SHELL is an interface between the user and an operating system. When the user logs in, Linux OS starts a shell for user then shell communicates with the kernel and interprets user commands.
Kernel controls all essential computer operations, and provides the restriction to hardware access, coordinates all executing utilities, and manages Resources between process. Using kernel only user can access utilities provided by operating system.
Types of Shell:-
1.) The Bourne Shell ( sh ) -
It was written by Steve Bourne at AT&T Bell Labs. It is the original UNIX shell. It is faster and more preferred by the Unix/Linux users.It is default shell for Solaris OS. It doesn't support advanced features like aliases, command history and built-in arithmetic expressions.
In Bourne shell, Command full-path name is /bin/sh and /sbin/sh,
Non-root user default prompt is $,
Root user default prompt is #.
2.) The C Shell (csh) was created by Bill Joy at the University of California at Berkeley. It incorporated features such as aliases and command history. It includes helpful programming features like built-in arithmetic and C-like expression syntax.
In C shell, Command full-path name is /bin/csh,
Non-root user default prompt is hostname %,
Root user default prompt is hostname #.
3.) The Korn Shell ( ksh ) -
It was written by David Korn at AT&T Bell Labs. It 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.
In Korn shell, Command full-path name is /bin/ksh,
Non-root user default prompt is $,
Root user default prompt is #.
4.) GNU Bourne-Again Shell ( bash ) -
It is compatible to the Bourne shell. It includes features from Korn and Bourne shell.
In GNU Bourne-Again shell, Command full-path name is /bin/bash,
Default prompt for a non-root user is bash-g.gg$
(g.ggindicates the shell version number like bash-3.50$),
Root user default prompt is bash-g.gg#.
T Shell –
Denoted as tsh
It was originally developed for the Plan 9 operating system, but has since been ported to other systems, including Linux, FreeBSD, and macOS.
Command full-path name is /bin/tcsh,
Default prompt for a non-root user is abhishekaslk(user):~>
Root user default prompt is root@abhishekaslk(user):~#.
Z Shell –
Denoted by zsh
Z Shell (zsh) was created by Paul Falstad in 1990 while he was a student at Princeton University. Z Shell is an extended version of the Bourne-Again Shell (bash), with additional features and capabilities.
Command full-path name is /bin/zsh,
Default prompt for a non-root user is abhishekaslk(user)%
Root user default prompt is root@abhishekaslk(user):~#
