1mq_send(3C) Standard C Library Functions mq_send(3C)
2
6 mq_send, mq_timedsend, mq_reltimedsend_np - send a message to a message
7 queue
8
10 #include <mqueue.h>
11 int mq_send(mqd_t mqdes, const char *msg_ptr, size_t msg_len,
13 unsigned msg_prio);
14 #include <mqueue.h>
17 #include <time.h>
18 int mq_timedsend(mqd_t mqdes, const char *msg_ptr,
20 size_t msg_len, unsigned msg_prio,
21 const struct timespec *restrict abs_timeout);
22 int mq_reltimedsend_np(mqd_t mqdes, const char *msg_ptr,
25 size_t msg_len, unsigned msg_prio,
26 const struct timespec *restrict rel_timeout);
27
30 The mq_send() function adds the message pointed to by the argument
31 msg_ptr to the message queue specified by mqdes. The msg_len argument
32 specifies the length of the message in bytes pointed to by msg_ptr. The
33 value of msg_len is less than or equal to the mq_msgsize attribute of
34 the message queue, or mq_send() fails.
35 If the specified message queue is not full, mq_send() behaves as if the
38 message is inserted into the message queue at the position indicated by
39 the msg_prio argument. A message with a larger numeric value of
40 msg_prio is inserted before messages with lower values of msg_prio. A
41 message will be inserted after other messages in the queue, if any,
42 with equal msg_prio. The value of msg_prio must be greater than zero
43 and less than or equal to MQ_PRIO_MAX.
44 If the specified message queue is full and O_NONBLOCK is not set in the
47 message queue description associated with mqdes (see mq_open(3C) and
48 mq_setattr(3C)), mq_send() blocks until space becomes available to
49 enqueue the message, or until mq_send() is interrupted by a signal. If
50 more than one thread is waiting to send when space becomes available in
51 the message queue, then the thread of the highest priority which has
52 been waiting the longest is unblocked to send its message. Otherwise,
53 it is unspecified which waiting thread is unblocked. If the specified
54 message queue is full and O_NONBLOCK is set in the message queue
55 description associated with mqdes, the message is not queued and
56 mq_send() returns an error.
57 The mq_timedsend() function adds a message to the message queue speci‐
60 fied by mqdes in the manner defined for the mq_send() function. How‐
61 ever, if the specified message queue is full and O_NONBLOCK is not set
62 in the message queue description associated with mqdes, the wait for
63 sufficient room in the queue is terminated when the specified timeout
64 expires. If O_NONBLOCK is set in the message queue description, this
65 function is equivalent to mq_send().
66 The mq_reltimedsend_np() function is identical to the mq_timedsend()
69 function, except that the timeout is specified as a relative time
70 interval.
71 For mq_timedsend(), the timeout expires when the absolute time speci‐
74 fied by abs_timeout passes, as measured by the CLOCK_REALTIME clock
75 (that is, when the value of that clock equals or exceeds abs_timeout),
76 or if the absolute time specified by abs_timeout has already been
77 passed at the time of the call.
78 For mq_reltimedsend_np(), the timeout expires when the time interval
81 specified by rel_timeout passes, as measured by the CLOCK_REALTIME
82 clock, or if the time interval specified by rel_timeout is negative at
83 the time of the call.
84 The resolution of the timeout is the resolution of the CLOCK_REALTIME
87 clock. The timespec argument is defined in the <time.h> header.
88 Under no circumstance does the operation fail with a timeout if there
91 is sufficient room in the queue to add the message immediately. The
92 validity of the timeout parameter need not be checked when there is
93 sufficient room in the queue.
94
96 Upon successful completion, mq_send(), mq_timedsend(), and mq_reltimed‐
97 send_np() return 0. Otherwise, no message is enqueued, the functions
98 return −1, and errno is set to indicate the error.
99
101 The mq_send(), mq_timedsend(), and mq_reltimedsend_np() functions will
102 fail if:
103 EAGAIN The O_NONBLOCK flag is set in the message queue descrip‐
105 tion associated with mqdes, and the specified message
106 queue is full.
107 EBADF The mqdes argument is not a valid message queue descriptor
110 open for writing.
111 EINTR A signal interrupted the function call.
114 EINVAL The value of msg_prio was outside the valid range.
117 EINVAL The process or thread would have blocked, and the timeout
120 parameter specified a nanoseconds field value less than
121 zero or greater than or equal to 1,000 million.
122 EMSGSIZE The specified message length, msg_len, exceeds the message
125 size attribute of the message queue.
126 ETIMEDOUT The O_NONBLOCK flag was not set when the message queue was
129 opened, but the timeout expired before the message could
130 be added to the queue.
131
134 See attributes(5) for descriptions of the following attributes:
135 ┌─────────────────────────────┬─────────────────────────────┐
140 │ATTRIBUTE TYPE │ATTRIBUTE VALUE │
141 ├─────────────────────────────┼─────────────────────────────┤
142 │Interface Stability │Committed │
143 ├─────────────────────────────┼─────────────────────────────┤
144 │MT-Level │MT-Safe │
145 ├─────────────────────────────┼─────────────────────────────┤
146 │Standard │See below. │
147 └─────────────────────────────┴─────────────────────────────┘
148 For mq_send() and mq_timedsend(), see standards(5).
151
153 sysconf(3C), mqueue.h(3HEAD), mq_open(3C), mq_receive(3C),
154 mq_setattr(3C), attributes(5), standards(5)
155SunOS 5.11 5 Feb 2008 mq_send(3C)