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Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)munmap.2 8.2 (Berkeley) 4/15/94 .\" .Dd October 16, 2008 .Dt MUNMAP 2 .Os .Sh NAME .Nm munmap .Nd remove a mapping .Sh SYNOPSIS .Fd #include <sys/mman.h> .Ft int .Fo munmap .Fa "void *addr" .Fa "size_t len" .Fc .Sh DESCRIPTION The .Fn munmap system call deletes the mappings for the specified address range, causing further references to addresses within the range to generate invalid memory references. .Sh DIRTY PAGE HANDLING How .Fn munmap handles a dirty page, depends on what type of memory is being unmapped: .Pp .Bl -tag -width "[System V Shared]" .It Bq 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. .It Bq 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. .It Bq 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 .Xr msync 2 . .El .Pp 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). .Sh RETURN VALUES Upon successful completion, .Nm munmap returns zero. Otherwise, a value of -1 is returned and .Va errno is set to indicate the error. .Sh ERRORS .Fn Munmap will fail if: .Bl -tag -width Er .\" =========== .It Bq Er EINVAL The .Fa addr parameter was not page aligned (i.e., a multiple of the page size). .\" =========== .It Bq Er EINVAL The .Fa len parameter was negative or zero. .\" =========== .It Bq Er EINVAL Some part of the region being unmapped is not part of the currently valid address space. .El .Sh LEGACY SYNOPSIS .Fd #include <sys/types.h> .Fd #include <sys/mman.h> .Pp The include file .In sys/types.h is necessary. .Pp .Ft int .br .Fo munmap .Fa "caddr_t addr" .Fa "size_t len" .Fc ; .Pp The type of .Fa addr has changed. .Sh "SEE ALSO" .Xr getpagesize 3 , .Xr msync 2 , .Xr munmap 2 , .Xr mprotect 2 , .Xr madvise 2 , .Xr mincore 2 , .Xr compat 5 .Sh HISTORY The .Fn munmap function first appeared in 4.4BSD.