This is perhaps the smallest program possible that uses argp. It won’t do much except give an error message and exit when there are any arguments, and prints a rather pointless message for ‘--help’.
/* This is (probably) the smallest possible program that
   uses argp.  It won’t do much except give an error
   messages and exit when there are any arguments, and print
   a (rather pointless) messages for –help. */
#include <stdlib.h>
#include <argp.h>
int
main (int argc, char **argv)
{
  argp_parse (0, argc, argv, 0, 0, 0);
  exit (0);
}