Copyright (c) 1988, 1991, 1993
The Regents of the University of California. 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.
@(#)getopt.3 8.5 (Berkeley) 4/27/95
.Dd April 27, 1995 .Dt GETOPT 3 .Os .Sh NAME .Nm getopt .Nd get option character from command line argument list .Sh LIBRARY .Lb libc .Sh SYNOPSIS .Fd #include \*[Lt]unistd.h\*[Gt] .Vt extern char *optarg; .Vt extern int optind; .Vt extern int optopt; .Vt extern int opterr; .Vt extern int optreset; .Ft int .Fn getopt "int argc" "char * const argv[]" "const char *optstring" .Sh DESCRIPTION The .Fn getopt function incrementally parses a command line argument list .Fa argv and returns the next .Em known option character. 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 elements: individual characters, and characters followed by a colon to indicate an option argument is to follow. For example, an option string .Li """x"" recognizes an option .Dq Fl x , and an option string .Li """x:"" recognizes an option and argument .Dq Fl x Ar argument . 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 . The variable .Va optopt saves the last .Em known option character returned by .Fn getopt .
p The variable .Va opterr and .Va optind are both initialized to 1. The .Va optind variable may be set to another value before a set of calls to .Fn getopt in order to skip over more or less argv entries.
p In order to use .Fn getopt to evaluate multiple sets of arguments, or to evaluate a single set of arguments multiple times, the variable .Va optreset must be set to 1 before the second and each additional set of calls to .Fn getopt , and the variable .Va optind must be reinitialized.
p The .Fn getopt function returns -1 when the argument list is exhausted. 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 returns -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 .Fa optstring or detects a missing option argument it writes an error message to .Va stderr and returns .Ql ? . Setting .Va opterr to a zero will disable these error messages. If .Va optstring has a leading .Ql : then a missing option argument causes a .Ql : to be returned in addition to suppressing any error messages.
p Option arguments are allowed to begin with .Dq Li - ; this is reasonable but reduces the amount of error checking possible. .Sh EXTENSIONS The .Va optreset variable was added to make it possible to call the .Fn getopt function multiple times. This is an extension to the .St -p1003.2 specification. .Sh EXAMPLES 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)) \*[Lt] 0) { (void)fprintf(stderr, "myname: %s: %s\en", optarg, strerror(errno)); exit(1); } break; case '?': default: usage(); } argc -= optind; argv += optind; .Ed .Sh HISTORY The .Fn getopt function appeared in 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 \*[Lt]stdio.h\*[Gt] .
p A single dash .Dq Li - may be specified as a 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 return -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 in most cases. 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] == '-' \*[Am]\*[Am] p[1] == ch \*[Am]\*[Am] !p[2]) length = atoi(++p); else length = atoi(argv[optind] + 1); break; } } .Ed