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getopt_long (3)

getopt_long (3) ( Solaris man: Библиотечные вызовы )

>> getopt_long (3) ( FreeBSD man: Библиотечные вызовы )

getopt_long (3) ( Русские man: Библиотечные вызовы )

getopt_long (3) ( Linux man: Библиотечные вызовы )

BSD mandoc

NAME



getopt_long

 
getopt_long_only

 - get long options from command line argument list

LIBRARY

Lb libc

SYNOPSIS

#include <getopt.h>
Vt extern char *optarg ; Vt extern int optind ; Vt extern int optopt ; Vt extern int opterr ; Vt extern int optreset ; int Fo getopt_long Fa int argc char * const *argv const char *optstring Fa const struct option *longopts int *longindex Fc Ft int Fo getopt_long_only Fa int argc char * const *argv const char *optstring Fa const struct option *longopts int *longindex Fc

DESCRIPTION

The getopt_long ();
function is similar to getopt(3) but it accepts options in two forms: words and characters. The getopt_long ();
function provides a superset of the functionality of getopt(3). The getopt_long ();
function can be used in two ways. In the first way, every long option understood by the program has a corresponding short option, and the option structure is only used to translate from long options to short options. When used in this fashion, getopt_long ();
behaves identically to getopt(3). This is a good way to add long option processing to an existing program with the minimum of rewriting.

In the second mechanism, a long option sets a flag in the Vt option structure passed, or will store a pointer to the command line argument in the Vt 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.,

"myprogram --myoption=somevalue"

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:

no_argument: no argument to the option is expect
required_argument: an argument to the option is required
optional_argument: an argument to the option may be presented.

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

The last element of the Fa 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

If the Fa flag field in Vt struct option is NULL getopt_long ();
and getopt_long_only ();
return the value specified in the Fa val field, which is usually just the corresponding short option. If Fa flag is not NULL these functions return 0 and store Fa val in the location pointed to by Fa flag . These functions return `:' if there was a missing option argument, `?' if the user specified an unknown or ambiguous option, and -1 when the argument list has been exhausted.

ENVIRONMENT

POSIXLY_CORRECT: If set, option processing stops when the first non-option is found and a leading `-' or `+' in the Fa 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,            Am]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

This section describes differences to the GNU implementation found in glibc-2.1.3:

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.)

HISTORY

The getopt_long ();
and getopt_long_only ();
functions first appeared in GNU libiberty. The first BSD implementation of getopt_long ();
appeared in Nx 1.5 , the first BSD implementation of getopt_long_only ();
in Ox 3.3 . Fx first included getopt_long ();
in Fx 5.0 , getopt_long_only ();
in Fx 5.2 .