int
getopt_long(
int argc
, char * const *argv
, const char *optstring
, struct option *long_options
, int *index
)
)
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).
getopt_long(
)
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
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.
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.
Abbreviated long option names are accepted when
getopt_long()
processes long options if the abbreviation is unique.
An exact match is always preferred for a defined long option.
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
required_argument
optional_argument
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
index
field is not
NULL
,
the integer it points to will be set to the index of the long option
in the
long_options
array.
The last element of the
long_options
array has to be filled with zeroes (see
EXAMPLES
section).
extern char *optarg;
extern int optind;
int bflag, ch, fd;
int daggerset;
/* options descriptor */
static struct option longopts[] = {
{ "buffy", no_argument, 0, 'b' },
{ "fluoride", required_argument, 0, '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)) < 0) {
(void)fprintf(stderr,
"myname: %s: %s\n", optarg, strerror(errno));
exit(1);
}
break;
case 0:
if(daggerset) {
fprintf(stderr,"Buffy will use her dagger to "
"apply fluoride to dracula's teeth\n");
}
break;
case '?':
default:
usage();
}
argc -= optind;
argv += optind;
o
GNU
NetBSD
o
Both
o
GNU
o
GNU
NetBSD
o
NULL
:
GNU
NetBSD
o
GNU
NetBSD
o
GNU
NetBSD
NULL
(the argument of the long option).
o
GNU
NetBSD
NULL
(as GNU's man page documents).
o
o
)
function first appeared in GNU libiberty.
The first
NetBSD
implementation appeared in 1.5.
The
argv
argument is not really const.