Return user's terminal name

      tty [-s]

   -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 -
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')

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