Ubuntu: PKG_CONFIG_PATH environment variable

Ubuntu: PKG_CONFIG_PATH environment variable


Question: Consider adjusting the PKG_CONFIG_PATH environment variable if you installed
software in a non-standard prefix. What does this mean ?

Solutions Sample (Please watch the whole video to see all solutions, in order of how many people found them helpful):

== This solution helped 1 person ==
It means you're trying to build something from source, and it can't find all of
the dependencies it needs. The pkg-config script it uses to find the
development files for those libraries, outputs this message.

== This solution helped 32 people ==
To see where pkg-config (version 0.24 or later) searches for installed
libraries by default, use the following command:
pkg-config --variable pc_path pkg-config
To modify that path, set the PKG_CONFIG_PATH environment variable. The man file
states PKG_CONFIG_PATH is:
A colon-separated (on Windows, semicolon-separated) list of
directories to search for .pc files. The default directory will
always be searched after searching the path; the default is libdir/
pkgconfig:datadir/pkgconfig where libdir is the libdir where pkg-
config and datadir is the datadir where pkg-config was installed.

== This solution helped 36 people ==
The first answer is not technically explicit enough. From the man page (open a
terminal, type man pkg-config):
pkg-config retrieves information about packages from
special metadata files. These files are named after the
package, and has a .pc extension. On most systems, pkg-
config looks in /usr/lib/pkgconfig, /usr/share/pkgconfig, /
usr/local/lib/pkgconfig and /usr/local/share/pkgconfig for
these files. It will additionally look in the colon-
separated (on Windows, semicolon-separated) list of
directories specified by the PKG_CONFIG_PATH environment
variable.
So the pkg-config program is not in the PKG_CONFIG_PATH directory; however, if
you install a library, for the information to use it in an automake script to
be accessible it needs to be in a directory pkg-config is aware of.

== This solution helped 48 people ==
PKG_CONFIG_PATH is a environment variable that specifies additional paths in
which pkg-config will search for its .pc files.
This variable is used to augment pkg-config's default search path. On a typical
Unix system, it will search in the directories /usr/lib/pkgconfig and /usr/
share/pkgconfig. This will usually cover system installed modules. However,
some local modules may be installed in a different prefix such as /usr/local.
In that case, it's necessary to prepend the search path so that pkg-config can
locate the .pc files.
The pkg-config program is used to retrieve information about installed
libraries in the system. The primary use of pkg-config is to provide the
necessary details for compiling and linking a program to a library. This
metadata is stored in pkg-config files. These files have the suffix .pc and
reside in specific locations known to the pkg-config tool.
To check the PKG_CONFIG_PATH value use this command:
echo $PKG_CONFIG_PATH
To set the PKG_CONFIG_PATH value use:
export PKG_CONFIG_PATH=/usr/lib/pkgconfig
or
export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig

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