I had problem in updating natbib, though the process should be simple. I have doubt exactly how the command texhash is to be used. Can anybody please tell?

I downloaded the latest natbib.zip, unzipped in a new directory, extracted the natbib.sty and bibentry.sty. Then I used

Code:
sudo texhash /usr/share
and then
Code:
source ~./bashrc
(This method is given in some previous post)
After this when I try to latex some file, I get the latex warning which says that the latest natbib.sty version is "unavailable" to the compiler. I have also checked that the extracted natbib.sty file is newer than the older version of natbib available. Why is this happening? I have also used
Code:
sudo texhash
and
Code:
sudo /usr/share....../natbib
i.e., giving the entire path for the actual location of natbib.sty file. All attempts failed. What am I doing wrong?