What is a Shell?
Shell is a special user program that provides an interface to the user to use operating system services. Operating systems include opening a file, deleting a file, opening a program, renaming a file, etc.
Essentially the Shell accepts human-readable commands from input sources such as keyboard-entry or file(Shell scripts) and pass this to the operating system to execute.
Put simply, the Shell is a special kind of kind of software that let you do some tasks from the command line interface (CLI).
A CLI would typically look like the image below
Our focus on this module is working with the CLI. Although, the concept of Shell
as we know it, is typical to Linux and Mac operating systems otherwise known as
Unix-based operating systems. The Window operating system provides cmd.exe and
powershell as equivalents of the Unix-based systems' CLI. It would suffice to
say that, the cmd.exe and powershell can also be used to interact with the
operating system. However, and, for uniformity, we will only be interacting with
the Unix-like shells. The WSL installed earlier in this module make it possible
for Windows user to do this.
In the Unix-based systems, we have different kinds of Shell interpreters, these include:
- bash - Bourne Again Shell
- zsh - Z Shell
- csh - C shell
- ksh - KornShell
- sh - Bourne shell
- fish - Friendly Interactive Shell
tip
An Shell interpreter, like interpreter studied in module one, is a program that takes a Shell command and translate it to something the computer can work with.
This book will focus solely on Bash because it's quite popular and probably the most wildly adopted. Bash syntax is also compatible with other kinds of shell.
On Windows based systems, configuring WSL might be tricky especially without prior experience with the CLI. I have included a video by Gary below which is more than enough to get you started.