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=VARIABLE
NAME] [--define-variable=VARIABLENAME=VARIABLEVALUE]
[--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 spe
cial metadata files. These files are named after the pack
age, 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 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 dis
played. 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 unde
fined.
--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 problem to be printed.
With "predicate" options such as "--exists" pkg-
config runs silently by default, because it's usu
ally 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_CON
FIG_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 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 use
ful with options such as "--cflags" or "--modver
sion" 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 pro
grams:
--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", dupli
cate flags are merged (maintaining proper order
ing), and flags for dependencies are included in
the output.
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 vari
able "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 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 com
pilation/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 implic
itly 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 com
mand 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-con
fig, and optionally whether the version number of a
package meets certain contraints. If all packages
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.
ENVIRONMENT VARIABLES
PKG_CONFIG_PATH
A colon-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_build
dir which may appear in .pc files. If the environ
ment variable is not set, the default value
'$(top_builddir)' will be used. This variable
should refer to the top builddir of the Makefile
where the compile/link flags reported by pkg-config
will be used. This only matters when compil
ing/linking against a package that hasn't yet been
installed.
PKG_CONFIG_DISABLE_UNINSTALLED
Normally if you request the package "foo" and the
package "foo-uninstalled" exists, pkg-config will
prefer the "-uninstalled" variant. This allows com
pilation/linking against uninstalled packages. If
this environment variable is set, it disables said
behavior.
AUTOCONF MACROS
PKG_CHECK_MODULES(VARIABLEBASE,MODULELIST[,ACTION-IF-
FOUND,[ACTION-IF-NOT-FOUND]])
The macro PKG_CHECK_MODULES can be used in config
ure.in to check whether modules exist. A typical
usage would be:
This would result in MYSTUFF_LIBS and
MYSTUFF_CFLAGS substitution variables, set to the
libs and cflags for the given module list. If a
module is missing or has the wrong version, by
default configure will abort with a message. To
replace the default action, specify an ACTION-IF-
NOT-FOUND. PKG_CHECK_MODULES will not print any
error messages if you specify your own ACTION-IF-
NOT-FOUND. However, it will set the variable
MYSTUFF_PKG_ERRORS, which you can use to display
what went wrong.
METADATA FILE SYNTAX
To add a library to the set of packages pkg-config knows
about, simply install a .pc file. You should install this
file to libdir/pkgconfig.
Here is an example file:
# This is a comment
prefix=/home/hp/unst # this defines a variable
exec_prefix=${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 "$${".
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 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
checking.
Conflicts:
This optional line allows pkg-config to perform
additional sanity checks, primarily to detect bro
ken 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 men
tioned package. If a user tries to use your pack
age 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 Penning
ton. 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
program.
BUGS
Hah!
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