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").
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
.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.
--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:
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 contraints.
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:
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.
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 where libdir
is the libdir where pkg-config 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
WINDOWS SPECIALITIES
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.
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.
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
Requires: glib-2.0 = 1.3.1
Conflicts: foobar <= 4.5
Libs: -L${libdir} -lgobject-1.3
Cflags: -I${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
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.
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.