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.
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12 getopts - parse utility options
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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 IEEE Std 1003.1-2001, 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 case,
37 if the first character in optstring is a colon ( ':' ), the shell vari‐
38 able OPTARG shall be set to the option character found, but no output
39 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 variable
48 specified by name shall be set to the colon character and the shell
49 variable OPTARG shall be set to the option character found.
50 * Otherwise, the shell variable specified by name shall be set to the
52 question-mark character, the shell variable OPTARG shall be unset,
53 and a diagnostic message shall be written to standard error. This
54 condition shall be considered to be an error detected in the way
55 arguments were presented to the invoking application, but shall not
56 be an error in getopts processing; a diagnostic message shall be
57 written as stated, but the exit status shall be zero.
58 When the end of options is encountered, the getopts utility shall exit
60 with a return value greater than zero; the shell variable OPTIND shall
61 be set to the index of the first non-option-argument, where the first
62 "--" argument is considered to be an option-argument if there are no
63 other non-option-arguments appearing before it, or the value "$#" +1 if
64 there are no non-option-arguments; the name variable shall be set to
65 the question-mark character. Any of the following shall identify the
66 end of options: the special option "--", finding an argument that does
67 not begin with a '-', or 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 Shell Execu‐
74 tion 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
91 A string containing the option characters recognized by the
92 utility invoking getopts. If a character is followed by a colon,
93 the option shall be expected to have an argument, which should
94 be supplied as a separate argument. Applications should specify
95 an option character and its option-argument as separate argu‐
96 ments, but getopts shall interpret the characters following an
97 option character requiring arguments as an argument whether or
98 not this is done. An explicit null option-argument need not be
99 recognized if it is not supplied as a separate argument when
100 getopts is invoked. (See also the getopt() function defined in
101 the System Interfaces volume of IEEE Std 1003.1-2001.) The
102 characters question-mark and colon shall not be used as option
103 characters by an application. The use of other option characters
104 that are not alphanumeric produces unspecified results. If the
105 option-argument is not supplied as a separate argument from the
106 option character, the value in OPTARG shall be stripped of the
107 option character and the '-' . The first character in optstring
108 determines how getopts behaves if an option character is not
109 known or an 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
116 to the invoking shell procedure. If args are given, they shall be
117 parsed instead of the positional parameters.
118
120 Not used.
121
123 None.
124
126 The following environment variables shall affect the execution of
127 getopts:
128 LANG Provide a default value for the internationalization variables
130 that are unset or null. (See the Base Definitions volume of
131 IEEE Std 1003.1-2001, Section 8.2, Internationalization Vari‐
132 ables for the precedence of internationalization variables used
133 to determine the values of locale categories.)
134 LC_ALL If set to a non-empty string value, override the values of all
136 the other internationalization variables.
137 LC_CTYPE
139 Determine the locale for the interpretation of sequences of
140 bytes of text data as characters (for example, single-byte as
141 opposed to multi-byte characters in arguments and input files).
142 LC_MESSAGES
144 Determine the locale that should be used to affect the format
145 and contents of diagnostic messages written to standard error.
146 NLSPATH
148 Determine the location of message catalogs for the processing of
149 LC_MESSAGES .
150 OPTIND This variable shall be used by the getopts utility as the index
152 of the next argument to be processed.
153
156 Default.
157
159 Not used.
160
162 Whenever an error is detected and the first character in the optstring
163 operand is not a colon ( ':' ), a diagnostic message shall be written
164 to standard error with the following information in an unspecified for‐
165 mat:
166 * The invoking program name shall be identified in the message. The
168 invoking program name shall be the value of the shell special param‐
169 eter 0 (see Special Parameters ) at the time the getopts utility is
170 invoked. A name equivalent to:
171 basename "$0"
174 may be used.
176 * If an option is found that was not specified in optstring, this
178 error is identified and the invalid option character shall be iden‐
179 tified in the message.
180 * If an option requiring an option-argument is found, but an option-
182 argument is not found, this error shall be identified and the
183 invalid option character shall be identified in the message.
184
186 None.
187
189 None.
190
192 The following exit values shall be returned:
193 0 An option, specified or unspecified by optstring, was found.
195 >0 The end of options was encountered or an error occurred.
197
200 Default.
201 The following sections are informative.
203
205 Since getopts affects the current shell execution environment, it is
206 generally provided as a shell regular built-in. If it is called in a
207 subshell or separate utility execution environment, such as one of the
208 following:
209 (getopts abc value "$@")
212 nohup getopts ...
213 find . -exec getopts ... \;
214 it does not affect the shell variables in the caller's environment.
216 Note that shell functions share OPTIND with the calling shell even
218 though the positional parameters are changed. If the calling shell and
219 any of its functions uses getopts to parse arguments, the results are
220 unspecified.
221
223 The following example script parses and displays its arguments:
224 aflag=
227 bflag=
228 while getopts ab: name
229 do
230 case $name in
231 a) aflag=1;;
232 b) bflag=1
233 bval="$OPTARG";;
234 ?) printf "Usage: %s: [-a] [-b value] args\n" $0
235 exit 2;;
236 esac
237 done
238 if [ ! -z "$aflag" ]; then
239 printf "Option -a specified\n"
240 fi
241 if [ ! -z "$bflag" ]; then
242 printf 'Option -b "%s" specified\n' "$bval"
243 fi
244 shift $(($OPTIND - 1))
245 printf "Remaining arguments are: %s\n" "$*"
246
248 The getopts utility was chosen in preference to the System V getopt
249 utility because getopts handles option-arguments containing <blank>s.
250 The OPTARG variable is not mentioned in the ENVIRONMENT VARIABLES sec‐
252 tion because it does not affect the execution of getopts; it is one of
253 the few "output-only" variables used by the standard utilities.
254 The colon is not allowed as an option character because that is not
256 historical behavior, and it violates the Utility Syntax Guidelines. The
257 colon is now specified to behave as in the KornShell version of the
258 getopts utility; when used as the first character in the optstring op‐
259 erand, it disables diagnostics concerning missing option-arguments and
260 unexpected option characters. This replaces the use of the OPTERR vari‐
261 able that was specified in an early proposal.
262 The formats of the diagnostic messages produced by the getopts utility
264 and the getopt() function are not fully specified because implementa‐
265 tions with superior (``friendlier") formats objected to the formats
266 used by some historical implementations. The standard developers con‐
267 sidered it important that the information in the messages used be uni‐
268 form between getopts and getopt(). Exact duplication of the messages
269 might not be possible, particularly if a utility is built on another
270 system that has a different getopt() function, but the messages must
271 have specific information included so that the program name, invalid
272 option character, and type of error can be distinguished by a user.
273 Only a rare application program intercepts a getopts standard error
275 message and wants to parse it. Therefore, implementations are free to
276 choose the most usable messages they can devise. The following formats
277 are used by many historical implementations:
278 "%s: illegal option -- %c\n", <program name>, <option character>
281 "%s: option requires an argument -- %c\n", <program name>, \
284 <option character>
285 Historical shells with built-in versions of getopt() or getopts have
287 used different formats, frequently not even indicating the option char‐
288 acter found in error.
289
291 None.
292
294 Special Parameters, the System Interfaces volume of
295 IEEE Std 1003.1-2001, getopt()
296
298 Portions of this text are reprinted and reproduced in electronic form
299 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
300 -- Portable Operating System Interface (POSIX), The Open Group Base
301 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
302 Electrical and Electronics Engineers, Inc and The Open Group. In the
303 event of any discrepancy between this version and the original IEEE and
304 The Open Group Standard, the original IEEE and The Open Group Standard
305 is the referee document. The original Standard can be obtained online
306 at http://www.opengroup.org/unix/online.html .
307IEEE/The Open Group 2003 GETOPTS(1P)