c/c++ time

1.获取以秒为单位的时间戳

1.1 C++风格

#include <iostream>
#include <ctime>
 
int main()
{
    std::time_t t = std::time(0);  // t is an integer type
    std::cout << t << " seconds since 01-Jan-1970\n";
    return 0;
}
           

1.2 C风格

#include <iostream>
#include <sys/time.h>
 
int main()
{
    unsigned long int sec1 = time(NULL);
    time_t sec2 = time(NULL);  // 这里的time_t不是std:time_t
    std::cout << sec1 << std::endl;
    std::cout << sec2 << std::endl;
    return 0;
}
           

2.获取以毫秒为单位的时间戳

2.1 C++风格

#include <iostream>
#include <chrono>
 
int main()
{
 
    std::chrono::milliseconds ms = std::chrono::duration_cast< std::chrono::milliseconds >(
        std::chrono::system_clock::now().time_since_epoch()
    );
 
    std::cout << ms.count() << std::endl;
    return 0;
}
           

2.2 C风格

#include <iostream>
#include <sys/time.h>
 
int main()
{
    struct timeval tp;
    gettimeofday(&tp, NULL);
    long int ms = tp.tv_sec * 1000 + tp.tv_usec / 1000;
    std:: cout << ms << std::endl;
    return 0;
}