getopt(3)
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getopt Subroutine
get option letter from argument vector
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SYNTAX
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)).
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
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
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getopt(3)
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++;
}
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
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getopt(3)
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 for the DG/UX
System.
Changing the value of the variable optind, or calling getopt with
different values of argv, may lead to unexpected results.
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