1GETOPTS(1P) POSIX Programmer's Manual GETOPTS(1P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 getopts — parse utility options
13
15 getopts optstring name [arg...]
16
18 The getopts utility shall retrieve options and option-arguments from a
19 list of parameters. It shall support the Utility Syntax Guidelines 3 to
20 10, inclusive, described in the Base Definitions volume of
21 POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines.
22 Each time it is invoked, the getopts utility shall place the value of
24 the next option in the shell variable specified by the name operand and
25 the index of the next argument to be processed in the shell variable
26 OPTIND. Whenever the shell is invoked, OPTIND shall be initialized to
27 1.
28 When the option requires an option-argument, the getopts utility shall
30 place it in the shell variable OPTARG. If no option was found, or if
31 the option that was found does not have an option-argument, OPTARG
32 shall be unset.
33 If an option character not contained in the optstring operand is found
35 where an option character is expected, the shell variable specified by
36 name shall be set to the <question-mark> ('?') character. In this
37 case, if the first character in optstring is a <colon> (':'), the shell
38 variable OPTARG shall be set to the option character found, but no out‐
39 put shall be written to standard error; otherwise, the shell variable
40 OPTARG shall be unset and a diagnostic message shall be written to
41 standard error. This condition shall be considered to be an error
42 detected in the way arguments were presented to the invoking applica‐
43 tion, but shall not be an error in getopts processing.
44 If an option-argument is missing:
46 * If the first character of optstring is a <colon>, the shell vari‐
48 able specified by name shall be set to the <colon> character and
49 the shell variable OPTARG shall be set to the option character
50 found.
51 * Otherwise, the shell variable specified by name shall be set to the
53 <question-mark> character, the shell variable OPTARG shall be
54 unset, and a diagnostic message shall be written to standard error.
55 This condition shall be considered to be an error detected in the
56 way arguments were presented to the invoking application, but shall
57 not be an error in getopts processing; a diagnostic message shall
58 be written as stated, but the exit status shall be zero.
59 When the end of options is encountered, the getopts utility shall exit
61 with a return value greater than zero; the shell variable OPTIND shall
62 be set to the index of the first operand, or the value "$#"+1 if there
63 are no operands; the name variable shall be set to the <question-mark>
64 character. Any of the following shall identify the end of options: the
65 first "--" argument that is not an option-argument, finding an argument
66 that is not an option-argument and does not begin with a '-', or
67 encountering an error.
68 The shell variables OPTIND and OPTARG shall be local to the caller of
70 getopts and shall not be exported by default.
71 The shell variable specified by the name operand, OPTIND, and OPTARG
73 shall affect the current shell execution environment; see Section 2.12,
74 Shell Execution Environment.
75 If the application sets OPTIND to the value 1, a new set of parameters
77 can be used: either the current positional parameters or new arg val‐
78 ues. Any other attempt to invoke getopts multiple times in a single
79 shell execution environment with parameters (positional parameters or
80 arg operands) that are not the same in all invocations, or with an
81 OPTIND value modified to be a value other than 1, produces unspecified
82 results.
83
85 None.
86
88 The following operands shall be supported:
89 optstring A string containing the option characters recognized by the
91 utility invoking getopts. If a character is followed by a
92 <colon>, the option shall be expected to have an argument,
93 which should be supplied as a separate argument. Applications
94 should specify an option character and its option-argument as
95 separate arguments, but getopts shall interpret the charac‐
96 ters following an option character requiring arguments as an
97 argument whether or not this is done. An explicit null
98 option-argument need not be recognized if it is not supplied
99 as a separate argument when getopts is invoked. (See also the
100 getopt() function defined in the System Interfaces volume of
101 POSIX.1‐2017.) The characters <question-mark> and <colon>
102 shall not be used as option characters by an application. The
103 use of other option characters that are not alphanumeric pro‐
104 duces unspecified results. If the option-argument is not sup‐
105 plied as a separate argument from the option character, the
106 value in OPTARG shall be stripped of the option character and
107 the '-'. The first character in optstring determines how
108 getopts behaves if an option character is not known or an
109 option-argument is missing.
110 name The name of a shell variable that shall be set by the getopts
112 utility to the option character that was found.
113 The getopts utility by default shall parse positional parameters passed
115 to the invoking shell procedure. If args are given, they shall be
116 parsed instead of the positional parameters.
117
119 Not used.
120
122 None.
123
125 The following environment variables shall affect the execution of
126 getopts:
127 LANG Provide a default value for the internationalization vari‐
129 ables that are unset or null. (See the Base Definitions vol‐
130 ume of POSIX.1‐2017, Section 8.2, Internationalization Vari‐
131 ables for the precedence of internationalization variables
132 used to determine the values of locale categories.)
133 LC_ALL If set to a non-empty string value, override the values of
135 all the other internationalization variables.
136 LC_CTYPE Determine the locale for the interpretation of sequences of
138 bytes of text data as characters (for example, single-byte as
139 opposed to multi-byte characters in arguments and input
140 files).
141 LC_MESSAGES
143 Determine the locale that should be used to affect the format
144 and contents of diagnostic messages written to standard
145 error.
146 NLSPATH Determine the location of message catalogs for the processing
148 of LC_MESSAGES.
149 OPTIND This variable shall be used by the getopts utility as the
151 index of the next argument to be processed.
152
154 Default.
155
157 Not used.
158
160 Whenever an error is detected and the first character in the optstring
161 operand is not a <colon> (':'), a diagnostic message shall be written
162 to standard error with the following information in an unspecified for‐
163 mat:
164 * The invoking program name shall be identified in the message. The
166 invoking program name shall be the value of the shell special
167 parameter 0 (see Section 2.5.2, Special Parameters) at the time the
168 getopts utility is invoked. A name equivalent to:
169 basename "$0"
172 may be used.
174 * If an option is found that was not specified in optstring, this
176 error is identified and the invalid option character shall be iden‐
177 tified in the message.
178 * If an option requiring an option-argument is found, but an option-
180 argument is not found, this error shall be identified and the
181 invalid option character shall be identified in the message.
182
184 None.
185
187 None.
188
190 The following exit values shall be returned:
191 0 An option, specified or unspecified by optstring, was found.
193 >0 The end of options was encountered or an error occurred.
195
197 Default.
198 The following sections are informative.
200
202 Since getopts affects the current shell execution environment, it is
203 generally provided as a shell regular built-in. If it is called in a
204 subshell or separate utility execution environment, such as one of the
205 following:
206 (getopts abc value "$@")
209 nohup getopts ...
210 find . -exec getopts ... \;
211 it does not affect the shell variables in the caller's environment.
213 Note that shell functions share OPTIND with the calling shell even
215 though the positional parameters are changed. If the calling shell and
216 any of its functions uses getopts to parse arguments, the results are
217 unspecified.
218
220 The following example script parses and displays its arguments:
221 aflag=
224 bflag=
225 while getopts ab: name
226 do
227 case $name in
228 a) aflag=1;;
229 b) bflag=1
230 bval="$OPTARG";;
231 ?) printf "Usage: %s: [-a] [-b value] args\n" $0
232 exit 2;;
233 esac
234 done
235 if [ ! -z "$aflag" ]; then
236 printf "Option -a specified\n"
237 fi
238 if [ ! -z "$bflag" ]; then
239 printf 'Option -b "%s" specified\n' "$bval"
240 fi
241 shift $(($OPTIND - 1))
242 printf "Remaining arguments are: %s\n$*"
243
245 The getopts utility was chosen in preference to the System V getopt
246 utility because getopts handles option-arguments containing <blank>
247 characters.
248 The OPTARG variable is not mentioned in the ENVIRONMENT VARIABLES sec‐
250 tion because it does not affect the execution of getopts; it is one of
251 the few ``output-only'' variables used by the standard utilities.
252 The <colon> is not allowed as an option character because that is not
254 historical behavior, and it violates the Utility Syntax Guidelines. The
255 <colon> is now specified to behave as in the KornShell version of the
256 getopts utility; when used as the first character in the optstring op‐
257 erand, it disables diagnostics concerning missing option-arguments and
258 unexpected option characters. This replaces the use of the OPTERR vari‐
259 able that was specified in an early proposal.
260 The formats of the diagnostic messages produced by the getopts utility
262 and the getopt() function are not fully specified because implementa‐
263 tions with superior (``friendlier'') formats objected to the formats
264 used by some historical implementations. The standard developers con‐
265 sidered it important that the information in the messages used be uni‐
266 form between getopts and getopt(). Exact duplication of the messages
267 might not be possible, particularly if a utility is built on another
268 system that has a different getopt() function, but the messages must
269 have specific information included so that the program name, invalid
270 option character, and type of error can be distinguished by a user.
271 Only a rare application program intercepts a getopts standard error
273 message and wants to parse it. Therefore, implementations are free to
274 choose the most usable messages they can devise. The following formats
275 are used by many historical implementations:
276 "%s: illegal option -- %c\n", <program name>, <option character>
279 "%s: option requires an argument -- %c\n", <program name>, \
281 <option character>
282 Historical shells with built-in versions of getopt() or getopts have
284 used different formats, frequently not even indicating the option char‐
285 acter found in error.
286
288 None.
289
291 Section 2.5.2, Special Parameters
292 The Base Definitions volume of POSIX.1‐2017, Chapter 8, Environment
294 Variables, Section 12.2, Utility Syntax Guidelines
295 The System Interfaces volume of POSIX.1‐2017, getopt()
297
299 Portions of this text are reprinted and reproduced in electronic form
300 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
301 table Operating System Interface (POSIX), The Open Group Base Specifi‐
302 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
303 Electrical and Electronics Engineers, Inc and The Open Group. In the
304 event of any discrepancy between this version and the original IEEE and
305 The Open Group Standard, the original IEEE and The Open Group Standard
306 is the referee document. The original Standard can be obtained online
307 at http://www.opengroup.org/unix/online.html .
308 Any typographical or formatting errors that appear in this page are
310 most likely to have been introduced during the conversion of the source
311 files to man page format. To report such errors, see https://www.ker‐
312 nel.org/doc/man-pages/reporting_bugs.html .
313IEEE/The Open Group 2017 GETOPTS(1P)