Updated: April 19, 2023 |
Send a message to a queue
#include <mqueue.h> int mq_send( mqd_t mqdes, const char * msg_ptr, size_t msg_len, unsigned int msg_prio );
The mq_send() 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 queue is maintained 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_send() blocks. It becomes unblocked when there's room on the queue to send the given message. If more than one mq_send() is blocked on a given queue, and space becomes available in that queue to send, then the mq_send() with the highest priority message is unblocked.
In the traditional (mqueue) implementation, calling write() with mqdes is analogous to calling mq_send() with a msg_prio of 0.
-1 if an error occurred (errno is set). Any other value indicates success.
See the example for mq_open().
Safety: | |
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Cancellation point | Yes |
Interrupt handler | No |
Signal handler | No |
Thread | Yes |