[求助]多个pipe怎么写
我想用C语言实现一下 ls -l | more | wc，写的代码如下，但没有输出，不知道哪里错了，请各位帮帮忙，谢谢各位。

C/C++ code

#include <stdio.h>#include <unistd.h>#include <sys/wait.h>int main(){    pid_t pid[3];    int pipe_fd[2];    int pipe_fd2[2];    int status;    char *prog1[3] = {"/bin/ls", "-l", NULL};    char *prog2[2] = {"/bin/more", NULL};    char *prog3[2] = {"/usr/bin/wc", NULL};    if(pipe(pipe_fd) < 0){        perror("pipe 1 failed");    }    if(pipe(pipe_fd2) < 0){            perror("pipe 2 failed");        }    if((pid[0] = fork()) < 0){        perror("fork failed");    }    if(pid[0] == 0){        close(pipe_fd[0]);        dup2(pipe_fd[1], 1);        close(pipe_fd[1]);        execvp(prog1[0], prog1);    }    if(pid[0] > 0){        pid[1] = fork();        if(pid[1] == 0){            close(pipe_fd[1]);            dup2(pipe_fd[0], 0);            close(pipe_fd[0]);            close(pipe_fd2[0]);            dup2(pipe_fd2[1], 1);            close(pipe_fd2[1]);            execvp(prog2[0], prog2);        }        if(pid[1]>0){            pid[2] = fork();            if(pid[2] == 0){                close(pipe_fd2[1]);                dup2(pipe_fd2[0], 0);                close(pipe_fd2[0]);                execvp(prog3[0], prog3);            }        }        close(pipe_fd[0]);        close(pipe_fd[1]);        close(pipe_fd2[0]);        close(pipe_fd2[1]);        waitpid(pid[1], &status, 0);    }    return 0;}

[解决办法]
你关闭的描述符还是不够，原则就是不用的描述符全部关闭，否则读取管道的那个进程不会结束输入

if(pid[0] == 0)
要关闭pipe_fd2
close(pipe_fd2[0]);
close(pipe_fd2[1]);

if(pid[2] == 0)
要关闭pipe_fd
close(pipe_fd[0]);
close(pipe_fd[1]);