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 do the parsing (the options
20 and the optstring in the SYNOPSIS), and the parameters which are to be
21 parsed (parameters in the SYNOPSIS). The second part will start at the
22 first non-option parameter that is not an option argument, or after the
23 first occurrence of '--'. If no '-o' or '--options' option is found in
24 the first part, the first parameter of the second part is used as the
25 short options string.
26 If the environment variable GETOPT_COMPATIBLE is set, or if the first
28 parameter is not an option (does not start with a '-', the first format
29 in the SYNOPSIS), getopt will generate output that is compatible with
30 that of other versions of getopt(1). It will still do parameter shuf‐
31 fling and recognize optional arguments (see section COMPATIBILITY for
32 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.
43
45 -a, --alternative
46 Allow long options to start with a single '-'.
47 -h, --help
49 Display help text and exit. No other output is generated.
50 -l, --longoptions longopts
52 The long (multi-character) options to be recognized. More than
53 one option name may be specified at once, by separating the
54 names with commas. This option may be given more than once, the
55 longopts are cumulative. Each long option name in longopts may
56 be followed by one colon to indicate it has a required argument,
57 and by two colons to indicate it has an optional argument.
58 -n, --name progname
60 The name that will be used by the getopt(3) routines when it
61 reports errors. Note that errors of getopt(1) are still
62 reported as coming from getopt.
63 -o, --options shortopts
65 The short (one-character) options to be recognized. If this
66 option is not found, the first parameter of getopt that does not
67 start with a '-' (and is not an option argument) is used as the
68 short options string. Each short option character in shortopts
69 may be followed by one colon to indicate it has a required argu‐
70 ment, and by two colons to indicate it has an optional argument.
71 The first character of shortopts may be '+' or '-' to influence
72 the way options are parsed and output is generated (see section
73 SCANNING MODES for details).
74 -q, --quiet
76 Disable error reporting by getopt(3).
77 -Q, --quiet-output
79 Do not generate normal output. Errors are still reported by
80 getopt(3), unless you also use -q.
81 -s, --shell shell
83 Set quoting conventions to those of shell. If the -s option is
84 not given, the BASH conventions are used. Valid arguments are
85 currently 'sh' 'bash', 'csh', and 'tcsh'.
86 -T, --test
88 Test if your getopt(1) is this enhanced version or an old ver‐
89 sion. This generates no output, and sets the error status to 4.
90 Other implementations of getopt(1), and this version if the
91 environment variable GETOPT_COMPATIBLE is set, will return '--'
92 and error status 0.
93 -u, --unquoted
95 Do not quote the output. Note that whitespace and special
96 (shell-dependent) characters can cause havoc in this mode (like
97 they do with other getopt(1) implementations).
98 -V, --version
100 Display version information and exit. No other output is gener‐
101 ated.
102
104 This section specifies the format of the second part of the parameters
105 of getopt (the parameters in the SYNOPSIS). The next section (OUTPUT)
106 describes the output that is generated. These parameters were typi‐
107 cally the parameters a shell function was called with. Care must be
108 taken that each parameter the shell function was called with corre‐
109 sponds to exactly one parameter in the parameter list of getopt (see
110 the EXAMPLES). All parsing is done by the GNU getopt(3) routines.
111 The parameters are parsed from left to right. Each parameter is clas‐
113 sified as a short option, a long option, an argument to an option, or a
114 non-option parameter.
115 A simple short option is a '-' followed by a short option character.
117 If the option has a required argument, it may be written directly after
118 the option character or as the next parameter (i.e. separated by white‐
119 space on the command line). If the option has an optional argument, it
120 must be written directly after the option character if present.
121 It is possible to specify several short options after one '-', as long
123 as all (except possibly the last) do not have required or optional
124 arguments.
125 A long option normally begins with '--' followed by the long option
127 name. If the option has a required argument, it may be written
128 directly after the long option name, separated by '=', or as the next
129 argument (i.e. separated by whitespace on the command line). If the
130 option has an optional argument, it must be written directly after the
131 long option name, separated by '=', if present (if you add the '=' but
132 nothing behind it, it is interpreted as if no argument was present;
133 this is a slight bug, see the BUGS). Long options may be abbreviated,
134 as long as the abbreviation is not ambiguous.
135 Each parameter not starting with a '-', and not a required argument of
137 a previous option, is a non-option parameter. Each parameter after a
138 '--' parameter is always interpreted as a non-option parameter. If the
139 environment variable POSIXLY_CORRECT is set, or if the short option
140 string started with a '+', all remaining parameters are interpreted as
141 non-option parameters as soon as the first non-option parameter is
142 found.
143
145 Output is generated for each element described in the previous section.
146 Output is done in the same order as the elements are specified in the
147 input, except for non-option parameters. Output can be done in compat‐
148 ible (unquoted) mode, or in such way that whitespace and other special
149 characters within arguments and non-option parameters are preserved
150 (see QUOTING). When the output is processed in the shell script, it
151 will seem to be composed of distinct elements that can be processed one
152 by one (by using the shift command in most shell languages). This is
153 imperfect in unquoted mode, as elements can be split at unexpected
154 places if they contain whitespace or special characters.
155 If there are problems parsing the parameters, for example because a
157 required argument is not found or an option is not recognized, an error
158 will be reported on stderr, there will be no output for the offending
159 element, and a non-zero error status is returned.
160 For a short option, a single '-' and the option character are generated
162 as one parameter. If the option has an argument, the next parameter
163 will be the argument. If the option takes an optional argument, but
164 none was found, the next parameter will be generated but be empty in
165 quoting mode, but no second parameter will be generated in unquoted
166 (compatible) mode. Note that many other getopt(1) implementations do
167 not support optional arguments.
168 If several short options were specified after a single '-', each will
170 be present in the output as a separate parameter.
171 For a long option, '--' and the full option name are generated as one
173 parameter. This is done regardless whether the option was abbreviated
174 or specified with a single '-' in the input. Arguments are handled as
175 with short options.
176 Normally, no non-option parameters output is generated until all
178 options and their arguments have been generated. Then '--' is gener‐
179 ated as a single parameter, and after it the non-option parameters in
180 the order they were found, each as a separate parameter. Only if the
181 first character of the short options string was a '-', non-option
182 parameter output is generated at the place they are found in the input
183 (this is not supported if the first format of the SYNOPSIS is used; in
184 that case all preceding occurrences of '-' and '+' are ignored).
185
187 In compatible mode, whitespace or 'special' characters in arguments or
188 non-option parameters are not handled correctly. As the output is fed
189 to the shell script, the script does not know how it is supposed to
190 break the output into separate parameters. To circumvent this problem,
191 this implementation offers quoting. The idea is that output is gener‐
192 ated with quotes around each parameter. When this output is once again
193 fed to the shell (usually by a shell eval command), it is split cor‐
194 rectly into separate parameters.
195 Quoting is not enabled if the environment variable GETOPT_COMPATIBLE is
197 set, if the first form of the SYNOPSIS is used, or if the option '-u'
198 is found.
199 Different shells use different quoting conventions. You can use the
201 '-s' option to select the shell you are using. The following shells
202 are currently supported: 'sh', 'bash', 'csh' and 'tcsh'. Actually,
203 only two 'flavors' are distinguished: sh-like quoting conventions and
204 csh-like quoting conventions. Chances are that if you use another
205 shell script language, one of these flavors can still be used.
206
208 The first character of the short options string may be a '-' or a '+'
209 to indicate a special scanning mode. If the first calling form in the
210 SYNOPSIS is used they are ignored; the environment variable
211 POSIXLY_CORRECT is still examined, though.
212 If the first character is '+', or if the environment variable
214 POSIXLY_CORRECT is set, parsing stops as soon as the first non-option
215 parameter (i.e. a parameter that does not start with a '-') is found
216 that is not an option argument. The remaining parameters are all
217 interpreted as non-option parameters.
218 If the first character is a '-', non-option parameters are outputted at
220 the place where they are found; in normal operation, they are all col‐
221 lected at the end of output after a '--' parameter has been generated.
222 Note that this '--' parameter is still generated, but it will always be
223 the last parameter in this mode.
224
226 This version of getopt(1) is written to be as compatible as possible to
227 other versions. Usually you can just replace them with this version
228 without any modifications, and with some advantages.
229 If the first character of the first parameter of getopt is not a '-',
231 getopt goes into compatibility mode. It will interpret its first
232 parameter as the string of short options, and all other arguments will
233 be parsed. It will still do parameter shuffling (i.e. all non-option
234 parameters are output at the end), unless the environment variable
235 POSIXLY_CORRECT is set.
236 The environment variable GETOPT_COMPATIBLE forces getopt into compati‐
238 bility mode. Setting both this environment variable and POSIXLY_COR‐
239 RECT offers 100% compatibility for 'difficult' programs. Usually,
240 though, neither is needed.
241 In compatibility mode, leading '-' and '+' characters in the short
243 options string are ignored.
244
246 getopt returns error code 0 for successful parsing, 1 if getopt(3)
247 returns errors, 2 if it does not understand its own parameters, 3 if an
248 internal error occurs like out-of-memory, and 4 if it is called with
249 -T.
250
252 Example scripts for (ba)sh and (t)csh are provided with the getopt(1)
253 distribution, and are optionally installed in /usr/share/getopt/ or
254 /usr/share/doc/ in the util-linux subdirectory.
255
257 POSIXLY_CORRECT
258 This environment variable is examined by the getopt(3) routines.
259 If it is set, parsing stops as soon as a parameter is found that
260 is not an option or an option argument. All remaining parame‐
261 ters are also interpreted as non-option parameters, regardless
262 whether they start with a '-'.
263 GETOPT_COMPATIBLE
265 Forces getopt to use the first calling format as specified in
266 the SYNOPSIS.
267
269 getopt(3) can parse long options with optional arguments that are given
270 an empty optional argument (but cannot do this for short options).
271 This getopt(1) treats optional arguments that are empty as if they were
272 not present.
273 The syntax if you do not want any short option variables at all is not
275 very intuitive (you have to set them explicitly to the empty string).
276
278 Frodo Looijaard ⟨frodo@frodo.looijaard.name⟩
279
281 bash(1), tcsh(1), getopt(3)
282
284 The getopt command is part of the util-linux package and is available
285 from Linux Kernel Archive ⟨https://www.kernel.org/pub/linux/utils/util-
286 linux/⟩.
287util-linux December 2014 GETOPT(1)