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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/mman.h>
45 .Ft int
46 .Fo msync
47 .Fa "void *addr"
48 .Fa "size_t len"
49 .Fa "int flags"
50 .Fc
51 .Sh DESCRIPTION
52 The
53 .Fn msync
54 system call writes modified whole pages back to the filesystem
55 and updates the file modification time.
56 Only those pages containing
57 .Fa addr
58 and
59 .Fa len-1
60 succeeding locations will be examined.
61 .Pp
62 The
63 .Fa flags
64 argument may be specified as follows:
65 .Bd -literal
66 MS_ASYNC Return immediately
67 MS_SYNC Perform synchronous writes
68 MS_INVALIDATE Invalidate all cached data
69 .Ed
70 .Pp
71 The
72 .Fa MS_ASYNC
73 flag is not permitted to be combined with other flags.
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 .\" ===========
83 .It Bq Er EBUSY
84 Some of the specified addresses are locked
85 and MS_INVALIDATE is specified.
86 .\" ===========
87 .It Bq Er EINVAL
88 .Fa addr
89 is not a multiple of the hardware page size.
90 .\" ===========
91 .It Bq Er EINVAL
92 .Fa len
93 is too large, or less than 1.
94 .\" ===========
95 .It Bq Er EINVAL
96 .Fa flags
97 is invalid
98 (e.g., it combines MS_ASYNC with another flag,
99 which is not permitted).
100 .\" ===========
101 .It Bq Er EIO
102 An I/O error occurs while writing to the file system.
103 .\" ===========
104 .It Bq Er ENOMEM
105 The specified address range is outside of the address range
106 of the process or includes an unmapped page.
107 .El
108 .Sh LEGACY SYNOPSIS
109 .Fd #include <sys/types.h>
110 .Fd #include <sys/mman.h>
111 .Pp
112 The include file
113 .In sys/types.h
114 is necessary.
115 .Sh SEE ALSO
116 .Xr madvise 2 ,
117 .Xr mincore 2 ,
118 .Xr mprotect 2 ,
119 .Xr munmap 2 ,
120 .Xr compat 5
121 .Sh HISTORY
122 The
123 .Fn msync
124 function first appeared in
125 .Bx 4.4 .