223 lines
8.8 KiB
XML
223 lines
8.8 KiB
XML
<chapter xmlns="http://docbook.org/ns/docbook"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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xml:id="chap-quick-start">
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<title>Quick Start to Adding a Package</title>
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<para>To add a package to Nixpkgs:
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<orderedlist>
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<listitem>
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<para>Checkout the Nixpkgs source tree:
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<screen>
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$ git clone git://github.com/NixOS/nixpkgs.git
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$ cd nixpkgs</screen>
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</para>
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</listitem>
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<listitem>
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<para>Find a good place in the Nixpkgs tree to add the Nix
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expression for your package. For instance, a library package
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typically goes into
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<filename>pkgs/development/libraries/<replaceable>pkgname</replaceable></filename>,
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while a web browser goes into
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<filename>pkgs/applications/networking/browsers/<replaceable>pkgname</replaceable></filename>.
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See <xref linkend="sec-organisation" /> for some hints on the tree
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organisation. Create a directory for your package, e.g.
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<screen>
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$ mkdir pkgs/development/libraries/libfoo</screen>
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</para>
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</listitem>
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<listitem>
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<para>In the package directory, create a Nix expression — a piece
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of code that describes how to build the package. In this case, it
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should be a <emphasis>function</emphasis> that is called with the
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package dependencies as arguments, and returns a build of the
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package in the Nix store. The expression should usually be called
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<filename>default.nix</filename>.
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<screen>
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$ emacs pkgs/development/libraries/libfoo/default.nix
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$ git add pkgs/development/libraries/libfoo/default.nix</screen>
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</para>
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<para>You can have a look at the existing Nix expressions under
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<filename>pkgs/</filename> to see how it’s done. Here are some
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good ones:
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<itemizedlist>
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<listitem>
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<para>GNU cpio: <link
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xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/tools/archivers/cpio/default.nix"><filename>pkgs/tools/archivers/cpio/default.nix</filename></link>.
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The simplest possible package. The generic builder in
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<varname>stdenv</varname> does everything for you. It has
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no dependencies beyond <varname>stdenv</varname>.</para>
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</listitem>
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<listitem>
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<para>GNU Hello: <link
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xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/misc/hello/ex-2/default.nix"><filename>pkgs/applications/misc/hello/ex-2/default.nix</filename></link>.
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Also trivial, but it specifies some <varname>meta</varname>
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attributes which is good practice.</para>
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</listitem>
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<listitem>
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<para>GNU Multiple Precision arithmetic library (GMP): <link
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xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/libraries/gmp/5.1.x.nix"><filename>pkgs/development/libraries/gmp/5.1.x.nix</filename></link>.
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Also done by the generic builder, but has a dependency on
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<varname>m4</varname>.</para>
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</listitem>
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<listitem>
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<para>Pan, a GTK-based newsreader: <link
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xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/networking/newsreaders/pan/default.nix"><filename>pkgs/applications/networking/newsreaders/pan/default.nix</filename></link>.
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Has an optional dependency on <varname>gtkspell</varname>,
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which is only built if <varname>spellCheck</varname> is
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<literal>true</literal>.</para>
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</listitem>
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<listitem>
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<para>Apache HTTPD: <link
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xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/servers/http/apache-httpd/2.4.nix"><filename>pkgs/servers/http/apache-httpd/2.4.nix</filename></link>.
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A bunch of optional features, variable substitutions in the
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configure flags, a post-install hook, and miscellaneous
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hackery.</para>
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</listitem>
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<listitem>
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<para>Thunderbird: <link
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xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/networking/mailreaders/thunderbird/default.nix"><filename>pkgs/applications/networking/mailreaders/thunderbird/default.nix</filename></link>.
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Lots of dependencies.</para>
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</listitem>
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<listitem>
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<para>JDiskReport, a Java utility: <link
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xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/tools/misc/jdiskreport/default.nix"><filename>pkgs/tools/misc/jdiskreport/default.nix</filename></link>
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(and the <link
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xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/tools/misc/jdiskreport/builder.sh">builder</link>).
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Nixpkgs doesn’t have a decent <varname>stdenv</varname> for
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Java yet so this is pretty ad-hoc.</para>
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</listitem>
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<listitem>
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<para>XML::Simple, a Perl module: <link
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xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/top-level/perl-packages.nix"><filename>pkgs/top-level/perl-packages.nix</filename></link>
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(search for the <varname>XMLSimple</varname> attribute).
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Most Perl modules are so simple to build that they are
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defined directly in <filename>perl-packages.nix</filename>;
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no need to make a separate file for them.</para>
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</listitem>
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<listitem>
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<para>Adobe Reader: <link
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xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/misc/adobe-reader/default.nix"><filename>pkgs/applications/misc/adobe-reader/default.nix</filename></link>.
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Shows how binary-only packages can be supported. In
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particular the <link
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xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/misc/adobe-reader/builder.sh">builder</link>
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uses <command>patchelf</command> to set the RUNPATH and ELF
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interpreter of the executables so that the right libraries
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are found at runtime.</para>
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</listitem>
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</itemizedlist>
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</para>
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<para>Some notes:
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<itemizedlist>
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<listitem>
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<para>All <varname linkend="chap-meta">meta</varname>
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attributes are optional, but it’s still a good idea to
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provide at least the <varname>description</varname>,
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<varname>homepage</varname> and <varname
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linkend="sec-meta-license">license</varname>.</para>
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</listitem>
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<listitem>
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<para>You can use <command>nix-prefetch-url</command> (or similar nix-prefetch-git, etc)
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<replaceable>url</replaceable> to get the SHA-256 hash of
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source distributions. There are similar commands as <command>nix-prefetch-git</command> and
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<command>nix-prefetch-hg</command> available in <literal>nix-prefetch-scripts</literal> package.</para>
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</listitem>
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<listitem>
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<para>A list of schemes for <literal>mirror://</literal>
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URLs can be found in <link
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xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/build-support/fetchurl/mirrors.nix"><filename>pkgs/build-support/fetchurl/mirrors.nix</filename></link>.</para>
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</listitem>
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</itemizedlist>
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</para>
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<para>The exact syntax and semantics of the Nix expression
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language, including the built-in function, are described in the
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Nix manual in the <link
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xlink:href="http://hydra.nixos.org/job/nix/trunk/tarball/latest/download-by-type/doc/manual/#chap-writing-nix-expressions">chapter
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on writing Nix expressions</link>.</para>
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</listitem>
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<listitem>
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<para>Add a call to the function defined in the previous step to
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<link
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xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/top-level/all-packages.nix"><filename>pkgs/top-level/all-packages.nix</filename></link>
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with some descriptive name for the variable,
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e.g. <varname>libfoo</varname>.
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<screen>
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$ emacs pkgs/top-level/all-packages.nix</screen>
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</para>
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<para>The attributes in that file are sorted by category (like
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“Development / Libraries”) that more-or-less correspond to the
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directory structure of Nixpkgs, and then by attribute name.</para>
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</listitem>
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<listitem>
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<para>To test whether the package builds, run the following command
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from the root of the nixpkgs source tree:
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<screen>
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$ nix-build -A libfoo</screen>
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where <varname>libfoo</varname> should be the variable name
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defined in the previous step. You may want to add the flag
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<option>-K</option> to keep the temporary build directory in case
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something fails. If the build succeeds, a symlink
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<filename>./result</filename> to the package in the Nix store is
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created.</para>
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</listitem>
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<listitem>
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<para>If you want to install the package into your profile
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(optional), do
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<screen>
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$ nix-env -f . -iA libfoo</screen>
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</para>
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</listitem>
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<listitem>
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<para>Optionally commit the new package and open a pull request, or send a patch to
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<literal>nix-dev@cs.uu.nl</literal>.</para>
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</listitem>
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</orderedlist>
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</para>
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</chapter>
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