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.