NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON
MQ_SEND(3) Linux Programmer's Manual MQ_SEND(3)
mq_send, mq_timedsend - send a message to a message queue
#include <mqueue.h>
mqd_t mq_send(mqd_t mqdes, const char *msg_ptr,
size_t msg_len, unsigned msg_prio);
#define _XOPEN_SOURCE 600
#include <time.h>
#include <mqueue.h>
mqd_t mq_timedsend(mqd_t mqdes, const char *msg_ptr,
size_t msg_len, unsigned msg_prio,
const struct timespec *abs_timeout);
Link with -lrt.
mq_send() adds the message pointed to by msg_ptr to the message queue referred
to by the descriptor mqdes. The msg_len argument specifies the length of the
message pointed to by msg_ptr; this length must be less than or equal to the
queue's mq_msgsize attribute. Zero-length messages are allowed.
The msg_prio argument is a non-negative integer that specifies the priority of
this message. Messages are placed on the queue in decreasing order of
priority, with newer messages of the same priority being placed after older
messages with the same priority.
If the message queue is already full (i.e., the number of messages on the
queue equals the queue's mq_maxmsg attribute), then, by default, mq_send()
blocks until sufficient space becomes available to allow the message to be
queued, or until the call is interrupted by a signal handler. If the
O_NONBLOCK flag is enabled for the message queue description, then the call
instead fails immediately with the error EAGAIN.
mq_timedsend() behaves just like mq_send(), except that if the queue is full
and the O_NONBLOCK flag is not enabled for the message queue description, then
abs_timeout points to a structure which specifies a ceiling on the time for
which the call will block. This ceiling is an absolute timeout in seconds and
nanoseconds since the Epoch (midnight on the morning of 1 January 1970),
specified in the following structure:
struct timespec {
time_t tv_sec; /* seconds */
long tv_nsec; /* nanoseconds */
};
If the message queue is full, and the timeout has already expired by the time
of the call, mq_timedsend() returns immediately.
On success, mq_send() and mq_timedsend() return zero; on error, -1 is
returned, with errno set to indicate the error.
EAGAIN The queue was empty, and the O_NONBLOCK flag was set for the message
queue description referred to by mqdes.
EBADF The descriptor specified in mqdes was invalid.
EINTR The call was interrupted by a signal handler; see signal(7).
EINVAL The call would have blocked, and abs_timeout was invalid, either
because tv_sec was less than zero, or because tv_nsec was less than
zero or greater than 1000 million.
EMSGSIZE
msg_len was greater than the mq_msgsize attribute of the message queue.
ETIMEDOUT
The call timed out before a message could be transferred.
POSIX.1-2001.
On Linux, mq_timedsend() is a system call, and mq_send() is a library function
layered on top of that system call.
mq_close(3), mq_getattr(3), mq_notify(3), mq_open(3), mq_receive(3),
mq_unlink(3), feature_test_macros(7), mq_overview(7), time(7)
This page is part of release 3.23 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
Linux 2008-09-29 MQ_SEND(3)