bionic (3) shm_unlink.3posix.gz

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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.


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>


       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 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 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.kernel.org/doc/man-pages/reporting_bugs.html .