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std::chrono::time_point<Clock,Duration>::time_since_epoch

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std::chrono::time_point
 
duration time_since_epoch() const;
 (C++11 起)
(C++14 前)
constexpr duration time_since_epoch() const;
 (C++14 起)

返回表示 *this 与 clock 的纪元间的时间量的 duration 。

参数

（无）

返回值

此 time_point 与 clock 的纪元间的时间量

示例

运行此代码
#include <iostream>
#include <chrono>
#include <ctime>
 
int main()
{
    auto p0 = std::chrono::time_point<std::chrono::system_clock>{};
    auto p1 = std::chrono::system_clock::now();
    auto p2 = p1 - std::chrono::hours(24);
 
    auto epoch_time = std::chrono::system_clock::to_time_t(p0);
    std::cout << "epoch: " << std::ctime(&epoch_time);
    auto today_time = std::chrono::system_clock::to_time_t(p1);
    std::cout << "today: " << std::ctime(&today_time);
 
    std::cout << "hours since epoch: "
              << std::chrono::duration_cast<std::chrono::hours>(
                   p1.time_since_epoch()).count() 
              << '\n';
    std::cout << "yesterday, hours since epoch: "
              << std::chrono::duration_cast<std::chrono::hours>(
                   p2.time_since_epoch()).count() 
              << '\n';
}

可能的输出： 

epoch: Thu Jan  1 00:00:00 1970
today: Fri Jun 30 10:44:11 2017
hours since epoch: 416338
yesterday, hours since epoch: 416314
来自“https://zh.cppreference.com/mwiki/index.php?title=cpp/chrono/time_point/time_since_epoch&oldid=59720”
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