NAME

LIBRARY

SYNOPSIS

extern char *optarg;
extern int optind;
extern int optopt;
extern int opterr;
extern int optreset;

int
getopt_long(int argc, char * const *argv, const char *optstring, const struct option *longopts, int *longindex);

int
getopt_long_only(int argc, char * const *argv, const char *optstring, const struct option *longopts, int *longindex);

DESCRIPTION

In the second mechanism, a long option sets a flag in the option structure passed, or will store a pointer to the command line argument in the option structure passed to it for options that take arguments. Additionally, the long option's argument may be specified as a single argument with an equal sign, e.g.,

When a long option is processed, the call to getopt_long() will return 0. For this reason, long option processing without shortcuts is not backwards compatible with getopt(3).

It is possible to combine these methods, providing for long options processing with short option equivalents for some options. Less frequently used options would be processed as long options only.

The getopt_long() call requires a structure to be initialized describing the long options. The structure is:

struct option {
	char *name;
	int has_arg;
	int *flag;
	int val;
};

The name field should contain the option name without the leading double dash.

The has_arg field should be one of:

If flag is not NULL, then the integer pointed to by it will be set to the value in the val field. If the flag field is NULL, then the val field will be returned. Setting flag to NULL and setting val to the corresponding short option will make this function act just like getopt(3).

If the longindex field is not NULL, then the integer pointed to by it will be set to the index of the long option relative to longopts.

The last element of the longopts array has to be filled with zeroes.

The getopt_long_only() function behaves identically to getopt_long() with the exception that long options may start with ‘-’ in addition to ‘--’. If an option starting with ‘-’ does not match a long option but does match a single-character option, the single-character option is returned.

RETURN VALUES

These functions return ‘:’ if there was a missing option argument and error messages are suppressed, ‘?’ if the user specified an unknown or ambiguous option, and -1 when the argument list has been exhausted. The default behavior when a missing option argument is encountered is to write an error and return ‘?’. Specifying ‘:’ in optstr will cause the error message to be suppressed and ‘:’ to be returned instead.

In addition to ‘:’, a leading ‘+’ or ‘-’ in optstr also has special meaning. If either of these are specified, they must appear before ‘:’.

A leading ‘+’ indicates that processing should be halted at the first non-option argument, matching the default behavior of getopt(3). The default behavior without ‘+’ is to permute non-option arguments to the end of argv.

A leading ‘-’ indicates that all non-option arguments should be treated as if they are arguments to a literal ‘1’ flag (i.e., the function call will return the value 1, rather than the char literal '1').

ENVIRONMENT

POSIXLY_CORRECT

If set, option processing stops when the first non-option is found and a leading ‘-’ or ‘+’ in the optstring is ignored.

EXAMPLES

int bflag, ch, fd;
int daggerset;

/* options descriptor */
static struct option longopts[] = {
	{ "buffy",	no_argument,		NULL, 		'b' },
	{ "fluoride",	required_argument,	NULL, 	       	'f' },
	{ "daggerset",	no_argument,		&daggerset,	1 },
	{ NULL,		0,			NULL, 		0 }
};

bflag = 0;
while ((ch = getopt_long(argc, argv, "bf:", longopts, NULL)) != -1) {
	switch (ch) {
	case 'b':
		bflag = 1;
		break;
	case 'f':
		if ((fd = open(optarg, O_RDONLY, 0)) == -1)
			err(1, "unable to open %s", optarg);
		break;
	case 0:
		if (daggerset) {
			fprintf(stderr,"Buffy will use her dagger to "
			    "apply fluoride to dracula's teeth\n");
		}
		break;
	default:
		usage();
	}
}
argc -= optind;
argv += optind;

IMPLEMENTATION DIFFERENCES

• Setting of optopt for long options with flag != NULL:

  GNU

  sets optopt to val.

  BSD

  sets optopt to 0 (since val would never be returned).

• Setting of optarg for long options without an argument that are invoked via ‘-W’ (‘W;’ in option string):

  GNU

  sets optarg to the option name (the argument of ‘-W’).

  BSD

  sets optarg to NULL (the argument of the long option).

• Handling of ‘-W’ with an argument that is not (a prefix to) a known long option (‘W;’ in option string):

  GNU

  returns ‘-W’ with optarg set to the unknown option.

  BSD

  treats this as an error (unknown option) and returns ‘?’ with optopt set to 0 and optarg set to NULL (as GNU's man page documents).

• BSD does not permute the argument vector at the same points in the calling sequence as GNU does. The aspects normally used by the caller (ordering after -1 is returned, value of optind relative to current positions) are the same, though. (We do fewer variable swaps.)

SEE ALSO

HISTORY

BUGS

The implementation can completely replace getopt(3), but right now we are using separate code.