I wanted to fetch username / id of the facebook user who has clicked on the link which is posted via feed dialog on his wall/ friend's wall.
Is there any way to accomplish this?
Currently we pass a static link to the post feed dialog api. Is there any mechanism to make this link fb-user-specific?
No, without authorizing the user, there is no way you can get any personal data (that includes the id). That´s for privacy/security reasons.
It is also not possible to use a dynamic link which is dynamic for every user that clicks on it.