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 (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       shm_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 postponed 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(), reuse 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. Otherwise, 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.

       ENAMETOOLONG
              The length of the name argument exceeds {PATH_MAX} or a pathname component is longer than {NAME_MAX}.

       ENOENT The named shared memory object does not exist.


       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
       None.

SEE ALSO
       close(), mmap(), munmap(), shmat(), shmctl(), shmdt(), shm_open(), the Base Definitions volume  of  IEEE Std 1003.1-2001,
       <sys/mman.h>

COPYRIGHT
       Portions  of  this  text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for
       Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6,  Copy-
       right (C) 2001-2003 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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                SHM_UNLINK(3P)