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	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. All advertising materials mentioning features or use of this software
	13	.\" must display the following acknowledgement:
	14	.\" This product includes software developed by the University of
	15	.\" California, Berkeley and its contributors.
	16	.\" 4. Neither the name of the University nor the names of its contributors
	17	.\" may be used to endorse or promote products derived from this software
	18	.\" without specific prior written permission.
	19	.\"
	20	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	21	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	22	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	23	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	24	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	25	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	26	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	27	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	28	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	29	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	30	.\" SUCH DAMAGE.
	31	.\"
	32	.\" @(#)msync.2 8.2 (Berkeley) 6/21/94
	33	.\" $FreeBSD: src/lib/libc/sys/msync.2,v 1.17 2000/04/21 09:41:53 phantom Exp $
	34	.\"
	35	.Dd June 21, 1994
	36	.Dt MSYNC 2
	37	.Os
	38	.Sh NAME
	39	.Nm msync
	40	.Nd synchronize a mapped region
	41	.Sh LIBRARY
	42	.Lb libc
	43	.Sh SYNOPSIS
	44	.Fd #include <sys/types.h>
	45	.Fd #include <sys/mman.h>
	46	.Ft int
	47	.Fn msync "void *addr" "size_t len" "int flags"
	48	.Sh DESCRIPTION
	49	The
	50	.Fn msync
	51	system call
	52	writes any modified pages back to the filesystem and updates
	53	the file modification time.
	54	If
	55	.Fa len
	56	is 0, all modified pages within the region containing
	57	.Fa addr
	58	will be flushed;
	59	if
	60	.Fa len
	61	is non-zero, only those pages containing
	62	.Fa addr
	63	and
	64	.Fa len-1
	65	succeeding locations will be examined.
	66	The
	67	.Fa flags
	68	argument may be specified as follows:
	69	.Bd -literal
	70	MS_ASYNC Return immediately
	71	MS_SYNC Perform synchronous writes
	72	MS_INVALIDATE Invalidate all cached data
	73	.Ed
	74	.Sh RETURN VALUES
	75	If any errors occur, -1 is returned and errno is set to indicate the
	76	error.
	77	Otherwise, a 0 value is returned.
	78	.Sh ERRORS
	79	.Fn msync
	80	will fail if:
	81	.Bl -tag -width Er
	82	.It Bq Er EINVAL
	83	.Fa addr
	84	is not a multiple of the hardware page size.
	85	.It Bq Er EINVAL
	86	.Fa len
	87	is too large or negative.
	88	.It Bq Er EINVAL
	89	.Fa flags
	90	was both MS_ASYNC and MS_INVALIDATE.
	91	Only one of these flags is allowed.
	92	.It Bq Er EIO
	93	An 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
	101	The
	102	.Fn msync
	103	function first appeared in
	104	.Bx 4.4 .