# PaCkAgE DaTaStReAm pkg-config 1 340 # end of header 070701000a67e3000081a40000000000000000000000014f86462f000001210000010000010007ffffffffffffffff0000001300000000pkg-config/pkginfo PKG=pkg-config NAME=pkg-config 0.26 SPARC 64bit Solaris 10 VERSION=0.26 PSTAMP=12th April 2012 VENDOR=Tollef Fog Heen EMAIL=http://pkg-config.freedesktop.org/wiki/ DESC=pkg-config compiling helper tool ARCH=sparc CATEGORY=utility CLASSES=none BASEDIR=/ ISTATES=S s 1 2 3 RSTATES=S s 1 2 3 070701000a67e2000081a40000000000000000000000014f86462f000003140000010000010007ffffffffffffffff0000001200000000pkg-config/pkgmap : 1 340 1 d none /usr ? ? ? 1 d none /usr/local ? ? ? 1 d none /usr/local/bin 0755 root root 1 f none /usr/local/bin/pkg-config 0755 root root 106280 65180 1334199848 1 d none /usr/local/share 0755 root root 1 d none /usr/local/share/aclocal 0755 root root 1 f none /usr/local/share/aclocal/pkg.m4 0644 root root 5651 51820 1334199848 1 d none /usr/local/share/doc 0755 root root 1 d none /usr/local/share/doc/pkg-config 0755 root root 1 f none /usr/local/share/doc/pkg-config/pkg-config-guide.html 0644 root root 17635 18511 1334199848 1 d none /usr/local/share/man 0755 root root 1 d none /usr/local/share/man/man1 0755 root root 1 f none /usr/local/share/man/man1/pkg-config.1 0644 root root 17710 45869 1334199848 1 i checkinstall 785 2565 1334199855 1 i pkginfo 289 22817 1334199855 07070100000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000b00000000TRAILER!!! 070701000a67e3000081a40000000000000000000000014f86462f000001210000010000010007ffffffffffffffff0000000800000000pkginfo PKG=pkg-config NAME=pkg-config 0.26 SPARC 64bit Solaris 10 VERSION=0.26 PSTAMP=12th April 2012 VENDOR=Tollef Fog Heen EMAIL=http://pkg-config.freedesktop.org/wiki/ DESC=pkg-config compiling helper tool ARCH=sparc CATEGORY=utility CLASSES=none BASEDIR=/ ISTATES=S s 1 2 3 RSTATES=S s 1 2 3 070701000a67e2000081a40000000000000000000000014f86462f000003140000010000010007ffffffffffffffff0000000700000000pkgmap : 1 340 1 d none /usr ? ? ? 1 d none /usr/local ? ? ? 1 d none /usr/local/bin 0755 root root 1 f none /usr/local/bin/pkg-config 0755 root root 106280 65180 1334199848 1 d none /usr/local/share 0755 root root 1 d none /usr/local/share/aclocal 0755 root root 1 f none /usr/local/share/aclocal/pkg.m4 0644 root root 5651 51820 1334199848 1 d none /usr/local/share/doc 0755 root root 1 d none /usr/local/share/doc/pkg-config 0755 root root 1 f none /usr/local/share/doc/pkg-config/pkg-config-guide.html 0644 root root 17635 18511 1334199848 1 d none /usr/local/share/man 0755 root root 1 d none /usr/local/share/man/man1 0755 root root 1 f none /usr/local/share/man/man1/pkg-config.1 0644 root root 17710 45869 1334199848 1 i checkinstall 785 2565 1334199855 1 i pkginfo 289 22817 1334199855 070701000a67f2000041ed0000000000000000000000024f86462f000000000000010000010007ffffffffffffffff0000000800000000install 070701000a67f3000081ed0000000000000000000000014f86462f000003110000010000010007ffffffffffffffff0000001500000000install/checkinstall #!/bin/sh # expected_bits="64" expected_release="5.10" expected_platform="sparc" # release=`uname -r` platform=`uname -p` bits=`isainfo -b` # if [ ${platform} != ${expected_platform} ]; then echo "\n\n\n\tThis package must be installed on a ${expected_platform} architecture\n" echo "\tAborting installation.\n\n\n" exit 1 fi if [ ${release} != ${expected_release} ]; then echo "\n\n\n\tThis package must be installed on a ${expected_release} machine\n" echo "\tAborting installation.\n\n\n" exit 1 fi if [ ${bits} != ${expected_bits} ]; then echo "\n\n\n\tThis package must be installed on a ${expected_bits} bit machine\n" echo "\tYour machine is running a ${bits} bit O.S. currently\n" echo "\tAborting installation.\n\n\n" exit 1 fi exit 0 070701000a67e4000041ed0000000000000000000000034f86462f000000000000010000010007ffffffffffffffff0000000500000000root 070701000a67e5000041ed0000000000000000000000034f86462f000000000000010000010007ffffffffffffffff0000000900000000root/usr 070701000a67e6000041ed0000000000000000000000044f86462f000000000000010000010007ffffffffffffffff0000000f00000000root/usr/local 070701000a67e9000041ed0000000000000000000000054f86462f000000000000010000010007ffffffffffffffff0000001500000000root/usr/local/share 070701000a67ef000041ed0000000000000000000000034f86462f000000000000010000010007ffffffffffffffff0000001900000000root/usr/local/share/man 070701000a67f0000041ed0000000000000000000000024f86462f000000000000010000010007ffffffffffffffff0000001e00000000root/usr/local/share/man/man1 070701000a67f1000081a40000000000000000000000014f8646280000452e0000010000010007ffffffffffffffff0000002b00000000root/usr/local/share/man/man1/pkg-config.1 .\" .\" pkg-config manual page. .\" (C) Red Hat, Inc. based on gnome-config man page (C) Miguel de Icaza (miguel@gnu.org) .\" . .\" Macros to disable groff line adjustment warnings that we can't easily .\" fix in the text. .ie \n(.g \{\ . de DW . nr .oldwarn \n[.warn] . warn 0 . . . de EW . warn \n[.oldwarn] . . .\} .el \ .\{ \ . de DW . . . de EW . . .\} . .TH pkg-config 1 .SH NAME pkg-config \- Return metainformation about installed libraries .SH SYNOPSIS .PP .B 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...] .SH DESCRIPTION The \fIpkg-config\fP 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: .PP .nf program: program.c cc program.c $(pkg-config --cflags --libs gnomeui) .fi .PP .I pkg-config retrieves information about packages from special metadata files. These files are named after the package, and has a .I .pc extension. On most systems, \fIpkg-config\fP looks in .I /usr/lib/pkgconfig, /usr/share/pkgconfig, /usr/local/lib/pkgconfig and .I /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. .PP The package name specified on the \fIpkg-config\fP command line is defined to be the name of the metadata file, minus the \fI.pc\fP 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"). .PP In addition to specifying a package name on the command line, the full path to a given \fI.pc\fP file may be given instead. This allows a user to directly query a particular \fI.pc\fP file. .\" .SH OPTIONS The following options are supported: .TP .I "--modversion" Requests that the version information of the libraries specified on the command line be displayed. If \fIpkg-config\fP 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 \fIpkg-config\fP exits successfully. If one or more libraries is unknown, .I pkg-config exits with a nonzero code, and the contents of stdout are undefined. .TP .I "--help" Displays a help message and terminates. .TP .I "--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 \fI.pc\fP file, then this option will cause errors explaining the problem to be printed. With "predicate" options such as "--exists" .I "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. .TP .I "--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 \fI.pc\fP file, then this option will keep errors explaining the problem from being printed. With "predicate" options such as "--exists" \fIpkg-config\fP 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. .TP .I "--errors-to-stdout" If printing errors, print them to stdout rather than the default stderr .PP The following options are used to compile and link programs: .TP .I "--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. \fIpkg-config\fP exits with a nonzero code if it can't find metadata for one or more of the packages on the command line. .TP .I "--cflags-only-I" This prints the -I part of "--cflags". That is, it defines the header search path but doesn't specify anything else. .TP .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. .TP .I "--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. .TP .I "--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. .TP .I "--variable=VARIABLENAME" This returns the value of a variable defined in a package's \fI.pc\fP file. Most packages define the variable "prefix", for example, so you can say: .nf $ pkg-config --variable=prefix glib-2.0 /usr/ .fi .TP .I "--define-variable=VARIABLENAME=VARIABLEVALUE" This sets a global value for a variable, overriding the value in any .I .pc files. Most packages define the variable "prefix", for example, so you can say: .nf $ pkg-config --print-errors --define-variable=prefix=/foo \e --variable=prefix glib-2.0 /foo .fi .TP .I "--print-variables" Returns a list of all variables defined in the package. .TP .I "--uninstalled" Normally if you request the package "foo" and the package "foo-uninstalled" exists, \fIpkg-config\fP will prefer the "-uninstalled" variant. This allows compilation/linking against uninstalled packages. If you specify the "--uninstalled" option, .I 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 .I 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.) .TP .I "--exists" .TP .I "--atleast-version=VERSION" .TP .I "--exact-version=VERSION" .TP .I "--max-version=VERSION" These options test whether the package or list of packages on the command line are known to \fIpkg-config\fP, and optionally whether the version number of a package meets certain constraints. If all packages exist and meet the specified version constraints, .I 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: .nf $ pkg-config --exists 'glib-2.0 >= 1.3.4 libxml = 1.8.3' .fi Remember to use \-\-print-errors if you want error messages. .TP .I "--msvc-syntax" This option is available only on Windows. It causes \fIpkg-config\fP to output -l and -L flags in the form recognized by the Microsoft Visual C++ command-line compiler, \fIcl\fP. Specifically, instead of .I -Lx:/some/path it prints \fI/libpath:x/some/path\fP, and instead of \fI-lfoo\fP it prints \fIfoo.lib\fP. Note that the --libs output consists of flags for the linker, and should be placed on the cl command line after a /link switch. .TP .I "--dont-define-prefix" This option is available only on Windows. It prevents \fIpkg-config\fP from automatically trying to override the value of the variable "prefix" in each .pc file. .TP .I "--prefix-variable=PREFIX" Also this option is available only on Windows. It sets the name of the variable that \fIpkg-config\fP automatically sets as described above. .TP .I "--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. .TP .I "--list-all" List all modules found in the \fIpkg-config\fP path. .TP -I "--print-provides" List all modules the given packages provides. .TP .I "--print-requires" List all modules the given packages requires. .TP .I "--print-requires-private" List all modules the given packages requires for static linking (see --static). .\" .SH ENVIRONMENT VARIABLES .TP .I "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 .I \%libdir/\fPpkgconfig:\fIdatadir\fP/pkgconfig where \fIlibdir\fP is the libdir for \fIpkg-config\fP and \fIdatadir\fP is the datadir for \fIpkg-config\fP when it was installed. .TP .I "PKG_CONFIG_DEBUG_SPEW" If set, causes \fIpkg-config\fP to print all kinds of debugging information and report all errors. .TP .I "PKG_CONFIG_TOP_BUILD_DIR" A value to set for the magic variable \fIpc_top_builddir\fP which may appear in \fI.pc\fP 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 \fIpkg-config\fP will be used. This only matters when compiling/linking against a package that hasn't yet been installed. .TP .I "PKG_CONFIG_DISABLE_UNINSTALLED" Normally if you request the package "foo" and the package "foo-uninstalled" exists, \fIpkg-config\fP will prefer the "-uninstalled" variant. This allows compilation/linking against uninstalled packages. If this environment variable is set, it disables said behavior. .TP .I "PKG_CONFIG_ALLOW_SYSTEM_CFLAGS" Don't strip -I/usr/include out of cflags. .TP .I "PKG_CONFIG_ALLOW_SYSTEM_LIBS" Don't strip -L/usr/lib out of libs .TP .I "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) .TP .I "PKG_CONFIG_LIBDIR" Replaces the default \fIpkg-config\fP search directory, usually \fI/usr/lib/pkgconfig\fP .\" .SH QUERYING PKG-CONFIG'S DEFAULTS .I pkg-config\fP can be used to query itself for the default search path, version number and other information, for instance using: .nf $ pkg-config --variable pc_path pkg-config .fi or .nf $ pkg-config --modversion pkg-config .fi .SH 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 \fIprefix\fP 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 \fIprefix\fP variable, then the overridden value of \fIprefix\fP is used instead. .\" .SH AUTOCONF MACROS .TP .I "PKG_CHECK_MODULES(VARIABLE-PREFIX, MODULES [,ACTION-IF-FOUND [,ACTION-IF-NOT-FOUND]])" The macro PKG_CHECK_MODULES can be used in \fIconfigure.ac\fP to check whether modules exist. A typical usage would be: .nf PKG_CHECK_MODULES([MYSTUFF], [gtk+-2.0 >= 1.3.5 libxml = 1.8.4]) .fi 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. .\" .TP .I "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. .\" .TP .I "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. .SH METADATA FILE SYNTAX To add a library to the set of packages \fIpkg-config\fP knows about, simply install a \fI.pc\fP file. You should install this file to .I libdir\fP/pkgconfig. .PP Here is an example file: .nf # 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 .fi .PP 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. .PP 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 \fIpkg-config\fP; variables do not, you can have any variables that you wish (however, users may expect to retrieve the usual directory name variables). .PP Note that variable references are written "${foo}"; you can escape literal "${" as "$${". .TP .I "Name:" This field should be a human-readable name for the package. Note that it is not the name passed as an argument to \fIpkg-config\fP. .TP .I "Description:" This should be a brief description of the package .TP .I "URL:" An URL where people can get more information about and download the package .TP .I "Version:" This should be the most-specific-possible package version string. .TP .I "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 \fIpkg-config\fP to perform extra sanity checks. You may only mention the same package one time on the .I "Requires:" line. If the version of a package is unspecified, any version will be used with no checking. .TP .I Requires.private: A list of packages required by this package. The difference from .I Requires is that the packages listed under .I 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, .I Requires.private shall be used exclusively to specify the dependencies between the libraries. .TP .I "Conflicts:" This optional line allows \fIpkg-config\fP to perform additional sanity checks, primarily to detect broken user installations. The syntax is the same as .I "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 \fIpkg-config\fP will complain. .TP .I "Libs:" This line should give the link flags specific to your package. Don't add any flags for required packages; \fIpkg-config\fP will add those automatically. .TP .I "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 .I Requires.private in that it references libraries that do not have package files installed. .TP .I "Cflags:" This line should list the compile flags specific to your package. Don't add any flags for required packages; \fIpkg-config\fP will add those automatically. .\" .SH AUTHOR .I 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. .I gnome-config was written by Miguel de Icaza, Raja Harinath and various hackers in the GNOME team. It was inspired by Owen Taylor's \fIgtk-config\fP program. .\" .SH BUGS \fIpkg-config\fP does not handle mixing of parameters with and without = well. Stick with one. Bugs can be reported at http://bugs.freedesktop.org/ under the .I pkg-config component. 070701000a67ec000041ed0000000000000000000000034f86462f000000000000010000010007ffffffffffffffff0000001900000000root/usr/local/share/doc 070701000a67ed000041ed0000000000000000000000024f86462f000000000000010000010007ffffffffffffffff0000002400000000root/usr/local/share/doc/pkg-config 070701000a67ee000081a40000000000000000000000014f864628000044e30000010000010007ffffffffffffffff0000003a00000000root/usr/local/share/doc/pkg-config/pkg-config-guide.html
This document aims to give an overview to using the pkg-config tool from the perspective of both a user and a developer. It reviews the concepts behind pkg-config, how to write pkg-config files to support your project, and how to use pkg-config to integrate with 3rd party projects.
More information on pkg-config can be found at the website and in the pkg-config(1) manual page.
This document assumes usage of pkg-config on a Unix-like operating system such as Linux. Some of the details may be different on other platforms.
Modern computer systems use many layered components to provide applications to the user. One of the difficulties in assembling these parts is properly integrating them. pkg-config collects metadata about the installed libraries on the system and easily provides it to the user.
Without a metadata system such as pkg-config, it can be very difficult to locate and obtain details about the services provided on a given computer. For a developer, installing pkg-config files with your package greatly eases adoption of your API.
The primary use of pkg-config is to provide the necessary details for compiling and linking a program to a library. This metadata is stored in pkg-config files. These files have the suffix .pc and reside in specific locations known to the pkg-config tool. This will be described in more detail later.
The file format contains predefined metadata keywords and freeform variables. An example may be illustrative:
prefix=/usr/local
exec_prefix=${prefix}
includedir=${prefix}/include
libdir=${exec_prefix}/lib
Name: foo
Description: The foo library
Version: 1.0.0
Cflags: -I${includedir}/foo
Libs: -L${libdir} -lfoo
The keyword definitions such as Name: begin with a keyword followed by a colon and the value. The variables such as prefix= are a string and value separated by an equals sign. The keywords are defined and exported by pkg-config. The variables are not necessary, but can be used by the keyword definitions for flexibility or to store data not covered by pkg-config.
Here is a short description of the keyword fields. A more in depth description of these fields and how to use them effectively will be given in the Writing pkg-config files section.
When creating pkg-config files for a package, it is first necessary to decide how they will be distributed. Each file is best used to describe a single library, so each package should have at least as many pkg-config files as they do installed libraries.
The package name is determined through the filename of the pkg-config metadata file. This is the portion of the filename prior to the .pc suffix. A common choice is to match the library name to the .pc name. For instance, a package installing libfoo.so would have a corresponding libfoo.pc file containing the pkg-config metadata. This choice is not necessary; the .pc file should simply be a unique identifier for your library. Following the above example, foo.pc or foolib.pc would probably work just as well.
The Name, Description and URL fields are purely informational and should be easy to fill in. The Version field is a bit trickier to ensure that it is usable by consumers of the data. pkg-config uses the algorithm from RPM for version comparisons. This works best with a dotted decimal number such as 1.2.3 since letters can cause unexpected results. The number should be monotonically increasing and be as specific as possible in describing the library. Usually it's sufficient to use the package's version number here since it's easy for consumers to track.
Before describing the more useful fields, it will be helpful to demonstrate variable definitions. The most common usage is to define the installation paths so that they don't clutter the metadata fields. Since the variables are expanded recursively, this is very helpful when used in conjunction with autoconf derived paths.
prefix=/usr/local
includedir=${prefix}/include
Cflags: -I${includedir}/foo
The most important pkg-config metadata fields are Requires, Requires.private, Cflags, Libs and Libs.private. They will define the metadata used by external projects to compile and link with the library.
Requires and Requires.private define other modules needed by the library. It is usually preferred to use the private variant of Requires to avoid exposing unnecessary libraries to the program that is linking with your library. If the program will not be using the symbols of the required library, it should not be linking directly to that library. See the discussion of overlinking for a more thorough explanation.
Since pkg-config always exposes the link flags of the Requires libraries, these modules will become direct dependencies of the program. On the other hand, libraries from Requires.private will only be included when static linking. For this reason, it is usually only appropriate to add modules from the same package in Requires.
The Libs field contains the link flags necessary to use that library. In addition, Libs and Libs.private contain link flags for other libraries not supported by pkg-config. Similar to the Requires field, it is preferred to add link flags for external libraries to the Libs.private field so programs do not acquire an additional direct dependency.
Finally, the Cflags contains the compiler flags for using the library. Unlike the Libs field, there is not a private variant of Cflags. This is because the data types and macro definitions are needed regardless of the linking scenario.
Assuming that there are .pc files installed on the system, the pkg-config tool is used to extract the metadata for usage. A short description of the options can be seen by executing pkg-config --help. A more in depth discussion can be found in the pkg-config(1) manual page. This section will provide a brief explanation of common usages.
Consider a system with two modules, foo and bar. Their .pc files might look like this:
foo.pc:
prefix=/usr
exec_prefix=${prefix}
includedir=${prefix}/include
libdir=${exec_prefix}/lib
Name: foo
Description: The foo library
Version: 1.0.0
Cflags: -I${includedir}/foo
Libs: -L${libdir} -lfoo
bar.pc:
prefix=/usr
exec_prefix=${prefix}
includedir=${prefix}/include
libdir=${exec_prefix}/lib
Name: bar
Description: The bar library
Version: 2.1.2
Requires.private: foo >= 0.7
Cflags: -I${includedir}
Libs: -L${libdir} -lbar
The version of the modules can be obtained with the --modversion option.
$ pkg-config --modversion foo 1.0.0 $ pkg-config --modversion bar 2.1.2
To print the link flags needed for each module, use the --libs option.
$ pkg-config --libs foo -lfoo $ pkg-config --libs bar -lbar
Notice that pkg-config has suppressed part of the Libs field for both modules. This is because it treats the -L flag specially and knows that the ${libdir} directory /usr/lib is part of the system linker search path. This keeps pkg-config from interfering with the linker operation.
Also, although foo is required by bar, the link flags for foo are not output. This is because foo is not directly needed by an application that only wants to use the bar library. For statically linking a bar application, we need both sets of linker flags:
$ pkg-config --libs --static bar -lbar -lfoo
pkg-config needs to output both sets of link flags in this case to ensure that the statically linked application will find all the necessary symbols. On the other hand, it will always output all the Cflags.
$ pkg-config --cflags bar -I/usr/include/foo $ pkg-config --cflags --static bar -I/usr/include/foo
Another useful option, --exists, can be used to test for a module's availability.
$ pkg-config --exists foo $ echo $? 0
One of the nicest features of pkg-config is providing version checking. It can be used to determine if a sufficient version is available.
$ pkg-config --libs "bar >= 2.7" Requested 'bar >= 2.7' but version of bar is 2.1.2
Some commands will provide more verbose output when combined with the --print-errors option.
$ pkg-config --exists --print-errors xoxo Package xoxo was not found in the pkg-config search path. Perhaps you should add the directory containing `xoxo.pc' to the PKG_CONFIG_PATH environment variable No package 'xoxo' found
The message above references the PKG_CONFIG_PATH environment variable. This variable is used to augment pkg-config's search path. On a typical Unix system, it will search in the directories /usr/lib/pkgconfig and /usr/share/pkgconfig. This will usually cover system installed modules. However, some local modules may be installed in a different prefix such as /usr/local. In that case, it's necessary to prepend the search path so that pkg-config can locate the .pc files.
$ pkg-config --modversion hello Package hello was not found in the pkg-config search path. Perhaps you should add the directory containing `hello.pc' to the PKG_CONFIG_PATH environment variable No package 'hello' found $ export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig $ pkg-config --modversion hello 1.0.0
A few autoconf macros are also provided to ease integration of pkg-config modules into projects.
The pkg-config output can easily be used on the compiler command line. Assuming the x library has a x.pc pkg-config file:
cc `pkg-config --cflags --libs x` -o myapp myapp.c
The integration can be more robust when used with autoconf and automake. By using the supplied PKG_CHECK_MODULES macro, the metadata is easily accessed in the build process.
configure.ac: PKG_CHECK_MODULES([X], [x]) Makefile.am: myapp_CFLAGS = $(X_CFLAGS) myapp_LDADD = $(X_LIBS)
If the x module is found, the macro will fill and substitute the X_CFLAGS and X_LIBS variables. If the module is not found, an error will be produced. Optional 3rd and 4th arguments can be supplied to PKG_CHECK_MODULES to control actions when the module is found or not.
If the x library has pkg-config support, add it to the Requires.private field. If it does not, augment the Cflags field with the necessary compiler flags for using the libx headers. In either case, pkg-config will output the compiler flags when --static is used or not.
Again, add the module to Requires.private if it supports pkg-config. In this case, the compiler flags will be emitted unnecessarily, but it ensures that the linker flags will be present when linking statically. If libx does not support pkg-config, add the necessary linker flags to Libs.private.
Copyright (C) 2010 Dan Nicholson.
This document is licensed under the
GNU General Public License, Version 2
or any later version.