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Shell command: pkg-config

pkg-config provides information about installed libraries/packages in the system and is useful in combination with compiling C/C++ files(?) and linking the resulting object files.
This information is stored in files with a .pc file suffix. These files are typically found under 
$ pkg-config --cflags sqlite3
$ pkg-config --libs   sqlite3

.pc file format

Example taken from man pkg-config: 
prefix=/home/hp/unst                     # This defines a variable (Query on command line with pkg-config --variable=prefix)
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

See also

The Linux kernel Makefile sets the variable HOSTPKG_CONFIG to the value pkg-config.
gtk-config, gnome-config
Perl seems to install pkg-config.pl under /usr/local/bin. The header of this Perl script says that the script is a «lightweight no-dependency version of pkg-config». The script simply invokes package.
Shell commands

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