From:	kagel AT quasar DOT bloomberg DOT com
Date:	Thu, 13 Feb 1997 12:36:05 -0500
Message-Id:	<9702131736.AA04929@quasar.bloomberg.com >
To:	cat AT sun4 DOT iol DOT unh DOT edu
Cc:	djgpp AT delorie DOT com
In-Reply-To:	<Pine.SUN.3.91.970210121009.24187A-100000@sun4.iol.unh.edu> (cat@sun4.iol.unh.edu)
Subject:	Re: I'd like to truncate a file but I don't know how
Reply-To:	kagel AT dg1 DOT bloomberg DOT com

   From: "Chris A. Triebel" <cat AT sun4 DOT iol DOT unh DOT edu>
   Newsgroups: comp.os.msdos.djgpp
   Date: Mon, 10 Feb 1997 12:13:05 -0500

   On 10 Feb 1997, Ian Miller wrote:

   > Date: 10 FEB 1997 14:02:19 +0000 
   > From: Ian Miller <itmiller AT dra DOT hmg DOT gb>
   > Newgroups: comp.os.msdos.djgpp
   > Subject: I'd like to truncate a file but I don't know how 
   > 
   > I'd like to say "truncate this file here" in one of my programs.
   > 
   > Can I/how do I do this with standard C/C++?
   > Can I/how do I do this with non-standard features of DJGPP C/C++?
   > 
   > At the moment, if I delete a word from a file (a dictionary file
   > as it happens) and shift everything down to reclaim the space,
   > I'm left with a load of spare space at the end that I can't get
   > rid of.
   > 
   > TIA,
   > -- 
   > Ian Miller, Dorset, UK
   > DJGPP 2.01, Win95 DOS box (LFN undefined, FNCASE=y)
   > 


   I don't know if this is a viable option for you, but what about importing 
   the entire file into memory, making changes, edits, and accesses from 
   local memory rather than from the file itself.  Then you can close the 
   file, open it with O_WRITE|O_TRUNC ( I think ) to purge the file and 
   write your new information out.  Of course that removes the possibility 
   of making a backup which you might want to do.

   cat

I believe that DJGPP includes the UNIX ftruncate() function which
truncates/expands an open file descriptor to a given length.  If the length is
longer than the actual file the file is extended with binary zeros and if
length is less than the current size of the file the file is truncated.  

-- 
Art S. Kagel, kagel AT quasar DOT bloomberg DOT com

A proverb is no proverb to you 'till life has illustrated it.  -- John Keats

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