getopt.c

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/* jgaa oct 9th 2000: Found this on www.
 * No copyright information given.
 * Slightly modidied.
 *
 * Origin: http://www.winsite.com/info/pc/win3/winsock/sossntr4.zip/SOSSNT/SRC/GETOPT.C.html
 */
 
 /* got this off net.sources  */
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
#include "getopt.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(*argv,stderr);fputs(s,stderr); \
    fputc(optopt,stderr);fputc('\n',stderr);return(BADCH);
 
int getopt(int argc, char * const *argv, const char *optstring)
{
    static char *place = EMSG;  /* option letter processing */
    register char   *oli;       /* option letter list index */
 
    if(!*place) {           /* update scanning pointer */
        if(optind >= argc || *(place = argv[optind]) != '-' || !*++place)
            return(EOF);
        if (*place == '-') {    /* found "--" */
            ++optind;
            return(EOF);
        }
    }               /* option letter okay? */
    if ((optopt = (int)*place++) == (int)':' || !(oli = strchr(optstring,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 (argc <= ++optind) {    /* no arg */
            place = EMSG;
            tell(": option requires an argument -- ");
        }
        else optarg = argv[optind]; /* white space */
        place = EMSG;
        ++optind;
    }
    return(optopt);         /* dump back option letter */
}