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.\" 31.Dd June 21, 1994 32.Dt MSYNC 2 33.Os 34.Sh NAME 35.Nm msync 36.Nd synchronize a mapped region 37.Sh LIBRARY 38.Lb libc 39.Sh SYNOPSIS 40.In sys/types.h 41.In sys/mman.h 42.Ft int 43.Fn msync "void *addr" "size_t len" "int flags" 44.Sh DESCRIPTION 45The 46.Fn msync 47system call 48writes any modified pages back to the filesystem and updates 49the file modification time. 50If 51.Fa len 52is 0, all modified pages within the region containing 53.Fa addr 54will be flushed; 55if 56.Fa len 57is non-zero, only those pages containing 58.Fa addr 59and 60.Fa len Ns -1 61succeeding locations will be examined. 62The 63.Fa flags 64argument may be specified as follows: 65.Bl -tag -width ".Dv MS_INVALIDATE" 66.It Dv MS_ASYNC 67Return immediately 68.It Dv MS_SYNC 69Perform synchronous writes 70.It Dv MS_INVALIDATE 71Invalidate all cached data 72.El 73.Sh RETURN VALUES 74.Rv -std msync 75.Sh ERRORS 76.Fn msync 77will fail if: 78.Bl -tag -width Er 79.It Bq Er EINVAL 80.Fa addr 81is not a multiple of the hardware page size. 82.It Bq Er EINVAL 83.Fa len 84is too large or negative. 85.It Bq Er EINVAL 86.Fa flags 87was both 88.Dv MS_ASYNC 89and 90.Dv MS_INVALIDATE . 91Only one of these flags is allowed. 92.It Bq Er EIO 93An I/O error occurred while writing to the file system. 94.El 95.Sh SEE ALSO 96.Xr madvise 2 , 97.Xr mincore 2 , 98.Xr mprotect 2 , 99.Xr munmap 2 100.Sh HISTORY 101The 102.Fn msync 103function first appeared in 104.Bx 4.4 . 105