I'm regularly suprised to find Unix/Linux folk who don't know "w" as a replacement for "who": less typing, and more information. If you don't know about this, try it - you'll like it.
The Posix compliant way to say "who am i" is "who -m", which works on most modern systems.
Although "who" looks at utmp by default, you can tell it to look elsewhere (wtmp, most likely). That can sometimes be useful, though "last" is more apt to be used for that.
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