18269e767SBrooks Davis.\" Copyright (c) 1980, 1991, 1993 28269e767SBrooks Davis.\" The Regents of the University of California. All rights reserved. 38269e767SBrooks Davis.\" 48269e767SBrooks Davis.\" Redistribution and use in source and binary forms, with or without 58269e767SBrooks Davis.\" modification, are permitted provided that the following conditions 68269e767SBrooks Davis.\" are met: 78269e767SBrooks Davis.\" 1. Redistributions of source code must retain the above copyright 88269e767SBrooks Davis.\" notice, this list of conditions and the following disclaimer. 98269e767SBrooks Davis.\" 2. Redistributions in binary form must reproduce the above copyright 108269e767SBrooks Davis.\" notice, this list of conditions and the following disclaimer in the 118269e767SBrooks Davis.\" documentation and/or other materials provided with the distribution. 128269e767SBrooks Davis.\" 3. Neither the name of the University nor the names of its contributors 138269e767SBrooks Davis.\" may be used to endorse or promote products derived from this software 148269e767SBrooks Davis.\" without specific prior written permission. 158269e767SBrooks Davis.\" 168269e767SBrooks Davis.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 178269e767SBrooks Davis.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 188269e767SBrooks Davis.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 198269e767SBrooks Davis.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 208269e767SBrooks Davis.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 218269e767SBrooks Davis.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 228269e767SBrooks Davis.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 238269e767SBrooks Davis.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 248269e767SBrooks Davis.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 258269e767SBrooks Davis.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 268269e767SBrooks Davis.\" SUCH DAMAGE. 278269e767SBrooks Davis.\" 288269e767SBrooks Davis.Dd December 1, 2017 298269e767SBrooks Davis.Dt SYNC 2 308269e767SBrooks Davis.Os 318269e767SBrooks Davis.Sh NAME 328269e767SBrooks Davis.Nm sync 338269e767SBrooks Davis.Nd "schedule file system updates" 348269e767SBrooks Davis.Sh LIBRARY 358269e767SBrooks Davis.Lb libc 368269e767SBrooks Davis.Sh SYNOPSIS 378269e767SBrooks Davis.In unistd.h 388269e767SBrooks Davis.Ft void 398269e767SBrooks Davis.Fn sync void 408269e767SBrooks Davis.Sh DESCRIPTION 418269e767SBrooks DavisThe 428269e767SBrooks Davis.Fn sync 438269e767SBrooks Davissystem call forces a write of dirty (modified) buffers 448269e767SBrooks Davisin the block buffer cache out 458269e767SBrooks Davisto disk. 468269e767SBrooks DavisThe kernel keeps this information in core to reduce 478269e767SBrooks Davisthe number of disk I/O transfers required by the system. 488269e767SBrooks DavisAs information in the cache is lost after a system crash, a 498269e767SBrooks Davis.Fn sync 508269e767SBrooks Davissystem call is issued 518269e767SBrooks Davisfrequently 528269e767SBrooks Davisby the kernel process 538269e767SBrooks Davis.Xr syncer 4 548269e767SBrooks Davis(about every 30 seconds). 558269e767SBrooks Davis.Pp 568269e767SBrooks DavisThe 578269e767SBrooks Davis.Xr fsync 2 588269e767SBrooks Davissystem call 598269e767SBrooks Davismay be used to synchronize individual file descriptor 608269e767SBrooks Davisattributes. 618269e767SBrooks Davis.Sh SEE ALSO 628269e767SBrooks Davis.Xr fsync 2 , 638269e767SBrooks Davis.Xr syncer 4 , 648269e767SBrooks Davis.Xr sync 8 658269e767SBrooks Davis.Sh HISTORY 668269e767SBrooks DavisThe 678269e767SBrooks Davis.Fn sync 688269e767SBrooks Davisfunction appeared in 698269e767SBrooks Davis.At v3 . 708269e767SBrooks Davis.Sh BUGS 718269e767SBrooks DavisThe 728269e767SBrooks Davis.Fn sync 738269e767SBrooks Davissystem call 748269e767SBrooks Davismay return before the buffers are completely flushed. 75