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_for std::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::nanoseconds std::chrono::microseconds std::chrono::milliseconds std::chrono::seconds std::chrono::minutes std::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 Time
void 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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