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.Tn GNU 77extension. 78For example, an option string 79.Li \&"x" 80recognizes an option 81.Dq Fl x , 82and an option string 83.Li \&"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 white space. 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.Ql -- 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.Ql \&? 156(question mark). 157If 158.Fa optstring 159has a leading 160.Ql \&: 161then a missing option argument causes 162.Ql \&: 163to be returned instead of 164.Ql \&? . 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 173#include <unistd.h> 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)) \*[Lt] 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 } 193} 194argc -= optind; 195argv += optind; 196.Ed 197.Sh DIAGNOSTICS 198If the 199.Fn getopt 200function encounters a character not found in the string 201.Fa optstring 202or detects 203a missing option argument it writes an error message to the 204.Dv stderr 205and returns 206.Ql \&? . 207Setting 208.Va opterr 209to a zero will disable these error messages. 210If 211.Fa optstring 212has a leading 213.Ql \&: 214then a missing option argument causes a 215.Ql \&: 216to be returned in addition to suppressing any error messages. 217.Pp 218Option arguments are allowed to begin with 219.Dq Li \- ; 220this is reasonable but reduces the amount of error checking possible. 221.Sh SEE ALSO 222.Xr getopt 1 , 223.Xr getopt_long 3 , 224.Xr getsubopt 3 225.Sh STANDARDS 226The 227.Va optreset 228variable was added to make it possible to call the 229.Fn getopt 230function multiple times. 231This is an extension to the 232.St -p1003.2 233specification. 234.Sh HISTORY 235The 236.Fn getopt 237function appeared in 238.Bx 4.3 . 239.Sh BUGS 240The 241.Fn getopt 242function was once specified to return 243.Dv EOF 244instead of \-1. 245This was changed by 246.St -p1003.2-92 247to decouple 248.Fn getopt 249from 250.In stdio.h . 251.Pp 252A single dash 253.Dq Li - 254may be specified as a character in 255.Fa optstring , 256however it should 257.Em never 258have an argument associated with it. 259This allows 260.Fn getopt 261to be used with programs that expect 262.Dq Li - 263as an option flag. 264This practice is wrong, and should not be used in any current development. 265It is provided for backward compatibility 266.Em only . 267Care should be taken not to use 268.Ql \&- 269as the first character in 270.Fa optstring 271to avoid a semantic conflict with 272.Tn GNU 273.Fn getopt , 274which assigns different meaning to an 275.Fa optstring 276that begins with a 277.Ql \&- . 278By default, a single dash causes 279.Fn getopt 280to return \-1. 281.Pp 282It is also possible to handle digits as option letters. 283This allows 284.Fn getopt 285to be used with programs that expect a number 286.Pq Dq Li \&-\&3 287as an option. 288This practice is wrong, and should not be used in any current development. 289It is provided for backward compatibility 290.Em only . 291The following code fragment works in most cases. 292.Bd -literal -offset indent 293int ch; 294long length; 295char *p, *ep; 296 297while ((ch = getopt(argc, argv, "0123456789")) != -1) 298 switch (ch) { 299 case '0': case '1': case '2': case '3': case '4': 300 case '5': case '6': case '7': case '8': case '9': 301 p = argv[optind - 1]; 302 if (p[0] == '-' \*[Am]\*[Am] p[1] == ch \*[Am]\*[Am] !p[2]) { 303 length = ch - '0'; 304 ep = ""; 305 } else if (argv[optind] \*[Am]\*[Am] argv[optind][1] == ch) { 306 length = strtol((p = argv[optind] + 1), 307 \*[Am]ep, 10); 308 optind++; 309 optreset = 1; 310 } else 311 usage(); 312 if (*ep != '\e0') 313 errx(EX_USAGE, "illegal number -- %s", p); 314 break; 315 } 316.Ed 317