Sometimes you want to find out what domains a user owns or which user owns a certain domain name on cpanel but you don't feel like going into WHM. Here are a couple ways...
Find out who owns 'domain.com':
By running that, we see that 'scott' owns it..
Now, lets find out what other domains (and subdomains) the user 'scott' owns:
Of course, you could have started off with the userdomains file in the first place grepping for the domain name.. but I wanted to show you a couple different ways
cat /etc/userdomains | grep 'scott'