Gnu/coreutils/tty-invocation

From Get docs

19.4 tty: Print file name of terminal on standard input

tty prints the file name of the terminal connected to its standard input. It prints ‘not a tty’ if standard input is not a terminal. Synopsis:

tty [option]…

The program accepts the following option. Also see Common options.

-s
--silent
--quiet

Print nothing; only return an exit status.

Exit status:

0 if standard input is a terminal
1 if standard input is a non-terminal file
2 if given incorrect arguments
3 if a write error occurs