regex pattern extract the opti-id <novel-li opti-id="aaa">

std::string str = "<novel-li opti-id=\"aaa\">";
  std::smatch result;
  std::regex re("opti-id=\"(.*?)\"");

  while (std::regex_search(str, result, re)) {
    for (auto x : result)
      std::cout << x << " ";
    std::cout << std::endl;
    str = result.suffix();
  }