All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
3. All advertising materials mentioning features or use of this software
must display the following acknowledgement:
This product includes software developed by the University of
California, Berkeley and its contributors.
4. Neither the name of the University nor the names of its contributors
may be used to endorse or promote products derived from this software
without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
from: @(#)getopt.3 6.16 (Berkeley) 4/19/91
$Id: getopt.3,v 1.3 1993/09/14 22:37:24 jtc Exp $
.Dd April 19, 1991 .Dt GETOPT 3 .Os BSD 4.3 .Sh NAME .Nm getopt .Nd get option letter from argv .Sh SYNOPSIS .Fd #include <stdlib.h> .Vt extern char *optarg .Vt extern int optind .Vt extern int opterr .Ft int .Fn getopt "int argc" "char * const *argv" "const char *optstring" .Sh DESCRIPTION The .Fn getopt function gets the next .Em known option character from .Fa argv . An option character is .Em known if it has been specified in the string of accepted option characters, .Fa optstring .
p The option string .Fa optstring may contain the following characters; letters and letters followed by a colon to indicate an option argument is to follow. It does not matter to .Fn getopt if a following argument has leading white space.
p On return from .Fn getopt , .Va optarg points to an option argument, if it is anticipated, and the variable .Va optind contains the index to the next .Fa argv argument for a subsequent call to .Fn getopt .
p The variable .Va opterr and .Va optind are both initialized to 1. In order to use .Fn getopt to evaluate multiple sets of arguments, or to evaluate a single set of arguments multiple times, .Va optind must be initialized to the number of argv entries to be skipped in each evaluation.
p The .Fn getopt function returns -1 when the argument list is exhausted, or a non-recognized option is encountered. The interpretation of options in the argument list may be cancelled by the option .Ql -- (double dash) which causes .Fn getopt to signal the end of argument processing and return -1. When all options have been processed (i.e., up to the first non-option argument), .Fn getopt returns -1. .Sh DIAGNOSTICS If the .Fn getopt function encounters a character not found in the string .Va optarg or detects a missing option argument it writes error message .Ql ? to the .Em stderr . Setting .Va opterr to a zero will disable these error messages. .Sh EXAMPLE d -literal -compact extern char *optarg; extern int optind; int bflag, ch, fd; bflag = 0; while ((ch = getopt(argc, argv, "bf:")) != -1) switch(ch) { case 'b': bflag = 1; break; case 'f': if ((fd = open(optarg, O_RDONLY, 0)) < 0) { (void)fprintf(stderr, "myname: unable to read file %s.\en", optarg); exit(1) ; } break; case '?': default: usage(); } argc -= optind; argv += optind; .Ed .Sh STANDARDS The .Fn getopt function conforms to .St -p1003.2-92 . .Sh HISTORY The .Fn getopt function appeared x 4.3 . .Sh BUGS The .Fn getopt function was once specified to return .Dv EOF instead of -1. This was changed by .St -p1003.2-92 to decouple .Fn getopt from
a <stdio.h> .
p Option arguments are allowed to begin with .Dq Li - ; this is reasonable but reduces the amount of error checking possible.
p A single dash .Dq Li - may be specified as an character in .Fa optstring , however it should .Em never have an argument associated with it. This allows .Fn getopt to be used with programs that expect .Dq Li - as an option flag. This practice is wrong, and should not be used in any current development. It is provided for backward compatibility .Em only . By default, a single dash causes .Fn getopt to returns -1. This is, we believe, compatible with System V.
p It is also possible to handle digits as option letters. This allows .Fn getopt to be used with programs that expect a number
q Dq Li -3 as an option. This practice is wrong, and should not be used in any current development. It is provided for backward compatibility .Em only . The following code fragment works fairly well. d -literal -offset indent int length; char *p; while ((c = getopt(argc, argv, "0123456789")) != -1) switch (c) { case '0': case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9': p = argv[optind - 1]; if (p[0] == '-' && p[1] == ch && !p[2]) length = atoi(++p); else length = atoi(argv[optind] + 1); break; } } .Ed