pkg-config
pkg-config(1) pkg-config(1)
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=VARIABLE-
VALUE] [--uninstalled] [--exists] [--atleast-version=VERSION]
[--exact-version=VERSION] [--max-version=VERSION] [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, with the extension
.pc. By default, pkg-config looks in the directory prefix/lib/pkgcon-
fig for these files; it will also look in the colon-separated (on Win-
dows, 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 speci-
fied 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_CON-
FIG_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 (main-
taining 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
--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 explic-
itly.)
--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 con-
traints. 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-con-
fig 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 com-
pile/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_LIBDIR
Replaces the default pkg-config search directory.
WINDOWS SPECIALITIES
If a .pc file is found in a directory that matches the usual conven-
tions (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 accord-
ingly.
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.
AUTOCONF MACROS
PKG_CHECK_MODULES(VARIABLEBASE,MODULELIST[,ACTION-IF-FOUND,[ACTION-IF-
NOT-FOUND]])
The macro PKG_CHECK_MODULES can be used in configure.in 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 substitu-
tion 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_MOD-
ULES 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.
If you want to use MYSTUFF_LIBS and MYSTUFF_CFLAGS as Make-
file.am variables (i.e. $(MYSTUFF_LIBS)) then you have to add
AC_SUBST(MYSTUFF_LIBS) to your configure.in so automake can
find the variable. You don’t need to do this if you use the
@MYSTUFF_LIBS@ syntax in your Makefile.am instead of
$(MYSTUFF_LIBS).
METADATA FILE SYNTAX
To add a library to the set of packages pkg-config knows about, simply
install a .pc file. You should install this file to libdir/pkgconfig.
Here is an example file:
# This is a comment
prefix=/home/hp/unst # this defines a variable
exec_prefix=${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${libdir}/glib/include
You would normally generate the file using configure, of course, so
that the prefix, etc. are set to the proper values.
Files have two kinds of line: keyword lines start with a keyword plus
a colon, and variable definitions start with an alphanumeric string
plus an equals sign. Keywords are defined in advance and have special
meaning to pkg-config; variables do not, you can have any variables
that you wish (however, users may expect to retrieve the usual direc-
tory name variables).
Note that variable references are written "${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-con-
fig.
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 opera-
tors =, <, >, >=, <=); 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 check-
ing.
Conflicts:
This optional line allows pkg-config to perform additional san-
ity 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 pack-
age. 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 Tay-
lor, and Raja Harinath submitted suggestions and some code. gnome-
config was written by Miguel de Icaza, Raja Harinath and various hack-
ers in the GNOME team. It was inspired by Owen Taylor’s gtk-config
program.
BUGS
Hah!
pkg-config(1)
