path: root/doc/manual/nix-shell.xml

<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-shell">

<refmeta>
  <refentrytitle>nix-shell</refentrytitle>
  <manvolnum>1</manvolnum>
  <refmiscinfo class="source">Nix</refmiscinfo>
  <refmiscinfo class="version"><xi:include href="version.txt" parse="text"/></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>--exclude</option> <replaceable>regexp</replaceable></arg>
    <arg><option>--pure</option></arg>
    <group choice='req'>
      <group choice='plain'>
        <group>
          <arg choice='plain'><option>--packages</option></arg>
          <arg choice='plain'><option>-p</option></arg>
        </group>
        <replaceable>packages</replaceable>
      </group>
      <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 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> instead of starting
    an interactive shell.  However, if you end the shell command with
    <literal>return</literal>, you still get an interactive shell.
    This can be useful for doing any additional
    initialisation.</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></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>

</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>

<para>To build the dependencies of the package Pan, and start an
interactive shell in which to build it:

<screen>
$ nix-shell '&lt;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 '&lt;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.  For instance,
the following starts a shell containing the packages
<literal>sqlite</literal> and <literal>libX11</literal>:

<screen>
$ nix-shell -E 'with import &lt;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>

</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>