usr/klibc/getopt.c

/*
 * getopt.c
 *
 * Simple POSIX getopt(), no GNU extensions...
 */

#include <stdint.h>
#include <unistd.h>
#include <string.h>

char *optarg;
int optind = 1;
int opterr, optopt;
static const char *__optptr;

int getopt(int argc, char *const *argv, const char *optstring)
{
	const char *carg = argv[optind];
	const char *osptr;
	int opt;

	/* We don't actually need argc */
	(void)argc;

	/* First, eliminate all non-option cases */

	if (!carg || carg[0] != '-' || !carg[1]) {
		return -1;
	}

	if (carg[1] == '-' && !carg[2]) {
		optind++;
		return -1;
	}

	if ((uintptr_t) (__optptr - carg) > (uintptr_t) strlen(carg)) {
		/* Someone frobbed optind, change to new opt. */
		__optptr = carg + 1;
	}

	opt = *__optptr++;

	if (opt != ':' && (osptr = strchr(optstring, opt))) {
		if (osptr[1] == ':') {
			if (*__optptr) {
				/* Argument-taking option with attached
				   argument */
				optarg = (char *)__optptr;
				optind++;
			} else {
				/* Argument-taking option with non-attached
				   argument */
				if (argv[optind + 1]) {
					optarg = (char *)argv[optind+1];
					optind += 2;
				} else {
					/* Missing argument */
					optind++;
					return (optstring[0] == ':')
						? ':' : '?';
				}
			}
			return opt;
		} else {
			/* Non-argument-taking option */
			/* __optptr will remember the exact position to
			   resume at */
			if (!*__optptr)
				optind++;
			return opt;
		}
	} else {
		/* Unknown option */
		optopt = opt;
		if (!*__optptr)
			optind++;
		return '?';
	}
}