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CHAPTER 13 INTRODUCING THE BASH SHELL There s another reason why the shell is used to run programs: you can specify how a particular program runs before starting it. For example, to launch the Totem Movie Player in full-screen mode playing the myvideofile.mpg file, you could type this: totem –fullscreen myvideofile.mpg This saves the bother of starting the program, loading a clip, and then selecting the full- screen option. After you ve typed the command once or twice, you ll be able to remember it for the next time. No matter how much you love the mouse, you ll have to admit that this method of running programs is more efficient. When you get used to using the shell, it s likely you ll have it open most of the time behind your other program windows. Getting Started with the Shell You can start the shell in a number of ways. The most common is to use a terminal emulator program. As its name suggests, this runs a shell inside a program window on your desktop. You can start GNOME Terminal, the built-in GNOME shell emulator, by clicking Applications . Accessories . Terminal, as shown in Figure 13-1. Figure 13-1. Start the The GNOME Terminal program from the Accessories submenu. You ll see the terminal window a blank, white window that s similar to a simple text editor window. It will show what s referred to as a command prompt: a few words followed by the dollar symbol: $. On my test system, this is what I see: keir@ubuntu:~$ The first part is my username the user account I created during installation and use to log in to the PC. After the @ sign is the name of the PC, which I also chose when installing Ubuntu. The name of the PC isn t important on most desktop PCs; it s a legacy from the days of Unix. After the colon is the current directory you re browsing. In this example, the ~ symbol appears instead of an actual path or directory name. This is merely Linux shorthand for the user s homedirectory. In other words, wherever I see a ~on my test PC, I read it as /home/keir/. After this is the dollar symbol ($), which indicates that I m currently logged in as an ordinary

206 CHAPTER 13 INTRODUCING THE BASH SHELL It s respected in the community. Using a shell earns you enormous brownie points when speaking to other Linux users. It separates the wheat from the chaff and the men from the boys (or women from the girls). If you intend to use Linux professionally, you will most certainly need to be a master at the shell. Seen in this light, learning at least a handful of shell commands is vital to truly mastering your PC. The drawback when using a command-line shell is that it s not entirely intuitive. Take for instance the command to change the network card s IP address: ifconfig eth0 192.168.0.15 up If you ve never used the shell before, it might as well be Sanskrit. What on earth does ifconfig mean? And why is there the word up at the end? Learning to use the shell involves learning terms like these. Hundreds of commands are available, but you really need to learn only around 10 or 20 for everyday use. The comparison with a new language is apt because, although you might think it daunting to learn new termi nology, with a bit of practice, it will all become second nature. Once you ve used a command a few times, you ll know how to use it in the future. The main thing to realize is that the shell is your friend. It s there to help you get stuff done as quickly as possible. When you become familiar with it, you ll see that it is a beautiful concept. The shell is simple, elegant, and powerful. When Should You Use the Shell? The amount of use the Linux shell sees is highly dependent on the user. Some Linux buffs couldn t manage without it. They use it to read and compose e-mail, and even to browse the Web (usually using the Mutt and Lynx programs, respectively). However, most people simply use it to manage files, view text files (like program docu mentation), and run programs. All kinds of programs including GUI and command-line can be started from the shell. As you ll learn in Chapter 29, unlike with Windows, installing a program on Ubuntu doesn t necessarily mean the program will automatically appear on the Applications menu. In fact, unless the installation routine is specifically made for the version of Linux you re running, this is unlikely. Therefore, using the shell is a necessity for most people. Note Unlike with DOS programs, Ubuntu programs that describe themselves as command-line are rarely designed to run solely via the command-line shell. All programs are like machines that take input at one end and output objects at the other. Where the input comes from and where the output goes to is by no means limited to the command line. Usually, with a command-line program, the input and output are provided via the shell, and the programmer makes special dispensation for this, but this way of working is why GUI programs often make use of what might be considered shell programs. You ll often find that a GUI program designed to, for example, burn CDs, will also require the installation of a command-line program that will actually do the hard work for it.

CHAPTER 13 INTRODUCING THE BASH SHELL Why Bother with the Shell? You might have followed the instructions in Part 2 of this book and consider yourself an expert in Linux. But the real measure of a Linux user comes from your abilities at the shell. In our modern age, the GUI is mistakenly considered progress. For instance, users of the Microsoft and Apple-based operating systems are quite used to using a mouse to navigate and perform various tasks. While it s handy in certain situations it would be difficult to imagine image editing without a mouse, for example in many other situations, such as when manipulating files, directly typing commands is far more efficient. Most modern Linux distributions prefer you to use the GUI to do nearly everything. This is because they acknowledge the dominance of Windows and realize they need to cater to mouse users who might not even know the shell exists (and, of course, programs like web browsers would be unusable without a GUI!). To this end, they provide GUI tools for just about every task you might wish to undertake. Ubuntu is strong in this regard, and you can configure a lot of things from the desktop. However, it s well worth developing at least some command-line shell skills, for a number of reasons: It s simple and fast. The shell is the simplest and fastest way of working with Ubuntu. As just one example, consider the task of changing the IP address of your network card. You could click the Systems menu, then the Administration option, then the Network option, and then double-click the entry in this list relating to your network card. That will take at least a minute or two if you know what you re doing, and perhaps longer if it s new to you. Alternatively, you could simply open a shell and type this: ifconfig eth0 192.168.0.15 up It s versatile. Everything can be done via the shell from deleting files, to configuring hardware, to creating MP3s. A lot of GUI programs actually make use of programs you can access via the shell. It s consistent among distributions. All Linux systems have shells and understand the same commands (broadly speaking). However, not all Linux systems will have Ubuntu s graphical configuration programs. SUSE Linux uses its own GUI configuration tool, as does Mandrake Linux. Therefore, if you ever need to use another system, or decide to switch distributions, a reliance on GUI tools will mean learning everything from scratch. Knowing a few shell commands will help you get started instantly. It s crucial for troubleshooting. The shell offers a vital way of fixing your system should it go wrong. Your Linux installation might be damaged to the extent that it cannot boot to the GUI, but you ll almost certainly be able to boot into a shell. A shell doesn t require much of the system other than the ability to display characters on the screen and take input from the keyboard, which most PCs can do, even when they re in a sorry state. This is why most rescue floppies offer shells to let you fix your system. It s useful for remote access. One handy thing about the shell is that you don t need to be in front of your PC to use it. Programs like ssh let you log in to your PC across the Internet and use the shell to control your PC (as described in Chapter 34). For example, you can access data on a remote machine, or even fix it when you re unable to attend the machine s location. This is why Linux is preferred on many server systems when the system administrator isn t always present on the site.

204 CHAPTER 13 INTRODUCING THE BASH SHELL Note Linux purists will point out another reason why the shell isn t exactly the same as a DOS command prompt within Windows: it doesn t run in virtual machine mode, a CPU trick by which part of the memory is subdivided to let programs run as if they had the PC all to themselves. Linux finds itself with the BASH shell largely because Linux is a clone of Unix. In the early days of Unix, the text-based shell was all that was offered as a way of letting users control the computer. Typing commands in directly is one of the most fundamental ways of controlling any type of computer and, in the evolutionary scale, comes straight after needing to set switches and watch blinking lights in order to run programs. That the BASH shell can trace its history back to the early days of Unix might sound like a tacit indication that the BASH is somehow primitive far from it. It s one of the most efficient and immediate ways of working with your computer. Many people consider the command- line shell to be a way of using a computer that has yet to be superseded by a better method. Note When you run a shell on a Linux system, the system refers to it as a tty device. This stands for teletypewriter, a direct reference to the old system of inputting data on what were effectively electronic typewriters connected to mainframe computers. These, in turn, took their names from the devices used to automate the sending and receiving of telegrams in the early part of the twentieth century. Most Linux distributions come with a choice of different kinds of shell programs. However, the default shell is BASH, as is the case in Ubuntu. BASH stands for Bourne Again SHell. This is based on the Bourne shell, a tried-and-tested program that originated in the early days of Unix. The other shells available include PDKSH (Public Domain Korn SHell, based on Korn Shell, another early Unix shell), and ZSH (Z SHell), a more recent addition. These are usually used by people who want to program Linux in various ways, or by those who simply aren t happy with BASH. The BASH shell is considered by many to be the best of all worlds in that it s easy enough for beginners to learn, yet is able to grow with them and offer additional capabilities as necessary. BASH is capable of scripting, for example, which means you can even create your own simple programs. Note Technically speaking, a shell refers to any type of user interface. The windowing system offered by Windows and Macintosh operating systems are a type of shell. However, many people in the Linux and Unix worlds use the word shell as shorthand for a shell that offers a command line.

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.

PART 4 The Shell and Beyond

CHAPTER 12 MANAGING YOUR FILES Summary This chapter has led you on your first steps in exploring the Linux file system. The file system is vitally important to how Linux works, and we ll go into it in much depth in upcoming chapters. Here, you were introduced to elementary concepts, such as where personal files are stored and the basic rules that govern what you can and cannot do with files. We also looked at the principle method of accessing files via the GUI: the Nautilus file manager. Additionally, you learned how to run programs manually, as well as how to access any Windows partition or files that may exist on your hard disk or across a network. In Part 4 of this book, starting in the next chapter, we will look at some of the underlying technology that makes Ubuntu work and how you can gain more control over your computer. Chapter 13 introduces the BASH shell perhaps the most powerful piece of software offered by Ubuntu to control your system.

198 CHAPTER 12 MANAGING YOUR FILES In the case of floppy disks, memory cards, and other USB storage devices, you ll need to right-click the icon and select Unmount Volume. Then you can then unplug and/or remove the device. This also applies when you re removing a memory card from a card reader before pulling out the card from the reader, it needs to be unmounted. Note It s necessary to close any files that were open on the device before unmounting, and even close any file browser windows that were accessing the device. If you fail to unmount the device, Ubuntu will still believe the device is attached. This shouldn t cause too many problems, but it could crash any programs that were accessing the device. Formatting Floppies Formatting floppy disks isn t done in Nautilus. Instead, you must use a special program called Floppy Formatter. To start this program, click Applications . System Tools . Floppy Formatter. You ll see the program window shown in Figure 12-10. Figure 12-10. Formatting floppy disks is done using the Floppy Formatter tool. Floppy Formatter is similar to the disk-formatting tool in Windows, and most of the options are self-explanatory. If you intend to share the disk with Windows users, make sure DOS (FAT) is selected in the File System Type box (it s possible to format a floppy using Ubuntu s own ext2 file system format, but there s little to be gained by doing so).

CHAPTER 12 MANAGING YOUR FILES Figure 12-9. Select Places . Computer to access your removable storage drives. Whenever you double-click any entry in the Computer window, it will open a Nautilus file browser window. You can copy files by clicking and dragging, and right-clicking files offers virtually all the options you could need. Tip You don t need to use Places . Computer each time to access your floppy, CD, or DVD drive. These drives are mounted in the /media folder on your hard disk. Just browse to /media/floppy, and /media/ cdrom. Ejecting Media from Drives Ubuntu isn t quite like Windows when it comes to ejecting or unplugging removable storage devices. In some cases, devices must be unmounted, which is to say that you need to tell Ubuntu that you re finished with the device in question and that you re about to unplug it. In the case of CD or DVD discs, you can simply hit the Eject button on the drive itself. Ubuntu is clever enough to realize that the disc is being ejected, so it will automatically unmount the drive.

196 CHAPTER 12 MANAGING YOUR FILES Figure 12-8. If the share requires a username and/or password, you ll be invited to enter these. Accessing Removable Storage Devices Ubuntu automatically makes available any CDs or DVDs you insert into your computer, and they ll appear instantly as icons on the desktop. The same is true of any card readers or USB memory devices that you use. Alternatively, you can access the storage devices by clicking Places . Computer. Here, you ll find icons for all of the storage devices attached to your computer, including the floppy disk drive, as shown in Figure 12-9. However, because of the way floppy disk drives work, Ubuntu isn t able to automatically detect if a floppy has been inserted. Instead, you ll need to double-click the icon, as with Windows. Note In days of old, special tools were used to access MS-DOS floppies under Linux, and you might hear some Linux old hands talking about them. Nowadays, you can simply use Nautilus without needing to take any special steps.