GETOPT_LONG(3) | Library Functions Manual | GETOPT_LONG(3) |
getopt_long
—
#include <getopt.h>
int
getopt_long
(int
argc, char * const
*argv, const char
*optstring, struct option
*long_options, int
*index);
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).
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
o
Both
o
GNU
o
o
NULL
:
o
o
o
o
o
getopt_long
() function first appeared in GNU
libiberty. The first NetBSD implementation appeared in
1.5.
The argv argument is not really const.
December 9, 2018 | NetBSD 9.0 |