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.