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Shell Programming in Unix, Linux and OS X, Fourth Edition by Patrick Wood, Stephen G. Kochan

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2. What Is the Shell?

In this chapter you’ll learn what the Unix command shell is, what it does and why it’s a vital part of every power user’s toolbox.

The Kernel and the Utilities

The Unix system is logically divided into two different areas: the kernel and the utilities (see Figure 2.1). Or, if you prefer, the kernel and everything else, generally all accessed through the shell.

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Figure 2.1 The Unix system

The kernel is the heart of the Unix system and resides in the computer’s memory from the time the computer is turned on and booted until the time it is shut down.

The various tools and utilities that make up the full Unix system experience ...

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