timer-skeleton.c

/* timer_create skeleton
 *
 * this is THE ONLY WAY to get something to actually happen every
 * second within the same millisecond, and not every second plus
 * a few milliseconds here or there so you eventually skip a count
 * 
 * don't forget to link with -lrt
 *
 */

#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; // initial wait
    value.it_value.tv_nsec = 0;
    value.it_interval.tv_sec = 1; // timer interval
    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("Caught timer signal: %d ... !!\n", sig);
}

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