posix man page for shm_unlink

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 correspond-
       ing 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.

       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 contains 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() functions to have semantics similar to normal file system operations.

SEE ALSO
       close(), 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 Technol-
       ogy  --	Portable  Operating  System  Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the Institute of
       Electrical 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 Stan-
       dard 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.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE
/The Open Group						       2013							    SHM_UNLINK(3P)