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FreeBSD 11.0 - man page for mq_close (freebsd section 2)

MQ_CLOSE(2)						      BSD System Calls Manual						       MQ_CLOSE(2)

mq_close -- close a message queue (REALTIME)
POSIX Real-time Library (librt, -lrt)
#include <mqueue.h> int mq_close(mqd_t mqdes);
The mq_close() system call removes the association between the message queue descriptor, mqdes, and its message queue. The results of using this message queue descriptor after successful return from this mq_close(), and until the return of this message queue descriptor from a sub- sequent mq_open(), are undefined. If the process has successfully attached a notification request to the message queue via this mqdes, this attachment will be removed, and the message queue is available for another process to attach for notification.
Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error.
The mq_close() system call will fail if: [EBADF] The mqdes argument is not a valid message queue descriptor.
mq_open(2), mq_unlink(2)
The mq_close() system call conforms to IEEE Std 1003.1-2004 (``POSIX.1'').
Support for POSIX message queues first appeared in FreeBSD 7.0.
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of Elec- trical 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
November 29, 2005 BSD