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/* Copyright (C) 1998 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 Library General Public License as

   published by the Free Software Foundation; either version 2 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

   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public

   License along with the GNU C Library; see the file COPYING.LIB.  If not,

   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,

   Boston, MA 02111-1307, USA.  */

#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)

        {

          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;

}