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GETOPT(3-BSD)       RISC/os Reference Manual        GETOPT(3-BSD)



NAME
     getopt - get option letter from argv

SYNOPSIS
     int getopt(argc, argv, optstring)
     int argc;
     char **argv;
     char *optstring;

     extern char *optarg;
     extern int optind;
     extern int opterr;

DESCRIPTION
     getopt returns the next option letter in argv that matches a
     letter in optstring.  optstring is a string of recognized
     option letters; if a letter is followed by a colon, the
     option is expected to have an argument that may or may not
     be separated from it by white space.  optarg is set to point
     to the start of the option argument on return from getopt.

     getopt places in optind the argv index of the next argument
     to be processed.  Because optind is external, it is normally
     initialized to zero automatically before the first call to
     getopt.

     When all options have been processed (i.e., up to the first
     non-option argument), getopt returns EOF.  The special
     option -- may be used to delimit the end of the options; EOF
     will be returned, and -- will be skipped.

DIAGNOSTICS
     getopt prints an error message on stderr and returns a ques-
     tion mark (?)  when it encounters an option letter not
     included in optstring.  Setting opterr to a zero will dis-
     able this error message.

EXAMPLE
     The following code fragment shows how one might process the
     arguments for a command that can take the mutually exclusive
     options a and b, and the options f and o, both of which
     require arguments:

          main(argc, argv)
          int argc;
          char **argv;
          {
               int c;
               extern int optind;
               extern char *optarg;
               .
               .



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               .
               while ((c = getopt(argc, argv, "abf:o:")) != EOF)
                    switch (c) {
                    case `a':
                         if (bflg)
                              errflg++;
                         else
                              aflg++;
                         break;
                    case `b':
                         if (aflg)
                              errflg++;
                         else
                              bproc();
                         break;
                    case `f':
                         ifile = optarg;
                         break;
                    case `o':
                         ofile = optarg;
                         break;
                    case `?':
                    default:
                         errflg++;
                         break;
                    }
               if (errflg) {
                    fprintf(stderr, "Usage: ...");
                    exit(2);
               }
               for (; optind < argc; optind++) {
                    .
                    .
                    .
               }
               .
               .
               .
          }

HISTORY
     Written by Henry Spencer, working from a Bell Labs manual
     page.  Modified by Keith Bostic to behave more like the Sys-
     tem V version.

BUGS
     ``-'' may be specified as an option letter, however it
     should never have an argument associated with it.  This
     allows getopt to be used with programs that think that ``-''
     means standard input.





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     Option arguments are allowed to begin with ``-''; this is
     reasonable but reduces the amount of error checking possi-
     ble.

     getopt is quite flexible but the obvious price must be paid:
     there is much it could do that it doesn't, like checking
     mutually exclusive options, checking type of option argu-
     ments, etc.















































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