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. 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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.\" $FreeBSD$ 32.\" 33.Dd June 5, 2014 34.Dt GETOPT 3 35.Os 36.Sh NAME 37.Nm getopt 38.Nd get option character from command line argument list 39.Sh LIBRARY 40.Lb libc 41.Sh SYNOPSIS 42.In unistd.h 43.Vt extern char *optarg ; 44.Vt extern int optind ; 45.Vt extern int optopt ; 46.Vt extern int opterr ; 47.Vt extern int optreset ; 48.Ft int 49.Fn getopt "int argc" "char * const argv[]" "const char *optstring" 50.Sh DESCRIPTION 51The 52.Fn getopt 53function incrementally parses a command line argument list 54.Fa argv 55and returns the next 56.Em known 57option character. 58An option character is 59.Em known 60if it has been specified in the string of accepted option characters, 61.Fa optstring . 62.Pp 63The option string 64.Fa optstring 65may contain the following elements: individual characters, and 66characters followed by a colon to indicate an option argument 67is to follow. 68If an individual character is followed by two colons, then the 69option argument is optional; 70.Va optarg 71is set to the rest of the current 72.Va argv 73word, or 74.Dv NULL 75if there were no more characters in the current word. 76This is a 77.Tn GNU 78extension. 79For example, an option string 80.Li \&"x" 81recognizes an option 82.Dq Fl x , 83and an option string 84.Li \&"x:" 85recognizes an option and argument 86.Dq Fl x Ar argument . 87It does not matter to 88.Fn getopt 89if a following argument has leading white space. 90.Pp 91On return from 92.Fn getopt , 93.Va optarg 94points to an option argument, if it is anticipated, 95and the variable 96.Va optind 97contains the index to the next 98.Fa argv 99argument for a subsequent call 100to 101.Fn getopt . 102The variable 103.Va optopt 104saves the last 105.Em known 106option character returned by 107.Fn getopt . 108.Pp 109The variables 110.Va opterr 111and 112.Va optind 113are both initialized to 1. 114The 115.Va optind 116variable may be set to another value before a set of calls to 117.Fn getopt 118in order to skip over more or less argv entries. 119.Pp 120In order to use 121.Fn getopt 122to evaluate multiple sets of arguments, or to evaluate a single set of 123arguments multiple times, 124the variable 125.Va optreset 126must be set to 1 before the second and each additional set of calls to 127.Fn getopt , 128and the variable 129.Va optind 130must be reinitialized. 131.Pp 132The 133.Fn getopt 134function returns \-1 when the argument list is exhausted. 135The interpretation of options in the argument list may be cancelled 136by the option 137.Ql -- 138(double dash) which causes 139.Fn getopt 140to signal the end of argument processing and return \-1. 141When all options have been processed (i.e., up to the first non-option 142argument), 143.Fn getopt 144returns \-1. 145.Sh RETURN VALUES 146The 147.Fn getopt 148function returns the next known option character in 149.Fa optstring . 150If 151.Fn getopt 152encounters a character not found in 153.Fa optstring 154or if it detects a missing option argument, 155it returns 156.Ql \&? 157(question mark). 158If 159.Fa optstring 160has a leading 161.Ql \&: 162then a missing option argument causes 163.Ql \&: 164to be returned instead of 165.Ql \&? . 166In either case, the variable 167.Va optopt 168is set to the character that caused the error. 169The 170.Fn getopt 171function returns \-1 when the argument list is exhausted. 172.Sh EXAMPLES 173.Bd -literal -compact 174#include <unistd.h> 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 the 205.Dv stderr 206and returns 207.Ql \&? . 208Setting 209.Va opterr 210to a zero will disable these error messages. 211If 212.Fa optstring 213has a leading 214.Ql \&: 215then a missing option argument causes a 216.Ql \&: 217to be returned in addition to suppressing any error messages. 218.Pp 219Option arguments are allowed to begin with 220.Dq Li \- ; 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.Dq Li - 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.Dq Li - 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.Ql \&- 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.Ql \&- . 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, *ep; 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 ep = ""; 306 } else if (argv[optind] \*[Am]\*[Am] argv[optind][1] == ch) { 307 length = strtol((p = argv[optind] + 1), 308 \*[Am]ep, 10); 309 optind++; 310 optreset = 1; 311 } else 312 usage(); 313 if (*ep != '\e0') 314 errx(EX_USAGE, "illegal number -- %s", p); 315 break; 316 } 317.Ed 318