#include <signal.h>
    #include <stdio.h>
    #include <string.h>
    #include <sys/time.h>

    void timer_handler (int signum)
    {
     static int count = 0;
     printf ("timer expired %d times\n", ++count);
    }

    int main ()
    {
        struct sigaction sa;
        struct itimerval timer;

        /* Install timer_handler as the signal handler for SIGVTALRM. */
        memset(&sa, 0, sizeof(sa));
        sa.sa_handler = &timer_handler;
        sigaction (SIGVTALRM, &sa, NULL);

        /* Configure the timer to expire after 1 sec... */
        timer.it_value.tv_sec = 1;
        timer.it_value.tv_usec = 0;
        /* ... and every 1000 msec after that. */
        timer.it_interval.tv_sec = 1;
        timer.it_interval.tv_usec = 0;
        /* Start a virtual timer. It counts down whenever this process is executing. */
        setitimer (ITIMER_VIRTUAL, &timer, NULL);

        /* Do busy work. */
        while (1);
            sleep(1);
    }