* Documented --attr / -A.

This commit is contained in:
Eelco Dolstra 2006-10-05 20:07:41 +00:00
parent 5d769de8a3
commit 8396b59286
5 changed files with 60 additions and 6 deletions

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@ -11,6 +11,13 @@
<command>nix-build</command>
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="opt-common-syn.xml#xpointer(/nop/*)" />
<arg><option>--arg</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>--add-drv-link</option></arg>
<arg><option>--drv-link </option><replaceable>drvlink</replaceable></arg>
<arg><option>--no-out-link</option></arg>

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@ -11,6 +11,13 @@
<command>nix-env</command>
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="opt-common-syn.xml#xpointer(/nop/*)" />
<arg><option>--arg</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>
<group choice='req'>
<arg choice='plain'><option>--file</option></arg>
@ -252,7 +259,7 @@ number of possible ways:
</refsection>
<refsection><title>Examples</title>
<refsection xml:id='refsec-nix-env-install-examples'><title>Examples</title>
<para>To install a specific version of <command>gcc</command> from the
active Nix expression:

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@ -11,6 +11,13 @@
<command>nix-instantiate</command>
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="opt-common-syn.xml#xpointer(/nop/*)" />
<arg><option>--arg</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>--add-root</option> <replaceable>path</replaceable></arg>
<arg><option>--indirect</option></arg>
<group choice='opt'>

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@ -224,8 +224,8 @@
<command>nix-build</command>. When evaluating Nix expressions, the
expression evaluator will automatically try to call functions that
it encounters. It can automatically call functions for which every
argument has a default value (e.g.,
<literal>{<replaceable>argName</replaceable> ?
argument has a <link linkend='ss-functions'>default value</link>
(e.g., <literal>{<replaceable>argName</replaceable> ?
<replaceable>defaultValue</replaceable>}:
<replaceable>...</replaceable></literal>). With
<option>--arg</option>, you can also call functions that have
@ -257,6 +257,32 @@
</varlistentry>
<varlistentry xml:id="opt-attr"><term><option>--attr</option> / <option>-A</option>
<replaceable>attrPath</replaceable></term>
<listitem><para>In <command>nix-env</command>,
<command>nix-instantiate</command> and <command>nix-build</command>,
<option>--attr</option> allows you to select an attribute from the
top-level Nix expression being evaluated. The <emphasis>attribute
path</emphasis> <replaceable>attrPath</replaceable> is a sequence of
attribute names separated by dots. For instance, given a top-level
Nix expression <replaceable>e</replaceable>, the attribute path
<literal>xorg.xorgserver</literal> would cause the expression
<literal><replaceable>e</replaceable>.xorg.xorgserver</literal> to
be used. See <link
linkend='refsec-nix-env-install-examples'><command>nix-env
--install</command></link> for some concrete examples.</para>
<para>In addition to attribute names, you can also specify array
indices. For instance, the attribute path
<literal>foo.3.bar</literal> selects the <literal>bar</literal>
attribute of the fourth element of the array in the
<literal>foo</literal> attribute of the top-level
expression.</para></listitem>
</varlistentry>
</variablelist>

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@ -428,7 +428,14 @@ lrwxrwxrwx ... 2006-09-29 10:43 result -> /nix/store/632d2b22514d...-hello-2.1.1
$ ./result/bin/hello
Hello, world!</screen>
</para>
The <link linkend='opt-attr'><option>-A</option></link> option selects
the <literal>hello</literal> attribute from
<filename>all-packages.nix</filename>. This is faster than using the
symbolic package name specified by the <literal>name</literal>
attribute (which also happens to be <literal>hello</literal>) and is
unambiguous (there can be multiple packages with the symbolic name
<literal>hello</literal>, but there can be only one attribute in a set
named <literal>hello</literal>).</para>
<para><command>nix-build</command> registers the
<filename>./result</filename> symlink as a garbage collection root, so
@ -470,8 +477,8 @@ So it is always safe to run multiple instances of Nix in parallel
<para>If you have a system with multiple CPUs, you may want to have
Nix build different derivations in parallel (insofar as possible).
Just pass the option <option linkend='opt-max-jobs'>-j
<replaceable>N</replaceable></option>, where
Just pass the option <link linkend='opt-max-jobs'><option>-j
<replaceable>N</replaceable></option></link>, where
<replaceable>N</replaceable> is the maximum number of jobs to be run
in parallel, or set. Typically this should be the number of
CPUs.</para>