testopt.c

#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
     
int main (int argc, char **argv)
{
	int aflag = 0;
	int bflag = 0;
	char *cvalue = NULL;
	int index;
	int c;

	opterr = 0;
     
    while ((c = getopt (argc, argv, "abc:")) != -1)
		switch (c) 
		{
			case 'a':
				aflag = 1;
			break;
			case 'b':
				bflag = 1;
			break;
			case 'c':
				cvalue = optarg;
			break;
			case '?':
			if (optopt == 'c')
				fprintf (stderr, "Option -%c requires an argument.\n", optopt);
			else if (isprint (optopt))
				fprintf (stderr, "Unknown option `-%c'.\n", optopt);
			else
				fprintf (stderr, "Unknown option character `\\x%x'.\n",optopt);
			return 1;
			default:
				abort ();
		}
	printf ("aflag = %d, bflag = %d, cvalue = %s\n", aflag, bflag, cvalue);
	for (index = optind; index < argc; index++)
		printf ("Non-option argument %s\n", argv[index]);
	return 0;
}