| 1 | .\" Copyright (c) 1985 Regents of the University of California.
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| 2 | .\" All rights reserved. The Berkeley software License Agreement
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| 3 | .\" specifies the terms and conditions for redistribution.
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| 4 | .\"
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| 5 | .\" @(#)getopt.3 6.4 (Berkeley) 5/27/86
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| 6 | .\"
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| 7 | .TH GETOPT 3 "May 27, 1986"
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| 8 | .UC 6
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| 9 | .SH NAME
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| 10 | getopt \- get option letter from argv
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| 11 | .SH SYNOPSIS
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| 12 | .ft B
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| 13 | int getopt(argc, argv, optstring)
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| 14 | .br
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| 15 | int argc;
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| 16 | .br
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| 17 | char **argv;
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| 18 | .br
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| 19 | char *optstring;
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| 20 | .sp
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| 21 | extern char *optarg;
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| 22 | .br
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| 23 | extern int optind;
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| 24 | .ft
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| 25 | .SH DESCRIPTION
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| 26 | .I Getopt
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| 27 | returns the next option letter in
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| 28 | .I argv
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| 29 | that matches a letter in
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| 30 | .IR optstring .
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| 31 | .I Optstring
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| 32 | is a string of recognized option letters;
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| 33 | if a letter is followed by a colon, the option is expected to have
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| 34 | an argument that may or may not be separated from it by white space.
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| 35 | .I Optarg
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| 36 | is set to point to the start of the option argument on return from
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| 37 | .IR getopt .
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| 38 | .PP
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| 39 | .I Getopt
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| 40 | places in
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| 41 | .I optind
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| 42 | the
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| 43 | .I argv
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| 44 | index of the next argument to be processed.
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| 45 | Because
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| 46 | .I optind
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| 47 | is external, it is normally initialized to zero automatically
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| 48 | before the first call to
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| 49 | .IR getopt .
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| 50 | .PP
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| 51 | When all options have been processed (i.e., up to the first
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| 52 | non-option argument),
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| 53 | .I getopt
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| 54 | returns
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| 55 | .BR EOF .
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| 56 | The special option
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| 57 | .B \-\-
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| 58 | may be used to delimit the end of the options;
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| 59 | .B EOF
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| 60 | will be returned, and
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| 61 | .B \-\-
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| 62 | will be skipped.
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| 63 | .SH DIAGNOSTICS
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| 64 | .I Getopt
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| 65 | prints an error message on
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| 66 | .I stderr
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| 67 | and returns a question mark
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| 68 | .RB ( ? )
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| 69 | when it encounters an option letter not included in
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| 70 | .IR optstring .
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| 71 | .SH EXAMPLE
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| 72 | The following code fragment shows how one might process the arguments
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| 73 | for a command that can take the mutually exclusive options
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| 74 | .B a
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| 75 | and
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| 76 | .BR b ,
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| 77 | and the options
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| 78 | .B f
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| 79 | and
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| 80 | .BR o ,
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| 81 | both of which require arguments:
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| 82 | .PP
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| 83 | .RS
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| 84 | .nf
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| 85 | main(argc, argv)
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| 86 | int argc;
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| 87 | char **argv;
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| 88 | {
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| 89 | int c;
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| 90 | extern int optind;
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| 91 | extern char *optarg;
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| 92 | \&.
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| 93 | \&.
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| 94 | \&.
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| 95 | while ((c = getopt(argc, argv, "abf:o:")) != EOF)
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| 96 | switch (c) {
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| 97 | case `a':
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| 98 | if (bflg)
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| 99 | errflg++;
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| 100 | else
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| 101 | aflg++;
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| 102 | break;
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| 103 | case `b':
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| 104 | if (aflg)
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| 105 | errflg++;
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| 106 | else
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| 107 | bproc();
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| 108 | break;
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| 109 | case `f':
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| 110 | ifile = optarg;
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| 111 | break;
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| 112 | case `o':
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| 113 | ofile = optarg;
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| 114 | break;
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| 115 | case `?':
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| 116 | default:
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| 117 | errflg++;
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| 118 | break;
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| 119 | }
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| 120 | if (errflg) {
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| 121 | fprintf(stderr, "Usage: ...");
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| 122 | exit(2);
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| 123 | }
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| 124 | for (; optind < argc; optind++) {
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| 125 | \&.
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| 126 | \&.
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| 127 | \&.
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| 128 | }
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| 129 | \&.
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| 130 | \&.
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| 131 | \&.
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| 132 | }
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| 133 | .RE
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| 134 | .SH HISTORY
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| 135 | Written by Henry Spencer, working from a Bell Labs manual page.
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| 136 | Modified by Keith Bostic to behave more like the System V version.
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| 137 | .SH BUGS
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| 138 | It is not obvious how
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| 139 | `\-'
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| 140 | standing alone should be treated; this version treats it as
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| 141 | a non-option argument, which is not always right.
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| 142 | .PP
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| 143 | Option arguments are allowed to begin with `\-';
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| 144 | this is reasonable but reduces the amount of error checking possible.
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| 145 | .PP
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| 146 | .I Getopt
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| 147 | is quite flexible but the obvious price must be paid: there is much
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| 148 | it could do that it doesn't, like
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| 149 | checking mutually exclusive options, checking type of
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| 150 | option arguments, etc.
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