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1.1       root        1: .TH GETOPT 3
                      2: .CT 2 data_man
                      3: .SH NAME
                      4: getopt \(mi get option letter from argv
                      5: .SH SYNOPSIS
                      6: .nf
                      7: .B int getopt (argc, argv, optstring)
                      8: .B int argc;
                      9: .B char **argv;
                     10: .B char *optstring;
                     11: .PP
                     12: .B extern char *optarg;
                     13: .B extern int optind;
                     14: .fi
                     15: .SH DESCRIPTION
                     16: .I Getopt
                     17: returns the next option letter in
                     18: .I argv
                     19: that matches a letter in
                     20: .IR optstring .
                     21: .I Optstring
                     22: is a string of recognized option letters;
                     23: if a letter is followed by a colon, the option
                     24: is expected to have an argument, which may or
                     25: may not be separated from it by white space.
                     26: .I Optarg
                     27: is set to point to the start of the option argument
                     28: on return from
                     29: .IR getopt .
                     30: .PP
                     31: .I Getopt
                     32: places in
                     33: .I optind
                     34: the
                     35: .I argv
                     36: index of the next argument to be processed.
                     37: Since
                     38: .I optind
                     39: is external, it is normally initialized to zero
                     40: automatically before the first call to
                     41: .IR getopt .
                     42: .PP
                     43: Option letters appear in nonempty clusters preceded by 
                     44: .BR - .
                     45: When all options have been processed
                     46: (i.e., up to the first non-option argument),
                     47: .I getopt
                     48: returns \-1.
                     49: The special option
                     50: .L --
                     51: may be used to delimit the end of the options;
                     52: \-1
                     53: will be returned, and
                     54: .L --
                     55: will be skipped.
                     56: .SH EXAMPLES
                     57: This fragment processes arguments
                     58: for a command that can take option
                     59: .B a
                     60: and option
                     61: .BR f ,
                     62: which requires an argument.
                     63: .PP
                     64: .EX
                     65: .ta \w'12345678'u +\w'12345678'u
                     66: main (argc, argv) char **argv;
                     67: {
                     68:        int c, errflg;
                     69:        extern int optind;
                     70:        extern char *optarg, *ifile;
                     71:        while((c = getopt(argc, argv, "af:")) != -1)
                     72:                switch (c){
                     73:                case 'a':  aflg=1; break;
                     74:                case 'f':  ifile = optarg; break;
                     75:                case '?':  errflg=1; break;
                     76:                }
                     77:        if(errflg){
                     78:                fprintf(stderr, "usage: . . . ");
                     79:                exit(2);
                     80:        }
                     81:        for( ; optind < argc; optind++){
                     82:                if(access(argv[optind], 4)){
                     83:                        ...
                     84:                }
                     85:        }
                     86:        ...
                     87: }
                     88: .EE
                     89: .SH SEE ALSO
                     90: .IR getflags (3)
                     91: .SH DIAGNOSTICS
                     92: .I Getopt
                     93: prints an error message on
                     94: .I stderr
                     95: and returns a
                     96: question mark
                     97: .L ?
                     98: when it encounters an option letter not included in
                     99: .IR optstring .

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