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<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>
<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>--command</option> <replaceable>cmd</replaceable></arg>
<arg><option>--exclude</option> <replaceable>regexp</replaceable></arg>
<arg><option>--pure</option></arg>
<arg><replaceable>path</replaceable></arg>
</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>
</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 '<nixpkgs>' -A pan
$ unpackPhase
$ cd pan-*
$ configurePhase
$ buildPhase
$ ./pan/gui/pan
</screen>
To clear the environment first, and do some additional automatic
initialisation of the interactive shell:
<screen>
$ nix-shell '<nixpkgs>' -A pan --pure \
--command 'export NIX_DEBUG=1; export NIX_CORES=8; return'
</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>
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