If you host lots of different sites for people, one of the things you might want to know is what versions of WordPress each site is running.
WordPress stores the version number in a variable named $wp_version which is set in the file version.php.
With that information in hand, you can write a bash command that you run from your /home directory to display all of the WordPress versions you have on your server:
find . -name version.php -type f|xargs grep ^\$wp_version
This is one of the aliases I have in my .bashrc file.