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 (con-
       sult 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 appropri-
       ate call to munlock().

       If a mapping removed from a typed memory object causes the corresponding address range of the memory pool to be  inacces-
       sible  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  sup-
       ported.

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 munmap() 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,  Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                    MUNMAP(3P)