Linux Command Line and Shell Scripting Bible. Christine Bresnahan

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СКАЧАТЬ style="font-size:15px;">      Most Linux distributions include more than one shell, although usually they pick one of them to be the default. If your Linux distribution includes multiple shells, feel free to experiment with different shells and see which one fits your needs.

The Linux Desktop Environment

      In the early days of Linux (the early 1990s) all that was available was a simple text interface to the Linux operating system. This text interface allowed administrators to start programs, control program operations, and move files around on the system.

      With the popularity of Microsoft Windows, computer users expected more than the old text interface to work with. This spurred more development in the OSS community, and the Linux graphical desktops emerged.

      Linux is famous for being able to do things in more than one way, and no place is this more relevant than in graphical desktops. There are a plethora of graphical desktops you can choose from in Linux. The following sections describe a few of the more popular ones.

The X Window System

      Two basic elements control your video environment: the video card in your PC and your monitor. To display fancy graphics on your computer, the Linux software needs to know how to talk to both of them. The X Window software is the core element in presenting graphics.

      The X Window software is a low-level program that works directly with the video card and monitor in the PC, and it controls how Linux applications can present fancy windows and graphics on your computer.

      Linux isn't the only operating system that uses X Window; versions are written for many different operating systems. In the Linux world, several different software packages can implement it.

      The most popular package is X.org. It provides an open source software implementation of the X Window system and supports many of the newer video cards used today.

      Two other X Window packages are gaining in popularity. The Fedora Linux distribution is experimenting with the Wayland software, and the Ubuntu Linux distribution has developed the Mir display server for use with its desktop environment.

      When you first install a Linux distribution, it attempts to detect your video card and monitor, and then it creates an X Window configuration file that contains the required information. During installation, you may notice a time when the installation program scans your monitor for supported video modes. Sometimes, this causes your monitor to go blank for a few seconds. Because there are lots of different types of video cards and monitors, this process can take a while to complete.

      The core X Window software produces a graphical display environment, but nothing else. Although this is fine for running individual applications, it is not useful for day-to-day computer use. No desktop environment allows users to manipulate files or launch programs. To do that, you need a desktop environment on top of the X Window system software.

The KDE Desktop

The K Desktop Environment (KDE) was first released in 1996 as an open source project to produce a graphical desktop similar to the Microsoft Windows environment. The KDE desktop incorporates all the features you are probably familiar with if you are a Windows user. Figure 1.3 shows a sample KDE 4 desktop running in the openSUSE Linux distribution.

Figure 1.3 The KDE 4 desktop on an openSUSE Linux system

      The KDE desktop allows you to place both application and file icons in a special area on the desktop. If you click an application icon, the Linux system starts the application. If you click a file icon, the KDE desktop attempts to determine what application to start to handle the file.

      The bar at the bottom of the desktop is called the Panel. The Panel consists of four parts:

      ● The K menu: Much like the Windows Start menu, the K menu contains links to start installed applications.

      ● Program shortcuts: These are quick links to start applications directly from the Panel.

      ● The taskbar: The taskbar shows icons for applications currently running on the desktop.

      ● Applets: These are small applications that have an icon in the Panel that often can change depending on information from the application.

      The Panel features are similar to what you would find in Windows. In addition to the desktop features, the KDE project has produced a wide assortment of applications that run in the KDE environment.

The GNOME Desktop

      The GNU Network Object Model Environment (GNOME) is another popular Linux desktop environment. First released in 1999, GNOME has become the default desktop environment for many Linux distributions. (However, the most popular is Red Hat Linux.)

      Although GNOME chose to depart from the standard Microsoft Windows look-and-feel, it incorporates many features that most Windows users are comfortable with:

      ● A desktop area for icons

      ● A panel area for showing running applications

      ● Drag-and-drop capabilities

Figure 1.4 shows the standard GNOME desktop used in the CentOS Linux distribution.

Figure 1.4 A GNOME desktop on a CentOS Linux system

      Not to be outdone by KDE, the GNOME developers have also produced a host of graphical applications that integrate with the GNOME desktop.

The Unity Desktop

      If you're using the Ubuntu Linux distribution, you'll notice that it's somewhat different from both the KDE and GNOME desktop environments. Canonical, the company responsible for developing Ubuntu, has decided to embark on its own Linux desktop environment, called Unity.

The Unity desktop gets its name from the goal of the project – to provide a single desktop experience for workstations, tablet devices, and mobile devices. The Unity desktop works the same whether you're running Ubuntu on a workstation or a mobile phone! Figure 1.5 shows an example of the Unity desktop in Ubuntu 14.04 LTS.

Figure 1.5 The Unity desktop on the Ubuntu Linux distribution

Other Desktops

      The downside to a graphical desktop environment is that it requires a fair amount of system resources to operate properly. In the early days of Linux, a hallmark and selling feature of Linux was its ability to operate on older, less powerful PCs that the newer Microsoft desktop products couldn't run on. However, with the popularity of KDE and GNOME desktops, this has changed, because it takes just as much memory to run a KDE or GNOME desktop as the latest Microsoft desktop environment.

      If you have an older PC, don't be discouraged. The Linux developers have banded together to take Linux back to its roots. They've created several low-memory–oriented graphical desktop applications that provide basic features that run perfectly fine on older PCs.

      Although these graphical desktops don't have a plethora of applications designed around them, they still run many basic graphical applications that support features such as word processing, spreadsheets, databases, drawing, and, of course, multimedia support.

Table 1.3 shows some of the smaller Linux graphical desktop environments that can СКАЧАТЬ