devtty(7)                      DG/UX 5.4R3.00                      devtty(7)


NAME
       devtty - control terminal pseudo-device

DESCRIPTION
       The file /dev/tty is, in each process, a synonym for the control
       terminal associated with that process.  The file is useful if you
       want a program to write messages on the terminal no matter how output
       has been redirected.  You can also use it when a program needs a
       filename for output and you do not want to find out which terminal is
       currently in use.

       If a process that has no control terminal opens a terminal file, the
       terminal becomes the control terminal for that process.  The control
       terminal is thereafter inherited by a child process during a fork(2)
       system call, even if the control terminal is closed.

       All operations on /dev/tty behave like operations on the actual
       control terminal special file (/dev/tty*), except for the special
       ioctl TIOCNOTTY, which is recognized only on the /dev/tty device:

                 ioctl(fildes, TIOCNOTTY, 0);

       TIOCNOTTY breaks the association of a process with its control
       terminal, and also sets the process group of the calling process to
       the process id of that process.  Further I/O requests to the file
       will fail with the external variable errno set to ENXIO.  Subsequent
       opens of /dev/tty will also fail with errno set to ENXIO.

FILES
       /dev/tty

SEE ALSO
       termio(7), ttcompat(7).
























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