1*d8b80295SApple OSS Distributions.\" $NetBSD: sync.2,v 1.4 1995/02/27 12:38:41 cgd Exp $ 2*d8b80295SApple OSS Distributions.\" 3*d8b80295SApple OSS Distributions.\" Copyright (c) 1980, 1991, 1993 4*d8b80295SApple OSS Distributions.\" The Regents of the University of California. All rights reserved. 5*d8b80295SApple OSS Distributions.\" 6*d8b80295SApple OSS Distributions.\" Redistribution and use in source and binary forms, with or without 7*d8b80295SApple OSS Distributions.\" modification, are permitted provided that the following conditions 8*d8b80295SApple OSS Distributions.\" are met: 9*d8b80295SApple OSS Distributions.\" 1. Redistributions of source code must retain the above copyright 10*d8b80295SApple OSS Distributions.\" notice, this list of conditions and the following disclaimer. 11*d8b80295SApple OSS Distributions.\" 2. Redistributions in binary form must reproduce the above copyright 12*d8b80295SApple OSS Distributions.\" notice, this list of conditions and the following disclaimer in the 13*d8b80295SApple OSS Distributions.\" documentation and/or other materials provided with the distribution. 14*d8b80295SApple OSS Distributions.\" 3. All advertising materials mentioning features or use of this software 15*d8b80295SApple OSS Distributions.\" must display the following acknowledgement: 16*d8b80295SApple OSS Distributions.\" This product includes software developed by the University of 17*d8b80295SApple OSS Distributions.\" California, Berkeley and its contributors. 18*d8b80295SApple OSS Distributions.\" 4. Neither the name of the University nor the names of its contributors 19*d8b80295SApple OSS Distributions.\" may be used to endorse or promote products derived from this software 20*d8b80295SApple OSS Distributions.\" without specific prior written permission. 21*d8b80295SApple OSS Distributions.\" 22*d8b80295SApple OSS Distributions.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23*d8b80295SApple OSS Distributions.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24*d8b80295SApple OSS Distributions.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25*d8b80295SApple OSS Distributions.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26*d8b80295SApple OSS Distributions.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27*d8b80295SApple OSS Distributions.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28*d8b80295SApple OSS Distributions.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29*d8b80295SApple OSS Distributions.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30*d8b80295SApple OSS Distributions.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31*d8b80295SApple OSS Distributions.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32*d8b80295SApple OSS Distributions.\" SUCH DAMAGE. 33*d8b80295SApple OSS Distributions.\" 34*d8b80295SApple OSS Distributions.\" @(#)sync.2 8.1 (Berkeley) 6/4/93 35*d8b80295SApple OSS Distributions.\" 36*d8b80295SApple OSS Distributions.Dd June 4, 1993 37*d8b80295SApple OSS Distributions.Dt SYNC 2 38*d8b80295SApple OSS Distributions.Os BSD 4 39*d8b80295SApple OSS Distributions.Sh NAME 40*d8b80295SApple OSS Distributions.Nm sync 41*d8b80295SApple OSS Distributions.Nd "synchronize disk block in-core status with that on disk" 42*d8b80295SApple OSS Distributions.Sh SYNOPSIS 43*d8b80295SApple OSS Distributions.Fd #include <unistd.h> 44*d8b80295SApple OSS Distributions.Ft void 45*d8b80295SApple OSS Distributions.Fo sync 46*d8b80295SApple OSS Distributions.Fa void 47*d8b80295SApple OSS Distributions.Fc 48*d8b80295SApple OSS Distributions.Sh DESCRIPTION 49*d8b80295SApple OSS DistributionsThe 50*d8b80295SApple OSS Distributions.Fn sync 51*d8b80295SApple OSS Distributionsfunction forces a write of dirty (modified) buffers 52*d8b80295SApple OSS Distributionsin the block buffer cache out 53*d8b80295SApple OSS Distributionsto disk. The kernel keeps this information in core to reduce 54*d8b80295SApple OSS Distributionsthe number of disk I/O transfers required by the system. 55*d8b80295SApple OSS DistributionsAs information in the cache is lost after a system crash a 56*d8b80295SApple OSS Distributions.Fn sync 57*d8b80295SApple OSS Distributionscall is issued 58*d8b80295SApple OSS Distributionsfrequently 59*d8b80295SApple OSS Distributionsby the user process 60*d8b80295SApple OSS Distributions.Xr update 8 61*d8b80295SApple OSS Distributions(about every 30 seconds). 62*d8b80295SApple OSS Distributions.Pp 63*d8b80295SApple OSS DistributionsThe function 64*d8b80295SApple OSS Distributions.Xr fsync 2 65*d8b80295SApple OSS Distributionsmay be used to synchronize individual file descriptor 66*d8b80295SApple OSS Distributionsattributes. 67*d8b80295SApple OSS Distributions.Sh SEE ALSO 68*d8b80295SApple OSS Distributions.Xr fsync 2 , 69*d8b80295SApple OSS Distributions.Xr sync 8 , 70*d8b80295SApple OSS Distributions.Xr update 8 71*d8b80295SApple OSS Distributions.Sh BUGS 72*d8b80295SApple OSS Distributions.Fn sync 73*d8b80295SApple OSS Distributionsmay return before the buffers are completely flushed. 74*d8b80295SApple OSS Distributions.Sh HISTORY 75*d8b80295SApple OSS DistributionsA 76*d8b80295SApple OSS Distributions.Fn sync 77*d8b80295SApple OSS Distributionsfunction call appeared in 78*d8b80295SApple OSS Distributions.At v6 . 79