path: root/lib/libc/stdlib/getopt_long.3

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.\"     @(#)getopt.3	8.5 (Berkeley) 4/27/95
.\" $FreeBSD$
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.Dd April 1, 2000
.Dt GETOPT_LONG 3
.Os
.Sh NAME
.Nm getopt_long
.Nd get long options from command line argument list
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In getopt.h
.Ft int
.Fo getopt_long
.Fa "int argc" "char * const *argv" "const char *optstring"
.Fa "struct option *long options" "int *index"
.Fc
.Sh DESCRIPTION
The
.Fn getopt_long
function is similar to
.Xr getopt 3
but it accepts options in two forms: words and characters.
The
.Fn getopt_long
function provides a superset of the functionality of
.Xr getopt 3 .
The
.Fn 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,
.Fn getopt_long
behaves identically to
.Xr getopt 3 .
This is a good way to add long option processing to an existing program
with the minimum of rewriting.
.Pp
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.,
.Pp
.Dl "myprogram --myoption=somevalue"
.Pp
When a long option is processed, the call to
.Fn getopt_long
will return 0.
For this reason, long option processing without
shortcuts is not backwards compatible with
.Xr getopt 3 .
.Pp
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.
.Pp
The
.Fn getopt_long
call requires a structure to be initialized describing the long
options.
The structure is:
.Bd -literal -offset indent
struct option {
	char *name;
	int has_arg;
	int *flag;
	int val;
};
.Ed
.Pp
The
.Va name
field should contain the option name without the leading double dash.
.Pp
The
.Va has_arg
field should be one of:
.Pp
.Bl -tag -width ".Dv optional_argument" -offset indent -compact
.It Dv no_argument
no argument to the option is expect
.It Dv required_argument
an argument to the option is required
.It Li optional_argument
an argument to the option may be presented.
.El
.Pp
If
.Va flag
is not
.Dv NULL ,
then the integer pointed to by it will be set to the
value in the
.Va val
field.
If the
.Va flag
field is
.Dv NULL ,
then the
.Va val
field will be returned.
Setting
.Va flag
to
.Dv NULL
and setting
.Va val
to the corresponding short option will make this function act just
like
.Xr getopt 3 .
.Sh EXAMPLES
.Bd -literal -compact
extern char *optarg;
extern int optind;
int bflag, ch, fd;
int daggerset;

/* options descriptor */
static struct option longopts[] = {
	{ "buffy",	no_argument,		0, 		'b' },
	{ "floride",	required_argument,	0, 	       	'f' },
	{ "daggerset",	no_argument,		\*[Am]daggerset,	1 },
	{ 0, 		0,			0, 		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)) \*[Lt] 0) {
			(void)fprintf(stderr,
			    "myname: %s: %s\en", optarg, strerror(errno));
			exit(1);
		}
		break;
	case 0:
		if(daggerset) {
			fprintf(stderr,"Buffy will use her dagger to "
				       "apply floride to dracula's teeth\en");
		}
		break;
	case '?':
	default:
		usage();
}
argc -= optind;
argv += optind;
.Ed
.Sh IMPLEMENTATION DIFFERENCES
This section describes differences to the
.Tn GNU
implementation
found in glibc-2.1.3:
.Bl -bullet
.It
Handling of
.Ql -
as first char of option string in presence of
environment variable
.Ev POSIXLY_CORRECT :
.Bl -tag -width ".Nx"
.It Tn GNU
ignores
.Ev POSIXLY_CORRECT
and returns non-options as
arguments to option '\e1'.
.It Nx
honors
.Ev POSIXLY_CORRECT
and stops at the first non-option.
.El
.It
Handling of
.Ql ::
in options string in presence of
.Ev POSIXLY_CORRECT :
.Bl -tag -width ".Nx"
.It Both
.Tn GNU
and
.Nx
ignore
.Ev POSIXLY_CORRECT
here and take
.Ql ::
to
mean the preceding option takes an optional argument.
.El
.It
Return value in case of missing argument if first character
(after
.Ql +
or
.Ql - )
in option string is not
.Ql \&: :
.Bl -tag -width ".Nx"
.It Tn GNU
returns
.Ql \&?
.It Nx
returns
.Ql \&:
(since
.Nx Ns 's
.Fn getopt
does).
.El
.It
Handling of
.Ql --a
in getopt:
.Bl -tag -width ".Nx"
.It Tn GNU
parses this as option
.Ql - ,
option
.Ql a .
.It Nx
parses this as
.Ql -- ,
and returns \-1 (ignoring the
.Ql a ) .
(Because the original
.Fn getopt
does.)
.El
.It
Setting of
.Va optopt
for long options with
.Va flag
!=
.Dv NULL :
.Bl -tag -width ".Nx"
.It Tn GNU
sets
.Va optopt
to
.Va val .
.It Nx
sets
.Va optopt
to 0 (since
.Va val
would never be returned).
.El
.It
Handling of
.Ql -W
with
.Ql W ;
in option string in
.Fn getopt
(not
.Fn getopt_long ) :
.Bl -tag -width ".Nx"
.It Tn GNU
causes a segfault.
.It Nx
returns \-1, with
.Va optind
pointing past the argument of
.Ql -W
(as if
.Ql "-W arg"
were
.Ql --arg ,
and thus
.Ql --
had been found).
.\" How should we treat W; in the option string when called via
.\" getopt?  Ignore the ';' or treat it as a ':'? Issue a warning?
.El
.It
Setting of
.Va optarg
for long options without an argument that are
invoked via
.Ql -W
.Ql ( W ;
in option string):
.Bl -tag -width ".Nx"
.It Tn GNU
sets
.Va optarg
to the option name (the argument of
.Ql -W ) .
.It Nx
sets
.Va optarg
to
.Dv NULL
(the argument of the long option).
.El
.It
Handling of
.Ql -W
with an argument that is not (a prefix to) a known
long option
.Ql ( W ;
in option string):
.Bl -tag -width ".Nx"
.It Tn GNU
returns
.Ql -W
with
.Va optarg
set to the unknown option.
.It Nx
treats this as an error (unknown option) and returns
.Ql \&?
with
.Va optopt
set to 0 and
.Va optarg
set to
.Dv NULL
(as
.Tn GNU Ns 's
man page documents).
.El
.It
The error messages are different.
.It
.Nx
does not permute the argument vector at the same points in
the calling sequence as
.Tn GNU
does.
The aspects normally used by
the caller (ordering after \-1 is returned, value of
.Va optind
relative
to current positions) are the same, though.
(We do fewer variable swaps.)
.El
.Sh SEE ALSO
.Xr getopt 3
.Sh HISTORY
The
.Fn getopt_long
function first appeared in
.Tn GNU
libiberty.
The first
.Nx
implementation appeared in 1.5.
.Sh BUGS
The implementation can completely replace
.Xr getopt 3 ,
but right now we are using separate code.