#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/wait.h>

typedef struct CLL {

 char ch;
 struct CLL *next;
} CLL;

char *readstring (int fd, int *len);

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

 int p2c[2]; //An array of two ints.  p[0] is for reading, p[1] is for writing.
 int c2p[2];

 pipe (p2c);  //Set up the pipe.
 pipe (c2p);
 int pid = fork ();
 if (pid==0) { //If I'm the child
  close (p2c[1]);
  close (c2p[0]);
  int strlength;
  char *info = readstring (p2c[0],&strlength); // Reads a string from standard input, which is now the pipe!
  write (1,"From my parent:  ",17);
  write (1,info,strlength);
  write (1,"\n",1);
  for (int i = 0; i < strlength; i++)
   if (info[i] >= 97 && info[i] <= 122) info[i]-=32;
  write (c2p[1],info,strlength);
  write (c2p[1],"\n",1);
  free (info);
  close (p2c[0]);
  close (c2p[1]);
 } else { //If I'm the parent
  close (p2c[0]);
  close (c2p[1]);
  write (1,"Enter a string:  ",17);
  int fkblen;
  char *fromkb = readstring (0,&fkblen);
  write (p2c[1],fromkb,fkblen);
  write (p2c[1],"\n",1);
  free (fromkb);
  fromkb = readstring (c2p[0],&fkblen);
  write (1,"From child:  ",13);
  write (1,fromkb,fkblen);
  write (1,"\n",1);
  wait (NULL);
  write (1,"Child has died!\n",16);
  free (fromkb);
  close (p2c[1]);
  close (c2p[0]);

 }
 return 0;
}


char *readstring (int fd, int *len) {

 CLL *L = NULL;
 int ct = 0;
 char buf;
 char *final;

 while (1) {
  read (fd,&buf,1);
  if (buf=='\n') break;
  CLL *N = malloc (sizeof (CLL));
  N->ch = buf;
  N->next = L;
  L = N;
  ct++;
 }
 final = malloc (ct+1);
 *len = ct;
 final[ct] = '\0';
 while (ct > 0) {
  ct--;
  final[ct] = L->ch;
  CLL *N = L;
  L = L->next;
  free (N);
 }
 return final;
}