<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"><xi:include href="../version.txt" parse="text"/></refmiscinfo>
</refmeta>

<refnamediv>
  <refname>nix-build</refname>
  <refpurpose>build a Nix expression</refpurpose>
</refnamediv>

<refsynopsisdiv>
  <cmdsynopsis>
    <command>nix-build</command>
    <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="opt-common-syn.xml#xmlns(db=http://docbook.org/ns/docbook)xpointer(/db:nop/*)" />
    <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">
  <xi:include href="opt-common.xml#xmlns(db=http://docbook.org/ns/docbook)xpointer(//db:variablelist[@xml:id='opt-common']/*)" />
</variablelist>

</refsection>


<refsection><title>Examples</title>

<screen>
$ nix-build '&lt;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 '&lt;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 '&lt;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 &lt;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>
  <xi:include href="env-common.xml#xmlns(db=http://docbook.org/ns/docbook)xpointer(//db:variablelist[@xml:id='env-common']/*)" />
</variablelist>

</refsection>


</refentry>
