TTY(7)TTY(7)NAMEtty - controlling terminal interface
The file /dev/tty is, in each process, a synonym for the control terminal
associated with the process group of that process, if any. 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.