// Operating Systems Homework 2 Fibonnaci Code by
// Edmond Spike Snell
// 2 . 20 . 2011

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

// main process to get command line argument and start child and parent process
int main(int argc, char *argv[]) {

  // Initialize fibonacci array and pid_t and set values of first two fibonacci numbers
  int fib[48];
  fib[0] = 0;
  fib[1] = 1;
  pid_t pid;

  if(argc < 2 ) {
    printf("Enter how many numbers you want generated as an argument.\n");
    exit(0);
  }

  if(atoi(argv[1]) < 0 ) {
    printf("Argument must be a positive number.\n");
    exit(0);
  }

  if(atoi(argv[1]) > 47 ) {
    printf("Argument too large for integers, enter a smaller number\n");
    exit(0);
  }

// this tries to start a fork process
pid = fork();

// if the fork fails exit with a code
if(pid < 0) {
  fprintf(stderr, "The fork was a failure.\n");
  return 1;
}


// The child process runs here
else if(pid == 0) {

  // start at the third fibonacci number
  int i = 2;

  // Handle the first three cases without generating more fibonacci numbers
  if (atoi(argv[1]) == 0) {
    printf("Fibonacci: ");
  }
  if (atoi(argv[1]) == 1) {
    printf("Fibonacci: 0 ");
  }
  if (atoi(argv[1]) == 2) {
    printf("Fibonacci: 0 1 ");
  }

  if (atoi(argv[1]) > 2) {

    printf("Fibonacci: 0 1 ");

    // Generate and print the remaining fibonnaci numbers
    while(i < atoi(argv[1])) {

      fib[i] = fib[i - 1] + fib[i - 2];
      printf("%d ", fib[(i)]);
      i++;

    }
  }

  printf("\n");

}


// The parent process runs here
else {

// Waiting for the child to complete
wait(NULL);

}

// The parent and child process are done so exit the program
return 0;
}