#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <unistd.h>

#define SHMKEY ((key_t) 7890)

#define MYSEED 1234

typedef struct
{
  int value;
} shared_mem;

shared_mem *counter; //shared variable

int read_val(){
return counter->value;
}

void write_val(int new_val){

counter->value = new_val;
}

void sayHello(int id, int max){

  int i=0;
  int temp=0;

  for(i=0;i<max;i++){

   temp = read_val();
   temp = temp + 1;
   write_val(temp);

  }
  if(id == 0)
      printf ("\nThe child's count was %d\n",read_val());
    else
      printf ("\nThe father's count was %d\n",read_val());

}


int main(int argc, char *argv[])
{

  int   shmid; //shared memory Id


  int   child1=0;
  int   max=1000;
  int finished,status;
  int val;

  max = atoi(argv[1]);  //obtaining the seed from the parameters, and turning it into a numeric value

  char *shmadd;
  shmadd = (char *) 0;

  if ((shmid = shmget (SHMKEY, sizeof(int), IPC_CREAT | 0666)) < 0)
    {
      perror ("shmget");
      val=1; //exit (1);
    }

  if ((counter = (shared_mem *) shmat (shmid, shmadd, 0)) == (shared_mem *) -1)
    {
      perror ("shmat");
      val=0; //exit (0);
    }

  counter->value = 0;

  if ((child1 = fork()) == 0){
    sayHello(child1,max);
  }

  if (child1 != 0){
    sayHello(child1,max);

    printf ("The child's id is %d \n",child1);

    finished = wait(&status); //Waiting for a child to finish and for getting its ID


    if(finished == child1){ //is child1?
      printf ("The child just finished with counter in %d\n",read_val());
    }

    if ((shmctl (shmid, IPC_RMID, (struct shmid_ds *) 0)) == -1)
	  {
	  perror ("shmctl");
	  val=-1; //exit (-1);
	  }
      printf ("\t\t  End of simulation.\n");

  }

  return val;
}