Thanks to anisha and citi!

You re most welcome, have any queries further? Feel free to post back, but this time PLEASE search Google before asking and do mention your efforts in your first post.

Nice explanations by anisha kaul and erictra. Especially for the people like me who has come from a poor "English" background. Highly appreciate the way anisha kaul explained.

There are so many people in this world, who dont know english but has a very good technical skills or interest in linux. I am also one of them. For those guys, this google and man pages does not gives the explanation what they want, but when they post in such a forums, they believe that they may get the information in the way they want. I knew that man pages has almost all the informations. But we are not up to that mark to understand its content. Personally i struggled a lot to understand these man pages and sometimes google too gave the same. Now it has been changed (or i have changed my mentality to read man pages) I have been started using LINUX since the beginning of 2008 and i had some idea now. So, Let me complete like this, whenever someone explains like how anisha kaul did, i feel really happy and it increases the confident of approaching this forum and even expecting the answers from the same user who solved/replied to my post last time.

Sorry if my post seemed so negative. I did not intend it to be that way. The OP was asking for something that could not have been answered/understood in a single post. This kind of knowldge and skills takes time to master. All I wanted to convey to the OP was that he should give himself time (read scripts etc) so that he could understand shells more.
BTW: Anisha you _did_ explain in one post what bash is. Hats off to you for that.