utility writes the name of the terminal attached to standard input 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:
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.