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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | VERSIONS | STANDARDS | HISTORY | SEE ALSO | COLOPHON |
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mq_send(3) Library Functions Manual mq_send(3)
mq_send, mq_timedsend - send a message to a message queue
Real-time library (librt, -lrt)
#include <mqueue.h>
int mq_send(mqd_t mqdes, const char msg_ptr[.msg_len],
size_t msg_len, unsigned int msg_prio);
#include <time.h>
#include <mqueue.h>
int mq_timedsend(mqd_t mqdes, const char msg_ptr[.msg_len],
size_t msg_len, unsigned int msg_prio,
const struct timespec *abs_timeout);
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 a timespec(3)
structure.
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 │
└─────────────────────────────────────┴───────────────┴─────────┘
On Linux, mq_timedsend() is a system call, and mq_send() is a
library function layered on top of that system call.
POSIX.1-2008.
POSIX.1-2001.
mq_close(3), mq_getattr(3), mq_notify(3), mq_open(3),
mq_receive(3), mq_unlink(3), timespec(3), mq_overview(7), time(7)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.9.1.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2024-06-26. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.9.1 2024-05-02 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)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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