如何在 C++ 中以微秒为单位获取时间戳？

Question

I have tried this and other codes I found online but they did not work. My IDE is Xcode. Edit: When I tried the code on the link, the variable long long microseconds always returned 0. I would like to print the timestamp in this manner: (hour:minute:microseconds). For example, 15:17:09:134613464312.

Answer 1

The method you use is correct.

If you the code between the two now() calls lasts less than a microseconds, microseconds will always be zero, since the number is not a floating point. If you have always zero, that means you need higher resolution (try nanoseconds).

Btw, if you simply want timestamp, you don't want to use this code since it is done to compute elapsed time between two time points. You can try something like this:

auto microseconds = std::chrono::duration_cast<std::chrono::microseconds>
    (std::chrono::high_resolution_clock::now().time_since_epoch()).count();

Which is really a timestamp and not a duration.

EDIT: To have the current microseconds count, you can do something like this:

#include <iostream>
#include <chrono>
#include <ctime>

using namespace std;
using namespace std::chrono;

using days = duration<int, ratio_multiply<hours::period, ratio<24> >::type>;

int main() {
    system_clock::time_point now = system_clock::now();
    system_clock::duration tp = now.time_since_epoch();
    days d = duration_cast<days>(tp);
    tp -= d;
    hours h = duration_cast<hours>(tp);
    tp -= h;
    minutes m = duration_cast<minutes>(tp);
    tp -= m;
    seconds s = duration_cast<seconds>(tp);
    tp -= s;
    cout << tp.count() << "\n";
    return 0;
}

This will print the current microseconds count.

Hours:Minutes:Seconds is pretty easy.