RTEMS 4.9.2 On-Line Library

Message Manager Receiving a Message

RTEMS C User's Guide

10.3.3: Receiving a Message

The rtems_message_queue_receive directive attempts to retrieve a message from the specified message queue. If at least one message is in the queue, then the message is removed from the queue, copied to the caller's message buffer, and returned immediately along with the length of the message. When messages are unavailable, one of the following situations applies:

By default, the calling task will wait forever for the message to arrive.
Specifying the RTEMS_NO_WAIT option forces an immediate return with an error status code.
Specifying a timeout limits the period the task will wait before returning with an error status.

If the task waits for a message, then it is placed in the message queue's task wait queue in either FIFO or task priority order. All tasks waiting on a message queue are returned an error code when the message queue is deleted.

RTEMS C User's Guide