2.4.4. Library use with GCC

A library is a reusable package of code. A C or C++ library consists of the library code and header files.

Typically, header files of a library will be placed in a different directory than your application’s code. To tell GCC where the header files are, use the -I option:

$ gcc ... -Iinclude_path ...

Replace include_path with the actual path to the header file directory.

For example, to specify a relative path some/interesting/directory:

$ gcc ... -Isome/interesting/directory ...

The -I option can be used multiple times to add multiple directories with header files. When looking for a header file, these directories are searched in the order of their appearance in the -I options.

To tell GCC where the archives or shared object files of a library are, use the -L option:

$ gcc ... -Llibrary_path -lfoo ...

Replace library_path with the actual path to the library directory.

The -L option can be used multiple times to add multiple directories. When looking for a library, these directories are searched in the order of their -L options.

The order of options matters: GCC cannot link against a library foo unless it knows the directory with this library. Therefore, use the -L options to specify library directories before using the -l options for linking against libraries.