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Merge pull request #2945 from danidiaz/doc001

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Expanded documentation for .nix-defexpr
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Eelco Dolstra 2019-08-15 15:03:21 +02:00 committed by GitHub
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doc/manual/command-ref/nix-env.xml
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@ -221,31 +221,53 @@ also <xref linkend="sec-common-options" />.</phrase></para>
<varlistentry><term><filename>~/.nix-defexpr</filename></term>
<listitem><para>A directory that contains the default Nix
<listitem><para>The source for the default Nix
expressions used by the <option>--install</option>,
<option>--upgrade</option>, and <option>--query
--available</option> operations to obtain derivations. The
--available</option> operations to obtain derivations. The
<option>--file</option> option may be used to override this
default.</para>
<para>The Nix expressions in this directory are combined into a
single set, with each file as an attribute that has the name of
the file. Thus, if <filename>~/.nix-defexpr</filename> contains
two files, <filename>foo</filename> and <filename>bar</filename>,
<para>If <filename>~/.nix-defexpr</filename> is a file,
it is loaded as a Nix expression. If the expression
is a set, it is used as the default Nix expression.
If the expression is a function, an empty set is passed
as argument and the return value is used as
the default Nix expression.</para>
<para>If <filename>~/.nix-defexpr</filename> is a directory
containing a <filename>default.nix</filename> file, that file
is loaded as in the above paragraph.</para>
<para>If <filename>~/.nix-defexpr</filename> is a directory without
a <filename>default.nix</filename> file, then its contents
(both files and subdirectories) are loaded as Nix expressions.
The expressions are combined into a single set, each expression
under an attribute with the same name as the original file
or subdirectory.
</para>
<para>For example, if <filename>~/.nix-defexpr</filename> contains
two files, <filename>foo.nix</filename> and <filename>bar.nix</filename>,
then the default Nix expression will essentially be
<programlisting>
{
foo = import ~/.nix-defexpr/foo;
bar = import ~/.nix-defexpr/bar;
foo = import ~/.nix-defexpr/foo.nix;
bar = import ~/.nix-defexpr/bar.nix;
}</programlisting>
</para>
<para>The file <filename>manifest.nix</filename> is always ignored.
Subdirectories without a <filename>default.nix</filename> file
are traversed recursively in search of more Nix expressions,
but the names of these intermediate directories are not
added to the attribute paths of the default Nix expression.</para>
<para>The command <command>nix-channel</command> places symlinks
to the downloaded Nix expressions from each subscribed channel in
this directory.</para>
</listitem>
</varlistentry>