interpreter that executes commands read from the standard input device
(keyboard) or from a file. Linux may use one of the following most popular shells
(In MS-DOS, Shell name is COMMAND.COM which is also used for same purpose,
but it's not as powerful as our Linux Shells are!)
Shell Name
Developed by
Where
Remark
BASH ( Bourne-Again
SHell )
Brian Fox and Chet
Ramey
Free Software
Foundation
Most common shell in
Linux. It's Freeware
shell.
CSH (C SHell)
Bill Joy
University of California
(For BSD)
The C shell's syntax and
usage are very similar to
the C programming
language.
KSH (Korn SHell)
David Korn
AT & T Bell Labs

Any of the above shell reads command from user (via Keyboard or Mouse) and tells
Linux O/s what users want. If we are giving commands from keyboard it is called
command line interface ( Usually in-front of $ prompt, This prompt is depend upon
your shell and Environment that you set or by your System Administrator,
therefore you may get different prompt ).
NOTE: To find your shell type following command
$ echo $SHELL
How to use Shell
To use shell (You start to use your shell as soon as you log into your system) you
have to simply type commands. Following is the list of common commands.
Linux Common Commands
NOTE that following commands are for New users or for Beginners only. The
purpose is if you use this command you will be more familiar with your shell and
secondly, you need some of these command in your Shell script. If you want to get
more information or help for this command try following commands For e.g. To see
help or options related with date command try
$ date --help
or To see help or options related with ls command (Here you will screen by screen
help, since help of ls command is quite big that can't fit on single screen )
Linux Shell Script Tutorial