tty - controlling terminal
The file /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.
In addition to the ioctl
(2) requests supported by the device that
refers to, the ioctl
(2) request TIOCNOTTY
Detach the calling process from its controlling terminal.
If the process is the session leader, then SIGHUP
signals are sent to the foreground process group and all processes in the
current session lose their controlling tty.
(2) call works only on file descriptors connected to
. 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 TIOCNOTTY
while if the open fails, it is obviously not attached to a terminal and does
not need to detach itself.