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

int pipe1[2]; 
int pipe2[2]; 
int pipe3[2];

void closeAll() {
  close(pipe1[0]);
  close(pipe1[1]);
  close(pipe2[0]);
  close(pipe2[1]);
  close(pipe3[0]);
  close(pipe3[1]);
}  

int launch(int in, int out, int synch /* alínea b)*/, char* prog) {
    dup2(out, 1);
    dup2(in, 0);
    closeAll(pipe1, pipe2, pipe3);
    read(synch, NULL, 1); // alínea b)
    execlp(prog, prog, NULL);  
    return -1;
}  

int main() {
     
  if (pipe(pipe1) == -1) {
    perror("pipe 1");
    return errno;
  }

  if (pipe(pipe2) == -1) {
    perror("pipe 2");
    return errno;
  }
  
  if (pipe(pipe3) == -1) {
    perror("pipe 3");
    return errno;
  }

  // alínea b)
  int pipeSynch[2]; 
  if (pipe(pipeSynch) == -1) { 
    perror("pipe synch");
    return errno;
  }

  // P1
  if (fork() == 0) 
    if (launch(pipe3[0], pipe1[1], pipeSynch[0], "P1.exe") == -1) {
      perror("P1");
      return errno;
    }
    
  // P2  
  if (fork() == 0) 
    if (launch(pipe1[0], pipe2[1], pipeSynch[0], "P2.exe") == -1) {
      perror("P2");
      return errno;
    }

  // P3
  if (fork() == 0) 
    if (launch(pipe2[0], pipe3[1], pipeSynch[0], "P3.exe")  == -1) {
      perror("P3");
      return errno;
    }
    
  // alínea b)
  write(pipeSynch[1], "123", 3); 
  close(pipeSynch[1]);
  
  // alínea c)
  int i = 0;
  for (; i< 3; i++)
    wait(NULL);
  
  return 0;
  
}