pkg-config(1) User Commands pkg-config(1)

NAME

pkg-config - Return metainformation about installed libraries

SYNOPSIS

pkg-config [--modversion] [--version] [--help] [--atleast-pkgconfig-
version=VERSION] [--print-errors] [--short-errors] [--silence-errors]
[--errors-to-stdout] [--debug] [--cflags] [--libs] [--libs-only-L]
[--libs-only-l] [--cflags-only-I] [--libs-only-other] [--cflags-only-
other] [--variable=VARIABLENAME] [--define-
variable=VARIABLENAME=VARIABLEVALUE] [--print-variables]
[--uninstalled] [--exists] [--atleast-version=VERSION] [--exact-
version=VERSION] [--max-version=VERSION] [--validate] [--list-all]
[--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.

--version
Displays the version of pkg-config and terminates.

--atleast-pkgconfig-version=VERSION
Requires at least the given version of pkg-config.

--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.

--short-errors
Print short error messages.

--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

--debug
Print debugging information. This is slightly different than
the PKG_CONFIG_DEBUG_SPEW environment variable, which also
enable "--print-errors".


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.

--cflags-only-other
This prints parts of "--cflags" not covered by "--cflags-only-
I".

--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.

--libs-only-other
This prints the parts of "--libs" not covered by "--libs-only-
L" and "--libs-only-l", such as "--pthread".

--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. Only the first VERSION comparing
option will be honored. Subsequent options of this type will
be ignored.

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.
When no output options are supplied to pkg-config, --exists is
implied.

--validate
Checks the syntax of a package's .pc file for validity. This
is the same as --exists except that dependencies are not
verified. This can be useful for package developers to test
their .pc file prior to release:
$ pkg-config --validate ./my-package.pc

--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.

--define-prefix
--dont-define-prefix
These options control whether pkg-config overrides the value
of the variable prefix in each .pc file. With --define-prefix,
pkg-config uses the installed location of the .pc file to
determine the prefix. --dont-define-prefix prevents this
behavior. The default is usually --define-prefix.

When this feature is enabled and a .pc file is found in a
directory named 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. This allows
the feature to work even when the variables have been expanded
in the .pc file.

--prefix-variable=PREFIX
Set the name of the variable that pkg-config overrides instead
of prefix when using the --define-prefix feature.

--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.

--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_SYSTEM_INCLUDE_PATH
A path variable containing system directories searched by the
compiler. This is normally /usr/include.

CPATH
C_INCLUDE_PATH
CPLUS_INCLUDE_PATH
Additional paths to append to PKG_CONFIG_SYSTEM_INCLUDE_PATH.
These correspond to environment variables used by many
compilers to affect the header search path. These are ignored
on Windows builds when --msvc-syntax is in use.

INCLUDE
Additional paths to append to PKG_CONFIG_SYSTEM_INCLUDE_PATH
on Windows builds when --msvc-syntax is in use. This
corresponds to the environment variable used by MSVC to add
directories to the include file search path.

PKG_CONFIG_ALLOW_SYSTEM_CFLAGS
Don't strip system paths out of Cflags. See
PKG_CONFIG_SYSTEM_INCLUDE_PATH for the definition of system
paths.

PKG_CONFIG_SYSTEM_LIBRARY_PATH
A path variable containing system directories searched by the
linker. This is normally /usr/lib:/lib but is dependent on
the pkg-config build and can contain other directories such as
/usr/lib64.

PKG_CONFIG_ALLOW_SYSTEM_LIBS
Don't strip system paths out of Libs. See
PKG_CONFIG_SYSTEM_LIBRARY_PATH for the definition of system
paths.

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:/usr/share/pkgconfig.

PKG_CONFIG_$PACKAGE_$VARIABLE
Overrides the variable VARIABLE in the package PACKAGE. The
environment variable should have the package name and package
variable upper cased with non-alphanumeric characters
converted to underscores. For example, setting
PKG_CONFIG_GLADEUI_2_0_CATALOGDIR will override the variable
"catalogdir" in the "gladeui-2.0" package.

PKG-CONFIG DERIVED VARIABLES
pkg-config sets a few metadata variables that can be used in .pc
files or queried at runtime.

pc_path
The default search path used by pkg-config when searching for
.pc files. This can be used in a query for the pkg-config
module itself itself:
$ pkg-config --variable pc_path pkg-config

pcfiledir
The installed location of the .pc file. This can be used to
query the location of the .pc file for a particular module,
but it can also be used to make .pc files relocatable. For
instance:
prefix=${pcfiledir}/../..
exec_prefix=${prefix}
libdir=${exec_prefix}/lib
includedir=${prefix}/include

pc_sysrootdir
The sysroot directory set by the user. When the sysroot
directory has not been set, this value is /. See the
PKG_CONFIG_SYSROOT_DIR environment variable for more details.

pc_top_builddir
Location of the user's top build directory when calling
pkg-config. This is useful to dynamically set paths in
uninstalled .pc files. See the PKG_CONFIG_TOP_BUILD_DIR
environment variable for more details.

WINDOWS SPECIALITIES

The pkg-config default search path is ignored on Windows. Instead,
the search path is constructed by using the installed directory of
pkg-config and then appending lib\pkgconfig and share\pkgconfig.
This can be augmented or replaced using the standard environment
variables described above.

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.

Also note that repeated usage of VARIABLE-PREFIX is not
recommended. After the first successful usage, subsequent
calls with the same VARIABLE-PREFIX will simply use the _LIBS
and _CFLAGS variables set from the previous usage without
calling pkg-config again.

PKG_PREREQ(MIN-VERSION)
Checks that the version of the pkg-config autoconf macros in
use is at least MIN-VERSION. This can be used to ensure a
particular pkg-config macro will be available.

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.

If the first call to PKG_PROG_PKG_CONFIG is conditional, then
it will not work correctly in all cases. Since many of the
other macros such as PKG_CHECK_MODULES require
PKG_PROG_PKG_CONFIG to know which pkg-config program to run,
PKG_PROG_PKG_CONFIG may be run for the first time from a
conditional from one of these macros. Therefore, if any of the
pkg-config macros will be used under a conditional, it's best
to run PKG_PROG_PKG_CONFIG before any of the other macros are
used.


PKG_CHECK_MODULES_STATIC(VARIABLE-PREFIX, MODULES [,ACTION-IF-FOUND
[,ACTION-IF-NOT-FOUND]])
Enables static linking through --static prior to calling
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_PROG_PKGCONFIG manually.


PKG_INSTALLDIR(DIRECTORY)

Substitutes the variable pkgconfigdir as the location where a
module should install pkg-config .pc files. By default the
directory is $libdir/pkgconfig, but the default can be changed
by passing DIRECTORY. The user can override through the
--with-pkgconfigdir parameter.

PKG_NOARCH_INSTALLDIR(DIRECTORY)

Substitutes the variable noarch_pkgconfigdir as the location
where a module should install arch-independent pkg-config .pc
files. By default the directory is $datadir/pkgconfig, but the
default can be changed by passing DIRECTORY. The user can
override through the --with-noarch-pkgconfigdir parameter.

PKG_CHECK_VAR(VARIABLE, MODULE, CONFIG-VARIABLE, [ACTION-IF-FOUND],
[ACTION-IF-NOT-FOUND])

Retrieves the value of the pkg-config variable CONFIG-VARIABLE
from MODULE and stores it in VARIABLE. Note that repeated
usage of VARIABLE is not recommended as the check will be
skipped if the variable is already set.

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)