C++11新特性，利用auto和std::chrono获取系统时间的方法

const std::string getCurrentSystemTime(){auto tt = std::chrono::system_clock::to_time_t(std::chrono::system_clock::now());struct tm* ptm = localtime(&tt);char date[60] = {0};sprintf(date, "%d-%02d-%02d      %02d:%02d:%02d",(int)ptm->tm_year + 1900,(int)ptm->tm_mon + 1,(int)ptm->tm_mday,(int)ptm->tm_hour,(int)ptm->tm_min,(int)ptm->tm_sec);return std::string(date);}