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

#define READ_END 0
#define WRITE_END 1


int
main() {

  pid_t c1_pid = fork();
  int c1_status = 0;

  int pipefd[2];

  if (pipe(pipefd) == -1) {
      perror("pipe");
      exit(EXIT_FAILURE);
  }


  if (c1_pid < 0) {
    perror("fork");
    exit(EXIT_FAILURE);
  } else if (c1_pid == 0) {
    // child 1

    printf("first child\n");

    dup2(pipefd[WRITE_END], STDOUT_FILENO);
    close(pipefd[WRITE_END]);
    close(pipefd[READ_END]);

    printf("hello world\n");

  } else {
    // parent

    pid_t c2_pid = fork();
    int c2_status = 0;

    if (c2_pid < 0) {
      perror("fork");
      exit(EXIT_FAILURE);
    } else if (c2_pid == 0) {
      // child 2

      printf("second child\n");

      dup2(pipefd[READ_END], STDIN_FILENO);
      close(pipefd[WRITE_END]);
      close(pipefd[READ_END]);

      char* myargs[2];
      myargs[0] = strdup("/bin/cat");
      myargs[1] = NULL;

      execvp(myargs[0], myargs);

    } else {
      // parent

      pid_t finished_c2_pid = waitpid(c2_pid, &c2_status, WUNTRACED);
      printf("finished c2 process: %d\n", finished_c2_pid);
    }

    close(pipefd[WRITE_END]);
    close(pipefd[READ_END]);

    pid_t finished_c1_pid = waitpid(c1_pid, &c1_status, WUNTRACED);
    printf("finished c1 process: %d\n", finished_c1_pid);
  }

  return 0;
}