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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 <stdlib.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 an 124.Dv EOF 125when the argument list is exhausted, or a non-recognized 126option is encountered. 127The interpretation of options in the argument list may be cancelled 128by the option 129.Ql -- 130(double dash) which causes 131.Fn getopt 132to signal the end of argument processing and return an 133.Dv EOF . 134When all options have been processed (i.e., up to the first non-option 135argument), 136.Fn getopt 137returns 138.Dv EOF . 139.Sh DIAGNOSTICS 140If the 141.Fn getopt 142function encounters a character not found in the string 143.Va optarg 144or detects 145a missing option argument it writes an error message and returns 146.Ql ? 147to the 148.Em stderr . 149Setting 150.Va opterr 151to a zero will disable these error messages. 152If 153.Va optstring 154has a leading 155.Ql \&: 156then a missing option argument causes a 157.Ql \&: 158to be returned in addition to suppressing any error messages. 159.Pp 160Option arguments are allowed to begin with 161.Dq Li \- ; 162this is reasonable but 163reduces the amount of error checking possible. 164.Sh EXTENSIONS 165The 166.Va optreset 167variable was added to make it possible to call the 168.Fn getopt 169function multiple times. 170This is an extension to the 171.St -p1003.2 172specification. 173.Sh EXAMPLE 174.Bd -literal -compact 175extern char *optarg; 176extern int optind; 177int bflag, ch, fd; 178 179bflag = 0; 180while ((ch = getopt(argc, argv, "bf:")) != EOF) 181 switch(ch) { 182 case 'b': 183 bflag = 1; 184 break; 185 case 'f': 186 if ((fd = open(optarg, O_RDONLY, 0)) < 0) { 187 (void)fprintf(stderr, 188 "myname: %s: %s\en", optarg, strerror(errno)); 189 exit(1); 190 } 191 break; 192 case '?': 193 default: 194 usage(); 195} 196argc -= optind; 197argv += optind; 198.Ed 199.Sh HISTORY 200The 201.Fn getopt 202function appeared 203.Bx 4.3 . 204.Sh BUGS 205A single dash 206.Dq Li - 207may be specified as an character in 208.Fa optstring , 209however it should 210.Em never 211have an argument associated with it. 212This allows 213.Fn getopt 214to be used with programs that expect 215.Dq Li - 216as an option flag. 217This practice is wrong, and should not be used in any current development. 218It is provided for backward compatibility 219.Em only . 220By default, a single dash causes 221.Fn getopt 222to return 223.Dv EOF . 224This is, we believe, compatible with System V. 225.Pp 226It is also possible to handle digits as option letters. 227This allows 228.Fn getopt 229to be used with programs that expect a number 230.Pq Dq Li \&-\&3 231as an option. 232This practice is wrong, and should not be used in any current development. 233It is provided for backward compatibility 234.Em only . 235The following code fragment works in most cases. 236.Bd -literal -offset indent 237int length; 238char *p; 239 240while ((c = getopt(argc, argv, "0123456789")) != EOF) 241 switch (c) { 242 case '0': case '1': case '2': case '3': case '4': 243 case '5': case '6': case '7': case '8': case '9': 244 p = argv[optind - 1]; 245 if (p[0] == '-' && p[1] == ch && !p[2]) 246 length = atoi(++p); 247 else 248 length = atoi(argv[optind] + 1); 249 break; 250 } 251} 252.Ed 253