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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 126.Ql ? 127if a non-recognized 128option is encountered. 129The interpretation of options in the argument list may be canceled 130by the option 131.Ql -- 132(double dash) which causes 133.Fn getopt 134to signal the end of argument processing and return an 135.Dv EOF . 136When all options have been processed (i.e., up to the first non-option 137argument), 138.Fn getopt 139returns 140.Dv EOF . 141.Sh DIAGNOSTICS 142If the 143.Fn getopt 144function encounters a character not found in the string 145.Va optarg 146or detects 147a missing option argument it writes an error message to the 148.Em stderr 149and returns 150.Ql ? . 151Setting 152.Va opterr 153to a zero will disable these error messages. 154If 155.Va optstring 156has a leading 157.Ql \&: 158then a missing option argument causes a 159.Ql \&: 160to be returned in addition to suppressing any error messages. 161.Pp 162Option arguments are allowed to begin with 163.Dq Li \- ; 164this is reasonable but 165reduces the amount of error checking possible. 166.Sh EXTENSIONS 167The 168.Va optreset 169variable was added to make it possible to call the 170.Fn getopt 171function multiple times. 172This is an extension to the 173.St -p1003.2 174specification. 175.Sh EXAMPLE 176.Bd -literal -compact 177extern char *optarg; 178extern int optind; 179int bflag, ch, fd; 180 181bflag = 0; 182while ((ch = getopt(argc, argv, "bf:")) != EOF) 183 switch(ch) { 184 case 'b': 185 bflag = 1; 186 break; 187 case 'f': 188 if ((fd = open(optarg, O_RDONLY, 0)) < 0) { 189 (void)fprintf(stderr, 190 "myname: %s: %s\en", optarg, strerror(errno)); 191 exit(1); 192 } 193 break; 194 case '?': 195 default: 196 usage(); 197} 198argc -= optind; 199argv += optind; 200.Ed 201.Sh HISTORY 202The 203.Fn getopt 204function appeared 205.Bx 4.3 . 206.Sh BUGS 207A single dash 208.Dq Li - 209may be specified as an character in 210.Fa optstring , 211however it should 212.Em never 213have an argument associated with it. 214This allows 215.Fn getopt 216to be used with programs that expect 217.Dq Li - 218as an option flag. 219This practice is wrong, and should not be used in any current development. 220It is provided for backward compatibility 221.Em only . 222By default, a single dash causes 223.Fn getopt 224to return 225.Dv EOF . 226This is, we believe, compatible with System V. 227.Pp 228It is also possible to handle digits as option letters. 229This allows 230.Fn getopt 231to be used with programs that expect a number 232.Pq Dq Li \&-\&3 233as an option. 234This practice is wrong, and should not be used in any current development. 235It is provided for backward compatibility 236.Em only . 237The following code fragment works in most cases. 238.Bd -literal -offset indent 239int length; 240char *p; 241 242while ((c = getopt(argc, argv, "0123456789")) != EOF) 243 switch (c) { 244 case '0': case '1': case '2': case '3': case '4': 245 case '5': case '6': case '7': case '8': case '9': 246 p = argv[optind - 1]; 247 if (p[0] == '-' && p[1] == ch && !p[2]) 248 length = atoi(++p); 249 else 250 length = atoi(argv[optind] + 1); 251 break; 252 } 253} 254.Ed 255