1.\" $NetBSD: posix_fadvise.2,v 1.5 2013/02/04 20:03:11 wiz Exp $ 2.\" 3.\" Copyright (c)2006,2009 YAMAMOTO Takashi, 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25.\" SUCH DAMAGE. 26.\" 27.\" ------------------------------------------------------------ 28.Dd February 4, 2013 29.Dt POSIX_FADVISE 2 30.Os 31.Sh NAME 32.Nm posix_fadvise 33.Nd hint at the future access pattern of a file 34.\" ------------------------------------------------------------ 35.Sh LIBRARY 36.Lb libc 37.\" ------------------------------------------------------------ 38.Sh SYNOPSIS 39.In fcntl.h 40.Ft int 41.Fn posix_fadvise "int fd" "off_t offset" "off_t size" "int hint" 42.\" ------------------------------------------------------------ 43.Sh DESCRIPTION 44.Fn posix_fadvise 45hints at the application's access pattern to the file and range 46given by 47the file descriptor, 48.Fa fd , 49and 50.Fa offset 51and 52.Fa size . 53If 54.Fa size 55is zero, it means to the end of file. 56.Pp 57.Fa hint 58should be one of the followings. 59.Pp 60.Bl -tag -offset indent -width POSIX_FADV_SEQUENTIAL -compact 61.It POSIX_FADV_NORMAL 62No hint. 63(default) 64.It POSIX_FADV_RANDOM 65Random access. 66.It POSIX_FADV_SEQUENTIAL 67Sequential access. 68(from lower offset to higher offset.) 69.It POSIX_FADV_WILLNEED 70Will be accessed. 71.It POSIX_FADV_DONTNEED 72Will not be accessed. 73.It POSIX_FADV_NOREUSE 74Will be accessed just once. 75.El 76.Pp 77Calling 78.Fn posix_fadvise 79doesn't alter the semantics of the operations, 80it is only a matter of performance. 81.\" ------------------------------------------------------------ 82.Sh RETURN VALUES 83On success, 84.Fn posix_fadvise 85returns 0. 86Otherwise, it returns an error number. 87.\" ------------------------------------------------------------ 88.Sh SEE ALSO 89.Xr errno 2 , 90.Xr madvise 2 91.\" ------------------------------------------------------------ 92.Sh BUGS 93For 94.Dv POSIX_FADV_NORMAL , 95.Dv POSIX_FADV_RANDOM , 96and 97.Dv POSIX_FADV_SEQUENTIAL , 98the current implementation ignores 99.Fa offset 100and 101.Fa size , 102and applies the hint to the whole file. 103