getopt.c

3DES加解密C源码

/* got this off net.sources */
#include <stdio.h>

/*
 * get option letter from argument vector
 */
int	opterr = 1,		/* useless, never set or used */
	optind = 1,		/* index into parent argv vector */
	optopt;			/* character checked for validity */
char	*optarg;		/* argument associated with option */

#define BADCH	(int)'?'
#define EMSG	""
#define tell(s)	fputs(*nargv,stderr);fputs(s,stderr); \
		fputc(optopt,stderr);fputc('\n',stderr);return(BADCH);

getopt(nargc,nargv,ostr)
int	nargc;
char	**nargv,
	*ostr;
{
	static char	*place = EMSG;	/* option letter processing */
	register char	*oli;		/* option letter list index */
	char	*index();

	if(!*place) {			/* update scanning pointer */
		if(optind >= nargc || *(place = nargv[optind]) != '-' || !*++place) return(EOF);
		if (*place == '-') {	/* found "--" */
			++optind;
			return(EOF);
		}
	}				/* option letter okay? */
	if ((optopt = (int)*place++) == (int)':' || !(oli = index(ostr,optopt))) {
		if(!*place) ++optind;
		tell(": illegal option -- ");
	}
	if (*++oli != ':') {		/* don't need argument */
		optarg = NULL;
		if (!*place) ++optind;
	}
	else {				/* need an argument */
		if (*place) optarg = place;	/* no white space */
		else if (nargc <= ++optind) {	/* no arg */
			place = EMSG;
			tell(": option requires an argument -- ");
		}
	 	else optarg = nargv[optind];	/* white space */
		place = EMSG;
		++optind;
	}
	return(optopt);			/* dump back option letter */
}