pkg-config

pkg-config is a tool that originated in Linux to view the meta information about installed libraries. It can be used to know things like:

• include path of header files
• link path of library files
• version of library
• etc.

When a library is built or installed, usually a .pc meta file is produced. .pc file contains all meta information such as link path, etc. For pkg-config to work with the library, the .pc file must be placed in the correct search location (PKG_CONFIG_PATH environment variable).

Example use

Say I want to use libpng to work with png images. I install libpng via say homebrew and now want to use it in my project as a library. How can I do that?

1. First let’s see what version of libpng do I have
   $ pkg-config --modversion libpng
1.6.43

2. Ok good. Where can I find the header files for libpng
$ pkg-config --cflags libpng
-I/opt/local/include/libpng16 -I/opt/local/include

3. Nice. What about the path of libraries to link?
   $ pkg-config --libs libpng
-L/opt/local/lib -lpng16

With these information I can easily use the library with my project like:
gcc pngViewr.c -o pngViewr -I/opt/local/include/libpng16 -I/opt/local/include -L/opt/local/lib -lpng16

or even better:
gcc pngViewr.c -o pngViewr $(pkg-config --libs -cflags libpng)