How do you make a precise countdown timer using clock_gettime? [migrated]
- by Joshun
Could somebody please explain how to make a countdown timer using clock_gettime, under Linux. I know you can use the clock() function to get cpu time, and multiply it by CLOCKS_PER_SEC to get actual time, but I'm told the clock() function is not well suited for this.
So far I have attempted this (a billion is to pause for one second)
#include <stdio.h>
#include <time.h>
#define BILLION 1000000000
int main()
{
struct timespec rawtime;
clock_gettime(CLOCK_MONOTONIC_RAW, &rawtime);
unsigned long int current = ( rawtime.tv_sec + rawtime.tv_nsec );
unsigned long int end = (( rawtime.tv_sec + rawtime.tv_nsec ) + BILLION );
while ( current < end )
{
clock_gettime(CLOCK_MONOTONIC_RAW, &rawtime);
current = ( rawtime.tv_sec + rawtime.tv_nsec );
}
return 0;
}
I know this wouldn't be very useful on its own, but once I've found out how to time correctly I can use this in my projects. I know that sleep() can be used for this purpose, but I want to code the timer myself so that I can better integrate it in my projects - such as the possibility of it returning the time left, as opposed to pausing the whole program.
