✏ EDIT: getopt_ext.h

/* Declarations for getopt (GNU extensions).
   Copyright (C) 1989-2018 Free Software Foundation, Inc.
   This file is part of the GNU C Library and is also part of gnulib.
   Patches to this file should be submitted to both projects.

The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

#ifndef _GETOPT_EXT_H
#define _GETOPT_EXT_H 1

/* This header should not be used directly; include getopt.h instead.
   Unlike most bits headers, it does not have a protective #error,
   because the guard macro for getopt.h in gnulib is not fixed.  */

__BEGIN_DECLS

/* Describe the long-named options requested by the application.
   The LONG_OPTIONS argument to getopt_long or getopt_long_only is a vector
   of 'struct option' terminated by an element containing a name which is
   zero.

The field 'has_arg' is:
   no_argument		(or 0) if the option does not take an argument,
   required_argument	(or 1) if the option requires an argument,
   optional_argument 	(or 2) if the option takes an optional argument.

If the field 'flag' is not NULL, it points to a variable that is set
   to the value given in the field 'val' when the option is found, but
   left unchanged if the option is not found.

To have a long-named option do something other than set an 'int' to
   a compiled-in constant, such as set a value from 'optarg', set the
   option's 'flag' field to zero and its 'val' field to a nonzero
   value (the equivalent single-letter option character, if there is
   one).  For long options that have a zero 'flag' field, 'getopt'
   returns the contents of the 'val' field.  */

struct option
{
  const char *name;
  /* has_arg can't be an enum because some compilers complain about
     type mismatches in all the code that assumes it is an int.  */
  int has_arg;
  int *flag;
  int val;
};

/* Names for the values of the 'has_arg' field of 'struct option'.  */

#define no_argument		0
#define required_argument	1
#define optional_argument	2

extern int getopt_long (int ___argc, char *__getopt_argv_const *___argv,
			const char *__shortopts,
		        const struct option *__longopts, int *__longind)
       __THROW __nonnull ((2, 3));
extern int getopt_long_only (int ___argc, char *__getopt_argv_const *___argv,
			     const char *__shortopts,
		             const struct option *__longopts, int *__longind)
       __THROW __nonnull ((2, 3));

__END_DECLS

#endif /* getopt_ext.h */

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