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When compiling software from source you might need to set variables such as {{{$CFLAGS}}} or {{{$LDFLAGS}}}. Here the {{{pkg-config}}} command comes handy. You can easily set this variables by typing (tcsh): 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 dir with a corresponding {{{*.pc}}} file. If that is the case you can easily set these variables by typing (tcsh):
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> setenv CFLAGS `"pkg-config --cflags PACKAGE-NAME"` > setenv CFLAGS "`pkg-config --cflags PACKAGE-NAME`"
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> setenv LDLAGS `"pkg-config --libs PACKAGE-NAME"` > setenv LDLAGS "`pkg-config --libs PACKAGE-NAME`"
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where {{{PACKAGE-NAME}}} is the package you need. However, {{{pkg-config}}} looks for packages contained in the {{{$PATH}}} variable only. If you need {{{pkg-config}}} to search in a non default path you may set the {{{$PKG_CONFIG_PATH}}} variable accordingly. This variable must contain paths leading to a directory containing {{{*.pc}}} files. Very often a package comes with a {{{pkg-config}}} directory containing the corresponding {{{*.pc}}} files. You may set multiple paths in the {{{$PKG_CONFIG_PATH}}} variable using {{{:}}} as separator. where {{{PACKAGE-NAME}}} is the package you need. However, by default {{{pkg-config}}} looks for {{{*.pc}}} files contained in {{{/usr/lib/pkgconfig}}} only. If you need {{{pkg-config}}} to search another path as well you may set the {{{$PKG_CONFIG_PATH}}} variable accordingly. This variable must contain paths leading to a directory containing {{{*.pc}}} files. Very often a package comes with a {{{pkg-config}}} directory containing the corresponding {{{*.pc}}} files. You may set multiple paths in the {{{$PKG_CONFIG_PATH}}} variable using {{{:}}} as separator. Here is an example setting two additional paths:

{{{
> setenv PKG_CONFIG_PATH "path1-to-*.pc-files:path2-to-*.pc-files"
}}}
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Remark: Paths contained in {{{$PKG_CONFIG_PATH}}} are preferred over the default paths by {{{pkg-config}}}. Remark: Paths contained in {{{$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 in {{{/usr/lib/pkgconfig}}} will not be considered.
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type {{{man pkg-config}}} fore further information. type {{{man pkg-config}}} for further information.

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 dir with a corresponding *.pc file. If that is the case you can easily set these variables by typing (tcsh): 

> setenv CFLAGS "`pkg-config --cflags PACKAGE-NAME`"

and 

> setenv LDLAGS "`pkg-config --libs PACKAGE-NAME`"

where PACKAGE-NAME is the package you need. However, by default pkg-config looks for *.pc files contained in /usr/lib/pkgconfig only. If you need pkg-config to search another path as well you may set the $PKG_CONFIG_PATH variable accordingly. This variable must contain paths leading to a directory containing *.pc files. Very often a package comes with a pkg-config directory containing the corresponding *.pc files. You may set multiple paths in the $PKG_CONFIG_PATH variable using : as separator. Here is an example setting two additional paths: 

> setenv 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 in /usr/lib/pkgconfig will not be considered.

Here is an example (again in tcsh): 

> setenv CFLAGS `"pkg-config --cflags gtk+-2.0"`

type man pkg-config for further information.

Workstations/Linux/Applications/PKGConfig (last edited 2020-09-10 09:22:14 by bonaccos)