORE_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix store (default
- <filename><replaceable>prefix</replaceable>/store</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_DATA_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix static data
- directory (default
- <filename><replaceable>prefix</replaceable>/share</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_LOG_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix log directory
- (default <filename><replaceable>prefix</replaceable>/var/log/nix</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_STATE_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix state directory
- (default <filename><replaceable>prefix</replaceable>/var/nix</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_CONF_DIR</envar></term>
-
- <listitem><para>Overrides the location of the system Nix configuration
- directory (default
- <filename><replaceable>prefix</replaceable>/etc/nix</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_USER_CONF_FILES</envar></term>
-
- <listitem><para>Overrides the location of the user Nix configuration files
- to load from (defaults to the XDG spec locations). The variable is treated
- as a list separated by the <literal>:</literal> token.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>TMPDIR</envar></term>
-
- <listitem><para>Use the specified directory to store temporary
- files. In particular, this includes temporary build directories;
- these can take up substantial amounts of disk space. The default is
- <filename>/tmp</filename>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="envar-remote"><term><envar>NIX_REMOTE</envar></term>
-
- <listitem><para>This variable should be set to
- <literal>daemon</literal> if you want to use the Nix daemon to
- execute Nix operations. This is necessary in <link linkend="ssec-multi-user">multi-user Nix installations</link>.
- If the Nix daemon's Unix socket is at some non-standard path,
- this variable should be set to <literal>unix://path/to/socket</literal>.
- Otherwise, it should be left unset.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_SHOW_STATS</envar></term>
-
- <listitem><para>If set to <literal>1</literal>, Nix will print some
- evaluation statistics, such as the number of values
- allocated.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_COUNT_CALLS</envar></term>
-
- <listitem><para>If set to <literal>1</literal>, Nix will print how
- often functions were called during Nix expression evaluation. This
- is useful for profiling your Nix expressions.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>GC_INITIAL_HEAP_SIZE</envar></term>
-
- <listitem><para>If Nix has been configured to use the Boehm garbage
- collector, this variable sets the initial size of the heap in bytes.
- It defaults to 384 MiB. Setting it to a low value reduces memory
- consumption, but will increase runtime due to the overhead of
- garbage collection.</para></listitem>
-
-</varlistentry>
-</variablelist>
-
-</refsection>
-
-
-</refentry>
-<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-nix-shell">
-
-<refmeta>
- <refentrytitle>nix-shell</refentrytitle>
- <manvolnum>1</manvolnum>
- <refmiscinfo class="source">Nix</refmiscinfo>
- <refmiscinfo class="version">3.0</refmiscinfo>
-</refmeta>
-
-<refnamediv>
- <refname>nix-shell</refname>
- <refpurpose>start an interactive shell based on a Nix expression</refpurpose>
-</refnamediv>
-
-<refsynopsisdiv>
- <cmdsynopsis>
- <command>nix-shell</command>
- <arg><option>--arg</option> <replaceable>name</replaceable> <replaceable>value</replaceable></arg>
- <arg><option>--argstr</option> <replaceable>name</replaceable> <replaceable>value</replaceable></arg>
- <arg>
- <group choice="req">
- <arg choice="plain"><option>--attr</option></arg>
- <arg choice="plain"><option>-A</option></arg>
- </group>
- <replaceable>attrPath</replaceable>
- </arg>
- <arg><option>--command</option> <replaceable>cmd</replaceable></arg>
- <arg><option>--run</option> <replaceable>cmd</replaceable></arg>
- <arg><option>--exclude</option> <replaceable>regexp</replaceable></arg>
- <arg><option>--pure</option></arg>
- <arg><option>--keep</option> <replaceable>name</replaceable></arg>
- <group choice="req">
- <arg choice="plain">
- <group choice="req">
- <arg choice="plain"><option>--packages</option></arg>
- <arg choice="plain"><option>-p</option></arg>
- </group>
- <arg choice="plain" rep="repeat">
- <group choice="req">
- <arg choice="plain"><replaceable>packages</replaceable></arg>
- <arg choice="plain"><replaceable>expressions</replaceable></arg>
- </group>
- </arg>
- </arg>
- <arg><replaceable>path</replaceable></arg>
- </group>
- </cmdsynopsis>
-</refsynopsisdiv>
-
-<refsection><title>Description</title>
-
-<para>The command <command>nix-shell</command> will build the
-dependencies of the specified derivation, but not the derivation
-itself. It will then start an interactive shell in which all
-environment variables defined by the derivation
-<replaceable>path</replaceable> have been set to their corresponding
-values, and the script <literal>$stdenv/setup</literal> has been
-sourced. This is useful for reproducing the environment of a
-derivation for development.</para>
-
-<para>If <replaceable>path</replaceable> is not given,
-<command>nix-shell</command> defaults to
-<filename>shell.nix</filename> if it exists, and
-<filename>default.nix</filename> otherwise.</para>
-
-<para>If <replaceable>path</replaceable> starts with
-<literal>http://</literal> or <literal>https://</literal>, it is
-interpreted as the URL of a tarball that will be downloaded and
-unpacked to a temporary location. The tarball must include a single
-top-level directory containing at least a file named
-<filename>default.nix</filename>.</para>
-
-<para>If the derivation defines the variable
-<varname>shellHook</varname>, it will be evaluated after
-<literal>$stdenv/setup</literal> has been sourced. Since this hook is
-not executed by regular Nix builds, it allows you to perform
-initialisation specific to <command>nix-shell</command>. For example,
-the derivation attribute
-
-<programlisting>
-shellHook =
- ''
- echo "Hello shell"
- '';
-</programlisting>
-
-will cause <command>nix-shell</command> to print <literal>Hello shell</literal>.</para>
-
-</refsection>
-
-
-<refsection><title>Options</title>
-
-<para>All options not listed here are passed to <command>nix-store
---realise</command>, except for <option>--arg</option> and
-<option>--attr</option> / <option>-A</option> which are passed to
-<command>nix-instantiate</command>. <phrase condition="manual">See
-also <xref linkend="sec-common-options"/>.</phrase></para>
-
-<variablelist>
-
- <varlistentry><term><option>--command</option> <replaceable>cmd</replaceable></term>
-
- <listitem><para>In the environment of the derivation, run the
- shell command <replaceable>cmd</replaceable>. This command is
- executed in an interactive shell. (Use <option>--run</option> to
- use a non-interactive shell instead.) However, a call to
- <literal>exit</literal> is implicitly added to the command, so the
- shell will exit after running the command. To prevent this, add
- <literal>return</literal> at the end; e.g. <literal>--command
- "echo Hello; return"</literal> will print <literal>Hello</literal>
- and then drop you into the interactive shell. This can be useful
- for doing any additional initialisation.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--run</option> <replaceable>cmd</replaceable></term>
-
- <listitem><para>Like <option>--command</option>, but executes the
- command in a non-interactive shell. This means (among other
- things) that if you hit Ctrl-C while the command is running, the
- shell exits.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--exclude</option> <replaceable>regexp</replaceable></term>
-
- <listitem><para>Do not build any dependencies whose store path
- matches the regular expression <replaceable>regexp</replaceable>.
- This option may be specified multiple times.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--pure</option></term>
-
- <listitem><para>If this flag is specified, the environment is
- almost entirely cleared before the interactive shell is started,
- so you get an environment that more closely corresponds to the
- “real” Nix build. A few variables, in particular
- <envar>HOME</envar>, <envar>USER</envar> and
- <envar>DISPLAY</envar>, are retained. Note that
- <filename>~/.bashrc</filename> and (depending on your Bash
- installation) <filename>/etc/bashrc</filename> are still sourced,
- so any variables set there will affect the interactive
- shell.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--packages</option> / <option>-p</option> <replaceable>packages</replaceable>…</term>
-
- <listitem><para>Set up an environment in which the specified
- packages are present. The command line arguments are interpreted
- as attribute names inside the Nix Packages collection. Thus,
- <literal>nix-shell -p libjpeg openjdk</literal> will start a shell
- in which the packages denoted by the attribute names
- <varname>libjpeg</varname> and <varname>openjdk</varname> are
- present.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>-i</option> <replaceable>interpreter</replaceable></term>
-
- <listitem><para>The chained script interpreter to be invoked by
- <command>nix-shell</command>. Only applicable in
- <literal>#!</literal>-scripts (described <link linkend="ssec-nix-shell-shebang">below</link>).</para>
-
- </listitem></varlistentry>
-
- <varlistentry><term><option>--keep</option> <replaceable>name</replaceable></term>
-
- <listitem><para>When a <option>--pure</option> shell is started,
- keep the listed environment variables.</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-<para>The following common options are supported:</para>
-
-<variablelist condition="manpage">
- <varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--help</option></term>
-
- <listitem><para>Prints out a summary of the command syntax and
- exits.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--version</option></term>
-
- <listitem><para>Prints out the Nix version number on standard output
- and exits.</para></listitem>
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--verbose</option> / <option>-v</option></term>
-
- <listitem>
-
- <para>Increases the level of verbosity of diagnostic messages
- printed on standard error. For each Nix operation, the information
- printed on standard output is well-defined; any diagnostic
- information is printed on standard error, never on standard
- output.</para>
-
- <para>This option may be specified repeatedly. Currently, the
- following verbosity levels exist:</para>
-
- <variablelist>
-
- <varlistentry><term>0</term>
- <listitem><para>“Errors only”: only print messages
- explaining why the Nix invocation failed.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>1</term>
- <listitem><para>“Informational”: print
- <emphasis>useful</emphasis> messages about what Nix is doing.
- This is the default.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>2</term>
- <listitem><para>“Talkative”: print more informational
- messages.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>3</term>
- <listitem><para>“Chatty”: print even more
- informational messages.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>4</term>
- <listitem><para>“Debug”: print debug
- information.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>5</term>
- <listitem><para>“Vomit”: print vast amounts of debug
- information.</para></listitem>
- </varlistentry>
-
- </variablelist>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--quiet</option></term>
-
- <listitem>
-
- <para>Decreases the level of verbosity of diagnostic messages
- printed on standard error. This is the inverse option to
- <option>-v</option> / <option>--verbose</option>.
- </para>
-
- <para>This option may be specified repeatedly. See the previous
- verbosity levels list.</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-log-format"><term><option>--log-format</option> <replaceable>format</replaceable></term>
-
- <listitem>
-
- <para>This option can be used to change the output of the log format, with
- <replaceable>format</replaceable> being one of:</para>
-
- <variablelist>
-
- <varlistentry><term>raw</term>
- <listitem><para>This is the raw format, as outputted by nix-build.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>internal-json</term>
- <listitem><para>Outputs the logs in a structured manner. NOTE: the json schema is not guarantees to be stable between releases.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>bar</term>
- <listitem><para>Only display a progress bar during the builds.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>bar-with-logs</term>
- <listitem><para>Display the raw logs, with the progress bar at the bottom.</para></listitem>
- </varlistentry>
-
- </variablelist>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--no-build-output</option> / <option>-Q</option></term>
-
- <listitem><para>By default, output written by builders to standard
- output and standard error is echoed to the Nix command's standard
- error. This option suppresses this behaviour. Note that the
- builder's standard output and error are always written to a log file
- in
- <filename><replaceable>prefix</replaceable>/nix/var/log/nix</filename>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-max-jobs"><term><option>--max-jobs</option> / <option>-j</option>
-<replaceable>number</replaceable></term>
-
- <listitem>
-
- <para>Sets the maximum number of build jobs that Nix will
- perform in parallel to the specified number. Specify
- <literal>auto</literal> to use the number of CPUs in the system.
- The default is specified by the <link linkend="conf-max-jobs"><literal>max-jobs</literal></link>
- configuration setting, which itself defaults to
- <literal>1</literal>. A higher value is useful on SMP systems or to
- exploit I/O latency.</para>
-
- <para> Setting it to <literal>0</literal> disallows building on the local
- machine, which is useful when you want builds to happen only on remote
- builders.</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-cores"><term><option>--cores</option></term>
-
- <listitem><para>Sets the value of the <envar>NIX_BUILD_CORES</envar>
- environment variable in the invocation of builders. Builders can
- use this variable at their discretion to control the maximum amount
- of parallelism. For instance, in Nixpkgs, if the derivation
- attribute <varname>enableParallelBuilding</varname> is set to
- <literal>true</literal>, the builder passes the
- <option>-j<replaceable>N</replaceable></option> flag to GNU Make.
- It defaults to the value of the <link linkend="conf-cores"><literal>cores</literal></link>
- configuration setting, if set, or <literal>1</literal> otherwise.
- The value <literal>0</literal> means that the builder should use all
- available CPU cores in the system.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-max-silent-time"><term><option>--max-silent-time</option></term>
-
- <listitem><para>Sets the maximum number of seconds that a builder
- can go without producing any data on standard output or standard
- error. The default is specified by the <link linkend="conf-max-silent-time"><literal>max-silent-time</literal></link>
- configuration setting. <literal>0</literal> means no
- time-out.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-timeout"><term><option>--timeout</option></term>
-
- <listitem><para>Sets the maximum number of seconds that a builder
- can run. The default is specified by the <link linkend="conf-timeout"><literal>timeout</literal></link>
- configuration setting. <literal>0</literal> means no
- timeout.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--keep-going</option> / <option>-k</option></term>
-
- <listitem><para>Keep going in case of failed builds, to the
- greatest extent possible. That is, if building an input of some
- derivation fails, Nix will still build the other inputs, but not the
- derivation itself. Without this option, Nix stops if any build
- fails (except for builds of substitutes), possibly killing builds in
- progress (in case of parallel or distributed builds).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--keep-failed</option> / <option>-K</option></term>
-
- <listitem><para>Specifies that in case of a build failure, the
- temporary directory (usually in <filename>/tmp</filename>) in which
- the build takes place should not be deleted. The path of the build
- directory is printed as an informational message.
- </para>
- </listitem>
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--fallback</option></term>
-
- <listitem>
-
- <para>Whenever Nix attempts to build a derivation for which
- substitutes are known for each output path, but realising the output
- paths through the substitutes fails, fall back on building the
- derivation.</para>
-
- <para>The most common scenario in which this is useful is when we
- have registered substitutes in order to perform binary distribution
- from, say, a network repository. If the repository is down, the
- realisation of the derivation will fail. When this option is
- specified, Nix will build the derivation instead. Thus,
- installation from binaries falls back on installation from source.
- This option is not the default since it is generally not desirable
- for a transient failure in obtaining the substitutes to lead to a
- full build from source (with the related consumption of
- resources).</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--no-build-hook</option></term>
-
- <listitem>
-
- <para>Disables the build hook mechanism. This allows to ignore remote
- builders if they are setup on the machine.</para>
-
- <para>It's useful in cases where the bandwidth between the client and the
- remote builder is too low. In that case it can take more time to upload the
- sources to the remote builder and fetch back the result than to do the
- computation locally.</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--readonly-mode</option></term>
-
- <listitem><para>When this option is used, no attempt is made to open
- the Nix database. Most Nix operations do need database access, so
- those operations will fail.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--arg</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
-
- <listitem><para>This option is accepted by
- <command>nix-env</command>, <command>nix-instantiate</command>,
- <command>nix-shell</command> and <command>nix-build</command>.
- When evaluating Nix expressions, the expression evaluator will
- automatically try to call functions that
- it encounters. It can automatically call functions for which every
- argument has a <link linkend="ss-functions">default value</link>
- (e.g., <literal>{ <replaceable>argName</replaceable> ?
- <replaceable>defaultValue</replaceable> }:
- <replaceable>...</replaceable></literal>). With
- <option>--arg</option>, you can also call functions that have
- arguments without a default value (or override a default value).
- That is, if the evaluator encounters a function with an argument
- named <replaceable>name</replaceable>, it will call it with value
- <replaceable>value</replaceable>.</para>
-
- <para>For instance, the top-level <literal>default.nix</literal> in
- Nixpkgs is actually a function:
-
-<programlisting>
-{ # The system (e.g., `i686-linux') for which to build the packages.
- system ? builtins.currentSystem
- <replaceable>...</replaceable>
-}: <replaceable>...</replaceable></programlisting>
-
- So if you call this Nix expression (e.g., when you do
- <literal>nix-env -i <replaceable>pkgname</replaceable></literal>),
- the function will be called automatically using the value <link linkend="builtin-currentSystem"><literal>builtins.currentSystem</literal></link>
- for the <literal>system</literal> argument. You can override this
- using <option>--arg</option>, e.g., <literal>nix-env -i
- <replaceable>pkgname</replaceable> --arg system
- \"i686-freebsd\"</literal>. (Note that since the argument is a Nix
- string literal, you have to escape the quotes.)</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--argstr</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
-
- <listitem><para>This option is like <option>--arg</option>, only the
- value is not a Nix expression but a string. So instead of
- <literal>--arg system \"i686-linux\"</literal> (the outer quotes are
- to keep the shell happy) you can say <literal>--argstr system
- i686-linux</literal>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-attr"><term><option>--attr</option> / <option>-A</option>
-<replaceable>attrPath</replaceable></term>
-
- <listitem><para>Select an attribute from the top-level Nix
- expression being evaluated. (<command>nix-env</command>,
- <command>nix-instantiate</command>, <command>nix-build</command> and
- <command>nix-shell</command> only.) The <emphasis>attribute
- path</emphasis> <replaceable>attrPath</replaceable> is a sequence of
- attribute names separated by dots. For instance, given a top-level
- Nix expression <replaceable>e</replaceable>, the attribute path
- <literal>xorg.xorgserver</literal> would cause the expression
- <literal><replaceable>e</replaceable>.xorg.xorgserver</literal> to
- be used. See <link linkend="refsec-nix-env-install-examples"><command>nix-env
- --install</command></link> for some concrete examples.</para>
-
- <para>In addition to attribute names, you can also specify array
- indices. For instance, the attribute path
- <literal>foo.3.bar</literal> selects the <literal>bar</literal>
- attribute of the fourth element of the array in the
- <literal>foo</literal> attribute of the top-level
- expression.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--expr</option> / <option>-E</option></term>
-
- <listitem><para>Interpret the command line arguments as a list of
- Nix expressions to be parsed and evaluated, rather than as a list
- of file names of Nix expressions.
- (<command>nix-instantiate</command>, <command>nix-build</command>
- and <command>nix-shell</command> only.)</para>
-
- <para>For <command>nix-shell</command>, this option is commonly used
- to give you a shell in which you can build the packages returned
- by the expression. If you want to get a shell which contain the
- <emphasis>built</emphasis> packages ready for use, give your
- expression to the <command>nix-shell -p</command> convenience flag
- instead.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-I"><term><option>-I</option> <replaceable>path</replaceable></term>
-
- <listitem><para>Add a path to the Nix expression search path. This
- option may be given multiple times. See the <envar linkend="env-NIX_PATH">NIX_PATH</envar> environment variable for
- information on the semantics of the Nix search path. Paths added
- through <option>-I</option> take precedence over
- <envar>NIX_PATH</envar>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--option</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
-
- <listitem><para>Set the Nix configuration option
- <replaceable>name</replaceable> to <replaceable>value</replaceable>.
- This overrides settings in the Nix configuration file (see
- <citerefentry><refentrytitle>nix.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--repair</option></term>
-
- <listitem><para>Fix corrupted or missing store paths by
- redownloading or rebuilding them. Note that this is slow because it
- requires computing a cryptographic hash of the contents of every
- path in the closure of the build. Also note the warning under
- <command>nix-store --repair-path</command>.</para></listitem>
-
-</varlistentry>
-</variablelist>
-
-</refsection>
-
-
-<refsection><title>Environment variables</title>
-
-<variablelist>
-
- <varlistentry><term><envar>NIX_BUILD_SHELL</envar></term>
-
- <listitem><para>Shell used to start the interactive environment.
- Defaults to the <command>bash</command> found in <envar>PATH</envar>.</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-</refsection>
-
-
-<refsection><title>Examples</title>
-
-<para>To build the dependencies of the package Pan, and start an
-interactive shell in which to build it:
-
-<screen>
-$ nix-shell '<nixpkgs>' -A pan
-[nix-shell]$ unpackPhase
-[nix-shell]$ cd pan-*
-[nix-shell]$ configurePhase
-[nix-shell]$ buildPhase
-[nix-shell]$ ./pan/gui/pan
-</screen>
-
-To clear the environment first, and do some additional automatic
-initialisation of the interactive shell:
-
-<screen>
-$ nix-shell '<nixpkgs>' -A pan --pure \
- --command 'export NIX_DEBUG=1; export NIX_CORES=8; return'
-</screen>
-
-Nix expressions can also be given on the command line using the
-<command>-E</command> and <command>-p</command> flags.
-For instance, the following starts a shell containing the packages
-<literal>sqlite</literal> and <literal>libX11</literal>:
-
-<screen>
-$ nix-shell -E 'with import <nixpkgs> { }; runCommand "dummy" { buildInputs = [ sqlite xorg.libX11 ]; } ""'
-</screen>
-
-A shorter way to do the same is:
-
-<screen>
-$ nix-shell -p sqlite xorg.libX11
-[nix-shell]$ echo $NIX_LDFLAGS
-… -L/nix/store/j1zg5v…-sqlite-3.8.0.2/lib -L/nix/store/0gmcz9…-libX11-1.6.1/lib …
-</screen>
-
-Note that <command>-p</command> accepts multiple full nix expressions that
-are valid in the <literal>buildInputs = [ ... ]</literal> shown above,
-not only package names. So the following is also legal:
-
-<screen>
-$ nix-shell -p sqlite 'git.override { withManual = false; }'
-</screen>
-
-The <command>-p</command> flag looks up Nixpkgs in the Nix search
-path. You can override it by passing <option>-I</option> or setting
-<envar>NIX_PATH</envar>. For example, the following gives you a shell
-containing the Pan package from a specific revision of Nixpkgs:
-
-<screen>
-$ nix-shell -p pan -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/8a3eea054838b55aca962c3fbde9c83c102b8bf2.tar.gz
-
-[nix-shell:~]$ pan --version
-Pan 0.139
-</screen>
-
-</para>
-
-</refsection>
-
-
-<refsection xml:id="ssec-nix-shell-shebang"><title>Use as a <literal>#!</literal>-interpreter</title>
-
-<para>You can use <command>nix-shell</command> as a script interpreter
-to allow scripts written in arbitrary languages to obtain their own
-dependencies via Nix. This is done by starting the script with the
-following lines:
-
-<programlisting>
-#! /usr/bin/env nix-shell
-#! nix-shell -i <replaceable>real-interpreter</replaceable> -p <replaceable>packages</replaceable>
-</programlisting>
-
-where <replaceable>real-interpreter</replaceable> is the “real” script
-interpreter that will be invoked by <command>nix-shell</command> after
-it has obtained the dependencies and initialised the environment, and
-<replaceable>packages</replaceable> are the attribute names of the
-dependencies in Nixpkgs.</para>
-
-<para>The lines starting with <literal>#! nix-shell</literal> specify
-<command>nix-shell</command> options (see above). Note that you cannot
-write <literal>#! /usr/bin/env nix-shell -i ...</literal> because
-many operating systems only allow one argument in
-<literal>#!</literal> lines.</para>
-
-<para>For example, here is a Python script that depends on Python and
-the <literal>prettytable</literal> package:
-
-<programlisting>
-#! /usr/bin/env nix-shell
-#! nix-shell -i python -p python pythonPackages.prettytable
-
-import prettytable
-
-# Print a simple table.
-t = prettytable.PrettyTable(["N", "N^2"])
-for n in range(1, 10): t.add_row([n, n * n])
-print t
-</programlisting>
-
-</para>
-
-<para>Similarly, the following is a Perl script that specifies that it
-requires Perl and the <literal>HTML::TokeParser::Simple</literal> and
-<literal>LWP</literal> packages:
-
-<programlisting>
-#! /usr/bin/env nix-shell
-#! nix-shell -i perl -p perl perlPackages.HTMLTokeParserSimple perlPackages.LWP
-
-use HTML::TokeParser::Simple;
-
-# Fetch nixos.org and print all hrefs.
-my $p = HTML::TokeParser::Simple->new(url => 'http://nixos.org/');
-
-while (my $token = $p->get_tag("a")) {
- my $href = $token->get_attr("href");
- print "$href\n" if $href;
-}
-</programlisting>
-
-</para>
-
-<para>Sometimes you need to pass a simple Nix expression to customize
-a package like Terraform:
-
-<programlisting><![CDATA[
-#! /usr/bin/env nix-shell
-#! nix-shell -i bash -p "terraform.withPlugins (plugins: [ plugins.openstack ])"
-
-terraform apply
-]]></programlisting>
-
-<note><para>You must use double quotes (<literal>"</literal>) when
-passing a simple Nix expression in a nix-shell shebang.</para></note>
-</para>
-
-<para>Finally, using the merging of multiple nix-shell shebangs the
-following Haskell script uses a specific branch of Nixpkgs/NixOS (the
-18.03 stable branch):
-
-<programlisting><![CDATA[
-#! /usr/bin/env nix-shell
-#! nix-shell -i runghc -p "haskellPackages.ghcWithPackages (ps: [ps.HTTP ps.tagsoup])"
-#! nix-shell -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-18.03.tar.gz
-
-import Network.HTTP
-import Text.HTML.TagSoup
-
--- Fetch nixos.org and print all hrefs.
-main = do
- resp <- Network.HTTP.simpleHTTP (getRequest "http://nixos.org/")
- body <- getResponseBody resp
- let tags = filter (isTagOpenName "a") $ parseTags body
- let tags' = map (fromAttrib "href") tags
- mapM_ putStrLn $ filter (/= "") tags'
-]]></programlisting>
-
-If you want to be even more precise, you can specify a specific
-revision of Nixpkgs:
-
-<programlisting>
-#! nix-shell -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/0672315759b3e15e2121365f067c1c8c56bb4722.tar.gz
-</programlisting>
-
-</para>
-
-<para>The examples above all used <option>-p</option> to get
-dependencies from Nixpkgs. You can also use a Nix expression to build
-your own dependencies. For example, the Python example could have been
-written as:
-
-<programlisting>
-#! /usr/bin/env nix-shell
-#! nix-shell deps.nix -i python
-</programlisting>
-
-where the file <filename>deps.nix</filename> in the same directory
-as the <literal>#!</literal>-script contains:
-
-<programlisting>
-with import <nixpkgs> {};
-
-runCommand "dummy" { buildInputs = [ python pythonPackages.prettytable ]; } ""
-</programlisting>
-
-</para>
-
-</refsection>
-
-
-<refsection condition="manpage"><title>Environment variables</title>
-
-<variablelist>
- <varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>IN_NIX_SHELL</envar></term>
-
- <listitem><para>Indicator that tells if the current environment was set up by
- <command>nix-shell</command>. Since Nix 2.0 the values are
- <literal>"pure"</literal> and <literal>"impure"</literal></para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="env-NIX_PATH"><term><envar>NIX_PATH</envar></term>
-
- <listitem>
-
- <para>A colon-separated list of directories used to look up Nix
- expressions enclosed in angle brackets (i.e.,
- <literal><<replaceable>path</replaceable>></literal>). For
- instance, the value
-
- <screen>
-/home/eelco/Dev:/etc/nixos</screen>
-
- will cause Nix to look for paths relative to
- <filename>/home/eelco/Dev</filename> and
- <filename>/etc/nixos</filename>, in this order. It is also
- possible to match paths against a prefix. For example, the value
-
- <screen>
-nixpkgs=/home/eelco/Dev/nixpkgs-branch:/etc/nixos</screen>
-
- will cause Nix to search for
- <literal><nixpkgs/<replaceable>path</replaceable>></literal> in
- <filename>/home/eelco/Dev/nixpkgs-branch/<replaceable>path</replaceable></filename>
- and
- <filename>/etc/nixos/nixpkgs/<replaceable>path</replaceable></filename>.</para>
-
- <para>If a path in the Nix search path starts with
- <literal>http://</literal> or <literal>https://</literal>, it is
- interpreted as the URL of a tarball that will be downloaded and
- unpacked to a temporary location. The tarball must consist of a
- single top-level directory. For example, setting
- <envar>NIX_PATH</envar> to
-
- <screen>
-nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-15.09.tar.gz</screen>
-
- tells Nix to download the latest revision in the Nixpkgs/NixOS
- 15.09 channel.</para>
-
- <para>A following shorthand can be used to refer to the official channels:
-
- <screen>nixpkgs=channel:nixos-15.09</screen>
- </para>
-
- <para>The search path can be extended using the <option linkend="opt-I">-I</option> option, which takes precedence over
- <envar>NIX_PATH</envar>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_IGNORE_SYMLINK_STORE</envar></term>
-
- <listitem>
-
- <para>Normally, the Nix store directory (typically
- <filename>/nix/store</filename>) is not allowed to contain any
- symlink components. This is to prevent “impure” builds. Builders
- sometimes “canonicalise” paths by resolving all symlink components.
- Thus, builds on different machines (with
- <filename>/nix/store</filename> resolving to different locations)
- could yield different results. This is generally not a problem,
- except when builds are deployed to machines where
- <filename>/nix/store</filename> resolves differently. If you are
- sure that you’re not going to do that, you can set
- <envar>NIX_IGNORE_SYMLINK_STORE</envar> to <envar>1</envar>.</para>
-
- <para>Note that if you’re symlinking the Nix store so that you can
- put it on another file system than the root file system, on Linux
- you’re better off using <literal>bind</literal> mount points, e.g.,
-
- <screen>
-$ mkdir /nix
-$ mount -o bind /mnt/otherdisk/nix /nix</screen>
-
- Consult the <citerefentry><refentrytitle>mount</refentrytitle>
- <manvolnum>8</manvolnum></citerefentry> manual page for details.</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_STORE_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix store (default
- <filename><replaceable>prefix</replaceable>/store</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_DATA_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix static data
- directory (default
- <filename><replaceable>prefix</replaceable>/share</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_LOG_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix log directory
- (default <filename><replaceable>prefix</replaceable>/var/log/nix</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_STATE_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix state directory
- (default <filename><replaceable>prefix</replaceable>/var/nix</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_CONF_DIR</envar></term>
-
- <listitem><para>Overrides the location of the system Nix configuration
- directory (default
- <filename><replaceable>prefix</replaceable>/etc/nix</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_USER_CONF_FILES</envar></term>
-
- <listitem><para>Overrides the location of the user Nix configuration files
- to load from (defaults to the XDG spec locations). The variable is treated
- as a list separated by the <literal>:</literal> token.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>TMPDIR</envar></term>
-
- <listitem><para>Use the specified directory to store temporary
- files. In particular, this includes temporary build directories;
- these can take up substantial amounts of disk space. The default is
- <filename>/tmp</filename>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="envar-remote"><term><envar>NIX_REMOTE</envar></term>
-
- <listitem><para>This variable should be set to
- <literal>daemon</literal> if you want to use the Nix daemon to
- execute Nix operations. This is necessary in <link linkend="ssec-multi-user">multi-user Nix installations</link>.
- If the Nix daemon's Unix socket is at some non-standard path,
- this variable should be set to <literal>unix://path/to/socket</literal>.
- Otherwise, it should be left unset.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_SHOW_STATS</envar></term>
-
- <listitem><para>If set to <literal>1</literal>, Nix will print some
- evaluation statistics, such as the number of values
- allocated.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_COUNT_CALLS</envar></term>
-
- <listitem><para>If set to <literal>1</literal>, Nix will print how
- often functions were called during Nix expression evaluation. This
- is useful for profiling your Nix expressions.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>GC_INITIAL_HEAP_SIZE</envar></term>
-
- <listitem><para>If Nix has been configured to use the Boehm garbage
- collector, this variable sets the initial size of the heap in bytes.
- It defaults to 384 MiB. Setting it to a low value reduces memory
- consumption, but will increase runtime due to the overhead of
- garbage collection.</para></listitem>
-
-</varlistentry>
-</variablelist>
-
-</refsection>
-
-
-</refentry>
-<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-nix-store">
-
-<refmeta>
- <refentrytitle>nix-store</refentrytitle>
- <manvolnum>1</manvolnum>
- <refmiscinfo class="source">Nix</refmiscinfo>
- <refmiscinfo class="version">3.0</refmiscinfo>
-</refmeta>
-
-<refnamediv>
- <refname>nix-store</refname>
- <refpurpose>manipulate or query the Nix store</refpurpose>
-</refnamediv>
-
-<refsynopsisdiv>
- <cmdsynopsis>
- <command>nix-store</command>
- <arg xmlns="http://docbook.org/ns/docbook"><option>--help</option></arg><arg xmlns="http://docbook.org/ns/docbook"><option>--version</option></arg><arg xmlns="http://docbook.org/ns/docbook" rep="repeat">
- <group choice="req">
- <arg choice="plain"><option>--verbose</option></arg>
- <arg choice="plain"><option>-v</option></arg>
- </group>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <arg choice="plain"><option>--quiet</option></arg>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <option>--log-format</option>
- <replaceable>format</replaceable>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <group choice="plain">
- <arg choice="plain"><option>--no-build-output</option></arg>
- <arg choice="plain"><option>-Q</option></arg>
- </group>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <group choice="req">
- <arg choice="plain"><option>--max-jobs</option></arg>
- <arg choice="plain"><option>-j</option></arg>
- </group>
- <replaceable>number</replaceable>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <option>--cores</option>
- <replaceable>number</replaceable>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <option>--max-silent-time</option>
- <replaceable>number</replaceable>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <option>--timeout</option>
- <replaceable>number</replaceable>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <group choice="plain">
- <arg choice="plain"><option>--keep-going</option></arg>
- <arg choice="plain"><option>-k</option></arg>
- </group>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <group choice="plain">
- <arg choice="plain"><option>--keep-failed</option></arg>
- <arg choice="plain"><option>-K</option></arg>
- </group>
-</arg><arg xmlns="http://docbook.org/ns/docbook"><option>--fallback</option></arg><arg xmlns="http://docbook.org/ns/docbook"><option>--readonly-mode</option></arg><arg xmlns="http://docbook.org/ns/docbook">
- <option>-I</option>
- <replaceable>path</replaceable>
-</arg><arg xmlns="http://docbook.org/ns/docbook">
- <option>--option</option>
- <replaceable>name</replaceable>
- <replaceable>value</replaceable>
-</arg><sbr xmlns="http://docbook.org/ns/docbook"/>
- <arg><option>--add-root</option> <replaceable>path</replaceable></arg>
- <arg><option>--indirect</option></arg>
- <arg choice="plain"><replaceable>operation</replaceable></arg>
- <arg rep="repeat"><replaceable>options</replaceable></arg>
- <arg rep="repeat"><replaceable>arguments</replaceable></arg>
- </cmdsynopsis>
-</refsynopsisdiv>
-
-
-<refsection><title>Description</title>
-
-<para>The command <command>nix-store</command> performs primitive
-operations on the Nix store. You generally do not need to run this
-command manually.</para>
-
-<para><command>nix-store</command> takes exactly one
-<emphasis>operation</emphasis> flag which indicates the subcommand to
-be performed. These are documented below.</para>
-
-</refsection>
-
-
-
-<!--######################################################################-->
-
-<refsection><title>Common options</title>
-
-<para>This section lists the options that are common to all
-operations. These options are allowed for every subcommand, though
-they may not always have an effect. <phrase condition="manual">See
-also <xref linkend="sec-common-options"/> for a list of common
-options.</phrase></para>
-
-<variablelist>
-
- <varlistentry xml:id="opt-add-root"><term><option>--add-root</option> <replaceable>path</replaceable></term>
-
- <listitem><para>Causes the result of a realisation
- (<option>--realise</option> and <option>--force-realise</option>)
- to be registered as a root of the garbage collector<phrase condition="manual"> (see <xref linkend="ssec-gc-roots"/>)</phrase>. The root is stored in
- <replaceable>path</replaceable>, which must be inside a directory
- that is scanned for roots by the garbage collector (i.e.,
- typically in a subdirectory of
- <filename>/nix/var/nix/gcroots/</filename>)
- <emphasis>unless</emphasis> the <option>--indirect</option> flag
- is used.</para>
-
- <para>If there are multiple results, then multiple symlinks will
- be created by sequentially numbering symlinks beyond the first one
- (e.g., <filename>foo</filename>, <filename>foo-2</filename>,
- <filename>foo-3</filename>, and so on).</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--indirect</option></term>
-
- <listitem>
-
- <para>In conjunction with <option>--add-root</option>, this option
- allows roots to be stored <emphasis>outside</emphasis> of the GC
- roots directory. This is useful for commands such as
- <command>nix-build</command> that place a symlink to the build
- result in the current directory; such a build result should not be
- garbage-collected unless the symlink is removed.</para>
-
- <para>The <option>--indirect</option> flag causes a uniquely named
- symlink to <replaceable>path</replaceable> to be stored in
- <filename>/nix/var/nix/gcroots/auto/</filename>. For instance,
-
- <screen>
-$ nix-store --add-root /home/eelco/bla/result --indirect -r <replaceable>...</replaceable>
-
-$ ls -l /nix/var/nix/gcroots/auto
-lrwxrwxrwx 1 ... 2005-03-13 21:10 dn54lcypm8f8... -> /home/eelco/bla/result
-
-$ ls -l /home/eelco/bla/result
-lrwxrwxrwx 1 ... 2005-03-13 21:10 /home/eelco/bla/result -> /nix/store/1r11343n6qd4...-f-spot-0.0.10</screen>
-
- Thus, when <filename>/home/eelco/bla/result</filename> is removed,
- the GC root in the <filename>auto</filename> directory becomes a
- dangling symlink and will be ignored by the collector.</para>
-
- <warning><para>Note that it is not possible to move or rename
- indirect GC roots, since the symlink in the
- <filename>auto</filename> directory will still point to the old
- location.</para></warning>
-
- </listitem>
-
- </varlistentry>
-
-</variablelist>
-
-<variablelist condition="manpage">
- <varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--help</option></term>
-
- <listitem><para>Prints out a summary of the command syntax and
- exits.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--version</option></term>
-
- <listitem><para>Prints out the Nix version number on standard output
- and exits.</para></listitem>
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--verbose</option> / <option>-v</option></term>
-
- <listitem>
-
- <para>Increases the level of verbosity of diagnostic messages
- printed on standard error. For each Nix operation, the information
- printed on standard output is well-defined; any diagnostic
- information is printed on standard error, never on standard
- output.</para>
-
- <para>This option may be specified repeatedly. Currently, the
- following verbosity levels exist:</para>
-
- <variablelist>
-
- <varlistentry><term>0</term>
- <listitem><para>“Errors only”: only print messages
- explaining why the Nix invocation failed.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>1</term>
- <listitem><para>“Informational”: print
- <emphasis>useful</emphasis> messages about what Nix is doing.
- This is the default.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>2</term>
- <listitem><para>“Talkative”: print more informational
- messages.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>3</term>
- <listitem><para>“Chatty”: print even more
- informational messages.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>4</term>
- <listitem><para>“Debug”: print debug
- information.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>5</term>
- <listitem><para>“Vomit”: print vast amounts of debug
- information.</para></listitem>
- </varlistentry>
-
- </variablelist>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--quiet</option></term>
-
- <listitem>
-
- <para>Decreases the level of verbosity of diagnostic messages
- printed on standard error. This is the inverse option to
- <option>-v</option> / <option>--verbose</option>.
- </para>
-
- <para>This option may be specified repeatedly. See the previous
- verbosity levels list.</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-log-format"><term><option>--log-format</option> <replaceable>format</replaceable></term>
-
- <listitem>
-
- <para>This option can be used to change the output of the log format, with
- <replaceable>format</replaceable> being one of:</para>
-
- <variablelist>
-
- <varlistentry><term>raw</term>
- <listitem><para>This is the raw format, as outputted by nix-build.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>internal-json</term>
- <listitem><para>Outputs the logs in a structured manner. NOTE: the json schema is not guarantees to be stable between releases.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>bar</term>
- <listitem><para>Only display a progress bar during the builds.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>bar-with-logs</term>
- <listitem><para>Display the raw logs, with the progress bar at the bottom.</para></listitem>
- </varlistentry>
-
- </variablelist>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--no-build-output</option> / <option>-Q</option></term>
-
- <listitem><para>By default, output written by builders to standard
- output and standard error is echoed to the Nix command's standard
- error. This option suppresses this behaviour. Note that the
- builder's standard output and error are always written to a log file
- in
- <filename><replaceable>prefix</replaceable>/nix/var/log/nix</filename>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-max-jobs"><term><option>--max-jobs</option> / <option>-j</option>
-<replaceable>number</replaceable></term>
-
- <listitem>
-
- <para>Sets the maximum number of build jobs that Nix will
- perform in parallel to the specified number. Specify
- <literal>auto</literal> to use the number of CPUs in the system.
- The default is specified by the <link linkend="conf-max-jobs"><literal>max-jobs</literal></link>
- configuration setting, which itself defaults to
- <literal>1</literal>. A higher value is useful on SMP systems or to
- exploit I/O latency.</para>
-
- <para> Setting it to <literal>0</literal> disallows building on the local
- machine, which is useful when you want builds to happen only on remote
- builders.</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-cores"><term><option>--cores</option></term>
-
- <listitem><para>Sets the value of the <envar>NIX_BUILD_CORES</envar>
- environment variable in the invocation of builders. Builders can
- use this variable at their discretion to control the maximum amount
- of parallelism. For instance, in Nixpkgs, if the derivation
- attribute <varname>enableParallelBuilding</varname> is set to
- <literal>true</literal>, the builder passes the
- <option>-j<replaceable>N</replaceable></option> flag to GNU Make.
- It defaults to the value of the <link linkend="conf-cores"><literal>cores</literal></link>
- configuration setting, if set, or <literal>1</literal> otherwise.
- The value <literal>0</literal> means that the builder should use all
- available CPU cores in the system.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-max-silent-time"><term><option>--max-silent-time</option></term>
-
- <listitem><para>Sets the maximum number of seconds that a builder
- can go without producing any data on standard output or standard
- error. The default is specified by the <link linkend="conf-max-silent-time"><literal>max-silent-time</literal></link>
- configuration setting. <literal>0</literal> means no
- time-out.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-timeout"><term><option>--timeout</option></term>
-
- <listitem><para>Sets the maximum number of seconds that a builder
- can run. The default is specified by the <link linkend="conf-timeout"><literal>timeout</literal></link>
- configuration setting. <literal>0</literal> means no
- timeout.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--keep-going</option> / <option>-k</option></term>
-
- <listitem><para>Keep going in case of failed builds, to the
- greatest extent possible. That is, if building an input of some
- derivation fails, Nix will still build the other inputs, but not the
- derivation itself. Without this option, Nix stops if any build
- fails (except for builds of substitutes), possibly killing builds in
- progress (in case of parallel or distributed builds).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--keep-failed</option> / <option>-K</option></term>
-
- <listitem><para>Specifies that in case of a build failure, the
- temporary directory (usually in <filename>/tmp</filename>) in which
- the build takes place should not be deleted. The path of the build
- directory is printed as an informational message.
- </para>
- </listitem>
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--fallback</option></term>
-
- <listitem>
-
- <para>Whenever Nix attempts to build a derivation for which
- substitutes are known for each output path, but realising the output
- paths through the substitutes fails, fall back on building the
- derivation.</para>
-
- <para>The most common scenario in which this is useful is when we
- have registered substitutes in order to perform binary distribution
- from, say, a network repository. If the repository is down, the
- realisation of the derivation will fail. When this option is
- specified, Nix will build the derivation instead. Thus,
- installation from binaries falls back on installation from source.
- This option is not the default since it is generally not desirable
- for a transient failure in obtaining the substitutes to lead to a
- full build from source (with the related consumption of
- resources).</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--no-build-hook</option></term>
-
- <listitem>
-
- <para>Disables the build hook mechanism. This allows to ignore remote
- builders if they are setup on the machine.</para>
-
- <para>It's useful in cases where the bandwidth between the client and the
- remote builder is too low. In that case it can take more time to upload the
- sources to the remote builder and fetch back the result than to do the
- computation locally.</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--readonly-mode</option></term>
-
- <listitem><para>When this option is used, no attempt is made to open
- the Nix database. Most Nix operations do need database access, so
- those operations will fail.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--arg</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
-
- <listitem><para>This option is accepted by
- <command>nix-env</command>, <command>nix-instantiate</command>,
- <command>nix-shell</command> and <command>nix-build</command>.
- When evaluating Nix expressions, the expression evaluator will
- automatically try to call functions that
- it encounters. It can automatically call functions for which every
- argument has a <link linkend="ss-functions">default value</link>
- (e.g., <literal>{ <replaceable>argName</replaceable> ?
- <replaceable>defaultValue</replaceable> }:
- <replaceable>...</replaceable></literal>). With
- <option>--arg</option>, you can also call functions that have
- arguments without a default value (or override a default value).
- That is, if the evaluator encounters a function with an argument
- named <replaceable>name</replaceable>, it will call it with value
- <replaceable>value</replaceable>.</para>
-
- <para>For instance, the top-level <literal>default.nix</literal> in
- Nixpkgs is actually a function:
-
-<programlisting>
-{ # The system (e.g., `i686-linux') for which to build the packages.
- system ? builtins.currentSystem
- <replaceable>...</replaceable>
-}: <replaceable>...</replaceable></programlisting>
-
- So if you call this Nix expression (e.g., when you do
- <literal>nix-env -i <replaceable>pkgname</replaceable></literal>),
- the function will be called automatically using the value <link linkend="builtin-currentSystem"><literal>builtins.currentSystem</literal></link>
- for the <literal>system</literal> argument. You can override this
- using <option>--arg</option>, e.g., <literal>nix-env -i
- <replaceable>pkgname</replaceable> --arg system
- \"i686-freebsd\"</literal>. (Note that since the argument is a Nix
- string literal, you have to escape the quotes.)</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--argstr</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
-
- <listitem><para>This option is like <option>--arg</option>, only the
- value is not a Nix expression but a string. So instead of
- <literal>--arg system \"i686-linux\"</literal> (the outer quotes are
- to keep the shell happy) you can say <literal>--argstr system
- i686-linux</literal>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-attr"><term><option>--attr</option> / <option>-A</option>
-<replaceable>attrPath</replaceable></term>
-
- <listitem><para>Select an attribute from the top-level Nix
- expression being evaluated. (<command>nix-env</command>,
- <command>nix-instantiate</command>, <command>nix-build</command> and
- <command>nix-shell</command> only.) The <emphasis>attribute
- path</emphasis> <replaceable>attrPath</replaceable> is a sequence of
- attribute names separated by dots. For instance, given a top-level
- Nix expression <replaceable>e</replaceable>, the attribute path
- <literal>xorg.xorgserver</literal> would cause the expression
- <literal><replaceable>e</replaceable>.xorg.xorgserver</literal> to
- be used. See <link linkend="refsec-nix-env-install-examples"><command>nix-env
- --install</command></link> for some concrete examples.</para>
-
- <para>In addition to attribute names, you can also specify array
- indices. For instance, the attribute path
- <literal>foo.3.bar</literal> selects the <literal>bar</literal>
- attribute of the fourth element of the array in the
- <literal>foo</literal> attribute of the top-level
- expression.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--expr</option> / <option>-E</option></term>
-
- <listitem><para>Interpret the command line arguments as a list of
- Nix expressions to be parsed and evaluated, rather than as a list
- of file names of Nix expressions.
- (<command>nix-instantiate</command>, <command>nix-build</command>
- and <command>nix-shell</command> only.)</para>
-
- <para>For <command>nix-shell</command>, this option is commonly used
- to give you a shell in which you can build the packages returned
- by the expression. If you want to get a shell which contain the
- <emphasis>built</emphasis> packages ready for use, give your
- expression to the <command>nix-shell -p</command> convenience flag
- instead.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-I"><term><option>-I</option> <replaceable>path</replaceable></term>
-
- <listitem><para>Add a path to the Nix expression search path. This
- option may be given multiple times. See the <envar linkend="env-NIX_PATH">NIX_PATH</envar> environment variable for
- information on the semantics of the Nix search path. Paths added
- through <option>-I</option> take precedence over
- <envar>NIX_PATH</envar>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--option</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
-
- <listitem><para>Set the Nix configuration option
- <replaceable>name</replaceable> to <replaceable>value</replaceable>.
- This overrides settings in the Nix configuration file (see
- <citerefentry><refentrytitle>nix.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--repair</option></term>
-
- <listitem><para>Fix corrupted or missing store paths by
- redownloading or rebuilding them. Note that this is slow because it
- requires computing a cryptographic hash of the contents of every
- path in the closure of the build. Also note the warning under
- <command>nix-store --repair-path</command>.</para></listitem>
-
-</varlistentry>
-</variablelist>
-
-</refsection>
-
-
-
-<!--######################################################################-->
-
-<refsection xml:id="rsec-nix-store-realise"><title>Operation <option>--realise</option></title>
-
-<refsection><title>Synopsis</title>
-
-<cmdsynopsis>
- <command>nix-store</command>
- <group choice="req">
- <arg choice="plain"><option>--realise</option></arg>
- <arg choice="plain"><option>-r</option></arg>
- </group>
- <arg choice="plain" rep="repeat"><replaceable>paths</replaceable></arg>
- <arg><option>--dry-run</option></arg>
-</cmdsynopsis>
-
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>The operation <option>--realise</option> essentially “builds”
-the specified store paths. Realisation is a somewhat overloaded term:
-
-<itemizedlist>
-
- <listitem><para>If the store path is a
- <emphasis>derivation</emphasis>, realisation ensures that the output
- paths of the derivation are <link linkend="gloss-validity">valid</link> (i.e., the output path and its
- closure exist in the file system). This can be done in several
- ways. First, it is possible that the outputs are already valid, in
- which case we are done immediately. Otherwise, there may be <link linkend="gloss-substitute">substitutes</link> that produce the
- outputs (e.g., by downloading them). Finally, the outputs can be
- produced by performing the build action described by the
- derivation.</para></listitem>
-
- <listitem><para>If the store path is not a derivation, realisation
- ensures that the specified path is valid (i.e., it and its closure
- exist in the file system). If the path is already valid, we are
- done immediately. Otherwise, the path and any missing paths in its
- closure may be produced through substitutes. If there are no
- (successful) subsitutes, realisation fails.</para></listitem>
-
-</itemizedlist>
-
-</para>
-
-<para>The output path of each derivation is printed on standard
-output. (For non-derivations argument, the argument itself is
-printed.)</para>
-
-<para>The following flags are available:</para>
-
-<variablelist>
-
- <varlistentry><term><option>--dry-run</option></term>
-
- <listitem><para>Print on standard error a description of what
- packages would be built or downloaded, without actually performing
- the operation.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--ignore-unknown</option></term>
-
- <listitem><para>If a non-derivation path does not have a
- substitute, then silently ignore it.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--check</option></term>
-
- <listitem><para>This option allows you to check whether a
- derivation is deterministic. It rebuilds the specified derivation
- and checks whether the result is bitwise-identical with the
- existing outputs, printing an error if that’s not the case. The
- outputs of the specified derivation must already exist. When used
- with <option>-K</option>, if an output path is not identical to
- the corresponding output from the previous build, the new output
- path is left in
- <filename>/nix/store/<replaceable>name</replaceable>.check.</filename></para>
-
- <para>See also the <option>build-repeat</option> configuration
- option, which repeats a derivation a number of times and prevents
- its outputs from being registered as “valid” in the Nix store
- unless they are identical.</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-<para>Special exit codes:</para>
-
-<variablelist>
-
- <varlistentry><term><literal>100</literal></term>
- <listitem><para>Generic build failure, the builder process
- returned with a non-zero exit code.</para></listitem>
- </varlistentry>
-
- <varlistentry><term><literal>101</literal></term>
- <listitem><para>Build timeout, the build was aborted because it
- did not complete within the specified <link linkend="conf-timeout"><literal>timeout</literal></link>.
- </para></listitem>
- </varlistentry>
-
- <varlistentry><term><literal>102</literal></term>
- <listitem><para>Hash mismatch, the build output was rejected
- because it does not match the specified <link linkend="fixed-output-drvs"><varname>outputHash</varname></link>.
- </para></listitem>
- </varlistentry>
-
- <varlistentry><term><literal>104</literal></term>
- <listitem><para>Not deterministic, the build succeeded in check
- mode but the resulting output is not binary reproducable.</para>
- </listitem>
- </varlistentry>
-
-</variablelist>
-
-<para>With the <option>--keep-going</option> flag it's possible for
-multiple failures to occur, in this case the 1xx status codes are or combined
-using binary or. <screen>
-1100100
- ^^^^
- |||`- timeout
- ||`-- output hash mismatch
- |`--- build failure
- `---- not deterministic
-</screen></para>
-
-</refsection>
-
-
-<refsection><title>Examples</title>
-
-<para>This operation is typically used to build store derivations
-produced by <link linkend="sec-nix-instantiate"><command>nix-instantiate</command></link>:
-
-<screen>
-$ nix-store -r $(nix-instantiate ./test.nix)
-/nix/store/31axcgrlbfsxzmfff1gyj1bf62hvkby2-aterm-2.3.1</screen>
-
-This is essentially what <link linkend="sec-nix-build"><command>nix-build</command></link> does.</para>
-
-<para>To test whether a previously-built derivation is deterministic:
-
-<screen>
-$ nix-build '<nixpkgs>' -A hello --check -K
-</screen>
-
-</para>
-
-</refsection>
-
-
-</refsection>
-
-
-
-<!--######################################################################-->
-
-<refsection xml:id="rsec-nix-store-serve"><title>Operation <option>--serve</option></title>
-
-<refsection><title>Synopsis</title>
-
-<cmdsynopsis>
- <command>nix-store</command>
- <arg choice="plain"><option>--serve</option></arg>
- <arg><option>--write</option></arg>
-</cmdsynopsis>
-
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>The operation <option>--serve</option> provides access to
-the Nix store over stdin and stdout, and is intended to be used
-as a means of providing Nix store access to a restricted ssh user.
-</para>
-
-<para>The following flags are available:</para>
-
-<variablelist>
-
- <varlistentry><term><option>--write</option></term>
-
- <listitem><para>Allow the connected client to request the realization
- of derivations. In effect, this can be used to make the host act
- as a remote builder.</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-</refsection>
-
-
-<refsection><title>Examples</title>
-
-<para>To turn a host into a build server, the
-<filename>authorized_keys</filename> file can be used to provide build
-access to a given SSH public key:
-
-<screen>
-$ cat <<EOF >>/root/.ssh/authorized_keys
-command="nice -n20 nix-store --serve --write" ssh-rsa AAAAB3NzaC1yc2EAAAA...
-EOF
-</screen>
-
-</para>
-
-</refsection>
-
-
-</refsection>
-
-
-
-<!--######################################################################-->
-
-<refsection xml:id="rsec-nix-store-gc"><title>Operation <option>--gc</option></title>
-
-<refsection><title>Synopsis</title>
-
-<cmdsynopsis>
- <command>nix-store</command>
- <arg choice="plain"><option>--gc</option></arg>
- <group>
- <arg choice="plain"><option>--print-roots</option></arg>
- <arg choice="plain"><option>--print-live</option></arg>
- <arg choice="plain"><option>--print-dead</option></arg>
- </group>
- <arg><option>--max-freed</option> <replaceable>bytes</replaceable></arg>
-</cmdsynopsis>
-
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>Without additional flags, the operation <option>--gc</option>
-performs a garbage collection on the Nix store. That is, all paths in
-the Nix store not reachable via file system references from a set of
-“roots”, are deleted.</para>
-
-<para>The following suboperations may be specified:</para>
-
-<variablelist>
-
- <varlistentry><term><option>--print-roots</option></term>
-
- <listitem><para>This operation prints on standard output the set
- of roots used by the garbage collector. What constitutes a root
- is described in <xref linkend="ssec-gc-roots"/>.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--print-live</option></term>
-
- <listitem><para>This operation prints on standard output the set
- of “live” store paths, which are all the store paths reachable
- from the roots. Live paths should never be deleted, since that
- would break consistency — it would become possible that
- applications are installed that reference things that are no
- longer present in the store.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--print-dead</option></term>
-
- <listitem><para>This operation prints out on standard output the
- set of “dead” store paths, which is just the opposite of the set
- of live paths: any path in the store that is not live (with
- respect to the roots) is dead.</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-<para>By default, all unreachable paths are deleted. The following
-options control what gets deleted and in what order:
-
-<variablelist>
-
- <varlistentry><term><option>--max-freed</option> <replaceable>bytes</replaceable></term>
-
- <listitem><para>Keep deleting paths until at least
- <replaceable>bytes</replaceable> bytes have been deleted, then
- stop. The argument <replaceable>bytes</replaceable> can be
- followed by the multiplicative suffix <literal>K</literal>,
- <literal>M</literal>, <literal>G</literal> or
- <literal>T</literal>, denoting KiB, MiB, GiB or TiB
- units.</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-</para>
-
-<para>The behaviour of the collector is also influenced by the <link linkend="conf-keep-outputs"><literal>keep-outputs</literal></link>
-and <link linkend="conf-keep-derivations"><literal>keep-derivations</literal></link>
-variables in the Nix configuration file.</para>
-
-<para>By default, the collector prints the total number of freed bytes
-when it finishes (or when it is interrupted). With
-<option>--print-dead</option>, it prints the number of bytes that would
-be freed.</para>
-
-</refsection>
-
-
-<refsection><title>Examples</title>
-
-<para>To delete all unreachable paths, just do:
-
-<screen>
-$ nix-store --gc
-deleting `/nix/store/kq82idx6g0nyzsp2s14gfsc38npai7lf-cairo-1.0.4.tar.gz.drv'
-<replaceable>...</replaceable>
-8825586 bytes freed (8.42 MiB)</screen>
-
-</para>
-
-<para>To delete at least 100 MiBs of unreachable paths:
-
-<screen>
-$ nix-store --gc --max-freed $((100 * 1024 * 1024))</screen>
-
-</para>
-
-</refsection>
-
-
-</refsection>
-
-
-
-<!--######################################################################-->
-
-<refsection><title>Operation <option>--delete</option></title>
-
-<refsection><title>Synopsis</title>
-
-<cmdsynopsis>
- <command>nix-store</command>
- <arg choice="plain"><option>--delete</option></arg>
- <arg><option>--ignore-liveness</option></arg>
- <arg choice="plain" rep="repeat"><replaceable>paths</replaceable></arg>
-</cmdsynopsis>
-
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>The operation <option>--delete</option> deletes the store paths
-<replaceable>paths</replaceable> from the Nix store, but only if it is
-safe to do so; that is, when the path is not reachable from a root of
-the garbage collector. This means that you can only delete paths that
-would also be deleted by <literal>nix-store --gc</literal>. Thus,
-<literal>--delete</literal> is a more targeted version of
-<literal>--gc</literal>.</para>
-
-<para>With the option <option>--ignore-liveness</option>, reachability
-from the roots is ignored. However, the path still won’t be deleted
-if there are other paths in the store that refer to it (i.e., depend
-on it).</para>
-
-</refsection>
-
-<refsection><title>Example</title>
-
-<screen>
-$ nix-store --delete /nix/store/zq0h41l75vlb4z45kzgjjmsjxvcv1qk7-mesa-6.4
-0 bytes freed (0.00 MiB)
-error: cannot delete path `/nix/store/zq0h41l75vlb4z45kzgjjmsjxvcv1qk7-mesa-6.4' since it is still alive</screen>
-
-</refsection>
-
-</refsection>
-
-
-
-<!--######################################################################-->
-
-<refsection xml:id="refsec-nix-store-query"><title>Operation <option>--query</option></title>
-
-<refsection><title>Synopsis</title>
-
-<cmdsynopsis>
- <command>nix-store</command>
- <group choice="req">
- <arg choice="plain"><option>--query</option></arg>
- <arg choice="plain"><option>-q</option></arg>
- </group>
- <group choice="req">
- <arg choice="plain"><option>--outputs</option></arg>
- <arg choice="plain"><option>--requisites</option></arg>
- <arg choice="plain"><option>-R</option></arg>
- <arg choice="plain"><option>--references</option></arg>
- <arg choice="plain"><option>--referrers</option></arg>
- <arg choice="plain"><option>--referrers-closure</option></arg>
- <arg choice="plain"><option>--deriver</option></arg>
- <arg choice="plain"><option>-d</option></arg>
- <arg choice="plain"><option>--graph</option></arg>
- <arg choice="plain"><option>--tree</option></arg>
- <arg choice="plain"><option>--binding</option> <replaceable>name</replaceable></arg>
- <arg choice="plain"><option>-b</option> <replaceable>name</replaceable></arg>
- <arg choice="plain"><option>--hash</option></arg>
- <arg choice="plain"><option>--size</option></arg>
- <arg choice="plain"><option>--roots</option></arg>
- </group>
- <arg><option>--use-output</option></arg>
- <arg><option>-u</option></arg>
- <arg><option>--force-realise</option></arg>
- <arg><option>-f</option></arg>
- <arg choice="plain" rep="repeat"><replaceable>paths</replaceable></arg>
-</cmdsynopsis>
-
-</refsection>
-
-
-<refsection><title>Description</title>
-
-<para>The operation <option>--query</option> displays various bits of
-information about the store paths . The queries are described below. At
-most one query can be specified. The default query is
-<option>--outputs</option>.</para>
-
-<para>The paths <replaceable>paths</replaceable> may also be symlinks
-from outside of the Nix store, to the Nix store. In that case, the
-query is applied to the target of the symlink.</para>
-
-
-</refsection>
-
-
-<refsection><title>Common query options</title>
-
-<variablelist>
-
- <varlistentry><term><option>--use-output</option></term>
- <term><option>-u</option></term>
-
- <listitem><para>For each argument to the query that is a store
- derivation, apply the query to the output path of the derivation
- instead.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--force-realise</option></term>
- <term><option>-f</option></term>
-
- <listitem><para>Realise each argument to the query first (see
- <link linkend="rsec-nix-store-realise"><command>nix-store
- --realise</command></link>).</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-</refsection>
-
-
-<refsection xml:id="nixref-queries"><title>Queries</title>
-
-<variablelist>
-
- <varlistentry><term><option>--outputs</option></term>
-
- <listitem><para>Prints out the <link linkend="gloss-output-path">output paths</link> of the store
- derivations <replaceable>paths</replaceable>. These are the paths
- that will be produced when the derivation is
- built.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--requisites</option></term>
- <term><option>-R</option></term>
-
- <listitem><para>Prints out the <link linkend="gloss-closure">closure</link> of the store path
- <replaceable>paths</replaceable>.</para>
-
- <para>This query has one option:</para>
-
- <variablelist>
-
- <varlistentry><term><option>--include-outputs</option></term>
-
- <listitem><para>Also include the output path of store
- derivations, and their closures.</para></listitem>
-
- </varlistentry>
-
- </variablelist>
-
- <para>This query can be used to implement various kinds of
- deployment. A <emphasis>source deployment</emphasis> is obtained
- by distributing the closure of a store derivation. A
- <emphasis>binary deployment</emphasis> is obtained by distributing
- the closure of an output path. A <emphasis>cache
- deployment</emphasis> (combined source/binary deployment,
- including binaries of build-time-only dependencies) is obtained by
- distributing the closure of a store derivation and specifying the
- option <option>--include-outputs</option>.</para>
-
- </listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--references</option></term>
-
- <listitem><para>Prints the set of <link linkend="gloss-reference">references</link> of the store paths
- <replaceable>paths</replaceable>, that is, their immediate
- dependencies. (For <emphasis>all</emphasis> dependencies, use
- <option>--requisites</option>.)</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--referrers</option></term>
-
- <listitem><para>Prints the set of <emphasis>referrers</emphasis> of
- the store paths <replaceable>paths</replaceable>, that is, the
- store paths currently existing in the Nix store that refer to one
- of <replaceable>paths</replaceable>. Note that contrary to the
- references, the set of referrers is not constant; it can change as
- store paths are added or removed.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--referrers-closure</option></term>
-
- <listitem><para>Prints the closure of the set of store paths
- <replaceable>paths</replaceable> under the referrers relation; that
- is, all store paths that directly or indirectly refer to one of
- <replaceable>paths</replaceable>. These are all the path currently
- in the Nix store that are dependent on
- <replaceable>paths</replaceable>.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--deriver</option></term>
- <term><option>-d</option></term>
-
- <listitem><para>Prints the <link linkend="gloss-deriver">deriver</link> of the store paths
- <replaceable>paths</replaceable>. If the path has no deriver
- (e.g., if it is a source file), or if the deriver is not known
- (e.g., in the case of a binary-only deployment), the string
- <literal>unknown-deriver</literal> is printed.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--graph</option></term>
-
- <listitem><para>Prints the references graph of the store paths
- <replaceable>paths</replaceable> in the format of the
- <command>dot</command> tool of AT&T's <link xlink:href="http://www.graphviz.org/">Graphviz package</link>.
- This can be used to visualise dependency graphs. To obtain a
- build-time dependency graph, apply this to a store derivation. To
- obtain a runtime dependency graph, apply it to an output
- path.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--tree</option></term>
-
- <listitem><para>Prints the references graph of the store paths
- <replaceable>paths</replaceable> as a nested ASCII tree.
- References are ordered by descending closure size; this tends to
- flatten the tree, making it more readable. The query only
- recurses into a store path when it is first encountered; this
- prevents a blowup of the tree representation of the
- graph.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--graphml</option></term>
-
- <listitem><para>Prints the references graph of the store paths
- <replaceable>paths</replaceable> in the <link xlink:href="http://graphml.graphdrawing.org/">GraphML</link> file format.
- This can be used to visualise dependency graphs. To obtain a
- build-time dependency graph, apply this to a store derivation. To
- obtain a runtime dependency graph, apply it to an output
- path.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--binding</option> <replaceable>name</replaceable></term>
- <term><option>-b</option> <replaceable>name</replaceable></term>
-
- <listitem><para>Prints the value of the attribute
- <replaceable>name</replaceable> (i.e., environment variable) of
- the store derivations <replaceable>paths</replaceable>. It is an
- error for a derivation to not have the specified
- attribute.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--hash</option></term>
-
- <listitem><para>Prints the SHA-256 hash of the contents of the
- store paths <replaceable>paths</replaceable> (that is, the hash of
- the output of <command>nix-store --dump</command> on the given
- paths). Since the hash is stored in the Nix database, this is a
- fast operation.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--size</option></term>
-
- <listitem><para>Prints the size in bytes of the contents of the
- store paths <replaceable>paths</replaceable> — to be precise, the
- size of the output of <command>nix-store --dump</command> on the
- given paths. Note that the actual disk space required by the
- store paths may be higher, especially on filesystems with large
- cluster sizes.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--roots</option></term>
-
- <listitem><para>Prints the garbage collector roots that point,
- directly or indirectly, at the store paths
- <replaceable>paths</replaceable>.</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-</refsection>
-
-
-<refsection><title>Examples</title>
-
-<para>Print the closure (runtime dependencies) of the
-<command>svn</command> program in the current user environment:
-
-<screen>
-$ nix-store -qR $(which svn)
-/nix/store/5mbglq5ldqld8sj57273aljwkfvj22mc-subversion-1.1.4
-/nix/store/9lz9yc6zgmc0vlqmn2ipcpkjlmbi51vv-glibc-2.3.4
-<replaceable>...</replaceable></screen>
-
-</para>
-
-<para>Print the build-time dependencies of <command>svn</command>:
-
-<screen>
-$ nix-store -qR $(nix-store -qd $(which svn))
-/nix/store/02iizgn86m42q905rddvg4ja975bk2i4-grep-2.5.1.tar.bz2.drv
-/nix/store/07a2bzxmzwz5hp58nf03pahrv2ygwgs3-gcc-wrapper.sh
-/nix/store/0ma7c9wsbaxahwwl04gbw3fcd806ski4-glibc-2.3.4.drv
-<replaceable>... lots of other paths ...</replaceable></screen>
-
-The difference with the previous example is that we ask the closure of
-the derivation (<option>-qd</option>), not the closure of the output
-path that contains <command>svn</command>.</para>
-
-<para>Show the build-time dependencies as a tree:
-
-<screen>
-$ nix-store -q --tree $(nix-store -qd $(which svn))
-/nix/store/7i5082kfb6yjbqdbiwdhhza0am2xvh6c-subversion-1.1.4.drv
-+---/nix/store/d8afh10z72n8l1cr5w42366abiblgn54-builder.sh
-+---/nix/store/fmzxmpjx2lh849ph0l36snfj9zdibw67-bash-3.0.drv
-| +---/nix/store/570hmhmx3v57605cqg9yfvvyh0nnb8k8-bash
-| +---/nix/store/p3srsbd8dx44v2pg6nbnszab5mcwx03v-builder.sh
-<replaceable>...</replaceable></screen>
-
-</para>
-
-<para>Show all paths that depend on the same OpenSSL library as
-<command>svn</command>:
-
-<screen>
-$ nix-store -q --referrers $(nix-store -q --binding openssl $(nix-store -qd $(which svn)))
-/nix/store/23ny9l9wixx21632y2wi4p585qhva1q8-sylpheed-1.0.0
-/nix/store/5mbglq5ldqld8sj57273aljwkfvj22mc-subversion-1.1.4
-/nix/store/dpmvp969yhdqs7lm2r1a3gng7pyq6vy4-subversion-1.1.3
-/nix/store/l51240xqsgg8a7yrbqdx1rfzyv6l26fx-lynx-2.8.5</screen>
-
-</para>
-
-<para>Show all paths that directly or indirectly depend on the Glibc
-(C library) used by <command>svn</command>:
-
-<screen>
-$ nix-store -q --referrers-closure $(ldd $(which svn) | grep /libc.so | awk '{print $3}')
-/nix/store/034a6h4vpz9kds5r6kzb9lhh81mscw43-libgnomeprintui-2.8.2
-/nix/store/15l3yi0d45prm7a82pcrknxdh6nzmxza-gawk-3.1.4
-<replaceable>...</replaceable></screen>
-
-Note that <command>ldd</command> is a command that prints out the
-dynamic libraries used by an ELF executable.</para>
-
-<para>Make a picture of the runtime dependency graph of the current
-user environment:
-
-<screen>
-$ nix-store -q --graph ~/.nix-profile | dot -Tps > graph.ps
-$ gv graph.ps</screen>
-
-</para>
-
-<para>Show every garbage collector root that points to a store path
-that depends on <command>svn</command>:
-
-<screen>
-$ nix-store -q --roots $(which svn)
-/nix/var/nix/profiles/default-81-link
-/nix/var/nix/profiles/default-82-link
-/nix/var/nix/profiles/per-user/eelco/profile-97-link
-</screen>
-
-</para>
-
-</refsection>
-
-
-</refsection>
-
-
-
-<!--######################################################################-->
-
-<!--
-<refsection xml:id="rsec-nix-store-reg-val"><title>Operation <option>-XXX-register-validity</option></title>
-
-<refsection><title>Synopsis</title>
-
-<cmdsynopsis>
- <command>nix-store</command>
- <arg choice='plain'><option>-XXX-register-validity</option></arg>
-</cmdsynopsis>
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>TODO</para>
-
-</refsection>
-
-</refsection>
--->
-
-
-
-<!--######################################################################-->
-
-<refsection><title>Operation <option>--add</option></title>
-
-<refsection><title>Synopsis</title>
-
-<cmdsynopsis>
- <command>nix-store</command>
- <arg choice="plain"><option>--add</option></arg>
- <arg choice="plain" rep="repeat"><replaceable>paths</replaceable></arg>
-</cmdsynopsis>
-
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>The operation <option>--add</option> adds the specified paths to
-the Nix store. It prints the resulting paths in the Nix store on
-standard output.</para>
-
-</refsection>
-
-<refsection><title>Example</title>
-
-<screen>
-$ nix-store --add ./foo.c
-/nix/store/m7lrha58ph6rcnv109yzx1nk1cj7k7zf-foo.c</screen>
-
-</refsection>
-
-</refsection>
-
-<!--######################################################################-->
-
-<refsection><title>Operation <option>--add-fixed</option></title>
-
-<refsection><title>Synopsis</title>
-
-<cmdsynopsis>
- <command>nix-store</command>
- <arg><option>--recursive</option></arg>
- <arg choice="plain"><option>--add-fixed</option></arg>
- <arg choice="plain"><replaceable>algorithm</replaceable></arg>
- <arg choice="plain" rep="repeat"><replaceable>paths</replaceable></arg>
-</cmdsynopsis>
-
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>The operation <option>--add-fixed</option> adds the specified paths to
-the Nix store. Unlike <option>--add</option> paths are registered using the
-specified hashing algorithm, resulting in the same output path as a fixed-output
-derivation. This can be used for sources that are not available from a public
-url or broke since the download expression was written.
-</para>
-
-<para>This operation has the following options:
-
-<variablelist>
-
- <varlistentry><term><option>--recursive</option></term>
-
- <listitem><para>
- Use recursive instead of flat hashing mode, used when adding directories
- to the store.
- </para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-</para>
-
-</refsection>
-
-<refsection><title>Example</title>
-
-<screen>
-$ nix-store --add-fixed sha256 ./hello-2.10.tar.gz
-/nix/store/3x7dwzq014bblazs7kq20p9hyzz0qh8g-hello-2.10.tar.gz</screen>
-
-</refsection>
-
-</refsection>
-
-
-
-<!--######################################################################-->
-
-<refsection xml:id="refsec-nix-store-verify"><title>Operation <option>--verify</option></title>
-
-<refsection>
- <title>Synopsis</title>
- <cmdsynopsis>
- <command>nix-store</command>
- <arg choice="plain"><option>--verify</option></arg>
- <arg><option>--check-contents</option></arg>
- <arg><option>--repair</option></arg>
- </cmdsynopsis>
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>The operation <option>--verify</option> verifies the internal
-consistency of the Nix database, and the consistency between the Nix
-database and the Nix store. Any inconsistencies encountered are
-automatically repaired. Inconsistencies are generally the result of
-the Nix store or database being modified by non-Nix tools, or of bugs
-in Nix itself.</para>
-
-<para>This operation has the following options:
-
-<variablelist>
-
- <varlistentry><term><option>--check-contents</option></term>
-
- <listitem><para>Checks that the contents of every valid store path
- has not been altered by computing a SHA-256 hash of the contents
- and comparing it with the hash stored in the Nix database at build
- time. Paths that have been modified are printed out. For large
- stores, <option>--check-contents</option> is obviously quite
- slow.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--repair</option></term>
-
- <listitem><para>If any valid path is missing from the store, or
- (if <option>--check-contents</option> is given) the contents of a
- valid path has been modified, then try to repair the path by
- redownloading it. See <command>nix-store --repair-path</command>
- for details.</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-</para>
-
-</refsection>
-
-
-</refsection>
-
-
-<!--######################################################################-->
-
-<refsection><title>Operation <option>--verify-path</option></title>
-
-<refsection>
- <title>Synopsis</title>
- <cmdsynopsis>
- <command>nix-store</command>
- <arg choice="plain"><option>--verify-path</option></arg>
- <arg choice="plain" rep="repeat"><replaceable>paths</replaceable></arg>
- </cmdsynopsis>
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>The operation <option>--verify-path</option> compares the
-contents of the given store paths to their cryptographic hashes stored
-in Nix’s database. For every changed path, it prints a warning
-message. The exit status is 0 if no path has changed, and 1
-otherwise.</para>
-
-</refsection>
-
-<refsection><title>Example</title>
-
-<para>To verify the integrity of the <command>svn</command> command and all its dependencies:
-
-<screen>
-$ nix-store --verify-path $(nix-store -qR $(which svn))
-</screen>
-
-</para>
-
-</refsection>
-
-</refsection>
-
-
-<!--######################################################################-->
-
-<refsection><title>Operation <option>--repair-path</option></title>
-
-<refsection>
- <title>Synopsis</title>
- <cmdsynopsis>
- <command>nix-store</command>
- <arg choice="plain"><option>--repair-path</option></arg>
- <arg choice="plain" rep="repeat"><replaceable>paths</replaceable></arg>
- </cmdsynopsis>
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>The operation <option>--repair-path</option> attempts to
-“repair” the specified paths by redownloading them using the available
-substituters. If no substitutes are available, then repair is not
-possible.</para>
-
-<warning><para>During repair, there is a very small time window during
-which the old path (if it exists) is moved out of the way and replaced
-with the new path. If repair is interrupted in between, then the
-system may be left in a broken state (e.g., if the path contains a
-critical system component like the GNU C Library).</para></warning>
-
-</refsection>
-
-<refsection><title>Example</title>
-
-<screen>
-$ nix-store --verify-path /nix/store/dj7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13
-path `/nix/store/dj7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13' was modified!
- expected hash `2db57715ae90b7e31ff1f2ecb8c12ec1cc43da920efcbe3b22763f36a1861588',
- got `481c5aa5483ebc97c20457bb8bca24deea56550d3985cda0027f67fe54b808e4'
-
-$ nix-store --repair-path /nix/store/dj7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13
-fetching path `/nix/store/d7a81wsm1ijwwpkks3725661h3263p5-glibc-2.13'...
-…
-</screen>
-
-</refsection>
-
-</refsection>
-
-
-<!--######################################################################-->
-
-<refsection xml:id="refsec-nix-store-dump"><title>Operation <option>--dump</option></title>
-
-<refsection>
- <title>Synopsis</title>
- <cmdsynopsis>
- <command>nix-store</command>
- <arg choice="plain"><option>--dump</option></arg>
- <arg choice="plain"><replaceable>path</replaceable></arg>
- </cmdsynopsis>
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>The operation <option>--dump</option> produces a NAR (Nix
-ARchive) file containing the contents of the file system tree rooted
-at <replaceable>path</replaceable>. The archive is written to
-standard output.</para>
-
-<para>A NAR archive is like a TAR or Zip archive, but it contains only
-the information that Nix considers important. For instance,
-timestamps are elided because all files in the Nix store have their
-timestamp set to 0 anyway. Likewise, all permissions are left out
-except for the execute bit, because all files in the Nix store have
-444 or 555 permission.</para>
-
-<para>Also, a NAR archive is <emphasis>canonical</emphasis>, meaning
-that “equal” paths always produce the same NAR archive. For instance,
-directory entries are always sorted so that the actual on-disk order
-doesn’t influence the result. This means that the cryptographic hash
-of a NAR dump of a path is usable as a fingerprint of the contents of
-the path. Indeed, the hashes of store paths stored in Nix’s database
-(see <link linkend="refsec-nix-store-query"><literal>nix-store -q
---hash</literal></link>) are SHA-256 hashes of the NAR dump of each
-store path.</para>
-
-<para>NAR archives support filenames of unlimited length and 64-bit
-file sizes. They can contain regular files, directories, and symbolic
-links, but not other types of files (such as device nodes).</para>
-
-<para>A Nix archive can be unpacked using <literal>nix-store
---restore</literal>.</para>
-
-</refsection>
-
-
-</refsection>
-
-
-<!--######################################################################-->
-
-<refsection><title>Operation <option>--restore</option></title>
-
-<refsection>
- <title>Synopsis</title>
- <cmdsynopsis>
- <command>nix-store</command>
- <arg choice="plain"><option>--restore</option></arg>
- <arg choice="plain"><replaceable>path</replaceable></arg>
- </cmdsynopsis>
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>The operation <option>--restore</option> unpacks a NAR archive
-to <replaceable>path</replaceable>, which must not already exist. The
-archive is read from standard input.</para>
-
-</refsection>
-
-
-</refsection>
-
-
-<!--######################################################################-->
-
-<refsection xml:id="refsec-nix-store-export"><title>Operation <option>--export</option></title>
-
-<refsection>
- <title>Synopsis</title>
- <cmdsynopsis>
- <command>nix-store</command>
- <arg choice="plain"><option>--export</option></arg>
- <arg choice="plain" rep="repeat"><replaceable>paths</replaceable></arg>
- </cmdsynopsis>
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>The operation <option>--export</option> writes a serialisation
-of the specified store paths to standard output in a format that can
-be imported into another Nix store with <command linkend="refsec-nix-store-import">nix-store --import</command>. This
-is like <command linkend="refsec-nix-store-dump">nix-store
---dump</command>, except that the NAR archive produced by that command
-doesn’t contain the necessary meta-information to allow it to be
-imported into another Nix store (namely, the set of references of the
-path).</para>
-
-<para>This command does not produce a <emphasis>closure</emphasis> of
-the specified paths, so if a store path references other store paths
-that are missing in the target Nix store, the import will fail. To
-copy a whole closure, do something like:
-
-<screen>
-$ nix-store --export $(nix-store -qR <replaceable>paths</replaceable>) > out</screen>
-
-To import the whole closure again, run:
-
-<screen>
-$ nix-store --import < out</screen>
-
-</para>
-
-</refsection>
-
-
-</refsection>
-
-
-<!--######################################################################-->
-
-<refsection xml:id="refsec-nix-store-import"><title>Operation <option>--import</option></title>
-
-<refsection>
- <title>Synopsis</title>
- <cmdsynopsis>
- <command>nix-store</command>
- <arg choice="plain"><option>--import</option></arg>
- </cmdsynopsis>
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>The operation <option>--import</option> reads a serialisation of
-a set of store paths produced by <command linkend="refsec-nix-store-export">nix-store --export</command> from
-standard input and adds those store paths to the Nix store. Paths
-that already exist in the Nix store are ignored. If a path refers to
-another path that doesn’t exist in the Nix store, the import
-fails.</para>
-
-</refsection>
-
-
-</refsection>
-
-
-<!--######################################################################-->
-
-<refsection><title>Operation <option>--optimise</option></title>
-
-<refsection>
- <title>Synopsis</title>
- <cmdsynopsis>
- <command>nix-store</command>
- <arg choice="plain"><option>--optimise</option></arg>
- </cmdsynopsis>
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>The operation <option>--optimise</option> reduces Nix store disk
-space usage by finding identical files in the store and hard-linking
-them to each other. It typically reduces the size of the store by
-something like 25-35%. Only regular files and symlinks are
-hard-linked in this manner. Files are considered identical when they
-have the same NAR archive serialisation: that is, regular files must
-have the same contents and permission (executable or non-executable),
-and symlinks must have the same contents.</para>
-
-<para>After completion, or when the command is interrupted, a report
-on the achieved savings is printed on standard error.</para>
-
-<para>Use <option>-vv</option> or <option>-vvv</option> to get some
-progress indication.</para>
-
-</refsection>
-
-<refsection><title>Example</title>
-
-<screen>
-$ nix-store --optimise
-hashing files in `/nix/store/qhqx7l2f1kmwihc9bnxs7rc159hsxnf3-gcc-4.1.1'
-<replaceable>...</replaceable>
-541838819 bytes (516.74 MiB) freed by hard-linking 54143 files;
-there are 114486 files with equal contents out of 215894 files in total
-</screen>
-
-</refsection>
-
-
-</refsection>
-
-
-<!--######################################################################-->
-
-<refsection><title>Operation <option>--read-log</option></title>
-
-<refsection>
- <title>Synopsis</title>
- <cmdsynopsis>
- <command>nix-store</command>
- <group choice="req">
- <arg choice="plain"><option>--read-log</option></arg>
- <arg choice="plain"><option>-l</option></arg>
- </group>
- <arg choice="plain" rep="repeat"><replaceable>paths</replaceable></arg>
- </cmdsynopsis>
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>The operation <option>--read-log</option> prints the build log
-of the specified store paths on standard output. The build log is
-whatever the builder of a derivation wrote to standard output and
-standard error. If a store path is not a derivation, the deriver of
-the store path is used.</para>
-
-<para>Build logs are kept in
-<filename>/nix/var/log/nix/drvs</filename>. However, there is no
-guarantee that a build log is available for any particular store path.
-For instance, if the path was downloaded as a pre-built binary through
-a substitute, then the log is unavailable.</para>
-
-</refsection>
-
-<refsection><title>Example</title>
-
-<screen>
-$ nix-store -l $(which ktorrent)
-building /nix/store/dhc73pvzpnzxhdgpimsd9sw39di66ph1-ktorrent-2.2.1
-unpacking sources
-unpacking source archive /nix/store/p8n1jpqs27mgkjw07pb5269717nzf5f8-ktorrent-2.2.1.tar.gz
-ktorrent-2.2.1/
-ktorrent-2.2.1/NEWS
-<replaceable>...</replaceable>
-</screen>
-
-</refsection>
-
-
-</refsection>
-
-
-<!--######################################################################-->
-
-<refsection><title>Operation <option>--dump-db</option></title>
-
-<refsection>
- <title>Synopsis</title>
- <cmdsynopsis>
- <command>nix-store</command>
- <arg choice="plain"><option>--dump-db</option></arg>
- <arg rep="repeat"><replaceable>paths</replaceable></arg>
- </cmdsynopsis>
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>The operation <option>--dump-db</option> writes a dump of the
-Nix database to standard output. It can be loaded into an empty Nix
-store using <option>--load-db</option>. This is useful for making
-backups and when migrating to different database schemas.</para>
-
-<para>By default, <option>--dump-db</option> will dump the entire Nix
-database. When one or more store paths is passed, only the subset of
-the Nix database for those store paths is dumped. As with
-<option>--export</option>, the user is responsible for passing all the
-store paths for a closure. See <option>--export</option> for an
-example.</para>
-
-</refsection>
-
-</refsection>
-
-
-<!--######################################################################-->
-
-<refsection><title>Operation <option>--load-db</option></title>
-
-<refsection>
- <title>Synopsis</title>
- <cmdsynopsis>
- <command>nix-store</command>
- <arg choice="plain"><option>--load-db</option></arg>
- </cmdsynopsis>
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>The operation <option>--load-db</option> reads a dump of the Nix
-database created by <option>--dump-db</option> from standard input and
-loads it into the Nix database.</para>
-
-</refsection>
-
-</refsection>
-
-
-<!--######################################################################-->
-
-<refsection><title>Operation <option>--print-env</option></title>
-
-<refsection>
- <title>Synopsis</title>
- <cmdsynopsis>
- <command>nix-store</command>
- <arg choice="plain"><option>--print-env</option></arg>
- <arg choice="plain"><replaceable>drvpath</replaceable></arg>
- </cmdsynopsis>
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>The operation <option>--print-env</option> prints out the
-environment of a derivation in a format that can be evaluated by a
-shell. The command line arguments of the builder are placed in the
-variable <envar>_args</envar>.</para>
-
-</refsection>
-
-<refsection><title>Example</title>
-
-<screen>
-$ nix-store --print-env $(nix-instantiate '<nixpkgs>' -A firefox)
-<replaceable>…</replaceable>
-export src; src='/nix/store/plpj7qrwcz94z2psh6fchsi7s8yihc7k-firefox-12.0.source.tar.bz2'
-export stdenv; stdenv='/nix/store/7c8asx3yfrg5dg1gzhzyq2236zfgibnn-stdenv'
-export system; system='x86_64-linux'
-export _args; _args='-e /nix/store/9krlzvny65gdc8s7kpb6lkx8cd02c25c-default-builder.sh'
-</screen>
-
-</refsection>
-
-</refsection>
-
-
-<!--######################################################################-->
-
-<refsection xml:id="rsec-nix-store-generate-binary-cache-key"><title>Operation <option>--generate-binary-cache-key</option></title>
-
-<refsection>
- <title>Synopsis</title>
- <cmdsynopsis>
- <command>nix-store</command>
- <arg choice="plain">
- <option>--generate-binary-cache-key</option>
- <option>key-name</option>
- <option>secret-key-file</option>
- <option>public-key-file</option>
- </arg>
- </cmdsynopsis>
-</refsection>
-
-<refsection><title>Description</title>
-
-<para>This command generates an <link xlink:href="http://ed25519.cr.yp.to/">Ed25519 key pair</link> that can
-be used to create a signed binary cache. It takes three mandatory
-parameters:
-
-<orderedlist>
-
- <listitem><para>A key name, such as
- <literal>cache.example.org-1</literal>, that is used to look up keys
- on the client when it verifies signatures. It can be anything, but
- it’s suggested to use the host name of your cache
- (e.g. <literal>cache.example.org</literal>) with a suffix denoting
- the number of the key (to be incremented every time you need to
- revoke a key).</para></listitem>
-
- <listitem><para>The file name where the secret key is to be
- stored.</para></listitem>
-
- <listitem><para>The file name where the public key is to be
- stored.</para></listitem>
-
-</orderedlist>
-
-</para>
-
-</refsection>
-
-</refsection>
-
-
-<!--######################################################################-->
-
-<refsection condition="manpage"><title>Environment variables</title>
-
-<variablelist>
- <varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>IN_NIX_SHELL</envar></term>
-
- <listitem><para>Indicator that tells if the current environment was set up by
- <command>nix-shell</command>. Since Nix 2.0 the values are
- <literal>"pure"</literal> and <literal>"impure"</literal></para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="env-NIX_PATH"><term><envar>NIX_PATH</envar></term>
-
- <listitem>
-
- <para>A colon-separated list of directories used to look up Nix
- expressions enclosed in angle brackets (i.e.,
- <literal><<replaceable>path</replaceable>></literal>). For
- instance, the value
-
- <screen>
-/home/eelco/Dev:/etc/nixos</screen>
-
- will cause Nix to look for paths relative to
- <filename>/home/eelco/Dev</filename> and
- <filename>/etc/nixos</filename>, in this order. It is also
- possible to match paths against a prefix. For example, the value
-
- <screen>
-nixpkgs=/home/eelco/Dev/nixpkgs-branch:/etc/nixos</screen>
-
- will cause Nix to search for
- <literal><nixpkgs/<replaceable>path</replaceable>></literal> in
- <filename>/home/eelco/Dev/nixpkgs-branch/<replaceable>path</replaceable></filename>
- and
- <filename>/etc/nixos/nixpkgs/<replaceable>path</replaceable></filename>.</para>
-
- <para>If a path in the Nix search path starts with
- <literal>http://</literal> or <literal>https://</literal>, it is
- interpreted as the URL of a tarball that will be downloaded and
- unpacked to a temporary location. The tarball must consist of a
- single top-level directory. For example, setting
- <envar>NIX_PATH</envar> to
-
- <screen>
-nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-15.09.tar.gz</screen>
-
- tells Nix to download the latest revision in the Nixpkgs/NixOS
- 15.09 channel.</para>
-
- <para>A following shorthand can be used to refer to the official channels:
-
- <screen>nixpkgs=channel:nixos-15.09</screen>
- </para>
-
- <para>The search path can be extended using the <option linkend="opt-I">-I</option> option, which takes precedence over
- <envar>NIX_PATH</envar>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_IGNORE_SYMLINK_STORE</envar></term>
-
- <listitem>
-
- <para>Normally, the Nix store directory (typically
- <filename>/nix/store</filename>) is not allowed to contain any
- symlink components. This is to prevent “impure” builds. Builders
- sometimes “canonicalise” paths by resolving all symlink components.
- Thus, builds on different machines (with
- <filename>/nix/store</filename> resolving to different locations)
- could yield different results. This is generally not a problem,
- except when builds are deployed to machines where
- <filename>/nix/store</filename> resolves differently. If you are
- sure that you’re not going to do that, you can set
- <envar>NIX_IGNORE_SYMLINK_STORE</envar> to <envar>1</envar>.</para>
-
- <para>Note that if you’re symlinking the Nix store so that you can
- put it on another file system than the root file system, on Linux
- you’re better off using <literal>bind</literal> mount points, e.g.,
-
- <screen>
-$ mkdir /nix
-$ mount -o bind /mnt/otherdisk/nix /nix</screen>
-
- Consult the <citerefentry><refentrytitle>mount</refentrytitle>
- <manvolnum>8</manvolnum></citerefentry> manual page for details.</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_STORE_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix store (default
- <filename><replaceable>prefix</replaceable>/store</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_DATA_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix static data
- directory (default
- <filename><replaceable>prefix</replaceable>/share</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_LOG_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix log directory
- (default <filename><replaceable>prefix</replaceable>/var/log/nix</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_STATE_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix state directory
- (default <filename><replaceable>prefix</replaceable>/var/nix</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_CONF_DIR</envar></term>
-
- <listitem><para>Overrides the location of the system Nix configuration
- directory (default
- <filename><replaceable>prefix</replaceable>/etc/nix</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_USER_CONF_FILES</envar></term>
-
- <listitem><para>Overrides the location of the user Nix configuration files
- to load from (defaults to the XDG spec locations). The variable is treated
- as a list separated by the <literal>:</literal> token.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>TMPDIR</envar></term>
-
- <listitem><para>Use the specified directory to store temporary
- files. In particular, this includes temporary build directories;
- these can take up substantial amounts of disk space. The default is
- <filename>/tmp</filename>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="envar-remote"><term><envar>NIX_REMOTE</envar></term>
-
- <listitem><para>This variable should be set to
- <literal>daemon</literal> if you want to use the Nix daemon to
- execute Nix operations. This is necessary in <link linkend="ssec-multi-user">multi-user Nix installations</link>.
- If the Nix daemon's Unix socket is at some non-standard path,
- this variable should be set to <literal>unix://path/to/socket</literal>.
- Otherwise, it should be left unset.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_SHOW_STATS</envar></term>
-
- <listitem><para>If set to <literal>1</literal>, Nix will print some
- evaluation statistics, such as the number of values
- allocated.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_COUNT_CALLS</envar></term>
-
- <listitem><para>If set to <literal>1</literal>, Nix will print how
- often functions were called during Nix expression evaluation. This
- is useful for profiling your Nix expressions.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>GC_INITIAL_HEAP_SIZE</envar></term>
-
- <listitem><para>If Nix has been configured to use the Boehm garbage
- collector, this variable sets the initial size of the heap in bytes.
- It defaults to 384 MiB. Setting it to a low value reduces memory
- consumption, but will increase runtime due to the overhead of
- garbage collection.</para></listitem>
-
-</varlistentry>
-</variablelist>
-
-</refsection>
-
-
-</refentry>
-
-</chapter>
-<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-utilities">
-
-<title>Utilities</title>
-
-<para>This section lists utilities that you can use when you
-work with Nix.</para>
-
-<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-nix-channel">
-
-<refmeta>
- <refentrytitle>nix-channel</refentrytitle>
- <manvolnum>1</manvolnum>
- <refmiscinfo class="source">Nix</refmiscinfo>
- <refmiscinfo class="version">3.0</refmiscinfo>
-</refmeta>
-
-<refnamediv>
- <refname>nix-channel</refname>
- <refpurpose>manage Nix channels</refpurpose>
-</refnamediv>
-
-<refsynopsisdiv>
- <cmdsynopsis>
- <command>nix-channel</command>
- <group choice="req">
- <arg choice="plain"><option>--add</option> <replaceable>url</replaceable> <arg choice="opt"><replaceable>name</replaceable></arg></arg>
- <arg choice="plain"><option>--remove</option> <replaceable>name</replaceable></arg>
- <arg choice="plain"><option>--list</option></arg>
- <arg choice="plain"><option>--update</option> <arg rep="repeat"><replaceable>names</replaceable></arg></arg>
- <arg choice="plain"><option>--rollback</option> <arg choice="opt"><replaceable>generation</replaceable></arg></arg>
- </group>
- </cmdsynopsis>
-</refsynopsisdiv>
-
-<refsection><title>Description</title>
-
-<para>A Nix channel is a mechanism that allows you to automatically
-stay up-to-date with a set of pre-built Nix expressions. A Nix
-channel is just a URL that points to a place containing a set of Nix
-expressions. <phrase condition="manual">See also <xref linkend="sec-channels"/>.</phrase></para>
-
-<para>To see the list of official NixOS channels, visit <link xlink:href="https://nixos.org/channels"/>.</para>
-
-<para>This command has the following operations:
-
-<variablelist>
-
- <varlistentry><term><option>--add</option> <replaceable>url</replaceable> [<replaceable>name</replaceable>]</term>
-
- <listitem><para>Adds a channel named
- <replaceable>name</replaceable> with URL
- <replaceable>url</replaceable> to the list of subscribed channels.
- If <replaceable>name</replaceable> is omitted, it defaults to the
- last component of <replaceable>url</replaceable>, with the
- suffixes <literal>-stable</literal> or
- <literal>-unstable</literal> removed.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--remove</option> <replaceable>name</replaceable></term>
-
- <listitem><para>Removes the channel named
- <replaceable>name</replaceable> from the list of subscribed
- channels.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--list</option></term>
-
- <listitem><para>Prints the names and URLs of all subscribed
- channels on standard output.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--update</option> [<replaceable>names</replaceable>…]</term>
-
- <listitem><para>Downloads the Nix expressions of all subscribed
- channels (or only those included in
- <replaceable>names</replaceable> if specified) and makes them the
- default for <command>nix-env</command> operations (by symlinking
- them from the directory
- <filename>~/.nix-defexpr</filename>).</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--rollback</option> [<replaceable>generation</replaceable>]</term>
-
- <listitem><para>Reverts the previous call to <command>nix-channel
- --update</command>. Optionally, you can specify a specific channel
- generation number to restore.</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-</para>
-
-<para>Note that <option>--add</option> does not automatically perform
-an update.</para>
-
-<para>The list of subscribed channels is stored in
-<filename>~/.nix-channels</filename>.</para>
-
-</refsection>
-
-<refsection><title>Examples</title>
-
-<para>To subscribe to the Nixpkgs channel and install the GNU Hello package:</para>
-
-<screen>
-$ nix-channel --add https://nixos.org/channels/nixpkgs-unstable
-$ nix-channel --update
-$ nix-env -iA nixpkgs.hello</screen>
-
-<para>You can revert channel updates using <option>--rollback</option>:</para>
-
-<screen>
-$ nix-instantiate --eval -E '(import <nixpkgs> {}).lib.version'
-"14.04.527.0e935f1"
-
-$ nix-channel --rollback
-switching from generation 483 to 482
-
-$ nix-instantiate --eval -E '(import <nixpkgs> {}).lib.version'
-"14.04.526.dbadfad"
-</screen>
-
-</refsection>
-
-<refsection><title>Files</title>
-
-<variablelist>
-
- <varlistentry><term><filename>/nix/var/nix/profiles/per-user/<replaceable>username</replaceable>/channels</filename></term>
-
- <listitem><para><command>nix-channel</command> uses a
- <command>nix-env</command> profile to keep track of previous
- versions of the subscribed channels. Every time you run
- <command>nix-channel --update</command>, a new channel generation
- (that is, a symlink to the channel Nix expressions in the Nix store)
- is created. This enables <command>nix-channel --rollback</command>
- to revert to previous versions.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><filename>~/.nix-defexpr/channels</filename></term>
-
- <listitem><para>This is a symlink to
- <filename>/nix/var/nix/profiles/per-user/<replaceable>username</replaceable>/channels</filename>. It
- ensures that <command>nix-env</command> can find your channels. In
- a multi-user installation, you may also have
- <filename>~/.nix-defexpr/channels_root</filename>, which links to
- the channels of the root user.</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-</refsection>
-
-<refsection><title>Channel format</title>
-
-<para>A channel URL should point to a directory containing the
-following files:</para>
-
-<variablelist>
-
- <varlistentry><term><filename>nixexprs.tar.xz</filename></term>
-
- <listitem><para>A tarball containing Nix expressions and files
- referenced by them (such as build scripts and patches). At the
- top level, the tarball should contain a single directory. That
- directory must contain a file <filename>default.nix</filename>
- that serves as the channel’s “entry point”.</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-</refsection>
-
-</refentry>
-<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-nix-collect-garbage">
-
-<refmeta>
- <refentrytitle>nix-collect-garbage</refentrytitle>
- <manvolnum>1</manvolnum>
- <refmiscinfo class="source">Nix</refmiscinfo>
- <refmiscinfo class="version">3.0</refmiscinfo>
-</refmeta>
-
-<refnamediv>
- <refname>nix-collect-garbage</refname>
- <refpurpose>delete unreachable store paths</refpurpose>
-</refnamediv>
-
-<refsynopsisdiv>
- <cmdsynopsis>
- <command>nix-collect-garbage</command>
- <arg><option>--delete-old</option></arg>
- <arg><option>-d</option></arg>
- <arg><option>--delete-older-than</option> <replaceable>period</replaceable></arg>
- <arg><option>--max-freed</option> <replaceable>bytes</replaceable></arg>
- <arg><option>--dry-run</option></arg>
- </cmdsynopsis>
-</refsynopsisdiv>
-
-<refsection><title>Description</title>
-
-<para>The command <command>nix-collect-garbage</command> is mostly an
-alias of <link linkend="rsec-nix-store-gc"><command>nix-store
---gc</command></link>, that is, it deletes all unreachable paths in
-the Nix store to clean up your system. However, it provides two
-additional options: <option>-d</option> (<option>--delete-old</option>),
-which deletes all old generations of all profiles in
-<filename>/nix/var/nix/profiles</filename> by invoking
-<literal>nix-env --delete-generations old</literal> on all profiles
-(of course, this makes rollbacks to previous configurations
-impossible); and
-<option>--delete-older-than</option> <replaceable>period</replaceable>,
-where period is a value such as <literal>30d</literal>, which deletes
-all generations older than the specified number of days in all profiles
-in <filename>/nix/var/nix/profiles</filename> (except for the generations
-that were active at that point in time).
-</para>
-
-</refsection>
-
-<refsection><title>Example</title>
-
-<para>To delete from the Nix store everything that is not used by the
-current generations of each profile, do
-
-<screen>
-$ nix-collect-garbage -d</screen>
-
-</para>
-
-</refsection>
-
-</refentry>
-<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" xml:id="sec-nix-copy-closure">
-
-<refmeta>
- <refentrytitle>nix-copy-closure</refentrytitle>
- <manvolnum>1</manvolnum>
- <refmiscinfo class="source">Nix</refmiscinfo>
- <refmiscinfo class="version">3.0</refmiscinfo>
-</refmeta>
-
-<refnamediv>
- <refname>nix-copy-closure</refname>
- <refpurpose>copy a closure to or from a remote machine via SSH</refpurpose>
-</refnamediv>
-
-<refsynopsisdiv>
- <cmdsynopsis>
- <command>nix-copy-closure</command>
- <group>
- <arg choice="plain"><option>--to</option></arg>
- <arg choice="plain"><option>--from</option></arg>
- </group>
- <arg><option>--gzip</option></arg>
- <!--
- <arg><option>- -show-progress</option></arg>
- -->
- <arg><option>--include-outputs</option></arg>
- <group>
- <arg choice="plain"><option>--use-substitutes</option></arg>
- <arg choice="plain"><option>-s</option></arg>
- </group>
- <arg><option>-v</option></arg>
- <arg choice="plain">
- <replaceable>user@</replaceable><replaceable>machine</replaceable>
- </arg>
- <arg choice="plain"><replaceable>paths</replaceable></arg>
- </cmdsynopsis>
-</refsynopsisdiv>
-
-
-<refsection><title>Description</title>
-
-<para><command>nix-copy-closure</command> gives you an easy and
-efficient way to exchange software between machines. Given one or
-more Nix store <replaceable>paths</replaceable> on the local
-machine, <command>nix-copy-closure</command> computes the closure of
-those paths (i.e. all their dependencies in the Nix store), and copies
-all paths in the closure to the remote machine via the
-<command>ssh</command> (Secure Shell) command. With the
-<option>--from</option>, the direction is reversed:
-the closure of <replaceable>paths</replaceable> on a remote machine is
-copied to the Nix store on the local machine.</para>
-
-<para>This command is efficient because it only sends the store paths
-that are missing on the target machine.</para>
-
-<para>Since <command>nix-copy-closure</command> calls
-<command>ssh</command>, you may be asked to type in the appropriate
-password or passphrase. In fact, you may be asked
-<emphasis>twice</emphasis> because <command>nix-copy-closure</command>
-currently connects twice to the remote machine, first to get the set
-of paths missing on the target machine, and second to send the dump of
-those paths. If this bothers you, use
-<command>ssh-agent</command>.</para>
-
-
-<refsection><title>Options</title>
-
-<variablelist>
-
- <varlistentry><term><option>--to</option></term>
-
- <listitem><para>Copy the closure of
- <replaceable>paths</replaceable> from the local Nix store to the
- Nix store on <replaceable>machine</replaceable>. This is the
- default.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--from</option></term>
-
- <listitem><para>Copy the closure of
- <replaceable>paths</replaceable> from the Nix store on
- <replaceable>machine</replaceable> to the local Nix
- store.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--gzip</option></term>
-
- <listitem><para>Enable compression of the SSH
- connection.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--include-outputs</option></term>
-
- <listitem><para>Also copy the outputs of store derivations
- included in the closure.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--use-substitutes</option> / <option>-s</option></term>
-
- <listitem><para>Attempt to download missing paths on the target
- machine using Nix’s substitute mechanism. Any paths that cannot
- be substituted on the target are still copied normally from the
- source. This is useful, for instance, if the connection between
- the source and target machine is slow, but the connection between
- the target machine and <literal>nixos.org</literal> (the default
- binary cache server) is fast.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>-v</option></term>
-
- <listitem><para>Show verbose output.</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-</refsection>
-
-
-<refsection><title>Environment variables</title>
-
-<variablelist>
-
- <varlistentry><term><envar>NIX_SSHOPTS</envar></term>
-
- <listitem><para>Additional options to be passed to
- <command>ssh</command> on the command line.</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-</refsection>
-
-
-<refsection><title>Examples</title>
-
-<para>Copy Firefox with all its dependencies to a remote machine:
-
-<screen>
-$ nix-copy-closure --to alice@itchy.labs $(type -tP firefox)</screen>
-
-</para>
-
-<para>Copy Subversion from a remote machine and then install it into a
-user environment:
-
-<screen>
-$ nix-copy-closure --from alice@itchy.labs \
- /nix/store/0dj0503hjxy5mbwlafv1rsbdiyx1gkdy-subversion-1.4.4
-$ nix-env -i /nix/store/0dj0503hjxy5mbwlafv1rsbdiyx1gkdy-subversion-1.4.4
-</screen>
-
-</para>
-
-</refsection>
-
-
-</refsection>
-
-</refentry>
-<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-nix-daemon">
-
-<refmeta>
- <refentrytitle>nix-daemon</refentrytitle>
- <manvolnum>8</manvolnum>
- <refmiscinfo class="source">Nix</refmiscinfo>
- <refmiscinfo class="version">3.0</refmiscinfo>
-</refmeta>
-
-<refnamediv>
- <refname>nix-daemon</refname>
- <refpurpose>Nix multi-user support daemon</refpurpose>
-</refnamediv>
-
-<refsynopsisdiv>
- <cmdsynopsis>
- <command>nix-daemon</command>
- </cmdsynopsis>
-</refsynopsisdiv>
-
-
-<refsection><title>Description</title>
-
-<para>The Nix daemon is necessary in multi-user Nix installations. It
-performs build actions and other operations on the Nix store on behalf
-of unprivileged users.</para>
-
-
-</refsection>
-
-</refentry>
-<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-nix-hash">
-
-<refmeta>
- <refentrytitle>nix-hash</refentrytitle>
- <manvolnum>1</manvolnum>
- <refmiscinfo class="source">Nix</refmiscinfo>
- <refmiscinfo class="version">3.0</refmiscinfo>
-</refmeta>
-
-<refnamediv>
- <refname>nix-hash</refname>
- <refpurpose>compute the cryptographic hash of a path</refpurpose>
-</refnamediv>
-
-<refsynopsisdiv>
- <cmdsynopsis>
- <command>nix-hash</command>
- <arg><option>--flat</option></arg>
- <arg><option>--base32</option></arg>
- <arg><option>--truncate</option></arg>
- <arg><option>--type</option> <replaceable>hashAlgo</replaceable></arg>
- <arg choice="plain" rep="repeat"><replaceable>path</replaceable></arg>
- </cmdsynopsis>
- <cmdsynopsis>
- <command>nix-hash</command>
- <arg choice="plain"><option>--to-base16</option></arg>
- <arg choice="plain" rep="repeat"><replaceable>hash</replaceable></arg>
- </cmdsynopsis>
- <cmdsynopsis>
- <command>nix-hash</command>
- <arg choice="plain"><option>--to-base32</option></arg>
- <arg choice="plain" rep="repeat"><replaceable>hash</replaceable></arg>
- </cmdsynopsis>
-</refsynopsisdiv>
-
-
-<refsection><title>Description</title>
-
-<para>The command <command>nix-hash</command> computes the
-cryptographic hash of the contents of each
-<replaceable>path</replaceable> and prints it on standard output. By
-default, it computes an MD5 hash, but other hash algorithms are
-available as well. The hash is printed in hexadecimal. To generate
-the same hash as <command>nix-prefetch-url</command> you have to
-specify multiple arguments, see below for an example.</para>
-
-<para>The hash is computed over a <emphasis>serialisation</emphasis>
-of each path: a dump of the file system tree rooted at the path. This
-allows directories and symlinks to be hashed as well as regular files.
-The dump is in the <emphasis>NAR format</emphasis> produced by <link linkend="refsec-nix-store-dump"><command>nix-store</command>
-<option>--dump</option></link>. Thus, <literal>nix-hash
-<replaceable>path</replaceable></literal> yields the same
-cryptographic hash as <literal>nix-store --dump
-<replaceable>path</replaceable> | md5sum</literal>.</para>
-
-</refsection>
-
-
-<refsection><title>Options</title>
-
-<variablelist>
-
- <varlistentry><term><option>--flat</option></term>
-
- <listitem><para>Print the cryptographic hash of the contents of
- each regular file <replaceable>path</replaceable>. That is, do
- not compute the hash over the dump of
- <replaceable>path</replaceable>. The result is identical to that
- produced by the GNU commands <command>md5sum</command> and
- <command>sha1sum</command>.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--base32</option></term>
-
- <listitem><para>Print the hash in a base-32 representation rather
- than hexadecimal. This base-32 representation is more compact and
- can be used in Nix expressions (such as in calls to
- <function>fetchurl</function>).</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--truncate</option></term>
-
- <listitem><para>Truncate hashes longer than 160 bits (such as
- SHA-256) to 160 bits.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--type</option> <replaceable>hashAlgo</replaceable></term>
-
- <listitem><para>Use the specified cryptographic hash algorithm,
- which can be one of <literal>md5</literal>,
- <literal>sha1</literal>, and
- <literal>sha256</literal>.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--to-base16</option></term>
-
- <listitem><para>Don’t hash anything, but convert the base-32 hash
- representation <replaceable>hash</replaceable> to
- hexadecimal.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--to-base32</option></term>
-
- <listitem><para>Don’t hash anything, but convert the hexadecimal
- hash representation <replaceable>hash</replaceable> to
- base-32.</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-</refsection>
-
-
-<refsection><title>Examples</title>
-
-<para>Computing the same hash as <command>nix-prefetch-url</command>:
-<screen>
-$ nix-prefetch-url file://<(echo test)
-1lkgqb6fclns49861dwk9rzb6xnfkxbpws74mxnx01z9qyv1pjpj
-$ nix-hash --type sha256 --flat --base32 <(echo test)
-1lkgqb6fclns49861dwk9rzb6xnfkxbpws74mxnx01z9qyv1pjpj
-</screen>
-</para>
-
-<para>Computing hashes:
-
-<screen>
-$ mkdir test
-$ echo "hello" > test/world
-
-$ nix-hash test/ <lineannotation>(MD5 hash; default)</lineannotation>
-8179d3caeff1869b5ba1744e5a245c04
-
-$ nix-store --dump test/ | md5sum <lineannotation>(for comparison)</lineannotation>
-8179d3caeff1869b5ba1744e5a245c04 -
-
-$ nix-hash --type sha1 test/
-e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
-
-$ nix-hash --type sha1 --base32 test/
-nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
-
-$ nix-hash --type sha256 --flat test/
-error: reading file `test/': Is a directory
-
-$ nix-hash --type sha256 --flat test/world
-5891b5b522d5df086d0ff0b110fbd9d21bb4fc7163af34d08286a2e846f6be03</screen>
-
-</para>
-
-<para>Converting between hexadecimal and base-32:
-
-<screen>
-$ nix-hash --type sha1 --to-base32 e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
-nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
-
-$ nix-hash --type sha1 --to-base16 nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
-e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6</screen>
-
-</para>
-
-</refsection>
-
-
-</refentry>
-<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-nix-instantiate">
-
-<refmeta>
- <refentrytitle>nix-instantiate</refentrytitle>
- <manvolnum>1</manvolnum>
- <refmiscinfo class="source">Nix</refmiscinfo>
- <refmiscinfo class="version">3.0</refmiscinfo>
-</refmeta>
-
-<refnamediv>
- <refname>nix-instantiate</refname>
- <refpurpose>instantiate store derivations from Nix expressions</refpurpose>
-</refnamediv>
-
-<refsynopsisdiv>
- <cmdsynopsis>
- <command>nix-instantiate</command>
- <group>
- <arg choice="plain"><option>--parse</option></arg>
- <arg choice="plain">
- <option>--eval</option>
- <arg><option>--strict</option></arg>
- <arg><option>--json</option></arg>
- <arg><option>--xml</option></arg>
- </arg>
- </group>
- <arg><option>--read-write-mode</option></arg>
- <arg><option>--arg</option> <replaceable>name</replaceable> <replaceable>value</replaceable></arg>
- <arg>
- <group choice="req">
- <arg choice="plain"><option>--attr</option></arg>
- <arg choice="plain"><option>-A</option></arg>
- </group>
- <replaceable>attrPath</replaceable>
- </arg>
- <arg><option>--add-root</option> <replaceable>path</replaceable></arg>
- <arg><option>--indirect</option></arg>
- <group>
- <arg choice="plain"><option>--expr</option></arg>
- <arg choice="plain"><option>-E</option></arg>
- </group>
- <arg choice="plain" rep="repeat"><replaceable>files</replaceable></arg>
- </cmdsynopsis>
- <cmdsynopsis>
- <command>nix-instantiate</command>
- <arg choice="plain"><option>--find-file</option></arg>
- <arg choice="plain" rep="repeat"><replaceable>files</replaceable></arg>
- </cmdsynopsis>
-</refsynopsisdiv>
-
-
-<refsection><title>Description</title>
-
-<para>The command <command>nix-instantiate</command> generates <link linkend="gloss-derivation">store derivations</link> from (high-level)
-Nix expressions. It evaluates the Nix expressions in each of
-<replaceable>files</replaceable> (which defaults to
-<replaceable>./default.nix</replaceable>). Each top-level expression
-should evaluate to a derivation, a list of derivations, or a set of
-derivations. The paths of the resulting store derivations are printed
-on standard output.</para>
-
-<para>If <replaceable>files</replaceable> is the character
-<literal>-</literal>, then a Nix expression will be read from standard
-input.</para>
-
-<para condition="manual">See also <xref linkend="sec-common-options"/> for a list of common options.</para>
-
-</refsection>
-
-
-<refsection><title>Options</title>
-
-<variablelist>
-
- <varlistentry>
- <term><option>--add-root</option> <replaceable>path</replaceable></term>
- <term><option>--indirect</option></term>
-
- <listitem><para>See the <link linkend="opt-add-root">corresponding
- options</link> in <command>nix-store</command>.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--parse</option></term>
-
- <listitem><para>Just parse the input files, and print their
- abstract syntax trees on standard output in ATerm
- format.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--eval</option></term>
-
- <listitem><para>Just parse and evaluate the input files, and print
- the resulting values on standard output. No instantiation of
- store derivations takes place.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--find-file</option></term>
-
- <listitem><para>Look up the given files in Nix’s search path (as
- specified by the <envar linkend="env-NIX_PATH">NIX_PATH</envar>
- environment variable). If found, print the corresponding absolute
- paths on standard output. For instance, if
- <envar>NIX_PATH</envar> is
- <literal>nixpkgs=/home/alice/nixpkgs</literal>, then
- <literal>nix-instantiate --find-file nixpkgs/default.nix</literal>
- will print
- <literal>/home/alice/nixpkgs/default.nix</literal>.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--strict</option></term>
-
- <listitem><para>When used with <option>--eval</option>,
- recursively evaluate list elements and attributes. Normally, such
- sub-expressions are left unevaluated (since the Nix expression
- language is lazy).</para>
-
- <warning><para>This option can cause non-termination, because lazy
- data structures can be infinitely large.</para></warning>
-
- </listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--json</option></term>
-
- <listitem><para>When used with <option>--eval</option>, print the resulting
- value as an JSON representation of the abstract syntax tree rather
- than as an ATerm.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--xml</option></term>
-
- <listitem><para>When used with <option>--eval</option>, print the resulting
- value as an XML representation of the abstract syntax tree rather than as
- an ATerm. The schema is the same as that used by the <link linkend="builtin-toXML"><function>toXML</function> built-in</link>.
- </para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--read-write-mode</option></term>
-
- <listitem><para>When used with <option>--eval</option>, perform
- evaluation in read/write mode so nix language features that
- require it will still work (at the cost of needing to do
- instantiation of every evaluated derivation). If this option is
- not enabled, there may be uninstantiated store paths in the final
- output.</para>
-
- </listitem>
-
- </varlistentry>
-
-</variablelist>
-
-<variablelist condition="manpage">
- <varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--help</option></term>
-
- <listitem><para>Prints out a summary of the command syntax and
- exits.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--version</option></term>
-
- <listitem><para>Prints out the Nix version number on standard output
- and exits.</para></listitem>
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--verbose</option> / <option>-v</option></term>
-
- <listitem>
-
- <para>Increases the level of verbosity of diagnostic messages
- printed on standard error. For each Nix operation, the information
- printed on standard output is well-defined; any diagnostic
- information is printed on standard error, never on standard
- output.</para>
-
- <para>This option may be specified repeatedly. Currently, the
- following verbosity levels exist:</para>
-
- <variablelist>
-
- <varlistentry><term>0</term>
- <listitem><para>“Errors only”: only print messages
- explaining why the Nix invocation failed.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>1</term>
- <listitem><para>“Informational”: print
- <emphasis>useful</emphasis> messages about what Nix is doing.
- This is the default.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>2</term>
- <listitem><para>“Talkative”: print more informational
- messages.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>3</term>
- <listitem><para>“Chatty”: print even more
- informational messages.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>4</term>
- <listitem><para>“Debug”: print debug
- information.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>5</term>
- <listitem><para>“Vomit”: print vast amounts of debug
- information.</para></listitem>
- </varlistentry>
-
- </variablelist>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--quiet</option></term>
-
- <listitem>
-
- <para>Decreases the level of verbosity of diagnostic messages
- printed on standard error. This is the inverse option to
- <option>-v</option> / <option>--verbose</option>.
- </para>
-
- <para>This option may be specified repeatedly. See the previous
- verbosity levels list.</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-log-format"><term><option>--log-format</option> <replaceable>format</replaceable></term>
-
- <listitem>
-
- <para>This option can be used to change the output of the log format, with
- <replaceable>format</replaceable> being one of:</para>
-
- <variablelist>
-
- <varlistentry><term>raw</term>
- <listitem><para>This is the raw format, as outputted by nix-build.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>internal-json</term>
- <listitem><para>Outputs the logs in a structured manner. NOTE: the json schema is not guarantees to be stable between releases.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>bar</term>
- <listitem><para>Only display a progress bar during the builds.</para></listitem>
- </varlistentry>
-
- <varlistentry><term>bar-with-logs</term>
- <listitem><para>Display the raw logs, with the progress bar at the bottom.</para></listitem>
- </varlistentry>
-
- </variablelist>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--no-build-output</option> / <option>-Q</option></term>
-
- <listitem><para>By default, output written by builders to standard
- output and standard error is echoed to the Nix command's standard
- error. This option suppresses this behaviour. Note that the
- builder's standard output and error are always written to a log file
- in
- <filename><replaceable>prefix</replaceable>/nix/var/log/nix</filename>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-max-jobs"><term><option>--max-jobs</option> / <option>-j</option>
-<replaceable>number</replaceable></term>
-
- <listitem>
-
- <para>Sets the maximum number of build jobs that Nix will
- perform in parallel to the specified number. Specify
- <literal>auto</literal> to use the number of CPUs in the system.
- The default is specified by the <link linkend="conf-max-jobs"><literal>max-jobs</literal></link>
- configuration setting, which itself defaults to
- <literal>1</literal>. A higher value is useful on SMP systems or to
- exploit I/O latency.</para>
-
- <para> Setting it to <literal>0</literal> disallows building on the local
- machine, which is useful when you want builds to happen only on remote
- builders.</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-cores"><term><option>--cores</option></term>
-
- <listitem><para>Sets the value of the <envar>NIX_BUILD_CORES</envar>
- environment variable in the invocation of builders. Builders can
- use this variable at their discretion to control the maximum amount
- of parallelism. For instance, in Nixpkgs, if the derivation
- attribute <varname>enableParallelBuilding</varname> is set to
- <literal>true</literal>, the builder passes the
- <option>-j<replaceable>N</replaceable></option> flag to GNU Make.
- It defaults to the value of the <link linkend="conf-cores"><literal>cores</literal></link>
- configuration setting, if set, or <literal>1</literal> otherwise.
- The value <literal>0</literal> means that the builder should use all
- available CPU cores in the system.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-max-silent-time"><term><option>--max-silent-time</option></term>
-
- <listitem><para>Sets the maximum number of seconds that a builder
- can go without producing any data on standard output or standard
- error. The default is specified by the <link linkend="conf-max-silent-time"><literal>max-silent-time</literal></link>
- configuration setting. <literal>0</literal> means no
- time-out.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-timeout"><term><option>--timeout</option></term>
-
- <listitem><para>Sets the maximum number of seconds that a builder
- can run. The default is specified by the <link linkend="conf-timeout"><literal>timeout</literal></link>
- configuration setting. <literal>0</literal> means no
- timeout.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--keep-going</option> / <option>-k</option></term>
-
- <listitem><para>Keep going in case of failed builds, to the
- greatest extent possible. That is, if building an input of some
- derivation fails, Nix will still build the other inputs, but not the
- derivation itself. Without this option, Nix stops if any build
- fails (except for builds of substitutes), possibly killing builds in
- progress (in case of parallel or distributed builds).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--keep-failed</option> / <option>-K</option></term>
-
- <listitem><para>Specifies that in case of a build failure, the
- temporary directory (usually in <filename>/tmp</filename>) in which
- the build takes place should not be deleted. The path of the build
- directory is printed as an informational message.
- </para>
- </listitem>
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--fallback</option></term>
-
- <listitem>
-
- <para>Whenever Nix attempts to build a derivation for which
- substitutes are known for each output path, but realising the output
- paths through the substitutes fails, fall back on building the
- derivation.</para>
-
- <para>The most common scenario in which this is useful is when we
- have registered substitutes in order to perform binary distribution
- from, say, a network repository. If the repository is down, the
- realisation of the derivation will fail. When this option is
- specified, Nix will build the derivation instead. Thus,
- installation from binaries falls back on installation from source.
- This option is not the default since it is generally not desirable
- for a transient failure in obtaining the substitutes to lead to a
- full build from source (with the related consumption of
- resources).</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--no-build-hook</option></term>
-
- <listitem>
-
- <para>Disables the build hook mechanism. This allows to ignore remote
- builders if they are setup on the machine.</para>
-
- <para>It's useful in cases where the bandwidth between the client and the
- remote builder is too low. In that case it can take more time to upload the
- sources to the remote builder and fetch back the result than to do the
- computation locally.</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--readonly-mode</option></term>
-
- <listitem><para>When this option is used, no attempt is made to open
- the Nix database. Most Nix operations do need database access, so
- those operations will fail.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--arg</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
-
- <listitem><para>This option is accepted by
- <command>nix-env</command>, <command>nix-instantiate</command>,
- <command>nix-shell</command> and <command>nix-build</command>.
- When evaluating Nix expressions, the expression evaluator will
- automatically try to call functions that
- it encounters. It can automatically call functions for which every
- argument has a <link linkend="ss-functions">default value</link>
- (e.g., <literal>{ <replaceable>argName</replaceable> ?
- <replaceable>defaultValue</replaceable> }:
- <replaceable>...</replaceable></literal>). With
- <option>--arg</option>, you can also call functions that have
- arguments without a default value (or override a default value).
- That is, if the evaluator encounters a function with an argument
- named <replaceable>name</replaceable>, it will call it with value
- <replaceable>value</replaceable>.</para>
-
- <para>For instance, the top-level <literal>default.nix</literal> in
- Nixpkgs is actually a function:
-
-<programlisting>
-{ # The system (e.g., `i686-linux') for which to build the packages.
- system ? builtins.currentSystem
- <replaceable>...</replaceable>
-}: <replaceable>...</replaceable></programlisting>
-
- So if you call this Nix expression (e.g., when you do
- <literal>nix-env -i <replaceable>pkgname</replaceable></literal>),
- the function will be called automatically using the value <link linkend="builtin-currentSystem"><literal>builtins.currentSystem</literal></link>
- for the <literal>system</literal> argument. You can override this
- using <option>--arg</option>, e.g., <literal>nix-env -i
- <replaceable>pkgname</replaceable> --arg system
- \"i686-freebsd\"</literal>. (Note that since the argument is a Nix
- string literal, you have to escape the quotes.)</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--argstr</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
-
- <listitem><para>This option is like <option>--arg</option>, only the
- value is not a Nix expression but a string. So instead of
- <literal>--arg system \"i686-linux\"</literal> (the outer quotes are
- to keep the shell happy) you can say <literal>--argstr system
- i686-linux</literal>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-attr"><term><option>--attr</option> / <option>-A</option>
-<replaceable>attrPath</replaceable></term>
-
- <listitem><para>Select an attribute from the top-level Nix
- expression being evaluated. (<command>nix-env</command>,
- <command>nix-instantiate</command>, <command>nix-build</command> and
- <command>nix-shell</command> only.) The <emphasis>attribute
- path</emphasis> <replaceable>attrPath</replaceable> is a sequence of
- attribute names separated by dots. For instance, given a top-level
- Nix expression <replaceable>e</replaceable>, the attribute path
- <literal>xorg.xorgserver</literal> would cause the expression
- <literal><replaceable>e</replaceable>.xorg.xorgserver</literal> to
- be used. See <link linkend="refsec-nix-env-install-examples"><command>nix-env
- --install</command></link> for some concrete examples.</para>
-
- <para>In addition to attribute names, you can also specify array
- indices. For instance, the attribute path
- <literal>foo.3.bar</literal> selects the <literal>bar</literal>
- attribute of the fourth element of the array in the
- <literal>foo</literal> attribute of the top-level
- expression.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--expr</option> / <option>-E</option></term>
-
- <listitem><para>Interpret the command line arguments as a list of
- Nix expressions to be parsed and evaluated, rather than as a list
- of file names of Nix expressions.
- (<command>nix-instantiate</command>, <command>nix-build</command>
- and <command>nix-shell</command> only.)</para>
-
- <para>For <command>nix-shell</command>, this option is commonly used
- to give you a shell in which you can build the packages returned
- by the expression. If you want to get a shell which contain the
- <emphasis>built</emphasis> packages ready for use, give your
- expression to the <command>nix-shell -p</command> convenience flag
- instead.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="opt-I"><term><option>-I</option> <replaceable>path</replaceable></term>
-
- <listitem><para>Add a path to the Nix expression search path. This
- option may be given multiple times. See the <envar linkend="env-NIX_PATH">NIX_PATH</envar> environment variable for
- information on the semantics of the Nix search path. Paths added
- through <option>-I</option> take precedence over
- <envar>NIX_PATH</envar>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--option</option> <replaceable>name</replaceable> <replaceable>value</replaceable></term>
-
- <listitem><para>Set the Nix configuration option
- <replaceable>name</replaceable> to <replaceable>value</replaceable>.
- This overrides settings in the Nix configuration file (see
- <citerefentry><refentrytitle>nix.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><option>--repair</option></term>
-
- <listitem><para>Fix corrupted or missing store paths by
- redownloading or rebuilding them. Note that this is slow because it
- requires computing a cryptographic hash of the contents of every
- path in the closure of the build. Also note the warning under
- <command>nix-store --repair-path</command>.</para></listitem>
-
-</varlistentry>
-</variablelist>
-
-</refsection>
-
-
-<refsection><title>Examples</title>
-
-<para>Instantiating store derivations from a Nix expression, and
-building them using <command>nix-store</command>:
-
-<screen>
-$ nix-instantiate test.nix <lineannotation>(instantiate)</lineannotation>
-/nix/store/cigxbmvy6dzix98dxxh9b6shg7ar5bvs-perl-BerkeleyDB-0.26.drv
-
-$ nix-store -r $(nix-instantiate test.nix) <lineannotation>(build)</lineannotation>
-<replaceable>...</replaceable>
-/nix/store/qhqk4n8ci095g3sdp93x7rgwyh9rdvgk-perl-BerkeleyDB-0.26 <lineannotation>(output path)</lineannotation>
-
-$ ls -l /nix/store/qhqk4n8ci095g3sdp93x7rgwyh9rdvgk-perl-BerkeleyDB-0.26
-dr-xr-xr-x 2 eelco users 4096 1970-01-01 01:00 lib
-...</screen>
-
-</para>
-
-<para>You can also give a Nix expression on the command line:
-
-<screen>
-$ nix-instantiate -E 'with import <nixpkgs> { }; hello'
-/nix/store/j8s4zyv75a724q38cb0r87rlczaiag4y-hello-2.8.drv
-</screen>
-
-This is equivalent to:
-
-<screen>
-$ nix-instantiate '<nixpkgs>' -A hello
-</screen>
-
-</para>
-
-<para>Parsing and evaluating Nix expressions:
-
-<screen>
-$ nix-instantiate --parse -E '1 + 2'
-1 + 2
-
-$ nix-instantiate --eval -E '1 + 2'
-3
-
-$ nix-instantiate --eval --xml -E '1 + 2'
-<![CDATA[<?xml version='1.0' encoding='utf-8'?>
-<expr>
- <int value="3" />
-</expr>]]></screen>
-
-</para>
-
-<para>The difference between non-strict and strict evaluation:
-
-<screen>
-$ nix-instantiate --eval --xml -E 'rec { x = "foo"; y = x; }'
-<replaceable>...</replaceable><![CDATA[
- <attr name="x">
- <string value="foo" />
- </attr>
- <attr name="y">
- <unevaluated />
- </attr>]]>
-<replaceable>...</replaceable></screen>
-
-Note that <varname>y</varname> is left unevaluated (the XML
-representation doesn’t attempt to show non-normal forms).
-
-<screen>
-$ nix-instantiate --eval --xml --strict -E 'rec { x = "foo"; y = x; }'
-<replaceable>...</replaceable><![CDATA[
- <attr name="x">
- <string value="foo" />
- </attr>
- <attr name="y">
- <string value="foo" />
- </attr>]]>
-<replaceable>...</replaceable></screen>
-
-</para>
-
-</refsection>
-
-
-<refsection condition="manpage"><title>Environment variables</title>
-
-<variablelist>
- <varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>IN_NIX_SHELL</envar></term>
-
- <listitem><para>Indicator that tells if the current environment was set up by
- <command>nix-shell</command>. Since Nix 2.0 the values are
- <literal>"pure"</literal> and <literal>"impure"</literal></para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="env-NIX_PATH"><term><envar>NIX_PATH</envar></term>
-
- <listitem>
-
- <para>A colon-separated list of directories used to look up Nix
- expressions enclosed in angle brackets (i.e.,
- <literal><<replaceable>path</replaceable>></literal>). For
- instance, the value
-
- <screen>
-/home/eelco/Dev:/etc/nixos</screen>
-
- will cause Nix to look for paths relative to
- <filename>/home/eelco/Dev</filename> and
- <filename>/etc/nixos</filename>, in this order. It is also
- possible to match paths against a prefix. For example, the value
-
- <screen>
-nixpkgs=/home/eelco/Dev/nixpkgs-branch:/etc/nixos</screen>
-
- will cause Nix to search for
- <literal><nixpkgs/<replaceable>path</replaceable>></literal> in
- <filename>/home/eelco/Dev/nixpkgs-branch/<replaceable>path</replaceable></filename>
- and
- <filename>/etc/nixos/nixpkgs/<replaceable>path</replaceable></filename>.</para>
-
- <para>If a path in the Nix search path starts with
- <literal>http://</literal> or <literal>https://</literal>, it is
- interpreted as the URL of a tarball that will be downloaded and
- unpacked to a temporary location. The tarball must consist of a
- single top-level directory. For example, setting
- <envar>NIX_PATH</envar> to
-
- <screen>
-nixpkgs=https://github.com/NixOS/nixpkgs/archive/nixos-15.09.tar.gz</screen>
-
- tells Nix to download the latest revision in the Nixpkgs/NixOS
- 15.09 channel.</para>
-
- <para>A following shorthand can be used to refer to the official channels:
-
- <screen>nixpkgs=channel:nixos-15.09</screen>
- </para>
-
- <para>The search path can be extended using the <option linkend="opt-I">-I</option> option, which takes precedence over
- <envar>NIX_PATH</envar>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_IGNORE_SYMLINK_STORE</envar></term>
-
- <listitem>
-
- <para>Normally, the Nix store directory (typically
- <filename>/nix/store</filename>) is not allowed to contain any
- symlink components. This is to prevent “impure” builds. Builders
- sometimes “canonicalise” paths by resolving all symlink components.
- Thus, builds on different machines (with
- <filename>/nix/store</filename> resolving to different locations)
- could yield different results. This is generally not a problem,
- except when builds are deployed to machines where
- <filename>/nix/store</filename> resolves differently. If you are
- sure that you’re not going to do that, you can set
- <envar>NIX_IGNORE_SYMLINK_STORE</envar> to <envar>1</envar>.</para>
-
- <para>Note that if you’re symlinking the Nix store so that you can
- put it on another file system than the root file system, on Linux
- you’re better off using <literal>bind</literal> mount points, e.g.,
-
- <screen>
-$ mkdir /nix
-$ mount -o bind /mnt/otherdisk/nix /nix</screen>
-
- Consult the <citerefentry><refentrytitle>mount</refentrytitle>
- <manvolnum>8</manvolnum></citerefentry> manual page for details.</para>
-
- </listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_STORE_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix store (default
- <filename><replaceable>prefix</replaceable>/store</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_DATA_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix static data
- directory (default
- <filename><replaceable>prefix</replaceable>/share</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_LOG_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix log directory
- (default <filename><replaceable>prefix</replaceable>/var/log/nix</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_STATE_DIR</envar></term>
-
- <listitem><para>Overrides the location of the Nix state directory
- (default <filename><replaceable>prefix</replaceable>/var/nix</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_CONF_DIR</envar></term>
-
- <listitem><para>Overrides the location of the system Nix configuration
- directory (default
- <filename><replaceable>prefix</replaceable>/etc/nix</filename>).</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_USER_CONF_FILES</envar></term>
-
- <listitem><para>Overrides the location of the user Nix configuration files
- to load from (defaults to the XDG spec locations). The variable is treated
- as a list separated by the <literal>:</literal> token.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>TMPDIR</envar></term>
-
- <listitem><para>Use the specified directory to store temporary
- files. In particular, this includes temporary build directories;
- these can take up substantial amounts of disk space. The default is
- <filename>/tmp</filename>.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook" xml:id="envar-remote"><term><envar>NIX_REMOTE</envar></term>
-
- <listitem><para>This variable should be set to
- <literal>daemon</literal> if you want to use the Nix daemon to
- execute Nix operations. This is necessary in <link linkend="ssec-multi-user">multi-user Nix installations</link>.
- If the Nix daemon's Unix socket is at some non-standard path,
- this variable should be set to <literal>unix://path/to/socket</literal>.
- Otherwise, it should be left unset.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_SHOW_STATS</envar></term>
-
- <listitem><para>If set to <literal>1</literal>, Nix will print some
- evaluation statistics, such as the number of values
- allocated.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>NIX_COUNT_CALLS</envar></term>
-
- <listitem><para>If set to <literal>1</literal>, Nix will print how
- often functions were called during Nix expression evaluation. This
- is useful for profiling your Nix expressions.</para></listitem>
-
-</varlistentry><varlistentry xmlns="http://docbook.org/ns/docbook"><term><envar>GC_INITIAL_HEAP_SIZE</envar></term>
-
- <listitem><para>If Nix has been configured to use the Boehm garbage
- collector, this variable sets the initial size of the heap in bytes.
- It defaults to 384 MiB. Setting it to a low value reduces memory
- consumption, but will increase runtime due to the overhead of
- garbage collection.</para></listitem>
-
-</varlistentry>
-</variablelist>
-
-</refsection>
-
-
-</refentry>
-<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-nix-prefetch-url">
-
-<refmeta>
- <refentrytitle>nix-prefetch-url</refentrytitle>
- <manvolnum>1</manvolnum>
- <refmiscinfo class="source">Nix</refmiscinfo>
- <refmiscinfo class="version">3.0</refmiscinfo>
-</refmeta>
-
-<refnamediv>
- <refname>nix-prefetch-url</refname>
- <refpurpose>copy a file from a URL into the store and print its hash</refpurpose>
-</refnamediv>
-
-<refsynopsisdiv>
- <cmdsynopsis>
- <command>nix-prefetch-url</command>
- <arg><option>--version</option></arg>
- <arg><option>--type</option> <replaceable>hashAlgo</replaceable></arg>
- <arg><option>--print-path</option></arg>
- <arg><option>--unpack</option></arg>
- <arg><option>--name</option> <replaceable>name</replaceable></arg>
- <arg choice="plain"><replaceable>url</replaceable></arg>
- <arg><replaceable>hash</replaceable></arg>
- </cmdsynopsis>
-</refsynopsisdiv>
-
-<refsection><title>Description</title>
-
-<para>The command <command>nix-prefetch-url</command> downloads the
-file referenced by the URL <replaceable>url</replaceable>, prints its
-cryptographic hash, and copies it into the Nix store. The file name
-in the store is
-<filename><replaceable>hash</replaceable>-<replaceable>baseName</replaceable></filename>,
-where <replaceable>baseName</replaceable> is everything following the
-final slash in <replaceable>url</replaceable>.</para>
-
-<para>This command is just a convenience for Nix expression writers.
-Often a Nix expression fetches some source distribution from the
-network using the <literal>fetchurl</literal> expression contained in
-Nixpkgs. However, <literal>fetchurl</literal> requires a
-cryptographic hash. If you don't know the hash, you would have to
-download the file first, and then <literal>fetchurl</literal> would
-download it again when you build your Nix expression. Since
-<literal>fetchurl</literal> uses the same name for the downloaded file
-as <command>nix-prefetch-url</command>, the redundant download can be
-avoided.</para>
-
-<para>If <replaceable>hash</replaceable> is specified, then a download
-is not performed if the Nix store already contains a file with the
-same hash and base name. Otherwise, the file is downloaded, and an
-error is signaled if the actual hash of the file does not match the
-specified hash.</para>
-
-<para>This command prints the hash on standard output. Additionally,
-if the option <option>--print-path</option> is used, the path of the
-downloaded file in the Nix store is also printed.</para>
-
-</refsection>
-
-
-<refsection><title>Options</title>
-
-<variablelist>
-
- <varlistentry><term><option>--type</option> <replaceable>hashAlgo</replaceable></term>
-
- <listitem><para>Use the specified cryptographic hash algorithm,
- which can be one of <literal>md5</literal>,
- <literal>sha1</literal>, and
- <literal>sha256</literal>.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--print-path</option></term>
-
- <listitem><para>Print the store path of the downloaded file on
- standard output.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--unpack</option></term>
-
- <listitem><para>Unpack the archive (which must be a tarball or zip
- file) and add the result to the Nix store. The resulting hash can
- be used with functions such as Nixpkgs’s
- <varname>fetchzip</varname> or
- <varname>fetchFromGitHub</varname>.</para></listitem>
-
- </varlistentry>
-
- <varlistentry><term><option>--name</option> <replaceable>name</replaceable></term>
-
- <listitem><para>Override the name of the file in the Nix store. By
- default, this is
- <literal><replaceable>hash</replaceable>-<replaceable>basename</replaceable></literal>,
- where <replaceable>basename</replaceable> is the last component of
- <replaceable>url</replaceable>. Overriding the name is necessary
- when <replaceable>basename</replaceable> contains characters that
- are not allowed in Nix store paths.</para></listitem>
-
- </varlistentry>
-
-</variablelist>
-
-</refsection>
-
-
-<refsection><title>Examples</title>
-
-<screen>
-$ nix-prefetch-url ftp://ftp.gnu.org/pub/gnu/hello/hello-2.10.tar.gz
-0ssi1wpaf7plaswqqjwigppsg5fyh99vdlb9kzl7c9lng89ndq1i
-
-$ nix-prefetch-url --print-path mirror://gnu/hello/hello-2.10.tar.gz
-0ssi1wpaf7plaswqqjwigppsg5fyh99vdlb9kzl7c9lng89ndq1i
-/nix/store/3x7dwzq014bblazs7kq20p9hyzz0qh8g-hello-2.10.tar.gz
-
-$ nix-prefetch-url --unpack --print-path https://github.com/NixOS/patchelf/archive/0.8.tar.gz
-079agjlv0hrv7fxnx9ngipx14gyncbkllxrp9cccnh3a50fxcmy7
-/nix/store/19zrmhm3m40xxaw81c8cqm6aljgrnwj2-0.8.tar.gz
-</screen>
-
-</refsection>
-
-
-</refentry>
-
-</chapter>
-<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-files">
-
-<title>Files</title>
-
-<para>This section lists configuration files that you can use when you
-work with Nix.</para>
-
-<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" xml:id="sec-conf-file" version="5">
-
-<refmeta>
- <refentrytitle>nix.conf</refentrytitle>
- <manvolnum>5</manvolnum>
- <refmiscinfo class="source">Nix</refmiscinfo>
- <refmiscinfo class="version">3.0</refmiscinfo>
-</refmeta>
-
-<refnamediv>
- <refname>nix.conf</refname>
- <refpurpose>Nix configuration file</refpurpose>
-</refnamediv>
-
-<refsection><title>Description</title>
-
-<para>By default Nix reads settings from the following places:</para>
-
-<para>The system-wide configuration file
-<filename><replaceable>sysconfdir</replaceable>/nix/nix.conf</filename>
-(i.e. <filename>/etc/nix/nix.conf</filename> on most systems), or
-<filename>$NIX_CONF_DIR/nix.conf</filename> if
-<envar>NIX_CONF_DIR</envar> is set. Values loaded in this file are not forwarded to the Nix daemon. The
-client assumes that the daemon has already loaded them.
-</para>
-
-<para>User-specific configuration files:</para>
-
-<para>
- If <envar>NIX_USER_CONF_FILES</envar> is set, then each path separated by
- <literal>:</literal> will be loaded in reverse order.
-</para>
-
-<para>
- Otherwise it will look for <filename>nix/nix.conf</filename> files in
- <envar>XDG_CONFIG_DIRS</envar> and <envar>XDG_CONFIG_HOME</envar>.
-
- The default location is <filename>$HOME/.config/nix.conf</filename> if
- those environment variables are unset.
-</para>
-
-<para>The configuration files consist of
-<literal><replaceable>name</replaceable> =
-<replaceable>value</replaceable></literal> pairs, one per line. Other
-files can be included with a line like <literal>include
-<replaceable>path</replaceable></literal>, where
-<replaceable>path</replaceable> is interpreted relative to the current
-conf file and a missing file is an error unless
-<literal>!include</literal> is used instead.
-Comments start with a <literal>#</literal> character. Here is an
-example configuration file:</para>
-
-<programlisting>
-keep-outputs = true # Nice for developers
-keep-derivations = true # Idem
-</programlisting>
-
-<para>You can override settings on the command line using the
-<option>--option</option> flag, e.g. <literal>--option keep-outputs
-false</literal>.</para>
-
-<para>The following settings are currently available:
-
-<variablelist>
-
-
- <varlistentry xml:id="conf-allowed-uris"><term><literal>allowed-uris</literal></term>
-
- <listitem>
-
- <para>A list of URI prefixes to which access is allowed in
- restricted evaluation mode. For example, when set to
- <literal>https://github.com/NixOS</literal>, builtin functions
- such as <function>fetchGit</function> are allowed to access
- <literal>https://github.com/NixOS/patchelf.git</literal>.</para>
-
- </listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="conf-allow-import-from-derivation"><term><literal>allow-import-from-derivation</literal></term>
-
- <listitem><para>By default, Nix allows you to <function>import</function> from a derivation,
- allowing building at evaluation time. With this option set to false, Nix will throw an error
- when evaluating an expression that uses this feature, allowing users to ensure their evaluation
- will not require any builds to take place.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="conf-allow-new-privileges"><term><literal>allow-new-privileges</literal></term>
-
- <listitem><para>(Linux-specific.) By default, builders on Linux
- cannot acquire new privileges by calling setuid/setgid programs or
- programs that have file capabilities. For example, programs such
- as <command>sudo</command> or <command>ping</command> will
- fail. (Note that in sandbox builds, no such programs are available
- unless you bind-mount them into the sandbox via the
- <option>sandbox-paths</option> option.) You can allow the
- use of such programs by enabling this option. This is impure and
- usually undesirable, but may be useful in certain scenarios
- (e.g. to spin up containers or set up userspace network interfaces
- in tests).</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="conf-allowed-users"><term><literal>allowed-users</literal></term>
-
- <listitem>
-
- <para>A list of names of users (separated by whitespace) that
- are allowed to connect to the Nix daemon. As with the
- <option>trusted-users</option> option, you can specify groups by
- prefixing them with <literal>@</literal>. Also, you can allow
- all users by specifying <literal>*</literal>. The default is
- <literal>*</literal>.</para>
-
- <para>Note that trusted users are always allowed to connect.</para>
-
- </listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="conf-auto-optimise-store"><term><literal>auto-optimise-store</literal></term>
-
- <listitem><para>If set to <literal>true</literal>, Nix
- automatically detects files in the store that have identical
- contents, and replaces them with hard links to a single copy.
- This saves disk space. If set to <literal>false</literal> (the
- default), you can still run <command>nix-store
- --optimise</command> to get rid of duplicate
- files.</para></listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-builders">
- <term><literal>builders</literal></term>
- <listitem>
- <para>A list of machines on which to perform builds. <phrase condition="manual">See <xref linkend="chap-distributed-builds"/> for details.</phrase></para>
- </listitem>
- </varlistentry>
-
-
- <varlistentry xml:id="conf-builders-use-substitutes"><term><literal>builders-use-substitutes</literal></term>
-
- <listitem><para>If set to <literal>true</literal>, Nix will instruct
- remote build machines to use their own binary substitutes if available. In
- practical terms, this means that remote hosts will fetch as many build
- dependencies as possible from their own substitutes (e.g, from
- <literal>cache.nixos.org</literal>), instead of waiting for this host to
- upload them all. This can drastically reduce build times if the network
- connection between this computer and the remote build host is slow. Defaults
- to <literal>false</literal>.</para></listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-build-users-group"><term><literal>build-users-group</literal></term>
-
- <listitem><para>This options specifies the Unix group containing
- the Nix build user accounts. In multi-user Nix installations,
- builds should not be performed by the Nix account since that would
- allow users to arbitrarily modify the Nix store and database by
- supplying specially crafted builders; and they cannot be performed
- by the calling user since that would allow him/her to influence
- the build result.</para>
-
- <para>Therefore, if this option is non-empty and specifies a valid
- group, builds will be performed under the user accounts that are a
- member of the group specified here (as listed in
- <filename>/etc/group</filename>). Those user accounts should not
- be used for any other purpose!</para>
-
- <para>Nix will never run two builds under the same user account at
- the same time. This is to prevent an obvious security hole: a
- malicious user writing a Nix expression that modifies the build
- result of a legitimate Nix expression being built by another user.
- Therefore it is good to have as many Nix build user accounts as
- you can spare. (Remember: uids are cheap.)</para>
-
- <para>The build users should have permission to create files in
- the Nix store, but not delete them. Therefore,
- <filename>/nix/store</filename> should be owned by the Nix
- account, its group should be the group specified here, and its
- mode should be <literal>1775</literal>.</para>
-
- <para>If the build users group is empty, builds will be performed
- under the uid of the Nix process (that is, the uid of the caller
- if <envar>NIX_REMOTE</envar> is empty, the uid under which the Nix
- daemon runs if <envar>NIX_REMOTE</envar> is
- <literal>daemon</literal>). Obviously, this should not be used in
- multi-user settings with untrusted users.</para>
-
- </listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="conf-compress-build-log"><term><literal>compress-build-log</literal></term>
-
- <listitem><para>If set to <literal>true</literal> (the default),
- build logs written to <filename>/nix/var/log/nix/drvs</filename>
- will be compressed on the fly using bzip2. Otherwise, they will
- not be compressed.</para></listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-connect-timeout"><term><literal>connect-timeout</literal></term>
-
- <listitem>
-
- <para>The timeout (in seconds) for establishing connections in
- the binary cache substituter. It corresponds to
- <command>curl</command>’s <option>--connect-timeout</option>
- option.</para>
-
- </listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="conf-cores"><term><literal>cores</literal></term>
-
- <listitem><para>Sets the value of the
- <envar>NIX_BUILD_CORES</envar> environment variable in the
- invocation of builders. Builders can use this variable at their
- discretion to control the maximum amount of parallelism. For
- instance, in Nixpkgs, if the derivation attribute
- <varname>enableParallelBuilding</varname> is set to
- <literal>true</literal>, the builder passes the
- <option>-j<replaceable>N</replaceable></option> flag to GNU Make.
- It can be overridden using the <option linkend="opt-cores">--cores</option> command line switch and
- defaults to <literal>1</literal>. The value <literal>0</literal>
- means that the builder should use all available CPU cores in the
- system.</para>
-
- <para>See also <xref linkend="chap-tuning-cores-and-jobs"/>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-diff-hook"><term><literal>diff-hook</literal></term>
- <listitem>
- <para>
- Absolute path to an executable capable of diffing build results.
- The hook executes if <xref linkend="conf-run-diff-hook"/> is
- true, and the output of a build is known to not be the same.
- This program is not executed to determine if two results are the
- same.
- </para>
-
- <para>
- The diff hook is executed by the same user and group who ran the
- build. However, the diff hook does not have write access to the
- store path just built.
- </para>
-
- <para>The diff hook program receives three parameters:</para>
-
- <orderedlist>
- <listitem>
- <para>
- A path to the previous build's results
- </para>
- </listitem>
-
- <listitem>
- <para>
- A path to the current build's results
- </para>
- </listitem>
-
- <listitem>
- <para>
- The path to the build's derivation
- </para>
- </listitem>
-
- <listitem>
- <para>
- The path to the build's scratch directory. This directory
- will exist only if the build was run with
- <option>--keep-failed</option>.
- </para>
- </listitem>
- </orderedlist>
-
- <para>
- The stderr and stdout output from the diff hook will not be
- displayed to the user. Instead, it will print to the nix-daemon's
- log.
- </para>
-
- <para>When using the Nix daemon, <literal>diff-hook</literal> must
- be set in the <filename>nix.conf</filename> configuration file, and
- cannot be passed at the command line.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-enforce-determinism">
- <term><literal>enforce-determinism</literal></term>
-
- <listitem><para>See <xref linkend="conf-repeat"/>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-extra-sandbox-paths">
- <term><literal>extra-sandbox-paths</literal></term>
-
- <listitem><para>A list of additional paths appended to
- <option>sandbox-paths</option>. Useful if you want to extend
- its default value.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="conf-extra-platforms"><term><literal>extra-platforms</literal></term>
-
- <listitem><para>Platforms other than the native one which
- this machine is capable of building for. This can be useful for
- supporting additional architectures on compatible machines:
- i686-linux can be built on x86_64-linux machines (and the default
- for this setting reflects this); armv7 is backwards-compatible with
- armv6 and armv5tel; some aarch64 machines can also natively run
- 32-bit ARM code; and qemu-user may be used to support non-native
- platforms (though this may be slow and buggy). Most values for this
- are not enabled by default because build systems will often
- misdetect the target platform and generate incompatible code, so you
- may wish to cross-check the results of using this option against
- proper natively-built versions of your
- derivations.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="conf-extra-substituters"><term><literal>extra-substituters</literal></term>
-
- <listitem><para>Additional binary caches appended to those
- specified in <option>substituters</option>. When used by
- unprivileged users, untrusted substituters (i.e. those not listed
- in <option>trusted-substituters</option>) are silently
- ignored.</para></listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-fallback"><term><literal>fallback</literal></term>
-
- <listitem><para>If set to <literal>true</literal>, Nix will fall
- back to building from source if a binary substitute fails. This
- is equivalent to the <option>--fallback</option> flag. The
- default is <literal>false</literal>.</para></listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-fsync-metadata"><term><literal>fsync-metadata</literal></term>
-
- <listitem><para>If set to <literal>true</literal>, changes to the
- Nix store metadata (in <filename>/nix/var/nix/db</filename>) are
- synchronously flushed to disk. This improves robustness in case
- of system crashes, but reduces performance. The default is
- <literal>true</literal>.</para></listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-hashed-mirrors"><term><literal>hashed-mirrors</literal></term>
-
- <listitem><para>A list of web servers used by
- <function>builtins.fetchurl</function> to obtain files by hash.
- Given a hash type <replaceable>ht</replaceable> and a base-16 hash
- <replaceable>h</replaceable>, Nix will try to download the file
- from
- <literal>hashed-mirror/<replaceable>ht</replaceable>/<replaceable>h</replaceable></literal>.
- This allows files to be downloaded even if they have disappeared
- from their original URI. For example, given the hashed mirror
- <literal>http://tarballs.example.com/</literal>, when building the
- derivation
-
-<programlisting>
-builtins.fetchurl {
- url = "https://example.org/foo-1.2.3.tar.xz";
- sha256 = "2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae";
-}
-</programlisting>
-
- Nix will attempt to download this file from
- <literal>http://tarballs.example.com/sha256/2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae</literal>
- first. If it is not available there, if will try the original URI.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="conf-http-connections"><term><literal>http-connections</literal></term>
-
- <listitem><para>The maximum number of parallel TCP connections
- used to fetch files from binary caches and by other downloads. It
- defaults to 25. 0 means no limit.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="conf-keep-build-log"><term><literal>keep-build-log</literal></term>
-
- <listitem><para>If set to <literal>true</literal> (the default),
- Nix will write the build log of a derivation (i.e. the standard
- output and error of its builder) to the directory
- <filename>/nix/var/log/nix/drvs</filename>. The build log can be
- retrieved using the command <command>nix-store -l
- <replaceable>path</replaceable></command>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="conf-keep-derivations"><term><literal>keep-derivations</literal></term>
-
- <listitem><para>If <literal>true</literal> (default), the garbage
- collector will keep the derivations from which non-garbage store
- paths were built. If <literal>false</literal>, they will be
- deleted unless explicitly registered as a root (or reachable from
- other roots).</para>
-
- <para>Keeping derivation around is useful for querying and
- traceability (e.g., it allows you to ask with what dependencies or
- options a store path was built), so by default this option is on.
- Turn it off to save a bit of disk space (or a lot if
- <literal>keep-outputs</literal> is also turned on).</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-keep-env-derivations"><term><literal>keep-env-derivations</literal></term>
-
- <listitem><para>If <literal>false</literal> (default), derivations
- are not stored in Nix user environments. That is, the derivations of
- any build-time-only dependencies may be garbage-collected.</para>
-
- <para>If <literal>true</literal>, when you add a Nix derivation to
- a user environment, the path of the derivation is stored in the
- user environment. Thus, the derivation will not be
- garbage-collected until the user environment generation is deleted
- (<command>nix-env --delete-generations</command>). To prevent
- build-time-only dependencies from being collected, you should also
- turn on <literal>keep-outputs</literal>.</para>
-
- <para>The difference between this option and
- <literal>keep-derivations</literal> is that this one is
- “sticky”: it applies to any user environment created while this
- option was enabled, while <literal>keep-derivations</literal>
- only applies at the moment the garbage collector is
- run.</para></listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-keep-outputs"><term><literal>keep-outputs</literal></term>
-
- <listitem><para>If <literal>true</literal>, the garbage collector
- will keep the outputs of non-garbage derivations. If
- <literal>false</literal> (default), outputs will be deleted unless
- they are GC roots themselves (or reachable from other roots).</para>
-
- <para>In general, outputs must be registered as roots separately.
- However, even if the output of a derivation is registered as a
- root, the collector will still delete store paths that are used
- only at build time (e.g., the C compiler, or source tarballs
- downloaded from the network). To prevent it from doing so, set
- this option to <literal>true</literal>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-max-build-log-size"><term><literal>max-build-log-size</literal></term>
-
- <listitem>
-
- <para>This option defines the maximum number of bytes that a
- builder can write to its stdout/stderr. If the builder exceeds
- this limit, it’s killed. A value of <literal>0</literal> (the
- default) means that there is no limit.</para>
-
- </listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-max-free"><term><literal>max-free</literal></term>
-
- <listitem><para>When a garbage collection is triggered by the
- <literal>min-free</literal> option, it stops as soon as
- <literal>max-free</literal> bytes are available. The default is
- infinity (i.e. delete all garbage).</para></listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-max-jobs"><term><literal>max-jobs</literal></term>
-
- <listitem><para>This option defines the maximum number of jobs
- that Nix will try to build in parallel. The default is
- <literal>1</literal>. The special value <literal>auto</literal>
- causes Nix to use the number of CPUs in your system. <literal>0</literal>
- is useful when using remote builders to prevent any local builds (except for
- <literal>preferLocalBuild</literal> derivation attribute which executes locally
- regardless). It can be
- overridden using the <option linkend="opt-max-jobs">--max-jobs</option> (<option>-j</option>)
- command line switch.</para>
-
- <para>See also <xref linkend="chap-tuning-cores-and-jobs"/>.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-max-silent-time"><term><literal>max-silent-time</literal></term>
-
- <listitem>
-
- <para>This option defines the maximum number of seconds that a
- builder can go without producing any data on standard output or
- standard error. This is useful (for instance in an automated
- build system) to catch builds that are stuck in an infinite
- loop, or to catch remote builds that are hanging due to network
- problems. It can be overridden using the <option linkend="opt-max-silent-time">--max-silent-time</option> command
- line switch.</para>
-
- <para>The value <literal>0</literal> means that there is no
- timeout. This is also the default.</para>
-
- </listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-min-free"><term><literal>min-free</literal></term>
-
- <listitem>
- <para>When free disk space in <filename>/nix/store</filename>
- drops below <literal>min-free</literal> during a build, Nix
- performs a garbage-collection until <literal>max-free</literal>
- bytes are available or there is no more garbage. A value of
- <literal>0</literal> (the default) disables this feature.</para>
- </listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-narinfo-cache-negative-ttl"><term><literal>narinfo-cache-negative-ttl</literal></term>
-
- <listitem>
-
- <para>The TTL in seconds for negative lookups. If a store path is
- queried from a substituter but was not found, there will be a
- negative lookup cached in the local disk cache database for the
- specified duration.</para>
-
- </listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-narinfo-cache-positive-ttl"><term><literal>narinfo-cache-positive-ttl</literal></term>
-
- <listitem>
-
- <para>The TTL in seconds for positive lookups. If a store path is
- queried from a substituter, the result of the query will be cached
- in the local disk cache database including some of the NAR
- metadata. The default TTL is a month, setting a shorter TTL for
- positive lookups can be useful for binary caches that have
- frequent garbage collection, in which case having a more frequent
- cache invalidation would prevent trying to pull the path again and
- failing with a hash mismatch if the build isn't reproducible.
- </para>
-
- </listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-netrc-file"><term><literal>netrc-file</literal></term>
-
- <listitem><para>If set to an absolute path to a <filename>netrc</filename>
- file, Nix will use the HTTP authentication credentials in this file when
- trying to download from a remote host through HTTP or HTTPS. Defaults to
- <filename>$NIX_CONF_DIR/netrc</filename>.</para>
-
- <para>The <filename>netrc</filename> file consists of a list of
- accounts in the following format:
-
-<screen>
-machine <replaceable>my-machine</replaceable>
-login <replaceable>my-username</replaceable>
-password <replaceable>my-password</replaceable>
-</screen>
-
- For the exact syntax, see <link xlink:href="https://ec.haxx.se/usingcurl-netrc.html">the
- <literal>curl</literal> documentation.</link></para>
-
- <note><para>This must be an absolute path, and <literal>~</literal>
- is not resolved. For example, <filename>~/.netrc</filename> won't
- resolve to your home directory's <filename>.netrc</filename>.</para></note>
- </listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="conf-plugin-files">
- <term><literal>plugin-files</literal></term>
- <listitem>
- <para>
- A list of plugin files to be loaded by Nix. Each of these
- files will be dlopened by Nix, allowing them to affect
- execution through static initialization. In particular, these
- plugins may construct static instances of RegisterPrimOp to
- add new primops or constants to the expression language,
- RegisterStoreImplementation to add new store implementations,
- RegisterCommand to add new subcommands to the
- <literal>nix</literal> command, and RegisterSetting to add new
- nix config settings. See the constructors for those types for
- more details.
- </para>
- <para>
- Since these files are loaded into the same address space as
- Nix itself, they must be DSOs compatible with the instance of
- Nix running at the time (i.e. compiled against the same
- headers, not linked to any incompatible libraries). They
- should not be linked to any Nix libs directly, as those will
- be available already at load time.
- </para>
- <para>
- If an entry in the list is a directory, all files in the
- directory are loaded as plugins (non-recursively).
- </para>
- </listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-pre-build-hook"><term><literal>pre-build-hook</literal></term>
-
- <listitem>
-
-
- <para>If set, the path to a program that can set extra
- derivation-specific settings for this system. This is used for settings
- that can't be captured by the derivation model itself and are too variable
- between different versions of the same system to be hard-coded into nix.
- </para>
-
- <para>The hook is passed the derivation path and, if sandboxes are enabled,
- the sandbox directory. It can then modify the sandbox and send a series of
- commands to modify various settings to stdout. The currently recognized
- commands are:</para>
-
- <variablelist>
- <varlistentry xml:id="extra-sandbox-paths">
- <term><literal>extra-sandbox-paths</literal></term>
-
- <listitem>
-
- <para>Pass a list of files and directories to be included in the
- sandbox for this build. One entry per line, terminated by an empty
- line. Entries have the same format as
- <literal>sandbox-paths</literal>.</para>
-
- </listitem>
-
- </varlistentry>
- </variablelist>
- </listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-post-build-hook">
- <term><literal>post-build-hook</literal></term>
- <listitem>
- <para>Optional. The path to a program to execute after each build.</para>
-
- <para>This option is only settable in the global
- <filename>nix.conf</filename>, or on the command line by trusted
- users.</para>
-
- <para>When using the nix-daemon, the daemon executes the hook as
- <literal>root</literal>. If the nix-daemon is not involved, the
- hook runs as the user executing the nix-build.</para>
-
- <itemizedlist>
- <listitem><para>The hook executes after an evaluation-time build.</para></listitem>
- <listitem><para>The hook does not execute on substituted paths.</para></listitem>
- <listitem><para>The hook's output always goes to the user's terminal.</para></listitem>
- <listitem><para>If the hook fails, the build succeeds but no further builds execute.</para></listitem>
- <listitem><para>The hook executes synchronously, and blocks other builds from progressing while it runs.</para></listitem>
- </itemizedlist>
-
- <para>The program executes with no arguments. The program's environment
- contains the following environment variables:</para>
-
- <variablelist>
- <varlistentry>
- <term><envar>DRV_PATH</envar></term>
- <listitem>
- <para>The derivation for the built paths.</para>
- <para>Example:
- <literal>/nix/store/5nihn1a7pa8b25l9zafqaqibznlvvp3f-bash-4.4-p23.drv</literal>
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
- <term><envar>OUT_PATHS</envar></term>
- <listitem>
- <para>Output paths of the built derivation, separated by a space character.</para>
- <para>Example:
- <literal>/nix/store/zf5lbh336mnzf1nlswdn11g4n2m8zh3g-bash-4.4-p23-dev
- /nix/store/rjxwxwv1fpn9wa2x5ssk5phzwlcv4mna-bash-4.4-p23-doc
- /nix/store/6bqvbzjkcp9695dq0dpl5y43nvy37pq1-bash-4.4-p23-info
- /nix/store/r7fng3kk3vlpdlh2idnrbn37vh4imlj2-bash-4.4-p23-man
- /nix/store/xfghy8ixrhz3kyy6p724iv3cxji088dx-bash-4.4-p23</literal>.
- </para>
- </listitem>
- </varlistentry>
- </variablelist>
-
- <para>See <xref linkend="chap-post-build-hook"/> for an example
- implementation.</para>
-
- </listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-repeat"><term><literal>repeat</literal></term>
-
- <listitem><para>How many times to repeat builds to check whether
- they are deterministic. The default value is 0. If the value is
- non-zero, every build is repeated the specified number of
- times. If the contents of any of the runs differs from the
- previous ones and <xref linkend="conf-enforce-determinism"/> is
- true, the build is rejected and the resulting store paths are not
- registered as “valid” in Nix’s database.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-require-sigs"><term><literal>require-sigs</literal></term>
-
- <listitem><para>If set to <literal>true</literal> (the default),
- any non-content-addressed path added or copied to the Nix store
- (e.g. when substituting from a binary cache) must have a valid
- signature, that is, be signed using one of the keys listed in
- <option>trusted-public-keys</option> or
- <option>secret-key-files</option>. Set to <literal>false</literal>
- to disable signature checking.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="conf-restrict-eval"><term><literal>restrict-eval</literal></term>
-
- <listitem>
-
- <para>If set to <literal>true</literal>, the Nix evaluator will
- not allow access to any files outside of the Nix search path (as
- set via the <envar>NIX_PATH</envar> environment variable or the
- <option>-I</option> option), or to URIs outside of
- <option>allowed-uri</option>. The default is
- <literal>false</literal>.</para>
-
- </listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-run-diff-hook"><term><literal>run-diff-hook</literal></term>
- <listitem>
- <para>
- If true, enable the execution of <xref linkend="conf-diff-hook"/>.
- </para>
-
- <para>
- When using the Nix daemon, <literal>run-diff-hook</literal> must
- be set in the <filename>nix.conf</filename> configuration file,
- and cannot be passed at the command line.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-sandbox"><term><literal>sandbox</literal></term>
-
- <listitem><para>If set to <literal>true</literal>, builds will be
- performed in a <emphasis>sandboxed environment</emphasis>, i.e.,
- they’re isolated from the normal file system hierarchy and will
- only see their dependencies in the Nix store, the temporary build
- directory, private versions of <filename>/proc</filename>,
- <filename>/dev</filename>, <filename>/dev/shm</filename> and
- <filename>/dev/pts</filename> (on Linux), and the paths configured with the
- <link linkend="conf-sandbox-paths"><literal>sandbox-paths</literal>
- option</link>. This is useful to prevent undeclared dependencies
- on files in directories such as <filename>/usr/bin</filename>. In
- addition, on Linux, builds run in private PID, mount, network, IPC
- and UTS namespaces to isolate them from other processes in the
- system (except that fixed-output derivations do not run in private
- network namespace to ensure they can access the network).</para>
-
- <para>Currently, sandboxing only work on Linux and macOS. The use
- of a sandbox requires that Nix is run as root (so you should use
- the <link linkend="conf-build-users-group">“build users”
- feature</link> to perform the actual builds under different users
- than root).</para>
-
- <para>If this option is set to <literal>relaxed</literal>, then
- fixed-output derivations and derivations that have the
- <varname>__noChroot</varname> attribute set to
- <literal>true</literal> do not run in sandboxes.</para>
-
- <para>The default is <literal>true</literal> on Linux and
- <literal>false</literal> on all other platforms.</para>
-
- </listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-sandbox-dev-shm-size"><term><literal>sandbox-dev-shm-size</literal></term>
-
- <listitem><para>This option determines the maximum size of the
- <literal>tmpfs</literal> filesystem mounted on
- <filename>/dev/shm</filename> in Linux sandboxes. For the format,
- see the description of the <option>size</option> option of
- <literal>tmpfs</literal> in
- <citerefentry><refentrytitle>mount</refentrytitle><manvolnum>8</manvolnum></citerefentry>. The
- default is <literal>50%</literal>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="conf-sandbox-paths">
- <term><literal>sandbox-paths</literal></term>
-
- <listitem><para>A list of paths bind-mounted into Nix sandbox
- environments. You can use the syntax
- <literal><replaceable>target</replaceable>=<replaceable>source</replaceable></literal>
- to mount a path in a different location in the sandbox; for
- instance, <literal>/bin=/nix-bin</literal> will mount the path
- <literal>/nix-bin</literal> as <literal>/bin</literal> inside the
- sandbox. If <replaceable>source</replaceable> is followed by
- <literal>?</literal>, then it is not an error if
- <replaceable>source</replaceable> does not exist; for example,
- <literal>/dev/nvidiactl?</literal> specifies that
- <filename>/dev/nvidiactl</filename> will only be mounted in the
- sandbox if it exists in the host filesystem.</para>
-
- <para>Depending on how Nix was built, the default value for this option
- may be empty or provide <filename>/bin/sh</filename> as a
- bind-mount of <command>bash</command>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="conf-secret-key-files"><term><literal>secret-key-files</literal></term>
-
- <listitem><para>A whitespace-separated list of files containing
- secret (private) keys. These are used to sign locally-built
- paths. They can be generated using <command>nix-store
- --generate-binary-cache-key</command>. The corresponding public
- key can be distributed to other users, who can add it to
- <option>trusted-public-keys</option> in their
- <filename>nix.conf</filename>.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="conf-show-trace"><term><literal>show-trace</literal></term>
-
- <listitem><para>Causes Nix to print out a stack trace in case of Nix
- expression evaluation errors.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="conf-substitute"><term><literal>substitute</literal></term>
-
- <listitem><para>If set to <literal>true</literal> (default), Nix
- will use binary substitutes if available. This option can be
- disabled to force building from source.</para></listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-stalled-download-timeout"><term><literal>stalled-download-timeout</literal></term>
- <listitem>
- <para>The timeout (in seconds) for receiving data from servers
- during download. Nix cancels idle downloads after this timeout's
- duration.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-substituters"><term><literal>substituters</literal></term>
-
- <listitem><para>A list of URLs of substituters, separated by
- whitespace. The default is
- <literal>https://cache.nixos.org</literal>.</para></listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-system"><term><literal>system</literal></term>
-
- <listitem><para>This option specifies the canonical Nix system
- name of the current installation, such as
- <literal>i686-linux</literal> or
- <literal>x86_64-darwin</literal>. Nix can only build derivations
- whose <literal>system</literal> attribute equals the value
- specified here. In general, it never makes sense to modify this
- value from its default, since you can use it to ‘lie’ about the
- platform you are building on (e.g., perform a Mac OS build on a
- Linux machine; the result would obviously be wrong). It only
- makes sense if the Nix binaries can run on multiple platforms,
- e.g., ‘universal binaries’ that run on <literal>x86_64-linux</literal> and
- <literal>i686-linux</literal>.</para>
-
- <para>It defaults to the canonical Nix system name detected by
- <filename>configure</filename> at build time.</para></listitem>
-
- </varlistentry>
-
-
- <varlistentry xml:id="conf-system-features"><term><literal>system-features</literal></term>
-
- <listitem><para>A set of system “features” supported by this
- machine, e.g. <literal>kvm</literal>. Derivations can express a
- dependency on such features through the derivation attribute
- <varname>requiredSystemFeatures</varname>. For example, the
- attribute
-
-<programlisting>
-requiredSystemFeatures = [ "kvm" ];
-</programlisting>
-
- ensures that the derivation can only be built on a machine with
- the <literal>kvm</literal> feature.</para>
-
- <para>This setting by default includes <literal>kvm</literal> if
- <filename>/dev/kvm</filename> is accessible, and the
- pseudo-features <literal>nixos-test</literal>,
- <literal>benchmark</literal> and <literal>big-parallel</literal>
- that are used in Nixpkgs to route builds to specific
- machines.</para>
-
- </listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-tarball-ttl"><term><literal>tarball-ttl</literal></term>
-
- <listitem>
- <para>Default: <literal>3600</literal> seconds.</para>
-
- <para>The number of seconds a downloaded tarball is considered
- fresh. If the cached tarball is stale, Nix will check whether
- it is still up to date using the ETag header. Nix will download
- a new version if the ETag header is unsupported, or the
- cached ETag doesn't match.
- </para>
-
- <para>Setting the TTL to <literal>0</literal> forces Nix to always
- check if the tarball is up to date.</para>
-
- <para>Nix caches tarballs in
- <filename>$XDG_CACHE_HOME/nix/tarballs</filename>.</para>
-
- <para>Files fetched via <envar>NIX_PATH</envar>,
- <function>fetchGit</function>, <function>fetchMercurial</function>,
- <function>fetchTarball</function>, and <function>fetchurl</function>
- respect this TTL.
- </para>
- </listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-timeout"><term><literal>timeout</literal></term>
-
- <listitem>
-
- <para>This option defines the maximum number of seconds that a
- builder can run. This is useful (for instance in an automated
- build system) to catch builds that are stuck in an infinite loop
- but keep writing to their standard output or standard error. It
- can be overridden using the <option linkend="opt-timeout">--timeout</option> command line
- switch.</para>
-
- <para>The value <literal>0</literal> means that there is no
- timeout. This is also the default.</para>
-
- </listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-trace-function-calls"><term><literal>trace-function-calls</literal></term>
-
- <listitem>
-
- <para>Default: <literal>false</literal>.</para>
-
- <para>If set to <literal>true</literal>, the Nix evaluator will
- trace every function call. Nix will print a log message at the
- "vomit" level for every function entrance and function exit.</para>
-
- <informalexample><screen>
-function-trace entered undefined position at 1565795816999559622
-function-trace exited undefined position at 1565795816999581277
-function-trace entered /nix/store/.../example.nix:226:41 at 1565795253249935150
-function-trace exited /nix/store/.../example.nix:226:41 at 1565795253249941684
-</screen></informalexample>
-
- <para>The <literal>undefined position</literal> means the function
- call is a builtin.</para>
-
- <para>Use the <literal>contrib/stack-collapse.py</literal> script
- distributed with the Nix source code to convert the trace logs
- in to a format suitable for <command>flamegraph.pl</command>.</para>
-
- </listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-trusted-public-keys"><term><literal>trusted-public-keys</literal></term>
-
- <listitem><para>A whitespace-separated list of public keys. When
- paths are copied from another Nix store (such as a binary cache),
- they must be signed with one of these keys. For example:
- <literal>cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
- hydra.nixos.org-1:CNHJZBh9K4tP3EKF6FkkgeVYsS3ohTl+oS0Qa8bezVs=</literal>.</para></listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-trusted-substituters"><term><literal>trusted-substituters</literal></term>
-
- <listitem><para>A list of URLs of substituters, separated by
- whitespace. These are not used by default, but can be enabled by
- users of the Nix daemon by specifying <literal>--option
- substituters <replaceable>urls</replaceable></literal> on the
- command line. Unprivileged users are only allowed to pass a
- subset of the URLs listed in <literal>substituters</literal> and
- <literal>trusted-substituters</literal>.</para></listitem>
-
- </varlistentry>
-
- <varlistentry xml:id="conf-trusted-users"><term><literal>trusted-users</literal></term>
-
- <listitem>
-
- <para>A list of names of users (separated by whitespace) that
- have additional rights when connecting to the Nix daemon, such
- as the ability to specify additional binary caches, or to import
- unsigned NARs. You can also specify groups by prefixing them
- with <literal>@</literal>; for instance,
- <literal>@wheel</literal> means all users in the
- <literal>wheel</literal> group. The default is
- <literal>root</literal>.</para>
-
- <warning><para>Adding a user to <option>trusted-users</option>
- is essentially equivalent to giving that user root access to the
- system. For example, the user can set
- <option>sandbox-paths</option> and thereby obtain read access to
- directories that are otherwise inacessible to
- them.</para></warning>
-
- </listitem>
-
- </varlistentry>
-
-</variablelist>
-</para>
-
-<refsection>
- <title>Deprecated Settings</title>
-
-<para>
-
-<variablelist>
-
- <varlistentry xml:id="conf-binary-caches">
- <term><literal>binary-caches</literal></term>
-
- <listitem><para><emphasis>Deprecated:</emphasis>
- <literal>binary-caches</literal> is now an alias to
- <xref linkend="conf-substituters"/>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-binary-cache-public-keys">
- <term><literal>binary-cache-public-keys</literal></term>
-
- <listitem><para><emphasis>Deprecated:</emphasis>
- <literal>binary-cache-public-keys</literal> is now an alias to
- <xref linkend="conf-trusted-public-keys"/>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-build-compress-log">
- <term><literal>build-compress-log</literal></term>
-
- <listitem><para><emphasis>Deprecated:</emphasis>
- <literal>build-compress-log</literal> is now an alias to
- <xref linkend="conf-compress-build-log"/>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-build-cores">
- <term><literal>build-cores</literal></term>
-
- <listitem><para><emphasis>Deprecated:</emphasis>
- <literal>build-cores</literal> is now an alias to
- <xref linkend="conf-cores"/>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-build-extra-chroot-dirs">
- <term><literal>build-extra-chroot-dirs</literal></term>
-
- <listitem><para><emphasis>Deprecated:</emphasis>
- <literal>build-extra-chroot-dirs</literal> is now an alias to
- <xref linkend="conf-extra-sandbox-paths"/>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-build-extra-sandbox-paths">
- <term><literal>build-extra-sandbox-paths</literal></term>
-
- <listitem><para><emphasis>Deprecated:</emphasis>
- <literal>build-extra-sandbox-paths</literal> is now an alias to
- <xref linkend="conf-extra-sandbox-paths"/>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-build-fallback">
- <term><literal>build-fallback</literal></term>
-
- <listitem><para><emphasis>Deprecated:</emphasis>
- <literal>build-fallback</literal> is now an alias to
- <xref linkend="conf-fallback"/>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-build-max-jobs">
- <term><literal>build-max-jobs</literal></term>
-
- <listitem><para><emphasis>Deprecated:</emphasis>
- <literal>build-max-jobs</literal> is now an alias to
- <xref linkend="conf-max-jobs"/>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-build-max-log-size">
- <term><literal>build-max-log-size</literal></term>
-
- <listitem><para><emphasis>Deprecated:</emphasis>
- <literal>build-max-log-size</literal> is now an alias to
- <xref linkend="conf-max-build-log-size"/>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-build-max-silent-time">
- <term><literal>build-max-silent-time</literal></term>
-
- <listitem><para><emphasis>Deprecated:</emphasis>
- <literal>build-max-silent-time</literal> is now an alias to
- <xref linkend="conf-max-silent-time"/>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-build-repeat">
- <term><literal>build-repeat</literal></term>
-
- <listitem><para><emphasis>Deprecated:</emphasis>
- <literal>build-repeat</literal> is now an alias to
- <xref linkend="conf-repeat"/>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-build-timeout">
- <term><literal>build-timeout</literal></term>
-
- <listitem><para><emphasis>Deprecated:</emphasis>
- <literal>build-timeout</literal> is now an alias to
- <xref linkend="conf-timeout"/>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-build-use-chroot">
- <term><literal>build-use-chroot</literal></term>
-
- <listitem><para><emphasis>Deprecated:</emphasis>
- <literal>build-use-chroot</literal> is now an alias to
- <xref linkend="conf-sandbox"/>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-build-use-sandbox">
- <term><literal>build-use-sandbox</literal></term>
-
- <listitem><para><emphasis>Deprecated:</emphasis>
- <literal>build-use-sandbox</literal> is now an alias to
- <xref linkend="conf-sandbox"/>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-build-use-substitutes">
- <term><literal>build-use-substitutes</literal></term>
-
- <listitem><para><emphasis>Deprecated:</emphasis>
- <literal>build-use-substitutes</literal> is now an alias to
- <xref linkend="conf-substitute"/>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-gc-keep-derivations">
- <term><literal>gc-keep-derivations</literal></term>
-
- <listitem><para><emphasis>Deprecated:</emphasis>
- <literal>gc-keep-derivations</literal> is now an alias to
- <xref linkend="conf-keep-derivations"/>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-gc-keep-outputs">
- <term><literal>gc-keep-outputs</literal></term>
-
- <listitem><para><emphasis>Deprecated:</emphasis>
- <literal>gc-keep-outputs</literal> is now an alias to
- <xref linkend="conf-keep-outputs"/>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-env-keep-derivations">
- <term><literal>env-keep-derivations</literal></term>
-
- <listitem><para><emphasis>Deprecated:</emphasis>
- <literal>env-keep-derivations</literal> is now an alias to
- <xref linkend="conf-keep-env-derivations"/>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-extra-binary-caches">
- <term><literal>extra-binary-caches</literal></term>
-
- <listitem><para><emphasis>Deprecated:</emphasis>
- <literal>extra-binary-caches</literal> is now an alias to
- <xref linkend="conf-extra-substituters"/>.</para></listitem>
- </varlistentry>
-
- <varlistentry xml:id="conf-trusted-binary-caches">
- <term><literal>trusted-binary-caches</literal></term>
-
- <listitem><para><emphasis>Deprecated:</emphasis>
- <literal>trusted-binary-caches</literal> is now an alias to
- <xref linkend="conf-trusted-substituters"/>.</para></listitem>
- </varlistentry>
-</variablelist>
-</para>
-</refsection>
-
-</refsection>
-
-</refentry>
-
-</chapter>
-
-</part>
- <appendix xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="part-glossary" xml:base="glossary/glossary.xml">
-
-<title>Glossary</title>
-
-
-<glosslist>
-
-
-<glossentry xml:id="gloss-derivation"><glossterm>derivation</glossterm>
-
- <glossdef><para>A description of a build action. The result of a
- derivation is a store object. Derivations are typically specified
- in Nix expressions using the <link linkend="ssec-derivation"><function>derivation</function>
- primitive</link>. These are translated into low-level
- <emphasis>store derivations</emphasis> (implicitly by
- <command>nix-env</command> and <command>nix-build</command>, or
- explicitly by <command>nix-instantiate</command>).</para></glossdef>
-
-</glossentry>
-
-
-<glossentry><glossterm>store</glossterm>
-
- <glossdef><para>The location in the file system where store objects
- live. Typically <filename>/nix/store</filename>.</para></glossdef>
-
-</glossentry>
-
-
-<glossentry><glossterm>store path</glossterm>
-
- <glossdef><para>The location in the file system of a store object,
- i.e., an immediate child of the Nix store
- directory.</para></glossdef>
-
-</glossentry>
-
-
-<glossentry><glossterm>store object</glossterm>
-
- <glossdef><para>A file that is an immediate child of the Nix store
- directory. These can be regular files, but also entire directory
- trees. Store objects can be sources (objects copied from outside of
- the store), derivation outputs (objects produced by running a build
- action), or derivations (files describing a build
- action).</para></glossdef>
-
-</glossentry>
-
-
-<glossentry xml:id="gloss-substitute"><glossterm>substitute</glossterm>
-
- <glossdef><para>A substitute is a command invocation stored in the
- Nix database that describes how to build a store object, bypassing
- the normal build mechanism (i.e., derivations). Typically, the
- substitute builds the store object by downloading a pre-built
- version of the store object from some server.</para></glossdef>
-
-</glossentry>
-
-
-<glossentry><glossterm>purity</glossterm>
-
- <glossdef><para>The assumption that equal Nix derivations when run
- always produce the same output. This cannot be guaranteed in
- general (e.g., a builder can rely on external inputs such as the
- network or the system time) but the Nix model assumes
- it.</para></glossdef>
-
-</glossentry>
-
-
-<glossentry><glossterm>Nix expression</glossterm>
-
- <glossdef><para>A high-level description of software packages and
- compositions thereof. Deploying software using Nix entails writing
- Nix expressions for your packages. Nix expressions are translated
- to derivations that are stored in the Nix store. These derivations
- can then be built.</para></glossdef>
-
-</glossentry>
-
-
-<glossentry xml:id="gloss-reference"><glossterm>reference</glossterm>
-
- <glossdef>
- <para>A store path <varname>P</varname> is said to have a
- reference to a store path <varname>Q</varname> if the store object
- at <varname>P</varname> contains the path <varname>Q</varname>
- somewhere. The <emphasis>references</emphasis> of a store path are
- the set of store paths to which it has a reference.
- </para>
- <para>A derivation can reference other derivations and sources
- (but not output paths), whereas an output path only references other
- output paths.
- </para>
- </glossdef>
-
-</glossentry>
-
-<glossentry xml:id="gloss-reachable"><glossterm>reachable</glossterm>
-
- <glossdef><para>A store path <varname>Q</varname> is reachable from
- another store path <varname>P</varname> if <varname>Q</varname> is in the
- <link linkend="gloss-closure">closure</link> of the
- <link linkend="gloss-reference">references</link> relation.
- </para></glossdef>
-</glossentry>
-
-<glossentry xml:id="gloss-closure"><glossterm>closure</glossterm>
-
- <glossdef><para>The closure of a store path is the set of store
- paths that are directly or indirectly “reachable” from that store
- path; that is, it’s the closure of the path under the <link linkend="gloss-reference">references</link> relation. For a package, the
- closure of its derivation is equivalent to the build-time
- dependencies, while the closure of its output path is equivalent to its
- runtime dependencies. For correct deployment it is necessary to deploy whole
- closures, since otherwise at runtime files could be missing. The command
- <command>nix-store -qR</command> prints out closures of store paths.
- </para>
- <para>As an example, if the store object at path <varname>P</varname> contains
- a reference to path <varname>Q</varname>, then <varname>Q</varname> is
- in the closure of <varname>P</varname>. Further, if <varname>Q</varname>
- references <varname>R</varname> then <varname>R</varname> is also in
- the closure of <varname>P</varname>.
- </para></glossdef>
-
-</glossentry>
-
-
-<glossentry xml:id="gloss-output-path"><glossterm>output path</glossterm>
-
- <glossdef><para>A store path produced by a derivation.</para></glossdef>
-
-</glossentry>
-
-
-<glossentry xml:id="gloss-deriver"><glossterm>deriver</glossterm>
-
- <glossdef><para>The deriver of an <link linkend="gloss-output-path">output path</link> is the store
- derivation that built it.</para></glossdef>
-
-</glossentry>
-
-
-<glossentry xml:id="gloss-validity"><glossterm>validity</glossterm>
-
- <glossdef><para>A store path is considered
- <emphasis>valid</emphasis> if it exists in the file system, is
- listed in the Nix database as being valid, and if all paths in its
- closure are also valid.</para></glossdef>
-
-</glossentry>
-
-
-<glossentry xml:id="gloss-user-env"><glossterm>user environment</glossterm>
-
- <glossdef><para>An automatically generated store object that
- consists of a set of symlinks to “active” applications, i.e., other
- store paths. These are generated automatically by <link linkend="sec-nix-env"><command>nix-env</command></link>. See <xref linkend="sec-profiles"/>.</para>
-
- </glossdef>
-
-</glossentry>
-
-
-<glossentry xml:id="gloss-profile"><glossterm>profile</glossterm>
-
- <glossdef><para>A symlink to the current <link linkend="gloss-user-env">user environment</link> of a user, e.g.,
- <filename>/nix/var/nix/profiles/default</filename>.</para></glossdef>
-
-</glossentry>
-
-
-<glossentry xml:id="gloss-nar"><glossterm>NAR</glossterm>
-
- <glossdef><para>A <emphasis>N</emphasis>ix
- <emphasis>AR</emphasis>chive. This is a serialisation of a path in
- the Nix store. It can contain regular files, directories and
- symbolic links. NARs are generated and unpacked using
- <command>nix-store --dump</command> and <command>nix-store
- --restore</command>.</para></glossdef>
-
-</glossentry>
-
-
-
-</glosslist>
-
-
-</appendix>
- <appendix xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xml:id="chap-hacking">
-
-<title>Hacking</title>
-
-<para>This section provides some notes on how to hack on Nix. To get
-the latest version of Nix from GitHub:
-<screen>
-$ git clone https://github.com/NixOS/nix.git
-$ cd nix
-</screen>
-</para>
-
-<para>To build Nix for the current operating system/architecture use
-
-<screen>
-$ nix-build
-</screen>
-
-or if you have a flakes-enabled nix:
-
-<screen>
-$ nix build
-</screen>
-
-This will build <literal>defaultPackage</literal> attribute defined in the <literal>flake.nix</literal> file.
-
-To build for other platforms add one of the following suffixes to it: aarch64-linux,
-i686-linux, x86_64-darwin, x86_64-linux.
-
-i.e.
-
-<screen>
-nix-build -A defaultPackage.x86_64-linux
-</screen>
-
-</para>
-
-<para>To build all dependencies and start a shell in which all
-environment variables are set up so that those dependencies can be
-found:
-<screen>
-$ nix-shell
-</screen>
-To build Nix itself in this shell:
-<screen>
-[nix-shell]$ ./bootstrap.sh
-[nix-shell]$ ./configure $configureFlags
-[nix-shell]$ make -j $NIX_BUILD_CORES
-</screen>
-To install it in <literal>$(pwd)/inst</literal> and test it:
-<screen>
-[nix-shell]$ make install
-[nix-shell]$ make installcheck
-[nix-shell]$ ./inst/bin/nix --version
-nix (Nix) 2.4
-</screen>
-
-If you have a flakes-enabled nix you can replace:
-
-<screen>
-$ nix-shell
-</screen>
-
-by:
-
-<screen>
-$ nix develop
-</screen>
-
-</para>
-
-</appendix>
- <appendix xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="sec-relnotes" xml:base="release-notes/release-notes.xml">
-
-<title>Nix Release Notes</title>
-
-<!--
-<partintro>
-<para>This section lists the release notes for each stable version of Nix.</para>
-</partintro>
--->
-
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-2.3">
-
-<title>Release 2.3 (2019-09-04)</title>
-
-<para>This is primarily a bug fix release. However, it makes some
-incompatible changes:</para>
-
-<itemizedlist>
-
- <listitem>
- <para>Nix now uses BSD file locks instead of POSIX file
- locks. Because of this, you should not use Nix 2.3 and previous
- releases at the same time on a Nix store.</para>
- </listitem>
-
-</itemizedlist>
-
-<para>It also has the following changes:</para>
-
-<itemizedlist>
-
- <listitem>
- <para><function>builtins.fetchGit</function>'s <varname>ref</varname>
- argument now allows specifying an absolute remote ref.
- Nix will automatically prefix <varname>ref</varname> with
- <literal>refs/heads</literal> only if <varname>ref</varname> doesn't
- already begin with <literal>refs/</literal>.
- </para>
- </listitem>
-
- <listitem>
- <para>The installer now enables sandboxing by default on Linux when the
- system has the necessary kernel support.
- </para>
- </listitem>
-
- <listitem>
- <para>The <literal>max-jobs</literal> setting now defaults to 1.</para>
- </listitem>
-
- <listitem>
- <para>New builtin functions:
- <literal>builtins.isPath</literal>,
- <literal>builtins.hashFile</literal>.
- </para>
- </listitem>
-
- <listitem>
- <para>The <command>nix</command> command has a new
- <option>--print-build-logs</option> (<option>-L</option>) flag to
- print build log output to stderr, rather than showing the last log
- line in the progress bar. To distinguish between concurrent
- builds, log lines are prefixed by the name of the package.
- </para>
- </listitem>
-
- <listitem>
- <para>Builds are now executed in a pseudo-terminal, and the
- <envar>TERM</envar> environment variable is set to
- <literal>xterm-256color</literal>. This allows many programs
- (e.g. <command>gcc</command>, <command>clang</command>,
- <command>cmake</command>) to print colorized log output.</para>
- </listitem>
-
- <listitem>
- <para>Add <option>--no-net</option> convenience flag. This flag
- disables substituters; sets the <literal>tarball-ttl</literal>
- setting to infinity (ensuring that any previously downloaded files
- are considered current); and disables retrying downloads and sets
- the connection timeout to the minimum. This flag is enabled
- automatically if there are no configured non-loopback network
- interfaces.</para>
- </listitem>
-
- <listitem>
- <para>Add a <literal>post-build-hook</literal> setting to run a
- program after a build has succeeded.</para>
- </listitem>
-
- <listitem>
- <para>Add a <literal>trace-function-calls</literal> setting to log
- the duration of Nix function calls to stderr.</para>
- </listitem>
-
-</itemizedlist>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-2.2">
-
-<title>Release 2.2 (2019-01-11)</title>
-
-<para>This is primarily a bug fix release. It also has the following
-changes:</para>
-
-<itemizedlist>
-
- <listitem>
- <para>In derivations that use structured attributes (i.e. that
- specify set the <varname>__structuredAttrs</varname> attribute to
- <literal>true</literal> to cause all attributes to be passed to
- the builder in JSON format), you can now specify closure checks
- per output, e.g.:
-
-<programlisting>
-outputChecks."out" = {
- # The closure of 'out' must not be larger than 256 MiB.
- maxClosureSize = 256 * 1024 * 1024;
-
- # It must not refer to C compiler or to the 'dev' output.
- disallowedRequisites = [ stdenv.cc "dev" ];
-};
-
-outputChecks."dev" = {
- # The 'dev' output must not be larger than 128 KiB.
- maxSize = 128 * 1024;
-};
-</programlisting>
-
- </para>
- </listitem>
-
-
- <listitem>
- <para>The derivation attribute
- <varname>requiredSystemFeatures</varname> is now enforced for
- local builds, and not just to route builds to remote builders.
- The supported features of a machine can be specified through the
- configuration setting <varname>system-features</varname>.</para>
-
- <para>By default, <varname>system-features</varname> includes
- <literal>kvm</literal> if <filename>/dev/kvm</filename>
- exists. For compatibility, it also includes the pseudo-features
- <literal>nixos-test</literal>, <literal>benchmark</literal> and
- <literal>big-parallel</literal> which are used by Nixpkgs to route
- builds to particular Hydra build machines.</para>
-
- </listitem>
-
- <listitem>
- <para>Sandbox builds are now enabled by default on Linux.</para>
- </listitem>
-
- <listitem>
- <para>The new command <command>nix doctor</command> shows
- potential issues with your Nix installation.</para>
- </listitem>
-
- <listitem>
- <para>The <literal>fetchGit</literal> builtin function now uses a
- caching scheme that puts different remote repositories in distinct
- local repositories, rather than a single shared repository. This
- may require more disk space but is faster.</para>
- </listitem>
-
- <listitem>
- <para>The <literal>dirOf</literal> builtin function now works on
- relative paths.</para>
- </listitem>
-
- <listitem>
- <para>Nix now supports <link xlink:href="https://www.w3.org/TR/SRI/">SRI hashes</link>,
- allowing the hash algorithm and hash to be specified in a single
- string. For example, you can write:
-
-<programlisting>
-import <nix/fetchurl.nix> {
- url = https://nixos.org/releases/nix/nix-2.1.3/nix-2.1.3.tar.xz;
- hash = "sha256-XSLa0FjVyADWWhFfkZ2iKTjFDda6mMXjoYMXLRSYQKQ=";
-};
-</programlisting>
-
- instead of
-
-<programlisting>
-import <nix/fetchurl.nix> {
- url = https://nixos.org/releases/nix/nix-2.1.3/nix-2.1.3.tar.xz;
- sha256 = "5d22dad058d5c800d65a115f919da22938c50dd6ba98c5e3a183172d149840a4";
-};
-</programlisting>
-
- </para>
-
- <para>In fixed-output derivations, the
- <varname>outputHashAlgo</varname> attribute is no longer mandatory
- if <varname>outputHash</varname> specifies the hash.</para>
-
- <para><command>nix hash-file</command> and <command>nix
- hash-path</command> now print hashes in SRI format by
- default. They also use SHA-256 by default instead of SHA-512
- because that's what we use most of the time in Nixpkgs.</para>
- </listitem>
-
- <listitem>
- <para>Integers are now 64 bits on all platforms.</para>
- </listitem>
-
- <listitem>
- <para>The evaluator now prints profiling statistics (enabled via
- the <envar>NIX_SHOW_STATS</envar> and
- <envar>NIX_COUNT_CALLS</envar> environment variables) in JSON
- format.</para>
- </listitem>
-
- <listitem>
- <para>The option <option>--xml</option> in <command>nix-store
- --query</command> has been removed. Instead, there now is an
- option <option>--graphml</option> to output the dependency graph
- in GraphML format.</para>
- </listitem>
-
- <listitem>
- <para>All <filename>nix-*</filename> commands are now symlinks to
- <filename>nix</filename>. This saves a bit of disk space.</para>
- </listitem>
-
- <listitem>
- <para><command>nix repl</command> now uses
- <literal>libeditline</literal> or
- <literal>libreadline</literal>.</para>
- </listitem>
-
-</itemizedlist>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-2.1">
-
-<title>Release 2.1 (2018-09-02)</title>
-
-<para>This is primarily a bug fix release. It also reduces memory
-consumption in certain situations. In addition, it has the following
-new features:</para>
-
-<itemizedlist>
-
- <listitem>
- <para>The Nix installer will no longer default to the Multi-User
- installation for macOS. You can still <link linkend="sect-multi-user-installation">instruct the installer to
- run in multi-user mode</link>.
- </para>
- </listitem>
-
- <listitem>
- <para>The Nix installer now supports performing a Multi-User
- installation for Linux computers which are running systemd. You
- can <link linkend="sect-multi-user-installation">select a Multi-User installation</link> by passing the
- <option>--daemon</option> flag to the installer: <command>sh <(curl
- https://nixos.org/nix/install) --daemon</command>.
- </para>
-
- <para>The multi-user installer cannot handle systems with SELinux.
- If your system has SELinux enabled, you can <link linkend="sect-single-user-installation">force the installer to run
- in single-user mode</link>.</para>
- </listitem>
-
- <listitem>
- <para>New builtin functions:
- <literal>builtins.bitAnd</literal>,
- <literal>builtins.bitOr</literal>,
- <literal>builtins.bitXor</literal>,
- <literal>builtins.fromTOML</literal>,
- <literal>builtins.concatMap</literal>,
- <literal>builtins.mapAttrs</literal>.
- </para>
- </listitem>
-
- <listitem>
- <para>The S3 binary cache store now supports uploading NARs larger
- than 5 GiB.</para>
- </listitem>
-
- <listitem>
- <para>The S3 binary cache store now supports uploading to
- S3-compatible services with the <literal>endpoint</literal>
- option.</para>
- </listitem>
-
- <listitem>
- <para>The flag <option>--fallback</option> is no longer required
- to recover from disappeared NARs in binary caches.</para>
- </listitem>
-
- <listitem>
- <para><command>nix-daemon</command> now respects
- <option>--store</option>.</para>
- </listitem>
-
- <listitem>
- <para><command>nix run</command> now respects
- <varname>nix-support/propagated-user-env-packages</varname>.</para>
- </listitem>
-
-</itemizedlist>
-
-<para>This release has contributions from
-
-Adrien Devresse,
-Aleksandr Pashkov,
-Alexandre Esteves,
-Amine Chikhaoui,
-Andrew Dunham,
-Asad Saeeduddin,
-aszlig,
-Ben Challenor,
-Ben Gamari,
-Benjamin Hipple,
-Bogdan Seniuc,
-Corey O'Connor,
-Daiderd Jordan,
-Daniel Peebles,
-Daniel Poelzleithner,
-Danylo Hlynskyi,
-Dmitry Kalinkin,
-Domen Kožar,
-Doug Beardsley,
-Eelco Dolstra,
-Erik Arvstedt,
-Félix Baylac-Jacqué,
-Gleb Peregud,
-Graham Christensen,
-Guillaume Maudoux,
-Ivan Kozik,
-John Arnold,
-Justin Humm,
-Linus Heckemann,
-Lorenzo Manacorda,
-Matthew Justin Bauer,
-Matthew O'Gorman,
-Maximilian Bosch,
-Michael Bishop,
-Michael Fiano,
-Michael Mercier,
-Michael Raskin,
-Michael Weiss,
-Nicolas Dudebout,
-Peter Simons,
-Ryan Trinkle,
-Samuel Dionne-Riel,
-Sean Seefried,
-Shea Levy,
-Symphorien Gibol,
-Tim Engler,
-Tim Sears,
-Tuomas Tynkkynen,
-volth,
-Will Dietz,
-Yorick van Pelt and
-zimbatm.
-</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-2.0">
-
-<title>Release 2.0 (2018-02-22)</title>
-
-<para>The following incompatible changes have been made:</para>
-
-<itemizedlist>
-
- <listitem>
- <para>The manifest-based substituter mechanism
- (<command>download-using-manifests</command>) has been <link xlink:href="https://github.com/NixOS/nix/commit/867967265b80946dfe1db72d40324b4f9af988ed">removed</link>. It
- has been superseded by the binary cache substituter mechanism
- since several years. As a result, the following programs have been
- removed:
-
- <itemizedlist>
- <listitem><para><command>nix-pull</command></para></listitem>
- <listitem><para><command>nix-generate-patches</command></para></listitem>
- <listitem><para><command>bsdiff</command></para></listitem>
- <listitem><para><command>bspatch</command></para></listitem>
- </itemizedlist>
- </para>
- </listitem>
-
- <listitem>
- <para>The “copy from other stores” substituter mechanism
- (<command>copy-from-other-stores</command> and the
- <envar>NIX_OTHER_STORES</envar> environment variable) has been
- removed. It was primarily used by the NixOS installer to copy
- available paths from the installation medium. The replacement is
- to use a chroot store as a substituter
- (e.g. <literal>--substituters /mnt</literal>), or to build into a
- chroot store (e.g. <literal>--store /mnt --substituters /</literal>).</para>
- </listitem>
-
- <listitem>
- <para>The command <command>nix-push</command> has been removed as
- part of the effort to eliminate Nix's dependency on Perl. You can
- use <command>nix copy</command> instead, e.g. <literal>nix copy
- --to file:///tmp/my-binary-cache <replaceable>paths…</replaceable></literal></para>
- </listitem>
-
- <listitem>
- <para>The “nested” log output feature (<option>--log-type
- pretty</option>) has been removed. As a result,
- <command>nix-log2xml</command> was also removed.</para>
- </listitem>
-
- <listitem>
- <para>OpenSSL-based signing has been <link xlink:href="https://github.com/NixOS/nix/commit/f435f8247553656774dd1b2c88e9de5d59cab203">removed</link>. This
- feature was never well-supported. A better alternative is provided
- by the <option>secret-key-files</option> and
- <option>trusted-public-keys</option> options.</para>
- </listitem>
-
- <listitem>
- <para>Failed build caching has been <link xlink:href="https://github.com/NixOS/nix/commit/8cffec84859cec8b610a2a22ab0c4d462a9351ff">removed</link>. This
- feature was introduced to support the Hydra continuous build
- system, but Hydra no longer uses it.</para>
- </listitem>
-
- <listitem>
- <para><filename>nix-mode.el</filename> has been removed from
- Nix. It is now <link xlink:href="https://github.com/NixOS/nix-mode">a separate
- repository</link> and can be installed through the MELPA package
- repository.</para>
- </listitem>
-
-</itemizedlist>
-
-<para>This release has the following new features:</para>
-
-<itemizedlist>
-
- <listitem>
- <para>It introduces a new command named <command>nix</command>,
- which is intended to eventually replace all
- <command>nix-*</command> commands with a more consistent and
- better designed user interface. It currently provides replacements
- for some (but not all) of the functionality provided by
- <command>nix-store</command>, <command>nix-build</command>,
- <command>nix-shell -p</command>, <command>nix-env -qa</command>,
- <command>nix-instantiate --eval</command>,
- <command>nix-push</command> and
- <command>nix-copy-closure</command>. It has the following major
- features:</para>
-
- <itemizedlist>
-
- <listitem>
- <para>Unlike the legacy commands, it has a consistent way to
- refer to packages and package-like arguments (like store
- paths). For example, the following commands all copy the GNU
- Hello package to a remote machine:
-
- <screen>nix copy --to ssh://machine nixpkgs.hello</screen>
- <screen>nix copy --to ssh://machine /nix/store/0i2jd68mp5g6h2sa5k9c85rb80sn8hi9-hello-2.10</screen>
- <screen>nix copy --to ssh://machine '(with import <nixpkgs> {}; hello)'</screen>
-
- By contrast, <command>nix-copy-closure</command> only accepted
- store paths as arguments.</para>
- </listitem>
-
- <listitem>
- <para>It is self-documenting: <option>--help</option> shows
- all available command-line arguments. If
- <option>--help</option> is given after a subcommand, it shows
- examples for that subcommand. <command>nix
- --help-config</command> shows all configuration
- options.</para>
- </listitem>
-
- <listitem>
- <para>It is much less verbose. By default, it displays a
- single-line progress indicator that shows how many packages
- are left to be built or downloaded, and (if there are running
- builds) the most recent line of builder output. If a build
- fails, it shows the last few lines of builder output. The full
- build log can be retrieved using <command>nix
- log</command>.</para>
- </listitem>
-
- <listitem>
- <para>It <link xlink:href="https://github.com/NixOS/nix/commit/b8283773bd64d7da6859ed520ee19867742a03ba">provides</link>
- all <filename>nix.conf</filename> configuration options as
- command line flags. For example, instead of <literal>--option
- http-connections 100</literal> you can write
- <literal>--http-connections 100</literal>. Boolean options can
- be written as
- <literal>--<replaceable>foo</replaceable></literal> or
- <literal>--no-<replaceable>foo</replaceable></literal>
- (e.g. <option>--no-auto-optimise-store</option>).</para>
- </listitem>
-
- <listitem>
- <para>Many subcommands have a <option>--json</option> flag to
- write results to stdout in JSON format.</para>
- </listitem>
-
- </itemizedlist>
-
- <warning><para>Please note that the <command>nix</command> command
- is a work in progress and the interface is subject to
- change.</para></warning>
-
- <para>It provides the following high-level (“porcelain”)
- subcommands:</para>
-
- <itemizedlist>
-
- <listitem>
- <para><command>nix build</command> is a replacement for
- <command>nix-build</command>.</para>
- </listitem>
-
- <listitem>
- <para><command>nix run</command> executes a command in an
- environment in which the specified packages are available. It
- is (roughly) a replacement for <command>nix-shell
- -p</command>. Unlike that command, it does not execute the
- command in a shell, and has a flag (<command>-c</command>)
- that specifies the unquoted command line to be
- executed.</para>
-
- <para>It is particularly useful in conjunction with chroot
- stores, allowing Linux users who do not have permission to
- install Nix in <command>/nix/store</command> to still use
- binary substitutes that assume
- <command>/nix/store</command>. For example,
-
- <screen>nix run --store ~/my-nix nixpkgs.hello -c hello --greeting 'Hi everybody!'</screen>
-
- downloads (or if not substitutes are available, builds) the
- GNU Hello package into
- <filename>~/my-nix/nix/store</filename>, then runs
- <command>hello</command> in a mount namespace where
- <filename>~/my-nix/nix/store</filename> is mounted onto
- <command>/nix/store</command>.</para>
- </listitem>
-
- <listitem>
- <para><command>nix search</command> replaces <command>nix-env
- -qa</command>. It searches the available packages for
- occurrences of a search string in the attribute name, package
- name or description. Unlike <command>nix-env -qa</command>, it
- has a cache to speed up subsequent searches.</para>
- </listitem>
-
- <listitem>
- <para><command>nix copy</command> copies paths between
- arbitrary Nix stores, generalising
- <command>nix-copy-closure</command> and
- <command>nix-push</command>.</para>
- </listitem>
-
- <listitem>
- <para><command>nix repl</command> replaces the external
- program <command>nix-repl</command>. It provides an
- interactive environment for evaluating and building Nix
- expressions. Note that it uses <literal>linenoise-ng</literal>
- instead of GNU Readline.</para>
- </listitem>
-
- <listitem>
- <para><command>nix upgrade-nix</command> upgrades Nix to the
- latest stable version. This requires that Nix is installed in
- a profile. (Thus it won’t work on NixOS, or if it’s installed
- outside of the Nix store.)</para>
- </listitem>
-
- <listitem>
- <para><command>nix verify</command> checks whether store paths
- are unmodified and/or “trusted” (see below). It replaces
- <command>nix-store --verify</command> and <command>nix-store
- --verify-path</command>.</para>
- </listitem>
-
- <listitem>
- <para><command>nix log</command> shows the build log of a
- package or path. If the build log is not available locally, it
- will try to obtain it from the configured substituters (such
- as <uri>cache.nixos.org</uri>, which now provides build
- logs).</para>
- </listitem>
-
- <listitem>
- <para><command>nix edit</command> opens the source code of a
- package in your editor.</para>
- </listitem>
-
- <listitem>
- <para><command>nix eval</command> replaces
- <command>nix-instantiate --eval</command>.</para>
- </listitem>
-
- <listitem>
- <para><command xlink:href="https://github.com/NixOS/nix/commit/d41c5eb13f4f3a37d80dbc6d3888644170c3b44a">nix
- why-depends</command> shows why one store path has another in
- its closure. This is primarily useful to finding the causes of
- closure bloat. For example,
-
- <screen>nix why-depends nixpkgs.vlc nixpkgs.libdrm.dev</screen>
-
- shows a chain of files and fragments of file contents that
- cause the VLC package to have the “dev” output of
- <literal>libdrm</literal> in its closure — an undesirable
- situation.</para>
- </listitem>
-
- <listitem>
- <para><command>nix path-info</command> shows information about
- store paths, replacing <command>nix-store -q</command>. A
- useful feature is the option <option>--closure-size</option>
- (<option>-S</option>). For example, the following command show
- the closure sizes of every path in the current NixOS system
- closure, sorted by size:
-
- <screen>nix path-info -rS /run/current-system | sort -nk2</screen>
-
- </para>
- </listitem>
-
- <listitem>
- <para><command>nix optimise-store</command> replaces
- <command>nix-store --optimise</command>. The main difference
- is that it has a progress indicator.</para>
- </listitem>
-
- </itemizedlist>
-
- <para>A number of low-level (“plumbing”) commands are also
- available:</para>
-
- <itemizedlist>
-
- <listitem>
- <para><command>nix ls-store</command> and <command>nix
- ls-nar</command> list the contents of a store path or NAR
- file. The former is primarily useful in conjunction with
- remote stores, e.g.
-
- <screen>nix ls-store --store https://cache.nixos.org/ -lR /nix/store/0i2jd68mp5g6h2sa5k9c85rb80sn8hi9-hello-2.10</screen>
-
- lists the contents of path in a binary cache.</para>
- </listitem>
-
- <listitem>
- <para><command>nix cat-store</command> and <command>nix
- cat-nar</command> allow extracting a file from a store path or
- NAR file.</para>
- </listitem>
-
- <listitem>
- <para><command>nix dump-path</command> writes the contents of
- a store path to stdout in NAR format. This replaces
- <command>nix-store --dump</command>.</para>
- </listitem>
-
- <listitem>
- <para><command xlink:href="https://github.com/NixOS/nix/commit/e8d6ee7c1b90a2fe6d824f1a875acc56799ae6e2">nix
- show-derivation</command> displays a store derivation in JSON
- format. This is an alternative to
- <command>pp-aterm</command>.</para>
- </listitem>
-
- <listitem>
- <para><command xlink:href="https://github.com/NixOS/nix/commit/970366266b8df712f5f9cedb45af183ef5a8357f">nix
- add-to-store</command> replaces <command>nix-store
- --add</command>.</para>
- </listitem>
-
- <listitem>
- <para><command>nix sign-paths</command> signs store
- paths.</para>
- </listitem>
-
- <listitem>
- <para><command>nix copy-sigs</command> copies signatures from
- one store to another.</para>
- </listitem>
-
- <listitem>
- <para><command>nix show-config</command> shows all
- configuration options and their current values.</para>
- </listitem>
-
- </itemizedlist>
-
- </listitem>
-
- <listitem>
- <para>The store abstraction that Nix has had for a long time to
- support store access via the Nix daemon has been extended
- significantly. In particular, substituters (which used to be
- external programs such as
- <command>download-from-binary-cache</command>) are now subclasses
- of the abstract <classname>Store</classname> class. This allows
- many Nix commands to operate on such store types. For example,
- <command>nix path-info</command> shows information about paths in
- your local Nix store, while <command>nix path-info --store
- https://cache.nixos.org/</command> shows information about paths
- in the specified binary cache. Similarly,
- <command>nix-copy-closure</command>, <command>nix-push</command>
- and substitution are all instances of the general notion of
- copying paths between different kinds of Nix stores.</para>
-
- <para>Stores are specified using an URI-like syntax,
- e.g. <uri>https://cache.nixos.org/</uri> or
- <uri>ssh://machine</uri>. The following store types are supported:
-
- <itemizedlist>
-
- <listitem>
-
- <para><classname>LocalStore</classname> (stori URI
- <literal>local</literal> or an absolute path) and the misnamed
- <classname>RemoteStore</classname> (<literal>daemon</literal>)
- provide access to a local Nix store, the latter via the Nix
- daemon. You can use <literal>auto</literal> or the empty
- string to auto-select a local or daemon store depending on
- whether you have write permission to the Nix store. It is no
- longer necessary to set the <envar>NIX_REMOTE</envar>
- environment variable to use the Nix daemon.</para>
-
- <para>As noted above, <classname>LocalStore</classname> now
- supports chroot builds, allowing the “physical” location of
- the Nix store
- (e.g. <filename>/home/alice/nix/store</filename>) to differ
- from its “logical” location (typically
- <filename>/nix/store</filename>). This allows non-root users
- to use Nix while still getting the benefits from prebuilt
- binaries from <uri>cache.nixos.org</uri>.</para>
-
- </listitem>
-
- <listitem>
-
- <para><classname>BinaryCacheStore</classname> is the abstract
- superclass of all binary cache stores. It supports writing
- build logs and NAR content listings in JSON format.</para>
-
- </listitem>
-
- <listitem>
-
- <para><classname>HttpBinaryCacheStore</classname>
- (<literal>http://</literal>, <literal>https://</literal>)
- supports binary caches via HTTP or HTTPS. If the server
- supports <literal>PUT</literal> requests, it supports
- uploading store paths via commands such as <command>nix
- copy</command>.</para>
-
- </listitem>
-
- <listitem>
-
- <para><classname>LocalBinaryCacheStore</classname>
- (<literal>file://</literal>) supports binary caches in the
- local filesystem.</para>
-
- </listitem>
-
- <listitem>
-
- <para><classname>S3BinaryCacheStore</classname>
- (<literal>s3://</literal>) supports binary caches stored in
- Amazon S3, if enabled at compile time.</para>
-
- </listitem>
-
- <listitem>
-
- <para><classname>LegacySSHStore</classname> (<literal>ssh://</literal>)
- is used to implement remote builds and
- <command>nix-copy-closure</command>.</para>
-
- </listitem>
-
- <listitem>
-
- <para><classname>SSHStore</classname>
- (<literal>ssh-ng://</literal>) supports arbitrary Nix
- operations on a remote machine via the same protocol used by
- <command>nix-daemon</command>.</para>
-
- </listitem>
-
- </itemizedlist>
-
- </para>
-
- </listitem>
-
- <listitem>
-
- <para>Security has been improved in various ways:
-
- <itemizedlist>
-
- <listitem>
- <para>Nix now stores signatures for local store
- paths. When paths are copied between stores (e.g., copied from
- a binary cache to a local store), signatures are
- propagated.</para>
-
- <para>Locally-built paths are signed automatically using the
- secret keys specified by the <option>secret-key-files</option>
- store option. Secret/public key pairs can be generated using
- <command>nix-store
- --generate-binary-cache-key</command>.</para>
-
- <para>In addition, locally-built store paths are marked as
- “ultimately trusted”, but this bit is not propagated when
- paths are copied between stores.</para>
- </listitem>
-
- <listitem>
- <para>Content-addressable store paths no longer require
- signatures — they can be imported into a store by unprivileged
- users even if they lack signatures.</para>
- </listitem>
-
- <listitem>
- <para>The command <command>nix verify</command> checks whether
- the specified paths are trusted, i.e., have a certain number
- of trusted signatures, are ultimately trusted, or are
- content-addressed.</para>
- </listitem>
-
- <listitem>
- <para>Substitutions from binary caches <link xlink:href="https://github.com/NixOS/nix/commit/ecbc3fedd3d5bdc5a0e1a0a51b29062f2874ac8b">now</link>
- require signatures by default. This was already the case on
- NixOS.</para>
- </listitem>
-
- <listitem>
- <para>In Linux sandbox builds, we <link xlink:href="https://github.com/NixOS/nix/commit/eba840c8a13b465ace90172ff76a0db2899ab11b">now</link>
- use <filename>/build</filename> instead of
- <filename>/tmp</filename> as the temporary build
- directory. This fixes potential security problems when a build
- accidentally stores its <envar>TMPDIR</envar> in some
- security-sensitive place, such as an RPATH.</para>
- </listitem>
-
- </itemizedlist>
-
- </para>
-
- </listitem>
-
- <listitem>
- <para><emphasis>Pure evaluation mode</emphasis>. With the
- <literal>--pure-eval</literal> flag, Nix enables a variant of the existing
- restricted evaluation mode that forbids access to anything that could cause
- different evaluations of the same command line arguments to produce a
- different result. This includes builtin functions such as
- <function>builtins.getEnv</function>, but more importantly,
- <emphasis>all</emphasis> filesystem or network access unless a content hash
- or commit hash is specified. For example, calls to
- <function>builtins.fetchGit</function> are only allowed if a
- <varname>rev</varname> attribute is specified.</para>
-
- <para>The goal of this feature is to enable true reproducibility
- and traceability of builds (including NixOS system configurations)
- at the evaluation level. For example, in the future,
- <command>nixos-rebuild</command> might build configurations from a
- Nix expression in a Git repository in pure mode. That expression
- might fetch other repositories such as Nixpkgs via
- <function>builtins.fetchGit</function>. The commit hash of the
- top-level repository then uniquely identifies a running system,
- and, in conjunction with that repository, allows it to be
- reproduced or modified.</para>
-
- </listitem>
-
- <listitem>
- <para>There are several new features to support binary
- reproducibility (i.e. to help ensure that multiple builds of the
- same derivation produce exactly the same output). When
- <option>enforce-determinism</option> is set to
- <literal>false</literal>, it’s <link xlink:href="https://github.com/NixOS/nix/commit/8bdf83f936adae6f2c907a6d2541e80d4120f051">no
- longer</link> a fatal error if build rounds produce different
- output. Also, a hook named <option>diff-hook</option> is <link xlink:href="https://github.com/NixOS/nix/commit/9a313469a4bdea2d1e8df24d16289dc2a172a169">provided</link>
- to allow you to run tools such as <command>diffoscope</command>
- when build rounds produce different output.</para>
- </listitem>
-
- <listitem>
- <para>Configuring remote builds is a lot easier now. Provided you
- are not using the Nix daemon, you can now just specify a remote
- build machine on the command line, e.g. <literal>--option builders
- 'ssh://my-mac x86_64-darwin'</literal>. The environment variable
- <envar>NIX_BUILD_HOOK</envar> has been removed and is no longer
- needed. The environment variable <envar>NIX_REMOTE_SYSTEMS</envar>
- is still supported for compatibility, but it is also possible to
- specify builders in <command>nix.conf</command> by setting the
- option <literal>builders =
- @<replaceable>path</replaceable></literal>.</para>
- </listitem>
-
- <listitem>
- <para>If a fixed-output derivation produces a result with an
- incorrect hash, the output path is moved to the location
- corresponding to the actual hash and registered as valid. Thus, a
- subsequent build of the fixed-output derivation with the correct
- hash is unnecessary.</para>
- </listitem>
-
- <listitem>
- <para><command>nix-shell</command> <link xlink:href="https://github.com/NixOS/nix/commit/ea59f39326c8e9dc42dfed4bcbf597fbce58797c">now</link>
- sets the <varname>IN_NIX_SHELL</varname> environment variable
- during evaluation and in the shell itself. This can be used to
- perform different actions depending on whether you’re in a Nix
- shell or in a regular build. Nixpkgs provides
- <varname>lib.inNixShell</varname> to check this variable during
- evaluation.</para>
- </listitem>
-
- <listitem>
- <para><envar>NIX_PATH</envar> is now lazy, so URIs in the path are
- only downloaded if they are needed for evaluation.</para>
- </listitem>
-
- <listitem>
- <para>You can now use
- <uri>channel:<replaceable>channel-name</replaceable></uri> as a
- short-hand for
- <uri>https://nixos.org/channels/<replaceable>channel-name</replaceable>/nixexprs.tar.xz</uri>. For
- example, <literal>nix-build channel:nixos-15.09 -A hello</literal>
- will build the GNU Hello package from the
- <literal>nixos-15.09</literal> channel. In the future, this may
- use Git to fetch updates more efficiently.</para>
- </listitem>
-
- <listitem>
- <para>When <option>--no-build-output</option> is given, the last
- 10 lines of the build log will be shown if a build
- fails.</para>
- </listitem>
-
- <listitem>
- <para>Networking has been improved:
-
- <itemizedlist>
-
- <listitem>
- <para>HTTP/2 is now supported. This makes binary cache lookups
- <link xlink:href="https://github.com/NixOS/nix/commit/90ad02bf626b885a5dd8967894e2eafc953bdf92">much
- more efficient</link>.</para>
- </listitem>
-
- <listitem>
- <para>We now retry downloads on many HTTP errors, making
- binary caches substituters more resilient to temporary
- failures.</para>
- </listitem>
-
- <listitem>
- <para>HTTP credentials can now be configured via the standard
- <filename>netrc</filename> mechanism.</para>
- </listitem>
-
- <listitem>
- <para>If S3 support is enabled at compile time,
- <uri>s3://</uri> URIs are <link xlink:href="https://github.com/NixOS/nix/commit/9ff9c3f2f80ba4108e9c945bbfda2c64735f987b">supported</link>
- in all places where Nix allows URIs.</para>
- </listitem>
-
- <listitem>
- <para>Brotli compression is now supported. In particular,
- <uri>cache.nixos.org</uri> build logs are now compressed using
- Brotli.</para>
- </listitem>
-
- </itemizedlist>
-
- </para>
-
- </listitem>
-
- <listitem>
- <para><command>nix-env</command> <link xlink:href="https://github.com/NixOS/nix/commit/b0cb11722626e906a73f10dd9a0c9eea29faf43a">now</link>
- ignores packages with bad derivation names (in particular those
- starting with a digit or containing a dot).</para>
- </listitem>
-
- <listitem>
- <para>Many configuration options have been renamed, either because
- they were unnecessarily verbose
- (e.g. <option>build-use-sandbox</option> is now just
- <option>sandbox</option>) or to reflect generalised behaviour
- (e.g. <option>binary-caches</option> is now
- <option>substituters</option> because it allows arbitrary store
- URIs). The old names are still supported for compatibility.</para>
- </listitem>
-
- <listitem>
- <para>The <option>max-jobs</option> option can <link xlink:href="https://github.com/NixOS/nix/commit/7251d048fa812d2551b7003bc9f13a8f5d4c95a5">now</link>
- be set to <literal>auto</literal> to use the number of CPUs in the
- system.</para>
- </listitem>
-
- <listitem>
- <para>Hashes can <link xlink:href="https://github.com/NixOS/nix/commit/c0015e87af70f539f24d2aa2bc224a9d8b84276b">now</link>
- be specified in base-64 format, in addition to base-16 and the
- non-standard base-32.</para>
- </listitem>
-
- <listitem>
- <para><command>nix-shell</command> now uses
- <varname>bashInteractive</varname> from Nixpkgs, rather than the
- <command>bash</command> command that happens to be in the caller’s
- <envar>PATH</envar>. This is especially important on macOS where
- the <command>bash</command> provided by the system is seriously
- outdated and cannot execute <literal>stdenv</literal>’s setup
- script.</para>
- </listitem>
-
- <listitem>
- <para>Nix can now automatically trigger a garbage collection if
- free disk space drops below a certain level during a build. This
- is configured using the <option>min-free</option> and
- <option>max-free</option> options.</para>
- </listitem>
-
- <listitem>
- <para><command>nix-store -q --roots</command> and
- <command>nix-store --gc --print-roots</command> now show temporary
- and in-memory roots.</para>
- </listitem>
-
- <listitem>
- <para>
- Nix can now be extended with plugins. See the documentation of
- the <option>plugin-files</option> option for more details.
- </para>
- </listitem>
-
-</itemizedlist>
-
-<para>The Nix language has the following new features:
-
-<itemizedlist>
-
- <listitem>
- <para>It supports floating point numbers. They are based on the
- C++ <literal>float</literal> type and are supported by the
- existing numerical operators. Export and import to and from JSON
- and XML works, too.</para>
- </listitem>
-
- <listitem>
- <para>Derivation attributes can now reference the outputs of the
- derivation using the <function>placeholder</function> builtin
- function. For example, the attribute
-
-<programlisting>
-configureFlags = "--prefix=${placeholder "out"} --includedir=${placeholder "dev"}";
-</programlisting>
-
- will cause the <envar>configureFlags</envar> environment variable
- to contain the actual store paths corresponding to the
- <literal>out</literal> and <literal>dev</literal> outputs.</para>
- </listitem>
-
-</itemizedlist>
-
-</para>
-
-<para>The following builtin functions are new or extended:
-
-<itemizedlist>
-
- <listitem>
- <para><function xlink:href="https://github.com/NixOS/nix/commit/38539b943a060d9cdfc24d6e5d997c0885b8aa2f">builtins.fetchGit</function>
- allows Git repositories to be fetched at evaluation time. Thus it
- differs from the <function>fetchgit</function> function in
- Nixpkgs, which fetches at build time and cannot be used to fetch
- Nix expressions during evaluation. A typical use case is to import
- external NixOS modules from your configuration, e.g.
-
- <programlisting>imports = [ (builtins.fetchGit https://github.com/edolstra/dwarffs + "/module.nix") ];</programlisting>
-
- </para>
- </listitem>
-
- <listitem>
- <para>Similarly, <function>builtins.fetchMercurial</function>
- allows you to fetch Mercurial repositories.</para>
- </listitem>
-
- <listitem>
- <para><function>builtins.path</function> generalises
- <function>builtins.filterSource</function> and path literals
- (e.g. <literal>./foo</literal>). It allows specifying a store path
- name that differs from the source path name
- (e.g. <literal>builtins.path { path = ./foo; name = "bar";
- }</literal>) and also supports filtering out unwanted
- files.</para>
- </listitem>
-
- <listitem>
- <para><function>builtins.fetchurl</function> and
- <function>builtins.fetchTarball</function> now support
- <varname>sha256</varname> and <varname>name</varname>
- attributes.</para>
- </listitem>
-
- <listitem>
- <para><function xlink:href="https://github.com/NixOS/nix/commit/b8867a0239b1930a16f9ef3f7f3e864b01416dff">builtins.split</function>
- splits a string using a POSIX extended regular expression as the
- separator.</para>
- </listitem>
-
- <listitem>
- <para><function xlink:href="https://github.com/NixOS/nix/commit/26d92017d3b36cff940dcb7d1611c42232edb81a">builtins.partition</function>
- partitions the elements of a list into two lists, depending on a
- Boolean predicate.</para>
- </listitem>
-
- <listitem>
- <para><literal><nix/fetchurl.nix></literal> now uses the
- content-addressable tarball cache at
- <uri>http://tarballs.nixos.org/</uri>, just like
- <function>fetchurl</function> in
- Nixpkgs. (f2682e6e18a76ecbfb8a12c17e3a0ca15c084197)</para>
- </listitem>
-
- <listitem>
- <para>In restricted and pure evaluation mode, builtin functions
- that download from the network (such as
- <function>fetchGit</function>) are permitted to fetch underneath a
- list of URI prefixes specified in the option
- <option>allowed-uris</option>.</para>
- </listitem>
-
-</itemizedlist>
-
-</para>
-
-<para>The Nix build environment has the following changes:
-
-<itemizedlist>
-
- <listitem>
- <para>Values such as Booleans, integers, (nested) lists and
- attribute sets can <link xlink:href="https://github.com/NixOS/nix/commit/6de33a9c675b187437a2e1abbcb290981a89ecb1">now</link>
- be passed to builders in a non-lossy way. If the special attribute
- <varname>__structuredAttrs</varname> is set to
- <literal>true</literal>, the other derivation attributes are
- serialised in JSON format and made available to the builder via
- the file <envar>.attrs.json</envar> in the builder’s temporary
- directory. This obviates the need for
- <varname>passAsFile</varname> since JSON files have no size
- restrictions, unlike process environments.</para>
-
- <para><link xlink:href="https://github.com/NixOS/nix/commit/2d5b1b24bf70a498e4c0b378704cfdb6471cc699">As
- a convenience to Bash builders</link>, Nix writes a script named
- <envar>.attrs.sh</envar> to the builder’s directory that
- initialises shell variables corresponding to all attributes that
- are representable in Bash. This includes non-nested (associative)
- arrays. For example, the attribute <literal>hardening.format =
- true</literal> ends up as the Bash associative array element
- <literal>${hardening[format]}</literal>.</para>
- </listitem>
-
- <listitem>
- <para>Builders can <link xlink:href="https://github.com/NixOS/nix/commit/88e6bb76de5564b3217be9688677d1c89101b2a3">now</link>
- communicate what build phase they are in by writing messages to
- the file descriptor specified in <envar>NIX_LOG_FD</envar>. The
- current phase is shown by the <command>nix</command> progress
- indicator.
- </para>
- </listitem>
-
- <listitem>
- <para>In Linux sandbox builds, we <link xlink:href="https://github.com/NixOS/nix/commit/a2d92bb20e82a0957067ede60e91fab256948b41">now</link>
- provide a default <filename>/bin/sh</filename> (namely
- <filename>ash</filename> from BusyBox).</para>
- </listitem>
-
- <listitem>
- <para>In structured attribute mode,
- <varname>exportReferencesGraph</varname> <link xlink:href="https://github.com/NixOS/nix/commit/c2b0d8749f7e77afc1c4b3e8dd36b7ee9720af4a">exports</link>
- extended information about closures in JSON format. In particular,
- it includes the sizes and hashes of paths. This is primarily
- useful for NixOS image builders.</para>
- </listitem>
-
- <listitem>
- <para>Builds are <link xlink:href="https://github.com/NixOS/nix/commit/21948deed99a3295e4d5666e027a6ca42dc00b40">now</link>
- killed as soon as Nix receives EOF on the builder’s stdout or
- stderr. This fixes a bug that allowed builds to hang Nix
- indefinitely, regardless of
- timeouts.</para>
- </listitem>
-
- <listitem>
- <para>The <option>sandbox-paths</option> configuration
- option can now specify optional paths by appending a
- <literal>?</literal>, e.g. <literal>/dev/nvidiactl?</literal> will
- bind-mount <varname>/dev/nvidiactl</varname> only if it
- exists.</para>
- </listitem>
-
- <listitem>
- <para>On Linux, builds are now executed in a user
- namespace with UID 1000 and GID 100.</para>
- </listitem>
-
-</itemizedlist>
-
-</para>
-
-<para>A number of significant internal changes were made:
-
-<itemizedlist>
-
- <listitem>
- <para>Nix no longer depends on Perl and all Perl components have
- been rewritten in C++ or removed. The Perl bindings that used to
- be part of Nix have been moved to a separate package,
- <literal>nix-perl</literal>.</para>
- </listitem>
-
- <listitem>
- <para>All <classname>Store</classname> classes are now
- thread-safe. <classname>RemoteStore</classname> supports multiple
- concurrent connections to the daemon. This is primarily useful in
- multi-threaded programs such as
- <command>hydra-queue-runner</command>.</para>
- </listitem>
-
-</itemizedlist>
-
-</para>
-
-<para>This release has contributions from
-
-Adrien Devresse,
-Alexander Ried,
-Alex Cruice,
-Alexey Shmalko,
-AmineChikhaoui,
-Andy Wingo,
-Aneesh Agrawal,
-Anthony Cowley,
-Armijn Hemel,
-aszlig,
-Ben Gamari,
-Benjamin Hipple,
-Benjamin Staffin,
-Benno Fünfstück,
-Bjørn Forsman,
-Brian McKenna,
-Charles Strahan,
-Chase Adams,
-Chris Martin,
-Christian Theune,
-Chris Warburton,
-Daiderd Jordan,
-Dan Connolly,
-Daniel Peebles,
-Dan Peebles,
-davidak,
-David McFarland,
-Dmitry Kalinkin,
-Domen Kožar,
-Eelco Dolstra,
-Emery Hemingway,
-Eric Litak,
-Eric Wolf,
-Fabian Schmitthenner,
-Frederik Rietdijk,
-Gabriel Gonzalez,
-Giorgio Gallo,
-Graham Christensen,
-Guillaume Maudoux,
-Harmen,
-Iavael,
-James Broadhead,
-James Earl Douglas,
-Janus Troelsen,
-Jeremy Shaw,
-Joachim Schiele,
-Joe Hermaszewski,
-Joel Moberg,
-Johannes 'fish' Ziemke,
-Jörg Thalheim,
-Jude Taylor,
-kballou,
-Keshav Kini,
-Kjetil Orbekk,
-Langston Barrett,
-Linus Heckemann,
-Ludovic Courtès,
-Manav Rathi,
-Marc Scholten,
-Markus Hauck,
-Matt Audesse,
-Matthew Bauer,
-Matthias Beyer,
-Matthieu Coudron,
-N1X,
-Nathan Zadoks,
-Neil Mayhew,
-Nicolas B. Pierron,
-Niklas Hambüchen,
-Nikolay Amiantov,
-Ole Jørgen Brønner,
-Orivej Desh,
-Peter Simons,
-Peter Stuart,
-Pyry Jahkola,
-regnat,
-Renzo Carbonara,
-Rhys,
-Robert Vollmert,
-Scott Olson,
-Scott R. Parish,
-Sergei Trofimovich,
-Shea Levy,
-Sheena Artrip,
-Spencer Baugh,
-Stefan Junker,
-Susan Potter,
-Thomas Tuegel,
-Timothy Allen,
-Tristan Hume,
-Tuomas Tynkkynen,
-tv,
-Tyson Whitehead,
-Vladimír Čunát,
-Will Dietz,
-wmertens,
-Wout Mertens,
-zimbatm and
-Zoran Plesivčak.
-</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.11.10">
-
-<title>Release 1.11.10 (2017-06-12)</title>
-
-<para>This release fixes a security bug in Nix’s “build user” build
-isolation mechanism. Previously, Nix builders had the ability to
-create setuid binaries owned by a <literal>nixbld</literal>
-user. Such a binary could then be used by an attacker to assume a
-<literal>nixbld</literal> identity and interfere with subsequent
-builds running under the same UID.</para>
-
-<para>To prevent this issue, Nix now disallows builders to create
-setuid and setgid binaries. On Linux, this is done using a seccomp BPF
-filter. Note that this imposes a small performance penalty (e.g. 1%
-when building GNU Hello). Using seccomp, we now also prevent the
-creation of extended attributes and POSIX ACLs since these cannot be
-represented in the NAR format and (in the case of POSIX ACLs) allow
-bypassing regular Nix store permissions. On macOS, the restriction is
-implemented using the existing sandbox mechanism, which now uses a
-minimal “allow all except the creation of setuid/setgid binaries”
-profile when regular sandboxing is disabled. On other platforms, the
-“build user” mechanism is now disabled.</para>
-
-<para>Thanks go to Linus Heckemann for discovering and reporting this
-bug.</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.11">
-
-<title>Release 1.11 (2016-01-19)</title>
-
-<para>This is primarily a bug fix release. It also has a number of new
-features:</para>
-
-<itemizedlist>
-
- <listitem>
- <para><command>nix-prefetch-url</command> can now download URLs
- specified in a Nix expression. For example,
-
-<screen>
-$ nix-prefetch-url -A hello.src
-</screen>
-
- will prefetch the file specified by the
- <function>fetchurl</function> call in the attribute
- <literal>hello.src</literal> from the Nix expression in the
- current directory, and print the cryptographic hash of the
- resulting file on stdout. This differs from <literal>nix-build -A
- hello.src</literal> in that it doesn't verify the hash, and is
- thus useful when you’re updating a Nix expression.</para>
-
- <para>You can also prefetch the result of functions that unpack a
- tarball, such as <function>fetchFromGitHub</function>. For example:
-
-<screen>
-$ nix-prefetch-url --unpack https://github.com/NixOS/patchelf/archive/0.8.tar.gz
-</screen>
-
- or from a Nix expression:
-
-<screen>
-$ nix-prefetch-url -A nix-repl.src
-</screen>
-
- </para>
-
- </listitem>
-
- <listitem>
- <para>The builtin function
- <function><nix/fetchurl.nix></function> now supports
- downloading and unpacking NARs. This removes the need to have
- multiple downloads in the Nixpkgs stdenv bootstrap process (like a
- separate busybox binary for Linux, or curl/mkdir/sh/bzip2 for
- Darwin). Now all those files can be combined into a single NAR,
- optionally compressed using <command>xz</command>.</para>
- </listitem>
-
- <listitem>
- <para>Nix now supports SHA-512 hashes for verifying fixed-output
- derivations, and in <function>builtins.hashString</function>.</para>
- </listitem>
-
- <listitem>
- <para>
- The new flag <option>--option build-repeat
- <replaceable>N</replaceable></option> will cause every build to
- be executed <replaceable>N</replaceable>+1 times. If the build
- output differs between any round, the build is rejected, and the
- output paths are not registered as valid. This is primarily
- useful to verify build determinism. (We already had a
- <option>--check</option> option to repeat a previously succeeded
- build. However, with <option>--check</option>, non-deterministic
- builds are registered in the DB. Preventing that is useful for
- Hydra to ensure that non-deterministic builds don't end up
- getting published to the binary cache.)
- </para>
- </listitem>
-
- <listitem>
- <para>
- The options <option>--check</option> and <option>--option
- build-repeat <replaceable>N</replaceable></option>, if they
- detect a difference between two runs of the same derivation and
- <option>-K</option> is given, will make the output of the other
- run available under
- <filename><replaceable>store-path</replaceable>-check</filename>. This
- makes it easier to investigate the non-determinism using tools
- like <command>diffoscope</command>, e.g.,
-
-<screen>
-$ nix-build pkgs/stdenv/linux -A stage1.pkgs.zlib --check -K
-error: derivation ‘/nix/store/l54i8wlw2265…-zlib-1.2.8.drv’ may not
-be deterministic: output ‘/nix/store/11a27shh6n2i…-zlib-1.2.8’
-differs from ‘/nix/store/11a27shh6n2i…-zlib-1.2.8-check’
-
-$ diffoscope /nix/store/11a27shh6n2i…-zlib-1.2.8 /nix/store/11a27shh6n2i…-zlib-1.2.8-check
-…
-├── lib/libz.a
-│ ├── metadata
-│ │ @@ -1,15 +1,15 @@
-│ │ -rw-r--r-- 30001/30000 3096 Jan 12 15:20 2016 adler32.o
-…
-│ │ +rw-r--r-- 30001/30000 3096 Jan 12 15:28 2016 adler32.o
-…
-</screen>
-
- </para></listitem>
-
- <listitem>
- <para>Improved FreeBSD support.</para>
- </listitem>
-
- <listitem>
- <para><command>nix-env -qa --xml --meta</command> now prints
- license information.</para>
- </listitem>
-
- <listitem>
- <para>The maximum number of parallel TCP connections that the
- binary cache substituter will use has been decreased from 150 to
- 25. This should prevent upsetting some broken NAT routers, and
- also improves performance.</para>
- </listitem>
-
- <listitem>
- <para>All "chroot"-containing strings got renamed to "sandbox".
- In particular, some Nix options got renamed, but the old names
- are still accepted as lower-priority aliases.
- </para>
- </listitem>
-
-</itemizedlist>
-
-<para>This release has contributions from Anders Claesson, Anthony
-Cowley, Bjørn Forsman, Brian McKenna, Danny Wilson, davidak, Eelco Dolstra,
-Fabian Schmitthenner, FrankHB, Ilya Novoselov, janus, Jim Garrison, John
-Ericson, Jude Taylor, Ludovic Courtès, Manuel Jacob, Mathnerd314,
-Pascal Wittmann, Peter Simons, Philip Potter, Preston Bennes, Rommel
-M. Martinez, Sander van der Burg, Shea Levy, Tim Cuthbertson, Tuomas
-Tynkkynen, Utku Demir and Vladimír Čunát.</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.10">
-
-<title>Release 1.10 (2015-09-03)</title>
-
-<para>This is primarily a bug fix release. It also has a number of new
-features:</para>
-
-<itemizedlist>
-
- <listitem>
- <para>A number of builtin functions have been added to reduce
- Nixpkgs/NixOS evaluation time and memory consumption:
- <function>all</function>,
- <function>any</function>,
- <function>concatStringsSep</function>,
- <function>foldl’</function>,
- <function>genList</function>,
- <function>replaceStrings</function>,
- <function>sort</function>.
- </para>
- </listitem>
-
- <listitem>
- <para>The garbage collector is more robust when the disk is full.</para>
- </listitem>
-
- <listitem>
- <para>Nix supports a new API for building derivations that doesn’t
- require a <literal>.drv</literal> file to be present on disk; it
- only requires an in-memory representation of the derivation. This
- is used by the Hydra continuous build system to make remote builds
- more efficient.</para>
- </listitem>
-
- <listitem>
- <para>The function <literal><nix/fetchurl.nix></literal> now
- uses a <emphasis>builtin</emphasis> builder (i.e. it doesn’t
- require starting an external process; the download is performed by
- Nix itself). This ensures that derivation paths don’t change when
- Nix is upgraded, and obviates the need for ugly hacks to support
- chroot execution.</para>
- </listitem>
-
- <listitem>
- <para><option>--version -v</option> now prints some configuration
- information, in particular what compile-time optional features are
- enabled, and the paths of various directories.</para>
- </listitem>
-
- <listitem>
- <para>Build users have their supplementary groups set correctly.</para>
- </listitem>
-
-</itemizedlist>
-
-<para>This release has contributions from Eelco Dolstra, Guillaume
-Maudoux, Iwan Aucamp, Jaka Hudoklin, Kirill Elagin, Ludovic Courtès,
-Manolis Ragkousis, Nicolas B. Pierron and Shea Levy.</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.9">
-
-<title>Release 1.9 (2015-06-12)</title>
-
-<para>In addition to the usual bug fixes, this release has the
-following new features:</para>
-
-<itemizedlist>
-
- <listitem>
- <para>Signed binary cache support. You can enable signature
- checking by adding the following to <filename>nix.conf</filename>:
-
-<programlisting>
-signed-binary-caches = *
-binary-cache-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
-</programlisting>
-
- This will prevent Nix from downloading any binary from the cache
- that is not signed by one of the keys listed in
- <option>binary-cache-public-keys</option>.</para>
-
- <para>Signature checking is only supported if you built Nix with
- the <literal>libsodium</literal> package.</para>
-
- <para>Note that while Nix has had experimental support for signed
- binary caches since version 1.7, this release changes the
- signature format in a backwards-incompatible way.</para>
-
- </listitem>
-
- <listitem>
-
- <para>Automatic downloading of Nix expression tarballs. In various
- places, you can now specify the URL of a tarball containing Nix
- expressions (such as Nixpkgs), which will be downloaded and
- unpacked automatically. For example:</para>
-
- <itemizedlist>
-
- <listitem><para>In <command>nix-env</command>:
-
-<screen>
-$ nix-env -f https://github.com/NixOS/nixpkgs-channels/archive/nixos-14.12.tar.gz -iA firefox
-</screen>
-
- This installs Firefox from the latest tested and built revision
- of the NixOS 14.12 channel.</para></listitem>
-
- <listitem><para>In <command>nix-build</command> and
- <command>nix-shell</command>:
-
-<screen>
-$ nix-build https://github.com/NixOS/nixpkgs/archive/master.tar.gz -A hello
-</screen>
-
- This builds GNU Hello from the latest revision of the Nixpkgs
- master branch.</para></listitem>
-
- <listitem><para>In the Nix search path (as specified via
- <envar>NIX_PATH</envar> or <option>-I</option>). For example, to
- start a shell containing the Pan package from a specific version
- of Nixpkgs:
-
-<screen>
-$ nix-shell -p pan -I nixpkgs=https://github.com/NixOS/nixpkgs-channels/archive/8a3eea054838b55aca962c3fbde9c83c102b8bf2.tar.gz
-</screen>
-
- </para></listitem>
-
- <listitem><para>In <command>nixos-rebuild</command> (on NixOS):
-
-<screen>
-$ nixos-rebuild test -I nixpkgs=https://github.com/NixOS/nixpkgs-channels/archive/nixos-unstable.tar.gz
-</screen>
-
- </para></listitem>
-
- <listitem><para>In Nix expressions, via the new builtin function <function>fetchTarball</function>:
-
-<programlisting>
-with import (fetchTarball https://github.com/NixOS/nixpkgs-channels/archive/nixos-14.12.tar.gz) {}; …
-</programlisting>
-
- (This is not allowed in restricted mode.)</para></listitem>
-
- </itemizedlist>
-
- </listitem>
-
- <listitem>
-
- <para><command>nix-shell</command> improvements:</para>
-
- <itemizedlist>
-
- <listitem><para><command>nix-shell</command> now has a flag
- <option>--run</option> to execute a command in the
- <command>nix-shell</command> environment,
- e.g. <literal>nix-shell --run make</literal>. This is like
- the existing <option>--command</option> flag, except that it
- uses a non-interactive shell (ensuring that hitting Ctrl-C won’t
- drop you into the child shell).</para></listitem>
-
- <listitem><para><command>nix-shell</command> can now be used as
- a <literal>#!</literal>-interpreter. This allows you to write
- scripts that dynamically fetch their own dependencies. For
- example, here is a Haskell script that, when invoked, first
- downloads GHC and the Haskell packages on which it depends:
-
-<programlisting>
-#! /usr/bin/env nix-shell
-#! nix-shell -i runghc -p haskellPackages.ghc haskellPackages.HTTP
-
-import Network.HTTP
-
-main = do
- resp <- Network.HTTP.simpleHTTP (getRequest "http://nixos.org/")
- body <- getResponseBody resp
- print (take 100 body)
-</programlisting>
-
- Of course, the dependencies are cached in the Nix store, so the
- second invocation of this script will be much
- faster.</para></listitem>
-
- </itemizedlist>
-
- </listitem>
-
- <listitem>
-
- <para>Chroot improvements:</para>
-
- <itemizedlist>
-
- <listitem><para>Chroot builds are now supported on Mac OS X
- (using its sandbox mechanism).</para></listitem>
-
- <listitem><para>If chroots are enabled, they are now used for
- all derivations, including fixed-output derivations (such as
- <function>fetchurl</function>). The latter do have network
- access, but can no longer access the host filesystem. If you
- need the old behaviour, you can set the option
- <option>build-use-chroot</option> to
- <literal>relaxed</literal>.</para></listitem>
-
- <listitem><para>On Linux, if chroots are enabled, builds are
- performed in a private PID namespace once again. (This
- functionality was lost in Nix 1.8.)</para></listitem>
-
- <listitem><para>Store paths listed in
- <option>build-chroot-dirs</option> are now automatically
- expanded to their closure. For instance, if you want
- <filename>/nix/store/…-bash/bin/sh</filename> mounted in your
- chroot as <filename>/bin/sh</filename>, you only need to say
- <literal>build-chroot-dirs =
- /bin/sh=/nix/store/…-bash/bin/sh</literal>; it is no longer
- necessary to specify the dependencies of Bash.</para></listitem>
-
- </itemizedlist>
-
- </listitem>
-
- <listitem><para>The new derivation attribute
- <varname>passAsFile</varname> allows you to specify that the
- contents of derivation attributes should be passed via files rather
- than environment variables. This is useful if you need to pass very
- long strings that exceed the size limit of the environment. The
- Nixpkgs function <function>writeTextFile</function> uses
- this.</para></listitem>
-
- <listitem><para>You can now use <literal>~</literal> in Nix file
- names to refer to your home directory, e.g. <literal>import
- ~/.nixpkgs/config.nix</literal>.</para></listitem>
-
- <listitem><para>Nix has a new option <option>restrict-eval</option>
- that allows limiting what paths the Nix evaluator has access to. By
- passing <literal>--option restrict-eval true</literal> to Nix, the
- evaluator will throw an exception if an attempt is made to access
- any file outside of the Nix search path. This is primarily intended
- for Hydra to ensure that a Hydra jobset only refers to its declared
- inputs (and is therefore reproducible).</para></listitem>
-
- <listitem><para><command>nix-env</command> now only creates a new
- “generation” symlink in <filename>/nix/var/nix/profiles</filename>
- if something actually changed.</para></listitem>
-
- <listitem><para>The environment variable <envar>NIX_PAGER</envar>
- can now be set to override <envar>PAGER</envar>. You can set it to
- <literal>cat</literal> to disable paging for Nix commands
- only.</para></listitem>
-
- <listitem><para>Failing <literal><...></literal>
- lookups now show position information.</para></listitem>
-
- <listitem><para>Improved Boehm GC use: we disabled scanning for
- interior pointers, which should reduce the “<literal>Repeated
- allocation of very large block</literal>” warnings and associated
- retention of memory.</para></listitem>
-
-</itemizedlist>
-
-<para>This release has contributions from aszlig, Benjamin Staffin,
-Charles Strahan, Christian Theune, Daniel Hahler, Danylo Hlynskyi
-Daniel Peebles, Dan Peebles, Domen Kožar, Eelco Dolstra, Harald van
-Dijk, Hoang Xuan Phu, Jaka Hudoklin, Jeff Ramnani, j-keck, Linquize,
-Luca Bruno, Michael Merickel, Oliver Dunkl, Rob Vermaas, Rok Garbas,
-Shea Levy, Tobias Geerinckx-Rice and William A. Kennington III.</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.8">
-
-<title>Release 1.8 (2014-12-14)</title>
-
-<itemizedlist>
-
- <listitem><para>Breaking change: to address a race condition, the
- remote build hook mechanism now uses <command>nix-store
- --serve</command> on the remote machine. This requires build slaves
- to be updated to Nix 1.8.</para></listitem>
-
- <listitem><para>Nix now uses HTTPS instead of HTTP to access the
- default binary cache,
- <literal>cache.nixos.org</literal>.</para></listitem>
-
- <listitem><para><command>nix-env</command> selectors are now regular
- expressions. For instance, you can do
-
-<screen>
-$ nix-env -qa '.*zip.*'
-</screen>
-
- to query all packages with a name containing
- <literal>zip</literal>.</para></listitem>
-
- <listitem><para><command>nix-store --read-log</command> can now
- fetch remote build logs. If a build log is not available locally,
- then ‘nix-store -l’ will now try to download it from the servers
- listed in the ‘log-servers’ option in nix.conf. For instance, if you
- have the configuration option
-
-<programlisting>
-log-servers = http://hydra.nixos.org/log
-</programlisting>
-
-then it will try to get logs from
-<literal>http://hydra.nixos.org/log/<replaceable>base name of the
-store path</replaceable></literal>. This allows you to do things like:
-
-<screen>
-$ nix-store -l $(which xterm)
-</screen>
-
- and get a log even if <command>xterm</command> wasn't built
- locally.</para></listitem>
-
- <listitem><para>New builtin functions:
- <function>attrValues</function>, <function>deepSeq</function>,
- <function>fromJSON</function>, <function>readDir</function>,
- <function>seq</function>.</para></listitem>
-
- <listitem><para><command>nix-instantiate --eval</command> now has a
- <option>--json</option> flag to print the resulting value in JSON
- format.</para></listitem>
-
- <listitem><para><command>nix-copy-closure</command> now uses
- <command>nix-store --serve</command> on the remote side to send or
- receive closures. This fixes a race condition between
- <command>nix-copy-closure</command> and the garbage
- collector.</para></listitem>
-
- <listitem><para>Derivations can specify the new special attribute
- <varname>allowedRequisites</varname>, which has a similar meaning to
- <varname>allowedReferences</varname>. But instead of only enforcing
- to explicitly specify the immediate references, it requires the
- derivation to specify all the dependencies recursively (hence the
- name, requisites) that are used by the resulting
- output.</para></listitem>
-
- <listitem><para>On Mac OS X, Nix now handles case collisions when
- importing closures from case-sensitive file systems. This is mostly
- useful for running NixOps on Mac OS X.</para></listitem>
-
- <listitem><para>The Nix daemon has new configuration options
- <option>allowed-users</option> (specifying the users and groups that
- are allowed to connect to the daemon) and
- <option>trusted-users</option> (specifying the users and groups that
- can perform privileged operations like specifying untrusted binary
- caches).</para></listitem>
-
- <listitem><para>The configuration option
- <option>build-cores</option> now defaults to the number of available
- CPU cores.</para></listitem>
-
- <listitem><para>Build users are now used by default when Nix is
- invoked as root. This prevents builds from accidentally running as
- root.</para></listitem>
-
- <listitem><para>Nix now includes systemd units and Upstart
- jobs.</para></listitem>
-
- <listitem><para>Speed improvements to <command>nix-store
- --optimise</command>.</para></listitem>
-
- <listitem><para>Language change: the <literal>==</literal> operator
- now ignores string contexts (the “dependencies” of a
- string).</para></listitem>
-
- <listitem><para>Nix now filters out Nix-specific ANSI escape
- sequences on standard error. They are supposed to be invisible, but
- some terminals show them anyway.</para></listitem>
-
- <listitem><para>Various commands now automatically pipe their output
- into the pager as specified by the <envar>PAGER</envar> environment
- variable.</para></listitem>
-
- <listitem><para>Several improvements to reduce memory consumption in
- the evaluator.</para></listitem>
-
-</itemizedlist>
-
-<para>This release has contributions from Adam Szkoda, Aristid
-Breitkreuz, Bob van der Linden, Charles Strahan, darealshinji, Eelco
-Dolstra, Gergely Risko, Joel Taylor, Ludovic Courtès, Marko Durkovic,
-Mikey Ariel, Paul Colomiets, Ricardo M. Correia, Ricky Elrod, Robert
-Helgesson, Rob Vermaas, Russell O'Connor, Shea Levy, Shell Turner,
-Sönke Hahn, Steve Purcell, Vladimír Čunát and Wout Mertens.</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.7">
-
-<title>Release 1.7 (2014-04-11)</title>
-
-<para>In addition to the usual bug fixes, this release has the
-following new features:</para>
-
-<itemizedlist>
-
- <listitem>
- <para>Antiquotation is now allowed inside of quoted attribute
- names (e.g. <literal>set."${foo}"</literal>). In the case where
- the attribute name is just a single antiquotation, the quotes can
- be dropped (e.g. the above example can be written
- <literal>set.${foo}</literal>). If an attribute name inside of a
- set declaration evaluates to <literal>null</literal> (e.g.
- <literal>{ ${null} = false; }</literal>), then that attribute is
- not added to the set.</para>
- </listitem>
-
- <listitem>
- <para>Experimental support for cryptographically signed binary
- caches. See <link xlink:href="https://github.com/NixOS/nix/commit/0fdf4da0e979f992db75cc17376e455ddc5a96d8">the
- commit for details</link>.</para>
- </listitem>
-
- <listitem>
- <para>An experimental new substituter,
- <command>download-via-ssh</command>, that fetches binaries from
- remote machines via SSH. Specifying the flags <literal>--option
- use-ssh-substituter true --option ssh-substituter-hosts
- <replaceable>user@hostname</replaceable></literal> will cause Nix
- to download binaries from the specified machine, if it has
- them.</para>
- </listitem>
-
- <listitem>
- <para><command>nix-store -r</command> and
- <command>nix-build</command> have a new flag,
- <option>--check</option>, that builds a previously built
- derivation again, and prints an error message if the output is not
- exactly the same. This helps to verify whether a derivation is
- truly deterministic. For example:
-
-<screen>
-$ nix-build '<nixpkgs>' -A patchelf
-<replaceable>…</replaceable>
-$ nix-build '<nixpkgs>' -A patchelf --check
-<replaceable>…</replaceable>
-error: derivation `/nix/store/1ipvxs…-patchelf-0.6' may not be deterministic:
- hash mismatch in output `/nix/store/4pc1dm…-patchelf-0.6.drv'
-</screen>
-
- </para>
-
- </listitem>
-
- <listitem>
- <para>The <command>nix-instantiate</command> flags
- <option>--eval-only</option> and <option>--parse-only</option>
- have been renamed to <option>--eval</option> and
- <option>--parse</option>, respectively.</para>
- </listitem>
-
- <listitem>
- <para><command>nix-instantiate</command>,
- <command>nix-build</command> and <command>nix-shell</command> now
- have a flag <option>--expr</option> (or <option>-E</option>) that
- allows you to specify the expression to be evaluated as a command
- line argument. For instance, <literal>nix-instantiate --eval -E
- '1 + 2'</literal> will print <literal>3</literal>.</para>
- </listitem>
-
- <listitem>
- <para><command>nix-shell</command> improvements:</para>
-
- <itemizedlist>
-
- <listitem>
- <para>It has a new flag, <option>--packages</option> (or
- <option>-p</option>), that sets up a build environment
- containing the specified packages from Nixpkgs. For example,
- the command
-
-<screen>
-$ nix-shell -p sqlite xorg.libX11 hello
-</screen>
-
- will start a shell in which the given packages are
- present.</para>
- </listitem>
-
- <listitem>
- <para>It now uses <filename>shell.nix</filename> as the
- default expression, falling back to
- <filename>default.nix</filename> if the former doesn’t
- exist. This makes it convenient to have a
- <filename>shell.nix</filename> in your project to set up a
- nice development environment.</para>
- </listitem>
-
- <listitem>
- <para>It evaluates the derivation attribute
- <varname>shellHook</varname>, if set. Since
- <literal>stdenv</literal> does not normally execute this hook,
- it allows you to do <command>nix-shell</command>-specific
- setup.</para>
- </listitem>
-
- <listitem>
- <para>It preserves the user’s timezone setting.</para>
- </listitem>
-
- </itemizedlist>
-
- </listitem>
-
- <listitem>
- <para>In chroots, Nix now sets up a <filename>/dev</filename>
- containing only a minimal set of devices (such as
- <filename>/dev/null</filename>). Note that it only does this if
- you <emphasis>don’t</emphasis> have <filename>/dev</filename>
- listed in your <option>build-chroot-dirs</option> setting;
- otherwise, it will bind-mount the <literal>/dev</literal> from
- outside the chroot.</para>
-
- <para>Similarly, if you don’t have <filename>/dev/pts</filename> listed
- in <option>build-chroot-dirs</option>, Nix will mount a private
- <literal>devpts</literal> filesystem on the chroot’s
- <filename>/dev/pts</filename>.</para>
-
- </listitem>
-
- <listitem>
- <para>New built-in function: <function>builtins.toJSON</function>,
- which returns a JSON representation of a value.</para>
- </listitem>
-
- <listitem>
- <para><command>nix-env -q</command> has a new flag
- <option>--json</option> to print a JSON representation of the
- installed or available packages.</para>
- </listitem>
-
- <listitem>
- <para><command>nix-env</command> now supports meta attributes with
- more complex values, such as attribute sets.</para>
- </listitem>
-
- <listitem>
- <para>The <option>-A</option> flag now allows attribute names with
- dots in them, e.g.
-
-<screen>
-$ nix-instantiate --eval '<nixos>' -A 'config.systemd.units."nscd.service".text'
-</screen>
-
- </para>
- </listitem>
-
- <listitem>
- <para>The <option>--max-freed</option> option to
- <command>nix-store --gc</command> now accepts a unit
- specifier. For example, <literal>nix-store --gc --max-freed
- 1G</literal> will free up to 1 gigabyte of disk space.</para>
- </listitem>
-
- <listitem>
- <para><command>nix-collect-garbage</command> has a new flag
- <option>--delete-older-than</option>
- <replaceable>N</replaceable><literal>d</literal>, which deletes
- all user environment generations older than
- <replaceable>N</replaceable> days. Likewise, <command>nix-env
- --delete-generations</command> accepts a
- <replaceable>N</replaceable><literal>d</literal> age limit.</para>
- </listitem>
-
- <listitem>
- <para>Nix now heuristically detects whether a build failure was
- due to a disk-full condition. In that case, the build is not
- flagged as “permanently failed”. This is mostly useful for Hydra,
- which needs to distinguish between permanent and transient build
- failures.</para>
- </listitem>
-
- <listitem>
- <para>There is a new symbol <literal>__curPos</literal> that
- expands to an attribute set containing its file name and line and
- column numbers, e.g. <literal>{ file = "foo.nix"; line = 10;
- column = 5; }</literal>. There also is a new builtin function,
- <varname>unsafeGetAttrPos</varname>, that returns the position of
- an attribute. This is used by Nixpkgs to provide location
- information in error messages, e.g.
-
-<screen>
-$ nix-build '<nixpkgs>' -A libreoffice --argstr system x86_64-darwin
-error: the package ‘libreoffice-4.0.5.2’ in ‘.../applications/office/libreoffice/default.nix:263’
- is not supported on ‘x86_64-darwin’
-</screen>
-
- </para>
- </listitem>
-
- <listitem>
- <para>The garbage collector is now more concurrent with other Nix
- processes because it releases certain locks earlier.</para>
- </listitem>
-
- <listitem>
- <para>The binary tarball installer has been improved. You can now
- install Nix by running:
-
-<screen>
-$ bash <(curl https://nixos.org/nix/install)
-</screen>
-
- </para>
- </listitem>
-
- <listitem>
- <para>More evaluation errors include position information. For
- instance, selecting a missing attribute will print something like
-
-<screen>
-error: attribute `nixUnstabl' missing, at /etc/nixos/configurations/misc/eelco/mandark.nix:216:15
-</screen>
-
- </para>
- </listitem>
-
- <listitem>
- <para>The command <command>nix-setuid-helper</command> is
- gone.</para>
- </listitem>
-
- <listitem>
- <para>Nix no longer uses Automake, but instead has a
- non-recursive, GNU Make-based build system.</para>
- </listitem>
-
- <listitem>
- <para>All installed libraries now have the prefix
- <literal>libnix</literal>. In particular, this gets rid of
- <literal>libutil</literal>, which could clash with libraries with
- the same name from other packages.</para>
- </listitem>
-
- <listitem>
- <para>Nix now requires a compiler that supports C++11.</para>
- </listitem>
-
-</itemizedlist>
-
-<para>This release has contributions from Danny Wilson, Domen Kožar,
-Eelco Dolstra, Ian-Woo Kim, Ludovic Courtès, Maxim Ivanov, Petr
-Rockai, Ricardo M. Correia and Shea Levy.</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.6.1">
-
-<title>Release 1.6.1 (2013-10-28)</title>
-
-<para>This is primarily a bug fix release. Changes of interest
-are:</para>
-
-<itemizedlist>
-
- <listitem>
- <para>Nix 1.6 accidentally changed the semantics of antiquoted
- paths in strings, such as <literal>"${/foo}/bar"</literal>. This
- release reverts to the Nix 1.5.3 behaviour.</para>
- </listitem>
-
- <listitem>
- <para>Previously, Nix optimised expressions such as
- <literal>"${<replaceable>expr</replaceable>}"</literal> to
- <replaceable>expr</replaceable>. Thus it neither checked whether
- <replaceable>expr</replaceable> could be coerced to a string, nor
- applied such coercions. This meant that
- <literal>"${123}"</literal> evaluatued to <literal>123</literal>,
- and <literal>"${./foo}"</literal> evaluated to
- <literal>./foo</literal> (even though
- <literal>"${./foo} "</literal> evaluates to
- <literal>"/nix/store/<replaceable>hash</replaceable>-foo "</literal>).
- Nix now checks the type of antiquoted expressions and
- applies coercions.</para>
- </listitem>
-
- <listitem>
- <para>Nix now shows the exact position of undefined variables. In
- particular, undefined variable errors in a <literal>with</literal>
- previously didn't show <emphasis>any</emphasis> position
- information, so this makes it a lot easier to fix such
- errors.</para>
- </listitem>
-
- <listitem>
- <para>Undefined variables are now treated consistently.
- Previously, the <function>tryEval</function> function would catch
- undefined variables inside a <literal>with</literal> but not
- outside. Now <function>tryEval</function> never catches undefined
- variables.</para>
- </listitem>
-
- <listitem>
- <para>Bash completion in <command>nix-shell</command> now works
- correctly.</para>
- </listitem>
-
- <listitem>
- <para>Stack traces are less verbose: they no longer show calls to
- builtin functions and only show a single line for each derivation
- on the call stack.</para>
- </listitem>
-
- <listitem>
- <para>New built-in function: <function>builtins.typeOf</function>,
- which returns the type of its argument as a string.</para>
- </listitem>
-
-</itemizedlist>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.6.0">
-
-<title>Release 1.6 (2013-09-10)</title>
-
-<para>In addition to the usual bug fixes, this release has several new
-features:</para>
-
-<itemizedlist>
-
- <listitem>
- <para>The command <command>nix-build --run-env</command> has been
- renamed to <command>nix-shell</command>.</para>
- </listitem>
-
- <listitem>
- <para><command>nix-shell</command> now sources
- <filename>$stdenv/setup</filename> <emphasis>inside</emphasis> the
- interactive shell, rather than in a parent shell. This ensures
- that shell functions defined by <literal>stdenv</literal> can be
- used in the interactive shell.</para>
- </listitem>
-
- <listitem>
- <para><command>nix-shell</command> has a new flag
- <option>--pure</option> to clear the environment, so you get an
- environment that more closely corresponds to the “real” Nix build.
- </para>
- </listitem>
-
- <listitem>
- <para><command>nix-shell</command> now sets the shell prompt
- (<envar>PS1</envar>) to ensure that Nix shells are distinguishable
- from your regular shells.</para>
- </listitem>
-
- <listitem>
- <para><command>nix-env</command> no longer requires a
- <literal>*</literal> argument to match all packages, so
- <literal>nix-env -qa</literal> is equivalent to <literal>nix-env
- -qa '*'</literal>.</para>
- </listitem>
-
- <listitem>
- <para><command>nix-env -i</command> has a new flag
- <option>--remove-all</option> (<option>-r</option>) to remove all
- previous packages from the profile. This makes it easier to do
- declarative package management similar to NixOS’s
- <option>environment.systemPackages</option>. For instance, if you
- have a specification <filename>my-packages.nix</filename> like this:
-
-<programlisting>
-with import <nixpkgs> {};
-[ thunderbird
- geeqie
- ...
-]
-</programlisting>
-
- then after any change to this file, you can run:
-
-<screen>
-$ nix-env -f my-packages.nix -ir
-</screen>
-
- to update your profile to match the specification.</para>
- </listitem>
-
- <listitem>
- <para>The ‘<literal>with</literal>’ language construct is now more
- lazy. It only evaluates its argument if a variable might actually
- refer to an attribute in the argument. For instance, this now
- works:
-
-<programlisting>
-let
- pkgs = with pkgs; { foo = "old"; bar = foo; } // overrides;
- overrides = { foo = "new"; };
-in pkgs.bar
-</programlisting>
-
- This evaluates to <literal>"new"</literal>, while previously it
- gave an “infinite recursion” error.</para>
- </listitem>
-
- <listitem>
- <para>Nix now has proper integer arithmetic operators. For
- instance, you can write <literal>x + y</literal> instead of
- <literal>builtins.add x y</literal>, or <literal>x <
- y</literal> instead of <literal>builtins.lessThan x y</literal>.
- The comparison operators also work on strings.</para>
- </listitem>
-
- <listitem>
- <para>On 64-bit systems, Nix integers are now 64 bits rather than
- 32 bits.</para>
- </listitem>
-
- <listitem>
- <para>When using the Nix daemon, the <command>nix-daemon</command>
- worker process now runs on the same CPU as the client, on systems
- that support setting CPU affinity. This gives a significant speedup
- on some systems.</para>
- </listitem>
-
- <listitem>
- <para>If a stack overflow occurs in the Nix evaluator, you now get
- a proper error message (rather than “Segmentation fault”) on some
- systems.</para>
- </listitem>
-
- <listitem>
- <para>In addition to directories, you can now bind-mount regular
- files in chroots through the (now misnamed) option
- <option>build-chroot-dirs</option>.</para>
- </listitem>
-
-</itemizedlist>
-
-<para>This release has contributions from Domen Kožar, Eelco Dolstra,
-Florian Friesdorf, Gergely Risko, Ivan Kozik, Ludovic Courtès and Shea
-Levy.</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.5.2">
-
-<title>Release 1.5.2 (2013-05-13)</title>
-
-<para>This is primarily a bug fix release. It has contributions from
-Eelco Dolstra, Lluís Batlle i Rossell and Shea Levy.</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.5">
-
-<title>Release 1.5 (2013-02-27)</title>
-
-<para>This is a brown paper bag release to fix a regression introduced
-by the hard link security fix in 1.4.</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.4">
-
-<title>Release 1.4 (2013-02-26)</title>
-
-<para>This release fixes a security bug in multi-user operation. It
-was possible for derivations to cause the mode of files outside of the
-Nix store to be changed to 444 (read-only but world-readable) by
-creating hard links to those files (<link xlink:href="https://github.com/NixOS/nix/commit/5526a282b5b44e9296e61e07d7d2626a79141ac4">details</link>).</para>
-
-<para>There are also the following improvements:</para>
-
-<itemizedlist>
-
- <listitem><para>New built-in function:
- <function>builtins.hashString</function>.</para></listitem>
-
- <listitem><para>Build logs are now stored in
- <filename>/nix/var/log/nix/drvs/<replaceable>XX</replaceable>/</filename>,
- where <replaceable>XX</replaceable> is the first two characters of
- the derivation. This is useful on machines that keep a lot of build
- logs (such as Hydra servers).</para></listitem>
-
- <listitem><para>The function <function>corepkgs/fetchurl</function>
- can now make the downloaded file executable. This will allow
- getting rid of all bootstrap binaries in the Nixpkgs source
- tree.</para></listitem>
-
- <listitem><para>Language change: The expression <literal>"${./path}
- ..."</literal> now evaluates to a string instead of a
- path.</para></listitem>
-
-</itemizedlist>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.3">
-
-<title>Release 1.3 (2013-01-04)</title>
-
-<para>This is primarily a bug fix release. When this version is first
-run on Linux, it removes any immutable bits from the Nix store and
-increases the schema version of the Nix store. (The previous release
-removed support for setting the immutable bit; this release clears any
-remaining immutable bits to make certain operations more
-efficient.)</para>
-
-<para>This release has contributions from Eelco Dolstra and Stuart
-Pernsteiner.</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.2">
-
-<title>Release 1.2 (2012-12-06)</title>
-
-<para>This release has the following improvements and changes:</para>
-
-<itemizedlist>
-
- <listitem>
- <para>Nix has a new binary substituter mechanism: the
- <emphasis>binary cache</emphasis>. A binary cache contains
- pre-built binaries of Nix packages. Whenever Nix wants to build a
- missing Nix store path, it will check a set of binary caches to
- see if any of them has a pre-built binary of that path. The
- configuration setting <option>binary-caches</option> contains a
- list of URLs of binary caches. For instance, doing
-<screen>
-$ nix-env -i thunderbird --option binary-caches http://cache.nixos.org
-</screen>
- will install Thunderbird and its dependencies, using the available
- pre-built binaries in <uri>http://cache.nixos.org</uri>.
- The main advantage over the old “manifest”-based method of getting
- pre-built binaries is that you don’t have to worry about your
- manifest being in sync with the Nix expressions you’re installing
- from; i.e., you don’t need to run <command>nix-pull</command> to
- update your manifest. It’s also more scalable because you don’t
- need to redownload a giant manifest file every time.
- </para>
-
- <para>A Nix channel can provide a binary cache URL that will be
- used automatically if you subscribe to that channel. If you use
- the Nixpkgs or NixOS channels
- (<uri>http://nixos.org/channels</uri>) you automatically get the
- cache <uri>http://cache.nixos.org</uri>.</para>
-
- <para>Binary caches are created using <command>nix-push</command>.
- For details on the operation and format of binary caches, see the
- <command>nix-push</command> manpage. More details are provided in
- <link xlink:href="https://nixos.org/nix-dev/2012-September/009826.html">this
- nix-dev posting</link>.</para>
- </listitem>
-
- <listitem>
- <para>Multiple output support should now be usable. A derivation
- can declare that it wants to produce multiple store paths by
- saying something like
-<programlisting>
-outputs = [ "lib" "headers" "doc" ];
-</programlisting>
- This will cause Nix to pass the intended store path of each output
- to the builder through the environment variables
- <literal>lib</literal>, <literal>headers</literal> and
- <literal>doc</literal>. Other packages can refer to a specific
- output by referring to
- <literal><replaceable>pkg</replaceable>.<replaceable>output</replaceable></literal>,
- e.g.
-<programlisting>
-buildInputs = [ pkg.lib pkg.headers ];
-</programlisting>
- If you install a package with multiple outputs using
- <command>nix-env</command>, each output path will be symlinked
- into the user environment.</para>
- </listitem>
-
- <listitem>
- <para>Dashes are now valid as part of identifiers and attribute
- names.</para>
- </listitem>
-
- <listitem>
- <para>The new operation <command>nix-store --repair-path</command>
- allows corrupted or missing store paths to be repaired by
- redownloading them. <command>nix-store --verify --check-contents
- --repair</command> will scan and repair all paths in the Nix
- store. Similarly, <command>nix-env</command>,
- <command>nix-build</command>, <command>nix-instantiate</command>
- and <command>nix-store --realise</command> have a
- <option>--repair</option> flag to detect and fix bad paths by
- rebuilding or redownloading them.</para>
- </listitem>
-
- <listitem>
- <para>Nix no longer sets the immutable bit on files in the Nix
- store. Instead, the recommended way to guard the Nix store
- against accidental modification on Linux is to make it a read-only
- bind mount, like this:
-
-<screen>
-$ mount --bind /nix/store /nix/store
-$ mount -o remount,ro,bind /nix/store
-</screen>
-
- Nix will automatically make <filename>/nix/store</filename>
- writable as needed (using a private mount namespace) to allow
- modifications.</para>
- </listitem>
-
- <listitem>
- <para>Store optimisation (replacing identical files in the store
- with hard links) can now be done automatically every time a path
- is added to the store. This is enabled by setting the
- configuration option <literal>auto-optimise-store</literal> to
- <literal>true</literal> (disabled by default).</para>
- </listitem>
-
- <listitem>
- <para>Nix now supports <command>xz</command> compression for NARs
- in addition to <command>bzip2</command>. It compresses about 30%
- better on typical archives and decompresses about twice as
- fast.</para>
- </listitem>
-
- <listitem>
- <para>Basic Nix expression evaluation profiling: setting the
- environment variable <envar>NIX_COUNT_CALLS</envar> to
- <literal>1</literal> will cause Nix to print how many times each
- primop or function was executed.</para>
- </listitem>
-
- <listitem>
- <para>New primops: <varname>concatLists</varname>,
- <varname>elem</varname>, <varname>elemAt</varname> and
- <varname>filter</varname>.</para>
- </listitem>
-
- <listitem>
- <para>The command <command>nix-copy-closure</command> has a new
- flag <option>--use-substitutes</option> (<option>-s</option>) to
- download missing paths on the target machine using the substitute
- mechanism.</para>
- </listitem>
-
- <listitem>
- <para>The command <command>nix-worker</command> has been renamed
- to <command>nix-daemon</command>. Support for running the Nix
- worker in “slave” mode has been removed.</para>
- </listitem>
-
- <listitem>
- <para>The <option>--help</option> flag of every Nix command now
- invokes <command>man</command>.</para>
- </listitem>
-
- <listitem>
- <para>Chroot builds are now supported on systemd machines.</para>
- </listitem>
-
-</itemizedlist>
-
-<para>This release has contributions from Eelco Dolstra, Florian
-Friesdorf, Mats Erik Andersson and Shea Levy.</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.1">
-
-<title>Release 1.1 (2012-07-18)</title>
-
-<para>This release has the following improvements:</para>
-
-<itemizedlist>
-
- <listitem>
- <para>On Linux, when doing a chroot build, Nix now uses various
- namespace features provided by the Linux kernel to improve
- build isolation. Namely:
- <itemizedlist>
- <listitem><para>The private network namespace ensures that
- builders cannot talk to the outside world (or vice versa): each
- build only sees a private loopback interface. This also means
- that two concurrent builds can listen on the same port (e.g. as
- part of a test) without conflicting with each
- other.</para></listitem>
- <listitem><para>The PID namespace causes each build to start as
- PID 1. Processes outside of the chroot are not visible to those
- on the inside. On the other hand, processes inside the chroot
- <emphasis>are</emphasis> visible from the outside (though with
- different PIDs).</para></listitem>
- <listitem><para>The IPC namespace prevents the builder from
- communicating with outside processes using SysV IPC mechanisms
- (shared memory, message queues, semaphores). It also ensures
- that all IPC objects are destroyed when the builder
- exits.</para></listitem>
- <listitem><para>The UTS namespace ensures that builders see a
- hostname of <literal>localhost</literal> rather than the actual
- hostname.</para></listitem>
- <listitem><para>The private mount namespace was already used by
- Nix to ensure that the bind-mounts used to set up the chroot are
- cleaned up automatically.</para></listitem>
- </itemizedlist>
- </para>
- </listitem>
-
- <listitem>
- <para>Build logs are now compressed using
- <command>bzip2</command>. The command <command>nix-store
- -l</command> decompresses them on the fly. This can be disabled
- by setting the option <literal>build-compress-log</literal> to
- <literal>false</literal>.</para>
- </listitem>
-
- <listitem>
- <para>The creation of build logs in
- <filename>/nix/var/log/nix/drvs</filename> can be disabled by
- setting the new option <literal>build-keep-log</literal> to
- <literal>false</literal>. This is useful, for instance, for Hydra
- build machines.</para>
- </listitem>
-
- <listitem>
- <para>Nix now reserves some space in
- <filename>/nix/var/nix/db/reserved</filename> to ensure that the
- garbage collector can run successfully if the disk is full. This
- is necessary because SQLite transactions fail if the disk is
- full.</para>
- </listitem>
-
- <listitem>
- <para>Added a basic <function>fetchurl</function> function. This
- is not intended to replace the <function>fetchurl</function> in
- Nixpkgs, but is useful for bootstrapping; e.g., it will allow us
- to get rid of the bootstrap binaries in the Nixpkgs source tree
- and download them instead. You can use it by doing
- <literal>import <nix/fetchurl.nix> { url =
- <replaceable>url</replaceable>; sha256 =
- "<replaceable>hash</replaceable>"; }</literal>. (Shea Levy)</para>
- </listitem>
-
- <listitem>
- <para>Improved RPM spec file. (Michel Alexandre Salim)</para>
- </listitem>
-
- <listitem>
- <para>Support for on-demand socket-based activation in the Nix
- daemon with <command>systemd</command>.</para>
- </listitem>
-
- <listitem>
- <para>Added a manpage for
- <citerefentry><refentrytitle>nix.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
- </listitem>
-
- <listitem>
- <para>When using the Nix daemon, the <option>-s</option> flag in
- <command>nix-env -qa</command> is now much faster.</para>
- </listitem>
-
-</itemizedlist>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-1.0">
-
-<title>Release 1.0 (2012-05-11)</title>
-
-<para>There have been numerous improvements and bug fixes since the
-previous release. Here are the most significant:</para>
-
-<itemizedlist>
-
- <listitem>
- <para>Nix can now optionally use the Boehm garbage collector.
- This significantly reduces the Nix evaluator’s memory footprint,
- especially when evaluating large NixOS system configurations. It
- can be enabled using the <option>--enable-gc</option> configure
- option.</para>
- </listitem>
-
- <listitem>
- <para>Nix now uses SQLite for its database. This is faster and
- more flexible than the old <emphasis>ad hoc</emphasis> format.
- SQLite is also used to cache the manifests in
- <filename>/nix/var/nix/manifests</filename>, resulting in a
- significant speedup.</para>
- </listitem>
-
- <listitem>
- <para>Nix now has an search path for expressions. The search path
- is set using the environment variable <envar>NIX_PATH</envar> and
- the <option>-I</option> command line option. In Nix expressions,
- paths between angle brackets are used to specify files that must
- be looked up in the search path. For instance, the expression
- <literal><nixpkgs/default.nix></literal> looks for a file
- <filename>nixpkgs/default.nix</filename> relative to every element
- in the search path.</para>
- </listitem>
-
- <listitem>
- <para>The new command <command>nix-build --run-env</command>
- builds all dependencies of a derivation, then starts a shell in an
- environment containing all variables from the derivation. This is
- useful for reproducing the environment of a derivation for
- development.</para>
- </listitem>
-
- <listitem>
- <para>The new command <command>nix-store --verify-path</command>
- verifies that the contents of a store path have not
- changed.</para>
- </listitem>
-
- <listitem>
- <para>The new command <command>nix-store --print-env</command>
- prints out the environment of a derivation in a format that can be
- evaluated by a shell.</para>
- </listitem>
-
- <listitem>
- <para>Attribute names can now be arbitrary strings. For instance,
- you can write <literal>{ "foo-1.2" = …; "bla bla" = …; }."bla
- bla"</literal>.</para>
- </listitem>
-
- <listitem>
- <para>Attribute selection can now provide a default value using
- the <literal>or</literal> operator. For instance, the expression
- <literal>x.y.z or e</literal> evaluates to the attribute
- <literal>x.y.z</literal> if it exists, and <literal>e</literal>
- otherwise.</para>
- </listitem>
-
- <listitem>
- <para>The right-hand side of the <literal>?</literal> operator can
- now be an attribute path, e.g., <literal>attrs ?
- a.b.c</literal>.</para>
- </listitem>
-
- <listitem>
- <para>On Linux, Nix will now make files in the Nix store immutable
- on filesystems that support it. This prevents accidental
- modification of files in the store by the root user.</para>
- </listitem>
-
- <listitem>
- <para>Nix has preliminary support for derivations with multiple
- outputs. This is useful because it allows parts of a package to
- be deployed and garbage-collected separately. For instance,
- development parts of a package such as header files or static
- libraries would typically not be part of the closure of an
- application, resulting in reduced disk usage and installation
- time.</para>
- </listitem>
-
- <listitem>
- <para>The Nix store garbage collector is faster and holds the
- global lock for a shorter amount of time.</para>
- </listitem>
-
- <listitem>
- <para>The option <option>--timeout</option> (corresponding to the
- configuration setting <literal>build-timeout</literal>) allows you
- to set an absolute timeout on builds — if a build runs for more than
- the given number of seconds, it is terminated. This is useful for
- recovering automatically from builds that are stuck in an infinite
- loop but keep producing output, and for which
- <literal>--max-silent-time</literal> is ineffective.</para>
- </listitem>
-
- <listitem>
- <para>Nix development has moved to GitHub (<link xlink:href="https://github.com/NixOS/nix"/>).</para>
- </listitem>
-
-</itemizedlist>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-0.16">
-
-<title>Release 0.16 (2010-08-17)</title>
-
-<para>This release has the following improvements:</para>
-
-<itemizedlist>
-
- <listitem>
- <para>The Nix expression evaluator is now much faster in most
- cases: typically, <link xlink:href="http://www.mail-archive.com/nix-dev@cs.uu.nl/msg04113.html">3
- to 8 times compared to the old implementation</link>. It also
- uses less memory. It no longer depends on the ATerm
- library.</para>
- </listitem>
-
- <listitem>
- <para>
- Support for configurable parallelism inside builders. Build
- scripts have always had the ability to perform multiple build
- actions in parallel (for instance, by running <command>make -j
- 2</command>), but this was not desirable because the number of
- actions to be performed in parallel was not configurable. Nix
- now has an option <option>--cores
- <replaceable>N</replaceable></option> as well as a configuration
- setting <varname>build-cores =
- <replaceable>N</replaceable></varname> that causes the
- environment variable <envar>NIX_BUILD_CORES</envar> to be set to
- <replaceable>N</replaceable> when the builder is invoked. The
- builder can use this at its discretion to perform a parallel
- build, e.g., by calling <command>make -j
- <replaceable>N</replaceable></command>. In Nixpkgs, this can be
- enabled on a per-package basis by setting the derivation
- attribute <varname>enableParallelBuilding</varname> to
- <literal>true</literal>.
- </para>
- </listitem>
-
- <listitem>
- <para><command>nix-store -q</command> now supports XML output
- through the <option>--xml</option> flag.</para>
- </listitem>
-
- <listitem>
- <para>Several bug fixes.</para>
- </listitem>
-
-</itemizedlist>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-0.15">
-
-<title>Release 0.15 (2010-03-17)</title>
-
-<para>This is a bug-fix release. Among other things, it fixes
-building on Mac OS X (Snow Leopard), and improves the contents of
-<filename>/etc/passwd</filename> and <filename>/etc/group</filename>
-in <literal>chroot</literal> builds.</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-0.14">
-
-<title>Release 0.14 (2010-02-04)</title>
-
-<para>This release has the following improvements:</para>
-
-<itemizedlist>
-
- <listitem>
- <para>The garbage collector now starts deleting garbage much
- faster than before. It no longer determines liveness of all paths
- in the store, but does so on demand.</para>
- </listitem>
-
- <listitem>
- <para>Added a new operation, <command>nix-store --query
- --roots</command>, that shows the garbage collector roots that
- directly or indirectly point to the given store paths.</para>
- </listitem>
-
- <listitem>
- <para>Removed support for converting Berkeley DB-based Nix
- databases to the new schema.</para>
- </listitem>
-
- <listitem>
- <para>Removed the <option>--use-atime</option> and
- <option>--max-atime</option> garbage collector options. They were
- not very useful in practice.</para>
- </listitem>
-
- <listitem>
- <para>On Windows, Nix now requires Cygwin 1.7.x.</para>
- </listitem>
-
- <listitem>
- <para>A few bug fixes.</para>
- </listitem>
-
-</itemizedlist>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-0.13">
-
-<title>Release 0.13 (2009-11-05)</title>
-
-<para>This is primarily a bug fix release. It has some new
-features:</para>
-
-<itemizedlist>
-
- <listitem>
- <para>Syntactic sugar for writing nested attribute sets. Instead of
-
-<programlisting>
-{
- foo = {
- bar = 123;
- xyzzy = true;
- };
- a = { b = { c = "d"; }; };
-}
-</programlisting>
-
- you can write
-
-<programlisting>
-{
- foo.bar = 123;
- foo.xyzzy = true;
- a.b.c = "d";
-}
-</programlisting>
-
- This is useful, for instance, in NixOS configuration files.</para>
-
- </listitem>
-
- <listitem>
- <para>Support for Nix channels generated by Hydra, the Nix-based
- continuous build system. (Hydra generates NAR archives on the
- fly, so the size and hash of these archives isn’t known in
- advance.)</para>
- </listitem>
-
- <listitem>
- <para>Support <literal>i686-linux</literal> builds directly on
- <literal>x86_64-linux</literal> Nix installations. This is
- implemented using the <function>personality()</function> syscall,
- which causes <command>uname</command> to return
- <literal>i686</literal> in child processes.</para>
- </listitem>
-
- <listitem>
- <para>Various improvements to the <literal>chroot</literal>
- support. Building in a <literal>chroot</literal> works quite well
- now.</para>
- </listitem>
-
- <listitem>
- <para>Nix no longer blocks if it tries to build a path and another
- process is already building the same path. Instead it tries to
- build another buildable path first. This improves
- parallelism.</para>
- </listitem>
-
- <listitem>
- <para>Support for large (> 4 GiB) files in NAR archives.</para>
- </listitem>
-
- <listitem>
- <para>Various (performance) improvements to the remote build
- mechanism.</para>
- </listitem>
-
- <listitem>
- <para>New primops: <varname>builtins.addErrorContext</varname> (to
- add a string to stack traces — useful for debugging),
- <varname>builtins.isBool</varname>,
- <varname>builtins.isString</varname>,
- <varname>builtins.isInt</varname>,
- <varname>builtins.intersectAttrs</varname>.</para>
- </listitem>
-
- <listitem>
- <para>OpenSolaris support (Sander van der Burg).</para>
- </listitem>
-
- <listitem>
- <para>Stack traces are no longer displayed unless the
- <option>--show-trace</option> option is used.</para>
- </listitem>
-
- <listitem>
- <para>The scoping rules for <literal>inherit
- (<replaceable>e</replaceable>) ...</literal> in recursive
- attribute sets have changed. The expression
- <replaceable>e</replaceable> can now refer to the attributes
- defined in the containing set.</para>
- </listitem>
-
-</itemizedlist>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-0.12">
-
-<title>Release 0.12 (2008-11-20)</title>
-
-<itemizedlist>
-
- <listitem>
- <para>Nix no longer uses Berkeley DB to store Nix store metadata.
- The principal advantages of the new storage scheme are: it works
- properly over decent implementations of NFS (allowing Nix stores
- to be shared between multiple machines); no recovery is needed
- when a Nix process crashes; no write access is needed for
- read-only operations; no more running out of Berkeley DB locks on
- certain operations.</para>
-
- <para>You still need to compile Nix with Berkeley DB support if
- you want Nix to automatically convert your old Nix store to the
- new schema. If you don’t need this, you can build Nix with the
- <filename>configure</filename> option
- <option>--disable-old-db-compat</option>.</para>
-
- <para>After the automatic conversion to the new schema, you can
- delete the old Berkeley DB files:
-
- <screen>
-$ cd /nix/var/nix/db
-$ rm __db* log.* derivers references referrers reserved validpaths DB_CONFIG</screen>
-
- The new metadata is stored in the directories
- <filename>/nix/var/nix/db/info</filename> and
- <filename>/nix/var/nix/db/referrer</filename>. Though the
- metadata is stored in human-readable plain-text files, they are
- not intended to be human-editable, as Nix is rather strict about
- the format.</para>
-
- <para>The new storage schema may or may not require less disk
- space than the Berkeley DB environment, mostly depending on the
- cluster size of your file system. With 1 KiB clusters (which
- seems to be the <literal>ext3</literal> default nowadays) it
- usually takes up much less space.</para>
- </listitem>
-
- <listitem><para>There is a new substituter that copies paths
- directly from other (remote) Nix stores mounted somewhere in the
- filesystem. For instance, you can speed up an installation by
- mounting some remote Nix store that already has the packages in
- question via NFS or <literal>sshfs</literal>. The environment
- variable <envar>NIX_OTHER_STORES</envar> specifies the locations of
- the remote Nix directories,
- e.g. <literal>/mnt/remote-fs/nix</literal>.</para></listitem>
-
- <listitem><para>New <command>nix-store</command> operations
- <option>--dump-db</option> and <option>--load-db</option> to dump
- and reload the Nix database.</para></listitem>
-
- <listitem><para>The garbage collector has a number of new options to
- allow only some of the garbage to be deleted. The option
- <option>--max-freed <replaceable>N</replaceable></option> tells the
- collector to stop after at least <replaceable>N</replaceable> bytes
- have been deleted. The option <option>--max-links
- <replaceable>N</replaceable></option> tells it to stop after the
- link count on <filename>/nix/store</filename> has dropped below
- <replaceable>N</replaceable>. This is useful for very large Nix
- stores on filesystems with a 32000 subdirectories limit (like
- <literal>ext3</literal>). The option <option>--use-atime</option>
- causes store paths to be deleted in order of ascending last access
- time. This allows non-recently used stuff to be deleted. The
- option <option>--max-atime <replaceable>time</replaceable></option>
- specifies an upper limit to the last accessed time of paths that may
- be deleted. For instance,
-
- <screen>
- $ nix-store --gc -v --max-atime $(date +%s -d "2 months ago")</screen>
-
- deletes everything that hasn’t been accessed in two months.</para></listitem>
-
- <listitem><para><command>nix-env</command> now uses optimistic
- profile locking when performing an operation like installing or
- upgrading, instead of setting an exclusive lock on the profile.
- This allows multiple <command>nix-env -i / -u / -e</command>
- operations on the same profile in parallel. If a
- <command>nix-env</command> operation sees at the end that the profile
- was changed in the meantime by another process, it will just
- restart. This is generally cheap because the build results are
- still in the Nix store.</para></listitem>
-
- <listitem><para>The option <option>--dry-run</option> is now
- supported by <command>nix-store -r</command> and
- <command>nix-build</command>.</para></listitem>
-
- <listitem><para>The information previously shown by
- <option>--dry-run</option> (i.e., which derivations will be built
- and which paths will be substituted) is now always shown by
- <command>nix-env</command>, <command>nix-store -r</command> and
- <command>nix-build</command>. The total download size of
- substitutable paths is now also shown. For instance, a build will
- show something like
-
- <screen>
-the following derivations will be built:
- /nix/store/129sbxnk5n466zg6r1qmq1xjv9zymyy7-activate-configuration.sh.drv
- /nix/store/7mzy971rdm8l566ch8hgxaf89x7lr7ik-upstart-jobs.drv
- ...
-the following paths will be downloaded/copied (30.02 MiB):
- /nix/store/4m8pvgy2dcjgppf5b4cj5l6wyshjhalj-samba-3.2.4
- /nix/store/7h1kwcj29ip8vk26rhmx6bfjraxp0g4l-libunwind-0.98.6
- ...</screen>
-
- </para></listitem>
-
- <listitem><para>Language features:
-
- <itemizedlist>
-
- <listitem><para>@-patterns as in Haskell. For instance, in a
- function definition
-
- <programlisting>f = args @ {x, y, z}: <replaceable>...</replaceable>;</programlisting>
-
- <varname>args</varname> refers to the argument as a whole, which
- is further pattern-matched against the attribute set pattern
- <literal>{x, y, z}</literal>.</para></listitem>
-
- <listitem><para>“<literal>...</literal>” (ellipsis) patterns.
- An attribute set pattern can now say <literal>...</literal> at
- the end of the attribute name list to specify that the function
- takes <emphasis>at least</emphasis> the listed attributes, while
- ignoring additional attributes. For instance,
-
- <programlisting>{stdenv, fetchurl, fuse, ...}: <replaceable>...</replaceable></programlisting>
-
- defines a function that accepts any attribute set that includes
- at least the three listed attributes.</para></listitem>
-
- <listitem><para>New primops:
- <varname>builtins.parseDrvName</varname> (split a package name
- string like <literal>"nix-0.12pre12876"</literal> into its name
- and version components, e.g. <literal>"nix"</literal> and
- <literal>"0.12pre12876"</literal>),
- <varname>builtins.compareVersions</varname> (compare two version
- strings using the same algorithm that <command>nix-env</command>
- uses), <varname>builtins.length</varname> (efficiently compute
- the length of a list), <varname>builtins.mul</varname> (integer
- multiplication), <varname>builtins.div</varname> (integer
- division).
- <!-- <varname>builtins.genericClosure</varname> -->
- </para></listitem>
-
- </itemizedlist>
-
- </para></listitem>
-
- <listitem><para><command>nix-prefetch-url</command> now supports
- <literal>mirror://</literal> URLs, provided that the environment
- variable <envar>NIXPKGS_ALL</envar> points at a Nixpkgs
- tree.</para></listitem>
-
- <listitem><para>Removed the commands
- <command>nix-pack-closure</command> and
- <command>nix-unpack-closure</command>. You can do almost the same
- thing but much more efficiently by doing <literal>nix-store --export
- $(nix-store -qR <replaceable>paths</replaceable>) > closure</literal> and
- <literal>nix-store --import <
- closure</literal>.</para></listitem>
-
- <listitem><para>Lots of bug fixes, including a big performance bug in
- the handling of <literal>with</literal>-expressions.</para></listitem>
-
-</itemizedlist>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ssec-relnotes-0.11">
-
-<title>Release 0.11 (2007-12-31)</title>
-
-<para>Nix 0.11 has many improvements over the previous stable release.
-The most important improvement is secure multi-user support. It also
-features many usability enhancements and language extensions, many of
-them prompted by NixOS, the purely functional Linux distribution based
-on Nix. Here is an (incomplete) list:</para>
-
-
-<itemizedlist>
-
-
- <listitem><para>Secure multi-user support. A single Nix store can
- now be shared between multiple (possible untrusted) users. This is
- an important feature for NixOS, where it allows non-root users to
- install software. The old setuid method for sharing a store between
- multiple users has been removed. Details for setting up a
- multi-user store can be found in the manual.</para></listitem>
-
-
- <listitem><para>The new command <command>nix-copy-closure</command>
- gives you an easy and efficient way to exchange software between
- machines. It copies the missing parts of the closure of a set of
- store path to or from a remote machine via
- <command>ssh</command>.</para></listitem>
-
-
- <listitem><para>A new kind of string literal: strings between double
- single-quotes (<literal>''</literal>) have indentation
- “intelligently” removed. This allows large strings (such as shell
- scripts or configuration file fragments in NixOS) to cleanly follow
- the indentation of the surrounding expression. It also requires
- much less escaping, since <literal>''</literal> is less common in
- most languages than <literal>"</literal>.</para></listitem>
-
-
- <listitem><para><command>nix-env</command> <option>--set</option>
- modifies the current generation of a profile so that it contains
- exactly the specified derivation, and nothing else. For example,
- <literal>nix-env -p /nix/var/nix/profiles/browser --set
- firefox</literal> lets the profile named
- <filename>browser</filename> contain just Firefox.</para></listitem>
-
-
- <listitem><para><command>nix-env</command> now maintains
- meta-information about installed packages in profiles. The
- meta-information is the contents of the <varname>meta</varname>
- attribute of derivations, such as <varname>description</varname> or
- <varname>homepage</varname>. The command <literal>nix-env -q --xml
- --meta</literal> shows all meta-information.</para></listitem>
-
-
- <listitem><para><command>nix-env</command> now uses the
- <varname>meta.priority</varname> attribute of derivations to resolve
- filename collisions between packages. Lower priority values denote
- a higher priority. For instance, the GCC wrapper package and the
- Binutils package in Nixpkgs both have a file
- <filename>bin/ld</filename>, so previously if you tried to install
- both you would get a collision. Now, on the other hand, the GCC
- wrapper declares a higher priority than Binutils, so the former’s
- <filename>bin/ld</filename> is symlinked in the user
- environment.</para></listitem>
-
-
- <listitem><para><command>nix-env -i / -u</command>: instead of
- breaking package ties by version, break them by priority and version
- number. That is, if there are multiple packages with the same name,
- then pick the package with the highest priority, and only use the
- version if there are multiple packages with the same
- priority.</para>
-
- <para>This makes it possible to mark specific versions/variant in
- Nixpkgs more or less desirable than others. A typical example would
- be a beta version of some package (e.g.,
- <literal>gcc-4.2.0rc1</literal>) which should not be installed even
- though it is the highest version, except when it is explicitly
- selected (e.g., <literal>nix-env -i
- gcc-4.2.0rc1</literal>).</para></listitem>
-
-
- <listitem><para><command>nix-env --set-flag</command> allows meta
- attributes of installed packages to be modified. There are several
- attributes that can be usefully modified, because they affect the
- behaviour of <command>nix-env</command> or the user environment
- build script:
-
- <itemizedlist>
-
- <listitem><para><varname>meta.priority</varname> can be changed
- to resolve filename clashes (see above).</para></listitem>
-
- <listitem><para><varname>meta.keep</varname> can be set to
- <literal>true</literal> to prevent the package from being
- upgraded or replaced. Useful if you want to hang on to an older
- version of a package.</para></listitem>
-
- <listitem><para><varname>meta.active</varname> can be set to
- <literal>false</literal> to “disable” the package. That is, no
- symlinks will be generated to the files of the package, but it
- remains part of the profile (so it won’t be garbage-collected).
- Set it back to <literal>true</literal> to re-enable the
- package.</para></listitem>
-
- </itemizedlist>
-
- </para></listitem>
-
-
- <listitem><para><command>nix-env -q</command> now has a flag
- <option>--prebuilt-only</option> (<option>-b</option>) that causes
- <command>nix-env</command> to show only those derivations whose
- output is already in the Nix store or that can be substituted (i.e.,
- downloaded from somewhere). In other words, it shows the packages
- that can be installed “quickly”, i.e., don’t need to be built from
- source. The <option>-b</option> flag is also available in
- <command>nix-env -i</command> and <command>nix-env -u</command> to
- filter out derivations for which no pre-built binary is
- available.</para></listitem>
-
-
- <listitem><para>The new option <option>--argstr</option> (in
- <command>nix-env</command>, <command>nix-instantiate</command> and
- <command>nix-build</command>) is like <option>--arg</option>, except
- that the value is a string. For example, <literal>--argstr system
- i686-linux</literal> is equivalent to <literal>--arg system
- \"i686-linux\"</literal> (note that <option>--argstr</option>
- prevents annoying quoting around shell arguments).</para></listitem>
-
-
- <listitem><para><command>nix-store</command> has a new operation
- <option>--read-log</option> (<option>-l</option>)
- <parameter>paths</parameter> that shows the build log of the given
- paths.</para></listitem>
-
-
- <!--
- <listitem><para>TODO: semantic cleanups of string concatenation
- etc. (mostly in r6740).</para></listitem>
- -->
-
-
- <listitem><para>Nix now uses Berkeley DB 4.5. The database is
- upgraded automatically, but you should be careful not to use old
- versions of Nix that still use Berkeley DB 4.4.</para></listitem>
-
-
- <!-- foo
- <listitem><para>TODO: option <option>- -reregister</option> in
- <command>nix-store - -register-validity</command>.</para></listitem>
- -->
-
-
- <listitem><para>The option <option>--max-silent-time</option>
- (corresponding to the configuration setting
- <literal>build-max-silent-time</literal>) allows you to set a
- timeout on builds — if a build produces no output on
- <literal>stdout</literal> or <literal>stderr</literal> for the given
- number of seconds, it is terminated. This is useful for recovering
- automatically from builds that are stuck in an infinite
- loop.</para></listitem>
-
-
- <listitem><para><command>nix-channel</command>: each subscribed
- channel is its own attribute in the top-level expression generated
- for the channel. This allows disambiguation (e.g. <literal>nix-env
- -i -A nixpkgs_unstable.firefox</literal>).</para></listitem>
-
-
- <listitem><para>The substitutes table has been removed from the
- database. This makes operations such as <command>nix-pull</command>
- and <command>nix-channel --update</command> much, much
- faster.</para></listitem>
-
-
- <listitem><para><command>nix-pull</command> now supports
- bzip2-compressed manifests. This speeds up
- channels.</para></listitem>
-
-
- <listitem><para><command>nix-prefetch-url</command> now has a
- limited form of caching. This is used by
- <command>nix-channel</command> to prevent unnecessary downloads when
- the channel hasn’t changed.</para></listitem>
-
-
- <listitem><para><command>nix-prefetch-url</command> now by default
- computes the SHA-256 hash of the file instead of the MD5 hash. In
- calls to <function>fetchurl</function> you should pass the
- <literal>sha256</literal> attribute instead of
- <literal>md5</literal>. You can pass either a hexadecimal or a
- base-32 encoding of the hash.</para></listitem>
-
-
- <listitem><para>Nix can now perform builds in an automatically
- generated “chroot”. This prevents a builder from accessing stuff
- outside of the Nix store, and thus helps ensure purity. This is an
- experimental feature.</para></listitem>
-
-
- <listitem><para>The new command <command>nix-store
- --optimise</command> reduces Nix store disk space usage by finding
- identical files in the store and hard-linking them to each other.
- It typically reduces the size of the store by something like
- 25-35%.</para></listitem>
-
-
- <listitem><para><filename>~/.nix-defexpr</filename> can now be a
- directory, in which case the Nix expressions in that directory are
- combined into an attribute set, with the file names used as the
- names of the attributes. The command <command>nix-env
- --import</command> (which set the
- <filename>~/.nix-defexpr</filename> symlink) is
- removed.</para></listitem>
-
-
- <listitem><para>Derivations can specify the new special attribute
- <varname>allowedReferences</varname> to enforce that the references
- in the output of a derivation are a subset of a declared set of
- paths. For example, if <varname>allowedReferences</varname> is an
- empty list, then the output must not have any references. This is
- used in NixOS to check that generated files such as initial ramdisks
- for booting Linux don’t have any dependencies.</para></listitem>
-
-
- <listitem><para>The new attribute
- <varname>exportReferencesGraph</varname> allows builders access to
- the references graph of their inputs. This is used in NixOS for
- tasks such as generating ISO-9660 images that contain a Nix store
- populated with the closure of certain paths.</para></listitem>
-
-
- <listitem><para>Fixed-output derivations (like
- <function>fetchurl</function>) can define the attribute
- <varname>impureEnvVars</varname> to allow external environment
- variables to be passed to builders. This is used in Nixpkgs to
- support proxy configuration, among other things.</para></listitem>
-
-
- <listitem><para>Several new built-in functions:
- <function>builtins.attrNames</function>,
- <function>builtins.filterSource</function>,
- <function>builtins.isAttrs</function>,
- <function>builtins.isFunction</function>,
- <function>builtins.listToAttrs</function>,
- <function>builtins.stringLength</function>,
- <function>builtins.sub</function>,
- <function>builtins.substring</function>,
- <function>throw</function>,
- <function>builtins.trace</function>,
- <function>builtins.readFile</function>.</para></listitem>
-
-
-</itemizedlist>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-relnotes-0.10.1">
-
-<title>Release 0.10.1 (2006-10-11)</title>
-
-<para>This release fixes two somewhat obscure bugs that occur when
-evaluating Nix expressions that are stored inside the Nix store
-(<literal>NIX-67</literal>). These do not affect most users.</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-relnotes-0.10">
-
-<title>Release 0.10 (2006-10-06)</title>
-
-<note><para>This version of Nix uses Berkeley DB 4.4 instead of 4.3.
-The database is upgraded automatically, but you should be careful not
-to use old versions of Nix that still use Berkeley DB 4.3. In
-particular, if you use a Nix installed through Nix, you should run
-
-<screen>
-$ nix-store --clear-substitutes</screen>
-
-first.</para></note>
-
-<warning><para>Also, the database schema has changed slighted to fix a
-performance issue (see below). When you run any Nix 0.10 command for
-the first time, the database will be upgraded automatically. This is
-irreversible.</para></warning>
-
-<itemizedlist>
-
-
- <!-- Usability / features -->
-
-
- <listitem><para><command>nix-env</command> usability improvements:
-
- <itemizedlist>
-
- <listitem><para>An option <option>--compare-versions</option>
- (or <option>-c</option>) has been added to <command>nix-env
- --query</command> to allow you to compare installed versions of
- packages to available versions, or vice versa. An easy way to
- see if you are up to date with what’s in your subscribed
- channels is <literal>nix-env -qc \*</literal>.</para></listitem>
-
- <listitem><para><literal>nix-env --query</literal> now takes as
- arguments a list of package names about which to show
- information, just like <option>--install</option>, etc.: for
- example, <literal>nix-env -q gcc</literal>. Note that to show
- all derivations, you need to specify
- <literal>\*</literal>.</para></listitem>
-
- <listitem><para><literal>nix-env -i
- <replaceable>pkgname</replaceable></literal> will now install
- the highest available version of
- <replaceable>pkgname</replaceable>, rather than installing all
- available versions (which would probably give collisions)
- (<literal>NIX-31</literal>).</para></listitem>
-
- <listitem><para><literal>nix-env (-i|-u) --dry-run</literal> now
- shows exactly which missing paths will be built or
- substituted.</para></listitem>
-
- <listitem><para><literal>nix-env -qa --description</literal>
- shows human-readable descriptions of packages, provided that
- they have a <literal>meta.description</literal> attribute (which
- most packages in Nixpkgs don’t have yet).</para></listitem>
-
- </itemizedlist>
-
- </para></listitem>
-
-
- <listitem><para>New language features:
-
- <itemizedlist>
-
- <listitem><para>Reference scanning (which happens after each
- build) is much faster and takes a constant amount of
- memory.</para></listitem>
-
- <listitem><para>String interpolation. Expressions like
-
-<programlisting>
-"--with-freetype2-library=" + freetype + "/lib"</programlisting>
-
- can now be written as
-
-<programlisting>
-"--with-freetype2-library=${freetype}/lib"</programlisting>
-
- You can write arbitrary expressions within
- <literal>${<replaceable>...</replaceable>}</literal>, not just
- identifiers.</para></listitem>
-
- <listitem><para>Multi-line string literals.</para></listitem>
-
- <listitem><para>String concatenations can now involve
- derivations, as in the example <code>"--with-freetype2-library="
- + freetype + "/lib"</code>. This was not previously possible
- because we need to register that a derivation that uses such a
- string is dependent on <literal>freetype</literal>. The
- evaluator now properly propagates this information.
- Consequently, the subpath operator (<literal>~</literal>) has
- been deprecated.</para></listitem>
-
- <listitem><para>Default values of function arguments can now
- refer to other function arguments; that is, all arguments are in
- scope in the default values
- (<literal>NIX-45</literal>).</para></listitem>
-
- <!--
- <listitem><para>TODO: domain checks (r5895).</para></listitem>
- -->
-
- <listitem><para>Lots of new built-in primitives, such as
- functions for list manipulation and integer arithmetic. See the
- manual for a complete list. All primops are now available in
- the set <varname>builtins</varname>, allowing one to test for
- the availability of primop in a backwards-compatible
- way.</para></listitem>
-
- <listitem><para>Real let-expressions: <literal>let x = ...;
- ... z = ...; in ...</literal>.</para></listitem>
-
- </itemizedlist>
-
- </para></listitem>
-
-
- <listitem><para>New commands <command>nix-pack-closure</command> and
- <command>nix-unpack-closure</command> than can be used to easily
- transfer a store path with all its dependencies to another machine.
- Very convenient whenever you have some package on your machine and
- you want to copy it somewhere else.</para></listitem>
-
-
- <listitem><para>XML support:
-
- <itemizedlist>
-
- <listitem><para><literal>nix-env -q --xml</literal> prints the
- installed or available packages in an XML representation for
- easy processing by other tools.</para></listitem>
-
- <listitem><para><literal>nix-instantiate --eval-only
- --xml</literal> prints an XML representation of the resulting
- term. (The new flag <option>--strict</option> forces ‘deep’
- evaluation of the result, i.e., list elements and attributes are
- evaluated recursively.)</para></listitem>
-
- <listitem><para>In Nix expressions, the primop
- <function>builtins.toXML</function> converts a term to an XML
- representation. This is primarily useful for passing structured
- information to builders.</para></listitem>
-
- </itemizedlist>
-
- </para></listitem>
-
-
- <listitem><para>You can now unambiguously specify which derivation to
- build or install in <command>nix-env</command>,
- <command>nix-instantiate</command> and <command>nix-build</command>
- using the <option>--attr</option> / <option>-A</option> flags, which
- takes an attribute name as argument. (Unlike symbolic package names
- such as <literal>subversion-1.4.0</literal>, attribute names in an
- attribute set are unique.) For instance, a quick way to perform a
- test build of a package in Nixpkgs is <literal>nix-build
- pkgs/top-level/all-packages.nix -A
- <replaceable>foo</replaceable></literal>. <literal>nix-env -q
- --attr</literal> shows the attribute names corresponding to each
- derivation.</para></listitem>
-
-
- <listitem><para>If the top-level Nix expression used by
- <command>nix-env</command>, <command>nix-instantiate</command> or
- <command>nix-build</command> evaluates to a function whose arguments
- all have default values, the function will be called automatically.
- Also, the new command-line switch <option>--arg
- <replaceable>name</replaceable>
- <replaceable>value</replaceable></option> can be used to specify
- function arguments on the command line.</para></listitem>
-
-
- <listitem><para><literal>nix-install-package --url
- <replaceable>URL</replaceable></literal> allows a package to be
- installed directly from the given URL.</para></listitem>
-
-
- <listitem><para>Nix now works behind an HTTP proxy server; just set
- the standard environment variables <envar>http_proxy</envar>,
- <envar>https_proxy</envar>, <envar>ftp_proxy</envar> or
- <envar>all_proxy</envar> appropriately. Functions such as
- <function>fetchurl</function> in Nixpkgs also respect these
- variables.</para></listitem>
-
-
- <listitem><para><literal>nix-build -o
- <replaceable>symlink</replaceable></literal> allows the symlink to
- the build result to be named something other than
- <literal>result</literal>.</para></listitem>
-
-
- <!-- Stability / performance / etc. -->
-
-
- <listitem><para>Platform support:
-
- <itemizedlist>
-
- <listitem><para>Support for 64-bit platforms, provided a <link xlink:href="http://bugzilla.sen.cwi.nl:8080/show_bug.cgi?id=606">suitably
- patched ATerm library</link> is used. Also, files larger than 2
- GiB are now supported.</para></listitem>
-
- <listitem><para>Added support for Cygwin (Windows,
- <literal>i686-cygwin</literal>), Mac OS X on Intel
- (<literal>i686-darwin</literal>) and Linux on PowerPC
- (<literal>powerpc-linux</literal>).</para></listitem>
-
- <listitem><para>Users of SMP and multicore machines will
- appreciate that the number of builds to be performed in parallel
- can now be specified in the configuration file in the
- <literal>build-max-jobs</literal> setting.</para></listitem>
-
- </itemizedlist>
-
- </para></listitem>
-
-
- <listitem><para>Garbage collector improvements:
-
- <itemizedlist>
-
- <listitem><para>Open files (such as running programs) are now
- used as roots of the garbage collector. This prevents programs
- that have been uninstalled from being garbage collected while
- they are still running. The script that detects these
- additional runtime roots
- (<filename>find-runtime-roots.pl</filename>) is inherently
- system-specific, but it should work on Linux and on all
- platforms that have the <command>lsof</command>
- utility.</para></listitem>
-
- <listitem><para><literal>nix-store --gc</literal>
- (a.k.a. <command>nix-collect-garbage</command>) prints out the
- number of bytes freed on standard output. <literal>nix-store
- --gc --print-dead</literal> shows how many bytes would be freed
- by an actual garbage collection.</para></listitem>
-
- <listitem><para><literal>nix-collect-garbage -d</literal>
- removes all old generations of <emphasis>all</emphasis> profiles
- before calling the actual garbage collector (<literal>nix-store
- --gc</literal>). This is an easy way to get rid of all old
- packages in the Nix store.</para></listitem>
-
- <listitem><para><command>nix-store</command> now has an
- operation <option>--delete</option> to delete specific paths
- from the Nix store. It won’t delete reachable (non-garbage)
- paths unless <option>--ignore-liveness</option> is
- specified.</para></listitem>
-
- </itemizedlist>
-
- </para></listitem>
-
-
- <listitem><para>Berkeley DB 4.4’s process registry feature is used
- to recover from crashed Nix processes.</para></listitem>
-
- <!-- <listitem><para>TODO: shared stores.</para></listitem> -->
-
- <listitem><para>A performance issue has been fixed with the
- <literal>referer</literal> table, which stores the inverse of the
- <literal>references</literal> table (i.e., it tells you what store
- paths refer to a given path). Maintaining this table could take a
- quadratic amount of time, as well as a quadratic amount of Berkeley
- DB log file space (in particular when running the garbage collector)
- (<literal>NIX-23</literal>).</para></listitem>
-
- <listitem><para>Nix now catches the <literal>TERM</literal> and
- <literal>HUP</literal> signals in addition to the
- <literal>INT</literal> signal. So you can now do a <literal>killall
- nix-store</literal> without triggering a database
- recovery.</para></listitem>
-
- <listitem><para><command>bsdiff</command> updated to version
- 4.3.</para></listitem>
-
- <listitem><para>Substantial performance improvements in expression
- evaluation and <literal>nix-env -qa</literal>, all thanks to <link xlink:href="http://valgrind.org/">Valgrind</link>. Memory use has
- been reduced by a factor 8 or so. Big speedup by memoisation of
- path hashing.</para></listitem>
-
- <listitem><para>Lots of bug fixes, notably:
-
- <itemizedlist>
-
- <listitem><para>Make sure that the garbage collector can run
- successfully when the disk is full
- (<literal>NIX-18</literal>).</para></listitem>
-
- <listitem><para><command>nix-env</command> now locks the profile
- to prevent races between concurrent <command>nix-env</command>
- operations on the same profile
- (<literal>NIX-7</literal>).</para></listitem>
-
- <listitem><para>Removed misleading messages from
- <literal>nix-env -i</literal> (e.g., <literal>installing
- `foo'</literal> followed by <literal>uninstalling
- `foo'</literal>) (<literal>NIX-17</literal>).</para></listitem>
-
- </itemizedlist>
-
- </para></listitem>
-
- <listitem><para>Nix source distributions are a lot smaller now since
- we no longer include a full copy of the Berkeley DB source
- distribution (but only the bits we need).</para></listitem>
-
- <listitem><para>Header files are now installed so that external
- programs can use the Nix libraries.</para></listitem>
-
-</itemizedlist>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-relnotes-0.9.2">
-
-<title>Release 0.9.2 (2005-09-21)</title>
-
-<para>This bug fix release fixes two problems on Mac OS X:
-
-<itemizedlist>
-
- <listitem><para>If Nix was linked against statically linked versions
- of the ATerm or Berkeley DB library, there would be dynamic link
- errors at runtime.</para></listitem>
-
- <listitem><para><command>nix-pull</command> and
- <command>nix-push</command> intermittently failed due to race
- conditions involving pipes and child processes with error messages
- such as <literal>open2: open(GLOB(0x180b2e4), >&=9) failed: Bad
- file descriptor at /nix/bin/nix-pull line 77</literal> (issue
- <literal>NIX-14</literal>).</para></listitem>
-
-</itemizedlist>
-
-</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-relnotes-0.9.1">
-
-<title>Release 0.9.1 (2005-09-20)</title>
-
-<para>This bug fix release addresses a problem with the ATerm library
-when the <option>--with-aterm</option> flag in
-<command>configure</command> was <emphasis>not</emphasis> used.</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-relnotes-0.9">
-
-<title>Release 0.9 (2005-09-16)</title>
-
-<para>NOTE: this version of Nix uses Berkeley DB 4.3 instead of 4.2.
-The database is upgraded automatically, but you should be careful not
-to use old versions of Nix that still use Berkeley DB 4.2. In
-particular, if you use a Nix installed through Nix, you should run
-
-<screen>
-$ nix-store --clear-substitutes</screen>
-
-first.</para>
-
-
-<itemizedlist>
-
- <listitem><para>Unpacking of patch sequences is much faster now
- since we no longer do redundant unpacking and repacking of
- intermediate paths.</para></listitem>
-
- <listitem><para>Nix now uses Berkeley DB 4.3.</para></listitem>
-
- <listitem><para>The <function>derivation</function> primitive is
- lazier. Attributes of dependent derivations can mutually refer to
- each other (as long as there are no data dependencies on the
- <varname>outPath</varname> and <varname>drvPath</varname> attributes
- computed by <function>derivation</function>).</para>
-
- <para>For example, the expression <literal>derivation
- attrs</literal> now evaluates to (essentially)
-
- <programlisting>
-attrs // {
- type = "derivation";
- outPath = derivation! attrs;
- drvPath = derivation! attrs;
-}</programlisting>
-
- where <function>derivation!</function> is a primop that does the
- actual derivation instantiation (i.e., it does what
- <function>derivation</function> used to do). The advantage is that
- it allows commands such as <command>nix-env -qa</command> and
- <command>nix-env -i</command> to be much faster since they no longer
- need to instantiate all derivations, just the
- <varname>name</varname> attribute.</para>
-
- <para>Also, it allows derivations to cyclically reference each
- other, for example,
-
- <programlisting>
-webServer = derivation {
- ...
- hostName = "svn.cs.uu.nl";
- services = [svnService];
-};
-
-svnService = derivation {
- ...
- hostName = webServer.hostName;
-};</programlisting>
-
- Previously, this would yield a black hole (infinite recursion).</para>
-
- </listitem>
-
- <listitem><para><command>nix-build</command> now defaults to using
- <filename>./default.nix</filename> if no Nix expression is
- specified.</para></listitem>
-
- <listitem><para><command>nix-instantiate</command>, when applied to
- a Nix expression that evaluates to a function, will call the
- function automatically if all its arguments have
- defaults.</para></listitem>
-
- <listitem><para>Nix now uses libtool to build dynamic libraries.
- This reduces the size of executables.</para></listitem>
-
- <listitem><para>A new list concatenation operator
- <literal>++</literal>. For example, <literal>[1 2 3] ++ [4 5
- 6]</literal> evaluates to <literal>[1 2 3 4 5
- 6]</literal>.</para></listitem>
-
- <listitem><para>Some currently undocumented primops to support
- low-level build management using Nix (i.e., using Nix as a Make
- replacement). See the commit messages for <literal>r3578</literal>
- and <literal>r3580</literal>.</para></listitem>
-
- <listitem><para>Various bug fixes and performance
- improvements.</para></listitem>
-
-</itemizedlist>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-relnotes-0.8.1">
-
-<title>Release 0.8.1 (2005-04-13)</title>
-
-<para>This is a bug fix release.</para>
-
-<itemizedlist>
-
- <listitem><para>Patch downloading was broken.</para></listitem>
-
- <listitem><para>The garbage collector would not delete paths that
- had references from invalid (but substitutable)
- paths.</para></listitem>
-
-</itemizedlist>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-relnotes-0.8">
-
-<title>Release 0.8 (2005-04-11)</title>
-
-<para>NOTE: the hashing scheme in Nix 0.8 changed (as detailed below).
-As a result, <command>nix-pull</command> manifests and channels built
-for Nix 0.7 and below will not work anymore. However, the Nix
-expression language has not changed, so you can still build from
-source. Also, existing user environments continue to work. Nix 0.8
-will automatically upgrade the database schema of previous
-installations when it is first run.</para>
-
-<para>If you get the error message
-
-<screen>
-you have an old-style manifest `/nix/var/nix/manifests/[...]'; please
-delete it</screen>
-
-you should delete previously downloaded manifests:
-
-<screen>
-$ rm /nix/var/nix/manifests/*</screen>
-
-If <command>nix-channel</command> gives the error message
-
-<screen>
-manifest `http://catamaran.labs.cs.uu.nl/dist/nix/channels/[channel]/MANIFEST'
-is too old (i.e., for Nix <= 0.7)</screen>
-
-then you should unsubscribe from the offending channel
-(<command>nix-channel --remove
-<replaceable>URL</replaceable></command>; leave out
-<literal>/MANIFEST</literal>), and subscribe to the same URL, with
-<literal>channels</literal> replaced by <literal>channels-v3</literal>
-(e.g., <link xlink:href="http://catamaran.labs.cs.uu.nl/dist/nix/channels-v3/nixpkgs-unstable"/>).</para>
-
-<para>Nix 0.8 has the following improvements:
-
-<itemizedlist>
-
- <listitem><para>The cryptographic hashes used in store paths are now
- 160 bits long, but encoded in base-32 so that they are still only 32
- characters long (e.g.,
- <filename>/nix/store/csw87wag8bqlqk7ipllbwypb14xainap-atk-1.9.0</filename>).
- (This is actually a 160 bit truncation of a SHA-256
- hash.)</para></listitem>
-
- <listitem><para>Big cleanups and simplifications of the basic store
- semantics. The notion of “closure store expressions” is gone (and
- so is the notion of “successors”); the file system references of a
- store path are now just stored in the database.</para>
-
- <para>For instance, given any store path, you can query its closure:
-
- <screen>
-$ nix-store -qR $(which firefox)
-... lots of paths ...</screen>
-
- Also, Nix now remembers for each store path the derivation that
- built it (the “deriver”):
-
- <screen>
-$ nix-store -qR $(which firefox)
-/nix/store/4b0jx7vq80l9aqcnkszxhymsf1ffa5jd-firefox-1.0.1.drv</screen>
-
- So to see the build-time dependencies, you can do
-
- <screen>
-$ nix-store -qR $(nix-store -qd $(which firefox))</screen>
-
- or, in a nicer format:
-
- <screen>
-$ nix-store -q --tree $(nix-store -qd $(which firefox))</screen>
-
- </para>
-
- <para>File system references are also stored in reverse. For
- instance, you can query all paths that directly or indirectly use a
- certain Glibc:
-
- <screen>
-$ nix-store -q --referrers-closure \
- /nix/store/8lz9yc6zgmc0vlqmn2ipcpkjlmbi51vv-glibc-2.3.4</screen>
-
- </para>
-
- </listitem>
-
- <listitem><para>The concept of fixed-output derivations has been
- formalised. Previously, functions such as
- <function>fetchurl</function> in Nixpkgs used a hack (namely,
- explicitly specifying a store path hash) to prevent changes to, say,
- the URL of the file from propagating upwards through the dependency
- graph, causing rebuilds of everything. This can now be done cleanly
- by specifying the <varname>outputHash</varname> and
- <varname>outputHashAlgo</varname> attributes. Nix itself checks
- that the content of the output has the specified hash. (This is
- important for maintaining certain invariants necessary for future
- work on secure shared stores.)</para></listitem>
-
- <listitem><para>One-click installation :-) It is now possible to
- install any top-level component in Nixpkgs directly, through the web
- — see, e.g., <link xlink:href="http://catamaran.labs.cs.uu.nl/dist/nixpkgs-0.8/"/>.
- All you have to do is associate
- <filename>/nix/bin/nix-install-package</filename> with the MIME type
- <literal>application/nix-package</literal> (or the extension
- <filename>.nixpkg</filename>), and clicking on a package link will
- cause it to be installed, with all appropriate dependencies. If you
- just want to install some specific application, this is easier than
- subscribing to a channel.</para></listitem>
-
- <listitem><para><command>nix-store -r
- <replaceable>PATHS</replaceable></command> now builds all the
- derivations PATHS in parallel. Previously it did them sequentially
- (though exploiting possible parallelism between subderivations).
- This is nice for build farms.</para></listitem>
-
- <listitem><para><command>nix-channel</command> has new operations
- <option>--list</option> and
- <option>--remove</option>.</para></listitem>
-
- <listitem><para>New ways of installing components into user
- environments:
-
- <itemizedlist>
-
- <listitem><para>Copy from another user environment:
-
- <screen>
-$ nix-env -i --from-profile .../other-profile firefox</screen>
-
- </para></listitem>
-
- <listitem><para>Install a store derivation directly (bypassing the
- Nix expression language entirely):
-
- <screen>
-$ nix-env -i /nix/store/z58v41v21xd3...-aterm-2.3.1.drv</screen>
-
- (This is used to implement <command>nix-install-package</command>,
- which is therefore immune to evolution in the Nix expression
- language.)</para></listitem>
-
- <listitem><para>Install an already built store path directly:
-
- <screen>
-$ nix-env -i /nix/store/hsyj5pbn0d9i...-aterm-2.3.1</screen>
-
- </para></listitem>
-
- <listitem><para>Install the result of a Nix expression specified
- as a command-line argument:
-
- <screen>
-$ nix-env -f .../i686-linux.nix -i -E 'x: x.firefoxWrapper'</screen>
-
- The difference with the normal installation mode is that
- <option>-E</option> does not use the <varname>name</varname>
- attributes of derivations. Therefore, this can be used to
- disambiguate multiple derivations with the same
- name.</para></listitem>
-
- </itemizedlist></para></listitem>
-
- <listitem><para>A hash of the contents of a store path is now stored
- in the database after a successful build. This allows you to check
- whether store paths have been tampered with: <command>nix-store
- --verify --check-contents</command>.</para></listitem>
-
- <listitem>
-
- <para>Implemented a concurrent garbage collector. It is now
- always safe to run the garbage collector, even if other Nix
- operations are happening simultaneously.</para>
-
- <para>However, there can still be GC races if you use
- <command>nix-instantiate</command> and <command>nix-store
- --realise</command> directly to build things. To prevent races,
- use the <option>--add-root</option> flag of those commands.</para>
-
- </listitem>
-
- <listitem><para>The garbage collector now finally deletes paths in
- the right order (i.e., topologically sorted under the “references”
- relation), thus making it safe to interrupt the collector without
- risking a store that violates the closure
- invariant.</para></listitem>
-
- <listitem><para>Likewise, the substitute mechanism now downloads
- files in the right order, thus preserving the closure invariant at
- all times.</para></listitem>
-
- <listitem><para>The result of <command>nix-build</command> is now
- registered as a root of the garbage collector. If the
- <filename>./result</filename> link is deleted, the GC root
- disappears automatically.</para></listitem>
-
- <listitem>
-
- <para>The behaviour of the garbage collector can be changed
- globally by setting options in
- <filename>/nix/etc/nix/nix.conf</filename>.
-
- <itemizedlist>
-
- <listitem><para><literal>gc-keep-derivations</literal> specifies
- whether deriver links should be followed when searching for live
- paths.</para></listitem>
-
- <listitem><para><literal>gc-keep-outputs</literal> specifies
- whether outputs of derivations should be followed when searching
- for live paths.</para></listitem>
-
- <listitem><para><literal>env-keep-derivations</literal>
- specifies whether user environments should store the paths of
- derivations when they are added (thus keeping the derivations
- alive).</para></listitem>
-
- </itemizedlist>
-
- </para></listitem>
-
- <listitem><para>New <command>nix-env</command> query flags
- <option>--drv-path</option> and
- <option>--out-path</option>.</para></listitem>
-
- <listitem><para><command>fetchurl</command> allows SHA-1 and SHA-256
- in addition to MD5. Just specify the attribute
- <varname>sha1</varname> or <varname>sha256</varname> instead of
- <varname>md5</varname>.</para></listitem>
-
- <listitem><para>Manual updates.</para></listitem>
-
-</itemizedlist>
-
-</para>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-relnotes-0.7">
-
-<title>Release 0.7 (2005-01-12)</title>
-
-<itemizedlist>
-
- <listitem><para>Binary patching. When upgrading components using
- pre-built binaries (through nix-pull / nix-channel), Nix can
- automatically download and apply binary patches to already installed
- components instead of full downloads. Patching is “smart”: if there
- is a <emphasis>sequence</emphasis> of patches to an installed
- component, Nix will use it. Patches are currently generated
- automatically between Nixpkgs (pre-)releases.</para></listitem>
-
- <listitem><para>Simplifications to the substitute
- mechanism.</para></listitem>
-
- <listitem><para>Nix-pull now stores downloaded manifests in
- <filename>/nix/var/nix/manifests</filename>.</para></listitem>
-
- <listitem><para>Metadata on files in the Nix store is canonicalised
- after builds: the last-modified timestamp is set to 0 (00:00:00
- 1/1/1970), the mode is set to 0444 or 0555 (readable and possibly
- executable by all; setuid/setgid bits are dropped), and the group is
- set to the default. This ensures that the result of a build and an
- installation through a substitute is the same; and that timestamp
- dependencies are revealed.</para></listitem>
-
-</itemizedlist>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-relnotes-0.6">
-
-<title>Release 0.6 (2004-11-14)</title>
-
-<itemizedlist>
-
- <listitem>
- <para>Rewrite of the normalisation engine.
-
- <itemizedlist>
-
- <listitem><para>Multiple builds can now be performed in parallel
- (option <option>-j</option>).</para></listitem>
-
- <listitem><para>Distributed builds. Nix can now call a shell
- script to forward builds to Nix installations on remote
- machines, which may or may not be of the same platform
- type.</para></listitem>
-
- <listitem><para>Option <option>--fallback</option> allows
- recovery from broken substitutes.</para></listitem>
-
- <listitem><para>Option <option>--keep-going</option> causes
- building of other (unaffected) derivations to continue if one
- failed.</para></listitem>
-
- </itemizedlist>
-
- </para>
-
- </listitem>
-
- <listitem><para>Improvements to the garbage collector (i.e., it
- should actually work now).</para></listitem>
-
- <listitem><para>Setuid Nix installations allow a Nix store to be
- shared among multiple users.</para></listitem>
-
- <listitem><para>Substitute registration is much faster
- now.</para></listitem>
-
- <listitem><para>A utility <command>nix-build</command> to build a
- Nix expression and create a symlink to the result int the current
- directory; useful for testing Nix derivations.</para></listitem>
-
- <listitem><para>Manual updates.</para></listitem>
-
- <listitem>
-
- <para><command>nix-env</command> changes:
-
- <itemizedlist>
-
- <listitem><para>Derivations for other platforms are filtered out
- (which can be overridden using
- <option>--system-filter</option>).</para></listitem>
-
- <listitem><para><option>--install</option> by default now
- uninstall previous derivations with the same
- name.</para></listitem>
-
- <listitem><para><option>--upgrade</option> allows upgrading to a
- specific version.</para></listitem>
-
- <listitem><para>New operation
- <option>--delete-generations</option> to remove profile
- generations (necessary for effective garbage
- collection).</para></listitem>
-
- <listitem><para>Nicer output (sorted,
- columnised).</para></listitem>
-
- </itemizedlist>
-
- </para>
-
- </listitem>
-
- <listitem><para>More sensible verbosity levels all around (builder
- output is now shown always, unless <option>-Q</option> is
- given).</para></listitem>
-
- <listitem>
-
- <para>Nix expression language changes:
-
- <itemizedlist>
-
- <listitem><para>New language construct: <literal>with
- <replaceable>E1</replaceable>;
- <replaceable>E2</replaceable></literal> brings all attributes
- defined in the attribute set <replaceable>E1</replaceable> in
- scope in <replaceable>E2</replaceable>.</para></listitem>
-
- <listitem><para>Added a <function>map</function>
- function.</para></listitem>
-
- <listitem><para>Various new operators (e.g., string
- concatenation).</para></listitem>
-
- </itemizedlist>
-
- </para>
-
- </listitem>
-
- <listitem><para>Expression evaluation is much
- faster.</para></listitem>
-
- <listitem><para>An Emacs mode for editing Nix expressions (with
- syntax highlighting and indentation) has been
- added.</para></listitem>
-
- <listitem><para>Many bug fixes.</para></listitem>
-
-</itemizedlist>
-
-</section>
-<section xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xi="http://www.w3.org/2001/XInclude" version="5.0" xml:id="ch-relnotes-0.5">
-
-<title>Release 0.5 and earlier</title>
-
-<para>Please refer to the Subversion commit log messages.</para>
-
-</section>
-
-</appendix>
-
-<!--
-<appendix>
- <title>Nix Release Notes</title>
- <xi:include href="release-notes/release-notes.xml"
- xpointer="xmlns(x=http://docbook.org/ns/docbook)xpointer(x:article/x:section)" />
- </appendix>
--->
-
-</book>
diff --git a/doc/manual/src/command-ref/conf-file.md.tmp b/doc/manual/src/command-ref/conf-file.md.tmp
deleted file mode 100644
index 93d52069b..000000000
--- a/doc/manual/src/command-ref/conf-file.md.tmp
+++ /dev/null
@@ -1,52 +0,0 @@
-# Name
-
-`nix.conf` - Nix configuration file
-
-# Description
-
-By default Nix reads settings from the following places:
-
- - The system-wide configuration file `sysconfdir/nix/nix.conf` (i.e.
- `/etc/nix/nix.conf` on most systems), or `$NIX_CONF_DIR/nix.conf` if
- `NIX_CONF_DIR` is set. Values loaded in this file are not forwarded
- to the Nix daemon. The client assumes that the daemon has already
- loaded them.
-
- - If `NIX_USER_CONF_FILES` is set, then each path separated by `:`
- will be loaded in reverse order.
-
- Otherwise it will look for `nix/nix.conf` files in `XDG_CONFIG_DIRS`
- and `XDG_CONFIG_HOME`. If these are unset, it will look in
- `$HOME/.config/nix.conf`.
-
- - If `NIX_CONFIG` is set, its contents is treated as the contents of
- a configuration file.
-
-The configuration files consist of `name = value` pairs, one per
-line. Other files can be included with a line like `include path`,
-where *path* is interpreted relative to the current conf file and a
-missing file is an error unless `!include` is used instead. Comments
-start with a `#` character. Here is an example configuration file:
-
- keep-outputs = true # Nice for developers
- keep-derivations = true # Idem
-
-You can override settings on the command line using the `--option`
-flag, e.g. `--option keep-outputs false`. Every configuration setting
-also has a corresponding command line flag, e.g. `--max-jobs 16`; for
-Boolean settings, there are two flags to enable or disable the setting
-(e.g. `--keep-failed` and `--no-keep-failed`).
-
-A configuration setting usually overrides any previous value. However,
-you can prefix the name of the setting by `extra-` to *append* to the
-previous value. For instance,
-
- substituters = a b
- extra-substituters = c d
-
-defines the `substituters` setting to be `a b c d`. This is also
-available as a command line flag (e.g. `--extra-substituters`).
-
-The following settings are currently available:
-
-EvalCommand::getEvalState()0
diff --git a/doc/manual/src/command-ref/nix.md b/doc/manual/src/command-ref/nix.md
deleted file mode 100644
index acc7da3a6..000000000
--- a/doc/manual/src/command-ref/nix.md
+++ /dev/null
@@ -1,3021 +0,0 @@
-# Name
-
-`nix` - a tool for reproducible and declarative configuration management
-
-# Synopsis
-
-`nix` [*flags*...] *subcommand*
-
-# Flags
-
- - `--debug`
- enable debug output
-
- - `--help`
- show usage information
-
- - `--help-config`
- show configuration options
-
- - `--log-format` *format*
- format of log output; `raw`, `internal-json`, `bar` or `bar-with-logs`
-
- - `--no-net`
- disable substituters and consider all previously downloaded files up-to-date
-
- - `--option` *name* *value*
- set a Nix configuration option (overriding `nix.conf`)
-
- - `--print-build-logs` / `L`
- print full build logs on stderr
-
- - `--quiet`
- decrease verbosity level
-
- - `--refresh`
- consider all previously downloaded files out-of-date
-
- - `--verbose` / `v`
- increase verbosity level
-
- - `--version`
- show version information
-
-# Subcommand `nix add-to-store`
-
-## Name
-
-`nix add-to-store` - add a path to the Nix store
-
-## Synopsis
-
-`nix add-to-store` [*flags*...] *path*
-
-## Description
-
-
-Copy the file or directory *path* to the Nix store, and
-print the resulting store path on standard output.
-
-
-
-## Flags
-
- - `--dry-run`
- show what this command would do without doing it
-
- - `--flat`
- add flat file to the Nix store
-
- - `--name` / `n` *name*
- name component of the store path
-
-# Subcommand `nix build`
-
-## Name
-
-`nix build` - build a derivation or fetch a store path
-
-## Synopsis
-
-`nix build` [*flags*...] *installables*...
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--derivation`
- operate on the store derivation rather than its outputs
-
- - `--dry-run`
- show what this command would do without doing it
-
- - `--expr` *expr*
- evaluate attributes from *expr*
-
- - `--file` / `f` *file*
- evaluate *file* rather than the default
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--no-link`
- do not create a symlink to the build result
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--out-link` / `o` *path*
- path of the symlink to the build result
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--profile` *path*
- profile to update
-
- - `--rebuild`
- rebuild an already built package and compare the result to the existing store paths
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--update-input` *input-path*
- update a specific flake input
-
-## Examples
-
-To build and run GNU Hello from NixOS 17.03:
-
-```console
-nix build -f channel:nixos-17.03 hello; ./result/bin/hello
-```
-
-To build the build.x86_64-linux attribute from release.nix:
-
-```console
-nix build -f release.nix build.x86_64-linux
-```
-
-To make a profile point at GNU Hello:
-
-```console
-nix build --profile /tmp/profile nixpkgs#hello
-```
-
-# Subcommand `nix bundle`
-
-## Name
-
-`nix bundle` - bundle an application so that it works outside of the Nix store
-
-## Synopsis
-
-`nix bundle` [*flags*...] *installable*
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--bundler` *flake-url*
- use custom bundler
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--derivation`
- operate on the store derivation rather than its outputs
-
- - `--expr` *expr*
- evaluate attributes from *expr*
-
- - `--file` / `f` *file*
- evaluate *file* rather than the default
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--out-link` / `o` *path*
- path of the symlink to the build result
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--update-input` *input-path*
- update a specific flake input
-
-## Examples
-
-To bundle Hello:
-
-```console
-nix bundle hello
-```
-
-# Subcommand `nix cat-nar`
-
-## Name
-
-`nix cat-nar` - print the contents of a file inside a NAR file on stdout
-
-## Synopsis
-
-`nix cat-nar` [*flags*...] *nar* *path*
-
-# Subcommand `nix cat-store`
-
-## Name
-
-`nix cat-store` - print the contents of a file in the Nix store on stdout
-
-## Synopsis
-
-`nix cat-store` [*flags*...] *path*
-
-# Subcommand `nix copy`
-
-## Name
-
-`nix copy` - copy paths between Nix stores
-
-## Synopsis
-
-`nix copy` [*flags*...] *installables*...
-
-## Flags
-
- - `--all`
- apply operation to the entire store
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--derivation`
- operate on the store derivation rather than its outputs
-
- - `--expr` *expr*
- evaluate attributes from *expr*
-
- - `--file` / `f` *file*
- evaluate *file* rather than the default
-
- - `--from` *store-uri*
- URI of the source Nix store
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--no-check-sigs`
- do not require that paths are signed by trusted keys
-
- - `--no-recursive`
- apply operation to specified paths only
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--substitute-on-destination` / `s`
- whether to try substitutes on the destination store (only supported by SSH)
-
- - `--to` *store-uri*
- URI of the destination Nix store
-
- - `--update-input` *input-path*
- update a specific flake input
-
-## Examples
-
-To copy Firefox from the local store to a binary cache in file:///tmp/cache:
-
-```console
-nix copy --to file:///tmp/cache $(type -p firefox)
-```
-
-To copy the entire current NixOS system closure to another machine via SSH:
-
-```console
-nix copy --to ssh://server /run/current-system
-```
-
-To copy a closure from another machine via SSH:
-
-```console
-nix copy --from ssh://server /nix/store/a6cnl93nk1wxnq84brbbwr6hxw9gp2w9-blender-2.79-rc2
-```
-
-To copy Hello to an S3 binary cache:
-
-```console
-nix copy --to s3://my-bucket?region=eu-west-1 nixpkgs#hello
-```
-
-To copy Hello to an S3-compatible binary cache:
-
-```console
-nix copy --to s3://my-bucket?region=eu-west-1&endpoint=example.com nixpkgs#hello
-```
-
-# Subcommand `nix copy-sigs`
-
-## Name
-
-`nix copy-sigs` - copy path signatures from substituters (like binary caches)
-
-## Synopsis
-
-`nix copy-sigs` [*flags*...] *installables*...
-
-## Flags
-
- - `--all`
- apply operation to the entire store
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--derivation`
- operate on the store derivation rather than its outputs
-
- - `--expr` *expr*
- evaluate attributes from *expr*
-
- - `--file` / `f` *file*
- evaluate *file* rather than the default
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--recursive` / `r`
- apply operation to closure of the specified paths
-
- - `--substituter` / `s` *store-uri*
- use signatures from specified store
-
- - `--update-input` *input-path*
- update a specific flake input
-
-# Subcommand `nix describe-stores`
-
-## Name
-
-`nix describe-stores` - show registered store types and their available options
-
-## Synopsis
-
-`nix describe-stores` [*flags*...]
-
-## Flags
-
- - `--json`
- produce JSON output
-
-# Subcommand `nix develop`
-
-## Name
-
-`nix develop` - run a bash shell that provides the build environment of a derivation
-
-## Synopsis
-
-`nix develop` [*flags*...] *installable*
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--build`
- run the build phase
-
- - `--check`
- run the check phase
-
- - `--command` / `c` *command* *args*
- command and arguments to be executed instead of an interactive shell
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--configure`
- run the configure phase
-
- - `--derivation`
- operate on the store derivation rather than its outputs
-
- - `--expr` *expr*
- evaluate attributes from *expr*
-
- - `--file` / `f` *file*
- evaluate *file* rather than the default
-
- - `--ignore-environment` / `i`
- clear the entire environment (except those specified with --keep)
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--install`
- run the install phase
-
- - `--installcheck`
- run the installcheck phase
-
- - `--keep` / `k` *name*
- keep specified environment variable
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--phase` *phase-name*
- phase to run (e.g. `build` or `configure`)
-
- - `--profile` *path*
- profile to update
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--redirect` *installable* *outputs-dir*
- redirect a store path to a mutable location
-
- - `--unset` / `u` *name*
- unset specified environment variable
-
- - `--update-input` *input-path*
- update a specific flake input
-
-## Examples
-
-To get the build environment of GNU hello:
-
-```console
-nix develop nixpkgs#hello
-```
-
-To get the build environment of the default package of flake in the current directory:
-
-```console
-nix develop
-```
-
-To store the build environment in a profile:
-
-```console
-nix develop --profile /tmp/my-shell nixpkgs#hello
-```
-
-To use a build environment previously recorded in a profile:
-
-```console
-nix develop /tmp/my-shell
-```
-
-To replace all occurences of a store path with a writable directory:
-
-```console
-nix develop --redirect nixpkgs#glibc.dev ~/my-glibc/outputs/dev
-```
-
-# Subcommand `nix diff-closures`
-
-## Name
-
-`nix diff-closures` - show what packages and versions were added and removed between two closures
-
-## Synopsis
-
-`nix diff-closures` [*flags*...] *before* *after*
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--derivation`
- operate on the store derivation rather than its outputs
-
- - `--expr` *expr*
- evaluate attributes from *expr*
-
- - `--file` / `f` *file*
- evaluate *file* rather than the default
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--update-input` *input-path*
- update a specific flake input
-
-## Examples
-
-To show what got added and removed between two versions of the NixOS system profile:
-
-```console
-nix diff-closures /nix/var/nix/profiles/system-655-link /nix/var/nix/profiles/system-658-link
-```
-
-# Subcommand `nix doctor`
-
-## Name
-
-`nix doctor` - check your system for potential problems and print a PASS or FAIL for each check
-
-## Synopsis
-
-`nix doctor` [*flags*...]
-
-# Subcommand `nix dump-path`
-
-## Name
-
-`nix dump-path` - dump a store path to stdout (in NAR format)
-
-## Synopsis
-
-`nix dump-path` [*flags*...] *installables*...
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--derivation`
- operate on the store derivation rather than its outputs
-
- - `--expr` *expr*
- evaluate attributes from *expr*
-
- - `--file` / `f` *file*
- evaluate *file* rather than the default
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--update-input` *input-path*
- update a specific flake input
-
-## Examples
-
-To get a NAR from the binary cache https://cache.nixos.org/:
-
-```console
-nix dump-path --store https://cache.nixos.org/ /nix/store/7crrmih8c52r8fbnqb933dxrsp44md93-glibc-2.25
-```
-
-# Subcommand `nix edit`
-
-## Name
-
-`nix edit` - open the Nix expression of a Nix package in $EDITOR
-
-## Synopsis
-
-`nix edit` [*flags*...] *installable*
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--derivation`
- operate on the store derivation rather than its outputs
-
- - `--expr` *expr*
- evaluate attributes from *expr*
-
- - `--file` / `f` *file*
- evaluate *file* rather than the default
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--update-input` *input-path*
- update a specific flake input
-
-## Examples
-
-To open the Nix expression of the GNU Hello package:
-
-```console
-nix edit nixpkgs#hello
-```
-
-# Subcommand `nix eval`
-
-## Name
-
-`nix eval` - evaluate a Nix expression
-
-## Synopsis
-
-`nix eval` [*flags*...] *installable*
-
-## Flags
-
- - `--apply` *expr*
- apply a function to each argument
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--derivation`
- operate on the store derivation rather than its outputs
-
- - `--expr` *expr*
- evaluate attributes from *expr*
-
- - `--file` / `f` *file*
- evaluate *file* rather than the default
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--json`
- produce JSON output
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--raw`
- print strings unquoted
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--update-input` *input-path*
- update a specific flake input
-
-## Examples
-
-To evaluate a Nix expression given on the command line:
-
-```console
-nix eval --expr '1 + 2'
-```
-
-To evaluate a Nix expression from a file or URI:
-
-```console
-nix eval -f ./my-nixpkgs hello.name
-```
-
-To get the current version of Nixpkgs:
-
-```console
-nix eval --raw nixpkgs#lib.version
-```
-
-To print the store path of the Hello package:
-
-```console
-nix eval --raw nixpkgs#hello
-```
-
-To get a list of checks in the 'nix' flake:
-
-```console
-nix eval nix#checks.x86_64-linux --apply builtins.attrNames
-```
-
-# Subcommand `nix flake`
-
-## Name
-
-`nix flake` - manage Nix flakes
-
-## Synopsis
-
-`nix flake` [*flags*...] *subcommand*
-
-# Subcommand `nix flake archive`
-
-## Name
-
-`nix flake archive` - copy a flake and all its inputs to a store
-
-## Synopsis
-
-`nix flake archive` [*flags*...] *flake-url*
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--dry-run`
- show what this command would do without doing it
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--json`
- produce JSON output
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--to` *store-uri*
- URI of the destination Nix store
-
- - `--update-input` *input-path*
- update a specific flake input
-
-## Examples
-
-To copy the dwarffs flake and its dependencies to a binary cache:
-
-```console
-nix flake archive --to file:///tmp/my-cache dwarffs
-```
-
-To fetch the dwarffs flake and its dependencies to the local Nix store:
-
-```console
-nix flake archive dwarffs
-```
-
-To print the store paths of the flake sources of NixOps without fetching them:
-
-```console
-nix flake archive --json --dry-run nixops
-```
-
-# Subcommand `nix flake check`
-
-## Name
-
-`nix flake check` - check whether the flake evaluates and run its tests
-
-## Synopsis
-
-`nix flake check` [*flags*...] *flake-url*
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--no-build`
- do not build checks
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--update-input` *input-path*
- update a specific flake input
-
-# Subcommand `nix flake clone`
-
-## Name
-
-`nix flake clone` - clone flake repository
-
-## Synopsis
-
-`nix flake clone` [*flags*...] *flake-url*
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--dest` / `f` *path*
- destination path
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--update-input` *input-path*
- update a specific flake input
-
-# Subcommand `nix flake info`
-
-## Name
-
-`nix flake info` - list info about a given flake
-
-## Synopsis
-
-`nix flake info` [*flags*...] *flake-url*
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--json`
- produce JSON output
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--update-input` *input-path*
- update a specific flake input
-
-# Subcommand `nix flake init`
-
-## Name
-
-`nix flake init` - create a flake in the current directory from a template
-
-## Synopsis
-
-`nix flake init` [*flags*...]
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--template` / `t` *template*
- the template to use
-
-## Examples
-
-To create a flake using the default template:
-
-```console
-nix flake init
-```
-
-To see available templates:
-
-```console
-nix flake show templates
-```
-
-To create a flake from a specific template:
-
-```console
-nix flake init -t templates#nixos-container
-```
-
-# Subcommand `nix flake list-inputs`
-
-## Name
-
-`nix flake list-inputs` - list flake inputs
-
-## Synopsis
-
-`nix flake list-inputs` [*flags*...] *flake-url*
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--json`
- produce JSON output
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--update-input` *input-path*
- update a specific flake input
-
-# Subcommand `nix flake new`
-
-## Name
-
-`nix flake new` - create a flake in the specified directory from a template
-
-## Synopsis
-
-`nix flake new` [*flags*...] *dest-dir*
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--template` / `t` *template*
- the template to use
-
-# Subcommand `nix flake show`
-
-## Name
-
-`nix flake show` - show the outputs provided by a flake
-
-## Synopsis
-
-`nix flake show` [*flags*...] *flake-url*
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--legacy`
- show the contents of the 'legacyPackages' output
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--update-input` *input-path*
- update a specific flake input
-
-# Subcommand `nix flake update`
-
-## Name
-
-`nix flake update` - update flake lock file
-
-## Synopsis
-
-`nix flake update` [*flags*...] *flake-url*
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--update-input` *input-path*
- update a specific flake input
-
-# Subcommand `nix hash-file`
-
-## Name
-
-`nix hash-file` - print cryptographic hash of a regular file
-
-## Synopsis
-
-`nix hash-file` [*flags*...] *paths*...
-
-## Flags
-
- - `--base16`
- print hash in base-16
-
- - `--base32`
- print hash in base-32 (Nix-specific)
-
- - `--base64`
- print hash in base-64
-
- - `--sri`
- print hash in SRI format
-
- - `--type` *hash-algo*
- hash algorithm ('md5', 'sha1', 'sha256', or 'sha512')
-
-# Subcommand `nix hash-path`
-
-## Name
-
-`nix hash-path` - print cryptographic hash of the NAR serialisation of a path
-
-## Synopsis
-
-`nix hash-path` [*flags*...] *paths*...
-
-## Flags
-
- - `--base16`
- print hash in base-16
-
- - `--base32`
- print hash in base-32 (Nix-specific)
-
- - `--base64`
- print hash in base-64
-
- - `--sri`
- print hash in SRI format
-
- - `--type` *hash-algo*
- hash algorithm ('md5', 'sha1', 'sha256', or 'sha512')
-
-# Subcommand `nix log`
-
-## Name
-
-`nix log` - show the build log of the specified packages or paths, if available
-
-## Synopsis
-
-`nix log` [*flags*...] *installable*
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--derivation`
- operate on the store derivation rather than its outputs
-
- - `--expr` *expr*
- evaluate attributes from *expr*
-
- - `--file` / `f` *file*
- evaluate *file* rather than the default
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--update-input` *input-path*
- update a specific flake input
-
-## Examples
-
-To get the build log of GNU Hello:
-
-```console
-nix log nixpkgs#hello
-```
-
-To get the build log of a specific path:
-
-```console
-nix log /nix/store/lmngj4wcm9rkv3w4dfhzhcyij3195hiq-thunderbird-52.2.1
-```
-
-To get a build log from a specific binary cache:
-
-```console
-nix log --store https://cache.nixos.org nixpkgs#hello
-```
-
-# Subcommand `nix ls-nar`
-
-## Name
-
-`nix ls-nar` - show information about a path inside a NAR file
-
-## Synopsis
-
-`nix ls-nar` [*flags*...] *nar* *path*
-
-## Flags
-
- - `--directory` / `d`
- show directories rather than their contents
-
- - `--json`
- produce JSON output
-
- - `--long` / `l`
- show more file information
-
- - `--recursive` / `R`
- list subdirectories recursively
-
-## Examples
-
-To list a specific file in a NAR:
-
-```console
-nix ls-nar -l hello.nar /bin/hello
-```
-
-# Subcommand `nix ls-store`
-
-## Name
-
-`nix ls-store` - show information about a path in the Nix store
-
-## Synopsis
-
-`nix ls-store` [*flags*...] *path*
-
-## Flags
-
- - `--directory` / `d`
- show directories rather than their contents
-
- - `--json`
- produce JSON output
-
- - `--long` / `l`
- show more file information
-
- - `--recursive` / `R`
- list subdirectories recursively
-
-## Examples
-
-To list the contents of a store path in a binary cache:
-
-```console
-nix ls-store --store https://cache.nixos.org/ -lR /nix/store/0i2jd68mp5g6h2sa5k9c85rb80sn8hi9-hello-2.10
-```
-
-# Subcommand `nix make-content-addressable`
-
-## Name
-
-`nix make-content-addressable` - rewrite a path or closure to content-addressable form
-
-## Synopsis
-
-`nix make-content-addressable` [*flags*...] *installables*...
-
-## Flags
-
- - `--all`
- apply operation to the entire store
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--derivation`
- operate on the store derivation rather than its outputs
-
- - `--expr` *expr*
- evaluate attributes from *expr*
-
- - `--file` / `f` *file*
- evaluate *file* rather than the default
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--json`
- produce JSON output
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--recursive` / `r`
- apply operation to closure of the specified paths
-
- - `--update-input` *input-path*
- update a specific flake input
-
-## Examples
-
-To create a content-addressable representation of GNU Hello (but not its dependencies):
-
-```console
-nix make-content-addressable nixpkgs#hello
-```
-
-To compute a content-addressable representation of the current NixOS system closure:
-
-```console
-nix make-content-addressable -r /run/current-system
-```
-
-# Subcommand `nix optimise-store`
-
-## Name
-
-`nix optimise-store` - replace identical files in the store by hard links
-
-## Synopsis
-
-`nix optimise-store` [*flags*...]
-
-## Examples
-
-To optimise the Nix store:
-
-```console
-nix optimise-store
-```
-
-# Subcommand `nix path-info`
-
-## Name
-
-`nix path-info` - query information about store paths
-
-## Synopsis
-
-`nix path-info` [*flags*...] *installables*...
-
-## Flags
-
- - `--all`
- apply operation to the entire store
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--closure-size` / `S`
- print sum size of the NAR dumps of the closure of each path
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--derivation`
- operate on the store derivation rather than its outputs
-
- - `--expr` *expr*
- evaluate attributes from *expr*
-
- - `--file` / `f` *file*
- evaluate *file* rather than the default
-
- - `--human-readable` / `h`
- with -s and -S, print sizes like 1K 234M 5.67G etc.
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--json`
- produce JSON output
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--recursive` / `r`
- apply operation to closure of the specified paths
-
- - `--sigs`
- show signatures
-
- - `--size` / `s`
- print size of the NAR dump of each path
-
- - `--update-input` *input-path*
- update a specific flake input
-
-## Examples
-
-To show the closure sizes of every path in the current NixOS system closure, sorted by size:
-
-```console
-nix path-info -rS /run/current-system | sort -nk2
-```
-
-To show a package's closure size and all its dependencies with human readable sizes:
-
-```console
-nix path-info -rsSh nixpkgs#rust
-```
-
-To check the existence of a path in a binary cache:
-
-```console
-nix path-info -r /nix/store/7qvk5c91...-geeqie-1.1 --store https://cache.nixos.org/
-```
-
-To print the 10 most recently added paths (using --json and the jq(1) command):
-
-```console
-nix path-info --json --all | jq -r 'sort_by(.registrationTime)[-11:-1][].path'
-```
-
-To show the size of the entire Nix store:
-
-```console
-nix path-info --json --all | jq 'map(.narSize) | add'
-```
-
-To show every path whose closure is bigger than 1 GB, sorted by closure size:
-
-```console
-nix path-info --json --all -S | jq 'map(select(.closureSize > 1e9)) | sort_by(.closureSize) | map([.path, .closureSize])'
-```
-
-# Subcommand `nix ping-store`
-
-## Name
-
-`nix ping-store` - test whether a store can be opened
-
-## Synopsis
-
-`nix ping-store` [*flags*...]
-
-## Examples
-
-To test whether connecting to a remote Nix store via SSH works:
-
-```console
-nix ping-store --store ssh://mac1
-```
-
-# Subcommand `nix print-dev-env`
-
-## Name
-
-`nix print-dev-env` - print shell code that can be sourced by bash to reproduce the build environment of a derivation
-
-## Synopsis
-
-`nix print-dev-env` [*flags*...] *installable*
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--derivation`
- operate on the store derivation rather than its outputs
-
- - `--expr` *expr*
- evaluate attributes from *expr*
-
- - `--file` / `f` *file*
- evaluate *file* rather than the default
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--profile` *path*
- profile to update
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--redirect` *installable* *outputs-dir*
- redirect a store path to a mutable location
-
- - `--update-input` *input-path*
- update a specific flake input
-
-## Examples
-
-To apply the build environment of GNU hello to the current shell:
-
-```console
-. <(nix print-dev-env nixpkgs#hello)
-```
-
-# Subcommand `nix profile`
-
-## Name
-
-`nix profile` - manage Nix profiles
-
-## Synopsis
-
-`nix profile` [*flags*...] *subcommand*
-
-# Subcommand `nix profile diff-closures`
-
-## Name
-
-`nix profile diff-closures` - show the closure difference between each generation of a profile
-
-## Synopsis
-
-`nix profile diff-closures` [*flags*...]
-
-## Flags
-
- - `--profile` *path*
- profile to update
-
-## Examples
-
-To show what changed between each generation of the NixOS system profile:
-
-```console
-nix profile diff-closure --profile /nix/var/nix/profiles/system
-```
-
-# Subcommand `nix profile info`
-
-## Name
-
-`nix profile info` - list installed packages
-
-## Synopsis
-
-`nix profile info` [*flags*...]
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--profile` *path*
- profile to update
-
-## Examples
-
-To show what packages are installed in the default profile:
-
-```console
-nix profile info
-```
-
-# Subcommand `nix profile install`
-
-## Name
-
-`nix profile install` - install a package into a profile
-
-## Synopsis
-
-`nix profile install` [*flags*...] *installables*...
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--derivation`
- operate on the store derivation rather than its outputs
-
- - `--expr` *expr*
- evaluate attributes from *expr*
-
- - `--file` / `f` *file*
- evaluate *file* rather than the default
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--profile` *path*
- profile to update
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--update-input` *input-path*
- update a specific flake input
-
-## Examples
-
-To install a package from Nixpkgs:
-
-```console
-nix profile install nixpkgs#hello
-```
-
-To install a package from a specific branch of Nixpkgs:
-
-```console
-nix profile install nixpkgs/release-19.09#hello
-```
-
-To install a package from a specific revision of Nixpkgs:
-
-```console
-nix profile install nixpkgs/1028bb33859f8dfad7f98e1c8d185f3d1aaa7340#hello
-```
-
-# Subcommand `nix profile remove`
-
-## Name
-
-`nix profile remove` - remove packages from a profile
-
-## Synopsis
-
-`nix profile remove` [*flags*...] *elements*...
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--profile` *path*
- profile to update
-
-## Examples
-
-To remove a package by attribute path:
-
-```console
-nix profile remove packages.x86_64-linux.hello
-```
-
-To remove all packages:
-
-```console
-nix profile remove '.*'
-```
-
-To remove a package by store path:
-
-```console
-nix profile remove /nix/store/rr3y0c6zyk7kjjl8y19s4lsrhn4aiq1z-hello-2.10
-```
-
-To remove a package by position:
-
-```console
-nix profile remove 3
-```
-
-# Subcommand `nix profile upgrade`
-
-## Name
-
-`nix profile upgrade` - upgrade packages using their most recent flake
-
-## Synopsis
-
-`nix profile upgrade` [*flags*...] *elements*...
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--derivation`
- operate on the store derivation rather than its outputs
-
- - `--expr` *expr*
- evaluate attributes from *expr*
-
- - `--file` / `f` *file*
- evaluate *file* rather than the default
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--profile` *path*
- profile to update
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--update-input` *input-path*
- update a specific flake input
-
-## Examples
-
-To upgrade all packages that were installed using a mutable flake reference:
-
-```console
-nix profile upgrade '.*'
-```
-
-To upgrade a specific package:
-
-```console
-nix profile upgrade packages.x86_64-linux.hello
-```
-
-# Subcommand `nix registry`
-
-## Name
-
-`nix registry` - manage the flake registry
-
-## Synopsis
-
-`nix registry` [*flags*...] *subcommand*
-
-# Subcommand `nix registry add`
-
-## Name
-
-`nix registry add` - add/replace flake in user flake registry
-
-## Synopsis
-
-`nix registry add` [*flags*...] *from-url* *to-url*
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
-# Subcommand `nix registry list`
-
-## Name
-
-`nix registry list` - list available Nix flakes
-
-## Synopsis
-
-`nix registry list` [*flags*...]
-
-# Subcommand `nix registry pin`
-
-## Name
-
-`nix registry pin` - pin a flake to its current version in user flake registry
-
-## Synopsis
-
-`nix registry pin` [*flags*...] *url*
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
-# Subcommand `nix registry remove`
-
-## Name
-
-`nix registry remove` - remove flake from user flake registry
-
-## Synopsis
-
-`nix registry remove` [*flags*...] *url*
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
-# Subcommand `nix repl`
-
-## Name
-
-`nix repl` - start an interactive environment for evaluating Nix expressions
-
-## Synopsis
-
-`nix repl` [*flags*...] *files*...
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
-## Examples
-
-Display all special commands within the REPL:
-
-```console
-nix repl
-nix-repl> :?
-```
-
-# Subcommand `nix run`
-
-## Name
-
-`nix run` - run a Nix application
-
-## Synopsis
-
-`nix run` [*flags*...] *installable* *args*...
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--derivation`
- operate on the store derivation rather than its outputs
-
- - `--expr` *expr*
- evaluate attributes from *expr*
-
- - `--file` / `f` *file*
- evaluate *file* rather than the default
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--update-input` *input-path*
- update a specific flake input
-
-## Examples
-
-To run Blender:
-
-```console
-nix run blender-bin
-```
-
-To run vim from nixpkgs:
-
-```console
-nix run nixpkgs#vim
-```
-
-To run vim from nixpkgs with arguments:
-
-```console
-nix run nixpkgs#vim -- --help
-```
-
-# Subcommand `nix search`
-
-## Name
-
-`nix search` - query available packages
-
-## Synopsis
-
-`nix search` [*flags*...] *installable* *regex*...
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--derivation`
- operate on the store derivation rather than its outputs
-
- - `--expr` *expr*
- evaluate attributes from *expr*
-
- - `--file` / `f` *file*
- evaluate *file* rather than the default
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--json`
- produce JSON output
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--update-input` *input-path*
- update a specific flake input
-
-## Examples
-
-To show all packages in the flake in the current directory:
-
-```console
-nix search
-```
-
-To show packages in the 'nixpkgs' flake containing 'blender' in its name or description:
-
-```console
-nix search nixpkgs blender
-```
-
-To search for Firefox or Chromium:
-
-```console
-nix search nixpkgs 'firefox|chromium'
-```
-
-To search for packages containing 'git' and either 'frontend' or 'gui':
-
-```console
-nix search nixpkgs git 'frontend|gui'
-```
-
-# Subcommand `nix shell`
-
-## Name
-
-`nix shell` - run a shell in which the specified packages are available
-
-## Synopsis
-
-`nix shell` [*flags*...] *installables*...
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--command` / `c` *command* *args*
- command and arguments to be executed; defaults to '$SHELL'
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--derivation`
- operate on the store derivation rather than its outputs
-
- - `--expr` *expr*
- evaluate attributes from *expr*
-
- - `--file` / `f` *file*
- evaluate *file* rather than the default
-
- - `--ignore-environment` / `i`
- clear the entire environment (except those specified with --keep)
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--keep` / `k` *name*
- keep specified environment variable
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--unset` / `u` *name*
- unset specified environment variable
-
- - `--update-input` *input-path*
- update a specific flake input
-
-## Examples
-
-To start a shell providing GNU Hello from NixOS 20.03:
-
-```console
-nix shell nixpkgs/nixos-20.03#hello
-```
-
-To start a shell providing youtube-dl from your 'nixpkgs' channel:
-
-```console
-nix shell nixpkgs#youtube-dl
-```
-
-To run GNU Hello:
-
-```console
-nix shell nixpkgs#hello -c hello --greeting 'Hi everybody!'
-```
-
-To run GNU Hello in a chroot store:
-
-```console
-nix shell --store ~/my-nix nixpkgs#hello -c hello
-```
-
-# Subcommand `nix show-config`
-
-## Name
-
-`nix show-config` - show the Nix configuration
-
-## Synopsis
-
-`nix show-config` [*flags*...]
-
-## Flags
-
- - `--json`
- produce JSON output
-
-# Subcommand `nix show-derivation`
-
-## Name
-
-`nix show-derivation` - show the contents of a store derivation
-
-## Synopsis
-
-`nix show-derivation` [*flags*...] *installables*...
-
-## Flags
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--derivation`
- operate on the store derivation rather than its outputs
-
- - `--expr` *expr*
- evaluate attributes from *expr*
-
- - `--file` / `f` *file*
- evaluate *file* rather than the default
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--recursive` / `r`
- include the dependencies of the specified derivations
-
- - `--update-input` *input-path*
- update a specific flake input
-
-## Examples
-
-To show the store derivation that results from evaluating the Hello package:
-
-```console
-nix show-derivation nixpkgs#hello
-```
-
-To show the full derivation graph (if available) that produced your NixOS system:
-
-```console
-nix show-derivation -r /run/current-system
-```
-
-# Subcommand `nix sign-paths`
-
-## Name
-
-`nix sign-paths` - sign the specified paths
-
-## Synopsis
-
-`nix sign-paths` [*flags*...] *installables*...
-
-## Flags
-
- - `--all`
- apply operation to the entire store
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--derivation`
- operate on the store derivation rather than its outputs
-
- - `--expr` *expr*
- evaluate attributes from *expr*
-
- - `--file` / `f` *file*
- evaluate *file* rather than the default
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--key-file` / `k` *file*
- file containing the secret signing key
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--recursive` / `r`
- apply operation to closure of the specified paths
-
- - `--update-input` *input-path*
- update a specific flake input
-
-# Subcommand `nix to-base16`
-
-## Name
-
-`nix to-base16` - convert a hash to base-16 representation
-
-## Synopsis
-
-`nix to-base16` [*flags*...] *strings*...
-
-## Flags
-
- - `--type` *hash-algo*
- hash algorithm ('md5', 'sha1', 'sha256', or 'sha512'). Optional as can also be gotten from SRI hash itself.
-
-# Subcommand `nix to-base32`
-
-## Name
-
-`nix to-base32` - convert a hash to base-32 representation
-
-## Synopsis
-
-`nix to-base32` [*flags*...] *strings*...
-
-## Flags
-
- - `--type` *hash-algo*
- hash algorithm ('md5', 'sha1', 'sha256', or 'sha512'). Optional as can also be gotten from SRI hash itself.
-
-# Subcommand `nix to-base64`
-
-## Name
-
-`nix to-base64` - convert a hash to base-64 representation
-
-## Synopsis
-
-`nix to-base64` [*flags*...] *strings*...
-
-## Flags
-
- - `--type` *hash-algo*
- hash algorithm ('md5', 'sha1', 'sha256', or 'sha512'). Optional as can also be gotten from SRI hash itself.
-
-# Subcommand `nix to-sri`
-
-## Name
-
-`nix to-sri` - convert a hash to SRI representation
-
-## Synopsis
-
-`nix to-sri` [*flags*...] *strings*...
-
-## Flags
-
- - `--type` *hash-algo*
- hash algorithm ('md5', 'sha1', 'sha256', or 'sha512'). Optional as can also be gotten from SRI hash itself.
-
-# Subcommand `nix upgrade-nix`
-
-## Name
-
-`nix upgrade-nix` - upgrade Nix to the latest stable version
-
-## Synopsis
-
-`nix upgrade-nix` [*flags*...]
-
-## Flags
-
- - `--dry-run`
- show what this command would do without doing it
-
- - `--nix-store-paths-url` *url*
- URL of the file that contains the store paths of the latest Nix release
-
- - `--profile` / `p` *profile-dir*
- the Nix profile to upgrade
-
-## Examples
-
-To upgrade Nix to the latest stable version:
-
-```console
-nix upgrade-nix
-```
-
-To upgrade Nix in a specific profile:
-
-```console
-nix upgrade-nix -p /nix/var/nix/profiles/per-user/alice/profile
-```
-
-# Subcommand `nix verify`
-
-## Name
-
-`nix verify` - verify the integrity of store paths
-
-## Synopsis
-
-`nix verify` [*flags*...] *installables*...
-
-## Flags
-
- - `--all`
- apply operation to the entire store
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--derivation`
- operate on the store derivation rather than its outputs
-
- - `--expr` *expr*
- evaluate attributes from *expr*
-
- - `--file` / `f` *file*
- evaluate *file* rather than the default
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--no-contents`
- do not verify the contents of each store path
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-trust`
- do not verify whether each store path is trusted
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--recursive` / `r`
- apply operation to closure of the specified paths
-
- - `--sigs-needed` / `n` *N*
- require that each path has at least N valid signatures
-
- - `--substituter` / `s` *store-uri*
- use signatures from specified store
-
- - `--update-input` *input-path*
- update a specific flake input
-
-## Examples
-
-To verify the entire Nix store:
-
-```console
-nix verify --all
-```
-
-To check whether each path in the closure of Firefox has at least 2 signatures:
-
-```console
-nix verify -r -n2 --no-contents $(type -p firefox)
-```
-
-# Subcommand `nix why-depends`
-
-## Name
-
-`nix why-depends` - show why a package has another package in its closure
-
-## Synopsis
-
-`nix why-depends` [*flags*...] *package* *dependency*
-
-## Flags
-
- - `--all` / `a`
- show all edges in the dependency graph leading from 'package' to 'dependency', rather than just a shortest path
-
- - `--arg` *name* *expr*
- argument to be passed to Nix functions
-
- - `--argstr` *name* *string*
- string-valued argument to be passed to Nix functions
-
- - `--commit-lock-file`
- commit changes to the lock file
-
- - `--derivation`
- operate on the store derivation rather than its outputs
-
- - `--expr` *expr*
- evaluate attributes from *expr*
-
- - `--file` / `f` *file*
- evaluate *file* rather than the default
-
- - `--impure`
- allow access to mutable paths and repositories
-
- - `--include` / `I` *path*
- add a path to the list of locations used to look up `<...>` file names
-
- - `--inputs-from` *flake-url*
- use the inputs of the specified flake as registry entries
-
- - `--no-registries`
- don't use flake registries
-
- - `--no-update-lock-file`
- do not allow any updates to the lock file
-
- - `--no-write-lock-file`
- do not write the newly generated lock file
-
- - `--override-flake` *original-ref* *resolved-ref*
- override a flake registry value
-
- - `--override-input` *input-path* *flake-url*
- override a specific flake input (e.g. `dwarffs/nixpkgs`)
-
- - `--recreate-lock-file`
- recreate lock file from scratch
-
- - `--update-input` *input-path*
- update a specific flake input
-
-## Examples
-
-To show one path through the dependency graph leading from Hello to Glibc:
-
-```console
-nix why-depends nixpkgs#hello nixpkgs#glibc
-```
-
-To show all files and paths in the dependency graph leading from Thunderbird to libX11:
-
-```console
-nix why-depends --all nixpkgs#thunderbird nixpkgs#xorg.libX11
-```
-
-To show why Glibc depends on itself:
-
-```console
-nix why-depends nixpkgs#glibc nixpkgs#glibc
-```
-
From 1e04b2568d4898d253891cd2a9da00754611d927 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Tue, 14 Sep 2021 10:52:43 -0600
Subject: [PATCH 036/188] remove version.txt
---
doc/manual/version.txt | 1 -
1 file changed, 1 deletion(-)
delete mode 100644 doc/manual/version.txt
diff --git a/doc/manual/version.txt b/doc/manual/version.txt
deleted file mode 100644
index f398a2061..000000000
--- a/doc/manual/version.txt
+++ /dev/null
@@ -1 +0,0 @@
-3.0
\ No newline at end of file
From cd8c232b554776031f61cee5f70a8825c60fbfdb Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Wed, 15 Sep 2021 16:16:53 -0600
Subject: [PATCH 037/188] add cout debugging
---
Makefile | 2 +-
src/libcmd/command.cc | 2 --
src/libexpr/eval.cc | 2 ++
src/libexpr/nixexpr.cc | 42 ++++++++++++++++++++++++++++++++++--------
src/libexpr/nixexpr.hh | 1 +
src/libexpr/parser.y | 11 +++++++++++
src/libexpr/primops.cc | 4 ++++
7 files changed, 53 insertions(+), 11 deletions(-)
diff --git a/Makefile b/Makefile
index bc2684eaa..ab8ab5ae1 100644
--- a/Makefile
+++ b/Makefile
@@ -15,7 +15,7 @@ makefiles = \
misc/systemd/local.mk \
misc/launchd/local.mk \
misc/upstart/local.mk \
- doc/manual/local.mk \
+ # doc/manual/local.mk \
tests/local.mk \
tests/plugins/local.mk
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 07f4208da..55f6ffd00 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -99,8 +99,6 @@ EvalCommand::EvalCommand()
// extern std::function<void(const Error & error, const std::map<std::string, Value *> & env)> debuggerHook;
extern std::function<void(const Error & error, const Env & env)> debuggerHook;
-
-
ref<EvalState> EvalCommand::getEvalState()
{
std::cout << "EvalCommand::getEvalState()" << startReplOnEvalErrors << std::endl;
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 69e3a4107..bcef2008f 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -918,6 +918,8 @@ LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char *
.errPos = pos
});
+ std::cout << "pre debuggerHook" << std::endl;
+
if (debuggerHook)
debuggerHook(error, env);
throw error;
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index 218e35f33..f8ded2157 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -3,7 +3,7 @@
#include "util.hh"
#include <cstdlib>
-
+#include <iostream>
namespace nix {
@@ -283,6 +283,7 @@ void ExprVar::bindVars(const std::shared_ptr<const StaticEnv> &env)
enclosing `with'. If there is no `with', then we can issue an
"undefined variable" error now. */
if (withLevel == -1)
+ std::cout << " throw UndefinedVarError({" << std::endl;
throw UndefinedVarError({
.msg = hintfmt("undefined variable '%1%'", name),
.errPos = pos
@@ -310,11 +311,12 @@ void ExprOpHasAttr::bindVars(const std::shared_ptr<const StaticEnv> &env)
void ExprAttrs::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
- const StaticEnv * dynamicEnv = env.get();
- auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, env.get())); // also make shared_ptr?
+ std::cout << "ExprAttrs::bindVars" << std::endl;
+ // auto dynamicEnv(env);
if (recursive) {
- dynamicEnv = newEnv.get();
+ // dynamicEnv = newEnv.get();
+ auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, env.get())); // also make shared_ptr?
unsigned int displ = 0;
for (auto & i : attrs)
@@ -322,16 +324,25 @@ void ExprAttrs::bindVars(const std::shared_ptr<const StaticEnv> &env)
for (auto & i : attrs)
i.second.e->bindVars(i.second.inherited ? env : newEnv);
+
+ for (auto & i : dynamicAttrs) {
+ i.nameExpr->bindVars(newEnv);
+ i.valueExpr->bindVars(newEnv);
+ }
}
- else
+ else {
for (auto & i : attrs)
i.second.e->bindVars(env);
- for (auto & i : dynamicAttrs) {
- i.nameExpr->bindVars(newEnv);
- i.valueExpr->bindVars(newEnv);
+ for (auto & i : dynamicAttrs) {
+ i.nameExpr->bindVars(env);
+ i.valueExpr->bindVars(env);
+ }
}
+
+ std::cout << "ExprAttrs::bindVars end" << std::endl;
+
}
void ExprList::bindVars(const std::shared_ptr<const StaticEnv> &env)
@@ -375,6 +386,7 @@ void ExprLet::bindVars(const std::shared_ptr<const StaticEnv> &env)
void ExprWith::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
+ std::cout << " ExprWith::bindVars " << std::endl;
/* Does this `with' have an enclosing `with'? If so, record its
level so that `lookupVar' can look up variables in the previous
`with' if this one doesn't contain the desired attribute. */
@@ -387,9 +399,23 @@ void ExprWith::bindVars(const std::shared_ptr<const StaticEnv> &env)
break;
}
+ std::cout << " ExprWith::bindVars 1" << std::endl;
+ attrs->show(std::cout);
+ std::cout << std::endl;
attrs->bindVars(env);
auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, env.get())); // also make shared_ptr?
+ std::cout << " ExprWith::bindVars 2" << std::endl;
+ std::cout << " body: " << std::endl;
+ body->show(std::cout);
+ std::cout << std::endl;
+
+ std::cout << "ExprWith::newenv: " << newEnv->vars.size() << std::endl;
+ for (auto i = newEnv->vars.begin(); i != newEnv->vars.end(); ++i)
+ std::cout << "EvalState::parse newEnv " << i->first << std::endl;
+
+
body->bindVars(newEnv);
+ std::cout << " ExprWith::bindVars 3" << std::endl;
}
void ExprIf::bindVars(const std::shared_ptr<const StaticEnv> &env)
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index 4c55cb64b..ce3ee9f4d 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -20,6 +20,7 @@ MakeError(UndefinedVarError, Error);
MakeError(MissingArgumentError, EvalError);
MakeError(RestrictedPathError, Error);
+extern std::function<void(const Error & error, const Env & env)> debuggerHook;
/* Position objects. */
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index d1e898677..a3432eb32 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -22,6 +22,8 @@
#include "eval.hh"
#include "globals.hh"
+#include <iostream>
+
namespace nix {
struct ParseData
@@ -572,6 +574,10 @@ namespace nix {
Expr * EvalState::parse(const char * text, FileOrigin origin,
const Path & path, const Path & basePath, std::shared_ptr<StaticEnv> & staticEnv)
{
+ std::cout << "EvalState::parse " << std::endl;
+ for (auto i = staticEnv->vars.begin(); i != staticEnv->vars.end(); ++i)
+ std::cout << "EvalState::parse staticEnv " << i->first << std::endl;
+
yyscan_t scanner;
ParseData data(*this);
data.origin = origin;
@@ -595,8 +601,13 @@ Expr * EvalState::parse(const char * text, FileOrigin origin,
if (res) throw ParseError(data.error.value());
+
+ std::cout << "EvalState::parse pre bindvars " << std::endl;
+
data.result->bindVars(staticEnv);
+ std::cout << "EvalState::parse post bindVars " << std::endl;
+
return data.result;
}
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 0400c8942..7a277a7f5 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -110,6 +110,8 @@ static void mkOutputString(EvalState & state, Value & v,
argument. */
static void import(EvalState & state, const Pos & pos, Value & vPath, Value * vScope, Value & v)
{
+ std::cout << " import " << std::endl;
+
PathSet context;
Path path = state.coerceToPath(pos, vPath, context);
@@ -194,6 +196,8 @@ static void import(EvalState & state, const Pos & pos, Value & vPath, Value * vS
env->values[displ++] = attr.value;
}
+ std::cout << "import staticenv: {} " << staticEnv << std::endl;
+
printTalkative("evaluating file '%1%'", realPath);
Expr * e = state.parseExprFromFile(resolveExprPath(realPath), staticEnv);
From 037d53d9d932dab0e24d919e3fcbf1a6c5538030 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Fri, 17 Sep 2021 16:58:54 -0600
Subject: [PATCH 038/188] turn off the stack usage thing
---
Makefile | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/Makefile b/Makefile
index ab8ab5ae1..b0636cf49 100644
--- a/Makefile
+++ b/Makefile
@@ -31,4 +31,5 @@ endif
include mk/lib.mk
-GLOBAL_CXXFLAGS += -g -Wall -include config.h -std=c++17 -fstack-usage
+# GLOBAL_CXXFLAGS += -g -Wall -include config.h -std=c++17 -fstack-usage
+GLOBAL_CXXFLAGS += -g -Wall -include config.h -std=c++17
From c7e3d830c1f305797b7a4c8b8199ba913d6b8a02 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Wed, 22 Sep 2021 16:22:53 -0600
Subject: [PATCH 039/188] more debug stuff
---
src/libcmd/installables.cc | 4 ++++
src/libexpr/nixexpr.cc | 41 ++++++++++++++++++++++++++++++++++----
src/libexpr/parser.y | 2 +-
src/libexpr/primops.cc | 3 +++
4 files changed, 45 insertions(+), 5 deletions(-)
diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index fd3e5cbba..bce666de5 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -619,6 +619,10 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
state->evalFile(lookupFileArg(*state, *file), *vFile);
else {
auto e = state->parseExprFromString(*expr, absPath("."));
+
+ int x = 5;
+ std::cout << "x =" << x << std::endl;
+
state->eval(e, *vFile);
}
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index f8ded2157..6db047bf7 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -315,12 +315,16 @@ void ExprAttrs::bindVars(const std::shared_ptr<const StaticEnv> &env)
// auto dynamicEnv(env);
if (recursive) {
+ std::cout << "recursive" << std::endl;
// dynamicEnv = newEnv.get();
- auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, env.get())); // also make shared_ptr?
+ // also make shared_ptr?
+ auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, env.get()));
unsigned int displ = 0;
- for (auto & i : attrs)
+ for (auto & i : attrs) {
+ std::cout << "newenvvar: " << i.first << std::endl;
newEnv->vars[i.first] = i.second.displ = displ++;
+ }
for (auto & i : attrs)
i.second.e->bindVars(i.second.inherited ? env : newEnv);
@@ -330,8 +334,8 @@ void ExprAttrs::bindVars(const std::shared_ptr<const StaticEnv> &env)
i.valueExpr->bindVars(newEnv);
}
}
-
else {
+ std::cout << "NOT recursive" << std::endl;
for (auto & i : attrs)
i.second.e->bindVars(env);
@@ -409,7 +413,7 @@ void ExprWith::bindVars(const std::shared_ptr<const StaticEnv> &env)
body->show(std::cout);
std::cout << std::endl;
- std::cout << "ExprWith::newenv: " << newEnv->vars.size() << std::endl;
+ std::cout << "ExprWith::newenv: (iswith, size); (" << newEnv->isWith << ", " << newEnv->vars.size() << ") " << std::endl;
for (auto i = newEnv->vars.begin(); i != newEnv->vars.end(); ++i)
std::cout << "EvalState::parse newEnv " << i->first << std::endl;
@@ -418,6 +422,35 @@ void ExprWith::bindVars(const std::shared_ptr<const StaticEnv> &env)
std::cout << " ExprWith::bindVars 3" << std::endl;
}
+/*
+void ExprWith::bindVars(const StaticEnv & env)
+{
+ // Does this `with' have an enclosing `with'? If so, record its
+ // level so that `lookupVar' can look up variables in the previous
+ // `with' if this one doesn't contain the desired attribute.
+ const StaticEnv * curEnv;
+ unsigned int level;
+ prevWith = 0;
+ for (curEnv = &env, level = 1; curEnv; curEnv = curEnv->up, level++)
+ if (curEnv->isWith) {
+ prevWith = level;
+ break;
+ }
+
+ attrs->bindVars(env);
+ std::cout << "ExprWith::bindVars env: " << env.vars.size(); // add std::endl;
+ for (auto i = env.vars.begin(); i != env.vars.end(); ++i)
+ {
+ std::cout << i->first << std::endl;
+ }
+
+ StaticEnv newEnv(true, &env);
+ body->bindVars(newEnv);
+}
+*/
+
+
+
void ExprIf::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
cond->bindVars(env);
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index a3432eb32..f10e73cda 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -574,7 +574,7 @@ namespace nix {
Expr * EvalState::parse(const char * text, FileOrigin origin,
const Path & path, const Path & basePath, std::shared_ptr<StaticEnv> & staticEnv)
{
- std::cout << "EvalState::parse " << std::endl;
+ std::cout << "EvalState::parse " << text << std::endl;
for (auto i = staticEnv->vars.begin(); i != staticEnv->vars.end(); ++i)
std::cout << "EvalState::parse staticEnv " << i->first << std::endl;
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 7a277a7f5..246a3140b 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -110,6 +110,9 @@ static void mkOutputString(EvalState & state, Value & v,
argument. */
static void import(EvalState & state, const Pos & pos, Value & vPath, Value * vScope, Value & v)
{
+ std::cout << " IMPORT " << std::endl;
+ std::cout << " import " << std::endl;
+ std::cout << " IMPORT " << std::endl;
std::cout << " import " << std::endl;
PathSet context;
From c07edb1932b0f747b563aceaecc5550f5ce192fb Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Wed, 22 Sep 2021 18:14:57 -0600
Subject: [PATCH 040/188] staticenv should be With
---
src/libexpr/eval.cc | 2 +-
src/libexpr/nixexpr.cc | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index bcef2008f..53a5c5bd2 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -976,7 +976,7 @@ void mkPath(Value & v, const char * s)
inline Value * EvalState::lookupVar(Env * env, const ExprVar & var, bool noEval)
{
- // std::cout << " EvalState::lookupVar" << std::endl;
+ std::cout << " EvalState::lookupVar" << var << std::endl;
for (size_t l = var.level; l; --l, env = env->up) ;
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index 6db047bf7..8b883e185 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -407,7 +407,7 @@ void ExprWith::bindVars(const std::shared_ptr<const StaticEnv> &env)
attrs->show(std::cout);
std::cout << std::endl;
attrs->bindVars(env);
- auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, env.get())); // also make shared_ptr?
+ auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(true, env.get())); // also make shared_ptr?
std::cout << " ExprWith::bindVars 2" << std::endl;
std::cout << " body: " << std::endl;
body->show(std::cout);
From b9d08b98da4ab18f0c1c8bee30bd4ad934a5cdcf Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Thu, 23 Sep 2021 13:02:39 -0600
Subject: [PATCH 041/188] ok was unconditoinally throwing on any With var
---
src/libcmd/installables.cc | 4 +--
src/libexpr/nixexpr.cc | 71 ++++++++++++++++++++++++--------------
2 files changed, 47 insertions(+), 28 deletions(-)
diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index bce666de5..f85bd4c13 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -618,10 +618,10 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
if (file)
state->evalFile(lookupFileArg(*state, *file), *vFile);
else {
+ std::cout << "pre parseExprFromString" << std::endl;
auto e = state->parseExprFromString(*expr, absPath("."));
- int x = 5;
- std::cout << "x =" << x << std::endl;
+ std::cout << "pre eval" << std::endl;
state->eval(e, *vFile);
}
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index 8b883e185..6ca0de72b 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -262,34 +262,52 @@ void ExprVar::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
/* Check whether the variable appears in the environment. If so,
set its level and displacement. */
- const StaticEnv * curEnv;
- unsigned int level;
- int withLevel = -1;
- for (curEnv = env.get(), level = 0; curEnv; curEnv = curEnv->up, level++) {
- if (curEnv->isWith) {
- if (withLevel == -1) withLevel = level;
- } else {
- StaticEnv::Vars::const_iterator i = curEnv->vars.find(name);
- if (i != curEnv->vars.end()) {
- fromWith = false;
- this->level = level;
- displ = i->second;
- return;
- }
- }
+
+ std::cout << "ExprVar::bindVars " << name << std::endl;
+
+ int a = 10;
+ if (name == "callPackage") {
+ a++; // try to make code that I can put a breakpoint on...
+ std::cout << "meh" << a + 10 << std::endl;
+ int withLevel = -1;
+ fromWith = true;
+ // this->level = withLevel;
}
- /* Otherwise, the variable must be obtained from the nearest
- enclosing `with'. If there is no `with', then we can issue an
- "undefined variable" error now. */
- if (withLevel == -1)
- std::cout << " throw UndefinedVarError({" << std::endl;
- throw UndefinedVarError({
- .msg = hintfmt("undefined variable '%1%'", name),
- .errPos = pos
- });
- fromWith = true;
- this->level = withLevel;
+ {
+
+ const StaticEnv * curEnv;
+ unsigned int level;
+ int withLevel = -1;
+ for (curEnv = env.get(), level = 0; curEnv; curEnv = curEnv->up, level++) {
+ if (curEnv->isWith) {
+ if (withLevel == -1) withLevel = level;
+ } else {
+ StaticEnv::Vars::const_iterator i = curEnv->vars.find(name);
+ if (i != curEnv->vars.end()) {
+ fromWith = false;
+ this->level = level;
+ displ = i->second;
+ return;
+ }
+ }
+ }
+
+
+ /* Otherwise, the variable must be obtained from the nearest
+ enclosing `with'. If there is no `with', then we can issue an
+ "undefined variable" error now. */
+ if (withLevel == -1)
+ {
+ std::cout << " throw UndefinedVarError({" << std::endl;
+ throw UndefinedVarError({
+ .msg = hintfmt("undefined variable (ExprVar bindvars) '%1%'", name),
+ .errPos = pos
+ });
+ }
+ fromWith = true;
+ this->level = withLevel;
+ }
}
void ExprSelect::bindVars(const std::shared_ptr<const StaticEnv> &env)
@@ -418,6 +436,7 @@ void ExprWith::bindVars(const std::shared_ptr<const StaticEnv> &env)
std::cout << "EvalState::parse newEnv " << i->first << std::endl;
+ std::cout << " body->bindVars(newEnv), iswith: " << newEnv->isWith << std::endl;
body->bindVars(newEnv);
std::cout << " ExprWith::bindVars 3" << std::endl;
}
From aad27143c67c863bd4886186bdf68f4796ca26c3 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Sat, 2 Oct 2021 13:47:36 -0600
Subject: [PATCH 042/188] storing staticenv bindings
---
src/libexpr/eval.cc | 23 +++++++++++++++++++++
src/libexpr/nixexpr.cc | 47 ++++++++++++++++++++++++++++++++++++++++++
src/libexpr/nixexpr.hh | 2 +-
3 files changed, 71 insertions(+), 1 deletion(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 53a5c5bd2..c2b6e7ea8 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -689,6 +689,29 @@ void printEnvBindings(const Env &env, int lv )
}
}
+void printStaticEnvBindings(const StaticEnv &se, int lvl)
+{
+ for (auto i = se.vars.begin(); i != se.vars.end(); ++i)
+ {
+ std::cout << lvl << i->first << std::endl;
+ }
+
+ if (se.up) {
+ printStaticEnvBindings(*se.up, ++lvl);
+ }
+
+}
+
+void printStaticEnvBindings(const Expr &expr)
+{
+ // just print the names for now
+ if (expr.staticenv)
+ {
+ printStaticEnvBindings(*expr.staticenv.get(), 0);
+ }
+
+}
+
void printEnvPosChain(const Env &env, int lv )
{
std::cout << "printEnvPosChain " << lv << std::endl;
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index 6ca0de72b..85b1d5e12 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -244,22 +244,33 @@ void Expr::bindVars(const std::shared_ptr<const StaticEnv> &env)
void ExprInt::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
+ if (debuggerHook)
+ staticenv = env;
}
void ExprFloat::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
+ if (debuggerHook)
+ staticenv = env;
}
void ExprString::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
+ if (debuggerHook)
+ staticenv = env;
}
void ExprPath::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
+ if (debuggerHook)
+ staticenv = env;
}
void ExprVar::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
+ if (debuggerHook)
+ staticenv = env;
+
/* Check whether the variable appears in the environment. If so,
set its level and displacement. */
@@ -312,6 +323,9 @@ void ExprVar::bindVars(const std::shared_ptr<const StaticEnv> &env)
void ExprSelect::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
+ if (debuggerHook)
+ staticenv = env;
+
e->bindVars(env);
if (def) def->bindVars(env);
for (auto & i : attrPath)
@@ -321,6 +335,9 @@ void ExprSelect::bindVars(const std::shared_ptr<const StaticEnv> &env)
void ExprOpHasAttr::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
+ if (debuggerHook)
+ staticenv = env;
+
e->bindVars(env);
for (auto & i : attrPath)
if (!i.symbol.set())
@@ -329,6 +346,9 @@ void ExprOpHasAttr::bindVars(const std::shared_ptr<const StaticEnv> &env)
void ExprAttrs::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
+ if (debuggerHook)
+ staticenv = env;
+
std::cout << "ExprAttrs::bindVars" << std::endl;
// auto dynamicEnv(env);
@@ -369,12 +389,18 @@ void ExprAttrs::bindVars(const std::shared_ptr<const StaticEnv> &env)
void ExprList::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
+ if (debuggerHook)
+ staticenv = env;
+
for (auto & i : elems)
i->bindVars(env);
}
void ExprLambda::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
+ if (debuggerHook)
+ staticenv = env;
+
auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, env.get())); // also make shared_ptr?
unsigned int displ = 0;
@@ -394,6 +420,9 @@ void ExprLambda::bindVars(const std::shared_ptr<const StaticEnv> &env)
void ExprLet::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
+ if (debuggerHook)
+ staticenv = env;
+
auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, env.get())); // also make shared_ptr?
unsigned int displ = 0;
@@ -408,6 +437,9 @@ void ExprLet::bindVars(const std::shared_ptr<const StaticEnv> &env)
void ExprWith::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
+ if (debuggerHook)
+ staticenv = env;
+
std::cout << " ExprWith::bindVars " << std::endl;
/* Does this `with' have an enclosing `with'? If so, record its
level so that `lookupVar' can look up variables in the previous
@@ -472,6 +504,9 @@ void ExprWith::bindVars(const StaticEnv & env)
void ExprIf::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
+ if (debuggerHook)
+ staticenv = env;
+
cond->bindVars(env);
then->bindVars(env);
else_->bindVars(env);
@@ -479,23 +514,35 @@ void ExprIf::bindVars(const std::shared_ptr<const StaticEnv> &env)
void ExprAssert::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
+ if (debuggerHook)
+ staticenv = env;
+
cond->bindVars(env);
body->bindVars(env);
}
void ExprOpNot::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
+ if (debuggerHook)
+ staticenv = env;
+
e->bindVars(env);
}
void ExprConcatStrings::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
+ if (debuggerHook)
+ staticenv = env;
+
for (auto & i : *es)
i->bindVars(env);
}
void ExprPos::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
+ if (debuggerHook)
+ staticenv = env;
+
}
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index ce3ee9f4d..341d80b35 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -85,7 +85,7 @@ struct Expr
virtual Value * maybeThunk(EvalState & state, Env & env);
virtual void setName(Symbol & name);
- std::shared_ptr<StaticEnv> staticenv;
+ std::shared_ptr<const StaticEnv> staticenv;
};
std::ostream & operator << (std::ostream & str, const Expr & e);
From 2ee1fa4afd69226f16305e792d5110fd36669c6b Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Mon, 11 Oct 2021 14:42:29 -0600
Subject: [PATCH 043/188] add nullable Expr argument
---
src/libcmd/command.cc | 4 +-
src/libexpr/eval.cc | 129 ++++++++++++++++++++++-------------------
src/libexpr/eval.hh | 2 +-
src/libexpr/nixexpr.hh | 2 +-
4 files changed, 74 insertions(+), 63 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 55f6ffd00..705b30d53 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -97,7 +97,7 @@ EvalCommand::EvalCommand()
});
}
// extern std::function<void(const Error & error, const std::map<std::string, Value *> & env)> debuggerHook;
-extern std::function<void(const Error & error, const Env & env)> debuggerHook;
+extern std::function<void(const Error & error, const Env & env, const Expr & expr)> debuggerHook;
ref<EvalState> EvalCommand::getEvalState()
{
@@ -105,7 +105,7 @@ ref<EvalState> EvalCommand::getEvalState()
if (!evalState) {
evalState = std::make_shared<EvalState>(searchPath, getStore());
if (startReplOnEvalErrors)
- debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error & error, const Env & env) {
+ debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error & error, const Env & env, const Expr & expr) {
printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error.what());
// printEnvPosChain(env);
printEnvBindings(env);
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index c2b6e7ea8..76c038593 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -36,7 +36,7 @@
namespace nix {
// std::function<void(const Error & error, const std::map<std::string, Value *> & env)> debuggerHook;
-std::function<void(const Error & error, const Env & env)> debuggerHook;
+std::function<void(const Error & error, const Env & env, const Expr & expr)> debuggerHook;
static char * dupString(const char * s)
{
@@ -806,17 +806,17 @@ valmap * mapEnvBindings(const Env &env)
evaluator. So here are some helper functions for throwing
exceptions. */
-LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, Env & env))
+LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, Env & env, Expr *expr))
{
// auto delenv = std::unique_ptr<valmap>(env);
auto error = EvalError(s, s2);
- if (debuggerHook)
- debuggerHook(error, env);
+ if (debuggerHook && expr)
+ debuggerHook(error, env, *expr);
throw error;
}
-LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2, Env & env))
+LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2, Env & env, Expr *expr))
{
// auto delenv = std::unique_ptr<valmap>(env);
auto error = EvalError({
@@ -824,22 +824,24 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const
.errPos = pos
});
- if (debuggerHook)
- debuggerHook(error, env);
+ if (debuggerHook && expr)
+ debuggerHook(error, env, *expr);
+
throw error;
}
-LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, const string & s3, Env & env))
+LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, const string & s3, Env & env, Expr *expr))
{
// auto delenv = std::unique_ptr<valmap>(env);
auto error = EvalError(s, s2, s3);
- if (debuggerHook)
- debuggerHook(error, env);
+ if (debuggerHook && expr)
+ debuggerHook(error, env, *expr);
+
throw error;
}
-LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2, const string & s3, Env & env))
+LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2, const string & s3, Env & env, Expr *expr))
{
// auto delenv = std::unique_ptr<valmap>(env);
auto error = EvalError({
@@ -847,12 +849,13 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const
.errPos = pos
});
- if (debuggerHook)
- debuggerHook(error, env);
+ if (debuggerHook && expr)
+ debuggerHook(error, env, *expr);
+
throw error;
}
-LocalNoInlineNoReturn(void throwEvalError(const Pos & p1, const char * s, const Symbol & sym, const Pos & p2, Env & env))
+LocalNoInlineNoReturn(void throwEvalError(const Pos & p1, const char * s, const Symbol & sym, const Pos & p2, Env & env, Expr *expr))
{
// p1 is where the error occurred; p2 is a position mentioned in the message.
// auto delenv = std::unique_ptr<valmap>(env);
@@ -861,12 +864,13 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & p1, const char * s, const
.errPos = p1
});
- if (debuggerHook)
- debuggerHook(error, env);
+ if (debuggerHook && expr)
+ debuggerHook(error, env, *expr);
+
throw error;
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, Env & env))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, Env & env, Expr *expr))
{
// auto delenv = std::unique_ptr<valmap>(env);
auto error = TypeError({
@@ -874,12 +878,13 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, Env &
.errPos = pos
});
- if (debuggerHook)
- debuggerHook(error, env);
+ if (debuggerHook && expr)
+ debuggerHook(error, env, *expr);
+
throw error;
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v, Env & env))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v, Env & env, Expr *expr))
{
// auto delenv = std::unique_ptr<valmap>(env);
auto error = TypeError({
@@ -887,12 +892,13 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
.errPos = pos
});
- if (debuggerHook)
- debuggerHook(error, env);
+ if (debuggerHook && expr)
+ debuggerHook(error, env, *expr);
+
throw error;
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const string &s2, Env & env))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const string &s2, Env & env, Expr *expr))
{
// auto delenv = std::unique_ptr<valmap>(env);
auto error = TypeError({
@@ -900,12 +906,13 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
.errPos = pos
});
- if (debuggerHook)
- debuggerHook(error, env);
+ if (debuggerHook && expr)
+ debuggerHook(error, env, *expr);
+
throw error;
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const ExprLambda & fun, const Symbol & s2, Env & env))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const ExprLambda & fun, const Symbol & s2, Env & env, Expr *expr))
{
// auto delenv = std::unique_ptr<valmap>(env);
auto error = TypeError({
@@ -913,12 +920,13 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
.errPos = pos
});
- if (debuggerHook)
- debuggerHook(error, env);
+ if (debuggerHook && expr)
+ debuggerHook(error, env, *expr);
+
throw error;
}
-LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s, const string & s1, Env & env))
+LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s, const string & s1, Env & env, Expr *expr))
{
// auto delenv = std::unique_ptr<valmap>(env);
auto error = AssertionError({
@@ -926,12 +934,13 @@ LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s,
.errPos = pos
});
- if (debuggerHook)
- debuggerHook(error, env);
+ if (debuggerHook && expr)
+ debuggerHook(error, env, *expr);
+
throw error;
}
-LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char * s, const string & s1, Env & env))
+LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char * s, const string & s1, Env & env, Expr *expr))
{
std::cout << "throwUndefinedVarError" << std::endl;
@@ -943,12 +952,13 @@ LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char *
std::cout << "pre debuggerHook" << std::endl;
- if (debuggerHook)
- debuggerHook(error, env);
+ if (debuggerHook && expr)
+ debuggerHook(error, env, *expr);
+
throw error;
}
-LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char * s, const string & s1, Env & env))
+LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char * s, const string & s1, Env & env, Expr *expr))
{
// auto delenv = std::unique_ptr<valmap>(env);
auto error = MissingArgumentError({
@@ -956,8 +966,9 @@ LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char
.errPos = pos
});
- if (debuggerHook)
- debuggerHook(error, env);
+ if (debuggerHook && expr)
+ debuggerHook(error, env, *expr);
+
throw error;
}
@@ -1020,7 +1031,7 @@ inline Value * EvalState::lookupVar(Env * env, const ExprVar & var, bool noEval)
}
if (!env->prevWith) {
std::cout << "pre throwUndefinedVarError" << std::endl;
- throwUndefinedVarError(var.pos, "undefined variable '%1%'", var.name, *env);
+ throwUndefinedVarError(var.pos, "undefined variable '%1%'", var.name, *env, 0);
}
for (size_t l = env->prevWith; l; --l, env = env->up) ;
}
@@ -1354,7 +1365,7 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
Bindings::iterator j = v.attrs->find(nameSym);
if (j != v.attrs->end())
throwEvalError(i.pos, "dynamic attribute '%1%' already defined at %2%", nameSym, *j->pos,
- env);
+ env, this);
// map1("value", &v)); // TODO dynamicAttrs to env?
i.valueExpr->setName(nameSym);
@@ -1445,7 +1456,7 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
} else {
state.forceAttrs(*vAttrs, pos);
if ((j = vAttrs->attrs->find(name)) == vAttrs->attrs->end())
- throwEvalError(pos, "attribute '%1%' missing", name, env);
+ throwEvalError(pos, "attribute '%1%' missing", name, env, this);
// mapBindings(*vAttrs->attrs));
}
vAttrs = j->value;
@@ -1573,7 +1584,7 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
pos,
"attempt to call something which is not a function but %1%",
showType(fun).c_str(),
- fakeEnv(1));
+ fakeEnv(1), 0);
// fun.env);
// map2("fun", &fun, "arg", &arg));
}
@@ -1612,7 +1623,7 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
"%1% called without required argument '%2%'",
lambda,
i.name,
- *fun.lambda.env);
+ *fun.lambda.env, &lambda);
// map2("fun", &fun, "arg", &arg));
env2.values[displ++] = i.def->maybeThunk(*this, env2);
} else {
@@ -1633,7 +1644,7 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
"%1% called with unexpected argument '%2%'",
lambda,
i.name,
- *fun.lambda.env);
+ *fun.lambda.env, &lambda);
// map2("fun", &fun, "arg", &arg));
abort(); // can't happen
}
@@ -1711,7 +1722,7 @@ this case it must have its arguments supplied either by default
values, or passed explicitly with '--arg' or '--argstr'. See
https://nixos.org/manual/nix/stable/#ss-functions.)",
i.name,
- *fun.lambda.env);
+ *fun.lambda.env, fun.lambda.fun);
// mapBindings(args));
// map1("fun", &fun)); // todo add bindings + fun
}
@@ -1761,7 +1772,7 @@ void ExprAssert::eval(EvalState & state, Env & env, Value & v)
if (!state.evalBool(env, cond, pos)) {
std::ostringstream out;
cond->show(out);
- throwAssertionError(pos, "assertion '%1%' failed", out.str(), env);
+ throwAssertionError(pos, "assertion '%1%' failed", out.str(), env, this);
}
body->eval(state, env, v);
}
@@ -1915,7 +1926,7 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
} else {
std::cerr << "envtype: " << showType(env.values[0]->type()) << std::endl;
- throwEvalError(pos, "cannot add %1% to an integer", showType(vTmp), env);
+ throwEvalError(pos, "cannot add %1% to an integer", showType(vTmp), env, this);
}
} else if (firstType == nFloat) {
if (vTmp.type() == nInt) {
@@ -1923,7 +1934,7 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
} else if (vTmp.type() == nFloat) {
nf += vTmp.fpoint;
} else
- throwEvalError(pos, "cannot add %1% to a float", showType(vTmp), env);
+ throwEvalError(pos, "cannot add %1% to a float", showType(vTmp), env, this);
} else
s << state.coerceToString(pos, vTmp, context, false, firstType == nString);
}
@@ -1984,7 +1995,7 @@ NixInt EvalState::forceInt(Value & v, const Pos & pos)
forceValue(v, pos);
if (v.type() != nInt)
throwTypeError(pos, "value is %1% while an integer was expected", v,
- fakeEnv(1));
+ fakeEnv(1), 0);
// map1("value", &v));
return v.integer;
}
@@ -1997,7 +2008,7 @@ NixFloat EvalState::forceFloat(Value & v, const Pos & pos)
return v.integer;
else if (v.type() != nFloat)
throwTypeError(pos, "value is %1% while a float was expected", v,
- fakeEnv(1));
+ fakeEnv(1), 0);
// map1("value", &v));
return v.fpoint;
}
@@ -2008,7 +2019,7 @@ bool EvalState::forceBool(Value & v, const Pos & pos)
forceValue(v, pos);
if (v.type() != nBool)
throwTypeError(pos, "value is %1% while a Boolean was expected", v,
- fakeEnv(1));
+ fakeEnv(1), 0);
// map1("value", &v));
return v.boolean;
}
@@ -2025,7 +2036,7 @@ void EvalState::forceFunction(Value & v, const Pos & pos)
forceValue(v, pos);
if (v.type() != nFunction && !isFunctor(v))
throwTypeError(pos, "value is %1% while a function was expected", v,
- fakeEnv(1));
+ fakeEnv(1), 0);
// map1("value", &v));
}
@@ -2035,7 +2046,7 @@ string EvalState::forceString(Value & v, const Pos & pos)
forceValue(v, pos);
if (v.type() != nString) {
throwTypeError(pos, "value is %1% while a string was expected", v,
- fakeEnv(1));
+ fakeEnv(1), 0);
// map1("value", &v));
}
return string(v.string.s);
@@ -2089,13 +2100,13 @@ string EvalState::forceStringNoCtx(Value & v, const Pos & pos)
throwEvalError(pos, "the string '%1%' is not allowed to refer to a store path (such as '%2%')",
v.string.s, v.string.context[0],
// b.has_value() ? mapBindings(*b.get()) : map0());
- fakeEnv(1));
+ fakeEnv(1), 0);
// map1("value", &v));
else
throwEvalError("the string '%1%' is not allowed to refer to a store path (such as '%2%')",
v.string.s, v.string.context[0],
// b.has_value() ? mapBindings(*b.get()) : map0());
- fakeEnv(1));
+ fakeEnv(1), 0);
// map1("value", &v));
}
return s;
@@ -2169,7 +2180,7 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
auto i = v.attrs->find(sOutPath);
if (i == v.attrs->end())
throwTypeError(pos, "cannot coerce a set to a string",
- fakeEnv(1));
+ fakeEnv(1), 0);
// map1("value", &v));
return coerceToString(pos, *i->value, context, coerceMore, copyToStore);
}
@@ -2201,7 +2212,7 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
}
throwTypeError(pos, "cannot coerce %1% to a string", v,
- fakeEnv(1));
+ fakeEnv(1), 0);
// map1("value", &v));
}
@@ -2211,7 +2222,7 @@ string EvalState::copyPathToStore(PathSet & context, const Path & path)
if (nix::isDerivation(path))
throwEvalError("file names are not allowed to end in '%1%'",
drvExtension,
- fakeEnv(1));
+ fakeEnv(1), 0);
// map0());
Path dstPath;
@@ -2237,7 +2248,7 @@ Path EvalState::coerceToPath(const Pos & pos, Value & v, PathSet & context)
string path = coerceToString(pos, v, context, false, false);
if (path == "" || path[0] != '/')
throwEvalError(pos, "string '%1%' doesn't represent an absolute path", path,
- fakeEnv(1));
+ fakeEnv(1), 0);
// map1("value", &v));
return path;
}
@@ -2320,7 +2331,7 @@ bool EvalState::eqValues(Value & v1, Value & v2)
throwEvalError("cannot compare %1% with %2%",
showType(v1),
showType(v2),
- fakeEnv(1));
+ fakeEnv(1), 0);
// map2("value1", &v1, "value2", &v2));
}
}
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 8edc17789..553e7861a 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -23,7 +23,7 @@ enum RepairFlag : bool;
typedef void (* PrimOpFun) (EvalState & state, const Pos & pos, Value * * args, Value & v);
-extern std::function<void(const Error & error, const Env & env)> debuggerHook;
+extern std::function<void(const Error & error, const Env & env, const Expr & expr)> debuggerHook;
struct PrimOp
{
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index 341d80b35..a78ea6215 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -20,7 +20,7 @@ MakeError(UndefinedVarError, Error);
MakeError(MissingArgumentError, EvalError);
MakeError(RestrictedPathError, Error);
-extern std::function<void(const Error & error, const Env & env)> debuggerHook;
+extern std::function<void(const Error & error, const Env & env, const Expr & expr)> debuggerHook;
/* Position objects. */
From 98eb13691a16d9472b822a92f32b439a6ee6e288 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Mon, 11 Oct 2021 16:32:43 -0600
Subject: [PATCH 044/188] print staticenv bindings
---
src/libcmd/command.cc | 12 +++++++++---
src/libexpr/eval.cc | 28 ++++++++++++++++++++++++++++
src/libexpr/eval.hh | 2 ++
3 files changed, 39 insertions(+), 3 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 705b30d53..d8e79953c 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -107,10 +107,16 @@ ref<EvalState> EvalCommand::getEvalState()
if (startReplOnEvalErrors)
debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error & error, const Env & env, const Expr & expr) {
printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error.what());
+
+ printStaticEnvBindings(expr);
+
// printEnvPosChain(env);
- printEnvBindings(env);
- auto vm = mapEnvBindings(env);
- runRepl(evalState, *vm);
+ // printEnvBindings(env);
+ if (expr.staticenv)
+ {
+ auto vm = mapStaticEnvBindings(*expr.staticenv.get(), env);
+ runRepl(evalState, *vm);
+ }
};
}
return ref<EvalState>(evalState);
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 76c038593..fba5f5031 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -712,6 +712,34 @@ void printStaticEnvBindings(const Expr &expr)
}
+void mapStaticEnvBindings(const StaticEnv &se, const Env &env, valmap & vm)
+{
+ // add bindings for the next level up first.
+ if (env.up && se.up) {
+ mapStaticEnvBindings( *se.up, *env.up,vm);
+ }
+
+ // iterate through staticenv bindings.
+
+ auto map = valmap();
+ for (auto iter = se.vars.begin(); iter != se.vars.end(); ++iter)
+ {
+ map[iter->first] = env.values[iter->second];
+ }
+
+ vm.merge(map);
+
+}
+
+
+valmap * mapStaticEnvBindings(const StaticEnv &se, const Env &env)
+{
+ auto vm = new valmap();
+ mapStaticEnvBindings(se, env, *vm);
+ return vm;
+}
+
+
void printEnvPosChain(const Env &env, int lv )
{
std::cout << "printEnvPosChain " << lv << std::endl;
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 553e7861a..29599cc6c 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -24,6 +24,7 @@ enum RepairFlag : bool;
typedef void (* PrimOpFun) (EvalState & state, const Pos & pos, Value * * args, Value & v);
extern std::function<void(const Error & error, const Env & env, const Expr & expr)> debuggerHook;
+void printStaticEnvBindings(const Expr &expr);
struct PrimOp
{
@@ -47,6 +48,7 @@ struct Env
void printEnvBindings(const Env &env, int lv = 0);
valmap * mapEnvBindings(const Env &env);
void printEnvPosChain(const Env &env, int lv = 0);
+valmap * mapStaticEnvBindings(const StaticEnv &se, const Env &env);
Value & mkString(Value & v, std::string_view s, const PathSet & context = PathSet());
From 427fb8d1581d7b20b0f5205cc59f3857275860c1 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Mon, 11 Oct 2021 16:48:10 -0600
Subject: [PATCH 045/188] comment out debugs
---
src/libcmd/installables.cc | 4 ++--
src/libexpr/eval.cc | 18 ++++++++--------
src/libexpr/nixexpr.cc | 42 +++++++++++++++++++-------------------
src/libexpr/parser.y | 10 ++++-----
src/libexpr/primops.cc | 8 ++++----
5 files changed, 41 insertions(+), 41 deletions(-)
diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index f85bd4c13..c3436acf9 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -618,10 +618,10 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
if (file)
state->evalFile(lookupFileArg(*state, *file), *vFile);
else {
- std::cout << "pre parseExprFromString" << std::endl;
+ // std::cout << "pre parseExprFromString" << std::endl;
auto e = state->parseExprFromString(*expr, absPath("."));
- std::cout << "pre eval" << std::endl;
+ // std::cout << "pre eval" << std::endl;
state->eval(e, *vFile);
}
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index fba5f5031..12f7e8979 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -742,13 +742,13 @@ valmap * mapStaticEnvBindings(const StaticEnv &se, const Env &env)
void printEnvPosChain(const Env &env, int lv )
{
- std::cout << "printEnvPosChain " << lv << std::endl;
+ // std::cout << "printEnvPosChain " << lv << std::endl;
- std::cout << "env" << env.values[0] << std::endl;
+ // std::cout << "env" << env.values[0] << std::endl;
if (env.values[0] && env.values[0]->type() == nAttrs) {
- std::cout << "im in the loop" << std::endl;
- std::cout << "pos " << env.values[0]->attrs->pos << std::endl;
+ // std::cout << "im in the loop" << std::endl;
+ // std::cout << "pos " << env.values[0]->attrs->pos << std::endl;
if (env.values[0]->attrs->pos) {
ErrPos ep(*env.values[0]->attrs->pos);
auto loc = getCodeLines(ep);
@@ -760,7 +760,7 @@ void printEnvPosChain(const Env &env, int lv )
}
}
- std::cout << "next env : " << env.up << std::endl;
+ // std::cout << "next env : " << env.up << std::endl;
if (env.up) {
printEnvPosChain(*env.up, ++lv);
@@ -970,7 +970,7 @@ LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s,
LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char * s, const string & s1, Env & env, Expr *expr))
{
- std::cout << "throwUndefinedVarError" << std::endl;
+ // std::cout << "throwUndefinedVarError" << std::endl;
// auto delenv = std::unique_ptr<valmap>(env);
auto error = UndefinedVarError({
@@ -978,7 +978,7 @@ LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char *
.errPos = pos
});
- std::cout << "pre debuggerHook" << std::endl;
+ // std::cout << "pre debuggerHook" << std::endl;
if (debuggerHook && expr)
debuggerHook(error, env, *expr);
@@ -1038,7 +1038,7 @@ void mkPath(Value & v, const char * s)
inline Value * EvalState::lookupVar(Env * env, const ExprVar & var, bool noEval)
{
- std::cout << " EvalState::lookupVar" << var << std::endl;
+ // std::cout << " EvalState::lookupVar" << var << std::endl;
for (size_t l = var.level; l; --l, env = env->up) ;
@@ -1058,7 +1058,7 @@ inline Value * EvalState::lookupVar(Env * env, const ExprVar & var, bool noEval)
return j->value;
}
if (!env->prevWith) {
- std::cout << "pre throwUndefinedVarError" << std::endl;
+ // std::cout << "pre throwUndefinedVarError" << std::endl;
throwUndefinedVarError(var.pos, "undefined variable '%1%'", var.name, *env, 0);
}
for (size_t l = env->prevWith; l; --l, env = env->up) ;
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index 85b1d5e12..8f88eabd5 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -274,12 +274,12 @@ void ExprVar::bindVars(const std::shared_ptr<const StaticEnv> &env)
/* Check whether the variable appears in the environment. If so,
set its level and displacement. */
- std::cout << "ExprVar::bindVars " << name << std::endl;
+ // std::cout << "ExprVar::bindVars " << name << std::endl;
int a = 10;
if (name == "callPackage") {
a++; // try to make code that I can put a breakpoint on...
- std::cout << "meh" << a + 10 << std::endl;
+ // std::cout << "meh" << a + 10 << std::endl;
int withLevel = -1;
fromWith = true;
// this->level = withLevel;
@@ -310,7 +310,7 @@ void ExprVar::bindVars(const std::shared_ptr<const StaticEnv> &env)
"undefined variable" error now. */
if (withLevel == -1)
{
- std::cout << " throw UndefinedVarError({" << std::endl;
+ // std::cout << " throw UndefinedVarError({" << std::endl;
throw UndefinedVarError({
.msg = hintfmt("undefined variable (ExprVar bindvars) '%1%'", name),
.errPos = pos
@@ -349,18 +349,18 @@ void ExprAttrs::bindVars(const std::shared_ptr<const StaticEnv> &env)
if (debuggerHook)
staticenv = env;
- std::cout << "ExprAttrs::bindVars" << std::endl;
+ // std::cout << "ExprAttrs::bindVars" << std::endl;
// auto dynamicEnv(env);
if (recursive) {
- std::cout << "recursive" << std::endl;
+ // std::cout << "recursive" << std::endl;
// dynamicEnv = newEnv.get();
// also make shared_ptr?
auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, env.get()));
unsigned int displ = 0;
for (auto & i : attrs) {
- std::cout << "newenvvar: " << i.first << std::endl;
+ // std::cout << "newenvvar: " << i.first << std::endl;
newEnv->vars[i.first] = i.second.displ = displ++;
}
@@ -373,7 +373,7 @@ void ExprAttrs::bindVars(const std::shared_ptr<const StaticEnv> &env)
}
}
else {
- std::cout << "NOT recursive" << std::endl;
+ // std::cout << "NOT recursive" << std::endl;
for (auto & i : attrs)
i.second.e->bindVars(env);
@@ -383,7 +383,7 @@ void ExprAttrs::bindVars(const std::shared_ptr<const StaticEnv> &env)
}
}
- std::cout << "ExprAttrs::bindVars end" << std::endl;
+ // std::cout << "ExprAttrs::bindVars end" << std::endl;
}
@@ -440,7 +440,7 @@ void ExprWith::bindVars(const std::shared_ptr<const StaticEnv> &env)
if (debuggerHook)
staticenv = env;
- std::cout << " ExprWith::bindVars " << std::endl;
+ // std::cout << " ExprWith::bindVars " << std::endl;
/* Does this `with' have an enclosing `with'? If so, record its
level so that `lookupVar' can look up variables in the previous
`with' if this one doesn't contain the desired attribute. */
@@ -453,24 +453,24 @@ void ExprWith::bindVars(const std::shared_ptr<const StaticEnv> &env)
break;
}
- std::cout << " ExprWith::bindVars 1" << std::endl;
- attrs->show(std::cout);
- std::cout << std::endl;
+ // std::cout << " ExprWith::bindVars 1" << std::endl;
+ // attrs->show(std::cout);
+ // std::cout << std::endl;
attrs->bindVars(env);
auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(true, env.get())); // also make shared_ptr?
- std::cout << " ExprWith::bindVars 2" << std::endl;
- std::cout << " body: " << std::endl;
- body->show(std::cout);
- std::cout << std::endl;
+ // std::cout << " ExprWith::bindVars 2" << std::endl;
+ // std::cout << " body: " << std::endl;
+ // body->show(std::cout);
+ // std::cout << std::endl;
- std::cout << "ExprWith::newenv: (iswith, size); (" << newEnv->isWith << ", " << newEnv->vars.size() << ") " << std::endl;
- for (auto i = newEnv->vars.begin(); i != newEnv->vars.end(); ++i)
- std::cout << "EvalState::parse newEnv " << i->first << std::endl;
+ // std::cout << "ExprWith::newenv: (iswith, size); (" << newEnv->isWith << ", " << newEnv->vars.size() << ") " << std::endl;
+ // for (auto i = newEnv->vars.begin(); i != newEnv->vars.end(); ++i)
+ // std::cout << "EvalState::parse newEnv " << i->first << std::endl;
- std::cout << " body->bindVars(newEnv), iswith: " << newEnv->isWith << std::endl;
+ // std::cout << " body->bindVars(newEnv), iswith: " << newEnv->isWith << std::endl;
body->bindVars(newEnv);
- std::cout << " ExprWith::bindVars 3" << std::endl;
+ // std::cout << " ExprWith::bindVars 3" << std::endl;
}
/*
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index f10e73cda..46bbce1f6 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -574,9 +574,9 @@ namespace nix {
Expr * EvalState::parse(const char * text, FileOrigin origin,
const Path & path, const Path & basePath, std::shared_ptr<StaticEnv> & staticEnv)
{
- std::cout << "EvalState::parse " << text << std::endl;
- for (auto i = staticEnv->vars.begin(); i != staticEnv->vars.end(); ++i)
- std::cout << "EvalState::parse staticEnv " << i->first << std::endl;
+ // std::cout << "EvalState::parse " << text << std::endl;
+ // for (auto i = staticEnv->vars.begin(); i != staticEnv->vars.end(); ++i)
+ // std::cout << "EvalState::parse staticEnv " << i->first << std::endl;
yyscan_t scanner;
ParseData data(*this);
@@ -602,11 +602,11 @@ Expr * EvalState::parse(const char * text, FileOrigin origin,
if (res) throw ParseError(data.error.value());
- std::cout << "EvalState::parse pre bindvars " << std::endl;
+ // std::cout << "EvalState::parse pre bindvars " << std::endl;
data.result->bindVars(staticEnv);
- std::cout << "EvalState::parse post bindVars " << std::endl;
+ // std::cout << "EvalState::parse post bindVars " << std::endl;
return data.result;
}
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 246a3140b..4b8ad3e9a 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -110,10 +110,10 @@ static void mkOutputString(EvalState & state, Value & v,
argument. */
static void import(EvalState & state, const Pos & pos, Value & vPath, Value * vScope, Value & v)
{
- std::cout << " IMPORT " << std::endl;
- std::cout << " import " << std::endl;
- std::cout << " IMPORT " << std::endl;
- std::cout << " import " << std::endl;
+ // std::cout << " IMPORT " << std::endl;
+ // std::cout << " import " << std::endl;
+ // std::cout << " IMPORT " << std::endl;
+ // std::cout << " import " << std::endl;
PathSet context;
Path path = state.coerceToPath(pos, vPath, context);
From 383ab600ee1f36f14677a0082473f5680193c12c Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Fri, 22 Oct 2021 13:41:04 -0600
Subject: [PATCH 046/188] show expr on error
---
src/libcmd/command.cc | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index d8e79953c..2d86dbd61 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -110,6 +110,10 @@ ref<EvalState> EvalCommand::getEvalState()
printStaticEnvBindings(expr);
+ std::cout << "expr: " << std::endl;
+ expr.show(std::cout);
+ std::cout << std::endl;
+
// printEnvPosChain(env);
// printEnvBindings(env);
if (expr.staticenv)
From cbc2f0fe31576a6403e179bdbbaf9aefa113555b Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Fri, 22 Oct 2021 14:02:47 -0600
Subject: [PATCH 047/188] remove dead code
---
src/libcmd/command.cc | 36 ----------
src/libexpr/eval.cc | 157 ------------------------------------------
src/libexpr/eval.hh | 3 -
3 files changed, 196 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 2d86dbd61..8d5098bc7 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -54,7 +54,6 @@ void StoreCommand::run()
run(getStore());
}
-/*
EvalCommand::EvalCommand()
{
addFlag({
@@ -64,39 +63,6 @@ EvalCommand::EvalCommand()
});
}
-extern std::function<void(const Error & error, const std::map<std::string, Value *> & env)> debuggerHook;
-
-ref<EvalState> EvalCommand::getEvalState()
-{
- if (!evalState) {
- evalState = std::make_shared<EvalState>(searchPath, getStore());
- if (startReplOnEvalErrors)
- debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error & error, const std::map<std::string, Value *> & env) {
- printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error.what());
- runRepl(evalState, env);
- };
- }
- return ref<EvalState>(evalState);
-}
-*/
-// ref<EvalState> EvalCommand::getEvalState()
-// {
-// if (!evalState)
-// evalState = std::make_shared<EvalState>(searchPath, getStore());
-// return ref<EvalState>(evalState);
-// }
-
-
-EvalCommand::EvalCommand()
-{
- // std::cout << "EvalCommand::EvalCommand()" << std::endl;
- addFlag({
- .longName = "debugger",
- .description = "start an interactive environment if evaluation fails",
- .handler = {&startReplOnEvalErrors, true},
- });
-}
-// extern std::function<void(const Error & error, const std::map<std::string, Value *> & env)> debuggerHook;
extern std::function<void(const Error & error, const Env & env, const Expr & expr)> debuggerHook;
ref<EvalState> EvalCommand::getEvalState()
@@ -114,8 +80,6 @@ ref<EvalState> EvalCommand::getEvalState()
expr.show(std::cout);
std::cout << std::endl;
- // printEnvPosChain(env);
- // printEnvBindings(env);
if (expr.staticenv)
{
auto vm = mapStaticEnvBindings(*expr.staticenv.get(), env);
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 12f7e8979..f286cbeec 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -619,75 +619,7 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
return {};
}
-// typedef std::map<std::string, Value *> valmap;
-/*void addEnv(Value * v, valmap &vmap)
-{
- if (v.isThunk()) {
- Env * env = v.thunk.env;
-
- Expr * expr = v.thunk.expr;
-
-}
-*/
-// LocalNoInline(valmap * map0())
-// {
-// return new valmap();
-// }
-
-// LocalNoInline(valmap * map1(const char *name, Value *v))
-// {
-// return new valmap({{name, v}});
-// }
-
-// LocalNoInline(valmap * map2(const char *name1, Value *v1, const char *name2, Value *v2))
-// {
-// return new valmap({{name1, v1}, {name2, v2}});
-// }
-
-// LocalNoInline(valmap * mapBindings(Bindings &b))
-// {
-// auto map = new valmap();
-// for (auto i = b.begin(); i != b.end(); ++i)
-// {
-// std::string s = i->name;
-// (*map)[s] = i->value;
-// }
-// return map;
-// }
-
-// LocalNoInline(void addBindings(string prefix, Bindings &b, valmap &valmap))
-// {
-// for (auto i = b.begin(); i != b.end(); ++i)
-// {
-// std::string s = prefix;
-// s += i->name;
-// valmap[s] = i->value;
-// }
-// }
-
-void printEnvBindings(const Env &env, int lv )
-{
- std::cout << "env " << lv << " type: " << env.type << std::endl;
- if (env.values[0]->type() == nAttrs) {
- Bindings::iterator j = env.values[0]->attrs->begin();
-
-
- while (j != env.values[0]->attrs->end()) {
- std::cout << lv << " env binding: " << j->name << std::endl;
- // if (countCalls && j->pos) attrSelects[*j->pos]++;
- // return j->value;
- j++;
- }
-
- }
-
- std::cout << "next env : " << env.up << std::endl;
-
- if (env.up) {
- printEnvBindings(*env.up, ++lv);
- }
-}
void printStaticEnvBindings(const StaticEnv &se, int lvl)
{
@@ -740,95 +672,6 @@ valmap * mapStaticEnvBindings(const StaticEnv &se, const Env &env)
}
-void printEnvPosChain(const Env &env, int lv )
-{
- // std::cout << "printEnvPosChain " << lv << std::endl;
-
- // std::cout << "env" << env.values[0] << std::endl;
-
- if (env.values[0] && env.values[0]->type() == nAttrs) {
- // std::cout << "im in the loop" << std::endl;
- // std::cout << "pos " << env.values[0]->attrs->pos << std::endl;
- if (env.values[0]->attrs->pos) {
- ErrPos ep(*env.values[0]->attrs->pos);
- auto loc = getCodeLines(ep);
- if (loc)
- printCodeLines(std::cout,
- std::__cxx11::to_string(lv),
- ep,
- *loc);
- }
- }
-
- // std::cout << "next env : " << env.up << std::endl;
-
- if (env.up) {
- printEnvPosChain(*env.up, ++lv);
- }
-}
-
-void mapEnvBindings(const Env &env, valmap & vm)
-{
- // add bindings for the next level up first.
- if (env.up) {
- mapEnvBindings(*env.up, vm);
- }
-
- // merge - and write over - higher level bindings.
- // note; skipping HasWithExpr that haven't been evaled yet.
- if (env.values[0] && env.values[0]->type() == nAttrs) {
- auto map = valmap();
-
- Bindings::iterator j = env.values[0]->attrs->begin();
-
- while (j != env.values[0]->attrs->end()) {
- map[j->name] = j->value;
- j++;
- }
- vm.merge(map);
- }
-}
-
-
-valmap * mapEnvBindings(const Env &env)
-{
- auto vm = new valmap();
-
- mapEnvBindings(env, *vm);
-
- return vm;
-}
-
-// LocalNoInline(valmap * mapEnvBindings(Env &env))
-// {
-// // NOT going to use this
-// if (env.valuemap) {
-// std::cout << "got static env" << std::endl;
-// }
-
-// // std::cout << "envsize: " << env.values.size() << std::endl;
-
-// // std::cout << "size_t size: " << sizeof(size_t) << std::endl;
-// // std::cout << "envsize: " << env.size << std::endl;
-// // std::cout << "envup: " << env.up << std::endl;
-
-// valmap *vm = env.up ? mapEnvBindings(*env.up) : new valmap();
-
-// /*
-// size_t i=0;
-// do {
-// std::cout << "env: " << i << " value: " << showType(*env.values[i]) << std::endl;
-// // std::cout << *env.values[i] << std::endl;
-// ++i;
-// } while(i < (std::min(env.size, (size_t)100)));
-
-
-// if (env.values[0]->type() == nAttrs)
-// addBindings(std::to_string((int)env.size), *env.values[0]->attrs, *vm);
-// */
-// return vm;
-// }
-
/* Every "format" object (even temporary) takes up a few hundred bytes
of stack space, which is a real killer in the recursive
evaluator. So here are some helper functions for throwing
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 29599cc6c..ae1e6ee60 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -45,9 +45,6 @@ struct Env
Value * values[0];
};
-void printEnvBindings(const Env &env, int lv = 0);
-valmap * mapEnvBindings(const Env &env);
-void printEnvPosChain(const Env &env, int lv = 0);
valmap * mapStaticEnvBindings(const StaticEnv &se, const Env &env);
Value & mkString(Value & v, std::string_view s, const PathSet & context = PathSet());
From e54f17eb46bc487abc38e70dfc2f1c617fb59d32 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Fri, 22 Oct 2021 14:27:04 -0600
Subject: [PATCH 048/188] remove more debug code
---
src/libcmd/command.cc | 3 +-
src/libcmd/installables.cc | 18 -------
src/libcmd/repl.cc | 1 -
src/libexpr/eval.cc | 98 ++++----------------------------------
src/libexpr/parser.y | 9 ----
src/libexpr/primops.cc | 7 ---
src/nix/flake.cc | 1 -
7 files changed, 9 insertions(+), 128 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 8d5098bc7..8a6dd71b2 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -67,7 +67,6 @@ extern std::function<void(const Error & error, const Env & env, const Expr & exp
ref<EvalState> EvalCommand::getEvalState()
{
- std::cout << "EvalCommand::getEvalState()" << startReplOnEvalErrors << std::endl;
if (!evalState) {
evalState = std::make_shared<EvalState>(searchPath, getStore());
if (startReplOnEvalErrors)
@@ -80,7 +79,7 @@ ref<EvalState> EvalCommand::getEvalState()
expr.show(std::cout);
std::cout << std::endl;
- if (expr.staticenv)
+ if (expr.staticenv)
{
auto vm = mapStaticEnvBindings(*expr.staticenv.get(), env);
runRepl(evalState, *vm);
diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index c3436acf9..7f7a89b37 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -249,20 +249,6 @@ void completeFlakeRefWithFragment(
completeFlakeRef(evalState->store, prefix);
}
-/*
-ref<EvalState> EvalCommand::getEvalState()
-{
- if (!evalState)
- evalState = std::make_shared<EvalState>(searchPath, getStore());
- return ref<EvalState>(evalState);
-}
-
-EvalCommand::~EvalCommand()
-{
- if (evalState)
- evalState->printStats();
-}
-*/
void completeFlakeRef(ref<Store> store, std::string_view prefix)
{
@@ -618,11 +604,7 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
if (file)
state->evalFile(lookupFileArg(*state, *file), *vFile);
else {
- // std::cout << "pre parseExprFromString" << std::endl;
auto e = state->parseExprFromString(*expr, absPath("."));
-
- // std::cout << "pre eval" << std::endl;
-
state->eval(e, *vFile);
}
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index e1b58cc76..bfc131d27 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -54,7 +54,6 @@ struct NixRepl
const static int envSize = 32768;
std::shared_ptr<StaticEnv> staticEnv;
- // StaticEnv staticEnv;
Env * env;
int displ;
StringSet varNames;
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index f286cbeec..73609c3d2 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -35,7 +35,6 @@
namespace nix {
-// std::function<void(const Error & error, const std::map<std::string, Value *> & env)> debuggerHook;
std::function<void(const Error & error, const Env & env, const Expr & expr)> debuggerHook;
static char * dupString(const char * s)
@@ -407,7 +406,8 @@ EvalState::EvalState(const Strings & _searchPath, ref<Store> store)
assert(gcInitialised);
- static_assert(sizeof(Env) <= 16 + sizeof(std::unique_ptr<void*>), "environment must be <= 16 bytes");
+ // static_assert(sizeof(Env) <= 16 + sizeof(std::unique_ptr<void*>), "environment must be <= 16 bytes");
+ static_assert(sizeof(Env) <= 16, "environment must be <= 16 bytes");
/* Initialise the Nix expression search path. */
if (!evalSettings.pureEval) {
@@ -646,13 +646,13 @@ void printStaticEnvBindings(const Expr &expr)
void mapStaticEnvBindings(const StaticEnv &se, const Env &env, valmap & vm)
{
- // add bindings for the next level up first.
+ // add bindings for the next level up first, so that the bindings for this level
+ // override the higher levels.
if (env.up && se.up) {
mapStaticEnvBindings( *se.up, *env.up,vm);
}
- // iterate through staticenv bindings.
-
+ // iterate through staticenv bindings and add them.
auto map = valmap();
for (auto iter = se.vars.begin(); iter != se.vars.end(); ++iter)
{
@@ -679,7 +679,6 @@ valmap * mapStaticEnvBindings(const StaticEnv &se, const Env &env)
LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, Env & env, Expr *expr))
{
- // auto delenv = std::unique_ptr<valmap>(env);
auto error = EvalError(s, s2);
if (debuggerHook && expr)
@@ -689,7 +688,6 @@ LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, Env
LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2, Env & env, Expr *expr))
{
- // auto delenv = std::unique_ptr<valmap>(env);
auto error = EvalError({
.msg = hintfmt(s, s2),
.errPos = pos
@@ -703,7 +701,6 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const
LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, const string & s3, Env & env, Expr *expr))
{
- // auto delenv = std::unique_ptr<valmap>(env);
auto error = EvalError(s, s2, s3);
if (debuggerHook && expr)
@@ -714,7 +711,6 @@ LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, con
LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2, const string & s3, Env & env, Expr *expr))
{
- // auto delenv = std::unique_ptr<valmap>(env);
auto error = EvalError({
.msg = hintfmt(s, s2, s3),
.errPos = pos
@@ -729,7 +725,6 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const
LocalNoInlineNoReturn(void throwEvalError(const Pos & p1, const char * s, const Symbol & sym, const Pos & p2, Env & env, Expr *expr))
{
// p1 is where the error occurred; p2 is a position mentioned in the message.
- // auto delenv = std::unique_ptr<valmap>(env);
auto error = EvalError({
.msg = hintfmt(s, sym, p2),
.errPos = p1
@@ -743,7 +738,6 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & p1, const char * s, const
LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, Env & env, Expr *expr))
{
- // auto delenv = std::unique_ptr<valmap>(env);
auto error = TypeError({
.msg = hintfmt(s),
.errPos = pos
@@ -757,7 +751,6 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, Env &
LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v, Env & env, Expr *expr))
{
- // auto delenv = std::unique_ptr<valmap>(env);
auto error = TypeError({
.msg = hintfmt(s, v),
.errPos = pos
@@ -771,7 +764,6 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const string &s2, Env & env, Expr *expr))
{
- // auto delenv = std::unique_ptr<valmap>(env);
auto error = TypeError({
.msg = hintfmt(s, s2),
.errPos = pos
@@ -785,7 +777,6 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const ExprLambda & fun, const Symbol & s2, Env & env, Expr *expr))
{
- // auto delenv = std::unique_ptr<valmap>(env);
auto error = TypeError({
.msg = hintfmt(s, fun.showNamePos(), s2),
.errPos = pos
@@ -799,7 +790,6 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s, const string & s1, Env & env, Expr *expr))
{
- // auto delenv = std::unique_ptr<valmap>(env);
auto error = AssertionError({
.msg = hintfmt(s, s1),
.errPos = pos
@@ -813,16 +803,11 @@ LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s,
LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char * s, const string & s1, Env & env, Expr *expr))
{
- // std::cout << "throwUndefinedVarError" << std::endl;
-
- // auto delenv = std::unique_ptr<valmap>(env);
auto error = UndefinedVarError({
.msg = hintfmt(s, s1),
.errPos = pos
});
- // std::cout << "pre debuggerHook" << std::endl;
-
if (debuggerHook && expr)
debuggerHook(error, env, *expr);
@@ -831,7 +816,6 @@ LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char *
LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char * s, const string & s1, Env & env, Expr *expr))
{
- // auto delenv = std::unique_ptr<valmap>(env);
auto error = MissingArgumentError({
.msg = hintfmt(s, s1),
.errPos = pos
@@ -881,8 +865,6 @@ void mkPath(Value & v, const char * s)
inline Value * EvalState::lookupVar(Env * env, const ExprVar & var, bool noEval)
{
- // std::cout << " EvalState::lookupVar" << var << std::endl;
-
for (size_t l = var.level; l; --l, env = env->up) ;
if (!var.fromWith) return env->values[var.displ];
@@ -901,7 +883,6 @@ inline Value * EvalState::lookupVar(Env * env, const ExprVar & var, bool noEval)
return j->value;
}
if (!env->prevWith) {
- // std::cout << "pre throwUndefinedVarError" << std::endl;
throwUndefinedVarError(var.pos, "undefined variable '%1%'", var.name, *env, 0);
}
for (size_t l = env->prevWith; l; --l, env = env->up) ;
@@ -930,25 +911,9 @@ Env & EvalState::allocEnv(size_t size)
nrEnvs++;
nrValuesInEnvs += size;
- // if (debuggerHook)
- // {
- // Env * env = (Env *) allocBytes(sizeof(DebugEnv) + size * sizeof(Value *));
- // // Env * env = new DebugEnv;
- // env->type = Env::Plain;
- // /* We assume that env->values has been cleared by the allocator; maybeThunk() and lookupVar fromWith expect this. */
-
- // return *env;
- // } else {
- Env * env = (Env *) allocBytes(sizeof(Env) + size * sizeof(Value *));
- env->type = Env::Plain;
- // env->size = size;
-
- /* We assume that env->values has been cleared by the allocator; maybeThunk() and lookupVar fromWith expect this. */
-
- return *env;
- // }
-
-
+ Env * env = (Env *) allocBytes(sizeof(Env) + size * sizeof(Value *));
+ env->type = Env::Plain;
+ return *env;
}
Env & fakeEnv(size_t size)
@@ -1237,7 +1202,6 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
if (j != v.attrs->end())
throwEvalError(i.pos, "dynamic attribute '%1%' already defined at %2%", nameSym, *j->pos,
env, this);
- // map1("value", &v)); // TODO dynamicAttrs to env?
i.valueExpr->setName(nameSym);
/* Keep sorted order so find can catch duplicates */
@@ -1594,8 +1558,6 @@ values, or passed explicitly with '--arg' or '--argstr'. See
https://nixos.org/manual/nix/stable/#ss-functions.)",
i.name,
*fun.lambda.env, fun.lambda.fun);
- // mapBindings(args));
- // map1("fun", &fun)); // todo add bindings + fun
}
}
}
@@ -1608,25 +1570,12 @@ https://nixos.org/manual/nix/stable/#ss-functions.)",
void ExprWith::eval(EvalState & state, Env & env, Value & v)
{
- // std::cout << "ExprWith::eval" << std::endl;
Env & env2(state.allocEnv(1));
env2.up = &env;
env2.prevWith = prevWith;
env2.type = Env::HasWithExpr;
env2.values[0] = (Value *) attrs; // ok DAG nasty. just smoosh this in.
// presumably evaluate later, lazily.
- // std::cout << "ExprWith::eval2" << std::endl;
-
- // can't load the valuemap until they've been evaled, which is not yet.
- // if (debuggerHook) {
- // std::cout << "ExprWith::eval3.0" << std::endl;
- // std::cout << "ExprWith attrs" << *attrs << std::endl;
- // state.forceAttrs(*(Value*) attrs);
- // std::cout << "ExprWith::eval3.5" << std::endl;
- // env2.valuemap.reset(mapBindings(*env2.values[0]->attrs));
- // std::cout << "ExprWith::eval4" << std::endl;
- // }
-
body->eval(state, env2, v);
}
@@ -1867,7 +1816,6 @@ NixInt EvalState::forceInt(Value & v, const Pos & pos)
if (v.type() != nInt)
throwTypeError(pos, "value is %1% while an integer was expected", v,
fakeEnv(1), 0);
- // map1("value", &v));
return v.integer;
}
@@ -1880,7 +1828,6 @@ NixFloat EvalState::forceFloat(Value & v, const Pos & pos)
else if (v.type() != nFloat)
throwTypeError(pos, "value is %1% while a float was expected", v,
fakeEnv(1), 0);
- // map1("value", &v));
return v.fpoint;
}
@@ -1891,7 +1838,6 @@ bool EvalState::forceBool(Value & v, const Pos & pos)
if (v.type() != nBool)
throwTypeError(pos, "value is %1% while a Boolean was expected", v,
fakeEnv(1), 0);
- // map1("value", &v));
return v.boolean;
}
@@ -1908,7 +1854,6 @@ void EvalState::forceFunction(Value & v, const Pos & pos)
if (v.type() != nFunction && !isFunctor(v))
throwTypeError(pos, "value is %1% while a function was expected", v,
fakeEnv(1), 0);
- // map1("value", &v));
}
@@ -1918,7 +1863,6 @@ string EvalState::forceString(Value & v, const Pos & pos)
if (v.type() != nString) {
throwTypeError(pos, "value is %1% while a string was expected", v,
fakeEnv(1), 0);
- // map1("value", &v));
}
return string(v.string.s);
}
@@ -1970,37 +1914,15 @@ string EvalState::forceStringNoCtx(Value & v, const Pos & pos)
if (pos)
throwEvalError(pos, "the string '%1%' is not allowed to refer to a store path (such as '%2%')",
v.string.s, v.string.context[0],
- // b.has_value() ? mapBindings(*b.get()) : map0());
fakeEnv(1), 0);
- // map1("value", &v));
else
throwEvalError("the string '%1%' is not allowed to refer to a store path (such as '%2%')",
v.string.s, v.string.context[0],
- // b.has_value() ? mapBindings(*b.get()) : map0());
fakeEnv(1), 0);
- // map1("value", &v));
}
return s;
}
-/*string EvalState::forceStringNoCtx(std::optional<Bindings*> b, Value & v, const Pos & pos)
-{
- string s = forceString(v, pos);
- if (v.string.context) {
- if (pos)
- throwEvalError(pos, "the string '%1%' is not allowed to refer to a store path (such as '%2%')",
- v.string.s, v.string.context[0],
- b.has_value() ? mapBindings(*b.get()) : map0());
- // map1("value", &v));
- else
- throwEvalError("the string '%1%' is not allowed to refer to a store path (such as '%2%')",
- v.string.s, v.string.context[0],
- b.has_value() ? mapBindings(*b.get()) : map0());
- // map1("value", &v));
- }
- return s;
-}*/
-
bool EvalState::isDerivation(Value & v)
{
@@ -2084,7 +2006,6 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
throwTypeError(pos, "cannot coerce %1% to a string", v,
fakeEnv(1), 0);
- // map1("value", &v));
}
@@ -2094,7 +2015,6 @@ string EvalState::copyPathToStore(PathSet & context, const Path & path)
throwEvalError("file names are not allowed to end in '%1%'",
drvExtension,
fakeEnv(1), 0);
- // map0());
Path dstPath;
auto i = srcToStore.find(path);
@@ -2120,7 +2040,6 @@ Path EvalState::coerceToPath(const Pos & pos, Value & v, PathSet & context)
if (path == "" || path[0] != '/')
throwEvalError(pos, "string '%1%' doesn't represent an absolute path", path,
fakeEnv(1), 0);
- // map1("value", &v));
return path;
}
@@ -2203,7 +2122,6 @@ bool EvalState::eqValues(Value & v1, Value & v2)
showType(v1),
showType(v2),
fakeEnv(1), 0);
- // map2("value1", &v1, "value2", &v2));
}
}
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index 46bbce1f6..d6d5c85f5 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -574,10 +574,6 @@ namespace nix {
Expr * EvalState::parse(const char * text, FileOrigin origin,
const Path & path, const Path & basePath, std::shared_ptr<StaticEnv> & staticEnv)
{
- // std::cout << "EvalState::parse " << text << std::endl;
- // for (auto i = staticEnv->vars.begin(); i != staticEnv->vars.end(); ++i)
- // std::cout << "EvalState::parse staticEnv " << i->first << std::endl;
-
yyscan_t scanner;
ParseData data(*this);
data.origin = origin;
@@ -601,13 +597,8 @@ Expr * EvalState::parse(const char * text, FileOrigin origin,
if (res) throw ParseError(data.error.value());
-
- // std::cout << "EvalState::parse pre bindvars " << std::endl;
-
data.result->bindVars(staticEnv);
- // std::cout << "EvalState::parse post bindVars " << std::endl;
-
return data.result;
}
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 4b8ad3e9a..0400c8942 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -110,11 +110,6 @@ static void mkOutputString(EvalState & state, Value & v,
argument. */
static void import(EvalState & state, const Pos & pos, Value & vPath, Value * vScope, Value & v)
{
- // std::cout << " IMPORT " << std::endl;
- // std::cout << " import " << std::endl;
- // std::cout << " IMPORT " << std::endl;
- // std::cout << " import " << std::endl;
-
PathSet context;
Path path = state.coerceToPath(pos, vPath, context);
@@ -199,8 +194,6 @@ static void import(EvalState & state, const Pos & pos, Value & vPath, Value * vS
env->values[displ++] = attr.value;
}
- std::cout << "import staticenv: {} " << staticEnv << std::endl;
-
printTalkative("evaluating file '%1%'", realPath);
Expr * e = state.parseExprFromFile(resolveExprPath(realPath), staticEnv);
diff --git a/src/nix/flake.cc b/src/nix/flake.cc
index 6af052008..62a413e27 100644
--- a/src/nix/flake.cc
+++ b/src/nix/flake.cc
@@ -408,7 +408,6 @@ struct CmdFlakeCheck : FlakeCommand
if (auto attr = v.attrs->get(state->symbols.create("description")))
state->forceStringNoCtx(*attr->value, *attr->pos);
- // state->forceStringNoCtx(std::optional(v.attrs), *attr->value, *attr->pos);
else
throw Error("template '%s' lacks attribute 'description'", attrPath);
From 71da988d47433543e70cd52dbdd6c907dd3cabda Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Fri, 22 Oct 2021 14:34:50 -0600
Subject: [PATCH 049/188] more debug removal
---
src/libcmd/local.mk | 2 +-
src/libexpr/eval.cc | 4 +---
2 files changed, 2 insertions(+), 4 deletions(-)
diff --git a/src/libcmd/local.mk b/src/libcmd/local.mk
index c282499b1..df904612b 100644
--- a/src/libcmd/local.mk
+++ b/src/libcmd/local.mk
@@ -10,6 +10,6 @@ libcmd_CXXFLAGS += -I src/libutil -I src/libstore -I src/libexpr -I src/libmain
libcmd_LDFLAGS = $(EDITLINE_LIBS) -llowdown
-libcmd_LIBS = libstore libutil libexpr libmain libfetchers libnix libwut
+libcmd_LIBS = libstore libutil libexpr libmain libfetchers libnix
$(eval $(call install-file-in, $(d)/nix-cmd.pc, $(prefix)/lib/pkgconfig, 0644))
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 73609c3d2..719dcc1b4 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -406,7 +406,6 @@ EvalState::EvalState(const Strings & _searchPath, ref<Store> store)
assert(gcInitialised);
- // static_assert(sizeof(Env) <= 16 + sizeof(std::unique_ptr<void*>), "environment must be <= 16 bytes");
static_assert(sizeof(Env) <= 16, "environment must be <= 16 bytes");
/* Initialise the Nix expression search path. */
@@ -1574,8 +1573,7 @@ void ExprWith::eval(EvalState & state, Env & env, Value & v)
env2.up = &env;
env2.prevWith = prevWith;
env2.type = Env::HasWithExpr;
- env2.values[0] = (Value *) attrs; // ok DAG nasty. just smoosh this in.
- // presumably evaluate later, lazily.
+ env2.values[0] = (Value *) attrs;
body->eval(state, env2, v);
}
From fb8377547bcb6d4dc6464ca34c0fe433e1cfda44 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Fri, 22 Oct 2021 14:49:58 -0600
Subject: [PATCH 050/188] more code cleanup
---
src/libexpr/eval.cc | 7 +--
src/libexpr/nixexpr.cc | 132 ++++++++++-------------------------------
src/libexpr/parser.y | 2 -
3 files changed, 33 insertions(+), 108 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 719dcc1b4..4dde92c0a 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -912,6 +912,9 @@ Env & EvalState::allocEnv(size_t size)
nrValuesInEnvs += size;
Env * env = (Env *) allocBytes(sizeof(Env) + size * sizeof(Value *));
env->type = Env::Plain;
+
+ /* We assume that env->values has been cleared by the allocator; maybeThunk() and lookupVar fromWith expect this. */
+
return *env;
}
@@ -925,7 +928,6 @@ Env & fakeEnv(size_t size)
return *env;
}
-
void EvalState::mkList(Value & v, size_t size)
{
v.mkList(size);
@@ -1291,7 +1293,6 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
state.forceAttrs(*vAttrs, pos);
if ((j = vAttrs->attrs->find(name)) == vAttrs->attrs->end())
throwEvalError(pos, "attribute '%1%' missing", name, env, this);
- // mapBindings(*vAttrs->attrs));
}
vAttrs = j->value;
pos2 = j->pos;
@@ -1419,8 +1420,6 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
"attempt to call something which is not a function but %1%",
showType(fun).c_str(),
fakeEnv(1), 0);
- // fun.env);
- // map2("fun", &fun, "arg", &arg));
}
ExprLambda & lambda(*fun.lambda.fun);
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index 8f88eabd5..65c7cac1d 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -273,52 +273,36 @@ void ExprVar::bindVars(const std::shared_ptr<const StaticEnv> &env)
/* Check whether the variable appears in the environment. If so,
set its level and displacement. */
-
- // std::cout << "ExprVar::bindVars " << name << std::endl;
-
- int a = 10;
- if (name == "callPackage") {
- a++; // try to make code that I can put a breakpoint on...
- // std::cout << "meh" << a + 10 << std::endl;
- int withLevel = -1;
- fromWith = true;
- // this->level = withLevel;
- }
-
- {
-
- const StaticEnv * curEnv;
- unsigned int level;
- int withLevel = -1;
- for (curEnv = env.get(), level = 0; curEnv; curEnv = curEnv->up, level++) {
- if (curEnv->isWith) {
- if (withLevel == -1) withLevel = level;
- } else {
- StaticEnv::Vars::const_iterator i = curEnv->vars.find(name);
- if (i != curEnv->vars.end()) {
- fromWith = false;
- this->level = level;
- displ = i->second;
- return;
- }
+ const StaticEnv * curEnv;
+ unsigned int level;
+ int withLevel = -1;
+ for (curEnv = env.get(), level = 0; curEnv; curEnv = curEnv->up, level++) {
+ if (curEnv->isWith) {
+ if (withLevel == -1) withLevel = level;
+ } else {
+ StaticEnv::Vars::const_iterator i = curEnv->vars.find(name);
+ if (i != curEnv->vars.end()) {
+ fromWith = false;
+ this->level = level;
+ displ = i->second;
+ return;
}
}
-
-
- /* Otherwise, the variable must be obtained from the nearest
- enclosing `with'. If there is no `with', then we can issue an
- "undefined variable" error now. */
- if (withLevel == -1)
- {
- // std::cout << " throw UndefinedVarError({" << std::endl;
- throw UndefinedVarError({
- .msg = hintfmt("undefined variable (ExprVar bindvars) '%1%'", name),
- .errPos = pos
- });
- }
- fromWith = true;
- this->level = withLevel;
}
+
+ /* Otherwise, the variable must be obtained from the nearest
+ enclosing `with'. If there is no `with', then we can issue an
+ "undefined variable" error now. */
+ if (withLevel == -1)
+ {
+ // std::cout << " throw UndefinedVarError({" << std::endl;
+ throw UndefinedVarError({
+ .msg = hintfmt("undefined variable (ExprVar bindvars) '%1%'", name),
+ .errPos = pos
+ });
+ }
+ fromWith = true;
+ this->level = withLevel;
}
void ExprSelect::bindVars(const std::shared_ptr<const StaticEnv> &env)
@@ -349,18 +333,11 @@ void ExprAttrs::bindVars(const std::shared_ptr<const StaticEnv> &env)
if (debuggerHook)
staticenv = env;
- // std::cout << "ExprAttrs::bindVars" << std::endl;
- // auto dynamicEnv(env);
-
if (recursive) {
- // std::cout << "recursive" << std::endl;
- // dynamicEnv = newEnv.get();
- // also make shared_ptr?
auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, env.get()));
unsigned int displ = 0;
for (auto & i : attrs) {
- // std::cout << "newenvvar: " << i.first << std::endl;
newEnv->vars[i.first] = i.second.displ = displ++;
}
@@ -373,7 +350,6 @@ void ExprAttrs::bindVars(const std::shared_ptr<const StaticEnv> &env)
}
}
else {
- // std::cout << "NOT recursive" << std::endl;
for (auto & i : attrs)
i.second.e->bindVars(env);
@@ -382,9 +358,6 @@ void ExprAttrs::bindVars(const std::shared_ptr<const StaticEnv> &env)
i.valueExpr->bindVars(env);
}
}
-
- // std::cout << "ExprAttrs::bindVars end" << std::endl;
-
}
void ExprList::bindVars(const std::shared_ptr<const StaticEnv> &env)
@@ -401,7 +374,7 @@ void ExprLambda::bindVars(const std::shared_ptr<const StaticEnv> &env)
if (debuggerHook)
staticenv = env;
- auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, env.get())); // also make shared_ptr?
+ auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, env.get()));
unsigned int displ = 0;
@@ -423,7 +396,7 @@ void ExprLet::bindVars(const std::shared_ptr<const StaticEnv> &env)
if (debuggerHook)
staticenv = env;
- auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, env.get())); // also make shared_ptr?
+ auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, env.get()));
unsigned int displ = 0;
for (auto & i : attrs->attrs)
@@ -440,7 +413,6 @@ void ExprWith::bindVars(const std::shared_ptr<const StaticEnv> &env)
if (debuggerHook)
staticenv = env;
- // std::cout << " ExprWith::bindVars " << std::endl;
/* Does this `with' have an enclosing `with'? If so, record its
level so that `lookupVar' can look up variables in the previous
`with' if this one doesn't contain the desired attribute. */
@@ -453,54 +425,10 @@ void ExprWith::bindVars(const std::shared_ptr<const StaticEnv> &env)
break;
}
- // std::cout << " ExprWith::bindVars 1" << std::endl;
- // attrs->show(std::cout);
- // std::cout << std::endl;
attrs->bindVars(env);
- auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(true, env.get())); // also make shared_ptr?
- // std::cout << " ExprWith::bindVars 2" << std::endl;
- // std::cout << " body: " << std::endl;
- // body->show(std::cout);
- // std::cout << std::endl;
-
- // std::cout << "ExprWith::newenv: (iswith, size); (" << newEnv->isWith << ", " << newEnv->vars.size() << ") " << std::endl;
- // for (auto i = newEnv->vars.begin(); i != newEnv->vars.end(); ++i)
- // std::cout << "EvalState::parse newEnv " << i->first << std::endl;
-
-
- // std::cout << " body->bindVars(newEnv), iswith: " << newEnv->isWith << std::endl;
- body->bindVars(newEnv);
- // std::cout << " ExprWith::bindVars 3" << std::endl;
-}
-
-/*
-void ExprWith::bindVars(const StaticEnv & env)
-{
- // Does this `with' have an enclosing `with'? If so, record its
- // level so that `lookupVar' can look up variables in the previous
- // `with' if this one doesn't contain the desired attribute.
- const StaticEnv * curEnv;
- unsigned int level;
- prevWith = 0;
- for (curEnv = &env, level = 1; curEnv; curEnv = curEnv->up, level++)
- if (curEnv->isWith) {
- prevWith = level;
- break;
- }
-
- attrs->bindVars(env);
- std::cout << "ExprWith::bindVars env: " << env.vars.size(); // add std::endl;
- for (auto i = env.vars.begin(); i != env.vars.end(); ++i)
- {
- std::cout << i->first << std::endl;
- }
-
- StaticEnv newEnv(true, &env);
+ auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(true, env.get()));
body->bindVars(newEnv);
}
-*/
-
-
void ExprIf::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index d6d5c85f5..d1e898677 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -22,8 +22,6 @@
#include "eval.hh"
#include "globals.hh"
-#include <iostream>
-
namespace nix {
struct ParseData
From 885f819922d7c4b3823090ca4c9ee832f5080bde Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Tue, 9 Nov 2021 11:20:14 -0700
Subject: [PATCH 051/188] remove dead code
---
src/libexpr/eval.cc | 5 -----
1 file changed, 5 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 4dde92c0a..32d51ab87 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -1433,8 +1433,6 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
size_t displ = 0;
if (!lambda.matchAttrs){
- // TODO: what is this arg? empty argument?
- // add empty valmap here?
env2.values[displ++] = &arg;
}
else {
@@ -1457,7 +1455,6 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
lambda,
i.name,
*fun.lambda.env, &lambda);
- // map2("fun", &fun, "arg", &arg));
env2.values[displ++] = i.def->maybeThunk(*this, env2);
} else {
attrsUsed++;
@@ -1478,7 +1475,6 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
lambda,
i.name,
*fun.lambda.env, &lambda);
- // map2("fun", &fun, "arg", &arg));
abort(); // can't happen
}
}
@@ -1971,7 +1967,6 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
if (i == v.attrs->end())
throwTypeError(pos, "cannot coerce a set to a string",
fakeEnv(1), 0);
- // map1("value", &v));
return coerceToString(pos, *i->value, context, coerceMore, copyToStore);
}
From 7e2a3db4eb663aa99aec7ebcc83d75cb948a2cb3 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Tue, 9 Nov 2021 13:14:49 -0700
Subject: [PATCH 052/188] cleanup
---
src/libexpr/eval.cc | 20 +++++++-------------
src/libexpr/eval.hh | 1 -
src/libexpr/nixexpr.cc | 1 -
3 files changed, 7 insertions(+), 15 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 32d51ab87..8e263334a 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -78,8 +78,6 @@ void printValue(std::ostream & str, std::set<const Value *> & active, const Valu
return;
}
- str << "internal type: " << v.internalType << std::endl;
-
switch (v.internalType) {
case tInt:
str << v.integer;
@@ -1569,7 +1567,7 @@ void ExprWith::eval(EvalState & state, Env & env, Value & v)
env2.prevWith = prevWith;
env2.type = Env::HasWithExpr;
env2.values[0] = (Value *) attrs;
-
+
body->eval(state, env2, v);
}
@@ -1737,8 +1735,6 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
nf = n;
nf += vTmp.fpoint;
} else {
- std::cerr << "envtype: " << showType(env.values[0]->type()) << std::endl;
-
throwEvalError(pos, "cannot add %1% to an integer", showType(vTmp), env, this);
}
} else if (firstType == nFloat) {
@@ -1829,7 +1825,7 @@ bool EvalState::forceBool(Value & v, const Pos & pos)
{
forceValue(v, pos);
if (v.type() != nBool)
- throwTypeError(pos, "value is %1% while a Boolean was expected", v,
+ throwTypeError(pos, "value is %1% while a Boolean was expected", v,
fakeEnv(1), 0);
return v.boolean;
}
@@ -1906,12 +1902,10 @@ string EvalState::forceStringNoCtx(Value & v, const Pos & pos)
if (v.string.context) {
if (pos)
throwEvalError(pos, "the string '%1%' is not allowed to refer to a store path (such as '%2%')",
- v.string.s, v.string.context[0],
- fakeEnv(1), 0);
+ v.string.s, v.string.context[0], fakeEnv(1), 0);
else
throwEvalError("the string '%1%' is not allowed to refer to a store path (such as '%2%')",
- v.string.s, v.string.context[0],
- fakeEnv(1), 0);
+ v.string.s, v.string.context[0], fakeEnv(1), 0);
}
return s;
}
@@ -1965,7 +1959,7 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
}
auto i = v.attrs->find(sOutPath);
if (i == v.attrs->end())
- throwTypeError(pos, "cannot coerce a set to a string",
+ throwTypeError(pos, "cannot coerce a set to a string",
fakeEnv(1), 0);
return coerceToString(pos, *i->value, context, coerceMore, copyToStore);
}
@@ -1996,7 +1990,7 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
}
}
- throwTypeError(pos, "cannot coerce %1% to a string", v,
+ throwTypeError(pos, "cannot coerce %1% to a string", v,
fakeEnv(1), 0);
}
@@ -2030,7 +2024,7 @@ Path EvalState::coerceToPath(const Pos & pos, Value & v, PathSet & context)
{
string path = coerceToString(pos, v, context, false, false);
if (path == "" || path[0] != '/')
- throwEvalError(pos, "string '%1%' doesn't represent an absolute path", path,
+ throwEvalError(pos, "string '%1%' doesn't represent an absolute path", path,
fakeEnv(1), 0);
return path;
}
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index ae1e6ee60..91e43ddfe 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -208,7 +208,6 @@ public:
string forceString(Value & v, const Pos & pos = noPos);
string forceString(Value & v, PathSet & context, const Pos & pos = noPos);
string forceStringNoCtx(Value & v, const Pos & pos = noPos);
- // string forceStringNoCtx(std::optional<Bindings*> b, Value & v, const Pos & pos = noPos);
/* Return true iff the value `v' denotes a derivation (i.e. a
set with attribute `type = "derivation"'). */
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index 65c7cac1d..9ccecca55 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -295,7 +295,6 @@ void ExprVar::bindVars(const std::shared_ptr<const StaticEnv> &env)
"undefined variable" error now. */
if (withLevel == -1)
{
- // std::cout << " throw UndefinedVarError({" << std::endl;
throw UndefinedVarError({
.msg = hintfmt("undefined variable (ExprVar bindvars) '%1%'", name),
.errPos = pos
From 69e26c5c4ba106bd16f60bfaac88ccf888b4383f Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Thu, 25 Nov 2021 08:23:07 -0700
Subject: [PATCH 053/188] more cleanup
---
src/libcmd/command.cc | 4 ++--
src/libexpr/eval.cc | 23 +++++++++++------------
src/libexpr/nixexpr.cc | 1 -
3 files changed, 13 insertions(+), 15 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 8a6dd71b2..2c62bfa7f 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -81,8 +81,8 @@ ref<EvalState> EvalCommand::getEvalState()
if (expr.staticenv)
{
- auto vm = mapStaticEnvBindings(*expr.staticenv.get(), env);
- runRepl(evalState, *vm);
+ auto vm = mapStaticEnvBindings(*expr.staticenv.get(), env);
+ runRepl(evalState, *vm);
}
};
}
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 8e263334a..11a61da26 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -620,7 +620,7 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
void printStaticEnvBindings(const StaticEnv &se, int lvl)
{
- for (auto i = se.vars.begin(); i != se.vars.end(); ++i)
+ for (auto i = se.vars.begin(); i != se.vars.end(); ++i)
{
std::cout << lvl << i->first << std::endl;
}
@@ -628,22 +628,21 @@ void printStaticEnvBindings(const StaticEnv &se, int lvl)
if (se.up) {
printStaticEnvBindings(*se.up, ++lvl);
}
-
+
}
void printStaticEnvBindings(const Expr &expr)
{
- // just print the names for now
- if (expr.staticenv)
- {
- printStaticEnvBindings(*expr.staticenv.get(), 0);
- }
-
+ // just print the names for now
+ if (expr.staticenv)
+ {
+ printStaticEnvBindings(*expr.staticenv.get(), 0);
+ }
}
void mapStaticEnvBindings(const StaticEnv &se, const Env &env, valmap & vm)
{
- // add bindings for the next level up first, so that the bindings for this level
+ // add bindings for the next level up first, so that the bindings for this level
// override the higher levels.
if (env.up && se.up) {
mapStaticEnvBindings( *se.up, *env.up,vm);
@@ -651,13 +650,13 @@ void mapStaticEnvBindings(const StaticEnv &se, const Env &env, valmap & vm)
// iterate through staticenv bindings and add them.
auto map = valmap();
- for (auto iter = se.vars.begin(); iter != se.vars.end(); ++iter)
+ for (auto iter = se.vars.begin(); iter != se.vars.end(); ++iter)
{
- map[iter->first] = env.values[iter->second];
+ map[iter->first] = env.values[iter->second];
}
vm.merge(map);
-
+
}
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index 9ccecca55..3e42789a2 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -3,7 +3,6 @@
#include "util.hh"
#include <cstdlib>
-#include <iostream>
namespace nix {
From e82aec4efcd06cbd60d57f401fb7e93ab595128c Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Tue, 30 Nov 2021 14:15:02 -0700
Subject: [PATCH 054/188] fix merge issues
---
src/libcmd/command.cc | 9 +--------
src/libcmd/repl.cc | 5 +++--
src/libexpr/eval.cc | 5 +++--
src/libexpr/nixexpr.cc | 14 +++++++-------
src/libexpr/primops.cc | 4 ++--
5 files changed, 16 insertions(+), 21 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 4c5d985aa..2e00b42ff 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -68,7 +68,7 @@ extern std::function<void(const Error & error, const Env & env, const Expr & exp
ref<EvalState> EvalCommand::getEvalState()
{
if (!evalState) {
- evalState = std::make_shared<EvalState>(searchPath, getStore());
+ evalState = std::make_shared<EvalState>(searchPath, getEvalStore(), getStore());
if (startReplOnEvalErrors)
debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error & error, const Env & env, const Expr & expr) {
printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error.what());
@@ -102,13 +102,6 @@ ref<Store> EvalCommand::getEvalStore()
return ref<Store>(evalStore);
}
-ref<EvalState> EvalCommand::getEvalState()
-{
- if (!evalState)
- evalState = std::make_shared<EvalState>(searchPath, getEvalStore(), getStore());
- return ref<EvalState>(evalState);
-}
-
BuiltPathsCommand::BuiltPathsCommand(bool recursive)
: recursive(recursive)
{
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 6faa9f9fa..910f0f694 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -205,6 +205,7 @@ void NixRepl::mainLoop(const std::vector<std::string> & files)
if (!files.empty()) {
for (auto & i : files)
loadedFiles.push_back(i);
+ }
reloadFiles();
if (!loadedFiles.empty()) notice("");
@@ -639,7 +640,7 @@ void NixRepl::addAttrsToScope(Value & attrs)
{
state->forceAttrs(attrs);
for (auto & i : *attrs.attrs)
- addVarToScope(i.name, *i.value);
+ addVarToScope(i.name, i.value);
notice("Added %1% variables.", attrs.attrs->size());
}
@@ -650,7 +651,7 @@ void NixRepl::addVarToScope(const Symbol & name, Value * v)
throw Error("environment full; cannot add more variables");
staticEnv->vars.emplace_back(name, displ);
staticEnv->sort();
- env->values[displ++] = &v;
+ env->values[displ++] = v;
varNames.insert((string) name);
}
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index a20123f34..8737930b5 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -591,7 +591,7 @@ Value * EvalState::addConstant(const string & name, Value & v)
void EvalState::addConstant(const string & name, Value * v)
{
- staticBaseEnv.vars.emplace_back(symbols.create(name), baseEnvDispl);
+ staticBaseEnv->vars.emplace_back(symbols.create(name), baseEnvDispl);
baseEnv.values[baseEnvDispl++] = v;
string name2 = string(name, 0, 2) == "__" ? string(name, 2) : name;
baseEnv.values[0]->attrs->push_back(Attr(symbols.create(name2), v));
@@ -1459,7 +1459,8 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
user. */
for (auto & i : *args[0]->attrs)
if (lambda.formals->argNames.find(i.name) == lambda.formals->argNames.end())
- throwTypeError(pos, "%1% called with unexpected argument '%2%'", lambda, i.name);
+ throwTypeError(pos, "%1% called with unexpected argument '%2%'",
+ lambda, i.name, *fun.lambda.env, &lambda);
abort(); // can't happen
}
}
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index 696b149e3..dd0031a7c 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -346,7 +346,7 @@ void ExprAttrs::bindVars(const std::shared_ptr<const StaticEnv> &env)
Displacement displ = 0;
for (auto & i : attrs)
- newEnv.vars.emplace_back(i.first, i.second.displ = displ++);
+ newEnv->vars.emplace_back(i.first, i.second.displ = displ++);
// No need to sort newEnv since attrs is in sorted order.
@@ -391,13 +391,13 @@ void ExprLambda::bindVars(const std::shared_ptr<const StaticEnv> &env)
Displacement displ = 0;
- if (!arg.empty()) newEnv.vars.emplace_back(arg, displ++);
+ if (!arg.empty()) newEnv->vars.emplace_back(arg, displ++);
if (hasFormals()) {
for (auto & i : formals->formals)
- newEnv.vars.emplace_back(i.name, displ++);
+ newEnv->vars.emplace_back(i.name, displ++);
- newEnv.sort();
+ newEnv->sort();
for (auto & i : formals->formals)
if (i.def) i.def->bindVars(newEnv);
@@ -406,7 +406,7 @@ void ExprLambda::bindVars(const std::shared_ptr<const StaticEnv> &env)
body->bindVars(newEnv);
}
-void ExprCall::bindVars(const StaticEnv & env)
+void ExprCall::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
if (debuggerHook)
staticenv = env;
@@ -416,7 +416,7 @@ void ExprCall::bindVars(const StaticEnv & env)
e->bindVars(env);
}
-void ExprLet::bindVars(const StaticEnv & env)
+void ExprLet::bindVars(const std::shared_ptr<const StaticEnv> &env)
{
if (debuggerHook)
staticenv = env;
@@ -425,7 +425,7 @@ void ExprLet::bindVars(const StaticEnv & env)
Displacement displ = 0;
for (auto & i : attrs->attrs)
- newEnv.vars.emplace_back(i.first, i.second.displ = displ++);
+ newEnv->vars.emplace_back(i.first, i.second.displ = displ++);
// No need to sort newEnv since attrs->attrs is in sorted order.
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index a9ee96bfa..2638b0076 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -188,7 +188,7 @@ static void import(EvalState & state, const Pos & pos, Value & vPath, Value * vS
unsigned int displ = 0;
for (auto & attr : *vScope->attrs) {
- staticEnv.vars.emplace_back(attr.name, displ);
+ staticEnv->vars.emplace_back(attr.name, displ);
env->values[displ++] = attr.value;
}
@@ -3750,7 +3750,7 @@ void EvalState::createBaseEnv()
because attribute lookups expect it to be sorted. */
baseEnv.values[0]->attrs->sort();
- staticBaseEnv.sort();
+ staticBaseEnv->sort();
/* Note: we have to initialize the 'derivation' constant *after*
building baseEnv/staticBaseEnv because it uses 'builtins'. */
From c151a9b4262dfc5fc251ed0ebcf862731b0f795c Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Tue, 30 Nov 2021 15:14:23 -0700
Subject: [PATCH 055/188] fix linking
---
src/libcmd/local.mk | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/src/libcmd/local.mk b/src/libcmd/local.mk
index 1ec258a54..4d42e4c8b 100644
--- a/src/libcmd/local.mk
+++ b/src/libcmd/local.mk
@@ -8,8 +8,8 @@ libcmd_SOURCES := $(wildcard $(d)/*.cc)
libcmd_CXXFLAGS += -I src/libutil -I src/libstore -I src/libexpr -I src/libmain -I src/libfetchers -I src/nix
-# libcmd_LDFLAGS = $(EDITLINE_LIBS) -llowdown
-libcmd_LDFLAGS += -llowdown -pthread
+libcmd_LDFLAGS = $(EDITLINE_LIBS) -llowdown -pthread
+# libcmd_LDFLAGS += -llowdown -pthread
libcmd_LIBS = libstore libutil libexpr libmain libfetchers libnix
From f317019edda7afac8590e68d4d979b03a2cdbf62 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Mon, 20 Dec 2021 12:32:21 -0700
Subject: [PATCH 056/188] :d error
---
src/libcmd/command.cc | 2 +-
src/libcmd/command.hh | 2 +
src/libcmd/repl.cc | 93 +++++++++++++++++++++++++++++++++++--------
src/libexpr/eval.hh | 1 +
src/libexpr/parser.y | 5 +++
5 files changed, 86 insertions(+), 17 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 2e00b42ff..b37959a2e 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -82,7 +82,7 @@ ref<EvalState> EvalCommand::getEvalState()
if (expr.staticenv)
{
auto vm = mapStaticEnvBindings(*expr.staticenv.get(), env);
- runRepl(evalState, *vm);
+ runRepl(evalState, ref<const Error>(&error), *vm);
}
};
}
diff --git a/src/libcmd/command.hh b/src/libcmd/command.hh
index 0d847d255..e27ee2e9e 100644
--- a/src/libcmd/command.hh
+++ b/src/libcmd/command.hh
@@ -314,6 +314,8 @@ void printClosureDiff(
void runRepl(
ref<EvalState> evalState,
+ std::optional<ref<const Error>> debugError,
const std::map<std::string, Value *> & extraEnv);
+
}
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 910f0f694..0eea2389b 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -50,6 +50,8 @@ struct NixRepl
ref<EvalState> state;
Bindings * autoArgs;
+ std::optional<ref<const Error>> debugError;
+
Strings loadedFiles;
const static int envSize = 32768;
@@ -70,6 +72,7 @@ struct NixRepl
void loadFile(const Path & path);
void loadFlake(const std::string & flakeRef);
void initEnv();
+ void loadFiles();
void reloadFiles();
void addAttrsToScope(Value & attrs);
void addVarToScope(const Symbol & name, Value * v);
@@ -199,6 +202,9 @@ namespace {
void NixRepl::mainLoop(const std::vector<std::string> & files)
{
+ std::cout << "iinitial mainLoop; " << std::endl;
+ // printStaticEnvBindings(*staticEnv, 0);
+
string error = ANSI_RED "error:" ANSI_NORMAL " ";
notice("Welcome to Nix " + nixVersion + ". Type :? for help.\n");
@@ -207,7 +213,7 @@ void NixRepl::mainLoop(const std::vector<std::string> & files)
loadedFiles.push_back(i);
}
- reloadFiles();
+ loadFiles();
if (!loadedFiles.empty()) notice("");
// Allow nix-repl specific settings in .inputrc
@@ -225,6 +231,9 @@ void NixRepl::mainLoop(const std::vector<std::string> & files)
std::string input;
+ std::cout << "pre MAINLOOP; " << std::endl;
+ // printStaticEnvBindings(*staticEnv, 0);
+
while (true) {
// When continuing input from previous lines, don't print a prompt, just align to the same
// number of chars as the prompt.
@@ -415,21 +424,40 @@ bool NixRepl::processLine(string line)
std::cout
<< "The following commands are available:\n"
<< "\n"
- << " <expr> Evaluate and print expression\n"
- << " <x> = <expr> Bind expression to variable\n"
- << " :a <expr> Add attributes from resulting set to scope\n"
- << " :b <expr> Build derivation\n"
- << " :e <expr> Open package or function in $EDITOR\n"
- << " :i <expr> Build derivation, then install result into current profile\n"
- << " :l <path> Load Nix expression and add it to scope\n"
- << " :lf <ref> Load Nix flake and add it to scope\n"
- << " :p <expr> Evaluate and print expression recursively\n"
- << " :q Exit nix-repl\n"
- << " :r Reload all files\n"
- << " :s <expr> Build dependencies of derivation, then start nix-shell\n"
- << " :t <expr> Describe result of evaluation\n"
- << " :u <expr> Build derivation, then start nix-shell\n"
- << " :doc <expr> Show documentation of a builtin function\n";
+ << " <expr> Evaluate and print expression\n"
+ << " <x> = <expr> Bind expression to variable\n"
+ << " :a <expr> Add attributes from resulting set to scope\n"
+ << " :b <expr> Build derivation\n"
+ << " :e <expr> Open package or function in $EDITOR\n"
+ << " :i <expr> Build derivation, then install result into current profile\n"
+ << " :l <path> Load Nix expression and add it to scope\n"
+ << " :lf <ref> Load Nix flake and add it to scope\n"
+ << " :p <expr> Evaluate and print expression recursively\n"
+ << " :q Exit nix-repl\n"
+ << " :r Reload all files\n"
+ << " :s <expr> Build dependencies of derivation, then start nix-shell\n"
+ << " :t <expr> Describe result of evaluation\n"
+ << " :u <expr> Build derivation, then start nix-shell\n"
+ << " :doc <expr> Show documentation of a builtin function\n"
+ << " :d <cmd> Debug mode commands\n"
+ << " :d stack Show call stack\n"
+ << " :d stack <int> Detail for step N\n"
+ << " :d error Show current error\n";
+ }
+
+ else if (command == ":d" || command == ":debug") {
+ std::cout << "debug: '" << arg << "'" << std::endl;
+ if (arg == "stack") {
+ }
+ else if (arg == "error") {
+ if (this->debugError.has_value()) {
+ showErrorInfo(std::cout, (*debugError)->info(), true);
+ }
+ else
+ {
+ notice("error information not available");
+ }
+ }
}
else if (command == ":a" || command == ":add") {
@@ -561,11 +589,13 @@ bool NixRepl::processLine(string line)
line[p + 1] != '=' &&
isVarName(name = removeWhitespace(string(line, 0, p))))
{
+ std::cout << "isvarname" << std::endl;
Expr * e = parseString(string(line, p + 1));
Value *v = new Value(*state->allocValue());
v->mkThunk(env, e);
addVarToScope(state->symbols.create(name), v);
} else {
+ std::cout << "evalstring" << std::endl;
Value v;
evalString(line, v);
printValue(std::cout, v, 1) << std::endl;
@@ -623,6 +653,12 @@ void NixRepl::reloadFiles()
{
initEnv();
+ loadFiles();
+}
+
+
+void NixRepl::loadFiles()
+{
Strings old = loadedFiles;
loadedFiles.clear();
@@ -649,12 +685,28 @@ void NixRepl::addVarToScope(const Symbol & name, Value * v)
{
if (displ >= envSize)
throw Error("environment full; cannot add more variables");
+ if (auto oldVar = staticEnv->find(name); oldVar != staticEnv->vars.end())
+ staticEnv->vars.erase(oldVar);
staticEnv->vars.emplace_back(name, displ);
staticEnv->sort();
env->values[displ++] = v;
varNames.insert((string) name);
+ notice("Added variable to scope: %1%", name);
+
}
+// version from master.
+// void NixRepl::addVarToScope(const Symbol & name, Value & v)
+// {
+// if (displ >= envSize)
+// throw Error("environment full; cannot add more variables");
+// if (auto oldVar = staticEnv.find(name); oldVar != staticEnv.vars.end())
+// staticEnv.vars.erase(oldVar);
+// staticEnv.vars.emplace_back(name, displ);
+// staticEnv.sort();
+// env->values[displ++] = &v;
+// varNames.insert((string) name);
+// }
Expr * NixRepl::parseString(string s)
{
@@ -665,8 +717,11 @@ Expr * NixRepl::parseString(string s)
void NixRepl::evalString(string s, Value & v)
{
+ std::cout << "pre partstirns:l" << std::endl;
Expr * e = parseString(s);
+ std::cout << "pre e->eval" << std::endl;
e->eval(*state, *env, v);
+ std::cout << "prev fv" << std::endl;
state->forceValue(v);
}
@@ -817,10 +872,13 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
void runRepl(
ref<EvalState> evalState,
+ std::optional<ref<const Error>> debugError,
const std::map<std::string, Value *> & extraEnv)
{
auto repl = std::make_unique<NixRepl>(evalState);
+ repl->debugError = debugError;
+
repl->initEnv();
std::set<std::string> names;
@@ -834,6 +892,9 @@ void runRepl(
printError(hintfmt("The following extra variables are in scope: %s\n", concatStringsSep(", ", names)).str());
// printError("The following extra variables are in scope: %s\n", concatStringsSep(", ", names));
+ std::cout << " pre repl->mainLoop({});" << std::endl;
+ // printStaticEnvBindings(*repl->staticEnv, 0);
+
repl->mainLoop({});
}
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 485c2df83..4b3e7d69a 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -26,6 +26,7 @@ typedef void (* PrimOpFun) (EvalState & state, const Pos & pos, Value * * args,
extern std::function<void(const Error & error, const Env & env, const Expr & expr)> debuggerHook;
void printStaticEnvBindings(const Expr &expr);
+void printStaticEnvBindings(const StaticEnv &se, int lvl = 0);
struct PrimOp
{
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index 58af0df7d..066dc4ecc 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -21,6 +21,7 @@
#include "nixexpr.hh"
#include "eval.hh"
#include "globals.hh"
+#include <iostream>
namespace nix {
@@ -615,6 +616,10 @@ Expr * EvalState::parse(const char * text, FileOrigin origin,
if (res) throw ParseError(data.error.value());
+ std::cout << " data.result->bindVars(staticEnv); " << std::endl;
+
+ // printStaticEnvBindings(*staticEnv, 0);
+
data.result->bindVars(staticEnv);
return data.result;
From b4a59a5eec5bdb94ee2bbc8365f024d5787abd60 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Wed, 22 Dec 2021 15:38:49 -0700
Subject: [PATCH 057/188] DebugStackTracker class in one place
---
src/libcmd/command.cc | 2 ++
src/libcmd/repl.cc | 1 +
src/libexpr/eval.cc | 65 ++++++++++++++++++++++++++++++++++++++++--
src/libexpr/eval.hh | 2 ++
src/libexpr/nixexpr.hh | 25 ++++++++++++++++
src/libutil/error.cc | 2 ++
src/libutil/logging.hh | 1 +
7 files changed, 96 insertions(+), 2 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index b37959a2e..0ada5fa3c 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -75,6 +75,8 @@ ref<EvalState> EvalCommand::getEvalState()
printStaticEnvBindings(expr);
+ std::cout << evalState->vCallFlake << std::endl;
+
std::cout << "expr: " << std::endl;
expr.show(std::cout);
std::cout << std::endl;
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 0eea2389b..2a925df64 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -451,6 +451,7 @@ bool NixRepl::processLine(string line)
}
else if (arg == "error") {
if (this->debugError.has_value()) {
+ // TODO user --show-trace setting?
showErrorInfo(std::cout, (*debugError)->info(), true);
}
else
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 8737930b5..00d2c1643 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -17,6 +17,7 @@
#include <sys/resource.h>
#include <iostream>
#include <fstream>
+#include <functional>
#include <sys/resource.h>
@@ -854,13 +855,20 @@ LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s,
LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char * s, const string & s1, Env & env, Expr *expr))
{
+ std::cout << "throwUndefinedVarError" << std::endl;
+
+ std::cout << "loggerSettings.showTrace: " << loggerSettings.showTrace << std::endl;
+
auto error = UndefinedVarError({
.msg = hintfmt(s, s1),
.errPos = pos
});
- if (debuggerHook && expr)
+ if (debuggerHook && expr) {
+
+ std::cout << "throwUndefinedVarError debuggerHook" << std::endl;
debuggerHook(error, env, *expr);
+ }
throw error;
}
@@ -888,6 +896,16 @@ LocalNoInline(void addErrorTrace(Error & e, const Pos & pos, const char * s, con
e.addTrace(pos, s, s2);
}
+// LocalNoInline(void makeErrorTrace(Error & e, const char * s, const string & s2))
+// {
+// Trace { .pos = e, .hint = hint }
+// }
+
+// LocalNoInline(void makeErrorTrace(Error & e, const Pos & pos, const char * s, const string & s2))
+// {
+// return Trace { .pos = e, .hint = hintfmt(s, s2); };
+// }
+
void mkString(Value & v, const char * s)
{
v.mkString(dupString(s));
@@ -934,7 +952,7 @@ inline Value * EvalState::lookupVar(Env * env, const ExprVar & var, bool noEval)
return j->value;
}
if (!env->prevWith) {
- throwUndefinedVarError(var.pos, "undefined variable '%1%'", var.name, *env, 0);
+ throwUndefinedVarError(var.pos, "undefined variable '%1%'", var.name, *env, (Expr*)&var);
}
for (size_t l = env->prevWith; l; --l, env = env->up) ;
}
@@ -1092,6 +1110,39 @@ void EvalState::resetFileCache()
fileParseCache.clear();
}
+class DebugTraceStacker {
+ public:
+ DebugTraceStacker(EvalState &evalState, Trace t)
+ :evalState(evalState), trace(t)
+ {
+ evalState.debugTraces.push_front(t);
+ }
+ ~DebugTraceStacker() {
+ // assert(evalState.debugTraces.front() == trace);
+ evalState.debugTraces.pop_front();
+ }
+
+ EvalState &evalState;
+ Trace trace;
+
+};
+
+// class DebugTraceStacker {
+// DebugTraceStacker(std::ref<EvalState> evalState, std::ref<Trace> t)
+// :evalState(evalState), trace(t)
+// {
+// evalState->debugTraces.push_front(t);
+// }
+// ~DebugTraceStacker() {
+// assert(evalState->debugTraces.pop_front() == trace);
+// }
+
+// std::ref<EvalState> evalState;
+// std::ref<Trace> trace;
+
+// };
+
+
void EvalState::cacheFile(
const Path & path,
@@ -1103,6 +1154,15 @@ void EvalState::cacheFile(
fileParseCache[resolvedPath] = e;
try {
+ std::unique_ptr<DebugTraceStacker> dts = debuggerHook ?
+ std::unique_ptr<DebugTraceStacker>(new DebugTraceStacker(*this,
+ Trace { .pos = (e->getPos() ? std::optional(ErrPos(*e->getPos())) : std::nullopt),
+ .hint = hintfmt("while evaluating the file '%1%':", resolvedPath)
+ }
+ )) : std::unique_ptr<DebugTraceStacker>();
+
+ // Trace( .pos = (e->getPos() ? std::optional(ErrPos(*e->getPos())):
+ // std::nullopt), hintfmt("while evaluating the file '%1%':", resolvedPath));
// Enforce that 'flake.nix' is a direct attrset, not a
// computation.
if (mustBeTrivial &&
@@ -1472,6 +1532,7 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
try {
lambda.body->eval(*this, env2, vCur);
} catch (Error & e) {
+ std::cout << "eval showErrorInfo showTrace: " << loggerSettings.showTrace.get() << std::endl;
if (loggerSettings.showTrace.get()) {
addErrorTrace(e, lambda.pos, "while evaluating %s",
(lambda.name.set()
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 4b3e7d69a..c3717b3c2 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -109,6 +109,8 @@ public:
RootValue vCallFlake = nullptr;
RootValue vImportedDrvToDerivation = nullptr;
+ std::list<Trace> debugTraces;
+
private:
SrcToStore srcToStore;
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index 825933fa1..a9a5f5316 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -84,6 +84,7 @@ struct Expr
virtual void setName(Symbol & name);
std::shared_ptr<const StaticEnv> staticenv;
+ virtual Pos* getPos() = 0;
};
std::ostream & operator << (std::ostream & str, const Expr & e);
@@ -100,6 +101,8 @@ struct ExprInt : Expr
ExprInt(NixInt n) : n(n) { mkInt(v, n); };
COMMON_METHODS
Value * maybeThunk(EvalState & state, Env & env);
+
+ Pos* getPos() { return 0; }
};
struct ExprFloat : Expr
@@ -109,6 +112,8 @@ struct ExprFloat : Expr
ExprFloat(NixFloat nf) : nf(nf) { mkFloat(v, nf); };
COMMON_METHODS
Value * maybeThunk(EvalState & state, Env & env);
+
+ Pos* getPos() { return 0; }
};
struct ExprString : Expr
@@ -118,6 +123,8 @@ struct ExprString : Expr
ExprString(const Symbol & s) : s(s) { mkString(v, s); };
COMMON_METHODS
Value * maybeThunk(EvalState & state, Env & env);
+
+ Pos* getPos() { return 0; }
};
/* Temporary class used during parsing of indented strings. */
@@ -125,6 +132,8 @@ struct ExprIndStr : Expr
{
string s;
ExprIndStr(const string & s) : s(s) { };
+
+ Pos* getPos() { return 0; }
};
struct ExprPath : Expr
@@ -134,6 +143,7 @@ struct ExprPath : Expr
ExprPath(const string & s) : s(s) { v.mkPath(this->s.c_str()); };
COMMON_METHODS
Value * maybeThunk(EvalState & state, Env & env);
+ Pos* getPos() { return 0; }
};
typedef uint32_t Level;
@@ -161,6 +171,7 @@ struct ExprVar : Expr
ExprVar(const Pos & pos, const Symbol & name) : pos(pos), name(name) { };
COMMON_METHODS
Value * maybeThunk(EvalState & state, Env & env);
+ Pos* getPos() { return &pos; }
};
struct ExprSelect : Expr
@@ -171,6 +182,7 @@ struct ExprSelect : Expr
ExprSelect(const Pos & pos, Expr * e, const AttrPath & attrPath, Expr * def) : pos(pos), e(e), def(def), attrPath(attrPath) { };
ExprSelect(const Pos & pos, Expr * e, const Symbol & name) : pos(pos), e(e), def(0) { attrPath.push_back(AttrName(name)); };
COMMON_METHODS
+ Pos* getPos() { return &pos; }
};
struct ExprOpHasAttr : Expr
@@ -179,6 +191,7 @@ struct ExprOpHasAttr : Expr
AttrPath attrPath;
ExprOpHasAttr(Expr * e, const AttrPath & attrPath) : e(e), attrPath(attrPath) { };
COMMON_METHODS
+ Pos* getPos() { return e->getPos(); }
};
struct ExprAttrs : Expr
@@ -207,6 +220,7 @@ struct ExprAttrs : Expr
ExprAttrs(const Pos &pos) : recursive(false), pos(pos) { };
ExprAttrs() : recursive(false), pos(noPos) { };
COMMON_METHODS
+ Pos* getPos() { return &pos; }
};
struct ExprList : Expr
@@ -214,6 +228,7 @@ struct ExprList : Expr
std::vector<Expr *> elems;
ExprList() { };
COMMON_METHODS
+ Pos* getPos() { return 0; }
};
struct Formal
@@ -252,6 +267,7 @@ struct ExprLambda : Expr
string showNamePos() const;
inline bool hasFormals() const { return formals != nullptr; }
COMMON_METHODS
+ Pos* getPos() { return &pos; }
};
struct ExprCall : Expr
@@ -263,6 +279,7 @@ struct ExprCall : Expr
: fun(fun), args(args), pos(pos)
{ }
COMMON_METHODS
+ Pos* getPos() { return &pos; }
};
struct ExprLet : Expr
@@ -271,6 +288,7 @@ struct ExprLet : Expr
Expr * body;
ExprLet(ExprAttrs * attrs, Expr * body) : attrs(attrs), body(body) { };
COMMON_METHODS
+ Pos* getPos() { return 0; }
};
struct ExprWith : Expr
@@ -280,6 +298,7 @@ struct ExprWith : Expr
size_t prevWith;
ExprWith(const Pos & pos, Expr * attrs, Expr * body) : pos(pos), attrs(attrs), body(body) { };
COMMON_METHODS
+ Pos* getPos() { return &pos; }
};
struct ExprIf : Expr
@@ -288,6 +307,7 @@ struct ExprIf : Expr
Expr * cond, * then, * else_;
ExprIf(const Pos & pos, Expr * cond, Expr * then, Expr * else_) : pos(pos), cond(cond), then(then), else_(else_) { };
COMMON_METHODS
+ Pos* getPos() { return &pos; }
};
struct ExprAssert : Expr
@@ -296,6 +316,7 @@ struct ExprAssert : Expr
Expr * cond, * body;
ExprAssert(const Pos & pos, Expr * cond, Expr * body) : pos(pos), cond(cond), body(body) { };
COMMON_METHODS
+ Pos* getPos() { return &pos; }
};
struct ExprOpNot : Expr
@@ -303,6 +324,7 @@ struct ExprOpNot : Expr
Expr * e;
ExprOpNot(Expr * e) : e(e) { };
COMMON_METHODS
+ Pos* getPos() { return 0; }
};
#define MakeBinOp(name, s) \
@@ -321,6 +343,7 @@ struct ExprOpNot : Expr
e1->bindVars(env); e2->bindVars(env); \
} \
void eval(EvalState & state, Env & env, Value & v); \
+ Pos* getPos() { return &pos; } \
};
MakeBinOp(ExprOpEq, "==")
@@ -339,6 +362,7 @@ struct ExprConcatStrings : Expr
ExprConcatStrings(const Pos & pos, bool forceString, vector<Expr *> * es)
: pos(pos), forceString(forceString), es(es) { };
COMMON_METHODS
+ Pos* getPos() { return &pos; }
};
struct ExprPos : Expr
@@ -346,6 +370,7 @@ struct ExprPos : Expr
Pos pos;
ExprPos(const Pos & pos) : pos(pos) { };
COMMON_METHODS
+ Pos* getPos() { return &pos; }
};
diff --git a/src/libutil/error.cc b/src/libutil/error.cc
index 203d79087..c2b9d2707 100644
--- a/src/libutil/error.cc
+++ b/src/libutil/error.cc
@@ -221,6 +221,8 @@ static std::string indent(std::string_view indentFirst, std::string_view indentR
std::ostream & showErrorInfo(std::ostream & out, const ErrorInfo & einfo, bool showTrace)
{
+ std::cout << "showErrorInfo showTrace: " << showTrace << std::endl;
+
std::string prefix;
switch (einfo.level) {
case Verbosity::lvlError: {
diff --git a/src/libutil/logging.hh b/src/libutil/logging.hh
index 96ad69790..f10a9af38 100644
--- a/src/libutil/logging.hh
+++ b/src/libutil/logging.hh
@@ -38,6 +38,7 @@ typedef uint64_t ActivityId;
struct LoggerSettings : Config
{
Setting<bool> showTrace{
+ // this, false, "show-trace",
this, false, "show-trace",
R"(
Where Nix should print out a stack trace in case of Nix
From bc20e54e0044e08c68a7af1f1e12d001baba8a74 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Wed, 22 Dec 2021 19:40:08 -0700
Subject: [PATCH 058/188] stack traces basically working
---
src/libcmd/repl.cc | 20 ++++++++++++
src/libexpr/eval.cc | 72 +++++++++++++++++++++++++++++++++-----------
src/libutil/error.hh | 3 ++
3 files changed, 78 insertions(+), 17 deletions(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 2a925df64..3289aea3e 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -448,6 +448,26 @@ bool NixRepl::processLine(string line)
else if (command == ":d" || command == ":debug") {
std::cout << "debug: '" << arg << "'" << std::endl;
if (arg == "stack") {
+ std::cout << "eval stack:" << std::endl;
+ for (auto iter = this->state->debugTraces.begin();
+ iter != this->state->debugTraces.end(); ++iter) {
+ std::cout << "\n" << "… " << iter->hint.str() << "\n";
+
+ if (iter->pos.has_value() && (*iter->pos)) {
+ auto pos = iter->pos.value();
+ std::cout << "\n";
+ printAtPos(pos, std::cout);
+
+ auto loc = getCodeLines(pos);
+ if (loc.has_value()) {
+ std::cout << "\n";
+ printCodeLines(std::cout, "", pos, *loc);
+ std::cout << "\n";
+ }
+ }
+ }
+
+
}
else if (arg == "error") {
if (this->debugError.has_value()) {
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 00d2c1643..c46113560 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -38,6 +38,23 @@ namespace nix {
std::function<void(const Error & error, const Env & env, const Expr & expr)> debuggerHook;
+class DebugTraceStacker {
+ public:
+ DebugTraceStacker(EvalState &evalState, Trace t)
+ :evalState(evalState), trace(t)
+ {
+ evalState.debugTraces.push_front(t);
+ }
+ ~DebugTraceStacker() {
+ // assert(evalState.debugTraces.front() == trace);
+ evalState.debugTraces.pop_front();
+ }
+
+ EvalState &evalState;
+ Trace trace;
+
+};
+
static char * dupString(const char * s)
{
char * t;
@@ -1110,23 +1127,6 @@ void EvalState::resetFileCache()
fileParseCache.clear();
}
-class DebugTraceStacker {
- public:
- DebugTraceStacker(EvalState &evalState, Trace t)
- :evalState(evalState), trace(t)
- {
- evalState.debugTraces.push_front(t);
- }
- ~DebugTraceStacker() {
- // assert(evalState.debugTraces.front() == trace);
- evalState.debugTraces.pop_front();
- }
-
- EvalState &evalState;
- Trace trace;
-
-};
-
// class DebugTraceStacker {
// DebugTraceStacker(std::ref<EvalState> evalState, std::ref<Trace> t)
// :evalState(evalState), trace(t)
@@ -1387,6 +1387,17 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
e->eval(state, env, vTmp);
try {
+ std::unique_ptr<DebugTraceStacker> dts =
+ debuggerHook ?
+ std::unique_ptr<DebugTraceStacker>(
+ new DebugTraceStacker(
+ state,
+ Trace { .pos = *pos2,
+ .hint = hintfmt(
+ "while evaluating the attribute '%1%'",
+ showAttrPath(state, env, attrPath))
+ }))
+ : std::unique_ptr<DebugTraceStacker>();
for (auto & i : attrPath) {
state.nrLookups++;
@@ -1530,6 +1541,21 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
/* Evaluate the body. */
try {
+ std::unique_ptr<DebugTraceStacker> dts =
+ debuggerHook ?
+ std::unique_ptr<DebugTraceStacker>(
+ new DebugTraceStacker(
+ *this,
+ Trace { .pos = lambda.pos,
+ .hint = hintfmt(
+ "while evaluating %s",
+ (lambda.name.set()
+ ? "'" + (string) lambda.name + "'"
+ : "anonymous lambda"))
+ }))
+ : std::unique_ptr<DebugTraceStacker>();
+
+
lambda.body->eval(*this, env2, vCur);
} catch (Error & e) {
std::cout << "eval showErrorInfo showTrace: " << loggerSettings.showTrace.get() << std::endl;
@@ -1924,6 +1950,18 @@ void EvalState::forceValueDeep(Value & v)
if (v.type() == nAttrs) {
for (auto & i : *v.attrs)
try {
+ std::unique_ptr<DebugTraceStacker> dts =
+ debuggerHook ?
+ std::unique_ptr<DebugTraceStacker>(
+ new DebugTraceStacker(
+ *this,
+ Trace { .pos = *i.pos,
+ .hint = hintfmt(
+ "while evaluating the attribute '%1%'", i.name)
+ }))
+ : std::unique_ptr<DebugTraceStacker>();
+
+
recurse(*i.value);
} catch (Error & e) {
addErrorTrace(e, *i.pos, "while evaluating the attribute '%1%'", i.name);
diff --git a/src/libutil/error.hh b/src/libutil/error.hh
index b6670c8b2..06301f709 100644
--- a/src/libutil/error.hh
+++ b/src/libutil/error.hh
@@ -106,6 +106,9 @@ void printCodeLines(std::ostream & out,
const ErrPos & errPos,
const LinesOfCode & loc);
+void printAtPos(const ErrPos & pos, std::ostream & out);
+
+
struct Trace {
std::optional<ErrPos> pos;
hintformat hint;
From 1bda6a01e1cb4d2b22ff2256fcbde044e2f04d24 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Thu, 23 Dec 2021 08:14:17 -0700
Subject: [PATCH 059/188] indenting
---
src/libexpr/eval.cc | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index c46113560..15eaef667 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -1542,18 +1542,18 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
/* Evaluate the body. */
try {
std::unique_ptr<DebugTraceStacker> dts =
- debuggerHook ?
- std::unique_ptr<DebugTraceStacker>(
- new DebugTraceStacker(
- *this,
- Trace { .pos = lambda.pos,
- .hint = hintfmt(
- "while evaluating %s",
- (lambda.name.set()
- ? "'" + (string) lambda.name + "'"
- : "anonymous lambda"))
- }))
- : std::unique_ptr<DebugTraceStacker>();
+ debuggerHook ?
+ std::unique_ptr<DebugTraceStacker>(
+ new DebugTraceStacker(
+ *this,
+ Trace {.pos = lambda.pos,
+ .hint = hintfmt(
+ "while evaluating %s",
+ (lambda.name.set()
+ ? "'" + (string) lambda.name + "'"
+ : "anonymous lambda"))
+ }))
+ : std::unique_ptr<DebugTraceStacker>();
lambda.body->eval(*this, env2, vCur);
From deb1fd66e8c884937827813c079135532913ca86 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Thu, 23 Dec 2021 09:08:41 -0700
Subject: [PATCH 060/188] makeDebugTraceStacker
---
src/libexpr/eval.cc | 93 +++++++++++++++------------------------------
1 file changed, 31 insertions(+), 62 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 15eaef667..d7deb550e 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -49,10 +49,8 @@ class DebugTraceStacker {
// assert(evalState.debugTraces.front() == trace);
evalState.debugTraces.pop_front();
}
-
EvalState &evalState;
Trace trace;
-
};
static char * dupString(const char * s)
@@ -882,8 +880,7 @@ LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char *
});
if (debuggerHook && expr) {
-
- std::cout << "throwUndefinedVarError debuggerHook" << std::endl;
+ std::cout << "throwUndefinedVarError debuggerHook" << std::endl;
debuggerHook(error, env, *expr);
}
@@ -913,15 +910,17 @@ LocalNoInline(void addErrorTrace(Error & e, const Pos & pos, const char * s, con
e.addTrace(pos, s, s2);
}
-// LocalNoInline(void makeErrorTrace(Error & e, const char * s, const string & s2))
-// {
-// Trace { .pos = e, .hint = hint }
-// }
+LocalNoInline(std::unique_ptr<DebugTraceStacker>
+ makeDebugTraceStacker(EvalState &state, std::optional<ErrPos> pos, const char * s, const string & s2))
+{
+ return std::unique_ptr<DebugTraceStacker>(
+ new DebugTraceStacker(
+ state,
+ Trace {.pos = pos,
+ .hint = hintfmt(s, s2)
+ }));
+}
-// LocalNoInline(void makeErrorTrace(Error & e, const Pos & pos, const char * s, const string & s2))
-// {
-// return Trace { .pos = e, .hint = hintfmt(s, s2); };
-// }
void mkString(Value & v, const char * s)
{
@@ -1127,20 +1126,6 @@ void EvalState::resetFileCache()
fileParseCache.clear();
}
-// class DebugTraceStacker {
-// DebugTraceStacker(std::ref<EvalState> evalState, std::ref<Trace> t)
-// :evalState(evalState), trace(t)
-// {
-// evalState->debugTraces.push_front(t);
-// }
-// ~DebugTraceStacker() {
-// assert(evalState->debugTraces.pop_front() == trace);
-// }
-
-// std::ref<EvalState> evalState;
-// std::ref<Trace> trace;
-
-// };
@@ -1154,15 +1139,14 @@ void EvalState::cacheFile(
fileParseCache[resolvedPath] = e;
try {
- std::unique_ptr<DebugTraceStacker> dts = debuggerHook ?
- std::unique_ptr<DebugTraceStacker>(new DebugTraceStacker(*this,
- Trace { .pos = (e->getPos() ? std::optional(ErrPos(*e->getPos())) : std::nullopt),
- .hint = hintfmt("while evaluating the file '%1%':", resolvedPath)
- }
- )) : std::unique_ptr<DebugTraceStacker>();
+ std::unique_ptr<DebugTraceStacker> dts =
+ debuggerHook ?
+ makeDebugTraceStacker(
+ *this,
+ (e->getPos() ? std::optional(ErrPos(*e->getPos())) : std::nullopt),
+ "while evaluating the file '%1%':", resolvedPath)
+ : std::unique_ptr<DebugTraceStacker>();
- // Trace( .pos = (e->getPos() ? std::optional(ErrPos(*e->getPos())):
- // std::nullopt), hintfmt("while evaluating the file '%1%':", resolvedPath));
// Enforce that 'flake.nix' is a direct attrset, not a
// computation.
if (mustBeTrivial &&
@@ -1387,16 +1371,13 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
e->eval(state, env, vTmp);
try {
- std::unique_ptr<DebugTraceStacker> dts =
- debuggerHook ?
- std::unique_ptr<DebugTraceStacker>(
- new DebugTraceStacker(
- state,
- Trace { .pos = *pos2,
- .hint = hintfmt(
- "while evaluating the attribute '%1%'",
- showAttrPath(state, env, attrPath))
- }))
+ std::unique_ptr<DebugTraceStacker> dts =
+ debuggerHook ?
+ makeDebugTraceStacker(
+ state,
+ *pos2,
+ "while evaluating the attribute '%1%'",
+ showAttrPath(state, env, attrPath))
: std::unique_ptr<DebugTraceStacker>();
for (auto & i : attrPath) {
@@ -1541,21 +1522,15 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
/* Evaluate the body. */
try {
- std::unique_ptr<DebugTraceStacker> dts =
- debuggerHook ?
- std::unique_ptr<DebugTraceStacker>(
- new DebugTraceStacker(
- *this,
- Trace {.pos = lambda.pos,
- .hint = hintfmt(
+ std::unique_ptr<DebugTraceStacker> dts =
+ debuggerHook ?
+ makeDebugTraceStacker(*this, lambda.pos,
"while evaluating %s",
(lambda.name.set()
? "'" + (string) lambda.name + "'"
: "anonymous lambda"))
- }))
: std::unique_ptr<DebugTraceStacker>();
-
lambda.body->eval(*this, env2, vCur);
} catch (Error & e) {
std::cout << "eval showErrorInfo showTrace: " << loggerSettings.showTrace.get() << std::endl;
@@ -1950,18 +1925,12 @@ void EvalState::forceValueDeep(Value & v)
if (v.type() == nAttrs) {
for (auto & i : *v.attrs)
try {
- std::unique_ptr<DebugTraceStacker> dts =
- debuggerHook ?
- std::unique_ptr<DebugTraceStacker>(
- new DebugTraceStacker(
- *this,
- Trace { .pos = *i.pos,
- .hint = hintfmt(
+ std::unique_ptr<DebugTraceStacker> dts =
+ debuggerHook ?
+ makeDebugTraceStacker(*this, *i.pos,
"while evaluating the attribute '%1%'", i.name)
- }))
: std::unique_ptr<DebugTraceStacker>();
-
recurse(*i.value);
} catch (Error & e) {
addErrorTrace(e, *i.pos, "while evaluating the attribute '%1%'", i.name);
From e5eebda19475ab4f25346128e5428c27e526c7ce Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Thu, 23 Dec 2021 13:36:39 -0700
Subject: [PATCH 061/188] DebugTrace
---
src/libcmd/command.cc | 2 +-
src/libcmd/command.hh | 4 +---
src/libcmd/repl.cc | 11 +++++------
src/libexpr/eval.cc | 22 +++++++++++++++-------
src/libexpr/eval.hh | 8 +++++++-
5 files changed, 29 insertions(+), 18 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 0ada5fa3c..6c0f84c4b 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -84,7 +84,7 @@ ref<EvalState> EvalCommand::getEvalState()
if (expr.staticenv)
{
auto vm = mapStaticEnvBindings(*expr.staticenv.get(), env);
- runRepl(evalState, ref<const Error>(&error), *vm);
+ runRepl(evalState, &error, *vm);
}
};
}
diff --git a/src/libcmd/command.hh b/src/libcmd/command.hh
index e27ee2e9e..e2c72256e 100644
--- a/src/libcmd/command.hh
+++ b/src/libcmd/command.hh
@@ -314,8 +314,6 @@ void printClosureDiff(
void runRepl(
ref<EvalState> evalState,
- std::optional<ref<const Error>> debugError,
+ const Error *debugError,
const std::map<std::string, Value *> & extraEnv);
-
-
}
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 3289aea3e..6859e5c07 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -50,7 +50,7 @@ struct NixRepl
ref<EvalState> state;
Bindings * autoArgs;
- std::optional<ref<const Error>> debugError;
+ const Error *debugError;
Strings loadedFiles;
@@ -470,13 +470,12 @@ bool NixRepl::processLine(string line)
}
else if (arg == "error") {
- if (this->debugError.has_value()) {
- // TODO user --show-trace setting?
- showErrorInfo(std::cout, (*debugError)->info(), true);
+ if (this->debugError) {
+ showErrorInfo(std::cout, debugError->info(), true);
}
else
{
- notice("error information not available");
+ notice("error information not available");
}
}
}
@@ -893,7 +892,7 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
void runRepl(
ref<EvalState> evalState,
- std::optional<ref<const Error>> debugError,
+ const Error *debugError,
const std::map<std::string, Value *> & extraEnv)
{
auto repl = std::make_unique<NixRepl>(evalState);
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index d7deb550e..b8d060276 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -40,7 +40,7 @@ std::function<void(const Error & error, const Env & env, const Expr & expr)> deb
class DebugTraceStacker {
public:
- DebugTraceStacker(EvalState &evalState, Trace t)
+ DebugTraceStacker(EvalState &evalState, DebugTrace t)
:evalState(evalState), trace(t)
{
evalState.debugTraces.push_front(t);
@@ -50,7 +50,7 @@ class DebugTraceStacker {
evalState.debugTraces.pop_front();
}
EvalState &evalState;
- Trace trace;
+ DebugTrace trace;
};
static char * dupString(const char * s)
@@ -911,12 +911,14 @@ LocalNoInline(void addErrorTrace(Error & e, const Pos & pos, const char * s, con
}
LocalNoInline(std::unique_ptr<DebugTraceStacker>
- makeDebugTraceStacker(EvalState &state, std::optional<ErrPos> pos, const char * s, const string & s2))
+ makeDebugTraceStacker(EvalState &state, Expr &expr, std::optional<ErrPos> pos, const char * s, const string & s2))
{
return std::unique_ptr<DebugTraceStacker>(
new DebugTraceStacker(
state,
- Trace {.pos = pos,
+ DebugTrace
+ {.pos = pos,
+ .expr = expr,
.hint = hintfmt(s, s2)
}));
}
@@ -1143,6 +1145,7 @@ void EvalState::cacheFile(
debuggerHook ?
makeDebugTraceStacker(
*this,
+ *e,
(e->getPos() ? std::optional(ErrPos(*e->getPos())) : std::nullopt),
"while evaluating the file '%1%':", resolvedPath)
: std::unique_ptr<DebugTraceStacker>();
@@ -1375,6 +1378,7 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
debuggerHook ?
makeDebugTraceStacker(
state,
+ *this,
*pos2,
"while evaluating the attribute '%1%'",
showAttrPath(state, env, attrPath))
@@ -1524,7 +1528,7 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
try {
std::unique_ptr<DebugTraceStacker> dts =
debuggerHook ?
- makeDebugTraceStacker(*this, lambda.pos,
+ makeDebugTraceStacker(*this, *lambda.body, lambda.pos,
"while evaluating %s",
(lambda.name.set()
? "'" + (string) lambda.name + "'"
@@ -1925,10 +1929,14 @@ void EvalState::forceValueDeep(Value & v)
if (v.type() == nAttrs) {
for (auto & i : *v.attrs)
try {
+
std::unique_ptr<DebugTraceStacker> dts =
debuggerHook ?
- makeDebugTraceStacker(*this, *i.pos,
- "while evaluating the attribute '%1%'", i.name)
+ // if the value is a thunk, we're evaling. otherwise no trace necessary.
+ (i.value->isThunk() ?
+ makeDebugTraceStacker(*this, *v.thunk.expr, *i.pos,
+ "while evaluating the attribute '%1%'", i.name)
+ : std::unique_ptr<DebugTraceStacker>())
: std::unique_ptr<DebugTraceStacker>();
recurse(*i.value);
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index c3717b3c2..c7a19e100 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -74,6 +74,12 @@ struct RegexCache;
std::shared_ptr<RegexCache> makeRegexCache();
+struct DebugTrace {
+ std::optional<ErrPos> pos;
+ Expr &expr;
+ hintformat hint;
+};
+
class EvalState
{
@@ -109,7 +115,7 @@ public:
RootValue vCallFlake = nullptr;
RootValue vImportedDrvToDerivation = nullptr;
- std::list<Trace> debugTraces;
+ std::list<DebugTrace> debugTraces;
private:
SrcToStore srcToStore;
From d0d589044512a77b345b7e576e2c45910c74eb02 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Mon, 27 Dec 2021 13:47:35 -0700
Subject: [PATCH 062/188] don't add underscore names to extras
---
src/libexpr/eval.cc | 34 +++++++++++++++++++++++++---------
1 file changed, 25 insertions(+), 9 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index b8d060276..377e1b2f8 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -716,18 +716,34 @@ void mapStaticEnvBindings(const StaticEnv &se, const Env &env, valmap & vm)
// add bindings for the next level up first, so that the bindings for this level
// override the higher levels.
if (env.up && se.up) {
- mapStaticEnvBindings( *se.up, *env.up,vm);
- }
+ mapStaticEnvBindings( *se.up, *env.up,vm);
- // iterate through staticenv bindings and add them.
- auto map = valmap();
- for (auto iter = se.vars.begin(); iter != se.vars.end(); ++iter)
+ // iterate through staticenv bindings and add them.
+ auto map = valmap();
+ for (auto iter = se.vars.begin(); iter != se.vars.end(); ++iter)
+ {
+ map[iter->first] = env.values[iter->second];
+ }
+
+ vm.merge(map);
+ }
+ else
{
- map[iter->first] = env.values[iter->second];
+ std::cout << " -------------------- " << std::endl;
+ // iterate through staticenv bindings and add them,
+ // except for the __* ones.
+ auto map = valmap();
+ for (auto iter = se.vars.begin(); iter != se.vars.end(); ++iter)
+ {
+ std::cout << iter->first << std::endl;
+ std::string s = iter->first;
+ if (s.substr(0,2) != "__") {
+ map[iter->first] = env.values[iter->second];
+ }
+ }
+
+ vm.merge(map);
}
-
- vm.merge(map);
-
}
From ff82ba98b41eb3e4b1ce96ed02504acea03eb29c Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Mon, 27 Dec 2021 14:06:04 -0700
Subject: [PATCH 063/188] don't add builtins to extras, initEnv() in regular
repl
---
src/libcmd/repl.cc | 3 ++-
src/libexpr/eval.cc | 20 ++------------------
2 files changed, 4 insertions(+), 19 deletions(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 6859e5c07..b14f43ec4 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -901,8 +901,8 @@ void runRepl(
repl->initEnv();
+ // add 'extra' vars.
std::set<std::string> names;
-
for (auto & [name, value] : extraEnv) {
// names.insert(ANSI_BOLD + name + ANSI_NORMAL);
names.insert(name);
@@ -951,6 +951,7 @@ struct CmdRepl : StoreCommand, MixEvalArgs
auto repl = std::make_unique<NixRepl>(evalState);
repl->autoArgs = getAutoArgs(*repl->state);
+ repl->initEnv();
repl->mainLoop(files);
}
};
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 377e1b2f8..d99e73471 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -715,8 +715,9 @@ void mapStaticEnvBindings(const StaticEnv &se, const Env &env, valmap & vm)
{
// add bindings for the next level up first, so that the bindings for this level
// override the higher levels.
+ // The top level bindings (builtins) are skipped since they are added for us by initEnv()
if (env.up && se.up) {
- mapStaticEnvBindings( *se.up, *env.up,vm);
+ mapStaticEnvBindings(*se.up, *env.up,vm);
// iterate through staticenv bindings and add them.
auto map = valmap();
@@ -725,23 +726,6 @@ void mapStaticEnvBindings(const StaticEnv &se, const Env &env, valmap & vm)
map[iter->first] = env.values[iter->second];
}
- vm.merge(map);
- }
- else
- {
- std::cout << " -------------------- " << std::endl;
- // iterate through staticenv bindings and add them,
- // except for the __* ones.
- auto map = valmap();
- for (auto iter = se.vars.begin(); iter != se.vars.end(); ++iter)
- {
- std::cout << iter->first << std::endl;
- std::string s = iter->first;
- if (s.substr(0,2) != "__") {
- map[iter->first] = env.values[iter->second];
- }
- }
-
vm.merge(map);
}
}
From 2a66c120e66953bf8d6cf6866eb2783549527d40 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Mon, 27 Dec 2021 14:48:34 -0700
Subject: [PATCH 064/188] by refernce for addVarToScope
---
src/libcmd/repl.cc | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index b14f43ec4..188bf75e4 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -75,7 +75,7 @@ struct NixRepl
void loadFiles();
void reloadFiles();
void addAttrsToScope(Value & attrs);
- void addVarToScope(const Symbol & name, Value * v);
+ void addVarToScope(const Symbol & name, Value & v);
Expr * parseString(string s);
void evalString(string s, Value & v);
@@ -613,7 +613,7 @@ bool NixRepl::processLine(string line)
Expr * e = parseString(string(line, p + 1));
Value *v = new Value(*state->allocValue());
v->mkThunk(env, e);
- addVarToScope(state->symbols.create(name), v);
+ addVarToScope(state->symbols.create(name), *v);
} else {
std::cout << "evalstring" << std::endl;
Value v;
@@ -696,12 +696,12 @@ void NixRepl::addAttrsToScope(Value & attrs)
{
state->forceAttrs(attrs);
for (auto & i : *attrs.attrs)
- addVarToScope(i.name, i.value);
+ addVarToScope(i.name, *i.value);
notice("Added %1% variables.", attrs.attrs->size());
}
-void NixRepl::addVarToScope(const Symbol & name, Value * v)
+void NixRepl::addVarToScope(const Symbol & name, Value & v)
{
if (displ >= envSize)
throw Error("environment full; cannot add more variables");
@@ -709,7 +709,7 @@ void NixRepl::addVarToScope(const Symbol & name, Value * v)
staticEnv->vars.erase(oldVar);
staticEnv->vars.emplace_back(name, displ);
staticEnv->sort();
- env->values[displ++] = v;
+ env->values[displ++] = &v;
varNames.insert((string) name);
notice("Added variable to scope: %1%", name);
@@ -906,7 +906,7 @@ void runRepl(
for (auto & [name, value] : extraEnv) {
// names.insert(ANSI_BOLD + name + ANSI_NORMAL);
names.insert(name);
- repl->addVarToScope(repl->state->symbols.create(name), value);
+ repl->addVarToScope(repl->state->symbols.create(name), *value);
}
printError(hintfmt("The following extra variables are in scope: %s\n", concatStringsSep(", ", names)).str());
From 6801a423fc9abdfd2cb7307f2970553bcfad089d Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Mon, 27 Dec 2021 16:28:45 -0700
Subject: [PATCH 065/188] :d env
---
src/libcmd/repl.cc | 26 +++++++++++++++-----------
src/libexpr/eval.cc | 7 +++++--
2 files changed, 20 insertions(+), 13 deletions(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 188bf75e4..3948ede02 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -402,7 +402,6 @@ StorePath NixRepl::getDerivationPath(Value & v) {
return drvPath;
}
-
bool NixRepl::processLine(string line)
{
if (line == "") return true;
@@ -441,7 +440,8 @@ bool NixRepl::processLine(string line)
<< " :doc <expr> Show documentation of a builtin function\n"
<< " :d <cmd> Debug mode commands\n"
<< " :d stack Show call stack\n"
- << " :d stack <int> Detail for step N\n"
+ // << " :d stack <int> Detail for stack level N\n"
+ << " :d env Show env stack\n"
<< " :d error Show current error\n";
}
@@ -466,17 +466,21 @@ bool NixRepl::processLine(string line)
}
}
}
-
-
+ } else if (arg == "env") {
+ std::cout << "env stack:" << std::endl;
+ auto iter = this->state->debugTraces.begin();
+ if (iter != this->state->debugTraces.end()) {
+ printStaticEnvBindings(iter->expr);
+ }
}
else if (arg == "error") {
- if (this->debugError) {
- showErrorInfo(std::cout, debugError->info(), true);
- }
- else
- {
- notice("error information not available");
- }
+ if (this->debugError) {
+ showErrorInfo(std::cout, debugError->info(), true);
+ }
+ else
+ {
+ notice("error information not available");
+ }
}
}
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index d99e73471..f1e6cfdf2 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -691,10 +691,14 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
void printStaticEnvBindings(const StaticEnv &se, int lvl)
{
+ std::cout << "Env level " << lvl << std::endl;
+
for (auto i = se.vars.begin(); i != se.vars.end(); ++i)
{
- std::cout << lvl << i->first << std::endl;
+ std::cout << i->first << " ";
}
+ std::cout << std::endl;
+ std::cout << std::endl;
if (se.up) {
printStaticEnvBindings(*se.up, ++lvl);
@@ -730,7 +734,6 @@ void mapStaticEnvBindings(const StaticEnv &se, const Env &env, valmap & vm)
}
}
-
valmap * mapStaticEnvBindings(const StaticEnv &se, const Env &env)
{
auto vm = new valmap();
From 9760fa8661f7562e0b8979338200904053cc4631 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Mon, 27 Dec 2021 17:35:27 -0700
Subject: [PATCH 066/188] add DebugTrace for the current error
---
src/libcmd/command.cc | 2 +-
src/libcmd/command.hh | 2 ++
src/libcmd/repl.cc | 10 ++++++++++
src/libexpr/eval.cc | 17 +----------------
src/libexpr/eval.hh | 18 ++++++++++++++++--
5 files changed, 30 insertions(+), 19 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 6c0f84c4b..897d81981 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -84,7 +84,7 @@ ref<EvalState> EvalCommand::getEvalState()
if (expr.staticenv)
{
auto vm = mapStaticEnvBindings(*expr.staticenv.get(), env);
- runRepl(evalState, &error, *vm);
+ runRepl(evalState, &error, expr, *vm);
}
};
}
diff --git a/src/libcmd/command.hh b/src/libcmd/command.hh
index e2c72256e..8af9eae27 100644
--- a/src/libcmd/command.hh
+++ b/src/libcmd/command.hh
@@ -312,8 +312,10 @@ void printClosureDiff(
const StorePath & afterPath,
std::string_view indent);
+
void runRepl(
ref<EvalState> evalState,
const Error *debugError,
+ const Expr &expr,
const std::map<std::string, Value *> & extraEnv);
}
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 3948ede02..4a61d2be4 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -897,6 +897,7 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
void runRepl(
ref<EvalState> evalState,
const Error *debugError,
+ const Expr &expr,
const std::map<std::string, Value *> & extraEnv)
{
auto repl = std::make_unique<NixRepl>(evalState);
@@ -905,6 +906,15 @@ void runRepl(
repl->initEnv();
+ // tack on a final DebugTrace for the error position.
+ DebugTraceStacker ldts(
+ *evalState,
+ DebugTrace
+ {.pos = debugError->info().errPos,
+ .expr = expr,
+ .hint = debugError->info().msg
+ });
+
// add 'extra' vars.
std::set<std::string> names;
for (auto & [name, value] : extraEnv) {
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index f1e6cfdf2..4bdcc052f 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -38,21 +38,6 @@ namespace nix {
std::function<void(const Error & error, const Env & env, const Expr & expr)> debuggerHook;
-class DebugTraceStacker {
- public:
- DebugTraceStacker(EvalState &evalState, DebugTrace t)
- :evalState(evalState), trace(t)
- {
- evalState.debugTraces.push_front(t);
- }
- ~DebugTraceStacker() {
- // assert(evalState.debugTraces.front() == trace);
- evalState.debugTraces.pop_front();
- }
- EvalState &evalState;
- DebugTrace trace;
-};
-
static char * dupString(const char * s)
{
char * t;
@@ -701,7 +686,7 @@ void printStaticEnvBindings(const StaticEnv &se, int lvl)
std::cout << std::endl;
if (se.up) {
- printStaticEnvBindings(*se.up, ++lvl);
+ printStaticEnvBindings(*se.up, ++lvl);
}
}
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index c7a19e100..2f8cc82b0 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -76,11 +76,10 @@ std::shared_ptr<RegexCache> makeRegexCache();
struct DebugTrace {
std::optional<ErrPos> pos;
- Expr &expr;
+ const Expr &expr;
hintformat hint;
};
-
class EvalState
{
public:
@@ -406,6 +405,21 @@ private:
friend void prim_match(EvalState & state, const Pos & pos, Value * * args, Value & v);
};
+class DebugTraceStacker {
+ public:
+ DebugTraceStacker(EvalState &evalState, DebugTrace t)
+ :evalState(evalState), trace(t)
+ {
+ evalState.debugTraces.push_front(t);
+ }
+ ~DebugTraceStacker()
+ {
+ // assert(evalState.debugTraces.front() == trace);
+ evalState.debugTraces.pop_front();
+ }
+ EvalState &evalState;
+ DebugTrace trace;
+};
/* Return a string representing the type of the value `v'. */
string showType(ValueType type);
From 4610e02d04c9f41ac355d2ca6a27d3a631ffefc6 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Mon, 27 Dec 2021 18:12:46 -0700
Subject: [PATCH 067/188] remove debug code
---
src/libcmd/command.cc | 10 +++++-----
src/libcmd/repl.cc | 18 ------------------
src/libexpr/eval.cc | 6 ------
src/libexpr/parser.y | 4 ----
src/libutil/error.cc | 2 --
5 files changed, 5 insertions(+), 35 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 897d81981..b97458b2d 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -73,13 +73,13 @@ ref<EvalState> EvalCommand::getEvalState()
debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error & error, const Env & env, const Expr & expr) {
printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error.what());
- printStaticEnvBindings(expr);
+ // printStaticEnvBindings(expr);
- std::cout << evalState->vCallFlake << std::endl;
+ // std::cout << evalState->vCallFlake << std::endl;
- std::cout << "expr: " << std::endl;
- expr.show(std::cout);
- std::cout << std::endl;
+ // std::cout << "expr: " << std::endl;
+ // expr.show(std::cout);
+ // std::cout << std::endl;
if (expr.staticenv)
{
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 4a61d2be4..64547344a 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -202,9 +202,6 @@ namespace {
void NixRepl::mainLoop(const std::vector<std::string> & files)
{
- std::cout << "iinitial mainLoop; " << std::endl;
- // printStaticEnvBindings(*staticEnv, 0);
-
string error = ANSI_RED "error:" ANSI_NORMAL " ";
notice("Welcome to Nix " + nixVersion + ". Type :? for help.\n");
@@ -231,9 +228,6 @@ void NixRepl::mainLoop(const std::vector<std::string> & files)
std::string input;
- std::cout << "pre MAINLOOP; " << std::endl;
- // printStaticEnvBindings(*staticEnv, 0);
-
while (true) {
// When continuing input from previous lines, don't print a prompt, just align to the same
// number of chars as the prompt.
@@ -446,7 +440,6 @@ bool NixRepl::processLine(string line)
}
else if (command == ":d" || command == ":debug") {
- std::cout << "debug: '" << arg << "'" << std::endl;
if (arg == "stack") {
std::cout << "eval stack:" << std::endl;
for (auto iter = this->state->debugTraces.begin();
@@ -613,13 +606,11 @@ bool NixRepl::processLine(string line)
line[p + 1] != '=' &&
isVarName(name = removeWhitespace(string(line, 0, p))))
{
- std::cout << "isvarname" << std::endl;
Expr * e = parseString(string(line, p + 1));
Value *v = new Value(*state->allocValue());
v->mkThunk(env, e);
addVarToScope(state->symbols.create(name), *v);
} else {
- std::cout << "evalstring" << std::endl;
Value v;
evalString(line, v);
printValue(std::cout, v, 1) << std::endl;
@@ -715,8 +706,6 @@ void NixRepl::addVarToScope(const Symbol & name, Value & v)
staticEnv->sort();
env->values[displ++] = &v;
varNames.insert((string) name);
- notice("Added variable to scope: %1%", name);
-
}
// version from master.
@@ -741,11 +730,8 @@ Expr * NixRepl::parseString(string s)
void NixRepl::evalString(string s, Value & v)
{
- std::cout << "pre partstirns:l" << std::endl;
Expr * e = parseString(s);
- std::cout << "pre e->eval" << std::endl;
e->eval(*state, *env, v);
- std::cout << "prev fv" << std::endl;
state->forceValue(v);
}
@@ -924,10 +910,6 @@ void runRepl(
}
printError(hintfmt("The following extra variables are in scope: %s\n", concatStringsSep(", ", names)).str());
- // printError("The following extra variables are in scope: %s\n", concatStringsSep(", ", names));
-
- std::cout << " pre repl->mainLoop({});" << std::endl;
- // printStaticEnvBindings(*repl->staticEnv, 0);
repl->mainLoop({});
}
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 4bdcc052f..2596fbe3a 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -858,17 +858,12 @@ LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s,
LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char * s, const string & s1, Env & env, Expr *expr))
{
- std::cout << "throwUndefinedVarError" << std::endl;
-
- std::cout << "loggerSettings.showTrace: " << loggerSettings.showTrace << std::endl;
-
auto error = UndefinedVarError({
.msg = hintfmt(s, s1),
.errPos = pos
});
if (debuggerHook && expr) {
- std::cout << "throwUndefinedVarError debuggerHook" << std::endl;
debuggerHook(error, env, *expr);
}
@@ -1525,7 +1520,6 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
lambda.body->eval(*this, env2, vCur);
} catch (Error & e) {
- std::cout << "eval showErrorInfo showTrace: " << loggerSettings.showTrace.get() << std::endl;
if (loggerSettings.showTrace.get()) {
addErrorTrace(e, lambda.pos, "while evaluating %s",
(lambda.name.set()
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index 066dc4ecc..c537aa0c2 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -616,10 +616,6 @@ Expr * EvalState::parse(const char * text, FileOrigin origin,
if (res) throw ParseError(data.error.value());
- std::cout << " data.result->bindVars(staticEnv); " << std::endl;
-
- // printStaticEnvBindings(*staticEnv, 0);
-
data.result->bindVars(staticEnv);
return data.result;
diff --git a/src/libutil/error.cc b/src/libutil/error.cc
index c2b9d2707..203d79087 100644
--- a/src/libutil/error.cc
+++ b/src/libutil/error.cc
@@ -221,8 +221,6 @@ static std::string indent(std::string_view indentFirst, std::string_view indentR
std::ostream & showErrorInfo(std::ostream & out, const ErrorInfo & einfo, bool showTrace)
{
- std::cout << "showErrorInfo showTrace: " << showTrace << std::endl;
-
std::string prefix;
switch (einfo.level) {
case Verbosity::lvlError: {
From 5954cbf3e9dca0e3b84e4bf2def74abb3d6f80cd Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Mon, 27 Dec 2021 18:29:55 -0700
Subject: [PATCH 068/188] more cleanup
---
src/libcmd/command.cc | 8 --------
src/libcmd/repl.cc | 14 --------------
src/libexpr/eval.cc | 4 ----
src/libexpr/nixexpr.hh | 40 ++++++++++++++++++----------------------
src/libutil/logging.hh | 1 -
5 files changed, 18 insertions(+), 49 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index b97458b2d..e44c737f5 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -73,14 +73,6 @@ ref<EvalState> EvalCommand::getEvalState()
debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error & error, const Env & env, const Expr & expr) {
printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error.what());
- // printStaticEnvBindings(expr);
-
- // std::cout << evalState->vCallFlake << std::endl;
-
- // std::cout << "expr: " << std::endl;
- // expr.show(std::cout);
- // std::cout << std::endl;
-
if (expr.staticenv)
{
auto vm = mapStaticEnvBindings(*expr.staticenv.get(), env);
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 64547344a..cf784db61 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -434,7 +434,6 @@ bool NixRepl::processLine(string line)
<< " :doc <expr> Show documentation of a builtin function\n"
<< " :d <cmd> Debug mode commands\n"
<< " :d stack Show call stack\n"
- // << " :d stack <int> Detail for stack level N\n"
<< " :d env Show env stack\n"
<< " :d error Show current error\n";
}
@@ -708,19 +707,6 @@ void NixRepl::addVarToScope(const Symbol & name, Value & v)
varNames.insert((string) name);
}
-// version from master.
-// void NixRepl::addVarToScope(const Symbol & name, Value & v)
-// {
-// if (displ >= envSize)
-// throw Error("environment full; cannot add more variables");
-// if (auto oldVar = staticEnv.find(name); oldVar != staticEnv.vars.end())
-// staticEnv.vars.erase(oldVar);
-// staticEnv.vars.emplace_back(name, displ);
-// staticEnv.sort();
-// env->values[displ++] = &v;
-// varNames.insert((string) name);
-// }
-
Expr * NixRepl::parseString(string s)
{
Expr * e = state->parseExprFromString(s, curDir, staticEnv);
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 2596fbe3a..ac437e69d 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -672,8 +672,6 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
return {};
}
-
-
void printStaticEnvBindings(const StaticEnv &se, int lvl)
{
std::cout << "Env level " << lvl << std::endl;
@@ -1112,8 +1110,6 @@ void EvalState::resetFileCache()
}
-
-
void EvalState::cacheFile(
const Path & path,
const Path & resolvedPath,
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index a9a5f5316..bfa215fda 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -99,10 +99,9 @@ struct ExprInt : Expr
NixInt n;
Value v;
ExprInt(NixInt n) : n(n) { mkInt(v, n); };
- COMMON_METHODS
Value * maybeThunk(EvalState & state, Env & env);
-
Pos* getPos() { return 0; }
+ COMMON_METHODS
};
struct ExprFloat : Expr
@@ -110,10 +109,9 @@ struct ExprFloat : Expr
NixFloat nf;
Value v;
ExprFloat(NixFloat nf) : nf(nf) { mkFloat(v, nf); };
- COMMON_METHODS
Value * maybeThunk(EvalState & state, Env & env);
-
Pos* getPos() { return 0; }
+ COMMON_METHODS
};
struct ExprString : Expr
@@ -121,10 +119,9 @@ struct ExprString : Expr
Symbol s;
Value v;
ExprString(const Symbol & s) : s(s) { mkString(v, s); };
- COMMON_METHODS
Value * maybeThunk(EvalState & state, Env & env);
-
Pos* getPos() { return 0; }
+ COMMON_METHODS
};
/* Temporary class used during parsing of indented strings. */
@@ -132,7 +129,6 @@ struct ExprIndStr : Expr
{
string s;
ExprIndStr(const string & s) : s(s) { };
-
Pos* getPos() { return 0; }
};
@@ -141,9 +137,9 @@ struct ExprPath : Expr
string s;
Value v;
ExprPath(const string & s) : s(s) { v.mkPath(this->s.c_str()); };
- COMMON_METHODS
Value * maybeThunk(EvalState & state, Env & env);
Pos* getPos() { return 0; }
+ COMMON_METHODS
};
typedef uint32_t Level;
@@ -169,9 +165,9 @@ struct ExprVar : Expr
ExprVar(const Symbol & name) : name(name) { };
ExprVar(const Pos & pos, const Symbol & name) : pos(pos), name(name) { };
- COMMON_METHODS
Value * maybeThunk(EvalState & state, Env & env);
Pos* getPos() { return &pos; }
+ COMMON_METHODS
};
struct ExprSelect : Expr
@@ -181,8 +177,8 @@ struct ExprSelect : Expr
AttrPath attrPath;
ExprSelect(const Pos & pos, Expr * e, const AttrPath & attrPath, Expr * def) : pos(pos), e(e), def(def), attrPath(attrPath) { };
ExprSelect(const Pos & pos, Expr * e, const Symbol & name) : pos(pos), e(e), def(0) { attrPath.push_back(AttrName(name)); };
- COMMON_METHODS
Pos* getPos() { return &pos; }
+ COMMON_METHODS
};
struct ExprOpHasAttr : Expr
@@ -190,8 +186,8 @@ struct ExprOpHasAttr : Expr
Expr * e;
AttrPath attrPath;
ExprOpHasAttr(Expr * e, const AttrPath & attrPath) : e(e), attrPath(attrPath) { };
- COMMON_METHODS
Pos* getPos() { return e->getPos(); }
+ COMMON_METHODS
};
struct ExprAttrs : Expr
@@ -219,16 +215,16 @@ struct ExprAttrs : Expr
DynamicAttrDefs dynamicAttrs;
ExprAttrs(const Pos &pos) : recursive(false), pos(pos) { };
ExprAttrs() : recursive(false), pos(noPos) { };
- COMMON_METHODS
Pos* getPos() { return &pos; }
+ COMMON_METHODS
};
struct ExprList : Expr
{
std::vector<Expr *> elems;
ExprList() { };
- COMMON_METHODS
Pos* getPos() { return 0; }
+ COMMON_METHODS
};
struct Formal
@@ -266,8 +262,8 @@ struct ExprLambda : Expr
void setName(Symbol & name);
string showNamePos() const;
inline bool hasFormals() const { return formals != nullptr; }
- COMMON_METHODS
Pos* getPos() { return &pos; }
+ COMMON_METHODS
};
struct ExprCall : Expr
@@ -278,8 +274,8 @@ struct ExprCall : Expr
ExprCall(const Pos & pos, Expr * fun, std::vector<Expr *> && args)
: fun(fun), args(args), pos(pos)
{ }
- COMMON_METHODS
Pos* getPos() { return &pos; }
+ COMMON_METHODS
};
struct ExprLet : Expr
@@ -287,8 +283,8 @@ struct ExprLet : Expr
ExprAttrs * attrs;
Expr * body;
ExprLet(ExprAttrs * attrs, Expr * body) : attrs(attrs), body(body) { };
- COMMON_METHODS
Pos* getPos() { return 0; }
+ COMMON_METHODS
};
struct ExprWith : Expr
@@ -297,8 +293,8 @@ struct ExprWith : Expr
Expr * attrs, * body;
size_t prevWith;
ExprWith(const Pos & pos, Expr * attrs, Expr * body) : pos(pos), attrs(attrs), body(body) { };
- COMMON_METHODS
Pos* getPos() { return &pos; }
+ COMMON_METHODS
};
struct ExprIf : Expr
@@ -306,8 +302,8 @@ struct ExprIf : Expr
Pos pos;
Expr * cond, * then, * else_;
ExprIf(const Pos & pos, Expr * cond, Expr * then, Expr * else_) : pos(pos), cond(cond), then(then), else_(else_) { };
- COMMON_METHODS
Pos* getPos() { return &pos; }
+ COMMON_METHODS
};
struct ExprAssert : Expr
@@ -315,16 +311,16 @@ struct ExprAssert : Expr
Pos pos;
Expr * cond, * body;
ExprAssert(const Pos & pos, Expr * cond, Expr * body) : pos(pos), cond(cond), body(body) { };
- COMMON_METHODS
Pos* getPos() { return &pos; }
+ COMMON_METHODS
};
struct ExprOpNot : Expr
{
Expr * e;
ExprOpNot(Expr * e) : e(e) { };
- COMMON_METHODS
Pos* getPos() { return 0; }
+ COMMON_METHODS
};
#define MakeBinOp(name, s) \
@@ -361,16 +357,16 @@ struct ExprConcatStrings : Expr
vector<Expr *> * es;
ExprConcatStrings(const Pos & pos, bool forceString, vector<Expr *> * es)
: pos(pos), forceString(forceString), es(es) { };
- COMMON_METHODS
Pos* getPos() { return &pos; }
+ COMMON_METHODS
};
struct ExprPos : Expr
{
Pos pos;
ExprPos(const Pos & pos) : pos(pos) { };
- COMMON_METHODS
Pos* getPos() { return &pos; }
+ COMMON_METHODS
};
diff --git a/src/libutil/logging.hh b/src/libutil/logging.hh
index f10a9af38..96ad69790 100644
--- a/src/libutil/logging.hh
+++ b/src/libutil/logging.hh
@@ -38,7 +38,6 @@ typedef uint64_t ActivityId;
struct LoggerSettings : Config
{
Setting<bool> showTrace{
- // this, false, "show-trace",
this, false, "show-trace",
R"(
Where Nix should print out a stack trace in case of Nix
From c6691089814ac16eb02bab968a97ea2b0fe942f2 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Mon, 3 Jan 2022 18:13:16 -0700
Subject: [PATCH 069/188] merge cleanup
---
src/libcmd/command.cc | 20 +++++++-------------
src/libcmd/repl.cc | 8 ++++----
2 files changed, 11 insertions(+), 17 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index b254a90f0..252bc1fad 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -68,7 +68,13 @@ extern std::function<void(const Error & error, const Env & env, const Expr & exp
ref<EvalState> EvalCommand::getEvalState()
{
if (!evalState) {
- evalState = std::make_shared<EvalState>(searchPath, getEvalStore(), getStore());
+ evalState =
+#if HAVE_BOEHMGC
+ std::allocate_shared<EvalState>(traceable_allocator<EvalState>(),
+#else
+ std::make_shared<EvalState>(
+#endif
+ searchPath, getEvalStore(), getStore());
if (startReplOnEvalErrors)
debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error & error, const Env & env, const Expr & expr) {
printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error.what());
@@ -96,18 +102,6 @@ ref<Store> EvalCommand::getEvalStore()
return ref<Store>(evalStore);
}
-ref<EvalState> EvalCommand::getEvalState()
-{
- if (!evalState) evalState =
-#if HAVE_BOEHMGC
- std::allocate_shared<EvalState>(traceable_allocator<EvalState>(),
-#else
- std::make_shared<EvalState>(
-#endif
- searchPath, getEvalStore(), getStore());
- return ref<EvalState>(evalState);
-}
-
BuiltPathsCommand::BuiltPathsCommand(bool recursive)
: recursive(recursive)
{
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index e7628082a..4cf93c26e 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -435,7 +435,7 @@ bool NixRepl::processLine(string line)
<< " :u <expr> Build derivation, then start nix-shell\n"
<< " :doc <expr> Show documentation of a builtin function\n"
<< " :log <expr> Show logs for a derivation\n"
- << " :st [bool] Enable, disable or toggle showing traces for errors\n";
+ << " :st [bool] Enable, disable or toggle showing traces for errors\n"
<< " :d <cmd> Debug mode commands\n"
<< " :d stack Show call stack\n"
<< " :d env Show env stack\n"
@@ -730,12 +730,12 @@ void NixRepl::addAttrsToScope(Value & attrs)
throw Error("environment full; cannot add more variables");
for (auto & i : *attrs.attrs) {
- staticEnv.vars.emplace_back(i.name, displ);
+ staticEnv->vars.emplace_back(i.name, displ);
env->values[displ++] = i.value;
varNames.insert((string) i.name);
}
- staticEnv.sort();
- staticEnv.deduplicate();
+ staticEnv->sort();
+ staticEnv->deduplicate();
notice("Added %1% variables.", attrs.attrs->size());
}
From 1b6b33d43d5fa4675848b39121f681ae330b2b86 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Mon, 3 Jan 2022 18:29:43 -0700
Subject: [PATCH 070/188] filter out underscore names
---
src/libexpr/eval.cc | 26 +++++++++++++++++++-------
1 file changed, 19 insertions(+), 7 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 851058b3e..86561c6b0 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -680,16 +680,28 @@ void printStaticEnvBindings(const StaticEnv &se, int lvl)
{
std::cout << "Env level " << lvl << std::endl;
- for (auto i = se.vars.begin(); i != se.vars.end(); ++i)
- {
- std::cout << i->first << " ";
- }
- std::cout << std::endl;
- std::cout << std::endl;
-
if (se.up) {
+ for (auto i = se.vars.begin(); i != se.vars.end(); ++i)
+ {
+ std::cout << i->first << " ";
+ }
+ std::cout << std::endl;
+ std::cout << std::endl;
+
printStaticEnvBindings(*se.up, ++lvl);
}
+ else
+ {
+ // for the top level, don't print the double underscore ones; they are in builtins.
+ for (auto i = se.vars.begin(); i != se.vars.end(); ++i)
+ {
+ if (((string)i->first).substr(0,2) != "__")
+ std::cout << i->first << " ";
+ }
+ std::cout << std::endl;
+ std::cout << std::endl;
+
+ }
}
From a4d8a799b7dd6b5368b7892747d18911f8ff9ba2 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Wed, 5 Jan 2022 12:21:18 -0700
Subject: [PATCH 071/188] tidy up debugtraces
---
src/libexpr/eval.cc | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 86561c6b0..d9c26106e 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -1151,14 +1151,14 @@ void EvalState::cacheFile(
fileParseCache[resolvedPath] = e;
try {
- std::unique_ptr<DebugTraceStacker> dts =
+ auto dts =
debuggerHook ?
makeDebugTraceStacker(
*this,
*e,
(e->getPos() ? std::optional(ErrPos(*e->getPos())) : std::nullopt),
"while evaluating the file '%1%':", resolvedPath)
- : std::unique_ptr<DebugTraceStacker>();
+ : nullptr;
// Enforce that 'flake.nix' is a direct attrset, not a
// computation.
@@ -1384,7 +1384,7 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
e->eval(state, env, vTmp);
try {
- std::unique_ptr<DebugTraceStacker> dts =
+ auto dts =
debuggerHook ?
makeDebugTraceStacker(
state,
@@ -1392,7 +1392,7 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
*pos2,
"while evaluating the attribute '%1%'",
showAttrPath(state, env, attrPath))
- : std::unique_ptr<DebugTraceStacker>();
+ : nullptr;
for (auto & i : attrPath) {
state.nrLookups++;
@@ -1536,14 +1536,14 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
/* Evaluate the body. */
try {
- std::unique_ptr<DebugTraceStacker> dts =
+ auto dts =
debuggerHook ?
makeDebugTraceStacker(*this, *lambda.body, lambda.pos,
"while evaluating %s",
(lambda.name.set()
? "'" + (string) lambda.name + "'"
: "anonymous lambda"))
- : std::unique_ptr<DebugTraceStacker>();
+ : nullptr;
lambda.body->eval(*this, env2, vCur);
} catch (Error & e) {
@@ -1939,14 +1939,14 @@ void EvalState::forceValueDeep(Value & v)
for (auto & i : *v.attrs)
try {
- std::unique_ptr<DebugTraceStacker> dts =
+ auto dts =
debuggerHook ?
// if the value is a thunk, we're evaling. otherwise no trace necessary.
(i.value->isThunk() ?
makeDebugTraceStacker(*this, *v.thunk.expr, *i.pos,
"while evaluating the attribute '%1%'", i.name)
- : std::unique_ptr<DebugTraceStacker>())
- : std::unique_ptr<DebugTraceStacker>();
+ : nullptr)
+ : nullptr;
recurse(*i.value);
} catch (Error & e) {
From bf8a065be0d0cdccf5b6bc1034dc3e1709b21bd5 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Wed, 5 Jan 2022 12:28:31 -0700
Subject: [PATCH 072/188] add colors; remove headings
---
src/libcmd/repl.cc | 2 --
src/libexpr/eval.cc | 7 ++++++-
2 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 4cf93c26e..4ecbf51b5 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -444,7 +444,6 @@ bool NixRepl::processLine(string line)
else if (command == ":d" || command == ":debug") {
if (arg == "stack") {
- std::cout << "eval stack:" << std::endl;
for (auto iter = this->state->debugTraces.begin();
iter != this->state->debugTraces.end(); ++iter) {
std::cout << "\n" << "… " << iter->hint.str() << "\n";
@@ -463,7 +462,6 @@ bool NixRepl::processLine(string line)
}
}
} else if (arg == "env") {
- std::cout << "env stack:" << std::endl;
auto iter = this->state->debugTraces.begin();
if (iter != this->state->debugTraces.end()) {
printStaticEnvBindings(iter->expr);
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index d9c26106e..585042b9d 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -679,12 +679,15 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
void printStaticEnvBindings(const StaticEnv &se, int lvl)
{
std::cout << "Env level " << lvl << std::endl;
-
+
if (se.up) {
+ std::cout << ANSI_MAGENTA;
for (auto i = se.vars.begin(); i != se.vars.end(); ++i)
{
std::cout << i->first << " ";
}
+ std::cout << ANSI_NORMAL;
+
std::cout << std::endl;
std::cout << std::endl;
@@ -692,12 +695,14 @@ void printStaticEnvBindings(const StaticEnv &se, int lvl)
}
else
{
+ std::cout << ANSI_MAGENTA;
// for the top level, don't print the double underscore ones; they are in builtins.
for (auto i = se.vars.begin(); i != se.vars.end(); ++i)
{
if (((string)i->first).substr(0,2) != "__")
std::cout << i->first << " ";
}
+ std::cout << ANSI_NORMAL;
std::cout << std::endl;
std::cout << std::endl;
From 84aeb74377ce41408680256813870271999e8208 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Wed, 5 Jan 2022 14:25:45 -0700
Subject: [PATCH 073/188] revert value-add
---
src/libcmd/repl.cc | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 4ecbf51b5..57463bd79 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -641,9 +641,9 @@ bool NixRepl::processLine(string line)
isVarName(name = removeWhitespace(string(line, 0, p))))
{
Expr * e = parseString(string(line, p + 1));
- Value *v = new Value(*state->allocValue());
- v->mkThunk(env, e);
- addVarToScope(state->symbols.create(name), *v);
+ Value & v(*state->allocValue());
+ v.mkThunk(env, e);
+ addVarToScope(state->symbols.create(name), v);
} else {
Value v;
evalString(line, v);
From c51b527c280ee08b3ce3ca6d229139c4292b3176 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Fri, 7 Jan 2022 16:37:44 -0700
Subject: [PATCH 074/188] add env to DebugTrace
---
src/libcmd/repl.cc | 1 +
src/libexpr/eval.cc | 9 ++++++---
src/libexpr/eval.hh | 6 +++++-
3 files changed, 12 insertions(+), 4 deletions(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 57463bd79..fdd63621f 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -927,6 +927,7 @@ void runRepl(
DebugTrace
{.pos = debugError->info().errPos,
.expr = expr,
+ .env = *repl->env,
.hint = debugError->info().msg
});
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 585042b9d..e01147169 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -913,7 +913,7 @@ LocalNoInline(void addErrorTrace(Error & e, const Pos & pos, const char * s, con
}
LocalNoInline(std::unique_ptr<DebugTraceStacker>
- makeDebugTraceStacker(EvalState &state, Expr &expr, std::optional<ErrPos> pos, const char * s, const string & s2))
+ makeDebugTraceStacker(EvalState &state, Expr &expr, Env &env, std::optional<ErrPos> pos, const char * s, const string & s2))
{
return std::unique_ptr<DebugTraceStacker>(
new DebugTraceStacker(
@@ -921,6 +921,7 @@ LocalNoInline(std::unique_ptr<DebugTraceStacker>
DebugTrace
{.pos = pos,
.expr = expr,
+ .env = env,
.hint = hintfmt(s, s2)
}));
}
@@ -1161,6 +1162,7 @@ void EvalState::cacheFile(
makeDebugTraceStacker(
*this,
*e,
+ this->baseEnv,
(e->getPos() ? std::optional(ErrPos(*e->getPos())) : std::nullopt),
"while evaluating the file '%1%':", resolvedPath)
: nullptr;
@@ -1394,6 +1396,7 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
makeDebugTraceStacker(
state,
*this,
+ env,
*pos2,
"while evaluating the attribute '%1%'",
showAttrPath(state, env, attrPath))
@@ -1543,7 +1546,7 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
try {
auto dts =
debuggerHook ?
- makeDebugTraceStacker(*this, *lambda.body, lambda.pos,
+ makeDebugTraceStacker(*this, *lambda.body, env2, lambda.pos,
"while evaluating %s",
(lambda.name.set()
? "'" + (string) lambda.name + "'"
@@ -1948,7 +1951,7 @@ void EvalState::forceValueDeep(Value & v)
debuggerHook ?
// if the value is a thunk, we're evaling. otherwise no trace necessary.
(i.value->isThunk() ?
- makeDebugTraceStacker(*this, *v.thunk.expr, *i.pos,
+ makeDebugTraceStacker(*this, *v.thunk.expr, *v.thunk.env, *i.pos,
"while evaluating the attribute '%1%'", i.name)
: nullptr)
: nullptr;
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 5dbb9b5e5..3c74bb4a1 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -77,6 +77,7 @@ std::shared_ptr<RegexCache> makeRegexCache();
struct DebugTrace {
std::optional<ErrPos> pos;
const Expr &expr;
+ const Env &env;
hintformat hint;
};
@@ -203,7 +204,7 @@ public:
trivial (i.e. doesn't require arbitrary computation). */
void evalFile(const Path & path, Value & v, bool mustBeTrivial = false);
- /* Like `cacheFile`, but with an already parsed expression. */
+ /* Like `evalFile`, but with an already parsed expression. */
void cacheFile(
const Path & path,
const Path & resolvedPath,
@@ -416,6 +417,9 @@ class DebugTraceStacker {
DebugTraceStacker(EvalState &evalState, DebugTrace t)
:evalState(evalState), trace(t)
{
+
+ // evalState.debuggerHook(const Error & error, const Env & env, const Expr & expr);
+
evalState.debugTraces.push_front(t);
}
~DebugTraceStacker()
From a963674d88f2f1af6181f126ed4288ec65b61fc6 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Sat, 8 Jan 2022 11:03:48 -0700
Subject: [PATCH 075/188] optinoal error; compiles
---
src/libcmd/command.cc | 9 +++++----
src/libcmd/repl.cc | 24 ++++++++++++++----------
src/libexpr/eval.cc | 33 ++++++++++++++++++++-------------
src/libexpr/eval.hh | 11 ++---------
src/libexpr/nixexpr.hh | 2 +-
5 files changed, 42 insertions(+), 37 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 252bc1fad..ed8f6d295 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -63,7 +63,7 @@ EvalCommand::EvalCommand()
});
}
-extern std::function<void(const Error & error, const Env & env, const Expr & expr)> debuggerHook;
+extern std::function<void(const Error * error, const Env & env, const Expr & expr)> debuggerHook;
ref<EvalState> EvalCommand::getEvalState()
{
@@ -76,13 +76,14 @@ ref<EvalState> EvalCommand::getEvalState()
#endif
searchPath, getEvalStore(), getStore());
if (startReplOnEvalErrors)
- debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error & error, const Env & env, const Expr & expr) {
- printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error.what());
+ debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error * error, const Env & env, const Expr & expr) {
+ if (error)
+ printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error->what());
if (expr.staticenv)
{
auto vm = mapStaticEnvBindings(*expr.staticenv.get(), env);
- runRepl(evalState, &error, expr, *vm);
+ runRepl(evalState, error, expr, *vm);
}
};
}
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index fdd63621f..e66cf4430 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -917,19 +917,23 @@ void runRepl(
{
auto repl = std::make_unique<NixRepl>(evalState);
- repl->debugError = debugError;
+ // repl->debugError = debugError;
repl->initEnv();
- // tack on a final DebugTrace for the error position.
- DebugTraceStacker ldts(
- *evalState,
- DebugTrace
- {.pos = debugError->info().errPos,
- .expr = expr,
- .env = *repl->env,
- .hint = debugError->info().msg
- });
+ // auto dts = debugError ?
+ // std::unique_ptr<DebugTraceStacker>(
+ // // tack on a final DebugTrace for the error position.
+ // new DebugTraceStacker(
+ // *evalState,
+ // DebugTrace
+ // {.pos = debugError->info().errPos,
+ // .expr = expr,
+ // .env = *repl->env,
+ // .hint = debugError->info().msg
+ // })
+ // )
+ // : nullptr;
// add 'extra' vars.
std::set<std::string> names;
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index e01147169..7b3745e52 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -36,7 +36,7 @@
namespace nix {
-std::function<void(const Error & error, const Env & env, const Expr & expr)> debuggerHook;
+std::function<void(const Error * error, const Env & env, const Expr & expr)> debuggerHook;
static char * dupString(const char * s)
{
@@ -756,7 +756,7 @@ LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, Env
auto error = EvalError(s, s2);
if (debuggerHook && expr)
- debuggerHook(error, env, *expr);
+ debuggerHook(&error, env, *expr);
throw error;
}
@@ -768,7 +768,7 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const
});
if (debuggerHook && expr)
- debuggerHook(error, env, *expr);
+ debuggerHook(&error, env, *expr);
throw error;
}
@@ -778,7 +778,7 @@ LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, con
auto error = EvalError(s, s2, s3);
if (debuggerHook && expr)
- debuggerHook(error, env, *expr);
+ debuggerHook(&error, env, *expr);
throw error;
}
@@ -791,7 +791,7 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const
});
if (debuggerHook && expr)
- debuggerHook(error, env, *expr);
+ debuggerHook(&error, env, *expr);
throw error;
}
@@ -805,7 +805,7 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & p1, const char * s, const
});
if (debuggerHook && expr)
- debuggerHook(error, env, *expr);
+ debuggerHook(&error, env, *expr);
throw error;
}
@@ -818,7 +818,7 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, Env &
});
if (debuggerHook && expr)
- debuggerHook(error, env, *expr);
+ debuggerHook(&error, env, *expr);
throw error;
}
@@ -831,7 +831,7 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
});
if (debuggerHook && expr)
- debuggerHook(error, env, *expr);
+ debuggerHook(&error, env, *expr);
throw error;
}
@@ -844,7 +844,7 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
});
if (debuggerHook && expr)
- debuggerHook(error, env, *expr);
+ debuggerHook(&error, env, *expr);
throw error;
}
@@ -857,7 +857,7 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
});
if (debuggerHook && expr)
- debuggerHook(error, env, *expr);
+ debuggerHook(&error, env, *expr);
throw error;
}
@@ -870,7 +870,7 @@ LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s,
});
if (debuggerHook && expr)
- debuggerHook(error, env, *expr);
+ debuggerHook(&error, env, *expr);
throw error;
}
@@ -883,7 +883,7 @@ LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char *
});
if (debuggerHook && expr) {
- debuggerHook(error, env, *expr);
+ debuggerHook(&error, env, *expr);
}
throw error;
@@ -897,7 +897,7 @@ LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char
});
if (debuggerHook && expr)
- debuggerHook(error, env, *expr);
+ debuggerHook(&error, env, *expr);
throw error;
}
@@ -926,6 +926,13 @@ LocalNoInline(std::unique_ptr<DebugTraceStacker>
}));
}
+DebugTraceStacker::DebugTraceStacker(EvalState &evalState, DebugTrace t)
+:evalState(evalState), trace(t)
+{
+ evalState.debugTraces.push_front(t);
+ if (debuggerHook)
+ debuggerHook(0, t.env, t.expr);
+}
void mkString(Value & v, const char * s)
{
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 3c74bb4a1..1a097ab8c 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -24,7 +24,7 @@ enum RepairFlag : bool;
typedef void (* PrimOpFun) (EvalState & state, const Pos & pos, Value * * args, Value & v);
-extern std::function<void(const Error & error, const Env & env, const Expr & expr)> debuggerHook;
+extern std::function<void(const Error * error, const Env & env, const Expr & expr)> debuggerHook;
void printStaticEnvBindings(const Expr &expr);
void printStaticEnvBindings(const StaticEnv &se, int lvl = 0);
@@ -414,14 +414,7 @@ private:
class DebugTraceStacker {
public:
- DebugTraceStacker(EvalState &evalState, DebugTrace t)
- :evalState(evalState), trace(t)
- {
-
- // evalState.debuggerHook(const Error & error, const Env & env, const Expr & expr);
-
- evalState.debugTraces.push_front(t);
- }
+ DebugTraceStacker(EvalState &evalState, DebugTrace t);
~DebugTraceStacker()
{
// assert(evalState.debugTraces.front() == trace);
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index c4c459f0b..8012c616e 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -18,7 +18,7 @@ MakeError(UndefinedVarError, Error);
MakeError(MissingArgumentError, EvalError);
MakeError(RestrictedPathError, Error);
-extern std::function<void(const Error & error, const Env & env, const Expr & expr)> debuggerHook;
+extern std::function<void(const Error * error, const Env & env, const Expr & expr)> debuggerHook;
/* Position objects. */
From 990bec78d30c5e23cd6aa83a6f98b1d4199bd8c3 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Sat, 8 Jan 2022 15:43:04 -0700
Subject: [PATCH 076/188] clear screen and show top debug trace
---
src/libcmd/command.cc | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index ed8f6d295..5848a15bf 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -77,8 +77,30 @@ ref<EvalState> EvalCommand::getEvalState()
searchPath, getEvalStore(), getStore());
if (startReplOnEvalErrors)
debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error * error, const Env & env, const Expr & expr) {
+ std::cout << "\033[2J\033[1;1H";
+
if (error)
printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error->what());
+ else
+ {
+ auto iter = evalState->debugTraces.begin();
+ if (iter != evalState->debugTraces.end()) {
+ std::cout << "\n" << "… " << iter->hint.str() << "\n";
+
+ if (iter->pos.has_value() && (*iter->pos)) {
+ auto pos = iter->pos.value();
+ std::cout << "\n";
+ printAtPos(pos, std::cout);
+
+ auto loc = getCodeLines(pos);
+ if (loc.has_value()) {
+ std::cout << "\n";
+ printCodeLines(std::cout, "", pos, *loc);
+ std::cout << "\n";
+ }
+ }
+ }
+ }
if (expr.staticenv)
{
From 412d58f0bb65104b0065dbf721a92b9e5dcdcdbb Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Thu, 3 Feb 2022 13:15:21 -0700
Subject: [PATCH 077/188] break() primop; step and go debug commands
---
src/libcmd/repl.cc | 16 +++++++++++++++-
src/libexpr/eval.cc | 3 ++-
src/libexpr/eval.hh | 1 +
src/libexpr/primops.cc | 22 ++++++++++++++++++++++
4 files changed, 40 insertions(+), 2 deletions(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index e66cf4430..5c14c7d3e 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -439,7 +439,11 @@ bool NixRepl::processLine(string line)
<< " :d <cmd> Debug mode commands\n"
<< " :d stack Show call stack\n"
<< " :d env Show env stack\n"
- << " :d error Show current error\n";
+ << " :d error Show current error\n"
+ << " :d go Go until end of program, exception, or builtins.break().\n"
+ << " :d step Go one step\n"
+ ;
+
}
else if (command == ":d" || command == ":debug") {
@@ -476,6 +480,16 @@ bool NixRepl::processLine(string line)
notice("error information not available");
}
}
+ else if (arg == "step") {
+ // set flag and exit repl.
+ state->debugStop = true;
+ return false;
+ }
+ else if (arg == "go") {
+ // set flag and exit repl.
+ state->debugStop = false;
+ return false;
+ }
}
else if (command == ":a" || command == ":add") {
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 7b3745e52..426cff2d3 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -417,6 +417,7 @@ EvalState::EvalState(
, repair(NoRepair)
, store(store)
, buildStore(buildStore ? buildStore : store)
+ , debugStop(true)
, regexCache(makeRegexCache())
, baseEnv(allocEnv(128))
, staticBaseEnv(new StaticEnv(false, 0))
@@ -930,7 +931,7 @@ DebugTraceStacker::DebugTraceStacker(EvalState &evalState, DebugTrace t)
:evalState(evalState), trace(t)
{
evalState.debugTraces.push_front(t);
- if (debuggerHook)
+ if (evalState.debugStop && debuggerHook)
debuggerHook(0, t.env, t.expr);
}
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 1a097ab8c..649fda778 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -115,6 +115,7 @@ public:
RootValue vCallFlake = nullptr;
RootValue vImportedDrvToDerivation = nullptr;
+ bool debugStop;
std::list<DebugTrace> debugTraces;
private:
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 66265f917..3a54e1490 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -710,6 +710,28 @@ static RegisterPrimOp primop_genericClosure(RegisterPrimOp::Info {
.fun = prim_genericClosure,
});
+static RegisterPrimOp primop_break({
+ .name = "break",
+ .args = {},
+ .doc = R"(
+ In debug mode, pause Nix expression evaluation and enter the repl.
+ )",
+ .fun = [](EvalState & state, const Pos & pos, Value * * args, Value & v)
+ {
+ // PathSet context;
+ // string s = state.coerceToString(pos, *args[0], context);
+ if (debuggerHook && !state.debugTraces.empty())
+ {
+ auto &dt = state.debugTraces.front();
+ // std::optional<ErrPos> pos;
+ // const Expr &expr;
+ // const Env &env;
+ // hintformat hint;
+ debuggerHook(nullptr, dt.env, dt.expr);
+ }
+ }
+});
+
static RegisterPrimOp primop_abort({
.name = "abort",
.args = {"s"},
From 3ddf864e1b2c5c27b2e6f7203e262c85bf760f7c Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Fri, 4 Feb 2022 14:50:25 -0700
Subject: [PATCH 078/188] print value in break
---
src/libcmd/command.cc | 3 ++-
src/libexpr/primops.cc | 6 +++++-
2 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 5848a15bf..701976265 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -77,7 +77,8 @@ ref<EvalState> EvalCommand::getEvalState()
searchPath, getEvalStore(), getStore());
if (startReplOnEvalErrors)
debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error * error, const Env & env, const Expr & expr) {
- std::cout << "\033[2J\033[1;1H";
+ // clear the screen.
+ // std::cout << "\033[2J\033[1;1H";
if (error)
printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error->what());
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 3a54e1490..48a10cd27 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -712,12 +712,13 @@ static RegisterPrimOp primop_genericClosure(RegisterPrimOp::Info {
static RegisterPrimOp primop_break({
.name = "break",
- .args = {},
+ .args = {"v"},
.doc = R"(
In debug mode, pause Nix expression evaluation and enter the repl.
)",
.fun = [](EvalState & state, const Pos & pos, Value * * args, Value & v)
{
+ std::cout << "primop_break, value: " << *args[0] << std::endl;
// PathSet context;
// string s = state.coerceToString(pos, *args[0], context);
if (debuggerHook && !state.debugTraces.empty())
@@ -728,6 +729,9 @@ static RegisterPrimOp primop_break({
// const Env &env;
// hintformat hint;
debuggerHook(nullptr, dt.env, dt.expr);
+
+ // returning the value we were passed.
+ v = *args[0];
}
}
});
From 195db83148d17484809ca8af0932b1be1803a29a Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Fri, 4 Feb 2022 17:35:56 -0700
Subject: [PATCH 079/188] a few merge fixes
---
src/libexpr/eval.cc | 24 ++++++++++++------------
src/libexpr/eval.hh | 4 ++--
2 files changed, 14 insertions(+), 14 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 790b00ace..6c89b87b7 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -860,18 +860,18 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
throw error;
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const string &s2, Env & env, Expr *expr))
-{
- auto error = TypeError({
- .msg = hintfmt(s, s2),
- .errPos = pos
- });
+// LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const string &s2, Env & env, Expr *expr))
+// {
+// auto error = TypeError({
+// .msg = hintfmt(s, s2),
+// .errPos = pos
+// });
- if (debuggerHook && expr)
- debuggerHook(&error, env, *expr);
+// if (debuggerHook && expr)
+// debuggerHook(&error, env, *expr);
- throw error;
-}
+// throw error;
+// }
LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const ExprLambda & fun, const Symbol & s2, Env & env, Expr *expr))
{
@@ -1243,7 +1243,7 @@ inline bool EvalState::evalBool(Env & env, Expr * e)
Value v;
e->eval(*this, env, v);
if (v.type() != nBool)
- throwTypeError("value is %1% while a Boolean was expected", v);
+ throwTypeError(noPos, "value is %1% while a Boolean was expected", v);
return v.boolean;
}
@@ -1262,7 +1262,7 @@ inline void EvalState::evalAttrs(Env & env, Expr * e, Value & v)
{
e->eval(*this, env, v);
if (v.type() != nAttrs)
- throwTypeError("value is %1% while a set was expected", v);
+ throwTypeError(noPos, "value is %1% while a set was expected", v);
}
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 8c4430bc8..a7d1207f2 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -195,7 +195,7 @@ public:
Expr * parseExprFromFile(const Path & path, std::shared_ptr<StaticEnv> & staticEnv);
/* Parse a Nix expression from the specified string. */
- Expr * parseExprFromString(std::string s, const Path & basePath, , std::shared_ptr<StaticEnv> & staticEnv);
+ Expr * parseExprFromString(std::string s, const Path & basePath, std::shared_ptr<StaticEnv> & staticEnv);
Expr * parseExprFromString(std::string s, const Path & basePath);
Expr * parseStdin();
@@ -331,7 +331,7 @@ private:
friend struct ExprLet;
Expr * parse(char * text, size_t length, FileOrigin origin, const PathView path,
- const Path & basePath, std::shared_ptr<StaticEnv> & staticEnv);
+ const PathView basePath, std::shared_ptr<StaticEnv> & staticEnv);
public:
From 7954a18a48a1301a6d7f781e36ea20ee2a62d480 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Fri, 4 Feb 2022 17:40:06 -0700
Subject: [PATCH 080/188] link change
---
src/libcmd/local.mk | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/src/libcmd/local.mk b/src/libcmd/local.mk
index 713c1bf11..a12837ce5 100644
--- a/src/libcmd/local.mk
+++ b/src/libcmd/local.mk
@@ -9,8 +9,8 @@ libcmd_SOURCES := $(wildcard $(d)/*.cc)
libcmd_CXXFLAGS += -I src/libutil -I src/libstore -I src/libexpr -I src/libmain -I src/libfetchers -I src/nix
# libcmd_LDFLAGS += -llowdown -pthread
-# libcmd_LDFLAGS = $(EDITLINE_LIBS) -llowdown -pthread
-libcmd_LDFLAGS += $(LOWDOWN_LIBS) -pthread
+libcmd_LDFLAGS = $(EDITLINE_LIBS) -llowdown -pthread
+# libcmd_LDFLAGS += $(LOWDOWN_LIBS) -pthread
libcmd_LIBS = libstore libutil libexpr libmain libfetchers libnix
From bc67cb5ad12b7d042067ba9727b0b8b37c5f3e53 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Thu, 10 Feb 2022 15:05:38 -0700
Subject: [PATCH 081/188] remove fakeEnv stuff and instead use last context
from the stack
---
src/libexpr/eval.cc | 122 +++++++++++++++++++++++---------------------
1 file changed, 65 insertions(+), 57 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 6c89b87b7..e584efbfb 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -775,12 +775,30 @@ valmap * mapStaticEnvBindings(const StaticEnv &se, const Env &env)
evaluator. So here are some helper functions for throwing
exceptions. */
-LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, Env & env, Expr *expr))
+LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, EvalState &evalState))
{
auto error = EvalError(s, s2);
- if (debuggerHook && expr)
- debuggerHook(&error, env, *expr);
+ if (debuggerHook && !evalState.debugTraces.empty()) {
+ DebugTrace &last = evalState.debugTraces.front();
+ debuggerHook(&error, last.env, last.expr);
+ }
+
+ throw error;
+}
+
+LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2, EvalState &evalState))
+{
+ auto error = EvalError({
+ .msg = hintfmt(s, s2),
+ .errPos = pos
+ });
+
+ if (debuggerHook && !evalState.debugTraces.empty()) {
+ DebugTrace &last = evalState.debugTraces.front();
+ debuggerHook(&error, last.env, last.expr);
+ }
+
throw error;
}
@@ -797,25 +815,32 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const
throw error;
}
-LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, const string & s3, Env & env, Expr *expr))
-{
- auto error = EvalError(s, s2, s3);
-
- if (debuggerHook && expr)
- debuggerHook(&error, env, *expr);
-
- throw error;
-}
-
-LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2, const string & s3, Env & env, Expr *expr))
+LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2, const string & s3, EvalState &evalState))
{
auto error = EvalError({
.msg = hintfmt(s, s2, s3),
.errPos = pos
});
- if (debuggerHook && expr)
- debuggerHook(&error, env, *expr);
+ if (debuggerHook && !evalState.debugTraces.empty()) {
+ DebugTrace &last = evalState.debugTraces.front();
+ debuggerHook(&error, last.env, last.expr);
+ }
+
+ throw error;
+}
+
+LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, const string & s3, EvalState &evalState))
+{
+ auto error = EvalError({
+ .msg = hintfmt(s, s2, s3),
+ .errPos = noPos
+ });
+
+ if (debuggerHook && !evalState.debugTraces.empty()) {
+ DebugTrace &last = evalState.debugTraces.front();
+ debuggerHook(&error, last.env, last.expr);
+ }
throw error;
}
@@ -834,45 +859,37 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & p1, const char * s, const
throw error;
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, Env & env, Expr *expr))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, EvalState &evalState))
{
auto error = TypeError({
.msg = hintfmt(s),
.errPos = pos
});
- if (debuggerHook && expr)
- debuggerHook(&error, env, *expr);
+ if (debuggerHook && !evalState.debugTraces.empty()) {
+ DebugTrace &last = evalState.debugTraces.front();
+ debuggerHook(&error, last.env, last.expr);
+ }
throw error;
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v, Env & env, Expr *expr))
+
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v, EvalState &evalState))
{
auto error = TypeError({
.msg = hintfmt(s, v),
.errPos = pos
});
- if (debuggerHook && expr)
- debuggerHook(&error, env, *expr);
+ if (debuggerHook && !evalState.debugTraces.empty()) {
+ DebugTrace &last = evalState.debugTraces.front();
+ debuggerHook(&error, last.env, last.expr);
+ }
throw error;
}
-// LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const string &s2, Env & env, Expr *expr))
-// {
-// auto error = TypeError({
-// .msg = hintfmt(s, s2),
-// .errPos = pos
-// });
-
-// if (debuggerHook && expr)
-// debuggerHook(&error, env, *expr);
-
-// throw error;
-// }
-
LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const ExprLambda & fun, const Symbol & s2, Env & env, Expr *expr))
{
auto error = TypeError({
@@ -886,13 +903,6 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
throw error;
}
-// LocalNoInlineNoReturn(void throwTypeError(const char * s, const Value & v, Env & env, Expr *expr))
-// {
-// auto error = TypeError({
-// .msg = hintfmt(s, showType(v))
-// .errPos = e ;
-// }
-
LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s, const string & s1, Env & env, Expr *expr))
{
auto error = AssertionError({
@@ -2053,8 +2063,8 @@ NixInt EvalState::forceInt(Value & v, const Pos & pos)
{
forceValue(v, pos);
if (v.type() != nInt)
- throwTypeError(pos, "value is %1% while an integer was expected", v,
- fakeEnv(1), 0);
+ throwTypeError(pos, "value is %1% while an integer was expected", v, *this);
+
return v.integer;
}
@@ -2066,7 +2076,7 @@ NixFloat EvalState::forceFloat(Value & v, const Pos & pos)
return v.integer;
else if (v.type() != nFloat)
throwTypeError(pos, "value is %1% while a float was expected", v,
- fakeEnv(1), 0);
+ *this);
return v.fpoint;
}
@@ -2076,7 +2086,7 @@ bool EvalState::forceBool(Value & v, const Pos & pos)
forceValue(v, pos);
if (v.type() != nBool)
throwTypeError(pos, "value is %1% while a Boolean was expected", v,
- fakeEnv(1), 0);
+ *this);
return v.boolean;
}
@@ -2092,7 +2102,7 @@ void EvalState::forceFunction(Value & v, const Pos & pos)
forceValue(v, pos);
if (v.type() != nFunction && !isFunctor(v))
throwTypeError(pos, "value is %1% while a function was expected", v,
- fakeEnv(1), 0);
+ *this);
}
@@ -2101,7 +2111,7 @@ std::string_view EvalState::forceString(Value & v, const Pos & pos)
forceValue(v, pos);
if (v.type() != nString) {
throwTypeError(pos, "value is %1% while a string was expected", v,
- fakeEnv(1), 0);
+ *this);
}
return v.string.s;
}
@@ -2152,10 +2162,10 @@ std::string_view EvalState::forceStringNoCtx(Value & v, const Pos & pos)
if (v.string.context) {
if (pos)
throwEvalError(pos, "the string '%1%' is not allowed to refer to a store path (such as '%2%')",
- v.string.s, v.string.context[0], fakeEnv(1), 0);
+ v.string.s, v.string.context[0], *this);
else
throwEvalError("the string '%1%' is not allowed to refer to a store path (such as '%2%')",
- v.string.s, v.string.context[0], fakeEnv(1), 0);
+ v.string.s, v.string.context[0], *this);
}
return s;
}
@@ -2210,8 +2220,7 @@ BackedStringView EvalState::coerceToString(const Pos & pos, Value & v, PathSet &
return std::move(*maybeString);
auto i = v.attrs->find(sOutPath);
if (i == v.attrs->end())
- throwTypeError(pos, "cannot coerce a set to a string",
- fakeEnv(1), 0);
+ throwTypeError(pos, "cannot coerce a set to a string", *this);
return coerceToString(pos, *i->value, context, coerceMore, copyToStore);
}
@@ -2240,8 +2249,7 @@ BackedStringView EvalState::coerceToString(const Pos & pos, Value & v, PathSet &
}
}
- throwTypeError(pos, "cannot coerce %1% to a string", v,
- fakeEnv(1), 0);
+ throwTypeError(pos, "cannot coerce %1% to a string", v, *this);
}
@@ -2250,7 +2258,7 @@ string EvalState::copyPathToStore(PathSet & context, const Path & path)
if (nix::isDerivation(path))
throwEvalError("file names are not allowed to end in '%1%'",
drvExtension,
- fakeEnv(1), 0);
+ *this);
Path dstPath;
auto i = srcToStore.find(path);
@@ -2276,7 +2284,7 @@ Path EvalState::coerceToPath(const Pos & pos, Value & v, PathSet & context)
string path = coerceToString(pos, v, context, false, false).toOwned();
if (path == "" || path[0] != '/')
throwEvalError(pos, "string '%1%' doesn't represent an absolute path", path,
- fakeEnv(1), 0);
+ *this);
return path;
}
@@ -2358,7 +2366,7 @@ bool EvalState::eqValues(Value & v1, Value & v2)
throwEvalError("cannot compare %1% with %2%",
showType(v1),
showType(v2),
- fakeEnv(1), 0);
+ *this);
}
}
From 3ff5ac3586f0e15e231489e5e36ae783e51e9bab Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Thu, 10 Feb 2022 16:01:49 -0700
Subject: [PATCH 082/188] update the eval-inline throw fns
---
src/libexpr/eval-inline.hh | 28 +++++++++++++++++++-------
src/libexpr/eval.cc | 41 ++++++++++++++++++++++----------------
2 files changed, 45 insertions(+), 24 deletions(-)
diff --git a/src/libexpr/eval-inline.hh b/src/libexpr/eval-inline.hh
index aef1f6351..7ed05950a 100644
--- a/src/libexpr/eval-inline.hh
+++ b/src/libexpr/eval-inline.hh
@@ -7,20 +7,34 @@
namespace nix {
-LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s))
+LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, EvalState &evalState))
{
- throw EvalError({
+ auto error = EvalError({
.msg = hintfmt(s),
.errPos = pos
});
+
+ if (debuggerHook && !evalState.debugTraces.empty()) {
+ DebugTrace &last = evalState.debugTraces.front();
+ debuggerHook(&error, last.env, last.expr);
+ }
+
+ throw error;
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v, EvalState &evalState))
{
- throw TypeError({
+ auto error = TypeError({
.msg = hintfmt(s, showType(v)),
.errPos = pos
});
+
+ if (debuggerHook && !evalState.debugTraces.empty()) {
+ DebugTrace &last = evalState.debugTraces.front();
+ debuggerHook(&error, last.env, last.expr);
+ }
+
+ throw error;
}
@@ -48,7 +62,7 @@ void EvalState::forceValue(Value & v, Callable getPos)
else if (v.isApp())
callFunction(*v.app.left, *v.app.right, v, noPos);
else if (v.isBlackhole())
- throwEvalError(getPos(), "infinite recursion encountered");
+ throwEvalError(getPos(), "infinite recursion encountered", *this);
}
@@ -63,7 +77,7 @@ inline void EvalState::forceAttrs(Value & v, Callable getPos)
{
forceValue(v, getPos);
if (v.type() != nAttrs)
- throwTypeError(getPos(), "value is %1% while a set was expected", v);
+ throwTypeError(getPos(), "value is %1% while a set was expected", v, *this);
}
@@ -71,7 +85,7 @@ inline void EvalState::forceList(Value & v, const Pos & pos)
{
forceValue(v, pos);
if (!v.isList())
- throwTypeError(pos, "value is %1% while a list was expected", v);
+ throwTypeError(pos, "value is %1% while a list was expected", v, *this);
}
/* Note: Various places expect the allocated memory to be zeroed. */
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index e584efbfb..79bdaff47 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -787,6 +787,19 @@ LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, Eva
throw error;
}
+LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, Env & env, Expr *expr))
+{
+ auto error = EvalError({
+ .msg = hintfmt(s),
+ .errPos = pos
+ });
+
+ if (debuggerHook && expr)
+ debuggerHook(&error, env, *expr);
+
+ throw error;
+}
+
LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2, EvalState &evalState))
{
auto error = EvalError({
@@ -875,17 +888,15 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, EvalS
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v, EvalState &evalState))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v, Env & env, Expr *expr))
{
auto error = TypeError({
.msg = hintfmt(s, v),
.errPos = pos
});
- if (debuggerHook && !evalState.debugTraces.empty()) {
- DebugTrace &last = evalState.debugTraces.front();
- debuggerHook(&error, last.env, last.expr);
- }
+ if (debuggerHook && expr)
+ debuggerHook(&error, env, *expr);
throw error;
}
@@ -1253,7 +1264,7 @@ inline bool EvalState::evalBool(Env & env, Expr * e)
Value v;
e->eval(*this, env, v);
if (v.type() != nBool)
- throwTypeError(noPos, "value is %1% while a Boolean was expected", v);
+ throwTypeError(noPos, "value is %1% while a Boolean was expected", v, env, e);
return v.boolean;
}
@@ -1263,7 +1274,7 @@ inline bool EvalState::evalBool(Env & env, Expr * e, const Pos & pos)
Value v;
e->eval(*this, env, v);
if (v.type() != nBool)
- throwTypeError(pos, "value is %1% while a Boolean was expected", v);
+ throwTypeError(pos, "value is %1% while a Boolean was expected", v, env, e);
return v.boolean;
}
@@ -1272,7 +1283,7 @@ inline void EvalState::evalAttrs(Env & env, Expr * e, Value & v)
{
e->eval(*this, env, v);
if (v.type() != nAttrs)
- throwTypeError(noPos, "value is %1% while a set was expected", v);
+ throwTypeError(noPos, "value is %1% while a set was expected", v, env, e);
}
@@ -1377,8 +1388,7 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
Symbol nameSym = state.symbols.create(nameVal.string.s);
Bindings::iterator j = v.attrs->find(nameSym);
if (j != v.attrs->end())
- throwEvalError(i.pos, "dynamic attribute '%1%' already defined at %2%", nameSym, *j->pos,
- env, this);
+ throwEvalError(i.pos, "dynamic attribute '%1%' already defined at %2%", nameSym, *j->pos, env, this);
i.valueExpr->setName(nameSym);
/* Keep sorted order so find can catch duplicates */
@@ -1697,7 +1707,7 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
}
else
- throwTypeError(pos, "attempt to call something which is not a function but %1%", vCur);
+ throwTypeError(pos, "attempt to call something which is not a function but %1%", vCur, *this);
}
vRes = vCur;
@@ -2005,7 +2015,7 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
v.mkFloat(nf);
else if (firstType == nPath) {
if (!context.empty())
- throwEvalError(pos, "a string that refers to a store path cannot be appended to a path");
+ throwEvalError(pos, "a string that refers to a store path cannot be appended to a path", env, this);
v.mkPath(canonPath(str()));
} else
v.mkStringMove(c_str(), context);
@@ -2256,9 +2266,7 @@ BackedStringView EvalState::coerceToString(const Pos & pos, Value & v, PathSet &
string EvalState::copyPathToStore(PathSet & context, const Path & path)
{
if (nix::isDerivation(path))
- throwEvalError("file names are not allowed to end in '%1%'",
- drvExtension,
- *this);
+ throwEvalError("file names are not allowed to end in '%1%'", drvExtension, *this);
Path dstPath;
auto i = srcToStore.find(path);
@@ -2283,8 +2291,7 @@ Path EvalState::coerceToPath(const Pos & pos, Value & v, PathSet & context)
{
string path = coerceToString(pos, v, context, false, false).toOwned();
if (path == "" || path[0] != '/')
- throwEvalError(pos, "string '%1%' doesn't represent an absolute path", path,
- *this);
+ throwEvalError(pos, "string '%1%' doesn't represent an absolute path", path, *this);
return path;
}
From 4cffb130e385bc3f4c5ca0482ad8c4dd22229cfe Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Fri, 11 Feb 2022 14:14:25 -0700
Subject: [PATCH 083/188] for primops, enter the debugger at the last
DebugTrace in the stack
---
src/libexpr/eval.cc | 13 +++-
src/libexpr/eval.hh | 2 +
src/libexpr/nixexpr.cc | 2 +-
src/libexpr/primops.cc | 167 +++++++++++++++++++++--------------------
4 files changed, 99 insertions(+), 85 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 79bdaff47..71a28bafa 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -437,7 +437,7 @@ EvalState::EvalState(
, emptyBindings(0)
, store(store)
, buildStore(buildStore ? buildStore : store)
- , debugStop(true)
+ , debugStop(false)
, regexCache(makeRegexCache())
#if HAVE_BOEHMGC
, valueAllocCache(std::allocate_shared<void *>(traceable_allocator<void *>(), nullptr))
@@ -787,6 +787,17 @@ LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, Eva
throw error;
}
+void EvalState::debug_throw(Error e) {
+ // call this in the situation where Expr and Env are inaccessible. The debugger will start in the last context
+ // that's in the DebugTrace stack.
+
+ if (debuggerHook && !debugTraces.empty()) {
+ DebugTrace &last = debugTraces.front();
+ debuggerHook(&e, last.env, last.expr);
+ }
+ throw e;
+}
+
LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, Env & env, Expr *expr))
{
auto error = EvalError({
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index a7d1207f2..1390c8885 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -118,6 +118,8 @@ public:
bool debugStop;
std::list<DebugTrace> debugTraces;
+ void debug_throw(Error e);
+
private:
SrcToStore srcToStore;
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index 41ee92d27..e09bd9484 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -305,7 +305,7 @@ void ExprVar::bindVars(const std::shared_ptr<const StaticEnv> &env)
if (withLevel == -1)
{
throw UndefinedVarError({
- .msg = hintfmt("undefined variable (ExprVar bindvars) '%1%'", name),
+ .msg = hintfmt("undefined variable '%1%'", name),
.errPos = pos
});
}
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 3b429f328..956c55e49 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -46,7 +46,7 @@ StringMap EvalState::realiseContext(const PathSet & context)
auto [ctxS, outputName] = decodeContext(i);
auto ctx = store->parseStorePath(ctxS);
if (!store->isValidPath(ctx))
- throw InvalidPathError(store->printStorePath(ctx));
+ debug_throw(InvalidPathError(store->printStorePath(ctx)));
if (!outputName.empty() && ctx.isDerivation()) {
drvs.push_back({ctx, {outputName}});
} else {
@@ -57,9 +57,9 @@ StringMap EvalState::realiseContext(const PathSet & context)
if (drvs.empty()) return {};
if (!evalSettings.enableImportFromDerivation)
- throw Error(
+ debug_throw(Error(
"cannot build '%1%' during evaluation because the option 'allow-import-from-derivation' is disabled",
- store->printStorePath(drvs.begin()->drvPath));
+ store->printStorePath(drvs.begin()->drvPath)));
/* Build/substitute the context. */
std::vector<DerivedPath> buildReqs;
@@ -71,8 +71,8 @@ StringMap EvalState::realiseContext(const PathSet & context)
auto outputPaths = store->queryDerivationOutputMap(drvPath);
for (auto & outputName : outputs) {
if (outputPaths.count(outputName) == 0)
- throw Error("derivation '%s' does not have an output named '%s'",
- store->printStorePath(drvPath), outputName);
+ debug_throw(Error("derivation '%s' does not have an output named '%s'",
+ store->printStorePath(drvPath), outputName));
res.insert_or_assign(
downstreamPlaceholder(*store, drvPath, outputName),
store->printStorePath(outputPaths.at(outputName))
@@ -318,17 +318,17 @@ void prim_importNative(EvalState & state, const Pos & pos, Value * * args, Value
void *handle = dlopen(path.c_str(), RTLD_LAZY | RTLD_LOCAL);
if (!handle)
- throw EvalError("could not open '%1%': %2%", path, dlerror());
+ state.debug_throw(EvalError("could not open '%1%': %2%", path, dlerror()));
dlerror();
ValueInitializer func = (ValueInitializer) dlsym(handle, sym.c_str());
if(!func) {
char *message = dlerror();
if (message)
- throw EvalError("could not load symbol '%1%' from '%2%': %3%", sym, path, message);
+ state.debug_throw(EvalError("could not load symbol '%1%' from '%2%': %3%", sym, path, message));
else
- throw EvalError("symbol '%1%' from '%2%' resolved to NULL when a function pointer was expected",
- sym, path);
+ state.debug_throw(EvalError("symbol '%1%' from '%2%' resolved to NULL when a function pointer was expected",
+ sym, path));
}
(func)(state, v);
@@ -344,10 +344,10 @@ void prim_exec(EvalState & state, const Pos & pos, Value * * args, Value & v)
auto elems = args[0]->listElems();
auto count = args[0]->listSize();
if (count == 0) {
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("at least one argument to 'exec' required"),
.errPos = pos
- });
+ }));
}
PathSet context;
auto program = state.coerceToString(pos, *elems[0], context, false, false).toOwned();
@@ -358,11 +358,11 @@ void prim_exec(EvalState & state, const Pos & pos, Value * * args, Value & v)
try {
auto _ = state.realiseContext(context); // FIXME: Handle CA derivations
} catch (InvalidPathError & e) {
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("cannot execute '%1%', since path '%2%' is not valid",
program, e.path),
.errPos = pos
- });
+ }));
}
auto output = runProgram(program, true, commandArgs);
@@ -545,7 +545,7 @@ struct CompareValues
if (v1->type() == nInt && v2->type() == nFloat)
return v1->integer < v2->fpoint;
if (v1->type() != v2->type())
- throw EvalError("cannot compare %1% with %2%", showType(*v1), showType(*v2));
+ state.debug_throw(EvalError("cannot compare %1% with %2%", showType(*v1), showType(*v2)));
switch (v1->type()) {
case nInt:
return v1->integer < v2->integer;
@@ -567,7 +567,8 @@ struct CompareValues
}
}
default:
- throw EvalError("cannot compare %1% with %2%", showType(*v1), showType(*v2));
+ state.debug_throw(EvalError("cannot compare %1% with %2%", showType(*v1), showType(*v2)));
+ return false;
}
}
};
@@ -597,10 +598,10 @@ static Bindings::iterator getAttr(
Pos aPos = *attrSet->pos;
if (aPos == noPos) {
- throw TypeError({
+ state.debug_throw(TypeError({
.msg = errorMsg,
.errPos = pos,
- });
+ }));
} else {
auto e = TypeError({
.msg = errorMsg,
@@ -610,7 +611,7 @@ static Bindings::iterator getAttr(
// Adding another trace for the function name to make it clear
// which call received wrong arguments.
e.addTrace(pos, hintfmt("while invoking '%s'", funcName));
- throw e;
+ state.debug_throw(e);
}
}
@@ -664,10 +665,10 @@ static void prim_genericClosure(EvalState & state, const Pos & pos, Value * * ar
Bindings::iterator key =
e->attrs->find(state.sKey);
if (key == e->attrs->end())
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("attribute 'key' required"),
.errPos = pos
- });
+ }));
state.forceValue(*key->value, pos);
if (!doneKeys.insert(key->value).second) continue;
@@ -734,7 +735,7 @@ static RegisterPrimOp primop_abort({
{
PathSet context;
string s = state.coerceToString(pos, *args[0], context).toOwned();
- throw Abort("evaluation aborted with the following error message: '%1%'", s);
+ state.debug_throw(Abort("evaluation aborted with the following error message: '%1%'", s));
}
});
@@ -752,7 +753,7 @@ static RegisterPrimOp primop_throw({
{
PathSet context;
string s = state.coerceToString(pos, *args[0], context).toOwned();
- throw ThrownError(s);
+ state.debug_throw(ThrownError(s));
}
});
@@ -1006,37 +1007,37 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
if (s == "recursive") ingestionMethod = FileIngestionMethod::Recursive;
else if (s == "flat") ingestionMethod = FileIngestionMethod::Flat;
else
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("invalid value '%s' for 'outputHashMode' attribute", s),
.errPos = posDrvName
- });
+ }));
};
auto handleOutputs = [&](const Strings & ss) {
outputs.clear();
for (auto & j : ss) {
if (outputs.find(j) != outputs.end())
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("duplicate derivation output '%1%'", j),
.errPos = posDrvName
- });
+ }));
/* !!! Check whether j is a valid attribute
name. */
/* Derivations cannot be named ‘drv’, because
then we'd have an attribute ‘drvPath’ in
the resulting set. */
if (j == "drv")
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("invalid derivation output name 'drv'" ),
.errPos = posDrvName
- });
+ }));
outputs.insert(j);
}
if (outputs.empty())
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("derivation cannot have an empty set of outputs"),
.errPos = posDrvName
- });
+ }));
};
try {
@@ -1155,23 +1156,23 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
/* Do we have all required attributes? */
if (drv.builder == "")
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("required attribute 'builder' missing"),
.errPos = posDrvName
- });
+ }));
if (drv.platform == "")
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("required attribute 'system' missing"),
.errPos = posDrvName
- });
+ }));
/* Check whether the derivation name is valid. */
if (isDerivation(drvName))
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("derivation names are not allowed to end in '%s'", drvExtension),
.errPos = posDrvName
- });
+ }));
if (outputHash) {
/* Handle fixed-output derivations.
@@ -1179,10 +1180,10 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
Ignore `__contentAddressed` because fixed output derivations are
already content addressed. */
if (outputs.size() != 1 || *(outputs.begin()) != "out")
- throw Error({
+ state.debug_throw(Error({
.msg = hintfmt("multiple outputs are not supported in fixed-output derivations"),
.errPos = posDrvName
- });
+ }));
std::optional<HashType> ht = parseHashTypeOpt(outputHashAlgo);
Hash h = newHashAllowEmpty(*outputHash, ht);
@@ -1350,10 +1351,10 @@ static RegisterPrimOp primop_toPath({
static void prim_storePath(EvalState & state, const Pos & pos, Value * * args, Value & v)
{
if (evalSettings.pureEval)
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("'%s' is not allowed in pure evaluation mode", "builtins.storePath"),
.errPos = pos
- });
+ }));
PathSet context;
Path path = state.checkSourcePath(state.coerceToPath(pos, *args[0], context));
@@ -1362,10 +1363,10 @@ static void prim_storePath(EvalState & state, const Pos & pos, Value * * args, V
e.g. nix-push does the right thing. */
if (!state.store->isStorePath(path)) path = canonPath(path, true);
if (!state.store->isInStore(path))
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("path '%1%' is not in the Nix store", path),
.errPos = pos
- });
+ }));
auto path2 = state.store->toStorePath(path).first;
if (!settings.readOnlyMode)
state.store->ensurePath(path2);
@@ -1468,7 +1469,7 @@ static void prim_readFile(EvalState & state, const Pos & pos, Value * * args, Va
auto path = realisePath(state, pos, *args[0]);
string s = readFile(path);
if (s.find((char) 0) != string::npos)
- throw Error("the contents of the file '%1%' cannot be represented as a Nix string", path);
+ state.debug_throw(Error("the contents of the file '%1%' cannot be represented as a Nix string", path));
StorePathSet refs;
if (state.store->isInStore(path)) {
try {
@@ -1520,10 +1521,10 @@ static void prim_findFile(EvalState & state, const Pos & pos, Value * * args, Va
auto rewrites = state.realiseContext(context);
path = rewriteStrings(path, rewrites);
} catch (InvalidPathError & e) {
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("cannot find '%1%', since path '%2%' is not valid", path, e.path),
.errPos = pos
- });
+ }));
}
@@ -1547,10 +1548,10 @@ static void prim_hashFile(EvalState & state, const Pos & pos, Value * * args, Va
auto type = state.forceStringNoCtx(*args[0], pos);
std::optional<HashType> ht = parseHashType(type);
if (!ht)
- throw Error({
+ state.debug_throw(Error({
.msg = hintfmt("unknown hash type '%1%'", type),
.errPos = pos
- });
+ }));
auto path = realisePath(state, pos, *args[1]);
@@ -1787,13 +1788,13 @@ static void prim_toFile(EvalState & state, const Pos & pos, Value * * args, Valu
for (auto path : context) {
if (path.at(0) != '/')
- throw EvalError( {
+ state.debug_throw(EvalError( {
.msg = hintfmt(
"in 'toFile': the file named '%1%' must not contain a reference "
"to a derivation but contains (%2%)",
name, path),
.errPos = pos
- });
+ }));
refs.insert(state.store->parseStorePath(path));
}
@@ -1951,7 +1952,7 @@ static void addPath(
? state.store->computeStorePathForPath(name, path, method, htSHA256, filter).first
: state.store->addToStore(name, path, method, htSHA256, filter, state.repair, refs));
if (expectedHash && expectedStorePath != state.store->parseStorePath(dstPath))
- throw Error("store path mismatch in (possibly filtered) path added from '%s'", path);
+ state.debug_throw(Error("store path mismatch in (possibly filtered) path added from '%s'", path));
} else
dstPath = state.store->printStorePath(*expectedStorePath);
@@ -1973,12 +1974,12 @@ static void prim_filterSource(EvalState & state, const Pos & pos, Value * * args
state.forceValue(*args[0], pos);
if (args[0]->type() != nFunction)
- throw TypeError({
+ state.debug_throw(TypeError({
.msg = hintfmt(
"first argument in call to 'filterSource' is not a function but %1%",
showType(*args[0])),
.errPos = pos
- });
+ }));
addPath(state, pos, std::string(baseNameOf(path)), path, args[0], FileIngestionMethod::Recursive, std::nullopt, v, context);
}
@@ -2062,16 +2063,16 @@ static void prim_path(EvalState & state, const Pos & pos, Value * * args, Value
else if (n == "sha256")
expectedHash = newHashAllowEmpty(state.forceStringNoCtx(*attr.value, *attr.pos), htSHA256);
else
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("unsupported argument '%1%' to 'addPath'", attr.name),
.errPos = *attr.pos
- });
+ }));
}
if (path.empty())
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("'path' required"),
.errPos = pos
- });
+ }));
if (name.empty())
name = baseNameOf(path);
@@ -2442,10 +2443,10 @@ static void prim_functionArgs(EvalState & state, const Pos & pos, Value * * args
return;
}
if (!args[0]->isLambda())
- throw TypeError({
+ state.debug_throw(TypeError({
.msg = hintfmt("'functionArgs' requires a function"),
.errPos = pos
- });
+ }));
if (!args[0]->lambda.fun->hasFormals()) {
v.mkAttrs(&state.emptyBindings);
@@ -2620,10 +2621,10 @@ static void elemAt(EvalState & state, const Pos & pos, Value & list, int n, Valu
{
state.forceList(list, pos);
if (n < 0 || (unsigned int) n >= list.listSize())
- throw Error({
- .msg = hintfmt("list index %1% is out of bounds", n),
+ state.debug_throw(Error({
+ .msg = hintfmt("list index %1% is out of boundz", n),
.errPos = pos
- });
+ }));
state.forceValue(*list.listElems()[n], pos);
v = *list.listElems()[n];
}
@@ -2668,10 +2669,10 @@ static void prim_tail(EvalState & state, const Pos & pos, Value * * args, Value
{
state.forceList(*args[0], pos);
if (args[0]->listSize() == 0)
- throw Error({
+ state.debug_throw(Error({
.msg = hintfmt("'tail' called on an empty list"),
.errPos = pos
- });
+ }));
state.mkList(v, args[0]->listSize() - 1);
for (unsigned int n = 0; n < v.listSize(); ++n)
@@ -2906,10 +2907,10 @@ static void prim_genList(EvalState & state, const Pos & pos, Value * * args, Val
auto len = state.forceInt(*args[1], pos);
if (len < 0)
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("cannot create list of size %1%", len),
.errPos = pos
- });
+ }));
state.mkList(v, len);
@@ -3213,10 +3214,10 @@ static void prim_div(EvalState & state, const Pos & pos, Value * * args, Value &
NixFloat f2 = state.forceFloat(*args[1], pos);
if (f2 == 0)
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("division by zero"),
.errPos = pos
- });
+ }));
if (args[0]->type() == nFloat || args[1]->type() == nFloat) {
v.mkFloat(state.forceFloat(*args[0], pos) / state.forceFloat(*args[1], pos));
@@ -3225,10 +3226,10 @@ static void prim_div(EvalState & state, const Pos & pos, Value * * args, Value &
NixInt i2 = state.forceInt(*args[1], pos);
/* Avoid division overflow as it might raise SIGFPE. */
if (i1 == std::numeric_limits<NixInt>::min() && i2 == -1)
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("overflow in integer division"),
.errPos = pos
- });
+ }));
v.mkInt(i1 / i2);
}
@@ -3356,10 +3357,10 @@ static void prim_substring(EvalState & state, const Pos & pos, Value * * args, V
auto s = state.coerceToString(pos, *args[2], context);
if (start < 0)
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("negative start position in 'substring'"),
.errPos = pos
- });
+ }));
v.mkString((unsigned int) start >= s->size() ? "" : s->substr(start, len), context);
}
@@ -3407,10 +3408,10 @@ static void prim_hashString(EvalState & state, const Pos & pos, Value * * args,
auto type = state.forceStringNoCtx(*args[0], pos);
std::optional<HashType> ht = parseHashType(type);
if (!ht)
- throw Error({
+ state.debug_throw(Error({
.msg = hintfmt("unknown hash type '%1%'", type),
.errPos = pos
- });
+ }));
PathSet context; // discarded
auto s = state.forceString(*args[1], context, pos);
@@ -3480,15 +3481,15 @@ void prim_match(EvalState & state, const Pos & pos, Value * * args, Value & v)
} catch (std::regex_error &e) {
if (e.code() == std::regex_constants::error_space) {
// limit is _GLIBCXX_REGEX_STATE_LIMIT for libstdc++
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("memory limit exceeded by regular expression '%s'", re),
.errPos = pos
- });
+ }));
} else {
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("invalid regular expression '%s'", re),
.errPos = pos
- });
+ }));
}
}
}
@@ -3585,15 +3586,15 @@ void prim_split(EvalState & state, const Pos & pos, Value * * args, Value & v)
} catch (std::regex_error &e) {
if (e.code() == std::regex_constants::error_space) {
// limit is _GLIBCXX_REGEX_STATE_LIMIT for libstdc++
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("memory limit exceeded by regular expression '%s'", re),
.errPos = pos
- });
+ }));
} else {
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("invalid regular expression '%s'", re),
.errPos = pos
- });
+ }));
}
}
}
@@ -3670,10 +3671,10 @@ static void prim_replaceStrings(EvalState & state, const Pos & pos, Value * * ar
state.forceList(*args[0], pos);
state.forceList(*args[1], pos);
if (args[0]->listSize() != args[1]->listSize())
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("'from' and 'to' arguments to 'replaceStrings' have different lengths"),
.errPos = pos
- });
+ }));
vector<string> from;
from.reserve(args[0]->listSize());
From e761bf0601a56db26c31891a3433c1319814fffa Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Mon, 14 Feb 2022 14:04:34 -0700
Subject: [PATCH 084/188] make an 'info' level error on break
---
src/libcmd/repl.cc | 16 +---------------
src/libexpr/primops.cc | 15 +++++++--------
2 files changed, 8 insertions(+), 23 deletions(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 51bbbbc57..db88aa9b6 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -931,24 +931,10 @@ void runRepl(
{
auto repl = std::make_unique<NixRepl>(evalState);
- // repl->debugError = debugError;
+ repl->debugError = debugError;
repl->initEnv();
- // auto dts = debugError ?
- // std::unique_ptr<DebugTraceStacker>(
- // // tack on a final DebugTrace for the error position.
- // new DebugTraceStacker(
- // *evalState,
- // DebugTrace
- // {.pos = debugError->info().errPos,
- // .expr = expr,
- // .env = *repl->env,
- // .hint = debugError->info().msg
- // })
- // )
- // : nullptr;
-
// add 'extra' vars.
std::set<std::string> names;
for (auto & [name, value] : extraEnv) {
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 956c55e49..25845bdc4 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -699,6 +699,7 @@ static RegisterPrimOp primop_genericClosure(RegisterPrimOp::Info {
.fun = prim_genericClosure,
});
+
static RegisterPrimOp primop_break({
.name = "break",
.args = {"v"},
@@ -707,17 +708,15 @@ static RegisterPrimOp primop_break({
)",
.fun = [](EvalState & state, const Pos & pos, Value * * args, Value & v)
{
- std::cout << "primop_break, value: " << *args[0] << std::endl;
- // PathSet context;
- // string s = state.coerceToString(pos, *args[0], context);
+ auto error = Error(ErrorInfo{
+ .level = lvlInfo,
+ .msg = hintfmt("breakpoint reached; value was %1%", *args[0]),
+ .errPos = pos,
+ });
if (debuggerHook && !state.debugTraces.empty())
{
auto &dt = state.debugTraces.front();
- // std::optional<ErrPos> pos;
- // const Expr &expr;
- // const Env &env;
- // hintformat hint;
- debuggerHook(nullptr, dt.env, dt.expr);
+ debuggerHook(&error, dt.env, dt.expr);
// returning the value we were passed.
v = *args[0];
From c9bc3735f639a4d022ab071feb5dabd451a0d016 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Tue, 15 Feb 2022 09:49:25 -0700
Subject: [PATCH 085/188] quit repl from step mode
---
src/libcmd/repl.cc | 22 +++++++++++++++-------
src/libexpr/eval.cc | 1 +
src/libexpr/eval.hh | 1 +
src/libexpr/primops.cc | 9 +++++++++
4 files changed, 26 insertions(+), 7 deletions(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index db88aa9b6..2b3dfcbd2 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -89,6 +89,7 @@ string removeWhitespace(string s)
s = chomp(s);
size_t n = s.find_first_not_of(" \n\r\t");
if (n != string::npos) s = string(s, n);
+
return s;
}
@@ -231,8 +232,12 @@ void NixRepl::mainLoop(const std::vector<std::string> & files)
// When continuing input from previous lines, don't print a prompt, just align to the same
// number of chars as the prompt.
if (!getLine(input, input.empty() ? "nix-repl> " : " "))
+ {
+ // ctrl-D should exit the debugger.
+ state->debugStop = false;
+ state->debugQuit = true;
break;
-
+ }
try {
if (!removeWhitespace(input).empty() && !processLine(input)) return;
} catch (ParseError & e) {
@@ -464,12 +469,12 @@ bool NixRepl::processLine(string line)
std::cout << "\n";
}
}
- }
+ }
} else if (arg == "env") {
auto iter = this->state->debugTraces.begin();
if (iter != this->state->debugTraces.end()) {
printStaticEnvBindings(iter->expr);
- }
+ }
}
else if (arg == "error") {
if (this->debugError) {
@@ -481,12 +486,12 @@ bool NixRepl::processLine(string line)
}
}
else if (arg == "step") {
- // set flag and exit repl.
+ // set flag to stop at next DebugTrace; exit repl.
state->debugStop = true;
return false;
}
else if (arg == "go") {
- // set flag and exit repl.
+ // set flag to run to next breakpoint or end of program; exit repl.
state->debugStop = false;
return false;
}
@@ -605,8 +610,11 @@ bool NixRepl::processLine(string line)
printValue(std::cout, v, 1000000000) << std::endl;
}
- else if (command == ":q" || command == ":quit")
+ else if (command == ":q" || command == ":quit") {
+ state->debugStop = false;
+ state->debugQuit = true;
return false;
+ }
else if (command == ":doc") {
Value v;
@@ -944,7 +952,7 @@ void runRepl(
}
printError(hintfmt("The following extra variables are in scope: %s\n", concatStringsSep(", ", names)).str());
-
+
repl->mainLoop({});
}
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 71a28bafa..3a835adb3 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -438,6 +438,7 @@ EvalState::EvalState(
, store(store)
, buildStore(buildStore ? buildStore : store)
, debugStop(false)
+ , debugQuit(false)
, regexCache(makeRegexCache())
#if HAVE_BOEHMGC
, valueAllocCache(std::allocate_shared<void *>(traceable_allocator<void *>(), nullptr))
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 1390c8885..e1d117c36 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -116,6 +116,7 @@ public:
RootValue vImportedDrvToDerivation = nullptr;
bool debugStop;
+ bool debugQuit;
std::list<DebugTrace> debugTraces;
void debug_throw(Error e);
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 25845bdc4..80d78e150 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -718,6 +718,15 @@ static RegisterPrimOp primop_break({
auto &dt = state.debugTraces.front();
debuggerHook(&error, dt.env, dt.expr);
+ if (state.debugQuit) {
+ // if the user elects to quit the repl, throw an exception.
+ throw Error(ErrorInfo{
+ .level = lvlInfo,
+ .msg = hintfmt("quit from debugger"),
+ .errPos = pos,
+ });
+ }
+
// returning the value we were passed.
v = *args[0];
}
From 3d94d3ba91d8cde069ca635aae4c070c85a99759 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Tue, 15 Feb 2022 15:46:45 -0700
Subject: [PATCH 086/188] Expr refs instead of pointers
---
src/libexpr/eval.cc | 76 ++++++++++++++++++++++-----------------------
1 file changed, 38 insertions(+), 38 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 3a835adb3..f21919598 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -799,15 +799,15 @@ void EvalState::debug_throw(Error e) {
throw e;
}
-LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, Env & env, Expr *expr))
+LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, Env & env, Expr &expr))
{
auto error = EvalError({
.msg = hintfmt(s),
.errPos = pos
});
- if (debuggerHook && expr)
- debuggerHook(&error, env, *expr);
+ if (debuggerHook)
+ debuggerHook(&error, env, expr);
throw error;
}
@@ -827,15 +827,15 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const
throw error;
}
-LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2, Env & env, Expr *expr))
+LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2, Env & env, Expr &expr))
{
auto error = EvalError({
.msg = hintfmt(s, s2),
.errPos = pos
});
- if (debuggerHook && expr)
- debuggerHook(&error, env, *expr);
+ if (debuggerHook)
+ debuggerHook(&error, env, expr);
throw error;
}
@@ -870,7 +870,7 @@ LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, con
throw error;
}
-LocalNoInlineNoReturn(void throwEvalError(const Pos & p1, const char * s, const Symbol & sym, const Pos & p2, Env & env, Expr *expr))
+LocalNoInlineNoReturn(void throwEvalError(const Pos & p1, const char * s, const Symbol & sym, const Pos & p2, Env & env, Expr &expr))
{
// p1 is where the error occurred; p2 is a position mentioned in the message.
auto error = EvalError({
@@ -878,8 +878,8 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & p1, const char * s, const
.errPos = p1
});
- if (debuggerHook && expr)
- debuggerHook(&error, env, *expr);
+ if (debuggerHook)
+ debuggerHook(&error, env, expr);
throw error;
}
@@ -900,68 +900,67 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, EvalS
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v, Env & env, Expr *expr))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v, Env & env, Expr &expr))
{
auto error = TypeError({
.msg = hintfmt(s, v),
.errPos = pos
});
- if (debuggerHook && expr)
- debuggerHook(&error, env, *expr);
+ if (debuggerHook)
+ debuggerHook(&error, env, expr);
throw error;
}
-LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const ExprLambda & fun, const Symbol & s2, Env & env, Expr *expr))
+LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const ExprLambda & fun, const Symbol & s2, Env & env, Expr &expr))
{
auto error = TypeError({
.msg = hintfmt(s, fun.showNamePos(), s2),
.errPos = pos
});
- if (debuggerHook && expr)
- debuggerHook(&error, env, *expr);
+ if (debuggerHook)
+ debuggerHook(&error, env, expr);
throw error;
}
-LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s, const string & s1, Env & env, Expr *expr))
+LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s, const string & s1, Env & env, Expr &expr))
{
auto error = AssertionError({
.msg = hintfmt(s, s1),
.errPos = pos
});
- if (debuggerHook && expr)
- debuggerHook(&error, env, *expr);
+ if (debuggerHook)
+ debuggerHook(&error, env, expr);
throw error;
}
-LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char * s, const string & s1, Env & env, Expr *expr))
+LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char * s, const string & s1, Env & env, Expr &expr))
{
auto error = UndefinedVarError({
.msg = hintfmt(s, s1),
.errPos = pos
});
- if (debuggerHook && expr) {
- debuggerHook(&error, env, *expr);
- }
+ if (debuggerHook)
+ debuggerHook(&error, env, expr);
throw error;
}
-LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char * s, const string & s1, Env & env, Expr *expr))
+LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char * s, const string & s1, Env & env, Expr &expr))
{
auto error = MissingArgumentError({
.msg = hintfmt(s, s1),
.errPos = pos
});
- if (debuggerHook && expr)
- debuggerHook(&error, env, *expr);
+ if (debuggerHook)
+ debuggerHook(&error, env, expr);
throw error;
}
@@ -1055,7 +1054,8 @@ inline Value * EvalState::lookupVar(Env * env, const ExprVar & var, bool noEval)
return j->value;
}
if (!env->prevWith) {
- throwUndefinedVarError(var.pos, "undefined variable '%1%'", var.name, *env, (Expr*)&var);
+ // TODO deal with const_cast
+ throwUndefinedVarError(var.pos, "undefined variable '%1%'", var.name, *env, *const_cast<ExprVar*>(&var));
}
for (size_t l = env->prevWith; l; --l, env = env->up) ;
}
@@ -1276,7 +1276,7 @@ inline bool EvalState::evalBool(Env & env, Expr * e)
Value v;
e->eval(*this, env, v);
if (v.type() != nBool)
- throwTypeError(noPos, "value is %1% while a Boolean was expected", v, env, e);
+ throwTypeError(noPos, "value is %1% while a Boolean was expected", v, env, *e);
return v.boolean;
}
@@ -1286,7 +1286,7 @@ inline bool EvalState::evalBool(Env & env, Expr * e, const Pos & pos)
Value v;
e->eval(*this, env, v);
if (v.type() != nBool)
- throwTypeError(pos, "value is %1% while a Boolean was expected", v, env, e);
+ throwTypeError(pos, "value is %1% while a Boolean was expected", v, env, *e);
return v.boolean;
}
@@ -1295,7 +1295,7 @@ inline void EvalState::evalAttrs(Env & env, Expr * e, Value & v)
{
e->eval(*this, env, v);
if (v.type() != nAttrs)
- throwTypeError(noPos, "value is %1% while a set was expected", v, env, e);
+ throwTypeError(noPos, "value is %1% while a set was expected", v, env, *e);
}
@@ -1400,7 +1400,7 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
Symbol nameSym = state.symbols.create(nameVal.string.s);
Bindings::iterator j = v.attrs->find(nameSym);
if (j != v.attrs->end())
- throwEvalError(i.pos, "dynamic attribute '%1%' already defined at %2%", nameSym, *j->pos, env, this);
+ throwEvalError(i.pos, "dynamic attribute '%1%' already defined at %2%", nameSym, *j->pos, env, *this);
i.valueExpr->setName(nameSym);
/* Keep sorted order so find can catch duplicates */
@@ -1498,7 +1498,7 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
} else {
state.forceAttrs(*vAttrs, pos);
if ((j = vAttrs->attrs->find(name)) == vAttrs->attrs->end())
- throwEvalError(pos, "attribute '%1%' missing", name, env, this);
+ throwEvalError(pos, "attribute '%1%' missing", name, env, *this);
}
vAttrs = j->value;
pos2 = j->pos;
@@ -1599,7 +1599,7 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
auto j = args[0]->attrs->get(i.name);
if (!j) {
if (!i.def) throwTypeError(pos, "%1% called without required argument '%2%'",
- lambda, i.name, *fun.lambda.env, &lambda);
+ lambda, i.name, *fun.lambda.env, lambda);
env2.values[displ++] = i.def->maybeThunk(*this, env2);
} else {
attrsUsed++;
@@ -1615,7 +1615,7 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
for (auto & i : *args[0]->attrs)
if (!lambda.formals->has(i.name))
throwTypeError(pos, "%1% called with unexpected argument '%2%'",
- lambda, i.name, *fun.lambda.env, &lambda);
+ lambda, i.name, *fun.lambda.env, lambda);
abort(); // can't happen
}
}
@@ -1790,7 +1790,7 @@ this case it must have its arguments supplied either by default
values, or passed explicitly with '--arg' or '--argstr'. See
https://nixos.org/manual/nix/stable/#ss-functions.)",
i.name,
- *fun.lambda.env, fun.lambda.fun);
+ *fun.lambda.env, *fun.lambda.fun);
}
}
}
@@ -1822,7 +1822,7 @@ void ExprAssert::eval(EvalState & state, Env & env, Value & v)
if (!state.evalBool(env, cond, pos)) {
std::ostringstream out;
cond->show(out);
- throwAssertionError(pos, "assertion '%1%' failed", out.str(), env, this);
+ throwAssertionError(pos, "assertion '%1%' failed", out.str(), env, *this);
}
body->eval(state, env, v);
}
@@ -1999,7 +1999,7 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
nf = n;
nf += vTmp.fpoint;
} else {
- throwEvalError(i_pos, "cannot add %1% to an integer", showType(vTmp), env, this);
+ throwEvalError(i_pos, "cannot add %1% to an integer", showType(vTmp), env, *this);
}
} else if (firstType == nFloat) {
if (vTmp.type() == nInt) {
@@ -2007,7 +2007,7 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
} else if (vTmp.type() == nFloat) {
nf += vTmp.fpoint;
} else
- throwEvalError(i_pos, "cannot add %1% to a float", showType(vTmp), env, this);
+ throwEvalError(i_pos, "cannot add %1% to a float", showType(vTmp), env, *this);
} else {
if (s.empty()) s.reserve(es->size());
/* skip canonization of first path, which would only be not
@@ -2027,7 +2027,7 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
v.mkFloat(nf);
else if (firstType == nPath) {
if (!context.empty())
- throwEvalError(pos, "a string that refers to a store path cannot be appended to a path", env, this);
+ throwEvalError(pos, "a string that refers to a store path cannot be appended to a path", env, *this);
v.mkPath(canonPath(str()));
} else
v.mkStringMove(c_str(), context);
From 2799fe4cdbe77e017544f2fe61ae9baef650dbe6 Mon Sep 17 00:00:00 2001
From: pennae <github@quasiparticle.net>
Date: Tue, 21 Dec 2021 19:34:40 +0100
Subject: [PATCH 087/188] enable LTO in optimized builds
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
gives 2-5% performance improvement across a board of tests.
LTO is broken when using clang; some libs link fine while others crash
the linker with a segfault in the llvm linker plugin. 🙁
---
Makefile | 3 ++-
Makefile.config.in | 1 +
configure.ac | 14 ++++++++++++++
doc/manual/src/release-notes/rl-next.md | 3 +++
mk/libraries.mk | 6 +++---
mk/programs.mk | 4 ++--
6 files changed, 25 insertions(+), 6 deletions(-)
diff --git a/Makefile b/Makefile
index 5040d2884..903787e1a 100644
--- a/Makefile
+++ b/Makefile
@@ -27,7 +27,8 @@ makefiles = \
OPTIMIZE = 1
ifeq ($(OPTIMIZE), 1)
- GLOBAL_CXXFLAGS += -O3
+ GLOBAL_CXXFLAGS += -O3 $(CXXLTO)
+ GLOBAL_LDFLAGS += $(CXXLTO)
else
GLOBAL_CXXFLAGS += -O0 -U_FORTIFY_SOURCE
endif
diff --git a/Makefile.config.in b/Makefile.config.in
index 3505f337e..d724853fa 100644
--- a/Makefile.config.in
+++ b/Makefile.config.in
@@ -7,6 +7,7 @@ CC = @CC@
CFLAGS = @CFLAGS@
CXX = @CXX@
CXXFLAGS = @CXXFLAGS@
+CXXLTO = @CXXLTO@
EDITLINE_LIBS = @EDITLINE_LIBS@
ENABLE_S3 = @ENABLE_S3@
GTEST_LIBS = @GTEST_LIBS@
diff --git a/configure.ac b/configure.ac
index 8a01c33ec..a86d88fad 100644
--- a/configure.ac
+++ b/configure.ac
@@ -147,6 +147,20 @@ if test "x$GCC_ATOMIC_BUILTINS_NEED_LIBATOMIC" = xyes; then
LDFLAGS="-latomic $LDFLAGS"
fi
+# LTO is currently broken with clang for unknown reasons; ld segfaults in the llvm plugin
+AC_ARG_ENABLE(lto, AS_HELP_STRING([--enable-lto],[Enable LTO (only supported with GCC) [default=no]]),
+ lto=$enableval, lto=no)
+if test "$lto" = yes; then
+ if $CXX --version | grep -q GCC; then
+ AC_SUBST(CXXLTO, [-flto=jobserver])
+ else
+ echo "error: LTO is only supported with GCC at the moment" >&2
+ exit 1
+ fi
+else
+ AC_SUBST(CXXLTO, [""])
+fi
+
PKG_PROG_PKG_CONFIG
AC_ARG_ENABLE(shared, AS_HELP_STRING([--enable-shared],[Build shared libraries for Nix [default=yes]]),
diff --git a/doc/manual/src/release-notes/rl-next.md b/doc/manual/src/release-notes/rl-next.md
index 7dd8387d8..d81e54e49 100644
--- a/doc/manual/src/release-notes/rl-next.md
+++ b/doc/manual/src/release-notes/rl-next.md
@@ -26,3 +26,6 @@
* Templates can now define a `welcomeText` attribute, which is printed out by
`nix flake {init,new} --template <template>`.
+
+* Nix can now be built with LTO by passing `--enable-lto` to `configure`.
+ LTO is currently only supported when building with GCC.
diff --git a/mk/libraries.mk b/mk/libraries.mk
index ffd7b5610..876148a55 100644
--- a/mk/libraries.mk
+++ b/mk/libraries.mk
@@ -91,7 +91,7 @@ define build-library
$(1)_PATH := $$(_d)/$$($(1)_NAME).$(SO_EXT)
$$($(1)_PATH): $$($(1)_OBJS) $$(_libs) | $$(_d)/
- $$(trace-ld) $(CXX) -o $$(abspath $$@) -shared $$(LDFLAGS) $$(GLOBAL_LDFLAGS) $$($(1)_OBJS) $$($(1)_LDFLAGS) $$($(1)_LDFLAGS_PROPAGATED) $$(foreach lib, $$($(1)_LIBS), $$($$(lib)_LDFLAGS_USE)) $$($(1)_LDFLAGS_UNINSTALLED)
+ +$$(trace-ld) $(CXX) -o $$(abspath $$@) -shared $$(LDFLAGS) $$(GLOBAL_LDFLAGS) $$($(1)_OBJS) $$($(1)_LDFLAGS) $$($(1)_LDFLAGS_PROPAGATED) $$(foreach lib, $$($(1)_LIBS), $$($$(lib)_LDFLAGS_USE)) $$($(1)_LDFLAGS_UNINSTALLED)
ifndef HOST_DARWIN
$(1)_LDFLAGS_USE += -Wl,-rpath,$$(abspath $$(_d))
@@ -105,7 +105,7 @@ define build-library
$$(eval $$(call create-dir, $$($(1)_INSTALL_DIR)))
$$($(1)_INSTALL_PATH): $$($(1)_OBJS) $$(_libs_final) | $(DESTDIR)$$($(1)_INSTALL_DIR)/
- $$(trace-ld) $(CXX) -o $$@ -shared $$(LDFLAGS) $$(GLOBAL_LDFLAGS) $$($(1)_OBJS) $$($(1)_LDFLAGS) $$($(1)_LDFLAGS_PROPAGATED) $$(foreach lib, $$($(1)_LIBS), $$($$(lib)_LDFLAGS_USE_INSTALLED))
+ +$$(trace-ld) $(CXX) -o $$@ -shared $$(LDFLAGS) $$(GLOBAL_LDFLAGS) $$($(1)_OBJS) $$($(1)_LDFLAGS) $$($(1)_LDFLAGS_PROPAGATED) $$(foreach lib, $$($(1)_LIBS), $$($$(lib)_LDFLAGS_USE_INSTALLED))
$(1)_LDFLAGS_USE_INSTALLED += -L$$(DESTDIR)$$($(1)_INSTALL_DIR) -l$$(patsubst lib%,%,$$(strip $$($(1)_NAME)))
ifndef HOST_DARWIN
@@ -125,7 +125,7 @@ define build-library
$(1)_PATH := $$(_d)/$$($(1)_NAME).a
$$($(1)_PATH): $$($(1)_OBJS) | $$(_d)/
- $$(trace-ld) $(LD) -Ur -o $$(_d)/$$($(1)_NAME).o $$?
+ +$$(trace-ld) $(LD) -Ur -o $$(_d)/$$($(1)_NAME).o $$?
$$(trace-ar) $(AR) crs $$@ $$(_d)/$$($(1)_NAME).o
$(1)_LDFLAGS_USE += $$($(1)_PATH) $$($(1)_LDFLAGS)
diff --git a/mk/programs.mk b/mk/programs.mk
index d0cf5baf0..0fc1990f7 100644
--- a/mk/programs.mk
+++ b/mk/programs.mk
@@ -32,7 +32,7 @@ define build-program
$$(eval $$(call create-dir, $$(_d)))
$$($(1)_PATH): $$($(1)_OBJS) $$(_libs) | $$(_d)/
- $$(trace-ld) $(CXX) -o $$@ $$(LDFLAGS) $$(GLOBAL_LDFLAGS) $$($(1)_OBJS) $$($(1)_LDFLAGS) $$(foreach lib, $$($(1)_LIBS), $$($$(lib)_LDFLAGS_USE))
+ +$$(trace-ld) $(CXX) -o $$@ $$(LDFLAGS) $$(GLOBAL_LDFLAGS) $$($(1)_OBJS) $$($(1)_LDFLAGS) $$(foreach lib, $$($(1)_LIBS), $$($$(lib)_LDFLAGS_USE))
$(1)_INSTALL_DIR ?= $$(bindir)
@@ -49,7 +49,7 @@ define build-program
_libs_final := $$(foreach lib, $$($(1)_LIBS), $$($$(lib)_INSTALL_PATH))
$(DESTDIR)$$($(1)_INSTALL_PATH): $$($(1)_OBJS) $$(_libs_final) | $(DESTDIR)$$($(1)_INSTALL_DIR)/
- $$(trace-ld) $(CXX) -o $$@ $$(LDFLAGS) $$(GLOBAL_LDFLAGS) $$($(1)_OBJS) $$($(1)_LDFLAGS) $$(foreach lib, $$($(1)_LIBS), $$($$(lib)_LDFLAGS_USE_INSTALLED))
+ +$$(trace-ld) $(CXX) -o $$@ $$(LDFLAGS) $$(GLOBAL_LDFLAGS) $$($(1)_OBJS) $$($(1)_LDFLAGS) $$(foreach lib, $$($(1)_LIBS), $$($$(lib)_LDFLAGS_USE_INSTALLED))
else
From 417aaf4ff7ac1ca501c5a460775fa25d8e078c8a Mon Sep 17 00:00:00 2001
From: regnat <rg@regnat.ovh>
Date: Wed, 22 Dec 2021 11:31:14 +0100
Subject: [PATCH 088/188] Correctly hijack the `file://` uri scheme with
`_NIX_FORCE_HTTP`
Setting the `_NIX_FORCE_HTTP` environment variable is supposed to force `file://` store urls to use the `HttpBinaryCacheStore` implementation rather than the `LocalBinaryCacheStore` one (very useful for testing).
However because of a name mismatch, the `LocalBinaryCacheStore` was still registering the `file` scheme when this variable was set, meaning that the actual store implementation picked up on `file://` uris was dependent on the registration order of the stores (itself dependent on the link order of the object files).
Fix this by making the `LocalBinaryCacheStore` gracefully not register the `file` uri scheme when the variable is set.
---
src/libstore/local-binary-cache-store.cc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/libstore/local-binary-cache-store.cc b/src/libstore/local-binary-cache-store.cc
index f754770f9..a3c3e4806 100644
--- a/src/libstore/local-binary-cache-store.cc
+++ b/src/libstore/local-binary-cache-store.cc
@@ -107,7 +107,7 @@ bool LocalBinaryCacheStore::fileExists(const std::string & path)
std::set<std::string> LocalBinaryCacheStore::uriSchemes()
{
- if (getEnv("_NIX_FORCE_HTTP_BINARY_CACHE_STORE") == "1")
+ if (getEnv("_NIX_FORCE_HTTP") == "1")
return {};
else
return {"file"};
From eaecaaa00ba79b05f49a908f2c96c6507d3a2d7b Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Mon, 14 Mar 2022 11:39:53 -0600
Subject: [PATCH 089/188] more debug_throw coverage of EvalErrors
---
src/libexpr/eval-cache.cc | 19 +++++++++++--------
src/libexpr/parser.y | 5 +++--
src/libexpr/primops.cc | 4 ++--
src/libexpr/primops/fetchTree.cc | 32 ++++++++++++++++----------------
src/libexpr/value-to-json.cc | 5 +++--
5 files changed, 35 insertions(+), 30 deletions(-)
diff --git a/src/libexpr/eval-cache.cc b/src/libexpr/eval-cache.cc
index d6b9ea29b..b102684ec 100644
--- a/src/libexpr/eval-cache.cc
+++ b/src/libexpr/eval-cache.cc
@@ -506,14 +506,14 @@ std::string AttrCursor::getString()
debug("using cached string attribute '%s'", getAttrPathStr());
return s->first;
} else
- throw TypeError("'%s' is not a string", getAttrPathStr());
+ root->state.debug_throw(TypeError("'%s' is not a string", getAttrPathStr()));
}
}
auto & v = forceValue();
if (v.type() != nString && v.type() != nPath)
- throw TypeError("'%s' is not a string but %s", getAttrPathStr(), showType(v.type()));
+ root->state.debug_throw(TypeError("'%s' is not a string but %s", getAttrPathStr(), showType(v.type())));
return v.type() == nString ? v.string.s : v.path;
}
@@ -537,7 +537,7 @@ string_t AttrCursor::getStringWithContext()
return *s;
}
} else
- throw TypeError("'%s' is not a string", getAttrPathStr());
+ root->state.debug_throw(TypeError("'%s' is not a string", getAttrPathStr()));
}
}
@@ -548,7 +548,10 @@ string_t AttrCursor::getStringWithContext()
else if (v.type() == nPath)
return {v.path, {}};
else
- throw TypeError("'%s' is not a string but %s", getAttrPathStr(), showType(v.type()));
+ {
+ root->state.debug_throw(TypeError("'%s' is not a string but %s", getAttrPathStr(), showType(v.type())));
+ return {v.path, {}}; // should never execute
+ }
}
bool AttrCursor::getBool()
@@ -561,14 +564,14 @@ bool AttrCursor::getBool()
debug("using cached Boolean attribute '%s'", getAttrPathStr());
return *b;
} else
- throw TypeError("'%s' is not a Boolean", getAttrPathStr());
+ root->state.debug_throw(TypeError("'%s' is not a Boolean", getAttrPathStr()));
}
}
auto & v = forceValue();
if (v.type() != nBool)
- throw TypeError("'%s' is not a Boolean", getAttrPathStr());
+ root->state.debug_throw(TypeError("'%s' is not a Boolean", getAttrPathStr()));
return v.boolean;
}
@@ -583,14 +586,14 @@ std::vector<Symbol> AttrCursor::getAttrs()
debug("using cached attrset attribute '%s'", getAttrPathStr());
return *attrs;
} else
- throw TypeError("'%s' is not an attribute set", getAttrPathStr());
+ root->state.debug_throw(TypeError("'%s' is not an attribute set", getAttrPathStr()));
}
}
auto & v = forceValue();
if (v.type() != nAttrs)
- throw TypeError("'%s' is not an attribute set", getAttrPathStr());
+ root->state.debug_throw(TypeError("'%s' is not an attribute set", getAttrPathStr()));
std::vector<Symbol> attrs;
for (auto & attr : *getValue().attrs)
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index d9291e7a2..184fba03e 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -783,13 +783,14 @@ Path EvalState::findFile(SearchPath & searchPath, const std::string_view path, c
if (hasPrefix(path, "nix/"))
return concatStrings(corepkgsPrefix, path.substr(4));
- throw ThrownError({
+ debug_throw(ThrownError({
.msg = hintfmt(evalSettings.pureEval
? "cannot look up '<%s>' in pure evaluation mode (use '--impure' to override)"
: "file '%s' was not found in the Nix search path (add it using $NIX_PATH or -I)",
path),
.errPos = pos
- });
+ }));
+ return Path(); // should never execute due to debug_throw above.
}
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 80d78e150..4908482cf 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -2542,7 +2542,7 @@ static void prim_zipAttrsWith(EvalState & state, const Pos & pos, Value * * args
attrsSeen[attr.name].first++;
} catch (TypeError & e) {
e.addTrace(pos, hintfmt("while invoking '%s'", "zipAttrsWith"));
- throw;
+ state.debug_throw(e);
}
}
@@ -3127,7 +3127,7 @@ static void prim_concatMap(EvalState & state, const Pos & pos, Value * * args, V
state.forceList(lists[n], lists[n].determinePos(args[0]->determinePos(pos)));
} catch (TypeError &e) {
e.addTrace(pos, hintfmt("while invoking '%s'", "concatMap"));
- throw;
+ state.debug_throw(e);
}
len += lists[n].listSize();
}
diff --git a/src/libexpr/primops/fetchTree.cc b/src/libexpr/primops/fetchTree.cc
index d09e2d9e1..c9fcbb8f5 100644
--- a/src/libexpr/primops/fetchTree.cc
+++ b/src/libexpr/primops/fetchTree.cc
@@ -108,16 +108,16 @@ static void fetchTree(
if (auto aType = args[0]->attrs->get(state.sType)) {
if (type)
- throw Error({
+ state.debug_throw(EvalError({
.msg = hintfmt("unexpected attribute 'type'"),
.errPos = pos
- });
+ }));
type = state.forceStringNoCtx(*aType->value, *aType->pos);
} else if (!type)
- throw Error({
+ state.debug_throw(EvalError({
.msg = hintfmt("attribute 'type' is missing in call to 'fetchTree'"),
.errPos = pos
- });
+ }));
attrs.emplace("type", type.value());
@@ -138,16 +138,16 @@ static void fetchTree(
else if (attr.value->type() == nInt)
attrs.emplace(attr.name, uint64_t(attr.value->integer));
else
- throw TypeError("fetchTree argument '%s' is %s while a string, Boolean or integer is expected",
- attr.name, showType(*attr.value));
+ state.debug_throw(TypeError("fetchTree argument '%s' is %s while a string, Boolean or integer is expected",
+ attr.name, showType(*attr.value)));
}
if (!params.allowNameArgument)
if (auto nameIter = attrs.find("name"); nameIter != attrs.end())
- throw Error({
+ state.debug_throw(EvalError({
.msg = hintfmt("attribute 'name' isn’t supported in call to 'fetchTree'"),
.errPos = pos
- });
+ }));
input = fetchers::Input::fromAttrs(std::move(attrs));
} else {
@@ -167,7 +167,7 @@ static void fetchTree(
input = lookupInRegistries(state.store, input).first;
if (evalSettings.pureEval && !input.isImmutable())
- throw Error("in pure evaluation mode, 'fetchTree' requires an immutable input, at %s", pos);
+ state.debug_throw(EvalError("in pure evaluation mode, 'fetchTree' requires an immutable input, at %s", pos));
auto [tree, input2] = input.fetch(state.store);
@@ -206,17 +206,17 @@ static void fetch(EvalState & state, const Pos & pos, Value * * args, Value & v,
else if (n == "name")
name = state.forceStringNoCtx(*attr.value, *attr.pos);
else
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("unsupported argument '%s' to '%s'", attr.name, who),
.errPos = *attr.pos
- });
+ }));
}
if (!url)
- throw EvalError({
+ state.debug_throw(EvalError({
.msg = hintfmt("'url' argument required"),
.errPos = pos
- });
+ }));
} else
url = state.forceStringNoCtx(*args[0], pos);
@@ -228,7 +228,7 @@ static void fetch(EvalState & state, const Pos & pos, Value * * args, Value & v,
name = baseNameOf(*url);
if (evalSettings.pureEval && !expectedHash)
- throw Error("in pure evaluation mode, '%s' requires a 'sha256' argument", who);
+ state.debug_throw(EvalError("in pure evaluation mode, '%s' requires a 'sha256' argument", who));
auto storePath =
unpack
@@ -240,8 +240,8 @@ static void fetch(EvalState & state, const Pos & pos, Value * * args, Value & v,
? state.store->queryPathInfo(storePath)->narHash
: hashFile(htSHA256, state.store->toRealPath(storePath));
if (hash != *expectedHash)
- throw Error((unsigned int) 102, "hash mismatch in file downloaded from '%s':\n specified: %s\n got: %s",
- *url, expectedHash->to_string(Base32, true), hash.to_string(Base32, true));
+ state.debug_throw(EvalError((unsigned int) 102, "hash mismatch in file downloaded from '%s':\n specified: %s\n got: %s",
+ *url, expectedHash->to_string(Base32, true), hash.to_string(Base32, true)));
}
state.allowPath(storePath);
diff --git a/src/libexpr/value-to-json.cc b/src/libexpr/value-to-json.cc
index 517da4c01..d8bf73cd5 100644
--- a/src/libexpr/value-to-json.cc
+++ b/src/libexpr/value-to-json.cc
@@ -84,7 +84,8 @@ void printValueAsJSON(EvalState & state, bool strict,
.msg = hintfmt("cannot convert %1% to JSON", showType(v)),
.errPos = v.determinePos(pos)
});
- throw e.addTrace(pos, hintfmt("message for the trace"));
+ e.addTrace(pos, hintfmt("message for the trace"));
+ state.debug_throw(e);
}
}
@@ -98,7 +99,7 @@ void printValueAsJSON(EvalState & state, bool strict,
void ExternalValueBase::printValueAsJSON(EvalState & state, bool strict,
JSONPlaceholder & out, PathSet & context) const
{
- throw TypeError("cannot convert %1% to JSON", showType());
+ state.debug_throw(TypeError("cannot convert %1% to JSON", showType()));
}
From 3dfab6e534e0a1cf71c000a4d2a74e050ba576ce Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Mon, 14 Mar 2022 11:58:11 -0600
Subject: [PATCH 090/188] have only one debuggerHook declaration
---
src/libcmd/command.cc | 4 ----
src/libexpr/eval.cc | 2 --
src/libexpr/eval.hh | 1 -
src/libexpr/nixexpr.cc | 3 +++
4 files changed, 3 insertions(+), 7 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 56288665a..18aa82577 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -93,10 +93,6 @@ EvalCommand::EvalCommand()
});
}
-extern std::function<void(const Error * error, const Env & env, const Expr & expr)> debuggerHook;
-
-
-
EvalCommand::~EvalCommand()
{
if (evalState)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index f21919598..6758677ca 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -37,8 +37,6 @@
namespace nix {
-std::function<void(const Error * error, const Env & env, const Expr & expr)> debuggerHook;
-
static char * allocString(size_t size)
{
char * t;
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index e1d117c36..5f4556053 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -25,7 +25,6 @@ enum RepairFlag : bool;
typedef void (* PrimOpFun) (EvalState & state, const Pos & pos, Value * * args, Value & v);
-extern std::function<void(const Error * error, const Env & env, const Expr & expr)> debuggerHook;
void printStaticEnvBindings(const Expr &expr);
void printStaticEnvBindings(const StaticEnv &se, int lvl = 0);
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index e09bd9484..add65c1a2 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -6,6 +6,9 @@
namespace nix {
+/* Launch the nix debugger */
+
+std::function<void(const Error * error, const Env & env, const Expr & expr)> debuggerHook;
/* Displaying abstract syntax trees. */
From 88a54108ebcdbeb1432d9afe5363557c25f94cfa Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Wed, 16 Mar 2022 12:09:47 -0600
Subject: [PATCH 091/188] formatting
---
src/libcmd/command.cc | 2 +-
src/libexpr/eval.hh | 2 +-
src/libexpr/primops.cc | 24 ++++++++++++------------
3 files changed, 14 insertions(+), 14 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 18aa82577..209c455fc 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -128,7 +128,7 @@ ref<EvalState> EvalCommand::getEvalState()
else
{
auto iter = evalState->debugTraces.begin();
- if (iter != evalState->debugTraces.end()) {
+ if (iter != evalState->debugTraces.end()) {
std::cout << "\n" << "… " << iter->hint.str() << "\n";
if (iter->pos.has_value() && (*iter->pos)) {
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 5f4556053..64c3dfac0 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -114,10 +114,10 @@ public:
RootValue vCallFlake = nullptr;
RootValue vImportedDrvToDerivation = nullptr;
+ /* Debugger */
bool debugStop;
bool debugQuit;
std::list<DebugTrace> debugTraces;
-
void debug_throw(Error e);
private:
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 4908482cf..9a26bae71 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -715,20 +715,20 @@ static RegisterPrimOp primop_break({
});
if (debuggerHook && !state.debugTraces.empty())
{
- auto &dt = state.debugTraces.front();
- debuggerHook(&error, dt.env, dt.expr);
+ auto &dt = state.debugTraces.front();
+ debuggerHook(&error, dt.env, dt.expr);
- if (state.debugQuit) {
- // if the user elects to quit the repl, throw an exception.
- throw Error(ErrorInfo{
- .level = lvlInfo,
- .msg = hintfmt("quit from debugger"),
- .errPos = pos,
- });
- }
+ if (state.debugQuit) {
+ // if the user elects to quit the repl, throw an exception.
+ throw Error(ErrorInfo{
+ .level = lvlInfo,
+ .msg = hintfmt("quit from debugger"),
+ .errPos = noPos,
+ });
+ }
- // returning the value we were passed.
- v = *args[0];
+ // returning the value we were passed.
+ v = *args[0];
}
}
});
From 1bec3fb337b86f87e7600fc6b6072ded1a7d4927 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Fri, 25 Mar 2022 18:15:31 -0600
Subject: [PATCH 092/188] add DebugTrace for error
---
src/libcmd/command.cc | 54 +++++++++++++++++++++++++++---------------
src/libexpr/eval.cc | 3 ++-
src/libexpr/eval.hh | 1 +
src/libexpr/nixexpr.hh | 40 +++++++++++++++----------------
4 files changed, 58 insertions(+), 40 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 209c455fc..34535802f 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -122,29 +122,45 @@ ref<EvalState> EvalCommand::getEvalState()
debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error * error, const Env & env, const Expr & expr) {
// clear the screen.
// std::cout << "\033[2J\033[1;1H";
-
+
+ auto dts =
+ error && expr.getPos() ?
+ std::unique_ptr<DebugTraceStacker>(
+ new DebugTraceStacker(
+ *evalState,
+ DebugTrace
+ {.pos = *expr.getPos(),
+ .expr = expr,
+ .env = env,
+ .hint = error->info().msg,
+ .is_error = true
+ }))
+ : nullptr;
+
+
if (error)
printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error->what());
- else
- {
- auto iter = evalState->debugTraces.begin();
- if (iter != evalState->debugTraces.end()) {
- std::cout << "\n" << "… " << iter->hint.str() << "\n";
- if (iter->pos.has_value() && (*iter->pos)) {
- auto pos = iter->pos.value();
- std::cout << "\n";
- printAtPos(pos, std::cout);
+ // else
+ // {
+ // auto iter = evalState->debugTraces.begin();
+ // if (iter != evalState->debugTraces.end()) {
+ // std::cout << "\n" << "… " << iter->hint.str() << "\n";
- auto loc = getCodeLines(pos);
- if (loc.has_value()) {
- std::cout << "\n";
- printCodeLines(std::cout, "", pos, *loc);
- std::cout << "\n";
- }
- }
- }
- }
+ // if (iter->pos.has_value() && (*iter->pos)) {
+ // auto pos = iter->pos.value();
+ // std::cout << "\n";
+ // printAtPos(pos, std::cout);
+
+ // auto loc = getCodeLines(pos);
+ // if (loc.has_value()) {
+ // std::cout << "\n";
+ // printCodeLines(std::cout, "", pos, *loc);
+ // std::cout << "\n";
+ // }
+ // }
+ // }
+ // }
if (expr.staticenv)
{
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 6758677ca..f162f3e0b 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -983,7 +983,8 @@ LocalNoInline(std::unique_ptr<DebugTraceStacker>
{.pos = pos,
.expr = expr,
.env = env,
- .hint = hintfmt(s, s2)
+ .hint = hintfmt(s, s2),
+ .is_error = false
}));
}
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 64c3dfac0..9de3475e8 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -77,6 +77,7 @@ struct DebugTrace {
const Expr &expr;
const Env &env;
hintformat hint;
+ bool is_error;
};
class EvalState
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index 64375b5ab..6419f882a 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -84,7 +84,7 @@ struct Expr
virtual void setName(Symbol & name);
std::shared_ptr<const StaticEnv> staticenv;
- virtual Pos* getPos() = 0;
+ virtual const Pos* getPos() const = 0;
};
std::ostream & operator << (std::ostream & str, const Expr & e);
@@ -100,7 +100,7 @@ struct ExprInt : Expr
Value v;
ExprInt(NixInt n) : n(n) { v.mkInt(n); };
Value * maybeThunk(EvalState & state, Env & env);
- Pos* getPos() { return 0; }
+ const Pos* getPos() const { return 0; }
COMMON_METHODS
};
@@ -110,7 +110,7 @@ struct ExprFloat : Expr
Value v;
ExprFloat(NixFloat nf) : nf(nf) { v.mkFloat(nf); };
Value * maybeThunk(EvalState & state, Env & env);
- Pos* getPos() { return 0; }
+ const Pos* getPos() const { return 0; }
COMMON_METHODS
};
@@ -120,7 +120,7 @@ struct ExprString : Expr
Value v;
ExprString(std::string s) : s(std::move(s)) { v.mkString(this->s.data()); };
Value * maybeThunk(EvalState & state, Env & env);
- Pos* getPos() { return 0; }
+ const Pos* getPos() const { return 0; }
COMMON_METHODS
};
@@ -130,7 +130,7 @@ struct ExprPath : Expr
Value v;
ExprPath(const string & s) : s(s) { v.mkPath(this->s.c_str()); };
Value * maybeThunk(EvalState & state, Env & env);
- Pos* getPos() { return 0; }
+ const Pos* getPos() const { return 0; }
COMMON_METHODS
};
@@ -158,7 +158,7 @@ struct ExprVar : Expr
ExprVar(const Symbol & name) : name(name) { };
ExprVar(const Pos & pos, const Symbol & name) : pos(pos), name(name) { };
Value * maybeThunk(EvalState & state, Env & env);
- Pos* getPos() { return &pos; }
+ const Pos* getPos() const { return &pos; }
COMMON_METHODS
};
@@ -169,7 +169,7 @@ struct ExprSelect : Expr
AttrPath attrPath;
ExprSelect(const Pos & pos, Expr * e, const AttrPath & attrPath, Expr * def) : pos(pos), e(e), def(def), attrPath(attrPath) { };
ExprSelect(const Pos & pos, Expr * e, const Symbol & name) : pos(pos), e(e), def(0) { attrPath.push_back(AttrName(name)); };
- Pos* getPos() { return &pos; }
+ const Pos* getPos() const { return &pos; }
COMMON_METHODS
};
@@ -178,7 +178,7 @@ struct ExprOpHasAttr : Expr
Expr * e;
AttrPath attrPath;
ExprOpHasAttr(Expr * e, const AttrPath & attrPath) : e(e), attrPath(attrPath) { };
- Pos* getPos() { return e->getPos(); }
+ const Pos* getPos() const { return e->getPos(); }
COMMON_METHODS
};
@@ -207,7 +207,7 @@ struct ExprAttrs : Expr
DynamicAttrDefs dynamicAttrs;
ExprAttrs(const Pos &pos) : recursive(false), pos(pos) { };
ExprAttrs() : recursive(false), pos(noPos) { };
- Pos* getPos() { return &pos; }
+ const Pos* getPos() const { return &pos; }
COMMON_METHODS
};
@@ -215,7 +215,7 @@ struct ExprList : Expr
{
std::vector<Expr *> elems;
ExprList() { };
- Pos* getPos() { return 0; }
+ const Pos* getPos() const { return 0; }
COMMON_METHODS
};
@@ -264,7 +264,7 @@ struct ExprLambda : Expr
void setName(Symbol & name);
string showNamePos() const;
inline bool hasFormals() const { return formals != nullptr; }
- Pos* getPos() { return &pos; }
+ const Pos* getPos() const { return &pos; }
COMMON_METHODS
};
@@ -276,7 +276,7 @@ struct ExprCall : Expr
ExprCall(const Pos & pos, Expr * fun, std::vector<Expr *> && args)
: fun(fun), args(args), pos(pos)
{ }
- Pos* getPos() { return &pos; }
+ const Pos* getPos() const { return &pos; }
COMMON_METHODS
};
@@ -285,7 +285,7 @@ struct ExprLet : Expr
ExprAttrs * attrs;
Expr * body;
ExprLet(ExprAttrs * attrs, Expr * body) : attrs(attrs), body(body) { };
- Pos* getPos() { return 0; }
+ const Pos* getPos() const { return 0; }
COMMON_METHODS
};
@@ -295,7 +295,7 @@ struct ExprWith : Expr
Expr * attrs, * body;
size_t prevWith;
ExprWith(const Pos & pos, Expr * attrs, Expr * body) : pos(pos), attrs(attrs), body(body) { };
- Pos* getPos() { return &pos; }
+ const Pos* getPos() const { return &pos; }
COMMON_METHODS
};
@@ -304,7 +304,7 @@ struct ExprIf : Expr
Pos pos;
Expr * cond, * then, * else_;
ExprIf(const Pos & pos, Expr * cond, Expr * then, Expr * else_) : pos(pos), cond(cond), then(then), else_(else_) { };
- Pos* getPos() { return &pos; }
+ const Pos* getPos() const { return &pos; }
COMMON_METHODS
};
@@ -313,7 +313,7 @@ struct ExprAssert : Expr
Pos pos;
Expr * cond, * body;
ExprAssert(const Pos & pos, Expr * cond, Expr * body) : pos(pos), cond(cond), body(body) { };
- Pos* getPos() { return &pos; }
+ const Pos* getPos() const { return &pos; }
COMMON_METHODS
};
@@ -321,7 +321,7 @@ struct ExprOpNot : Expr
{
Expr * e;
ExprOpNot(Expr * e) : e(e) { };
- Pos* getPos() { return 0; }
+ const Pos* getPos() const { return 0; }
COMMON_METHODS
};
@@ -341,7 +341,7 @@ struct ExprOpNot : Expr
e1->bindVars(env); e2->bindVars(env); \
} \
void eval(EvalState & state, Env & env, Value & v); \
- Pos* getPos() { return &pos; } \
+ const Pos* getPos() const { return &pos; } \
};
MakeBinOp(ExprOpEq, "==")
@@ -359,7 +359,7 @@ struct ExprConcatStrings : Expr
vector<std::pair<Pos, Expr *> > * es;
ExprConcatStrings(const Pos & pos, bool forceString, vector<std::pair<Pos, Expr *> > * es)
: pos(pos), forceString(forceString), es(es) { };
- Pos* getPos() { return &pos; }
+ const Pos* getPos() const { return &pos; }
COMMON_METHODS
};
@@ -367,7 +367,7 @@ struct ExprPos : Expr
{
Pos pos;
ExprPos(const Pos & pos) : pos(pos) { };
- Pos* getPos() { return &pos; }
+ const Pos* getPos() const { return &pos; }
COMMON_METHODS
};
From 14f515544bf7ea3c894fbc21d1393e69aa115784 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Mon, 28 Mar 2022 12:09:21 -0600
Subject: [PATCH 093/188] debugTraceIndex
---
src/libcmd/repl.cc | 99 ++++++++++++++++++++++++++++++++++++----------
1 file changed, 78 insertions(+), 21 deletions(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 2b3dfcbd2..f0a8ef676 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -49,7 +49,8 @@ struct NixRepl
ref<EvalState> state;
Bindings * autoArgs;
- const Error *debugError;
+ const Error *debugError;
+ int debugTraceIndex;
Strings loadedFiles;
@@ -96,6 +97,7 @@ string removeWhitespace(string s)
NixRepl::NixRepl(ref<EvalState> state)
: state(state)
+ , debugTraceIndex(0)
, staticEnv(new StaticEnv(false, state->staticBaseEnv.get()))
, historyFile(getDataDir() + "/nix/repl-history")
{
@@ -403,6 +405,28 @@ StorePath NixRepl::getDerivationPath(Value & v) {
return drvPath;
}
+std::ostream& showDebugTrace(std::ostream &out, const DebugTrace &dt)
+{
+ if (dt.is_error)
+ out << ANSI_RED "error: " << ANSI_NORMAL;
+ out << dt.hint.str() << "\n";
+
+ if (dt.pos.has_value() && (*dt.pos)) {
+ auto pos = dt.pos.value();
+ out << "\n";
+ printAtPos(pos, out);
+
+ auto loc = getCodeLines(pos);
+ if (loc.has_value()) {
+ out << "\n";
+ printCodeLines(out, "", pos, *loc);
+ out << "\n";
+ }
+ }
+
+ return out;
+}
+
bool NixRepl::processLine(string line)
{
if (line == "") return true;
@@ -444,7 +468,7 @@ bool NixRepl::processLine(string line)
<< " :d <cmd> Debug mode commands\n"
<< " :d stack Show call stack\n"
<< " :d env Show env stack\n"
- << " :d error Show current error\n"
+ << " :d show <idx> Show current trace, or change to call stack index\n"
<< " :d go Go until end of program, exception, or builtins.break().\n"
<< " :d step Go one step\n"
;
@@ -453,30 +477,63 @@ bool NixRepl::processLine(string line)
else if (command == ":d" || command == ":debug") {
if (arg == "stack") {
+ int idx = 0;
for (auto iter = this->state->debugTraces.begin();
- iter != this->state->debugTraces.end(); ++iter) {
- std::cout << "\n" << "… " << iter->hint.str() << "\n";
-
- if (iter->pos.has_value() && (*iter->pos)) {
- auto pos = iter->pos.value();
- std::cout << "\n";
- printAtPos(pos, std::cout);
-
- auto loc = getCodeLines(pos);
- if (loc.has_value()) {
- std::cout << "\n";
- printCodeLines(std::cout, "", pos, *loc);
- std::cout << "\n";
- }
- }
- }
+ iter != this->state->debugTraces.end();
+ ++iter, ++idx) {
+ std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
+ showDebugTrace(std::cout, *iter);
+ }
} else if (arg == "env") {
- auto iter = this->state->debugTraces.begin();
- if (iter != this->state->debugTraces.end()) {
- printStaticEnvBindings(iter->expr);
+ int idx = 0;
+ for (auto iter = this->state->debugTraces.begin();
+ iter != this->state->debugTraces.end();
+ ++iter, ++idx) {
+ if (idx == this->debugTraceIndex)
+ {
+ // std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
+ printStaticEnvBindings(iter->expr);
+ break;
+ }
+ // std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
+ // showDebugTrace(std::cout, *iter);
+ }
+
+ // auto iter = this->state->debugTraces.begin();
+ // if (iter != this->state->debugTraces.end()) {
+ // printStaticEnvBindings(iter->expr);
+ // }
+ }
+ else if (arg.compare(0,4,"show") == 0) {
+ try {
+ // change the DebugTrace index.
+ debugTraceIndex = stoi(arg.substr(4));
+
+ // std::cout << "idx: " << idx << std::endl;
+ // debugTraceIndex = idx;
+
+ }
+ catch (...)
+ {
+ debugTraceIndex = 0;
+ }
+
+ int idx = 0;
+ for (auto iter = this->state->debugTraces.begin();
+ iter != this->state->debugTraces.end();
+ ++iter, ++idx) {
+ if (idx == this->debugTraceIndex)
+ {
+ std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
+ showDebugTrace(std::cout, *iter);
+ break;
+ }
+ // std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
+ // showDebugTrace(std::cout, *iter);
}
}
else if (arg == "error") {
+ // TODO: remove, along with debugError.
if (this->debugError) {
showErrorInfo(std::cout, debugError->info(), true);
}
From 5ab7bdf0b14199da8423a8f2e433b2d6beef1e69 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Mon, 28 Mar 2022 15:28:59 -0600
Subject: [PATCH 094/188] load debug trace staticenv on 'show'
---
src/libcmd/repl.cc | 35 ++++++++++++++++++++++-------------
1 file changed, 22 insertions(+), 13 deletions(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index f0a8ef676..2e3a3b6df 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -78,6 +78,7 @@ struct NixRepl
void addVarToScope(const Symbol & name, Value & v);
Expr * parseString(string s);
void evalString(string s, Value & v);
+ void loadDebugTraceEnv(DebugTrace &dt);
typedef set<Value *> ValuesSeen;
std::ostream & printValue(std::ostream & str, Value & v, unsigned int maxDepth);
@@ -427,6 +428,25 @@ std::ostream& showDebugTrace(std::ostream &out, const DebugTrace &dt)
return out;
}
+void NixRepl::loadDebugTraceEnv(DebugTrace &dt)
+{
+ if (dt.expr.staticenv)
+ {
+ initEnv();
+
+ auto vm = std::make_unique<valmap>(*(mapStaticEnvBindings(*dt.expr.staticenv.get(), dt.env)));
+
+ // add staticenv vars.
+ for (auto & [name, value] : *(vm.get())) {
+ this->addVarToScope(this->state->symbols.create(name), *value);
+ }
+ }
+ else
+ {
+ initEnv();
+ }
+}
+
bool NixRepl::processLine(string line)
{
if (line == "") return true;
@@ -491,31 +511,18 @@ bool NixRepl::processLine(string line)
++iter, ++idx) {
if (idx == this->debugTraceIndex)
{
- // std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
printStaticEnvBindings(iter->expr);
break;
}
- // std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
- // showDebugTrace(std::cout, *iter);
}
-
- // auto iter = this->state->debugTraces.begin();
- // if (iter != this->state->debugTraces.end()) {
- // printStaticEnvBindings(iter->expr);
- // }
}
else if (arg.compare(0,4,"show") == 0) {
try {
// change the DebugTrace index.
debugTraceIndex = stoi(arg.substr(4));
-
- // std::cout << "idx: " << idx << std::endl;
- // debugTraceIndex = idx;
-
}
catch (...)
{
- debugTraceIndex = 0;
}
int idx = 0;
@@ -526,6 +533,8 @@ bool NixRepl::processLine(string line)
{
std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
showDebugTrace(std::cout, *iter);
+ printStaticEnvBindings(iter->expr);
+ loadDebugTraceEnv(*iter);
break;
}
// std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
From c0a567e1963faaf9b16f772d6b4e76496a88ed32 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Tue, 29 Mar 2022 16:44:47 -0600
Subject: [PATCH 095/188] remove const_cast
---
src/libexpr/eval.cc | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index f162f3e0b..cc0380d4a 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -937,7 +937,7 @@ LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s,
throw error;
}
-LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char * s, const string & s1, Env & env, Expr &expr))
+LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char * s, const string & s1, Env & env, const Expr &expr))
{
auto error = UndefinedVarError({
.msg = hintfmt(s, s1),
@@ -1053,8 +1053,7 @@ inline Value * EvalState::lookupVar(Env * env, const ExprVar & var, bool noEval)
return j->value;
}
if (!env->prevWith) {
- // TODO deal with const_cast
- throwUndefinedVarError(var.pos, "undefined variable '%1%'", var.name, *env, *const_cast<ExprVar*>(&var));
+ throwUndefinedVarError(var.pos, "undefined variable '%1%'", var.name, *env, var);
}
for (size_t l = env->prevWith; l; --l, env = env->up) ;
}
From 1096d17b65834a7e1ff29d1afdf09536cc9d7a8d Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Thu, 31 Mar 2022 09:37:36 -0600
Subject: [PATCH 096/188] show 'with' bindings as well as static
---
src/libcmd/repl.cc | 10 +++---
src/libexpr/eval.cc | 76 ++++++++++++++++++++++++++++++++++-----------
src/libexpr/eval.hh | 4 +--
3 files changed, 65 insertions(+), 25 deletions(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 2e3a3b6df..5de4cdf76 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -511,7 +511,7 @@ bool NixRepl::processLine(string line)
++iter, ++idx) {
if (idx == this->debugTraceIndex)
{
- printStaticEnvBindings(iter->expr);
+ printEnvBindings(iter->expr, iter->env);
break;
}
}
@@ -533,7 +533,7 @@ bool NixRepl::processLine(string line)
{
std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
showDebugTrace(std::cout, *iter);
- printStaticEnvBindings(iter->expr);
+ printEnvBindings(iter->expr, iter->env);
loadDebugTraceEnv(*iter);
break;
}
@@ -1010,14 +1010,14 @@ void runRepl(
repl->initEnv();
// add 'extra' vars.
- std::set<std::string> names;
+ // std::set<std::string> names;
for (auto & [name, value] : extraEnv) {
// names.insert(ANSI_BOLD + name + ANSI_NORMAL);
- names.insert(name);
+ // names.insert(name);
repl->addVarToScope(repl->state->symbols.create(name), *value);
}
- printError(hintfmt("The following extra variables are in scope: %s\n", concatStringsSep(", ", names)).str());
+ // printError(hintfmt("The following extra variables are in scope: %s\n", concatStringsSep(", ", names)).str());
repl->mainLoop({});
}
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index cc0380d4a..7c67f2ea8 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -699,22 +699,46 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
return {};
}
-void printStaticEnvBindings(const StaticEnv &se, int lvl)
+
+// just for the current level of StaticEnv, not the whole chain.
+void printStaticEnvBindings(const StaticEnv &se)
+{
+ std::cout << ANSI_MAGENTA;
+ for (auto i = se.vars.begin(); i != se.vars.end(); ++i)
+ {
+ std::cout << i->first << " ";
+ }
+ std::cout << ANSI_NORMAL;
+ std::cout << std::endl;
+}
+
+// just for the current level of Env, not the whole chain.
+void printWithBindings(const Env &env)
+{
+ if (env.type == Env::HasWithAttrs)
+ {
+ std::cout << "with: ";
+ std::cout << ANSI_MAGENTA;
+ Bindings::iterator j = env.values[0]->attrs->begin();
+ while (j != env.values[0]->attrs->end()) {
+ std::cout << j->name << " ";
+ ++j;
+ }
+ std::cout << ANSI_NORMAL;
+ std::cout << std::endl;
+ }
+}
+
+void printEnvBindings(const StaticEnv &se, const Env &env, int lvl)
{
std::cout << "Env level " << lvl << std::endl;
- if (se.up) {
- std::cout << ANSI_MAGENTA;
- for (auto i = se.vars.begin(); i != se.vars.end(); ++i)
- {
- std::cout << i->first << " ";
- }
- std::cout << ANSI_NORMAL;
-
+ if (se.up && env.up) {
+ std::cout << "static: ";
+ printStaticEnvBindings(se);
+ printWithBindings(env);
std::cout << std::endl;
- std::cout << std::endl;
-
- printStaticEnvBindings(*se.up, ++lvl);
+ printEnvBindings(*se.up, *env.up, ++lvl);
}
else
{
@@ -727,18 +751,19 @@ void printStaticEnvBindings(const StaticEnv &se, int lvl)
}
std::cout << ANSI_NORMAL;
std::cout << std::endl;
+ printWithBindings(env); // probably nothing there for the top level.
std::cout << std::endl;
}
-
}
-void printStaticEnvBindings(const Expr &expr)
+// TODO: add accompanying env for With stuff.
+void printEnvBindings(const Expr &expr, const Env &env)
{
// just print the names for now
if (expr.staticenv)
{
- printStaticEnvBindings(*expr.staticenv.get(), 0);
+ printEnvBindings(*expr.staticenv.get(), env, 0);
}
}
@@ -750,11 +775,26 @@ void mapStaticEnvBindings(const StaticEnv &se, const Env &env, valmap & vm)
if (env.up && se.up) {
mapStaticEnvBindings(*se.up, *env.up,vm);
- // iterate through staticenv bindings and add them.
auto map = valmap();
- for (auto iter = se.vars.begin(); iter != se.vars.end(); ++iter)
+ if (env.type == Env::HasWithAttrs)
{
- map[iter->first] = env.values[iter->second];
+ std::cout << "(env.type == Env::HasWithAttrs)" << std::endl;
+ Bindings::iterator j = env.values[0]->attrs->begin();
+ while (j != env.values[0]->attrs->end()) {
+ // std::cout << "adding : " << j->name << std::endl;
+ map[j->name] = j->value;
+ // if (countCalls) attrSelects[*j->pos]++;
+ // return j->value;
+ ++j;
+ }
+ }
+ else
+ {
+ // iterate through staticenv bindings and add them.
+ for (auto iter = se.vars.begin(); iter != se.vars.end(); ++iter)
+ {
+ map[iter->first] = env.values[iter->second];
+ }
}
vm.merge(map);
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 9de3475e8..1c569fc36 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -25,8 +25,8 @@ enum RepairFlag : bool;
typedef void (* PrimOpFun) (EvalState & state, const Pos & pos, Value * * args, Value & v);
-void printStaticEnvBindings(const Expr &expr);
-void printStaticEnvBindings(const StaticEnv &se, int lvl = 0);
+void printEnvBindings(const Expr &expr, const Env &env);
+void printEnvBindings(const StaticEnv &se, const Env &env, int lvl = 0);
struct PrimOp
{
From f41c18b2210ac36743f03ea218860b7941f4264e Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Thu, 31 Mar 2022 09:39:18 -0600
Subject: [PATCH 097/188] comments
---
src/libexpr/eval.cc | 3 ---
1 file changed, 3 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 7c67f2ea8..399cf126d 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -781,10 +781,7 @@ void mapStaticEnvBindings(const StaticEnv &se, const Env &env, valmap & vm)
std::cout << "(env.type == Env::HasWithAttrs)" << std::endl;
Bindings::iterator j = env.values[0]->attrs->begin();
while (j != env.values[0]->attrs->end()) {
- // std::cout << "adding : " << j->name << std::endl;
map[j->name] = j->value;
- // if (countCalls) attrSelects[*j->pos]++;
- // return j->value;
++j;
}
}
From 5cfd038bd8bcd65c45f08f6c3665cd49e6643714 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Wed, 6 Apr 2022 19:08:29 -0600
Subject: [PATCH 098/188] show expr pos if DebugTrace one is noPos
---
src/libcmd/command.cc | 2 +-
src/libcmd/repl.cc | 8 +++++---
2 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 34535802f..cc353cbb4 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -129,7 +129,7 @@ ref<EvalState> EvalCommand::getEvalState()
new DebugTraceStacker(
*evalState,
DebugTrace
- {.pos = *expr.getPos(),
+ {.pos = (error->info().errPos ? *error->info().errPos : *expr.getPos()),
.expr = expr,
.env = env,
.hint = error->info().msg,
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 5de4cdf76..416635f16 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -412,9 +412,11 @@ std::ostream& showDebugTrace(std::ostream &out, const DebugTrace &dt)
out << ANSI_RED "error: " << ANSI_NORMAL;
out << dt.hint.str() << "\n";
- if (dt.pos.has_value() && (*dt.pos)) {
- auto pos = dt.pos.value();
- out << "\n";
+ // prefer direct pos, but if noPos then try the expr.
+ auto pos = (*dt.pos ? *dt.pos :
+ (dt.expr.getPos() ? *dt.expr.getPos() : noPos));
+
+ if (pos) {
printAtPos(pos, out);
auto loc = getCodeLines(pos);
From f37562187f2673535a8e636e7ea5b37662b5a65a Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Thu, 7 Apr 2022 11:17:31 -0600
Subject: [PATCH 099/188] free valmap on exit
---
src/libcmd/command.cc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index cc353cbb4..e3c8fb29f 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -164,7 +164,7 @@ ref<EvalState> EvalCommand::getEvalState()
if (expr.staticenv)
{
- auto vm = mapStaticEnvBindings(*expr.staticenv.get(), env);
+ std::unique_ptr<valmap> vm(mapStaticEnvBindings(*expr.staticenv.get(), env));
runRepl(evalState, error, expr, *vm);
}
};
From d29af88d58283293d919066acd792fafd5e60689 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Thu, 7 Apr 2022 11:17:57 -0600
Subject: [PATCH 100/188] newline before env
---
src/libcmd/repl.cc | 1 +
1 file changed, 1 insertion(+)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 416635f16..376aa35cd 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -535,6 +535,7 @@ bool NixRepl::processLine(string line)
{
std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
showDebugTrace(std::cout, *iter);
+ std::cout << std::endl;
printEnvBindings(iter->expr, iter->env);
loadDebugTraceEnv(*iter);
break;
From 50b52d51109c430fb2ac69ed5337a6a985e4a486 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Thu, 7 Apr 2022 12:03:18 -0600
Subject: [PATCH 101/188] remove debug code
---
src/libexpr/eval.cc | 1 -
1 file changed, 1 deletion(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 399cf126d..4211d72dd 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -778,7 +778,6 @@ void mapStaticEnvBindings(const StaticEnv &se, const Env &env, valmap & vm)
auto map = valmap();
if (env.type == Env::HasWithAttrs)
{
- std::cout << "(env.type == Env::HasWithAttrs)" << std::endl;
Bindings::iterator j = env.values[0]->attrs->begin();
while (j != env.values[0]->attrs->end()) {
map[j->name] = j->value;
From d2ec9b4e15718e42720787140d7825dcbfd73249 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Thu, 7 Apr 2022 12:09:47 -0600
Subject: [PATCH 102/188] in debugger mode, print the current error when
another repl returns.
---
src/libcmd/repl.cc | 56 ++++++++++++++++++++++++++--------------------
1 file changed, 32 insertions(+), 24 deletions(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 376aa35cd..31d0019d4 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -203,6 +203,30 @@ namespace {
}
}
+std::ostream& showDebugTrace(std::ostream &out, const DebugTrace &dt)
+{
+ if (dt.is_error)
+ out << ANSI_RED "error: " << ANSI_NORMAL;
+ out << dt.hint.str() << "\n";
+
+ // prefer direct pos, but if noPos then try the expr.
+ auto pos = (*dt.pos ? *dt.pos :
+ (dt.expr.getPos() ? *dt.expr.getPos() : noPos));
+
+ if (pos) {
+ printAtPos(pos, out);
+
+ auto loc = getCodeLines(pos);
+ if (loc.has_value()) {
+ out << "\n";
+ printCodeLines(out, "", pos, *loc);
+ out << "\n";
+ }
+ }
+
+ return out;
+}
+
void NixRepl::mainLoop(const std::vector<std::string> & files)
{
string error = ANSI_RED "error:" ANSI_NORMAL " ";
@@ -251,6 +275,14 @@ void NixRepl::mainLoop(const std::vector<std::string> & files)
} else {
printMsg(lvlError, e.msg());
}
+ } catch (EvalError & e) {
+ // in debugger mode, an EvalError should trigger another repl session.
+ // when that session returns the exception will land here. No need to show it again;
+ // show the error for this repl session instead.
+ if (debuggerHook && !this->state->debugTraces.empty())
+ showDebugTrace(std::cout, this->state->debugTraces.front());
+ else
+ printMsg(lvlError, e.msg());
} catch (Error & e) {
printMsg(lvlError, e.msg());
} catch (Interrupted & e) {
@@ -406,30 +438,6 @@ StorePath NixRepl::getDerivationPath(Value & v) {
return drvPath;
}
-std::ostream& showDebugTrace(std::ostream &out, const DebugTrace &dt)
-{
- if (dt.is_error)
- out << ANSI_RED "error: " << ANSI_NORMAL;
- out << dt.hint.str() << "\n";
-
- // prefer direct pos, but if noPos then try the expr.
- auto pos = (*dt.pos ? *dt.pos :
- (dt.expr.getPos() ? *dt.expr.getPos() : noPos));
-
- if (pos) {
- printAtPos(pos, out);
-
- auto loc = getCodeLines(pos);
- if (loc.has_value()) {
- out << "\n";
- printCodeLines(out, "", pos, *loc);
- out << "\n";
- }
- }
-
- return out;
-}
-
void NixRepl::loadDebugTraceEnv(DebugTrace &dt)
{
if (dt.expr.staticenv)
From b8b8ec710160cfd343a8fce33ec8734e23c98444 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Fri, 8 Apr 2022 12:34:27 -0600
Subject: [PATCH 103/188] move throw to preverve Error type; turn off debugger
for tryEval
---
src/libcmd/repl.cc | 2 +-
src/libexpr/eval-cache.cc | 46 ++++-
src/libexpr/eval.cc | 26 +--
src/libexpr/eval.hh | 2 +-
src/libexpr/parser.y | 7 +-
src/libexpr/primops.cc | 337 +++++++++++++++++++++++--------
src/libexpr/primops/fetchTree.cc | 74 +++++--
src/libexpr/value-to-json.cc | 7 +-
8 files changed, 361 insertions(+), 140 deletions(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 3dd55e104..2e7974b5d 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -50,7 +50,7 @@ struct NixRepl
ref<EvalState> state;
Bindings * autoArgs;
- const Error *debugError;
+ const Error *debugError;
int debugTraceIndex;
Strings loadedFiles;
diff --git a/src/libexpr/eval-cache.cc b/src/libexpr/eval-cache.cc
index 9f6152561..0608d8378 100644
--- a/src/libexpr/eval-cache.cc
+++ b/src/libexpr/eval-cache.cc
@@ -528,14 +528,22 @@ std::string AttrCursor::getString()
debug("using cached string attribute '%s'", getAttrPathStr());
return s->first;
} else
- root->state.debug_throw(TypeError("'%s' is not a string", getAttrPathStr()));
+ {
+ auto e = TypeError("'%s' is not a string", getAttrPathStr());
+ root->state.debugLastTrace(e);
+ throw e;
+ }
}
}
auto & v = forceValue();
if (v.type() != nString && v.type() != nPath)
- root->state.debug_throw(TypeError("'%s' is not a string but %s", getAttrPathStr(), showType(v.type())));
+ {
+ auto e = TypeError("'%s' is not a string but %s", getAttrPathStr(), showType(v.type()));
+ root->state.debugLastTrace(e);
+ throw e;
+ }
return v.type() == nString ? v.string.s : v.path;
}
@@ -559,7 +567,11 @@ string_t AttrCursor::getStringWithContext()
return *s;
}
} else
- root->state.debug_throw(TypeError("'%s' is not a string", getAttrPathStr()));
+ {
+ auto e = TypeError("'%s' is not a string", getAttrPathStr());
+ root->state.debugLastTrace(e);
+ throw e;
+ }
}
}
@@ -571,7 +583,9 @@ string_t AttrCursor::getStringWithContext()
return {v.path, {}};
else
{
- root->state.debug_throw(TypeError("'%s' is not a string but %s", getAttrPathStr(), showType(v.type())));
+ auto e = TypeError("'%s' is not a string but %s", getAttrPathStr(), showType(v.type()));
+ root->state.debugLastTrace(e);
+ throw e;
return {v.path, {}}; // should never execute
}
}
@@ -586,14 +600,22 @@ bool AttrCursor::getBool()
debug("using cached Boolean attribute '%s'", getAttrPathStr());
return *b;
} else
- root->state.debug_throw(TypeError("'%s' is not a Boolean", getAttrPathStr()));
+ {
+ auto e = TypeError("'%s' is not a Boolean", getAttrPathStr());
+ root->state.debugLastTrace(e);
+ throw e;
+ }
}
}
auto & v = forceValue();
if (v.type() != nBool)
- root->state.debug_throw(TypeError("'%s' is not a Boolean", getAttrPathStr()));
+ {
+ auto e = TypeError("'%s' is not a Boolean", getAttrPathStr());
+ root->state.debugLastTrace(e);
+ throw e;
+ }
return v.boolean;
}
@@ -608,14 +630,22 @@ std::vector<Symbol> AttrCursor::getAttrs()
debug("using cached attrset attribute '%s'", getAttrPathStr());
return *attrs;
} else
- root->state.debug_throw(TypeError("'%s' is not an attribute set", getAttrPathStr()));
+ {
+ auto e = TypeError("'%s' is not an attribute set", getAttrPathStr());
+ root->state.debugLastTrace(e);
+ throw e;
+ }
}
}
auto & v = forceValue();
if (v.type() != nAttrs)
- root->state.debug_throw(TypeError("'%s' is not an attribute set", getAttrPathStr()));
+ {
+ auto e = TypeError("'%s' is not an attribute set", getAttrPathStr());
+ root->state.debugLastTrace(e);
+ throw e;
+ }
std::vector<Symbol> attrs;
for (auto & attr : *getValue().attrs)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 5ad7e546c..7d02222cf 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -833,15 +833,13 @@ LocalNoInlineNoReturn(void throwEvalError(const char * s, const std::string & s2
throw error;
}
-void EvalState::debug_throw(Error e) {
+void EvalState::debugLastTrace(Error & e) {
// call this in the situation where Expr and Env are inaccessible. The debugger will start in the last context
// that's in the DebugTrace stack.
-
if (debuggerHook && !debugTraces.empty()) {
DebugTrace &last = debugTraces.front();
debuggerHook(&e, last.env, last.expr);
}
- throw e;
}
LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const Suggestions & suggestions, const char * s, const std::string & s2, Env & env, Expr &expr))
@@ -865,10 +863,7 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const
.errPos = pos
});
- if (debuggerHook && !evalState.debugTraces.empty()) {
- DebugTrace &last = evalState.debugTraces.front();
- debuggerHook(&error, last.env, last.expr);
- }
+ evalState.debugLastTrace(error);
throw error;
}
@@ -906,10 +901,7 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const
.errPos = pos
});
- if (debuggerHook && !evalState.debugTraces.empty()) {
- DebugTrace &last = evalState.debugTraces.front();
- debuggerHook(&error, last.env, last.expr);
- }
+ evalState.debugLastTrace(error);
throw error;
}
@@ -921,10 +913,7 @@ LocalNoInlineNoReturn(void throwEvalError(const char * s, const std::string & s2
.errPos = noPos
});
- if (debuggerHook && !evalState.debugTraces.empty()) {
- DebugTrace &last = evalState.debugTraces.front();
- debuggerHook(&error, last.env, last.expr);
- }
+ evalState.debugLastTrace(error);
throw error;
}
@@ -950,10 +939,7 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, EvalS
.errPos = pos
});
- if (debuggerHook && !evalState.debugTraces.empty()) {
- DebugTrace &last = evalState.debugTraces.front();
- debuggerHook(&error, last.env, last.expr);
- }
+ evalState.debugLastTrace(error);
throw error;
}
@@ -972,8 +958,6 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
throw error;
}
-// LocalNoInlineNoReturn(void throwTypeError(const char * s, const Value & v));
-
LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const ExprLambda & fun, const Symbol & s2, Env & env, Expr &expr))
{
auto error = TypeError({
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 2ced5bea9..11f5707a4 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -119,7 +119,7 @@ public:
bool debugStop;
bool debugQuit;
std::list<DebugTrace> debugTraces;
- void debug_throw(Error e);
+ void debugLastTrace(Error & e);
private:
SrcToStore srcToStore;
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index 4182f36d5..ecfa5b7c2 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -783,14 +783,15 @@ Path EvalState::findFile(SearchPath & searchPath, const std::string_view path, c
if (hasPrefix(path, "nix/"))
return concatStrings(corepkgsPrefix, path.substr(4));
- debug_throw(ThrownError({
+ auto e = ThrownError({
.msg = hintfmt(evalSettings.pureEval
? "cannot look up '<%s>' in pure evaluation mode (use '--impure' to override)"
: "file '%s' was not found in the Nix search path (add it using $NIX_PATH or -I)",
path),
.errPos = pos
- }));
- return Path(); // should never execute due to debug_throw above.
+ });
+ debugLastTrace(e);
+ throw e;
}
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index c40c54247..b1d2f5f40 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -46,7 +46,11 @@ StringMap EvalState::realiseContext(const PathSet & context)
auto [ctx, outputName] = decodeContext(*store, i);
auto ctxS = store->printStorePath(ctx);
if (!store->isValidPath(ctx))
- debug_throw(InvalidPathError(store->printStorePath(ctx)));
+ {
+ auto e = InvalidPathError(store->printStorePath(ctx));
+ debugLastTrace(e);
+ throw e;
+ }
if (!outputName.empty() && ctx.isDerivation()) {
drvs.push_back({ctx, {outputName}});
} else {
@@ -57,9 +61,13 @@ StringMap EvalState::realiseContext(const PathSet & context)
if (drvs.empty()) return {};
if (!evalSettings.enableImportFromDerivation)
- debug_throw(Error(
+ {
+ auto e = Error(
"cannot build '%1%' during evaluation because the option 'allow-import-from-derivation' is disabled",
- store->printStorePath(drvs.begin()->drvPath)));
+ store->printStorePath(drvs.begin()->drvPath));
+ debugLastTrace(e);
+ throw e;
+ }
/* Build/substitute the context. */
std::vector<DerivedPath> buildReqs;
@@ -71,8 +79,12 @@ StringMap EvalState::realiseContext(const PathSet & context)
auto outputPaths = store->queryDerivationOutputMap(drvPath);
for (auto & outputName : outputs) {
if (outputPaths.count(outputName) == 0)
- debug_throw(Error("derivation '%s' does not have an output named '%s'",
- store->printStorePath(drvPath), outputName));
+ {
+ auto e = Error("derivation '%s' does not have an output named '%s'",
+ store->printStorePath(drvPath), outputName);
+ debugLastTrace(e);
+ throw e;
+ }
res.insert_or_assign(
downstreamPlaceholder(*store, drvPath, outputName),
store->printStorePath(outputPaths.at(outputName))
@@ -318,17 +330,29 @@ void prim_importNative(EvalState & state, const Pos & pos, Value * * args, Value
void *handle = dlopen(path.c_str(), RTLD_LAZY | RTLD_LOCAL);
if (!handle)
- state.debug_throw(EvalError("could not open '%1%': %2%", path, dlerror()));
+ {
+ auto e = EvalError("could not open '%1%': %2%", path, dlerror());
+ state.debugLastTrace(e);
+ throw e;
+ }
dlerror();
ValueInitializer func = (ValueInitializer) dlsym(handle, sym.c_str());
if(!func) {
char *message = dlerror();
if (message)
- state.debug_throw(EvalError("could not load symbol '%1%' from '%2%': %3%", sym, path, message));
+ {
+ auto e = EvalError("could not load symbol '%1%' from '%2%': %3%", sym, path, message);
+ state.debugLastTrace(e);
+ throw e;
+ }
else
- state.debug_throw(EvalError("symbol '%1%' from '%2%' resolved to NULL when a function pointer was expected",
- sym, path));
+ {
+ auto e = EvalError("symbol '%1%' from '%2%' resolved to NULL when a function pointer was expected",
+ sym, path);
+ state.debugLastTrace(e);
+ throw e;
+ }
}
(func)(state, v);
@@ -344,10 +368,12 @@ void prim_exec(EvalState & state, const Pos & pos, Value * * args, Value & v)
auto elems = args[0]->listElems();
auto count = args[0]->listSize();
if (count == 0) {
- state.debug_throw(EvalError({
+ auto e = EvalError({
.msg = hintfmt("at least one argument to 'exec' required"),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
}
PathSet context;
auto program = state.coerceToString(pos, *elems[0], context, false, false).toOwned();
@@ -358,11 +384,13 @@ void prim_exec(EvalState & state, const Pos & pos, Value * * args, Value & v)
try {
auto _ = state.realiseContext(context); // FIXME: Handle CA derivations
} catch (InvalidPathError & e) {
- state.debug_throw(EvalError({
+ auto ee = EvalError({
.msg = hintfmt("cannot execute '%1%', since path '%2%' is not valid",
program, e.path),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(ee);
+ throw ee;
}
auto output = runProgram(program, true, commandArgs);
@@ -545,7 +573,11 @@ struct CompareValues
if (v1->type() == nInt && v2->type() == nFloat)
return v1->integer < v2->fpoint;
if (v1->type() != v2->type())
- state.debug_throw(EvalError("cannot compare %1% with %2%", showType(*v1), showType(*v2)));
+ {
+ auto e = EvalError("cannot compare %1% with %2%", showType(*v1), showType(*v2));
+ state.debugLastTrace(e);
+ throw e;
+ }
switch (v1->type()) {
case nInt:
return v1->integer < v2->integer;
@@ -567,8 +599,11 @@ struct CompareValues
}
}
default:
- state.debug_throw(EvalError("cannot compare %1% with %2%", showType(*v1), showType(*v2)));
- return false;
+ {
+ auto e = EvalError("cannot compare %1% with %2%", showType(*v1), showType(*v2));
+ state.debugLastTrace(e);
+ throw e;
+ }
}
}
};
@@ -598,10 +633,12 @@ static Bindings::iterator getAttr(
Pos aPos = *attrSet->pos;
if (aPos == noPos) {
- state.debug_throw(TypeError({
+ auto e = TypeError({
.msg = errorMsg,
.errPos = pos,
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
} else {
auto e = TypeError({
.msg = errorMsg,
@@ -611,7 +648,8 @@ static Bindings::iterator getAttr(
// Adding another trace for the function name to make it clear
// which call received wrong arguments.
e.addTrace(pos, hintfmt("while invoking '%s'", funcName));
- state.debug_throw(e);
+ state.debugLastTrace(e);
+ throw e;
}
}
@@ -665,10 +703,14 @@ static void prim_genericClosure(EvalState & state, const Pos & pos, Value * * ar
Bindings::iterator key =
e->attrs->find(state.sKey);
if (key == e->attrs->end())
- state.debug_throw(EvalError({
+ {
+ auto e = EvalError({
.msg = hintfmt("attribute 'key' required"),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
state.forceValue(*key->value, pos);
if (!doneKeys.insert(key->value).second) continue;
@@ -768,7 +810,11 @@ static RegisterPrimOp primop_abort({
{
PathSet context;
auto s = state.coerceToString(pos, *args[0], context).toOwned();
- state.debug_throw(Abort("evaluation aborted with the following error message: '%1%'", s));
+ {
+ auto e = Abort("evaluation aborted with the following error message: '%1%'", s);
+ state.debugLastTrace(e);
+ throw e;
+ }
}
});
@@ -786,7 +832,9 @@ static RegisterPrimOp primop_throw({
{
PathSet context;
auto s = state.coerceToString(pos, *args[0], context).toOwned();
- state.debug_throw(ThrownError(s));
+ auto e = ThrownError(s);
+ state.debugLastTrace(e);
+ throw e;
}
});
@@ -851,6 +899,8 @@ static RegisterPrimOp primop_floor({
static void prim_tryEval(EvalState & state, const Pos & pos, Value * * args, Value & v)
{
auto attrs = state.buildBindings(2);
+ auto saveDebuggerHook = debuggerHook;
+ debuggerHook = 0;
try {
state.forceValue(*args[0], pos);
attrs.insert(state.sValue, args[0]);
@@ -859,6 +909,7 @@ static void prim_tryEval(EvalState & state, const Pos & pos, Value * * args, Val
attrs.alloc(state.sValue).mkBool(false);
attrs.alloc("success").mkBool(false);
}
+ debuggerHook = saveDebuggerHook;
v.mkAttrs(attrs);
}
@@ -1041,37 +1092,53 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
if (s == "recursive") ingestionMethod = FileIngestionMethod::Recursive;
else if (s == "flat") ingestionMethod = FileIngestionMethod::Flat;
else
- state.debug_throw(EvalError({
+ {
+ auto e = EvalError({
.msg = hintfmt("invalid value '%s' for 'outputHashMode' attribute", s),
.errPos = posDrvName
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
};
auto handleOutputs = [&](const Strings & ss) {
outputs.clear();
for (auto & j : ss) {
if (outputs.find(j) != outputs.end())
- state.debug_throw(EvalError({
+ {
+ auto e = EvalError({
.msg = hintfmt("duplicate derivation output '%1%'", j),
.errPos = posDrvName
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
/* !!! Check whether j is a valid attribute
name. */
/* Derivations cannot be named ‘drv’, because
then we'd have an attribute ‘drvPath’ in
the resulting set. */
if (j == "drv")
- state.debug_throw(EvalError({
+ {
+ auto e = EvalError({
.msg = hintfmt("invalid derivation output name 'drv'" ),
.errPos = posDrvName
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
outputs.insert(j);
}
if (outputs.empty())
- state.debug_throw(EvalError({
+ {
+ auto e = EvalError({
.msg = hintfmt("derivation cannot have an empty set of outputs"),
.errPos = posDrvName
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
};
try {
@@ -1196,23 +1263,35 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
/* Do we have all required attributes? */
if (drv.builder == "")
- state.debug_throw(EvalError({
+ {
+ auto e = EvalError({
.msg = hintfmt("required attribute 'builder' missing"),
.errPos = posDrvName
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
if (drv.platform == "")
- state.debug_throw(EvalError({
+ {
+ auto e = EvalError({
.msg = hintfmt("required attribute 'system' missing"),
.errPos = posDrvName
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
/* Check whether the derivation name is valid. */
if (isDerivation(drvName))
- state.debug_throw(EvalError({
+ {
+ auto e = EvalError({
.msg = hintfmt("derivation names are not allowed to end in '%s'", drvExtension),
.errPos = posDrvName
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
if (outputHash) {
/* Handle fixed-output derivations.
@@ -1220,10 +1299,14 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
Ignore `__contentAddressed` because fixed output derivations are
already content addressed. */
if (outputs.size() != 1 || *(outputs.begin()) != "out")
- state.debug_throw(Error({
+ {
+ auto e = Error({
.msg = hintfmt("multiple outputs are not supported in fixed-output derivations"),
.errPos = posDrvName
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
auto h = newHashAllowEmpty(*outputHash, parseHashTypeOpt(outputHashAlgo));
@@ -1386,10 +1469,14 @@ static RegisterPrimOp primop_toPath({
static void prim_storePath(EvalState & state, const Pos & pos, Value * * args, Value & v)
{
if (evalSettings.pureEval)
- state.debug_throw(EvalError({
+ {
+ auto e = EvalError({
.msg = hintfmt("'%s' is not allowed in pure evaluation mode", "builtins.storePath"),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
PathSet context;
Path path = state.checkSourcePath(state.coerceToPath(pos, *args[0], context));
@@ -1398,10 +1485,14 @@ static void prim_storePath(EvalState & state, const Pos & pos, Value * * args, V
e.g. nix-push does the right thing. */
if (!state.store->isStorePath(path)) path = canonPath(path, true);
if (!state.store->isInStore(path))
- state.debug_throw(EvalError({
+ {
+ auto e = EvalError({
.msg = hintfmt("path '%1%' is not in the Nix store", path),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
auto path2 = state.store->toStorePath(path).first;
if (!settings.readOnlyMode)
state.store->ensurePath(path2);
@@ -1504,7 +1595,11 @@ static void prim_readFile(EvalState & state, const Pos & pos, Value * * args, Va
auto path = realisePath(state, pos, *args[0]);
auto s = readFile(path);
if (s.find((char) 0) != std::string::npos)
- state.debug_throw(Error("the contents of the file '%1%' cannot be represented as a Nix string", path));
+ {
+ auto e = Error("the contents of the file '%1%' cannot be represented as a Nix string", path);
+ state.debugLastTrace(e);
+ throw e;
+ }
StorePathSet refs;
if (state.store->isInStore(path)) {
try {
@@ -1556,10 +1651,12 @@ static void prim_findFile(EvalState & state, const Pos & pos, Value * * args, Va
auto rewrites = state.realiseContext(context);
path = rewriteStrings(path, rewrites);
} catch (InvalidPathError & e) {
- state.debug_throw(EvalError({
+ auto ee = EvalError({
.msg = hintfmt("cannot find '%1%', since path '%2%' is not valid", path, e.path),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(ee);
+ throw ee;
}
@@ -1583,10 +1680,14 @@ static void prim_hashFile(EvalState & state, const Pos & pos, Value * * args, Va
auto type = state.forceStringNoCtx(*args[0], pos);
std::optional<HashType> ht = parseHashType(type);
if (!ht)
- state.debug_throw(Error({
+ {
+ auto e = Error({
.msg = hintfmt("unknown hash type '%1%'", type),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
auto path = realisePath(state, pos, *args[1]);
@@ -1823,13 +1924,17 @@ static void prim_toFile(EvalState & state, const Pos & pos, Value * * args, Valu
for (auto path : context) {
if (path.at(0) != '/')
- state.debug_throw(EvalError( {
+ {
+ auto e = EvalError( {
.msg = hintfmt(
"in 'toFile': the file named '%1%' must not contain a reference "
"to a derivation but contains (%2%)",
name, path),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
refs.insert(state.store->parseStorePath(path));
}
@@ -1986,7 +2091,11 @@ static void addPath(
? state.store->computeStorePathForPath(name, path, method, htSHA256, filter).first
: state.store->addToStore(name, path, method, htSHA256, filter, state.repair, refs);
if (expectedHash && expectedStorePath != dstPath)
- state.debug_throw(Error("store path mismatch in (possibly filtered) path added from '%s'", path));
+ {
+ auto e = Error("store path mismatch in (possibly filtered) path added from '%s'", path);
+ state.debugLastTrace(e);
+ throw e;
+ }
state.allowAndSetStorePathString(dstPath, v);
} else
state.allowAndSetStorePathString(*expectedStorePath, v);
@@ -2004,12 +2113,16 @@ static void prim_filterSource(EvalState & state, const Pos & pos, Value * * args
state.forceValue(*args[0], pos);
if (args[0]->type() != nFunction)
- state.debug_throw(TypeError({
+ {
+ auto e = TypeError({
.msg = hintfmt(
"first argument in call to 'filterSource' is not a function but %1%",
showType(*args[0])),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
addPath(state, pos, std::string(baseNameOf(path)), path, args[0], FileIngestionMethod::Recursive, std::nullopt, v, context);
}
@@ -2093,16 +2206,24 @@ static void prim_path(EvalState & state, const Pos & pos, Value * * args, Value
else if (n == "sha256")
expectedHash = newHashAllowEmpty(state.forceStringNoCtx(*attr.value, *attr.pos), htSHA256);
else
- state.debug_throw(EvalError({
+ {
+ auto e = EvalError({
.msg = hintfmt("unsupported argument '%1%' to 'addPath'", attr.name),
.errPos = *attr.pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
}
if (path.empty())
- state.debug_throw(EvalError({
+ {
+ auto e = EvalError({
.msg = hintfmt("'path' required"),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
if (name.empty())
name = baseNameOf(path);
@@ -2473,10 +2594,14 @@ static void prim_functionArgs(EvalState & state, const Pos & pos, Value * * args
return;
}
if (!args[0]->isLambda())
- state.debug_throw(TypeError({
+ {
+ auto e = TypeError({
.msg = hintfmt("'functionArgs' requires a function"),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
if (!args[0]->lambda.fun->hasFormals()) {
v.mkAttrs(&state.emptyBindings);
@@ -2564,7 +2689,8 @@ static void prim_zipAttrsWith(EvalState & state, const Pos & pos, Value * * args
attrsSeen[attr.name].first++;
} catch (TypeError & e) {
e.addTrace(pos, hintfmt("while invoking '%s'", "zipAttrsWith"));
- state.debug_throw(e);
+ state.debugLastTrace(e);
+ throw e;
}
}
@@ -2651,10 +2777,14 @@ static void elemAt(EvalState & state, const Pos & pos, Value & list, int n, Valu
{
state.forceList(list, pos);
if (n < 0 || (unsigned int) n >= list.listSize())
- state.debug_throw(Error({
+ {
+ auto e = Error({
.msg = hintfmt("list index %1% is out of boundz", n),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
state.forceValue(*list.listElems()[n], pos);
v = *list.listElems()[n];
}
@@ -2699,10 +2829,14 @@ static void prim_tail(EvalState & state, const Pos & pos, Value * * args, Value
{
state.forceList(*args[0], pos);
if (args[0]->listSize() == 0)
- state.debug_throw(Error({
+ {
+ auto e = Error({
.msg = hintfmt("'tail' called on an empty list"),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
state.mkList(v, args[0]->listSize() - 1);
for (unsigned int n = 0; n < v.listSize(); ++n)
@@ -2937,10 +3071,14 @@ static void prim_genList(EvalState & state, const Pos & pos, Value * * args, Val
auto len = state.forceInt(*args[1], pos);
if (len < 0)
- state.debug_throw(EvalError({
+ {
+ auto e = EvalError({
.msg = hintfmt("cannot create list of size %1%", len),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
state.mkList(v, len);
@@ -3149,7 +3287,8 @@ static void prim_concatMap(EvalState & state, const Pos & pos, Value * * args, V
state.forceList(lists[n], lists[n].determinePos(args[0]->determinePos(pos)));
} catch (TypeError &e) {
e.addTrace(pos, hintfmt("while invoking '%s'", "concatMap"));
- state.debug_throw(e);
+ state.debugLastTrace(e);
+ throw e;
}
len += lists[n].listSize();
}
@@ -3244,10 +3383,14 @@ static void prim_div(EvalState & state, const Pos & pos, Value * * args, Value &
NixFloat f2 = state.forceFloat(*args[1], pos);
if (f2 == 0)
- state.debug_throw(EvalError({
+ {
+ auto e = EvalError({
.msg = hintfmt("division by zero"),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
if (args[0]->type() == nFloat || args[1]->type() == nFloat) {
v.mkFloat(state.forceFloat(*args[0], pos) / state.forceFloat(*args[1], pos));
@@ -3256,10 +3399,14 @@ static void prim_div(EvalState & state, const Pos & pos, Value * * args, Value &
NixInt i2 = state.forceInt(*args[1], pos);
/* Avoid division overflow as it might raise SIGFPE. */
if (i1 == std::numeric_limits<NixInt>::min() && i2 == -1)
- state.debug_throw(EvalError({
+ {
+ auto e = EvalError({
.msg = hintfmt("overflow in integer division"),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
v.mkInt(i1 / i2);
}
@@ -3387,10 +3534,14 @@ static void prim_substring(EvalState & state, const Pos & pos, Value * * args, V
auto s = state.coerceToString(pos, *args[2], context);
if (start < 0)
- state.debug_throw(EvalError({
+ {
+ auto e = EvalError({
.msg = hintfmt("negative start position in 'substring'"),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
v.mkString((unsigned int) start >= s->size() ? "" : s->substr(start, len), context);
}
@@ -3438,10 +3589,14 @@ static void prim_hashString(EvalState & state, const Pos & pos, Value * * args,
auto type = state.forceStringNoCtx(*args[0], pos);
std::optional<HashType> ht = parseHashType(type);
if (!ht)
- state.debug_throw(Error({
+ {
+ auto e = Error({
.msg = hintfmt("unknown hash type '%1%'", type),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
PathSet context; // discarded
auto s = state.forceString(*args[1], context, pos);
@@ -3511,15 +3666,19 @@ void prim_match(EvalState & state, const Pos & pos, Value * * args, Value & v)
} catch (std::regex_error &e) {
if (e.code() == std::regex_constants::error_space) {
// limit is _GLIBCXX_REGEX_STATE_LIMIT for libstdc++
- state.debug_throw(EvalError({
+ auto e = EvalError({
.msg = hintfmt("memory limit exceeded by regular expression '%s'", re),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
} else {
- state.debug_throw(EvalError({
+ auto e = EvalError({
.msg = hintfmt("invalid regular expression '%s'", re),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
}
}
}
@@ -3616,15 +3775,19 @@ void prim_split(EvalState & state, const Pos & pos, Value * * args, Value & v)
} catch (std::regex_error &e) {
if (e.code() == std::regex_constants::error_space) {
// limit is _GLIBCXX_REGEX_STATE_LIMIT for libstdc++
- state.debug_throw(EvalError({
+ auto e = EvalError({
.msg = hintfmt("memory limit exceeded by regular expression '%s'", re),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
} else {
- state.debug_throw(EvalError({
+ auto e = EvalError({
.msg = hintfmt("invalid regular expression '%s'", re),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
}
}
}
@@ -3701,10 +3864,14 @@ static void prim_replaceStrings(EvalState & state, const Pos & pos, Value * * ar
state.forceList(*args[0], pos);
state.forceList(*args[1], pos);
if (args[0]->listSize() != args[1]->listSize())
- state.debug_throw(EvalError({
+ {
+ auto e = EvalError({
.msg = hintfmt("'from' and 'to' arguments to 'replaceStrings' have different lengths"),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
std::vector<std::string> from;
from.reserve(args[0]->listSize());
diff --git a/src/libexpr/primops/fetchTree.cc b/src/libexpr/primops/fetchTree.cc
index bae0fb1e4..131cc87dc 100644
--- a/src/libexpr/primops/fetchTree.cc
+++ b/src/libexpr/primops/fetchTree.cc
@@ -108,16 +108,25 @@ static void fetchTree(
if (auto aType = args[0]->attrs->get(state.sType)) {
if (type)
- state.debug_throw(EvalError({
+ {
+ auto e = EvalError({
.msg = hintfmt("unexpected attribute 'type'"),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+
+ }
type = state.forceStringNoCtx(*aType->value, *aType->pos);
} else if (!type)
- state.debug_throw(EvalError({
+ {
+ auto e = EvalError({
.msg = hintfmt("attribute 'type' is missing in call to 'fetchTree'"),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
attrs.emplace("type", type.value());
@@ -138,16 +147,24 @@ static void fetchTree(
else if (attr.value->type() == nInt)
attrs.emplace(attr.name, uint64_t(attr.value->integer));
else
- state.debug_throw(TypeError("fetchTree argument '%s' is %s while a string, Boolean or integer is expected",
- attr.name, showType(*attr.value)));
+ {
+ auto e = TypeError("fetchTree argument '%s' is %s while a string, Boolean or integer is expected",
+ attr.name, showType(*attr.value));
+ state.debugLastTrace(e);
+ throw e;
+ }
}
if (!params.allowNameArgument)
if (auto nameIter = attrs.find("name"); nameIter != attrs.end())
- state.debug_throw(EvalError({
+ {
+ auto e = EvalError({
.msg = hintfmt("attribute 'name' isn’t supported in call to 'fetchTree'"),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
input = fetchers::Input::fromAttrs(std::move(attrs));
} else {
@@ -167,7 +184,11 @@ static void fetchTree(
input = lookupInRegistries(state.store, input).first;
if (evalSettings.pureEval && !input.isLocked())
- state.debug_throw(EvalError("in pure evaluation mode, 'fetchTree' requires a locked input, at %s", pos));
+ {
+ auto e = EvalError("in pure evaluation mode, 'fetchTree' requires a locked input, at %s", pos);
+ state.debugLastTrace(e);
+ throw e;
+ }
auto [tree, input2] = input.fetch(state.store);
@@ -205,18 +226,25 @@ static void fetch(EvalState & state, const Pos & pos, Value * * args, Value & v,
expectedHash = newHashAllowEmpty(state.forceStringNoCtx(*attr.value, *attr.pos), htSHA256);
else if (n == "name")
name = state.forceStringNoCtx(*attr.value, *attr.pos);
- else
- state.debug_throw(EvalError({
- .msg = hintfmt("unsupported argument '%s' to '%s'", attr.name, who),
- .errPos = *attr.pos
- }));
+ else {
+ auto e = EvalError({
+ .msg = hintfmt("unsupported argument '%s' to '%s'", attr.name, who),
+ .errPos = *attr.pos
+ });
+ state.debugLastTrace(e);
+ throw e;
}
+ }
if (!url)
- state.debug_throw(EvalError({
+ {
+ auto e = EvalError({
.msg = hintfmt("'url' argument required"),
.errPos = pos
- }));
+ });
+ state.debugLastTrace(e);
+ throw e;
+ }
} else
url = state.forceStringNoCtx(*args[0], pos);
@@ -228,7 +256,11 @@ static void fetch(EvalState & state, const Pos & pos, Value * * args, Value & v,
name = baseNameOf(*url);
if (evalSettings.pureEval && !expectedHash)
- state.debug_throw(EvalError("in pure evaluation mode, '%s' requires a 'sha256' argument", who));
+ {
+ auto e = EvalError("in pure evaluation mode, '%s' requires a 'sha256' argument", who);
+ state.debugLastTrace(e);
+ throw e;
+ }
// early exit if pinned and already in the store
if (expectedHash && expectedHash->type == htSHA256) {
@@ -255,8 +287,12 @@ static void fetch(EvalState & state, const Pos & pos, Value * * args, Value & v,
? state.store->queryPathInfo(storePath)->narHash
: hashFile(htSHA256, state.store->toRealPath(storePath));
if (hash != *expectedHash)
- state.debug_throw(EvalError((unsigned int) 102, "hash mismatch in file downloaded from '%s':\n specified: %s\n got: %s",
- *url, expectedHash->to_string(Base32, true), hash.to_string(Base32, true)));
+ {
+ auto e = EvalError((unsigned int) 102, "hash mismatch in file downloaded from '%s':\n specified: %s\n got: %s",
+ *url, expectedHash->to_string(Base32, true), hash.to_string(Base32, true));
+ state.debugLastTrace(e);
+ throw e;
+ }
}
state.allowAndSetStorePathString(storePath, v);
diff --git a/src/libexpr/value-to-json.cc b/src/libexpr/value-to-json.cc
index d8bf73cd5..2f34feb1f 100644
--- a/src/libexpr/value-to-json.cc
+++ b/src/libexpr/value-to-json.cc
@@ -85,7 +85,8 @@ void printValueAsJSON(EvalState & state, bool strict,
.errPos = v.determinePos(pos)
});
e.addTrace(pos, hintfmt("message for the trace"));
- state.debug_throw(e);
+ state.debugLastTrace(e);
+ throw e;
}
}
@@ -99,7 +100,9 @@ void printValueAsJSON(EvalState & state, bool strict,
void ExternalValueBase::printValueAsJSON(EvalState & state, bool strict,
JSONPlaceholder & out, PathSet & context) const
{
- state.debug_throw(TypeError("cannot convert %1% to JSON", showType()));
+ auto e = TypeError("cannot convert %1% to JSON", showType());
+ state.debugLastTrace(e);
+ throw e;
}
From a86c2a8481c5bedb992d7126bc342a34b9c4902e Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Fri, 8 Apr 2022 13:30:18 -0600
Subject: [PATCH 104/188] remove 'debugError', dead code
---
src/libcmd/command.cc | 27 +--------------------------
src/libcmd/command.hh | 1 -
src/libcmd/repl.cc | 19 -------------------
3 files changed, 1 insertion(+), 46 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 5cb8728e9..5ef3b4bc6 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -120,9 +120,6 @@ ref<EvalState> EvalCommand::getEvalState()
;
if (startReplOnEvalErrors)
debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error * error, const Env & env, const Expr & expr) {
- // clear the screen.
- // std::cout << "\033[2J\033[1;1H";
-
auto dts =
error && expr.getPos() ?
std::unique_ptr<DebugTraceStacker>(
@@ -137,35 +134,13 @@ ref<EvalState> EvalCommand::getEvalState()
}))
: nullptr;
-
if (error)
printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error->what());
- // else
- // {
- // auto iter = evalState->debugTraces.begin();
- // if (iter != evalState->debugTraces.end()) {
- // std::cout << "\n" << "… " << iter->hint.str() << "\n";
-
- // if (iter->pos.has_value() && (*iter->pos)) {
- // auto pos = iter->pos.value();
- // std::cout << "\n";
- // printAtPos(pos, std::cout);
-
- // auto loc = getCodeLines(pos);
- // if (loc.has_value()) {
- // std::cout << "\n";
- // printCodeLines(std::cout, "", pos, *loc);
- // std::cout << "\n";
- // }
- // }
- // }
- // }
-
if (expr.staticenv)
{
std::unique_ptr<valmap> vm(mapStaticEnvBindings(*expr.staticenv.get(), env));
- runRepl(evalState, error, expr, *vm);
+ runRepl(evalState, expr, *vm);
}
};
}
diff --git a/src/libcmd/command.hh b/src/libcmd/command.hh
index 94ad80210..9247d401e 100644
--- a/src/libcmd/command.hh
+++ b/src/libcmd/command.hh
@@ -274,7 +274,6 @@ void printClosureDiff(
void runRepl(
ref<EvalState> evalState,
- const Error *debugError,
const Expr &expr,
const std::map<std::string, Value *> & extraEnv);
}
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 2e7974b5d..22a6439b4 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -50,7 +50,6 @@ struct NixRepl
ref<EvalState> state;
Bindings * autoArgs;
- const Error *debugError;
int debugTraceIndex;
Strings loadedFiles;
@@ -552,16 +551,6 @@ bool NixRepl::processLine(std::string line)
// showDebugTrace(std::cout, *iter);
}
}
- else if (arg == "error") {
- // TODO: remove, along with debugError.
- if (this->debugError) {
- showErrorInfo(std::cout, debugError->info(), true);
- }
- else
- {
- notice("error information not available");
- }
- }
else if (arg == "step") {
// set flag to stop at next DebugTrace; exit repl.
state->debugStop = true;
@@ -1024,26 +1013,18 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
void runRepl(
ref<EvalState> evalState,
- const Error *debugError,
const Expr &expr,
const std::map<std::string, Value *> & extraEnv)
{
auto repl = std::make_unique<NixRepl>(evalState);
- repl->debugError = debugError;
-
repl->initEnv();
// add 'extra' vars.
- // std::set<std::string> names;
for (auto & [name, value] : extraEnv) {
- // names.insert(ANSI_BOLD + name + ANSI_NORMAL);
- // names.insert(name);
repl->addVarToScope(repl->state->symbols.create(name), *value);
}
- // printError(hintfmt("The following extra variables are in scope: %s\n", concatStringsSep(", ", names)).str());
-
repl->mainLoop({});
}
From 27d45f9eb3c151afed8a20f1adc1d4dd1a200f09 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Fri, 8 Apr 2022 15:46:12 -0600
Subject: [PATCH 105/188] minor cleanup
---
src/libcmd/repl.cc | 2 --
src/libexpr/eval.cc | 45 +++++++++++++++-----------------
src/libexpr/parser.y | 1 -
src/libexpr/primops/fetchTree.cc | 15 ++++++-----
4 files changed, 29 insertions(+), 34 deletions(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 22a6439b4..edd74c993 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -547,8 +547,6 @@ bool NixRepl::processLine(std::string line)
loadDebugTraceEnv(*iter);
break;
}
- // std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
- // showDebugTrace(std::cout, *iter);
}
}
else if (arg == "step") {
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 7d02222cf..914739f70 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -789,6 +789,7 @@ void mapStaticEnvBindings(const StaticEnv &se, const Env &env, valmap & vm)
auto map = valmap();
if (env.type == Env::HasWithAttrs)
{
+ // add 'with' bindings.
Bindings::iterator j = env.values[0]->attrs->begin();
while (j != env.values[0]->attrs->end()) {
map[j->name] = j->value;
@@ -1485,15 +1486,15 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
try {
auto dts =
- debuggerHook ?
- makeDebugTraceStacker(
- state,
- *this,
- env,
- *pos2,
- "while evaluating the attribute '%1%'",
- showAttrPath(state, env, attrPath))
- : nullptr;
+ debuggerHook ?
+ makeDebugTraceStacker(
+ state,
+ *this,
+ env,
+ *pos2,
+ "while evaluating the attribute '%1%'",
+ showAttrPath(state, env, attrPath))
+ : nullptr;
for (auto & i : attrPath) {
state.nrLookups++;
@@ -2082,13 +2083,13 @@ void EvalState::forceValueDeep(Value & v)
try {
auto dts =
- debuggerHook ?
- // if the value is a thunk, we're evaling. otherwise no trace necessary.
- (i.value->isThunk() ?
- makeDebugTraceStacker(*this, *v.thunk.expr, *v.thunk.env, *i.pos,
- "while evaluating the attribute '%1%'", i.name)
- : nullptr)
- : nullptr;
+ debuggerHook ?
+ // if the value is a thunk, we're evaling. otherwise no trace necessary.
+ (i.value->isThunk() ?
+ makeDebugTraceStacker(*this, *v.thunk.expr, *v.thunk.env, *i.pos,
+ "while evaluating the attribute '%1%'", i.name)
+ : nullptr)
+ : nullptr;
recurse(*i.value);
} catch (Error & e) {
@@ -2123,8 +2124,7 @@ NixFloat EvalState::forceFloat(Value & v, const Pos & pos)
if (v.type() == nInt)
return v.integer;
else if (v.type() != nFloat)
- throwTypeError(pos, "value is %1% while a float was expected", v,
- *this);
+ throwTypeError(pos, "value is %1% while a float was expected", v, *this);
return v.fpoint;
}
@@ -2133,8 +2133,7 @@ bool EvalState::forceBool(Value & v, const Pos & pos)
{
forceValue(v, pos);
if (v.type() != nBool)
- throwTypeError(pos, "value is %1% while a Boolean was expected", v,
- *this);
+ throwTypeError(pos, "value is %1% while a Boolean was expected", v, *this);
return v.boolean;
}
@@ -2149,8 +2148,7 @@ void EvalState::forceFunction(Value & v, const Pos & pos)
{
forceValue(v, pos);
if (v.type() != nFunction && !isFunctor(v))
- throwTypeError(pos, "value is %1% while a function was expected", v,
- *this);
+ throwTypeError(pos, "value is %1% while a function was expected", v, *this);
}
@@ -2158,8 +2156,7 @@ std::string_view EvalState::forceString(Value & v, const Pos & pos)
{
forceValue(v, pos);
if (v.type() != nString) {
- throwTypeError(pos, "value is %1% while a string was expected", v,
- *this);
+ throwTypeError(pos, "value is %1% while a string was expected", v, *this);
}
return v.string.s;
}
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index ecfa5b7c2..1a5832e6b 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -23,7 +23,6 @@
#include "nixexpr.hh"
#include "eval.hh"
#include "globals.hh"
-#include <iostream>
namespace nix {
diff --git a/src/libexpr/primops/fetchTree.cc b/src/libexpr/primops/fetchTree.cc
index 131cc87dc..c7b73b83d 100644
--- a/src/libexpr/primops/fetchTree.cc
+++ b/src/libexpr/primops/fetchTree.cc
@@ -226,13 +226,14 @@ static void fetch(EvalState & state, const Pos & pos, Value * * args, Value & v,
expectedHash = newHashAllowEmpty(state.forceStringNoCtx(*attr.value, *attr.pos), htSHA256);
else if (n == "name")
name = state.forceStringNoCtx(*attr.value, *attr.pos);
- else {
- auto e = EvalError({
- .msg = hintfmt("unsupported argument '%s' to '%s'", attr.name, who),
- .errPos = *attr.pos
- });
- state.debugLastTrace(e);
- throw e;
+ else
+ {
+ auto e = EvalError({
+ .msg = hintfmt("unsupported argument '%s' to '%s'", attr.name, who),
+ .errPos = *attr.pos
+ });
+ state.debugLastTrace(e);
+ throw e;
}
}
From 31bcd5562693aec52a09d7f0d7ecae0b1a7ae9e4 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Fri, 8 Apr 2022 15:53:24 -0600
Subject: [PATCH 106/188] clean up makefiles
---
Makefile | 3 +--
doc/manual/manual.is-valid | 0
src/libcmd/local.mk | 2 --
3 files changed, 1 insertion(+), 4 deletions(-)
delete mode 100644 doc/manual/manual.is-valid
diff --git a/Makefile b/Makefile
index 02228910a..5040d2884 100644
--- a/Makefile
+++ b/Makefile
@@ -18,7 +18,7 @@ makefiles = \
misc/systemd/local.mk \
misc/launchd/local.mk \
misc/upstart/local.mk \
- # doc/manual/local.mk \
+ doc/manual/local.mk \
tests/local.mk \
tests/plugins/local.mk
@@ -34,5 +34,4 @@ endif
include mk/lib.mk
-# GLOBAL_CXXFLAGS += -g -Wall -include config.h -std=c++17 -fstack-usage
GLOBAL_CXXFLAGS += -g -Wall -include config.h -std=c++17 -I src
diff --git a/doc/manual/manual.is-valid b/doc/manual/manual.is-valid
deleted file mode 100644
index e69de29bb..000000000
diff --git a/src/libcmd/local.mk b/src/libcmd/local.mk
index a12837ce5..73a1a1086 100644
--- a/src/libcmd/local.mk
+++ b/src/libcmd/local.mk
@@ -8,9 +8,7 @@ libcmd_SOURCES := $(wildcard $(d)/*.cc)
libcmd_CXXFLAGS += -I src/libutil -I src/libstore -I src/libexpr -I src/libmain -I src/libfetchers -I src/nix
-# libcmd_LDFLAGS += -llowdown -pthread
libcmd_LDFLAGS = $(EDITLINE_LIBS) -llowdown -pthread
-# libcmd_LDFLAGS += $(LOWDOWN_LIBS) -pthread
libcmd_LIBS = libstore libutil libexpr libmain libfetchers libnix
From 3aaf02839f1491e6d766661209904f74efde8970 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Fri, 8 Apr 2022 16:22:27 -0600
Subject: [PATCH 107/188] trace stack, not call stack
---
src/libcmd/repl.cc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index edd74c993..07e433293 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -495,7 +495,7 @@ bool NixRepl::processLine(std::string line)
<< " :log <expr> Show logs for a derivation\n"
<< " :st [bool] Enable, disable or toggle showing traces for errors\n"
<< " :d <cmd> Debug mode commands\n"
- << " :d stack Show call stack\n"
+ << " :d stack Show trace stack\n"
<< " :d env Show env stack\n"
<< " :d show <idx> Show current trace, or change to call stack index\n"
<< " :d go Go until end of program, exception, or builtins.break().\n"
From f5757a0804e0278e1ad2ac7a46adeb3dc96ce034 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Fri, 8 Apr 2022 16:34:20 -0600
Subject: [PATCH 108/188] revise command help
---
src/libcmd/repl.cc | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 07e433293..5c25183cc 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -497,7 +497,8 @@ bool NixRepl::processLine(std::string line)
<< " :d <cmd> Debug mode commands\n"
<< " :d stack Show trace stack\n"
<< " :d env Show env stack\n"
- << " :d show <idx> Show current trace, or change to call stack index\n"
+ << " :d show Show current trace\n"
+ << " :d show <idx> Change to another trace in the stack\n"
<< " :d go Go until end of program, exception, or builtins.break().\n"
<< " :d step Go one step\n"
;
From a61841ac41646ad0345cef547facd2c20f1da957 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Sat, 9 Apr 2022 07:45:23 -0600
Subject: [PATCH 109/188] don't use std::map merge
---
src/libexpr/eval.cc | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 914739f70..876bf8f37 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -784,15 +784,14 @@ void mapStaticEnvBindings(const StaticEnv &se, const Env &env, valmap & vm)
// override the higher levels.
// The top level bindings (builtins) are skipped since they are added for us by initEnv()
if (env.up && se.up) {
- mapStaticEnvBindings(*se.up, *env.up,vm);
+ mapStaticEnvBindings(*se.up, *env.up, vm);
- auto map = valmap();
if (env.type == Env::HasWithAttrs)
{
// add 'with' bindings.
Bindings::iterator j = env.values[0]->attrs->begin();
while (j != env.values[0]->attrs->end()) {
- map[j->name] = j->value;
+ vm[j->name] = j->value;
++j;
}
}
@@ -801,11 +800,9 @@ void mapStaticEnvBindings(const StaticEnv &se, const Env &env, valmap & vm)
// iterate through staticenv bindings and add them.
for (auto iter = se.vars.begin(); iter != se.vars.end(); ++iter)
{
- map[iter->first] = env.values[iter->second];
+ vm[iter->first] = env.values[iter->second];
}
}
-
- vm.merge(map);
}
}
From 8b197c492e4e2878eb58bb2994fb8d7f8044bf90 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Sat, 9 Apr 2022 21:54:41 -0600
Subject: [PATCH 110/188] remove comma
---
src/libexpr/eval.cc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 876bf8f37..d0e147733 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -845,7 +845,7 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const Suggestions & s
auto error = EvalError({
.msg = hintfmt(s, s2),
.errPos = pos,
- .suggestions = suggestions,
+ .suggestions = suggestions
});
if (debuggerHook)
From 2a5632c70dcb686a7764c23a5f330fcb9a33c8a1 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Fri, 29 Apr 2022 10:02:17 -0600
Subject: [PATCH 111/188] incorporate PosIdx changes, symbol changes.
---
src/libcmd/command.cc | 4 +-
src/libcmd/repl.cc | 16 +--
src/libexpr/eval-inline.hh | 6 +-
src/libexpr/eval.cc | 211 ++++++++++++++++++++++---------------
src/libexpr/eval.hh | 67 ++++++++----
src/libexpr/nixexpr.cc | 6 +-
src/libexpr/nixexpr.hh | 9 +-
src/libexpr/primops.cc | 10 +-
8 files changed, 204 insertions(+), 125 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 82b35d16f..3e789adba 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -126,7 +126,7 @@ ref<EvalState> EvalCommand::getEvalState()
new DebugTraceStacker(
*evalState,
DebugTrace
- {.pos = (error->info().errPos ? *error->info().errPos : *expr.getPos()),
+ {.pos = (error->info().errPos ? *error->info().errPos : evalState->positions[expr.getPos()]),
.expr = expr,
.env = env,
.hint = error->info().msg,
@@ -139,7 +139,7 @@ ref<EvalState> EvalCommand::getEvalState()
if (expr.staticenv)
{
- std::unique_ptr<valmap> vm(mapStaticEnvBindings(*expr.staticenv.get(), env));
+ std::unique_ptr<valmap> vm(mapStaticEnvBindings(evalState->symbols, *expr.staticenv.get(), env));
runRepl(evalState, expr, *vm);
}
};
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index d9ba7e7a4..40299e910 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -203,7 +203,7 @@ namespace {
}
}
-std::ostream& showDebugTrace(std::ostream &out, const DebugTrace &dt)
+std::ostream& showDebugTrace(std::ostream &out, const PosTable &positions, const DebugTrace &dt)
{
if (dt.is_error)
out << ANSI_RED "error: " << ANSI_NORMAL;
@@ -211,7 +211,7 @@ std::ostream& showDebugTrace(std::ostream &out, const DebugTrace &dt)
// prefer direct pos, but if noPos then try the expr.
auto pos = (*dt.pos ? *dt.pos :
- (dt.expr.getPos() ? *dt.expr.getPos() : noPos));
+ positions[(dt.expr.getPos() ? dt.expr.getPos() : noPos)]);
if (pos) {
printAtPos(pos, out);
@@ -280,7 +280,7 @@ void NixRepl::mainLoop(const std::vector<std::string> & files)
// when that session returns the exception will land here. No need to show it again;
// show the error for this repl session instead.
if (debuggerHook && !this->state->debugTraces.empty())
- showDebugTrace(std::cout, this->state->debugTraces.front());
+ showDebugTrace(std::cout, this->state->positions, this->state->debugTraces.front());
else
printMsg(lvlError, e.msg());
} catch (Error & e) {
@@ -443,7 +443,7 @@ void NixRepl::loadDebugTraceEnv(DebugTrace &dt)
{
initEnv();
- auto vm = std::make_unique<valmap>(*(mapStaticEnvBindings(*dt.expr.staticenv.get(), dt.env)));
+ auto vm = std::make_unique<valmap>(*(mapStaticEnvBindings(this->state->symbols, *dt.expr.staticenv.get(), dt.env)));
// add staticenv vars.
for (auto & [name, value] : *(vm.get())) {
@@ -514,7 +514,7 @@ bool NixRepl::processLine(std::string line)
iter != this->state->debugTraces.end();
++iter, ++idx) {
std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
- showDebugTrace(std::cout, *iter);
+ showDebugTrace(std::cout, this->state->positions, *iter);
}
} else if (arg == "env") {
int idx = 0;
@@ -523,7 +523,7 @@ bool NixRepl::processLine(std::string line)
++iter, ++idx) {
if (idx == this->debugTraceIndex)
{
- printEnvBindings(iter->expr, iter->env);
+ printEnvBindings(state->symbols,iter->expr, iter->env);
break;
}
}
@@ -544,9 +544,9 @@ bool NixRepl::processLine(std::string line)
if (idx == this->debugTraceIndex)
{
std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
- showDebugTrace(std::cout, *iter);
+ showDebugTrace(std::cout, this->state->positions, *iter);
std::cout << std::endl;
- printEnvBindings(iter->expr, iter->env);
+ printEnvBindings(state->symbols,iter->expr, iter->env);
loadDebugTraceEnv(*iter);
break;
}
diff --git a/src/libexpr/eval-inline.hh b/src/libexpr/eval-inline.hh
index 4e0826101..f2f4ba725 100644
--- a/src/libexpr/eval-inline.hh
+++ b/src/libexpr/eval-inline.hh
@@ -103,7 +103,7 @@ void EvalState::forceValue(Value & v, Callable getPos)
else if (v.isApp())
callFunction(*v.app.left, *v.app.right, v, noPos);
else if (v.isBlackhole())
- throwEvalError(getPos(), "infinite recursion encountered", *this);
+ throwEvalError(getPos(), "infinite recursion encountered");
}
@@ -120,7 +120,7 @@ inline void EvalState::forceAttrs(Value & v, Callable getPos)
{
forceValue(v, getPos);
if (v.type() != nAttrs)
- throwTypeError(getPos(), "value is %1% while a set was expected", v, *this);
+ throwTypeError(getPos(), "value is %1% while a set was expected", v);
}
@@ -129,7 +129,7 @@ inline void EvalState::forceList(Value & v, const PosIdx pos)
{
forceValue(v, pos);
if (!v.isList())
- throwTypeError(pos, "value is %1% while a list was expected", v, *this);
+ throwTypeError(pos, "value is %1% while a list was expected", v);
}
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 896242e0c..7058d117f 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -714,19 +714,19 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
// just for the current level of StaticEnv, not the whole chain.
-void printStaticEnvBindings(const StaticEnv &se)
+void printStaticEnvBindings(const SymbolTable &st, const StaticEnv &se)
{
std::cout << ANSI_MAGENTA;
for (auto i = se.vars.begin(); i != se.vars.end(); ++i)
{
- std::cout << i->first << " ";
+ std::cout << st[i->first] << " ";
}
std::cout << ANSI_NORMAL;
std::cout << std::endl;
}
// just for the current level of Env, not the whole chain.
-void printWithBindings(const Env &env)
+void printWithBindings(const SymbolTable &st, const Env &env)
{
if (env.type == Env::HasWithAttrs)
{
@@ -734,7 +734,7 @@ void printWithBindings(const Env &env)
std::cout << ANSI_MAGENTA;
Bindings::iterator j = env.values[0]->attrs->begin();
while (j != env.values[0]->attrs->end()) {
- std::cout << j->name << " ";
+ std::cout << st[j->name] << " ";
++j;
}
std::cout << ANSI_NORMAL;
@@ -742,16 +742,16 @@ void printWithBindings(const Env &env)
}
}
-void printEnvBindings(const StaticEnv &se, const Env &env, int lvl)
+void printEnvBindings(const SymbolTable &st, const StaticEnv &se, const Env &env, int lvl)
{
std::cout << "Env level " << lvl << std::endl;
if (se.up && env.up) {
std::cout << "static: ";
- printStaticEnvBindings(se);
- printWithBindings(env);
+ printStaticEnvBindings(st, se);
+ printWithBindings(st, env);
std::cout << std::endl;
- printEnvBindings(*se.up, *env.up, ++lvl);
+ printEnvBindings(st, *se.up, *env.up, ++lvl);
}
else
{
@@ -759,41 +759,41 @@ void printEnvBindings(const StaticEnv &se, const Env &env, int lvl)
// for the top level, don't print the double underscore ones; they are in builtins.
for (auto i = se.vars.begin(); i != se.vars.end(); ++i)
{
- if (((std::string)i->first).substr(0,2) != "__")
- std::cout << i->first << " ";
+ if (((std::string)st[i->first]).substr(0,2) != "__")
+ std::cout << st[i->first] << " ";
}
std::cout << ANSI_NORMAL;
std::cout << std::endl;
- printWithBindings(env); // probably nothing there for the top level.
+ printWithBindings(st, env); // probably nothing there for the top level.
std::cout << std::endl;
}
}
// TODO: add accompanying env for With stuff.
-void printEnvBindings(const Expr &expr, const Env &env)
+void printEnvBindings(const SymbolTable &st, const Expr &expr, const Env &env)
{
// just print the names for now
if (expr.staticenv)
{
- printEnvBindings(*expr.staticenv.get(), env, 0);
+ printEnvBindings(st, *expr.staticenv.get(), env, 0);
}
}
-void mapStaticEnvBindings(const StaticEnv &se, const Env &env, valmap & vm)
+void mapStaticEnvBindings(const SymbolTable &st, const StaticEnv &se, const Env &env, valmap & vm)
{
// add bindings for the next level up first, so that the bindings for this level
// override the higher levels.
// The top level bindings (builtins) are skipped since they are added for us by initEnv()
if (env.up && se.up) {
- mapStaticEnvBindings(*se.up, *env.up, vm);
+ mapStaticEnvBindings(st, *se.up, *env.up, vm);
if (env.type == Env::HasWithAttrs)
{
// add 'with' bindings.
Bindings::iterator j = env.values[0]->attrs->begin();
while (j != env.values[0]->attrs->end()) {
- vm[j->name] = j->value;
+ vm[st[j->name]] = j->value;
++j;
}
}
@@ -802,24 +802,45 @@ void mapStaticEnvBindings(const StaticEnv &se, const Env &env, valmap & vm)
// iterate through staticenv bindings and add them.
for (auto iter = se.vars.begin(); iter != se.vars.end(); ++iter)
{
- vm[iter->first] = env.values[iter->second];
+ vm[st[iter->first]] = env.values[iter->second];
}
}
}
}
-valmap * mapStaticEnvBindings(const StaticEnv &se, const Env &env)
+valmap * mapStaticEnvBindings(const SymbolTable &st,const StaticEnv &se, const Env &env)
{
auto vm = new valmap();
- mapStaticEnvBindings(se, env, *vm);
+ mapStaticEnvBindings(st, se, env, *vm);
return vm;
}
+void EvalState::debugLastTrace(Error & e) const {
+ // call this in the situation where Expr and Env are inaccessible. The debugger will start in the last context
+ // that's in the DebugTrace stack.
+ if (debuggerHook && !debugTraces.empty()) {
+ const DebugTrace &last = debugTraces.front();
+ debuggerHook(&e, last.env, last.expr);
+ }
+}
+
/* Every "format" object (even temporary) takes up a few hundred bytes
of stack space, which is a real killer in the recursive
evaluator. So here are some helper functions for throwing
exceptions. */
+void EvalState::throwEvalError(const PosIdx pos, const char * s, Env & env, Expr &expr) const
+{
+ auto error = EvalError({
+ .msg = hintfmt(s),
+ .errPos = positions[pos]
+ });
+
+ if (debuggerHook)
+ debuggerHook(&error, env, expr);
+
+ throw error;
+}
void EvalState::throwEvalError(const PosIdx pos, const char * s) const
{
@@ -828,25 +849,7 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s) const
.errPos = positions[pos]
});
- if (debuggerHook && !debugTraces.empty()) {
- DebugTrace &last = debugTraces.front();
- debuggerHook(&error, last.env, last.expr);
- }
-
- throw error;
-}
-
-void EvalState::throwTypeError(const PosIdx pos, const char * s, const Value & v) const
-{
- auto error = TypeError({
- .msg = hintfmt(s, showType(v)),
- .errPos = positions[pos]
- });
-
- if (debuggerHook && !debugTraces.empty()) {
- DebugTrace &last = debugTraces.front();
- debuggerHook(&error, last.env, last.expr);
- }
+ debugLastTrace(error);
throw error;
}
@@ -855,23 +858,11 @@ void EvalState::throwEvalError(const char * s, const std::string & s2) const
{
auto error = EvalError(s, s2);
- if (debuggerHook && !debugTraces.empty()) {
- DebugTrace &last = debugTraces.front();
- debuggerHook(&error, last.env, last.expr);
- }
+ debugLastTrace(error);
throw error;
}
-void EvalState::debugLastTrace(Error & e) {
- // call this in the situation where Expr and Env are inaccessible. The debugger will start in the last context
- // that's in the DebugTrace stack.
- if (debuggerHook && !debugTraces.empty()) {
- DebugTrace &last = debugTraces.front();
- debuggerHook(&e, last.env, last.expr);
- }
-}
-
void EvalState::throwEvalError(const PosIdx pos, const Suggestions & suggestions, const char * s,
const std::string & s2, Env & env, Expr &expr) const
{
@@ -899,16 +890,43 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::stri
throw error;
}
-void EvalState::throwEvalError(const char * s, const std::string & s2, const std::string & s3, Env & env, Expr &expr) const
+void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::string & s2, Env & env, Expr &expr) const
{
auto error = EvalError({
- .msg = hintfmt(s),
- .errPos = pos
+ .msg = hintfmt(s, s2),
+ .errPos = positions[pos]
});
if (debuggerHook)
debuggerHook(&error, env, expr);
+
+ throw error;
+}
+
+void EvalState::throwEvalError(const char * s, const std::string & s2,
+ const std::string & s3) const
+{
+ auto error = EvalError({
+ .msg = hintfmt(s, s2),
+ .errPos = positions[noPos]
+ });
+
+ debugLastTrace(error);
+
+ throw error;
+}
+
+void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::string & s2,
+ const std::string & s3) const
+{
+ auto error = EvalError({
+ .msg = hintfmt(s, s2),
+ .errPos = positions[pos]
+ });
+
+ debugLastTrace(error);
+
throw error;
}
@@ -917,7 +935,7 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::stri
{
auto error = EvalError({
.msg = hintfmt(s, s2),
- .errPos = pos
+ .errPos = positions[pos]
});
if (debuggerHook)
@@ -966,6 +984,31 @@ void EvalState::throwEvalError(const PosIdx p1, const char * s, const Symbol sym
throw error;
}
+void EvalState::throwTypeError(const PosIdx pos, const char * s, const Value & v) const
+{
+ auto error = TypeError({
+ .msg = hintfmt(s, showType(v)),
+ .errPos = positions[pos]
+ });
+
+ debugLastTrace(error);
+
+ throw error;
+}
+
+void EvalState::throwTypeError(const PosIdx pos, const char * s, const Value & v, Env & env, Expr &expr) const
+{
+ auto error = TypeError({
+ .msg = hintfmt(s, showType(v)),
+ .errPos = positions[pos]
+ });
+
+ if (debuggerHook)
+ debuggerHook(&error, env, expr);
+
+ throw error;
+}
+
void EvalState::throwTypeError(const PosIdx pos, const char * s) const
{
auto error = TypeError({
@@ -973,7 +1016,7 @@ void EvalState::throwTypeError(const PosIdx pos, const char * s) const
.errPos = positions[pos]
});
- evalState.debugLastTrace(error);
+ debugLastTrace(error);
throw error;
}
@@ -1010,9 +1053,8 @@ void EvalState::throwTypeError(const PosIdx pos, const Suggestions & suggestions
void EvalState::throwTypeError(const char * s, const Value & v, Env & env, Expr &expr) const
{
auto error = TypeError({
- .msg = hintfmt(s, fun.showNamePos(), s2),
- .errPos = pos,
- .suggestions = suggestions,
+ .msg = hintfmt(s, showType(v)),
+ .errPos = positions[expr.getPos()],
});
if (debuggerHook)
@@ -1070,8 +1112,8 @@ void EvalState::addErrorTrace(Error & e, const PosIdx pos, const char * s, const
e.addTrace(positions[pos], s, s2);
}
-LocalNoInline(std::unique_ptr<DebugTraceStacker>
- makeDebugTraceStacker(EvalState &state, Expr &expr, Env &env, std::optional<ErrPos> pos, const char * s, const std::string & s2))
+std::unique_ptr<DebugTraceStacker> makeDebugTraceStacker(EvalState &state, Expr &expr, Env &env,
+ std::optional<ErrPos> pos, const char * s, const std::string & s2)
{
return std::unique_ptr<DebugTraceStacker>(
new DebugTraceStacker(
@@ -1150,7 +1192,7 @@ inline Value * EvalState::lookupVar(Env * env, const ExprVar & var, bool noEval)
return j->value;
}
if (!env->prevWith)
- throwUndefinedVarError(var.pos, "undefined variable '%1%'", symbols[var.name], *env, var);
+ throwUndefinedVarError(var.pos, "undefined variable '%1%'", symbols[var.name], *env, const_cast<ExprVar&>(var));
for (size_t l = env->prevWith; l; --l, env = env->up) ;
}
}
@@ -1293,7 +1335,7 @@ void EvalState::cacheFile(
*this,
*e,
this->baseEnv,
- (e->getPos() ? std::optional(ErrPos(*e->getPos())) : std::nullopt),
+ (e->getPos() ? std::optional(ErrPos(positions[e->getPos()])) : std::nullopt),
"while evaluating the file '%1%':", resolvedPath)
: nullptr;
@@ -1528,7 +1570,7 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
state,
*this,
env,
- *pos2,
+ state.positions[pos2],
"while evaluating the attribute '%1%'",
showAttrPath(state, env, attrPath))
: nullptr;
@@ -1694,10 +1736,10 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
try {
auto dts =
debuggerHook ?
- makeDebugTraceStacker(*this, *lambda.body, env2, lambda.pos,
+ makeDebugTraceStacker(*this, *lambda.body, env2, positions[lambda.pos],
"while evaluating %s",
- (lambda.name.set()
- ? "'" + (std::string) lambda.name + "'"
+ (lambda.name
+ ? concatStrings("'", symbols[lambda.name], "'")
: "anonymous lambda"))
: nullptr;
@@ -1786,7 +1828,7 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
}
else
- throwTypeError(pos, "attempt to call something which is not a function but %1%", vCur, *this);
+ throwTypeError(pos, "attempt to call something which is not a function but %1%", vCur);
}
vRes = vCur;
@@ -1855,7 +1897,7 @@ void EvalState::autoCallFunction(Bindings & args, Value & fun, Value & res)
Nix attempted to evaluate a function as a top level expression; in
this case it must have its arguments supplied either by default
values, or passed explicitly with '--arg' or '--argstr'. See
-https://nixos.org/manual/nix/stable/#ss-functions.)", symbols[i.name],,
+https://nixos.org/manual/nix/stable/#ss-functions.)", symbols[i.name],
*fun.lambda.env, *fun.lambda.fun);
}
}
@@ -2092,7 +2134,7 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
v.mkFloat(nf);
else if (firstType == nPath) {
if (!context.empty())
- state.throwEvalError(pos, "a string that refers to a store path cannot be appended to a path", env, *this););
+ state.throwEvalError(pos, "a string that refers to a store path cannot be appended to a path", env, *this);
v.mkPath(canonPath(str()));
} else
v.mkStringMove(c_str(), context);
@@ -2124,8 +2166,8 @@ void EvalState::forceValueDeep(Value & v)
debuggerHook ?
// if the value is a thunk, we're evaling. otherwise no trace necessary.
(i.value->isThunk() ?
- makeDebugTraceStacker(*this, *v.thunk.expr, *v.thunk.env, *i.pos,
- "while evaluating the attribute '%1%'", i.name)
+ makeDebugTraceStacker(*this, *v.thunk.expr, *v.thunk.env, positions[i.pos],
+ "while evaluating the attribute '%1%'", symbols[i.name])
: nullptr)
: nullptr;
@@ -2150,7 +2192,7 @@ NixInt EvalState::forceInt(Value & v, const PosIdx pos)
{
forceValue(v, pos);
if (v.type() != nInt)
- throwTypeError(pos, "value is %1% while an integer was expected", v, *this);
+ throwTypeError(pos, "value is %1% while an integer was expected", v);
return v.integer;
}
@@ -2162,7 +2204,7 @@ NixFloat EvalState::forceFloat(Value & v, const PosIdx pos)
if (v.type() == nInt)
return v.integer;
else if (v.type() != nFloat)
- throwTypeError(pos, "value is %1% while a float was expected", v, *this);
+ throwTypeError(pos, "value is %1% while a float was expected", v);
return v.fpoint;
}
@@ -2171,7 +2213,7 @@ bool EvalState::forceBool(Value & v, const PosIdx pos)
{
forceValue(v, pos);
if (v.type() != nBool)
- throwTypeError(pos, "value is %1% while a Boolean was expected", v, *this);
+ throwTypeError(pos, "value is %1% while a Boolean was expected", v);
return v.boolean;
}
@@ -2186,7 +2228,7 @@ void EvalState::forceFunction(Value & v, const PosIdx pos)
{
forceValue(v, pos);
if (v.type() != nFunction && !isFunctor(v))
- throwTypeError(pos, "value is %1% while a function was expected", v, *this);
+ throwTypeError(pos, "value is %1% while a function was expected", v);
}
@@ -2194,7 +2236,7 @@ std::string_view EvalState::forceString(Value & v, const PosIdx pos)
{
forceValue(v, pos);
if (v.type() != nString) {
- throwTypeError(pos, "value is %1% while a string was expected", v, *this);
+ throwTypeError(pos, "value is %1% while a string was expected", v);
}
return v.string.s;
}
@@ -2254,10 +2296,10 @@ std::string_view EvalState::forceStringNoCtx(Value & v, const PosIdx pos)
if (v.string.context) {
if (pos)
throwEvalError(pos, "the string '%1%' is not allowed to refer to a store path (such as '%2%')",
- v.string.s, v.string.context[0], *this);
+ v.string.s, v.string.context[0]);
else
throwEvalError("the string '%1%' is not allowed to refer to a store path (such as '%2%')",
- v.string.s, v.string.context[0], *this);
+ v.string.s, v.string.context[0]);
}
return s;
}
@@ -2312,7 +2354,7 @@ BackedStringView EvalState::coerceToString(const PosIdx pos, Value & v, PathSet
return std::move(*maybeString);
auto i = v.attrs->find(sOutPath);
if (i == v.attrs->end())
- throwTypeError(pos, "cannot coerce a set to a string", *this);
+ throwTypeError(pos, "cannot coerce a set to a string");
return coerceToString(pos, *i->value, context, coerceMore, copyToStore);
}
@@ -2341,14 +2383,14 @@ BackedStringView EvalState::coerceToString(const PosIdx pos, Value & v, PathSet
}
}
- throwTypeError(pos, "cannot coerce %1% to a string", v, *this);
+ throwTypeError(pos, "cannot coerce %1% to a string", v);
}
std::string EvalState::copyPathToStore(PathSet & context, const Path & path)
{
if (nix::isDerivation(path))
- throwEvalError("file names are not allowed to end in '%1%'", drvExtension, *this);
+ throwEvalError("file names are not allowed to end in '%1%'", drvExtension);
Path dstPath;
auto i = srcToStore.find(path);
@@ -2373,7 +2415,7 @@ Path EvalState::coerceToPath(const PosIdx pos, Value & v, PathSet & context)
{
auto path = coerceToString(pos, v, context, false, false).toOwned();
if (path == "" || path[0] != '/')
- throwEvalError(pos, "string '%1%' doesn't represent an absolute path", path, *this);
+ throwEvalError(pos, "string '%1%' doesn't represent an absolute path", path);
return path;
}
@@ -2466,8 +2508,7 @@ bool EvalState::eqValues(Value & v1, Value & v2)
default:
throwEvalError("cannot compare %1% with %2%",
showType(v1),
- showType(v2),
- *this);
+ showType(v2));
}
}
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 76bd63ca6..2e7df13fc 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -25,8 +25,8 @@ enum RepairFlag : bool;
typedef void (* PrimOpFun) (EvalState & state, const PosIdx pos, Value * * args, Value & v);
-void printEnvBindings(const Expr &expr, const Env &env);
-void printEnvBindings(const StaticEnv &se, const Env &env, int lvl = 0);
+void printEnvBindings(const SymbolTable &st, const Expr &expr, const Env &env);
+void printEnvBindings(const SymbolTable &st, const StaticEnv &se, const Env &env, int lvl = 0);
struct PrimOp
{
@@ -47,7 +47,7 @@ struct Env
Value * values[0];
};
-valmap * mapStaticEnvBindings(const StaticEnv &se, const Env &env);
+valmap * mapStaticEnvBindings(const SymbolTable &st, const StaticEnv &se, const Env &env);
void copyContext(const Value & v, PathSet & context);
@@ -123,7 +123,7 @@ public:
bool debugStop;
bool debugQuit;
std::list<DebugTrace> debugTraces;
- void debugLastTrace(Error & e);
+ void debugLastTrace(Error & e) const;
private:
SrcToStore srcToStore;
@@ -273,35 +273,66 @@ public:
[[gnu::noinline, gnu::noreturn]]
void throwEvalError(const PosIdx pos, const char * s) const;
[[gnu::noinline, gnu::noreturn]]
- void throwTypeError(const PosIdx pos, const char * s, const Value & v) const;
+ void throwEvalError(const PosIdx pos, const char * s,
+ Env & env, Expr & expr) const;
[[gnu::noinline, gnu::noreturn]]
void throwEvalError(const char * s, const std::string & s2) const;
[[gnu::noinline, gnu::noreturn]]
- void throwEvalError(const PosIdx pos, const Suggestions & suggestions, const char * s,
- const std::string & s2) const;
- [[gnu::noinline, gnu::noreturn]]
void throwEvalError(const PosIdx pos, const char * s, const std::string & s2) const;
[[gnu::noinline, gnu::noreturn]]
- void throwEvalError(const char * s, const std::string & s2, const std::string & s3) const;
+ void throwEvalError(const char * s, const std::string & s2,
+ Env & env, Expr & expr) const;
+ [[gnu::noinline, gnu::noreturn]]
+ void throwEvalError(const PosIdx pos, const char * s, const std::string & s2,
+ Env & env, Expr & expr) const;
+ [[gnu::noinline, gnu::noreturn]]
+ void throwEvalError(const char * s, const std::string & s2, const std::string & s3,
+ Env & env, Expr & expr) const;
+ [[gnu::noinline, gnu::noreturn]]
+ void throwEvalError(const PosIdx pos, const char * s, const std::string & s2, const std::string & s3,
+ Env & env, Expr & expr) const;
[[gnu::noinline, gnu::noreturn]]
void throwEvalError(const PosIdx pos, const char * s, const std::string & s2, const std::string & s3) const;
[[gnu::noinline, gnu::noreturn]]
- void throwEvalError(const PosIdx p1, const char * s, const Symbol sym, const PosIdx p2) const;
+ void throwEvalError(const char * s, const std::string & s2, const std::string & s3) const;
+ [[gnu::noinline, gnu::noreturn]]
+ void throwEvalError(const PosIdx pos, const Suggestions & suggestions, const char * s, const std::string & s2,
+ Env & env, Expr &expr) const;
+ [[gnu::noinline, gnu::noreturn]]
+ void throwEvalError(const PosIdx p1, const char * s, const Symbol sym, const PosIdx p2,
+ Env & env, Expr & expr) const;
+
+ [[gnu::noinline, gnu::noreturn]]
+ void throwTypeError(const PosIdx pos, const char * s, const Value & v) const;
+ [[gnu::noinline, gnu::noreturn]]
+ void throwTypeError(const PosIdx pos, const char * s, const Value & v,
+ Env & env, Expr & expr) const;
[[gnu::noinline, gnu::noreturn]]
void throwTypeError(const PosIdx pos, const char * s) const;
[[gnu::noinline, gnu::noreturn]]
- void throwTypeError(const PosIdx pos, const char * s, const ExprLambda & fun, const Symbol s2) const;
+ void throwTypeError(const PosIdx pos, const char * s,
+ Env & env, Expr & expr) const;
[[gnu::noinline, gnu::noreturn]]
- void throwTypeError(const PosIdx pos, const Suggestions & suggestions, const char * s,
- const ExprLambda & fun, const Symbol s2) const;
+ void throwTypeError(const PosIdx pos, const char * s, const ExprLambda & fun, const Symbol s2,
+ Env & env, Expr & expr) const;
[[gnu::noinline, gnu::noreturn]]
- void throwTypeError(const char * s, const Value & v) const;
+ void throwTypeError(const PosIdx pos, const Suggestions & suggestions, const char * s, const ExprLambda & fun, const Symbol s2,
+ Env & env, Expr & expr) const;
[[gnu::noinline, gnu::noreturn]]
- void throwAssertionError(const PosIdx pos, const char * s, const std::string & s1) const;
+ void throwTypeError(const char * s, const Value & v,
+ Env & env, Expr & expr) const;
+
[[gnu::noinline, gnu::noreturn]]
- void throwUndefinedVarError(const PosIdx pos, const char * s, const std::string & s1) const;
+ void throwAssertionError(const PosIdx pos, const char * s, const std::string & s1,
+ Env & env, Expr & expr) const;
+
[[gnu::noinline, gnu::noreturn]]
- void throwMissingArgumentError(const PosIdx pos, const char * s, const std::string & s1) const;
+ void throwUndefinedVarError(const PosIdx pos, const char * s, const std::string & s1,
+ Env & env, Expr & expr) const;
+
+ [[gnu::noinline, gnu::noreturn]]
+ void throwMissingArgumentError(const PosIdx pos, const char * s, const std::string & s1,
+ Env & env, Expr & expr) const;
[[gnu::noinline]]
void addErrorTrace(Error & e, const char * s, const std::string & s2) const;
@@ -480,7 +511,7 @@ private:
class DebugTraceStacker {
public:
DebugTraceStacker(EvalState &evalState, DebugTrace t);
- ~DebugTraceStacker()
+ ~DebugTraceStacker()
{
// assert(evalState.debugTraces.front() == trace);
evalState.debugTraces.pop_front();
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index efaeba7c6..c6e545729 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -437,11 +437,11 @@ void ExprLambda::bindVars(const EvalState & es, const std::shared_ptr<const Stat
new StaticEnv(
false, env.get(),
(hasFormals() ? formals->formals.size() : 0) +
- (!arg ? 0 : 1));
+ (!arg ? 0 : 1)));
Displacement displ = 0;
- if (arg) newEnv.vars.emplace_back(arg, displ++);
+ if (arg) newEnv->vars.emplace_back(arg, displ++);
if (hasFormals()) {
for (auto & i : formals->formals)
@@ -506,7 +506,7 @@ void ExprWith::bindVars(const EvalState & es, const std::shared_ptr<const Static
staticenv = env;
attrs->bindVars(es, env);
- StaticEnv newEnv(true, &env);
+ auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(true, env.get()));
body->bindVars(es, newEnv);
}
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index d275a51e9..82fff6dcf 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -278,7 +278,12 @@ struct ExprList : Expr
{
std::vector<Expr *> elems;
ExprList() { };
- const PosIdx getPos() const { return pos; }
+ const PosIdx getPos() const
+ { if (elems.empty())
+ return noPos;
+ else
+ return elems.front()->getPos();
+ }
COMMON_METHODS
};
@@ -389,7 +394,7 @@ struct ExprOpNot : Expr
{
Expr * e;
ExprOpNot(Expr * e) : e(e) { };
- const Pos* getPos() const { return 0; }
+ const PosIdx getPos() const { return noPos; }
COMMON_METHODS
};
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 212ce3de9..e2267d154 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -774,12 +774,14 @@ static RegisterPrimOp primop_break({
.doc = R"(
In debug mode, pause Nix expression evaluation and enter the repl.
)",
- .fun = [](EvalState & state, const Pos & pos, Value * * args, Value & v)
+ .fun = [](EvalState & state, const PosIdx pos, Value * * args, Value & v)
{
+ PathSet context;
+ auto s = state.coerceToString(pos, *args[0], context).toOwned();
auto error = Error(ErrorInfo{
.level = lvlInfo,
- .msg = hintfmt("breakpoint reached; value was %1%", *args[0]),
- .errPos = pos,
+ .msg = hintfmt("breakpoint reached; value was %1%", s),
+ .errPos = state.positions[pos],
});
if (debuggerHook && !state.debugTraces.empty())
{
@@ -791,7 +793,7 @@ static RegisterPrimOp primop_break({
throw Error(ErrorInfo{
.level = lvlInfo,
.msg = hintfmt("quit from debugger"),
- .errPos = noPos,
+ .errPos = state.positions[noPos],
});
}
From ca6cba8b81502450f8e377112ce11303ccedc760 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Fri, 29 Apr 2022 10:51:10 -0600
Subject: [PATCH 112/188] fix 'suggestions' error
---
src/libexpr/eval.cc | 28 +---------------------------
1 file changed, 1 insertion(+), 27 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 7058d117f..294168392 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -866,7 +866,7 @@ void EvalState::throwEvalError(const char * s, const std::string & s2) const
void EvalState::throwEvalError(const PosIdx pos, const Suggestions & suggestions, const char * s,
const std::string & s2, Env & env, Expr &expr) const
{
- auto error = EvalError({
+ auto error = EvalError(ErrorInfo{
.msg = hintfmt(s, s2),
.errPos = positions[pos],
.suggestions = suggestions,
@@ -944,32 +944,6 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::stri
throw error;
}
-/*
-LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const std::string & s2, const std::string & s3, EvalState &evalState))
-{
- auto error = EvalError({
- .msg = hintfmt(s, s2, s3),
- .errPos = positions[pos]
- });
-
- evalState.debugLastTrace(error);
-
- throw error;
-}
-
-LocalNoInlineNoReturn(void throwEvalError(const char * s, const std::string & s2, const std::string & s3, EvalState &evalState))
-{
- auto error = EvalError({
- .msg = hintfmt(s, s2, s3),
- .errPos = noPos
- });
-
- evalState.debugLastTrace(error);
-
- throw error;
-}
-*/
-
void EvalState::throwEvalError(const PosIdx p1, const char * s, const Symbol sym, const PosIdx p2, Env & env, Expr &expr) const
{
// p1 is where the error occurred; p2 is a position mentioned in the message.
From 172a83d22a3c984b6b569b5528d2338059bb748b Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Fri, 29 Apr 2022 11:24:54 -0600
Subject: [PATCH 113/188] line endings
---
src/libcmd/command.cc | 2 +-
src/libcmd/repl.cc | 10 +++++-----
src/libexpr/eval.cc | 12 ++++++------
src/libexpr/nixexpr.cc | 4 ++--
4 files changed, 14 insertions(+), 14 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 3e789adba..56d529461 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -125,7 +125,7 @@ ref<EvalState> EvalCommand::getEvalState()
std::unique_ptr<DebugTraceStacker>(
new DebugTraceStacker(
*evalState,
- DebugTrace
+ DebugTrace
{.pos = (error->info().errPos ? *error->info().errPos : evalState->positions[expr.getPos()]),
.expr = expr,
.env = env,
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 40299e910..b94831064 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -276,10 +276,10 @@ void NixRepl::mainLoop(const std::vector<std::string> & files)
printMsg(lvlError, e.msg());
}
} catch (EvalError & e) {
- // in debugger mode, an EvalError should trigger another repl session.
+ // in debugger mode, an EvalError should trigger another repl session.
// when that session returns the exception will land here. No need to show it again;
// show the error for this repl session instead.
- if (debuggerHook && !this->state->debugTraces.empty())
+ if (debuggerHook && !this->state->debugTraces.empty())
showDebugTrace(std::cout, this->state->positions, this->state->debugTraces.front());
else
printMsg(lvlError, e.msg());
@@ -511,7 +511,7 @@ bool NixRepl::processLine(std::string line)
if (arg == "stack") {
int idx = 0;
for (auto iter = this->state->debugTraces.begin();
- iter != this->state->debugTraces.end();
+ iter != this->state->debugTraces.end();
++iter, ++idx) {
std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
showDebugTrace(std::cout, this->state->positions, *iter);
@@ -519,7 +519,7 @@ bool NixRepl::processLine(std::string line)
} else if (arg == "env") {
int idx = 0;
for (auto iter = this->state->debugTraces.begin();
- iter != this->state->debugTraces.end();
+ iter != this->state->debugTraces.end();
++iter, ++idx) {
if (idx == this->debugTraceIndex)
{
@@ -539,7 +539,7 @@ bool NixRepl::processLine(std::string line)
int idx = 0;
for (auto iter = this->state->debugTraces.begin();
- iter != this->state->debugTraces.end();
+ iter != this->state->debugTraces.end();
++iter, ++idx) {
if (idx == this->debugTraceIndex)
{
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 294168392..10dba69e7 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -730,7 +730,7 @@ void printWithBindings(const SymbolTable &st, const Env &env)
{
if (env.type == Env::HasWithAttrs)
{
- std::cout << "with: ";
+ std::cout << "with: ";
std::cout << ANSI_MAGENTA;
Bindings::iterator j = env.values[0]->attrs->begin();
while (j != env.values[0]->attrs->end()) {
@@ -747,13 +747,13 @@ void printEnvBindings(const SymbolTable &st, const StaticEnv &se, const Env &env
std::cout << "Env level " << lvl << std::endl;
if (se.up && env.up) {
- std::cout << "static: ";
+ std::cout << "static: ";
printStaticEnvBindings(st, se);
printWithBindings(st, env);
std::cout << std::endl;
printEnvBindings(st, *se.up, *env.up, ++lvl);
}
- else
+ else
{
std::cout << ANSI_MAGENTA;
// for the top level, don't print the double underscore ones; they are in builtins.
@@ -784,7 +784,7 @@ void mapStaticEnvBindings(const SymbolTable &st, const StaticEnv &se, const Env
{
// add bindings for the next level up first, so that the bindings for this level
// override the higher levels.
- // The top level bindings (builtins) are skipped since they are added for us by initEnv()
+ // The top level bindings (builtins) are skipped since they are added for us by initEnv()
if (env.up && se.up) {
mapStaticEnvBindings(st, *se.up, *env.up, vm);
@@ -1086,13 +1086,13 @@ void EvalState::addErrorTrace(Error & e, const PosIdx pos, const char * s, const
e.addTrace(positions[pos], s, s2);
}
-std::unique_ptr<DebugTraceStacker> makeDebugTraceStacker(EvalState &state, Expr &expr, Env &env,
+std::unique_ptr<DebugTraceStacker> makeDebugTraceStacker(EvalState &state, Expr &expr, Env &env,
std::optional<ErrPos> pos, const char * s, const std::string & s2)
{
return std::unique_ptr<DebugTraceStacker>(
new DebugTraceStacker(
state,
- DebugTrace
+ DebugTrace
{.pos = pos,
.expr = expr,
.env = env,
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index c6e545729..5624c4780 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -352,7 +352,7 @@ void ExprVar::bindVars(const EvalState & es, const std::shared_ptr<const StaticE
/* Otherwise, the variable must be obtained from the nearest
enclosing `with'. If there is no `with', then we can issue an
"undefined variable" error now. */
- if (withLevel == -1)
+ if (withLevel == -1)
{
throw UndefinedVarError({
.msg = hintfmt("undefined variable '%1%'", es.symbols[name]),
@@ -392,7 +392,7 @@ void ExprAttrs::bindVars(const EvalState & es, const std::shared_ptr<const Stati
staticenv = env;
if (recursive) {
- auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, env.get(), recursive ? attrs.size() : 0));
+ auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, env.get(), recursive ? attrs.size() : 0));
Displacement displ = 0;
for (auto & i : attrs)
From c94180386182c8cd9e2a4a8053afb5938940c1d2 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Fri, 29 Apr 2022 11:27:38 -0600
Subject: [PATCH 114/188] spacing
---
src/libutil/error.hh | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/libutil/error.hh b/src/libutil/error.hh
index 6eb80fb9e..a53e9802e 100644
--- a/src/libutil/error.hh
+++ b/src/libutil/error.hh
@@ -99,6 +99,7 @@ struct ErrPos {
};
std::optional<LinesOfCode> getCodeLines(const ErrPos & errPos);
+
void printCodeLines(std::ostream & out,
const std::string & prefix,
const ErrPos & errPos,
@@ -106,7 +107,6 @@ void printCodeLines(std::ostream & out,
void printAtPos(const ErrPos & pos, std::ostream & out);
-
struct Trace {
std::optional<ErrPos> pos;
hintformat hint;
From c81ffa692e56cd8a1069aea95159008a342e0f46 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Fri, 29 Apr 2022 11:35:50 -0600
Subject: [PATCH 115/188] remove 'libnix'
---
src/libcmd/local.mk | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/libcmd/local.mk b/src/libcmd/local.mk
index 73a1a1086..3a4de6bcb 100644
--- a/src/libcmd/local.mk
+++ b/src/libcmd/local.mk
@@ -10,6 +10,6 @@ libcmd_CXXFLAGS += -I src/libutil -I src/libstore -I src/libexpr -I src/libmain
libcmd_LDFLAGS = $(EDITLINE_LIBS) -llowdown -pthread
-libcmd_LIBS = libstore libutil libexpr libmain libfetchers libnix
+libcmd_LIBS = libstore libutil libexpr libmain libfetchers
$(eval $(call install-file-in, $(d)/nix-cmd.pc, $(libdir)/pkgconfig, 0644))
From 240124f7b1761073c4db24305a5decdeb597f549 Mon Sep 17 00:00:00 2001
From: "Travis A. Everett" <travis.a.everett@gmail.com>
Date: Wed, 4 May 2022 16:55:59 -0500
Subject: [PATCH 116/188] darwin-install: fix break from bad vimrc
It looks like the `--noplugin` flag added in #5489 wasn't enough to
skirt this class of vim-init error, so this is swing 2 at a full fix.
Fixes #6462.
---
scripts/create-darwin-volume.sh | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/scripts/create-darwin-volume.sh b/scripts/create-darwin-volume.sh
index 4bac4b7ba..aee7ff4bf 100755
--- a/scripts/create-darwin-volume.sh
+++ b/scripts/create-darwin-volume.sh
@@ -442,9 +442,13 @@ add_nix_vol_fstab_line() {
local escaped_mountpoint="${NIX_ROOT/ /'\\\'040}"
shift
- # wrap `ex` to work around a problem with vim plugins breaking exit codes;
- # (see https://github.com/NixOS/nix/issues/5468)
- # we'd prefer EDITOR="/usr/bin/ex --noplugin" but vifs doesn't word-split
+ # wrap `ex` to work around a problem with vim plugins breaking exit codes
+ # (see github.com/NixOS/nix/issues/5468)
+ #
+ # the first draft used `--noplugin`, but github.com/NixOS/nix/issues/6462
+ # suggests we need the less-semantic `-u NONE`
+ #
+ # we'd prefer EDITOR="/usr/bin/ex -u NONE" but vifs doesn't word-split
# the EDITOR env.
#
# TODO: at some point we should switch to `--clean`, but it wasn't added
@@ -452,7 +456,7 @@ add_nix_vol_fstab_line() {
# minver 10.12.6 seems to have released with vim 7.4
cat > "$SCRATCH/ex_cleanroom_wrapper" <<EOF
#!/bin/sh
-/usr/bin/ex --noplugin "\$@"
+/usr/bin/ex -u NONE "\$@"
EOF
chmod 755 "$SCRATCH/ex_cleanroom_wrapper"
@@ -646,8 +650,9 @@ EOF
task "Configuring /etc/synthetic.conf to make a mount-point at $NIX_ROOT" >&2
# technically /etc/synthetic.d/nix is supported in Big Sur+
# but handling both takes even more code...
+ # Note: `-u NONE` disables vim plugins/rc; see note on --clean earlier
_sudo "to add Nix to /etc/synthetic.conf" \
- /usr/bin/ex --noplugin /etc/synthetic.conf <<EOF
+ /usr/bin/ex -u NONE /etc/synthetic.conf <<EOF
:a
${NIX_ROOT:1}
.
@@ -815,7 +820,8 @@ setup_volume_daemon() {
local volume_uuid="$2"
if ! test_voldaemon; then
task "Configuring LaunchDaemon to mount '$NIX_VOLUME_LABEL'" >&2
- _sudo "to install the Nix volume mounter" /usr/bin/ex --noplugin "$NIX_VOLUME_MOUNTD_DEST" <<EOF
+ # Note: `-u NONE` disables vim plugins/rc; see note on --clean earlier
+ _sudo "to install the Nix volume mounter" /usr/bin/ex -u NONE "$NIX_VOLUME_MOUNTD_DEST" <<EOF
:a
$(generate_mount_daemon "$cmd_type" "$volume_uuid")
.
From dd8b91eebc0d31c9f8016609b36d89f58d8c4d19 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Thu, 5 May 2022 12:29:14 +0200
Subject: [PATCH 117/188] Style fixes
In particular, use std::make_shared and enumerate(). Also renamed some
fields to fit naming conventions.
---
src/libcmd/command.cc | 28 +++---
src/libcmd/command.hh | 3 +-
src/libcmd/repl.cc | 85 ++++++----------
src/libexpr/eval.cc | 217 +++++++++++++++++++----------------------
src/libexpr/eval.hh | 33 +++----
src/libexpr/nixexpr.cc | 101 +++++++++----------
src/libexpr/nixexpr.hh | 45 ++++-----
src/libexpr/primops.cc | 40 +++-----
8 files changed, 247 insertions(+), 305 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 56d529461..12cd5ed83 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -121,25 +121,23 @@ ref<EvalState> EvalCommand::getEvalState()
if (startReplOnEvalErrors)
debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error * error, const Env & env, const Expr & expr) {
auto dts =
- error && expr.getPos() ?
- std::unique_ptr<DebugTraceStacker>(
- new DebugTraceStacker(
- *evalState,
- DebugTrace
- {.pos = (error->info().errPos ? *error->info().errPos : evalState->positions[expr.getPos()]),
- .expr = expr,
- .env = env,
- .hint = error->info().msg,
- .is_error = true
- }))
- : nullptr;
+ error && expr.getPos()
+ ? std::make_unique<DebugTraceStacker>(
+ *evalState,
+ DebugTrace {
+ .pos = error->info().errPos ? *error->info().errPos : evalState->positions[expr.getPos()],
+ .expr = expr,
+ .env = env,
+ .hint = error->info().msg,
+ .isError = true
+ })
+ : nullptr;
if (error)
printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error->what());
- if (expr.staticenv)
- {
- std::unique_ptr<valmap> vm(mapStaticEnvBindings(evalState->symbols, *expr.staticenv.get(), env));
+ if (expr.staticEnv) {
+ auto vm = mapStaticEnvBindings(evalState->symbols, *expr.staticEnv.get(), env);
runRepl(evalState, expr, *vm);
}
};
diff --git a/src/libcmd/command.hh b/src/libcmd/command.hh
index db4d4c023..354877bc5 100644
--- a/src/libcmd/command.hh
+++ b/src/libcmd/command.hh
@@ -275,6 +275,7 @@ void printClosureDiff(
void runRepl(
ref<EvalState> evalState,
- const Expr &expr,
+ const Expr & expr,
const std::map<std::string, Value *> & extraEnv);
+
}
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index b94831064..c35f29a2f 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -51,7 +51,7 @@ struct NixRepl
ref<EvalState> state;
Bindings * autoArgs;
- int debugTraceIndex;
+ size_t debugTraceIndex;
Strings loadedFiles;
@@ -79,7 +79,7 @@ struct NixRepl
void addVarToScope(const Symbol name, Value & v);
Expr * parseString(std::string s);
void evalString(std::string s, Value & v);
- void loadDebugTraceEnv(DebugTrace &dt);
+ void loadDebugTraceEnv(DebugTrace & dt);
typedef std::set<Value *> ValuesSeen;
std::ostream & printValue(std::ostream & str, Value & v, unsigned int maxDepth);
@@ -203,15 +203,16 @@ namespace {
}
}
-std::ostream& showDebugTrace(std::ostream &out, const PosTable &positions, const DebugTrace &dt)
+static std::ostream & showDebugTrace(std::ostream & out, const PosTable & positions, const DebugTrace & dt)
{
- if (dt.is_error)
+ if (dt.isError)
out << ANSI_RED "error: " << ANSI_NORMAL;
out << dt.hint.str() << "\n";
// prefer direct pos, but if noPos then try the expr.
- auto pos = (*dt.pos ? *dt.pos :
- positions[(dt.expr.getPos() ? dt.expr.getPos() : noPos)]);
+ auto pos = *dt.pos
+ ? *dt.pos
+ : positions[dt.expr.getPos() ? dt.expr.getPos() : noPos];
if (pos) {
printAtPos(pos, out);
@@ -258,8 +259,7 @@ void NixRepl::mainLoop(const std::vector<std::string> & files)
while (true) {
// When continuing input from previous lines, don't print a prompt, just align to the same
// number of chars as the prompt.
- if (!getLine(input, input.empty() ? "nix-repl> " : " "))
- {
+ if (!getLine(input, input.empty() ? "nix-repl> " : " ")) {
// ctrl-D should exit the debugger.
state->debugStop = false;
state->debugQuit = true;
@@ -279,8 +279,8 @@ void NixRepl::mainLoop(const std::vector<std::string> & files)
// in debugger mode, an EvalError should trigger another repl session.
// when that session returns the exception will land here. No need to show it again;
// show the error for this repl session instead.
- if (debuggerHook && !this->state->debugTraces.empty())
- showDebugTrace(std::cout, this->state->positions, this->state->debugTraces.front());
+ if (debuggerHook && !state->debugTraces.empty())
+ showDebugTrace(std::cout, state->positions, state->debugTraces.front());
else
printMsg(lvlError, e.msg());
} catch (Error & e) {
@@ -437,22 +437,16 @@ StorePath NixRepl::getDerivationPath(Value & v) {
return *drvPath;
}
-void NixRepl::loadDebugTraceEnv(DebugTrace &dt)
+void NixRepl::loadDebugTraceEnv(DebugTrace & dt)
{
- if (dt.expr.staticenv)
- {
- initEnv();
+ initEnv();
- auto vm = std::make_unique<valmap>(*(mapStaticEnvBindings(this->state->symbols, *dt.expr.staticenv.get(), dt.env)));
+ if (dt.expr.staticEnv) {
+ auto vm = mapStaticEnvBindings(state->symbols, *dt.expr.staticEnv.get(), dt.env);
// add staticenv vars.
- for (auto & [name, value] : *(vm.get())) {
- this->addVarToScope(this->state->symbols.create(name), *value);
- }
- }
- else
- {
- initEnv();
+ for (auto & [name, value] : *(vm.get()))
+ addVarToScope(state->symbols.create(name), *value);
}
}
@@ -509,45 +503,31 @@ bool NixRepl::processLine(std::string line)
else if (command == ":d" || command == ":debug") {
if (arg == "stack") {
- int idx = 0;
- for (auto iter = this->state->debugTraces.begin();
- iter != this->state->debugTraces.end();
- ++iter, ++idx) {
- std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
- showDebugTrace(std::cout, this->state->positions, *iter);
+ for (const auto & [idx, i] : enumerate(state->debugTraces)) {
+ std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
+ showDebugTrace(std::cout, state->positions, i);
}
} else if (arg == "env") {
- int idx = 0;
- for (auto iter = this->state->debugTraces.begin();
- iter != this->state->debugTraces.end();
- ++iter, ++idx) {
- if (idx == this->debugTraceIndex)
- {
- printEnvBindings(state->symbols,iter->expr, iter->env);
- break;
- }
+ for (const auto & [idx, i] : enumerate(state->debugTraces)) {
+ if (idx == debugTraceIndex) {
+ printEnvBindings(state->symbols, i.expr, i.env);
+ break;
+ }
}
}
- else if (arg.compare(0,4,"show") == 0) {
+ else if (arg.compare(0, 4, "show") == 0) {
try {
// change the DebugTrace index.
debugTraceIndex = stoi(arg.substr(4));
- }
- catch (...)
- {
- }
+ } catch (...) { }
- int idx = 0;
- for (auto iter = this->state->debugTraces.begin();
- iter != this->state->debugTraces.end();
- ++iter, ++idx) {
- if (idx == this->debugTraceIndex)
- {
+ for (const auto & [idx, i] : enumerate(state->debugTraces)) {
+ if (idx == debugTraceIndex) {
std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
- showDebugTrace(std::cout, this->state->positions, *iter);
+ showDebugTrace(std::cout, state->positions, i);
std::cout << std::endl;
- printEnvBindings(state->symbols,iter->expr, iter->env);
- loadDebugTraceEnv(*iter);
+ printEnvBindings(state->symbols, i.expr, i.env);
+ loadDebugTraceEnv(i);
break;
}
}
@@ -1032,9 +1012,8 @@ void runRepl(
repl->initEnv();
// add 'extra' vars.
- for (auto & [name, value] : extraEnv) {
+ for (auto & [name, value] : extraEnv)
repl->addVarToScope(repl->state->symbols.create(name), *value);
- }
repl->mainLoop({});
}
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 10dba69e7..ca0eec6e3 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -466,7 +466,7 @@ EvalState::EvalState(
, env1AllocCache(std::make_shared<void *>(nullptr))
#endif
, baseEnv(allocEnv(128))
- , staticBaseEnv(new StaticEnv(false, 0))
+ , staticBaseEnv{std::make_shared<StaticEnv>(false, nullptr)}
{
countCalls = getEnv("NIX_COUNT_CALLS").value_or("0") != "0";
@@ -524,7 +524,7 @@ void EvalState::allowPath(const StorePath & storePath)
allowedPaths->insert(store->toRealPath(storePath));
}
-void EvalState::allowAndSetStorePathString(const StorePath &storePath, Value & v)
+void EvalState::allowAndSetStorePathString(const StorePath & storePath, Value & v)
{
allowPath(storePath);
@@ -714,22 +714,19 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
// just for the current level of StaticEnv, not the whole chain.
-void printStaticEnvBindings(const SymbolTable &st, const StaticEnv &se)
+void printStaticEnvBindings(const SymbolTable & st, const StaticEnv & se)
{
std::cout << ANSI_MAGENTA;
- for (auto i = se.vars.begin(); i != se.vars.end(); ++i)
- {
- std::cout << st[i->first] << " ";
- }
+ for (auto & i : se.vars)
+ std::cout << st[i.first] << " ";
std::cout << ANSI_NORMAL;
std::cout << std::endl;
}
// just for the current level of Env, not the whole chain.
-void printWithBindings(const SymbolTable &st, const Env &env)
+void printWithBindings(const SymbolTable & st, const Env & env)
{
- if (env.type == Env::HasWithAttrs)
- {
+ if (env.type == Env::HasWithAttrs) {
std::cout << "with: ";
std::cout << ANSI_MAGENTA;
Bindings::iterator j = env.values[0]->attrs->begin();
@@ -742,7 +739,7 @@ void printWithBindings(const SymbolTable &st, const Env &env)
}
}
-void printEnvBindings(const SymbolTable &st, const StaticEnv &se, const Env &env, int lvl)
+void printEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env, int lvl)
{
std::cout << "Env level " << lvl << std::endl;
@@ -752,16 +749,13 @@ void printEnvBindings(const SymbolTable &st, const StaticEnv &se, const Env &env
printWithBindings(st, env);
std::cout << std::endl;
printEnvBindings(st, *se.up, *env.up, ++lvl);
- }
- else
- {
+ } else {
std::cout << ANSI_MAGENTA;
- // for the top level, don't print the double underscore ones; they are in builtins.
- for (auto i = se.vars.begin(); i != se.vars.end(); ++i)
- {
- if (((std::string)st[i->first]).substr(0,2) != "__")
- std::cout << st[i->first] << " ";
- }
+ // for the top level, don't print the double underscore ones;
+ // they are in builtins.
+ for (auto & i : se.vars)
+ if (!hasPrefix(st[i.first], "__"))
+ std::cout << st[i.first] << " ";
std::cout << ANSI_NORMAL;
std::cout << std::endl;
printWithBindings(st, env); // probably nothing there for the top level.
@@ -771,56 +765,50 @@ void printEnvBindings(const SymbolTable &st, const StaticEnv &se, const Env &env
}
// TODO: add accompanying env for With stuff.
-void printEnvBindings(const SymbolTable &st, const Expr &expr, const Env &env)
+void printEnvBindings(const SymbolTable & st, const Expr & expr, const Env & env)
{
// just print the names for now
- if (expr.staticenv)
- {
- printEnvBindings(st, *expr.staticenv.get(), env, 0);
+ if (expr.staticEnv)
+ printEnvBindings(st, *expr.staticEnv.get(), env, 0);
+}
+
+void mapStaticEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env, valmap & vm)
+{
+ // add bindings for the next level up first, so that the bindings for this level
+ // override the higher levels.
+ // The top level bindings (builtins) are skipped since they are added for us by initEnv()
+ if (env.up && se.up) {
+ mapStaticEnvBindings(st, *se.up, *env.up, vm);
+
+ if (env.type == Env::HasWithAttrs) {
+ // add 'with' bindings.
+ Bindings::iterator j = env.values[0]->attrs->begin();
+ while (j != env.values[0]->attrs->end()) {
+ vm[st[j->name]] = j->value;
+ ++j;
+ }
+ } else {
+ // iterate through staticenv bindings and add them.
+ for (auto & i : se.vars)
+ vm[st[i.first]] = env.values[i.second];
+ }
}
}
-void mapStaticEnvBindings(const SymbolTable &st, const StaticEnv &se, const Env &env, valmap & vm)
+std::unique_ptr<valmap> mapStaticEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env)
{
- // add bindings for the next level up first, so that the bindings for this level
- // override the higher levels.
- // The top level bindings (builtins) are skipped since they are added for us by initEnv()
- if (env.up && se.up) {
- mapStaticEnvBindings(st, *se.up, *env.up, vm);
-
- if (env.type == Env::HasWithAttrs)
- {
- // add 'with' bindings.
- Bindings::iterator j = env.values[0]->attrs->begin();
- while (j != env.values[0]->attrs->end()) {
- vm[st[j->name]] = j->value;
- ++j;
- }
- }
- else
- {
- // iterate through staticenv bindings and add them.
- for (auto iter = se.vars.begin(); iter != se.vars.end(); ++iter)
- {
- vm[st[iter->first]] = env.values[iter->second];
- }
- }
- }
-}
-
-valmap * mapStaticEnvBindings(const SymbolTable &st,const StaticEnv &se, const Env &env)
-{
- auto vm = new valmap();
+ auto vm = std::make_unique<valmap>();
mapStaticEnvBindings(st, se, env, *vm);
return vm;
}
-
-void EvalState::debugLastTrace(Error & e) const {
- // call this in the situation where Expr and Env are inaccessible. The debugger will start in the last context
- // that's in the DebugTrace stack.
+void EvalState::debugLastTrace(Error & e) const
+{
+ // Call this in the situation where Expr and Env are inaccessible.
+ // The debugger will start in the last context that's in the
+ // DebugTrace stack.
if (debuggerHook && !debugTraces.empty()) {
- const DebugTrace &last = debugTraces.front();
+ const DebugTrace & last = debugTraces.front();
debuggerHook(&e, last.env, last.expr);
}
}
@@ -829,7 +817,7 @@ void EvalState::debugLastTrace(Error & e) const {
of stack space, which is a real killer in the recursive
evaluator. So here are some helper functions for throwing
exceptions. */
-void EvalState::throwEvalError(const PosIdx pos, const char * s, Env & env, Expr &expr) const
+void EvalState::throwEvalError(const PosIdx pos, const char * s, Env & env, Expr & expr) const
{
auto error = EvalError({
.msg = hintfmt(s),
@@ -864,7 +852,7 @@ void EvalState::throwEvalError(const char * s, const std::string & s2) const
}
void EvalState::throwEvalError(const PosIdx pos, const Suggestions & suggestions, const char * s,
- const std::string & s2, Env & env, Expr &expr) const
+ const std::string & s2, Env & env, Expr & expr) const
{
auto error = EvalError(ErrorInfo{
.msg = hintfmt(s, s2),
@@ -890,7 +878,7 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::stri
throw error;
}
-void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::string & s2, Env & env, Expr &expr) const
+void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::string & s2, Env & env, Expr & expr) const
{
auto error = EvalError({
.msg = hintfmt(s, s2),
@@ -900,7 +888,6 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::stri
if (debuggerHook)
debuggerHook(&error, env, expr);
-
throw error;
}
@@ -931,7 +918,7 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::stri
}
void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::string & s2,
- const std::string & s3, Env & env, Expr &expr) const
+ const std::string & s3, Env & env, Expr & expr) const
{
auto error = EvalError({
.msg = hintfmt(s, s2),
@@ -944,7 +931,7 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::stri
throw error;
}
-void EvalState::throwEvalError(const PosIdx p1, const char * s, const Symbol sym, const PosIdx p2, Env & env, Expr &expr) const
+void EvalState::throwEvalError(const PosIdx p1, const char * s, const Symbol sym, const PosIdx p2, Env & env, Expr & expr) const
{
// p1 is where the error occurred; p2 is a position mentioned in the message.
auto error = EvalError({
@@ -970,7 +957,7 @@ void EvalState::throwTypeError(const PosIdx pos, const char * s, const Value & v
throw error;
}
-void EvalState::throwTypeError(const PosIdx pos, const char * s, const Value & v, Env & env, Expr &expr) const
+void EvalState::throwTypeError(const PosIdx pos, const char * s, const Value & v, Env & env, Expr & expr) const
{
auto error = TypeError({
.msg = hintfmt(s, showType(v)),
@@ -1086,27 +1073,31 @@ void EvalState::addErrorTrace(Error & e, const PosIdx pos, const char * s, const
e.addTrace(positions[pos], s, s2);
}
-std::unique_ptr<DebugTraceStacker> makeDebugTraceStacker(EvalState &state, Expr &expr, Env &env,
- std::optional<ErrPos> pos, const char * s, const std::string & s2)
+static std::unique_ptr<DebugTraceStacker> makeDebugTraceStacker(
+ EvalState & state,
+ Expr & expr,
+ Env & env,
+ std::optional<ErrPos> pos,
+ const char * s,
+ const std::string & s2)
{
- return std::unique_ptr<DebugTraceStacker>(
- new DebugTraceStacker(
- state,
- DebugTrace
- {.pos = pos,
- .expr = expr,
- .env = env,
- .hint = hintfmt(s, s2),
- .is_error = false
- }));
+ return std::make_unique<DebugTraceStacker>(state,
+ DebugTrace {
+ .pos = pos,
+ .expr = expr,
+ .env = env,
+ .hint = hintfmt(s, s2),
+ .isError = false
+ });
}
-DebugTraceStacker::DebugTraceStacker(EvalState &evalState, DebugTrace t)
-:evalState(evalState), trace(t)
+DebugTraceStacker::DebugTraceStacker(EvalState & evalState, DebugTrace t)
+ : evalState(evalState)
+ , trace(std::move(t))
{
- evalState.debugTraces.push_front(t);
+ evalState.debugTraces.push_front(trace);
if (evalState.debugStop && debuggerHook)
- debuggerHook(0, t.env, t.expr);
+ debuggerHook(nullptr, trace.env, trace.expr);
}
void Value::mkString(std::string_view s)
@@ -1303,15 +1294,14 @@ void EvalState::cacheFile(
fileParseCache[resolvedPath] = e;
try {
- auto dts =
- debuggerHook ?
- makeDebugTraceStacker(
- *this,
- *e,
- this->baseEnv,
- (e->getPos() ? std::optional(ErrPos(positions[e->getPos()])) : std::nullopt),
- "while evaluating the file '%1%':", resolvedPath)
- : nullptr;
+ auto dts = debuggerHook
+ ? makeDebugTraceStacker(
+ *this,
+ *e,
+ this->baseEnv,
+ e->getPos() ? std::optional(ErrPos(positions[e->getPos()])) : std::nullopt,
+ "while evaluating the file '%1%':", resolvedPath)
+ : nullptr;
// Enforce that 'flake.nix' is a direct attrset, not a
// computation.
@@ -1538,15 +1528,14 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
e->eval(state, env, vTmp);
try {
- auto dts =
- debuggerHook ?
- makeDebugTraceStacker(
- state,
- *this,
- env,
- state.positions[pos2],
- "while evaluating the attribute '%1%'",
- showAttrPath(state, env, attrPath))
+ auto dts = debuggerHook
+ ? makeDebugTraceStacker(
+ state,
+ *this,
+ env,
+ state.positions[pos2],
+ "while evaluating the attribute '%1%'",
+ showAttrPath(state, env, attrPath))
: nullptr;
for (auto & i : attrPath) {
@@ -1708,14 +1697,14 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
/* Evaluate the body. */
try {
- auto dts =
- debuggerHook ?
- makeDebugTraceStacker(*this, *lambda.body, env2, positions[lambda.pos],
- "while evaluating %s",
- (lambda.name
- ? concatStrings("'", symbols[lambda.name], "'")
- : "anonymous lambda"))
- : nullptr;
+ auto dts = debuggerHook
+ ? makeDebugTraceStacker(
+ *this, *lambda.body, env2, positions[lambda.pos],
+ "while evaluating %s",
+ lambda.name
+ ? concatStrings("'", symbols[lambda.name], "'")
+ : "anonymous lambda")
+ : nullptr;
lambda.body->eval(*this, env2, vCur);
} catch (Error & e) {
@@ -2135,14 +2124,10 @@ void EvalState::forceValueDeep(Value & v)
if (v.type() == nAttrs) {
for (auto & i : *v.attrs)
try {
-
- auto dts =
- debuggerHook ?
- // if the value is a thunk, we're evaling. otherwise no trace necessary.
- (i.value->isThunk() ?
- makeDebugTraceStacker(*this, *v.thunk.expr, *v.thunk.env, positions[i.pos],
- "while evaluating the attribute '%1%'", symbols[i.name])
- : nullptr)
+ // If the value is a thunk, we're evaling. Otherwise no trace necessary.
+ auto dts = debuggerHook && i.value->isThunk()
+ ? makeDebugTraceStacker(*this, *v.thunk.expr, *v.thunk.env, positions[i.pos],
+ "while evaluating the attribute '%1%'", symbols[i.name])
: nullptr;
recurse(*i.value);
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 2e7df13fc..f3852e248 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -25,8 +25,8 @@ enum RepairFlag : bool;
typedef void (* PrimOpFun) (EvalState & state, const PosIdx pos, Value * * args, Value & v);
-void printEnvBindings(const SymbolTable &st, const Expr &expr, const Env &env);
-void printEnvBindings(const SymbolTable &st, const StaticEnv &se, const Env &env, int lvl = 0);
+void printEnvBindings(const SymbolTable & st, const Expr & expr, const Env & env);
+void printEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env, int lvl = 0);
struct PrimOp
{
@@ -47,7 +47,7 @@ struct Env
Value * values[0];
};
-valmap * mapStaticEnvBindings(const SymbolTable &st, const StaticEnv &se, const Env &env);
+std::unique_ptr<valmap> mapStaticEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env);
void copyContext(const Value & v, PathSet & context);
@@ -75,10 +75,10 @@ std::shared_ptr<RegexCache> makeRegexCache();
struct DebugTrace {
std::optional<ErrPos> pos;
- const Expr &expr;
- const Env &env;
+ const Expr & expr;
+ const Env & env;
hintformat hint;
- bool is_error;
+ bool isError;
};
class EvalState
@@ -297,7 +297,7 @@ public:
void throwEvalError(const char * s, const std::string & s2, const std::string & s3) const;
[[gnu::noinline, gnu::noreturn]]
void throwEvalError(const PosIdx pos, const Suggestions & suggestions, const char * s, const std::string & s2,
- Env & env, Expr &expr) const;
+ Env & env, Expr & expr) const;
[[gnu::noinline, gnu::noreturn]]
void throwEvalError(const PosIdx p1, const char * s, const Symbol sym, const PosIdx p2,
Env & env, Expr & expr) const;
@@ -508,16 +508,15 @@ private:
friend struct Value;
};
-class DebugTraceStacker {
- public:
- DebugTraceStacker(EvalState &evalState, DebugTrace t);
- ~DebugTraceStacker()
- {
- // assert(evalState.debugTraces.front() == trace);
- evalState.debugTraces.pop_front();
- }
- EvalState &evalState;
- DebugTrace trace;
+struct DebugTraceStacker {
+ DebugTraceStacker(EvalState & evalState, DebugTrace t);
+ ~DebugTraceStacker()
+ {
+ // assert(evalState.debugTraces.front() == trace);
+ evalState.debugTraces.pop_front();
+ }
+ EvalState & evalState;
+ DebugTrace trace;
};
/* Return a string representing the type of the value `v'. */
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index 5624c4780..213cf93fa 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -296,39 +296,38 @@ std::string showAttrPath(const SymbolTable & symbols, const AttrPath & attrPath)
/* Computing levels/displacements for variables. */
-void Expr::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> &env)
+void Expr::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
abort();
}
-void ExprInt::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> &env)
+void ExprInt::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticenv = env;
+ staticEnv = env;}
+
+void ExprFloat::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
+{
+ if (debuggerHook)
+ staticEnv = env;
}
-void ExprFloat::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> &env)
+void ExprString::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticenv = env;
+ staticEnv = env;
}
-void ExprString::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> &env)
+void ExprPath::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticenv = env;
+ staticEnv = env;
}
-void ExprPath::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> &env)
+void ExprVar::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticenv = env;
-}
-
-void ExprVar::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> &env)
-{
- if (debuggerHook)
- staticenv = env;
+ staticEnv = env;
/* Check whether the variable appears in the environment. If so,
set its level and displacement. */
@@ -353,20 +352,18 @@ void ExprVar::bindVars(const EvalState & es, const std::shared_ptr<const StaticE
enclosing `with'. If there is no `with', then we can issue an
"undefined variable" error now. */
if (withLevel == -1)
- {
throw UndefinedVarError({
.msg = hintfmt("undefined variable '%1%'", es.symbols[name]),
.errPos = es.positions[pos]
});
- }
fromWith = true;
this->level = withLevel;
}
-void ExprSelect::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> &env)
+void ExprSelect::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticenv = env;
+ staticEnv = env;
e->bindVars(es, env);
if (def) def->bindVars(es, env);
@@ -375,10 +372,10 @@ void ExprSelect::bindVars(const EvalState & es, const std::shared_ptr<const Stat
i.expr->bindVars(es, env);
}
-void ExprOpHasAttr::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> &env)
+void ExprOpHasAttr::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticenv = env;
+ staticEnv = env;
e->bindVars(es, env);
for (auto & i : attrPath)
@@ -386,13 +383,13 @@ void ExprOpHasAttr::bindVars(const EvalState & es, const std::shared_ptr<const S
i.expr->bindVars(es, env);
}
-void ExprAttrs::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> &env)
+void ExprAttrs::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticenv = env;
+ staticEnv = env;
if (recursive) {
- auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, env.get(), recursive ? attrs.size() : 0));
+ auto newEnv = std::make_shared<StaticEnv>(false, env.get(), recursive ? attrs.size() : 0);
Displacement displ = 0;
for (auto & i : attrs)
@@ -419,25 +416,24 @@ void ExprAttrs::bindVars(const EvalState & es, const std::shared_ptr<const Stati
}
}
-void ExprList::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> &env)
+void ExprList::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticenv = env;
+ staticEnv = env;
for (auto & i : elems)
i->bindVars(es, env);
}
-void ExprLambda::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> &env)
+void ExprLambda::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticenv = env;
+ staticEnv = env;
- auto newEnv = std::shared_ptr<StaticEnv>(
- new StaticEnv(
- false, env.get(),
- (hasFormals() ? formals->formals.size() : 0) +
- (!arg ? 0 : 1)));
+ auto newEnv = std::make_shared<StaticEnv>(
+ false, env.get(),
+ (hasFormals() ? formals->formals.size() : 0) +
+ (!arg ? 0 : 1));
Displacement displ = 0;
@@ -456,22 +452,22 @@ void ExprLambda::bindVars(const EvalState & es, const std::shared_ptr<const Stat
body->bindVars(es, newEnv);
}
-void ExprCall::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> &env)
+void ExprCall::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticenv = env;
+ staticEnv = env;
fun->bindVars(es, env);
for (auto e : args)
e->bindVars(es, env);
}
-void ExprLet::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> &env)
+void ExprLet::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticenv = env;
+ staticEnv = env;
- auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, env.get(), attrs->attrs.size()));
+ auto newEnv = std::make_shared<StaticEnv>(false, env.get(), attrs->attrs.size());
Displacement displ = 0;
for (auto & i : attrs->attrs)
@@ -485,10 +481,10 @@ void ExprLet::bindVars(const EvalState & es, const std::shared_ptr<const StaticE
body->bindVars(es, newEnv);
}
-void ExprWith::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> &env)
+void ExprWith::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticenv = env;
+ staticEnv = env;
/* Does this `with' have an enclosing `with'? If so, record its
level so that `lookupVar' can look up variables in the previous
@@ -503,54 +499,53 @@ void ExprWith::bindVars(const EvalState & es, const std::shared_ptr<const Static
}
if (debuggerHook)
- staticenv = env;
+ staticEnv = env;
attrs->bindVars(es, env);
- auto newEnv = std::shared_ptr<StaticEnv>(new StaticEnv(true, env.get()));
+ auto newEnv = std::make_shared<StaticEnv>(true, env.get());
body->bindVars(es, newEnv);
}
-void ExprIf::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> &env)
+void ExprIf::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticenv = env;
+ staticEnv = env;
cond->bindVars(es, env);
then->bindVars(es, env);
else_->bindVars(es, env);
}
-void ExprAssert::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> &env)
+void ExprAssert::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticenv = env;
+ staticEnv = env;
cond->bindVars(es, env);
body->bindVars(es, env);
}
-void ExprOpNot::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> &env)
+void ExprOpNot::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticenv = env;
+ staticEnv = env;
e->bindVars(es, env);
}
-void ExprConcatStrings::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> &env)
+void ExprConcatStrings::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticenv = env;
+ staticEnv = env;
for (auto & i : *this->es)
i.second->bindVars(es, env);
}
-void ExprPos::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> &env)
+void ExprPos::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticenv = env;
-
+ staticEnv = env;
}
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index 82fff6dcf..c4a509f31 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -148,8 +148,8 @@ struct Expr
virtual void eval(EvalState & state, Env & env, Value & v);
virtual Value * maybeThunk(EvalState & state, Env & env);
virtual void setName(Symbol name);
- std::shared_ptr<const StaticEnv> staticenv;
- virtual const PosIdx getPos() const = 0;
+ std::shared_ptr<const StaticEnv> staticEnv;
+ virtual PosIdx getPos() const { return noPos; }
};
#define COMMON_METHODS \
@@ -163,7 +163,6 @@ struct ExprInt : Expr
Value v;
ExprInt(NixInt n) : n(n) { v.mkInt(n); };
Value * maybeThunk(EvalState & state, Env & env);
- const PosIdx getPos() const { return noPos; }
COMMON_METHODS
};
@@ -173,7 +172,6 @@ struct ExprFloat : Expr
Value v;
ExprFloat(NixFloat nf) : nf(nf) { v.mkFloat(nf); };
Value * maybeThunk(EvalState & state, Env & env);
- const PosIdx getPos() const { return noPos; }
COMMON_METHODS
};
@@ -183,7 +181,6 @@ struct ExprString : Expr
Value v;
ExprString(std::string s) : s(std::move(s)) { v.mkString(this->s.data()); };
Value * maybeThunk(EvalState & state, Env & env);
- const PosIdx getPos() const { return noPos; }
COMMON_METHODS
};
@@ -193,7 +190,6 @@ struct ExprPath : Expr
Value v;
ExprPath(std::string s) : s(std::move(s)) { v.mkPath(this->s.c_str()); };
Value * maybeThunk(EvalState & state, Env & env);
- const PosIdx getPos() const { return noPos; }
COMMON_METHODS
};
@@ -221,7 +217,7 @@ struct ExprVar : Expr
ExprVar(Symbol name) : name(name) { };
ExprVar(const PosIdx & pos, Symbol name) : pos(pos), name(name) { };
Value * maybeThunk(EvalState & state, Env & env);
- const PosIdx getPos() const { return pos; }
+ PosIdx getPos() const override { return pos; }
COMMON_METHODS
};
@@ -232,7 +228,7 @@ struct ExprSelect : Expr
AttrPath attrPath;
ExprSelect(const PosIdx & pos, Expr * e, const AttrPath & attrPath, Expr * def) : pos(pos), e(e), def(def), attrPath(attrPath) { };
ExprSelect(const PosIdx & pos, Expr * e, Symbol name) : pos(pos), e(e), def(0) { attrPath.push_back(AttrName(name)); };
- const PosIdx getPos() const { return pos; }
+ PosIdx getPos() const override { return pos; }
COMMON_METHODS
};
@@ -241,7 +237,7 @@ struct ExprOpHasAttr : Expr
Expr * e;
AttrPath attrPath;
ExprOpHasAttr(Expr * e, const AttrPath & attrPath) : e(e), attrPath(attrPath) { };
- const PosIdx getPos() const { return e->getPos(); }
+ PosIdx getPos() const override { return e->getPos(); }
COMMON_METHODS
};
@@ -270,7 +266,7 @@ struct ExprAttrs : Expr
DynamicAttrDefs dynamicAttrs;
ExprAttrs(const PosIdx &pos) : recursive(false), pos(pos) { };
ExprAttrs() : recursive(false) { };
- const PosIdx getPos() const { return pos; }
+ PosIdx getPos() const override { return pos; }
COMMON_METHODS
};
@@ -278,13 +274,12 @@ struct ExprList : Expr
{
std::vector<Expr *> elems;
ExprList() { };
- const PosIdx getPos() const
- { if (elems.empty())
- return noPos;
- else
- return elems.front()->getPos();
- }
COMMON_METHODS
+
+ PosIdx getPos() const override
+ {
+ return elems.empty() ? noPos : elems.front()->getPos();
+ }
};
struct Formal
@@ -337,7 +332,7 @@ struct ExprLambda : Expr
void setName(Symbol name);
std::string showNamePos(const EvalState & state) const;
inline bool hasFormals() const { return formals != nullptr; }
- const PosIdx getPos() const { return pos; }
+ PosIdx getPos() const override { return pos; }
COMMON_METHODS
};
@@ -349,7 +344,7 @@ struct ExprCall : Expr
ExprCall(const PosIdx & pos, Expr * fun, std::vector<Expr *> && args)
: fun(fun), args(args), pos(pos)
{ }
- const PosIdx getPos() const { return pos; }
+ PosIdx getPos() const override { return pos; }
COMMON_METHODS
};
@@ -358,7 +353,6 @@ struct ExprLet : Expr
ExprAttrs * attrs;
Expr * body;
ExprLet(ExprAttrs * attrs, Expr * body) : attrs(attrs), body(body) { };
- const PosIdx getPos() const { return noPos; }
COMMON_METHODS
};
@@ -368,7 +362,7 @@ struct ExprWith : Expr
Expr * attrs, * body;
size_t prevWith;
ExprWith(const PosIdx & pos, Expr * attrs, Expr * body) : pos(pos), attrs(attrs), body(body) { };
- const PosIdx getPos() const { return pos; }
+ PosIdx getPos() const override { return pos; }
COMMON_METHODS
};
@@ -377,7 +371,7 @@ struct ExprIf : Expr
PosIdx pos;
Expr * cond, * then, * else_;
ExprIf(const PosIdx & pos, Expr * cond, Expr * then, Expr * else_) : pos(pos), cond(cond), then(then), else_(else_) { };
- const PosIdx getPos() const { return pos; }
+ PosIdx getPos() const override { return pos; }
COMMON_METHODS
};
@@ -386,7 +380,7 @@ struct ExprAssert : Expr
PosIdx pos;
Expr * cond, * body;
ExprAssert(const PosIdx & pos, Expr * cond, Expr * body) : pos(pos), cond(cond), body(body) { };
- const PosIdx getPos() const { return pos; }
+ PosIdx getPos() const override { return pos; }
COMMON_METHODS
};
@@ -394,7 +388,6 @@ struct ExprOpNot : Expr
{
Expr * e;
ExprOpNot(Expr * e) : e(e) { };
- const PosIdx getPos() const { return noPos; }
COMMON_METHODS
};
@@ -414,7 +407,7 @@ struct ExprOpNot : Expr
e1->bindVars(es, env); e2->bindVars(es, env); \
} \
void eval(EvalState & state, Env & env, Value & v); \
- const PosIdx getPos() const { return pos; } \
+ PosIdx getPos() const override { return pos; } \
};
MakeBinOp(ExprOpEq, "==")
@@ -432,7 +425,7 @@ struct ExprConcatStrings : Expr
std::vector<std::pair<PosIdx, Expr *> > * es;
ExprConcatStrings(const PosIdx & pos, bool forceString, std::vector<std::pair<PosIdx, Expr *> > * es)
: pos(pos), forceString(forceString), es(es) { };
- const PosIdx getPos() const { return pos; }
+ PosIdx getPos() const override { return pos; }
COMMON_METHODS
};
@@ -440,7 +433,7 @@ struct ExprPos : Expr
{
PosIdx pos;
ExprPos(const PosIdx & pos) : pos(pos) { };
- const PosIdx getPos() const { return pos; }
+ PosIdx getPos() const override { return pos; }
COMMON_METHODS
};
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 41476abe3..27976dc74 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -227,7 +227,7 @@ static void import(EvalState & state, const PosIdx pos, Value & vPath, Value * v
Env * env = &state.allocEnv(vScope->attrs->size());
env->up = &state.baseEnv;
- auto staticEnv = std::shared_ptr<StaticEnv>(new StaticEnv(false, state.staticBaseEnv.get(), vScope->attrs->size()));
+ auto staticEnv = std::make_shared<StaticEnv>(false, state.staticBaseEnv.get(), vScope->attrs->size());
unsigned int displ = 0;
for (auto & attr : *vScope->attrs) {
@@ -329,8 +329,7 @@ void prim_importNative(EvalState & state, const PosIdx pos, Value * * args, Valu
std::string sym(state.forceStringNoCtx(*args[1], pos));
void *handle = dlopen(path.c_str(), RTLD_LAZY | RTLD_LOCAL);
- if (!handle)
- {
+ if (!handle) {
auto e = EvalError("could not open '%1%': %2%", path, dlerror());
state.debugLastTrace(e);
throw e;
@@ -340,14 +339,11 @@ void prim_importNative(EvalState & state, const PosIdx pos, Value * * args, Valu
ValueInitializer func = (ValueInitializer) dlsym(handle, sym.c_str());
if(!func) {
char *message = dlerror();
- if (message)
- {
+ if (message) {
auto e = EvalError("could not load symbol '%1%' from '%2%': %3%", sym, path, message);
state.debugLastTrace(e);
throw e;
- }
- else
- {
+ } else {
auto e = EvalError("symbol '%1%' from '%2%' resolved to NULL when a function pointer was expected",
sym, path);
state.debugLastTrace(e);
@@ -573,8 +569,7 @@ struct CompareValues
return v1->fpoint < v2->integer;
if (v1->type() == nInt && v2->type() == nFloat)
return v1->integer < v2->fpoint;
- if (v1->type() != v2->type())
- {
+ if (v1->type() != v2->type()) {
auto e = EvalError("cannot compare %1% with %2%", showType(*v1), showType(*v2));
state.debugLastTrace(e);
throw e;
@@ -599,12 +594,11 @@ struct CompareValues
return (*this)(v1->listElems()[i], v2->listElems()[i]);
}
}
- default:
- {
- auto e = EvalError("cannot compare %1% with %2%", showType(*v1), showType(*v2));
- state.debugLastTrace(e);
- throw e;
- }
+ default: {
+ auto e = EvalError("cannot compare %1% with %2%", showType(*v1), showType(*v2));
+ state.debugLastTrace(e);
+ throw e;
+ }
}
}
};
@@ -703,8 +697,7 @@ static void prim_genericClosure(EvalState & state, const PosIdx pos, Value * * a
Bindings::iterator key =
e->attrs->find(state.sKey);
- if (key == e->attrs->end())
- {
+ if (key == e->attrs->end()) {
auto e = EvalError({
.msg = hintfmt("attribute 'key' required"),
.errPos = state.positions[pos]
@@ -772,7 +765,7 @@ static RegisterPrimOp primop_break({
.name = "break",
.args = {"v"},
.doc = R"(
- In debug mode, pause Nix expression evaluation and enter the repl.
+ In debug mode (enabled using `--debugger`), pause Nix expression evaluation and enter the REPL.
)",
.fun = [](EvalState & state, const PosIdx pos, Value * * args, Value & v)
{
@@ -783,16 +776,15 @@ static RegisterPrimOp primop_break({
.msg = hintfmt("breakpoint reached; value was %1%", s),
.errPos = state.positions[pos],
});
- if (debuggerHook && !state.debugTraces.empty())
- {
- auto &dt = state.debugTraces.front();
+ if (debuggerHook && !state.debugTraces.empty()) {
+ auto & dt = state.debugTraces.front();
debuggerHook(&error, dt.env, dt.expr);
if (state.debugQuit) {
// if the user elects to quit the repl, throw an exception.
throw Error(ErrorInfo{
.level = lvlInfo,
- .msg = hintfmt("quit from debugger"),
+ .msg = hintfmt("quit the debugger"),
.errPos = state.positions[noPos],
});
}
@@ -903,7 +895,7 @@ static void prim_tryEval(EvalState & state, const PosIdx pos, Value * * args, Va
{
auto attrs = state.buildBindings(2);
auto saveDebuggerHook = debuggerHook;
- debuggerHook = 0;
+ debuggerHook = nullptr;
try {
state.forceValue(*args[0], pos);
attrs.insert(state.sValue, args[0]);
From 58645a78ab7c1654c513a1121511ee01551630bc Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Thu, 5 May 2022 12:37:43 +0200
Subject: [PATCH 118/188] builtins.break: Return argument when debugging is not
enabled
---
src/libexpr/primops.cc | 25 ++++++++++++++-----------
1 file changed, 14 insertions(+), 11 deletions(-)
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 27976dc74..1871d4b9b 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -766,32 +766,35 @@ static RegisterPrimOp primop_break({
.args = {"v"},
.doc = R"(
In debug mode (enabled using `--debugger`), pause Nix expression evaluation and enter the REPL.
+ Otherwise, return the argument `v`.
)",
.fun = [](EvalState & state, const PosIdx pos, Value * * args, Value & v)
{
- PathSet context;
- auto s = state.coerceToString(pos, *args[0], context).toOwned();
- auto error = Error(ErrorInfo{
- .level = lvlInfo,
- .msg = hintfmt("breakpoint reached; value was %1%", s),
- .errPos = state.positions[pos],
- });
if (debuggerHook && !state.debugTraces.empty()) {
+ PathSet context;
+ auto s = state.coerceToString(pos, *args[0], context).toOwned();
+
+ auto error = Error(ErrorInfo {
+ .level = lvlInfo,
+ .msg = hintfmt("breakpoint reached; value was %1%", s),
+ .errPos = state.positions[pos],
+ });
+
auto & dt = state.debugTraces.front();
debuggerHook(&error, dt.env, dt.expr);
if (state.debugQuit) {
- // if the user elects to quit the repl, throw an exception.
+ // If the user elects to quit the repl, throw an exception.
throw Error(ErrorInfo{
.level = lvlInfo,
.msg = hintfmt("quit the debugger"),
.errPos = state.positions[noPos],
});
}
-
- // returning the value we were passed.
- v = *args[0];
}
+
+ // Return the value we were passed.
+ v = *args[0];
}
});
From ce304d01544c799500bfffe48b7b0e85da888cd6 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Thu, 5 May 2022 15:24:57 -0600
Subject: [PATCH 119/188] rename debug commands to be more gdb-like; hide them
except in debug mode
---
src/libcmd/repl.cc | 47 ++++++++++++++++++++++++++++------------------
1 file changed, 29 insertions(+), 18 deletions(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index c35f29a2f..37e454b21 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -484,30 +484,38 @@ bool NixRepl::processLine(std::string line)
<< " :p <expr> Evaluate and print expression recursively\n"
<< " :q Exit nix-repl\n"
<< " :r Reload all files\n"
- << " :s <expr> Build dependencies of derivation, then start nix-shell\n"
+ << " :sh <expr> Build dependencies of derivation, then start nix-shell\n"
<< " :t <expr> Describe result of evaluation\n"
<< " :u <expr> Build derivation, then start nix-shell\n"
<< " :doc <expr> Show documentation of a builtin function\n"
<< " :log <expr> Show logs for a derivation\n"
- << " :st [bool] Enable, disable or toggle showing traces for errors\n"
- << " :d <cmd> Debug mode commands\n"
- << " :d stack Show trace stack\n"
- << " :d env Show env stack\n"
- << " :d show Show current trace\n"
- << " :d show <idx> Change to another trace in the stack\n"
- << " :d go Go until end of program, exception, or builtins.break().\n"
- << " :d step Go one step\n"
+ << " :te [bool] Enable, disable or toggle showing traces for errors\n"
;
+ if (debuggerHook) {
+ std::cout
+ << "\n"
+ << " Debug mode commands\n"
+ << " :env Show env stack\n"
+ << " :bt Show trace stack\n"
+ << " :st Show current trace\n"
+ << " :st <idx> Change to another trace in the stack\n"
+ << " :c Go until end of program, exception, or builtins.break().\n"
+ << " :s Go one step\n"
+ ;
+ }
}
- else if (command == ":d" || command == ":debug") {
- if (arg == "stack") {
+ else if (debuggerHook) {
+
+ if (command == ":bt" || command == ":backtrace") {
for (const auto & [idx, i] : enumerate(state->debugTraces)) {
std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
showDebugTrace(std::cout, state->positions, i);
}
- } else if (arg == "env") {
+ }
+
+ else if (command == ":env") {
for (const auto & [idx, i] : enumerate(state->debugTraces)) {
if (idx == debugTraceIndex) {
printEnvBindings(state->symbols, i.expr, i.env);
@@ -515,10 +523,11 @@ bool NixRepl::processLine(std::string line)
}
}
}
- else if (arg.compare(0, 4, "show") == 0) {
+
+ else if (command == ":st") {
try {
// change the DebugTrace index.
- debugTraceIndex = stoi(arg.substr(4));
+ debugTraceIndex = stoi(arg);
} catch (...) { }
for (const auto & [idx, i] : enumerate(state->debugTraces)) {
@@ -532,12 +541,14 @@ bool NixRepl::processLine(std::string line)
}
}
}
- else if (arg == "step") {
+
+ else if (command == ":s" || command == ":step") {
// set flag to stop at next DebugTrace; exit repl.
state->debugStop = true;
return false;
}
- else if (arg == "go") {
+
+ else if (command == ":c" || command == ":continue") {
// set flag to run to next breakpoint or end of program; exit repl.
state->debugStop = false;
return false;
@@ -613,7 +624,7 @@ bool NixRepl::processLine(std::string line)
runNix("nix-shell", {state->store->printStorePath(drvPath)});
}
- else if (command == ":b" || command == ":bl" || command == ":i" || command == ":s" || command == ":log") {
+ else if (command == ":b" || command == ":bl" || command == ":i" || command == ":sh" || command == ":log") {
Value v;
evalString(arg, v);
StorePath drvPath = getDerivationPath(v);
@@ -703,7 +714,7 @@ bool NixRepl::processLine(std::string line)
throw Error("value does not have documentation");
}
- else if (command == ":st" || command == ":show-trace") {
+ else if (command == ":te" || command == ":trace-enable") {
if (arg == "false" || (arg == "" && loggerSettings.showTrace)) {
std::cout << "not showing error traces\n";
loggerSettings.showTrace = false;
From 09fcfee9252920b170e031b397709368a305bbc3 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Thu, 5 May 2022 15:34:59 -0600
Subject: [PATCH 120/188] don't print the 'break' argument
---
src/libexpr/primops.cc | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 1871d4b9b..5ee917f19 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -771,12 +771,9 @@ static RegisterPrimOp primop_break({
.fun = [](EvalState & state, const PosIdx pos, Value * * args, Value & v)
{
if (debuggerHook && !state.debugTraces.empty()) {
- PathSet context;
- auto s = state.coerceToString(pos, *args[0], context).toOwned();
-
auto error = Error(ErrorInfo {
.level = lvlInfo,
- .msg = hintfmt("breakpoint reached; value was %1%", s),
+ .msg = hintfmt("breakpoint reached"),
.errPos = state.positions[pos],
});
From f400c5466d45d342709483799d9b9c2ac24cf967 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Thu, 5 May 2022 15:43:23 -0600
Subject: [PATCH 121/188] rename valmap
---
src/libexpr/eval.cc | 6 +++---
src/libexpr/eval.hh | 4 ++--
2 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index ca0eec6e3..659b97658 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -772,7 +772,7 @@ void printEnvBindings(const SymbolTable & st, const Expr & expr, const Env & env
printEnvBindings(st, *expr.staticEnv.get(), env, 0);
}
-void mapStaticEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env, valmap & vm)
+void mapStaticEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env, ValMap & vm)
{
// add bindings for the next level up first, so that the bindings for this level
// override the higher levels.
@@ -795,9 +795,9 @@ void mapStaticEnvBindings(const SymbolTable & st, const StaticEnv & se, const En
}
}
-std::unique_ptr<valmap> mapStaticEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env)
+std::unique_ptr<ValMap> mapStaticEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env)
{
- auto vm = std::make_unique<valmap>();
+ auto vm = std::make_unique<ValMap>();
mapStaticEnvBindings(st, se, env, *vm);
return vm;
}
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index f3852e248..22f034e27 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -37,7 +37,7 @@ struct PrimOp
const char * doc = nullptr;
};
-typedef std::map<std::string, Value *> valmap;
+typedef std::map<std::string, Value *> ValMap;
struct Env
{
@@ -47,7 +47,7 @@ struct Env
Value * values[0];
};
-std::unique_ptr<valmap> mapStaticEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env);
+std::unique_ptr<ValMap> mapStaticEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env);
void copyContext(const Value & v, PathSet & context);
From dea998b2f29eaad67b3003550fcfdf9d31045d4c Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Thu, 5 May 2022 20:26:10 -0600
Subject: [PATCH 122/188] traceable_allocator
---
src/libcmd/command.hh | 2 +-
src/libcmd/repl.cc | 2 +-
src/libexpr/eval.hh | 6 +++++-
3 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/src/libcmd/command.hh b/src/libcmd/command.hh
index 354877bc5..454197b1c 100644
--- a/src/libcmd/command.hh
+++ b/src/libcmd/command.hh
@@ -276,6 +276,6 @@ void printClosureDiff(
void runRepl(
ref<EvalState> evalState,
const Expr & expr,
- const std::map<std::string, Value *> & extraEnv);
+ const ValMap & extraEnv);
}
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 37e454b21..950195572 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -1016,7 +1016,7 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
void runRepl(
ref<EvalState> evalState,
const Expr &expr,
- const std::map<std::string, Value *> & extraEnv)
+ const ValMap & extraEnv)
{
auto repl = std::make_unique<NixRepl>(evalState);
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 22f034e27..65b1466ea 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -37,7 +37,11 @@ struct PrimOp
const char * doc = nullptr;
};
-typedef std::map<std::string, Value *> ValMap;
+#if HAVE_BOEHMGC
+ typedef std::map<std::string, Value *, std::less<std::string>, traceable_allocator<std::pair<const std::string, Value *> > > ValMap;
+#else
+ typedef std::map<std::string, Value *> ValMap;
+#endif
struct Env
{
From 99d69ac23faf06598ca0aabd61d22a575db848df Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Thu, 5 May 2022 21:23:03 -0600
Subject: [PATCH 123/188] fix repl bug
---
src/libcmd/repl.cc | 77 ++++++++++++++++++++++------------------------
1 file changed, 37 insertions(+), 40 deletions(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 950195572..8f0b1bfc0 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -506,53 +506,50 @@ bool NixRepl::processLine(std::string line)
}
- else if (debuggerHook) {
+ else if (debuggerHook && (command == ":bt" || command == ":backtrace")) {
+ for (const auto & [idx, i] : enumerate(state->debugTraces)) {
+ std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
+ showDebugTrace(std::cout, state->positions, i);
+ }
+ }
- if (command == ":bt" || command == ":backtrace") {
- for (const auto & [idx, i] : enumerate(state->debugTraces)) {
- std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
- showDebugTrace(std::cout, state->positions, i);
+ else if (debuggerHook && (command == ":env")) {
+ for (const auto & [idx, i] : enumerate(state->debugTraces)) {
+ if (idx == debugTraceIndex) {
+ printEnvBindings(state->symbols, i.expr, i.env);
+ break;
}
}
+ }
- else if (command == ":env") {
- for (const auto & [idx, i] : enumerate(state->debugTraces)) {
- if (idx == debugTraceIndex) {
- printEnvBindings(state->symbols, i.expr, i.env);
- break;
- }
- }
+ else if (debuggerHook && (command == ":st")) {
+ try {
+ // change the DebugTrace index.
+ debugTraceIndex = stoi(arg);
+ } catch (...) { }
+
+ for (const auto & [idx, i] : enumerate(state->debugTraces)) {
+ if (idx == debugTraceIndex) {
+ std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
+ showDebugTrace(std::cout, state->positions, i);
+ std::cout << std::endl;
+ printEnvBindings(state->symbols, i.expr, i.env);
+ loadDebugTraceEnv(i);
+ break;
+ }
}
+ }
- else if (command == ":st") {
- try {
- // change the DebugTrace index.
- debugTraceIndex = stoi(arg);
- } catch (...) { }
+ else if (debuggerHook && (command == ":s" || command == ":step")) {
+ // set flag to stop at next DebugTrace; exit repl.
+ state->debugStop = true;
+ return false;
+ }
- for (const auto & [idx, i] : enumerate(state->debugTraces)) {
- if (idx == debugTraceIndex) {
- std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
- showDebugTrace(std::cout, state->positions, i);
- std::cout << std::endl;
- printEnvBindings(state->symbols, i.expr, i.env);
- loadDebugTraceEnv(i);
- break;
- }
- }
- }
-
- else if (command == ":s" || command == ":step") {
- // set flag to stop at next DebugTrace; exit repl.
- state->debugStop = true;
- return false;
- }
-
- else if (command == ":c" || command == ":continue") {
- // set flag to run to next breakpoint or end of program; exit repl.
- state->debugStop = false;
- return false;
- }
+ else if (debuggerHook && (command == ":c" || command == ":continue")) {
+ // set flag to run to next breakpoint or end of program; exit repl.
+ state->debugStop = false;
+ return false;
}
else if (command == ":a" || command == ":add") {
From 2c9fafdc9e43f6da39c289888dedbbbf0ea0b208 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Fri, 6 May 2022 08:47:21 -0600
Subject: [PATCH 124/188] trying debugThrow
---
src/libexpr/eval-cache.cc | 25 ++---
src/libexpr/eval.cc | 103 +++++++--------------
src/libexpr/eval.hh | 6 +-
src/libexpr/parser.y | 3 +-
src/libexpr/primops.cc | 153 ++++++++++++-------------------
src/libexpr/primops/fetchTree.cc | 27 ++----
src/libexpr/value-to-json.cc | 5 +-
7 files changed, 115 insertions(+), 207 deletions(-)
diff --git a/src/libexpr/eval-cache.cc b/src/libexpr/eval-cache.cc
index e9d9d02a4..af213a484 100644
--- a/src/libexpr/eval-cache.cc
+++ b/src/libexpr/eval-cache.cc
@@ -556,8 +556,7 @@ std::string AttrCursor::getString()
} else
{
auto e = TypeError("'%s' is not a string", getAttrPathStr());
- root->state.debugLastTrace(e);
- throw e;
+ root->state.debugThrowLastTrace(e);
}
}
}
@@ -567,8 +566,7 @@ std::string AttrCursor::getString()
if (v.type() != nString && v.type() != nPath)
{
auto e = TypeError("'%s' is not a string but %s", getAttrPathStr(), showType(v.type()));
- root->state.debugLastTrace(e);
- throw e;
+ root->state.debugThrowLastTrace(e);
}
return v.type() == nString ? v.string.s : v.path;
@@ -595,8 +593,7 @@ string_t AttrCursor::getStringWithContext()
} else
{
auto e = TypeError("'%s' is not a string", getAttrPathStr());
- root->state.debugLastTrace(e);
- throw e;
+ root->state.debugThrowLastTrace(e);
}
}
}
@@ -610,9 +607,7 @@ string_t AttrCursor::getStringWithContext()
else
{
auto e = TypeError("'%s' is not a string but %s", getAttrPathStr(), showType(v.type()));
- root->state.debugLastTrace(e);
- throw e;
- return {v.path, {}}; // should never execute
+ root->state.debugThrowLastTrace(e);
}
}
@@ -628,8 +623,7 @@ bool AttrCursor::getBool()
} else
{
auto e = TypeError("'%s' is not a Boolean", getAttrPathStr());
- root->state.debugLastTrace(e);
- throw e;
+ root->state.debugThrowLastTrace(e);
}
}
}
@@ -639,8 +633,7 @@ bool AttrCursor::getBool()
if (v.type() != nBool)
{
auto e = TypeError("'%s' is not a Boolean", getAttrPathStr());
- root->state.debugLastTrace(e);
- throw e;
+ root->state.debugThrowLastTrace(e);
}
return v.boolean;
@@ -691,8 +684,7 @@ std::vector<Symbol> AttrCursor::getAttrs()
} else
{
auto e = TypeError("'%s' is not an attribute set", getAttrPathStr());
- root->state.debugLastTrace(e);
- throw e;
+ root->state.debugThrowLastTrace(e);
}
}
}
@@ -702,8 +694,7 @@ std::vector<Symbol> AttrCursor::getAttrs()
if (v.type() != nAttrs)
{
auto e = TypeError("'%s' is not an attribute set", getAttrPathStr());
- root->state.debugLastTrace(e);
- throw e;
+ root->state.debugThrowLastTrace(e);
}
std::vector<Symbol> attrs;
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 659b97658..54872669a 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -802,8 +802,9 @@ std::unique_ptr<ValMap> mapStaticEnvBindings(const SymbolTable & st, const Stati
return vm;
}
-void EvalState::debugLastTrace(Error & e) const
+void EvalState::debugThrowLastTrace(Error & e) const
{
+ std::cout << "debugThrowLastTrace(Error & e) const" << (debuggerHook == nullptr) << std::endl;
// Call this in the situation where Expr and Env are inaccessible.
// The debugger will start in the last context that's in the
// DebugTrace stack.
@@ -811,6 +812,18 @@ void EvalState::debugLastTrace(Error & e) const
const DebugTrace & last = debugTraces.front();
debuggerHook(&e, last.env, last.expr);
}
+
+ throw e;
+}
+
+
+void EvalState::debugThrow(const Error &error, const Env & env, const Expr & expr) const
+{
+ std::cout << "debugThrow" << (debuggerHook == nullptr) << std::endl;
+ if (debuggerHook)
+ debuggerHook(&error, env, expr);
+
+ throw error;
}
/* Every "format" object (even temporary) takes up a few hundred bytes
@@ -824,10 +837,7 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, Env & env, Expr
.errPos = positions[pos]
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
-
- throw error;
+ debugThrow(error, env, expr);
}
void EvalState::throwEvalError(const PosIdx pos, const char * s) const
@@ -837,18 +847,14 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s) const
.errPos = positions[pos]
});
- debugLastTrace(error);
-
- throw error;
+ debugThrowLastTrace(error);
}
void EvalState::throwEvalError(const char * s, const std::string & s2) const
{
auto error = EvalError(s, s2);
- debugLastTrace(error);
-
- throw error;
+ debugThrowLastTrace(error);
}
void EvalState::throwEvalError(const PosIdx pos, const Suggestions & suggestions, const char * s,
@@ -860,10 +866,7 @@ void EvalState::throwEvalError(const PosIdx pos, const Suggestions & suggestions
.suggestions = suggestions,
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
-
- throw error;
+ debugThrow(error, env, expr);
}
void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::string & s2) const
@@ -873,9 +876,7 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::stri
.errPos = positions[pos]
});
- debugLastTrace(error);
-
- throw error;
+ debugThrowLastTrace(error);
}
void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::string & s2, Env & env, Expr & expr) const
@@ -885,10 +886,7 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::stri
.errPos = positions[pos]
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
-
- throw error;
+ debugThrow(error, env, expr);
}
void EvalState::throwEvalError(const char * s, const std::string & s2,
@@ -899,9 +897,7 @@ void EvalState::throwEvalError(const char * s, const std::string & s2,
.errPos = positions[noPos]
});
- debugLastTrace(error);
-
- throw error;
+ debugThrowLastTrace(error);
}
void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::string & s2,
@@ -912,9 +908,7 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::stri
.errPos = positions[pos]
});
- debugLastTrace(error);
-
- throw error;
+ debugThrowLastTrace(error);
}
void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::string & s2,
@@ -925,10 +919,7 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::stri
.errPos = positions[pos]
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
-
- throw error;
+ debugThrow(error, env, expr);
}
void EvalState::throwEvalError(const PosIdx p1, const char * s, const Symbol sym, const PosIdx p2, Env & env, Expr & expr) const
@@ -939,10 +930,7 @@ void EvalState::throwEvalError(const PosIdx p1, const char * s, const Symbol sym
.errPos = positions[p1]
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
-
- throw error;
+ debugThrow(error, env, expr);
}
void EvalState::throwTypeError(const PosIdx pos, const char * s, const Value & v) const
@@ -952,9 +940,7 @@ void EvalState::throwTypeError(const PosIdx pos, const char * s, const Value & v
.errPos = positions[pos]
});
- debugLastTrace(error);
-
- throw error;
+ debugThrowLastTrace(error);
}
void EvalState::throwTypeError(const PosIdx pos, const char * s, const Value & v, Env & env, Expr & expr) const
@@ -964,10 +950,7 @@ void EvalState::throwTypeError(const PosIdx pos, const char * s, const Value & v
.errPos = positions[pos]
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
-
- throw error;
+ debugThrow(error, env, expr);
}
void EvalState::throwTypeError(const PosIdx pos, const char * s) const
@@ -977,9 +960,7 @@ void EvalState::throwTypeError(const PosIdx pos, const char * s) const
.errPos = positions[pos]
});
- debugLastTrace(error);
-
- throw error;
+ debugThrowLastTrace(error);
}
void EvalState::throwTypeError(const PosIdx pos, const char * s, const ExprLambda & fun,
@@ -990,10 +971,7 @@ void EvalState::throwTypeError(const PosIdx pos, const char * s, const ExprLambd
.errPos = positions[pos]
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
-
- throw error;
+ debugThrow(error, env, expr);
}
void EvalState::throwTypeError(const PosIdx pos, const Suggestions & suggestions, const char * s,
@@ -1005,10 +983,7 @@ void EvalState::throwTypeError(const PosIdx pos, const Suggestions & suggestions
.suggestions = suggestions,
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
-
- throw error;
+ debugThrow(error, env, expr);
}
void EvalState::throwTypeError(const char * s, const Value & v, Env & env, Expr &expr) const
@@ -1018,10 +993,7 @@ void EvalState::throwTypeError(const char * s, const Value & v, Env & env, Expr
.errPos = positions[expr.getPos()],
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
-
- throw error;
+ debugThrow(error, env, expr);
}
void EvalState::throwAssertionError(const PosIdx pos, const char * s, const std::string & s1, Env & env, Expr &expr) const
@@ -1031,10 +1003,7 @@ void EvalState::throwAssertionError(const PosIdx pos, const char * s, const std:
.errPos = positions[pos]
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
-
- throw error;
+ debugThrow(error, env, expr);
}
void EvalState::throwUndefinedVarError(const PosIdx pos, const char * s, const std::string & s1, Env & env, Expr &expr) const
@@ -1044,10 +1013,7 @@ void EvalState::throwUndefinedVarError(const PosIdx pos, const char * s, const s
.errPos = positions[pos]
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
-
- throw error;
+ debugThrow(error, env, expr);
}
void EvalState::throwMissingArgumentError(const PosIdx pos, const char * s, const std::string & s1, Env & env, Expr &expr) const
@@ -1057,10 +1023,7 @@ void EvalState::throwMissingArgumentError(const PosIdx pos, const char * s, cons
.errPos = positions[pos]
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
-
- throw error;
+ debugThrow(error, env, expr);
}
void EvalState::addErrorTrace(Error & e, const char * s, const std::string & s2) const
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 65b1466ea..add104a84 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -127,7 +127,11 @@ public:
bool debugStop;
bool debugQuit;
std::list<DebugTrace> debugTraces;
- void debugLastTrace(Error & e) const;
+
+ [[gnu::noinline, gnu::noreturn]]
+ void debugThrow(const Error &error, const Env & env, const Expr & expr) const;
+ [[gnu::noinline, gnu::noreturn]]
+ void debugThrowLastTrace(Error & e) const;
private:
SrcToStore srcToStore;
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index 8edafdd57..b960cd8df 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -789,8 +789,7 @@ Path EvalState::findFile(SearchPath & searchPath, const std::string_view path, c
path),
.errPos = positions[pos]
});
- debugLastTrace(e);
- throw e;
+ debugThrowLastTrace(e);
}
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 5ee917f19..34471dd8f 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -48,8 +48,7 @@ StringMap EvalState::realiseContext(const PathSet & context)
if (!store->isValidPath(ctx))
{
auto e = InvalidPathError(store->printStorePath(ctx));
- debugLastTrace(e);
- throw e;
+ debugThrowLastTrace(e);
}
if (!outputName.empty() && ctx.isDerivation()) {
drvs.push_back({ctx, {outputName}});
@@ -65,8 +64,7 @@ StringMap EvalState::realiseContext(const PathSet & context)
auto e = Error(
"cannot build '%1%' during evaluation because the option 'allow-import-from-derivation' is disabled",
store->printStorePath(drvs.begin()->drvPath));
- debugLastTrace(e);
- throw e;
+ debugThrowLastTrace(e);
}
/* Build/substitute the context. */
@@ -82,8 +80,7 @@ StringMap EvalState::realiseContext(const PathSet & context)
if (!outputPath) {
auto e = Error("derivation '%s' does not have an output named '%s'",
store->printStorePath(drvPath), outputName);
- debugLastTrace(e);
- throw e;
+ debugThrowLastTrace(e);
}
res.insert_or_assign(
downstreamPlaceholder(*store, drvPath, outputName),
@@ -331,8 +328,7 @@ void prim_importNative(EvalState & state, const PosIdx pos, Value * * args, Valu
void *handle = dlopen(path.c_str(), RTLD_LAZY | RTLD_LOCAL);
if (!handle) {
auto e = EvalError("could not open '%1%': %2%", path, dlerror());
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
dlerror();
@@ -341,13 +337,11 @@ void prim_importNative(EvalState & state, const PosIdx pos, Value * * args, Valu
char *message = dlerror();
if (message) {
auto e = EvalError("could not load symbol '%1%' from '%2%': %3%", sym, path, message);
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
} else {
auto e = EvalError("symbol '%1%' from '%2%' resolved to NULL when a function pointer was expected",
sym, path);
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
}
@@ -368,8 +362,7 @@ void prim_exec(EvalState & state, const PosIdx pos, Value * * args, Value & v)
.msg = hintfmt("at least one argument to 'exec' required"),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
PathSet context;
auto program = state.coerceToString(pos, *elems[0], context, false, false).toOwned();
@@ -385,8 +378,7 @@ void prim_exec(EvalState & state, const PosIdx pos, Value * * args, Value & v)
program, e.path),
.errPos = state.positions[pos]
});
- state.debugLastTrace(ee);
- throw ee;
+ state.debugThrowLastTrace(ee);
}
auto output = runProgram(program, true, commandArgs);
@@ -571,8 +563,7 @@ struct CompareValues
return v1->integer < v2->fpoint;
if (v1->type() != v2->type()) {
auto e = EvalError("cannot compare %1% with %2%", showType(*v1), showType(*v2));
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
switch (v1->type()) {
case nInt:
@@ -596,8 +587,7 @@ struct CompareValues
}
default: {
auto e = EvalError("cannot compare %1% with %2%", showType(*v1), showType(*v2));
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
}
}
@@ -632,8 +622,7 @@ static Bindings::iterator getAttr(
.msg = errorMsg,
.errPos = state.positions[pos],
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
} else {
auto e = TypeError({
.msg = errorMsg,
@@ -643,8 +632,7 @@ static Bindings::iterator getAttr(
// Adding another trace for the function name to make it clear
// which call received wrong arguments.
e.addTrace(state.positions[pos], hintfmt("while invoking '%s'", funcName));
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
}
@@ -702,8 +690,7 @@ static void prim_genericClosure(EvalState & state, const PosIdx pos, Value * * a
.msg = hintfmt("attribute 'key' required"),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
state.forceValue(*key->value, pos);
@@ -807,8 +794,7 @@ static RegisterPrimOp primop_abort({
auto s = state.coerceToString(pos, *args[0], context).toOwned();
{
auto e = Abort("evaluation aborted with the following error message: '%1%'", s);
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
}
});
@@ -828,8 +814,7 @@ static RegisterPrimOp primop_throw({
PathSet context;
auto s = state.coerceToString(pos, *args[0], context).toOwned();
auto e = ThrownError(s);
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
});
@@ -893,6 +878,7 @@ static RegisterPrimOp primop_floor({
* else => {success=false; value=false;} */
static void prim_tryEval(EvalState & state, const PosIdx pos, Value * * args, Value & v)
{
+ std::cout << "priatraynasdf0" << std::endl;
auto attrs = state.buildBindings(2);
auto saveDebuggerHook = debuggerHook;
debuggerHook = nullptr;
@@ -900,7 +886,15 @@ static void prim_tryEval(EvalState & state, const PosIdx pos, Value * * args, Va
state.forceValue(*args[0], pos);
attrs.insert(state.sValue, args[0]);
attrs.alloc("success").mkBool(true);
+ std::cout << "priatraynasdf0000" << std::endl;
} catch (AssertionError & e) {
+ std::cout << "priatraynasdf" << std::endl;
+
+ attrs.alloc(state.sValue).mkBool(false);
+ attrs.alloc("success").mkBool(false);
+ } catch (Error & e) {
+ std::cout << "priatraERASERynasdf" << std::endl;
+
attrs.alloc(state.sValue).mkBool(false);
attrs.alloc("success").mkBool(false);
}
@@ -1092,8 +1086,7 @@ static void prim_derivationStrict(EvalState & state, const PosIdx pos, Value * *
.msg = hintfmt("invalid value '%s' for 'outputHashMode' attribute", s),
.errPos = state.positions[posDrvName]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
};
@@ -1106,8 +1099,7 @@ static void prim_derivationStrict(EvalState & state, const PosIdx pos, Value * *
.msg = hintfmt("duplicate derivation output '%1%'", j),
.errPos = state.positions[posDrvName]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
/* !!! Check whether j is a valid attribute
name. */
@@ -1120,8 +1112,7 @@ static void prim_derivationStrict(EvalState & state, const PosIdx pos, Value * *
.msg = hintfmt("invalid derivation output name 'drv'" ),
.errPos = state.positions[posDrvName]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
outputs.insert(j);
}
@@ -1131,8 +1122,7 @@ static void prim_derivationStrict(EvalState & state, const PosIdx pos, Value * *
.msg = hintfmt("derivation cannot have an empty set of outputs"),
.errPos = state.positions[posDrvName]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
};
@@ -1263,8 +1253,7 @@ static void prim_derivationStrict(EvalState & state, const PosIdx pos, Value * *
.msg = hintfmt("required attribute 'builder' missing"),
.errPos = state.positions[posDrvName]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
if (drv.platform == "")
@@ -1273,8 +1262,7 @@ static void prim_derivationStrict(EvalState & state, const PosIdx pos, Value * *
.msg = hintfmt("required attribute 'system' missing"),
.errPos = state.positions[posDrvName]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
/* Check whether the derivation name is valid. */
@@ -1284,8 +1272,7 @@ static void prim_derivationStrict(EvalState & state, const PosIdx pos, Value * *
.msg = hintfmt("derivation names are not allowed to end in '%s'", drvExtension),
.errPos = state.positions[posDrvName]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
if (outputHash) {
@@ -1299,8 +1286,7 @@ static void prim_derivationStrict(EvalState & state, const PosIdx pos, Value * *
.msg = hintfmt("multiple outputs are not supported in fixed-output derivations"),
.errPos = state.positions[posDrvName]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
auto h = newHashAllowEmpty(*outputHash, parseHashTypeOpt(outputHashAlgo));
@@ -1474,8 +1460,7 @@ static void prim_storePath(EvalState & state, const PosIdx pos, Value * * args,
.msg = hintfmt("'%s' is not allowed in pure evaluation mode", "builtins.storePath"),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
PathSet context;
@@ -1490,8 +1475,7 @@ static void prim_storePath(EvalState & state, const PosIdx pos, Value * * args,
.msg = hintfmt("path '%1%' is not in the Nix store", path),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
auto path2 = state.store->toStorePath(path).first;
if (!settings.readOnlyMode)
@@ -1597,8 +1581,7 @@ static void prim_readFile(EvalState & state, const PosIdx pos, Value * * args, V
if (s.find((char) 0) != std::string::npos)
{
auto e = Error("the contents of the file '%1%' cannot be represented as a Nix string", path);
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
StorePathSet refs;
if (state.store->isInStore(path)) {
@@ -1655,8 +1638,7 @@ static void prim_findFile(EvalState & state, const PosIdx pos, Value * * args, V
.msg = hintfmt("cannot find '%1%', since path '%2%' is not valid", path, e.path),
.errPos = state.positions[pos]
});
- state.debugLastTrace(ee);
- throw ee;
+ state.debugThrowLastTrace(ee);
}
@@ -1685,8 +1667,7 @@ static void prim_hashFile(EvalState & state, const PosIdx pos, Value * * args, V
.msg = hintfmt("unknown hash type '%1%'", type),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
auto path = realisePath(state, pos, *args[1]);
@@ -1932,8 +1913,7 @@ static void prim_toFile(EvalState & state, const PosIdx pos, Value * * args, Val
name, path),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
refs.insert(state.store->parseStorePath(path));
}
@@ -2094,8 +2074,7 @@ static void addPath(
if (expectedHash && expectedStorePath != dstPath)
{
auto e = Error("store path mismatch in (possibly filtered) path added from '%s'", path);
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
state.allowAndSetStorePathString(dstPath, v);
} else
@@ -2121,8 +2100,7 @@ static void prim_filterSource(EvalState & state, const PosIdx pos, Value * * arg
showType(*args[0])),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
addPath(state, pos, std::string(baseNameOf(path)), path, args[0], FileIngestionMethod::Recursive, std::nullopt, v, context);
@@ -2212,8 +2190,7 @@ static void prim_path(EvalState & state, const PosIdx pos, Value * * args, Value
.msg = hintfmt("unsupported argument '%1%' to 'addPath'", state.symbols[attr.name]),
.errPos = state.positions[attr.pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
}
if (path.empty())
@@ -2222,8 +2199,7 @@ static void prim_path(EvalState & state, const PosIdx pos, Value * * args, Value
.msg = hintfmt("'path' required"),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
if (name.empty())
name = baseNameOf(path);
@@ -2601,8 +2577,7 @@ static void prim_functionArgs(EvalState & state, const PosIdx pos, Value * * arg
.msg = hintfmt("'functionArgs' requires a function"),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
if (!args[0]->lambda.fun->hasFormals()) {
@@ -2691,8 +2666,7 @@ static void prim_zipAttrsWith(EvalState & state, const PosIdx pos, Value * * arg
attrsSeen[attr.name].first++;
} catch (TypeError & e) {
e.addTrace(state.positions[pos], hintfmt("while invoking '%s'", "zipAttrsWith"));
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
}
@@ -2784,8 +2758,7 @@ static void elemAt(EvalState & state, const PosIdx pos, Value & list, int n, Val
.msg = hintfmt("list index %1% is out of bounds", n),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
state.forceValue(*list.listElems()[n], pos);
v = *list.listElems()[n];
@@ -2836,8 +2809,7 @@ static void prim_tail(EvalState & state, const PosIdx pos, Value * * args, Value
.msg = hintfmt("'tail' called on an empty list"),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
state.mkList(v, args[0]->listSize() - 1);
@@ -3078,8 +3050,7 @@ static void prim_genList(EvalState & state, const PosIdx pos, Value * * args, Va
.msg = hintfmt("cannot create list of size %1%", len),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
state.mkList(v, len);
@@ -3289,8 +3260,7 @@ static void prim_concatMap(EvalState & state, const PosIdx pos, Value * * args,
state.forceList(lists[n], lists[n].determinePos(args[0]->determinePos(pos)));
} catch (TypeError &e) {
e.addTrace(state.positions[pos], hintfmt("while invoking '%s'", "concatMap"));
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
len += lists[n].listSize();
}
@@ -3390,8 +3360,7 @@ static void prim_div(EvalState & state, const PosIdx pos, Value * * args, Value
.msg = hintfmt("division by zero"),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
if (args[0]->type() == nFloat || args[1]->type() == nFloat) {
@@ -3406,8 +3375,7 @@ static void prim_div(EvalState & state, const PosIdx pos, Value * * args, Value
.msg = hintfmt("overflow in integer division"),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
v.mkInt(i1 / i2);
@@ -3541,8 +3509,7 @@ static void prim_substring(EvalState & state, const PosIdx pos, Value * * args,
.msg = hintfmt("negative start position in 'substring'"),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
v.mkString((unsigned int) start >= s->size() ? "" : s->substr(start, len), context);
@@ -3596,8 +3563,7 @@ static void prim_hashString(EvalState & state, const PosIdx pos, Value * * args,
.msg = hintfmt("unknown hash type '%1%'", type),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
PathSet context; // discarded
@@ -3672,15 +3638,13 @@ void prim_match(EvalState & state, const PosIdx pos, Value * * args, Value & v)
.msg = hintfmt("memory limit exceeded by regular expression '%s'", re),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
} else {
auto e = EvalError({
.msg = hintfmt("invalid regular expression '%s'", re),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
}
}
@@ -3781,15 +3745,13 @@ void prim_split(EvalState & state, const PosIdx pos, Value * * args, Value & v)
.msg = hintfmt("memory limit exceeded by regular expression '%s'", re),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
} else {
auto e = EvalError({
.msg = hintfmt("invalid regular expression '%s'", re),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
}
}
@@ -3871,8 +3833,7 @@ static void prim_replaceStrings(EvalState & state, const PosIdx pos, Value * * a
.msg = hintfmt("'from' and 'to' arguments to 'replaceStrings' have different lengths"),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
std::vector<std::string> from;
diff --git a/src/libexpr/primops/fetchTree.cc b/src/libexpr/primops/fetchTree.cc
index 55fe7da24..e4fa3c5f9 100644
--- a/src/libexpr/primops/fetchTree.cc
+++ b/src/libexpr/primops/fetchTree.cc
@@ -113,8 +113,7 @@ static void fetchTree(
.msg = hintfmt("unexpected attribute 'type'"),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
type = state.forceStringNoCtx(*aType->value, aType->pos);
} else if (!type)
@@ -123,8 +122,7 @@ static void fetchTree(
.msg = hintfmt("attribute 'type' is missing in call to 'fetchTree'"),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
attrs.emplace("type", type.value());
@@ -149,8 +147,7 @@ static void fetchTree(
{
auto e = TypeError("fetchTree argument '%s' is %s while a string, Boolean or integer is expected",
state.symbols[attr.name], showType(*attr.value));
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
}
@@ -161,8 +158,7 @@ static void fetchTree(
.msg = hintfmt("attribute 'name' isn’t supported in call to 'fetchTree'"),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
input = fetchers::Input::fromAttrs(std::move(attrs));
@@ -185,8 +181,7 @@ static void fetchTree(
if (evalSettings.pureEval && !input.isLocked())
{
auto e = EvalError("in pure evaluation mode, 'fetchTree' requires a locked input, at %s", state.positions[pos]);
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
auto [tree, input2] = input.fetch(state.store);
@@ -231,8 +226,7 @@ static void fetch(EvalState & state, const PosIdx pos, Value * * args, Value & v
.msg = hintfmt("unsupported argument '%s' to '%s'", n, who),
.errPos = state.positions[attr.pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
}
@@ -242,8 +236,7 @@ static void fetch(EvalState & state, const PosIdx pos, Value * * args, Value & v
.msg = hintfmt("'url' argument required"),
.errPos = state.positions[pos]
});
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
} else
url = state.forceStringNoCtx(*args[0], pos);
@@ -258,8 +251,7 @@ static void fetch(EvalState & state, const PosIdx pos, Value * * args, Value & v
if (evalSettings.pureEval && !expectedHash)
{
auto e = EvalError("in pure evaluation mode, '%s' requires a 'sha256' argument", who);
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
// early exit if pinned and already in the store
@@ -290,8 +282,7 @@ static void fetch(EvalState & state, const PosIdx pos, Value * * args, Value & v
{
auto e = EvalError((unsigned int) 102, "hash mismatch in file downloaded from '%s':\n specified: %s\n got: %s",
*url, expectedHash->to_string(Base32, true), hash.to_string(Base32, true));
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
}
diff --git a/src/libexpr/value-to-json.cc b/src/libexpr/value-to-json.cc
index 34f3a34c8..6a95e0414 100644
--- a/src/libexpr/value-to-json.cc
+++ b/src/libexpr/value-to-json.cc
@@ -85,7 +85,7 @@ void printValueAsJSON(EvalState & state, bool strict,
.errPos = state.positions[v.determinePos(pos)]
});
e.addTrace(state.positions[pos], hintfmt("message for the trace"));
- state.debugLastTrace(e);
+ state.debugThrowLastTrace(e);
throw e;
}
}
@@ -101,8 +101,7 @@ void ExternalValueBase::printValueAsJSON(EvalState & state, bool strict,
JSONPlaceholder & out, PathSet & context) const
{
auto e = TypeError("cannot convert %1% to JSON", showType());
- state.debugLastTrace(e);
- throw e;
+ state.debugThrowLastTrace(e);
}
From fc66f48812383dad59ebdbabdd29bec34ed31921 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Fri, 6 May 2022 09:09:49 -0600
Subject: [PATCH 125/188] debugError()
---
src/libexpr/eval.cc | 43 +++++++++++++++++++------------------------
src/libexpr/eval.hh | 2 ++
2 files changed, 21 insertions(+), 24 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 659b97658..c5e33a279 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -813,6 +813,13 @@ void EvalState::debugLastTrace(Error & e) const
}
}
+void debugError(Error * e, Env & env, Expr & expr)
+{
+ if (debuggerHook)
+ debuggerHook(e, env, expr);
+}
+
+
/* Every "format" object (even temporary) takes up a few hundred bytes
of stack space, which is a real killer in the recursive
evaluator. So here are some helper functions for throwing
@@ -824,8 +831,7 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, Env & env, Expr
.errPos = positions[pos]
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
+ debugError(&error, env, expr);
throw error;
}
@@ -860,8 +866,7 @@ void EvalState::throwEvalError(const PosIdx pos, const Suggestions & suggestions
.suggestions = suggestions,
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
+ debugError(&error, env, expr);
throw error;
}
@@ -885,8 +890,7 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::stri
.errPos = positions[pos]
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
+ debugError(&error, env, expr);
throw error;
}
@@ -925,8 +929,7 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::stri
.errPos = positions[pos]
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
+ debugError(&error, env, expr);
throw error;
}
@@ -939,8 +942,7 @@ void EvalState::throwEvalError(const PosIdx p1, const char * s, const Symbol sym
.errPos = positions[p1]
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
+ debugError(&error, env, expr);
throw error;
}
@@ -964,8 +966,7 @@ void EvalState::throwTypeError(const PosIdx pos, const char * s, const Value & v
.errPos = positions[pos]
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
+ debugError(&error, env, expr);
throw error;
}
@@ -990,8 +991,7 @@ void EvalState::throwTypeError(const PosIdx pos, const char * s, const ExprLambd
.errPos = positions[pos]
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
+ debugError(&error, env, expr);
throw error;
}
@@ -1005,8 +1005,7 @@ void EvalState::throwTypeError(const PosIdx pos, const Suggestions & suggestions
.suggestions = suggestions,
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
+ debugError(&error, env, expr);
throw error;
}
@@ -1018,8 +1017,7 @@ void EvalState::throwTypeError(const char * s, const Value & v, Env & env, Expr
.errPos = positions[expr.getPos()],
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
+ debugError(&error, env, expr);
throw error;
}
@@ -1031,8 +1029,7 @@ void EvalState::throwAssertionError(const PosIdx pos, const char * s, const std:
.errPos = positions[pos]
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
+ debugError(&error, env, expr);
throw error;
}
@@ -1044,8 +1041,7 @@ void EvalState::throwUndefinedVarError(const PosIdx pos, const char * s, const s
.errPos = positions[pos]
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
+ debugError(&error, env, expr);
throw error;
}
@@ -1057,8 +1053,7 @@ void EvalState::throwMissingArgumentError(const PosIdx pos, const char * s, cons
.errPos = positions[pos]
});
- if (debuggerHook)
- debuggerHook(&error, env, expr);
+ debugError(&error, env, expr);
throw error;
}
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 65b1466ea..db78e29b5 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -85,6 +85,8 @@ struct DebugTrace {
bool isError;
};
+void debugError(Error * e, Env & env, Expr & expr);
+
class EvalState
{
public:
From 7c75f1d52b3078608be29cbe0b009875829cc03f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophane=20Hufschmitt?=
<theophane.hufschmitt@tweag.io>
Date: Tue, 10 May 2022 11:56:47 +0200
Subject: [PATCH 126/188] Expand the testing section of the hacking docs
- Make it clear what the different kind of tests are, where they live
and how they can be ran
- Ask people to primarily write unit tests
---
doc/manual/src/contributing/hacking.md | 41 ++++++++++++++++++--------
1 file changed, 29 insertions(+), 12 deletions(-)
diff --git a/doc/manual/src/contributing/hacking.md b/doc/manual/src/contributing/hacking.md
index 90a8f1f94..7ce8d8de6 100644
--- a/doc/manual/src/contributing/hacking.md
+++ b/doc/manual/src/contributing/hacking.md
@@ -71,18 +71,6 @@ To install it in `$(pwd)/outputs` and test it:
nix (Nix) 3.0
```
-To run a functional test:
-
-```console
-make tests/test-name-should-auto-complete.sh.test
-```
-
-To run the unit-tests for C++ code:
-
-```
-make check
-```
-
If you have a flakes-enabled Nix you can replace:
```console
@@ -94,3 +82,32 @@ by:
```console
$ nix develop
```
+
+## Testing
+
+Nix comes with three different flavors of tests: unit, functional and integration.
+
+Most tests are currently written as functional tests.
+**However**, it is preferable (as much as it makes sense) to primarily test new code with unit tests.
+
+### Unit-tests
+
+The unit-tests for each Nix library (`libexpr`, `libstore`, etc..) are defined
+under `src/{library_name}/tests` using the
+[googletest](https://google.github.io/googletest/) framework.
+
+You can run the whole testsuite with `make check`, or the tests for a specific component with `make libfoo-tests_RUN`. Finer-grained filtering is also possible using the [--gtest_filter](https://google.github.io/googletest/advanced.html#running-a-subset-of-the-tests) command-line option.
+
+### Functional tests
+
+The functional tests reside under the `tests` directory and are listed in `tests/local.mk`.
+The whole testsuite can be run with `make install && make installcheck`.
+Individual tests can be run with `make tests/{testName}.sh.test`.
+
+### Integration tests
+
+The integration tests are defined in the Nix flake under the `hydraJobs.tests` attribute.
+These tests include everything that needs to interact with external services or run Nix in a non-trivial distributed setup.
+Because these tests are expensive and require more than what the standard github-actions setup provides, they only run on the master branch (on <https://hydra.nixos.org/jobset/nix/master>).
+
+You can run them manually with `nix build .#hydraJobs.tests.{testName}` or `nix-build -A hydraJobs.tests.{testName}`
From 2998527b185a41157be6ead42fd03a66601c4f56 Mon Sep 17 00:00:00 2001
From: Jimmy Reichley <jimmyqpublik@gmail.com>
Date: Tue, 10 May 2022 16:53:22 -0400
Subject: [PATCH 127/188] Allow setting bash-prompt-prefix nix develop
configuration
---
src/libexpr/flake/config.cc | 2 +-
src/nix/develop.cc | 6 ++++++
2 files changed, 7 insertions(+), 1 deletion(-)
diff --git a/src/libexpr/flake/config.cc b/src/libexpr/flake/config.cc
index 92ec27046..3e9d264b4 100644
--- a/src/libexpr/flake/config.cc
+++ b/src/libexpr/flake/config.cc
@@ -31,7 +31,7 @@ static void writeTrustedList(const TrustedList & trustedList)
void ConfigFile::apply()
{
- std::set<std::string> whitelist{"bash-prompt", "bash-prompt-suffix", "flake-registry"};
+ std::set<std::string> whitelist{"bash-prompt", "bash-prompt-prefix", "bash-prompt-suffix", "flake-registry"};
for (auto & [name, value] : settings) {
diff --git a/src/nix/develop.cc b/src/nix/develop.cc
index 3a99fff6f..2a3fc0213 100644
--- a/src/nix/develop.cc
+++ b/src/nix/develop.cc
@@ -18,6 +18,9 @@ struct DevelopSettings : Config
Setting<std::string> bashPrompt{this, "", "bash-prompt",
"The bash prompt (`PS1`) in `nix develop` shells."};
+ Setting<std::string> bashPromptPrefix{this, "", "bash-prompt-prefix",
+ "Prefix prepended to the `PS1` environment variable in `nix develop` shells."};
+
Setting<std::string> bashPromptSuffix{this, "", "bash-prompt-suffix",
"Suffix appended to the `PS1` environment variable in `nix develop` shells."};
};
@@ -482,6 +485,9 @@ struct CmdDevelop : Common, MixEnvironment
if (developSettings.bashPrompt != "")
script += fmt("[ -n \"$PS1\" ] && PS1=%s;\n",
shellEscape(developSettings.bashPrompt.get()));
+ if (developSettings.bashPromptPrefix != "")
+ script += fmt("[ -n \"$PS1\" ] && PS1=%s\"$PS1\";\n",
+ shellEscape(developSettings.bashPromptPrefix.get()));
if (developSettings.bashPromptSuffix != "")
script += fmt("[ -n \"$PS1\" ] && PS1+=%s;\n",
shellEscape(developSettings.bashPromptSuffix.get()));
From 584475acf9f4b8eda2a451901f6f9af35ae976e0 Mon Sep 17 00:00:00 2001
From: Jimmy Reichley <jimmyqpublik@gmail.com>
Date: Tue, 10 May 2022 16:55:25 -0400
Subject: [PATCH 128/188] Add documentation for bash-prompt-prefix
---
src/nix/develop.md | 4 ++--
src/nix/flake.md | 7 ++++---
2 files changed, 6 insertions(+), 5 deletions(-)
diff --git a/src/nix/develop.md b/src/nix/develop.md
index 8bcff66c9..e036ec6b9 100644
--- a/src/nix/develop.md
+++ b/src/nix/develop.md
@@ -80,8 +80,8 @@ initialised by `stdenv` and exits. This build environment can be
recorded into a profile using `--profile`.
The prompt used by the `bash` shell can be customised by setting the
-`bash-prompt` and `bash-prompt-suffix` settings in `nix.conf` or in
-the flake's `nixConfig` attribute.
+`bash-prompt`, `bash-prompt-prefix`, and `bash-prompt-suffix` settings in
+`nix.conf` or in the flake's `nixConfig` attribute.
# Flake output attributes
diff --git a/src/nix/flake.md b/src/nix/flake.md
index c8251eb74..aa3f9f303 100644
--- a/src/nix/flake.md
+++ b/src/nix/flake.md
@@ -331,9 +331,10 @@ The following attributes are supported in `flake.nix`:
* `nixConfig`: a set of `nix.conf` options to be set when evaluating any
part of a flake. In the interests of security, only a small set of
- whitelisted options (currently `bash-prompt`, `bash-prompt-suffix`,
- and `flake-registry`) are allowed to be set without confirmation so long as
- `accept-flake-config` is not set in the global configuration.
+ whitelisted options (currently `bash-prompt`, `bash-prompt-prefix`,
+ `bash-prompt-suffix`, and `flake-registry`) are allowed to be set without
+ confirmation so long as `accept-flake-config` is not set in the global
+ configuration.
## Flake inputs
From aefc6c4f41bfac0c76807c234fd0a786dd40f140 Mon Sep 17 00:00:00 2001
From: Eli Kogan-Wang <elikowa@gmail.com>
Date: Wed, 11 May 2022 12:15:08 +0200
Subject: [PATCH 129/188] Add priority for nix profile install
---
src/libstore/builtins/buildenv.cc | 3 ++-
src/nix/profile.cc | 29 +++++++++++++++++++++++++++--
tests/nix-profile.sh | 16 ++++++++++++++++
3 files changed, 45 insertions(+), 3 deletions(-)
diff --git a/src/libstore/builtins/buildenv.cc b/src/libstore/builtins/buildenv.cc
index 6f6ad57cb..c17c76e71 100644
--- a/src/libstore/builtins/buildenv.cc
+++ b/src/libstore/builtins/buildenv.cc
@@ -93,8 +93,9 @@ static void createLinks(State & state, const Path & srcDir, const Path & dstDir,
auto prevPriority = state.priorities[dstFile];
if (prevPriority == priority)
throw Error(
- "packages '%1%' and '%2%' have the same priority %3%; "
+ "files '%1%' and '%2%' have the same priority %3%; "
"use 'nix-env --set-flag priority NUMBER INSTALLED_PKGNAME' "
+ "or 'nix profile --priority NUMBER INSTALLED_PKGNAME' "
"to change the priority of one of the conflicting packages"
" (0 being the highest priority)",
srcFile, readLink(dstFile), priority);
diff --git a/src/nix/profile.cc b/src/nix/profile.cc
index 685776bec..fb8bef670 100644
--- a/src/nix/profile.cc
+++ b/src/nix/profile.cc
@@ -37,7 +37,7 @@ struct ProfileElement
StorePathSet storePaths;
std::optional<ProfileElementSource> source;
bool active = true;
- // FIXME: priority
+ int priority = 5;
std::string describe() const
{
@@ -116,6 +116,9 @@ struct ProfileManifest
for (auto & p : e["storePaths"])
element.storePaths.insert(state.store->parseStorePath((std::string) p));
element.active = e["active"];
+ if(e.contains("priority")) {
+ element.priority = e["priority"];
+ }
if (e.value(sUrl, "") != "") {
element.source = ProfileElementSource {
parseFlakeRef(e[sOriginalUrl]),
@@ -153,6 +156,7 @@ struct ProfileManifest
nlohmann::json obj;
obj["storePaths"] = paths;
obj["active"] = element.active;
+ obj["priority"] = element.priority;
if (element.source) {
obj["originalUrl"] = element.source->originalRef.to_string();
obj["url"] = element.source->resolvedRef.to_string();
@@ -177,7 +181,7 @@ struct ProfileManifest
for (auto & element : elements) {
for (auto & path : element.storePaths) {
if (element.active)
- pkgs.emplace_back(store->printStorePath(path), true, 5);
+ pkgs.emplace_back(store->printStorePath(path), true, element.priority);
references.insert(path);
}
}
@@ -259,6 +263,23 @@ builtPathsPerInstallable(
struct CmdProfileInstall : InstallablesCommand, MixDefaultProfile
{
+ std::optional<int> priority;
+ CmdProfileInstall() {
+ addFlag({
+ .longName = "priority",
+ .description = "The priority of the package to install.",
+ .labels = {"priority"},
+ .handler = {[&](std::string s) {
+ try{
+ priority = std::stoi(s);
+ } catch (std::invalid_argument & e) {
+ throw ParseError("invalid priority '%s'", s);
+ }
+ }},
+ // .completer = // no completer since number
+ });
+ };
+
std::string description() override
{
return "install a package into a profile";
@@ -282,6 +303,10 @@ struct CmdProfileInstall : InstallablesCommand, MixDefaultProfile
for (auto & installable : installables) {
ProfileElement element;
+ if(priority) {
+ element.priority = *priority;
+ };
+
if (auto installable2 = std::dynamic_pointer_cast<InstallableFlake>(installable)) {
// FIXME: make build() return this?
auto [attrPath, resolvedRef, drv] = installable2->toDerivation();
diff --git a/tests/nix-profile.sh b/tests/nix-profile.sh
index f8da3d929..1cc724483 100644
--- a/tests/nix-profile.sh
+++ b/tests/nix-profile.sh
@@ -120,3 +120,19 @@ nix profile install "$flake1Dir^man"
(! [ -e $TEST_HOME/.nix-profile/bin/hello ])
[ -e $TEST_HOME/.nix-profile/share/man ]
(! [ -e $TEST_HOME/.nix-profile/include ])
+
+# test priority
+nix profile remove 0
+
+# Make another flake.
+flake2Dir=$TEST_ROOT/flake2
+printf World > $flake1Dir/who
+cp -r $flake1Dir $flake2Dir
+printf World2 > $flake2Dir/who
+
+nix profile install $flake1Dir
+[[ $($TEST_HOME/.nix-profile/bin/hello) = "Hello World" ]]
+nix profile install $flake2Dir --priority 100
+[[ $($TEST_HOME/.nix-profile/bin/hello) = "Hello World" ]]
+nix profile install $flake2Dir --priority 0
+[[ $($TEST_HOME/.nix-profile/bin/hello) = "Hello World2" ]]
From 65a913d29be7305b2c743fb92c93f0e6bb12d610 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophane=20Hufschmitt?=
<theophane.hufschmitt@tweag.io>
Date: Thu, 12 May 2022 12:02:31 +0200
Subject: [PATCH 130/188] =?UTF-8?q?Don=E2=80=99t=20recommend=20writing=20u?=
=?UTF-8?q?nit=20tests?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
As asked in <https://github.com/NixOS/nix/pull/6517#discussion_r869416905>
---
doc/manual/src/contributing/hacking.md | 3 ---
1 file changed, 3 deletions(-)
diff --git a/doc/manual/src/contributing/hacking.md b/doc/manual/src/contributing/hacking.md
index 7ce8d8de6..59ce5cac7 100644
--- a/doc/manual/src/contributing/hacking.md
+++ b/doc/manual/src/contributing/hacking.md
@@ -87,9 +87,6 @@ $ nix develop
Nix comes with three different flavors of tests: unit, functional and integration.
-Most tests are currently written as functional tests.
-**However**, it is preferable (as much as it makes sense) to primarily test new code with unit tests.
-
### Unit-tests
The unit-tests for each Nix library (`libexpr`, `libstore`, etc..) are defined
From 1ea13084c9aac84e7877f9051f656eb5ea519d8a Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Thu, 12 May 2022 13:59:58 -0600
Subject: [PATCH 131/188] template-ize debugThrow
---
src/libexpr/eval.cc | 24 ------------------------
src/libexpr/eval.hh | 24 ++++++++++++++++++++++--
2 files changed, 22 insertions(+), 26 deletions(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 54872669a..8ba3688d8 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -802,30 +802,6 @@ std::unique_ptr<ValMap> mapStaticEnvBindings(const SymbolTable & st, const Stati
return vm;
}
-void EvalState::debugThrowLastTrace(Error & e) const
-{
- std::cout << "debugThrowLastTrace(Error & e) const" << (debuggerHook == nullptr) << std::endl;
- // Call this in the situation where Expr and Env are inaccessible.
- // The debugger will start in the last context that's in the
- // DebugTrace stack.
- if (debuggerHook && !debugTraces.empty()) {
- const DebugTrace & last = debugTraces.front();
- debuggerHook(&e, last.env, last.expr);
- }
-
- throw e;
-}
-
-
-void EvalState::debugThrow(const Error &error, const Env & env, const Expr & expr) const
-{
- std::cout << "debugThrow" << (debuggerHook == nullptr) << std::endl;
- if (debuggerHook)
- debuggerHook(&error, env, expr);
-
- throw error;
-}
-
/* Every "format" object (even temporary) takes up a few hundred bytes
of stack space, which is a real killer in the recursive
evaluator. So here are some helper functions for throwing
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index add104a84..1e728002a 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -128,10 +128,30 @@ public:
bool debugQuit;
std::list<DebugTrace> debugTraces;
+ template<class E>
[[gnu::noinline, gnu::noreturn]]
- void debugThrow(const Error &error, const Env & env, const Expr & expr) const;
+ void debugThrow(const E &error, const Env & env, const Expr & expr) const
+ {
+ if (debuggerHook)
+ debuggerHook(&error, env, expr);
+
+ throw error;
+ }
+
+ template<class E>
[[gnu::noinline, gnu::noreturn]]
- void debugThrowLastTrace(Error & e) const;
+ void debugThrowLastTrace(E & e) const
+ {
+ // Call this in the situation where Expr and Env are inaccessible.
+ // The debugger will start in the last context that's in the
+ // DebugTrace stack.
+ if (debuggerHook && !debugTraces.empty()) {
+ const DebugTrace & last = debugTraces.front();
+ debuggerHook(&e, last.env, last.expr);
+ }
+
+ throw e;
+ }
private:
SrcToStore srcToStore;
From 2d0d1ec99d032ce236ee0b8194ac2da762e7f462 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Thu, 12 May 2022 14:15:35 -0600
Subject: [PATCH 132/188] remove debug code
---
src/libexpr/primops.cc | 6 ------
1 file changed, 6 deletions(-)
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index d2b94b95c..8ef8fe7f5 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -878,7 +878,6 @@ static RegisterPrimOp primop_floor({
* else => {success=false; value=false;} */
static void prim_tryEval(EvalState & state, const PosIdx pos, Value * * args, Value & v)
{
- std::cout << "priatraynasdf0" << std::endl;
auto attrs = state.buildBindings(2);
auto saveDebuggerHook = debuggerHook;
debuggerHook = nullptr;
@@ -886,15 +885,10 @@ static void prim_tryEval(EvalState & state, const PosIdx pos, Value * * args, Va
state.forceValue(*args[0], pos);
attrs.insert(state.sValue, args[0]);
attrs.alloc("success").mkBool(true);
- std::cout << "priatraynasdf0000" << std::endl;
} catch (AssertionError & e) {
- std::cout << "priatraynasdf" << std::endl;
-
attrs.alloc(state.sValue).mkBool(false);
attrs.alloc("success").mkBool(false);
} catch (Error & e) {
- std::cout << "priatraERASERynasdf" << std::endl;
-
attrs.alloc(state.sValue).mkBool(false);
attrs.alloc("success").mkBool(false);
}
From 2acdb90438f315e145f97218b1b34f75b40ebc70 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Thu, 12 May 2022 14:20:45 -0600
Subject: [PATCH 133/188] remove debug code
---
src/libexpr/primops.cc | 3 ---
1 file changed, 3 deletions(-)
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 8ef8fe7f5..ff5ae8809 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -888,9 +888,6 @@ static void prim_tryEval(EvalState & state, const PosIdx pos, Value * * args, Va
} catch (AssertionError & e) {
attrs.alloc(state.sValue).mkBool(false);
attrs.alloc("success").mkBool(false);
- } catch (Error & e) {
- attrs.alloc(state.sValue).mkBool(false);
- attrs.alloc("success").mkBool(false);
}
debuggerHook = saveDebuggerHook;
v.mkAttrs(attrs);
From 8150b93968c648c6d273aaffaffba94096ec3faf Mon Sep 17 00:00:00 2001
From: Tom Bereknyei <tomberek@gmail.com>
Date: Fri, 13 May 2022 11:12:11 -0400
Subject: [PATCH 134/188] fix: alignment during flake show of legacyPackages
Fixes:
https://github.com/NixOS/nix/issues/6240
https://github.com/NixOS/nix/issues/6045
---
src/nix/flake.cc | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/src/nix/flake.cc b/src/nix/flake.cc
index 1938ce4e6..f55929751 100644
--- a/src/nix/flake.cc
+++ b/src/nix/flake.cc
@@ -1076,9 +1076,13 @@ struct CmdFlakeShow : FlakeCommand, MixJSON
else if (attrPath.size() > 0 && attrPathS[0] == "legacyPackages") {
if (attrPath.size() == 1)
recurse();
- else if (!showLegacy)
- logger->warn(fmt("%s: " ANSI_WARNING "omitted" ANSI_NORMAL " (use '--legacy' to show)", headerPrefix));
- else {
+ else if (!showLegacy){
+ if (!json)
+ logger->cout(fmt("%s " ANSI_WARNING "omitted" ANSI_NORMAL " (use '--legacy' to show)", headerPrefix));
+ else {
+ logger->warn(fmt("%s omitted (use '--legacy' to show)", concatStringsSep(".", attrPathS)));
+ }
+ } else {
if (visitor.isDerivation())
showDerivation();
else if (attrPath.size() <= 2)
From be2b19041eeec53fba24f7c2494f3f700a4ec595 Mon Sep 17 00:00:00 2001
From: Eli Kogan-Wang <elikowa@gmail.com>
Date: Fri, 13 May 2022 22:02:28 +0200
Subject: [PATCH 135/188] Integrate review changes
---
src/libcmd/installables.cc | 11 ++++++++---
src/libcmd/installables.hh | 3 ++-
src/libexpr/eval-cache.cc | 22 ++++++++++++++++++++++
src/libexpr/eval-cache.hh | 3 +++
src/libstore/builtins/buildenv.cc | 2 +-
src/nix/profile.cc | 25 ++++++++++++-------------
tests/nix-profile.sh | 2 ++
7 files changed, 50 insertions(+), 18 deletions(-)
diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index a94e60aca..3f6dfd592 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -609,7 +609,7 @@ InstallableFlake::InstallableFlake(
throw UsageError("'--arg' and '--argstr' are incompatible with flakes");
}
-std::tuple<std::string, FlakeRef, InstallableValue::DerivationInfo> InstallableFlake::toDerivation()
+std::tuple<std::string, FlakeRef, InstallableValue::DerivationInfo, std::optional<NixInt>> InstallableFlake::toDerivation()
{
auto attr = getCursor(*state);
@@ -621,11 +621,15 @@ std::tuple<std::string, FlakeRef, InstallableValue::DerivationInfo> InstallableF
auto drvPath = attr->forceDerivation();
std::set<std::string> outputsToInstall;
+ std::optional<NixInt> priority;
- if (auto aMeta = attr->maybeGetAttr(state->sMeta))
+ if (auto aMeta = attr->maybeGetAttr(state->sMeta)) {
if (auto aOutputsToInstall = aMeta->maybeGetAttr("outputsToInstall"))
for (auto & s : aOutputsToInstall->getListOfStrings())
outputsToInstall.insert(s);
+ if (auto aPriority = aMeta->maybeGetAttr("priority"))
+ priority = aPriority->getInt();
+ }
if (outputsToInstall.empty() || std::get_if<AllOutputs>(&outputsSpec)) {
outputsToInstall.clear();
@@ -643,9 +647,10 @@ std::tuple<std::string, FlakeRef, InstallableValue::DerivationInfo> InstallableF
auto drvInfo = DerivationInfo {
.drvPath = std::move(drvPath),
.outputsToInstall = std::move(outputsToInstall),
+ .priority = priority,
};
- return {attrPath, getLockedFlake()->flake.lockedRef, std::move(drvInfo)};
+ return {attrPath, getLockedFlake()->flake.lockedRef, std::move(drvInfo), priority};
}
std::vector<InstallableValue::DerivationInfo> InstallableFlake::toDerivations()
diff --git a/src/libcmd/installables.hh b/src/libcmd/installables.hh
index 1a5a96153..d7b61f1b8 100644
--- a/src/libcmd/installables.hh
+++ b/src/libcmd/installables.hh
@@ -142,6 +142,7 @@ struct InstallableValue : Installable
{
StorePath drvPath;
std::set<std::string> outputsToInstall;
+ std::optional<NixInt> priority;
};
virtual std::vector<DerivationInfo> toDerivations() = 0;
@@ -176,7 +177,7 @@ struct InstallableFlake : InstallableValue
Value * getFlakeOutputs(EvalState & state, const flake::LockedFlake & lockedFlake);
- std::tuple<std::string, FlakeRef, DerivationInfo> toDerivation();
+ std::tuple<std::string, FlakeRef, DerivationInfo, std::optional<NixInt>> toDerivation();
std::vector<DerivationInfo> toDerivations() override;
diff --git a/src/libexpr/eval-cache.cc b/src/libexpr/eval-cache.cc
index 0eb4bc79e..b4bce512b 100644
--- a/src/libexpr/eval-cache.cc
+++ b/src/libexpr/eval-cache.cc
@@ -621,6 +621,28 @@ bool AttrCursor::getBool()
return v.boolean;
}
+NixInt AttrCursor::getInt()
+{
+ if (root->db) {
+ if (!cachedValue)
+ cachedValue = root->db->getAttr(getKey());
+ if (cachedValue && !std::get_if<placeholder_t>(&cachedValue->second)) {
+ if (auto i = std::get_if<NixInt>(&cachedValue->second)) {
+ debug("using cached Integer attribute '%s'", getAttrPathStr());
+ return *i;
+ } else
+ throw TypeError("'%s' is not an Integer", getAttrPathStr());
+ }
+ }
+
+ auto & v = forceValue();
+
+ if (v.type() != nInt)
+ throw TypeError("'%s' is not an Integer", getAttrPathStr());
+
+ return v.integer;
+}
+
std::vector<std::string> AttrCursor::getListOfStrings()
{
if (root->db) {
diff --git a/src/libexpr/eval-cache.hh b/src/libexpr/eval-cache.hh
index 636e293ad..105e9217b 100644
--- a/src/libexpr/eval-cache.hh
+++ b/src/libexpr/eval-cache.hh
@@ -63,6 +63,7 @@ typedef std::variant<
misc_t,
failed_t,
bool,
+ NixInt,
std::vector<std::string>
> AttrValue;
@@ -116,6 +117,8 @@ public:
bool getBool();
+ NixInt getInt();
+
std::vector<std::string> getListOfStrings();
std::vector<Symbol> getAttrs();
diff --git a/src/libstore/builtins/buildenv.cc b/src/libstore/builtins/buildenv.cc
index c17c76e71..58ef89a1c 100644
--- a/src/libstore/builtins/buildenv.cc
+++ b/src/libstore/builtins/buildenv.cc
@@ -95,7 +95,7 @@ static void createLinks(State & state, const Path & srcDir, const Path & dstDir,
throw Error(
"files '%1%' and '%2%' have the same priority %3%; "
"use 'nix-env --set-flag priority NUMBER INSTALLED_PKGNAME' "
- "or 'nix profile --priority NUMBER INSTALLED_PKGNAME' "
+ "or 'nix profile install --priority NUMBER INSTALLED_PKGNAME' "
"to change the priority of one of the conflicting packages"
" (0 being the highest priority)",
srcFile, readLink(dstFile), priority);
diff --git a/src/nix/profile.cc b/src/nix/profile.cc
index fb8bef670..ca5041873 100644
--- a/src/nix/profile.cc
+++ b/src/nix/profile.cc
@@ -269,14 +269,7 @@ struct CmdProfileInstall : InstallablesCommand, MixDefaultProfile
.longName = "priority",
.description = "The priority of the package to install.",
.labels = {"priority"},
- .handler = {[&](std::string s) {
- try{
- priority = std::stoi(s);
- } catch (std::invalid_argument & e) {
- throw ParseError("invalid priority '%s'", s);
- }
- }},
- // .completer = // no completer since number
+ .handler = {&priority},
});
};
@@ -303,21 +296,27 @@ struct CmdProfileInstall : InstallablesCommand, MixDefaultProfile
for (auto & installable : installables) {
ProfileElement element;
- if(priority) {
- element.priority = *priority;
- };
+
if (auto installable2 = std::dynamic_pointer_cast<InstallableFlake>(installable)) {
// FIXME: make build() return this?
- auto [attrPath, resolvedRef, drv] = installable2->toDerivation();
+ auto [attrPath, resolvedRef, drv, priority] = installable2->toDerivation();
element.source = ProfileElementSource {
installable2->flakeRef,
resolvedRef,
attrPath,
installable2->outputsSpec
};
+
+ if(drv.priority) {
+ element.priority = *drv.priority;
+ }
}
+ if(priority) { // if --priority was specified we want to override the priority of the installable
+ element.priority = *priority;
+ };
+
element.updateStorePaths(getEvalStore(), store, builtPaths[installable.get()]);
manifest.elements.push_back(std::move(element));
@@ -476,7 +475,7 @@ struct CmdProfileUpgrade : virtual SourceExprCommand, MixDefaultProfile, MixProf
Strings{},
lockFlags);
- auto [attrPath, resolvedRef, drv] = installable->toDerivation();
+ auto [attrPath, resolvedRef, drv, priority] = installable->toDerivation();
if (element.source->resolvedRef == resolvedRef) continue;
diff --git a/tests/nix-profile.sh b/tests/nix-profile.sh
index 1cc724483..7ba3235fa 100644
--- a/tests/nix-profile.sh
+++ b/tests/nix-profile.sh
@@ -136,3 +136,5 @@ nix profile install $flake2Dir --priority 100
[[ $($TEST_HOME/.nix-profile/bin/hello) = "Hello World" ]]
nix profile install $flake2Dir --priority 0
[[ $($TEST_HOME/.nix-profile/bin/hello) = "Hello World2" ]]
+# nix profile install $flake1Dir --priority 100
+# [[ $($TEST_HOME/.nix-profile/bin/hello) = "Hello World" ]]
From 6faa56ea1f7f8b708e8c931f41b627541a023c79 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Sun, 15 May 2022 12:05:34 -0600
Subject: [PATCH 136/188] remove extra argument
---
src/libcmd/command.cc | 2 +-
src/libcmd/command.hh | 1 -
src/libcmd/repl.cc | 1 -
3 files changed, 1 insertion(+), 3 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 12cd5ed83..bf97a3de8 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -138,7 +138,7 @@ ref<EvalState> EvalCommand::getEvalState()
if (expr.staticEnv) {
auto vm = mapStaticEnvBindings(evalState->symbols, *expr.staticEnv.get(), env);
- runRepl(evalState, expr, *vm);
+ runRepl(evalState, *vm);
}
};
}
diff --git a/src/libcmd/command.hh b/src/libcmd/command.hh
index 454197b1c..196bd3aaa 100644
--- a/src/libcmd/command.hh
+++ b/src/libcmd/command.hh
@@ -275,7 +275,6 @@ void printClosureDiff(
void runRepl(
ref<EvalState> evalState,
- const Expr & expr,
const ValMap & extraEnv);
}
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 8f0b1bfc0..deac3d408 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -1012,7 +1012,6 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
void runRepl(
ref<EvalState> evalState,
- const Expr &expr,
const ValMap & extraEnv)
{
auto repl = std::make_unique<NixRepl>(evalState);
From 86ba0a702c63b4a8ff79a07f9303318feb330642 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Sun, 15 May 2022 12:05:51 -0600
Subject: [PATCH 137/188] fix thunk issue
---
src/libexpr/eval.cc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index c36bb59fb..d9ea92cc0 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -2073,7 +2073,7 @@ void EvalState::forceValueDeep(Value & v)
try {
// If the value is a thunk, we're evaling. Otherwise no trace necessary.
auto dts = debuggerHook && i.value->isThunk()
- ? makeDebugTraceStacker(*this, *v.thunk.expr, *v.thunk.env, positions[i.pos],
+ ? makeDebugTraceStacker(*this, *i.value->thunk.expr, *i.value->thunk.env, positions[i.pos],
"while evaluating the attribute '%1%'", symbols[i.name])
: nullptr;
From c81d24f1c70cc454c9a88cea70048d8563f60784 Mon Sep 17 00:00:00 2001
From: Eli Kogan-Wang <elikowa@gmail.com>
Date: Mon, 16 May 2022 02:28:21 +0200
Subject: [PATCH 138/188] Add int to eval-cache, bump eval cache schema version
---
src/libexpr/eval-cache.cc | 24 +++++++++++++++++++++++-
src/libexpr/eval-cache.hh | 1 +
2 files changed, 24 insertions(+), 1 deletion(-)
diff --git a/src/libexpr/eval-cache.cc b/src/libexpr/eval-cache.cc
index b4bce512b..bf811c8ed 100644
--- a/src/libexpr/eval-cache.cc
+++ b/src/libexpr/eval-cache.cc
@@ -47,7 +47,7 @@ struct AttrDb
{
auto state(_state->lock());
- Path cacheDir = getCacheDir() + "/nix/eval-cache-v3";
+ Path cacheDir = getCacheDir() + "/nix/eval-cache-v4";
createDirs(cacheDir);
Path dbPath = cacheDir + "/" + fingerprint.to_string(Base16, false) + ".sqlite";
@@ -175,6 +175,24 @@ struct AttrDb
});
}
+ AttrId setInt(
+ AttrKey key,
+ int n)
+ {
+ return doSQLite([&]()
+ {
+ auto state(_state->lock());
+
+ state->insertAttribute.use()
+ (key.first)
+ (symbols[key.second])
+ (AttrType::Int)
+ (n).exec();
+
+ return state->db.getLastInsertedRowId();
+ });
+ }
+
AttrId setListOfStrings(
AttrKey key,
const std::vector<std::string> & l)
@@ -287,6 +305,8 @@ struct AttrDb
}
case AttrType::Bool:
return {{rowId, queryAttribute.getInt(2) != 0}};
+ case AttrType::Int:
+ return {{rowId, queryAttribute.getInt(2)}};
case AttrType::ListOfStrings:
return {{rowId, tokenizeString<std::vector<std::string>>(queryAttribute.getStr(2), "\t")}};
case AttrType::Missing:
@@ -426,6 +446,8 @@ Value & AttrCursor::forceValue()
cachedValue = {root->db->setString(getKey(), v.path), string_t{v.path, {}}};
else if (v.type() == nBool)
cachedValue = {root->db->setBool(getKey(), v.boolean), v.boolean};
+ else if (v.type() == nInt)
+ cachedValue = {root->db->setInt(getKey(), v.integer), v.integer};
else if (v.type() == nAttrs)
; // FIXME: do something?
else
diff --git a/src/libexpr/eval-cache.hh b/src/libexpr/eval-cache.hh
index 105e9217b..ec255c60d 100644
--- a/src/libexpr/eval-cache.hh
+++ b/src/libexpr/eval-cache.hh
@@ -45,6 +45,7 @@ enum AttrType {
Failed = 5,
Bool = 6,
ListOfStrings = 7,
+ Int = 8,
};
struct placeholder_t {};
From 27d0f6747d7e70be4b9ade28ce77444e6135cadb Mon Sep 17 00:00:00 2001
From: Eli Kogan-Wang <elikowa@gmail.com>
Date: Mon, 16 May 2022 15:17:35 +0200
Subject: [PATCH 139/188] resolve redundant priority passing, wrap NixInt in
eval-cache variant
---
src/libcmd/installables.cc | 4 ++--
src/libcmd/installables.hh | 2 +-
src/libexpr/eval-cache.cc | 6 +++---
src/libexpr/eval-cache.hh | 3 ++-
src/nix/profile.cc | 4 ++--
5 files changed, 10 insertions(+), 9 deletions(-)
diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index 3f6dfd592..635ce19b6 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -609,7 +609,7 @@ InstallableFlake::InstallableFlake(
throw UsageError("'--arg' and '--argstr' are incompatible with flakes");
}
-std::tuple<std::string, FlakeRef, InstallableValue::DerivationInfo, std::optional<NixInt>> InstallableFlake::toDerivation()
+std::tuple<std::string, FlakeRef, InstallableValue::DerivationInfo> InstallableFlake::toDerivation()
{
auto attr = getCursor(*state);
@@ -650,7 +650,7 @@ std::tuple<std::string, FlakeRef, InstallableValue::DerivationInfo, std::optiona
.priority = priority,
};
- return {attrPath, getLockedFlake()->flake.lockedRef, std::move(drvInfo), priority};
+ return {attrPath, getLockedFlake()->flake.lockedRef, std::move(drvInfo)};
}
std::vector<InstallableValue::DerivationInfo> InstallableFlake::toDerivations()
diff --git a/src/libcmd/installables.hh b/src/libcmd/installables.hh
index d7b61f1b8..5d715210e 100644
--- a/src/libcmd/installables.hh
+++ b/src/libcmd/installables.hh
@@ -177,7 +177,7 @@ struct InstallableFlake : InstallableValue
Value * getFlakeOutputs(EvalState & state, const flake::LockedFlake & lockedFlake);
- std::tuple<std::string, FlakeRef, DerivationInfo, std::optional<NixInt>> toDerivation();
+ std::tuple<std::string, FlakeRef, DerivationInfo> toDerivation();
std::vector<DerivationInfo> toDerivations() override;
diff --git a/src/libexpr/eval-cache.cc b/src/libexpr/eval-cache.cc
index bf811c8ed..6b3c27fd5 100644
--- a/src/libexpr/eval-cache.cc
+++ b/src/libexpr/eval-cache.cc
@@ -306,7 +306,7 @@ struct AttrDb
case AttrType::Bool:
return {{rowId, queryAttribute.getInt(2) != 0}};
case AttrType::Int:
- return {{rowId, queryAttribute.getInt(2)}};
+ return {{rowId, (int_t) queryAttribute.getInt(2)}};
case AttrType::ListOfStrings:
return {{rowId, tokenizeString<std::vector<std::string>>(queryAttribute.getStr(2), "\t")}};
case AttrType::Missing:
@@ -649,9 +649,9 @@ NixInt AttrCursor::getInt()
if (!cachedValue)
cachedValue = root->db->getAttr(getKey());
if (cachedValue && !std::get_if<placeholder_t>(&cachedValue->second)) {
- if (auto i = std::get_if<NixInt>(&cachedValue->second)) {
+ if (auto i = std::get_if<int_t>(&cachedValue->second)) {
debug("using cached Integer attribute '%s'", getAttrPathStr());
- return *i;
+ return (*i).x;
} else
throw TypeError("'%s' is not an Integer", getAttrPathStr());
}
diff --git a/src/libexpr/eval-cache.hh b/src/libexpr/eval-cache.hh
index ec255c60d..68b5952eb 100644
--- a/src/libexpr/eval-cache.hh
+++ b/src/libexpr/eval-cache.hh
@@ -52,6 +52,7 @@ struct placeholder_t {};
struct missing_t {};
struct misc_t {};
struct failed_t {};
+struct int_t { NixInt x; int_t(NixInt x) : x(x) {}; };
typedef uint64_t AttrId;
typedef std::pair<AttrId, Symbol> AttrKey;
typedef std::pair<std::string, NixStringContext> string_t;
@@ -64,7 +65,7 @@ typedef std::variant<
misc_t,
failed_t,
bool,
- NixInt,
+ int_t,
std::vector<std::string>
> AttrValue;
diff --git a/src/nix/profile.cc b/src/nix/profile.cc
index ca5041873..1aae347df 100644
--- a/src/nix/profile.cc
+++ b/src/nix/profile.cc
@@ -300,7 +300,7 @@ struct CmdProfileInstall : InstallablesCommand, MixDefaultProfile
if (auto installable2 = std::dynamic_pointer_cast<InstallableFlake>(installable)) {
// FIXME: make build() return this?
- auto [attrPath, resolvedRef, drv, priority] = installable2->toDerivation();
+ auto [attrPath, resolvedRef, drv] = installable2->toDerivation();
element.source = ProfileElementSource {
installable2->flakeRef,
resolvedRef,
@@ -475,7 +475,7 @@ struct CmdProfileUpgrade : virtual SourceExprCommand, MixDefaultProfile, MixProf
Strings{},
lockFlags);
- auto [attrPath, resolvedRef, drv, priority] = installable->toDerivation();
+ auto [attrPath, resolvedRef, drv] = installable->toDerivation();
if (element.source->resolvedRef == resolvedRef) continue;
From e53349dd6e4a710eb7abff78722853cad418e9d2 Mon Sep 17 00:00:00 2001
From: Eli Kogan-Wang <elikowa@gmail.com>
Date: Mon, 16 May 2022 16:16:06 +0200
Subject: [PATCH 140/188] change priority conflict message
---
src/libstore/builtins/buildenv.cc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/libstore/builtins/buildenv.cc b/src/libstore/builtins/buildenv.cc
index 58ef89a1c..47458a388 100644
--- a/src/libstore/builtins/buildenv.cc
+++ b/src/libstore/builtins/buildenv.cc
@@ -95,7 +95,7 @@ static void createLinks(State & state, const Path & srcDir, const Path & dstDir,
throw Error(
"files '%1%' and '%2%' have the same priority %3%; "
"use 'nix-env --set-flag priority NUMBER INSTALLED_PKGNAME' "
- "or 'nix profile install --priority NUMBER INSTALLED_PKGNAME' "
+ "or type 'nix profile install --help' if using 'nix profile' to find out how"
"to change the priority of one of the conflicting packages"
" (0 being the highest priority)",
srcFile, readLink(dstFile), priority);
From 43a2c1367292733d3e0aa2e57137c897fb66d8f6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophane=20Hufschmitt?=
<theophane.hufschmitt@tweag.io>
Date: Mon, 16 May 2022 16:36:21 +0200
Subject: [PATCH 141/188] Make nix::eval_cache::int_t more idiomatic
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Don’t explicitely give it a constructor, but use aggregate
initialization instead (also prevents having an implicit coertion, which
is probably good here)
---
src/libexpr/eval-cache.cc | 6 +++---
src/libexpr/eval-cache.hh | 2 +-
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/src/libexpr/eval-cache.cc b/src/libexpr/eval-cache.cc
index 6b3c27fd5..6a2e775d0 100644
--- a/src/libexpr/eval-cache.cc
+++ b/src/libexpr/eval-cache.cc
@@ -306,7 +306,7 @@ struct AttrDb
case AttrType::Bool:
return {{rowId, queryAttribute.getInt(2) != 0}};
case AttrType::Int:
- return {{rowId, (int_t) queryAttribute.getInt(2)}};
+ return {{rowId, int_t{queryAttribute.getInt(2)}}};
case AttrType::ListOfStrings:
return {{rowId, tokenizeString<std::vector<std::string>>(queryAttribute.getStr(2), "\t")}};
case AttrType::Missing:
@@ -447,7 +447,7 @@ Value & AttrCursor::forceValue()
else if (v.type() == nBool)
cachedValue = {root->db->setBool(getKey(), v.boolean), v.boolean};
else if (v.type() == nInt)
- cachedValue = {root->db->setInt(getKey(), v.integer), v.integer};
+ cachedValue = {root->db->setInt(getKey(), v.integer), int_t{v.integer}};
else if (v.type() == nAttrs)
; // FIXME: do something?
else
@@ -651,7 +651,7 @@ NixInt AttrCursor::getInt()
if (cachedValue && !std::get_if<placeholder_t>(&cachedValue->second)) {
if (auto i = std::get_if<int_t>(&cachedValue->second)) {
debug("using cached Integer attribute '%s'", getAttrPathStr());
- return (*i).x;
+ return i->x;
} else
throw TypeError("'%s' is not an Integer", getAttrPathStr());
}
diff --git a/src/libexpr/eval-cache.hh b/src/libexpr/eval-cache.hh
index 68b5952eb..c93e55b93 100644
--- a/src/libexpr/eval-cache.hh
+++ b/src/libexpr/eval-cache.hh
@@ -52,7 +52,7 @@ struct placeholder_t {};
struct missing_t {};
struct misc_t {};
struct failed_t {};
-struct int_t { NixInt x; int_t(NixInt x) : x(x) {}; };
+struct int_t { NixInt x; };
typedef uint64_t AttrId;
typedef std::pair<AttrId, Symbol> AttrKey;
typedef std::pair<std::string, NixStringContext> string_t;
From 667074b5867ffe40e3f1c59bd8e4ebf259f86aaa Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Mon, 16 May 2022 09:20:51 -0600
Subject: [PATCH 142/188] first whack at passing evalState as an arg to
debuggerHook.
---
src/libcmd/command.cc | 11 ++++++-----
src/libcmd/command.hh | 2 +-
src/libcmd/repl.cc | 2 +-
src/libexpr/eval.cc | 2 +-
src/libexpr/eval.hh | 4 ++--
src/libexpr/nixexpr.cc | 2 +-
src/libexpr/nixexpr.hh | 2 +-
src/libexpr/primops.cc | 2 +-
src/libutil/ref.hh | 2 +-
9 files changed, 15 insertions(+), 14 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index bf97a3de8..ee5102a6a 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -119,13 +119,14 @@ ref<EvalState> EvalCommand::getEvalState()
#endif
;
if (startReplOnEvalErrors)
- debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error * error, const Env & env, const Expr & expr) {
+ // debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error * error, const Env & env, const Expr & expr) {
+ debuggerHook = [](const EvalState & evalState, const Error * error, const Env & env, const Expr & expr) {
auto dts =
error && expr.getPos()
? std::make_unique<DebugTraceStacker>(
- *evalState,
+ evalState,
DebugTrace {
- .pos = error->info().errPos ? *error->info().errPos : evalState->positions[expr.getPos()],
+ .pos = error->info().errPos ? *error->info().errPos : evalState.positions[expr.getPos()],
.expr = expr,
.env = env,
.hint = error->info().msg,
@@ -137,8 +138,8 @@ ref<EvalState> EvalCommand::getEvalState()
printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error->what());
if (expr.staticEnv) {
- auto vm = mapStaticEnvBindings(evalState->symbols, *expr.staticEnv.get(), env);
- runRepl(evalState, *vm);
+ auto vm = mapStaticEnvBindings(evalState.symbols, *expr.staticEnv.get(), env);
+ runRepl(*const_cast<EvalState*>(&evalState), *vm);
}
};
}
diff --git a/src/libcmd/command.hh b/src/libcmd/command.hh
index 196bd3aaa..8b37be901 100644
--- a/src/libcmd/command.hh
+++ b/src/libcmd/command.hh
@@ -274,7 +274,7 @@ void printClosureDiff(
void runRepl(
- ref<EvalState> evalState,
+ EvalState & evalState,
const ValMap & extraEnv);
}
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index deac3d408..cb5d5bb34 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -1011,7 +1011,7 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
}
void runRepl(
- ref<EvalState> evalState,
+ EvalState& evalState,
const ValMap & extraEnv)
{
auto repl = std::make_unique<NixRepl>(evalState);
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index d9ea92cc0..3c998f7b6 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -1044,7 +1044,7 @@ DebugTraceStacker::DebugTraceStacker(EvalState & evalState, DebugTrace t)
{
evalState.debugTraces.push_front(trace);
if (evalState.debugStop && debuggerHook)
- debuggerHook(nullptr, trace.env, trace.expr);
+ debuggerHook(evalState, nullptr, trace.env, trace.expr);
}
void Value::mkString(std::string_view s)
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index f274278be..26717a6f8 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -136,7 +136,7 @@ public:
void debugThrow(const E &error, const Env & env, const Expr & expr) const
{
if (debuggerHook)
- debuggerHook(&error, env, expr);
+ debuggerHook(*this, &error, env, expr);
throw error;
}
@@ -150,7 +150,7 @@ public:
// DebugTrace stack.
if (debuggerHook && !debugTraces.empty()) {
const DebugTrace & last = debugTraces.front();
- debuggerHook(&e, last.env, last.expr);
+ debuggerHook(*this, &e, last.env, last.expr);
}
throw e;
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index 213cf93fa..a7b7b8aad 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -10,7 +10,7 @@ namespace nix {
/* Launch the nix debugger */
-std::function<void(const Error * error, const Env & env, const Expr & expr)> debuggerHook;
+std::function<void(const EvalState & evalState,const Error * error, const Env & env, const Expr & expr)> debuggerHook;
/* Displaying abstract syntax trees. */
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index c4a509f31..856676033 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -22,7 +22,7 @@ MakeError(UndefinedVarError, Error);
MakeError(MissingArgumentError, EvalError);
MakeError(RestrictedPathError, Error);
-extern std::function<void(const Error * error, const Env & env, const Expr & expr)> debuggerHook;
+extern std::function<void(const EvalState & evalState, const Error * error, const Env & env, const Expr & expr)> debuggerHook;
/* Position objects. */
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index ff5ae8809..e56e6314b 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -765,7 +765,7 @@ static RegisterPrimOp primop_break({
});
auto & dt = state.debugTraces.front();
- debuggerHook(&error, dt.env, dt.expr);
+ debuggerHook(state, &error, dt.env, dt.expr);
if (state.debugQuit) {
// If the user elects to quit the repl, throw an exception.
diff --git a/src/libutil/ref.hh b/src/libutil/ref.hh
index f9578afc7..bf26321db 100644
--- a/src/libutil/ref.hh
+++ b/src/libutil/ref.hh
@@ -7,7 +7,7 @@
namespace nix {
/* A simple non-nullable reference-counted pointer. Actually a wrapper
- around std::shared_ptr that prevents non-null constructions. */
+ around std::shared_ptr that prevents null constructions. */
template<typename T>
class ref
{
From 685107c6c8ed9ffaa74101ebc78489903eaf88c0 Mon Sep 17 00:00:00 2001
From: Cole Helbling <cole.e.helbling@outlook.com>
Date: Mon, 16 May 2022 11:46:44 -0700
Subject: [PATCH 143/188] flake: use github: reference to nixpkgs
This allows flakes that don't override the Nixpkgs input and also have a
different flake registry.
---
flake.lock | 10 ++++++----
flake.nix | 4 ++--
2 files changed, 8 insertions(+), 6 deletions(-)
diff --git a/flake.lock b/flake.lock
index cd79fa85e..31c1910df 100644
--- a/flake.lock
+++ b/flake.lock
@@ -26,9 +26,10 @@
"type": "github"
},
"original": {
- "id": "nixpkgs",
+ "owner": "NixOS",
"ref": "nixos-21.05-small",
- "type": "indirect"
+ "repo": "nixpkgs",
+ "type": "github"
}
},
"nixpkgs-regression": {
@@ -41,9 +42,10 @@
"type": "github"
},
"original": {
- "id": "nixpkgs",
+ "owner": "NixOS",
+ "repo": "nixpkgs",
"rev": "215d4d0fd80ca5163643b03a33fde804a29cc1e2",
- "type": "indirect"
+ "type": "github"
}
},
"root": {
diff --git a/flake.nix b/flake.nix
index dd3a25e9e..b33d7d1b3 100644
--- a/flake.nix
+++ b/flake.nix
@@ -1,8 +1,8 @@
{
description = "The purely functional package manager";
- inputs.nixpkgs.url = "nixpkgs/nixos-21.05-small";
- inputs.nixpkgs-regression.url = "nixpkgs/215d4d0fd80ca5163643b03a33fde804a29cc1e2";
+ inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-21.05-small";
+ inputs.nixpkgs-regression.url = "github:NixOS/nixpkgs/215d4d0fd80ca5163643b03a33fde804a29cc1e2";
inputs.lowdown-src = { url = "github:kristapsdz/lowdown"; flake = false; };
outputs = { self, nixpkgs, nixpkgs-regression, lowdown-src }:
From b8e44dc62bb884b5c887852733819a909129d850 Mon Sep 17 00:00:00 2001
From: zhujun <zhujun@taobao.com>
Date: Wed, 18 May 2022 14:05:26 +0800
Subject: [PATCH 144/188] primop_match: fix example letter case in document
---
src/libexpr/primops.cc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 28fea276e..fe4d0fc5f 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -3529,7 +3529,7 @@ static RegisterPrimOp primop_match({
builtins.match "[[:space:]]+([[:upper:]]+)[[:space:]]+" " FOO "
```
- Evaluates to `[ "foo" ]`.
+ Evaluates to `[ "FOO" ]`.
)s",
.fun = prim_match,
});
From 169384abb2bcfb687c8ad5959896738a76f3452e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Na=C3=AFm=20Favier?= <n@monade.li>
Date: Wed, 18 May 2022 11:33:04 +0200
Subject: [PATCH 145/188] Do not attempt to write a lock file in
builtins.getFlake
Fixes https://github.com/NixOS/nix/issues/6541
---
src/libexpr/flake/flake.cc | 1 +
tests/flakes.sh | 1 +
2 files changed, 2 insertions(+)
diff --git a/src/libexpr/flake/flake.cc b/src/libexpr/flake/flake.cc
index cbf4f0a6f..35c841897 100644
--- a/src/libexpr/flake/flake.cc
+++ b/src/libexpr/flake/flake.cc
@@ -723,6 +723,7 @@ static void prim_getFlake(EvalState & state, const PosIdx pos, Value * * args, V
lockFlake(state, flakeRef,
LockFlags {
.updateLockFile = false,
+ .writeLockFile = false,
.useRegistries = !evalSettings.pureEval && fetchSettings.useRegistries,
.allowMutable = !evalSettings.pureEval,
}),
diff --git a/tests/flakes.sh b/tests/flakes.sh
index 24601784f..9a1f0ab6a 100644
--- a/tests/flakes.sh
+++ b/tests/flakes.sh
@@ -163,6 +163,7 @@ nix build -o $TEST_ROOT/result --expr "(builtins.getFlake \"git+file://$flake1Di
# But should succeed in impure mode.
(! nix build -o $TEST_ROOT/result flake2#bar --impure)
nix build -o $TEST_ROOT/result flake2#bar --impure --no-write-lock-file
+nix eval --expr "builtins.getFlake \"$flake2Dir\"" --impure
# Building a local flake with an unlocked dependency should fail with --no-update-lock-file.
nix build -o $TEST_ROOT/result $flake2Dir#bar --no-update-lock-file 2>&1 | grep 'requires lock file changes'
From 5b8c1deb18e0e6fc7a83fb8101cf5fc8dba38843 Mon Sep 17 00:00:00 2001
From: Tony Olagbaiye <me@fron.io>
Date: Fri, 16 Oct 2020 00:35:24 +0100
Subject: [PATCH 146/188] fetchTree: Allow fetching plain files
Add a new `file` fetcher type, which will fetch a plain file over
http(s), or from the local file.
Because plain `http(s)://` or `file://` urls can already correspond to
`tarball` inputs (if the path ends-up with a know archive extension),
the URL parsing logic is a bit convuluted in that:
- {http,https,file}:// urls will be interpreted as either a tarball or a
file input, depending on the extensions of the path part (so
`https://foo.com/bar` will be a `file` input and
`https://foo.com/bar.tar.gz` as a `tarball` input)
- `file+{something}://` urls will be interpreted as `file` urls (with
the `file+` part removed)
- `tarball+{something}://` urls will be interpreted as `tarball` urls (with
the `tarball+` part removed)
Fix #3785
Co-Authored-By: Tony Olagbaiye <me@fron.io>
---
doc/manual/src/release-notes/rl-next.md | 3 +
src/libfetchers/tarball.cc | 90 +++++++++++++++-----
src/libutil/url.cc | 18 ++++
src/libutil/url.hh | 15 ++++
src/nix/flake.md | 14 +++-
tests/fetchTree-file.sh | 105 ++++++++++++++++++++++++
tests/local.mk | 1 +
7 files changed, 221 insertions(+), 25 deletions(-)
create mode 100644 tests/fetchTree-file.sh
diff --git a/doc/manual/src/release-notes/rl-next.md b/doc/manual/src/release-notes/rl-next.md
index efd893662..9f00893fd 100644
--- a/doc/manual/src/release-notes/rl-next.md
+++ b/doc/manual/src/release-notes/rl-next.md
@@ -24,3 +24,6 @@
Selecting derivation outputs using the attribute selection syntax
(e.g. `nixpkgs#glibc.dev`) no longer works.
+
+* `builtins.fetchTree` (and flake inputs) can now be used to fetch plain files
+ over the `http(s)` and `file` protocols in addition to directory tarballs.
diff --git a/src/libfetchers/tarball.cc b/src/libfetchers/tarball.cc
index dde0ad761..09acb74d3 100644
--- a/src/libfetchers/tarball.cc
+++ b/src/libfetchers/tarball.cc
@@ -6,6 +6,7 @@
#include "archive.hh"
#include "tarfile.hh"
#include "types.hh"
+#include "split.hh"
namespace nix::fetchers {
@@ -168,24 +169,34 @@ std::pair<Tree, time_t> downloadTarball(
};
}
-struct TarballInputScheme : InputScheme
+// An input scheme corresponding to a curable ressource
+struct CurlInputScheme : InputScheme
{
+ virtual const std::string inputType() const = 0;
+ const std::set<std::string> transportUrlSchemes = {"file", "http", "https"};
+
+ const bool hasTarballExtension(std::string_view path) const
+ {
+ return hasSuffix(path, ".zip") || hasSuffix(path, ".tar")
+ || hasSuffix(path, ".tgz") || hasSuffix(path, ".tar.gz")
+ || hasSuffix(path, ".tar.xz") || hasSuffix(path, ".tar.bz2")
+ || hasSuffix(path, ".tar.zst");
+ }
+
+ virtual bool isValidURL(const ParsedURL & url) const = 0;
+
std::optional<Input> inputFromURL(const ParsedURL & url) override
{
- if (url.scheme != "file" && url.scheme != "http" && url.scheme != "https") return {};
-
- if (!hasSuffix(url.path, ".zip")
- && !hasSuffix(url.path, ".tar")
- && !hasSuffix(url.path, ".tgz")
- && !hasSuffix(url.path, ".tar.gz")
- && !hasSuffix(url.path, ".tar.xz")
- && !hasSuffix(url.path, ".tar.bz2")
- && !hasSuffix(url.path, ".tar.zst"))
- return {};
+ if (!isValidURL(url))
+ return std::nullopt;
Input input;
- input.attrs.insert_or_assign("type", "tarball");
- input.attrs.insert_or_assign("url", url.to_string());
+
+ auto urlWithoutApplicationScheme = url;
+ urlWithoutApplicationScheme.scheme = parseUrlScheme(url.scheme).transport;
+
+ input.attrs.insert_or_assign("type", inputType());
+ input.attrs.insert_or_assign("url", urlWithoutApplicationScheme.to_string());
auto narHash = url.query.find("narHash");
if (narHash != url.query.end())
input.attrs.insert_or_assign("narHash", narHash->second);
@@ -194,14 +205,17 @@ struct TarballInputScheme : InputScheme
std::optional<Input> inputFromAttrs(const Attrs & attrs) override
{
- if (maybeGetStrAttr(attrs, "type") != "tarball") return {};
+ auto type = maybeGetStrAttr(attrs, "type");
+ if (type != inputType()) return {};
+ std::set<std::string> allowedNames = {"type", "url", "narHash", "name", "unpack"};
for (auto & [name, value] : attrs)
- if (name != "type" && name != "url" && /* name != "hash" && */ name != "narHash" && name != "name")
- throw Error("unsupported tarball input attribute '%s'", name);
+ if (!allowedNames.count(name))
+ throw Error("unsupported %s input attribute '%s'", *type, name);
Input input;
input.attrs = attrs;
+
//input.locked = (bool) maybeGetStrAttr(input.attrs, "hash");
return input;
}
@@ -209,14 +223,9 @@ struct TarballInputScheme : InputScheme
ParsedURL toURL(const Input & input) override
{
auto url = parseURL(getStrAttr(input.attrs, "url"));
- // NAR hashes are preferred over file hashes since tar/zip files
- // don't have a canonical representation.
+ // NAR hashes are preferred over file hashes since tar/zip files // don't have a canonical representation.
if (auto narHash = input.getNarHash())
url.query.insert_or_assign("narHash", narHash->to_string(SRI, true));
- /*
- else if (auto hash = maybeGetStrAttr(input.attrs, "hash"))
- url.query.insert_or_assign("hash", Hash(*hash).to_string(SRI, true));
- */
return url;
}
@@ -225,6 +234,42 @@ struct TarballInputScheme : InputScheme
return true;
}
+};
+
+struct FileInputScheme : CurlInputScheme
+{
+ const std::string inputType() const override { return "file"; }
+
+ bool isValidURL(const ParsedURL & url) const override
+ {
+ auto parsedUrlScheme = parseUrlScheme(url.scheme);
+ return transportUrlSchemes.count(std::string(parsedUrlScheme.transport))
+ && (parsedUrlScheme.application
+ ? parsedUrlScheme.application.value() == inputType()
+ : !hasTarballExtension(url.path));
+ }
+
+ std::pair<StorePath, Input> fetch(ref<Store> store, const Input & input) override
+ {
+ auto file = downloadFile(store, getStrAttr(input.attrs, "url"), input.getName(), false);
+ return {std::move(file.storePath), input};
+ }
+};
+
+struct TarballInputScheme : CurlInputScheme
+{
+ const std::string inputType() const override { return "tarball"; }
+
+ bool isValidURL(const ParsedURL & url) const override
+ {
+ auto parsedUrlScheme = parseUrlScheme(url.scheme);
+
+ return transportUrlSchemes.count(std::string(parsedUrlScheme.transport))
+ && (parsedUrlScheme.application
+ ? parsedUrlScheme.application.value() == inputType()
+ : hasTarballExtension(url.path));
+ }
+
std::pair<StorePath, Input> fetch(ref<Store> store, const Input & input) override
{
auto tree = downloadTarball(store, getStrAttr(input.attrs, "url"), input.getName(), false).first;
@@ -233,5 +278,6 @@ struct TarballInputScheme : InputScheme
};
static auto rTarballInputScheme = OnStartup([] { registerInputScheme(std::make_unique<TarballInputScheme>()); });
+static auto rFileInputScheme = OnStartup([] { registerInputScheme(std::make_unique<FileInputScheme>()); });
}
diff --git a/src/libutil/url.cc b/src/libutil/url.cc
index f6232d255..5b7abeb49 100644
--- a/src/libutil/url.cc
+++ b/src/libutil/url.cc
@@ -1,6 +1,7 @@
#include "url.hh"
#include "url-parts.hh"
#include "util.hh"
+#include "split.hh"
namespace nix {
@@ -136,4 +137,21 @@ bool ParsedURL::operator ==(const ParsedURL & other) const
&& fragment == other.fragment;
}
+/**
+ * Parse a URL scheme of the form '(applicationScheme\+)?transportScheme'
+ * into a tuple '(applicationScheme, transportScheme)'
+ *
+ * > parseUrlScheme("http") == ParsedUrlScheme{ {}, "http"}
+ * > parseUrlScheme("tarball+http") == ParsedUrlScheme{ {"tarball"}, "http"}
+ */
+ParsedUrlScheme parseUrlScheme(std::string_view scheme)
+{
+ auto application = splitPrefixTo(scheme, '+');
+ auto transport = scheme;
+ return ParsedUrlScheme {
+ .application = application,
+ .transport = transport,
+ };
+}
+
}
diff --git a/src/libutil/url.hh b/src/libutil/url.hh
index 6e77142e3..2a9fb34c1 100644
--- a/src/libutil/url.hh
+++ b/src/libutil/url.hh
@@ -27,4 +27,19 @@ std::map<std::string, std::string> decodeQuery(const std::string & query);
ParsedURL parseURL(const std::string & url);
+/*
+ * Although that’s not really standardized anywhere, an number of tools
+ * use a scheme of the form 'x+y' in urls, where y is the “transport layer”
+ * scheme, and x is the “application layer” scheme.
+ *
+ * For example git uses `git+https` to designate remotes using a Git
+ * protocol over http.
+ */
+struct ParsedUrlScheme {
+ std::optional<std::string_view> application;
+ std::string_view transport;
+};
+
+ParsedUrlScheme parseUrlScheme(std::string_view scheme);
+
}
diff --git a/src/nix/flake.md b/src/nix/flake.md
index aa3f9f303..a1ab43281 100644
--- a/src/nix/flake.md
+++ b/src/nix/flake.md
@@ -181,9 +181,17 @@ Currently the `type` attribute can be one of the following:
* `tarball`: Tarballs. The location of the tarball is specified by the
attribute `url`.
- In URL form, the schema must be `http://`, `https://` or `file://`
- URLs and the extension must be `.zip`, `.tar`, `.tgz`, `.tar.gz`,
- `.tar.xz`, `.tar.bz2` or `.tar.zst`.
+ In URL form, the schema must be `tarball+http://`, `tarball+https://` or `tarball+file://`.
+ If the extension corresponds to a known archive format (`.zip`, `.tar`,
+ `.tgz`, `.tar.gz`, `.tar.xz`, `.tar.bz2` or `.tar.zst`), then the `tarball+`
+ can be dropped.
+
+* `file`: Plain files or directory tarballs, either over http(s) or from the local
+ disk.
+
+ In URL form, the schema must be `file+http://`, `file+https://` or `file+file://`.
+ If the extension doesn’t correspond to a known archive format (as defined by the
+ `tarball` fetcher), then the `file+` prefix can be dropped.
* `github`: A more efficient way to fetch repositories from
GitHub. The following attributes are required:
diff --git a/tests/fetchTree-file.sh b/tests/fetchTree-file.sh
new file mode 100644
index 000000000..1c0ce39ce
--- /dev/null
+++ b/tests/fetchTree-file.sh
@@ -0,0 +1,105 @@
+source common.sh
+
+clearStore
+
+cd "$TEST_ROOT"
+
+test_fetch_file () {
+ echo foo > test_input
+
+ input_hash="$(nix hash path test_input)"
+
+ nix eval --impure --file - <<EOF
+ let
+ tree = builtins.fetchTree { type = "file"; url = "file://$PWD/test_input"; };
+ in
+ assert (tree.narHash == "$input_hash");
+ tree
+EOF
+}
+
+# Make sure that `http(s)` and `file` flake inputs are properly extracted when
+# they should be, and treated as opaque files when they should be
+test_file_flake_input () {
+ rm -fr "$TEST_ROOT/testFlake";
+ mkdir "$TEST_ROOT/testFlake";
+ pushd testFlake
+
+ mkdir inputs
+ echo foo > inputs/test_input_file
+ tar cfa test_input.tar.gz inputs
+ cp test_input.tar.gz test_input_no_ext
+ input_tarball_hash="$(nix hash path test_input.tar.gz)"
+ input_directory_hash="$(nix hash path inputs)"
+
+ cat <<EOF > flake.nix
+ {
+ inputs.no_ext_default_no_unpack = {
+ url = "file://$PWD/test_input_no_ext";
+ flake = false;
+ };
+ inputs.no_ext_explicit_unpack = {
+ url = "tarball+file://$PWD/test_input_no_ext";
+ flake = false;
+ };
+ inputs.tarball_default_unpack = {
+ url = "file://$PWD/test_input.tar.gz";
+ flake = false;
+ };
+ inputs.tarball_explicit_no_unpack = {
+ url = "file+file://$PWD/test_input.tar.gz";
+ flake = false;
+ };
+ outputs = { ... }: {};
+ }
+EOF
+
+ nix flake update
+ nix eval --file - <<EOF
+ with (builtins.fromJSON (builtins.readFile ./flake.lock));
+
+ # Url inputs whose extension doesn’t match a know archive format should
+ # not be unpacked by default
+ assert (nodes.no_ext_default_no_unpack.locked.type == "file");
+ assert (nodes.no_ext_default_no_unpack.locked.unpack or false == false);
+ assert (nodes.no_ext_default_no_unpack.locked.narHash == "$input_tarball_hash");
+
+ # For backwards compatibility, flake inputs that correspond to the
+ # old 'tarball' fetcher should still have their type set to 'tarball'
+ assert (nodes.tarball_default_unpack.locked.type == "tarball");
+ # Unless explicitely specified, the 'unpack' parameter shouldn’t appear here
+ # because that would break older Nix versions
+ assert (!nodes.tarball_default_unpack.locked ? unpack);
+ assert (nodes.tarball_default_unpack.locked.narHash == "$input_directory_hash");
+
+ # Explicitely passing the unpack parameter should enforce the desired behavior
+ assert (nodes.no_ext_explicit_unpack.locked.narHash == nodes.tarball_default_unpack.locked.narHash);
+ assert (nodes.tarball_explicit_no_unpack.locked.narHash == nodes.no_ext_default_no_unpack.locked.narHash);
+ true
+EOF
+ popd
+
+ [[ -z "${NIX_DAEMON_PACKAGE}" ]] && return 0
+
+ # Ensure that a lockfile generated by the current Nix for tarball inputs
+ # can still be read by an older Nix
+
+ cat <<EOF > flake.nix
+ {
+ inputs.tarball = {
+ url = "file://$PWD/test_input.tar.gz";
+ flake = false;
+ };
+ outputs = { self, tarball }: {
+ foo = builtins.readFile "${tarball}/test_input_file";
+ };
+ }
+ nix flake update
+
+ clearStore
+ "$NIX_DAEMON_PACKAGE/bin/nix" eval .#foo
+EOF
+}
+
+test_fetch_file
+test_file_flake_input
diff --git a/tests/local.mk b/tests/local.mk
index e3c4ff4eb..2932d2b13 100644
--- a/tests/local.mk
+++ b/tests/local.mk
@@ -23,6 +23,7 @@ nix_tests = \
fetchGit.sh \
fetchurl.sh \
fetchPath.sh \
+ fetchTree-file.sh \
simple.sh \
referrers.sh \
optimise-store.sh \
From 357fb84dbaad0b056704915c6a43764cda63ee7f Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Thu, 19 May 2022 10:48:10 -0600
Subject: [PATCH 147/188] use an expr->StaticEnv table in evalState
---
src/libcmd/command.cc | 5 ++-
src/libcmd/repl.cc | 9 +++--
src/libexpr/eval.cc | 8 ++--
src/libexpr/eval.hh | 12 +++++-
src/libexpr/nixexpr.cc | 83 +++++++++++++++++++++---------------------
src/libexpr/nixexpr.hh | 7 ++--
6 files changed, 68 insertions(+), 56 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index bf97a3de8..b8c3b0846 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -136,8 +136,9 @@ ref<EvalState> EvalCommand::getEvalState()
if (error)
printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error->what());
- if (expr.staticEnv) {
- auto vm = mapStaticEnvBindings(evalState->symbols, *expr.staticEnv.get(), env);
+ auto se = evalState->getStaticEnv(expr);
+ if (se) {
+ auto vm = mapStaticEnvBindings(evalState->symbols, *se.get(), env);
runRepl(evalState, *vm);
}
};
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index deac3d408..43c2ce65e 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -441,8 +441,9 @@ void NixRepl::loadDebugTraceEnv(DebugTrace & dt)
{
initEnv();
- if (dt.expr.staticEnv) {
- auto vm = mapStaticEnvBindings(state->symbols, *dt.expr.staticEnv.get(), dt.env);
+ auto se = state->getStaticEnv(dt.expr);
+ if (se) {
+ auto vm = mapStaticEnvBindings(state->symbols, *se.get(), dt.env);
// add staticenv vars.
for (auto & [name, value] : *(vm.get()))
@@ -516,7 +517,7 @@ bool NixRepl::processLine(std::string line)
else if (debuggerHook && (command == ":env")) {
for (const auto & [idx, i] : enumerate(state->debugTraces)) {
if (idx == debugTraceIndex) {
- printEnvBindings(state->symbols, i.expr, i.env);
+ printEnvBindings(*state, i.expr, i.env);
break;
}
}
@@ -533,7 +534,7 @@ bool NixRepl::processLine(std::string line)
std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
showDebugTrace(std::cout, state->positions, i);
std::cout << std::endl;
- printEnvBindings(state->symbols, i.expr, i.env);
+ printEnvBindings(*state, i.expr, i.env);
loadDebugTraceEnv(i);
break;
}
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index d9ea92cc0..c9e4a05b7 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -772,12 +772,12 @@ void printEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env &
}
}
-// TODO: add accompanying env for With stuff.
-void printEnvBindings(const SymbolTable & st, const Expr & expr, const Env & env)
+void printEnvBindings(const EvalState &es, const Expr & expr, const Env & env)
{
// just print the names for now
- if (expr.staticEnv)
- printEnvBindings(st, *expr.staticEnv.get(), env, 0);
+ auto se = es.getStaticEnv(expr);
+ if (se)
+ printEnvBindings(es.symbols, *se, env, 0);
}
void mapStaticEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env, ValMap & vm)
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index f274278be..0543cb35c 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -25,7 +25,7 @@ enum RepairFlag : bool;
typedef void (* PrimOpFun) (EvalState & state, const PosIdx pos, Value * * args, Value & v);
-void printEnvBindings(const SymbolTable & st, const Expr & expr, const Env & env);
+void printEnvBindings(const EvalState &es, const Expr & expr, const Env & env);
void printEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env, int lvl = 0);
struct PrimOp
@@ -130,6 +130,16 @@ public:
bool debugStop;
bool debugQuit;
std::list<DebugTrace> debugTraces;
+ std::map<const Expr*, const std::shared_ptr<const StaticEnv> > exprEnvs;
+ const std::shared_ptr<const StaticEnv> getStaticEnv(const Expr &expr) const
+ {
+ auto i = exprEnvs.find(&expr);
+ if (i != exprEnvs.end())
+ return i->second;
+ else
+ return std::shared_ptr<const StaticEnv>();;
+ }
+
template<class E>
[[gnu::noinline, gnu::noreturn]]
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index 213cf93fa..4fb43707e 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -296,38 +296,39 @@ std::string showAttrPath(const SymbolTable & symbols, const AttrPath & attrPath)
/* Computing levels/displacements for variables. */
-void Expr::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
+void Expr::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
abort();
}
-void ExprInt::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
+void ExprInt::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticEnv = env;}
-
-void ExprFloat::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
-{
- if (debuggerHook)
- staticEnv = env;
+ es.exprEnvs.insert(std::make_pair(this, env));
}
-void ExprString::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
+void ExprFloat::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticEnv = env;
+ es.exprEnvs.insert(std::make_pair(this, env));
}
-void ExprPath::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
+void ExprString::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticEnv = env;
+ es.exprEnvs.insert(std::make_pair(this, env));
}
-void ExprVar::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
+void ExprPath::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticEnv = env;
+ es.exprEnvs.insert(std::make_pair(this, env));
+}
+
+void ExprVar::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
+{
+ if (debuggerHook)
+ es.exprEnvs.insert(std::make_pair(this, env));
/* Check whether the variable appears in the environment. If so,
set its level and displacement. */
@@ -360,10 +361,10 @@ void ExprVar::bindVars(const EvalState & es, const std::shared_ptr<const StaticE
this->level = withLevel;
}
-void ExprSelect::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
+void ExprSelect::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticEnv = env;
+ es.exprEnvs.insert(std::make_pair(this, env));
e->bindVars(es, env);
if (def) def->bindVars(es, env);
@@ -372,10 +373,10 @@ void ExprSelect::bindVars(const EvalState & es, const std::shared_ptr<const Stat
i.expr->bindVars(es, env);
}
-void ExprOpHasAttr::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
+void ExprOpHasAttr::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticEnv = env;
+ es.exprEnvs.insert(std::make_pair(this, env));
e->bindVars(es, env);
for (auto & i : attrPath)
@@ -383,10 +384,10 @@ void ExprOpHasAttr::bindVars(const EvalState & es, const std::shared_ptr<const S
i.expr->bindVars(es, env);
}
-void ExprAttrs::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
+void ExprAttrs::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticEnv = env;
+ es.exprEnvs.insert(std::make_pair(this, env));
if (recursive) {
auto newEnv = std::make_shared<StaticEnv>(false, env.get(), recursive ? attrs.size() : 0);
@@ -416,19 +417,19 @@ void ExprAttrs::bindVars(const EvalState & es, const std::shared_ptr<const Stati
}
}
-void ExprList::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
+void ExprList::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticEnv = env;
+ es.exprEnvs.insert(std::make_pair(this, env));
for (auto & i : elems)
i->bindVars(es, env);
}
-void ExprLambda::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
+void ExprLambda::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticEnv = env;
+ es.exprEnvs.insert(std::make_pair(this, env));
auto newEnv = std::make_shared<StaticEnv>(
false, env.get(),
@@ -452,20 +453,20 @@ void ExprLambda::bindVars(const EvalState & es, const std::shared_ptr<const Stat
body->bindVars(es, newEnv);
}
-void ExprCall::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
+void ExprCall::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticEnv = env;
+ es.exprEnvs.insert(std::make_pair(this, env));
fun->bindVars(es, env);
for (auto e : args)
e->bindVars(es, env);
}
-void ExprLet::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
+void ExprLet::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticEnv = env;
+ es.exprEnvs.insert(std::make_pair(this, env));
auto newEnv = std::make_shared<StaticEnv>(false, env.get(), attrs->attrs.size());
@@ -481,10 +482,10 @@ void ExprLet::bindVars(const EvalState & es, const std::shared_ptr<const StaticE
body->bindVars(es, newEnv);
}
-void ExprWith::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
+void ExprWith::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticEnv = env;
+ es.exprEnvs.insert(std::make_pair(this, env));
/* Does this `with' have an enclosing `with'? If so, record its
level so that `lookupVar' can look up variables in the previous
@@ -499,53 +500,53 @@ void ExprWith::bindVars(const EvalState & es, const std::shared_ptr<const Static
}
if (debuggerHook)
- staticEnv = env;
+ es.exprEnvs.insert(std::make_pair(this, env));
attrs->bindVars(es, env);
auto newEnv = std::make_shared<StaticEnv>(true, env.get());
body->bindVars(es, newEnv);
}
-void ExprIf::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
+void ExprIf::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticEnv = env;
+ es.exprEnvs.insert(std::make_pair(this, env));
cond->bindVars(es, env);
then->bindVars(es, env);
else_->bindVars(es, env);
}
-void ExprAssert::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
+void ExprAssert::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticEnv = env;
+ es.exprEnvs.insert(std::make_pair(this, env));
cond->bindVars(es, env);
body->bindVars(es, env);
}
-void ExprOpNot::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
+void ExprOpNot::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticEnv = env;
+ es.exprEnvs.insert(std::make_pair(this, env));
e->bindVars(es, env);
}
-void ExprConcatStrings::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
+void ExprConcatStrings::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticEnv = env;
+ es.exprEnvs.insert(std::make_pair(this, env));
for (auto & i : *this->es)
i.second->bindVars(es, env);
}
-void ExprPos::bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env)
+void ExprPos::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
if (debuggerHook)
- staticEnv = env;
+ es.exprEnvs.insert(std::make_pair(this, env));
}
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index c4a509f31..e923f36a4 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -144,18 +144,17 @@ struct Expr
{
virtual ~Expr() { };
virtual void show(const SymbolTable & symbols, std::ostream & str) const;
- virtual void bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env);
+ virtual void bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env);
virtual void eval(EvalState & state, Env & env, Value & v);
virtual Value * maybeThunk(EvalState & state, Env & env);
virtual void setName(Symbol name);
- std::shared_ptr<const StaticEnv> staticEnv;
virtual PosIdx getPos() const { return noPos; }
};
#define COMMON_METHODS \
void show(const SymbolTable & symbols, std::ostream & str) const; \
void eval(EvalState & state, Env & env, Value & v); \
- void bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env);
+ void bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env);
struct ExprInt : Expr
{
@@ -402,7 +401,7 @@ struct ExprOpNot : Expr
{ \
str << "("; e1->show(symbols, str); str << " " s " "; e2->show(symbols, str); str << ")"; \
} \
- void bindVars(const EvalState & es, const std::shared_ptr<const StaticEnv> & env) \
+ void bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env) \
{ \
e1->bindVars(es, env); e2->bindVars(es, env); \
} \
From cebef6a25031e984a30d823f19b4cdc414ee9b48 Mon Sep 17 00:00:00 2001
From: Artturin <Artturin@artturin.com>
Date: Thu, 19 May 2022 21:16:07 +0300
Subject: [PATCH 148/188] nix-daemon.service: sync LimitNOFILE with the nixos
service
https://github.com/NixOS/nixpkgs/blob/5628480acda2985cc334d0c5ec85512858ed60f9/nixos/modules/services/misc/nix-daemon.nix#L737
Closes https://github.com/NixOS/nix/issues/6007
---
misc/systemd/nix-daemon.service.in | 1 +
1 file changed, 1 insertion(+)
diff --git a/misc/systemd/nix-daemon.service.in b/misc/systemd/nix-daemon.service.in
index 24d894898..e3ac42beb 100644
--- a/misc/systemd/nix-daemon.service.in
+++ b/misc/systemd/nix-daemon.service.in
@@ -9,6 +9,7 @@ ConditionPathIsReadWrite=@localstatedir@/nix/daemon-socket
[Service]
ExecStart=@@bindir@/nix-daemon nix-daemon --daemon
KillMode=process
+LimitNOFILE=4096
[Install]
WantedBy=multi-user.target
From 7ddef73d026d79adc0c4f3fd1518d88d1331c38c Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Thu, 19 May 2022 12:44:40 -0600
Subject: [PATCH 149/188] de-const evalState exceptions
---
src/libcmd/command.cc | 7 +++---
src/libcmd/command.hh | 3 ++-
src/libcmd/repl.cc | 4 +++-
src/libexpr/eval.cc | 38 ++++++++++++++++-----------------
src/libexpr/eval.hh | 48 +++++++++++++++++++++---------------------
src/libexpr/nixexpr.cc | 2 +-
src/libexpr/nixexpr.hh | 2 +-
7 files changed, 54 insertions(+), 50 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 9cf2ff5e3..a7d7bfb17 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -118,9 +118,10 @@ ref<EvalState> EvalCommand::getEvalState()
searchPath, getEvalStore(), getStore())
#endif
;
+ // TODO move this somewhere else. Its only here to get the evalState ptr!
if (startReplOnEvalErrors)
// debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error * error, const Env & env, const Expr & expr) {
- debuggerHook = [](const EvalState & evalState, const Error * error, const Env & env, const Expr & expr) {
+ debuggerHook = [](EvalState & evalState, const Error * error, const Env & env, const Expr & expr) {
auto dts =
error && expr.getPos()
? std::make_unique<DebugTraceStacker>(
@@ -137,9 +138,9 @@ ref<EvalState> EvalCommand::getEvalState()
if (error)
printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error->what());
- auto se = evalState->getStaticEnv(expr);
+ auto se = evalState.getStaticEnv(expr);
if (se) {
- auto vm = mapStaticEnvBindings(evalState->symbols, *se.get(), env);
+ auto vm = mapStaticEnvBindings(evalState.symbols, *se.get(), env);
runRepl(evalState, *vm);
}
};
diff --git a/src/libcmd/command.hh b/src/libcmd/command.hh
index 8b37be901..04bffa8df 100644
--- a/src/libcmd/command.hh
+++ b/src/libcmd/command.hh
@@ -274,7 +274,8 @@ void printClosureDiff(
void runRepl(
- EvalState & evalState,
+ ref<EvalState> evalState,
+ // EvalState & evalState,
const ValMap & extraEnv);
}
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 5b17f2fb2..5aecf3ac3 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -96,6 +96,7 @@ std::string removeWhitespace(std::string s)
}
+// NixRepl::NixRepl(ref<EvalState> state)
NixRepl::NixRepl(ref<EvalState> state)
: state(state)
, debugTraceIndex(0)
@@ -1012,7 +1013,8 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
}
void runRepl(
- EvalState& evalState,
+ ref<EvalState> evalState,
+ // EvalState& evalState,
const ValMap & extraEnv)
{
auto repl = std::make_unique<NixRepl>(evalState);
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index bd1cbaab5..f95ff4931 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -814,7 +814,7 @@ std::unique_ptr<ValMap> mapStaticEnvBindings(const SymbolTable & st, const Stati
of stack space, which is a real killer in the recursive
evaluator. So here are some helper functions for throwing
exceptions. */
-void EvalState::throwEvalError(const PosIdx pos, const char * s, Env & env, Expr & expr) const
+void EvalState::throwEvalError(const PosIdx pos, const char * s, Env & env, Expr & expr)
{
auto error = EvalError({
.msg = hintfmt(s),
@@ -824,7 +824,7 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, Env & env, Expr
debugThrow(error, env, expr);
}
-void EvalState::throwEvalError(const PosIdx pos, const char * s) const
+void EvalState::throwEvalError(const PosIdx pos, const char * s)
{
auto error = EvalError({
.msg = hintfmt(s),
@@ -834,7 +834,7 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s) const
debugThrowLastTrace(error);
}
-void EvalState::throwEvalError(const char * s, const std::string & s2) const
+void EvalState::throwEvalError(const char * s, const std::string & s2)
{
auto error = EvalError(s, s2);
@@ -842,7 +842,7 @@ void EvalState::throwEvalError(const char * s, const std::string & s2) const
}
void EvalState::throwEvalError(const PosIdx pos, const Suggestions & suggestions, const char * s,
- const std::string & s2, Env & env, Expr & expr) const
+ const std::string & s2, Env & env, Expr & expr)
{
auto error = EvalError(ErrorInfo{
.msg = hintfmt(s, s2),
@@ -853,7 +853,7 @@ void EvalState::throwEvalError(const PosIdx pos, const Suggestions & suggestions
debugThrow(error, env, expr);
}
-void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::string & s2) const
+void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::string & s2)
{
auto error = EvalError({
.msg = hintfmt(s, s2),
@@ -863,7 +863,7 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::stri
debugThrowLastTrace(error);
}
-void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::string & s2, Env & env, Expr & expr) const
+void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::string & s2, Env & env, Expr & expr)
{
auto error = EvalError({
.msg = hintfmt(s, s2),
@@ -874,7 +874,7 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::stri
}
void EvalState::throwEvalError(const char * s, const std::string & s2,
- const std::string & s3) const
+ const std::string & s3)
{
auto error = EvalError({
.msg = hintfmt(s, s2),
@@ -885,7 +885,7 @@ void EvalState::throwEvalError(const char * s, const std::string & s2,
}
void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::string & s2,
- const std::string & s3) const
+ const std::string & s3)
{
auto error = EvalError({
.msg = hintfmt(s, s2),
@@ -896,7 +896,7 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::stri
}
void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::string & s2,
- const std::string & s3, Env & env, Expr & expr) const
+ const std::string & s3, Env & env, Expr & expr)
{
auto error = EvalError({
.msg = hintfmt(s, s2),
@@ -906,7 +906,7 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::stri
debugThrow(error, env, expr);
}
-void EvalState::throwEvalError(const PosIdx p1, const char * s, const Symbol sym, const PosIdx p2, Env & env, Expr & expr) const
+void EvalState::throwEvalError(const PosIdx p1, const char * s, const Symbol sym, const PosIdx p2, Env & env, Expr & expr)
{
// p1 is where the error occurred; p2 is a position mentioned in the message.
auto error = EvalError({
@@ -917,7 +917,7 @@ void EvalState::throwEvalError(const PosIdx p1, const char * s, const Symbol sym
debugThrow(error, env, expr);
}
-void EvalState::throwTypeError(const PosIdx pos, const char * s, const Value & v) const
+void EvalState::throwTypeError(const PosIdx pos, const char * s, const Value & v)
{
auto error = TypeError({
.msg = hintfmt(s, showType(v)),
@@ -927,7 +927,7 @@ void EvalState::throwTypeError(const PosIdx pos, const char * s, const Value & v
debugThrowLastTrace(error);
}
-void EvalState::throwTypeError(const PosIdx pos, const char * s, const Value & v, Env & env, Expr & expr) const
+void EvalState::throwTypeError(const PosIdx pos, const char * s, const Value & v, Env & env, Expr & expr)
{
auto error = TypeError({
.msg = hintfmt(s, showType(v)),
@@ -937,7 +937,7 @@ void EvalState::throwTypeError(const PosIdx pos, const char * s, const Value & v
debugThrow(error, env, expr);
}
-void EvalState::throwTypeError(const PosIdx pos, const char * s) const
+void EvalState::throwTypeError(const PosIdx pos, const char * s)
{
auto error = TypeError({
.msg = hintfmt(s),
@@ -948,7 +948,7 @@ void EvalState::throwTypeError(const PosIdx pos, const char * s) const
}
void EvalState::throwTypeError(const PosIdx pos, const char * s, const ExprLambda & fun,
- const Symbol s2, Env & env, Expr &expr) const
+ const Symbol s2, Env & env, Expr &expr)
{
auto error = TypeError({
.msg = hintfmt(s, fun.showNamePos(*this), symbols[s2]),
@@ -959,7 +959,7 @@ void EvalState::throwTypeError(const PosIdx pos, const char * s, const ExprLambd
}
void EvalState::throwTypeError(const PosIdx pos, const Suggestions & suggestions, const char * s,
- const ExprLambda & fun, const Symbol s2, Env & env, Expr &expr) const
+ const ExprLambda & fun, const Symbol s2, Env & env, Expr &expr)
{
auto error = TypeError(ErrorInfo {
.msg = hintfmt(s, fun.showNamePos(*this), symbols[s2]),
@@ -970,7 +970,7 @@ void EvalState::throwTypeError(const PosIdx pos, const Suggestions & suggestions
debugThrow(error, env, expr);
}
-void EvalState::throwTypeError(const char * s, const Value & v, Env & env, Expr &expr) const
+void EvalState::throwTypeError(const char * s, const Value & v, Env & env, Expr &expr)
{
auto error = TypeError({
.msg = hintfmt(s, showType(v)),
@@ -980,7 +980,7 @@ void EvalState::throwTypeError(const char * s, const Value & v, Env & env, Expr
debugThrow(error, env, expr);
}
-void EvalState::throwAssertionError(const PosIdx pos, const char * s, const std::string & s1, Env & env, Expr &expr) const
+void EvalState::throwAssertionError(const PosIdx pos, const char * s, const std::string & s1, Env & env, Expr &expr)
{
auto error = AssertionError({
.msg = hintfmt(s, s1),
@@ -990,7 +990,7 @@ void EvalState::throwAssertionError(const PosIdx pos, const char * s, const std:
debugThrow(error, env, expr);
}
-void EvalState::throwUndefinedVarError(const PosIdx pos, const char * s, const std::string & s1, Env & env, Expr &expr) const
+void EvalState::throwUndefinedVarError(const PosIdx pos, const char * s, const std::string & s1, Env & env, Expr &expr)
{
auto error = UndefinedVarError({
.msg = hintfmt(s, s1),
@@ -1000,7 +1000,7 @@ void EvalState::throwUndefinedVarError(const PosIdx pos, const char * s, const s
debugThrow(error, env, expr);
}
-void EvalState::throwMissingArgumentError(const PosIdx pos, const char * s, const std::string & s1, Env & env, Expr &expr) const
+void EvalState::throwMissingArgumentError(const PosIdx pos, const char * s, const std::string & s1, Env & env, Expr &expr)
{
auto error = MissingArgumentError({
.msg = hintfmt(s, s1),
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 5227c7ce1..763150dae 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -143,7 +143,7 @@ public:
template<class E>
[[gnu::noinline, gnu::noreturn]]
- void debugThrow(const E &error, const Env & env, const Expr & expr) const
+ void debugThrow(const E &error, const Env & env, const Expr & expr)
{
if (debuggerHook)
debuggerHook(*this, &error, env, expr);
@@ -153,7 +153,7 @@ public:
template<class E>
[[gnu::noinline, gnu::noreturn]]
- void debugThrowLastTrace(E & e) const
+ void debugThrowLastTrace(E & e)
{
// Call this in the situation where Expr and Env are inaccessible.
// The debugger will start in the last context that's in the
@@ -312,68 +312,68 @@ public:
std::string_view forceStringNoCtx(Value & v, const PosIdx pos = noPos);
[[gnu::noinline, gnu::noreturn]]
- void throwEvalError(const PosIdx pos, const char * s) const;
+ void throwEvalError(const PosIdx pos, const char * s);
[[gnu::noinline, gnu::noreturn]]
void throwEvalError(const PosIdx pos, const char * s,
- Env & env, Expr & expr) const;
+ Env & env, Expr & expr);
[[gnu::noinline, gnu::noreturn]]
- void throwEvalError(const char * s, const std::string & s2) const;
+ void throwEvalError(const char * s, const std::string & s2);
[[gnu::noinline, gnu::noreturn]]
- void throwEvalError(const PosIdx pos, const char * s, const std::string & s2) const;
+ void throwEvalError(const PosIdx pos, const char * s, const std::string & s2);
[[gnu::noinline, gnu::noreturn]]
void throwEvalError(const char * s, const std::string & s2,
- Env & env, Expr & expr) const;
+ Env & env, Expr & expr);
[[gnu::noinline, gnu::noreturn]]
void throwEvalError(const PosIdx pos, const char * s, const std::string & s2,
- Env & env, Expr & expr) const;
+ Env & env, Expr & expr);
[[gnu::noinline, gnu::noreturn]]
void throwEvalError(const char * s, const std::string & s2, const std::string & s3,
- Env & env, Expr & expr) const;
+ Env & env, Expr & expr);
[[gnu::noinline, gnu::noreturn]]
void throwEvalError(const PosIdx pos, const char * s, const std::string & s2, const std::string & s3,
- Env & env, Expr & expr) const;
+ Env & env, Expr & expr);
[[gnu::noinline, gnu::noreturn]]
- void throwEvalError(const PosIdx pos, const char * s, const std::string & s2, const std::string & s3) const;
+ void throwEvalError(const PosIdx pos, const char * s, const std::string & s2, const std::string & s3);
[[gnu::noinline, gnu::noreturn]]
- void throwEvalError(const char * s, const std::string & s2, const std::string & s3) const;
+ void throwEvalError(const char * s, const std::string & s2, const std::string & s3);
[[gnu::noinline, gnu::noreturn]]
void throwEvalError(const PosIdx pos, const Suggestions & suggestions, const char * s, const std::string & s2,
- Env & env, Expr & expr) const;
+ Env & env, Expr & expr);
[[gnu::noinline, gnu::noreturn]]
void throwEvalError(const PosIdx p1, const char * s, const Symbol sym, const PosIdx p2,
- Env & env, Expr & expr) const;
+ Env & env, Expr & expr);
[[gnu::noinline, gnu::noreturn]]
- void throwTypeError(const PosIdx pos, const char * s, const Value & v) const;
+ void throwTypeError(const PosIdx pos, const char * s, const Value & v);
[[gnu::noinline, gnu::noreturn]]
void throwTypeError(const PosIdx pos, const char * s, const Value & v,
- Env & env, Expr & expr) const;
+ Env & env, Expr & expr);
[[gnu::noinline, gnu::noreturn]]
- void throwTypeError(const PosIdx pos, const char * s) const;
+ void throwTypeError(const PosIdx pos, const char * s);
[[gnu::noinline, gnu::noreturn]]
void throwTypeError(const PosIdx pos, const char * s,
- Env & env, Expr & expr) const;
+ Env & env, Expr & expr);
[[gnu::noinline, gnu::noreturn]]
void throwTypeError(const PosIdx pos, const char * s, const ExprLambda & fun, const Symbol s2,
- Env & env, Expr & expr) const;
+ Env & env, Expr & expr);
[[gnu::noinline, gnu::noreturn]]
void throwTypeError(const PosIdx pos, const Suggestions & suggestions, const char * s, const ExprLambda & fun, const Symbol s2,
- Env & env, Expr & expr) const;
+ Env & env, Expr & expr);
[[gnu::noinline, gnu::noreturn]]
void throwTypeError(const char * s, const Value & v,
- Env & env, Expr & expr) const;
+ Env & env, Expr & expr);
[[gnu::noinline, gnu::noreturn]]
void throwAssertionError(const PosIdx pos, const char * s, const std::string & s1,
- Env & env, Expr & expr) const;
+ Env & env, Expr & expr);
[[gnu::noinline, gnu::noreturn]]
void throwUndefinedVarError(const PosIdx pos, const char * s, const std::string & s1,
- Env & env, Expr & expr) const;
+ Env & env, Expr & expr);
[[gnu::noinline, gnu::noreturn]]
void throwMissingArgumentError(const PosIdx pos, const char * s, const std::string & s1,
- Env & env, Expr & expr) const;
+ Env & env, Expr & expr);
[[gnu::noinline]]
void addErrorTrace(Error & e, const char * s, const std::string & s2) const;
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index cb5e1c3f2..21b71d7c9 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -10,7 +10,7 @@ namespace nix {
/* Launch the nix debugger */
-std::function<void(const EvalState & evalState,const Error * error, const Env & env, const Expr & expr)> debuggerHook;
+std::function<void(EvalState & evalState,const Error * error, const Env & env, const Expr & expr)> debuggerHook;
/* Displaying abstract syntax trees. */
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index 80b6afa3e..fdafb1711 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -22,7 +22,7 @@ MakeError(UndefinedVarError, Error);
MakeError(MissingArgumentError, EvalError);
MakeError(RestrictedPathError, Error);
-extern std::function<void(const EvalState & evalState, const Error * error, const Env & env, const Expr & expr)> debuggerHook;
+extern std::function<void(EvalState & evalState, const Error * error, const Env & env, const Expr & expr)> debuggerHook;
/* Position objects. */
From 0600df86b8bc59633457f7ceb79e84c8ea3fed17 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Thu, 19 May 2022 17:01:23 -0600
Subject: [PATCH 150/188] 'debugMode'
---
src/libcmd/command.cc | 49 ++++++++++++++++++++++--------------------
src/libcmd/repl.cc | 14 ++++++------
src/libexpr/eval.cc | 38 ++++++++++++++++++++++++++------
src/libexpr/eval.hh | 19 ++++++++++------
src/libexpr/nixexpr.cc | 40 +++++++++++++++++-----------------
src/libexpr/nixexpr.hh | 2 +-
src/libexpr/primops.cc | 10 ++++-----
7 files changed, 103 insertions(+), 69 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index a7d7bfb17..a4ea5bc33 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -118,32 +118,35 @@ ref<EvalState> EvalCommand::getEvalState()
searchPath, getEvalStore(), getStore())
#endif
;
+
+ evalState->debugMode = startReplOnEvalErrors;
// TODO move this somewhere else. Its only here to get the evalState ptr!
- if (startReplOnEvalErrors)
- // debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error * error, const Env & env, const Expr & expr) {
- debuggerHook = [](EvalState & evalState, const Error * error, const Env & env, const Expr & expr) {
- auto dts =
- error && expr.getPos()
- ? std::make_unique<DebugTraceStacker>(
- evalState,
- DebugTrace {
- .pos = error->info().errPos ? *error->info().errPos : evalState.positions[expr.getPos()],
- .expr = expr,
- .env = env,
- .hint = error->info().msg,
- .isError = true
- })
- : nullptr;
+ // if (startReplOnEvalErrors)
+
+ // // debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error * error, const Env & env, const Expr & expr) {
+ // debuggerHook = [](EvalState & evalState, const Error * error, const Env & env, const Expr & expr) {
+ // auto dts =
+ // error && expr.getPos()
+ // ? std::make_unique<DebugTraceStacker>(
+ // evalState,
+ // DebugTrace {
+ // .pos = error->info().errPos ? *error->info().errPos : evalState.positions[expr.getPos()],
+ // .expr = expr,
+ // .env = env,
+ // .hint = error->info().msg,
+ // .isError = true
+ // })
+ // : nullptr;
- if (error)
- printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error->what());
+ // if (error)
+ // printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error->what());
- auto se = evalState.getStaticEnv(expr);
- if (se) {
- auto vm = mapStaticEnvBindings(evalState.symbols, *se.get(), env);
- runRepl(evalState, *vm);
- }
- };
+ // auto se = evalState.getStaticEnv(expr);
+ // if (se) {
+ // auto vm = mapStaticEnvBindings(evalState.symbols, *se.get(), env);
+ // runRepl(evalState, *vm);
+ // }
+ // };
}
return ref<EvalState>(evalState);
}
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 5aecf3ac3..6bf23cc61 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -280,7 +280,7 @@ void NixRepl::mainLoop(const std::vector<std::string> & files)
// in debugger mode, an EvalError should trigger another repl session.
// when that session returns the exception will land here. No need to show it again;
// show the error for this repl session instead.
- if (debuggerHook && !state->debugTraces.empty())
+ if (state->debugMode && !state->debugTraces.empty())
showDebugTrace(std::cout, state->positions, state->debugTraces.front());
else
printMsg(lvlError, e.msg());
@@ -493,7 +493,7 @@ bool NixRepl::processLine(std::string line)
<< " :log <expr> Show logs for a derivation\n"
<< " :te [bool] Enable, disable or toggle showing traces for errors\n"
;
- if (debuggerHook) {
+ if (state->debugMode) {
std::cout
<< "\n"
<< " Debug mode commands\n"
@@ -508,14 +508,14 @@ bool NixRepl::processLine(std::string line)
}
- else if (debuggerHook && (command == ":bt" || command == ":backtrace")) {
+ else if (state->debugMode && (command == ":bt" || command == ":backtrace")) {
for (const auto & [idx, i] : enumerate(state->debugTraces)) {
std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
showDebugTrace(std::cout, state->positions, i);
}
}
- else if (debuggerHook && (command == ":env")) {
+ else if (state->debugMode && (command == ":env")) {
for (const auto & [idx, i] : enumerate(state->debugTraces)) {
if (idx == debugTraceIndex) {
printEnvBindings(*state, i.expr, i.env);
@@ -524,7 +524,7 @@ bool NixRepl::processLine(std::string line)
}
}
- else if (debuggerHook && (command == ":st")) {
+ else if (state->debugMode && (command == ":st")) {
try {
// change the DebugTrace index.
debugTraceIndex = stoi(arg);
@@ -542,13 +542,13 @@ bool NixRepl::processLine(std::string line)
}
}
- else if (debuggerHook && (command == ":s" || command == ":step")) {
+ else if (state->debugMode && (command == ":s" || command == ":step")) {
// set flag to stop at next DebugTrace; exit repl.
state->debugStop = true;
return false;
}
- else if (debuggerHook && (command == ":c" || command == ":continue")) {
+ else if (state->debugMode && (command == ":c" || command == ":continue")) {
// set flag to run to next breakpoint or end of program; exit repl.
state->debugStop = false;
return false;
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index f95ff4931..1cde4a9ab 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -463,6 +463,7 @@ EvalState::EvalState(
, emptyBindings(0)
, store(store)
, buildStore(buildStore ? buildStore : store)
+ , debugMode(false)
, debugStop(false)
, debugQuit(false)
, regexCache(makeRegexCache())
@@ -810,6 +811,31 @@ std::unique_ptr<ValMap> mapStaticEnvBindings(const SymbolTable & st, const Stati
return vm;
}
+void EvalState::debugRepl(const Error * error, const Env & env, const Expr & expr)
+{
+ auto dts =
+ error && expr.getPos()
+ ? std::make_unique<DebugTraceStacker>(
+ *this,
+ DebugTrace {
+ .pos = error->info().errPos ? *error->info().errPos : positions[expr.getPos()],
+ .expr = expr,
+ .env = env,
+ .hint = error->info().msg,
+ .isError = true
+ })
+ : nullptr;
+
+ if (error)
+ printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error->what());
+
+ auto se = getStaticEnv(expr);
+ if (se) {
+ auto vm = mapStaticEnvBindings(symbols, *se.get(), env);
+ runRepl(*this, *vm);
+ }
+}
+
/* Every "format" object (even temporary) takes up a few hundred bytes
of stack space, which is a real killer in the recursive
evaluator. So here are some helper functions for throwing
@@ -1043,8 +1069,8 @@ DebugTraceStacker::DebugTraceStacker(EvalState & evalState, DebugTrace t)
, trace(std::move(t))
{
evalState.debugTraces.push_front(trace);
- if (evalState.debugStop && debuggerHook)
- debuggerHook(evalState, nullptr, trace.env, trace.expr);
+ if (evalState.debugStop && evalState.debugMode)
+ evalState.debugRepl(nullptr, trace.env, trace.expr);
}
void Value::mkString(std::string_view s)
@@ -1241,7 +1267,7 @@ void EvalState::cacheFile(
fileParseCache[resolvedPath] = e;
try {
- auto dts = debuggerHook
+ auto dts = debugMode
? makeDebugTraceStacker(
*this,
*e,
@@ -1475,7 +1501,7 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
e->eval(state, env, vTmp);
try {
- auto dts = debuggerHook
+ auto dts = state.debugMode
? makeDebugTraceStacker(
state,
*this,
@@ -1644,7 +1670,7 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
/* Evaluate the body. */
try {
- auto dts = debuggerHook
+ auto dts = debugMode
? makeDebugTraceStacker(
*this, *lambda.body, env2, positions[lambda.pos],
"while evaluating %s",
@@ -2072,7 +2098,7 @@ void EvalState::forceValueDeep(Value & v)
for (auto & i : *v.attrs)
try {
// If the value is a thunk, we're evaling. Otherwise no trace necessary.
- auto dts = debuggerHook && i.value->isThunk()
+ auto dts = debugMode && i.value->isThunk()
? makeDebugTraceStacker(*this, *i.value->thunk.expr, *i.value->thunk.env, positions[i.pos],
"while evaluating the attribute '%1%'", symbols[i.name])
: nullptr;
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 763150dae..711a4d6be 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -25,9 +25,6 @@ enum RepairFlag : bool;
typedef void (* PrimOpFun) (EvalState & state, const PosIdx pos, Value * * args, Value & v);
-void printEnvBindings(const EvalState &es, const Expr & expr, const Env & env);
-void printEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env, int lvl = 0);
-
struct PrimOp
{
PrimOpFun fun;
@@ -51,6 +48,11 @@ struct Env
Value * values[0];
};
+extern void runRepl(ref<EvalState> evalState, const ValMap & extraEnv);
+
+void printEnvBindings(const EvalState &es, const Expr & expr, const Env & env);
+void printEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env, int lvl = 0);
+
std::unique_ptr<ValMap> mapStaticEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env);
void copyContext(const Value & v, PathSet & context);
@@ -127,6 +129,7 @@ public:
RootValue vImportedDrvToDerivation = nullptr;
/* Debugger */
+ bool debugMode;
bool debugStop;
bool debugQuit;
std::list<DebugTrace> debugTraces;
@@ -140,13 +143,14 @@ public:
return std::shared_ptr<const StaticEnv>();;
}
+ void debugRepl(const Error * error, const Env & env, const Expr & expr);
template<class E>
[[gnu::noinline, gnu::noreturn]]
void debugThrow(const E &error, const Env & env, const Expr & expr)
{
- if (debuggerHook)
- debuggerHook(*this, &error, env, expr);
+ if (debugMode)
+ debugRepl(&error, env, expr);
throw error;
}
@@ -158,14 +162,15 @@ public:
// Call this in the situation where Expr and Env are inaccessible.
// The debugger will start in the last context that's in the
// DebugTrace stack.
- if (debuggerHook && !debugTraces.empty()) {
+ if (debugMode && !debugTraces.empty()) {
const DebugTrace & last = debugTraces.front();
- debuggerHook(*this, &e, last.env, last.expr);
+ debugRepl(&e, last.env, last.expr);
}
throw e;
}
+
private:
SrcToStore srcToStore;
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index 21b71d7c9..b40791694 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -10,7 +10,7 @@ namespace nix {
/* Launch the nix debugger */
-std::function<void(EvalState & evalState,const Error * error, const Env & env, const Expr & expr)> debuggerHook;
+// std::function<void(EvalState & evalState,const Error * error, const Env & env, const Expr & expr)> debuggerHook;
/* Displaying abstract syntax trees. */
@@ -303,31 +303,31 @@ void Expr::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env
void ExprInt::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (debuggerHook)
+ if (es.debugMode)
es.exprEnvs.insert(std::make_pair(this, env));
}
void ExprFloat::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (debuggerHook)
+ if (es.debugMode)
es.exprEnvs.insert(std::make_pair(this, env));
}
void ExprString::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (debuggerHook)
+ if (es.debugMode)
es.exprEnvs.insert(std::make_pair(this, env));
}
void ExprPath::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (debuggerHook)
+ if (es.debugMode)
es.exprEnvs.insert(std::make_pair(this, env));
}
void ExprVar::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (debuggerHook)
+ if (es.debugMode)
es.exprEnvs.insert(std::make_pair(this, env));
/* Check whether the variable appears in the environment. If so,
@@ -363,7 +363,7 @@ void ExprVar::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> &
void ExprSelect::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (debuggerHook)
+ if (es.debugMode)
es.exprEnvs.insert(std::make_pair(this, env));
e->bindVars(es, env);
@@ -375,7 +375,7 @@ void ExprSelect::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv>
void ExprOpHasAttr::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (debuggerHook)
+ if (es.debugMode)
es.exprEnvs.insert(std::make_pair(this, env));
e->bindVars(es, env);
@@ -386,7 +386,7 @@ void ExprOpHasAttr::bindVars(EvalState & es, const std::shared_ptr<const StaticE
void ExprAttrs::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (debuggerHook)
+ if (es.debugMode)
es.exprEnvs.insert(std::make_pair(this, env));
if (recursive) {
@@ -419,7 +419,7 @@ void ExprAttrs::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv>
void ExprList::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (debuggerHook)
+ if (es.debugMode)
es.exprEnvs.insert(std::make_pair(this, env));
for (auto & i : elems)
@@ -428,7 +428,7 @@ void ExprList::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> &
void ExprLambda::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (debuggerHook)
+ if (es.debugMode)
es.exprEnvs.insert(std::make_pair(this, env));
auto newEnv = std::make_shared<StaticEnv>(
@@ -455,7 +455,7 @@ void ExprLambda::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv>
void ExprCall::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (debuggerHook)
+ if (es.debugMode)
es.exprEnvs.insert(std::make_pair(this, env));
fun->bindVars(es, env);
@@ -465,7 +465,7 @@ void ExprCall::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> &
void ExprLet::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (debuggerHook)
+ if (es.debugMode)
es.exprEnvs.insert(std::make_pair(this, env));
auto newEnv = std::make_shared<StaticEnv>(false, env.get(), attrs->attrs.size());
@@ -484,7 +484,7 @@ void ExprLet::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> &
void ExprWith::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (debuggerHook)
+ if (es.debugMode)
es.exprEnvs.insert(std::make_pair(this, env));
/* Does this `with' have an enclosing `with'? If so, record its
@@ -499,7 +499,7 @@ void ExprWith::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> &
break;
}
- if (debuggerHook)
+ if (es.debugMode)
es.exprEnvs.insert(std::make_pair(this, env));
attrs->bindVars(es, env);
@@ -509,7 +509,7 @@ void ExprWith::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> &
void ExprIf::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (debuggerHook)
+ if (es.debugMode)
es.exprEnvs.insert(std::make_pair(this, env));
cond->bindVars(es, env);
@@ -519,7 +519,7 @@ void ExprIf::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & e
void ExprAssert::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (debuggerHook)
+ if (es.debugMode)
es.exprEnvs.insert(std::make_pair(this, env));
cond->bindVars(es, env);
@@ -528,7 +528,7 @@ void ExprAssert::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv>
void ExprOpNot::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (debuggerHook)
+ if (es.debugMode)
es.exprEnvs.insert(std::make_pair(this, env));
e->bindVars(es, env);
@@ -536,7 +536,7 @@ void ExprOpNot::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv>
void ExprConcatStrings::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (debuggerHook)
+ if (es.debugMode)
es.exprEnvs.insert(std::make_pair(this, env));
for (auto & i : *this->es)
@@ -545,7 +545,7 @@ void ExprConcatStrings::bindVars(EvalState & es, const std::shared_ptr<const Sta
void ExprPos::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (debuggerHook)
+ if (es.debugMode)
es.exprEnvs.insert(std::make_pair(this, env));
}
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index fdafb1711..6a5d02ed1 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -22,7 +22,7 @@ MakeError(UndefinedVarError, Error);
MakeError(MissingArgumentError, EvalError);
MakeError(RestrictedPathError, Error);
-extern std::function<void(EvalState & evalState, const Error * error, const Env & env, const Expr & expr)> debuggerHook;
+// extern std::function<void(EvalState & evalState, const Error * error, const Env & env, const Expr & expr)> debuggerHook;
/* Position objects. */
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index e56e6314b..f7429197a 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -757,7 +757,7 @@ static RegisterPrimOp primop_break({
)",
.fun = [](EvalState & state, const PosIdx pos, Value * * args, Value & v)
{
- if (debuggerHook && !state.debugTraces.empty()) {
+ if (state.debugMode && !state.debugTraces.empty()) {
auto error = Error(ErrorInfo {
.level = lvlInfo,
.msg = hintfmt("breakpoint reached"),
@@ -765,7 +765,7 @@ static RegisterPrimOp primop_break({
});
auto & dt = state.debugTraces.front();
- debuggerHook(state, &error, dt.env, dt.expr);
+ state.debugRepl(&error, dt.env, dt.expr);
if (state.debugQuit) {
// If the user elects to quit the repl, throw an exception.
@@ -879,8 +879,8 @@ static RegisterPrimOp primop_floor({
static void prim_tryEval(EvalState & state, const PosIdx pos, Value * * args, Value & v)
{
auto attrs = state.buildBindings(2);
- auto saveDebuggerHook = debuggerHook;
- debuggerHook = nullptr;
+ auto saveDebugMode = state.debugMode;
+ state.debugMode = false;
try {
state.forceValue(*args[0], pos);
attrs.insert(state.sValue, args[0]);
@@ -889,7 +889,7 @@ static void prim_tryEval(EvalState & state, const PosIdx pos, Value * * args, Va
attrs.alloc(state.sValue).mkBool(false);
attrs.alloc("success").mkBool(false);
}
- debuggerHook = saveDebuggerHook;
+ state.debugMode = saveDebugMode;
v.mkAttrs(attrs);
}
From 884d59178735bcb5d5db7db97a05ad62a175493b Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Fri, 20 May 2022 10:33:50 -0600
Subject: [PATCH 151/188] debugRepl ftn pointer
---
src/libcmd/command.cc | 27 +++++++++++++++++++++++++++
src/libexpr/eval.cc | 12 ++++++++----
src/libexpr/eval.hh | 10 +++++-----
src/libexpr/primops.cc | 2 +-
4 files changed, 41 insertions(+), 10 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index a4ea5bc33..b61b9b61d 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -120,7 +120,34 @@ ref<EvalState> EvalCommand::getEvalState()
;
evalState->debugMode = startReplOnEvalErrors;
+
// TODO move this somewhere else. Its only here to get the evalState ptr!
+ if (startReplOnEvalErrors) {
+ evalState->debugRepl = &runRepl;
+ };
+ // // debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error * error, const Env & env, const Expr & expr) {
+ // debuggerHook = [](EvalState & evalState, const Error * error, const Env & env, const Expr & expr) {
+ // auto dts =
+ // error && expr.getPos()
+ // ? std::make_unique<DebugTraceStacker>(
+ // evalState,
+ // DebugTrace {
+ // .pos = error->info().errPos ? *error->info().errPos : evalState.positions[expr.getPos()],
+ // .expr = expr,
+ // .env = env,
+ // .hint = error->info().msg,
+ // .isError = true
+ // })
+ // : nullptr;
+
+ // if (error)
+ // printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error->what());
+
+ // auto se = evalState.getStaticEnv(expr);
+ // if (se) {
+ // auto vm = mapStaticEnvBindings(evalState.symbols, *se.get(), env);
+ // runRepl(evalState, *vm);
+ // }
// if (startReplOnEvalErrors)
// // debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error * error, const Env & env, const Expr & expr) {
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 1cde4a9ab..5faecdbe3 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -463,7 +463,7 @@ EvalState::EvalState(
, emptyBindings(0)
, store(store)
, buildStore(buildStore ? buildStore : store)
- , debugMode(false)
+ , debugRepl(0)
, debugStop(false)
, debugQuit(false)
, regexCache(makeRegexCache())
@@ -811,8 +811,12 @@ std::unique_ptr<ValMap> mapStaticEnvBindings(const SymbolTable & st, const Stati
return vm;
}
-void EvalState::debugRepl(const Error * error, const Env & env, const Expr & expr)
+void EvalState::runDebugRepl(const Error * error, const Env & env, const Expr & expr)
{
+ // double check we've got the debugRepl ftn pointer.
+ if (!debugRepl)
+ return;
+
auto dts =
error && expr.getPos()
? std::make_unique<DebugTraceStacker>(
@@ -832,7 +836,7 @@ void EvalState::debugRepl(const Error * error, const Env & env, const Expr & exp
auto se = getStaticEnv(expr);
if (se) {
auto vm = mapStaticEnvBindings(symbols, *se.get(), env);
- runRepl(*this, *vm);
+ (debugRepl)(*this, *vm);
}
}
@@ -1070,7 +1074,7 @@ DebugTraceStacker::DebugTraceStacker(EvalState & evalState, DebugTrace t)
{
evalState.debugTraces.push_front(trace);
if (evalState.debugStop && evalState.debugMode)
- evalState.debugRepl(nullptr, trace.env, trace.expr);
+ evalState.runDebugRepl(nullptr, trace.env, trace.expr);
}
void Value::mkString(std::string_view s)
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 711a4d6be..90bd5497b 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -48,8 +48,6 @@ struct Env
Value * values[0];
};
-extern void runRepl(ref<EvalState> evalState, const ValMap & extraEnv);
-
void printEnvBindings(const EvalState &es, const Expr & expr, const Env & env);
void printEnvBindings(const SymbolTable & st, const StaticEnv & se, const Env & env, int lvl = 0);
@@ -129,6 +127,8 @@ public:
RootValue vImportedDrvToDerivation = nullptr;
/* Debugger */
+ void (* debugRepl)(EvalState & es, const ValMap & extraEnv);
+
bool debugMode;
bool debugStop;
bool debugQuit;
@@ -143,14 +143,14 @@ public:
return std::shared_ptr<const StaticEnv>();;
}
- void debugRepl(const Error * error, const Env & env, const Expr & expr);
+ void runDebugRepl(const Error * error, const Env & env, const Expr & expr);
template<class E>
[[gnu::noinline, gnu::noreturn]]
void debugThrow(const E &error, const Env & env, const Expr & expr)
{
if (debugMode)
- debugRepl(&error, env, expr);
+ runDebugRepl(&error, env, expr);
throw error;
}
@@ -164,7 +164,7 @@ public:
// DebugTrace stack.
if (debugMode && !debugTraces.empty()) {
const DebugTrace & last = debugTraces.front();
- debugRepl(&e, last.env, last.expr);
+ runDebugRepl(&e, last.env, last.expr);
}
throw e;
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index f7429197a..3ca377b7c 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -765,7 +765,7 @@ static RegisterPrimOp primop_break({
});
auto & dt = state.debugTraces.front();
- state.debugRepl(&error, dt.env, dt.expr);
+ state.runDebugRepl(&error, dt.env, dt.expr);
if (state.debugQuit) {
// If the user elects to quit the repl, throw an exception.
From 982c8a959b0a686c1c532429b206507c7641e083 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Fri, 20 May 2022 12:45:36 -0600
Subject: [PATCH 152/188] remove special tryEval behavior
---
src/libexpr/primops.cc | 3 ---
1 file changed, 3 deletions(-)
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index ff5ae8809..1727a276c 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -879,8 +879,6 @@ static RegisterPrimOp primop_floor({
static void prim_tryEval(EvalState & state, const PosIdx pos, Value * * args, Value & v)
{
auto attrs = state.buildBindings(2);
- auto saveDebuggerHook = debuggerHook;
- debuggerHook = nullptr;
try {
state.forceValue(*args[0], pos);
attrs.insert(state.sValue, args[0]);
@@ -889,7 +887,6 @@ static void prim_tryEval(EvalState & state, const PosIdx pos, Value * * args, Va
attrs.alloc(state.sValue).mkBool(false);
attrs.alloc("success").mkBool(false);
}
- debuggerHook = saveDebuggerHook;
v.mkAttrs(attrs);
}
From 81a9bf0ad2ff3244096ed14299c65c0b32c0aca0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Na=C3=AFm=20Camille=20Favier?= <n@monade.li>
Date: Sat, 21 May 2022 14:41:24 +0200
Subject: [PATCH 153/188] =?UTF-8?q?typo:=20defaultApps=20=E2=86=92=20defau?=
=?UTF-8?q?ltApp?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
---
src/nix/flake.cc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/nix/flake.cc b/src/nix/flake.cc
index 1938ce4e6..500116eaf 100644
--- a/src/nix/flake.cc
+++ b/src/nix/flake.cc
@@ -509,7 +509,7 @@ struct CmdFlakeCheck : FlakeCommand
std::string_view replacement =
name == "defaultPackage" ? "packages.<system>.default" :
- name == "defaultApps" ? "apps.<system>.default" :
+ name == "defaultApp" ? "apps.<system>.default" :
name == "defaultTemplate" ? "templates.default" :
name == "defaultBundler" ? "bundlers.<system>.default" :
name == "overlay" ? "overlays.default" :
From 34ffaa9f5786fafa68c55bae99c5512506f7f0db Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Sun, 22 May 2022 18:57:45 -0600
Subject: [PATCH 154/188] changning repl to use EvalState& instead of ref
---
src/libcmd/command.hh | 3 +-
src/libcmd/repl.cc | 145 +++++++++++++++++++++---------------------
2 files changed, 74 insertions(+), 74 deletions(-)
diff --git a/src/libcmd/command.hh b/src/libcmd/command.hh
index 196bd3aaa..b064f490a 100644
--- a/src/libcmd/command.hh
+++ b/src/libcmd/command.hh
@@ -274,7 +274,6 @@ void printClosureDiff(
void runRepl(
- ref<EvalState> evalState,
+ EvalState &evalState,
const ValMap & extraEnv);
-
}
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 43c2ce65e..7b9ad9d71 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -48,7 +48,8 @@ struct NixRepl
#endif
{
std::string curDir;
- ref<EvalState> state;
+ EvalState &state;
+ // ref<EvalState> state;
Bindings * autoArgs;
size_t debugTraceIndex;
@@ -63,7 +64,7 @@ struct NixRepl
const Path historyFile;
- NixRepl(ref<EvalState> state);
+ NixRepl(EvalState &state);
~NixRepl();
void mainLoop(const std::vector<std::string> & files);
StringSet completePrefix(const std::string & prefix);
@@ -96,10 +97,10 @@ std::string removeWhitespace(std::string s)
}
-NixRepl::NixRepl(ref<EvalState> state)
+NixRepl::NixRepl(EvalState &state)
: state(state)
, debugTraceIndex(0)
- , staticEnv(new StaticEnv(false, state->staticBaseEnv.get()))
+ , staticEnv(new StaticEnv(false, state.staticBaseEnv.get()))
, historyFile(getDataDir() + "/nix/repl-history")
{
curDir = absPath(".");
@@ -261,8 +262,8 @@ void NixRepl::mainLoop(const std::vector<std::string> & files)
// number of chars as the prompt.
if (!getLine(input, input.empty() ? "nix-repl> " : " ")) {
// ctrl-D should exit the debugger.
- state->debugStop = false;
- state->debugQuit = true;
+ state.debugStop = false;
+ state.debugQuit = true;
break;
}
try {
@@ -279,8 +280,8 @@ void NixRepl::mainLoop(const std::vector<std::string> & files)
// in debugger mode, an EvalError should trigger another repl session.
// when that session returns the exception will land here. No need to show it again;
// show the error for this repl session instead.
- if (debuggerHook && !state->debugTraces.empty())
- showDebugTrace(std::cout, state->positions, state->debugTraces.front());
+ if (debuggerHook && !state.debugTraces.empty())
+ showDebugTrace(std::cout, state.positions, state.debugTraces.front());
else
printMsg(lvlError, e.msg());
} catch (Error & e) {
@@ -386,11 +387,11 @@ StringSet NixRepl::completePrefix(const std::string & prefix)
Expr * e = parseString(expr);
Value v;
- e->eval(*state, *env, v);
- state->forceAttrs(v, noPos);
+ e->eval(state, *env, v);
+ state.forceAttrs(v, noPos);
for (auto & i : *v.attrs) {
- std::string_view name = state->symbols[i.name];
+ std::string_view name = state.symbols[i.name];
if (name.substr(0, cur2.size()) != cur2) continue;
completions.insert(concatStrings(prev, expr, ".", name));
}
@@ -426,14 +427,14 @@ static bool isVarName(std::string_view s)
StorePath NixRepl::getDerivationPath(Value & v) {
- auto drvInfo = getDerivation(*state, v, false);
+ auto drvInfo = getDerivation(state, v, false);
if (!drvInfo)
throw Error("expression does not evaluate to a derivation, so I can't build it");
auto drvPath = drvInfo->queryDrvPath();
if (!drvPath)
throw Error("expression did not evaluate to a valid derivation (no 'drvPath' attribute)");
- if (!state->store->isValidPath(*drvPath))
- throw Error("expression evaluated to invalid derivation '%s'", state->store->printStorePath(*drvPath));
+ if (!state.store->isValidPath(*drvPath))
+ throw Error("expression evaluated to invalid derivation '%s'", state.store->printStorePath(*drvPath));
return *drvPath;
}
@@ -441,13 +442,13 @@ void NixRepl::loadDebugTraceEnv(DebugTrace & dt)
{
initEnv();
- auto se = state->getStaticEnv(dt.expr);
+ auto se = state.getStaticEnv(dt.expr);
if (se) {
- auto vm = mapStaticEnvBindings(state->symbols, *se.get(), dt.env);
+ auto vm = mapStaticEnvBindings(state.symbols, *se.get(), dt.env);
// add staticenv vars.
for (auto & [name, value] : *(vm.get()))
- addVarToScope(state->symbols.create(name), *value);
+ addVarToScope(state.symbols.create(name), *value);
}
}
@@ -508,16 +509,16 @@ bool NixRepl::processLine(std::string line)
}
else if (debuggerHook && (command == ":bt" || command == ":backtrace")) {
- for (const auto & [idx, i] : enumerate(state->debugTraces)) {
+ for (const auto & [idx, i] : enumerate(state.debugTraces)) {
std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
- showDebugTrace(std::cout, state->positions, i);
+ showDebugTrace(std::cout, state.positions, i);
}
}
else if (debuggerHook && (command == ":env")) {
- for (const auto & [idx, i] : enumerate(state->debugTraces)) {
+ for (const auto & [idx, i] : enumerate(state.debugTraces)) {
if (idx == debugTraceIndex) {
- printEnvBindings(*state, i.expr, i.env);
+ printEnvBindings(state, i.expr, i.env);
break;
}
}
@@ -529,12 +530,12 @@ bool NixRepl::processLine(std::string line)
debugTraceIndex = stoi(arg);
} catch (...) { }
- for (const auto & [idx, i] : enumerate(state->debugTraces)) {
+ for (const auto & [idx, i] : enumerate(state.debugTraces)) {
if (idx == debugTraceIndex) {
std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
- showDebugTrace(std::cout, state->positions, i);
+ showDebugTrace(std::cout, state.positions, i);
std::cout << std::endl;
- printEnvBindings(*state, i.expr, i.env);
+ printEnvBindings(state, i.expr, i.env);
loadDebugTraceEnv(i);
break;
}
@@ -543,13 +544,13 @@ bool NixRepl::processLine(std::string line)
else if (debuggerHook && (command == ":s" || command == ":step")) {
// set flag to stop at next DebugTrace; exit repl.
- state->debugStop = true;
+ state.debugStop = true;
return false;
}
else if (debuggerHook && (command == ":c" || command == ":continue")) {
// set flag to run to next breakpoint or end of program; exit repl.
- state->debugStop = false;
+ state.debugStop = false;
return false;
}
@@ -560,7 +561,7 @@ bool NixRepl::processLine(std::string line)
}
else if (command == ":l" || command == ":load") {
- state->resetFileCache();
+ state.resetFileCache();
loadFile(arg);
}
@@ -569,7 +570,7 @@ bool NixRepl::processLine(std::string line)
}
else if (command == ":r" || command == ":reload") {
- state->resetFileCache();
+ state.resetFileCache();
reloadFiles();
}
@@ -580,15 +581,15 @@ bool NixRepl::processLine(std::string line)
const auto [file, line] = [&] () -> std::pair<std::string, uint32_t> {
if (v.type() == nPath || v.type() == nString) {
PathSet context;
- auto filename = state->coerceToString(noPos, v, context).toOwned();
- state->symbols.create(filename);
+ auto filename = state.coerceToString(noPos, v, context).toOwned();
+ state.symbols.create(filename);
return {filename, 0};
} else if (v.isLambda()) {
- auto pos = state->positions[v.lambda.fun->pos];
+ auto pos = state.positions[v.lambda.fun->pos];
return {pos.file, pos.line};
} else {
// assume it's a derivation
- return findPackageFilename(*state, v, arg);
+ return findPackageFilename(state, v, arg);
}
}();
@@ -602,7 +603,7 @@ bool NixRepl::processLine(std::string line)
runProgram2(RunOptions { .program = editor, .searchPath = true, .args = args });
// Reload right after exiting the editor
- state->resetFileCache();
+ state.resetFileCache();
reloadFiles();
}
@@ -616,30 +617,30 @@ bool NixRepl::processLine(std::string line)
Value v, f, result;
evalString(arg, v);
evalString("drv: (import <nixpkgs> {}).runCommand \"shell\" { buildInputs = [ drv ]; } \"\"", f);
- state->callFunction(f, v, result, PosIdx());
+ state.callFunction(f, v, result, PosIdx());
StorePath drvPath = getDerivationPath(result);
- runNix("nix-shell", {state->store->printStorePath(drvPath)});
+ runNix("nix-shell", {state.store->printStorePath(drvPath)});
}
else if (command == ":b" || command == ":bl" || command == ":i" || command == ":sh" || command == ":log") {
Value v;
evalString(arg, v);
StorePath drvPath = getDerivationPath(v);
- Path drvPathRaw = state->store->printStorePath(drvPath);
+ Path drvPathRaw = state.store->printStorePath(drvPath);
if (command == ":b" || command == ":bl") {
- state->store->buildPaths({DerivedPath::Built{drvPath}});
- auto drv = state->store->readDerivation(drvPath);
+ state.store->buildPaths({DerivedPath::Built{drvPath}});
+ auto drv = state.store->readDerivation(drvPath);
logger->cout("\nThis derivation produced the following outputs:");
- for (auto & [outputName, outputPath] : state->store->queryDerivationOutputMap(drvPath)) {
- auto localStore = state->store.dynamic_pointer_cast<LocalFSStore>();
+ for (auto & [outputName, outputPath] : state.store->queryDerivationOutputMap(drvPath)) {
+ auto localStore = state.store.dynamic_pointer_cast<LocalFSStore>();
if (localStore && command == ":bl") {
std::string symlink = "repl-result-" + outputName;
localStore->addPermRoot(outputPath, absPath(symlink));
- logger->cout(" ./%s -> %s", symlink, state->store->printStorePath(outputPath));
+ logger->cout(" ./%s -> %s", symlink, state.store->printStorePath(outputPath));
} else {
- logger->cout(" %s -> %s", outputName, state->store->printStorePath(outputPath));
+ logger->cout(" %s -> %s", outputName, state.store->printStorePath(outputPath));
}
}
} else if (command == ":i") {
@@ -651,7 +652,7 @@ bool NixRepl::processLine(std::string line)
});
auto subs = getDefaultSubstituters();
- subs.push_front(state->store);
+ subs.push_front(state.store);
bool foundLog = false;
RunPager pager;
@@ -684,15 +685,15 @@ bool NixRepl::processLine(std::string line)
}
else if (command == ":q" || command == ":quit") {
- state->debugStop = false;
- state->debugQuit = true;
+ state.debugStop = false;
+ state.debugQuit = true;
return false;
}
else if (command == ":doc") {
Value v;
evalString(arg, v);
- if (auto doc = state->getDoc(v)) {
+ if (auto doc = state.getDoc(v)) {
std::string markdown;
if (!doc->args.empty() && doc->name) {
@@ -736,9 +737,9 @@ bool NixRepl::processLine(std::string line)
isVarName(name = removeWhitespace(line.substr(0, p))))
{
Expr * e = parseString(line.substr(p + 1));
- Value & v(*state->allocValue());
+ Value & v(*state.allocValue());
v.mkThunk(env, e);
- addVarToScope(state->symbols.create(name), v);
+ addVarToScope(state.symbols.create(name), v);
} else {
Value v;
evalString(line, v);
@@ -755,8 +756,8 @@ void NixRepl::loadFile(const Path & path)
loadedFiles.remove(path);
loadedFiles.push_back(path);
Value v, v2;
- state->evalFile(lookupFileArg(*state, path), v);
- state->autoCallFunction(*autoArgs, v, v2);
+ state.evalFile(lookupFileArg(state, path), v);
+ state.autoCallFunction(*autoArgs, v, v2);
addAttrsToScope(v2);
}
@@ -771,8 +772,8 @@ void NixRepl::loadFlake(const std::string & flakeRefS)
Value v;
- flake::callFlake(*state,
- flake::lockFlake(*state, flakeRef,
+ flake::callFlake(state,
+ flake::lockFlake(state, flakeRef,
flake::LockFlags {
.updateLockFile = false,
.useRegistries = !evalSettings.pureEval,
@@ -785,14 +786,14 @@ void NixRepl::loadFlake(const std::string & flakeRefS)
void NixRepl::initEnv()
{
- env = &state->allocEnv(envSize);
- env->up = &state->baseEnv;
+ env = &state.allocEnv(envSize);
+ env->up = &state.baseEnv;
displ = 0;
staticEnv->vars.clear();
varNames.clear();
- for (auto & i : state->staticBaseEnv->vars)
- varNames.emplace(state->symbols[i.first]);
+ for (auto & i : state.staticBaseEnv->vars)
+ varNames.emplace(state.symbols[i.first]);
}
@@ -821,14 +822,14 @@ void NixRepl::loadFiles()
void NixRepl::addAttrsToScope(Value & attrs)
{
- state->forceAttrs(attrs, [&]() { return attrs.determinePos(noPos); });
+ state.forceAttrs(attrs, [&]() { return attrs.determinePos(noPos); });
if (displ + attrs.attrs->size() >= envSize)
throw Error("environment full; cannot add more variables");
for (auto & i : *attrs.attrs) {
staticEnv->vars.emplace_back(i.name, displ);
env->values[displ++] = i.value;
- varNames.emplace(state->symbols[i.name]);
+ varNames.emplace(state.symbols[i.name]);
}
staticEnv->sort();
staticEnv->deduplicate();
@@ -845,13 +846,13 @@ void NixRepl::addVarToScope(const Symbol name, Value & v)
staticEnv->vars.emplace_back(name, displ);
staticEnv->sort();
env->values[displ++] = &v;
- varNames.emplace(state->symbols[name]);
+ varNames.emplace(state.symbols[name]);
}
Expr * NixRepl::parseString(std::string s)
{
- Expr * e = state->parseExprFromString(std::move(s), curDir, staticEnv);
+ Expr * e = state.parseExprFromString(std::move(s), curDir, staticEnv);
return e;
}
@@ -859,8 +860,8 @@ Expr * NixRepl::parseString(std::string s)
void NixRepl::evalString(std::string s, Value & v)
{
Expr * e = parseString(s);
- e->eval(*state, *env, v);
- state->forceValue(v, [&]() { return v.determinePos(noPos); });
+ e->eval(state, *env, v);
+ state.forceValue(v, [&]() { return v.determinePos(noPos); });
}
@@ -890,7 +891,7 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
str.flush();
checkInterrupt();
- state->forceValue(v, [&]() { return v.determinePos(noPos); });
+ state.forceValue(v, [&]() { return v.determinePos(noPos); });
switch (v.type()) {
@@ -919,14 +920,14 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
case nAttrs: {
seen.insert(&v);
- bool isDrv = state->isDerivation(v);
+ bool isDrv = state.isDerivation(v);
if (isDrv) {
str << "«derivation ";
- Bindings::iterator i = v.attrs->find(state->sDrvPath);
+ Bindings::iterator i = v.attrs->find(state.sDrvPath);
PathSet context;
if (i != v.attrs->end())
- str << state->store->printStorePath(state->coerceToStorePath(i->pos, *i->value, context));
+ str << state.store->printStorePath(state.coerceToStorePath(i->pos, *i->value, context));
else
str << "???";
str << "»";
@@ -938,7 +939,7 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
typedef std::map<std::string, Value *> Sorted;
Sorted sorted;
for (auto & i : *v.attrs)
- sorted.emplace(state->symbols[i.name], i.value);
+ sorted.emplace(state.symbols[i.name], i.value);
for (auto & i : sorted) {
if (isVarName(i.first))
@@ -988,7 +989,7 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
case nFunction:
if (v.isLambda()) {
std::ostringstream s;
- s << state->positions[v.lambda.fun->pos];
+ s << state.positions[v.lambda.fun->pos];
str << ANSI_BLUE "«lambda @ " << filterANSIEscapes(s.str()) << "»" ANSI_NORMAL;
} else if (v.isPrimOp()) {
str << ANSI_MAGENTA "«primop»" ANSI_NORMAL;
@@ -1012,7 +1013,7 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
}
void runRepl(
- ref<EvalState> evalState,
+ EvalState &evalState,
const ValMap & extraEnv)
{
auto repl = std::make_unique<NixRepl>(evalState);
@@ -1021,7 +1022,7 @@ void runRepl(
// add 'extra' vars.
for (auto & [name, value] : extraEnv)
- repl->addVarToScope(repl->state->symbols.create(name), *value);
+ repl->addVarToScope(repl->state.symbols.create(name), *value);
repl->mainLoop({});
}
@@ -1057,8 +1058,8 @@ struct CmdRepl : StoreCommand, MixEvalArgs
auto evalState = make_ref<EvalState>(searchPath, store);
- auto repl = std::make_unique<NixRepl>(evalState);
- repl->autoArgs = getAutoArgs(*repl->state);
+ auto repl = std::make_unique<NixRepl>(*evalState);
+ repl->autoArgs = getAutoArgs(repl->state);
repl->initEnv();
repl->mainLoop(files);
}
From 7ccb2700c0401c553631e07aeb49e08f976274a3 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Sun, 22 May 2022 19:15:58 -0600
Subject: [PATCH 155/188] comments
---
src/libcmd/command.cc | 50 ------------------------------------------
src/libexpr/nixexpr.cc | 4 ----
src/libexpr/nixexpr.hh | 2 --
3 files changed, 56 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index b61b9b61d..c1d9eefc6 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -121,59 +121,9 @@ ref<EvalState> EvalCommand::getEvalState()
evalState->debugMode = startReplOnEvalErrors;
- // TODO move this somewhere else. Its only here to get the evalState ptr!
if (startReplOnEvalErrors) {
evalState->debugRepl = &runRepl;
};
- // // debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error * error, const Env & env, const Expr & expr) {
- // debuggerHook = [](EvalState & evalState, const Error * error, const Env & env, const Expr & expr) {
- // auto dts =
- // error && expr.getPos()
- // ? std::make_unique<DebugTraceStacker>(
- // evalState,
- // DebugTrace {
- // .pos = error->info().errPos ? *error->info().errPos : evalState.positions[expr.getPos()],
- // .expr = expr,
- // .env = env,
- // .hint = error->info().msg,
- // .isError = true
- // })
- // : nullptr;
-
- // if (error)
- // printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error->what());
-
- // auto se = evalState.getStaticEnv(expr);
- // if (se) {
- // auto vm = mapStaticEnvBindings(evalState.symbols, *se.get(), env);
- // runRepl(evalState, *vm);
- // }
- // if (startReplOnEvalErrors)
-
- // // debuggerHook = [evalState{ref<EvalState>(evalState)}](const Error * error, const Env & env, const Expr & expr) {
- // debuggerHook = [](EvalState & evalState, const Error * error, const Env & env, const Expr & expr) {
- // auto dts =
- // error && expr.getPos()
- // ? std::make_unique<DebugTraceStacker>(
- // evalState,
- // DebugTrace {
- // .pos = error->info().errPos ? *error->info().errPos : evalState.positions[expr.getPos()],
- // .expr = expr,
- // .env = env,
- // .hint = error->info().msg,
- // .isError = true
- // })
- // : nullptr;
-
- // if (error)
- // printError("%s\n\n" ANSI_BOLD "Starting REPL to allow you to inspect the current state of the evaluator.\n" ANSI_NORMAL, error->what());
-
- // auto se = evalState.getStaticEnv(expr);
- // if (se) {
- // auto vm = mapStaticEnvBindings(evalState.symbols, *se.get(), env);
- // runRepl(evalState, *vm);
- // }
- // };
}
return ref<EvalState>(evalState);
}
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index b40791694..52d48122c 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -8,10 +8,6 @@
namespace nix {
-/* Launch the nix debugger */
-
-// std::function<void(EvalState & evalState,const Error * error, const Env & env, const Expr & expr)> debuggerHook;
-
/* Displaying abstract syntax trees. */
static void showString(std::ostream & str, std::string_view s)
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index 6a5d02ed1..9b3a9f5d0 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -22,8 +22,6 @@ MakeError(UndefinedVarError, Error);
MakeError(MissingArgumentError, EvalError);
MakeError(RestrictedPathError, Error);
-// extern std::function<void(EvalState & evalState, const Error * error, const Env & env, const Expr & expr)> debuggerHook;
-
/* Position objects. */
struct Pos
From 13d02af0799f5d2f7a53825936d587e22edcacb6 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Sun, 22 May 2022 21:45:24 -0600
Subject: [PATCH 156/188] remove redundant 'debugMode' flag
---
src/libcmd/command.cc | 2 --
src/libcmd/repl.cc | 14 +++++++-------
src/libexpr/eval.cc | 12 ++++++------
src/libexpr/eval.hh | 6 ++----
src/libexpr/nixexpr.cc | 38 +++++++++++++++++++-------------------
src/libexpr/primops.cc | 2 +-
6 files changed, 35 insertions(+), 39 deletions(-)
diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index c1d9eefc6..7f8072d75 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -119,8 +119,6 @@ ref<EvalState> EvalCommand::getEvalState()
#endif
;
- evalState->debugMode = startReplOnEvalErrors;
-
if (startReplOnEvalErrors) {
evalState->debugRepl = &runRepl;
};
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index d335a56cd..940a287c7 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -280,7 +280,7 @@ void NixRepl::mainLoop(const std::vector<std::string> & files)
// in debugger mode, an EvalError should trigger another repl session.
// when that session returns the exception will land here. No need to show it again;
// show the error for this repl session instead.
- if (state.debugMode && !state.debugTraces.empty())
+ if (state.debugRepl && !state.debugTraces.empty())
showDebugTrace(std::cout, state.positions, state.debugTraces.front());
else
printMsg(lvlError, e.msg());
@@ -493,7 +493,7 @@ bool NixRepl::processLine(std::string line)
<< " :log <expr> Show logs for a derivation\n"
<< " :te [bool] Enable, disable or toggle showing traces for errors\n"
;
- if (state.debugMode) {
+ if (state.debugRepl) {
std::cout
<< "\n"
<< " Debug mode commands\n"
@@ -508,14 +508,14 @@ bool NixRepl::processLine(std::string line)
}
- else if (state.debugMode && (command == ":bt" || command == ":backtrace")) {
+ else if (state.debugRepl && (command == ":bt" || command == ":backtrace")) {
for (const auto & [idx, i] : enumerate(state.debugTraces)) {
std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
showDebugTrace(std::cout, state.positions, i);
}
}
- else if (state.debugMode && (command == ":env")) {
+ else if (state.debugRepl && (command == ":env")) {
for (const auto & [idx, i] : enumerate(state.debugTraces)) {
if (idx == debugTraceIndex) {
printEnvBindings(state, i.expr, i.env);
@@ -524,7 +524,7 @@ bool NixRepl::processLine(std::string line)
}
}
- else if (state.debugMode && (command == ":st")) {
+ else if (state.debugRepl && (command == ":st")) {
try {
// change the DebugTrace index.
debugTraceIndex = stoi(arg);
@@ -542,13 +542,13 @@ bool NixRepl::processLine(std::string line)
}
}
- else if (state.debugMode && (command == ":s" || command == ":step")) {
+ else if (state.debugRepl && (command == ":s" || command == ":step")) {
// set flag to stop at next DebugTrace; exit repl.
state.debugStop = true;
return false;
}
- else if (state.debugMode && (command == ":c" || command == ":continue")) {
+ else if (state.debugRepl && (command == ":c" || command == ":continue")) {
// set flag to run to next breakpoint or end of program; exit repl.
state.debugStop = false;
return false;
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 5faecdbe3..c457df380 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -813,7 +813,7 @@ std::unique_ptr<ValMap> mapStaticEnvBindings(const SymbolTable & st, const Stati
void EvalState::runDebugRepl(const Error * error, const Env & env, const Expr & expr)
{
- // double check we've got the debugRepl ftn pointer.
+ // double check we've got the debugRepl function pointer.
if (!debugRepl)
return;
@@ -1073,7 +1073,7 @@ DebugTraceStacker::DebugTraceStacker(EvalState & evalState, DebugTrace t)
, trace(std::move(t))
{
evalState.debugTraces.push_front(trace);
- if (evalState.debugStop && evalState.debugMode)
+ if (evalState.debugStop && evalState.debugRepl)
evalState.runDebugRepl(nullptr, trace.env, trace.expr);
}
@@ -1271,7 +1271,7 @@ void EvalState::cacheFile(
fileParseCache[resolvedPath] = e;
try {
- auto dts = debugMode
+ auto dts = debugRepl
? makeDebugTraceStacker(
*this,
*e,
@@ -1505,7 +1505,7 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
e->eval(state, env, vTmp);
try {
- auto dts = state.debugMode
+ auto dts = state.debugRepl
? makeDebugTraceStacker(
state,
*this,
@@ -1674,7 +1674,7 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
/* Evaluate the body. */
try {
- auto dts = debugMode
+ auto dts = debugRepl
? makeDebugTraceStacker(
*this, *lambda.body, env2, positions[lambda.pos],
"while evaluating %s",
@@ -2102,7 +2102,7 @@ void EvalState::forceValueDeep(Value & v)
for (auto & i : *v.attrs)
try {
// If the value is a thunk, we're evaling. Otherwise no trace necessary.
- auto dts = debugMode && i.value->isThunk()
+ auto dts = debugRepl && i.value->isThunk()
? makeDebugTraceStacker(*this, *i.value->thunk.expr, *i.value->thunk.env, positions[i.pos],
"while evaluating the attribute '%1%'", symbols[i.name])
: nullptr;
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 90bd5497b..c86075ae3 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -128,8 +128,6 @@ public:
/* Debugger */
void (* debugRepl)(EvalState & es, const ValMap & extraEnv);
-
- bool debugMode;
bool debugStop;
bool debugQuit;
std::list<DebugTrace> debugTraces;
@@ -149,7 +147,7 @@ public:
[[gnu::noinline, gnu::noreturn]]
void debugThrow(const E &error, const Env & env, const Expr & expr)
{
- if (debugMode)
+ if (debugRepl)
runDebugRepl(&error, env, expr);
throw error;
@@ -162,7 +160,7 @@ public:
// Call this in the situation where Expr and Env are inaccessible.
// The debugger will start in the last context that's in the
// DebugTrace stack.
- if (debugMode && !debugTraces.empty()) {
+ if (debugRepl && !debugTraces.empty()) {
const DebugTrace & last = debugTraces.front();
runDebugRepl(&e, last.env, last.expr);
}
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index 52d48122c..7c623a07d 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -299,31 +299,31 @@ void Expr::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env
void ExprInt::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (es.debugMode)
+ if (es.debugRepl)
es.exprEnvs.insert(std::make_pair(this, env));
}
void ExprFloat::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (es.debugMode)
+ if (es.debugRepl)
es.exprEnvs.insert(std::make_pair(this, env));
}
void ExprString::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (es.debugMode)
+ if (es.debugRepl)
es.exprEnvs.insert(std::make_pair(this, env));
}
void ExprPath::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (es.debugMode)
+ if (es.debugRepl)
es.exprEnvs.insert(std::make_pair(this, env));
}
void ExprVar::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (es.debugMode)
+ if (es.debugRepl)
es.exprEnvs.insert(std::make_pair(this, env));
/* Check whether the variable appears in the environment. If so,
@@ -359,7 +359,7 @@ void ExprVar::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> &
void ExprSelect::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (es.debugMode)
+ if (es.debugRepl)
es.exprEnvs.insert(std::make_pair(this, env));
e->bindVars(es, env);
@@ -371,7 +371,7 @@ void ExprSelect::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv>
void ExprOpHasAttr::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (es.debugMode)
+ if (es.debugRepl)
es.exprEnvs.insert(std::make_pair(this, env));
e->bindVars(es, env);
@@ -382,7 +382,7 @@ void ExprOpHasAttr::bindVars(EvalState & es, const std::shared_ptr<const StaticE
void ExprAttrs::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (es.debugMode)
+ if (es.debugRepl)
es.exprEnvs.insert(std::make_pair(this, env));
if (recursive) {
@@ -415,7 +415,7 @@ void ExprAttrs::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv>
void ExprList::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (es.debugMode)
+ if (es.debugRepl)
es.exprEnvs.insert(std::make_pair(this, env));
for (auto & i : elems)
@@ -424,7 +424,7 @@ void ExprList::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> &
void ExprLambda::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (es.debugMode)
+ if (es.debugRepl)
es.exprEnvs.insert(std::make_pair(this, env));
auto newEnv = std::make_shared<StaticEnv>(
@@ -451,7 +451,7 @@ void ExprLambda::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv>
void ExprCall::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (es.debugMode)
+ if (es.debugRepl)
es.exprEnvs.insert(std::make_pair(this, env));
fun->bindVars(es, env);
@@ -461,7 +461,7 @@ void ExprCall::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> &
void ExprLet::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (es.debugMode)
+ if (es.debugRepl)
es.exprEnvs.insert(std::make_pair(this, env));
auto newEnv = std::make_shared<StaticEnv>(false, env.get(), attrs->attrs.size());
@@ -480,7 +480,7 @@ void ExprLet::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> &
void ExprWith::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (es.debugMode)
+ if (es.debugRepl)
es.exprEnvs.insert(std::make_pair(this, env));
/* Does this `with' have an enclosing `with'? If so, record its
@@ -495,7 +495,7 @@ void ExprWith::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> &
break;
}
- if (es.debugMode)
+ if (es.debugRepl)
es.exprEnvs.insert(std::make_pair(this, env));
attrs->bindVars(es, env);
@@ -505,7 +505,7 @@ void ExprWith::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> &
void ExprIf::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (es.debugMode)
+ if (es.debugRepl)
es.exprEnvs.insert(std::make_pair(this, env));
cond->bindVars(es, env);
@@ -515,7 +515,7 @@ void ExprIf::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & e
void ExprAssert::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (es.debugMode)
+ if (es.debugRepl)
es.exprEnvs.insert(std::make_pair(this, env));
cond->bindVars(es, env);
@@ -524,7 +524,7 @@ void ExprAssert::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv>
void ExprOpNot::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (es.debugMode)
+ if (es.debugRepl)
es.exprEnvs.insert(std::make_pair(this, env));
e->bindVars(es, env);
@@ -532,7 +532,7 @@ void ExprOpNot::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv>
void ExprConcatStrings::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (es.debugMode)
+ if (es.debugRepl)
es.exprEnvs.insert(std::make_pair(this, env));
for (auto & i : *this->es)
@@ -541,7 +541,7 @@ void ExprConcatStrings::bindVars(EvalState & es, const std::shared_ptr<const Sta
void ExprPos::bindVars(EvalState & es, const std::shared_ptr<const StaticEnv> & env)
{
- if (es.debugMode)
+ if (es.debugRepl)
es.exprEnvs.insert(std::make_pair(this, env));
}
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 60a70f336..b24d4c68a 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -757,7 +757,7 @@ static RegisterPrimOp primop_break({
)",
.fun = [](EvalState & state, const PosIdx pos, Value * * args, Value & v)
{
- if (state.debugMode && !state.debugTraces.empty()) {
+ if (state.debugRepl && !state.debugTraces.empty()) {
auto error = Error(ErrorInfo {
.level = lvlInfo,
.msg = hintfmt("breakpoint reached"),
From ba035f7dd03232d093a1265778b9587bab92cf1d Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Mon, 23 May 2022 10:13:47 -0600
Subject: [PATCH 157/188] comment
---
src/libcmd/repl.cc | 1 -
1 file changed, 1 deletion(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 940a287c7..d7201b321 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -49,7 +49,6 @@ struct NixRepl
{
std::string curDir;
EvalState &state;
- // ref<EvalState> state;
Bindings * autoArgs;
size_t debugTraceIndex;
From d1c270431ab017c48c28801bb93091c091e9d49d Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Mon, 23 May 2022 22:01:52 +0000
Subject: [PATCH 158/188] Bump zeebe-io/backport-action from 0.0.7 to 0.0.8
Bumps [zeebe-io/backport-action](https://github.com/zeebe-io/backport-action) from 0.0.7 to 0.0.8.
- [Release notes](https://github.com/zeebe-io/backport-action/releases)
- [Commits](https://github.com/zeebe-io/backport-action/compare/v0.0.7...v0.0.8)
---
updated-dependencies:
- dependency-name: zeebe-io/backport-action
dependency-type: direct:production
update-type: version-update:semver-patch
...
Signed-off-by: dependabot[bot] <support@github.com>
---
.github/workflows/backport.yml | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/.github/workflows/backport.yml b/.github/workflows/backport.yml
index dd481160f..3a2d4de0e 100644
--- a/.github/workflows/backport.yml
+++ b/.github/workflows/backport.yml
@@ -15,7 +15,7 @@ jobs:
fetch-depth: 0
- name: Create backport PRs
# should be kept in sync with `version`
- uses: zeebe-io/backport-action@v0.0.7
+ uses: zeebe-io/backport-action@v0.0.8
with:
# Config README: https://github.com/zeebe-io/backport-action#backport-action
github_token: ${{ secrets.GITHUB_TOKEN }}
From b916c08feba5173c3455890cff615fd46464409a Mon Sep 17 00:00:00 2001
From: Maximilian Bosch <maximilian@mbosch.me>
Date: Tue, 24 May 2022 14:20:48 +0200
Subject: [PATCH 159/188] libfetchers: drop `getGitDir` and hardcode `.git`
As discussed[1] this is most likely not desirable.
[1] https://github.com/NixOS/nix/pull/6440#issuecomment-1120876248
---
src/libfetchers/git.cc | 11 +++--------
1 file changed, 3 insertions(+), 8 deletions(-)
diff --git a/src/libfetchers/git.cc b/src/libfetchers/git.cc
index d23a820a4..a71bff76f 100644
--- a/src/libfetchers/git.cc
+++ b/src/libfetchers/git.cc
@@ -26,11 +26,6 @@ namespace {
// old version of git, which will ignore unrecognized `-c` options.
const std::string gitInitialBranch = "__nix_dummy_branch";
-std::string getGitDir()
-{
- return getEnv("GIT_DIR").value_or(".git");
-}
-
bool isCacheFileWithinTtl(const time_t now, const struct stat & st)
{
return st.st_mtime + settings.tarballTtl > now;
@@ -152,7 +147,7 @@ struct WorkdirInfo
WorkdirInfo getWorkdirInfo(const Input & input, const Path & workdir)
{
const bool submodules = maybeGetBoolAttr(input.attrs, "submodules").value_or(false);
- auto gitDir = getGitDir();
+ std::string gitDir(".git");
auto env = getEnv();
// Set LC_ALL to C: because we rely on the error messages from git rev-parse to determine what went wrong
@@ -370,7 +365,7 @@ struct GitInputScheme : InputScheme
{
auto sourcePath = getSourcePath(input);
assert(sourcePath);
- auto gitDir = getGitDir();
+ auto gitDir = ".git";
runProgram("git", true,
{ "-C", *sourcePath, "--git-dir", gitDir, "add", "--force", "--intent-to-add", "--", std::string(file) });
@@ -396,7 +391,7 @@ struct GitInputScheme : InputScheme
std::pair<StorePath, Input> fetch(ref<Store> store, const Input & _input) override
{
Input input(_input);
- auto gitDir = getGitDir();
+ auto gitDir = ".git";
std::string name = input.getName();
From cbf60bec6ff900e6759b439b782c8cef163b3046 Mon Sep 17 00:00:00 2001
From: Yorick van Pelt <yorick@yorickvanpelt.nl>
Date: Tue, 24 May 2022 16:26:40 +0200
Subject: [PATCH 160/188] configure.ac: check for sandbox-shell's
FEATURE_SH_STANDALONE
See also: https://bugs.archlinux.org/task/73998. Busybox's
FEATURE_SH_STANDALONE feature causes other busybox applets to
leak into the sandbox, where system() calls will start preferring
them over tools in $PATH. On arch, this even includes `ar`.
Let's check for this evil feature and disallow using this as a
sandbox shell.
---
configure.ac | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/configure.ac b/configure.ac
index 8a01c33ec..715c70de1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -294,6 +294,17 @@ esac
AC_ARG_WITH(sandbox-shell, AS_HELP_STRING([--with-sandbox-shell=PATH],[path of a statically-linked shell to use as /bin/sh in sandboxes]),
sandbox_shell=$withval)
AC_SUBST(sandbox_shell)
+if ! test -z ${sandbox_shell+x}; then
+ AC_MSG_CHECKING([whether sandbox-shell has the standalone feature])
+ # busybox shell sometimes allows executing other busybox applets,
+ # even if they are not in the path, breaking our sandbox
+ if PATH= $sandbox_shell -c "busybox" 2>&1 | grep -qv "not found"; then
+ AC_MSG_RESULT(enabled)
+ AC_MSG_ERROR([Please disable busybox FEATURE_SH_STANDALONE])
+ else
+ AC_MSG_RESULT(disabled)
+ fi
+fi
# Expand all variables in config.status.
test "$prefix" = NONE && prefix=$ac_default_prefix
From 7e52472759bfecbbfc9146fd0992361ea930f195 Mon Sep 17 00:00:00 2001
From: Yorick van Pelt <yorick@yorickvanpelt.nl>
Date: Tue, 24 May 2022 17:00:27 +0200
Subject: [PATCH 161/188] configure.ac: don't run sandbox-shell test when cross
compiling
---
configure.ac | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/configure.ac b/configure.ac
index 715c70de1..789dfdb3c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -294,7 +294,7 @@ esac
AC_ARG_WITH(sandbox-shell, AS_HELP_STRING([--with-sandbox-shell=PATH],[path of a statically-linked shell to use as /bin/sh in sandboxes]),
sandbox_shell=$withval)
AC_SUBST(sandbox_shell)
-if ! test -z ${sandbox_shell+x}; then
+if test ${cross_compiling:-no} = no && ! test -z ${sandbox_shell+x}; then
AC_MSG_CHECKING([whether sandbox-shell has the standalone feature])
# busybox shell sometimes allows executing other busybox applets,
# even if they are not in the path, breaking our sandbox
From 91b7d5373acdc5d9b3f2c13d16b9850ab5fc9e9d Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Wed, 25 May 2022 12:32:22 +0200
Subject: [PATCH 162/188] Style tweaks
---
src/libcmd/command.hh | 2 +-
src/libcmd/repl.cc | 8 +-
src/libexpr/eval-cache.cc | 40 +----
src/libexpr/eval.cc | 114 ++++--------
src/libexpr/eval.hh | 10 +-
src/libexpr/parser.y | 5 +-
src/libexpr/primops.cc | 294 ++++++++++---------------------
src/libexpr/primops/fetchTree.cc | 59 ++-----
src/libexpr/value-to-json.cc | 3 +-
9 files changed, 165 insertions(+), 370 deletions(-)
diff --git a/src/libcmd/command.hh b/src/libcmd/command.hh
index b064f490a..916695102 100644
--- a/src/libcmd/command.hh
+++ b/src/libcmd/command.hh
@@ -274,6 +274,6 @@ void printClosureDiff(
void runRepl(
- EvalState &evalState,
+ EvalState & evalState,
const ValMap & extraEnv);
}
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index d7201b321..7d8bbdb7e 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -48,7 +48,7 @@ struct NixRepl
#endif
{
std::string curDir;
- EvalState &state;
+ EvalState & state;
Bindings * autoArgs;
size_t debugTraceIndex;
@@ -63,11 +63,11 @@ struct NixRepl
const Path historyFile;
- NixRepl(EvalState &state);
+ NixRepl(EvalState & state);
~NixRepl();
void mainLoop(const std::vector<std::string> & files);
StringSet completePrefix(const std::string & prefix);
- bool getLine(std::string & input, const std::string &prompt);
+ bool getLine(std::string & input, const std::string & prompt);
StorePath getDerivationPath(Value & v);
bool processLine(std::string line);
void loadFile(const Path & path);
@@ -96,7 +96,7 @@ std::string removeWhitespace(std::string s)
}
-NixRepl::NixRepl(EvalState &state)
+NixRepl::NixRepl(EvalState & state)
: state(state)
, debugTraceIndex(0)
, staticEnv(new StaticEnv(false, state.staticBaseEnv.get()))
diff --git a/src/libexpr/eval-cache.cc b/src/libexpr/eval-cache.cc
index af213a484..1be98fc95 100644
--- a/src/libexpr/eval-cache.cc
+++ b/src/libexpr/eval-cache.cc
@@ -554,20 +554,14 @@ std::string AttrCursor::getString()
debug("using cached string attribute '%s'", getAttrPathStr());
return s->first;
} else
- {
- auto e = TypeError("'%s' is not a string", getAttrPathStr());
- root->state.debugThrowLastTrace(e);
- }
+ root->state.debugThrowLastTrace(TypeError("'%s' is not a string", getAttrPathStr()));
}
}
auto & v = forceValue();
if (v.type() != nString && v.type() != nPath)
- {
- auto e = TypeError("'%s' is not a string but %s", getAttrPathStr(), showType(v.type()));
- root->state.debugThrowLastTrace(e);
- }
+ root->state.debugThrowLastTrace(TypeError("'%s' is not a string but %s", getAttrPathStr(), showType(v.type())));
return v.type() == nString ? v.string.s : v.path;
}
@@ -591,10 +585,7 @@ string_t AttrCursor::getStringWithContext()
return *s;
}
} else
- {
- auto e = TypeError("'%s' is not a string", getAttrPathStr());
- root->state.debugThrowLastTrace(e);
- }
+ root->state.debugThrowLastTrace(TypeError("'%s' is not a string", getAttrPathStr()));
}
}
@@ -605,10 +596,7 @@ string_t AttrCursor::getStringWithContext()
else if (v.type() == nPath)
return {v.path, {}};
else
- {
- auto e = TypeError("'%s' is not a string but %s", getAttrPathStr(), showType(v.type()));
- root->state.debugThrowLastTrace(e);
- }
+ root->state.debugThrowLastTrace(TypeError("'%s' is not a string but %s", getAttrPathStr(), showType(v.type())));
}
bool AttrCursor::getBool()
@@ -621,20 +609,14 @@ bool AttrCursor::getBool()
debug("using cached Boolean attribute '%s'", getAttrPathStr());
return *b;
} else
- {
- auto e = TypeError("'%s' is not a Boolean", getAttrPathStr());
- root->state.debugThrowLastTrace(e);
- }
+ root->state.debugThrowLastTrace(TypeError("'%s' is not a Boolean", getAttrPathStr()));
}
}
auto & v = forceValue();
if (v.type() != nBool)
- {
- auto e = TypeError("'%s' is not a Boolean", getAttrPathStr());
- root->state.debugThrowLastTrace(e);
- }
+ root->state.debugThrowLastTrace(TypeError("'%s' is not a Boolean", getAttrPathStr()));
return v.boolean;
}
@@ -682,20 +664,14 @@ std::vector<Symbol> AttrCursor::getAttrs()
debug("using cached attrset attribute '%s'", getAttrPathStr());
return *attrs;
} else
- {
- auto e = TypeError("'%s' is not an attribute set", getAttrPathStr());
- root->state.debugThrowLastTrace(e);
- }
+ root->state.debugThrowLastTrace(TypeError("'%s' is not an attribute set", getAttrPathStr()));
}
}
auto & v = forceValue();
if (v.type() != nAttrs)
- {
- auto e = TypeError("'%s' is not an attribute set", getAttrPathStr());
- root->state.debugThrowLastTrace(e);
- }
+ root->state.debugThrowLastTrace(TypeError("'%s' is not an attribute set", getAttrPathStr()));
std::vector<Symbol> attrs;
for (auto & attr : *getValue().attrs)
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index c457df380..6dc7918b1 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -816,7 +816,7 @@ void EvalState::runDebugRepl(const Error * error, const Env & env, const Expr &
// double check we've got the debugRepl function pointer.
if (!debugRepl)
return;
-
+
auto dts =
error && expr.getPos()
? std::make_unique<DebugTraceStacker>(
@@ -846,198 +846,160 @@ void EvalState::runDebugRepl(const Error * error, const Env & env, const Expr &
exceptions. */
void EvalState::throwEvalError(const PosIdx pos, const char * s, Env & env, Expr & expr)
{
- auto error = EvalError({
+ debugThrow(EvalError({
.msg = hintfmt(s),
.errPos = positions[pos]
- });
-
- debugThrow(error, env, expr);
+ }), env, expr);
}
void EvalState::throwEvalError(const PosIdx pos, const char * s)
{
- auto error = EvalError({
+ debugThrowLastTrace(EvalError({
.msg = hintfmt(s),
.errPos = positions[pos]
- });
-
- debugThrowLastTrace(error);
+ }));
}
void EvalState::throwEvalError(const char * s, const std::string & s2)
{
- auto error = EvalError(s, s2);
-
- debugThrowLastTrace(error);
+ debugThrowLastTrace(EvalError(s, s2));
}
void EvalState::throwEvalError(const PosIdx pos, const Suggestions & suggestions, const char * s,
const std::string & s2, Env & env, Expr & expr)
{
- auto error = EvalError(ErrorInfo{
+ debugThrow(EvalError(ErrorInfo{
.msg = hintfmt(s, s2),
.errPos = positions[pos],
.suggestions = suggestions,
- });
-
- debugThrow(error, env, expr);
+ }), env, expr);
}
void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::string & s2)
{
- auto error = EvalError({
+ debugThrowLastTrace(EvalError({
.msg = hintfmt(s, s2),
.errPos = positions[pos]
- });
-
- debugThrowLastTrace(error);
+ }));
}
void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::string & s2, Env & env, Expr & expr)
{
- auto error = EvalError({
+ debugThrow(EvalError({
.msg = hintfmt(s, s2),
.errPos = positions[pos]
- });
-
- debugThrow(error, env, expr);
+ }), env, expr);
}
void EvalState::throwEvalError(const char * s, const std::string & s2,
const std::string & s3)
{
- auto error = EvalError({
+ debugThrowLastTrace(EvalError({
.msg = hintfmt(s, s2),
.errPos = positions[noPos]
- });
-
- debugThrowLastTrace(error);
+ }));
}
void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::string & s2,
const std::string & s3)
{
- auto error = EvalError({
+ debugThrowLastTrace(EvalError({
.msg = hintfmt(s, s2),
.errPos = positions[pos]
- });
-
- debugThrowLastTrace(error);
+ }));
}
void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::string & s2,
const std::string & s3, Env & env, Expr & expr)
{
- auto error = EvalError({
+ debugThrow(EvalError({
.msg = hintfmt(s, s2),
.errPos = positions[pos]
- });
-
- debugThrow(error, env, expr);
+ }), env, expr);
}
void EvalState::throwEvalError(const PosIdx p1, const char * s, const Symbol sym, const PosIdx p2, Env & env, Expr & expr)
{
// p1 is where the error occurred; p2 is a position mentioned in the message.
- auto error = EvalError({
+ debugThrow(EvalError({
.msg = hintfmt(s, symbols[sym], positions[p2]),
.errPos = positions[p1]
- });
-
- debugThrow(error, env, expr);
+ }), env, expr);
}
void EvalState::throwTypeError(const PosIdx pos, const char * s, const Value & v)
{
- auto error = TypeError({
+ debugThrowLastTrace(TypeError({
.msg = hintfmt(s, showType(v)),
.errPos = positions[pos]
- });
-
- debugThrowLastTrace(error);
+ }));
}
void EvalState::throwTypeError(const PosIdx pos, const char * s, const Value & v, Env & env, Expr & expr)
{
- auto error = TypeError({
+ debugThrow(TypeError({
.msg = hintfmt(s, showType(v)),
.errPos = positions[pos]
- });
-
- debugThrow(error, env, expr);
+ }), env, expr);
}
void EvalState::throwTypeError(const PosIdx pos, const char * s)
{
- auto error = TypeError({
+ debugThrowLastTrace(TypeError({
.msg = hintfmt(s),
.errPos = positions[pos]
- });
-
- debugThrowLastTrace(error);
+ }));
}
void EvalState::throwTypeError(const PosIdx pos, const char * s, const ExprLambda & fun,
const Symbol s2, Env & env, Expr &expr)
{
- auto error = TypeError({
+ debugThrow(TypeError({
.msg = hintfmt(s, fun.showNamePos(*this), symbols[s2]),
.errPos = positions[pos]
- });
-
- debugThrow(error, env, expr);
+ }), env, expr);
}
void EvalState::throwTypeError(const PosIdx pos, const Suggestions & suggestions, const char * s,
const ExprLambda & fun, const Symbol s2, Env & env, Expr &expr)
{
- auto error = TypeError(ErrorInfo {
+ debugThrow(TypeError(ErrorInfo {
.msg = hintfmt(s, fun.showNamePos(*this), symbols[s2]),
.errPos = positions[pos],
.suggestions = suggestions,
- });
-
- debugThrow(error, env, expr);
+ }), env, expr);
}
void EvalState::throwTypeError(const char * s, const Value & v, Env & env, Expr &expr)
{
- auto error = TypeError({
+ debugThrow(TypeError({
.msg = hintfmt(s, showType(v)),
.errPos = positions[expr.getPos()],
- });
-
- debugThrow(error, env, expr);
+ }), env, expr);
}
void EvalState::throwAssertionError(const PosIdx pos, const char * s, const std::string & s1, Env & env, Expr &expr)
{
- auto error = AssertionError({
+ debugThrow(AssertionError({
.msg = hintfmt(s, s1),
.errPos = positions[pos]
- });
-
- debugThrow(error, env, expr);
+ }), env, expr);
}
void EvalState::throwUndefinedVarError(const PosIdx pos, const char * s, const std::string & s1, Env & env, Expr &expr)
{
- auto error = UndefinedVarError({
+ debugThrow(UndefinedVarError({
.msg = hintfmt(s, s1),
.errPos = positions[pos]
- });
-
- debugThrow(error, env, expr);
+ }), env, expr);
}
void EvalState::throwMissingArgumentError(const PosIdx pos, const char * s, const std::string & s1, Env & env, Expr &expr)
{
- auto error = MissingArgumentError({
+ debugThrow(MissingArgumentError({
.msg = hintfmt(s, s1),
.errPos = positions[pos]
- });
-
- debugThrow(error, env, expr);
+ }), env, expr);
}
void EvalState::addErrorTrace(Error & e, const char * s, const std::string & s2) const
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index c86075ae3..3444815fd 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -131,11 +131,11 @@ public:
bool debugStop;
bool debugQuit;
std::list<DebugTrace> debugTraces;
- std::map<const Expr*, const std::shared_ptr<const StaticEnv> > exprEnvs;
- const std::shared_ptr<const StaticEnv> getStaticEnv(const Expr &expr) const
+ std::map<const Expr*, const std::shared_ptr<const StaticEnv>> exprEnvs;
+ const std::shared_ptr<const StaticEnv> getStaticEnv(const Expr & expr) const
{
auto i = exprEnvs.find(&expr);
- if (i != exprEnvs.end())
+ if (i != exprEnvs.end())
return i->second;
else
return std::shared_ptr<const StaticEnv>();;
@@ -145,7 +145,7 @@ public:
template<class E>
[[gnu::noinline, gnu::noreturn]]
- void debugThrow(const E &error, const Env & env, const Expr & expr)
+ void debugThrow(E && error, const Env & env, const Expr & expr)
{
if (debugRepl)
runDebugRepl(&error, env, expr);
@@ -155,7 +155,7 @@ public:
template<class E>
[[gnu::noinline, gnu::noreturn]]
- void debugThrowLastTrace(E & e)
+ void debugThrowLastTrace(E && e)
{
// Call this in the situation where Expr and Env are inaccessible.
// The debugger will start in the last context that's in the
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index b960cd8df..e3e0ac168 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -782,14 +782,13 @@ Path EvalState::findFile(SearchPath & searchPath, const std::string_view path, c
if (hasPrefix(path, "nix/"))
return concatStrings(corepkgsPrefix, path.substr(4));
- auto e = ThrownError({
+ debugThrowLastTrace(ThrownError({
.msg = hintfmt(evalSettings.pureEval
? "cannot look up '<%s>' in pure evaluation mode (use '--impure' to override)"
: "file '%s' was not found in the Nix search path (add it using $NIX_PATH or -I)",
path),
.errPos = positions[pos]
- });
- debugThrowLastTrace(e);
+ }));
}
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index b24d4c68a..96cd84b82 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -46,10 +46,7 @@ StringMap EvalState::realiseContext(const PathSet & context)
auto [ctx, outputName] = decodeContext(*store, i);
auto ctxS = store->printStorePath(ctx);
if (!store->isValidPath(ctx))
- {
- auto e = InvalidPathError(store->printStorePath(ctx));
- debugThrowLastTrace(e);
- }
+ debugThrowLastTrace(InvalidPathError(store->printStorePath(ctx)));
if (!outputName.empty() && ctx.isDerivation()) {
drvs.push_back({ctx, {outputName}});
} else {
@@ -60,12 +57,9 @@ StringMap EvalState::realiseContext(const PathSet & context)
if (drvs.empty()) return {};
if (!evalSettings.enableImportFromDerivation)
- {
- auto e = Error(
+ debugThrowLastTrace(Error(
"cannot build '%1%' during evaluation because the option 'allow-import-from-derivation' is disabled",
- store->printStorePath(drvs.begin()->drvPath));
- debugThrowLastTrace(e);
- }
+ store->printStorePath(drvs.begin()->drvPath)));
/* Build/substitute the context. */
std::vector<DerivedPath> buildReqs;
@@ -77,11 +71,9 @@ StringMap EvalState::realiseContext(const PathSet & context)
const auto outputPaths = store->queryDerivationOutputMap(drvPath);
for (auto & outputName : outputs) {
auto outputPath = get(outputPaths, outputName);
- if (!outputPath) {
- auto e = Error("derivation '%s' does not have an output named '%s'",
- store->printStorePath(drvPath), outputName);
- debugThrowLastTrace(e);
- }
+ if (!outputPath)
+ debugThrowLastTrace(Error("derivation '%s' does not have an output named '%s'",
+ store->printStorePath(drvPath), outputName));
res.insert_or_assign(
downstreamPlaceholder(*store, drvPath, outputName),
store->printStorePath(*outputPath)
@@ -326,23 +318,17 @@ void prim_importNative(EvalState & state, const PosIdx pos, Value * * args, Valu
std::string sym(state.forceStringNoCtx(*args[1], pos));
void *handle = dlopen(path.c_str(), RTLD_LAZY | RTLD_LOCAL);
- if (!handle) {
- auto e = EvalError("could not open '%1%': %2%", path, dlerror());
- state.debugThrowLastTrace(e);
- }
+ if (!handle)
+ state.debugThrowLastTrace(EvalError("could not open '%1%': %2%", path, dlerror()));
dlerror();
ValueInitializer func = (ValueInitializer) dlsym(handle, sym.c_str());
if(!func) {
char *message = dlerror();
- if (message) {
- auto e = EvalError("could not load symbol '%1%' from '%2%': %3%", sym, path, message);
- state.debugThrowLastTrace(e);
- } else {
- auto e = EvalError("symbol '%1%' from '%2%' resolved to NULL when a function pointer was expected",
- sym, path);
- state.debugThrowLastTrace(e);
- }
+ if (message)
+ state.debugThrowLastTrace(EvalError("could not load symbol '%1%' from '%2%': %3%", sym, path, message));
+ else
+ state.debugThrowLastTrace(EvalError("symbol '%1%' from '%2%' resolved to NULL when a function pointer was expected", sym, path));
}
(func)(state, v);
@@ -357,13 +343,11 @@ void prim_exec(EvalState & state, const PosIdx pos, Value * * args, Value & v)
state.forceList(*args[0], pos);
auto elems = args[0]->listElems();
auto count = args[0]->listSize();
- if (count == 0) {
- auto e = EvalError({
+ if (count == 0)
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("at least one argument to 'exec' required"),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
PathSet context;
auto program = state.coerceToString(pos, *elems[0], context, false, false).toOwned();
Strings commandArgs;
@@ -373,12 +357,11 @@ void prim_exec(EvalState & state, const PosIdx pos, Value * * args, Value & v)
try {
auto _ = state.realiseContext(context); // FIXME: Handle CA derivations
} catch (InvalidPathError & e) {
- auto ee = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("cannot execute '%1%', since path '%2%' is not valid",
program, e.path),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(ee);
+ }));
}
auto output = runProgram(program, true, commandArgs);
@@ -561,10 +544,8 @@ struct CompareValues
return v1->fpoint < v2->integer;
if (v1->type() == nInt && v2->type() == nFloat)
return v1->integer < v2->fpoint;
- if (v1->type() != v2->type()) {
- auto e = EvalError("cannot compare %1% with %2%", showType(*v1), showType(*v2));
- state.debugThrowLastTrace(e);
- }
+ if (v1->type() != v2->type())
+ state.debugThrowLastTrace(EvalError("cannot compare %1% with %2%", showType(*v1), showType(*v2)));
switch (v1->type()) {
case nInt:
return v1->integer < v2->integer;
@@ -585,10 +566,8 @@ struct CompareValues
return (*this)(v1->listElems()[i], v2->listElems()[i]);
}
}
- default: {
- auto e = EvalError("cannot compare %1% with %2%", showType(*v1), showType(*v2));
- state.debugThrowLastTrace(e);
- }
+ default:
+ state.debugThrowLastTrace(EvalError("cannot compare %1% with %2%", showType(*v1), showType(*v2)));
}
}
};
@@ -618,11 +597,10 @@ static Bindings::iterator getAttr(
auto aPos = attrSet->pos;
if (!aPos) {
- auto e = TypeError({
+ state.debugThrowLastTrace(TypeError({
.msg = errorMsg,
.errPos = state.positions[pos],
- });
- state.debugThrowLastTrace(e);
+ }));
} else {
auto e = TypeError({
.msg = errorMsg,
@@ -685,13 +663,11 @@ static void prim_genericClosure(EvalState & state, const PosIdx pos, Value * * a
Bindings::iterator key =
e->attrs->find(state.sKey);
- if (key == e->attrs->end()) {
- auto e = EvalError({
+ if (key == e->attrs->end())
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("attribute 'key' required"),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
state.forceValue(*key->value, pos);
if (!doneKeys.insert(key->value).second) continue;
@@ -792,10 +768,7 @@ static RegisterPrimOp primop_abort({
{
PathSet context;
auto s = state.coerceToString(pos, *args[0], context).toOwned();
- {
- auto e = Abort("evaluation aborted with the following error message: '%1%'", s);
- state.debugThrowLastTrace(e);
- }
+ state.debugThrowLastTrace(Abort("evaluation aborted with the following error message: '%1%'", s));
}
});
@@ -813,8 +786,7 @@ static RegisterPrimOp primop_throw({
{
PathSet context;
auto s = state.coerceToString(pos, *args[0], context).toOwned();
- auto e = ThrownError(s);
- state.debugThrowLastTrace(e);
+ state.debugThrowLastTrace(ThrownError(s));
}
});
@@ -1069,49 +1041,37 @@ static void prim_derivationStrict(EvalState & state, const PosIdx pos, Value * *
if (s == "recursive") ingestionMethod = FileIngestionMethod::Recursive;
else if (s == "flat") ingestionMethod = FileIngestionMethod::Flat;
else
- {
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("invalid value '%s' for 'outputHashMode' attribute", s),
.errPos = state.positions[posDrvName]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
};
auto handleOutputs = [&](const Strings & ss) {
outputs.clear();
for (auto & j : ss) {
if (outputs.find(j) != outputs.end())
- {
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("duplicate derivation output '%1%'", j),
.errPos = state.positions[posDrvName]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
/* !!! Check whether j is a valid attribute
name. */
/* Derivations cannot be named ‘drv’, because
then we'd have an attribute ‘drvPath’ in
the resulting set. */
if (j == "drv")
- {
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("invalid derivation output name 'drv'" ),
.errPos = state.positions[posDrvName]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
outputs.insert(j);
}
if (outputs.empty())
- {
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("derivation cannot have an empty set of outputs"),
.errPos = state.positions[posDrvName]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
};
try {
@@ -1236,32 +1196,23 @@ static void prim_derivationStrict(EvalState & state, const PosIdx pos, Value * *
/* Do we have all required attributes? */
if (drv.builder == "")
- {
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("required attribute 'builder' missing"),
.errPos = state.positions[posDrvName]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
if (drv.platform == "")
- {
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("required attribute 'system' missing"),
.errPos = state.positions[posDrvName]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
/* Check whether the derivation name is valid. */
if (isDerivation(drvName))
- {
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("derivation names are not allowed to end in '%s'", drvExtension),
.errPos = state.positions[posDrvName]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
if (outputHash) {
/* Handle fixed-output derivations.
@@ -1269,13 +1220,10 @@ static void prim_derivationStrict(EvalState & state, const PosIdx pos, Value * *
Ignore `__contentAddressed` because fixed output derivations are
already content addressed. */
if (outputs.size() != 1 || *(outputs.begin()) != "out")
- {
- auto e = Error({
+ state.debugThrowLastTrace(Error({
.msg = hintfmt("multiple outputs are not supported in fixed-output derivations"),
.errPos = state.positions[posDrvName]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
auto h = newHashAllowEmpty(*outputHash, parseHashTypeOpt(outputHashAlgo));
@@ -1443,13 +1391,10 @@ static RegisterPrimOp primop_toPath({
static void prim_storePath(EvalState & state, const PosIdx pos, Value * * args, Value & v)
{
if (evalSettings.pureEval)
- {
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("'%s' is not allowed in pure evaluation mode", "builtins.storePath"),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
PathSet context;
Path path = state.checkSourcePath(state.coerceToPath(pos, *args[0], context));
@@ -1458,13 +1403,10 @@ static void prim_storePath(EvalState & state, const PosIdx pos, Value * * args,
e.g. nix-push does the right thing. */
if (!state.store->isStorePath(path)) path = canonPath(path, true);
if (!state.store->isInStore(path))
- {
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("path '%1%' is not in the Nix store", path),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
auto path2 = state.store->toStorePath(path).first;
if (!settings.readOnlyMode)
state.store->ensurePath(path2);
@@ -1567,10 +1509,7 @@ static void prim_readFile(EvalState & state, const PosIdx pos, Value * * args, V
auto path = realisePath(state, pos, *args[0]);
auto s = readFile(path);
if (s.find((char) 0) != std::string::npos)
- {
- auto e = Error("the contents of the file '%1%' cannot be represented as a Nix string", path);
- state.debugThrowLastTrace(e);
- }
+ state.debugThrowLastTrace(Error("the contents of the file '%1%' cannot be represented as a Nix string", path));
StorePathSet refs;
if (state.store->isInStore(path)) {
try {
@@ -1622,14 +1561,12 @@ static void prim_findFile(EvalState & state, const PosIdx pos, Value * * args, V
auto rewrites = state.realiseContext(context);
path = rewriteStrings(path, rewrites);
} catch (InvalidPathError & e) {
- auto ee = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("cannot find '%1%', since path '%2%' is not valid", path, e.path),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(ee);
+ }));
}
-
searchPath.emplace_back(prefix, path);
}
@@ -1650,13 +1587,10 @@ static void prim_hashFile(EvalState & state, const PosIdx pos, Value * * args, V
auto type = state.forceStringNoCtx(*args[0], pos);
std::optional<HashType> ht = parseHashType(type);
if (!ht)
- {
- auto e = Error({
+ state.debugThrowLastTrace(Error({
.msg = hintfmt("unknown hash type '%1%'", type),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
auto path = realisePath(state, pos, *args[1]);
@@ -1893,16 +1827,13 @@ static void prim_toFile(EvalState & state, const PosIdx pos, Value * * args, Val
for (auto path : context) {
if (path.at(0) != '/')
- {
- auto e = EvalError( {
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt(
"in 'toFile': the file named '%1%' must not contain a reference "
"to a derivation but contains (%2%)",
name, path),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
refs.insert(state.store->parseStorePath(path));
}
@@ -2060,10 +1991,7 @@ static void addPath(
? state.store->computeStorePathForPath(name, path, method, htSHA256, filter).first
: state.store->addToStore(name, path, method, htSHA256, filter, state.repair, refs);
if (expectedHash && expectedStorePath != dstPath)
- {
- auto e = Error("store path mismatch in (possibly filtered) path added from '%s'", path);
- state.debugThrowLastTrace(e);
- }
+ state.debugThrowLastTrace(Error("store path mismatch in (possibly filtered) path added from '%s'", path));
state.allowAndSetStorePathString(dstPath, v);
} else
state.allowAndSetStorePathString(*expectedStorePath, v);
@@ -2081,15 +2009,12 @@ static void prim_filterSource(EvalState & state, const PosIdx pos, Value * * arg
state.forceValue(*args[0], pos);
if (args[0]->type() != nFunction)
- {
- auto e = TypeError({
+ state.debugThrowLastTrace(TypeError({
.msg = hintfmt(
"first argument in call to 'filterSource' is not a function but %1%",
showType(*args[0])),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
addPath(state, pos, std::string(baseNameOf(path)), path, args[0], FileIngestionMethod::Recursive, std::nullopt, v, context);
}
@@ -2173,22 +2098,16 @@ static void prim_path(EvalState & state, const PosIdx pos, Value * * args, Value
else if (n == "sha256")
expectedHash = newHashAllowEmpty(state.forceStringNoCtx(*attr.value, attr.pos), htSHA256);
else
- {
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("unsupported argument '%1%' to 'addPath'", state.symbols[attr.name]),
.errPos = state.positions[attr.pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
}
if (path.empty())
- {
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("'path' required"),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
if (name.empty())
name = baseNameOf(path);
@@ -2560,13 +2479,10 @@ static void prim_functionArgs(EvalState & state, const PosIdx pos, Value * * arg
return;
}
if (!args[0]->isLambda())
- {
- auto e = TypeError({
+ state.debugThrowLastTrace(TypeError({
.msg = hintfmt("'functionArgs' requires a function"),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
if (!args[0]->lambda.fun->hasFormals()) {
v.mkAttrs(&state.emptyBindings);
@@ -2741,13 +2657,10 @@ static void elemAt(EvalState & state, const PosIdx pos, Value & list, int n, Val
{
state.forceList(list, pos);
if (n < 0 || (unsigned int) n >= list.listSize())
- {
- auto e = Error({
+ state.debugThrowLastTrace(Error({
.msg = hintfmt("list index %1% is out of bounds", n),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
state.forceValue(*list.listElems()[n], pos);
v = *list.listElems()[n];
}
@@ -2792,13 +2705,10 @@ static void prim_tail(EvalState & state, const PosIdx pos, Value * * args, Value
{
state.forceList(*args[0], pos);
if (args[0]->listSize() == 0)
- {
- auto e = Error({
+ state.debugThrowLastTrace(Error({
.msg = hintfmt("'tail' called on an empty list"),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
state.mkList(v, args[0]->listSize() - 1);
for (unsigned int n = 0; n < v.listSize(); ++n)
@@ -3033,13 +2943,10 @@ static void prim_genList(EvalState & state, const PosIdx pos, Value * * args, Va
auto len = state.forceInt(*args[1], pos);
if (len < 0)
- {
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("cannot create list of size %1%", len),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
state.mkList(v, len);
@@ -3343,13 +3250,10 @@ static void prim_div(EvalState & state, const PosIdx pos, Value * * args, Value
NixFloat f2 = state.forceFloat(*args[1], pos);
if (f2 == 0)
- {
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("division by zero"),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
if (args[0]->type() == nFloat || args[1]->type() == nFloat) {
v.mkFloat(state.forceFloat(*args[0], pos) / state.forceFloat(*args[1], pos));
@@ -3358,13 +3262,10 @@ static void prim_div(EvalState & state, const PosIdx pos, Value * * args, Value
NixInt i2 = state.forceInt(*args[1], pos);
/* Avoid division overflow as it might raise SIGFPE. */
if (i1 == std::numeric_limits<NixInt>::min() && i2 == -1)
- {
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("overflow in integer division"),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
v.mkInt(i1 / i2);
}
@@ -3492,13 +3393,10 @@ static void prim_substring(EvalState & state, const PosIdx pos, Value * * args,
auto s = state.coerceToString(pos, *args[2], context);
if (start < 0)
- {
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("negative start position in 'substring'"),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
v.mkString((unsigned int) start >= s->size() ? "" : s->substr(start, len), context);
}
@@ -3546,13 +3444,10 @@ static void prim_hashString(EvalState & state, const PosIdx pos, Value * * args,
auto type = state.forceStringNoCtx(*args[0], pos);
std::optional<HashType> ht = parseHashType(type);
if (!ht)
- {
- auto e = Error({
+ state.debugThrowLastTrace(Error({
.msg = hintfmt("unknown hash type '%1%'", type),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
PathSet context; // discarded
auto s = state.forceString(*args[1], context, pos);
@@ -3622,18 +3517,15 @@ void prim_match(EvalState & state, const PosIdx pos, Value * * args, Value & v)
} catch (std::regex_error &e) {
if (e.code() == std::regex_constants::error_space) {
// limit is _GLIBCXX_REGEX_STATE_LIMIT for libstdc++
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("memory limit exceeded by regular expression '%s'", re),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- } else {
- auto e = EvalError({
+ }));
+ } else
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("invalid regular expression '%s'", re),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
}
}
@@ -3729,18 +3621,15 @@ void prim_split(EvalState & state, const PosIdx pos, Value * * args, Value & v)
} catch (std::regex_error &e) {
if (e.code() == std::regex_constants::error_space) {
// limit is _GLIBCXX_REGEX_STATE_LIMIT for libstdc++
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("memory limit exceeded by regular expression '%s'", re),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- } else {
- auto e = EvalError({
+ }));
+ } else
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("invalid regular expression '%s'", re),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
}
}
@@ -3816,13 +3705,10 @@ static void prim_replaceStrings(EvalState & state, const PosIdx pos, Value * * a
state.forceList(*args[0], pos);
state.forceList(*args[1], pos);
if (args[0]->listSize() != args[1]->listSize())
- {
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("'from' and 'to' arguments to 'replaceStrings' have different lengths"),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
std::vector<std::string> from;
from.reserve(args[0]->listSize());
diff --git a/src/libexpr/primops/fetchTree.cc b/src/libexpr/primops/fetchTree.cc
index e4fa3c5f9..e5eeea520 100644
--- a/src/libexpr/primops/fetchTree.cc
+++ b/src/libexpr/primops/fetchTree.cc
@@ -108,22 +108,16 @@ static void fetchTree(
if (auto aType = args[0]->attrs->get(state.sType)) {
if (type)
- {
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("unexpected attribute 'type'"),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
type = state.forceStringNoCtx(*aType->value, aType->pos);
} else if (!type)
- {
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("attribute 'type' is missing in call to 'fetchTree'"),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
attrs.emplace("type", type.value());
@@ -144,22 +138,16 @@ static void fetchTree(
else if (attr.value->type() == nInt)
attrs.emplace(state.symbols[attr.name], uint64_t(attr.value->integer));
else
- {
- auto e = TypeError("fetchTree argument '%s' is %s while a string, Boolean or integer is expected",
- state.symbols[attr.name], showType(*attr.value));
- state.debugThrowLastTrace(e);
- }
+ state.debugThrowLastTrace(TypeError("fetchTree argument '%s' is %s while a string, Boolean or integer is expected",
+ state.symbols[attr.name], showType(*attr.value)));
}
if (!params.allowNameArgument)
if (auto nameIter = attrs.find("name"); nameIter != attrs.end())
- {
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("attribute 'name' isn’t supported in call to 'fetchTree'"),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
input = fetchers::Input::fromAttrs(std::move(attrs));
} else {
@@ -179,10 +167,7 @@ static void fetchTree(
input = lookupInRegistries(state.store, input).first;
if (evalSettings.pureEval && !input.isLocked())
- {
- auto e = EvalError("in pure evaluation mode, 'fetchTree' requires a locked input, at %s", state.positions[pos]);
- state.debugThrowLastTrace(e);
- }
+ state.debugThrowLastTrace(EvalError("in pure evaluation mode, 'fetchTree' requires a locked input, at %s", state.positions[pos]));
auto [tree, input2] = input.fetch(state.store);
@@ -221,23 +206,17 @@ static void fetch(EvalState & state, const PosIdx pos, Value * * args, Value & v
else if (n == "name")
name = state.forceStringNoCtx(*attr.value, attr.pos);
else
- {
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("unsupported argument '%s' to '%s'", n, who),
.errPos = state.positions[attr.pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
}
if (!url)
- {
- auto e = EvalError({
+ state.debugThrowLastTrace(EvalError({
.msg = hintfmt("'url' argument required"),
.errPos = state.positions[pos]
- });
- state.debugThrowLastTrace(e);
- }
+ }));
} else
url = state.forceStringNoCtx(*args[0], pos);
@@ -249,10 +228,7 @@ static void fetch(EvalState & state, const PosIdx pos, Value * * args, Value & v
name = baseNameOf(*url);
if (evalSettings.pureEval && !expectedHash)
- {
- auto e = EvalError("in pure evaluation mode, '%s' requires a 'sha256' argument", who);
- state.debugThrowLastTrace(e);
- }
+ state.debugThrowLastTrace(EvalError("in pure evaluation mode, '%s' requires a 'sha256' argument", who));
// early exit if pinned and already in the store
if (expectedHash && expectedHash->type == htSHA256) {
@@ -279,11 +255,8 @@ static void fetch(EvalState & state, const PosIdx pos, Value * * args, Value & v
? state.store->queryPathInfo(storePath)->narHash
: hashFile(htSHA256, state.store->toRealPath(storePath));
if (hash != *expectedHash)
- {
- auto e = EvalError((unsigned int) 102, "hash mismatch in file downloaded from '%s':\n specified: %s\n got: %s",
- *url, expectedHash->to_string(Base32, true), hash.to_string(Base32, true));
- state.debugThrowLastTrace(e);
- }
+ state.debugThrowLastTrace(EvalError((unsigned int) 102, "hash mismatch in file downloaded from '%s':\n specified: %s\n got: %s",
+ *url, expectedHash->to_string(Base32, true), hash.to_string(Base32, true)));
}
state.allowAndSetStorePathString(storePath, v);
diff --git a/src/libexpr/value-to-json.cc b/src/libexpr/value-to-json.cc
index 6a95e0414..03504db61 100644
--- a/src/libexpr/value-to-json.cc
+++ b/src/libexpr/value-to-json.cc
@@ -100,8 +100,7 @@ void printValueAsJSON(EvalState & state, bool strict,
void ExternalValueBase::printValueAsJSON(EvalState & state, bool strict,
JSONPlaceholder & out, PathSet & context) const
{
- auto e = TypeError("cannot convert %1% to JSON", showType());
- state.debugThrowLastTrace(e);
+ state.debugThrowLastTrace(TypeError("cannot convert %1% to JSON", showType()));
}
From 2f8a34cddcdd738afebde38e83b2315d3e305152 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Wed, 25 May 2022 15:05:39 +0200
Subject: [PATCH 163/188] Fix warning
---
src/nix/profile.cc | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/src/nix/profile.cc b/src/nix/profile.cc
index 1aae347df..3814e7d5a 100644
--- a/src/nix/profile.cc
+++ b/src/nix/profile.cc
@@ -263,7 +263,8 @@ builtPathsPerInstallable(
struct CmdProfileInstall : InstallablesCommand, MixDefaultProfile
{
- std::optional<int> priority;
+ std::optional<int64_t> priority;
+
CmdProfileInstall() {
addFlag({
.longName = "priority",
From d8398d33c9a09e1f5599127ae6d477e7e0868b55 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Wed, 25 May 2022 15:29:27 +0200
Subject: [PATCH 164/188] Typo
---
src/libfetchers/tarball.cc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/libfetchers/tarball.cc b/src/libfetchers/tarball.cc
index 09acb74d3..6c551bd93 100644
--- a/src/libfetchers/tarball.cc
+++ b/src/libfetchers/tarball.cc
@@ -169,7 +169,7 @@ std::pair<Tree, time_t> downloadTarball(
};
}
-// An input scheme corresponding to a curable ressource
+// An input scheme corresponding to a curl-downloadable resource.
struct CurlInputScheme : InputScheme
{
virtual const std::string inputType() const = 0;
From 27ebb97d0a51a3198f2c95cbdccd6f56274c19ee Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Wed, 25 May 2022 15:45:10 +0200
Subject: [PATCH 165/188] Handle EOFs in string literals correctly
We can't return a STR token without setting a valid StringToken,
otherwise the parser will crash.
Fixes #6562.
---
src/libexpr/lexer.l | 2 +-
tests/lang/parse-fail-eof-in-string.nix | 3 +++
2 files changed, 4 insertions(+), 1 deletion(-)
create mode 100644 tests/lang/parse-fail-eof-in-string.nix
diff --git a/src/libexpr/lexer.l b/src/libexpr/lexer.l
index 4c28b976e..462b3b602 100644
--- a/src/libexpr/lexer.l
+++ b/src/libexpr/lexer.l
@@ -198,7 +198,7 @@ or { return OR_KW; }
(...|\$[^\{\"\\]|\\.|\$\\.)+ would have triggered.
This is technically invalid, but we leave the problem to the
parser who fails with exact location. */
- return STR;
+ return EOF;
}
\'\'(\ *\n)? { PUSH_STATE(IND_STRING); return IND_STRING_OPEN; }
diff --git a/tests/lang/parse-fail-eof-in-string.nix b/tests/lang/parse-fail-eof-in-string.nix
new file mode 100644
index 000000000..19775d2ec
--- /dev/null
+++ b/tests/lang/parse-fail-eof-in-string.nix
@@ -0,0 +1,3 @@
+# https://github.com/NixOS/nix/issues/6562
+# Note that this file must not end with a newline.
+a 1"$
\ No newline at end of file
From b4c24a29c62259a068c8270be62cf5a412e1e35c Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Wed, 25 May 2022 10:21:20 -0600
Subject: [PATCH 166/188] back to ref<EvalState> in NixRepl
---
src/libcmd/command.hh | 2 +-
src/libcmd/repl.cc | 156 +++++++++++++++++++++---------------------
src/libexpr/eval.cc | 2 +-
src/libexpr/eval.hh | 5 +-
4 files changed, 82 insertions(+), 83 deletions(-)
diff --git a/src/libcmd/command.hh b/src/libcmd/command.hh
index 916695102..8982f21d0 100644
--- a/src/libcmd/command.hh
+++ b/src/libcmd/command.hh
@@ -274,6 +274,6 @@ void printClosureDiff(
void runRepl(
- EvalState & evalState,
+ ref<EvalState> evalState,
const ValMap & extraEnv);
}
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 7d8bbdb7e..993dcd634 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -48,7 +48,7 @@ struct NixRepl
#endif
{
std::string curDir;
- EvalState & state;
+ ref<EvalState> state;
Bindings * autoArgs;
size_t debugTraceIndex;
@@ -63,7 +63,7 @@ struct NixRepl
const Path historyFile;
- NixRepl(EvalState & state);
+ NixRepl(ref<EvalState> state);
~NixRepl();
void mainLoop(const std::vector<std::string> & files);
StringSet completePrefix(const std::string & prefix);
@@ -96,10 +96,10 @@ std::string removeWhitespace(std::string s)
}
-NixRepl::NixRepl(EvalState & state)
+NixRepl::NixRepl(ref<EvalState> state)
: state(state)
, debugTraceIndex(0)
- , staticEnv(new StaticEnv(false, state.staticBaseEnv.get()))
+ , staticEnv(new StaticEnv(false, state->staticBaseEnv.get()))
, historyFile(getDataDir() + "/nix/repl-history")
{
curDir = absPath(".");
@@ -261,8 +261,8 @@ void NixRepl::mainLoop(const std::vector<std::string> & files)
// number of chars as the prompt.
if (!getLine(input, input.empty() ? "nix-repl> " : " ")) {
// ctrl-D should exit the debugger.
- state.debugStop = false;
- state.debugQuit = true;
+ state->debugStop = false;
+ state->debugQuit = true;
break;
}
try {
@@ -279,8 +279,8 @@ void NixRepl::mainLoop(const std::vector<std::string> & files)
// in debugger mode, an EvalError should trigger another repl session.
// when that session returns the exception will land here. No need to show it again;
// show the error for this repl session instead.
- if (state.debugRepl && !state.debugTraces.empty())
- showDebugTrace(std::cout, state.positions, state.debugTraces.front());
+ if (state->debugRepl && !state->debugTraces.empty())
+ showDebugTrace(std::cout, state->positions, state->debugTraces.front());
else
printMsg(lvlError, e.msg());
} catch (Error & e) {
@@ -386,11 +386,11 @@ StringSet NixRepl::completePrefix(const std::string & prefix)
Expr * e = parseString(expr);
Value v;
- e->eval(state, *env, v);
- state.forceAttrs(v, noPos);
+ e->eval(*state, *env, v);
+ state->forceAttrs(v, noPos);
for (auto & i : *v.attrs) {
- std::string_view name = state.symbols[i.name];
+ std::string_view name = state->symbols[i.name];
if (name.substr(0, cur2.size()) != cur2) continue;
completions.insert(concatStrings(prev, expr, ".", name));
}
@@ -426,14 +426,14 @@ static bool isVarName(std::string_view s)
StorePath NixRepl::getDerivationPath(Value & v) {
- auto drvInfo = getDerivation(state, v, false);
+ auto drvInfo = getDerivation(*state, v, false);
if (!drvInfo)
throw Error("expression does not evaluate to a derivation, so I can't build it");
auto drvPath = drvInfo->queryDrvPath();
if (!drvPath)
throw Error("expression did not evaluate to a valid derivation (no 'drvPath' attribute)");
- if (!state.store->isValidPath(*drvPath))
- throw Error("expression evaluated to invalid derivation '%s'", state.store->printStorePath(*drvPath));
+ if (!state->store->isValidPath(*drvPath))
+ throw Error("expression evaluated to invalid derivation '%s'", state->store->printStorePath(*drvPath));
return *drvPath;
}
@@ -441,13 +441,13 @@ void NixRepl::loadDebugTraceEnv(DebugTrace & dt)
{
initEnv();
- auto se = state.getStaticEnv(dt.expr);
+ auto se = state->getStaticEnv(dt.expr);
if (se) {
- auto vm = mapStaticEnvBindings(state.symbols, *se.get(), dt.env);
+ auto vm = mapStaticEnvBindings(state->symbols, *se.get(), dt.env);
// add staticenv vars.
for (auto & [name, value] : *(vm.get()))
- addVarToScope(state.symbols.create(name), *value);
+ addVarToScope(state->symbols.create(name), *value);
}
}
@@ -492,7 +492,7 @@ bool NixRepl::processLine(std::string line)
<< " :log <expr> Show logs for a derivation\n"
<< " :te [bool] Enable, disable or toggle showing traces for errors\n"
;
- if (state.debugRepl) {
+ if (state->debugRepl) {
std::cout
<< "\n"
<< " Debug mode commands\n"
@@ -507,49 +507,49 @@ bool NixRepl::processLine(std::string line)
}
- else if (state.debugRepl && (command == ":bt" || command == ":backtrace")) {
- for (const auto & [idx, i] : enumerate(state.debugTraces)) {
+ else if (state->debugRepl && (command == ":bt" || command == ":backtrace")) {
+ for (const auto & [idx, i] : enumerate(state->debugTraces)) {
std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
- showDebugTrace(std::cout, state.positions, i);
+ showDebugTrace(std::cout, state->positions, i);
}
}
- else if (state.debugRepl && (command == ":env")) {
- for (const auto & [idx, i] : enumerate(state.debugTraces)) {
+ else if (state->debugRepl && (command == ":env")) {
+ for (const auto & [idx, i] : enumerate(state->debugTraces)) {
if (idx == debugTraceIndex) {
- printEnvBindings(state, i.expr, i.env);
+ printEnvBindings(*state, i.expr, i.env);
break;
}
}
}
- else if (state.debugRepl && (command == ":st")) {
+ else if (state->debugRepl && (command == ":st")) {
try {
// change the DebugTrace index.
debugTraceIndex = stoi(arg);
} catch (...) { }
- for (const auto & [idx, i] : enumerate(state.debugTraces)) {
+ for (const auto & [idx, i] : enumerate(state->debugTraces)) {
if (idx == debugTraceIndex) {
std::cout << "\n" << ANSI_BLUE << idx << ANSI_NORMAL << ": ";
- showDebugTrace(std::cout, state.positions, i);
+ showDebugTrace(std::cout, state->positions, i);
std::cout << std::endl;
- printEnvBindings(state, i.expr, i.env);
+ printEnvBindings(*state, i.expr, i.env);
loadDebugTraceEnv(i);
break;
}
}
}
- else if (state.debugRepl && (command == ":s" || command == ":step")) {
+ else if (state->debugRepl && (command == ":s" || command == ":step")) {
// set flag to stop at next DebugTrace; exit repl.
- state.debugStop = true;
+ state->debugStop = true;
return false;
}
- else if (state.debugRepl && (command == ":c" || command == ":continue")) {
+ else if (state->debugRepl && (command == ":c" || command == ":continue")) {
// set flag to run to next breakpoint or end of program; exit repl.
- state.debugStop = false;
+ state->debugStop = false;
return false;
}
@@ -560,7 +560,7 @@ bool NixRepl::processLine(std::string line)
}
else if (command == ":l" || command == ":load") {
- state.resetFileCache();
+ state->resetFileCache();
loadFile(arg);
}
@@ -569,7 +569,7 @@ bool NixRepl::processLine(std::string line)
}
else if (command == ":r" || command == ":reload") {
- state.resetFileCache();
+ state->resetFileCache();
reloadFiles();
}
@@ -580,15 +580,15 @@ bool NixRepl::processLine(std::string line)
const auto [file, line] = [&] () -> std::pair<std::string, uint32_t> {
if (v.type() == nPath || v.type() == nString) {
PathSet context;
- auto filename = state.coerceToString(noPos, v, context).toOwned();
- state.symbols.create(filename);
+ auto filename = state->coerceToString(noPos, v, context).toOwned();
+ state->symbols.create(filename);
return {filename, 0};
} else if (v.isLambda()) {
- auto pos = state.positions[v.lambda.fun->pos];
+ auto pos = state->positions[v.lambda.fun->pos];
return {pos.file, pos.line};
} else {
// assume it's a derivation
- return findPackageFilename(state, v, arg);
+ return findPackageFilename(*state, v, arg);
}
}();
@@ -602,7 +602,7 @@ bool NixRepl::processLine(std::string line)
runProgram2(RunOptions { .program = editor, .searchPath = true, .args = args });
// Reload right after exiting the editor
- state.resetFileCache();
+ state->resetFileCache();
reloadFiles();
}
@@ -616,30 +616,30 @@ bool NixRepl::processLine(std::string line)
Value v, f, result;
evalString(arg, v);
evalString("drv: (import <nixpkgs> {}).runCommand \"shell\" { buildInputs = [ drv ]; } \"\"", f);
- state.callFunction(f, v, result, PosIdx());
+ state->callFunction(f, v, result, PosIdx());
StorePath drvPath = getDerivationPath(result);
- runNix("nix-shell", {state.store->printStorePath(drvPath)});
+ runNix("nix-shell", {state->store->printStorePath(drvPath)});
}
else if (command == ":b" || command == ":bl" || command == ":i" || command == ":sh" || command == ":log") {
Value v;
evalString(arg, v);
StorePath drvPath = getDerivationPath(v);
- Path drvPathRaw = state.store->printStorePath(drvPath);
+ Path drvPathRaw = state->store->printStorePath(drvPath);
if (command == ":b" || command == ":bl") {
- state.store->buildPaths({DerivedPath::Built{drvPath}});
- auto drv = state.store->readDerivation(drvPath);
+ state->store->buildPaths({DerivedPath::Built{drvPath}});
+ auto drv = state->store->readDerivation(drvPath);
logger->cout("\nThis derivation produced the following outputs:");
- for (auto & [outputName, outputPath] : state.store->queryDerivationOutputMap(drvPath)) {
- auto localStore = state.store.dynamic_pointer_cast<LocalFSStore>();
+ for (auto & [outputName, outputPath] : state->store->queryDerivationOutputMap(drvPath)) {
+ auto localStore = state->store.dynamic_pointer_cast<LocalFSStore>();
if (localStore && command == ":bl") {
std::string symlink = "repl-result-" + outputName;
localStore->addPermRoot(outputPath, absPath(symlink));
- logger->cout(" ./%s -> %s", symlink, state.store->printStorePath(outputPath));
+ logger->cout(" ./%s -> %s", symlink, state->store->printStorePath(outputPath));
} else {
- logger->cout(" %s -> %s", outputName, state.store->printStorePath(outputPath));
+ logger->cout(" %s -> %s", outputName, state->store->printStorePath(outputPath));
}
}
} else if (command == ":i") {
@@ -651,7 +651,7 @@ bool NixRepl::processLine(std::string line)
});
auto subs = getDefaultSubstituters();
- subs.push_front(state.store);
+ subs.push_front(state->store);
bool foundLog = false;
RunPager pager;
@@ -684,15 +684,15 @@ bool NixRepl::processLine(std::string line)
}
else if (command == ":q" || command == ":quit") {
- state.debugStop = false;
- state.debugQuit = true;
+ state->debugStop = false;
+ state->debugQuit = true;
return false;
}
else if (command == ":doc") {
Value v;
evalString(arg, v);
- if (auto doc = state.getDoc(v)) {
+ if (auto doc = state->getDoc(v)) {
std::string markdown;
if (!doc->args.empty() && doc->name) {
@@ -736,9 +736,9 @@ bool NixRepl::processLine(std::string line)
isVarName(name = removeWhitespace(line.substr(0, p))))
{
Expr * e = parseString(line.substr(p + 1));
- Value & v(*state.allocValue());
+ Value & v(*state->allocValue());
v.mkThunk(env, e);
- addVarToScope(state.symbols.create(name), v);
+ addVarToScope(state->symbols.create(name), v);
} else {
Value v;
evalString(line, v);
@@ -755,8 +755,8 @@ void NixRepl::loadFile(const Path & path)
loadedFiles.remove(path);
loadedFiles.push_back(path);
Value v, v2;
- state.evalFile(lookupFileArg(state, path), v);
- state.autoCallFunction(*autoArgs, v, v2);
+ state->evalFile(lookupFileArg(*state, path), v);
+ state->autoCallFunction(*autoArgs, v, v2);
addAttrsToScope(v2);
}
@@ -771,8 +771,8 @@ void NixRepl::loadFlake(const std::string & flakeRefS)
Value v;
- flake::callFlake(state,
- flake::lockFlake(state, flakeRef,
+ flake::callFlake(*state,
+ flake::lockFlake(*state, flakeRef,
flake::LockFlags {
.updateLockFile = false,
.useRegistries = !evalSettings.pureEval,
@@ -785,14 +785,14 @@ void NixRepl::loadFlake(const std::string & flakeRefS)
void NixRepl::initEnv()
{
- env = &state.allocEnv(envSize);
- env->up = &state.baseEnv;
+ env = &state->allocEnv(envSize);
+ env->up = &state->baseEnv;
displ = 0;
staticEnv->vars.clear();
varNames.clear();
- for (auto & i : state.staticBaseEnv->vars)
- varNames.emplace(state.symbols[i.first]);
+ for (auto & i : state->staticBaseEnv->vars)
+ varNames.emplace(state->symbols[i.first]);
}
@@ -821,14 +821,14 @@ void NixRepl::loadFiles()
void NixRepl::addAttrsToScope(Value & attrs)
{
- state.forceAttrs(attrs, [&]() { return attrs.determinePos(noPos); });
+ state->forceAttrs(attrs, [&]() { return attrs.determinePos(noPos); });
if (displ + attrs.attrs->size() >= envSize)
throw Error("environment full; cannot add more variables");
for (auto & i : *attrs.attrs) {
staticEnv->vars.emplace_back(i.name, displ);
env->values[displ++] = i.value;
- varNames.emplace(state.symbols[i.name]);
+ varNames.emplace(state->symbols[i.name]);
}
staticEnv->sort();
staticEnv->deduplicate();
@@ -845,13 +845,13 @@ void NixRepl::addVarToScope(const Symbol name, Value & v)
staticEnv->vars.emplace_back(name, displ);
staticEnv->sort();
env->values[displ++] = &v;
- varNames.emplace(state.symbols[name]);
+ varNames.emplace(state->symbols[name]);
}
Expr * NixRepl::parseString(std::string s)
{
- Expr * e = state.parseExprFromString(std::move(s), curDir, staticEnv);
+ Expr * e = state->parseExprFromString(std::move(s), curDir, staticEnv);
return e;
}
@@ -859,8 +859,8 @@ Expr * NixRepl::parseString(std::string s)
void NixRepl::evalString(std::string s, Value & v)
{
Expr * e = parseString(s);
- e->eval(state, *env, v);
- state.forceValue(v, [&]() { return v.determinePos(noPos); });
+ e->eval(*state, *env, v);
+ state->forceValue(v, [&]() { return v.determinePos(noPos); });
}
@@ -890,7 +890,7 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
str.flush();
checkInterrupt();
- state.forceValue(v, [&]() { return v.determinePos(noPos); });
+ state->forceValue(v, [&]() { return v.determinePos(noPos); });
switch (v.type()) {
@@ -919,14 +919,14 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
case nAttrs: {
seen.insert(&v);
- bool isDrv = state.isDerivation(v);
+ bool isDrv = state->isDerivation(v);
if (isDrv) {
str << "«derivation ";
- Bindings::iterator i = v.attrs->find(state.sDrvPath);
+ Bindings::iterator i = v.attrs->find(state->sDrvPath);
PathSet context;
if (i != v.attrs->end())
- str << state.store->printStorePath(state.coerceToStorePath(i->pos, *i->value, context));
+ str << state->store->printStorePath(state->coerceToStorePath(i->pos, *i->value, context));
else
str << "???";
str << "»";
@@ -938,7 +938,7 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
typedef std::map<std::string, Value *> Sorted;
Sorted sorted;
for (auto & i : *v.attrs)
- sorted.emplace(state.symbols[i.name], i.value);
+ sorted.emplace(state->symbols[i.name], i.value);
for (auto & i : sorted) {
if (isVarName(i.first))
@@ -988,7 +988,7 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
case nFunction:
if (v.isLambda()) {
std::ostringstream s;
- s << state.positions[v.lambda.fun->pos];
+ s << state->positions[v.lambda.fun->pos];
str << ANSI_BLUE "«lambda @ " << filterANSIEscapes(s.str()) << "»" ANSI_NORMAL;
} else if (v.isPrimOp()) {
str << ANSI_MAGENTA "«primop»" ANSI_NORMAL;
@@ -1012,7 +1012,7 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
}
void runRepl(
- EvalState &evalState,
+ ref<EvalState>evalState,
const ValMap & extraEnv)
{
auto repl = std::make_unique<NixRepl>(evalState);
@@ -1021,7 +1021,7 @@ void runRepl(
// add 'extra' vars.
for (auto & [name, value] : extraEnv)
- repl->addVarToScope(repl->state.symbols.create(name), *value);
+ repl->addVarToScope(repl->state->symbols.create(name), *value);
repl->mainLoop({});
}
@@ -1057,8 +1057,8 @@ struct CmdRepl : StoreCommand, MixEvalArgs
auto evalState = make_ref<EvalState>(searchPath, store);
- auto repl = std::make_unique<NixRepl>(*evalState);
- repl->autoArgs = getAutoArgs(repl->state);
+ auto repl = std::make_unique<NixRepl>(evalState);
+ repl->autoArgs = getAutoArgs(*repl->state);
repl->initEnv();
repl->mainLoop(files);
}
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 6dc7918b1..18baf1cb7 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -836,7 +836,7 @@ void EvalState::runDebugRepl(const Error * error, const Env & env, const Expr &
auto se = getStaticEnv(expr);
if (se) {
auto vm = mapStaticEnvBindings(symbols, *se.get(), env);
- (debugRepl)(*this, *vm);
+ (debugRepl)(ref<EvalState>(shared_from_this()), *vm);
}
}
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 3444815fd..d793e2a31 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -13,7 +13,6 @@
#include <unordered_map>
#include <mutex>
-
namespace nix {
@@ -88,7 +87,7 @@ struct DebugTrace {
void debugError(Error * e, Env & env, Expr & expr);
-class EvalState
+class EvalState : public std::enable_shared_from_this<EvalState>
{
public:
SymbolTable symbols;
@@ -127,7 +126,7 @@ public:
RootValue vImportedDrvToDerivation = nullptr;
/* Debugger */
- void (* debugRepl)(EvalState & es, const ValMap & extraEnv);
+ void (* debugRepl)(ref<EvalState> es, const ValMap & extraEnv);
bool debugStop;
bool debugQuit;
std::list<DebugTrace> debugTraces;
From 6031a36208dd174f05f094898d8ad35e5366106f Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Wed, 25 May 2022 10:38:13 -0600
Subject: [PATCH 167/188] add --debugger to rl-next list
---
doc/manual/src/release-notes/rl-next.md | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/doc/manual/src/release-notes/rl-next.md b/doc/manual/src/release-notes/rl-next.md
index efd893662..a808e145a 100644
--- a/doc/manual/src/release-notes/rl-next.md
+++ b/doc/manual/src/release-notes/rl-next.md
@@ -24,3 +24,16 @@
Selecting derivation outputs using the attribute selection syntax
(e.g. `nixpkgs#glibc.dev`) no longer works.
+
+* Running nix with the new `--debugger` flag will cause it to start a repl session if
+ there is an exception thrown during eval, or if `builtins.break` is called. From
+ there one can inspect symbol values and evaluate nix expressions. In debug mode
+ the following new repl commands are available:
+ ```
+ :env Show env stack
+ :bt Show trace stack
+ :st Show current trace
+ :st <idx> Change to another trace in the stack
+ :c Go until end of program, exception, or builtins.break().
+ :s Go one step
+ ```
From 9068d32e12750542b59418501ce1bd3835e92400 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@protonmail.com>
Date: Wed, 25 May 2022 12:55:58 -0600
Subject: [PATCH 168/188] remove parens from repl help
---
src/libcmd/repl.cc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 993dcd634..458e824c5 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -500,7 +500,7 @@ bool NixRepl::processLine(std::string line)
<< " :bt Show trace stack\n"
<< " :st Show current trace\n"
<< " :st <idx> Change to another trace in the stack\n"
- << " :c Go until end of program, exception, or builtins.break().\n"
+ << " :c Go until end of program, exception, or builtins.break\n"
<< " :s Go one step\n"
;
}
From c156155239dafd68104a843916d8d737e6e61bed Mon Sep 17 00:00:00 2001
From: Robert Hensing <robert@roberthensing.nl>
Date: Thu, 26 May 2022 10:53:06 +0200
Subject: [PATCH 169/188] createUnixDomainSocket: listen(unix, 5 -> 100)
This solves the error
error: cannot connect to socket at '/nix/var/nix/daemon-socket/socket': Connection refused
on build farm systems that are loaded but operating normally.
I've seen this happen on an M1 mac running a loaded hercules-ci-agent.
Hercules CI uses multiple worker processes, which may connect to
the Nix daemon around the same time. It's not unthinkable that
the Nix daemon listening process isn't scheduled until after 6
workers try to connect, especially on a system under load with
many workers.
Is the increase safe?
The number is the number of connections that the kernel will buffer
while the listening process hasn't `accept`-ed them yet.
It did not - and will not - restrict the total number of daemon
forks that a client can create.
History
The number 5 has remained unchanged since the introduction in
nix-worker with 0130ef88ea in 2006.
---
src/libutil/util.cc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index d4d78329d..1c19938a8 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -1818,7 +1818,7 @@ AutoCloseFD createUnixDomainSocket(const Path & path, mode_t mode)
if (chmod(path.c_str(), mode) == -1)
throw SysError("changing permissions on '%1%'", path);
- if (listen(fdSocket.get(), 5) == -1)
+ if (listen(fdSocket.get(), 100) == -1)
throw SysError("cannot listen on socket '%1%'", path);
return fdSocket;
From 9acc770ce4bf0e748b41d2f9515c436ae6960c6d Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Wed, 25 May 2022 15:49:41 +0200
Subject: [PATCH 170/188] Remove pre-C++11 hackiness
---
src/libexpr/eval.hh | 4 ++--
src/libexpr/get-drvs.hh | 2 +-
src/libexpr/nixexpr.hh | 4 ++--
src/libexpr/parser.y | 16 ++++++++--------
src/libexpr/primops.cc | 2 +-
src/libexpr/value.hh | 6 +++---
6 files changed, 17 insertions(+), 17 deletions(-)
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index d793e2a31..0a32d5885 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -173,7 +173,7 @@ private:
/* A cache from path names to parse trees. */
#if HAVE_BOEHMGC
- typedef std::map<Path, Expr *, std::less<Path>, traceable_allocator<std::pair<const Path, Expr *> > > FileParseCache;
+ typedef std::map<Path, Expr *, std::less<Path>, traceable_allocator<std::pair<const Path, Expr *>>> FileParseCache;
#else
typedef std::map<Path, Expr *> FileParseCache;
#endif
@@ -181,7 +181,7 @@ private:
/* A cache from path names to values. */
#if HAVE_BOEHMGC
- typedef std::map<Path, Value, std::less<Path>, traceable_allocator<std::pair<const Path, Value> > > FileEvalCache;
+ typedef std::map<Path, Value, std::less<Path>, traceable_allocator<std::pair<const Path, Value>>> FileEvalCache;
#else
typedef std::map<Path, Value> FileEvalCache;
#endif
diff --git a/src/libexpr/get-drvs.hh b/src/libexpr/get-drvs.hh
index 7cc1abef2..bbd2d3c47 100644
--- a/src/libexpr/get-drvs.hh
+++ b/src/libexpr/get-drvs.hh
@@ -73,7 +73,7 @@ public:
#if HAVE_BOEHMGC
-typedef std::list<DrvInfo, traceable_allocator<DrvInfo> > DrvInfos;
+typedef std::list<DrvInfo, traceable_allocator<DrvInfo>> DrvInfos;
#else
typedef std::list<DrvInfo> DrvInfos;
#endif
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index 9b3a9f5d0..8813c61a9 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -419,8 +419,8 @@ struct ExprConcatStrings : Expr
{
PosIdx pos;
bool forceString;
- std::vector<std::pair<PosIdx, Expr *> > * es;
- ExprConcatStrings(const PosIdx & pos, bool forceString, std::vector<std::pair<PosIdx, Expr *> > * es)
+ std::vector<std::pair<PosIdx, Expr *>> * es;
+ ExprConcatStrings(const PosIdx & pos, bool forceString, std::vector<std::pair<PosIdx, Expr *>> * es)
: pos(pos), forceString(forceString), es(es) { };
PosIdx getPos() const override { return pos; }
COMMON_METHODS
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index e3e0ac168..8cbc2da4d 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -193,7 +193,7 @@ static Formals * toFormals(ParseData & data, ParserFormals * formals,
static Expr * stripIndentation(const PosIdx pos, SymbolTable & symbols,
- std::vector<std::pair<PosIdx, std::variant<Expr *, StringToken> > > & es)
+ std::vector<std::pair<PosIdx, std::variant<Expr *, StringToken>>> & es)
{
if (es.empty()) return new ExprString("");
@@ -233,7 +233,7 @@ static Expr * stripIndentation(const PosIdx pos, SymbolTable & symbols,
}
/* Strip spaces from each line. */
- auto * es2 = new std::vector<std::pair<PosIdx, Expr *> >;
+ auto * es2 = new std::vector<std::pair<PosIdx, Expr *>>;
atStartOfLine = true;
size_t curDropped = 0;
size_t n = es.size();
@@ -320,8 +320,8 @@ void yyerror(YYLTYPE * loc, yyscan_t scanner, ParseData * data, const char * err
StringToken uri;
StringToken str;
std::vector<nix::AttrName> * attrNames;
- std::vector<std::pair<nix::PosIdx, nix::Expr *> > * string_parts;
- std::vector<std::pair<nix::PosIdx, std::variant<nix::Expr *, StringToken> > > * ind_string_parts;
+ std::vector<std::pair<nix::PosIdx, nix::Expr *>> * string_parts;
+ std::vector<std::pair<nix::PosIdx, std::variant<nix::Expr *, StringToken>>> * ind_string_parts;
}
%type <e> start expr expr_function expr_if expr_op
@@ -415,7 +415,7 @@ expr_op
| expr_op UPDATE expr_op { $$ = new ExprOpUpdate(CUR_POS, $1, $3); }
| expr_op '?' attrpath { $$ = new ExprOpHasAttr($1, *$3); }
| expr_op '+' expr_op
- { $$ = new ExprConcatStrings(CUR_POS, false, new std::vector<std::pair<PosIdx, Expr *> >({{makeCurPos(@1, data), $1}, {makeCurPos(@3, data), $3}})); }
+ { $$ = new ExprConcatStrings(CUR_POS, false, new std::vector<std::pair<PosIdx, Expr *>>({{makeCurPos(@1, data), $1}, {makeCurPos(@3, data), $3}})); }
| expr_op '-' expr_op { $$ = new ExprCall(CUR_POS, new ExprVar(data->symbols.create("__sub")), {$1, $3}); }
| expr_op '*' expr_op { $$ = new ExprCall(CUR_POS, new ExprVar(data->symbols.create("__mul")), {$1, $3}); }
| expr_op '/' expr_op { $$ = new ExprCall(CUR_POS, new ExprVar(data->symbols.create("__div")), {$1, $3}); }
@@ -503,9 +503,9 @@ string_parts_interpolated
: string_parts_interpolated STR
{ $$ = $1; $1->emplace_back(makeCurPos(@2, data), new ExprString(std::string($2))); }
| string_parts_interpolated DOLLAR_CURLY expr '}' { $$ = $1; $1->emplace_back(makeCurPos(@2, data), $3); }
- | DOLLAR_CURLY expr '}' { $$ = new std::vector<std::pair<PosIdx, Expr *> >; $$->emplace_back(makeCurPos(@1, data), $2); }
+ | DOLLAR_CURLY expr '}' { $$ = new std::vector<std::pair<PosIdx, Expr *>>; $$->emplace_back(makeCurPos(@1, data), $2); }
| STR DOLLAR_CURLY expr '}' {
- $$ = new std::vector<std::pair<PosIdx, Expr *> >;
+ $$ = new std::vector<std::pair<PosIdx, Expr *>>;
$$->emplace_back(makeCurPos(@1, data), new ExprString(std::string($1)));
$$->emplace_back(makeCurPos(@2, data), $3);
}
@@ -528,7 +528,7 @@ path_start
ind_string_parts
: ind_string_parts IND_STR { $$ = $1; $1->emplace_back(makeCurPos(@2, data), $2); }
| ind_string_parts DOLLAR_CURLY expr '}' { $$ = $1; $1->emplace_back(makeCurPos(@2, data), $3); }
- | { $$ = new std::vector<std::pair<PosIdx, std::variant<Expr *, StringToken> > >; }
+ | { $$ = new std::vector<std::pair<PosIdx, std::variant<Expr *, StringToken>>>; }
;
binds
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 11542b06b..aab6919d4 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -574,7 +574,7 @@ struct CompareValues
#if HAVE_BOEHMGC
-typedef std::list<Value *, gc_allocator<Value *> > ValueList;
+typedef std::list<Value *, gc_allocator<Value *>> ValueList;
#else
typedef std::list<Value *> ValueList;
#endif
diff --git a/src/libexpr/value.hh b/src/libexpr/value.hh
index 58a8a56a0..2008df74d 100644
--- a/src/libexpr/value.hh
+++ b/src/libexpr/value.hh
@@ -404,9 +404,9 @@ public:
#if HAVE_BOEHMGC
-typedef std::vector<Value *, traceable_allocator<Value *> > ValueVector;
-typedef std::map<Symbol, Value *, std::less<Symbol>, traceable_allocator<std::pair<const Symbol, Value *> > > ValueMap;
-typedef std::map<Symbol, ValueVector, std::less<Symbol>, traceable_allocator<std::pair<const Symbol, ValueVector> > > ValueVectorMap;
+typedef std::vector<Value *, traceable_allocator<Value *>> ValueVector;
+typedef std::map<Symbol, Value *, std::less<Symbol>, traceable_allocator<std::pair<const Symbol, Value *>>> ValueMap;
+typedef std::map<Symbol, ValueVector, std::less<Symbol>, traceable_allocator<std::pair<const Symbol, ValueVector>>> ValueVectorMap;
#else
typedef std::vector<Value *> ValueVector;
typedef std::map<Symbol, Value *> ValueMap;
From 8f4548d40147b735035fcf454c487ebf4bc1ddfe Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Wed, 25 May 2022 17:14:45 +0200
Subject: [PATCH 171/188] Tweak IN_NIX_SHELL description
---
doc/manual/src/command-ref/env-common.md | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/doc/manual/src/command-ref/env-common.md b/doc/manual/src/command-ref/env-common.md
index 6e2403461..0b28a85ba 100644
--- a/doc/manual/src/command-ref/env-common.md
+++ b/doc/manual/src/command-ref/env-common.md
@@ -4,7 +4,7 @@ Most Nix commands interpret the following environment variables:
- `IN_NIX_SHELL`\
Indicator that tells if the current environment was set up by
- `nix-shell`. Since Nix 2.0 the values are `"pure"` and `"impure"`
+ `nix-shell`. It can have the values `pure` or `impure`.
- `NIX_PATH`\
A colon-separated list of directories used to look up Nix
From 5b270402032151d478d5c5ecc3d99c12bcab0476 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Thu, 26 May 2022 14:49:17 +0200
Subject: [PATCH 172/188] Remove unused Perl dependency
---
flake.nix | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)
diff --git a/flake.nix b/flake.nix
index dd3a25e9e..a6877cb82 100644
--- a/flake.nix
+++ b/flake.nix
@@ -135,11 +135,6 @@
}))
nlohmann_json
];
-
- perlDeps =
- [ perl
- perlPackages.DBDSQLite
- ];
};
installScriptFor = systems:
@@ -673,7 +668,7 @@
outputs = [ "out" "dev" "doc" ];
nativeBuildInputs = nativeBuildDeps;
- buildInputs = buildDeps ++ propagatedDeps ++ awsDeps ++ perlDeps;
+ buildInputs = buildDeps ++ propagatedDeps ++ awsDeps;
inherit configureFlags;
From 4de84e095d0f1fa7f3b5db8904496ffd2752d73e Mon Sep 17 00:00:00 2001
From: Jan Tojnar <jtojnar@gmail.com>
Date: Wed, 25 May 2022 18:51:04 +0200
Subject: [PATCH 173/188] doc: Introduce pre-processor for adding anchors to
text
It is now possible to use the following syntax to insert anchors into the text:
[]{#anchor-name}
The anchor will allow linking to the location it is placed by appending #anchor-name to the URL.
Additionally, it is possible to create a link pointing to its own location by adding text between the square brackets:
[`--add-root`]{#opt-add-root}
---
doc/manual/anchors.py | 56 +++++++++++++++++++++++++++++++++++++++++++
doc/manual/book.toml | 3 +++
doc/manual/local.mk | 2 +-
3 files changed, 60 insertions(+), 1 deletion(-)
create mode 100755 doc/manual/anchors.py
diff --git a/doc/manual/anchors.py b/doc/manual/anchors.py
new file mode 100755
index 000000000..2a93b2a67
--- /dev/null
+++ b/doc/manual/anchors.py
@@ -0,0 +1,56 @@
+#!/usr/bin/env python3
+
+import argparse
+import json
+import re
+import sys
+
+
+empty_anchor_regex = re.compile(r"\[\]\{#(?P<anchor>[^\}]+?)\}")
+anchor_regex = re.compile(r"\[(?P<text>[^\]]+?)\]\{#(?P<anchor>[^\}]+?)\}")
+
+
+def transform_anchors_html(content):
+ content = empty_anchor_regex.sub(r'<a name="\g<anchor>"></a>', content)
+ content = anchor_regex.sub(r'<a href="#\g<anchor>" id="\g<anchor>">\g<text></a>', content)
+ return content
+
+
+def transform_anchors_strip(content):
+ content = empty_anchor_regex.sub(r'', content)
+ content = anchor_regex.sub(r'\g<text>', content)
+ return content
+
+
+def map_contents_recursively(transformer, chapter):
+ chapter["Chapter"]["content"] = transformer(chapter["Chapter"]["content"])
+ for sub_item in chapter["Chapter"]["sub_items"]:
+ map_contents_recursively(transformer, sub_item)
+
+
+def supports_command(args):
+ sys.exit(0)
+
+
+def process_command(args):
+ context, book = json.load(sys.stdin)
+ transformer = transform_anchors_html if context["renderer"] == "html" else transform_anchors_strip
+ for section in book["sections"]:
+ map_contents_recursively(transformer, section)
+ print(json.dumps(book))
+
+
+if __name__ == "__main__":
+ parser = argparse.ArgumentParser(
+ description="mdBook preprocessor adding anchors."
+ )
+ parser.set_defaults(command=process_command)
+
+ subparsers = parser.add_subparsers()
+
+ supports_parser = subparsers.add_parser("supports", help="Check if given renderer is supported")
+ supports_parser.add_argument("renderer", type=str)
+ supports_parser.set_defaults(command=supports_command)
+
+ args = parser.parse_args()
+ args.command(args)
diff --git a/doc/manual/book.toml b/doc/manual/book.toml
index fee41dfb3..75554d11f 100644
--- a/doc/manual/book.toml
+++ b/doc/manual/book.toml
@@ -1,2 +1,5 @@
[output.html]
additional-css = ["custom.css"]
+
+[preprocessor.anchors]
+command = "python3 doc/manual/anchors.py"
diff --git a/doc/manual/local.mk b/doc/manual/local.mk
index c1ce8aaeb..910d0a03b 100644
--- a/doc/manual/local.mk
+++ b/doc/manual/local.mk
@@ -97,7 +97,7 @@ doc/manual/generated/man1/nix3-manpages: $(d)/src/command-ref/new-cli
done
@touch $@
-$(docdir)/manual/index.html: $(MANUAL_SRCS) $(d)/book.toml $(d)/custom.css $(d)/src/SUMMARY.md $(d)/src/command-ref/new-cli $(d)/src/command-ref/conf-file.md $(d)/src/expressions/builtins.md $(call rwildcard, $(d)/src, *.md)
+$(docdir)/manual/index.html: $(MANUAL_SRCS) $(d)/book.toml $(d)/anchors.py $(d)/custom.css $(d)/src/SUMMARY.md $(d)/src/command-ref/new-cli $(d)/src/command-ref/conf-file.md $(d)/src/expressions/builtins.md $(call rwildcard, $(d)/src, *.md)
$(trace-gen) RUST_LOG=warn mdbook build doc/manual -d $(DESTDIR)$(docdir)/manual
endif
From 3272afa17b68d25c8070e58819f2e56f075c764d Mon Sep 17 00:00:00 2001
From: Jan Tojnar <jtojnar@gmail.com>
Date: Thu, 26 May 2022 16:47:40 +0200
Subject: [PATCH 174/188] doc: Port anchors preprocessor to jq script
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Python is only pulled into the build closure by Mercurial, which might end up being removed.
Let’s port the script to jq, which is more likely to stay.
---
doc/manual/anchors.jq | 31 ++++++++++++++++++++++++
doc/manual/anchors.py | 56 -------------------------------------------
doc/manual/book.toml | 3 ++-
doc/manual/local.mk | 2 +-
flake.nix | 2 +-
5 files changed, 35 insertions(+), 59 deletions(-)
create mode 100755 doc/manual/anchors.jq
delete mode 100755 doc/manual/anchors.py
diff --git a/doc/manual/anchors.jq b/doc/manual/anchors.jq
new file mode 100755
index 000000000..72309779c
--- /dev/null
+++ b/doc/manual/anchors.jq
@@ -0,0 +1,31 @@
+"\\[\\]\\{#(?<anchor>[^\\}]+?)\\}" as $empty_anchor_regex |
+"\\[(?<text>[^\\]]+?)\\]\\{#(?<anchor>[^\\}]+?)\\}" as $anchor_regex |
+
+
+def transform_anchors_html:
+ . | gsub($empty_anchor_regex; "<a name=\"" + .anchor + "\"></a>")
+ | gsub($anchor_regex; "<a href=\"#" + .anchor + "\" id=\"" + .anchor + "\">" + .text + "</a>");
+
+
+def transform_anchors_strip:
+ . | gsub($empty_anchor_regex; "")
+ | gsub($anchor_regex; .text);
+
+
+def map_contents_recursively(transformer):
+ . + {
+ Chapter: (.Chapter + {
+ content: .Chapter.content | transformer,
+ sub_items: .Chapter.sub_items | map(map_contents_recursively(transformer)),
+ }),
+ };
+
+
+def process_command:
+ .[0] as $context |
+ .[1] as $body |
+ $body + {
+ sections: $body.sections | map(map_contents_recursively(if $context.renderer == "html" then transform_anchors_html else transform_anchors_strip end)),
+ };
+
+process_command
diff --git a/doc/manual/anchors.py b/doc/manual/anchors.py
deleted file mode 100755
index 2a93b2a67..000000000
--- a/doc/manual/anchors.py
+++ /dev/null
@@ -1,56 +0,0 @@
-#!/usr/bin/env python3
-
-import argparse
-import json
-import re
-import sys
-
-
-empty_anchor_regex = re.compile(r"\[\]\{#(?P<anchor>[^\}]+?)\}")
-anchor_regex = re.compile(r"\[(?P<text>[^\]]+?)\]\{#(?P<anchor>[^\}]+?)\}")
-
-
-def transform_anchors_html(content):
- content = empty_anchor_regex.sub(r'<a name="\g<anchor>"></a>', content)
- content = anchor_regex.sub(r'<a href="#\g<anchor>" id="\g<anchor>">\g<text></a>', content)
- return content
-
-
-def transform_anchors_strip(content):
- content = empty_anchor_regex.sub(r'', content)
- content = anchor_regex.sub(r'\g<text>', content)
- return content
-
-
-def map_contents_recursively(transformer, chapter):
- chapter["Chapter"]["content"] = transformer(chapter["Chapter"]["content"])
- for sub_item in chapter["Chapter"]["sub_items"]:
- map_contents_recursively(transformer, sub_item)
-
-
-def supports_command(args):
- sys.exit(0)
-
-
-def process_command(args):
- context, book = json.load(sys.stdin)
- transformer = transform_anchors_html if context["renderer"] == "html" else transform_anchors_strip
- for section in book["sections"]:
- map_contents_recursively(transformer, section)
- print(json.dumps(book))
-
-
-if __name__ == "__main__":
- parser = argparse.ArgumentParser(
- description="mdBook preprocessor adding anchors."
- )
- parser.set_defaults(command=process_command)
-
- subparsers = parser.add_subparsers()
-
- supports_parser = subparsers.add_parser("supports", help="Check if given renderer is supported")
- supports_parser.add_argument("renderer", type=str)
- supports_parser.set_defaults(command=supports_command)
-
- args = parser.parse_args()
- args.command(args)
diff --git a/doc/manual/book.toml b/doc/manual/book.toml
index 75554d11f..ff6b79c07 100644
--- a/doc/manual/book.toml
+++ b/doc/manual/book.toml
@@ -2,4 +2,5 @@
additional-css = ["custom.css"]
[preprocessor.anchors]
-command = "python3 doc/manual/anchors.py"
+renderers = ["html"]
+command = "jq --from-file doc/manual/anchors.jq"
diff --git a/doc/manual/local.mk b/doc/manual/local.mk
index 910d0a03b..371ed6f21 100644
--- a/doc/manual/local.mk
+++ b/doc/manual/local.mk
@@ -97,7 +97,7 @@ doc/manual/generated/man1/nix3-manpages: $(d)/src/command-ref/new-cli
done
@touch $@
-$(docdir)/manual/index.html: $(MANUAL_SRCS) $(d)/book.toml $(d)/anchors.py $(d)/custom.css $(d)/src/SUMMARY.md $(d)/src/command-ref/new-cli $(d)/src/command-ref/conf-file.md $(d)/src/expressions/builtins.md $(call rwildcard, $(d)/src, *.md)
+$(docdir)/manual/index.html: $(MANUAL_SRCS) $(d)/book.toml $(d)/anchors.jq $(d)/custom.css $(d)/src/SUMMARY.md $(d)/src/command-ref/new-cli $(d)/src/command-ref/conf-file.md $(d)/src/expressions/builtins.md $(call rwildcard, $(d)/src, *.md)
$(trace-gen) RUST_LOG=warn mdbook build doc/manual -d $(DESTDIR)$(docdir)/manual
endif
diff --git a/flake.nix b/flake.nix
index dd3a25e9e..536fcf9fa 100644
--- a/flake.nix
+++ b/flake.nix
@@ -102,7 +102,7 @@
# Tests
buildPackages.git
buildPackages.mercurial # FIXME: remove? only needed for tests
- buildPackages.jq
+ buildPackages.jq # Also for custom mdBook preprocessor.
]
++ lib.optionals stdenv.hostPlatform.isLinux [(buildPackages.util-linuxMinimal or buildPackages.utillinuxMinimal)];
From 7708a34a514ddeb1420886309ae9870d8757f7ce Mon Sep 17 00:00:00 2001
From: Jan Tojnar <jtojnar@gmail.com>
Date: Wed, 25 May 2022 12:36:46 +0200
Subject: [PATCH 175/188] doc: Add anchors to long lists
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Added using the following sed scripts:
- For command-ref/opt-common.md:
s~- `(--?)([^`]+)`~- [`\1\2`]{#opt-\2}~g
- For expressions/builtin-constants.md:
s~- `(builtins\.?)([^`]+)`~- [`\1\2`]{#builtins-\2}~g
- For expressions/advanced-attributes.md
s~^ - `([^`]+)`~ - [`\1`]{#adv-attr-\1}~g
and manually adjusted outputHashAlgo & outputHashMode.
- For glossary.md
s~^ - (`([^`]+)`|(.+)) ?\\~ - [\1]{#gloss-\2\3}\\~g;
s~(gloss-\w+) ~\1-~g
and manually adjusted anchors for Nix expression, user environment, NAR, ∅ and ε.
- For command-ref/env-common.md
s~^ - `([^`]+)`~ - [`\1`]{#env-\1}~g'
---
doc/manual/src/command-ref/env-common.md | 30 ++++++-------
doc/manual/src/command-ref/nix-build.md | 6 +--
doc/manual/src/command-ref/opt-common.md | 42 +++++++++----------
.../src/expressions/advanced-attributes.md | 22 +++++-----
.../src/expressions/builtin-constants.md | 2 +-
doc/manual/src/glossary.md | 36 ++++++++--------
6 files changed, 69 insertions(+), 69 deletions(-)
diff --git a/doc/manual/src/command-ref/env-common.md b/doc/manual/src/command-ref/env-common.md
index 6e2403461..ab048074a 100644
--- a/doc/manual/src/command-ref/env-common.md
+++ b/doc/manual/src/command-ref/env-common.md
@@ -2,11 +2,11 @@
Most Nix commands interpret the following environment variables:
- - `IN_NIX_SHELL`\
+ - [`IN_NIX_SHELL`]{#env-IN_NIX_SHELL}\
Indicator that tells if the current environment was set up by
`nix-shell`. Since Nix 2.0 the values are `"pure"` and `"impure"`
- - `NIX_PATH`\
+ - [`NIX_PATH`]{#env-NIX_PATH}\
A colon-separated list of directories used to look up Nix
expressions enclosed in angle brackets (i.e., `<path>`). For
instance, the value
@@ -44,7 +44,7 @@ Most Nix commands interpret the following environment variables:
The Nix search path can also be extended using the `-I` option to
many Nix commands, which takes precedence over `NIX_PATH`.
- - `NIX_IGNORE_SYMLINK_STORE`\
+ - [`NIX_IGNORE_SYMLINK_STORE`]{#env-NIX_IGNORE_SYMLINK_STORE}\
Normally, the Nix store directory (typically `/nix/store`) is not
allowed to contain any symlink components. This is to prevent
“impure” builds. Builders sometimes “canonicalise” paths by
@@ -66,41 +66,41 @@ Most Nix commands interpret the following environment variables:
Consult the mount 8 manual page for details.
- - `NIX_STORE_DIR`\
+ - [`NIX_STORE_DIR`]{#env-NIX_STORE_DIR}\
Overrides the location of the Nix store (default `prefix/store`).
- - `NIX_DATA_DIR`\
+ - [`NIX_DATA_DIR`]{#env-NIX_DATA_DIR}\
Overrides the location of the Nix static data directory (default
`prefix/share`).
- - `NIX_LOG_DIR`\
+ - [`NIX_LOG_DIR`]{#env-NIX_LOG_DIR}\
Overrides the location of the Nix log directory (default
`prefix/var/log/nix`).
- - `NIX_STATE_DIR`\
+ - [`NIX_STATE_DIR`]{#env-NIX_STATE_DIR}\
Overrides the location of the Nix state directory (default
`prefix/var/nix`).
- - `NIX_CONF_DIR`\
+ - [`NIX_CONF_DIR`]{#env-NIX_CONF_DIR}\
Overrides the location of the system Nix configuration directory
(default `prefix/etc/nix`).
- - `NIX_CONFIG`\
+ - [`NIX_CONFIG`]{#env-NIX_CONFIG}\
Applies settings from Nix configuration from the environment.
The content is treated as if it was read from a Nix configuration file.
Settings are separated by the newline character.
- - `NIX_USER_CONF_FILES`\
+ - [`NIX_USER_CONF_FILES`]{#env-NIX_USER_CONF_FILES}\
Overrides the location of the user Nix configuration files to load
from (defaults to the XDG spec locations). The variable is treated
as a list separated by the `:` token.
- - `TMPDIR`\
+ - [`TMPDIR`]{#env-TMPDIR}\
Use the specified directory to store temporary files. In particular,
this includes temporary build directories; these can take up
substantial amounts of disk space. The default is `/tmp`.
- - `NIX_REMOTE`\
+ - [`NIX_REMOTE`]{#env-NIX_REMOTE}\
This variable should be set to `daemon` if you want to use the Nix
daemon to execute Nix operations. This is necessary in [multi-user
Nix installations](../installation/multi-user.md). If the Nix
@@ -108,16 +108,16 @@ Most Nix commands interpret the following environment variables:
should be set to `unix://path/to/socket`. Otherwise, it should be
left unset.
- - `NIX_SHOW_STATS`\
+ - [`NIX_SHOW_STATS`]{#env-NIX_SHOW_STATS}\
If set to `1`, Nix will print some evaluation statistics, such as
the number of values allocated.
- - `NIX_COUNT_CALLS`\
+ - [`NIX_COUNT_CALLS`]{#env-NIX_COUNT_CALLS}\
If set to `1`, Nix will print how often functions were called during
Nix expression evaluation. This is useful for profiling your Nix
expressions.
- - `GC_INITIAL_HEAP_SIZE`\
+ - [`GC_INITIAL_HEAP_SIZE`]{#env-GC_INITIAL_HEAP_SIZE}\
If Nix has been configured to use the Boehm garbage collector, this
variable sets the initial size of the heap in bytes. It defaults to
384 MiB. Setting it to a low value reduces memory consumption, but
diff --git a/doc/manual/src/command-ref/nix-build.md b/doc/manual/src/command-ref/nix-build.md
index 43de7a6e6..aacb32a25 100644
--- a/doc/manual/src/command-ref/nix-build.md
+++ b/doc/manual/src/command-ref/nix-build.md
@@ -47,16 +47,16 @@ All options not listed here are passed to `nix-store
--realise`, except for `--arg` and `--attr` / `-A` which are passed to
`nix-instantiate`.
- - `--no-out-link`\
+ - [`--no-out-link`]{#opt-no-out-link}\
Do not create a symlink to the output path. Note that as a result
the output does not become a root of the garbage collector, and so
might be deleted by `nix-store
--gc`.
- - `--dry-run`\
+ - [`--dry-run`]{#opt-dry-run}\
Show what store paths would be built or downloaded.
- - `--out-link` / `-o` *outlink*\
+ - [`--out-link`]{#opt-out-link} / `-o` *outlink*\
Change the name of the symlink to the output path created from
`result` to *outlink*.
diff --git a/doc/manual/src/command-ref/opt-common.md b/doc/manual/src/command-ref/opt-common.md
index 7ee1a26bc..51d7de18a 100644
--- a/doc/manual/src/command-ref/opt-common.md
+++ b/doc/manual/src/command-ref/opt-common.md
@@ -2,13 +2,13 @@
Most Nix commands accept the following command-line options:
- - `--help`\
+ - [`--help`]{#opt-help}\
Prints out a summary of the command syntax and exits.
- - `--version`\
+ - [`--version`]{#opt-version}\
Prints out the Nix version number on standard output and exits.
- - `--verbose` / `-v`\
+ - [`--verbose`]{#opt-verbose} / `-v`\
Increases the level of verbosity of diagnostic messages printed on
standard error. For each Nix operation, the information printed on
standard output is well-defined; any diagnostic information is
@@ -37,14 +37,14 @@ Most Nix commands accept the following command-line options:
- 5\
“Vomit”: print vast amounts of debug information.
- - `--quiet`\
+ - [`--quiet`]{#opt-quiet}\
Decreases the level of verbosity of diagnostic messages printed on
standard error. This is the inverse option to `-v` / `--verbose`.
This option may be specified repeatedly. See the previous verbosity
levels list.
- - `--log-format` *format*\
+ - [`--log-format`]{#opt-log-format} *format*\
This option can be used to change the output of the log format, with
*format* being one of:
@@ -66,14 +66,14 @@ Most Nix commands accept the following command-line options:
- bar-with-logs\
Display the raw logs, with the progress bar at the bottom.
- - `--no-build-output` / `-Q`\
+ - [`--no-build-output`]{#opt-no-build-output} / `-Q`\
By default, output written by builders to standard output and
standard error is echoed to the Nix command's standard error. This
option suppresses this behaviour. Note that the builder's standard
output and error are always written to a log file in
`prefix/nix/var/log/nix`.
- - `--max-jobs` / `-j` *number*\
+ - [`--max-jobs`]{#opt-max-jobs} / `-j` *number*\
Sets the maximum number of build jobs that Nix will perform in
parallel to the specified number. Specify `auto` to use the number
of CPUs in the system. The default is specified by the `max-jobs`
@@ -83,7 +83,7 @@ Most Nix commands accept the following command-line options:
Setting it to `0` disallows building on the local machine, which is
useful when you want builds to happen only on remote builders.
- - `--cores`\
+ - [`--cores`]{#opt-cores}\
Sets the value of the `NIX_BUILD_CORES` environment variable in
the invocation of builders. Builders can use this variable at
their discretion to control the maximum amount of parallelism. For
@@ -94,18 +94,18 @@ Most Nix commands accept the following command-line options:
means that the builder should use all available CPU cores in the
system.
- - `--max-silent-time`\
+ - [`--max-silent-time`]{#opt-max-silent-time}\
Sets the maximum number of seconds that a builder can go without
producing any data on standard output or standard error. The
default is specified by the `max-silent-time` configuration
setting. `0` means no time-out.
- - `--timeout`\
+ - [`--timeout`]{#opt-timeout}\
Sets the maximum number of seconds that a builder can run. The
default is specified by the `timeout` configuration setting. `0`
means no timeout.
- - `--keep-going` / `-k`\
+ - [`--keep-going`]{#opt-keep-going} / `-k`\
Keep going in case of failed builds, to the greatest extent
possible. That is, if building an input of some derivation fails,
Nix will still build the other inputs, but not the derivation
@@ -113,13 +113,13 @@ Most Nix commands accept the following command-line options:
for builds of substitutes), possibly killing builds in progress (in
case of parallel or distributed builds).
- - `--keep-failed` / `-K`\
+ - [`--keep-failed`]{#opt-keep-failed} / `-K`\
Specifies that in case of a build failure, the temporary directory
(usually in `/tmp`) in which the build takes place should not be
deleted. The path of the build directory is printed as an
informational message.
- - `--fallback`\
+ - [`--fallback`]{#opt-fallback}\
Whenever Nix attempts to build a derivation for which substitutes
are known for each output path, but realising the output paths
through the substitutes fails, fall back on building the derivation.
@@ -134,12 +134,12 @@ Most Nix commands accept the following command-line options:
failure in obtaining the substitutes to lead to a full build from
source (with the related consumption of resources).
- - `--readonly-mode`\
+ - [`--readonly-mode`]{#opt-readonly-mode}\
When this option is used, no attempt is made to open the Nix
database. Most Nix operations do need database access, so those
operations will fail.
- - `--arg` *name* *value*\
+ - [`--arg`]{#opt-arg} *name* *value*\
This option is accepted by `nix-env`, `nix-instantiate`,
`nix-shell` and `nix-build`. When evaluating Nix expressions, the
expression evaluator will automatically try to call functions that
@@ -170,13 +170,13 @@ Most Nix commands accept the following command-line options:
since the argument is a Nix string literal, you have to escape the
quotes.)
- - `--argstr` *name* *value*\
+ - [`--argstr`]{#opt-argstr} *name* *value*\
This option is like `--arg`, only the value is not a Nix
expression but a string. So instead of `--arg system
\"i686-linux\"` (the outer quotes are to keep the shell happy) you
can say `--argstr system i686-linux`.
- - `--attr` / `-A` *attrPath*\
+ - [`--attr`]{#opt-attr} / `-A` *attrPath*\
Select an attribute from the top-level Nix expression being
evaluated. (`nix-env`, `nix-instantiate`, `nix-build` and
`nix-shell` only.) The *attribute path* *attrPath* is a sequence
@@ -191,7 +191,7 @@ Most Nix commands accept the following command-line options:
attribute of the fourth element of the array in the `foo` attribute
of the top-level expression.
- - `--expr` / `-E`\
+ - [`--expr`]{#opt-expr} / `-E`\
Interpret the command line arguments as a list of Nix expressions to
be parsed and evaluated, rather than as a list of file names of Nix
expressions. (`nix-instantiate`, `nix-build` and `nix-shell` only.)
@@ -202,17 +202,17 @@ Most Nix commands accept the following command-line options:
use, give your expression to the `nix-shell -p` convenience flag
instead.
- - `-I` *path*\
+ - [`-I`]{#opt-I} *path*\
Add a path to the Nix expression search path. This option may be
given multiple times. See the `NIX_PATH` environment variable for
information on the semantics of the Nix search path. Paths added
through `-I` take precedence over `NIX_PATH`.
- - `--option` *name* *value*\
+ - [`--option`]{#opt-option} *name* *value*\
Set the Nix configuration option *name* to *value*. This overrides
settings in the Nix configuration file (see nix.conf5).
- - `--repair`\
+ - [`--repair`]{#opt-repair}\
Fix corrupted or missing store paths by redownloading or rebuilding
them. Note that this is slow because it requires computing a
cryptographic hash of the contents of every path in the closure of
diff --git a/doc/manual/src/expressions/advanced-attributes.md b/doc/manual/src/expressions/advanced-attributes.md
index 000595815..2e7e80ed0 100644
--- a/doc/manual/src/expressions/advanced-attributes.md
+++ b/doc/manual/src/expressions/advanced-attributes.md
@@ -2,7 +2,7 @@
Derivations can declare some infrequently used optional attributes.
- - `allowedReferences`\
+ - [`allowedReferences`]{#adv-attr-allowedReferences}\
The optional attribute `allowedReferences` specifies a list of legal
references (dependencies) of the output of the builder. For example,
@@ -17,7 +17,7 @@ Derivations can declare some infrequently used optional attributes.
booting Linux don’t have accidental dependencies on other paths in
the Nix store.
- - `allowedRequisites`\
+ - [`allowedRequisites`]{#adv-attr-allowedRequisites}\
This attribute is similar to `allowedReferences`, but it specifies
the legal requisites of the whole closure, so all the dependencies
recursively. For example,
@@ -30,7 +30,7 @@ Derivations can declare some infrequently used optional attributes.
runtime dependency than `foobar`, and in addition it enforces that
`foobar` itself doesn't introduce any other dependency itself.
- - `disallowedReferences`\
+ - [`disallowedReferences`]{#adv-attr-disallowedReferences}\
The optional attribute `disallowedReferences` specifies a list of
illegal references (dependencies) of the output of the builder. For
example,
@@ -42,7 +42,7 @@ Derivations can declare some infrequently used optional attributes.
enforces that the output of a derivation cannot have a direct
runtime dependencies on the derivation `foo`.
- - `disallowedRequisites`\
+ - [`disallowedRequisites`]{#adv-attr-disallowedRequisites}\
This attribute is similar to `disallowedReferences`, but it
specifies illegal requisites for the whole closure, so all the
dependencies recursively. For example,
@@ -55,7 +55,7 @@ Derivations can declare some infrequently used optional attributes.
dependency on `foobar` or any other derivation depending recursively
on `foobar`.
- - `exportReferencesGraph`\
+ - [`exportReferencesGraph`]{#adv-attr-exportReferencesGraph}\
This attribute allows builders access to the references graph of
their inputs. The attribute is a list of inputs in the Nix store
whose references graph the builder needs to know. The value of
@@ -84,7 +84,7 @@ Derivations can declare some infrequently used optional attributes.
with a Nix store containing the closure of a bootable NixOS
configuration).
- - `impureEnvVars`\
+ - [`impureEnvVars`]{#adv-attr-impureEnvVars}\
This attribute allows you to specify a list of environment variables
that should be passed from the environment of the calling user to
the builder. Usually, the environment is cleared completely when the
@@ -112,7 +112,7 @@ Derivations can declare some infrequently used optional attributes.
> environmental variables come from the environment of the
> `nix-build`.
- - `outputHash`; `outputHashAlgo`; `outputHashMode`\
+ - [`outputHash`]{#adv-attr-outputHash}; [`outputHashAlgo`]{#adv-attr-outputHashAlgo}; [`outputHashMode`]{#adv-attr-outputHashMode}\
These attributes declare that the derivation is a so-called
*fixed-output derivation*, which means that a cryptographic hash of
the output is already known in advance. When the build of a
@@ -208,7 +208,7 @@ Derivations can declare some infrequently used optional attributes.
[`nix-hash` command](../command-ref/nix-hash.md) for information
about converting to and from base-32 notation.)
- - `__contentAddressed`
+ - [`__contentAddressed`]{#adv-attr-__contentAddressed}
If this **experimental** attribute is set to true, then the derivation
outputs will be stored in a content-addressed location rather than the
traditional input-addressed one.
@@ -216,7 +216,7 @@ Derivations can declare some infrequently used optional attributes.
Setting this attribute also requires setting `outputHashMode` and `outputHashAlgo` like for *fixed-output derivations* (see above).
- - `passAsFile`\
+ - [`passAsFile`]{#adv-attr-passAsFile}\
A list of names of attributes that should be passed via files rather
than environment variables. For example, if you have
@@ -234,7 +234,7 @@ Derivations can declare some infrequently used optional attributes.
builder, since most operating systems impose a limit on the size
of the environment (typically, a few hundred kilobyte).
- - `preferLocalBuild`\
+ - [`preferLocalBuild`]{#adv-attr-preferLocalBuild}\
If this attribute is set to `true` and [distributed building is
enabled](../advanced-topics/distributed-builds.md), then, if
possible, the derivation will be built locally instead of forwarded
@@ -242,7 +242,7 @@ Derivations can declare some infrequently used optional attributes.
where the cost of doing a download or remote build would exceed
the cost of building locally.
- - `allowSubstitutes`\
+ - [`allowSubstitutes`]{#adv-attr-allowSubstitutes}\
If this attribute is set to `false`, then Nix will always build this
derivation; it will not try to substitute its outputs. This is
useful for very trivial derivations (such as `writeText` in Nixpkgs)
diff --git a/doc/manual/src/expressions/builtin-constants.md b/doc/manual/src/expressions/builtin-constants.md
index 1404289e5..78d066a82 100644
--- a/doc/manual/src/expressions/builtin-constants.md
+++ b/doc/manual/src/expressions/builtin-constants.md
@@ -14,7 +14,7 @@ Here are the constants built into the Nix expression evaluator:
This allows a Nix expression to fall back gracefully on older Nix
installations that don’t have the desired built-in function.
- - `builtins.currentSystem`\
+ - [`builtins.currentSystem`]{#builtins-currentSystem}\
The built-in value `currentSystem` evaluates to the Nix platform
identifier for the Nix installation on which the expression is being
evaluated, such as `"i686-linux"` or `"x86_64-darwin"`.
diff --git a/doc/manual/src/glossary.md b/doc/manual/src/glossary.md
index 71ff13275..3448b971b 100644
--- a/doc/manual/src/glossary.md
+++ b/doc/manual/src/glossary.md
@@ -1,48 +1,48 @@
# Glossary
- - derivation\
+ - [derivation]{#gloss-derivation}\
A description of a build action. The result of a derivation is a
store object. Derivations are typically specified in Nix expressions
using the [`derivation` primitive](expressions/derivations.md). These are
translated into low-level *store derivations* (implicitly by
`nix-env` and `nix-build`, or explicitly by `nix-instantiate`).
- - store\
+ - [store]{#gloss-store}\
The location in the file system where store objects live. Typically
`/nix/store`.
- - store path\
+ - [store path]{#gloss-store-path}\
The location in the file system of a store object, i.e., an
immediate child of the Nix store directory.
- - store object\
+ - [store object]{#gloss-store-object}\
A file that is an immediate child of the Nix store directory. These
can be regular files, but also entire directory trees. Store objects
can be sources (objects copied from outside of the store),
derivation outputs (objects produced by running a build action), or
derivations (files describing a build action).
- - substitute\
+ - [substitute]{#gloss-substitute}\
A substitute is a command invocation stored in the Nix database that
describes how to build a store object, bypassing the normal build
mechanism (i.e., derivations). Typically, the substitute builds the
store object by downloading a pre-built version of the store object
from some server.
- - purity\
+ - [purity]{#gloss-purity}\
The assumption that equal Nix derivations when run always produce
the same output. This cannot be guaranteed in general (e.g., a
builder can rely on external inputs such as the network or the
system time) but the Nix model assumes it.
- - Nix expression\
+ - [Nix expression]{#gloss-nix-expression}\
A high-level description of software packages and compositions
thereof. Deploying software using Nix entails writing Nix
expressions for your packages. Nix expressions are translated to
derivations that are stored in the Nix store. These derivations can
then be built.
- - reference\
+ - [reference]{#gloss-reference}\
A store path `P` is said to have a reference to a store path `Q` if
the store object at `P` contains the path `Q` somewhere. The
*references* of a store path are the set of store paths to which it
@@ -52,11 +52,11 @@
output paths), whereas an output path only references other output
paths.
- - reachable\
+ - [reachable]{#gloss-reachable}\
A store path `Q` is reachable from another store path `P` if `Q`
is in the *closure* of the *references* relation.
- - closure\
+ - [closure]{#gloss-closure}\
The closure of a store path is the set of store paths that are
directly or indirectly “reachable” from that store path; that is,
it’s the closure of the path under the *references* relation. For
@@ -71,34 +71,34 @@
to path `Q`, then `Q` is in the closure of `P`. Further, if `Q`
references `R` then `R` is also in the closure of `P`.
- - output path\
+ - [output path]{#gloss-output-path}\
A store path produced by a derivation.
- - deriver\
+ - [deriver]{#gloss-deriver}\
The deriver of an *output path* is the store
derivation that built it.
- - validity\
+ - [validity]{#gloss-validity}\
A store path is considered *valid* if it exists in the file system,
is listed in the Nix database as being valid, and if all paths in
its closure are also valid.
- - user environment\
+ - [user environment]{#gloss-user-env}\
An automatically generated store object that consists of a set of
symlinks to “active” applications, i.e., other store paths. These
are generated automatically by
[`nix-env`](command-ref/nix-env.md). See *profiles*.
- - profile\
+ - [profile]{#gloss-profile}\
A symlink to the current *user environment* of a user, e.g.,
`/nix/var/nix/profiles/default`.
- - NAR\
+ - [NAR]{#gloss-nar}\
A *N*ix *AR*chive. This is a serialisation of a path in the Nix
store. It can contain regular files, directories and symbolic
links. NARs are generated and unpacked using `nix-store --dump`
and `nix-store --restore`.
- - `∅` \
+ - [`∅`]{#gloss-emtpy-set}\
The empty set symbol. In the context of profile history, this denotes a package is not present in a particular version of the profile.
- - `ε` \
+ - [`ε`]{#gloss-epsilon}\
The epsilon symbol. In the context of a package, this means the version is empty. More precisely, the derivation does not have a version attribute.
From a793863b97efde14189b031326e48ac0f448fafc Mon Sep 17 00:00:00 2001
From: Jan Tojnar <jtojnar@gmail.com>
Date: Wed, 25 May 2022 13:53:07 +0200
Subject: [PATCH 176/188] doc: Manually insert some anchors
---
doc/manual/src/advanced-topics/diff-hook.md | 2 +-
doc/manual/src/command-ref/nix-store.md | 2 +-
doc/manual/src/expressions/derivations.md | 2 +-
doc/manual/src/installation/installing-binary.md | 3 ++-
4 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/doc/manual/src/advanced-topics/diff-hook.md b/doc/manual/src/advanced-topics/diff-hook.md
index 7a2622b3d..161e64b2a 100644
--- a/doc/manual/src/advanced-topics/diff-hook.md
+++ b/doc/manual/src/advanced-topics/diff-hook.md
@@ -101,7 +101,7 @@ In particular, notice the
`/nix/store/krpqk0l9ib0ibi1d2w52z293zw455cap-unstable.check` output. Nix
has copied the build results to that directory where you can examine it.
-> **Note**
+> []{#check-dirs-are-unregistered} **Note**
>
> Check paths are not protected against garbage collection, and this
> path will be deleted on the next garbage collection.
diff --git a/doc/manual/src/command-ref/nix-store.md b/doc/manual/src/command-ref/nix-store.md
index 7db9f0c1c..dc8faba68 100644
--- a/doc/manual/src/command-ref/nix-store.md
+++ b/doc/manual/src/command-ref/nix-store.md
@@ -22,7 +22,7 @@ This section lists the options that are common to all operations. These
options are allowed for every subcommand, though they may not always
have an effect.
- - `--add-root` *path*\
+ - [`--add-root`]{#opt-add-root} *path*\
Causes the result of a realisation (`--realise` and
`--force-realise`) to be registered as a root of the garbage
collector. *path* will be created as a symlink to the resulting
diff --git a/doc/manual/src/expressions/derivations.md b/doc/manual/src/expressions/derivations.md
index d26a33b7f..3391ec0d8 100644
--- a/doc/manual/src/expressions/derivations.md
+++ b/doc/manual/src/expressions/derivations.md
@@ -4,7 +4,7 @@ The most important built-in function is `derivation`, which is used to
describe a single derivation (a build action). It takes as input a set,
the attributes of which specify the inputs of the build.
- - There must be an attribute named `system` whose value must be a
+ - There must be an attribute named [`system`]{#attr-system} whose value must be a
string specifying a Nix system type, such as `"i686-linux"` or
`"x86_64-darwin"`. (To figure out your system type, run `nix -vv
--version`.) The build can only be performed on a machine and
diff --git a/doc/manual/src/installation/installing-binary.md b/doc/manual/src/installation/installing-binary.md
index e5fb50088..9fb9c80c3 100644
--- a/doc/manual/src/installation/installing-binary.md
+++ b/doc/manual/src/installation/installing-binary.md
@@ -186,7 +186,8 @@ and `/etc/zshrc` which you may remove.
> read-only root will prevent you from manually deleting the empty `/nix`
> mountpoint.
-# macOS Installation <a name="sect-macos-installation-change-store-prefix"></a><a name="sect-macos-installation-encrypted-volume"></a><a name="sect-macos-installation-symlink"></a><a name="sect-macos-installation-recommended-notes"></a>
+# macOS Installation
+[]{#sect-macos-installation-change-store-prefix}[]{#sect-macos-installation-encrypted-volume}[]{#sect-macos-installation-symlink}[]{#sect-macos-installation-recommended-notes}
<!-- Note: anchors above to catch permalinks to old explanations -->
We believe we have ironed out how to cleanly support the read-only root
From 26d1877d6ec7118180be14fc39b471fa53bc0caa Mon Sep 17 00:00:00 2001
From: Jan Tojnar <jtojnar@gmail.com>
Date: Wed, 25 May 2022 08:07:02 +0200
Subject: [PATCH 177/188] doc: Add redirects for the DocBook manual
There are still many links to the old manual on the web and
having them end up on the Introduction page is a bad user experience.
---
doc/manual/book.toml | 1 +
doc/manual/redirects.js | 337 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 338 insertions(+)
create mode 100644 doc/manual/redirects.js
diff --git a/doc/manual/book.toml b/doc/manual/book.toml
index ff6b79c07..5f78a7614 100644
--- a/doc/manual/book.toml
+++ b/doc/manual/book.toml
@@ -1,5 +1,6 @@
[output.html]
additional-css = ["custom.css"]
+additional-js = ["redirects.js"]
[preprocessor.anchors]
renderers = ["html"]
diff --git a/doc/manual/redirects.js b/doc/manual/redirects.js
new file mode 100644
index 000000000..19f928c7e
--- /dev/null
+++ b/doc/manual/redirects.js
@@ -0,0 +1,337 @@
+// Redirects from old DocBook manual.
+var redirects = {
+ "#part-advanced-topics": "advanced-topics/advanced-topics.html",
+ "#chap-tuning-cores-and-jobs": "advanced-topics/cores-vs-jobs.html",
+ "#chap-diff-hook": "advanced-topics/diff-hook.html",
+ "#check-dirs-are-unregistered": "advanced-topics/diff-hook.html#check-dirs-are-unregistered",
+ "#chap-distributed-builds": "advanced-topics/distributed-builds.html",
+ "#chap-post-build-hook": "advanced-topics/post-build-hook.html",
+ "#chap-post-build-hook-caveats": "advanced-topics/post-build-hook.html#implementation-caveats",
+ "#part-command-ref": "command-ref/command-ref.html",
+ "#conf-allow-import-from-derivation": "command-ref/conf-file.html#conf-allow-import-from-derivation",
+ "#conf-allow-new-privileges": "command-ref/conf-file.html#conf-allow-new-privileges",
+ "#conf-allowed-uris": "command-ref/conf-file.html#conf-allowed-uris",
+ "#conf-allowed-users": "command-ref/conf-file.html#conf-allowed-users",
+ "#conf-auto-optimise-store": "command-ref/conf-file.html#conf-auto-optimise-store",
+ "#conf-binary-cache-public-keys": "command-ref/conf-file.html#conf-binary-cache-public-keys",
+ "#conf-binary-caches": "command-ref/conf-file.html#conf-binary-caches",
+ "#conf-build-compress-log": "command-ref/conf-file.html#conf-build-compress-log",
+ "#conf-build-cores": "command-ref/conf-file.html#conf-build-cores",
+ "#conf-build-extra-chroot-dirs": "command-ref/conf-file.html#conf-build-extra-chroot-dirs",
+ "#conf-build-extra-sandbox-paths": "command-ref/conf-file.html#conf-build-extra-sandbox-paths",
+ "#conf-build-fallback": "command-ref/conf-file.html#conf-build-fallback",
+ "#conf-build-max-jobs": "command-ref/conf-file.html#conf-build-max-jobs",
+ "#conf-build-max-log-size": "command-ref/conf-file.html#conf-build-max-log-size",
+ "#conf-build-max-silent-time": "command-ref/conf-file.html#conf-build-max-silent-time",
+ "#conf-build-repeat": "command-ref/conf-file.html#conf-build-repeat",
+ "#conf-build-timeout": "command-ref/conf-file.html#conf-build-timeout",
+ "#conf-build-use-chroot": "command-ref/conf-file.html#conf-build-use-chroot",
+ "#conf-build-use-sandbox": "command-ref/conf-file.html#conf-build-use-sandbox",
+ "#conf-build-use-substitutes": "command-ref/conf-file.html#conf-build-use-substitutes",
+ "#conf-build-users-group": "command-ref/conf-file.html#conf-build-users-group",
+ "#conf-builders": "command-ref/conf-file.html#conf-builders",
+ "#conf-builders-use-substitutes": "command-ref/conf-file.html#conf-builders-use-substitutes",
+ "#conf-compress-build-log": "command-ref/conf-file.html#conf-compress-build-log",
+ "#conf-connect-timeout": "command-ref/conf-file.html#conf-connect-timeout",
+ "#conf-cores": "command-ref/conf-file.html#conf-cores",
+ "#conf-diff-hook": "command-ref/conf-file.html#conf-diff-hook",
+ "#conf-enforce-determinism": "command-ref/conf-file.html#conf-enforce-determinism",
+ "#conf-env-keep-derivations": "command-ref/conf-file.html#conf-env-keep-derivations",
+ "#conf-extra-binary-caches": "command-ref/conf-file.html#conf-extra-binary-caches",
+ "#conf-extra-platforms": "command-ref/conf-file.html#conf-extra-platforms",
+ "#conf-extra-sandbox-paths": "command-ref/conf-file.html#conf-extra-sandbox-paths",
+ "#conf-extra-substituters": "command-ref/conf-file.html#conf-extra-substituters",
+ "#conf-fallback": "command-ref/conf-file.html#conf-fallback",
+ "#conf-fsync-metadata": "command-ref/conf-file.html#conf-fsync-metadata",
+ "#conf-gc-keep-derivations": "command-ref/conf-file.html#conf-gc-keep-derivations",
+ "#conf-gc-keep-outputs": "command-ref/conf-file.html#conf-gc-keep-outputs",
+ "#conf-hashed-mirrors": "command-ref/conf-file.html#conf-hashed-mirrors",
+ "#conf-http-connections": "command-ref/conf-file.html#conf-http-connections",
+ "#conf-keep-build-log": "command-ref/conf-file.html#conf-keep-build-log",
+ "#conf-keep-derivations": "command-ref/conf-file.html#conf-keep-derivations",
+ "#conf-keep-env-derivations": "command-ref/conf-file.html#conf-keep-env-derivations",
+ "#conf-keep-outputs": "command-ref/conf-file.html#conf-keep-outputs",
+ "#conf-max-build-log-size": "command-ref/conf-file.html#conf-max-build-log-size",
+ "#conf-max-free": "command-ref/conf-file.html#conf-max-free",
+ "#conf-max-jobs": "command-ref/conf-file.html#conf-max-jobs",
+ "#conf-max-silent-time": "command-ref/conf-file.html#conf-max-silent-time",
+ "#conf-min-free": "command-ref/conf-file.html#conf-min-free",
+ "#conf-narinfo-cache-negative-ttl": "command-ref/conf-file.html#conf-narinfo-cache-negative-ttl",
+ "#conf-narinfo-cache-positive-ttl": "command-ref/conf-file.html#conf-narinfo-cache-positive-ttl",
+ "#conf-netrc-file": "command-ref/conf-file.html#conf-netrc-file",
+ "#conf-plugin-files": "command-ref/conf-file.html#conf-plugin-files",
+ "#conf-post-build-hook": "command-ref/conf-file.html#conf-post-build-hook",
+ "#conf-pre-build-hook": "command-ref/conf-file.html#conf-pre-build-hook",
+ "#conf-repeat": "command-ref/conf-file.html#conf-repeat",
+ "#conf-require-sigs": "command-ref/conf-file.html#conf-require-sigs",
+ "#conf-restrict-eval": "command-ref/conf-file.html#conf-restrict-eval",
+ "#conf-run-diff-hook": "command-ref/conf-file.html#conf-run-diff-hook",
+ "#conf-sandbox": "command-ref/conf-file.html#conf-sandbox",
+ "#conf-sandbox-dev-shm-size": "command-ref/conf-file.html#conf-sandbox-dev-shm-size",
+ "#conf-sandbox-paths": "command-ref/conf-file.html#conf-sandbox-paths",
+ "#conf-secret-key-files": "command-ref/conf-file.html#conf-secret-key-files",
+ "#conf-show-trace": "command-ref/conf-file.html#conf-show-trace",
+ "#conf-stalled-download-timeout": "command-ref/conf-file.html#conf-stalled-download-timeout",
+ "#conf-substitute": "command-ref/conf-file.html#conf-substitute",
+ "#conf-substituters": "command-ref/conf-file.html#conf-substituters",
+ "#conf-system": "command-ref/conf-file.html#conf-system",
+ "#conf-system-features": "command-ref/conf-file.html#conf-system-features",
+ "#conf-tarball-ttl": "command-ref/conf-file.html#conf-tarball-ttl",
+ "#conf-timeout": "command-ref/conf-file.html#conf-timeout",
+ "#conf-trace-function-calls": "command-ref/conf-file.html#conf-trace-function-calls",
+ "#conf-trusted-binary-caches": "command-ref/conf-file.html#conf-trusted-binary-caches",
+ "#conf-trusted-public-keys": "command-ref/conf-file.html#conf-trusted-public-keys",
+ "#conf-trusted-substituters": "command-ref/conf-file.html#conf-trusted-substituters",
+ "#conf-trusted-users": "command-ref/conf-file.html#conf-trusted-users",
+ "#extra-sandbox-paths": "command-ref/conf-file.html#extra-sandbox-paths",
+ "#sec-conf-file": "command-ref/conf-file.html",
+ "#env-NIX_PATH": "command-ref/env-common.html#env-NIX_PATH",
+ "#env-common": "command-ref/env-common.html",
+ "#envar-remote": "command-ref/env-common.html#env-NIX_REMOTE",
+ "#sec-common-env": "command-ref/env-common.html",
+ "#ch-files": "command-ref/files.html",
+ "#ch-main-commands": "command-ref/main-commands.html",
+ "#opt-out-link": "command-ref/nix-build.html#opt-out-link",
+ "#sec-nix-build": "command-ref/nix-build.html",
+ "#sec-nix-channel": "command-ref/nix-channel.html",
+ "#sec-nix-collect-garbage": "command-ref/nix-collect-garbage.html",
+ "#sec-nix-copy-closure": "command-ref/nix-copy-closure.html",
+ "#sec-nix-daemon": "command-ref/nix-daemon.html",
+ "#refsec-nix-env-install-examples": "command-ref/nix-env.html#examples",
+ "#rsec-nix-env-install": "command-ref/nix-env.html#operation---install",
+ "#rsec-nix-env-set": "command-ref/nix-env.html#operation---set",
+ "#rsec-nix-env-set-flag": "command-ref/nix-env.html#operation---set-flag",
+ "#rsec-nix-env-upgrade": "command-ref/nix-env.html#operation---upgrade",
+ "#sec-nix-env": "command-ref/nix-env.html",
+ "#ssec-version-comparisons": "command-ref/nix-env.html#versions",
+ "#sec-nix-hash": "command-ref/nix-hash.html",
+ "#sec-nix-instantiate": "command-ref/nix-instantiate.html",
+ "#sec-nix-prefetch-url": "command-ref/nix-prefetch-url.html",
+ "#sec-nix-shell": "command-ref/nix-shell.html",
+ "#ssec-nix-shell-shebang": "command-ref/nix-shell.html#use-as-a--interpreter",
+ "#nixref-queries": "command-ref/nix-store.html#queries",
+ "#opt-add-root": "command-ref/nix-store.html#opt-add-root",
+ "#refsec-nix-store-dump": "command-ref/nix-store.html#operation---dump",
+ "#refsec-nix-store-export": "command-ref/nix-store.html#operation---export",
+ "#refsec-nix-store-import": "command-ref/nix-store.html#operation---import",
+ "#refsec-nix-store-query": "command-ref/nix-store.html#operation---query",
+ "#refsec-nix-store-verify": "command-ref/nix-store.html#operation---verify",
+ "#rsec-nix-store-gc": "command-ref/nix-store.html#operation---gc",
+ "#rsec-nix-store-generate-binary-cache-key": "command-ref/nix-store.html#operation---generate-binary-cache-key",
+ "#rsec-nix-store-realise": "command-ref/nix-store.html#operation---realise",
+ "#rsec-nix-store-serve": "command-ref/nix-store.html#operation---serve",
+ "#sec-nix-store": "command-ref/nix-store.html",
+ "#opt-I": "command-ref/opt-common.html#opt-I",
+ "#opt-attr": "command-ref/opt-common.html#opt-attr",
+ "#opt-common": "command-ref/opt-common.html",
+ "#opt-cores": "command-ref/opt-common.html#opt-cores",
+ "#opt-log-format": "command-ref/opt-common.html#opt-log-format",
+ "#opt-max-jobs": "command-ref/opt-common.html#opt-max-jobs",
+ "#opt-max-silent-time": "command-ref/opt-common.html#opt-max-silent-time",
+ "#opt-timeout": "command-ref/opt-common.html#opt-timeout",
+ "#sec-common-options": "command-ref/opt-common.html",
+ "#ch-utilities": "command-ref/utilities.html",
+ "#chap-hacking": "contributing/hacking.html",
+ "#adv-attr-allowSubstitutes": "expressions/advanced-attributes.html#adv-attr-allowSubstitutes",
+ "#adv-attr-allowedReferences": "expressions/advanced-attributes.html#adv-attr-allowedReferences",
+ "#adv-attr-allowedRequisites": "expressions/advanced-attributes.html#adv-attr-allowedRequisites",
+ "#adv-attr-disallowedReferences": "expressions/advanced-attributes.html#adv-attr-disallowedReferences",
+ "#adv-attr-disallowedRequisites": "expressions/advanced-attributes.html#adv-attr-disallowedRequisites",
+ "#adv-attr-exportReferencesGraph": "expressions/advanced-attributes.html#adv-attr-exportReferencesGraph",
+ "#adv-attr-impureEnvVars": "expressions/advanced-attributes.html#adv-attr-impureEnvVars",
+ "#adv-attr-outputHash": "expressions/advanced-attributes.html#adv-attr-outputHash",
+ "#adv-attr-outputHashAlgo": "expressions/advanced-attributes.html#adv-attr-outputHashAlgo",
+ "#adv-attr-outputHashMode": "expressions/advanced-attributes.html#adv-attr-outputHashMode",
+ "#adv-attr-passAsFile": "expressions/advanced-attributes.html#adv-attr-passAsFile",
+ "#adv-attr-preferLocalBuild": "expressions/advanced-attributes.html#adv-attr-preferLocalBuild",
+ "#fixed-output-drvs": "expressions/advanced-attributes.html#adv-attr-outputHash",
+ "#sec-advanced-attributes": "expressions/advanced-attributes.html",
+ "#sec-arguments": "expressions/arguments-variables.html",
+ "#sec-build-script": "expressions/build-script.html",
+ "#builtin-abort": "expressions/builtins.html#builtins-abort",
+ "#builtin-add": "expressions/builtins.html#builtins-add",
+ "#builtin-all": "expressions/builtins.html#builtins-all",
+ "#builtin-any": "expressions/builtins.html#builtins-any",
+ "#builtin-attrNames": "expressions/builtins.html#builtins-attrNames",
+ "#builtin-attrValues": "expressions/builtins.html#builtins-attrValues",
+ "#builtin-baseNameOf": "expressions/builtins.html#builtins-baseNameOf",
+ "#builtin-bitAnd": "expressions/builtins.html#builtins-bitAnd",
+ "#builtin-bitOr": "expressions/builtins.html#builtins-bitOr",
+ "#builtin-bitXor": "expressions/builtins.html#builtins-bitXor",
+ "#builtin-builtins": "expressions/builtins.html#builtins-builtins",
+ "#builtin-compareVersions": "expressions/builtins.html#builtins-compareVersions",
+ "#builtin-concatLists": "expressions/builtins.html#builtins-concatLists",
+ "#builtin-concatStringsSep": "expressions/builtins.html#builtins-concatStringsSep",
+ "#builtin-currentSystem": "expressions/builtins.html#builtins-currentSystem",
+ "#builtin-deepSeq": "expressions/builtins.html#builtins-deepSeq",
+ "#builtin-derivation": "expressions/builtins.html#builtins-derivation",
+ "#builtin-dirOf": "expressions/builtins.html#builtins-dirOf",
+ "#builtin-div": "expressions/builtins.html#builtins-div",
+ "#builtin-elem": "expressions/builtins.html#builtins-elem",
+ "#builtin-elemAt": "expressions/builtins.html#builtins-elemAt",
+ "#builtin-fetchGit": "expressions/builtins.html#builtins-fetchGit",
+ "#builtin-fetchTarball": "expressions/builtins.html#builtins-fetchTarball",
+ "#builtin-fetchurl": "expressions/builtins.html#builtins-fetchurl",
+ "#builtin-filterSource": "expressions/builtins.html#builtins-filterSource",
+ "#builtin-foldl-prime": "expressions/builtins.html#builtins-foldl-prime",
+ "#builtin-fromJSON": "expressions/builtins.html#builtins-fromJSON",
+ "#builtin-functionArgs": "expressions/builtins.html#builtins-functionArgs",
+ "#builtin-genList": "expressions/builtins.html#builtins-genList",
+ "#builtin-getAttr": "expressions/builtins.html#builtins-getAttr",
+ "#builtin-getEnv": "expressions/builtins.html#builtins-getEnv",
+ "#builtin-hasAttr": "expressions/builtins.html#builtins-hasAttr",
+ "#builtin-hashFile": "expressions/builtins.html#builtins-hashFile",
+ "#builtin-hashString": "expressions/builtins.html#builtins-hashString",
+ "#builtin-head": "expressions/builtins.html#builtins-head",
+ "#builtin-import": "expressions/builtins.html#builtins-import",
+ "#builtin-intersectAttrs": "expressions/builtins.html#builtins-intersectAttrs",
+ "#builtin-isAttrs": "expressions/builtins.html#builtins-isAttrs",
+ "#builtin-isBool": "expressions/builtins.html#builtins-isBool",
+ "#builtin-isFloat": "expressions/builtins.html#builtins-isFloat",
+ "#builtin-isFunction": "expressions/builtins.html#builtins-isFunction",
+ "#builtin-isInt": "expressions/builtins.html#builtins-isInt",
+ "#builtin-isList": "expressions/builtins.html#builtins-isList",
+ "#builtin-isNull": "expressions/builtins.html#builtins-isNull",
+ "#builtin-isString": "expressions/builtins.html#builtins-isString",
+ "#builtin-length": "expressions/builtins.html#builtins-length",
+ "#builtin-lessThan": "expressions/builtins.html#builtins-lessThan",
+ "#builtin-listToAttrs": "expressions/builtins.html#builtins-listToAttrs",
+ "#builtin-map": "expressions/builtins.html#builtins-map",
+ "#builtin-match": "expressions/builtins.html#builtins-match",
+ "#builtin-mul": "expressions/builtins.html#builtins-mul",
+ "#builtin-parseDrvName": "expressions/builtins.html#builtins-parseDrvName",
+ "#builtin-path": "expressions/builtins.html#builtins-path",
+ "#builtin-pathExists": "expressions/builtins.html#builtins-pathExists",
+ "#builtin-placeholder": "expressions/builtins.html#builtins-placeholder",
+ "#builtin-readDir": "expressions/builtins.html#builtins-readDir",
+ "#builtin-readFile": "expressions/builtins.html#builtins-readFile",
+ "#builtin-removeAttrs": "expressions/builtins.html#builtins-removeAttrs",
+ "#builtin-replaceStrings": "expressions/builtins.html#builtins-replaceStrings",
+ "#builtin-seq": "expressions/builtins.html#builtins-seq",
+ "#builtin-sort": "expressions/builtins.html#builtins-sort",
+ "#builtin-split": "expressions/builtins.html#builtins-split",
+ "#builtin-splitVersion": "expressions/builtins.html#builtins-splitVersion",
+ "#builtin-stringLength": "expressions/builtins.html#builtins-stringLength",
+ "#builtin-sub": "expressions/builtins.html#builtins-sub",
+ "#builtin-substring": "expressions/builtins.html#builtins-substring",
+ "#builtin-tail": "expressions/builtins.html#builtins-tail",
+ "#builtin-throw": "expressions/builtins.html#builtins-throw",
+ "#builtin-toFile": "expressions/builtins.html#builtins-toFile",
+ "#builtin-toJSON": "expressions/builtins.html#builtins-toJSON",
+ "#builtin-toPath": "expressions/builtins.html#builtins-toPath",
+ "#builtin-toString": "expressions/builtins.html#builtins-toString",
+ "#builtin-toXML": "expressions/builtins.html#builtins-toXML",
+ "#builtin-trace": "expressions/builtins.html#builtins-trace",
+ "#builtin-tryEval": "expressions/builtins.html#builtins-tryEval",
+ "#builtin-typeOf": "expressions/builtins.html#builtins-typeOf",
+ "#ssec-builtins": "expressions/builtins.html",
+ "#attr-system": "expressions/derivations.html#attr-system",
+ "#ssec-derivation": "expressions/derivations.html",
+ "#ch-expression-language": "expressions/expression-language.html",
+ "#sec-expression-syntax": "expressions/expression-syntax.html",
+ "#sec-generic-builder": "expressions/generic-builder.html",
+ "#sec-constructs": "expressions/language-constructs.html",
+ "#sect-let-expressions": "expressions/language-constructs.html#let-expressions",
+ "#ss-functions": "expressions/language-constructs.html#functions",
+ "#sec-language-operators": "expressions/language-operators.html",
+ "#table-operators": "expressions/language-operators.html",
+ "#ssec-values": "expressions/language-values.html",
+ "#sec-building-simple": "expressions/simple-building-testing.html",
+ "#ch-simple-expression": "expressions/simple-expression.html",
+ "#chap-writing-nix-expressions": "expressions/writing-nix-expressions.html",
+ "#gloss-closure": "glossary.html#gloss-closure",
+ "#gloss-derivation": "glossary.html#gloss-derivation",
+ "#gloss-deriver": "glossary.html#gloss-deriver",
+ "#gloss-nar": "glossary.html#gloss-nar",
+ "#gloss-output-path": "glossary.html#gloss-output-path",
+ "#gloss-profile": "glossary.html#gloss-profile",
+ "#gloss-reachable": "glossary.html#gloss-reachable",
+ "#gloss-reference": "glossary.html#gloss-reference",
+ "#gloss-substitute": "glossary.html#gloss-substitute",
+ "#gloss-user-env": "glossary.html#gloss-user-env",
+ "#gloss-validity": "glossary.html#gloss-validity",
+ "#part-glossary": "glossary.html",
+ "#sec-building-source": "installation/building-source.html",
+ "#ch-env-variables": "installation/env-variables.html",
+ "#sec-installer-proxy-settings": "installation/env-variables.html#proxy-environment-variables",
+ "#sec-nix-ssl-cert-file": "installation/env-variables.html#nix_ssl_cert_file",
+ "#sec-nix-ssl-cert-file-with-nix-daemon-and-macos": "installation/env-variables.html#nix_ssl_cert_file-with-macos-and-the-nix-daemon",
+ "#chap-installation": "installation/installation.html",
+ "#ch-installing-binary": "installation/installing-binary.html",
+ "#sect-macos-installation": "installation/installing-binary.html#macos-installation",
+ "#sect-macos-installation-change-store-prefix": "installation/installing-binary.html#macos-installation",
+ "#sect-macos-installation-encrypted-volume": "installation/installing-binary.html#macos-installation",
+ "#sect-macos-installation-recommended-notes": "installation/installing-binary.html#macos-installation",
+ "#sect-macos-installation-symlink": "installation/installing-binary.html#macos-installation",
+ "#sect-multi-user-installation": "installation/installing-binary.html#multi-user-installation",
+ "#sect-nix-install-binary-tarball": "installation/installing-binary.html#installing-from-a-binary-tarball",
+ "#sect-nix-install-pinned-version-url": "installation/installing-binary.html#installing-a-pinned-nix-version-from-a-url",
+ "#sect-single-user-installation": "installation/installing-binary.html#single-user-installation",
+ "#ch-installing-source": "installation/installing-source.html",
+ "#ssec-multi-user": "installation/multi-user.html",
+ "#ch-nix-security": "installation/nix-security.html",
+ "#sec-obtaining-source": "installation/obtaining-source.html",
+ "#sec-prerequisites-source": "installation/prerequisites-source.html",
+ "#sec-single-user": "installation/single-user.html",
+ "#ch-supported-platforms": "installation/supported-platforms.html",
+ "#ch-upgrading-nix": "installation/upgrading.html",
+ "#ch-about-nix": "introduction.html",
+ "#chap-introduction": "introduction.html",
+ "#ch-basic-package-mgmt": "package-management/basic-package-mgmt.html",
+ "#ssec-binary-cache-substituter": "package-management/binary-cache-substituter.html",
+ "#sec-channels": "package-management/channels.html",
+ "#ssec-copy-closure": "package-management/copy-closure.html",
+ "#sec-garbage-collection": "package-management/garbage-collection.html",
+ "#ssec-gc-roots": "package-management/garbage-collector-roots.html",
+ "#chap-package-management": "package-management/package-management.html",
+ "#sec-profiles": "package-management/profiles.html",
+ "#ssec-s3-substituter": "package-management/s3-substituter.html",
+ "#ssec-s3-substituter-anonymous-reads": "package-management/s3-substituter.html#anonymous-reads-to-your-s3-compatible-binary-cache",
+ "#ssec-s3-substituter-authenticated-reads": "package-management/s3-substituter.html#authenticated-reads-to-your-s3-binary-cache",
+ "#ssec-s3-substituter-authenticated-writes": "package-management/s3-substituter.html#authenticated-writes-to-your-s3-compatible-binary-cache",
+ "#sec-sharing-packages": "package-management/sharing-packages.html",
+ "#ssec-ssh-substituter": "package-management/ssh-substituter.html",
+ "#chap-quick-start": "quick-start.html",
+ "#sec-relnotes": "release-notes/release-notes.html",
+ "#ch-relnotes-0.10.1": "release-notes/rl-0.10.1.html",
+ "#ch-relnotes-0.10": "release-notes/rl-0.10.html",
+ "#ssec-relnotes-0.11": "release-notes/rl-0.11.html",
+ "#ssec-relnotes-0.12": "release-notes/rl-0.12.html",
+ "#ssec-relnotes-0.13": "release-notes/rl-0.13.html",
+ "#ssec-relnotes-0.14": "release-notes/rl-0.14.html",
+ "#ssec-relnotes-0.15": "release-notes/rl-0.15.html",
+ "#ssec-relnotes-0.16": "release-notes/rl-0.16.html",
+ "#ch-relnotes-0.5": "release-notes/rl-0.5.html",
+ "#ch-relnotes-0.6": "release-notes/rl-0.6.html",
+ "#ch-relnotes-0.7": "release-notes/rl-0.7.html",
+ "#ch-relnotes-0.8.1": "release-notes/rl-0.8.1.html",
+ "#ch-relnotes-0.8": "release-notes/rl-0.8.html",
+ "#ch-relnotes-0.9.1": "release-notes/rl-0.9.1.html",
+ "#ch-relnotes-0.9.2": "release-notes/rl-0.9.2.html",
+ "#ch-relnotes-0.9": "release-notes/rl-0.9.html",
+ "#ssec-relnotes-1.0": "release-notes/rl-1.0.html",
+ "#ssec-relnotes-1.1": "release-notes/rl-1.1.html",
+ "#ssec-relnotes-1.10": "release-notes/rl-1.10.html",
+ "#ssec-relnotes-1.11.10": "release-notes/rl-1.11.10.html",
+ "#ssec-relnotes-1.11": "release-notes/rl-1.11.html",
+ "#ssec-relnotes-1.2": "release-notes/rl-1.2.html",
+ "#ssec-relnotes-1.3": "release-notes/rl-1.3.html",
+ "#ssec-relnotes-1.4": "release-notes/rl-1.4.html",
+ "#ssec-relnotes-1.5.1": "release-notes/rl-1.5.1.html",
+ "#ssec-relnotes-1.5.2": "release-notes/rl-1.5.2.html",
+ "#ssec-relnotes-1.5": "release-notes/rl-1.5.html",
+ "#ssec-relnotes-1.6.1": "release-notes/rl-1.6.1.html",
+ "#ssec-relnotes-1.6.0": "release-notes/rl-1.6.html",
+ "#ssec-relnotes-1.7": "release-notes/rl-1.7.html",
+ "#ssec-relnotes-1.8": "release-notes/rl-1.8.html",
+ "#ssec-relnotes-1.9": "release-notes/rl-1.9.html",
+ "#ssec-relnotes-2.0": "release-notes/rl-2.0.html",
+ "#ssec-relnotes-2.1": "release-notes/rl-2.1.html",
+ "#ssec-relnotes-2.2": "release-notes/rl-2.2.html",
+ "#ssec-relnotes-2.3": "release-notes/rl-2.3.html"
+};
+
+var isRoot = (document.location.pathname.endsWith('/') || document.location.pathname.endsWith('/index.html')) && path_to_root === '';
+if (isRoot && redirects[document.location.hash]) {
+ document.location.href = path_to_root + redirects[document.location.hash];
+}
From b36d5172cb2cd99f8ae5262b3e3536cceac76b50 Mon Sep 17 00:00:00 2001
From: Sergei Trofimovich <slyich@gmail.com>
Date: Thu, 26 May 2022 18:36:10 +0100
Subject: [PATCH 178/188] src/libutil/json.cc: add missing <cstdint> include
for gcc-13
Without the change llvm build fails on this week's gcc-13 snapshot as:
src/libutil/json.cc: In function 'void nix::toJSON(std::ostream&, const char*, const char*)':
src/libutil/json.cc:33:22: error: 'uint16_t' was not declared in this scope
33 | put(hex[(uint16_t(*i) >> 12) & 0xf]);
| ^~~~~~~~
src/libutil/json.cc:5:1: note: 'uint16_t' is defined in header '<cstdint>'; did you forget to '#include <cstdint>'?
4 | #include <cstring>
+++ |+#include <cstdint>
5 |
---
src/libutil/json.cc | 1 +
1 file changed, 1 insertion(+)
diff --git a/src/libutil/json.cc b/src/libutil/json.cc
index 3a981376f..b0a5d7e75 100644
--- a/src/libutil/json.cc
+++ b/src/libutil/json.cc
@@ -1,6 +1,7 @@
#include "json.hh"
#include <iomanip>
+#include <cstdint>
#include <cstring>
namespace nix {
From ec07a70979a86cc436de7e46e03789b4606d25ab Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Fri, 27 May 2022 11:25:05 +0200
Subject: [PATCH 179/188] Style fix
---
src/libexpr/primops.cc | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index aab6919d4..eea274301 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -3514,7 +3514,7 @@ void prim_match(EvalState & state, const PosIdx pos, Value * * args, Value & v)
(v.listElems()[i] = state.allocValue())->mkString(match[i + 1].str());
}
- } catch (std::regex_error &e) {
+ } catch (std::regex_error & e) {
if (e.code() == std::regex_constants::error_space) {
// limit is _GLIBCXX_REGEX_STATE_LIMIT for libstdc++
state.debugThrowLastTrace(EvalError({
@@ -3618,7 +3618,7 @@ void prim_split(EvalState & state, const PosIdx pos, Value * * args, Value & v)
assert(idx == 2 * len + 1);
- } catch (std::regex_error &e) {
+ } catch (std::regex_error & e) {
if (e.code() == std::regex_constants::error_space) {
// limit is _GLIBCXX_REGEX_STATE_LIMIT for libstdc++
state.debugThrowLastTrace(EvalError({
From 027fd45230b74c67e65d06e7073c04b62c60eb4e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophane=20Hufschmitt?=
<theophane.hufschmitt@tweag.io>
Date: Fri, 27 May 2022 16:15:28 +0200
Subject: [PATCH 180/188] Fix a segfault in the git fetcher
The git fetcher code used to dereference the (potentially empty) `ref`
input attribute. This was magically working, probably because the
compiler somehow outsmarted us, but is now blowing up with newer nixpkgs
versions.
Fix that by not trying to access this field while we don't know for sure
that it has been defined.
Fix #6554
---
src/libfetchers/git.cc | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/src/libfetchers/git.cc b/src/libfetchers/git.cc
index a71bff76f..9cbd39247 100644
--- a/src/libfetchers/git.cc
+++ b/src/libfetchers/git.cc
@@ -449,11 +449,10 @@ struct GitInputScheme : InputScheme
}
}
- const Attrs unlockedAttrs({
+ Attrs unlockedAttrs({
{"type", cacheType},
{"name", name},
{"url", actualUrl},
- {"ref", *input.getRef()},
});
Path repoDir;
@@ -466,6 +465,7 @@ struct GitInputScheme : InputScheme
head = "master";
}
input.attrs.insert_or_assign("ref", *head);
+ unlockedAttrs.insert_or_assign("ref", *head);
}
if (!input.getRev())
@@ -482,6 +482,7 @@ struct GitInputScheme : InputScheme
head = "master";
}
input.attrs.insert_or_assign("ref", *head);
+ unlockedAttrs.insert_or_assign("ref", *head);
}
if (auto res = getCache()->lookup(store, unlockedAttrs)) {
From 8e8e9d8705a68e1be63d6d8059c6c07127826525 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Mon, 30 May 2022 11:32:37 +0200
Subject: [PATCH 181/188] Respect the outputSpecified attribute
E.g. 'nix build nixpkgs#libxml2.dev' will build the 'dev' output.
---
doc/manual/src/release-notes/rl-next.md | 3 --
src/libcmd/installables.cc | 9 +++++-
src/libexpr/eval.cc | 1 +
src/libexpr/eval.hh | 3 +-
src/libexpr/get-drvs.cc | 37 +++++++++++++++++--------
5 files changed, 36 insertions(+), 17 deletions(-)
diff --git a/doc/manual/src/release-notes/rl-next.md b/doc/manual/src/release-notes/rl-next.md
index 878916dc9..7151751dd 100644
--- a/doc/manual/src/release-notes/rl-next.md
+++ b/doc/manual/src/release-notes/rl-next.md
@@ -22,9 +22,6 @@
`meta.outputsToInstall` attribute if it exists, or all outputs
otherwise.
- Selecting derivation outputs using the attribute selection syntax
- (e.g. `nixpkgs#glibc.dev`) no longer works.
-
* Running nix with the new `--debugger` flag will cause it to start a repl session if
there is an exception thrown during eval, or if `builtins.break` is called. From
there one can inspect symbol values and evaluate nix expressions. In debug mode
diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index 635ce19b6..21db2b08b 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -623,7 +623,14 @@ std::tuple<std::string, FlakeRef, InstallableValue::DerivationInfo> InstallableF
std::set<std::string> outputsToInstall;
std::optional<NixInt> priority;
- if (auto aMeta = attr->maybeGetAttr(state->sMeta)) {
+ if (auto aOutputSpecified = attr->maybeGetAttr(state->sOutputSpecified)) {
+ if (aOutputSpecified->getBool()) {
+ if (auto aOutputName = attr->maybeGetAttr("outputName"))
+ outputsToInstall = { aOutputName->getString() };
+ }
+ }
+
+ else if (auto aMeta = attr->maybeGetAttr(state->sMeta)) {
if (auto aOutputsToInstall = aMeta->maybeGetAttr("outputsToInstall"))
for (auto & s : aOutputsToInstall->getListOfStrings())
outputsToInstall.insert(s);
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 18baf1cb7..40462afdf 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -459,6 +459,7 @@ EvalState::EvalState(
, sKey(symbols.create("key"))
, sPath(symbols.create("path"))
, sPrefix(symbols.create("prefix"))
+ , sOutputSpecified(symbols.create("outputSpecified"))
, repair(NoRepair)
, emptyBindings(0)
, store(store)
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 0a32d5885..7b8732169 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -103,7 +103,8 @@ public:
sOutputHash, sOutputHashAlgo, sOutputHashMode,
sRecurseForDerivations,
sDescription, sSelf, sEpsilon, sStartSet, sOperator, sKey, sPath,
- sPrefix;
+ sPrefix,
+ sOutputSpecified;
Symbol sDerivationNix;
/* If set, force copying files to the Nix store even if they
diff --git a/src/libexpr/get-drvs.cc b/src/libexpr/get-drvs.cc
index d616b3921..346741dd5 100644
--- a/src/libexpr/get-drvs.cc
+++ b/src/libexpr/get-drvs.cc
@@ -132,23 +132,36 @@ DrvInfo::Outputs DrvInfo::queryOutputs(bool withPaths, bool onlyOutputsToInstall
} else
outputs.emplace("out", withPaths ? std::optional{queryOutPath()} : std::nullopt);
}
+
if (!onlyOutputsToInstall || !attrs)
return outputs;
- /* Check for `meta.outputsToInstall` and return `outputs` reduced to that. */
- const Value * outTI = queryMeta("outputsToInstall");
- if (!outTI) return outputs;
- const auto errMsg = Error("this derivation has bad 'meta.outputsToInstall'");
- /* ^ this shows during `nix-env -i` right under the bad derivation */
- if (!outTI->isList()) throw errMsg;
- Outputs result;
- for (auto elem : outTI->listItems()) {
- if (elem->type() != nString) throw errMsg;
- auto out = outputs.find(elem->string.s);
- if (out == outputs.end()) throw errMsg;
+ Bindings::iterator i;
+ if (attrs && (i = attrs->find(state->sOutputSpecified)) != attrs->end() && state->forceBool(*i->value, i->pos)) {
+ Outputs result;
+ auto out = outputs.find(queryOutputName());
+ if (out == outputs.end())
+ throw Error("derivation does not have output '%s'", queryOutputName());
result.insert(*out);
+ return result;
+ }
+
+ else {
+ /* Check for `meta.outputsToInstall` and return `outputs` reduced to that. */
+ const Value * outTI = queryMeta("outputsToInstall");
+ if (!outTI) return outputs;
+ const auto errMsg = Error("this derivation has bad 'meta.outputsToInstall'");
+ /* ^ this shows during `nix-env -i` right under the bad derivation */
+ if (!outTI->isList()) throw errMsg;
+ Outputs result;
+ for (auto elem : outTI->listItems()) {
+ if (elem->type() != nString) throw errMsg;
+ auto out = outputs.find(elem->string.s);
+ if (out == outputs.end()) throw errMsg;
+ result.insert(*out);
+ }
+ return result;
}
- return result;
}
From b8faa837429cbcb4f950248571c761c98895e7cd Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Mon, 30 May 2022 13:24:04 +0200
Subject: [PATCH 182/188] HttpBinaryCacheStore::getFile(): Don't throw an
exception
This violates the noexcept specification.
Fixes #6445.
---
src/libstore/http-binary-cache-store.cc | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/src/libstore/http-binary-cache-store.cc b/src/libstore/http-binary-cache-store.cc
index 3cb5efdbf..73bcd6e81 100644
--- a/src/libstore/http-binary-cache-store.cc
+++ b/src/libstore/http-binary-cache-store.cc
@@ -161,7 +161,12 @@ protected:
void getFile(const std::string & path,
Callback<std::optional<std::string>> callback) noexcept override
{
- checkEnabled();
+ try {
+ checkEnabled();
+ } catch (...) {
+ callback.rethrow();
+ return;
+ }
auto request(makeRequest(path));
From 6378f0bb328437de759f7ed8405fcafbb3bcac54 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Mon, 30 May 2022 13:27:13 +0200
Subject: [PATCH 183/188] RemoteStore::queryRealisationUncached(): Fix
potential noexcept violation
---
src/libstore/remote-store.cc | 56 +++++++++++++++++-------------------
1 file changed, 27 insertions(+), 29 deletions(-)
diff --git a/src/libstore/remote-store.cc b/src/libstore/remote-store.cc
index 14aeba75c..bc36aef5d 100644
--- a/src/libstore/remote-store.cc
+++ b/src/libstore/remote-store.cc
@@ -718,36 +718,34 @@ void RemoteStore::registerDrvOutput(const Realisation & info)
void RemoteStore::queryRealisationUncached(const DrvOutput & id,
Callback<std::shared_ptr<const Realisation>> callback) noexcept
{
- auto conn(getConnection());
-
- if (GET_PROTOCOL_MINOR(conn->daemonVersion) < 27) {
- warn("the daemon is too old to support content-addressed derivations, please upgrade it to 2.4");
- try {
- callback(nullptr);
- } catch (...) { return callback.rethrow(); }
- }
-
- conn->to << wopQueryRealisation;
- conn->to << id.to_string();
- conn.processStderr();
-
- auto real = [&]() -> std::shared_ptr<const Realisation> {
- if (GET_PROTOCOL_MINOR(conn->daemonVersion) < 31) {
- auto outPaths = worker_proto::read(
- *this, conn->from, Phantom<std::set<StorePath>> {});
- if (outPaths.empty())
- return nullptr;
- return std::make_shared<const Realisation>(Realisation { .id = id, .outPath = *outPaths.begin() });
- } else {
- auto realisations = worker_proto::read(
- *this, conn->from, Phantom<std::set<Realisation>> {});
- if (realisations.empty())
- return nullptr;
- return std::make_shared<const Realisation>(*realisations.begin());
- }
- }();
-
try {
+ auto conn(getConnection());
+
+ if (GET_PROTOCOL_MINOR(conn->daemonVersion) < 27) {
+ warn("the daemon is too old to support content-addressed derivations, please upgrade it to 2.4");
+ return callback(nullptr);
+ }
+
+ conn->to << wopQueryRealisation;
+ conn->to << id.to_string();
+ conn.processStderr();
+
+ auto real = [&]() -> std::shared_ptr<const Realisation> {
+ if (GET_PROTOCOL_MINOR(conn->daemonVersion) < 31) {
+ auto outPaths = worker_proto::read(
+ *this, conn->from, Phantom<std::set<StorePath>> {});
+ if (outPaths.empty())
+ return nullptr;
+ return std::make_shared<const Realisation>(Realisation { .id = id, .outPath = *outPaths.begin() });
+ } else {
+ auto realisations = worker_proto::read(
+ *this, conn->from, Phantom<std::set<Realisation>> {});
+ if (realisations.empty())
+ return nullptr;
+ return std::make_shared<const Realisation>(*realisations.begin());
+ }
+ }();
+
callback(std::shared_ptr<const Realisation>(real));
} catch (...) { return callback.rethrow(); }
}
From 948515efb775c22df5a2585443a0c7f86d2dc64d Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Mon, 30 May 2022 13:35:28 +0200
Subject: [PATCH 184/188] Set meta.platforms
'nix-serve' in nixpkgs expects the nix package to set this.
---
flake.nix | 1 +
1 file changed, 1 insertion(+)
diff --git a/flake.nix b/flake.nix
index 77b016ff0..6e0e4d423 100644
--- a/flake.nix
+++ b/flake.nix
@@ -380,6 +380,7 @@
postUnpack = "sourceRoot=$sourceRoot/perl";
};
+ meta.platforms = systems;
};
lowdown-nix = with final; currentStdenv.mkDerivation rec {
From 452dba510de2f500eae35bbb9dfb5ff825ca0351 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Mon, 30 May 2022 14:01:35 +0200
Subject: [PATCH 185/188] Mark nix-perl as a Perl module
The call to perl.withPackages in nix-serve expects this.
---
flake.nix | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/flake.nix b/flake.nix
index 6e0e4d423..1aa4c4479 100644
--- a/flake.nix
+++ b/flake.nix
@@ -348,7 +348,7 @@
strictDeps = true;
- passthru.perl-bindings = with final; currentStdenv.mkDerivation {
+ passthru.perl-bindings = with final; perl.pkgs.toPerlModule (currentStdenv.mkDerivation {
name = "nix-perl-${version}";
src = self;
@@ -378,7 +378,7 @@
enableParallelBuilding = true;
postUnpack = "sourceRoot=$sourceRoot/perl";
- };
+ });
meta.platforms = systems;
};
From de13b445730e94a24690fed6480f86a5f9c102c8 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Mon, 30 May 2022 20:39:38 +0200
Subject: [PATCH 186/188] Branch 2.9 release notes
---
doc/manual/src/SUMMARY.md.in | 1 +
doc/manual/src/release-notes/rl-2.9.md | 47 +++++++++++++++++++++++++
doc/manual/src/release-notes/rl-next.md | 38 --------------------
3 files changed, 48 insertions(+), 38 deletions(-)
create mode 100644 doc/manual/src/release-notes/rl-2.9.md
diff --git a/doc/manual/src/SUMMARY.md.in b/doc/manual/src/SUMMARY.md.in
index 860222337..825a8b4c0 100644
--- a/doc/manual/src/SUMMARY.md.in
+++ b/doc/manual/src/SUMMARY.md.in
@@ -72,6 +72,7 @@
- [CLI guideline](contributing/cli-guideline.md)
- [Release Notes](release-notes/release-notes.md)
- [Release X.Y (202?-??-??)](release-notes/rl-next.md)
+ - [Release 2.9 (2022-05-30)](release-notes/rl-2.9.md)
- [Release 2.8 (2022-04-19)](release-notes/rl-2.8.md)
- [Release 2.7 (2022-03-07)](release-notes/rl-2.7.md)
- [Release 2.6 (2022-01-24)](release-notes/rl-2.6.md)
diff --git a/doc/manual/src/release-notes/rl-2.9.md b/doc/manual/src/release-notes/rl-2.9.md
new file mode 100644
index 000000000..ab4b9e42f
--- /dev/null
+++ b/doc/manual/src/release-notes/rl-2.9.md
@@ -0,0 +1,47 @@
+# Release 2.9 (2022-05-30)
+
+* Running Nix with the new `--debugger` flag will cause it to start a
+ repl session if if an exception is thrown during evaluation, or if
+ `builtins.break` is called. From there you can inspect the values
+ of variables and evaluate Nix expressions. In debug mode, the
+ following new repl commands are available:
+
+ ```
+ :env Show env stack
+ :bt Show trace stack
+ :st Show current trace
+ :st <idx> Change to another trace in the stack
+ :c Go until end of program, exception, or builtins.break().
+ :s Go one step
+ ```
+
+ Read more about the debugger
+ [here](https://www.zknotes.com/note/5970).
+
+* Nix now provides better integration with zsh's `run-help`
+ feature. It is now included in the Nix installation in the form of
+ an autoloadable shell function, `run-help-nix`. It picks up Nix
+ subcommands from the currently typed in command and directs the user
+ to the associated man pages.
+
+* `nix repl` has a new build-and-link (`:bl`) command that builds a
+ derivation while creating GC root symlinks.
+
+* The path produced by `builtins.toFile` is now allowed to be imported
+ or read even with restricted evaluation. Note that this will not
+ work with a read-only store.
+
+* `nix build` has a new `--print-out-paths` flag to print the
+ resulting output paths. This matches the default behaviour of
+ `nix-build`.
+
+* You can now specify which outputs of a derivation `nix` should
+ operate on using the syntax `installable^outputs`,
+ e.g. `nixpkgs#glibc^dev,static` or `nixpkgs#glibc^*`. By default,
+ `nix` will use the outputs specified by the derivation's
+ `meta.outputsToInstall` attribute if it exists, or all outputs
+ otherwise.
+
+* `builtins.fetchTree` (and flake inputs) can now be used to fetch
+ plain files over the `http(s)` and `file` protocols in addition to
+ directory tarballs.
diff --git a/doc/manual/src/release-notes/rl-next.md b/doc/manual/src/release-notes/rl-next.md
index 7151751dd..c869b5e2f 100644
--- a/doc/manual/src/release-notes/rl-next.md
+++ b/doc/manual/src/release-notes/rl-next.md
@@ -1,39 +1 @@
# Release X.Y (202?-??-??)
-
-* Nix now provides better integration with zsh's run-help feature. It is now
- included in the Nix installation in the form of an autoloadable shell
- function, run-help-nix. It picks up Nix subcommands from the currently typed
- in command and directs the user to the associated man pages.
-
-* `nix repl` has a new build-'n-link (`:bl`) command that builds a derivation
- while creating GC root symlinks.
-
-* The path produced by `builtins.toFile` is now allowed to be imported or read
- even with restricted evaluation. Note that this will not work with a
- read-only store.
-
-* `nix build` has a new `--print-out-paths` flag to print the resulting output paths.
- This matches the default behaviour of `nix-build`.
-
-* You can now specify which outputs of a derivation `nix` should
- operate on using the syntax `installable^outputs`,
- e.g. `nixpkgs#glibc^dev,static` or `nixpkgs#glibc^*`. By default,
- `nix` will use the outputs specified by the derivation's
- `meta.outputsToInstall` attribute if it exists, or all outputs
- otherwise.
-
-* Running nix with the new `--debugger` flag will cause it to start a repl session if
- there is an exception thrown during eval, or if `builtins.break` is called. From
- there one can inspect symbol values and evaluate nix expressions. In debug mode
- the following new repl commands are available:
- ```
- :env Show env stack
- :bt Show trace stack
- :st Show current trace
- :st <idx> Change to another trace in the stack
- :c Go until end of program, exception, or builtins.break().
- :s Go one step
- ```
-
-* `builtins.fetchTree` (and flake inputs) can now be used to fetch plain files
- over the `http(s)` and `file` protocols in addition to directory tarballs.
From 929ab5b195cb063f7f38e7d6aceb262aaabbeee0 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Mon, 30 May 2022 21:11:20 +0200
Subject: [PATCH 187/188] Bump version
---
.version | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/.version b/.version
index f3ac133c5..f161b5d80 100644
--- a/.version
+++ b/.version
@@ -1 +1 @@
-2.9.0
\ No newline at end of file
+2.10.0
\ No newline at end of file
From 04a699b8a9cebd83ece0011ec3a99e38a2adc3a8 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Tue, 31 May 2022 10:37:51 +0200
Subject: [PATCH 188/188] Typo
---
doc/manual/src/release-notes/rl-2.9.md | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/doc/manual/src/release-notes/rl-2.9.md b/doc/manual/src/release-notes/rl-2.9.md
index ab4b9e42f..98cc4235d 100644
--- a/doc/manual/src/release-notes/rl-2.9.md
+++ b/doc/manual/src/release-notes/rl-2.9.md
@@ -1,7 +1,7 @@
# Release 2.9 (2022-05-30)
* Running Nix with the new `--debugger` flag will cause it to start a
- repl session if if an exception is thrown during evaluation, or if
+ repl session if an exception is thrown during evaluation, or if
`builtins.break` is called. From there you can inspect the values
of variables and evaluate Nix expressions. In debug mode, the
following new repl commands are available: