Gengetopt is described as 'This program generates a C function that uses getopt_long function to parse the command line options, to validate them and fills a struct' and is an app in the os & utilities category. There are 1 alternatives to Gengetopt for Mac, Linux and BSD. The best Gengetopt alternative is yuck, which is both free and Open Source.
yuck, Your Umbrella Command Kit, is a bog-standard command line option parser for C that works with only household ingredients (a C compiler and the m4 macro processor) and comes with all the knickknackery and whatnots.