getopt.c

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/*
 * getopt - get option letter from argv
 *
 * Copyright (c) Henry Spencer.
 * Written by Henry Spencer.
 *
 * This software is not subject to any license of the American Telephone
 * and Telegraph Company or of the Regents of the University of California.
 *
 * Permission is granted to anyone to use this software for any purpose on
 * any computer system, and to alter it and redistribute it freely, subject
 * to the following restrictions:
 *
 * 1. The author is not responsible for the consequences of use of this
 *    software, no matter how awful, even if they arise from flaws in it.
 *
 * 2. The origin of this software must not be misrepresented, either by
 *    explicit claim or by omission.  Since few users ever read sources,
 *    credits must appear in the documentation.
 *
 * 3. Altered versions must be plainly marked as such, and must not be
 *    misrepresented as being the original software.  Since few users
 *    ever read sources, credits must appear in the documentation.
 *
 * 4. This notice may not be removed or altered.
 */

/*
 * changed index() calls to strchr() - darwin, oct 87.
 */

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

char *optarg;			/* Global argument pointer. */
int optind = 0;			/* Global argv index. */

static char *scan = NULL;	/* Private scan pointer. */

extern char *strchr();

int getopt(argc, argv, optstring)
     int argc;
     char *argv[];
     char *optstring;
{
	register char c;
	register char *place;

	optarg = NULL;

	if (scan == NULL || *scan == '\0') {
		if (optind == 0)
			optind++;

		if (optind >= argc || argv[optind][0] != '-' || argv[optind][1] == '\0')
			return (EOF);
		if (strcmp(argv[optind], "--") == 0) {
			optind++;
			return (EOF);
		}
		scan = argv[optind] + 1;
		optind++;
	}
	c = *scan++;
	place = strchr(optstring, c);

	if (place == NULL || c == ':') {
		fprintf(stderr, "%s: unknown option -%c\n", argv[0], c);
		return ('?');
	}
	place++;
	if (*place == ':') {
		if (*scan != '\0') {
			optarg = scan;
			scan = NULL;
		} else if (optind < argc) {
			optarg = argv[optind];
			optind++;
		} else {
			fprintf(stderr, "%s: -%c argument missing\n", argv[0], c);
			return ('?');
		}
	}
	return (c);
}