8.2.2 Specifying Default Shell Program

There are various Shell programs available in Linux, and other Shell programs may be provided depending on the distribution. If you have other Shell programs you need, you can also use the Shell program.

On Linux, information about the Shell program currently installed on the system is stored in the “/etc/shells” file. If you check the information just like below, you can see that you can use various Shell programs. One of these several Shell programs installed in the system is specified as the Shell program used by default in the system.

8.2 Shell Program

8.2.1 Shell and BASH (Bourne Again Shell)

When we execute a command in the Terminal program, the Shell program accepts and interprets the command internally, instructs the system kernel to process it, and when processing is complete, it receives the result from the kernel and returns it to the Terminal program. Since the Shell is between the Terminal and system kernels, and handles all requests that the Terminal program requires, the Terminal program does not need to know anything about the system kernel. It is called a Shell in the sense that it serves to provide the necessary services to external Terminals that needs to receive services from the kernel while enclosing the system kernel as if the clamShell surrounds the contents.

8.1.3 Working on Terminal Screen

Next, let’s see exactly where the current position is on the Terminal screen. If you want to know the current directory location on Linux, use “pwd” command.

pi@raspberrypi ~ $ pwd

/home/pi

The above example shows that when you run the “pwd” command, it tells that “/home/pi” is the current directory location. “~” is displayed on the screen, but in reality, it means “/home/pi”. The current directory location specified in the home directory for the first time will be changed as user move the user’s working directory to another directory. Then, the position displayed on the screen is changed accordingly.

8.1.2 Configuration of Terminal Screen

The Terminal screen provided in the Pi system has certain rules. First, let’s look at the information displayed on the Terminal screen.

If you connect to the system at first and log on to “pi” account, the parts as below appears on the Terminal screen.

8.1 Terminal program

8.1.1 How to Start Terminal Program

When you issue commands to the system to do the desired work on the Raspberry Pi system, you uses the Terminal screen. Although the Raspberry Pi system supports the window and can do some work in the window, most work still needs to be done manually by typing the command on the Terminal program screen.

There are several ways to start a Terminal program on the Raspberry Pi system. You can start the Terminal program from the local console, start the Terminal program from the remote connection, or start the Terminal program from the window.

Chapter 8 Terminal and Shell Program

Chapter’s Main Topics

When you issue a command to the system to do desired work on the Raspberry Pi system, in most cases, you use the Shell command on the Terminal screen. This chapter describes how to use the Terminal program and the basic method to use the Shell command.

It includes descriptions on the following topics:
■ Terminal program

■ Shell program