Intorduction ~ Linux Command and Shell Scripting Series.

Quick Start
Linux Shell Scripting Tutorial
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Introduction  :

Salam to all  In This Tutorial Series you Will learn a complete linux command and shell scripting . If u are beginner then you are at right place . No extra things I have included in my tutorial cover all the Basic things In short span of Time . To get the most benefit from thisTutorial you need to install  a Unix machine, preferably with AIX, HP-UX,
Linux,Ubuntu,Backtrack or Solaris installed. I urge everyone to study this entire Tutorial . Every Tutorial hits a different topic using a different approach. All of the shell scripts in this Tutorials are realworld examples of how to solve a problem. I hope you enjoy this Tutorial as much as I enjoyed writing it. Let’s get started!

Tutorial  1

Quick Introduction to Linux

1. What Linux is ?
2. Who developed the Linux ?
3. Different Linux Distribution ?
4. Where I can use Linux ?


What Linux is ?
Linux is 
1. Free
2. Unix Like
3. Open Source
4. Network operating system




Free
Linux is free.
First ,It's available free of cost (You don't have to pay to use this OS, other OSes like MS-Windows or Commercial version of Unix may cost you money)
Second free means freedom to use Linux, i.e. when you get Linux you will also get source code of Linux, so you can modify OS (Yes OS! Linux OS!!) according to your taste.
It also offers many Software applications, programming languages, and development tools etc. Most of the Program/Software/OS are under GNU General Public License (GPL).


Unix Like
Unix is almost 35 year old Os.
In 1964 OS called MULTICS (Multiplexed Information and Computing System) was developed by Bell Labs, MIT & General Electric. But this OS was not the successful one.
Then Ken Thompson (System programmer of Bell Labs) thinks he could do better (In 1991, Linus Torvalds felt he could do better than Minix - History repeats itself.). So Ken Thompson wrote OS on PDP - 7 Computer, assembler and few utilities, this is know as Unix (1969). But this version of Unix is not portable. Then Unix was rewrote in C. Because Unix written in 'C', it is portable. It means Unix can run on varity of Hardware platform (1970-71).
At the same time Unix was started to distribute to Universities. There students and professor started more experiments on Unix. Because of this Unix gain more popularity, also several new features are added to Unix. Then US govt. & military uses Unix for there inter-network (now it is know as INTERNET).
So Unix is Multi-user, Multitasking, Internet-aware Network OS. Linux almost had same Unix Like feature
for e.g.
1. Like Unix, Linux is also written is C.
2. Like Unix, Linux is also the Multi-user/Multitasking/32 or 64 bit Network OS.
3. Like Unix, Linux is rich in Development/Programming environment.
4. Like Unix, Linux runs on different hardware platform .


Open Source
Linux is developed under the GNU Public License. This is sometimes referred to as a "copyleft", to
distinguish it from a copyright.
Under GPL the source code is available to anyone who wants it, and can be freely modified, developed,
and so forth. There are only a few restrictions on the use of the code. If you make changes to the
programs , you have to make those changes available to everyone.


For more details, please visit the open-source home page.


Who developed the Linux?
In 1991, Linus Torvalds studding Unix at the University, where he used special educational experimental purpose operating system called Minix (small version of Unix). But Minix had it's own limitations. Linus felt he could do better than the Minix. So he developed his own version of Minix, which is now know as Linux. Linux is Open Source From the start of the day. 


How to get Linux?
Linux available for download over the net, this is useful if your internet connection is fast. Another way is order the CD-ROMs which saves time, and the installation from CD-ROM is fast/automatic. Various Linux distributions available. Following are important Linux distributions. 


Red Hat Linux:  http://www.redhat.com/
SuSE Linux:  http://www.suse.com/
Mandrake Linux:  http://www.mandrakesoft.com
Caldera Linux:  http://www.calderasystems.com/
Debian GNU/Linux:  http://www.debian.org/
Slackware Linux:  http://www.slackware.com/


How to Install Linux
There is lot of tutorial on internet just search on Google .


Where I can use Linux ?
You can use Linux as Server Os or as stand alone Os on your PC. (But it is best suited for Server.) As a server Os it provides different services/network resources to client. Server Os must be

•  Stable
•  Robust
•  Secure
•  High Performance

What Kernel Is ?
Kernel is heart of Linux Os.
It manages resource of Linux Os. Resources means facilities available in Linux. For e.g. Facility to store data, print data on printer, memory, file management etc . Kernel decides who will use this resource, for how long and when. It runs your programs (or set up to execute binary files)
The kernel acts as an intermediary between the computer hardware and various programs/application/shell. 


What's Linux Shell
A shell is an environment in which we can run our commands, programs, and shell Scripts .  .
Computer understand the language of 0's and 1's called binary language. In early days of computing, instruction are provided using binary language, which is difficult for all of us, to read and write. So in Os there is special program called Shell. Shell accepts your instruction or commands in English (mostly) and if it’s a valid command, it is pass to kernel. Shell is a user program or it's environment provided for user interaction. Shell is an command language interpreter that executes commands read from the standard
input device (keyboard) or from a file. Shell is not part of system kernel, but uses the system kernel to execute programs, create files etc.


Several shell available with Linux including
Tip: To find all available shells in your system type following command
$ cat /etc/shells


Tip: To find your current shell type following command
$ echo $SHELL
Note that
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! Any of the above shell reads command from user (via Keyboard or Mouse) and tells Linux Os what users want. If we are giving commands from keyboard it is called command line interface.

Thanks :)