c++ 获取时间戳

1. c++ 获取时间戳：

   #include <iostream>
   #include <iomanip>
   #include <ctime>
   #include <chrono>
   #include <sstream>
   
   int main()
   {
         
         
   	    std::chrono::system_clock::time_point now = std::chrono::system_clock::now();
   	    int64_t timepoint = std::chrono::duration_cast<std::chrono::milliseconds>(now.time_since_epoch()).count();
   	
   	    std::chrono::system_clock::time_point convert = std::chrono::time_point<std::chrono::system_clock>(std::chrono::milliseconds(timepoint));
   	
   	    std::time_t t = std::chrono::system_clock::to_time_t(convert);
   	    std::string time_str = std::ctime(&t);
   	
   	    std::tm tm_ = *std::localtime(&t);
   	    std::stringstream time12;
   	    time12 << std::put_time(&tm_, "%H:%M:%S %p");
   	    
   	    std::cout << "now\n";
   	    std::cout << "timepoint " << timepoint << std::endl;
   	    std::cout << "time " << time_str << std::endl;
   	    std::cout << "time12 " << time12.str() << std::endl;
   }
   

    https://en.cppreference.com/w/cpp/chrono/time_point
    http://www.informit.com/articles/article.aspx?p=1881386&seqNum=2
    https://blog.csdn.net/q229827701/article/details/51272753