godot_alarm.c

/*
  Author:      John Otander
  For:         BSU CS 297
  Date:        3/12/2014

  Run Program: $ gcc godot.c -ogodot
               $ ./godot <ALARM_INTERVAL>
*/

#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <pthread.h>
#include <sysexits.h>
#include <signal.h>

#define MAX_COUNT 1000000000

// Alarm handler.
static void onalarm(int signo);

pid_t pid;

int main(int argc, char **argv)
{
  int i, num_cpus, random_number, between_nums, status, alarm_interval;

  // Argument error checking.
  if (argc != 2) {
    fprintf(stderr, "Usage: godot <ALARM_INTERVAL>\n");
    exit(EXIT_FAILURE);
  }
  
  // Set alarm interval.
  alarm_interval = atoi(argv[1]);

  // Set number count for numbers between 90-110 to 0.
  between_nums = 0;

  // Get the number of CPUs.
  num_cpus = sysconf(_SC_NPROCESSORS_ONLN);

  // Set alarm handler, and the interval.
  signal(SIGALRM, onalarm);
  alarm(alarm_interval);

  // Fork a new child for every CPU.
  for (i = 0; i < num_cpus; i++) {
    if(pid != 0) {
      pid = fork();
    }
  }

  // Loop 4eva, or until the alarm sounds.
  while(1) {
    // Seed with srandom with pid.
    srandom(getpid());

    // Generate random numbers.
    for (i = 0; i < MAX_COUNT; i++) {
      random_number = random();

      // Increment between_numbers if appropriate.
      if(random_number < 110 && random_number > 90)
        between_nums++;
    }

    printf("Generated %d special random numbers.\n", between_nums);
    sleep(1);
  }

  exit(EXIT_SUCCESS);
}

// Kill child process.
static void onalarm(int signo)
{
  printf("ALARM INTERVAL REACHED\n");
  kill(pid, SIGKILL);
}