TTY(1) BSD Reference Manual TTY(1)
tty - return user's terminal name
The tty utility writes the name of the terminal attached to standard in-
put to standard output. The name that is written is the string returned
by ttyname(3). If the standard input is not a terminal, the message
``not a tty'' is written. The options are as follows:
-s Don't write the terminal name; only the exit status is affected
when this option is specified. The -s option is deprecated in
favor of the ``test -t 0'' command.
Tty exits 0 if the standard input is a terminal, 1 if the standard input
is not a terminal, and >1 if an error occurs.
The tty function is expected to be IEEE Std1003.2 (``POSIX'') compatible.
4.4BSD June 6, 1993 1