CURLINFO_SIZE_UPLOAD man page
CURLINFO_SIZE_UPLOAD — get the number of uploaded bytes
CURLcode curl_easy_getinfo(CURL *handle, CURLINFO_SIZE_UPLOAD, double *uploadp);
Pass a pointer to a double to receive the total amount of bytes that were uploaded.
Added in 7.4.1
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.