On the SitePoint WordPress blog they've posted a tutorial showing you how to install and use the WP-CLI tool to manage your WordPress-powered websites.

Speeding up your work process should be one of your top priorities. Simply put, if you do more work in less time, then you will have more time to work on more projects, study and rest. WP-CLI is one of the command line tools specifically made to manage your WordPress websites through the command line. With a few simple commands, you can manage WordPress without even needing to login to your WordPress admin and navigate through the pages.

They start with some of the requirements to use the WP-CLI tool and follow it with the steps to get it installed and moved to the right place on your system. They then show off some of the functionality the command-line tool has to offer including:

• working with the WP cache
• installing WordPress core
• installing themes and plugins

The WP-CLI tool also helps you keep your WordPress installation up to date, including core and themes/plugins too.