TTY(4)              Linux Programmer's Manual              TTY(4)

       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 supported:

              Detach the current  process  from  its  controlling
              terminal,  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  con-
              nected  to  /dev/tty;  this  is used by daemon pro-
              cesses when they are invoked by a user at a  termi-
              nal.  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),  termios(2),  console(4),

Linux                    January 21, 1992                       1