diff --git a/CHANGELOG.md b/CHANGELOG.md
index 843c398..6bac023 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## 0.1.0
 
+- Add a mandatory action argument to the CLI.  The existing diff functionality
+  is under the `diff` command.  A new `list` command is now implemented as well
+  (issue #5).
+
 - Optimized first level dependency calculation to read depenencies from
   `nix-store` rather than walking a directory tree manually (issue #4).  This
   also fixes nvd's support for things other than simple `buildEnv`s, e.g. file
diff --git a/src/nvd b/src/nvd
index 32a2726..d551bc7 100755
--- a/src/nvd
+++ b/src/nvd
@@ -19,6 +19,7 @@
 # See the nvd(1) man page for user-facing docs.
 
 # Package install state (by pname):
+# I: Installed (unchanged)
 # A: Added to closure
 # R: Removed from closure
 # U: Upgrade
@@ -36,6 +37,7 @@
 # R: Package manifest only available on the right; selected there.
 
 import argparse
+import fnmatch
 import os
 import os.path
 import re
@@ -46,24 +48,7 @@ from pathlib import Path
 from subprocess import PIPE
 from typing import Dict, List, Optional, Tuple, Union
 
-parser = argparse.ArgumentParser(
-    description="Nix/NixOS package version diff tool",
-    epilog="See the nvd(1) manual page for more information.",
-)
-parser.add_argument(
-    "--color",
-    default="auto",
-    help="Controls use of colour; one of 'auto', 'never', 'always'.")
-parser.add_argument(
-    "root1",
-    help="The first Nix store ptah to compare.")
-parser.add_argument(
-    "root2",
-    help="The second Nix store path to compare.")
-
-ARGS = parser.parse_args()
-
-USE_COLOUR = ARGS.color == "always" or (ARGS.color == "auto" and sys.stdout.isatty())
+USE_COLOUR = False
 
 SGR_RESET = 0
 SGR_BOLD = 1
@@ -85,6 +70,7 @@ def sgr(*args):
         return ""
     return "\x1b[" + ";".join(str(arg) for arg in args) + "m"
 
+INST_INSTALLED = "I"
 INST_ADDED = sgr(SGR_FG + SGR_BRIGHT + SGR_GREEN) + "A"
 INST_REMOVED = sgr(SGR_FG + SGR_BRIGHT + SGR_RED) + "R"
 INST_UPGRADED = sgr(SGR_FG + SGR_BRIGHT + SGR_CYAN) + "U"
@@ -257,6 +243,9 @@ class PackageManifest:
     def contains_pname(self, pname: str) -> bool:
         return pname in self._packages_by_pname
 
+    def all_pnames(self):
+        return self._packages_by_pname.keys()
+
 class PackageManifestPair:
     def __init__(
             self,
@@ -378,6 +367,10 @@ def print_package_list(
         "Expect either one versions map, or a fixed install state."
     have_single_version = right_versions_map is None
 
+    if not pnames:
+        print("No packages to display.")
+        return
+
     count = 1
     count_width = len(str(len(pnames)))
     count_format_str = "#{:0" + str(count_width) + "d}"
@@ -430,9 +423,51 @@ def print_package_list(
         ))
         count += 1
 
-def main():
-    left_path = Path(ARGS.root1)
-    right_path = Path(ARGS.root2)
+def run_list(*, root, only_selected, name_patterns):
+    path = Path(root)
+
+    if not path.exists():
+        sys.stderr.write(f"Path does not exist: {path}\n")
+        sys.exit(1)
+
+    path = path.resolve()
+    if (path / "sw").is_dir():
+        manifest = PackageManifest.parse_tree((path / "sw").resolve())
+    else:
+        manifest = PackageManifest.parse_tree(path / "sw")
+
+    closure_paths: List[str] = subprocess.run(
+        ["nix-store", "-qR", str(path)],
+        stdout=PIPE,
+        text=True,
+    ).stdout.rstrip("\n").split("\n")
+
+    closure_map: Dict[str, List[str]] = closure_paths_to_map(closure_paths)
+
+    if only_selected:
+        target_pnames = list(manifest.all_pnames())
+    else:
+        target_pnames = list(closure_map.keys())
+
+    target_pnames = [
+        pname
+        for pname in target_pnames
+        if all(fnmatch.fnmatch(pname, pattern) for pattern in name_patterns)
+    ]
+
+    target_pnames.sort()
+
+    print_package_list(
+        pnames=target_pnames,
+        manifest_pair=PackageManifestPair(manifest, manifest),
+        left_versions_map=closure_map,
+        right_versions_map=None,
+        fixed_install_state=INST_INSTALLED,
+    )
+
+def run_diff(*, root1, root2):
+    left_path = Path(root1)
+    right_path = Path(root2)
 
     if not left_path.exists():
         sys.stderr.write(f"Path does not exist: {left_path}\n")
@@ -547,6 +582,67 @@ def main():
         f"delta {right_only_paths_count - left_only_paths_count:+d})."
     )
 
+def parse_args():
+    parser = argparse.ArgumentParser(
+        description="Nix/NixOS package version diff tool",
+        epilog="See the nvd(1) manual page for more information.",
+    )
+
+    parser.add_argument(
+        "--color",
+        default="auto",
+        help="Controls use of colour; one of 'auto', 'never', 'always'.")
+
+    subparsers = parser.add_subparsers(dest="action")
+
+    diff_parser = subparsers.add_parser(
+        "diff",
+        help="Diff two Nix store paths and their closures.")
+    diff_parser.add_argument(
+        "root1",
+        help="The first Nix store path to compare.")
+    diff_parser.add_argument(
+        "root2",
+        help="The second Nix store path to compare.")
+
+    list_parser = subparsers.add_parser(
+        "list",
+        help="List packages in the closure of a Nix store path.")
+    list_parser.add_argument(
+        "-r", "--root",
+        default="/run/current-system",
+        help="The The Nix store path to work with.")
+    list_parser.add_argument(
+        "-s", "--selected",
+        dest="only_selected",
+        action="store_true",
+        help="Only show selected packages (direct dependencies).")
+    list_parser.add_argument(
+        nargs="*",
+        default=[],
+        dest="name_patterns",
+        help="Patterns (globs) that must all match package names.")
+
+    return parser.parse_args()
+
+def main():
+    global USE_COLOUR
+
+    args = parse_args()
+    action = args.action
+    USE_COLOUR = args.color == "always" or (args.color == "auto" and sys.stdout.isatty())
+    del args.action
+    del args.color
+
+    if action is None:
+        print("nvd: Subcommand required, see 'nvd --help'.")
+        sys.exit(1)
+
+    {
+        "list": run_list,
+        "diff": run_diff,
+    }[action](**vars(args))
+
 # Importing this module is kinda broken because of the constant initializations
 # at the top.
 if __name__ == "__main__":
diff --git a/src/nvd.1 b/src/nvd.1
index 0a921e2..8c68756 100644
--- a/src/nvd.1
+++ b/src/nvd.1
@@ -1,28 +1,52 @@
-.TH nvd 1 2021-04-09 nvd "User Commands"
+.TH nvd 1 2021-05-16 nvd "User Commands"
 .SH NAME
 nvd \- Nix/NixOS package version diff tool
 .SH SYNOPSIS
 .P
 .B nvd [ -h | --help ]
 .P
-.B nvd [ --color=(auto|always|never) ] root1 root2
+.B nvd [ --color=(auto|always|never) ] diff
+.I root1
+.I root2
+.P
+.B nvd [ --color=(auto|always|never) ] list
+.RS
+.B [ -r|--root
+.I store-path
+.B ]
+.br
+.B [ -s|--selected ]
+.br
+.B [
+.I name-pattern
+.B ]*
+.RE
 .SH DESCRIPTION
 .P
 .B nvd
-is a tool for diffing the versions of all store paths in the closures of two Nix
-store paths, neatly summarizing the differences.  This is mainly intended for
-comparing two system configurations and is inspired by the output of
+is a tool for working with Nix store paths and their closures, grouped by
+package name, with nice presentation for package versions.  This is mainly
+intended for listing installed packages and comparing two system configurations,
+and is inspired by the output of
 .B emerge -pv
 from Gentoo's Portage package manager.
 .B nvd
 could also be likened to the output of Debian's
+.B apt list -i
+and
 .B apt upgrade -V,
 or any equivalent from other distributions' package managers.
 .B nvd
 isn't limited to comparing system configurations though, and can work with any
 two store paths.
+.P The
+.B diff
+command compares the packages and package versions included in two closures.
+The
+.B list
+command displays the list of packages included in a closure, optionally filtered
+to some criteria.
 .P
-When given two system configurations,
 .B nvd
 distinguishes between packages that are explicitly included in
 .B environment.systemPackages,
@@ -88,14 +112,41 @@ detects whether stdout is a terminal and only uses colour if it is.  Passing
 forces colour to always be used, and passing
 .B never
 forces colour to never be used.
+.TP
+-r|--root <store-path>
+For the
+.B list
+command, this is the root store path to use, or a link to the store path to use.
+.TP
+-s|--selected
+For the
+.B list
+command, only print out selected packages (direct dependencies).
+.TP
+<name-pattern>
+For the
+.B list
+command, only print out names matching all of the given patterns.  The character
+.B ?
+matches exactly one of any character, and the character
+.B *
+matches zero or more of any character.
 .SH OUTPUT
 .P
-The output of
+If the
+.B diff
+command is requested, then the output of
 .B nvd
 displays the given names of the two store paths being compared on the first two
-lines, then changed packages on subsequent lines, one line per package, grouped
-by the type of change.  Newly added or removed packages, packages with version
-or count changes, and packages with selection state changes are displayed.  Hash changes are
+lines.  After this, for both the
+.B diff
+and
+.B list
+commands, package names, versions, and other information is printed out, with
+one line per package name, in lexicographic order.  When producing a diff,
+packages are grouped by the type of change: newly added or removed packages,
+packages with version or count changes, and packages with selection state
+changes.  Hash changes are
 .B not
 considered important, and will not cause a package to be displayed, however
 changes in the number of times a package
@@ -132,6 +183,7 @@ removed, upgraded or downgraded.  The possibilities here are:
 .P
 .RS
 .EX
+I: Installed (no change).
 A: Package is newly added to the closure.
 R: All versions of the package are being removed the closure.
 U: The package is being upgraded.
@@ -140,7 +192,15 @@ C: None of the above apply; unspecified changes.
 .EE
 .RE
 .P
-Packages can be displayed with
+The
+.B list
+command displays only the
+.B I
+state, and the
+.B diff
+command can display all states but the
+.B I
+state.  Packages can be displayed with
 .B C
 install state for a few different reasons, including the number of copies of an
 existing version in the closure changing, or due to the selection state changing
@@ -200,7 +260,7 @@ plus additional versions of some existing packages:
 .P
 .RS
 .EX
-$ nvd /nix/var/nix/profiles/system-{29,30}-link
+$ nvd diff /nix/var/nix/profiles/system-{29,30}-link
 <<< /nix/var/nix/profiles/system-29-link
 >>> /nix/var/nix/profiles/system-30-link
 Version changes:
@@ -232,7 +292,7 @@ have been installed.
 .P
 .RS
 .EX
-$ nvd /nix/var/nix/profiles/system-{33,34}-link
+$ nvd diff /nix/var/nix/profiles/system-{33,34}-link
 <<< /nix/var/nix/profiles/system/system-33-link
 >>> /nix/var/nix/profiles/system/system-34-link
 Version changes:
@@ -263,7 +323,7 @@ one, despite this actually being a newer commit than the old one:
 .P
 .RS
 .EX
-$ nvd /nix/var/nix/profiles/system-{43,44}-link
+$ nvd diff /nix/var/nix/profiles/system-{43,44}-link
 <<< /nix/var/nix/profiles/system/system-43-link
 >>> /nix/var/nix/profiles/system/system-44-link
 Version changes:
@@ -278,7 +338,7 @@ to output no packages at all if no versions have changed:
 .P
 .RS
 .EX
-$ nvd /nix/var/nix/profiles/system-{23,24}-link
+$ nvd diff /nix/var/nix/profiles/system-{23,24}-link
 <<< /nix/var/nix/profiles/system/system-23-link
 >>> /nix/var/nix/profiles/system/system-24-link
 No version or selection state changes.