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26 .TH MQ_SEND 3 2014-06-03 "Linux" "Linux Programmer's Manual"
28 mq_send, mq_timedsend \- send a message to a message queue
31 .B #include <mqueue.h>
33 .BI "int mq_send(mqd_t " mqdes ", const char *" msg_ptr ,
34 .BI " size_t " msg_len ", unsigned int " msg_prio );
37 .B #include <mqueue.h>
39 .BI "int mq_timedsend(mqd_t " mqdes ", const char *" msg_ptr ,
40 .BI " size_t " msg_len ", unsigned int " msg_prio ,
41 .BI " const struct timespec *" abs_timeout );
44 Link with \fI\-lrt\fP.
48 Feature Test Macro Requirements for glibc (see
49 .BR feature_test_macros (7)):
54 _XOPEN_SOURCE\ >=\ 600 || _POSIX_C_SOURCE\ >=\ 200112L
59 adds the message pointed to by
61 to the message queue referred to by the descriptor
65 argument specifies the length of the message pointed to by
67 this length must be less than or equal to the queue's
70 Zero-length messages are allowed.
74 argument is a nonnegative integer that specifies the priority
76 Messages are placed on the queue in decreasing order of priority,
77 with newer messages of the same priority being placed after
78 older messages with the same priority.
80 If the message queue is already full
81 (i.e., the number of messages on the queue equals the queue's
83 attribute), then, by default,
85 blocks until sufficient space becomes available to allow the message
86 to be queued, or until the call is interrupted by a signal handler.
89 flag is enabled for the message queue description,
90 then the call instead fails immediately with the error
96 except that if the queue is full and the
98 flag is not enabled for the message queue description, then
100 points to a structure which specifies a ceiling on the time for which
102 This ceiling is an absolute timeout in seconds and nanoseconds
103 since the Epoch, 1970-01-01 00:00:00 +0000 (UTC), and it is
104 specified in the following structure:
109 time_t tv_sec; /* seconds */
110 long tv_nsec; /* nanoseconds */
115 If the message queue is full,
116 and the timeout has already expired by the time of the call,
124 return zero; on error, \-1 is returned, with
126 set to indicate the error.
130 The queue was full, and the
132 flag was set for the message queue description referred to by
136 The descriptor specified in
141 The call was interrupted by a signal handler; see
145 The call would have blocked, and
147 was invalid, either because
149 was less than zero, or because
151 was less than zero or greater than 1000 million.
157 attribute of the message queue.
160 The call timed out before a message could be transferred.
162 .SS Multithreading (see pthreads(7))
167 functions are thread-safe.
173 is a system call, and
175 is a library function layered on top of that system call.