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MUNMAP(3P)                 POSIX Programmer's Manual                MUNMAP(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
       munmap - unmap pages of memory
SYNOPSIS
       #include <sys/mman.h>
       int munmap(void *addr, size_t len);

DESCRIPTION
       The munmap() function shall remove any mappings for those entire  pages
       containing  any  part  of  the address space of the process starting at
       addr and continuing for len bytes.  Further references to  these  pages
       shall  result  in the generation of a SIGSEGV signal to the process. If
       there are no mappings in the specified address range, then munmap() has
       no effect.
       The  implementation  shall  require that addr be a multiple of the page
       size {PAGESIZE}.
       If a mapping to be removed was private, any modifications made in  this
       address range shall be discarded.
       Any  memory  locks  (see  mlock()  and mlockall()) associated with this
       address range shall be  removed,  as  if  by  an  appropriate  call  to
       munlock().
       If  a mapping removed from a typed memory object causes the correspond-
       ing address range of the memory pool to be inaccessible by any  process
       in the system except through allocatable mappings (that is, mappings of
       typed memory objects opened  with  the  POSIX_TYPED_MEM_MAP_ALLOCATABLE
       flag),  then that range of the memory pool shall become deallocated and
       may  become  available  to  satisfy  future  typed  memory   allocation
       requests.
       A   mapping  removed  from  a  typed  memory  object  opened  with  the
       POSIX_TYPED_MEM_MAP_ALLOCATABLE flag shall not affect in  any  way  the
       availability of that typed memory for allocation.
       The  behavior  of  this  function is unspecified if the mapping was not
       established by a call to mmap().
RETURN VALUE
       Upon successful completion, munmap()  shall  return  0;  otherwise,  it
       shall return -1 and set errno to indicate the error.
ERRORS
       The munmap() function shall fail if:
       EINVAL Addresses  in  the  range  [addr,addr+len) are outside the valid
              range for the address space of a process.
       EINVAL The len argument is 0.
       EINVAL The addr argument is not a multiple of the page size as returned
              by sysconf().

       The following sections are informative.
EXAMPLES
       None.
APPLICATION USAGE
       The  munmap()  function  is  only  supported if the Memory Mapped Files
       option or the Shared Memory Objects option is supported.
RATIONALE
       The munmap() function corresponds to SVR4, just as the mmap()  function
       does.
       It  is  possible that an application has applied process memory locking
       to a region that contains shared memory. If this has occurred, the mun-
       map() call ignores those locks and, if necessary, causes those locks to
       be removed.
FUTURE DIRECTIONS
       None.
SEE ALSO
       mlock(), mlockall(),  mmap(),  posix_typed_mem_open(),  sysconf(),  the
       Base    Definitions   volume   of   IEEE Std 1003.1-2001,   <signal.h>,
       <sys/mman.h>
COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
       Specifications  Issue  6,  Copyright  (C) 2001-2003 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 .

IEEE/The Open Group                  2003                           MUNMAP(3P)