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This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface
may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface
may not be implemented on Linux.
NAME
mqueue.h — message queues (REALTIME)
SYNOPSIS
#include <mqueue.h>
DESCRIPTION
The <mqueue.h> header shall define the mqd_t type, which is used for message queue descriptors. This is
not an array type.
The <mqueue.h> header shall define the pthread_attr_t, size_t, and ssize_t types as described in
<sys/types.h>.
The <mqueue.h> header shall define the struct timespec structure as described in <time.h>.
The tag sigevent shall be declared as naming an incomplete structure type, the contents of which are
described in the <signal.h> header.
The <mqueue.h> header shall define 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. An mq_attr
structure shall 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 shall be declared as functions and may also be defined as macros. Function prototypes shall
be provided.
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 mq_send(mqd_t, const char *, size_t, unsigned);
int mq_setattr(mqd_t, const struct mq_attr *restrict,
struct mq_attr *restrict);
ssize_t mq_timedreceive(mqd_t, char *restrict, size_t,
unsigned *restrict, const struct timespec *restrict);
int mq_timedsend(mqd_t, const char *, size_t, unsigned,
const struct timespec *);
int mq_unlink(const char *);
Inclusion of the <mqueue.h> header may make visible symbols defined in the headers <fcntl.h>, <signal.h>,
and <time.h>.
The following sections are informative.
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
<fcntl.h>, <signal.h>, <sys_types.h>, <time.h>
The System Interfaces volume of POSIX.1‐2017, mq_close(), mq_getattr(), mq_notify(), mq_open(),
mq_receive(), mq_send(), mq_setattr(), mq_unlink()
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original
IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document.
The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page are most likely to have been introduced
during the conversion of the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .