Chapter i. Introduction

i. Introduction

This book is the most comprehensive beginner's guide to Unix on the market. If you have never used Unix before, jump right inthis book was written first and foremost for you. If you are an experienced Unix user wondering about Mac OS X, take it from us, Mac OS X really is Unixnot almost, not sort of, but actual, real Unix with the Lovely Mac Interface.

This book deals almost exclusively with the command-line interface to Darwinwhich is the version of Unix that Mac OS X is built upon. Unix is an operating system, and obviously you have used other operating systems in the pastat the very least, you have used the Macintosh operating system, and perhaps Windows, or even DOS. Unix is different. The other operating systems have a sharp distinction between the operating system itself and the applications you use with it. In Unix, the distinction is much less clear.

In learning Unix, you will use a collection of separate applications to do things like copy files, create new folders, view such information as file size and date modified, and perform all the tasks that in other operating systems are part of the one big application that is the "operating system."

It has been said that if Unix were an airplane, it would have been built by all the frequent fliers who over the years showed up at the airport with new and/or improved pieces for the airplane. Each time someone had a better, faster (and sometimes even easier) way of doing something, all the other frequent fliersalong with the engineers working for the airplane manufacturerwould crowd around and argue over the benefits of the new tool.

In many cases a new tool (or toy) became a standard part of the airplane. Unix was invented in 1969, but it wasn't until the early 1980s that engineers at the University of California, Berkeley, added the code for communicating on the Internet directly into the core (or kernel ) of Unix. The tools for viewing files and monitoring the operating system have evolved constantly over the years.

New tools are added frequently. Each of them is a separate piece of software, with its own collection of features, options, and tricks for using it; and all of them (or almost all) are designed to be combined with each other in the way that words are combined to make a sentence .

All this means that Unix has evolved organically over the past 30-plus years, and continues to evolve , very much as a language evolves. In this book, we teach you how to think and act in Unix step-by-step, providing you with both a sequential learning process and a reference you can return to in the days to come as you become more and more adept.

Learning Unix is like learning a languageit all comes together to make some kind of sense, but there are idiosyncrasies and bits of historical stuff that pop up. It is not smoothly monolithic, but rather it is gloriously rich and complex. Instead of words, though, Unix has tools.

In Unix we call these tools commands , and you will start thinking about "which command to use" just as if you were some kind of authority figure, or wizard, which indeed you are on your way to becoming. Unix experts sometimes speak of "invoking" commands, as if they were magic spells. Perhaps that is not far from the truth.

You will see more similarity between Unix and language as you recognize that Unix commands achieve much of their value from the ways in which they can be combined with each other and even modified as the need arises.

This book teaches you how to perform the tasks necessary to accomplish traditional actions with your computer. Performing a task in Unix is frequently a matter of using two or more commands in a particular sequence. For example, you will use one command to create a new folder, another command to move within that folder, then another command to create a file, and still another command to set the permissions on the file so that you can control who is allowed to use it.

Unix is a world where a string of commands displays a specificity so unique, it results in an exact execution of your intention . Although such an incantation may seem obscure to a novice, the experienced user will see only directness, simplicity, and precision. We'll help you move from the former to the latter.