int
mq_send(
mqd_t mqdes
const char *msg_ptr
size_t msg_len
unsigned msg_prio
)
int
mq_timedsend(
mqd_t mqdes
const char *msg_ptr
size_t msg_len
unsigned msg_prio
const struct timespec *abs_timeout
)
)
function will add the message pointed to by the argument
msg_ptr
to the message queue specified by
mqdes
.
The
msg_len
argument specifies the length of the message, in bytes, pointed to by
msg_ptr
.
The value of
msg_len
will be less than or equal to the
mq_msgsize
attribute of the message queue, or
mq_send(
)
will fail.
If the specified message queue is not full,
mq_send()
behaves as if the message is inserted into the message queue at the
position indicated by the
msg_prio
argument.
A message with a larger numeric value of
msg_prio
will be inserted before messages with lower values of
msg_prio
.
A message will be inserted after other messages in the queue,
if any, with equal
msg_prio
.
The value of
msg_prio
will be less than
{MQ_PRIO_MAX
}.
If the specified message queue is full and
O_NONBLOCK
is not set in the message queue description associated with
mqdes
,
mq_send()
blocks until space becomes available to enqueue the message, or until
mq_send(
)
is interrupted by a signal.
If more than one thread is waiting to send when space becomes available
in the message queue, then the thread of the highest priority that has
been waiting the longest will be unblocked to send its message.
If the specified message queue is full and
O_NONBLOCK
is set in the message queue description associated with
mqdes
,
the message will not be queued and
mq_send()
will return an error.
The
mq_timedsend()
function will add a message to the message queue specified by
mqdes
in the manner defined for the
mq_send()
function.
However, if the specified message queue is full and
O_NONBLOCK
is not set in the message queue description associated with
mqdes
,
the wait for sufficient room in the queue will be terminated
when the specified timeout expires.
If
O_NONBLOCK
is set in the message queue description, this function will be equivalent to
mq_send().
The timeout will expire when the absolute time specified by
abs_timeout
passes, as measured by the clock on which timeouts are based (that is,
when the value of that clock equals or exceeds
abs_timeout
),
or if the absolute time specified by
abs_timeout
has already been passed at the time of the call.
The resolution of the timeout is based on the CLOCK_REALTIME clock.
The
timespec
argument is defined in the
<time.h>
header.
Under no circumstance will the operation fail with a timeout if there is
sufficient room in the queue to add the message immediately.
The validity of the
abs_timeout
parameter need not be checked when there is sufficient room in the queue.
)
and
mq_timedsend(
)
functions return a value of zero.
Otherwise, no message will be enqueued,
the functions will return -1, and the global variable
errno
will be set to indicate the error.
)
and
mq_timedsend(
)
functions fail if:
EAGAIN
]
O_NONBLOCK
flag is set in the message queue description associated with
mqdes
,
and the specified message queue is full.
EBADF
]
mqdes
argument is not a valid message queue descriptor open for writing.
EINTR
]
)
or
mq_timedsend(
).
EINVAL
]
msg_prio
was outside the valid range, or
the process or thread would have blocked, and the
abs_timeout
parameter specified a nanoseconds field value less than zero
or greater than or equal to 1000 million.
EMSGSIZE
]
msg_len
,
exceeds the message size attribute of the message queue.
ETIMEDOUT
]
O_NONBLOCK
flag was not set when the message queue was opened,
but the timeout expired before the message could be added to the queue.
)
and
mq_timedsend(
)
functions first appeared in
NetBSD5.0.