term% cat index.txt GETOPT(3) Library Functions Manual GETOPT(3)
NAME
getopt - 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 argu‐
ment which 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 pro‐
cessed. Since optind is external, it is normally initialized to zero
automatically before the first call to getopt.
Option letters appear in nonempty clusters preceded by `-'. When all
options have been processed (i.e., up to the first non-option argu‐
ment), getopt returns EOF. The special option `--' may be used to de‐
limit 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
This fragment processes arguments for a command that can take option a
and option f, which requires an argument.
main (argc, argv) char ∗∗argv;
{
int c;
extern int optind;
extern char ∗∗optarg, ∗∗ifile;
while ((c = getopt (argc, argv, "af:")) != -1)
switch (c) {
case 'a': aflg++;
break;
case 'f': ifile = optarg;
break;
case '?': errflg++;
}
if (errflg) {
fprintf (stderr, "usage: . . . ");
exit (2);
}
for( ; optind < argc; optind++) {
if (access (argv[optind], 4)) {
...
GETOPT(3)