NAME

mq_getattr — get message queue attributes (REALTIME)

LIBRARY

POSIX Real-time Library (librt, -lrt)

SYNOPSIS

#include <mqueue.h>

int
mq_getattr(mqd_t mqdes, struct mq_attr *mqstat);

DESCRIPTION

The mq_getattr() function will obtain status information and attributes of the message queue and the open message queue description associated with the message queue descriptor.

The mqdes argument specifies a message queue descriptor.

The results are returned in the mq_attr structure referenced by the mqstat argument.

Upon return, the following members have the values associated with the open message queue description as set when the message queue was opened and as modified by subsequent mq_setattr(3) calls: mq_flags.

The following attributes of the message queue will be returned as set at message queue creation: mq_maxmsg, mq_msgsize.

Upon return, the following members within the mq_attr structure referenced by the mqstat argument will be set to the current state of the message queue:

mq_curmsgs

The number of messages currently on the queue.

RETURN VALUES

The mq_getattr() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

ERRORS

The mq_getattr() function may fail if:

[EBADF]

The mqdes argument is not a valid message queue descriptor.

SEE ALSO

mq(3), mq_setattr(3)

STANDARDS

This function conforms to the IEEE Std 1003.1-2001 (“POSIX.1”) standard.

HISTORY

This function first appeared in NetBSD 5.0.

COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 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.