Preface

Mac OS X (pronounced "Mac OS Ten"), the latest incarnation of the Macintosh operating system, is a radical departure from previous versions. Not only is there a whole new look and feel (dubbed "Aqua"), there are huge differences under the hood. All the old, familiar Macintosh system software has been replaced with another operating system, called Unix. Unix is a multiuser, multitasking operating system. Being multiuser means Mac OS X allows multiple users to share the same system, each having the ability to customize the desktop, create files that can be kept private from other users, and to make settings that will automatically be restored whenever that person uses the computer. Being multitasking means the computer can easily run many different applications at the same time, and that if one application crashes or hangs, the entire system doesn't need to be rebooted.

The fact that Mac OS X is Unix under the hood doesn't matter to users who simply want to use its slick graphical interface to run their applications or manage their files. But it opens up worlds of possibilities for users who want to dig a little deeper. The Unix command-line interface, which is accessible through a Mac application called the Terminal, provides an enormous amount of power for advanced users. What's more, once you've learned to use Unix in OS X, you'll also be able to use the command line in other versions of Unix such as Linux.

This book is designed to teach the basics of Unix to Macintosh users. We tell you how to use the command line (which Unix users refer to as "the shell") and the filesystem, as well as some of the most useful commands. Unix is a complex and powerful system, so we only scratch the surface, but we also tell you how to deepen your Unix knowledge once you're ready for more.