For the most part, computer operating systems all have a “shell.” When people talk about the “command line” … they are talking about the prompt in a shell. The concept of a shell, and the way we think of a shell today mostly stems from its implementation on Unix systems. A shell is a computer program that has a human interface and a number of built in or accessible functions (mostly other programs) that humans can invoke to make the computer do something. On ‘servers’ and on most computers back in the old days, the shell would typically appear as a prompt on a computer screen, and that would be all you would get. You type stuff in, and the computer types stuff as well, and between the two of you, stuff happens. On a computer with a graphical user interface (GUI), there is still a shell, but it looks different. The shell is less tangible to the human user, but the GUI itself is a program that provides the user interface, and it may either be the shell itself or it may be invoked automatically as the computer starts up by the shell. Continue reading Learning the Bash Shell →