1SHM_UNLINK(3P)             POSIX Programmer's Manual            SHM_UNLINK(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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NAME

12       shm_unlink - remove a shared memory object (REALTIME)
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SYNOPSIS

15       #include <sys/mman.h>
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17       int shm_unlink(const char *name);
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DESCRIPTION

21       The shm_unlink() function shall remove the name of  the  shared  memory
22       object named by the string pointed to by name.
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24       If  one  or  more references to the shared memory object exist when the
25       object is unlinked, the  name  shall  be  removed  before  shm_unlink()
26       returns,  but  the removal of the memory object contents shall be post‐
27       poned until all open and map references to  the  shared  memory  object
28       have been removed.
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30       Even  if the object continues to exist after the last shm_unlink(), re‐
31       use of the name shall subsequently cause shm_open() to behave as if  no
32       shared memory object of this name exists (that is, shm_open() will fail
33       if O_CREAT is not set, or will create a new  shared  memory  object  if
34       O_CREAT is set).
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RETURN VALUE

37       Upon  successful  completion, a value of zero shall be returned. Other‐
38       wise, a value of -1 shall be returned and errno  set  to  indicate  the
39       error.  If  -1 is returned, the named shared memory object shall not be
40       changed by this function call.
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ERRORS

43       The shm_unlink() function shall fail if:
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45       EACCES Permission is denied to unlink the named shared memory object.
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47       ENAMETOOLONG
48              The length of the name argument exceeds {PATH_MAX} or a pathname
49              component is longer than {NAME_MAX}.
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51       ENOENT The named shared memory object does not exist.
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54       The following sections are informative.
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EXAMPLES

57       None.
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APPLICATION USAGE

60       Names  of  memory  objects  that were allocated with open() are deleted
61       with unlink() in the usual fashion. Names of memory objects  that  were
62       allocated  with shm_open() are deleted with shm_unlink(). Note that the
63       actual memory object is not destroyed until the last close and unmap on
64       it have occurred if it was already in use.
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RATIONALE

67       None.
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FUTURE DIRECTIONS

70       None.
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SEE ALSO

73       close(),  mmap(), munmap(), shmat(), shmctl(), shmdt(), shm_open(), the
74       Base Definitions volume of IEEE Std 1003.1-2001, <sys/mman.h>
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77       Portions of this text are reprinted and reproduced in  electronic  form
78       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
79       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
80       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
81       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
82       event of any discrepancy between this version and the original IEEE and
83       The Open Group Standard, the original IEEE and The Open Group  Standard
84       is  the  referee document. The original Standard can be obtained online
85       at http://www.opengroup.org/unix/online.html .
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89IEEE/The Open Group                  2003                       SHM_UNLINK(3P)
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