freebsd-nq/lib/libc/sys/sync.2

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.\"     @(#)sync.2	8.1 (Berkeley) 6/4/93
.\" $FreeBSD$
.\"
.Dd December 1, 2017
.Dt SYNC 2
.Os
.Sh NAME
.Nm sync
.Nd "schedule file system updates"
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In unistd.h
.Ft void
.Fn sync void
.Sh DESCRIPTION
The
.Fn sync
system call forces a write of dirty (modified) buffers
in the block buffer cache out
to disk.
The kernel keeps this information in core to reduce
the number of disk I/O transfers required by the system.
As information in the cache is lost after a system crash, a
.Fn sync
system call is issued
frequently
by the kernel process
.Xr syncer 4
(about every 30 seconds).
.Pp
The
.Xr fsync 2
system call
may be used to synchronize individual file descriptor
attributes.
.Sh SEE ALSO
.Xr fsync 2 ,
.Xr syncer 4 ,
.Xr sync 8
.Sh HISTORY
The
.Fn sync
function appeared in
.At v3 .
.Sh BUGS
The
.Fn sync
system call
may return before the buffers are completely flushed.
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.\" Copyright (c) 1980, 1991, 1993`
			`.\" The Regents of the University of California. All rights reserved.`
			`.\"`
			`.\" Redistribution and use in source and binary forms, with or without`
			`.\" modification, are permitted provided that the following conditions`
			`.\" are met:`
			`.\" 1. Redistributions of source code must retain the above copyright`
			`.\" notice, this list of conditions and the following disclaimer.`
			`.\" 2. Redistributions in binary form must reproduce the above copyright`
			`.\" notice, this list of conditions and the following disclaimer in the`
			`.\" documentation and/or other materials provided with the distribution.`
Renumber copyright clause 4 Renumber cluase 4 to 3, per what everybody else did when BSD granted them permission to remove clause 3. My insistance on keeping the same numbering for legal reasons is too pedantic, so give up on that point. Submitted by: Jan Schaumann <jschauma@stevens.edu> Pull Request: https://github.com/freebsd/freebsd/pull/96 2017-02-28 23:42:47 +00:00			`.\" 3. Neither the name of the University nor the names of its contributors`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.\" may be used to endorse or promote products derived from this software`
			`.\" without specific prior written permission.`
			`.\"`
			.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
			`.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE`
			`.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE`
			`.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE`
			`.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL`
			`.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS`
			`.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)`
			`.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT`
			`.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY`
			`.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF`
			`.\" SUCH DAMAGE.`
			`.\"`
			`.\" @(#)sync.2 8.1 (Berkeley) 6/4/93`
$Id$ -> $FreeBSD$ 1999-08-28 00:22:10 +00:00			`.\" $FreeBSD$`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.\"`
Correct history for Unix 2nd Edition through 6th Edition for the system calls. Man pages are missing for v2 and v5, so any entries for those versions were inferred by new implementations of these functions in libc. Obtained from: http://www.tuhs.org/cgi-bin/utree.pl 2017-12-01 22:48:20 +00:00			`.Dd December 1, 2017`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Dt SYNC 2`
mdoc(7) police: removed HISTORY info from the .Os call. 2001-07-10 13:41:46 +00:00			`.Os`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Sh NAME`
			`.Nm sync`
Uniformly refer to a file system as "file system". Approved by: re 2002-12-12 17:26:04 +00:00			`.Nd "schedule file system updates"`
Introduce ".Lb" macro to libc manpages. More libraries manpages updates following. 2000-04-21 09:42:15 +00:00			`.Sh LIBRARY`
			`.Lb libc`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Sh SYNOPSIS`
mdoc(7) police: Use the new .In macro for #include statements. 2001-10-01 16:09:29 +00:00			`.In unistd.h`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Ft void`
			`.Fn sync void`
			`.Sh DESCRIPTION`
Remove whitespace at EOL. 2001-07-15 07:53:42 +00:00			`The`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Fn sync`
mdoc(7) police: Tidy up the syscall language. Stop calling system calls "function calls". Use "The .Fn system call" a-la "The .Nm utility". When referring to a non-BSD implementation in the HISTORY section, call syscall a function, to be safe. 2002-12-18 09:22:32 +00:00			`system call forces a write of dirty (modified) buffers`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`in the block buffer cache out`
Remove single-space hard sentence breaks. These degrade the quality of the typeset output, tend to make diffs harder to read and provide bad examples for new-comers to mdoc. 2000-03-02 09:14:21 +00:00			`to disk.`
			`The kernel keeps this information in core to reduce`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`the number of disk I/O transfers required by the system.`
mdoc(7) police: Tidy up the syscall language. Stop calling system calls "function calls". Use "The .Fn system call" a-la "The .Nm utility". When referring to a non-BSD implementation in the HISTORY section, call syscall a function, to be safe. 2002-12-18 09:22:32 +00:00			`As information in the cache is lost after a system crash, a`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Fn sync`
mdoc(7) police: Tidy up the syscall language. Stop calling system calls "function calls". Use "The .Fn system call" a-la "The .Nm utility". When referring to a non-BSD implementation in the HISTORY section, call syscall a function, to be safe. 2002-12-18 09:22:32 +00:00			`system call is issued`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`frequently`
syncer(4) is a kernel process, not a user process Noticed by: Geoffrey Thomas <gthomas@mokafive.com> Approved by: hrs (mentor) 2014-02-27 04:06:34 +00:00			`by the kernel process`
Update stale references to update(4) with references to the new syncer(4) manual page. 2000-07-19 07:39:08 +00:00			`.Xr syncer 4`
Remove whitespace at EOL. 2001-07-15 07:53:42 +00:00			`(about every 30 seconds).`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Pp`
mdoc(7) police: Tidy up the syscall language. Stop calling system calls "function calls". Use "The .Fn system call" a-la "The .Nm utility". When referring to a non-BSD implementation in the HISTORY section, call syscall a function, to be safe. 2002-12-18 09:22:32 +00:00			`The`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Xr fsync 2`
mdoc(7) police: Tidy up the syscall language. Stop calling system calls "function calls". Use "The .Fn system call" a-la "The .Nm utility". When referring to a non-BSD implementation in the HISTORY section, call syscall a function, to be safe. 2002-12-18 09:22:32 +00:00			`system call`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`may be used to synchronize individual file descriptor`
			`attributes.`
			`.Sh SEE ALSO`
			`.Xr fsync 2 ,`
Update stale references to update(4) with references to the new syncer(4) manual page. 2000-07-19 07:39:08 +00:00			`.Xr syncer 4 ,`
Added a update(4) man page to describe the kernel initiated update process and changed all of the old references to update(8) to update(4). 1996-02-12 00:45:47 +00:00			`.Xr sync 8`
BSD 4.4 Lite Lib Sources 1994-05-27 05:00:24 +00:00			`.Sh HISTORY`
mdoc(7) police: Tidy up the syscall language. Stop calling system calls "function calls". Use "The .Fn system call" a-la "The .Nm utility". When referring to a non-BSD implementation in the HISTORY section, call syscall a function, to be safe. 2002-12-18 09:22:32 +00:00			`The`
Correctly use .Fn instead of .Nm to reference function names in a bunch of man pages. Use the correct .Bx (BSD UNIX) or .At (AT&T UNIX) macros instead of explicitly specifying the version in the text in a bunch of man pages. 1996-08-22 23:31:07 +00:00			`.Fn sync`
mdoc(7) police: Tidy up the syscall language. Stop calling system calls "function calls". Use "The .Fn system call" a-la "The .Nm utility". When referring to a non-BSD implementation in the HISTORY section, call syscall a function, to be safe. 2002-12-18 09:22:32 +00:00			`function appeared in`
Correct history for Unix 2nd Edition through 6th Edition for the system calls. Man pages are missing for v2 and v5, so any entries for those versions were inferred by new implementations of these functions in libc. Obtained from: http://www.tuhs.org/cgi-bin/utree.pl 2017-12-01 22:48:20 +00:00			`.At v3 .`
Sort sections. 2005-01-20 09:17:07 +00:00			`.Sh BUGS`
			`The`
			`.Fn sync`
			`system call`
			`may return before the buffers are completely flushed.`