Signals

#include <unistd.h>         // write
#include <sys/time.h>       // ITIMER_REAL, struct itimerval, setitimer
#include <time.h>           // struct timespec, nanosleep
#include <signal.h>         // SIGALRM, struct sigaction, sigemptyset, sigaction
#include <stdio.h>          // printf
#include <stdlib.h>         // EXIT_SUCCESS


void tmr_hndlr(int);


int main(void)
{
  struct itimerval int_time  = { .it_interval = { .tv_sec = 3, .tv_usec = 0 },
                                 .it_value    = { .tv_sec = 3, .tv_usec = 0 }	};
  struct timespec sleep_time = { .tv_sec = 2, .tv_nsec = 0 };
  struct sigaction sa_timer  = { .sa_handler = &tmr_hndlr };

  sigemptyset(&sa_timer.sa_mask);
  sigaction(SIGALRM, &sa_timer, NULL);
  setitimer(ITIMER_REAL, &int_time, NULL);

	while (1)
	{
  	nanosleep(&sleep_time, NULL);
  	printf("Endlosschleife!\n");
	}

	return EXIT_SUCCESS;
}


/* function to be called on timer interrupt */
void tmr_hndlr(int i)
{
  (void)i;
  const char str[] = "Timer\n";
  write(1, str, sizeof (str));
}