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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 8.5 (Berkeley) 4/27/95 33.\" 34.Dd April 27, 1995 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 <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. 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 \-1 124when the argument list is exhausted, or 125.Ql ? 126if a non-recognized 127option is encountered. 128The interpretation of options in the argument list may be canceled 129by the option 130.Ql -- 131(double dash) which causes 132.Fn getopt 133to signal the end of argument processing and returns \-1. 134When all options have been processed (i.e., up to the first non-option 135argument), 136.Fn getopt 137returns \-1. 138.Sh DIAGNOSTICS 139If the 140.Fn getopt 141function encounters a character not found in the string 142.Va optarg 143or detects 144a missing option argument it writes an error message to the 145.Em stderr 146and returns 147.Ql ? . 148Setting 149.Va opterr 150to a zero will disable these error messages. 151If 152.Va optstring 153has a leading 154.Ql \&: 155then a missing option argument causes a 156.Ql \&: 157to be returned in addition to suppressing any error messages. 158.Pp 159Option arguments are allowed to begin with 160.Dq Li \- ; 161this is reasonable but 162reduces the amount of error checking possible. 163.Sh EXTENSIONS 164The 165.Va optreset 166variable was added to make it possible to call the 167.Fn getopt 168function multiple times. 169This is an extension to the 170.St -p1003.2 171specification. 172.Sh EXAMPLE 173.Bd -literal -compact 174extern char *optarg; 175extern int optind; 176int bflag, ch, fd; 177 178bflag = 0; 179while ((ch = getopt(argc, argv, "bf:")) != -1) 180 switch(ch) { 181 case 'b': 182 bflag = 1; 183 break; 184 case 'f': 185 if ((fd = open(optarg, O_RDONLY, 0)) < 0) { 186 (void)fprintf(stderr, 187 "myname: %s: %s\en", optarg, strerror(errno)); 188 exit(1); 189 } 190 break; 191 case '?': 192 default: 193 usage(); 194} 195argc -= optind; 196argv += optind; 197.Ed 198.Sh HISTORY 199The 200.Fn getopt 201function appeared 202.Bx 4.3 . 203.Sh BUGS 204The 205.Fn getopt 206function was once specified to return 207.Dv EOF 208instead of \-1. 209This was changed by 210.St -p1003.2-92 211to decouple 212.Fn getopt 213from 214.Pa <stdio.h> . 215.Pp 216A single dash 217.Dq Li - 218may be specified as a character in 219.Fa optstring , 220however it should 221.Em never 222have an argument associated with it. 223This allows 224.Fn getopt 225to be used with programs that expect 226.Dq Li - 227as an option flag. 228This practice is wrong, and should not be used in any current development. 229It is provided for backward compatibility 230.Em only . 231By default, a single dash causes 232.Fn getopt 233to return \-1. 234This is, we believe, compatible with System V. 235.Pp 236It is also possible to handle digits as option letters. 237This allows 238.Fn getopt 239to be used with programs that expect a number 240.Pq Dq Li \&-\&3 241as an option. 242This practice is wrong, and should not be used in any current development. 243It is provided for backward compatibility 244.Em only . 245The following code fragment works in most cases. 246.Bd -literal -offset indent 247int length; 248char *p; 249 250while ((c = getopt(argc, argv, "0123456789")) != -1) 251 switch (c) { 252 case '0': case '1': case '2': case '3': case '4': 253 case '5': case '6': case '7': case '8': case '9': 254 p = argv[optind - 1]; 255 if (p[0] == '-' && p[1] == ch && !p[2]) 256 length = atoi(++p); 257 else 258 length = atoi(argv[optind] + 1); 259 break; 260 } 261} 262.Ed 263