Unix os Basics configration

Shell in unix acts as a command interpreter between user and Unix kernel as well as provides a strong scripting language .

Following are the different types of Unix shells ,

B shell , /bin/sh – This is the default Unix shell for many Unix operating systems .
Bourne shell was written by S. R. Bourne and its more emphasis is to use it as a scripting language rather than an interactive shell .
Some of the features are :
Provided support for environment variables using parameters and exportable variables.
Redirection of program output and error .
Command substitution using back quotes: `command`.
embed a file/commands using input redirector <<
“for ~ do ~ done” loops
“case ~ in ~ esac” for selecting and responding to a data value .

C-shell /bin/csh was designed to provide the interactive features lacking in b shell such as job control and aliasing .

K shell /bin/ksh – was created by David Korn and has features of both B shell and C shell along with some additional features .

Bash – the Bourne again shell was developed by GNU project .It is based on B shell language and has features of C and K shells.

tcsh is the default shell of FreeBSD and its descendants. Essentially it is C shell with programmable command line completion, command-line editing, and a few other features.

Zsh is a shell designed for interactive use and it has many of the useful features of bash, ksh, and tcsh along with many new features.
Unix Shells configuration files :

b shell
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    shell prompt : $
    executable file : /bin/sh

    Read on interactive/non interactive login to bash
    /etc/profile
    ~/.profile

bash shell
—————————————————–

    shell prompt : $
    executable file : /bin/bash

    Read on interactive/non interactive login to bash
    /etc/profile
    ~/.profile
    ~/.bash_profile
    ~/.bash_login

    Always read on invoking bash
    ~/.bashrc

    /etc/profile login login login
    ~/.profile login login

csh shell
——————————————————

    shell prompt : %
    executable file : /bin/csh

    Read on csh shell invocation .
    /etc/csh.cshrc
    ~/.cshrc

    Read on interactive/non interactive login to tcsh shell
    /etc/.login
    ~/.login
    ~/.logout
    /etc/csh.login

ksh
—————————————————–

    shell prompt : $
    executable file : /bin/ksh

    Read on interactive/non interactive login to bash
    /etc/profile
    ~/.profile

tcsh shell
——————————————————

    shell prompt : &
    executable file : /bin/tcsh

    Read on tcsh shell invocation .
    ~/.tcshrc
    /etc/csh.cshrc
    ~/.cshrc

    Read on interactive/non interactive login to tcsh shell
    /etc/.login
    ~/.login
    ~/.logout
    /etc/csh.login

zsh
—————————————————–

    shell prompt : $
    executable file : zsh

    Configuration files :

    Always read on invoking zsh
    ~/.zshenv always
    /etc/zshenv always

    only read on interactive login to zsh.
    ~/.zshrc
    /etc/zshrc

    Read on interactive/non interactive login to zsh
    /etc/zprofile login
    /etc/zlogin login
    /etc/zlogout login
    /.zprofile login
    ~/.zlogin login
    ~/.zlogout login