Return user's terminal name
Syntax tty [-s] Options -s 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.
“Behind every great fortune there is a crime” ~ Honore de Balzac
tty man page - Apple.com
env - Display, set, or remove environment variables
id - Print user and group id's
uname - Print system information
users - Print login names of users currently logged in
who - Print who is currently logged in
whoami - Print the current user id and name (`id -un')