fopen and redirects

I am using fopen with a url to open a remote file (read only of course). The url I am providing results in a redirect and the fopen seems to be smart enough to follow the redirect to return the actual file contents. How can I get at the redirected filename? The problem is the file contains html and relative references in href's buried in the html are relative to the redirected location and not my original location, and I would like to subsequently open some of those files (like a crawler does). thanks in advance, Warren Vail