如何在当前时间的打印输出中获得更高的精度（几分之一秒）？ [英] How to get higher precision (fractions of a second) in a printout of current time?

问题描述

我尝试了几种从 system_clock 打印时间的方法，但我不能得到除整秒之外的任何东西：

I've tried a couple methods to print out time from the system_clock but I can't get anything other than whole seconds:

system_clock::time_point now = system_clock::now();
std::time_t now_c = system_clock::to_time_t(now);

std::cout<<ctime(&now_c);
std::cout<<std::put_time(std::localtime(&now_c), "%T")<<" ";

now（）高精度数据，或者我只是找不到提取打印信息的功能？

Does the now() function actually hold high precision data, or is that I just can't find the function that extracts that information for printing?

注意：我不是要计算时间间隔。我想要几分之一秒的当前时间，并通过 cout 打印出来。我只是找不到一个办法做到这一点。

Note: I am not looking to calculate a time interval. I want the current time with fractions of a second, and to print it out via cout. I just can't find a way to do this.

我知道 std :: chrono :: high_resolution_clock ，但也没有办法打印出它的 now（）。此外， setprecision 函数对 put_time 或 ctime

And I know about std::chrono::high_resolution_clock but also see no way to print out its now(). Additionally, the setprecision function has no effect on the output of put_time or ctime.

推荐答案

我已经得到了没有解决这个问题的答案。解决方案

解决方案

您可以执行以下操作：

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

std::string GetLocalTime() {
  auto now(std::chrono::system_clock::now());
  auto seconds_since_epoch(
      std::chrono::duration_cast<std::chrono::seconds>(now.time_since_epoch()));

  // Construct time_t using 'seconds_since_epoch' rather than 'now' since it is
  // implementation-defined whether the value is rounded or truncated.
  std::time_t now_t(
      std::chrono::system_clock::to_time_t(
          std::chrono::system_clock::time_point(seconds_since_epoch)));

  char temp[10];
  if (!std::strftime(temp, 10, "%H:%M:%S.", std::localtime(&now_t)))
    return "";

  return std::string(temp) +
      std::to_string((now.time_since_epoch() - seconds_since_epoch).count());
}

int main() {
  std::cout << GetLocalTime() << '\n';
  return 0;
}

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