отправить сообщение в очередь сообщений (send a message to a message queue)
Имя (Name)
mq_send, mq_timedsend - send a message to a message queue
Синопсис (Synopsis)
#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
Описание (Description)
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.
Возвращаемое значение (Return value)
On success, mq_send() and mq_timedsend() return zero; on error,
-1 is returned, with errno set to indicate the error.
Ошибки (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.
Атрибуты (Attributes)
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│mq_send(), mq_timedsend() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
Стандарты (Conforming to)
POSIX.1-2001, POSIX.1-2008.
Примечание (Note)
On Linux, mq_timedsend() is a system call, and mq_send() is a
library function layered on top of that system call.
Смотри также (See also)
mq_close(3), mq_getattr(3), mq_notify(3), mq_open(3),
mq_receive(3), mq_unlink(3), mq_overview(7), time(7)
