GETOPT(3C) (C Programming Language Utilities) GETOPT(3C)
NAME
getopt - get option letter from argument vector
SYNOPSIS
int getopt (argc, argv, optstring)
int argc;
char **argv, *opstring;
extern char *optarg;
extern int optind, opterr;
DESCRIPTION
getopt returns the next option letter in argv that matches a
letter in optstring. It supports all the rules of the
command syntax standard (see intro(1)). So all new commands
will adhere to the command syntax standard, they should use
getopts(1) or getopt(3C) to parse positional parameters and
check for options that are legal for that command.
optstring must contain the option letters the command using
getopt will recognize; if a letter is followed by a colon,
the option is expected to have an argument, or group of
arguments, which must be separated from it by white space.
optarg is set to point to the start of the option-argument
on return from getopt.
getopt places in optind the argv index of the next argument
to be processed. optind is external and is initialized to 1
before the first call to getopt.
When all options have been processed (i.e., up to the first
non-option argument), getopt returns -1. The special option
``--'' may be used to delimit the end of the options; when
it is encountered, -1 will be returned, and ``--'' will be
skipped.
DIAGNOSTICS
getopt prints an error message on standard error and returns
a question mark (?) when it encounters an option letter not
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GETOPT(3C) (C Programming Language Utilities) GETOPT(3C)
included in optstring or no option-argument after an option
that expects one. This error message may be disabled by
setting opterr to 0.
EXAMPLE
The following code fragment shows how one might process the
arguments for a command that can take the mutually exclusive
options a and b, and the option o, which requires an
option-argument:
main (argc, argv)
int argc;
char **argv;
{
int c;
extern char *optarg;
extern int optind;
.
.
.
while ((c = getopt(argc, argv, "abo:")) != -1)
switch (c) {
case 'a':
if (bflg)
errflg++;
else
aflg++;
break;
case 'b':
if (aflg)
errflg++;
else
bproc( );
break;
case 'o':
ofile = optarg;
break;
case '?':
errflg++;
}
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GETOPT(3C) (C Programming Language Utilities) GETOPT(3C)
if (errflg) {
(void)fprintf(stderr, "usage: . . . ");
exit (2);
}
for ( ; optind < argc; optind++) {
if (access(argv[optind], 4)) {
.
.
.
}
WARNING
Although the following command syntax rule (see intro(1))
relaxations are permitted under the current implementation,
they should not be used because they may not be supported in
future releases of the system. As in the EXAMPLE section
above, a and b are options, and the option o requires an
option-argument:
cmd -aboxxx file (Rule 5 violation: options with
option-arguments must not be grouped with other options)
cmd -ab -oxxx file (Rule 6 violation: there must be
white space after an option that takes an option-argument)
SEE ALSO
getopts(1), intro(1) in the User's Reference Manual.
Page 3 May 1989