---
name: "mq_close"
section: "2"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/mq_close"
---

# mq\_close(2)

close a message queue (REALTIME)

## NAME

**mq\_close** – close a message queue (REALTIME)

## LIBRARY

library “librt”

## SYNOPSIS

**#include \<mqueue.h\>**

*int*\

**mq\_close**(*mqd\_t mqdes*);

## DESCRIPTION

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 subsequent **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.

## RETURN VALUES

The **mq\_close()** 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\_close**() system call will fail if:

- \[EBADF\]

  The *mqdes* argument is not a valid message queue descriptor.

## SEE ALSO

[mq\_open(2)](/mq_open/2.md), [mq\_unlink(2)](/mq_unlink/2.md)

## STANDARDS

The **mq\_close**() system call conforms to IEEE Std 1003.1-2004 (“POSIX.1”).

## HISTORY

Support for POSIX message queues first appeared in FreeBSD 7.0.

## COPYRIGHT

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 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.