C++ 11之前并未提供专门的休眠函数。c语言的sleep、usleep其实都是系统提供的函数，不同的系统函数的功能还有些差异。

在Windows系统中，sleep的参数是毫秒。

sleep(2*1000); //sleep for 2 seconds

在类Unix系统中，sleep()函数的单位是秒。

sleep(2); //sleep for 2 seconds

从C++11开始，中C++标准库提供了专门的线程休眠函数，使得你的代码可以独立于不同的平台。

std::this_thread::sleep_forstd::this_thread::sleep_untill

1. 让线程休眠一段时间

std::this_thread::sleep_for用于Block当前线程一段时间。

template< class Rep, class Period >void sleep_for( const std::chrono::duration<Rep, Period>& sleep_duration );

sleep的时间间隔从纳秒到小时都有具体的定义。

std::chrono::nanosecondsstd::chrono::microsecondsstd::chrono::millisecondsstd::chrono::secondsstd::chrono::minutesstd::chrono::hours

比如我们想要一个线程休眠100ms。

std::this_thread::sleep_for(std::chrono::milliseconds(100));

我们想要一个线程休眠1分钟：

std::this_thread::sleep_for(std::chrono::minutes(1));

完整的代码示例：

#include <iostream>#include <chrono>#include <thread> int main() { std::cout << "Hello waiter\n" << std::flush; auto start = std::chrono::high_resolution_clock::now(); std::this_thread::sleep_for(std::chrono::milliseconds(2000)); auto end = std::chrono::high_resolution_clock::now(); std::chrono::duration<double, std::milli> elapsed = end-start; std::cout << "Waited " << elapsed.count() << " ms\n";}

输出：

Hello waiter
Waited 2000.12 ms

2. 休眠直至到一个时间点

template< class Clock, class Duration >void sleep_until( const std::chrono::time_point<Clock,Duration>& sleep_time )

sleep_until会阻塞当前线程直至未来某个时间点到达。

#include <iostream>#include <thread>#include <chrono>// Print Current Timevoid print_time_point(std::chrono::system_clock::time_point timePoint) { std::time_t timeStamp = std::chrono::system_clock::to_time_t(timePoint); std::cout << std::ctime(&timeStamp) << std::endl;}void threadFunc() { std::cout<<"Current Time :: "; // Print Current Time print_time_point(std::chrono::system_clock::now()); // create a time point pointing to 10 second in future std::chrono::system_clock::time_point timePoint = std::chrono::system_clock::now() + std::chrono::seconds(10); std::cout << "Going to Sleep Until :: "; print_time_point(timePoint); // Sleep Till specified time point // Accepts std::chrono::system_clock::time_point as argument std::this_thread::sleep_until(timePoint); std::cout<<"Current Time :: "; // Print Current Time print_time_point(std::chrono::system_clock::now());}int main() { std::thread th(&threadFunc); th.join(); return 0;}

程序输出：

Current Time :: Sun Oct 11 02:57:38 2020

Going to Sleep Until :: Sun Oct 11 02:57:48 2020

Current Time :: Sun Oct 11 02:57:48 2020

参考材料

1.https://baike.baidu.com/item/sleep%E5%87%BD%E6%95%B0/6735027

2.https://thispointer.com/how-to-put-a-thread-to-sleep-in-c11-sleep_for-sleep_until/

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