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From: uh@pcsbst.UUCP (Michael Uhlenberg)
Newsgroups: net.unix-wizards
Subject: Undocumented feature in Sys5: synchronous write
Message-ID: <267@pcsbst.UUCP>
Date: Tue, 8-May-84 09:47:48 EDT
Article-I.D.: pcsbst.267
Posted: Tue May  8 09:47:48 1984
Date-Received: Fri, 11-May-84 00:17:31 EDT
Organization: PCS Munich Germany
Lines: 15


Normally, writes to normal files are cached in the buffer pool and
written out to disk with some delay.
Some database people asked me to introduce a "write-through" system
call, i.e. a write that writes data immediately to disk, thus avoiding
disk consistency problems after a system crash. Looking at the Sys5 code,
I found that the code for doing this is already there: in <sys/file.h>
you have
	#define FSYNC   00020
but an appropriate define
	#define O_SYNC  00020
is missing from <fcntl.h> and also the docu doesn't mention it.
However, you can or 020 to your open mode, and get the desired effect.
-- 
Michael "Es gibt ein neues Uuuuunix" Uhlenberg