Linux user login and logout details and process.
 

Hello,
I am creating small logic for recording linux users terminal session but for that I need to study whole process of how the linux user login into the system all background process,
all environment variables in this scenario, is there someone who can help me out of this.?

We can help you if you have SPECIFIC questions, but there is a wealth of information regarding the Linux login process you can (and should have), researched on your own. For example, the first two hits in Google for "how does the linux login process work" are:
http://www.linuxnix.com/how-login-pr...work-in-linux/
http://www.comptechdoc.org/os/linux/...x_hllogin.html

...with many more.

But I still haven't got the answer. How can I run "exit" command on users tty when the user hits "X" button of putty..???

That was not the question you asked - not remotely.

That is a putty question, not a Linux login question. You would have to see if putty allows you to issue remote commands in response to actions such as the X button.

nope....I am asking for the logic....how can I run exit command while user session closed.

Nope. You cannot run any command while the user session is closed.

You will need to provide a much more complete description of what you are trying to do before anyone can provide help.

Please see this article for thoughts on asking a complete quesstion.

...and asking for handouts, rather than reading the abundant research, won't get you the answer either.
...and if this is YOUR PROGRAM, isn't it up to YOU to write the logic??? And common sense will tell you that you can't run ANY commands if there isn't an active session. This is very much like asking, "How do I load a web page, after I close my browser?"