1 .\" Copyright (c) 1993 by Thomas Koenig (ig25@rz.uni-karlsruhe.de)
2 .\" and Copyright 2006-2008, Michael Kerrisk <mtk.manpages@gmail.com>
4 .\" %%%LICENSE_START(VERBATIM)
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22 .\" Formatted or processed versions of this manual, if unaccompanied by
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26 .\" Modified Sat Jul 24 19:27:50 1993 by Rik Faith (faith@cs.unc.edu)
27 .\" Modified Mon Aug 30 22:02:34 1995 by Jim Van Zandt <jrv@vanzandt.mv.com>
28 .\" longindex is a pointer, has_arg can take 3 values, using consistent
29 .\" names for optstring and longindex, "\n" in formats fixed. Documenting
30 .\" opterr and getopt_long_only. Clarified explanations (borrowing heavily
31 .\" from the source code).
32 .\" Modified 8 May 1998 by Joseph S. Myers (jsm28@cam.ac.uk)
33 .\" Modified 990715, aeb: changed `EOF' into `-1' since that is what POSIX
34 .\" says; moreover, EOF is not defined in <unistd.h>.
35 .\" Modified 2002-02-16, joey: added information about nonexistent
36 .\" option character and colon as first option character
37 .\" Modified 2004-07-28, Michael Kerrisk <mtk.manpages@gmail.com>
38 .\" Added text to explain how to order both '[-+]' and ':' at
39 .\" the start of optstring
40 .\" Modified 2006-12-15, mtk, Added getopt() example program.
42 .TH GETOPT 3 2021-03-22 "GNU" "Linux Programmer's Manual"
44 getopt, getopt_long, getopt_long_only,
45 optarg, optind, opterr, optopt \- Parse command-line options
48 .B #include <unistd.h>
50 .BI "int getopt(int " argc ", char *const " argv [],
51 .BI " const char *" optstring );
53 .BI "extern char *" optarg ;
54 .BI "extern int " optind ", " opterr ", " optopt ;
56 .B #include <getopt.h>
58 .BI "int getopt_long(int " argc ", char *const " argv [],
59 .BI " const char *" optstring ,
60 .BI " const struct option *" longopts ", int *" longindex );
61 .BI "int getopt_long_only(int " argc ", char *const " argv [],
62 .BI " const char *" optstring ,
63 .BI " const struct option *" longopts ", int *" longindex );
67 Feature Test Macro Requirements for glibc (see
68 .BR feature_test_macros (7)):
73 _POSIX_C_SOURCE >= 2 || _XOPEN_SOURCE
77 .BR getopt_long_only ():
84 function parses the command-line arguments.
89 are the argument count and array as passed to the
91 function on program invocation.
92 An element of \fIargv\fP that starts with \(aq\-\(aq
93 (and is not exactly "\-" or "\-\-")
95 The characters of this element
96 (aside from the initial \(aq\-\(aq) are option characters.
99 is called repeatedly, it returns successively each of the option characters
100 from each of the option elements.
104 is the index of the next element to be processed in
106 The system initializes this value to 1.
107 The caller can reset it to 1 to restart scanning of the same
109 or when scanning a new argument vector.
113 finds another option character, it returns that
114 character, updating the external variable \fIoptind\fP and a static
115 variable \fInextchar\fP so that the next call to
118 resume the scan with the following option character or
121 If there are no more option characters,
124 Then \fIoptind\fP is the index in \fIargv\fP of the first
125 \fIargv\fP-element that is not an option.
128 is a string containing the legitimate option characters.
129 A legitimate option character is any visible one byte
133 would return nonzero) that is not \(aq\-\(aq, \(aq:\(aq, or \(aq;\(aq.
135 character is followed by a colon, the option requires an argument, so
137 places a pointer to the following text in the same
138 \fIargv\fP-element, or the text of the following \fIargv\fP-element, in
140 Two colons mean an option takes
141 an optional arg; if there is text in the current \fIargv\fP-element
142 (i.e., in the same word as the option name itself, for example, "\-oarg"),
143 then it is returned in \fIoptarg\fP, otherwise \fIoptarg\fP is set to zero.
144 This is a GNU extension.
149 followed by a semicolon, then
151 is treated as the long option
155 option is reserved by POSIX.2 for implementation extensions.)
156 This behavior is a GNU extension, not available with libraries before
161 permutes the contents of \fIargv\fP as it
162 scans, so that eventually all the nonoptions are at the end.
163 Two other scanning modes are also implemented.
164 If the first character of
165 \fIoptstring\fP is \(aq+\(aq or the environment variable
167 is set, then option processing stops as soon as a nonoption argument is
169 If \(aq+\(aq is not the first character of
171 it is treated as a normal option.
174 behaviour is required in this case
176 will contain two \(aq+\(aq symbols.
177 If the first character of \fIoptstring\fP is \(aq\-\(aq, then
178 each nonoption \fIargv\fP-element is handled as if it were the argument of
179 an option with character code 1. (This is used by programs that were
180 written to expect options and other \fIargv\fP-elements in any order
181 and that care about the ordering of the two.)
182 The special argument "\-\-" forces an end of option-scanning regardless
183 of the scanning mode.
185 While processing the option list,
187 can detect two kinds of errors:
188 (1) an option character that was not specified in
190 and (2) a missing option argument
191 (i.e., an option at the end of the command line without an expected argument).
192 Such errors are handled and reported as follows:
196 prints an error message on standard error,
197 places the erroneous option character in
199 and returns \(aq?\(aq as the function result.
201 If the caller has set the global variable
205 does not print an error message.
206 The caller can determine that there was an error by testing whether
207 the function return value is \(aq?\(aq.
210 has a nonzero value.)
212 If the first character
213 (following any optional \(aq+\(aq or \(aq\-\(aq described above)
215 is a colon (\(aq:\(aq), then
217 likewise does not print an error message.
218 In addition, it returns \(aq:\(aq instead of \(aq?\(aq to
219 indicate a missing option argument.
220 This allows the caller to distinguish the two different types of errors.
222 .SS getopt_long() and getopt_long_only()
227 except that it also accepts long options, started with two dashes.
228 (If the program accepts only long options, then
230 should be specified as an empty string (""), not NULL.)
231 Long option names may be abbreviated if the abbreviation is
232 unique or is an exact match for some defined option.
234 may take a parameter, of the form
237 .BR "\-\-arg param" .
240 is a pointer to the first element of an array of
257 The meanings of the different fields are:
260 is the name of the long option.
264 \fBno_argument\fP (or 0) if the option does not take an argument;
265 \fBrequired_argument\fP (or 1) if the option requires an argument; or
266 \fBoptional_argument\fP (or 2) if the option takes an optional argument.
269 specifies how results are returned for a long option.
274 (For example, the calling program may set \fIval\fP to the equivalent short
279 \fIflag\fP points to a variable which is set to \fIval\fP if the
280 option is found, but left unchanged if the option is not found.
283 is the value to return, or to load into the variable pointed
286 The last element of the array has to be filled with zeros.
288 If \fIlongindex\fP is not NULL, it
289 points to a variable which is set to the index of the long option relative to
292 .BR getopt_long_only ()
295 but \(aq\-\(aq as well
296 as "\-\-" can indicate a long option.
297 If an option that starts with \(aq\-\(aq
298 (not "\-\-") doesn't match a long option, but does match a short option,
299 it is parsed as a short option instead.
301 If an option was successfully found, then
303 returns the option character.
304 If all command-line options have been parsed, then
309 encounters an option character that was not in
311 then \(aq?\(aq is returned.
314 encounters an option with a missing argument,
315 then the return value depends on the first character in
317 if it is \(aq:\(aq, then \(aq:\(aq is returned; otherwise \(aq?\(aq is returned.
321 .BR getopt_long_only ()
322 also return the option
323 character when a short option is recognized.
324 For a long option, they
325 return \fIval\fP if \fIflag\fP is NULL, and 0 otherwise.
326 Error and \-1 returns are the same as for
328 plus \(aq?\(aq for an
329 ambiguous match or an extraneous parameter.
333 If this is set, then option processing stops as soon as a nonoption
334 argument is encountered.
336 .B _<PID>_GNU_nonoption_argv_flags_
337 This variable was used by
339 2.0 to communicate to glibc which arguments are the results of
340 wildcard expansion and so should not be considered as options.
341 This behavior was removed in
343 version 2.01, but the support remains in glibc.
345 For an explanation of the terms used in this section, see
353 Interface Attribute Value
357 .BR getopt_long_only ()
359 MT-Unsafe race:getopt env
368 POSIX.1-2001, POSIX.1-2008, and POSIX.2,
369 provided the environment variable
372 Otherwise, the elements of \fIargv\fP aren't really
374 because these functions permute them.
377 is used in the prototype to be compatible with other systems.
379 The use of \(aq+\(aq and \(aq\-\(aq in
383 On some older implementations,
387 SUSv1 permitted the declaration to appear in either
391 POSIX.1-1996 marked the use of
393 for this purpose as LEGACY.
394 POSIX.1-2001 does not require the declaration to appear in
397 .BR getopt_long "() and " getopt_long_only ():
398 These functions are GNU extensions.
400 A program that scans multiple argument vectors,
401 or rescans the same vector more than once,
402 and wants to make use of GNU extensions such as \(aq+\(aq
403 and \(aq\-\(aq at the start of
405 or changes the value of
412 to 0, rather than the traditional value of 1.
413 (Resetting to 0 forces the invocation of an internal initialization
414 routine that rechecks
416 and checks for GNU extensions in
419 Command-line arguments are parsed in strict order
420 meaning that an option requiring an argument will consume the next argument,
421 regardless of whether that argument is the correctly specified option argument
422 or simply the next option
423 (in the scenario the user mis-specifies the command line).
426 is specified as "1n:"
427 and the user specifies the command line arguments incorrectly as
428 .IR "prog\ \-n\ \-1" ,
431 option will be given the
435 option will be considered to have not been specified.
438 The following trivial example program uses
440 to handle two program options:
442 with no associated value; and
444 which expects an associated value.
452 main(int argc, char *argv[])
460 while ((opt = getopt(argc, argv, "nt:")) != \-1) {
466 nsecs = atoi(optarg);
469 default: /* \(aq?\(aq */
470 fprintf(stderr, "Usage: %s [\-t nsecs] [\-n] name\en",
476 printf("flags=%d; tfnd=%d; nsecs=%d; optind=%d\en",
477 flags, tfnd, nsecs, optind);
479 if (optind >= argc) {
480 fprintf(stderr, "Expected argument after options\en");
484 printf("name argument = %s\en", argv[optind]);
486 /* Other code omitted */
492 The following example program illustrates the use of
494 with most of its features.
497 #include <stdio.h> /* for printf */
498 #include <stdlib.h> /* for exit */
502 main(int argc, char *argv[])
505 int digit_optind = 0;
508 int this_option_optind = optind ? optind : 1;
509 int option_index = 0;
510 static struct option long_options[] = {
511 {"add", required_argument, 0, 0 },
512 {"append", no_argument, 0, 0 },
513 {"delete", required_argument, 0, 0 },
514 {"verbose", no_argument, 0, 0 },
515 {"create", required_argument, 0, \(aqc\(aq},
516 {"file", required_argument, 0, 0 },
520 c = getopt_long(argc, argv, "abc:d:012",
521 long_options, &option_index);
527 printf("option %s", long_options[option_index].name);
529 printf(" with arg %s", optarg);
536 if (digit_optind != 0 && digit_optind != this_option_optind)
537 printf("digits occur in two different argv\-elements.\en");
538 digit_optind = this_option_optind;
539 printf("option %c\en", c);
543 printf("option a\en");
547 printf("option b\en");
551 printf("option c with value \(aq%s\(aq\en", optarg);
555 printf("option d with value \(aq%s\(aq\en", optarg);
562 printf("?? getopt returned character code 0%o ??\en", c);
567 printf("non\-option ARGV\-elements: ");
568 while (optind < argc)
569 printf("%s ", argv[optind++]);