1GETOPTS(P) POSIX Programmer's Manual GETOPTS(P)
2
6 getopts - parse utility options
7
9 getopts optstring name [arg...]
10
12 The getopts utility shall retrieve options and option-arguments from a
13 list of parameters. It shall support the Utility Syntax Guidelines 3 to
14 10, inclusive, described in the Base Definitions volume of
15 IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
16 Each time it is invoked, the getopts utility shall place the value of
18 the next option in the shell variable specified by the name operand and
19 the index of the next argument to be processed in the shell variable
20 OPTIND . Whenever the shell is invoked, OPTIND shall be initialized to
21 1.
22 When the option requires an option-argument, the getopts utility shall
24 place it in the shell variable OPTARG . If no option was found, or if
25 the option that was found does not have an option-argument, OPTARG
26 shall be unset.
27 If an option character not contained in the optstring operand is found
29 where an option character is expected, the shell variable specified by
30 name shall be set to the question-mark ( '?' ) character. In this case,
31 if the first character in optstring is a colon ( ':' ), the shell vari‐
32 able OPTARG shall be set to the option character found, but no output
33 shall be written to standard error; otherwise, the shell variable
34 OPTARG shall be unset and a diagnostic message shall be written to
35 standard error. This condition shall be considered to be an error
36 detected in the way arguments were presented to the invoking applica‐
37 tion, but shall not be an error in getopts processing.
38 If an option-argument is missing:
40 * If the first character of optstring is a colon, the shell variable
42 specified by name shall be set to the colon character and the shell
43 variable OPTARG shall be set to the option character found.
44 * Otherwise, the shell variable specified by name shall be set to the
46 question-mark character, the shell variable OPTARG shall be unset,
47 and a diagnostic message shall be written to standard error. This
48 condition shall be considered to be an error detected in the way
49 arguments were presented to the invoking application, but shall not
50 be an error in getopts processing; a diagnostic message shall be
51 written as stated, but the exit status shall be zero.
52 When the end of options is encountered, the getopts utility shall exit
54 with a return value greater than zero; the shell variable OPTIND shall
55 be set to the index of the first non-option-argument, where the first
56 "--" argument is considered to be an option-argument if there are no
57 other non-option-arguments appearing before it, or the value "$#" +1 if
58 there are no non-option-arguments; the name variable shall be set to
59 the question-mark character. Any of the following shall identify the
60 end of options: the special option "--" , finding an argument that does
61 not begin with a '-' , or encountering an error.
62 The shell variables OPTIND and OPTARG shall be local to the caller of
64 getopts and shall not be exported by default.
65 The shell variable specified by the name operand, OPTIND , and OPTARG
67 shall affect the current shell execution environment; see Shell Execu‐
68 tion Environment .
69 If the application sets OPTIND to the value 1, a new set of parameters
71 can be used: either the current positional parameters or new arg val‐
72 ues. Any other attempt to invoke getopts multiple times in a single
73 shell execution environment with parameters (positional parameters or
74 arg operands) that are not the same in all invocations, or with an
75 OPTIND value modified to be a value other than 1, produces unspecified
76 results.
77
79 None.
80
82 The following operands shall be supported:
83 optstring
85 A string containing the option characters recognized by the
86 utility invoking getopts. If a character is followed by a colon,
87 the option shall be expected to have an argument, which should
88 be supplied as a separate argument. Applications should specify
89 an option character and its option-argument as separate argu‐
90 ments, but getopts shall interpret the characters following an
91 option character requiring arguments as an argument whether or
92 not this is done. An explicit null option-argument need not be
93 recognized if it is not supplied as a separate argument when
94 getopts is invoked. (See also the getopt() function defined in
95 the System Interfaces volume of IEEE Std 1003.1-2001.) The
96 characters question-mark and colon shall not be used as option
97 characters by an application. The use of other option characters
98 that are not alphanumeric produces unspecified results. If the
99 option-argument is not supplied as a separate argument from the
100 option character, the value in OPTARG shall be stripped of the
101 option character and the '-' . The first character in optstring
102 determines how getopts behaves if an option character is not
103 known or an option-argument is missing.
104 name The name of a shell variable that shall be set by the getopts
106 utility to the option character that was found.
107 The getopts utility by default shall parse positional parameters passed
110 to the invoking shell procedure. If args are given, they shall be
111 parsed instead of the positional parameters.
112
114 Not used.
115
117 None.
118
120 The following environment variables shall affect the execution of
121 getopts:
122 LANG Provide a default value for the internationalization variables
124 that are unset or null. (See the Base Definitions volume of
125 IEEE Std 1003.1-2001, Section 8.2, Internationalization Vari‐
126 ables for the precedence of internationalization variables used
127 to determine the values of locale categories.)
128 LC_ALL If set to a non-empty string value, override the values of all
130 the other internationalization variables.
131 LC_CTYPE
133 Determine the locale for the interpretation of sequences of
134 bytes of text data as characters (for example, single-byte as
135 opposed to multi-byte characters in arguments and input files).
136 LC_MESSAGES
138 Determine the locale that should be used to affect the format
139 and contents of diagnostic messages written to standard error.
140 NLSPATH
142 Determine the location of message catalogs for the processing of
143 LC_MESSAGES .
144 OPTIND This variable shall be used by the getopts utility as the index
146 of the next argument to be processed.
147
150 Default.
151
153 Not used.
154
156 Whenever an error is detected and the first character in the optstring
157 operand is not a colon ( ':' ), a diagnostic message shall be written
158 to standard error with the following information in an unspecified for‐
159 mat:
160 * The invoking program name shall be identified in the message. The
162 invoking program name shall be the value of the shell special param‐
163 eter 0 (see Special Parameters ) at the time the getopts utility is
164 invoked. A name equivalent to:
165 basename "$0"
168 may be used.
170 * If an option is found that was not specified in optstring, this
172 error is identified and the invalid option character shall be iden‐
173 tified in the message.
174 * If an option requiring an option-argument is found, but an option-
176 argument is not found, this error shall be identified and the
177 invalid option character shall be identified in the message.
178
180 None.
181
183 None.
184
186 The following exit values shall be returned:
187 0 An option, specified or unspecified by optstring, was found.
189 >0 The end of options was encountered or an error occurred.
191
194 Default.
195 The following sections are informative.
197
199 Since getopts affects the current shell execution environment, it is
200 generally provided as a shell regular built-in. If it is called in a
201 subshell or separate utility execution environment, such as one of the
202 following:
203 (getopts abc value "$@")
206 nohup getopts ...
207 find . -exec getopts ... \;
208 it does not affect the shell variables in the caller's environment.
210 Note that shell functions share OPTIND with the calling shell even
212 though the positional parameters are changed. If the calling shell and
213 any of its functions uses getopts to parse arguments, the results are
214 unspecified.
215
217 The following example script parses and displays its arguments:
218 aflag=
221 bflag=
222 while getopts ab: name
223 do
224 case $name in
225 a) aflag=1;;
226 b) bflag=1
227 bval="$OPTARG";;
228 ?) printf "Usage: %s: [-a] [-b value] args\n" $0
229 exit 2;;
230 esac
231 done
232 if [ ! -z "$aflag" ]; then
233 printf "Option -a specified\n"
234 fi
235 if [ ! -z "$bflag" ]; then
236 printf 'Option -b "%s" specified\n' "$bval"
237 fi
238 shift $(($OPTIND - 1))
239 printf "Remaining arguments are: %s\n" "$*"
240
242 The getopts utility was chosen in preference to the System V getopt
243 utility because getopts handles option-arguments containing <blank>s.
244 The OPTARG variable is not mentioned in the ENVIRONMENT VARIABLES sec‐
246 tion because it does not affect the execution of getopts; it is one of
247 the few "output-only" variables used by the standard utilities.
248 The colon is not allowed as an option character because that is not
250 historical behavior, and it violates the Utility Syntax Guidelines. The
251 colon is now specified to behave as in the KornShell version of the
252 getopts utility; when used as the first character in the optstring op‐
253 erand, it disables diagnostics concerning missing option-arguments and
254 unexpected option characters. This replaces the use of the OPTERR vari‐
255 able that was specified in an early proposal.
256 The formats of the diagnostic messages produced by the getopts utility
258 and the getopt() function are not fully specified because implementa‐
259 tions with superior (``friendlier") formats objected to the formats
260 used by some historical implementations. The standard developers con‐
261 sidered it important that the information in the messages used be uni‐
262 form between getopts and getopt(). Exact duplication of the messages
263 might not be possible, particularly if a utility is built on another
264 system that has a different getopt() function, but the messages must
265 have specific information included so that the program name, invalid
266 option character, and type of error can be distinguished by a user.
267 Only a rare application program intercepts a getopts standard error
269 message and wants to parse it. Therefore, implementations are free to
270 choose the most usable messages they can devise. The following formats
271 are used by many historical implementations:
272 "%s: illegal option -- %c\n", <program name>, <option character>
275 "%s: option requires an argument -- %c\n", <program name>, \
278 <option character>
279 Historical shells with built-in versions of getopt() or getopts have
281 used different formats, frequently not even indicating the option char‐
282 acter found in error.
283
285 None.
286
288 Special Parameters , the System Interfaces volume of
289 IEEE Std 1003.1-2001, getopt()
290
292 Portions of this text are reprinted and reproduced in electronic form
293 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
294 -- Portable Operating System Interface (POSIX), The Open Group Base
295 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
296 Electrical and Electronics Engineers, Inc and The Open Group. In the
297 event of any discrepancy between this version and the original IEEE and
298 The Open Group Standard, the original IEEE and The Open Group Standard
299 is the referee document. The original Standard can be obtained online
300 at http://www.opengroup.org/unix/online.html .
301IEEE/The Open Group 2003 GETOPTS(P)