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

#include <sys/types.h>
#include <sys/wait.h>

#include <sys/time.h>


int main(int argc, char **argv)
{
  int mypid = getpid();
  int mykid;
  int kidcount;

  time_t zerotime = time(NULL);

  if(argc > 1)
    {
      kidcount = atoi(argv[1]);
    }
  else
    {
      printf("Please supply a kid count !\n");
      exit(1);
    }


  printf("%d: Starting %d child processes\n",mypid,kidcount);
  int i;
  for(i=0; i<kidcount; i++)
    {
      start_random_kid();
    }
  sleep(1);
  printf("%d: Now waiting for %d child processes\n",mypid,kidcount);
  for(i=0; i<kidcount; i++)
    {
      int status;
      int mykid;
      mykid = waitpid(-1, &status, 0);
      if(mykid == -1)
	{
	  perror("Error: ");
	}
      else
	{
	  printf("%d: At %d elapsed seconds, child process %d has finished with exit code %d\n",
		 mypid,
		 time(NULL)-zerotime,
		 mykid,
		 WEXITSTATUS(status));
	}
    }

}


int start_random_kid()
{
  int mykid = fork();
  if(mykid == 0)
    {
      // Child process path
      int mypid = getpid();
      int myparent = getppid();

      struct timeval tv;
      gettimeofday(&tv,NULL);
      int howlong = rand_r((unsigned int *)&tv.tv_usec) % 20 + 5;

      printf("  %d: This is child process %d of parent %d which will sleep for %d seconds then exit with code %d\n",mypid,mypid,myparent,howlong,
	     mypid % 100);
      fflush(NULL);

      sleep(howlong);
      
      exit(mypid % 100);
    }
}