1GETOPT(1) User Commands GETOPT(1)
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6 getopt - parse command options (enhanced)
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9 getopt optstring parameters
10 getopt [options] [--] optstring parameters
11 getopt [options] -o|--options optstring [options] [--] parameters
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14 getopt is used to break up (parse) options in command lines for easy
15 parsing by shell procedures, and to check for legal options. It uses
16 the GNU getopt(3) routines to do this.
17 The parameters getopt is called with can be divided into two parts:
19 options which modify the way getopt will parse (options and
20 -o|--options optstring in the SYNOPSIS), and the parameters which are
21 to be parsed (parameters in the SYNOPSIS). The second part will start
22 at the first non-option parameter that is not an option argument, or
23 after the first occurrence of '--'. If no '-o' or '--options' option
24 is found in the first part, the first parameter of the second part is
25 used as the short options string.
26 If the environment variable GETOPT_COMPATIBLE is set, or if its first
28 parameter is not an option (does not start with a '-', this is the
29 first format in the SYNOPSIS), getopt will generate output that is com‐
30 patible with that of other versions of getopt(1). It will still do
31 parameter shuffling and recognize optional arguments (see section COM‐
32 PATIBILITY for more information).
33 Traditional implementations of getopt(1) are unable to cope with white‐
35 space and other (shell-specific) special characters in arguments and
36 non-option parameters. To solve this problem, this implementation can
37 generate quoted output which must once again be interpreted by the
38 shell (usually by using the eval command). This has the effect of pre‐
39 serving those characters, but you must call getopt in a way that is no
40 longer compatible with other versions (the second or third format in
41 the SYNOPSIS). To determine whether this enhanced version of getopt(1)
42 is installed, a special test option (-T) can be used.
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45 -a, --alternative
46 Allow long options to start with a single '-'.
47 -h, --help
49 Output a small usage guide and exit successfully. No other out‐
50 put is generated.
51 -l, --longoptions longopts
53 The long (multi-character) options to be recognized. More than
54 one option name may be specified at once, by separating the
55 names with commas. This option may be given more than once, the
56 longopts are cumulative. Each long option name in longopts may
57 be followed by one colon to indicate it has a required argument,
58 and by two colons to indicate it has an optional argument.
59 -n, --name progname
61 The name that will be used by the getopt(3) routines when it
62 reports errors. Note that errors of getopt(1) are still
63 reported as coming from getopt.
64 -o, --options shortopts
66 The short (one-character) options to be recognized. If this
67 option is not found, the first parameter of getopt that does not
68 start with a '-' (and is not an option argument) is used as the
69 short options string. Each short option character in shortopts
70 may be followed by one colon to indicate it has a required argu‐
71 ment, and by two colons to indicate it has an optional argument.
72 The first character of shortopts may be '+' or '-' to influence
73 the way options are parsed and output is generated (see section
74 SCANNING MODES for details).
75 -q, --quiet
77 Disable error reporting by getopt(3).
78 -Q, --quiet-output
80 Do not generate normal output. Errors are still reported by
81 getopt(3), unless you also use -q.
82 -s, --shell shell
84 Set quoting conventions to those of shell. If no -s argument is
85 found, the BASH conventions are used. Valid arguments are cur‐
86 rently 'sh' 'bash', 'csh', and 'tcsh'.
87 -u, --unquoted
89 Do not quote the output. Note that whitespace and special
90 (shell-dependent) characters can cause havoc in this mode (like
91 they do with other getopt(1) implementations).
92 -T, --test
94 Test if your getopt(1) is this enhanced version or an old ver‐
95 sion. This generates no output, and sets the error status to 4.
96 Other implementations of getopt(1), and this version if the
97 environment variable GETOPT_COMPATIBLE is set, will return '--'
98 and error status 0.
99 -V, --version
101 Output version information and exit successfully. No other out‐
102 put is generated.
103
105 This section specifies the format of the second part of the parameters
106 of getopt (the parameters in the SYNOPSIS). The next section (OUTPUT)
107 describes the output that is generated. These parameters were typi‐
108 cally the parameters a shell function was called with. Care must be
109 taken that each parameter the shell function was called with corre‐
110 sponds to exactly one parameter in the parameter list of getopt (see
111 the EXAMPLES). All parsing is done by the GNU getopt(3) routines.
112 The parameters are parsed from left to right. Each parameter is clas‐
114 sified as a short option, a long option, an argument to an option, or a
115 non-option parameter.
116 A simple short option is a '-' followed by a short option character.
118 If the option has a required argument, it may be written directly after
119 the option character or as the next parameter (ie. separated by white‐
120 space on the command line). If the option has an optional argument, it
121 must be written directly after the option character if present.
122 It is possible to specify several short options after one '-', as long
124 as all (except possibly the last) do not have required or optional
125 arguments.
126 A long option normally begins with '--' followed by the long option
128 name. If the option has a required argument, it may be written
129 directly after the long option name, separated by '=', or as the next
130 argument (i.e. separated by whitespace on the command line). If the
131 option has an optional argument, it must be written directly after the
132 long option name, separated by '=', if present (if you add the '=' but
133 nothing behind it, it is interpreted as if no argument was present;
134 this is a slight bug, see the BUGS). Long options may be abbreviated,
135 as long as the abbreviation is not ambiguous.
136 Each parameter not starting with a '-', and not a required argument of
138 a previous option, is a non-option parameter. Each parameter after a
139 '--' parameter is always interpreted as a non-option parameter. If the
140 environment variable POSIXLY_CORRECT is set, or if the short option
141 string started with a '+', all remaining parameters are interpreted as
142 non-option parameters as soon as the first non-option parameter is
143 found.
144
146 Output is generated for each element described in the previous section.
147 Output is done in the same order as the elements are specified in the
148 input, except for non-option parameters. Output can be done in compat‐
149 ible (unquoted) mode, or in such way that whitespace and other special
150 characters within arguments and non-option parameters are preserved
151 (see QUOTING). When the output is processed in the shell script, it
152 will seem to be composed of distinct elements that can be processed one
153 by one (by using the shift command in most shell languages). This is
154 imperfect in unquoted mode, as elements can be split at unexpected
155 places if they contain whitespace or special characters.
156 If there are problems parsing the parameters, for example because a
158 required argument is not found or an option is not recognized, an error
159 will be reported on stderr, there will be no output for the offending
160 element, and a non-zero error status is returned.
161 For a short option, a single '-' and the option character are generated
163 as one parameter. If the option has an argument, the next parameter
164 will be the argument. If the option takes an optional argument, but
165 none was found, the next parameter will be generated but be empty in
166 quoting mode, but no second parameter will be generated in unquoted
167 (compatible) mode. Note that many other getopt(1) implementations do
168 not support optional arguments.
169 If several short options were specified after a single '-', each will
171 be present in the output as a separate parameter.
172 For a long option, '--' and the full option name are generated as one
174 parameter. This is done regardless whether the option was abbreviated
175 or specified with a single '-' in the input. Arguments are handled as
176 with short options.
177 Normally, no non-option parameters output is generated until all
179 options and their arguments have been generated. Then '--' is gener‐
180 ated as a single parameter, and after it the non-option parameters in
181 the order they were found, each as a separate parameter. Only if the
182 first character of the short options string was a '-', non-option
183 parameter output is generated at the place they are found in the input
184 (this is not supported if the first format of the SYNOPSIS is used; in
185 that case all preceding occurrences of '-' and '+' are ignored).
186
188 In compatible mode, whitespace or 'special' characters in arguments or
189 non-option parameters are not handled correctly. As the output is fed
190 to the shell script, the script does not know how it is supposed to
191 break the output into separate parameters. To circumvent this problem,
192 this implementation offers quoting. The idea is that output is gener‐
193 ated with quotes around each parameter. When this output is once again
194 fed to the shell (usually by a shell eval command), it is split cor‐
195 rectly into separate parameters.
196 Quoting is not enabled if the environment variable GETOPT_COMPATIBLE is
198 set, if the first form of the SYNOPSIS is used, or if the option '-u'
199 is found.
200 Different shells use different quoting conventions. You can use the
202 '-s' option to select the shell you are using. The following shells
203 are currently supported: 'sh', 'bash', 'csh' and 'tcsh'. Actually,
204 only two 'flavors' are distinguished: sh-like quoting conventions and
205 csh-like quoting conventions. Chances are that if you use another
206 shell script language, one of these flavors can still be used.
207
209 The first character of the short options string may be a '-' or a '+'
210 to indicate a special scanning mode. If the first calling form in the
211 SYNOPSIS is used they are ignored; the environment variable
212 POSIXLY_CORRECT is still examined, though.
213 If the first character is '+', or if the environment variable
215 POSIXLY_CORRECT is set, parsing stops as soon as the first non-option
216 parameter (ie. a parameter that does not start with a '-') is found
217 that is not an option argument. The remaining parameters are all
218 interpreted as non-option parameters.
219 If the first character is a '-', non-option parameters are outputted at
221 the place where they are found; in normal operation, they are all col‐
222 lected at the end of output after a '--' parameter has been generated.
223 Note that this '--' parameter is still generated, but it will always be
224 the last parameter in this mode.
225
227 This version of getopt(1) is written to be as compatible as possible to
228 other versions. Usually you can just replace them with this version
229 without any modifications, and with some advantages.
230 If the first character of the first parameter of getopt is not a '-',
232 getopt goes into compatibility mode. It will interpret its first
233 parameter as the string of short options, and all other arguments will
234 be parsed. It will still do parameter shuffling (ie. all non-option
235 parameters are outputted at the end), unless the environment variable
236 POSIXLY_CORRECT is set.
237 The environment variable GETOPT_COMPATIBLE forces getopt into compati‐
239 bility mode. Setting both this environment variable and POSIXLY_COR‐
240 RECT offers 100% compatibility for 'difficult' programs. Usually,
241 though, neither is needed.
242 In compatibility mode, leading '-' and '+' characters in the short
244 options string are ignored.
245
247 getopt returns error code 0 for successful parsing, 1 if getopt(3)
248 returns errors, 2 if it does not understand its own parameters, 3 if an
249 internal error occurs like out-of-memory, and 4 if it is called with
250 -T.
251
253 Example scripts for (ba)sh and (t)csh are provided with the getopt(1)
254 distribution, and are optionally installed in /usr/share/getopt/ or
255 /usr/share/docs/ in util-linux subdirectory.
256
258 POSIXLY_CORRECT
259 This environment variable is examined by the getopt(3) routines.
260 If it is set, parsing stops as soon as a parameter is found that
261 is not an option or an option argument. All remaining parame‐
262 ters are also interpreted as non-option parameters, regardless
263 whether they start with a '-'.
264 GETOPT_COMPATIBLE
266 Forces getopt to use the first calling format as specified in
267 the SYNOPSIS.
268
270 getopt(3) can parse long options with optional arguments that are given
271 an empty optional argument (but can not do this for short options).
272 This getopt(1) treats optional arguments that are empty as if they were
273 not present.
274 The syntax if you do not want any short option variables at all is not
276 very intuitive (you have to set them explicitly to the empty string).
277
279 Frodo Looijaard ⟨frodo@frodo.looijaard.name⟩
280
282 getopt(3), bash(1), tcsh(1).
283
285 The getopt command is part of the util-linux package and is available
286 from Linux Kernel Archive ⟨ftp://ftp.kernel.org/pub/linux/utils/util-
287 linux/⟩.
288util-linux June 2012 GETOPT(1)