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Just be warned that with great power comes great responsibility: You can really screw things up if you don't know what you're doing. You have control over a wide variety of parameters for QuickTime, Safari, iTunes, your login window and more. You can automate the rebuilding of your Mail mailboxes, Spotlight index and more. OnyX comes in handy when it comes to the deletion of Internet cache files that can screw things up, like DNS and browser caches, or individual system cache files, OnyX is a godsend. This free utility gives you access to a huge variety of system maintenance, performance optimization and customization features by adding a graphical user interface to commands that you'd otherwise need to know Unix to be able to do anything with. That's where Titanium Software's OnyX comes into play. But unless you know what you're doing it's really easy to get frustrated.
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Because OS X is a Unix-based operating system, you can do a lot more under the hood when you're accessing the operating system from a command line using the Terminal program.
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