I am creating a process with 2 children, 1 of the children is responsible to read questions (line by line from a file), output every question and reading the answer, and the other one is responsable to measure the time elapsed and notify the user at each past 1 minute about the remaining time. My problem is that i couldn't find any useful example of how i can make this set time function to work. Here is what i have tried so far. The problem is that it outputs the same elapsed time every time and never gets out from the loop.

#include<time.h>
#define T 600000

int main(){
  clock_t start, end;
  double elapsed;
  start = clock();
  end = start + T;
  while(clock() < end){
     elapsed = (double) (end - clock()) / CLOCKS_PER_SEC;
     printf("you have %f seconds left\n", elapsed);
     sleep(60);
  }
  return 0;
}