linux管道学习（二）

int main()
{
    char* pipename = "pipe";
    mkfifo(pipename,0777);
    int pid = fork();
    if(pid < 0)    
    {
        printf("Error In Fork\n");
        exit(-1);
    }

    if(pid == 0)
    {
        printf("In Child Process\n");
        int fd = open(pipename,O_WRONLY|O_NONBLOCK);
        node testnode;
        testnode.a = 10;
        testnode.b = 20;
        
        write(fd,&testnode,sizeof(testnode));

        testnode.a = 11;
        testnode.b = 22;

        write(fd,&testnode,sizeof(testnode));

        close(fd);
        printf("Child Process Is Over \n");
    }
    if(pid > 0)
    {
        
        printf("In Parent Process\n");
        
        int fd = open(pipename,O_RDONLY);

        node testnode;
        read(fd,&testnode,sizeof(node));
        printf("Msg From Child node a = %d,b = %ld \n",testnode.a,testnode.b);

        read(fd,&testnode,sizeof(node));
        printf("Msg From Child node a = %d,b = %ld \n",testnode.a,testnode.b);

        close(fd);
        
        waitpid(pid,NULL,0);
        printf("Praent Process Is Over \n");
    }

    
}

在阻塞情况下，管道会阻塞直到有内容写入

读取时如果管道为空会等待有内容可以读取

在打开管道的时候可以选择非阻塞方式O_NONBLOCK

如果是非阻塞方式则忽略当前管道状态

命名管道不仅可以在有亲缘关系的进程中进行通信，也可以在无亲缘关系的进程中通信。