Make a web site - CHAPTER 13 Introducing the BASH
CHAPTER 13 Introducing the BASH Shell As you learned in Chapter 1, strictly speaking, the word Linux refers to just the kernel, which is the fundamental, invisible program that runs your PC and lets everything happen. However, on its own, the kernel is completely useless. It needs programs to let users interact with the PC and do cool stuff, and it needs a lot of system files (also referred to as libraries) to provide vital functions. The GNU Project provides many of these low-level pieces of code and programs. This is why many people refer to the Linux operating system as GNU/Linux, giving credit to the fact that, without the GNU components, Linux wouldn t have gotten off the starting blocks. The GNU Project provides various shell programs, too. Some of these offer graphical functionality, but most are text only. These text shell programs are also known as terminal programs, and they re often colloquially referred to as command-line prompts, in reference to the most important component they provide. This kind of shell lets you take control of your system in a quick and efficient way. Like a GUI, it s another way of interfacing with your computer, except that you type commands, rather than use a mouse. By learning how to use the shell, you ll become the true master of your own system. In this part of the book, you ll learn all you need to know about using the shell. This chapter introduces the BASH shell, which is the default one in Ubuntu. What Is the BASH Shell? The best way of explaining the BASH shell to a Windows user is to compare it to the DOS command prompt. It lets you issue commands directly to the operating system via the keyboard without needing to mess around with the mouse and windows (although it is sometimes possible to use the mouse within a BASH shell to copy and paste text, and sometimes to control simple text- based menus). The big difference is that the BASH shell has commands for just about everything you might do on your system, whereas the DOS command prompt is restricted to tools capable of manipulating and viewing files and directories, and on Windows 2000/XP machines, configuring certain system settings. In the old days, the DOS command prompt was also the visible layer of an entire operating system in which DOS programs were designed to be run. However, the shell is merely one of the many ways of accessing the Linux kernel and subsystems. It s true that many programs are designed to run via the BASH shell, but technically speaking, most actually run on the Linux operating system, and simply take input and show their input via the BASH shell.