Crate pkg_config

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A build dependency for Cargo libraries to find system artifacts through the pkg-config utility.

This library will shell out to pkg-config as part of build scripts and probe the system to determine how to link to a specified library. The Config structure serves as a method of configuring how pkg-config is invoked in a builder style.

After running pkg-config all appropriate Cargo metadata will be printed on stdout if the search was successful.

§Environment variables

A number of environment variables are available to globally configure how this crate will invoke pkg-config:

  • FOO_NO_PKG_CONFIG - if set, this will disable running pkg-config when probing for the library named foo.


There are also a number of environment variables which can configure how a library is linked to (dynamically vs statically). These variables control whether the --static flag is passed. Note that this behavior can be overridden by configuring explicitly on Config. The variables are checked in the following order:

  • FOO_STATIC - pass --static for the library foo
  • FOO_DYNAMIC - do not pass --static for the library foo
  • PKG_CONFIG_ALL_STATIC - pass --static for all libraries
  • PKG_CONFIG_ALL_DYNAMIC - do not pass --static for all libraries


In cross-compilation context, it is useful to manage separately PKG_CONFIG_PATH and a few other variables for the host and the target platform.


Each of these variables can also be supplied with certain prefixes and suffixes, in the following prioritized order:

  1. <var>_<target> - for example, PKG_CONFIG_PATH_x86_64-unknown-linux-gnu
  2. <var>_<target_with_underscores> - for example, PKG_CONFIG_PATH_x86_64_unknown_linux_gnu
  3. <build-kind>_<var> - for example, HOST_PKG_CONFIG_PATH or TARGET_PKG_CONFIG_PATH
  4. <var> - a plain PKG_CONFIG_PATH

This crate will allow pkg-config to be used in cross-compilation if PKG_CONFIG_SYSROOT_DIR or PKG_CONFIG is set. You can set PKG_CONFIG_ALLOW_CROSS=1 to bypass the compatibility check, but please note that enabling use of pkg-config in cross-compilation without appropriate sysroot and search paths set is likely to break builds.


Find the system library named foo, with minimum version 1.2.3:

fn main() {

Find the system library named foo, with no version requirement (not recommended):

fn main() {

Configure how library foo is linked to.

fn main() {



  • Represents all reasons pkg-config might not succeed or be run at all.


  • Run pkg-config to get the value of a variable from a package using --variable.
  • Simple shortcut for using all default options for finding a library.