Thanks in advance.
I wanna know the facebook graph api URL, Which Should give me the location name(from where the user is posting the comment).
From that I wanna store the location name in DB.
Same for Twitter, flickr.
I may be misunderstanding what you are after here, but won't all requests from the API come from the same server or block of servers? Is that what you mean by location, as in request.referer ?
There is a bundle of data about the user that is sent to you. If you look at the Omniauth docs, they do a great job of leveling out the differences between the various services in this regard. But if the user's location is not part of that bundle of data, then knowing the service that they used isn't going to get you any closer to it, unless all you are after is whether they used Facebook, Twitter, Flickr or whatever to authenticate.