message: refactor: not ouput result on screen
diff: @@ -184,7 +184,8 @@ int main() {
  return 0;
  }
  - FILE* output = stdout;
  + //FILE* output = stdout;
  + FILE* output = NULL; //not update result on the screen
  ResultSet rs;
  bool ret = current_database->query(sparql, rs, output);
  