/*
Copyright 2006 Paul... don't copy this for your hw...
Author: Paul Picazo (http://pr.erau.edu/~picazdb3/)
Course: CS420 (OS)
Instructor : Matt Jaffe
*/
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <time.h>

int main(int argc, char* argv[])
{
  //print a nice line break so our output is distinctly visible
  printf("\n");

  //save (will go to children) original process id for later
  int thepid = getpid();
  int fid; //we will store result of the fork() here

  int n = 0;  //n + 1 will be the # of the child
  int numchildren; //numchildren is the number of child processes to start
  
  //usage: fork [int], with [int] being the number of child processes
  //if not given, defaults to 10
  if(argc == 2)
  {
    numchildren = atoi(argv[1]);
  }
  else
  {
    numchildren = 10; 
  }
  //print the parent info from the parent process before any forks
  printf("Parent Process (%d) starting.\n",thepid); 
  

  //loop will only continue when it is the parent process
  while((thepid == getpid()) && n < numchildren)
  {
    fid = fork(); //do the actual fork
    if(fid == 0) //this branch taken only by the children
    {
      int cpid = getpid(); //store the child id
      int ppid = getppid(); //store the parent id

      //In order to visualize the processes running concurrently,
      //we will artificially delay each process between 1-10 secs

      //Random seed needs to have more than the tick because
      //the ticks have a high chance of not being unique
      srand48( (unsigned)time( NULL ) * cpid );
      int waittime = (int) 10 * (lrand48() / (2147483649.0));
      sleep(waittime);

      //print the childs info from the child process
      printf("\tFrom Child Process #%d (%d) Parent (%d) : %d secs\n",
        n + 1, cpid, ppid, waittime); 
    }
    else if(fid < 0)  //fork was not successful
    {
      printf("ERROR: could not fork on fork #%d\n", n+1);
    }
    else  //this branch taken only by the parent
    {
      //print the parent info from the parent after forks
	    printf("Parent Process (%d) spawning child #%d (%d)\n",
        thepid, n+1, fid);
      n++;
    }
 }
 if(fid != 0) //if not a child
 {
   int status;
   //wait until all children have terminated
   while (wait(&status) != -1)
   {}
   printf("Parent Process (%d)", thepid);
   printf(" is done waiting for children and will now terminate!\n\n");
 }
 return 0;
}