/* Copyright (C) 1998-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   Contributed by Zack Weinberg <zack@rabi.phys.columbia.edu>, 1998.

   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/>.  */

#include <errno.h>

#include <stdlib.h>

#include <sys/ioctl.h>

#include <termios.h>

/* Unlock the slave pseudo terminal associated with the master pseudo

   terminal specified by FD.  */

int

unlockpt (int fd)

{

#ifdef TIOCSPTLCK

  int save_errno = errno;

  int unlock = 0;

  if (__ioctl (fd, TIOCSPTLCK, &unlock))

    {

      if (errno == EINVAL)

	{

	  __set_errno (save_errno);

	  return 0;

	}

      else

	return -1;

    }

#endif

  /* If we have no TIOCSPTLCK ioctl, all slave pseudo terminals are

     unlocked by default.  */

  return 0;

}