MQ_SEND(3) Linux Programmer's Manual MQ_SEND(3)NAME
mq_send, mq_timedsend - send a message to a message queue
SYNOPSIS
#include <mqueue.h>
int mq_send(mqd_t mqdes, const char *msg_ptr,
size_t msg_len, unsigned msg_prio);
#include <time.h>
#include <mqueue.h>
int mq_timedsend(mqd_t mqdes, const char *msg_ptr,
size_t msg_len, unsigned msg_prio,
const struct timespec *abs_timeout);
Link with -lrt.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
mq_timedsend():
_XOPEN_SOURCE >= 600 || _POSIX_C_SOURCE >= 200112L
DESCRIPTIONmq_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 nonnegative integer that specifies the pri‐
ority 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 han‐
dler. If the O_NONBLOCK flag is enabled for the message queue descrip‐
tion, 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, 1970-01-01
00:00:00 +0000 (UTC), and it is 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.
RETURN VALUE
On success, mq_send() and mq_timedsend() return zero; on error, -1 is
returned, with errno set to indicate the error.
ERRORS
EAGAIN The queue was full, and the O_NONBLOCK flag was set for the mes‐
sage 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.
CONFORMING TO
POSIX.1-2001.
NOTES
On Linux, mq_timedsend() is a system call, and mq_send() is a library
function layered on top of that system call.
SEE ALSOmq_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)COLOPHON
This page is part of release 3.27 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 2010-09-20 MQ_SEND(3)
