originating UID

[jfason at rhythms.net]

when you run sudo what is the command that gives the originating users
UID/username?  Put another way, what command would give a users name that
kicked off the sudo <scriptname>

For example, if you create a script and want it to write to a log the
changes that were made by "<username> `data`".  I know about sudolog, but
what I want is when the script runs it will say something like "hello <user>
you are running a script to remove users" or something.