.\" Copyright (c) 2017 pkgconf authors (see AUTHORS).
.\"
.\" Permission to use, copy, modify, and/or distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" This software is provided 'as is' and without any warranty, express or
.\" implied.  In no event shall the authors be liable for any damages arising
.\" from the use of this software.
.Dd December 15, 2017
.Dt PC 5
.Os
.Sh NAME
.Nm file.pc
.Nd pkg-config file format
.Sh DESCRIPTION
pkg-config files provide a useful mechanism for storing various information
about libraries and packages on a given system.
Information stored by
.Nm .pc
files include compiler and linker flags necessary to use a given library, as
well as any other relevant metadata.
.Pp
These
.Nm .pc
files are processed by a utility called
.Nm pkg-config ,
of which
.Nm pkgconf
is an implementation.
.\"
.Ss FILE SYNTAX
The
.Nm .pc
file follows a format inspired by RFC822.
Comments are prefixed by a pound sign, hash sign or octothorpe (#), and variable
assignment is similar to POSIX shell.
Properties are defined using RFC822-style stanzas.
.\"
.Ss VARIABLES
.\"
Variable definitions start with an alphanumeric string, followed by an equal sign,
and then the value the variable should contain.
.Pp
Variable references are always written as "${variable}".
It is possible to escape literal "${" as "$${".
.\"
.Ss PROPERTIES
.\"
Properties are set using RFC822-style stanzas which consist of a keyword, followed
by a colon (:) and then the value the property should be set to.
Variable substitution is always performed regardless of property type.
.Pp
There are three types of property:
.\"
.Bl -tag -width indent
.\"
.It Literal
The property will be set to the text of the value.
.\"
.It Dependency List
The property will be set to a list of dependencies parsed from the
text.
Dependency lists are defined by this ABNF syntax:
.Bd -literal
package-list = *WSP *( package-spec *( package-sep ) )
package-sep  = WSP / ","
.\"
package-spec = package-key [ ver-op package-version ]
ver-op       = "<" / "<=" / "=" / "!=" / ">=" / ">"
.Ed
.\"
.It Fragment List
The property will be set to a list of fragments parsed from the text.
The input text must be in a format that is suitable for passing to a POSIX
shell without any shell expansions after variable substitution has been done.
.\"
.El
.Ss PROPERTY KEYWORDS
.Bl -tag -width indent
.\"
.It Name
The displayed name of the package.
(mandatory; literal)
.It Version
The version of the package.
(mandatory; literal)
.It Description
A description of the package.
(mandatory; literal)
.It URL
A URL to a webpage for the package.
This is used to recommend where newer versions of the package can be acquired.
(mandatory; literal)
.It Cflags
Required compiler flags.
These flags are always used, regardless of whether static compilation is requested.
(optional; fragment list)
.It Cflags.private
Required compiler flags for static compilation.
(optional; fragment list; pkgconf extension)
.It Libs
Required linking flags for this package.
Libraries this package depends on for linking against it, which are not
described as dependencies should be specified here.
(optional; fragment list)
.It Libs.private
Required linking flags for this package that are only required when linking
statically.
Libraries this package depends on for linking against it statically, which are
not described as dependencies should be specified here.
(optional; fragment list)
.It Requires
Required dependencies that must be met for the package to be usable.
All dependencies must be satisfied or the pkg-config implementation must not use
the package.
(optional; dependency list)
.It Requires.private
Required dependencies that must be met for the package to be usable for static linking.
All dependencies must be satisfied or the pkg-config implementation must not use
the package for static linking.
(optional; dependency list)
.It Conflicts
Dependencies that must not be met for the package to be usable.
If any package in the proposed dependency solution match any dependency in the
Conflicts list, the package being considered is not usable.
(optional; dependency list)
.It Provides
Dependencies that may be provided by an alternate package.
If a package cannot be found, the entire package collection is scanned for
providers which can match the requested dependency.
(optional; dependency list; pkgconf extension)
.El
.Ss EXTENSIONS
Features that have been marked as a pkgconf extension are only guaranteed to work
with the pkgconf implementation of pkg-config.
Other implementations may or may not support the extensions.
.Pp
Accordingly, it is suggested that
.Nm .pc
files which absolutely depend on these extensions declare a requirement on the
pkgconf virtual.
.Sh EXAMPLES
An example .pc file:
.Bd -literal
# This is a comment
prefix=/home/kaniini/pkg   # this defines a variable
exec_prefix=${prefix}      # defining another variable with a substitution
libdir=${exec_prefix}/lib
includedir=${prefix}/include

Name: libfoo                                  # human-readable name
Description: an example library called libfoo # human-readable description
Version: 1.0
URL: http://www.pkgconf.org
Requires: libbar > 2.0.0
Conflicts: libbaz <= 3.0.0
Libs: -L${libdir} -lfoo
Libs.private: -lm
Cflags: -I${includedir}/libfoo
.Ed
.Sh SEE ALSO
.Xr pkgconf 1 ,
.Xr pkg.m4 7