103 lines
3.2 KiB
Groff
103 lines
3.2 KiB
Groff
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.\" $NetBSD: posix_fadvise.2,v 1.3 2009/06/09 11:21:33 yamt Exp $
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.\"
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.\" Copyright (c)2006,2009 YAMAMOTO Takashi,
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" ------------------------------------------------------------
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.Dd June 9, 2009
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.Dt POSIX_FADVISE 2
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.Os
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.Sh NAME
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.Nm posix_fadvise
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.Nd hint at the future access pattern of a file
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.\" ------------------------------------------------------------
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.Sh LIBRARY
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.Lb libc
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.\" ------------------------------------------------------------
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.Sh SYNOPSIS
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.In sys/fcntl.h
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.Ft int
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.Fn posix_fadvise "int fd" "off_t offset" "off_t size" "int hint"
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.\" ------------------------------------------------------------
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.Sh DESCRIPTION
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.Fn posix_fadvise
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hints at the application's access pattern to the file and range
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given by
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the file descriptor,
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.Fa fd ,
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and
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.Fa offset
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and
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.Fa size .
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If
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.Fa size
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is zero, it means to the end of file.
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.Pp
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.Fa hint
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should be one of the followings.
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.Pp
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.Bl -tag -offset indent -width POSIX_FADV_SEQUENTIAL -compact
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.It POSIX_FADV_NORMAL
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No hint.
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(default)
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.It POSIX_FADV_RANDOM
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Random access.
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.It POSIX_FADV_SEQUENTIAL
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Sequential access.
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(from lower offset to higher offset.)
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.It POSIX_FADV_WILLNEED
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Will be accessed.
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.It POSIX_FADV_DONTNEED
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Will not be accessed.
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.It POSIX_FADV_NOREUSE
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Will be accessed just once.
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.El
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.Pp
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Calling
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.Fn posix_fadvise
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doesn't alter the semantics of the operations,
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it is only a matter of performance.
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.\" ------------------------------------------------------------
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.Sh RETURN VALUES
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On success,
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.Fn posix_fadvise
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returns 0.
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Otherwise, it returns an error number.
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.\" ------------------------------------------------------------
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.Sh SEE ALSO
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.Xr errno 2 ,
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.Xr madvise 2
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.\" ------------------------------------------------------------
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.Sh BUGS
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For
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.Dv POSIX_FADV_NORMAL ,
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.Dv POSIX_FADV_RANDOM ,
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and
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.Dv POSIX_FADV_SEQUENTIAL ,
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the current implementation ignores
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.Fa offset
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and
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.Fa size ,
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and applies the hint to the whole file.
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