#include <errno.h>
#include <string.h>
#include <dos.h>

int	optind	= 1;	/* index of which argument is next	*/
char   *optarg;		/* pointer to argument of current option */
int	opterr	= 1;	/* allow error message	*/
int	badopt	= 0;	/* allow the function to pass the bad arg */

static	char   *letP = NULL;	/* remember next option char's location */
static	char	SW = 0;		/* DOS switch character, either '-' or '/' */


int	getopt(int argc, char *argv[], char *optionS)
{
	unsigned char ch;
	char *optP;
 
	if (SW == 0) {
		/* get SW using dos call 0x37 */
		_AX = 0x3700;
		geninterrupt(0x21);
		SW = _DL;
	}

	if (argc > optind) {
		if (letP == NULL) {
			if ((letP = argv[optind]) == NULL || 
				*(letP++) != SW)  goto gopEOF;
			if (*letP == SW) {
				optind++;  goto gopEOF;
			}
		}
		if (0 == (ch = *(letP++))) {
			optind++;  goto gopEOF;
		}
		if (':' == ch  ||  (optP = strchr(optionS, ch)) == NULL)  
			goto gopError;
		if (':' == *(++optP)) {
			optind++;
			if (0 == *letP) {
				if (argc <= optind)  goto  gopError;
				letP = argv[optind++];
			}
			optarg = letP;
			letP = NULL;
		} else {
			if (0 == *letP) {
				optind++;
				letP = NULL;
			}
			optarg = NULL;
		}
		return ch;
	}
gopEOF:
	optarg = letP = NULL;
	return EOF;

gopError:
	optarg = NULL;
	errno  = EINVAL;
	if (opterr)
		perror ("get command line option");
	badopt = ch;
	return ('?');
}