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


#define MAX_SIZE 100
class data_struct {
public:
  int size;
  int sequence[MAX_SIZE];
};



int main(int argc, char * argv[])
{
  int n = 0;

//the argument lines of code are to help you with the first homework
  if(argc < 2)
    {
      printf("You do not have enough arguments\n");
      exit(0);
    }
  else
    n = atoi(argv[1]);
  if(n > MAX_SIZE)
    {
      printf("Largest F(n) is n=100, printing first 100\n");
      n = 100;
    }

//shared memory stuff
//create a segment with shmget
  int segment_id =shmget(IPC_PRIVATE, sizeof(data_struct), S_IRUSR | S_IWUSR);
  data_struct * s = (data_struct *)shmat(segment_id, NULL, 0); // attach
  printf("s->size is %d\n", s->size);
  s->size = n;
  printf("s->size is now %d\n", s->size);
  shmdt(s); //detach the segment
  printf("value of the pointer is %d\n",s);
  //printf("value of s->size is %d\n",s->size); // this would core dump
  s = (data_struct *)shmat(segment_id,NULL,0); //attach
  printf("we've reattached, s->size is now %d\n",s->size);

  printf("-------------------------------------\n");
  shmdt(s); //detact the segment pointed to by s
  shmctl(segment_id, IPC_RMID, NULL); // destroy a segment
  exit(0);
}