Hi can anybody say about SIGHUP signal. I read its for hangup but i didnot understand whats meant by that. Pls tell me in very simple sense. Pls don't refer me to any website. I want our knowledge because its easier to learn from u than from website. Thanks.

it's a method for the OS and other programs to send specific signals between each other. SIGHUP is basically like a "I'm asking you nicely to quit" message.

Here's some other examples of Linux Signals:
http://www.comptechdoc.org/os/linux/...pgsignals.html

There's something interesting if you would like to know;SIGHUP can be intercepted and handled,like all SIG signals except SIGKILL and SIGSTOP.

It originally dates from the old days, when everything was dial-up (eg ARPANet, precursor to internet).
It literally means hang-up the phone line, which is why you use

nohup prog

to ensure a prog keeps running when you logout, otherwise it dies, because its still attached to the terminal session, even if you use '&'. '&' only puts it in the background, its still connected to your term session.
These days SIGHUP is in fact usually used to get a prog eg Apache to re-read its config file on the fly ie without an explicit re-start.

HTH