bsd man page for tty

TTY(1)							      General Commands Manual							    TTY(1)

NAME
       tty - get terminal name

SYNOPSIS
       tty [ -s ]

DESCRIPTION
       Tty  prints  the  pathname  of  the user's terminal unless the -s (silent) is given. In either case, the exit value is zero if the standard
       input is a terminal and one if it is not.

DIAGNOSTICS
       `not a tty' if the standard input file is not a terminal.

7th Edition							  April 29, 1985							    TTY(1)