linux管道学习（二）

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

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

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

         testnode.a = ;
         testnode.b = ;

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

         close(fd);
         printf("Child Process Is Over \n");
     }
     if(pid > )
     {

         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,);
         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。