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#include <mqueue.h>
The <mqueue.h> header defines the mqd_t type, which is used for message queue descriptors. This will not be an array type. A message queue descriptor may be implemented using a file descriptor, in which case applications can open up to at least OPEN_MAX file and message queues.
The <mqueue.h> header defines the sigevent structure (as described in <signal.h>, see signal.h(3HEAD)) and the mq_attr structure, which is used in getting and setting the attributes of a message queue. Attributes are initially set when the message queue is created. A mq_attr structure has the following members:
long mq_flags message queue flags
long mq_maxmsg maximum number of messages
long mq_msgsize maximum message size
long mq_curmsgs number of messages currently queued
Inclusion of the <mqueue.h> header may make visible symbols defined in the headers <fcntl.h>, <signal.h>, <sys/types.h>, and <time.h>.
See attributes(5) for descriptions of the following attributes:
| ATTRIBUTE TYPE ATTRIBUTE VALUE |
| Interface Stability Standard |
fcntl.h(3HEAD), signal.h(3HEAD), time.h(3HEAD), types.h(3HEAD), attributes(5), standards(5)