Re: Shortening an IFS file

Tim,

Thanks. ftruncate is what I was looking for. I didn't find it by my
obviously lame search of the Infoma... uh, Knowledge center. (It's right
there under the category of IFS APIs. Searching for truncate or even trunc
finds it.)

Thanks again,
Michael



From: Tim Bronski <tim.bronski@xxxxxxxxx>
To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx>
Date: 03/12/2015 12:07 PM
Subject: Re: Shortening an IFS file
Sent by: "MIDRANGE-L" <midrange-l-bounces@xxxxxxxxxxxx>



If you open the file with O_TRUNC then the data will be cleared and the
size will be set to 0.
If you want to read in the data, change it and write back a different
size then open the file for O_RDWR, read your data, write your new data
back where you want it and then use ftruncate(fd, newsize); with the new
length and then close. Is that what you're looking to do?

Tim

On 3/12/2015 4:19 PM, MichaelQuigley@xxxxxxxxxx wrote:

So do you open the file without o_Trunc, read the data in, close the

file,

open it with o_Trunc, process the data already read, and write the
modified data back out? When the file is opened with o_Trunc, it wipes

out

the existing data before it can be read. (Unless I've done something

wrong

or simply don't understand.)

"MIDRANGE-L" <midrange-l-bounces@xxxxxxxxxxxx> wrote on 03/12/2015
10:14:08 AM:

From: Tim Brown <tim.bronski@xxxxxxxxx>
To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx>
Date: 03/12/2015 10:14 AM
Subject: Re: Shortening an IFS file
Sent by: "MIDRANGE-L" <midrange-l-bounces@xxxxxxxxxxxx>

I might have read your email too quickly. If you want to clear the

contents

of a file before writing back to it then use the open option i

suggested.

If you want to keep the contents up to a particular size then use

ftruncate.

On Mar 12, 2015 2:40 PM, "Tim Bronski" <tim.bronski@xxxxxxxxx> wrote:

If you're using open() then you should have O_TRUNC or'ed as a flag.

On 3/12/2015 2:32 PM, MichaelQuigley@xxxxxxxxxx wrote:

I'm writing a utility to remove some filler data from an IFS file.

I'm

using the The utility works great except that when I write the data

back

to the IFS, there is original data past where I want the new EOF to

be. I

can't for the life of me figure out how to shorten the file and set a

new

(shorter) end of file.

Any help would be greatly appreciated.

Thanks,
Michael Quigley
Computer Services
The Way International
www.TheWay.org

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