On Mon, May 16, 2011 at 3:02 PM, V.Ravikumar <ravikumar.vallabhu@gmail.com> wrote:

If a  file modified by some user then how can we detect that user who modified it.

SystemTap can help you. Have a look at following examples:-
http://sourceware.org/systemtap/wiki/WSFileMonitor 
http://sourceware.org/systemtap/wiki/WSFileMonitor2

--
Regards,
Neependra
www.neependra.net