This is a great start for a script with potential. What would make it better is to be able to pipe a list of directories from a text file with Joomla installs/dirs to update recursively!
For a Joomla hosting company (like mine), this could give you the ability to add sites (/home/joomlasite) in say a cPanel setup to update to the latest and greatest Joomla.
That is a big expense from a hosting perspective.
Owner's reply:
Yep
That's the idea, I'm thinking of adding a search on /var/www/html and /home/ for joomla install and then prompt for confirmation and process