Chapter 18: Linux Shell Commands

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Introduction

Shells were briefly introduced in Chapter 3, “Basics of the Linux Operating System,” and we examined a few very basic shell commands in that chapter. However, we did not delve deeply into how to work within a shell. In this chapter we will explore shells in more depth. Some of the previous commands may be covered briefly again, and you will be introduced to a number of new shell commands.

Using the shell is an important part of working with a Linux machine. Before there were graphical interfaces such as KDE and GNOME, shell commands were the only way to use Linux or Unix. Many Linux aficionados still find the shell to be the most efficient way to perform many tasks.

In this chapter we will examine a variety of shell tasks, grouped together by functionality. That way we can look at a series of shell commands that all have similar operations. At the end of this chapter, if you follow along and execute these commands on your own Linux machine, you should be familiar with Linux shell commands. It is highly recommended that you use each of the commands mentioned in this chapter. Reading them without any experience using them will not help you to learn them.

It has been 15 chapters since we discussed shells, and it might be prudent to review what a shell is. A shell, if you will recall, is a simple text-based interface with your computer. You enter text, and it appears in a screen. That screen usually has a simple mono color background (often blue or black), and the text is a simple font. The response you get back from the computer is also in this plain font on the same simple screen. There are no fancy buttons, drop-down menus, or other graphical elements. In Windows NT, 2000, and XP you have a shell called the command prompt. In Windows 95 and Windows 98 it was called the DOS prompt.

As was previously mentioned, in Linux there are several different shells you can work with, including Bourne, Bourne-again (bash), and C shell. The vast majority of commands are common to all shells. In this chapter we will explore only those commands that are shared by all shells. Therefore, you can select any shell as your default shell. If you will recall, when you establish a user account, you can set that user’s default shell. That is the shell he will get when he invokes the terminal window. However, unless you have some compelling reason to select one of the other shells, it is probably best to leave the default as the bash shell.

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