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From: dbg@u1100a.UUCP (D B Grooms)
Newsgroups: comp.unix.wizards
Subject: Re: BSD to SysV
Message-ID: <1596@u1100a.UUCP>
Date: Tue, 27-Oct-87 16:29:23 EST
Article-I.D.: u1100a.1596
Posted: Tue Oct 27 16:29:23 1987
Date-Received: Fri, 30-Oct-87 05:20:48 EST
References: <9940@brl-adm.ARPA> <31892@sun.uucp>
Reply-To: dbg@u1100a.UUCP (D B Grooms)
Organization: Bell Communications Research, Piscataway, NJ
Lines: 22

> Has anyone figured out how to perform the BSD functions ``fsync()''
> and ``ftruncate()'' in System V?
>
>>...
>>
>>Unless you're truncating a file to zero length, you can't do "ftruncate()"
>>except by making a copy of the file up to the new length, doing a "creat" or
>>"open" with O_TRUNC to truncate the original file to zero length, and then
>>copying the truncated copy on top of the original file.

For efficiency, it would be better to "mv" the original file to one with a 
new name, "creat" the original file, and copy the desired size from the 
newly named file to the original.  This involves only one copy operation
instead of two.
				Dave Grooms
				Bell Communications Research
				{ihnp4,bellcore,pyuxww}!u1100a!dbg
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