CURLcode curl_easy_getinfo(CURL *handle, CURLINFO_CONTENT_TYPE, char **ct);
DESCRIPTIONPass a pointer to a char pointer to receive the content-type of the downloaded object. This is the value read from the Content-Type: field. If you get NULL, it means that the server didn't send a valid Content-Type header or that the protocol used doesn't support this.
The ct pointer will be NULL or pointing to private memory you MUST NOT free it - it gets freed when you call curl_easy_cleanup(3) on the corresponding CURL handle.