tty - controlling terminal


     The file /dev/tty is a character file with  major  number  5
     and  minor  number  0,  usually of mode 0666 and
     root.tty.  It is a synonym for the controlling terminal of a
     process, if any.

     In addition to the ioctl() requests supported by the  device
     that  tty  refers  to, the following ioctl() request is sup-

          Detach the current process from its controlling  termi-
          nal,  and  remove  it  from  its current process group,
          without attaching it to a new process group  (that  is,
          set  its  process group ID to zero).  This ioctl() call
          only works on file descriptors connected  to  /dev/tty;
          this  is used by daemon processes when they are invoked
          by a user at a terminal.  The process attempts to  open
          /dev/tty; if the open succeeds, it detaches itself from
          the terminal by using  TIOCNOTTY,  while  if  the  open
          fails,  it  is obviously not attached to a terminal and
          does not need to detach itself.




     mknod(1), chown(1), getty(1), console(4), ttys(4)