CURLINFO_REDIRECT_URL man page
CURLINFO_REDIRECT_URL — get the URL a redirect would go to
CURLcode curl_easy_getinfo(CURL *handle, CURLINFO_REDIRECT_URL, char **urlp);
Pass a pointer to a char pointer to receive the URL a redirect would take you to if you would enable CURLOPT_FOLLOWLOCATION(3). This can come very handy if you think using the built-in libcurl redirect logic isn't good enough for you but you would still prefer to avoid implementing all the magic of figuring out the new URL.
Added in 7.18.2
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
curl_easy_getinfo(3), CURLOPT_FOLLOWLOCATION(3), CURLOPT_URL(3).