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

int main(void)
{
    int fd[2], p;
    char c;

    p = pipe(fd);
    assert(p != -1);

    pid_t pr = fork();
    assert(pr != -1);

    switch (pr)
    {
    case 0:
        close(fd[0]);
        dup2(fd[1], 1);
        execl("/usr/bin/ls", "ls", ".", NULL);
        exit(0);

    default:
        close(fd[1]);
        dup2(fd[0], 0);
        execl("/usr/bin/wc", "wc", "-l", NULL);
    }

    close(fd[0]);
    return 0;
}