<TITLE>getopt</TITLE>
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<h3>GETOPT(3) Linux Programmer's Manual GETOPT(3)
</h3>
<h3>NAME
</h3> getopt - Read command line options
<h3>SYNOPSIS
</h3> #include <unistd.h>
int getopt(int argc, char * const argv[],
const char *optstring);
extern char *optarg;
extern int optind, opterr, optopt;
#include <getopt.h>
int getopt_long(int argc, char * const argv[],
const char *shortopts,
const struct option *longopts, int longind);
<h3>DESCRIPTION
</h3> The getopt() function parses the command line arguments.
Its arguments argc and argv are the argument count and
array as passed to the main() function on program invoca-
tion. optstring is a list of available option characters.
If such a character is followed by a colon, the option
takes an argument, which is placed in optarg.
The external variable optind is the index of the next
array element of argv[] to be processed; it communicates
from one call of getopt() to the next which element to
process.
The getopt_long() function works like getopt() except that
it also accepts long options, started out by two dashes.
If these take values, it is either in the form --arg=value
or --arg value. It takes the additional arguments lon-
gopts which is a pointer to the first element of an array
of struct option declared in <getopt.h> as
struct option {
const char *name;
int has_arg;
int *flag;
int val;
};
The meaning of the different fields are:
name is the name of the long option.
has_arg
is a boolean value which should be set to nonzero
if the long option takes a value.
flag determines the return value if getopt_long()
<h3>GNU April 25, 1993 1
</h3>
<h3>GETOPT(3) Linux Programmer's Manual GETOPT(3)
</h3>
returns a value for a long option; if it is non-
zero, zero is returned as a function value, other-
wise val.
val determines the value to return if flag is zero.
The last element of the array has to be filled with
zeroes.
The option_index points to the index of the long option
relative to longopts.
<h3>RETURN VALUE
</h3> The getopt() function returns the option character if the
option was found successfully, ':' if there was a missing
parameter for one of the options, '?' for an unknown
option character and -1 for the end of the option list.
<h3>EXAMPLE
</h3> The following example program, from the source code,
illustrates the use of getopt_long() with most of its fea-
tures.
#include <stdio.h>
int
main (argc, argv)
int argc;
char **argv;
{
int c;
int digit_optind = 0;
while (1)
{
int this_option_optind = optind ? optind : 1;
int option_index = 0;
static struct option long_options[] =
{
{"add", 1, 0, 0},
{"append", 0, 0, 0},
{"delete", 1, 0, 0},
{"verbose", 0, 0, 0},
{"create", 1, 0, 'c'},
{"file", 1, 0, 0},
{0, 0, 0, 0}
};
c = getopt_long (argc, argv, "abc:d:012",
long_options, &option_index);
if (c == -1)
break;
switch (c)
<h3>GNU April 25, 1993 2
</h3>
<h3>GETOPT(3) Linux Programmer's Manual GETOPT(3)
</h3>
{
case 0:
printf ("option %s", long_options[option_index].name);
if (optarg)
printf (" with arg %s", optarg);
printf ("0);
break;
case '0':
case '1':
case '2':
if (digit_optind != 0 && digit_optind != this_option_optind)
printf ("digits occur in two different argv-elements.0);
digit_optind = this_option_optind;
printf ("option %c0, c);
break;
case 'a':
printf ("option a0);
break;
case 'b':
printf ("option b0);
break;
case 'c':
printf ("option c with value `%s'0, optarg);
break;
case 'd':
printf ("option d with value `%s'0, optarg);
break;
case '?':
break;
default:
printf ("?? getopt returned character code 0%o ??0, c);
}
}
if (optind < argc)
{
printf ("non-option ARGV-elements: ");
while (optind < argc)
printf ("%s ", argv[optind++]);
printf ("0);
}
exit (0);
}
<h3>BUGS
</h3> This manpage is confusing.
<h3>GNU April 25, 1993 3
</h3>
<h3>GETOPT(3) Linux Programmer's Manual GETOPT(3)
</h3>
<h3>CONFORMS TO
</h3> getopt() :
POSIX.1
<h3>GNU April 25, 1993 4
</h3>
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