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authorderaadt <>1995-10-18 08:42:23 +0000
committerderaadt <>1995-10-18 08:42:23 +0000
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1.\" Copyright (c) 1988, 1991, 1993
2.\" The Regents of the University of California. All rights reserved.
3.\"
4.\" Redistribution and use in source and binary forms, with or without
5.\" modification, are permitted provided that the following conditions
6.\" are met:
7.\" 1. Redistributions of source code must retain the above copyright
8.\" notice, this list of conditions and the following disclaimer.
9.\" 2. Redistributions in binary form must reproduce the above copyright
10.\" notice, this list of conditions and the following disclaimer in the
11.\" documentation and/or other materials provided with the distribution.
12.\" 3. All advertising materials mentioning features or use of this software
13.\" must display the following acknowledgement:
14.\" This product includes software developed by the University of
15.\" California, Berkeley and its contributors.
16.\" 4. Neither the name of the University nor the names of its contributors
17.\" may be used to endorse or promote products derived from this software
18.\" without specific prior written permission.
19.\"
20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30.\" SUCH DAMAGE.
31.\"
32.\" @(#)getopt.3 8.4 (Berkeley) 4/19/94
33.\"
34.Dd April 19, 1994
35.Dt GETOPT 3
36.Os BSD 4.3
37.Sh NAME
38.Nm getopt
39.Nd get option character from command line argument list
40.Sh SYNOPSIS
41.Fd #include <unistd.h>
42.Vt extern char *optarg;
43.Vt extern int optind;
44.Vt extern int optopt;
45.Vt extern int opterr;
46.Vt extern int optreset;
47.Ft int
48.Fn getopt "int argc" "char * const *argv" "const char *optstring"
49.Sh DESCRIPTION
50The
51.Fn getopt
52function incrementally parses a command line argument list
53.Fa argv
54and returns the next
55.Em known
56option character.
57An option character is
58.Em known
59if it has been specified in the string of accepted option characters,
60.Fa optstring .
61.Pp
62The option string
63.Fa optstring
64may contain the following elements: individual characters, and
65characters followed by a colon to indicate an option argument
66is to follow.
67For example, an option string
68.Li "\&""x""
69recognizes an option
70.Dq Fl x ,
71and an option string
72.Li "\&""x:""
73recognizes an option and argument
74.Dq Fl x Ar argument .
75It does not matter to
76.Fn getopt
77if a following argument has leading white space.
78.Pp
79On return from
80.Fn getopt ,
81.Va optarg
82points to an option argument, if it is anticipated,
83and the variable
84.Va optind
85contains the index to the next
86.Fa argv
87argument for a subsequent call
88to
89.Fn getopt .
90The variable
91.Va optopt
92saves the last
93.Em known
94option character returned by
95.Fn getopt .
96.Pp
97The variable
98.Va opterr
99and
100.Va optind
101are both initialized to 1.
102The
103.Va optind
104variable may be set to another value before a set of calls to
105.Fn getopt
106in order to skip over more or less argv entries.
107.Pp
108In order to use
109.Fn getopt
110to evaluate multiple sets of arguments, or to evaluate a single set of
111arguments multiple times,
112the variable
113.Va optreset
114must be set to 1 before the second and each additional set of calls to
115.Fn getopt ,
116and the variable
117.Va optind
118must be reinitialized.
119.Pp
120The
121.Fn getopt
122function
123returns \-1
124when the argument list is exhausted, or a non-recognized
125option is encountered.
126The interpretation of options in the argument list may be cancelled
127by the option
128.Ql --
129(double dash) which causes
130.Fn getopt
131to signal the end of argument processing and returns \-1.
132When all options have been processed (i.e., up to the first non-option
133argument),
134.Fn getopt
135returns \-1.
136.Sh DIAGNOSTICS
137If the
138.Fn getopt
139function encounters a character not found in the string
140.Va optarg
141or detects
142a missing option argument it writes an error message and returns
143.Ql ?
144to the
145.Em stderr .
146Setting
147.Va opterr
148to a zero will disable these error messages.
149If
150.Va optstring
151has a leading
152.Ql \&:
153then a missing option argument causes a
154.Ql \&:
155to be returned in addition to suppressing any error messages.
156.Pp
157Option arguments are allowed to begin with
158.Dq Li \- ;
159this is reasonable but
160reduces the amount of error checking possible.
161.Sh EXTENSIONS
162The
163.Va optreset
164variable was added to make it possible to call the
165.Fn getopt
166function multiple times.
167This is an extension to the
168.St -p1003.2
169specification.
170.Sh EXAMPLE
171.Bd -literal -compact
172extern char *optarg;
173extern int optind;
174int bflag, ch, fd;
175
176bflag = 0;
177while ((ch = getopt(argc, argv, "bf:")) != -1)
178 switch(ch) {
179 case 'b':
180 bflag = 1;
181 break;
182 case 'f':
183 if ((fd = open(optarg, O_RDONLY, 0)) < 0) {
184 (void)fprintf(stderr,
185 "myname: %s: %s\en", optarg, strerror(errno));
186 exit(1);
187 }
188 break;
189 case '?':
190 default:
191 usage();
192}
193argc -= optind;
194argv += optind;
195.Ed
196.Sh HISTORY
197The
198.Fn getopt
199function appeared
200.Bx 4.3 .
201.Sh BUGS
202The
203.Fn getopt
204function was once specified to return
205.Dv EOF
206instead of \-1.
207This was changed by
208.St -p1003.2-92
209to decouple
210.Fn getopt
211from
212.Pa <stdio.h> .
213.Pp
214A single dash
215.Dq Li -
216may be specified as an character in
217.Fa optstring ,
218however it should
219.Em never
220have an argument associated with it.
221This allows
222.Fn getopt
223to be used with programs that expect
224.Dq Li -
225as an option flag.
226This practice is wrong, and should not be used in any current development.
227It is provided for backward compatibility
228.Em only .
229By default, a single dash causes
230.Fn getopt
231to return \-1.
232This is, we believe, compatible with System V.
233.Pp
234It is also possible to handle digits as option letters.
235This allows
236.Fn getopt
237to be used with programs that expect a number
238.Pq Dq Li \&-\&3
239as an option.
240This practice is wrong, and should not be used in any current development.
241It is provided for backward compatibility
242.Em only .
243The following code fragment works in most cases.
244.Bd -literal -offset indent
245int length;
246char *p;
247
248while ((c = getopt(argc, argv, "0123456789")) != -1)
249 switch (c) {
250 case '0': case '1': case '2': case '3': case '4':
251 case '5': case '6': case '7': case '8': case '9':
252 p = argv[optind - 1];
253 if (p[0] == '-' && p[1] == ch && !p[2])
254 length = atoi(++p);
255 else
256 length = atoi(argv[optind] + 1);
257 break;
258 }
259}
260.Ed