RE: What is a technique to start a program periodically?

On Thu, 3 Nov 2005, Scott Klement wrote:

How about setting up a 60-second interval timer by calling the setitimer() function. Will that solve the problem?

<begin timer.c>
#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <unistd.h>
#include <signal.h>
#include <time.h>

/* The action that will happen when the timer expires */
void action (int arg);

/* The action that will happen when the user presses Control-C */
void interrupt (int arg);

int
main ()
{
  void (*alarmhandler) (int);
  void (*inthandler) (int);
  struct tm *timerstart;
  struct timeval starttime;
  struct timeval curtime;
  struct timeval interval;
  struct itimerval timing;

  /* set up the signal handler */
  alarmhandler = action;
  signal (SIGALRM, alarmhandler);
  inthandler = interrupt;
  signal (SIGINT, inthandler);

  /* set up the timer start time */
  if (gettimeofday (&curtime, NULL) < 0)
    {
      printf ("error occurred getting the time of day!\n");
      return (-1);
    }

  /* set the timer to go off at 13:45 today */
  timerstart = localtime (&curtime.tv_sec);
  timerstart->tm_sec = ;
  timerstart->tm_min = 45;
  timerstart->tm_hour = 13;
  starttime.tv_sec = mktime (timerstart);
  starttime.tv_usec = 0;
  printf ("The timer will go off at %04d-%02d-%02d %02d:%02d:%02d\n",
          timerstart->tm_year + 1900, timerstart->tm_mon + 1,
          timerstart->tm_mday, timerstart->tm_hour, timerstart->tm_min,
          timerstart->tm_sec);
  curtime.tv_sec = difftime (starttime.tv_sec, curtime.tv_sec);
  curtime.tv_usec = 0;

  /* set up the timer interval to 1 second */
  interval.tv_sec = 1;
  interval.tv_usec = 0;

  /* create the timer */
  timing.it_interval = interval;
  timing.it_value = curtime;

  printf ("Waiting for the timer (press Control-C to abort)...\n");
  if (setitimer (ITIMER_REAL, &timing, NULL) < 0)
    {
      printf ("error occurred in the timer!\n");
      return (-1);
    }

  /* wait for the signal to occur */
  while (1)
    {
      pause ();
    }
  return (0);
}


/* This function is where you do whatever work you need to when
 * the timer goes off */
void
action (int arg)
{
  printf ("The timer went off!\n");
  return;
}


void
interrupt (int arg)
{
  printf ("Shutting down!\n");
  exit (0);
}
<end timer.c>

James Rich

It's not the software that's free; it's you.
        - billyskank on Groklaw