C++ 实现文件拷贝：

    bool copyFile(const std::string& source, const std::string& target)
    {
        bool success = true;
        try
        {
            // mkdir()，父目录必须存在
            // 如果目录已经存返回 false，OS API 调用失败时会抛出异常
            if (!fs::create_directories(fs::path(target).parent_path()))
            {
                std::cerr << "Target directory is existed. " << std::endl;
                LOG_STREAM(user, info) << "Target directory is existed. ";
            }
            if (!fs::copy_file(source, target, fs::copy_options::overwrite_existing))
            {
                success = false;
            }
        } catch (std::filesystem::filesystem_error const& ex)
        {
            LOG_STREAM(user, warn) << "Failed to copy file: " << ex.what();
            success = false;
        }
        return success;
    }