What is Linux Shell?

Posted on Sep 2, 2008 01:10:23 AM

Computer understands the language of zeros and ones known as binary language. In early days of computing, instruction provided using binary language, which is difficult for all of us, to read and write. Therefore, in operating system there is special program called shell. Shell accepts your instruction or commands in english language and if it is a valid command, kernel will process your request.

Shell is a user program or it is environment provided for user interaction. It a command language interpreter that executes commands read from the standard input device (keyboard) or from a file.

To find all available shells in your system type following command:

$ cat /etc/shells

Note that each shell does the same job, but each understand different command syntax and provides different built-in functions.

Under MS-DOS, shell name is COMMAND.COM which is also used for same purpose, but it is not as powerful as our Linux Shells are!
Command line interface (CLI)

Shell provides an interface to the Linux where you can type or enter commands using the keyboard it know as command line interface (CLI).

To find out your current shell type following command:
$ echo $SHELL
$ ps $$