Send a message to a message queue
#include <mqueue.h> #include <time.h> int mq_timedsend( mqd_t mqdes, const char * msg_ptr, size_t msg_len, unsigned int msg_prio, const struct timespec * abs_timeout ); int mq_timedsend_monotonic( mqd_t mqdes, const char * msg_ptr, size_t msg_len, unsigned int msg_prio, const struct timespec * abs_timeout );
Use the -l c option to qcc to link against this library. This library is usually included automatically.
Use the -l mq option to qcc to link against this library.
The mq_timedsend() function puts a message of size msg_len and pointed to by msg_ptr into the queue indicated by mqdes. The new message has a priority of msg_prio. The mq_timedsend_monotonic() function is a QNX Neutrino extension; it's similar to mq_timedsend(), but it uses CLOCK_MONOTONIC, so the timeout isn't affected by changes to the system time.
|The message queue manager needs to be running. Neutrino supports two implementations of message queues: a traditional implementation, and an alternate one that uses the mq server and a queue in kernel space. For more information, see the entries for mq and mqueue in the Utilities Reference, as well as the POSIX Message Queues: Two Implementations technote.|
The queue maintained is in priority order, and in FIFO order within the same priority.
If the number of elements on the specified queue is equal to its mq_maxmsg, and O_NONBLOCK wasn't set (in the oflag argument to mq_open()), the call to mq_timedsend() blocks. It becomes unblocked when there's room on the queue to send the given message. If more than one mq_timedsend() is blocked on a given queue, and space becomes available in that queue to send, then the mq_timedsend() with the highest priority message is unblocked.
-1 if an error occurred (errno is set). Any other value indicates success.
See the example for mq_timedreceive().
mq_timedsend() is POSIX 1003.1 MSG; mq_timedsend_monotonic() is QNX Neutrino
mq_close(), mq_open(), mq_receive(), mq_send(), mq_timedreceive(), timespec
mq, mqueue in the Utilities Reference
“POSIX message queues” in the “Interprocess Communication (IPC)” chapter of System Architecture
POSIX Message Queues: Two Implementations technote.