Post transfer info

Remember how libcurl transfers are associated with easy handles. Each transfer has such a handle and when a transfer is completed, before the handle is cleaned or reused for another transfer, it can be used to extract information from the previous operation.

Your friend for doing this is called curl_easy_getinfo() and you tell it which specific information you are interested in and it returns that if it can.

When you use this function, you pass in the easy handle, which information you want and a pointer to a variable to hold the answer. You must pass in a pointer to a variable of the correct type or you risk that things go side-ways. These information values are designed to be provided after the transfer is completed.

The data you receive can be a long, a 'char *', a 'struct curl_slist *', a double or a socket.

This is how you extract the Content-Type: value from the previous HTTP transfer:

CURLcode res;
char *content_type;
res = curl_easy_getinfo(curl, CURLINFO_CONTENT_TYPE, &content_type);

If you want to extract the local port number that was used in that connection:

CURLcode res;
long port_number;
res = curl_easy_getinfo(curl, CURLINFO_LOCAL_PORT, &port_number);

Available information