libargp is a portable library providing the command-line parsing functionality of the argp module of the GNU Portability Library (Gnulib).
The source code directly utilitises the source of Gnulib, which is generally synchronised with the source of the GNU C Library (glibc).
To build the library, simply run ./build from the root directory of the project. This produces all output in the output subdirectory.
To install the library, first build it, then run ./install as superuser from the root directory of the project. This will install the library under the default prefix directory /usr/local.
A custom prefix directory can be specified by setting the INSTALL_PREFIX environment variable before installing.
The API is documented in the online manual for the GNU C Library.
An imported version of the source code for the Gnulib module is contained within the project directory. If you wish to update this imported version to the latest source for Gnulib, you first need to obtain a copy of Gnulib. This package contains the source for GNU code (including the relevant module), along with the program gnulib-tool, which can import such GNU code into a separate project.
To update the imported source code, first ensure that the gnulib-tool program of Gnulib (or a symbolic link pointing to it) can be found via PATH environment variable. Then simply run ./update-source from the root directory of the project. You will be notified whether the update succeeds or fails; if it fails then the previous imported source will remain intact.