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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | 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>
int mq_send(mqd_t mqdes, const char *msg_ptr,
size_t msg_len, unsigned int msg_prio);
#include <time.h>
#include <mqueue.h>
int mq_timedsend(mqd_t mqdes, const char *msg_ptr,
size_t msg_len, unsigned int msg_prio,
const struct timespec *abs_timeout);
Link with -lrt.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
mq_timedsend():
_POSIX_C_SOURCE >= 200112L
mq_send() adds the message pointed to by msg_ptr to the message queue
referred to by the message queue 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
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.
See mq_overview(7) for details on the range for the message 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
how long the call will block. This value is an absolute timeout in
seconds and nanoseconds since the Epoch, 1970-01-01 00:00:00 +0000
(UTC), 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 full, and the O_NONBLOCK flag was set for the
message queue description referred to by mqdes.
EBADF The descriptor specified in mqdes was invalid or not opened
for writing.
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.
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────┼───────────────┼─────────┤
│mq_send(), mq_timedsend() │ Thread safety │ MT-Safe │
└──────────────────────────┴───────────────┴─────────┘
POSIX.1-2001, POSIX.1-2008.
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), mq_overview(7), time(7)
This page is part of release 4.12 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2016-12-12 MQ_SEND(3)
Pages that refer to this page: syscalls(2), mq_close(3), mq_getattr(3), mq_notify(3), mq_open(3), mq_receive(3), mq_unlink(3), mq_overview(7), signal(7)