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.\"     @(#)getopt.3	8.5 (Berkeley) 4/27/95
.\"
.Dd November 19, 1998
.Dt GETOPT_LONG 3
.Os NetBSD 4.4
.Sh NAME
.Nm getopt_long
.Nd get long options from command line argument list
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Fd #include <getopt.h>
.Vt struct option {
.Vt	char *	name;
.Vt	int  has_arg;
.Vt	int * flag;
.Vt	int val;
.Vt };
.Vt extern char *optarg;
.Vt extern int   optind;
.Vt extern int   optopt;
.Vt extern int   opterr;
.Vt extern int   optreset;
.Ft int
.Fn getopt "int argc" "char * const *argv" "const char *optstring"
.Ft int
.Fn getopt_long "int argc" "char * const *argv" "const char *optstring"
"struct options *long options" "int *index"
.Sh DESCRIPTION
The
.Fn getopt
function incrementally parses a command line argument list
.Fa argv
and returns the next
.Em known
option character.
An option character is
.Em known
if it has been specified in the string of accepted option characters,
.Fa optstring .
.Pp
The 
.Fn getopt_long
function is similar to 
.Fn getopt
but it accepts options in two forms: words and characters. The
.Fn getopt_long
function provides a superset of of the functionality of 
.Fn getopt
The additional functionality is described in the section GETOPT_LONG.
.Pp
The option string
.Fa optstring
may contain the following elements: individual characters, and
characters followed by a colon to indicate an option argument
is to follow.
For example, an option string
.Li "\&""x""
recognizes an option
.Dq Fl x ,
and an option string
.Li "\&""x:""
recognizes an option and argument
.Dq Fl x Ar argument .
It does not matter to
.Fn getopt
if a following argument has leading white space.
.Pp
On return from
.Fn getopt ,
.Va optarg
points to an option argument, if it is anticipated,
and the variable
.Va optind
contains the index to the next
.Fa argv
argument for a subsequent call
to
.Fn getopt .
The variable
.Va optopt
saves the last
.Em known
option character returned by
.Fn getopt .
.Pp
The variable
.Va opterr
and
.Va optind
are both initialized to 1.
The
.Va optind
variable may be set to another value before a set of calls to
.Fn getopt
in order to skip over more or less argv entries.
.Pp
In order to use
.Fn getopt
to evaluate multiple sets of arguments, or to evaluate a single set of
arguments multiple times,
the variable
.Va optreset
must be set to 1 before the second and each additional set of calls to
.Fn getopt ,
and the variable
.Va optind
must be reinitialized.
.Pp
The
.Fn getopt
function
returns \-1
when the argument list is exhausted, or a non-recognized
option is encountered.
The interpretation of options in the argument list may be cancelled
by the option
.Ql --
(double dash) which causes
.Fn getopt
to signal the end of argument processing and returns \-1.
When all options have been processed (i.e., up to the first non-option
argument),
.Fn getopt
returns \-1.
.Sh GETOPT_LONG
.Pp
.Fn getopt_long
can be used in two ways. In the first way, every long option understood
by the program has a coresponding short option, and the option
structure is only used to translate from long option to short
options. When used in this fashion, 
.Fn getopt_long
behaves identically to 
.Fn getopt.
This is good way to add long option processing to an existing program
with the minimum of rewriting.
.Pp
In the second mechanism, a long option set a flag in the 
.Fa option
structure passed, or will store a pointer to the command line argument
in the 
.Fa 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
.Bd -literal
myprogram --myoption=somevalue
.Ed
.Pp
When a long option is processed the call to 
.Fn getopt_long
will return 0. For this reason, long option processing without
shortcuts are not backwards compatible with 
.Fn getopt.
.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.
.Sh USAGE OF GETOPT_LONG
.Pp
The 
.Fn getopt_long
call requires a structure to be initialized describing the long
options. The structure is:
.Bd -literal
struct option {
    char *	name;
    int  has_arg;
    int * flag;
    int val;
};
.Ed
.Pp
The 
.Fa name
field should contain the option name without the leading double dash.
.Pp
The 
.Fa has_arg
field should be one of
.Bl -tag
.It no_argument
no argument to the option is expect.
.It required_argument
an argument to the option is required.
.It optional_argument
an argument to the option may be presented.
.El
.Pp
If
.Fa flag
is non-NULL, then the integer pointed to by it will set to the value 
in the 
.Fa val
field. If the 
.Fa flag 
field is NULL, then the 
.Fa val
field will be returned. Setting 
.Fa flag
to NULL and setting
.Fa val
to the corresponding short option will make this function act just
like
.Fa getopt.
.Sh DIAGNOSTICS
If the
.Fn getopt
function encounters a character not found in the string
.Fa optstring
or detects
a missing option argument it writes an error message to
.Va stderr
and returns
.Ql ? .
Setting
.Va opterr
to a zero will disable these error messages.
If
.Va optstring
has a leading
.Ql \&:
then a missing option argument causes a
.Ql \&:
to be returned in addition to suppressing any error messages.
.Pp
Option arguments are allowed to begin with
.Dq Li \- ;
this is reasonable but
reduces the amount of error checking possible.
.Sh GETOPT_LONG
.Sh EXTENSIONS
The
.Va optreset
variable was added to make it possible to call the
.Fn getopt
function multiple times.
This is an extension to the
.St -p1003.2
specification.
.Sh EXAMPLE
.Bd -literal -compact
extern char *optarg;
extern int optind;
int bflag, ch, fd;

bflag = 0;
while ((ch = getopt(argc, argv, "bf:")) != -1)
	switch(ch) {
	case 'b':
		bflag = 1;
		break;
	case 'f':
		if ((fd = open(optarg, O_RDONLY, 0)) < 0) {
			(void)fprintf(stderr,
			    "myname: %s: %s\en", optarg, strerror(errno));
			exit(1);
		}
		break;
	case '?':
	default:
		usage();
}
argc -= optind;
argv += optind;
.Ed
.Sh LONG EXAMPLE 
.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, &daggerset, 1},
  {0, 		   0,                0, 0}
};

bflag = 0;
while ((ch = getopt_long(argc, argv, "bf:")) != -1)
	switch(ch) {
	case 'b':
		bflag = 1;
		break;
	case 'f':
		if ((fd = open(optarg, O_RDONLY, 0)) < 0) {
			(void)fprintf(stderr,
			    "myname: %s: %s\en", optarg, strerror(errno));
			exit(1);
		}
		break;
	case 0:
		if(daggerset) {
			fprintf(stderr,"Buffy will put use her dagger"
				       "to apply floride to dracula's teeth");
		}
		break;
	case '?':
	default:
		usage();
}
argc -= optind;
argv += optind;
.Ed
.Sh HISTORY
The
.Fn getopt
function appeared
.Bx 4.3 .
The 
.Fn getopt_long
function first appeared in GNU libiberty. This implementation was
imported to NetBSD from a Kerberos distribution.
.Sh BUGS
The
.Fn getopt
function was once specified to return
.Dv EOF
instead of \-1.
This was changed by
.St -p1003.2-92
to decouple
.Fn getopt
from
.Pa <stdio.h> .
.Pp
A single dash
.Dq Li -
may be specified as an character in
.Fa optstring ,
however it should
.Em never
have an argument associated with it.
This allows
.Fn getopt
to be used with programs that expect
.Dq Li -
as an option flag.
This practice is wrong, and should not be used in any current development.
It is provided for backward compatibility
.Em only .
By default, a single dash causes
.Fn getopt
to return \-1.
This is, we believe, compatible with System V.
.Pp
It is also possible to handle digits as option letters.
This allows
.Fn getopt
to be used with programs that expect a number
.Pq Dq Li \&-\&3
as an option.
This practice is wrong, and should not be used in any current development.
It is provided for backward compatibility
.Em only .
The following code fragment works in most cases.
.Bd -literal -offset indent
int length;
char *p;

while ((c = getopt(argc, argv, "0123456789")) != -1)
	switch (c) {
	case '0': case '1': case '2': case '3': case '4':
	case '5': case '6': case '7': case '8': case '9':
		p = argv[optind - 1];
		if (p[0] == '-' && p[1] == ch && !p[2])
			length = atoi(++p);
		else
			length = atoi(argv[optind] + 1);
		break;
	}
}
.Ed
.Pp
The 
.Fa optional_argument
always eats the following argument unless the argument is included via
the 
.Em --option=argument 
notation.