munmap(2) [osf1 man page]

munmap(2)							System Calls Manual							 munmap(2)

NAME

       munmap - Unmaps a mapped region

SYNOPSIS

       #include <sys/mman.h>

       int munmap (	 void *addr,	  size_t len );

       [Tru64  UNIX]  The  following  definition of the munmap() function does not conform to current standards and is supported only for backward
       compatibility (see standards(5)):

       #include <sys/mman.h>

       int munmap (	 caddr_t addr,	    size_t len );

STANDARDS

       Interfaces documented on this reference page conform to industry standards as follows:

       munmap():  XSH5.0

       Refer to the standards(5) reference page for more information about industry standards and associated tags.

PARAMETERS

       Specifies the address of the region to be unmapped.  Specifies the length in bytes of the region to be unmapped.

DESCRIPTION

       The munmap() function unmaps a mapped file or shared memory region.

       The addr and len parameters specify the address and length in bytes, respectively, of the region to be unmapped.  The len parameter must be
       a  multiple  of	the  page  size  as  returned  by  sysconf(_SC_PAGE_SIZE).   If  len  is  not  a  multiple of the page size as returned by
       sysconf(_SC_PAGE_SIZE), the length of the region will be rounded up to the next multiple of the page size.

       The result of using an address which lies in an unmapped region and not in any subsequently mapped region is undefined.

RETURN VALUES

       Upon successful completion, the munmap() function returns 0 (zero).  Otherwise, munmap() returns -1 and sets errno to indicate the error.

ERRORS

       If the munmap() function fails, errno may be set to one of the following values:

       The range [addr, addr + len) includes an invalid address.  The addr  parameter  is  not	a  multiple  of  the  page  size  as  returned	by
       sysconf(_SC_PAGE_SIZE).

	      The len parameter is 0 (zero).

RELATED INFORMATION

       Functions: mmap(2), sysconf(3)

       Standards: standards(5) delim off

																	 munmap(2)

MUNMAP(2)						      BSD System Calls Manual							 MUNMAP(2)

NAME

     munmap -- remove a mapping

SYNOPSIS

     #include <sys/mman.h>

     int
     munmap(void *addr, size_t len);

DESCRIPTION

     The munmap() system call deletes the mappings for the specified address range, causing further references to addresses within the range to
     generate invalid memory references.

DIRTY PAGE HANDLING

     How munmap() handles a dirty page, depends on what type of memory is being unmapped:

     [Anonymous]	If the memory is anonymous memory and if the last reference is going away, then the contents are discarded by definition
			of anonymous memory.

     [System V Shared]	If the memory mapping was created using System V shared memory, then the contents persist until the System V memory region
			is destroyed or the system is rebooted.

     [File mapping]	If the mapping maps data from a file (MAP_SHARED), then the memory will eventually be written back to disk if it's dirty.
			This will happen automatically at some point in the future (implementation dependent).	Note: to force the memory to be
			written back to the disk, use msync(2).

     If there are still other references to the memory when the munmap is done, then nothing is done to the memory itself and it may be swapped
     out if need be. The memory will continue to persist until the last reference goes away (except for System V shared memory in which case, see
     above).

RETURN VALUES

     Upon successful completion, munmap returns zero.  Otherwise, a value of -1 is returned and errno is set to indicate the error.

ERRORS

     Munmap() will fail if:

     [EINVAL]		The addr parameter was not page aligned (i.e., a multiple of the page size).

     [EINVAL]		The len parameter was negative or zero.

     [EINVAL]		Some part of the region being unmapped is not part of the currently valid address space.

LEGACY SYNOPSIS

     #include <sys/types.h>
     #include <sys/mman.h>

     The include file <sys/types.h> is necessary.

     int
     munmap(caddr_t addr, size_t len);

     The type of addr has changed.

SEE ALSO

     getpagesize(3), msync(2), munmap(2), mprotect(2), madvise(2), mincore(2), compat(5)

HISTORY

     The munmap() function first appeared in 4.4BSD.

BSD
								 October 16, 2008							       BSD