periodic.c

#include <stdio.h>
#include <stdlib.h>

#include <signal.h>
#include <sys/time.h>
#include <unistd.h>

struct periodic_info
{
	sigset_t alarm_sig;
};

static int make_periodic (unsigned int period, struct periodic_info *info)
{
	int ret;
	struct itimerval value;

	/* Block SIGALRM in this thread */
	sigemptyset (&(info->alarm_sig));
	sigaddset (&(info->alarm_sig), SIGALRM);
	pthread_sigmask (SIG_BLOCK, &(info->alarm_sig), NULL);

	/* Set the timer to go off after the first period and then
	   repetitively */
#if 0
	value.it_value.tv_sec = period/1000000;
	value.it_value.tv_usec = period%1000000;
	value.it_interval.tv_sec = period/1000000;
	value.it_interval.tv_usec = period%1000000;
#endif


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



	ret = setitimer (ITIMER_REAL, &value, NULL);
	if (ret != 0)
		perror ("Failed to set timer");
	return ret;
}

static void wait_period (struct periodic_info *info)
{
	int sig;

	/* Wait for the next SIGALRM */
	sigwait (&(info->alarm_sig), &sig);
}



int main(int argc,char*argv[])
{
	struct periodic_info info;

	make_periodic (10000, &info);
	while (1)
	{
		/* Do useful work */
		printf("hello world!\n");
		wait_period (&info);
	}


}