#include <stdio.h>
#include <sys/types.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <unistd.h>
#include <fcntl.h>
/*
/ Eliasz Zurawka
/ Sept 29/07
/ PROG40000_Fall2007_Asg1
/ Question 2
*/

int main(int argc, char **argv) 
{
  
  if(argc != 2) {
    printf("usage: elFork filename");
  }
  
  char *outputPath = argv[1];
  int output;
  
  if((output = open(outputPath, O_RDONLY)) == -1) {
    printf("Could not open %s\n", outputPath);
    exit(2);
  }
  pid_t pid1, pid2;
  int status1, status2;
  
  if((pid1 = fork())< 0) {
    printf("error forking, exiting");
    exit(1);
  }
  
  if(pid1 == 0) {
    system("ps");
  }
  else {
    pid2 = fork();
    if(pid2 == 0) {
      char readBuf[10]; memset(readBuf, 0, 10);
      ssize_t r1 = read(output, readBuf, 9);
      printf("\n\n Child Read: %s", readBuf);
    } 
    else {
      char readBuf[10]; memset(readBuf, 0, 10);
      ssize_t r1 = read(output, readBuf, 9);
      printf("\n\nParent Read: %s", readBuf);
      
      while((waitpid(pid1, &status1, WNOHANG) == 0) ||
	    (waitpid(pid2, &status2, WNOHANG) == 0)) {
	//do Nothing
      }

      r1 = read(output, readBuf, 9);
      printf("\n\nParent Read: %s", readBuf);
      exit(0);
    }
  }

  exit(0);
}