What the Hell is a Shell?

You see the term ‘Shell’ tossed around a lot these days. The Bourne Shell (sh), Bash (Bourne Again Shell), Powershell, etc. What actually is a “shell”?

Put simply, a shell is an interface that lets a user interact with the Operating System. A shell could be a command-line interface or a graphical user interface.

For the purpose of this post, we’ll be looking at command-line interface shells. I wanted to do a couple of posts about the Linux/Unix Command Line and thought it would be good to dive right in and explore a Unix (or Unix-like) Shell.

Many people will often times use words like terminal, command-line, shell, or bash interchangeably - but it’s important to note the difference. Let’s start with some terminology.

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Terminology:

• Terminal - the actual window filled with text. When most people say “terminal” they actually mean “terminal emulator” - and it does just that. It emulates an old school video or text terminal within your operating system.
  • Most Unix or Unix-like operating systems ship with a default terminal emulator, but you can install others without issue.
• Command Line - the actual place where you enter your commands. Letters appear here when you type on your keyboard. Usually has a blinking cursor.
• Shell - the software that runs inside the terminal window and sends your commands to the operating system. Some examples:
  • Bourne Shell and Bash
  • Powershell
  • Zsh
  • Fish Shell
  • …and many more!

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How the Shell Works

Scripting

Popular Shells

Bash

Zsh

Fish Shell

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