tty - 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 need 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.
tty: AES, SVID2, SVID3, XPG2, XPG3, XPG4, FIPS 151-2, POSIX.1
Hewlett-Packard Company - 1 - HP-UX Release 11i: November 2000