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.\"     @(#)sync.2	8.1 (Berkeley) 6/4/93
.\" %FreeBSD: src/lib/libc/sys/sync.2,v 1.6.2.3 2000/07/20 07:37:41 sheldonh Exp %
.\"
.\" $FreeBSD$
.Dd June 4, 1993
.Dt SYNC 2
.Os BSD 4
.Sh 名称
.Nm sync
.Nd ファイルシステムの更新をスケジュールする
.Sh ライブラリ
.Lb libc
.Sh 書式
.Fd #include <unistd.h>
.Ft void
.Fn sync void
.Sh 解説
.Fn sync
関数は、ブロックバッファキャッシュの修正済み
バッファをディスクに強制的に書き出します。カーネルは
この情報をメモリ上に維持し、システムが要求するディスク I/O
転送の数を減らします。システムのクラッシュ後に
キャッシュの情報が失われると、ユーザプロセス
.Xr syncer 4
が
.Fn sync
を頻繁に呼び出します
(約 30 秒ごと)。
.Pp
それぞれのファイル記述子属性の同期を取るには、関数
.Xr fsync 2
を使用します。
.Sh 関連項目
.Xr fsync 2 ,
.Xr syncer 4 ,
.Xr sync 8
.Sh バグ
.Fn sync
は、バッファが完全にフラッシュされる前に戻る
ことがあります。
.Sh 歴史
.Fn sync
関数呼び出しは、
.At v6
で登場しました。