1.\" Copyright (c) 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)msync.2 8.2 (Berkeley) 6/21/94 29.\" $FreeBSD: src/lib/libc/sys/msync.2,v 1.16.2.5 2001/12/14 18:34:01 ru Exp $ 30.\" $DragonFly: src/lib/libc/sys/msync.2,v 1.2 2003/06/17 04:26:47 dillon Exp $ 31.\" 32.Dd June 21, 1994 33.Dt MSYNC 2 34.Os 35.Sh NAME 36.Nm msync 37.Nd synchronize a mapped region 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In sys/types.h 42.In sys/mman.h 43.Ft int 44.Fn msync "void *addr" "size_t len" "int flags" 45.Sh DESCRIPTION 46The 47.Fn msync 48system call 49writes any modified pages back to the filesystem and updates 50the file modification time. 51If 52.Fa len 53is 0, all modified pages within the region containing 54.Fa addr 55will be flushed; 56if 57.Fa len 58is non-zero, only those pages containing 59.Fa addr 60and 61.Fa len-1 62succeeding locations will be examined. 63The 64.Fa flags 65argument may be specified as follows: 66.Bd -literal 67MS_ASYNC Return immediately 68MS_SYNC Perform synchronous writes 69MS_INVALIDATE Invalidate all cached data 70.Ed 71.Sh RETURN VALUES 72.Rv -std msync 73.Sh ERRORS 74.Fn msync 75will fail if: 76.Bl -tag -width Er 77.It Bq Er EINVAL 78.Fa addr 79is not a multiple of the hardware page size. 80.It Bq Er EINVAL 81.Fa len 82is too large or negative. 83.It Bq Er EINVAL 84.Fa flags 85was both MS_ASYNC and MS_INVALIDATE. 86Only one of these flags is allowed. 87.It Bq Er EIO 88An I/O error occurred while writing to the file system. 89.El 90.Sh SEE ALSO 91.Xr madvise 2 , 92.Xr mincore 2 , 93.Xr mprotect 2 , 94.Xr munmap 2 95.Sh HISTORY 96The 97.Fn msync 98function first appeared in 99.Bx 4.4 . 100