1MQ_SEND(3)                 Linux Programmer's Manual                MQ_SEND(3)
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NAME

6       mq_send, mq_timedsend - send a message to a message queue
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SYNOPSIS

9       #include <mqueue.h>
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11       mqd_t mq_send(mqd_t mqdes, const char *msg_ptr,
12                      size_t msg_len, unsigned msg_prio);
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14       #define _XOPEN_SOURCE 600
15       #include <time.h>
16       #include <mqueue.h>
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18       mqd_t mq_timedsend(mqd_t mqdes, const char *msg_ptr,
19                      size_t msg_len, unsigned msg_prio,
20                      const struct timespec *abs_timeout);
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DESCRIPTION

23       mq_send()  adds  the message pointed to by msg_ptr to the message queue
24       referred to by the descriptor mqdes.  The  msg_len  argument  specifies
25       the  length  of  the message pointed to by msg_ptr; this length must be
26       less than or equal to the queue's  mq_msgsize  attribute.   Zero-length
27       messages are allowed.
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29       The msg_prio argument is a non-negative integer that specifies the pri‐
30       ority of this message.  Messages are placed on the queue in  decreasing
31       order  of  priority,  with  newer  messages  of the same priority being
32       placed after older messages with the same priority.
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34       If the message queue is already full (i.e., the number of  messages  on
35       the  queue  equals  the queue's mq_maxmsg attribute), then, by default,
36       mq_send() blocks until sufficient space becomes available to allow  the
37       message to be queued, or until the call is interrupted by a signal han‐
38       dler.  If the O_NONBLOCK flag is enabled for the message queue descrip‐
39       tion, then the call instead fails immediately with the error EAGAIN.
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41       mq_timedsend() behaves just like mq_send(), except that if the queue is
42       full and the O_NONBLOCK flag is  not  enabled  for  the  message  queue
43       description,  then  abs_timeout points to a structure which specifies a
44       ceiling on the time for which the call will block.  This ceiling is  an
45       absolute  timeout  in seconds and nanoseconds since the Epoch (midnight
46       on the morning of 1 January 1970), specified in  the  following  struc‐
47       ture:
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49              struct timespec {
50                  time_t tv_sec;        /* seconds */
51                  long   tv_nsec;       /* nanoseconds */
52              };
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54       If  the  message  queue is full, and the timeout has already expired by
55       the time of the call, mq_timedsend() returns immediately.
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RETURN VALUE

58       On success, mq_send() and mq_timedsend() return zero; on error,  -1  is
59       returned, with errno set to indicate the error.
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ERRORS

62       EAGAIN The  queue  was  empty,  and the O_NONBLOCK flag was set for the
63              message queue description referred to by mqdes.
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65       EBADF  The descriptor specified in mqdes was invalid.
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67       EMSGSIZE
68              msg_len was greater than the mq_msgsize attribute of the message
69              queue.
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71       EINTR  The call was interrupted by a signal handler.
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73       EINVAL The call would have blocked, and abs_timeout was invalid, either
74              because tv_sec was less than zero, or because tv_nsec  was  less
75              than zero or greater than 1000 million.
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77       ETIMEDOUT
78              The call timed out before a message could be transferred.
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CONFORMING TO

81       POSIX.1-2001.
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SEE ALSO

84       mq_close(3),  mq_getattr(3),  mq_notify(3),  mq_open(3), mq_receive(3),
85       mq_unlink(3), feature_test_macros(7), mq_overview(7)
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89Linux 2.6.16                      2006-02-25                        MQ_SEND(3)
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