SHM_UNLINK(3)              POSIX Programmer's Manual             SHM_UNLINK(3)



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

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.1-2017, <sys_mman.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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.opengroup.org/unix/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                  2017                        SHM_UNLINK(3)
