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Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)getopt.3 8.5 (Berkeley) 4/27/95 .\" $FreeBSD$ .\" .Dd April 27, 1995 .Dt GETOPT 3 .Os BSD 4.3 .Sh NAME .Nm getopt .Nd get option character from command line argument list .Sh LIBRARY .Lb libc .Sh SYNOPSIS .Fd #include .Vt extern char *optarg; .Vt extern int optind; .Vt extern int optopt; .Vt extern int opterr; .Vt extern int optreset; .Ft int .Fn getopt "int argc" "char * const *argv" "const char *optstring" .Sh DESCRIPTION The .Fn getopt function incrementally parses a command line argument list .Fa argv and returns the next .Em known option character. An option character is .Em known if it has been specified in the string of accepted option characters, .Fa optstring . .Pp The option string .Fa optstring may contain the following elements: individual characters, and characters followed by a colon to indicate an option argument is to follow. For example, an option string .Li "\&""x"" recognizes an option .Dq Fl x , and an option string .Li "\&""x:"" recognizes an option and argument .Dq Fl x Ar argument . It does not matter to .Fn getopt if a following argument has leading white space. .Pp On return from .Fn getopt , .Va optarg points to an option argument, if it is anticipated, and the variable .Va optind contains the index to the next .Fa argv argument for a subsequent call to .Fn getopt . The variable .Va optopt saves the last .Em known option character returned by .Fn getopt . .Pp The variable .Va opterr and .Va optind are both initialized to 1. The .Va optind variable may be set to another value before a set of calls to .Fn getopt in order to skip over more or less argv entries. .Pp In order to use .Fn getopt to evaluate multiple sets of arguments, or to evaluate a single set of arguments multiple times, the variable .Va optreset must be set to 1 before the second and each additional set of calls to .Fn getopt , and the variable .Va optind must be reinitialized. .Pp The .Fn getopt function returns \-1 when the argument list is exhausted, or .Ql ? if a non-recognized option is encountered. The interpretation of options in the argument list may be cancelled by the option .Ql -- (double dash) which causes .Fn getopt to signal the end of argument processing and return \-1. When all options have been processed (i.e., up to the first non-option argument), .Fn getopt returns \-1. .Sh DIAGNOSTICS If the .Fn getopt function encounters a character not found in the string .Va optarg or detects a missing option argument it writes an error message to the .Em stderr and returns .Ql ? . Setting .Va opterr to a zero will disable these error messages. If .Va optstring has a leading .Ql \&: then a missing option argument causes a .Ql \&: to be returned in addition to suppressing any error messages. .Pp Option arguments are allowed to begin with .Dq Li \- ; this is reasonable but reduces the amount of error checking possible. .Sh EXTENSIONS The .Va optreset variable was added to make it possible to call the .Fn getopt function multiple times. This is an extension to the .St -p1003.2 specification. .Sh EXAMPLE .Bd -literal -compact int bflag, ch, fd; bflag = 0; while ((ch = getopt(argc, argv, "bf:")) != -1) switch (ch) { case 'b': bflag = 1; break; case 'f': if ((fd = open(optarg, O_RDONLY, 0)) < 0) err(1, "%s", optarg); break; case '?': default: usage(); } argc -= optind; argv += optind; .Ed .Sh HISTORY The .Fn getopt function appeared in .Bx 4.3 . .Sh BUGS The .Fn getopt function was once specified to return .Dv EOF instead of \-1. This was changed by .St -p1003.2-92 to decouple .Fn getopt from .Pa . .Pp A single dash .Dq Li - may be specified as a character in .Fa optstring , however it should .Em never have an argument associated with it. This allows .Fn getopt to be used with programs that expect .Dq Li - as an option flag. This practice is wrong, and should not be used in any current development. It is provided for backward compatibility .Em only . By default, a single dash causes .Fn getopt to return \-1. This is, we believe, compatible with System V. .Pp It is also possible to handle digits as option letters. This allows .Fn getopt to be used with programs that expect a number .Pq Dq Li \&-\&3 as an option. This practice is wrong, and should not be used in any current development. It is provided for backward compatibility .Em only . The following code fragment works in most (but not all) cases. .Bd -literal -offset indent int length; char *p, *ep; while ((ch = getopt(argc, argv, "0123456789")) != -1) switch (ch) { case '0': case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9': p = argv[optind - 1]; if (p[0] == '-' && p[1] == ch && !p[2]) length = strtol(++p, &ep, 10); else if (argv[optind] && argv[optind][1] == ch) { length = strtol((p = argv[optind] + 1), &ep, 10); optind++; optreset = 1; } else usage(); if (*ep != '\0') errx(EX_USAGE, "illegal number -- %s", p); break; } .Ed