How to create a timer?

[hasanfarhan33]

Hello, can anyone tell me what to do in order to create a timer in seconds?
do i have to use if?
if(int i = 0 , i<=60, i++)
{
cout<<i;
}

[adam2016]

https://linux.die.net/man/3/gmtime

you can use a while loop to print the updated time

[Thomas1965]

This code is from jonnin from this forum somewhere.

int start = clock();
double diff;
do
{
  // do stuff
  diff = (clock()-start)/(double)(CLOCKS_PER_SEC);

} while diff < 60.0;
//time is up here... 

[jonnin]

there is probably a better way, mind you. That is just one crude and simple way to do it.
windows has an actual timer event thingy you can use. Probably all OS do, I don't know... all my stuff had to run as fast as it could, but was never actually scheduled!

[SamuelAdams]

You can use a timer to count up, down, subtract 2 times. What did you have in mind ?

[Ganado]

I think developing a non-busy-loop timer requires OS-specific functionality to work. The reason you'd want a non-busy-loop is so that your OS doesn't needlessly burn up CPU cycles.

Unless I'm mistaken, the best thing you can do in C++ by itself (besides a busy loop) is std::this_thread::sleep_for http://en.cppreference.com/w/cpp/thread/sleep_for
But this is not necessarily the most precise, because sleep functions tend to only allow you to give a minimum time to sleep for, and you can get variable results depend on what your OS's scheduler is doing.

#include <iostream>
#include <chrono>
#include <thread>
 
int main()
{
    using namespace std::chrono_literals;

    for (int i = 0; i < 60; i++)
    {
        std::this_thread::sleep_for(1s);
        std::cout << i << std::endl;
    }
}

If you want to use external C++ libraries, SFML's sf::Clock can measure time in a similar way to Thomas1965's example
https://www.sfml-dev.org/documentation/2.3/classsf_1_1Clock.php
Note that this counts as a busy-loop.

sf::Clock clock;
for (int i = 0; i < 60; i++)
{
    std::cout << i << std::endl;
    while (clock.getElapsedTime().asMilliseconds() < 1000)
    {
        /* wait, or do other stuff while waiting */
    }
    clock.restart();
}

I think using waitable timers is the most resource-efficient method to making periodic events happen, but I have not actually used them in my code in C++, so maybe someone else can say if I'm right or wrong. https://msdn.microsoft.com/en-us/library/windows/desktop/ms687012(v=vs.85).aspx
I'm sure Linux-based systems have some equivalent.

Languages like C# and Java have waitable Timers built in, where they trigger an event on each set interval.

static void myTimer_Tick(Object myObject, EventArgs myEventArgs)
{
    // do stuff in here every 2000 ms, like print out i.
}

static void myFunction()
{
    System.Windows.Forms.Timer myTimer = new System.Windows.Forms.Timer();

    myTimer.Tick += new EventHandler(myTimer_Tick);
    myTimer.Interval = 2000;  // event will happen every 2000 ms
    myTimer.Start();
}

I do not not know if C# or Java have microsecond-precision waitable timers built-in.

[jonnin]

windows c++ has a timer object, but last I used it was like win 98 it probably is a little different now. Those, as I recall, were also low resolution.

but a thread should be good enough. Sleep gets you to a certain resolution, then the thread can swap to a high performance timer busy wait loop to get the final few cpu cycles, wasting only a little effort.

clock is a busy-loop if you don't put it in a thread with a sleep, yes. It is not a good way to do it for anything complicated.