From owner-freebsd-questions  Wed Feb 26 14:20:57 2003
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Date: Thu, 27 Feb 2003 00:20:09 +0200
From: Giorgos Keramidas <keramida@ceid.upatras.gr>
To: Tijl Coosemans <tijl@ulyssis.org>
Cc: freebsd-questions@FreeBSD.ORG
Subject: Re: cat
Message-ID: <20030226222009.GB78804@gothmog.gr>
References: <20030226175613.5e61f45e.tijl@ulyssis.org>
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On 2003-02-26 17:56, Tijl Coosemans <tijl@ulyssis.org> wrote:
> I want to remove CRs from text files so what I did is this:
>
> cat filename | tr -d '\r' > filename
>
> However, I often end up with an empty file. Just out of
> interest, somebody who knows why that is?

The shell opens filename for input and then attempts to reopen it once
more for output, at the same time.  The '>' operator truncates the
file.  You will get much better and more predictable results if you
use a temporary file to store the intermediate result of tr(1):

	$ tr -d '\r' < filename > filename.tmp
	$ mv filename.tmp filename

- Giorgos

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