1*43a90889SApple OSS Distributions.\" $NetBSD: sync.2,v 1.4 1995/02/27 12:38:41 cgd Exp $ 2*43a90889SApple OSS Distributions.\" 3*43a90889SApple OSS Distributions.\" Copyright (c) 1980, 1991, 1993 4*43a90889SApple OSS Distributions.\" The Regents of the University of California. All rights reserved. 5*43a90889SApple OSS Distributions.\" 6*43a90889SApple OSS Distributions.\" Redistribution and use in source and binary forms, with or without 7*43a90889SApple OSS Distributions.\" modification, are permitted provided that the following conditions 8*43a90889SApple OSS Distributions.\" are met: 9*43a90889SApple OSS Distributions.\" 1. Redistributions of source code must retain the above copyright 10*43a90889SApple OSS Distributions.\" notice, this list of conditions and the following disclaimer. 11*43a90889SApple OSS Distributions.\" 2. Redistributions in binary form must reproduce the above copyright 12*43a90889SApple OSS Distributions.\" notice, this list of conditions and the following disclaimer in the 13*43a90889SApple OSS Distributions.\" documentation and/or other materials provided with the distribution. 14*43a90889SApple OSS Distributions.\" 3. All advertising materials mentioning features or use of this software 15*43a90889SApple OSS Distributions.\" must display the following acknowledgement: 16*43a90889SApple OSS Distributions.\" This product includes software developed by the University of 17*43a90889SApple OSS Distributions.\" California, Berkeley and its contributors. 18*43a90889SApple OSS Distributions.\" 4. Neither the name of the University nor the names of its contributors 19*43a90889SApple OSS Distributions.\" may be used to endorse or promote products derived from this software 20*43a90889SApple OSS Distributions.\" without specific prior written permission. 21*43a90889SApple OSS Distributions.\" 22*43a90889SApple OSS Distributions.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23*43a90889SApple OSS Distributions.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24*43a90889SApple OSS Distributions.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25*43a90889SApple OSS Distributions.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26*43a90889SApple OSS Distributions.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27*43a90889SApple OSS Distributions.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28*43a90889SApple OSS Distributions.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29*43a90889SApple OSS Distributions.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30*43a90889SApple OSS Distributions.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31*43a90889SApple OSS Distributions.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32*43a90889SApple OSS Distributions.\" SUCH DAMAGE. 33*43a90889SApple OSS Distributions.\" 34*43a90889SApple OSS Distributions.\" @(#)sync.2 8.1 (Berkeley) 6/4/93 35*43a90889SApple OSS Distributions.\" 36*43a90889SApple OSS Distributions.Dd June 4, 1993 37*43a90889SApple OSS Distributions.Dt SYNC 2 38*43a90889SApple OSS Distributions.Os BSD 4 39*43a90889SApple OSS Distributions.Sh NAME 40*43a90889SApple OSS Distributions.Nm sync 41*43a90889SApple OSS Distributions.Nd "synchronize disk block in-core status with that on disk" 42*43a90889SApple OSS Distributions.Sh SYNOPSIS 43*43a90889SApple OSS Distributions.Fd #include <unistd.h> 44*43a90889SApple OSS Distributions.Ft void 45*43a90889SApple OSS Distributions.Fo sync 46*43a90889SApple OSS Distributions.Fa void 47*43a90889SApple OSS Distributions.Fc 48*43a90889SApple OSS Distributions.Sh DESCRIPTION 49*43a90889SApple OSS DistributionsThe 50*43a90889SApple OSS Distributions.Fn sync 51*43a90889SApple OSS Distributionsfunction forces a write of dirty (modified) buffers 52*43a90889SApple OSS Distributionsin the block buffer cache out 53*43a90889SApple OSS Distributionsto disk. The kernel keeps this information in core to reduce 54*43a90889SApple OSS Distributionsthe number of disk I/O transfers required by the system. 55*43a90889SApple OSS DistributionsAs information in the cache is lost after a system crash a 56*43a90889SApple OSS Distributions.Fn sync 57*43a90889SApple OSS Distributionscall is issued 58*43a90889SApple OSS Distributionsfrequently 59*43a90889SApple OSS Distributionsby the user process 60*43a90889SApple OSS Distributions.Xr update 8 61*43a90889SApple OSS Distributions(about every 30 seconds). 62*43a90889SApple OSS Distributions.Pp 63*43a90889SApple OSS DistributionsThe function 64*43a90889SApple OSS Distributions.Xr fsync 2 65*43a90889SApple OSS Distributionsmay be used to synchronize individual file descriptor 66*43a90889SApple OSS Distributionsattributes. 67*43a90889SApple OSS Distributions.Sh SEE ALSO 68*43a90889SApple OSS Distributions.Xr fsync 2 , 69*43a90889SApple OSS Distributions.Xr sync 8 , 70*43a90889SApple OSS Distributions.Xr update 8 71*43a90889SApple OSS Distributions.Sh BUGS 72*43a90889SApple OSS Distributions.Fn sync 73*43a90889SApple OSS Distributionsmay return before the buffers are completely flushed. 74*43a90889SApple OSS Distributions.Sh HISTORY 75*43a90889SApple OSS DistributionsA 76*43a90889SApple OSS Distributions.Fn sync 77*43a90889SApple OSS Distributionsfunction call appeared in 78*43a90889SApple OSS Distributions.At v6 . 79