通信方式--管道（父子进程通信）

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<unistd.h>
/*进程间通信（IPC机制)
  通信方式有： 管道 有名管道 消息队列 信号量  共享内存 套接字
  管道：是一种半双工的通信方式 只能在具有亲缘关系的进程间使用
  有名管道：也是半双工的通信方式，但是它允许无亲缘关系进程间的通信
*/
#if 0
//实现父子进程之间相互发送消息
int main()
{
    char *parent_talk[] = {"Hello","Can you tell me,what is time?","OMG,i have to go,Bye.",NULL};
    char *child_talk[] = {"Hi","No problem.","See you again.",NULL};
    int  fd1[2];
        int  fd2[2];
    int res=pipe(fd1);
    if(res == -1)
    {
        printf("create pipe error.\n");
        exit(1);
    }
    res = pipe(fd2);
       if(res == -1)
    {
        printf("create pipe erroe.\n");
        exit(1);
    }
    pid_t pid;
    pid = fork();
    if(pid == 0) //子进程
    {
        close(fd1[1]);//子进程关闭fd1的写端，关闭fd2的读端
        close(fd2[0]);
        char buf[256];
        int i;
        char *talk = child_talk[i];
        while(talk != NULL)
        {
            sleep(5);
            read(fd1[0],buf,256);
            printf("From Parent Msg:>%s\n",buf);
            write(fd2[1],talk,strlen(talk)+1);
            i++;
            talk = child_talk[i];
        }
        close(fd1[0]);
        close(fd2[1]);
    }
    else if(pid > 0)
    {
        close(fd1[0]); //父进程关闭fd1的读端，关闭fd2的读端
        close(fd2[1]);

        char buf[256];
        int i = 0;
        char *talk = parent_talk[i];
        while(talk != NULL)
        {
            write(fd1[1],talk,strlen(talk)+1);
            read(fd2[0],buf,256);
            printf("From Child Msf:>%s\n",buf);
            i++;
            talk = parent_talk[i];
        }
        close(fd1[1]);
        close(fd2[0]);
        int status;
        wait(&status);
    }
    return 0;
}
#endif