管道pipe和dup2的简单使用

#include <stdio.h>            // ls -l | more
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>

int main(void)
{
    int fd[2];
    pid_t pid;

    if(pipe(fd) < 0)
    {
        perror("pipe error!");
        exit(0);
    }
    if((pid = fork()) < 0)
    {
        perror("fork error!");
        exit(1);
    }
    else if(pid == 0)
    {
        close(fd[0]);    //pipe read closed
        close(1);
        dup2(fd[1], 1);
        execl("/bin/ls", "ls", "-l", NULL);
        exit(1);
    }
    else
    {
        close(fd[1]);    //pipe write closed
        close(0);
        dup2(fd[0], 0);
        execl("/bin/more", "more", NULL);
        exit(1);
    }
    return 0;
}