进程的管道通信

#include <unistd.h>
#include <sys/types.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>

int main()
{
    int pipe_fd[2];
    pid_t pid;
    char buf_r[100];
    char* p_wbuf;
    int r_num;
    
    memset(buf_r,0,sizeof(buf_r));
    
    /*创建管道*/
    if(pipe(pipe_fd)<0)
    {
        printf("pipe create error\n");
        return -1;
    }
    
    /*创建子进程*/
    if((pid=fork())==0)  //子进程 OR 父进程？  /fork返回值是0是子进程
    {
        printf("\n");
        close(pipe_fd[1]);
        sleep(2); /*为什么要睡眠*/
        if((r_num=read(pipe_fd[0],buf_r,100))>0)
        {
            printf(   "%d numbers read from the pipe is %s\n",r_num,buf_r);
        }    
        close(pipe_fd[0]);
        exit(0);
      }
    else if(pid>0)  //fork返回值是1是父进程
    {
        close(pipe_fd[0]);
        if(write(pipe_fd[1],"Hello",5)!=-1)
            printf("parent write1 Hello!\n");
        if(write(pipe_fd[1]," Pipe",5)!=-1)
            printf("parent write2 Pipe!\n");
        close(pipe_fd[1]);
        sleep(3);
        waitpid(pid,NULL,0); /*等待子进程结束*/
        exit(0);
    }
    return 0;
}

此管道为无名管道，用在父子进程通信，还有有名管道可以用在任意进程通信。

waitpid(pid,NULL,0); /*等待子进程结束*/   运行到此处需要停止，然后运行子进程
close(pipe_fd[1]);  说明pipe_fd[1]) 是文件描述符
可以看出先创建管道 然后在fork子进程