redhat man page for tty

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

NAME
       tty - controlling terminal

DESCRIPTION
       The  file /dev/tty is a character file with major number 5 and minor number 0, usually of mode 0666 and owner.group root.tty.  It is a syn-
       onym 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:

       TIOCNOTTY
	      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 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.

FILES
       /dev/tty

SEE ALSO
       mknod(1), chown(1), getty(1), termios(3), console(4), ttys(4)

Linux								    1992-01-21								    TTY(4)