I was perusing my logs recently and noticed that some of the blog reader robots send subscriber information in the user agent of the http request header.

For example

Feedfetcher-Google; (+http://www.google.com/feedfetcher.html; XXX subscribers; feed-id=9794374963400689406)
NewsGatorOnline/2.0 (http://www.newsgator.com; XXX subscribers)
livedoor FeedFetcher/0.01 (http://reader.livedoor.com/; XXX subscribers)
Bloglines/3.1 (http://www.bloglines.com; XXX subscribers)

Of course this won't show all of your subscribers but, it is a good way to know what to expect when posting new content. It can also be a good way to see how your community is growing.

I didnt quite get it,Did you code it on your root file??

Thats just a snippet from my access log

you can try feedburner or others, it can show your subscriber number.