Path: utzoo!attcan!uunet!tut.cis.ohio-state.edu!mailrus!uflorida!haven!adm!smoke!gwyn
From: gwyn@smoke.BRL.MIL (Doug Gwyn)
Newsgroups: comp.unix.questions
Subject: Re: Set file size in SYSV
Message-ID: <10723@smoke.BRL.MIL>
Date: 13 Aug 89 00:14:32 GMT
References: <708@msa3b.UUCP>
Reply-To: gwyn@brl.arpa (Doug Gwyn)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 11

In article <708@msa3b.UUCP> kevin@msa3b.UUCP (Kevin P. Kleinfelter) writes:
>O.K. I give up.  How do you set the size of a file in SYSV.
>In particular, I want to take a file which is 1000 bytes, and truncate
>it to 500 bytes WITHOUT COPYING IT.

Not possible in UNIX System V through SVR3.2, probably supported in SVR4.0.

You can simulate this operation by snarfing the intended ultimate file
contents somewhere safe (like an in-memory array, if it will fit, or
a temp file), then use creat() to truncate the file to 0 length, then
write back the desired final contents.