Shell Scripting Features

     Command features

• >     :-   Redirect output
• >>   :-   Append to file
• <     :-   Redirect input
• <<   :-   "Here" document (redirect input)
• |       :-   Pipe output
• &     :-   Run process in background.
• ;       :-   Separate commands on same line
• *      :-   Match any character(s) in filename
• ?      :-   Match single character in filename
• [ ]    :-   Match any characters enclosed
• ( )    :-   Execute in subshell
• ` `    :-   Substitute output of enclosed command
• " "   :-    Partial quote (allows variable and command expansion)
• ' '     :-    Full quote (no expansion)
• \      :-    Quote following character
• $var :-    Use value for variable
• $$    :-    Process id
• $0    :-    Command name
• $n    :-    nth argument (n from 0 to 9)
• $*    :-    All arguments as a simple word
• #      :-    Begin comment
• bg    :-    Background execution
• break :-   Break from loop statements
• cd    :-     Change directories
• cont :-     Resume a program loop
• echo :-    Display output
• eval  :-    Evaluate arguments
• exec :-    Execute a new shell
• fg    :-     Foreground execution
• jobs :-     Show active jobs
• kill   :-    Terminate running jobs
• newgrp :-  Change to a new group
• shift  :-      Shift positional parameters
• stop  :-     Suspend a background job
• suspend :- Suspend a foreground job
• time   :-    Time a command
• umask :-   Set or list file permissions
• unset  :-    Erase variable or function definitions
• wait   :-    Wait for a background job to finish

Text editors

Usage of editors 

It is very important to be able to use at least one text mode editor. Knowing how to use an editor on your system is the first step to independence.We will need to master an editor by the next chapter as we need it to edit files that influence our environment.As an advanced user, you may want to start writing scripts, or books, develop websites or new programs. Mastering an editor will immensely improve your productivity as well as your capabilities. Our focus is on text editors, which can also be used on systems without a graphical environment and in terminal windows. The additional advantage of mastering a text editor is in using it on remote machines.Since you don't need to transfer the entire graphical environment over the network, working with text editors tremendously improves network speed.There are, as usual, multiple ways to handle the problem. Let's see what editors are commonly available.

Emacs is the extensible, customizable, self-documenting, real-time display editor, known on many UNIX and other systems. The text being edited is visible on the screen and is updated automatically as you type your commands. It is a real-time editor because the display is updated very frequently, usually after each character or pair of characters you type. This minimizes the amount of information you must keep in your head as you edit. Emacs is called advanced because it provides facilities that go beyond simple insertion and deletion: controlling subprocesses; automatic indentation of programs; viewing two or more files at once; editing formatted text; and dealing in terms  of characters, words, lines, sentences, paragraphs, and pages, as well as expressions and comments in several different programming languages.

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About Linux Operating System in the Enviorment

Red Hat

 Red Hat is a billion dollar commercial Linux company in the world that puts a lot of effort in developing Linux. They have hundreds of Linux specialists  in the company those are known for their
excellent support. They give their products (Red Hat Enterprise Linux and Fedora)
away for free. While Red Hat Enterprise Linux (RHEL) is well tested before release
and supported for up to seven years after release, Fedora is a distro with faster updates
but without support. Distributions like CentOS, Oracle Enterprise Linux and Scientific Linux are based on Red Hat Enterprise Linux and share many of the same principles, directories and
system administration techniques. Linux Mint, Edubuntu and many other *buntu
named distributions are based on Ubuntu and thus share a lot with Debian. There are
hundreds of other Linux distributions.which are as follows:-

Ubuntu

Canonical started sending out free compact discs with Ubuntu Linux in 2004 and
quickly became popular for home users (many switching from Microsoft Windows).
Canonical wants Ubuntu to be an easy to use graphical Linux desktop without need
to ever see a command line. Of course they also want to make a profit by selling
support for Ubuntu.

 Debian

There is no company behind Debian. Instead there are thousands of well organised
developers that elect a Debian Project Leader every two years. Debian is seen as one
of the most stable Linux distributions. It is also the basis of every release of Ubuntu.
Debian comes in three versions: stable, testing and unstable. Every Debian release is
named after a character in the movie Toy Story.

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