• The shell is a command line interpreter, it translates the user entered command and converts them into the language which is understood by the kernel.

• Shell scripting is nothing but the list of commands which are listed in a script in the order of execution.

1. The C shell (csh):- It includes helpful programming features like built-in arithmetic and C-like expression syntax.
2. The Bourne Shell (sh) :- It is the original UNIX shell. It is faster and more preferred. It lacks features for interactive use like the ability to recall previous commands.
3. The Korn Shell (ksh):- is a superset of the Bourne shell.So it supports everything in the Bourne shell.It has interactive features. It includes features like built-in arithmetic and C-like arrays, functions, and string-manipulation facilities.It is faster than C shell. It is compatible with script written for C shell.
4. Bourne Again Shell (bash) :- It is compatible to the Bourne shell. It includes features from Korn and Bourne shell.

• At the start of shell script its recommended to add the shebang (#! - shaa-bang) comment for the user to identify which shell is being used.

• The operator #! known as the shebang operator is used to define the shell in which the script is going to run.

• The Shebang for shell script is mostly not necessary when your code is independent of the type of shell, and would run on any type (bash, ksh, csh etc). Eg:- #!/bin/sh --- for Bourne shell #!/bin/bash -- for Bourne again shell. This indicates the path of the shell

  #!/bin/bash
  
  #write your script here
  

--> we will learn about the concept of the shell scripting in this project.