Linux Command Line and Shell Scripting Bible. Christine Bresnahan
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Название: Linux Command Line and Shell Scripting Bible
Автор: Christine Bresnahan
Издательство: Автор
Жанр: Зарубежная образовательная литература
isbn: 9781118984192
isbn:
Figure 2.5 shows what the basic xterm display looks like running on a graphical Linux desktop. You can see it is very basic.
Figure 2.5 The xterm Terminal
The xterm terminal emulator can be tricky to find these days. Often, it is not included in a desktop environment graphical menu arrangement.
In Ubuntu's Unity desktop, xterm is installed by default. You can access it via Dash⇨Search and type xterm. xterm shows up in the Dash home area as an application named XTerm. Click that icon to open the xterm terminal emulator.
Note
You may see another terminal called UXTerm when you search for xterm on Ubuntu. This is simply the xterm emulator package with Unicode support.
In the GNOME and KDE desktop environment, xterm is not installed by default. You must install it first (see Chapter 9 for help on installing software packages). After it's installed, you must start xterm from another terminal emulator. Open a terminal emulator for CLI access, type xterm, and press Enter. Also, remember that you can create your own desktop launcher to startup xterm.
The xterm package allows you to set individual features using command line parameters. The following sections discuss these features and how to change them.
The list of xterm command line parameters is extensive. You can control lots of features to customize the terminal emulation features, such as enabling or disabling individual VT emulations.
Note
xterm has a huge number of configuration options – so many that they cannot all be covered here. Extensive documentation is available via the bash manual. Accessing the bash manual is covered in Chapter 3. In addition, the xterm development team provides some excellent help on its website: http://invisible-island.net/xterm/.
You can invoke certain configuration options by adding a parameter to the xterm command. For example, to have the xterm emulate a DEC VT100 terminal, type the command xterm – ti vt100 and press Enter. Table 2.17 shows some parameters you can include when invoking the xterm terminal emulator software.
Table 2.17 xterm Command Line Parameters
Some xterm command line parameters use a plus sign (+) or minus sign (-) to signify how a feature is set. A plus sign may turn a feature on, while a minus sign turns it off. However, the opposite can be true as well. A plus sign may disable a feature, while a minus sign enables it, such as when using the bc parameter. Table 2.18 lists some of the more common features you can set using the +/– command line parameters.
Table 2.18 xterm +/– Command Line Parameters
It is important to note that not all implementations of xterm support all these command line parameters. You can determine which parameters your xterm implements by using the – help parameter when you start xterm on your system.
Now that you have been introduced to three terminal emulator packages, the big question is which is the best terminal emulator to use? There is no definite answer to that question. Which terminal emulator package you use depends upon your individual needs and desires. But it is great to have so many choices.
Summary
To start learning Linux command line commands, you need access to a CLI. In the world of graphical interfaces, this can sometimes be challenging. This chapter discussed different interfaces you should consider to get to the Linux command line.
First, this chapter discussed the difference between accessing the CLI via a virtual console terminal (a terminal outside the GUI) and a graphical terminal emulation package (a terminal inside the GUI). We took a brief look at the basic differences between these two access methods.
Next, we explored in detail accessing the CLI via a virtual console terminal, including specifics on how to change console terminal configuration options such as background color.
After looking at virtual console terminals, the chapter traveled through accessing the CLI via a graphical terminal emulator. Primarily, we covered three different types of terminal emulators: GNOME Terminal, Konsole Terminal, and xterm.
This chapter also covered the GNOME desktop project's GNOME terminal emulation package. GNOME Terminal is typically installed by default on the GNOME desktop environment. It provides convenient ways to set many terminal features via menu options and shortcut keys.
We also covered the KDE desktop project's Konsole terminal emulation package. The Konsole Terminal is typically installed by default on the KDE desktop environment. It provides several nice features, such as the ability to monitor a terminal for silence.
Finally, we covered the xterm terminal emulator package. xterm was the first terminal emulator available for Linux. It can emulate older terminal hardware such as the VT and Tektronix terminals.
In the next chapter, you start looking at the Linux command line commands. It walks you through the commands necessary to navigate around the Linux filesystem, and to create, delete, and manipulate files.
Chapter 3
Basic bash Shell Commands
Interacting with the shell
Using the bash manual
Traversing the filesystem
Listing files and directories
Managing files and directories
Viewing file contents
The default shell used in many Linux distributions is the GNU bash shell. This chapter describes the basic features available in the bash shell, such as the bash manual, tab auto-completion and how to display a file's contents. You will walk through how to work with Linux files and directories using the basic commands provided by the bash shell. If you're already comfortable with the basics in the Linux environment, feel free to skip this chapter and continue with Chapter 4 to see more advanced commands.
Starting the Shell
The GNU bash shell is a program that provides interactive access to the Linux system. It runs as a regular program and is normally started whenever a user logs in to a terminal. The shell that the system starts depends on your user ID configuration.
The /etc/passwd file contains a list of all the system user accounts, along with some basic configuration information about each user. Here's a sample entry from a /etc/passwd file:
Each entry has seven data fields, with fields separated by colons. The system uses the data in these fields to assign specific features for the user. Most of these entries are discussed in more detail in Chapter 7. For now, just pay attention to the last field, which specifies the user's shell program.
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