Terminal versus Shell

The graphical user interface (GUI) is pretty self-explanatory. You can easily get around and connect to the internet and open up your web browser. All of that is pretty easy, as you can see in the following screenshot.

Figure 16: The Graphical User Interface

You can use Ubuntu Software to install new software programs on your system.

You can use Dash the same way you would use the Start menu on Microsoft Win-dows to launch your applications.

LibreOffice Writer is an excellent word processor that has the same function-ality as Microsoft Word with only one difference; it's free!

Right now, you can be a casual Linux user, which means you can use Linux to do the basic tasks that everyday users do: surfing YouTube, sending Emails, searching Google, etc. However, to be a power user, you need to be proficient at using the Linux Command Line Interface.

To access the Linux Command Line Interface, you need to open the Terminal Emulator, which is often referred to as the Terminal for simplicity.

WHAT IS A TERMINAL EMULATOR?

A Terminal Emulator is a program that emulates (mimics) a physical Terminal (Console). The Terminal interacts with the Shell (the Command Line Interface).

Ok, now you might be scratching your head, asking yourself: "What is a Shell?"

WHAT IS A SHELL?

The Shell is a command-line interpreter, that is to say, it is a program that processes and executes commands.

Alright, enough with all the theory here. Let's walk through an example to under-stand and tie everything together. Go ahead and open the Terminal by clicking on the Dash and then search Terminal. You can also use the shortcut Ctrl+Alt+T to open the Terminal. When the Terminal opens, you will see a new window, as shown in the following screenshot.

Figure 17: The Terminal

It looks kind of similar to the Command Prompt on Microsoft Windows. Alright, now type date on your Terminal and then hit Enter:

elliot?ubuntu-linux:-$ date 
Tue Feb 17 16:39:13 CST 2020

Now let's discuss what happened, date is a Linux command that prints the current date and time, right after you hit Enter, the Shell (which is working behind the scenes) then executed the command date and displayed the output on your Terminal.

You shouldn't be confused between the Terminal and the Shell. The Termi-nal is the window you see on your screen where you can type in your commands while the Shell is responsible for executing the commands. That's it, nothing more and nothing less.

You should also know that if you type any gibberish, you will get a command not found error as shown in the following example:

elliot?ubuntu-linux:-$ blabla 
blabla: command not found