58 lines
1.6 KiB
XML
58 lines
1.6 KiB
XML
|
<chapter xmlns="http://docbook.org/ns/docbook"
|
||
|
|
xmlns:xlink="http://www.w3.org/1999/xlink"
|
||
|
|
xml:id="chap-functions">
|
||
|
|
|
||
|
|
<title>Functions reference</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
The nixpkgs repository has several utility functions to manipulate Nix expressions.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<section xml:id="sec-pkgs-overridePackages">
|
||
|
|
<title>pkgs.overridePackages</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
This function inside the nixpkgs expression (<varname>pkgs</varname>)
|
||
|
|
can be used to override the set of packages itself.
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
Warning: this function is expensive and must not be used from within
|
||
|
|
the nixpkgs repository.
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
Example usage:
|
||
|
|
|
||
|
|
<programlisting>let
|
||
|
|
pkgs = import <nixpkgs> {};
|
||
|
|
newpkgs = pkgs.overridePackages (self: super: {
|
||
|
|
foo = super.foo.override { ... };
|
||
|
|
};
|
||
|
|
in ...</programlisting>
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
The resulting <varname>newpkgs</varname> will have the new <varname>foo</varname>
|
||
|
|
expression, and all other expressions depending on <varname>foo</varname> will also
|
||
|
|
use the new <varname>foo</varname> expression.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
The behavior of this function is similar to <link
|
||
|
|
linkend="sec-modify-via-packageOverrides">config.packageOverrides</link>.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
The <varname>self</varname> parameter refers to the final package set with the
|
||
|
|
applied overrides. Using this parameter may lead to infinite recursion if not
|
||
|
|
used consciously.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
The <varname>super</varname> parameter refers to the old package set.
|
||
|
|
It's equivalent to <varname>pkgs</varname> in the above example.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
</section>
|
||
|
|
|
||
|
|
</chapter>
|