#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <assert.h>
#include <sys/wait.h>
#include <fcntl.h>
int main(int argc, char *argv[])
{
	pid_t p1,p2;
	int fd[2];

	assert(pipe(fd) == 0);

	p1 = fork();
	if (p1 == 0){
	close(fd[0]);
	dup2(fd[1],STDOUT_FILENO);
	close(fd[1]);
	execlp("ls","ls",NULL);
	assert(0);
	}


	p2 = fork();
	if (p2 == 0){
		int out = open("output.txt",O_CREAT|O_WRONLY|O_APPEND,0644);
		dup2(out,STDOUT_FILENO);
		close(out);
	close(fd[1]);
	dup2(fd[0],STDIN_FILENO);
	close(fd[0]);
	execlp("wc","wc",NULL);
	assert(0);
	}

	close(fd[0]);
	close(fd[1]);
	wait(NULL);
	wait(NULL);
	return 0;
}