Basic of Shell | Shell Type | Shell Command Execution Process | Command Execution Order

Basic of Shell | Shell Type | Shell Command Execution Process | Command Execution Order


Shell 

A shell is a user interface that takes the commands from the keyboard and gives them to the OS to perform. Shell is environment in which we can run our program, command and scripts. or We can say that SHELL is a program which provides the interface between the user and an operating system

Command Execution Process

1 - We gives the command from the keyboard

2 - Shell process with the help of Terminal Emulator and pass to Kernel

3 - Kernel Process and Give result for command progress

4 - Terminal Emulator takes result and  display the output with the help of monitor

Command Execution Process, Shell
Command Execution Process


Command Execution Order

1 - User Enter the Command with the help of Keyboard

2 - Terminal Emulator 1th Check Build in Command with help of shell

3 - If build in Command exist it will process with the help of Kernel and Print the Display
   
      If Build in command not exist, it  will Check Alias of Command and process

      If Command alias not exist, it will check command in local Hard Disk Drive

      If  Local Command not exist in HDD, Print " Command not Found" in Display

Shell Command Execution Order
Shell Command Execution Order

Type of Shell

1 - Sh   :  Bourne SHell
2 - csh  :  C Shell
3 - ksh  :  Korn Shell
4 - Bash: Bourne Again SHell
5 - Dash: Debian Almquist shell
6 - Fish : Friendly Interactive Shell
7 - Zsh  : Z Shell

How can we change Shell in Unix/Linux like Operating system ?

we can check all available shell in the system with following command
cat /etc/shells
We can change shell using following chsh ( Change Shell ) command
chsh
Prompt for a password, and some don't.

/bin/zsh  # Type in the path and name of your new shell.



Thanks






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