pkg-config - Return metainformation about installed libraries
pkg-config [--modversion] [--help] [--print-errors] [--silence-errors] [--cflags] [--libs] [--libs-only-L] [--libs-only-l] [--cflags-only-I] [--variable=VARIABLENAME] [--define-variable=VARIABLENAME=VARIABLEVALUE] [--uninstalled] [--exists] [--atleast-version=VERSION] [--exactversion=VERSION] [--max-version=VERSION] [LIBRARIES...]
The pkg-config program is used to retrieve information about installed libraries in the system. It is typically used to compile and link against one or more libraries. Here is a typical usage scenario in a Makefile:
program: program.c
cc program.c `pkg-config --cflags --libs gnomeui`
pkg-config retrieves information about packages from special metadata files. These files are named after the package, with the extension .pc. By default, pkg-config looks in the directory prefix/lib/pkgconfig for these files; it will also look in the colon-separated (on Windows, semicolon-separated) list of directories specified by the PKG_CONFIG_PATH environment variable.
The package name specified on the pkg-config command line is defined to be the name of the metadata file, minus the .pc extension. If a library can install multiple versions simultaneously, it must give each version its own name (for example, GTK 1.2 might have the package name “gtk+" while GTK 2.0 has “gtk+-2.0").
The following options are supported:
The following options are used to compile and link programs:
Rather than using the version-test options, you can simply give a version constraint after each package name, for example: $ pkg-config --exists ’glib-2.0 >= 1.3.4 libxml = 1.8.3’ Remember to use --print-errors if you want error messages.
If a .pc file is found in a directory that matches the usual conventions (i.e., ends with \lib\pkgconfig), the prefix for that package is assumed to be the grandparent of the directory where the file was found, and the prefix variable is overridden for that file accordingly.
In addition to the PKG_CONFIG_PATH environment variable, the Registry keys HKEY_CURRENT_USER\Software\pkgconfig\PKG_CONFIG_PATH and HKEY_LOCAL_MACHINE\Software\pkgconfig\PKG_CONFIG_PATH can be used to specify directories to search for .pc files. Each (string) value in these keys is treated as a directory where to look for .pc files.
The macro PKG_CHECK_MODULES can be used in configure.ac to check whether modules exist. A typical usage would be: PKG_CHECK_MODULES([MYSTUFF], [gtk+-2.0 >= 1.3.5 libxml = 1.8.4])
This would result in MYSTUFF_LIBS and MYSTUFF_CFLAGS substitution variables, set to the libs and cflags for the given module list. If a module is missing or has the wrong version, by default configure will abort with a message. To replace the default action, specify an ACTION-IF-NOT-FOUND. PKG_CHECK_MODULES will not print any error messages if you specify your own ACTION-IF-NOT-FOUND. However, it will set the variable MYSTUFF_PKG_ERRORS, which you can use to display what went wrong.
Note that if there is a possibility the first call to PKG_CHECK_MODULES might not happen, you should be sure to include an explicit call to PKG_PROG_PKG_CONFIG in your configure.ac
Defines the PKG_CONFIG variable to the best pkg-config available, useful if you need pkg-config but don't want to use PKG_CHECK_MODULES.
Check to see whether a particular set of modules exists. Similar to PKG_CHECK_MODULES(), but does not set variables or print errors.
Similar to PKG_CHECK_MODULES, make sure that the first instance of this or PKG_CHECK_MODULES is called, or make sure to call PKG_CHECK_EXISTS manually
To add a library to the set of packages pkg-config knows about, simply install a .pc file. You should install this file to libdir/pkgconfig.
Here is an example file:
# This is a comment
prefix=/home/hp/unst # this defines a variable
exec_prefix=${prefix} # defining another variable in terms of the
first
libdir=${exec_prefix}/lib
includedir=${prefix}/include
Name: GObject # human-readable name
Description: Object/type system for GLib # human-readable
description
Version: 1.3.1
URL: http://www.gtk.org
Requires: glib-2.0 = 1.3.1
Conflicts: foobar <= 4.5
Libs: -L${libdir} -lgobject-1.3
Libs.private: -lm
Cflags: -I${includedir}/glib-2.0 -I${libdir}/glib/include
You would normally generate the file using configure, of course, so that the prefix, etc. are set to the proper values.
Files have two kinds of line: keyword lines start with a keyword plus a colon, and variable definitions start with an alphanumeric string plus an equals sign. Keywords are defined in advance and have special meaning to pkg-config; variables do not, you can have any variables that you wish (however, users may expect to retrieve the usual directory name variables).
Note that variable references are written “${foo}"; you can escape literal “${” as “$${".
Name: This field should be a human-readable name for the package. Note that it is not the name passed as an argument to pkg-config.
Description: This should be a brief description of the package
URL: An URL where people can get more information about and download the package
Version: This should be the most-specific-possible package version string.
Requires: This is a comma-separated list of packages that are required by your package. Flags from dependent packages will be merged in to the flags reported for your package. Optionally, you can specify the version of the required package (using the operators =, <, >, >=, <=); specifying a version allows pkg-config to perform extra sanity checks. You may only mention the same package one time on the Requires: line. If the version of a package is unspecified, any version will be used with no checking.
Conflicts: This optional line allows pkg-config to perform additional sanity checks, primarily to detect broken user installations. The syntax is the same as Requires: except that you can list the same package more than once here, for example “foobar = 1.2.3, foobar = 1.2.5, foobar >= 1.3", if you have reason to do so. If a version isn’t specified, then your package conflicts with all versions of the mentioned package. If a user tries to use your package and a conflicting package at the same time, then pkg_config will complain.
Libs: This line should give the link flags specific to your package. Don’t add any flags for required packages; pkg-config will add those automatically.
Libs.private: This line should list any private libraries in use. Private libraries are libraries which are not exposed through your library, but are needed in the case of static linking.
Cflags: This line should list the compile flags specific to your package. Don’t add any flags for required packages; pkg-config will add those automatically.
pkg-config was written by James Henstridge, rewritten by Martijn van Beers, and rewritten again by Havoc Pennington. Tim Janik, Owen Taylor, and Raja Harinath submitted suggestions and some code. gnome-config was written by Miguel de Icaza, Raja Harinath and various hackers in the GNOME team. It was inspired by Owen Taylor's gtk-config program.
pkg-config does not handle mixing of parameters with and without well. Stick with one.