Message Queuing for 003:posix IPC

1: FIFO requires that a process be read-open before it is written to a pipe, compared to FIFO. Message Queuing does not need to have to wait for a message to arrive on the queue.

2:posix Each read always returns the highest priority, System V can return any priority.

3: Put a message into an empty queue, POSIX allows to generate a signal, or start a thread, system is not available.

Basic operation function of 4:posix:

1 #include <mqueue.h>2
3 mqd_t mq_open (constcharint  oflag,...); 4 5 int mq_close (mqd_t mqds); 6 7 int mq_unlink (mqd_t mqds);

Properties of the 5.mqd_t mq_attr

struct mq_attr{long//0,o_nonblock block or non-blocking long mq_maxmsg; // Maximum number of messages a queue can hold Long // maximum length of a message long MQ_CURMSGA; // number of current queue messages };

Message Queuing for 003:posix IPC