mq_getattr.2 (2010 09)

mq_getattr(2) mq_getattr(2)

NAME

mq_getattr - get status information and attributes associated with a message queue

SYNOPSIS

#include <sys/mqueue.h>

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

DESCRIPTION

The mq_getattr() system call collects status information and attributes associated with the message

queue speciﬁed by mqdes which is copied into the

mq_attr structure referenced by mqstat .

Upon a successful return, the mq_msgsize and mq_maxmsg ﬁelds within the mq_attr structure contain

the maximum size of a message for this queue and the maximum number of messages that can be queued

at any time. The mq_curmsgs ﬁeld contains the number of messages currently on the queue. In addition,

the mq_ﬂags ﬁeld contains the message queue blocking status associated with this mqdes.

To use this function, link in the realtime library by specifying

-lrt on the compiler or linker command

line.

RETURN VALUE

mq_getattr() returns the following values:

0 Successful completion.

-1 Failure. errno is set to indicate the error.

ERRORS

mq_getattr() fails, errno is set to one of the following values:

[EBADF] mqdes is not a valid message queue descriptor.

[EINVAL] mqstat does not point to a valid mq_attr structure.

[ENOSYS] mq_getattr() is not supported by the implementation.