text: /* Assign a given terminal as controlling terminal and as standard input,
     standard output, standard error of the current process.
     Copyright (C) 2010-2015 Free Software Foundation, Inc.
  
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
     the Free Software Foundation; either version 3 of the License, or
     (at your option) any later version.
  
     This program 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 General Public License for more details.
  
     You should have received a copy of the GNU General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  
  #include <config.h>
  
  /* Currently no specification header.  */
  
  #include <fcntl.h>
  #include <unistd.h>
  #include <sys/ioctl.h>
  
  int
  login_tty (int slave_fd)
  {
    int i;
  
    /* Create a new session.  */
    setsid ();
  
    /* Make fd the controlling terminal for the current process.
       On BSD and OSF/1: There is ioctl TIOCSCTTY for this purpose.
       On Solaris:
         A terminal becomes the controlling terminal of a session
         if it is being open()ed, at a moment when
           1. it is not already the controlling terminal of some session, and
           2. the process that open()s it is a session leader that does not have
              a controlling terminal.
         We assume condition 1, try to ensure condition 2, and then open() it.
     */
    for (i = 0; i < 3; i++)
      if (i != slave_fd)
        close (i);
  #ifdef TIOCSCTTY
    if (ioctl (slave_fd, TIOCSCTTY, NULL) < 0)
      return -1;
  #else
    {
      char *slave_name;
      int dummy_fd;
  
      slave_name = ttyname (slave_fd);
      if (slave_name == NULL)
        return -1;
      dummy_fd = open (slave_name, O_RDWR);
      if (dummy_fd < 0)
        return -1;
      close (dummy_fd);
    }
  #endif
  
    /* Assign fd to the standard input, standard output, and standard error of
       the current process.  */
    for (i = 0; i < 3; i++)
      if (slave_fd != i)
        if (dup2 (slave_fd, i) < 0)
          return -1;
    if (slave_fd >= 3)
      close (slave_fd);
  
    return 0;
  }
  