.\" Copyright (c) 1993 Michael Haardt (michael@moria.de),
.\"     Fri Apr  2 11:32:09 MET DST 1993
.\"
.\" SPDX-License-Identifier: GPL-2.0-or-later
.\"
.\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
.\" Modified 2003-04-07 by Michael Kerrisk
.\"
.TH tty 4 2022-10-30 "Linux man-pages 6.04"
.SH NAME
tty \- controlling terminal
.SH DESCRIPTION
The file
.I /dev/tty
is a character file with major number 5 and
minor number 0, usually with mode 0666 and ownership root:tty.
It is a synonym for the controlling terminal of a process, if any.
.PP
In addition to the
.BR ioctl (2)
requests supported by the device that
.B tty
refers to, the
.BR ioctl (2)
request
.B TIOCNOTTY
is supported.
.SS TIOCNOTTY
Detach the calling process from its controlling terminal.
.PP
If the process is the session leader,
then
.B SIGHUP
and
.B SIGCONT
signals are sent to the foreground process group
and all processes in the current session lose their controlling tty.
.PP
This
.BR ioctl (2)
call works only on file descriptors connected
to
.IR /dev/tty .
It is used by daemon processes when they are invoked
by a user at a terminal.
The process attempts to open
.IR /dev/tty .
If the open succeeds, it
detaches itself from the terminal by using
.BR TIOCNOTTY ,
while if the
open fails, it is obviously not attached to a terminal and does not need
to detach itself.
.SH FILES
.I /dev/tty
.SH SEE ALSO
.BR chown (1),
.BR mknod (1),
.BR ioctl (2),
.BR ioctl_console (2),
.BR ioctl_tty (2),
.BR termios (3),
.BR ttyS (4),
.BR vcs (4),
.BR pty (7),
.BR agetty (8),
.BR mingetty (8)