SHM_UNLINK(3P) POSIX Programmer's Manual SHM_UNLINK(3P)PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding
Linux manual page for details of Linux behavior), or the interface may
not be implemented on Linux.
NAMEshm_unlink — remove a shared memory object (REALTIME)
SYNOPSIS
#include <sys/mman.h>
int shm_unlink(const char *name);
DESCRIPTION
The shm_unlink() function shall remove the name of the shared memory
object named by the string pointed to by name.
If one or more references to the shared memory object exist when the
object is unlinked, the name shall be removed before shm_unlink()
returns, but the removal of the memory object contents shall be post‐
poned until all open and map references to the shared memory object
have been removed.
Even if the object continues to exist after the last shm_unlink(), re‐
use of the name shall subsequently cause shm_open() to behave as if no
shared memory object of this name exists (that is, shm_open() will fail
if O_CREAT is not set, or will create a new shared memory object if
O_CREAT is set).
RETURN VALUE
Upon successful completion, a value of zero shall be returned. Other‐
wise, a value of −1 shall be returned and errno set to indicate the
error. If −1 is returned, the named shared memory object shall not be
changed by this function call.
ERRORS
The shm_unlink() function shall fail if:
EACCES Permission is denied to unlink the named shared memory object.
ENOENT The named shared memory object does not exist.
The shm_unlink() function may fail if:
ENAMETOOLONG
The length of the name argument exceeds {_POSIX_PATH_MAX} on
systems that do not support the XSI option or exceeds
{_XOPEN_PATH_MAX} on XSI systems, or has a pathname component
that is longer than {_POSIX_NAME_MAX} on systems that do not
support the XSI option or longer than {_XOPEN_NAME_MAX} on XSI
systems. A call to shm_unlink() with a name argument that con‐
tains the same shared memory object name as was previously used
in a successful shm_open() call shall not give an [ENAMETOOLONG]
error.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
Names of memory objects that were allocated with open() are deleted
with unlink() in the usual fashion. Names of memory objects that were
allocated with shm_open() are deleted with shm_unlink(). Note that the
actual memory object is not destroyed until the last close and unmap on
it have occurred if it was already in use.
RATIONALE
None.
FUTURE DIRECTIONS
A future version might require the shm_open() and shm_unlink() func‐
tions to have semantics similar to normal file system operations.
SEE ALSOclose(), mmap(), munmap(), shmat(), shmctl(), shmdt(), shm_open()
The Base Definitions volume of POSIX.1‐2008, <sys_mman.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the source
files to man page format. To report such errors, see https://www.ker‐
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 SHM_UNLINK(3P)
