1.\" $NetBSD: getopt.3,v 1.34 2014/06/05 22:09:50 wiz Exp $ 2.\" 3.\" Copyright (c) 1988, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)getopt.3 8.5 (Berkeley) 4/27/95 31.\" 32.Dd June 5, 2014 33.Dt GETOPT 3 34.Os 35.Sh NAME 36.Nm getopt 37.Nd get option character from command line argument list 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In 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. 67If an individual character is followed by two colons, then the 68option argument is optional; 69.Va optarg 70is set to the rest of the current 71.Va argv 72word, or 73.Dv NULL 74if there were no more characters in the current word. 75This is a 76.Nx 77extension. 78For example, an option string 79.Qq x 80recognizes an option 81.Dq Fl x , 82and an option string 83.Qq x: 84recognizes an option and argument 85.Dq Fl x Ar argument . 86It does not matter to 87.Fn getopt 88if a following argument has leading whitespace. 89.Pp 90On return from 91.Fn getopt , 92.Va optarg 93points to an option argument, if it is anticipated, 94and the variable 95.Va optind 96contains the index to the next 97.Fa argv 98argument for a subsequent call 99to 100.Fn getopt . 101The variable 102.Va optopt 103saves the last 104.Em known 105option character returned by 106.Fn getopt . 107.Pp 108The variables 109.Va opterr 110and 111.Va optind 112are both initialized to 1. 113The 114.Va optind 115variable may be set to another value before a set of calls to 116.Fn getopt 117in order to skip over more or less argv entries. 118.Pp 119In order to use 120.Fn getopt 121to evaluate multiple sets of arguments, or to evaluate a single set of 122arguments multiple times, 123the variable 124.Va optreset 125must be set to 1 before the second and each additional set of calls to 126.Fn getopt , 127and the variable 128.Va optind 129must be reinitialized. 130.Pp 131The 132.Fn getopt 133function returns \-1 when the argument list is exhausted. 134The interpretation of options in the argument list may be cancelled 135by the option 136.Dq -- 137(double dash) which causes 138.Fn getopt 139to signal the end of argument processing and return \-1. 140When all options have been processed (i.e., up to the first non-option 141argument), 142.Fn getopt 143returns \-1. 144.Sh RETURN VALUES 145The 146.Fn getopt 147function returns the next known option character in 148.Fa optstring . 149If 150.Fn getopt 151encounters a character not found in 152.Fa optstring 153or if it detects a missing option argument, 154it returns 155.Sq \&? 156(question mark). 157If 158.Fa optstring 159has a leading 160.Sq \&: 161then a missing option argument causes 162.Sq \&: 163to be returned instead of 164.Sq \&? . 165In either case, the variable 166.Va optopt 167is set to the character that caused the error. 168The 169.Fn getopt 170function returns \-1 when the argument list is exhausted. 171.Sh EXAMPLES 172.Bd -literal -compact 173extern char *optarg; 174extern int optind; 175int bflag, ch, fd; 176 177bflag = 0; 178while ((ch = getopt(argc, argv, "bf:")) != -1) { 179 switch (ch) { 180 case 'b': 181 bflag = 1; 182 break; 183 case 'f': 184 if ((fd = open(optarg, O_RDONLY, 0)) \*[Lt] 0) { 185 (void)fprintf(stderr, 186 "myname: %s: %s\en", optarg, strerror(errno)); 187 exit(1); 188 } 189 break; 190 case '?': 191 default: 192 usage(); 193 } 194} 195argc -= optind; 196argv += optind; 197.Ed 198.Sh DIAGNOSTICS 199If the 200.Fn getopt 201function encounters a character not found in the string 202.Fa optstring 203or detects 204a missing option argument it writes an error message to 205.Em stderr 206and returns 207.Sq \&? . 208Setting 209.Va opterr 210to a zero will disable these error messages. 211If 212.Fa optstring 213has a leading 214.Sq \&: 215then a missing option argument causes a 216.Sq \&: 217to be returned in addition to suppressing any error messages. 218.Pp 219Option arguments are allowed to begin with 220.Sq - ; 221this is reasonable but reduces the amount of error checking possible. 222.Sh SEE ALSO 223.Xr getopt 1 , 224.Xr getopt_long 3 , 225.Xr getsubopt 3 226.Sh STANDARDS 227The 228.Va optreset 229variable was added to make it possible to call the 230.Fn getopt 231function multiple times. 232This is an extension to the 233.St -p1003.2 234specification. 235.Sh HISTORY 236The 237.Fn getopt 238function appeared in 239.Bx 4.3 . 240.Sh BUGS 241The 242.Fn getopt 243function was once specified to return 244.Dv EOF 245instead of \-1. 246This was changed by 247.St -p1003.2-92 248to decouple 249.Fn getopt 250from 251.In stdio.h . 252.Pp 253A single dash 254.Pq Sq - 255may be specified as a character in 256.Fa optstring , 257however it should 258.Em never 259have an argument associated with it. 260This allows 261.Fn getopt 262to be used with programs that expect 263.Sq - 264as an option flag. 265This practice is wrong, and should not be used in any current development. 266It is provided for backward compatibility 267.Em only . 268Care should be taken not to use 269.Sq - 270as the first character in 271.Fa optstring 272to avoid a semantic conflict with 273.Tn GNU 274.Fn getopt , 275which assigns different meaning to an 276.Fa optstring 277that begins with a 278.Sq - . 279By default, a single dash causes 280.Fn getopt 281to return \-1. 282.Pp 283It is also possible to handle digits as option letters. 284This allows 285.Fn getopt 286to be used with programs that expect a number 287.Pq Dq Li \-3 288as an option. 289This practice is wrong, and should not be used in any current development. 290It is provided for backward compatibility 291.Em only . 292The following code fragment works in most cases. 293.Bd -literal -offset indent 294int ch; 295long length; 296char *p; 297 298while ((ch = getopt(argc, argv, "0123456789")) != -1) { 299 switch (ch) { 300 case '0': case '1': case '2': case '3': case '4': 301 case '5': case '6': case '7': case '8': case '9': 302 p = argv[optind - 1]; 303 if (p[0] == '-' \*[Am]\*[Am] p[1] == ch \*[Am]\*[Am] !p[2]) 304 length = ch - '0'; 305 else 306 length = strtol(argv[optind] + 1, NULL, 10); 307 break; 308 } 309} 310.Ed 311