How to get actual login username when using sudo su

I’ve had the need to find out the actual username of someone logged in and working as root (via sudo su -) to put it into a subversion commit message. This quick little bash script does the trick, and just echos the username.

#!/bin/bash

PID=$$ # get PID of current process
LogUID=`cat /proc/"$PID"/loginuid` # get loginuid of current process
username=`getent passwd "$LogUID" | awk -F ":" '{print $1}'` # translate loginuid to username
echo "$username"

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