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

#define CHILDREN 3

int main(void)
{
  pid_t p[CHILDREN];
  int fd[CHILDREN - 1][2];

  int i;
  for (i = 0; i < CHILDREN - 1; i++)
  {
    if (pipe(fd[i]) == -1)
    {
      perror("pipe failed\n");
      return 1;
    }
  }

  for (i = 0; i < CHILDREN; i++)
  {
    p[i] = fork();
    if (p[i] < 0)
    {
      perror("fork failed\n");
      exit(-1);
    }
    if (p[i] == 0)
      break;
  }

  switch (i)
  {
  // Filho 1
  case 0:
    close(fd[0][0]);
    close(fd[1][0]);
    close(fd[1][1]);

    // Output para pipe
    dup2(fd[0][1], 1);

    close(fd[0][1]);

    execlp("ls", "ls", "-la", (char *)NULL);
    perror("error executing 'ls -la'");
    exit(-1);
    break;
  // Filho 2
  case 1:
    close(fd[0][1]);
    close(fd[1][0]);

    // Input e output para pipe
    dup2(fd[0][0], 0);
    dup2(fd[1][1], 1);

    close(fd[0][0]);
    close(fd[1][1]);

    execlp("sort", "sort", NULL);
    perror("error executing 'sort'");
    exit(-1);
    break;
  // Filho 3
  case 2:
    close(fd[0][0]);
    close(fd[1][1]);
    close(fd[0][1]);

    dup2(fd[1][0], 0);

    close(fd[1][0]);

    execlp("wc", "wc", "-l", (char *)NULL);
    perror("error executing 'wc -l'");
    exit(-1);
    break;
  // Pai
  case CHILDREN:
    for (i = 0; i < CHILDREN - 1; i++)
    {
      close(fd[i][0]);
      close(fd[i][1]);
    }

    for (i = 0; i < CHILDREN; i++)
      wait(NULL);
    break;
  default:
    printf("Something went wrong.\n");
  }
  return 0;
}