coreutils: tty invocation

1 
1 19.4 ‘tty’: Print file name of terminal on standard input
1 =========================================================
1 
1 ‘tty’ prints the file name of the terminal connected to its standard
1 input.  It prints ‘not a tty’ if standard input is not a terminal.
1 Synopsis:
1 
1      tty [OPTION]...
1 
11    The program accepts the following option.  Also see ⇒Common
 options.
1 
1 ‘-s’
1 ‘--silent’
1 ‘--quiet’
1      Print nothing; only return an exit status.
1 
1    Exit status:
1 
1      0 if standard input is a terminal
1      1 if standard input is a non-terminal file
1      2 if given incorrect arguments
1      3 if a write error occurs
1