|Initial release||November 3, 1971|
|Operating system||Unix and Unix-like|
tty stands for TeleTYpewriter.
tty command is commonly used to check if the output medium is a terminal. The command prints the file name of the terminal connected to standard input. If no file is detected (in case, it's being run as part of a script or the command is being piped) "
not a tty" is printed to stdin and the command exits with an exit status of 1. The command also can be run on silent mode (
tty -s) where no output is produced, and the command exits with an appropriate exit status.