进程间通信-FIFI(命名管道)

比眉伴天荒 2022-08-02 15:59 208阅读 0赞

与无名管道不同，FIFO可用于无关系的进程之间  
1.管道读写端操作，如果读写端有一方读或写没打开，则另一端阻塞直到打开（非阻塞情况下会成功打开）  
2.如果管道buf满了没有剩余空间，则写端会阻塞直到管道有pipe\_buf的空间（如果管道是以非阻塞打开的，则空间满了继续写那么出错返回）  
3.读段会一直阻塞直到写端向读端写入数据（非阻塞情况下出错返回）  
4.多个读段去读，如果读的buf<PIPE\_BUF则读取操作时原子操作，如果buf>PIPE\_BUF则读取操作是非原子的，读取出来的数据是混乱的

直至最后一个访问管道的进程结束，内存里的管道数据会被删除，但是管道还在

int main()
    {
    	FILE 					* b_fd;
    	int	   					  b_ret, b_num = 0;
    	char					* b_fifo_name = "/tmp/fifo";
    	pid_t					  b_pid[10];
    	unlink(b_fifo_name);
    	b_ret = mkfifo(b_fifo_name, 0777);
    	if(b_ret < 0)
    	{
    		printf("mkfifo fail line = %d, fun = %s, file = %s", __LINE__, __func__, __FILE__);
    		return -1;
    	}
    
    	b_pid[b_num] = fork();
    	if(b_pid[b_num] < 0)
    	{
    		return -1;
    	}
    	if(0 == b_pid[b_num])
    	{
    		/*子线程*/
    		ipc_pipe_fun1();
    	}
    	b_num++;
    
    	b_pid[b_num] = fork();
    	if(b_pid[b_num] < 0)
    	{
    		return -1;
    	}
    	if(0 == b_pid[b_num])
    	{
    		/*子线程*/
    		ipc_pipe_fun1();
    	}
    	b_num++;
    
    	b_pid[b_num] = fork();
    	if(b_pid[b_num] < 0)
    	{
    		return -1;
    	}
    	if(0 == b_pid[b_num])
    	{
    		/*子线程*/
    		ipc_pipe_fun2();
    	}
    	b_num++;
    
    	while(1)
    	{
    		sleep(10000);
    	}
    	return 0;
    }
    
    
    int ipc_pipe_fun1()
    {
    	int 	  b_ret = 0, b_ttl = 0;
    	char	  b_buf[4098];
    	int		  b_fd = open("/tmp/fifo", O_RDONLY|O_NONBLOCK);
    
    	
    	while(1)
    	{
    		memset(b_buf, 0, sizeof(b_buf));
    		b_ret = read(b_fd, b_buf, 100);
    		printf("b_ret = %d, b_buf = %s\n", b_ret, b_buf);
    	}
    	
    	return 0;
    }
    
    int ipc_pipe_fun2()
    {
    	int 	b_ret;
    	char	b_buf[100];
    	int		b_num = 0, b_len = 0, b_ttl = 0;
    	char  * b_mall = (char *)malloc(65535);
    	int		b_fd = open("/tmp/fifo", O_WRONLY|O_NONBLOCK);
    	
    	while(1)
    	{
    		memset(b_buf, 0, sizeof(b_buf));
    		sprintf(b_buf, "%d|", b_num);
    		b_num = (++b_num)%1000000;
    		printf("==================\n");
    		b_len = write(b_fd, b_buf, 100);
    		b_ttl += b_len;
    		printf("b_ttl = %d, b_len = %d, b_buf = %s\n", b_ttl, b_len, b_buf);
    	}
    	
    	return 0;
    }