/* 
 * A demo program for an interval timer.
 * Works for me on my various Linux systems.
 * (Your Mileage May Vary.)
 *
 * davekw7x
 *
 */

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

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

/* 
 * I'll make this global so that the alarm handler
 * function can change the interval if necessary
 */
struct itimerval it;


/* Put stuff here to perform periodic task.
 * Note that you might have to change the values
 * in the itimerval struct to compensate for
 * variations in "real" time-of-day time due
 * to the inexactness of Linux system time
 * versus wall clock time
 */
void sigalrm_handler(int sig)
{
    static unsigned count = 0;

    printf("Alarm number %5u at %d\n", ++count, time(0));

}

int main()
{
    char buffer[BUFSIZ];


    it.it_value.tv_sec     = 1;       /* start in 1 second      */
    it.it_value.tv_usec    = 0;
    it.it_interval.tv_sec  = 5;       /* repeat every 5 seconds */
    it.it_interval.tv_usec = 0;

    signal(SIGALRM, sigalrm_handler); /* Install the handler    */


    /* Here's your main program loop. The alarm handler
     * function does its thing regardless of this
     */
    printf("Started timer at %d\n\n", time(0));
    setitimer(ITIMER_REAL, &it, NULL);/* turn on interval timer */

    printf("Type any old thing at all.");
    printf("  To exit the program, enter a blank line.\n\n");
    while (fgets(buffer, sizeof(buffer), stdin) && (strlen(buffer) > 1)) {
        printf("You entered: %s\n", buffer);
    }

    printf("Bye\n");
    return 0;
}