Calling a function at exact every second using a timer?

Question

I need to call a function every second exactly as I want to store the data based on the every second so I cannot miss the second? What is best method in C?

Below is a skeleton of the timer_create method is this reliable enough?

#include <stdio.h>
#include <time.h>
#include <signal.h>

timer_t gTimerid;

void start_timer(void)
{        
  struct itimerspec value;

  value.it_value.tv_sec = 1;
  value.it_value.tv_nsec = 0;  
  value.it_interval.tv_sec = 1;
  value.it_interval.tv_nsec = 0;

  timer_create (CLOCK_REALTIME, NULL, &gTimerid);    
  timer_settime (gTimerid, 0, &value, NULL);
}

void stop_timer(void)
{        
  struct itimerspec value;

  value.it_value.tv_sec = 0;
  value.it_value.tv_nsec = 0;    
  value.it_interval.tv_sec = 0;
  value.it_interval.tv_nsec = 0;

  timer_settime (gTimerid, 0, &value, NULL);        
}

void timer_callback(int sig)
{    
  printf(" Catched timer signal: %d ... !!\n", sig);     
}

int main(int ac, char **av)
{
    (void) signal(SIGALRM, timer_callback);
    start_timer();
    while(1);
}

Answer 1

On Linux and other POSIX systems, timer_create is the function you're looking for. Set the timer to be delivered via a signal and it will be very reliable. Don't use the older ualarm or setitimer apis which are deprecated and have various ugly issues that you probably don't want to get into unless you're already an expert on realtime unix stuff...