Before graphical user interfaces came into vogue , the only way to interact with an operating system was via the command line shell (often known simply as the shell ). The shell allows users to type in commands for the operating system and the operating system to display the output that results from the execution of these commands.
Despite the rise of GUIs such as GNOME and KDE and predictions of the complete demise of the command line shell, the shell has held steady as the user interface of choice for a large number of users ”sometimes as a last resort when the GUI fails, but often simply because it is a very flexible and powerful tool. In fact, the shell has evolved into a tool that allows users to do pretty much all that can be done using the operating system, and far beyond what a GUI would permit.
This chapter discusses the following:
The command line shell and its background
Shell commands, shortcut keys, and aliases
The command line syntax
Managing multiple tasks at the same time
Using the shell as a scripting language