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)):

           _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

       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

       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.

              msg_len was greater than the mq_msgsize attribute of the message

              The call timed out before a message could be transferred.

       For an explanation of the terms used in this section, see

       │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 5.07 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

Linux                             2017-09-15                        MQ_SEND(3)