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.1‐2017, <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 .