Getopt example from manual

getopt.c

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>

int main(int argc, char *argv[])
{
  int flags, opt;
  int nsecs, tfnd;

  nsecs = 0;
  tfnd = 0;
  flags = 0;
  while ((opt = getopt(argc, argv, "nt:")) != -1)
  {
    switch (opt)
    {
    case 'n':
      flags = 1;
      break;
    case 't':
      nsecs = atoi(optarg);
      tfnd = 1;
      break;
    default: /* '?' */
      fprintf(stderr, "Usage: %s [-t nsecs] [-n] name\n", argv[0]);
      exit(EXIT_FAILURE);
    }
  }

  printf("flags=%d; tfnd=%d; optind=%d\n", flags, tfnd, optind);

  if (optind >= argc)
  {
    fprintf(stderr, "Expected argument after options\n");
    exit(EXIT_FAILURE);
  }

  printf("name argument = %s\n", argv[optind]);

  /* Other code omitted */

  exit(EXIT_SUCCESS);
}