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 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 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 tty.

       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 TIOCNOTTY,
       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), ioctl_console(2), ioctl_tty(2),
       termios(3), ttyS(4), vcs(4), pty(7), agetty(8), mingetty(8)

       This page is part of release 5.07 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

Linux                             2019-03-06                            TTY(4)