GETOPT(3)GETOPT(3)NAMEgetopt - get option letter from argv
SYNOPSIS
int getopt(argc, argv, optstring)
int argc;
char **argv;
char *optstring;
extern char *optarg;
extern int optind;
DESCRIPTION
Getopt returns the next option letter in argv that matches a letter in
optstring. Optstring is a string of recognized option letters; if a
letter is followed by a colon, the option is expected to have an
argument that may or may not 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. Because optind is external, it is normally initialized to
zero automatically before the first call to getopt.
When all options have been processed (i.e., up to the first non-option
argument), getopt returns EOF. The special option -- may be used to
delimit the end of the options; EOF will be returned, and -- will be
skipped.
DIAGNOSTICS
Getopt prints an error message on stderr and returns a question mark
(?) when it encounters an option letter not included in optstring.
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 options f and o, both of which require arguments:
main(argc, argv)
int argc;
char **argv;
{
int c;
extern int optind;
extern char *optarg;
.
.
.
while ((c = getopt(argc, argv, "abf:o:")) != EOF)
switch (c) {
case `a':
if (bflg)
errflg++;
else
aflg++;
break;
case `b':
if (aflg)
errflg++;
else
bproc();
break;
case `f':
ifile = optarg;
break;
case `o':
ofile = optarg;
break;
case `?':
default:
errflg++;
break;
}
if (errflg) {
fprintf(stderr, "Usage: ...");
exit(2);
}
for (; optind < argc; optind++) {
.
.
.
}
.
.
.
}
HISTORY
Written by Henry Spencer, working from a Bell Labs manual page.
Modified by Keith Bostic to behave more like the System V version.
BUGS
It is not obvious how `-' standing alone should be treated; this
version treats it as a non-option argument, which is not always right.
Option arguments are allowed to begin with `-'; this is reasonable but
reduces the amount of error checking possible.
Getopt is quite flexible but the obvious price must be paid: there is
much it could do that it doesn't, like checking mutually exclusive
options, checking type of option arguments, etc.
4.3 Berkeley Distribution May 27, 1986 GETOPT(3)
