The Open Group Base Specifications Issue 7
IEEE Std 1003.1-2008, 2016 Edition
Copyright © 2001-2016 The IEEE and The Open Group


mq_unlink - remove a message queue (REALTIME)


[MSG] [Option Start] #include <mqueue.h>

int mq_unlink(const char *
name); [Option End]


The mq_unlink() function shall remove the message queue named by the string name. If one or more processes have the message queue open when mq_unlink() is called, destruction of the message queue shall be postponed until all references to the message queue have been closed. However, the mq_unlink() call need not block until all references have been closed; it may return immediately.

After a successful call to mq_unlink(), reuse of the name shall subsequently cause mq_open() to behave as if no message queue of this name exists (that is, mq_open() will fail if O_CREAT is not set, or will create a new message queue if O_CREAT is set).


Upon successful completion, the function shall return a value of zero. Otherwise, the named message queue shall be unchanged by this function call, and the function shall return a value of -1 and set errno to indicate the error.


The mq_unlink() function shall fail if:

Permission is denied to unlink the named message queue.
The call to mq_unlink() blocked waiting for all references to the named message queue to be closed and a signal interrupted the call.
The named message queue does not exist.

The mq_unlink() function may fail if:

The length of the name argument exceeds {_POSIX_PATH_MAX} on systems that do not support the XSI option [XSI] [Option Start]  or exceeds {_XOPEN_PATH_MAX} on XSI systems, [Option End]  or has a pathname component that is longer than {_POSIX_NAME_MAX} on systems that do not support the XSI option [XSI] [Option Start]  or longer than {_XOPEN_NAME_MAX} on XSI systems. [Option End]  A call to mq_unlink() with a name argument that contains the same message queue name as was previously used in a successful mq_open() call shall not give an [ENAMETOOLONG] error.

The following sections are informative.








A future version might require the mq_open() and mq_unlink() functions to have semantics similar to normal file system operations.


mq_close, mq_open, msgctl, msgget, msgrcv, msgsnd

XBD <mqueue.h>


First released in Issue 5. Included for alignment with the POSIX Realtime Extension.

Issue 6

The mq_unlink() function is marked as part of the Message Passing option.

The Open Group Corrigendum U021/5 is applied, clarifying that upon unsuccessful completion, the named message queue is unchanged by this function.

The [ENOSYS] error condition has been removed as stubs need not be provided if an implementation does not support the Message Passing option.

Issue 7

Austin Group Interpretation 1003.1-2001 #077 is applied, changing [ENAMETOOLONG] from a ``shall fail'' to a ``may fail'' error .

Austin Group Interpretation 1003.1-2001 #141 is applied.

POSIX.1-2008, Technical Corrigendum 2, XSH/TC2-2008/0230 [504] is applied.

End of informative text.


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