The real power of
Linux lies in the shell. So, if you aspire to master Linux, you must
conquer the shell. Once you’ve done so, you’ll have the
ability to direct your system to do almost anything. This chapter
describes the powerful bash shell. The chapter
also briefly explains shell variables, shell scripts, and shell
aliases, preparing you for an in-depth, continuing study of Linux and
its shell.
The component of Linux that interprets
and executes commands is called the shell.
Usually, you’ll access the shell via a terminal window, as
explained in Chapter 5 and Chapter 6. However, the section “Using Virtual
Consoles” later in this chapter explains how to use a virtual
console. Linux supports a variety of different shells, but the most
popular is the bash shell. The Linux
bash shell presents the user with a
Command Line Interface (CLI). CLIs are familiar
to Windows users who have worked in the MS-DOS window, and indeed the
Windows MS-DOS Prompt window is a kind of command-line shell. The
Linux bash shell works much like the MS-DOS
Prompt window; you type text commands and the system responds by
displaying text replies. As your first Linux command, type w and press Enter. Your contents of the terminal window
should look something like this:
[bill@home bill]$ w
11:12am up 6 min, 1 user, load average: 0.00, 0.08, 0.05
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
bill tty1 11:11am 0.00s 0.20s 0.11s -bash
The
w command tells Linux to display the
system status and a list of all system users. In the example, the
output of the command tells you that it’s now 11:12 a.m., that
the system has been up for six minutes, and that only one
user—bill—is currently logged in.
Notice that the command output is very terse, packing much
information into a few lines. Such output is typical of Linux
commands. At first, you may find Linux output cryptic and difficult
to read, but over time you’ll grow to appreciate the efficiency
with which Linux communicates information.
Linux provides many commands besides the w command—so many that you may despair of learning and recalling them. Actually, the number of commands you’ll use regularly is fairly small. Soon, these will become second nature to you.
Try a second command, the date command:
[bill@home bill]$ date
Fri Oct 5 11:15:20 PST 2001The date command displays the current date and time.
If you find working with MS-DOS distasteful or intimidating, you may not immediately enjoy working with the Linux command line. However, give yourself some time to adjust. The Linux command line has several features that make it easier to use, and more powerful, than MS-DOS.