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 owner.group root.tty. It is a synonym for the controlling terminal of a
process, if any.
In addition to the ioctl(2) requests supported by the device that tty refers to, the
ioctl(2) request TIOCNOTTY is supported.
Detach the calling process from its controlling terminal.
If the process is the session leader, then SIGHUP and SIGCONT signals are sent to the
foreground process group and all processes in the current session lose their controlling
This ioctl(2) call works only on file descriptors connected to /dev/tty. It 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 TIOC-
NOTTY, while if the open fails, it is obviously not attached to a terminal and does not
need to detach itself.
chown(1), mknod(1), ioctl(2), termios(3), console(4), tty_ioctl(4), ttyS(4), agetty(8),
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Linux 2003-04-07 TTY(4)