getopt.c

/*
 * *    @(#)getopt.c    2.3 (smail) 5/30/87 
 */

/*
 * Here's something you've all been waiting for:  the AT&T public domain
 * source for getopt(3).  It is the code which was given out at the 1985
 * UNIFORUM conference in Dallas. I obtained it by electronic mail directly
 * from AT&T.  The people there assure me that it is indeed in the public
 * domain. 
 *
 * There is no manual page. That is because the one they gave out at UNIFORUM
 * was slightly different from the current System V Release 2 manual page. 
 * The difference apparently involved a note about the famous rules 5 and 6,
 * recommending using white space between an option and its first argument,
 * and not grouping options that have arguments. Getopt itself is currently
 * lenient about both of these things White space is allowed, but not
 * mandatory, and the last option in a group can have an argument.  That
 * particular version of the man page evidently has no official existence,
 * and my source at AT&T did not send a copy. The current SVR2 man page
 * reflects the actual behavior of this getopt. However, I am not about to
 * post a copy of anything licensed by AT&T. 
 */

#ifdef BSD
 #include <strings.h>
#else
 #define index strchr
 #include <string.h>
#endif

/* LINTLIBRARY */
#ifndef NULL
#define NULL    0
#endif

#define EOF    (-1)
#define ERR(s, c)    if(opterr){\
    extern int write(int, void *, unsigned);\
    char errbuf[2];\
    errbuf[0] = (char)c; errbuf[1] = '\n';\
    (void) write(2, strlwr(argv[0]), (unsigned)strlen(argv[0]));\
    (void) write(2, s, (unsigned)strlen(s));\
    (void) write(2, errbuf, 2);}

extern char    *index();

int             opterr = 1;
int             optind = 1;
int             optopt;
char           *optarg;

int getopt(int argc, char *argv[], char *opts)
{
      static int      sp = 1;
      register int    c;
      register char  *cp;

      if (sp == 1)
      {
            if (optind >= argc || argv[optind][0] != '-' ||
                  argv[optind][1] == '\0')
                        return (EOF);
            else if (strcmp(argv[optind], "--") == 0)
            {
                  optind++;
                  return (EOF);
            }
      }
      optopt = c = argv[optind][sp];
      if (c == ':' || (cp = index(opts, c)) == NULL)
      {
            ERR(": illegal option -- ", c);
            if (argv[optind][++sp] == '\0')
            {
                  optind++;
                  sp = 1;
            }
            return ('?');
      }
      if (*++cp == ':')
      {
            if (argv[optind][sp + 1] != '\0')
                  optarg = &argv[optind++][sp + 1];
            else if (++optind >= argc)
            {
                  ERR(": option requires an argument -- ", c);
                  sp = 1;
                  return ('?');
            }
            else  optarg = argv[optind++];
            sp = 1;
      }
      else
      {
            if (argv[optind][++sp] == '\0')
            {
                  sp = 1;
                  optind++;
            }
            optarg = NULL;
      }
      return (c);
}