code: добавил вариант

main.cpp

@@ -54,6 +54,7 @@ download(const string& address)
     if(curl)
     {
         CURLcode res;
+        double file_size;
         curl_easy_setopt(curl, CURLOPT_URL, address.c_str());
         curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
         curl_easy_setopt(curl, CURLOPT_WRITEDATA, &buffer);
@@ -63,6 +64,11 @@ download(const string& address)
             fprintf(stderr, "curl_easy_perform() failed: %s\n",curl_easy_strerror(res));
             exit(1);
         }
+        else
+        {
+            res = curl_easy_getinfo(curl, CURLINFO_CONTENT_LENGTH_DOWNLOAD, &file_size);
+            cerr<<"File size: "<<file_size<<" bytes";
+        }
         curl_easy_cleanup(curl);
     }