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From: ken@turtlevax.UUCP (Ken Turkowski)
Newsgroups: net.unix-wizards
Subject: Re: truncating a file opened via open()
Message-ID: <786@turtlevax.UUCP>
Date: Mon, 10-Jun-85 19:46:54 EDT
Article-I.D.: turtleva.786
Posted: Mon Jun 10 19:46:54 1985
Date-Received: Tue, 11-Jun-85 08:28:24 EDT
References: <340@cmu-cs-edu1.ARPA>
Reply-To: ken@turtlevax.UUCP (Ken Turkowski)
Organization: CADLINC, Inc. @ Menlo Park, CA
Lines: 20

In article <340@cmu-cs-edu1.ARPA> hua@cmu-cs-edu1.ARPA (Ernest Hua) writes:
>Does anyone have any idea how to truncate a file at the current point in
>writing if it is opened by open()?  I cannot use creat() because the file
>is being used by another process, and I cannot use unlink() it is likely
>that it is linked.  If the updated contents is longer than the original,
>it is not a problem because the file length is just extended.  But if the
>updated contents is shorter, the file does not shrink.  We have 4.1BSD on
>several 780's and 750's.

try

size = lseek(fd, 0L, 1);	/* tell(fd) */
ftruncate(fd, size);		/* int fd, size; */

It's yet another undocumented feature on 4.2.
-- 

Ken Turkowski @ CADLINC, Menlo Park, CA
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