Besides allowing you to start programs, the shell command prompt also provides a compilation
of special commands used by the shell to interact with the Linux system. These
commands are used to work with files and directories contained in the file system, display
programs that are running in the kernel (called processes), and control user accounts used
to log into the Linux system.
The shell structure also provides a rudimentary programming environment that can be
used to help provide structured scripts for automating shell commands. This is where shell
scripting comes in. By combining shell commands, program statements, and programs
within a script, you can simulate a complete programming environment with just the shell.
There are several shells available for the Linux operating system. The different shells have
different capabilities, such as the commands they provide and the way commands can be
scripted. The openSUSE Linux 10.3 Linux distribution supports many types of shells, as
shown in Table 8.1
TABLE 8.1 Linux Shells
Shell Description
sh The Bourne shell, the original shell written by Steven Bourne for Unix
bash The Bourne-again shell, an Open Source project to emulate the functionality
of the Bourne shell
csh The C shell, written by Bill Joy, that emulates the C programming language
ksh The Korn shell, written by Dave Korn, that combines features of the C shell
and the Bourne shell
tcsh An Open Source modification of the C shell
zsh The Z shell, an Open Source shell which provides advanced programming
techniques, such as processing floating point numbers
By far the most common shell used on Linux systems is bash.
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