Writing your own shell… stuck on pipes?

I spent several hours nail down how to do pipe if you are writing your own shell. Most of the online reference is focusing 2 commands only. Here is the example of having 3 commands pipe together: ls -al | sort | cat -n

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

static const int PIPE_READ = 0;
static const int PIPE_WRITE = 1;

int main(int argc, char **argv)
{
    int status;
    int fd[2];
    pid_t pid;

    pid = fork();
    if (pid == 0) {

        pipe(fd);
        if (fork() == 0) {
            dup2(fd[PIPE_WRITE], STDOUT_FILENO);
            close(fd[PIPE_READ]);
            close(fd[PIPE_WRITE]);

            pipe(fd);
            if (fork() == 0) {
                dup2(fd[PIPE_WRITE], STDOUT_FILENO);
                close(fd[PIPE_READ]);
                close(fd[PIPE_WRITE]);
                execlp("ls", "ls", "-la", NULL);
            } else {
                dup2(fd[PIPE_READ], STDIN_FILENO);
                close(fd[PIPE_WRITE]);
                close(fd[PIPE_READ]);
            }

            execlp("sort", "sort", NULL);
        } else {
            dup2(fd[PIPE_READ], STDIN_FILENO);
            close(fd[PIPE_WRITE]);
            close(fd[PIPE_READ]);
        }

        /* IMPORTANT: don't add any wait/waitpid here */
        //waitpid(pid2, &status, 0);

        execlp("cat", "cat", "-n", NULL);
    }
    waitpid(pid, &status, 0);
    return EXIT_SUCCESS;
}

You can easily refactor this to a recursive function. Pay attention to not have the waitpid/wait() at the first and second command, or your child processes will block at wait.