devtty(7)
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devtty Special File
control terminal pseudo-device
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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), tty(7).
DG/UX 4.00 Page 1
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