The Single UNIX ® Specification, Version 2
Copyright © 1997 The Open Group


mqueue.h - message queues (REALTIME)


#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>) 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 will have at least the following fields:

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

The following are declared as functions and may also be declared as macros. Function prototypes must be provided for use with an ISO C compiler.

int      mq_close(mqd_t);
int      mq_getattr(mqd_t, struct mq_attr *);
int      mq_notify(mqd_t, const struct sigevent *);
mqd_t    mq_open(const char *, int, ...);
ssize_t  mq_receive(mqd_t, char *, size_t, unsigned int *);
int      mq_send(mqd_t, const char *, size_t, unsigned int);
int      mq_setattr(mqd_t, const struct mq_attr *, struct mq_attr *);
int      mq_unlink(const char *);

Inclusion of the <mqueue.h> header may make visible symbols defined in the headers <fcntl.h>, <signal.h>, <sys/types.h> and <time.h>.






<fcntl.h>, <signal.h>, <sys/types.h>, <time.h>.

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Copyright © 1997 The Open Group
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