freebsd-skq/lib/libc/sys/msync.2

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.\" @(#)msync.2 8.2 (Berkeley) 6/21/94
.\" $FreeBSD$
.\"
.Dd June 21, 1994
.Dt MSYNC 2
.Os
.Sh NAME
.Nm msync
.Nd synchronize a mapped region
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/mman.h
.Ft int
.Fn msync "void *addr" "size_t len" "int flags"
.Sh DESCRIPTION
The
.Fn msync
system call
writes any modified pages back to the file system and updates
the file modification time.
If
.Fa len
is 0, all modified pages within the region containing
.Fa addr
will be flushed;
if
.Fa len
is non-zero, only those pages containing
.Fa addr
and
.Fa len-1
succeeding locations will be examined.
The
.Fa flags
argument may be specified as follows:
.Bd -literal
MS_ASYNC Return immediately
MS_SYNC Perform synchronous writes
MS_INVALIDATE Invalidate all cached data
.Ed
.Sh RETURN VALUES
.Rv -std msync
.Sh ERRORS
The
.Fn msync
system call
will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The
.Fa addr
argument
is not a multiple of the hardware page size.
.It Bq Er EINVAL
The
.Fa len
argument
is too large or negative.
.It Bq Er EINVAL
The
.Fa flags
argument
was both MS_ASYNC and MS_INVALIDATE.
Only one of these flags is allowed.
.It Bq Er EIO
An I/O error occurred while writing to the file system.
.El
.Sh SEE ALSO
.Xr madvise 2 ,
.Xr mincore 2 ,
.Xr mprotect 2 ,
.Xr munmap 2
.Sh HISTORY
The
.Fn msync
system call first appeared in
.Bx 4.4 .