The file /dev/tty is,
in each process, a synonym
for the control terminal associated with the process group of that process,
It is useful for programs or shell sequences that wish to
be sure of writing messages on the terminal
no matter how output has been redirected.
It can also be used for programs that demand the name of a file
for output, when typed output is desired
and it is tiresome to find out what terminal
is currently in use.