Sleep function in C++

Is there a function like Sleep(time); that pauses the program for X millis开发者_如何学Ceconds, but in C++?

Which header should I add and what is the function's signature?

Use std::this_thread::sleep_for:

#include <chrono>
#include <thread>

std::chrono::milliseconds timespan(111605); // or whatever

std::this_thread::sleep_for(timespan);

There is also the complementary std::this_thread::sleep_until.

Prior to C++11, C++ had no thread concept and no sleep capability, so your solution was necessarily platform dependent. Here's a snippet that defines a sleep function for Windows or Unix:

#ifdef _WIN32
    #include <windows.h>

    void sleep(unsigned milliseconds)
    {
        Sleep(milliseconds);
    }
#else
    #include <unistd.h>
    
    void sleep(unsigned milliseconds)
    {
        usleep(milliseconds * 1000); // takes microseconds
    }
#endif

But a much simpler pre-C++11 method is to use boost::this_thread::sleep.

You'll need at least C++11.

#include <thread>
#include <chrono>

...

std::this_thread::sleep_for(std::chrono::milliseconds(200));

For Windows:

#include "windows.h" 
Sleep(10);

For Unix:

#include <unistd.h>
usleep(10)

On Unix, include #include <unistd.h>.

The call you're interested in is usleep(). Which takes microseconds, so you should multiply your millisecond value by 1000 and pass the result to usleep().

Just use it...

Firstly include the unistd.h header file, #include<unistd.h>, and use this function for pausing your program execution for desired number of seconds:

sleep(x);

x can take any value in seconds.

If you want to pause the program for 5 seconds it is like this:

sleep(5);

It is correct and I use it frequently.

It is valid for C and C++.

Prior to C++11, there was no portable way to do this.

A portable way is to use Boost or Ace library. There is ACE_OS::sleep(); in ACE.

The simplest way I found for C++ 11 was this:

Your includes:

#include <chrono>
#include <thread>

Your code (this is an example for sleep 1000 millisecond):

std::chrono::duration<int, std::milli> timespan(1000);
std::this_thread::sleep_for(timespan);

The duration could be configured to any of the following:

std::chrono::nanoseconds   duration</*signed integer type of at least 64 bits*/, std::nano>
std::chrono::microseconds  duration</*signed integer type of at least 55 bits*/, std::micro>
std::chrono::milliseconds  duration</*signed integer type of at least 45 bits*/, std::milli>
std::chrono::seconds       duration</*signed integer type of at least 35 bits*/, std::ratio<1>>  
std::chrono::minutes       duration</*signed integer type of at least 29 bits*/, std::ratio<60>>
std::chrono::hours         duration</*signed integer type of at least 23 bits*/, std::ratio<3600>>

For a short solution use

#include <thread>

using namespace std;
using namespace std::this_thread;

void f() {
    sleep_for(200ms);
}

Recently I was learning about chrono library and thought of implementing a sleep function on my own. Here is the code,

#include <cmath>
#include <chrono>

template <typename rep = std::chrono::seconds::rep, 
          typename period = std::chrono::seconds::period>
void sleep(std::chrono::duration<rep, period> sec)
{
    using sleep_duration = std::chrono::duration<long double, std::nano>;

    std::chrono::steady_clock::time_point start = std::chrono::steady_clock::now();
    std::chrono::steady_clock::time_point end = std::chrono::steady_clock::now();

    long double elapsed_time = 
    std::chrono::duration_cast<sleep_duration>(end - start).count();

    long double sleep_time = 
    std::chrono::duration_cast<sleep_duration>(sec).count();

    while (std::isgreater(sleep_time, elapsed_time)) {
        end = std::chrono::steady_clock::now();
        elapsed_time = std::chrono::duration_cast<sleep_duration>(end - start).count(); 
    }
}

We can use it with any std::chrono::duration type (By default it takes std::chrono::seconds as argument). For example,

#include <cmath>
#include <chrono>

template <typename rep = std::chrono::seconds::rep, 
          typename period = std::chrono::seconds::period>
void sleep(std::chrono::duration<rep, period> sec)
{
    using sleep_duration = std::chrono::duration<long double, std::nano>;

    std::chrono::steady_clock::time_point start = std::chrono::steady_clock::now();
    std::chrono::steady_clock::time_point end = std::chrono::steady_clock::now();

    long double elapsed_time = 
    std::chrono::duration_cast<sleep_duration>(end - start).count();

    long double sleep_time = 
    std::chrono::duration_cast<sleep_duration>(sec).count();

    while (std::isgreater(sleep_time, elapsed_time)) {
        end = std::chrono::steady_clock::now();
        elapsed_time = std::chrono::duration_cast<sleep_duration>(end - start).count(); 
    }
}

using namespace std::chrono_literals;
int main (void) {
    std::chrono::steady_clock::time_point start1 = std::chrono::steady_clock::now();
    
    sleep(5s);  // sleep for 5 seconds
    
    std::chrono::steady_clock::time_point end1 = std::chrono::steady_clock::now();
    
    std::cout << std::setprecision(9) << std::fixed;
    std::cout << "Elapsed time was: " << std::chrono::duration_cast<std::chrono::seconds>(end1-start1).count() << "s\n";
    
    std::chrono::steady_clock::time_point start2 = std::chrono::steady_clock::now();

    sleep(500000ns);  // sleep for 500000 nano seconds/500 micro seconds
    // same as writing: sleep(500us)
    
    std::chrono::steady_clock::time_point end2 = std::chrono::steady_clock::now();
    
    std::cout << "Elapsed time was: " << std::chrono::duration_cast<std::chrono::microseconds>(end2-start2).count() << "us\n";
    return 0;
}

For more information, visit https://en.cppreference.com/w/cpp/header/chrono and see this cppcon talk of Howard Hinnant, https://www.youtube.com/watch?v=P32hvk8b13M. He has two more talks on chrono library. And you can always use the library function, std::this_thread::sleep_for

Note: Outputs may not be accurate. So, don't expect it to give exact timings.

I like the solution proposed by @Ben Voigt -- it does not rely on anything outside of C++, but he did not mention an important detail to make the code work. So I am putting the full code, please notice the line starting with using.

#include <thread>
#include <chrono>

...

using namespace std::chrono_literals;
std::this_thread::sleep_for(200ms);