shm_unlink(3p) — Linux manual page

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
       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(3p), mmap(3p), munmap(3p), shmat(3p), shmctl(3p),
       shmdt(3p), shm_open(3p)

       The Base Definitions volume of POSIX.1‐2017, sys_mman.h(0p)

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(3P)

Pages that refer to this page: sys_mman.h(0p), shmat(3p), shmctl(3p), shmdt(3p), shmget(3p), shm_open(3p)

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