#rev 2020-09-10 bonaccos


= PKG-CONFIG =

== Using pkg-config to set variables ==

When compiling software from source you might need to set variables such as `CFLAGS` or `LDFLAGS`. Here the `pkg-config` command comes handy. Nevertheless, `pkg-config` only works with libraries supporting `pkg-config`, meaning that there is a '''/pkgconfig''' sub-directory in the library directory with a corresponding `*.pc` file. If that is the case you can easily set these variables by typing (bash):

{{{
export CFLAGS="`pkg-config --cflags PACKAGE-NAME`"
}}}
and

{{{
export LDLAGS="`pkg-config --libs PACKAGE-NAME`"
}}}

where '''PACKAGE-NAME''' is the package you need. However, by default `pkg-config` looks for '''*.pc''' files in system defined paths only. If you need `pkg-config` to search another path as well you may set the `PKG_CONFIG_PATH` variable accordingly. This variable contain paths leading to a directory containing `*.pc'` files. A package might come with a `pkg-config` directory containing the corresponding `*.pc` files. You may set multiple paths in the `PKG_CONFIG_PATH` variable using colon (`:`) as separator.

Here is an example setting two additional paths:

{{{
export PKG_CONFIG_PATH="path1-to-*.pc-files:path2-to-*.pc-files"
}}}

It is important to note that the `--libs` option sometimes only returns the link time directory, omitting the run time directory. Therefore, you might have to correct the `LDFLAGS` variable accordingly.

Remark: Paths contained in `PKG_CONFIG_PATH` are preferred over the default path by `pkg-config`. This means if a corresponding `*.pc` file is found in the `PKG_CONFIG_PATH` directories, a `*.pc` with the same name for instance in `/usr/lib/pkgconfig` will not be considered.

Here is an example:

{{{
export CFLAGS="`pkg-config --cflags gtk+-2.0`"
}}}

More details can be found in the [[https://manpages.debian.org/buster/pkgconf/pkg-config.1.en.html|pkg-config(1) manpage]].

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[[CategoryLXSW]]