forked from mirrors/nixpkgs
220 lines
9 KiB
XML
220 lines
9 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>
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To add a package to Nixpkgs:
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<orderedlist>
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<listitem>
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<para>
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Checkout the Nixpkgs source tree:
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<screen>
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$ git clone https://github.com/NixOS/nixpkgs
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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>
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Find a good place in the Nixpkgs tree to add the Nix expression for your
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package. For instance, a library package 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>
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In the package directory, create a Nix expression — a piece of code that
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describes how to build the package. In this case, it should be a
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<emphasis>function</emphasis> that is called with the package dependencies
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as arguments, and returns a build of the package in the Nix store. The
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expression should usually be called <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>
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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 good
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ones:
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<itemizedlist>
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<listitem>
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<para>
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GNU Hello:
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<link
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xlink:href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/applications/misc/hello/default.nix"><filename>pkgs/applications/misc/hello/default.nix</filename></link>.
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Trivial package, which specifies some <varname>meta</varname>
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attributes which is good practice.
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</para>
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</listitem>
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<listitem>
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<para>
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GNU cpio:
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<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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Also a simple package. The generic builder in <varname>stdenv</varname>
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does everything for you. It has no dependencies beyond
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<varname>stdenv</varname>.
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</para>
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</listitem>
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<listitem>
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<para>
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GNU Multiple Precision arithmetic library (GMP):
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<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>.
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</para>
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</listitem>
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<listitem>
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<para>
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Pan, a GTK-based newsreader:
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<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>, which is
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only built if <varname>spellCheck</varname> is <literal>true</literal>.
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</para>
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</listitem>
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<listitem>
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<para>
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Apache HTTPD:
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<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 configure
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flags, a post-install hook, and miscellaneous hackery.
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</para>
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</listitem>
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<listitem>
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<para>
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Thunderbird:
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<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.
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</para>
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</listitem>
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<listitem>
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<para>
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JDiskReport, a Java utility:
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<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
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<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 Java yet
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so this is pretty ad-hoc.
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</para>
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</listitem>
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<listitem>
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<para>
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XML::Simple, a Perl module:
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<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). Most Perl
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modules are so simple to build that they are defined directly in
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<filename>perl-packages.nix</filename>; no need to make a separate file
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for them.
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</para>
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</listitem>
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<listitem>
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<para>
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Adobe Reader:
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<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 particular the
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<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 interpreter
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of the executables so that the right libraries are found at runtime.
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</para>
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</listitem>
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</itemizedlist>
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</para>
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<para>
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Some notes:
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<itemizedlist>
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<listitem>
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<para>
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All <varname linkend="chap-meta">meta</varname> attributes are
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optional, but it’s still a good idea to provide at least the
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<varname>description</varname>, <varname>homepage</varname> and
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<varname
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linkend="sec-meta-license">license</varname>.
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</para>
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</listitem>
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<listitem>
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<para>
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You can use <command>nix-prefetch-url</command>
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<replaceable>url</replaceable> to get the SHA-256 hash of source
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distributions. There are similar commands as
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<command>nix-prefetch-git</command> and
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<command>nix-prefetch-hg</command> available in
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<literal>nix-prefetch-scripts</literal> package.
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</para>
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</listitem>
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<listitem>
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<para>
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A list of schemes for <literal>mirror://</literal> URLs can be found in
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<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>.
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</para>
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</listitem>
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</itemizedlist>
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</para>
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<para>
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The exact syntax and semantics of the Nix expression language, including
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the built-in function, are described in the Nix manual in the
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<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>.
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</para>
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</listitem>
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<listitem>
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<para>
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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, e.g.
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<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>
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The attributes in that file are sorted by category (like “Development /
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Libraries”) that more-or-less correspond to the directory structure of
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Nixpkgs, and then by attribute name.
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</para>
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</listitem>
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<listitem>
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<para>
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To test whether the package builds, run the following command from the
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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 defined in the
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previous step. You may want to add the flag <option>-K</option> to keep
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the temporary build directory in case something fails. If the build
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succeeds, a symlink <filename>./result</filename> to the package in the
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Nix store is created.
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</para>
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</listitem>
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<listitem>
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<para>
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If you want to install the package into your profile (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>
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Optionally commit the new package and open a pull request, or send a patch
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to <literal>https://groups.google.com/forum/#!forum/nix-devel</literal>.
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</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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