mq_setattr(3R)
NAME
mq_setattr, mq_getattr − set/get message queue attributes
SYNOPSIS
cc [ flag ... ] file ... −lposix4 [ library ... ]
#include <mqueue.h>
int mq_setattr(mqd_t mqdes, const struct mq_attr ∗mqstat,
struct mq_attr∗ omqstat);
int mq_getattr(mqd_t mqdes, struct mq_attr ∗mqstat);
struct mq_attr {
longmq_flags;/∗ message queue flags ∗/
longmq_maxmsg;/∗ maximum number of messages ∗/
longmq_msgsize;/∗ maximum message size ∗/
longmq_curmsgs;/∗ number of messages currently queued ∗/
...
};
DESCRIPTION
mq_setattr() is used to set attributes associated with the message queue specified by mqdes.
The message queue attributes corresponding to the following members defined in the mq_attr structure are set to the specified values upon successful completion of mq_setattr():
mq_flags The value of this member is either 0 or O_NONBLOCK.
The values of mq_maxmsg, mq_msgsize, and mq_curmsgs are ignored by mq_setattr().
If omqstat is non-NULL, mq_setattr() stores, in the location referenced by omqstat, the previous message queue attributes and the current queue status. These values are the same as would be returned by a call to mq_getattr() at that point. mq_getattr() is used to get status information and attributes associated with the message queue specified in mqdes. Upon return, the mq_flags member of the mq_attr structure referenced by mqstat has the value that was set when the message queue was created but also with modifications made by subsequent mq_setattr() calls.
The following attributes were set at message queue creation:
mq_maxmsg
mq_msgsize
Upon return, the mq_curmsgs (the number of messages currently on the queue) member of the mq_attr structure referenced by mqstat is set according to the current state of the message queue.
RETURN VALUES
Upon successful completion, these function(s) return 0; otherwise, they return −1, and set errno to indicate the error condition.
mq_setattr(), if successful, also changes the attributes of the message queue as specified.
ERRORS
EBADF mqdes is not a valid message queue descriptor.
ENOSYS mq_setattr() and mq_getattr() are not supported by this implementation.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| MT-Level | MT-Safe |
SEE ALSO
mq_open(3R), mq_receive(3R), mq_send(3R), attributes(5)
SunOS 5.6 — Last change: 30 Dec 1996