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.
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.