Provided by: pkg-config_0.26-1ubuntu4_amd64 
NAME
pkg-config - Return metainformation about installed libraries
SYNOPSIS
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] [--print-variables] [--uninstalled] [--exists] [--atleast-
version=VERSION] [--exact-version=VERSION] [--max-version=VERSION] [--list-all] [LIBRARIES...] [--print-
provides] [--print-requires] [--print-requires-private] [LIBRARIES...]
DESCRIPTION
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, 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.
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").
In addition to specifying a package name on the command line, the full path to a given .pc file may be
given instead. This allows a user to directly query a particular .pc file.
OPTIONS
The following options are supported:
--modversion
Requests that the version information of the libraries specified on the command line be displayed.
If pkg-config can find all the libraries on the command line, each library's version string is
printed to stdout, one version per line. In this case pkg-config exits successfully. If one or
more libraries is unknown, pkg-config exits with a nonzero code, and the contents of stdout are
undefined.
--help Displays a help message and terminates.
--print-errors
If one or more of the modules on the command line, or their dependencies, are not found, or if an
error occurs in parsing a .pc file, then this option will cause errors explaining the problem to
be printed. With "predicate" options such as "--exists" pkg-config runs silently by default,
because it's usually used in scripts that want to control what's output. This option can be used
alone (to just print errors encountered locating modules on the command line) or with other
options. The PKG_CONFIG_DEBUG_SPEW environment variable overrides this option.
--silence-errors
If one or more of the modules on the command line, or their dependencies, are not found, or if an
error occurs in parsing a a .pc file, then this option will keep errors explaining the problem
from being printed. With "predicate" options such as "--exists" pkg-config runs silently by
default, because it's usually used in scripts that want to control what's output. So this option
is only useful with options such as "--cflags" or "--modversion" that print errors by default. The
PKG_CONFIG_DEBUG_SPEW environment variable overrides this option.
--errors-to-stdout
If printing errors, print them to stdout rather than the default stderr
The following options are used to compile and link programs:
--cflags
This prints pre-processor and compile flags required to compile the packages on the command line,
including flags for all their dependencies. Flags are "compressed" so that each identical flag
appears only once. pkg-config exits with a nonzero code if it can't find metadata for one or more
of the packages on the command line.
--cflags-only-I
This prints the -I part of "--cflags". That is, it defines the header search path but doesn't
specify anything else.
--libs This option is identical to "--cflags", only it prints the link flags. As with "--cflags",
duplicate flags are merged (maintaining proper ordering), and flags for dependencies are included
in the output.
--libs-only-L
This prints the -L/-R part of "--libs". That is, it defines the library search path but doesn't
specify which libraries to link with.
--libs-only-l
This prints the -l part of "--libs" for the libraries specified on the command line. Note that the
union of "--libs-only-l" and "--libs-only-L" may be smaller than "--libs", due to flags such as
-rdynamic.
--variable=VARIABLENAME
This returns the value of a variable defined in a package's .pc file. Most packages define the
variable "prefix", for example, so you can say:
$ pkg-config --variable=prefix glib-2.0
/usr/
--define-variable=VARIABLENAME=VARIABLEVALUE
This sets a global value for a variable, overriding the value in any .pc files. Most packages
define the variable "prefix", for example, so you can say:
$ pkg-config --print-errors --define-variable=prefix=/foo \
--variable=prefix glib-2.0
/foo
--print-variables
Returns a list of all variables defined in the package.
--uninstalled
Normally if you request the package "foo" and the package "foo-uninstalled" exists, pkg-config
will prefer the "-uninstalled" variant. This allows compilation/linking against uninstalled
packages. If you specify the "--uninstalled" option, pkg-config will return successfully if any
"-uninstalled" packages are being used, and return failure (false) otherwise. (The
PKG_CONFIG_DISABLE_UNINSTALLED environment variable keeps pkg-config from implicitly choosing
"-uninstalled" packages, so if that variable is set, they will only have been used if you pass a
name like "foo-uninstalled" on the command line explicitly.)
--exists
--atleast-version=VERSION
--exact-version=VERSION
--max-version=VERSION
These options test whether the package or list of packages on the command line are known to pkg-
config, and optionally whether the version number of a package meets certain constraints. If all
packages exist and meet the specified version constraints, pkg-config exits successfully.
Otherwise it exits unsuccessfully.
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.
--msvc-syntax
This option is available only on Windows. It causes pkg-config to output -l and -L flags in the
form recognized by the Microsoft Visual C++ command-line compiler, cl. Specifically, instead of
-Lx:/some/path it prints /libpath:x/some/path, and instead of -lfoo it prints foo.lib. Note that
the --libs output consists of flags for the linker, and should be placed on the cl command line
after a /link switch.
--dont-define-prefix
This option is available only on Windows. It prevents pkg-config from automatically trying to
override the value of the variable "prefix" in each .pc file.
--prefix-variable=PREFIX
Also this option is available only on Windows. It sets the name of the variable that pkg-config
automatically sets as described above.
--static
Output libraries suitable for static linking. That means including any private libraries in the
output. This relies on proper tagging in the .pc files, else a too large number of libraries will
ordinarily be output.
--list-all
List all modules found in the pkg-config path.
-I "--print-provides"
List all modules the given packages provides.
--print-requires
List all modules the given packages requires.
--print-requires-private
List all modules the given packages requires for static linking (see --static).
ENVIRONMENT VARIABLES
PKG_CONFIG_PATH
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 for pkg-config and datadir is the
datadir for pkg-config when it was installed.
PKG_CONFIG_DEBUG_SPEW
If set, causes pkg-config to print all kinds of debugging information and report all errors.
PKG_CONFIG_TOP_BUILD_DIR
A value to set for the magic variable pc_top_builddir which may appear in .pc files. If the
environment variable is not set, the default value '$(top_builddir)' will be used. This variable
should refer to the top builddir of the Makefile where the compile/link flags reported by pkg-
config will be used. This only matters when compiling/linking against a package that hasn't yet
been installed.
PKG_CONFIG_DISABLE_UNINSTALLED
Normally if you request the package "foo" and the package "foo-uninstalled" exists, pkg-config
will prefer the "-uninstalled" variant. This allows compilation/linking against uninstalled
packages. If this environment variable is set, it disables said behavior.
PKG_CONFIG_ALLOW_SYSTEM_CFLAGS
Don't strip -I/usr/include out of cflags.
PKG_CONFIG_ALLOW_SYSTEM_LIBS
Don't strip -L/usr/lib out of libs
PKG_CONFIG_SYSROOT_DIR
Modify -I and -L to use the directories located in target sysroot. this option is useful when
cross-compiling packages that use pkg-config to determine CFLAGS and LDFLAGS. -I and -L are
modified to point to the new system root. this means that a -I/usr/include/libfoo will become
-I/var/target/usr/include/libfoo with a PKG_CONFIG_SYSROOT_DIR equal to /var/target (same rule
apply to -L)
PKG_CONFIG_LIBDIR
Replaces the default pkg-config search directory, usually /usr/lib/pkgconfig
QUERYING PKG-CONFIG'S DEFAULTS
pkg-config can be used to query itself for the default search path, version number and other information,
for instance using:
$ pkg-config --variable pc_path pkg-config
or
$ pkg-config --modversion pkg-config
WINDOWS SPECIALITIES
If a .pc file is found in a directory that matches the usual conventions (i.e., ends with \lib\pkgconfig
or \share\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.
If the value of a variable in a .pc file begins with the original, non-overridden, value of the prefix
variable, then the overridden value of prefix is used instead.
AUTOCONF MACROS
PKG_CHECK_MODULES(VARIABLE-PREFIX, MODULES [,ACTION-IF-FOUND [,ACTION-IF-NOT-FOUND]])
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.
PKG_PROG_PKG_CONFIG([MIN-VERSION])
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.
PKG_CHECK_EXISTS(MODULES, [ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])
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.
METADATA FILE SYNTAX
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, so that the prefix, etc. are set to the proper
values. The GNU Autoconf manual recommends generating files like .pc files at build time rather than
configure time, so when you build the .pc file is a matter of taste and preference.
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.
Requires.private:
A list of packages required by this package. The difference from Requires is that the packages
listed under Requires.private are not taken into account when a flag list is computed for
dynamically linked executable (i.e., when --static was not specified). In the situation where
each .pc file corresponds to a library, Requires.private shall be used exclusively to specify the
dependencies between the libraries.
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. This differs from
Requires.private in that it references libraries that do not have package files installed.
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.
AUTHOR
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.
BUGS
pkg-config does not handle mixing of parameters with and without = well. Stick with one.
Bugs can be reported at http://bugs.freedesktop.org/ under the pkg-config component.
pkg-config(1)