MySQL server, my bootable floppy router/firewall, or my wife's iMac and explore and use
any of those computer systems from a shell.
Special shell features enable you to gather data input and direct data output between
commands and the Linux file system. To save on typing, you can find, edit, and repeat
commands from your shell history. Many power users hardly touch a graphical interface,
doing most of their work from a shell.
You can gather commands into a file using programming constructs such as conditional
checks, loops, and case statements to quickly do complex operations that would be
difficult to retype over and over. Programs consisting of commands that are stored
and run from a file are referred to as shell scripts. Most Linux system administrators
use shell scripts to automate tasks such as backing up data, monitoring log files, or
checking system health.
The shell is a command language interpreter. If you have used Microsoft operating systems, you'll
see that using a shell in Linux is similar to -- but generally much more powerful than -- the inter-
preter used to run commands in DOS or in the CMD command interface. You can happily use
Linux from a graphical desktop interface, but as you grow into Linux you will surely need to use
the shell at some point to track down a problem or administer some features.
How to use the shell isn't obvious at first, but with the right help you can quickly learn many of
the most important shell features. This chapter is your guide to working with the Linux system
commands, processes, and file system from the shell. It describes the shell environment and helps
you tailor it to your needs. It also explains how to use and move around the file system.
Starting a Shell
There are several ways to get to a shell interface in Linux. Three of the most common are the shell
prompt, Terminal window, and virtual terminal. They're discussed in the following sections.
Using the Shell Prompt
If your Linux system has no graphical user interface (or one that isn't working at the moment), you
will most likely see a shell prompt after you log in. Typing commands from the shell will probably
be your primary means of using the Linux system.
The default prompt for a regular user is simply a dollar sign:
$
The default prompt for the root user is a pound sign (also called a hash mark):
#
36
Linux First Steps
Part I
