getopt.c

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/*
 * From: [e-mail] (Doug Gwyn <gwyn>) Newsgroups: net.sources
 * Subject: getopt library routine Date: 30 Mar 85 04:45:33 GMT
 */
/*
 * getopt -- public domain version of standard System V routine
 * 
 * Strictly enforces the System V Command Syntax Standard; provided by D A
 * Gwyn of BRL for generic ANSI C implementations
 * 
 * #define STRICT to prevent acceptance of clustered options with arguments
 * and ommision of whitespace between option and arg.
 */

/*
 * Modified by Manuel Novoa III on 1/5/01 to use weak symbols.
 * Programs needing long options will link gnu_getopt instead.
 */

#include <stdio.h>
#include <string.h>

extern int opterr;	/* error => print message */
extern int optind;	/* next argv[] index */
extern int optopt;	/* Set for unknown arguments */
extern char *optarg;	/* option parameter if any */

static int Err(name, mess, c) /* returns '?' */
char *name;						/* program name argv[0] */
char *mess;						/* specific message */
int c;							/* defective option letter */
{
	optopt = c;
	if (opterr) {
		(void) fprintf(stderr, "%s: %s -- %c\n", name, mess, c);
	}

	return '?';					/* erroneous-option marker */
}

int __attribute__ ((__weak__)) getopt (int argc, char *const *argv, const char *optstring)
{
	static int sp = 1;			/* position within argument */
	register int osp;			/* saved `sp' for param test */

#ifndef STRICT
	register int oind;			/* saved `optind' for param test */
#endif
	register int c;				/* option letter */
	register char *cp;			/* -> option in `optstring' */

	optarg = NULL;
	
	/* initialise getopt vars */
	if (optind == 0)
	  {
	    optind = 1;
	    opterr = 1;
	    optopt = 1;
	    optarg = NULL;
	  }
	  
	if (sp == 1) {				/* fresh argument */
		if (optind >= argc		/* no more arguments */
			|| argv[optind][0] != '-'	/* no more options */
			|| argv[optind][1] == '\0'	/* not option; stdin */
			)
			return EOF;
		else if (strcmp(argv[optind], "--") == 0) {
			++optind;			/* skip over "--" */
			return EOF;			/* "--" marks end of options */
		}
	}

	c = argv[optind][sp];		/* option letter */
	osp = sp++;					/* get ready for next letter */

#ifndef STRICT
	oind = optind;				/* save optind for param test */
#endif
	if (argv[optind][sp] == '\0') {	/* end of argument */
		++optind;				/* get ready for next try */
		sp = 1;					/* beginning of next argument */
	}

	if (c == ':' || c == '?'	/* optstring syntax conflict */
		|| (cp = strchr(optstring, c)) == NULL /* not found */ ) {
		return Err(argv[0], "illegal option", c);
	}

	if (cp[1] == ':') {			/* option takes parameter */
#ifdef STRICT
		if (osp != 1) {
			return Err(argv[0], "option must not be clustered", c);
		}

		/* reset by end of argument */
		if (sp != 1) {
			return Err(argv[0], "option must be followed by white space",
					   c);
		}
#else
		if (oind == optind) {	/* argument w/o whitespace */
			optarg = &argv[optind][sp];
			sp = 1;				/* beginning of next argument */
		}

		else
#endif
		if (optind >= argc) {
			return Err(argv[0], "option requires an argument", c);
		}

		else					/* argument w/ whitespace */
			optarg = argv[optind];

		++optind;				/* skip over parameter */
	}

	return c;
}