CURLE_OK(which has the value zero) if everything is fine and dandy and it returns a non-zero number if a problem was detected. There are almost one hundred
CURLcodeerrors in use, and you can find them all in the
curl/curl.hheader file and documented in the libcurl-errors man page.
curl_easy_strerror()function—but be aware that these errors are rarely phrased in a way that is suitable for anyone to expose in a UI or to an end user:
CURLOPT_ERRORBUFFERoption to point out a buffer in your program and then libcurl will store a related error message there before it returns an error: