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Re: minor 'cat' enhancement w/ patch

From: Tom Warzeka
Subject: Re: minor 'cat' enhancement w/ patch
Date: Tue, 12 Feb 2013 00:08:03 -0500
User-agent: Mozilla/5.0 (X11; Linux i686; rv:18.0) Gecko/20100101 Firefox/18.0 SeaMonkey/2.15.1

I didn't mean to imply that any other character would generally be better than '$'. I just thought there might be some utility in specifying the end character within 'cat' for whatever purpose a user might have, and I happen to use it with 'sed' for trailing white space detection. However, I understand your rationale for not including this patch. Thanks for the 'grep' tips, though!

-- Tom

On 02/11/2013 10:57 AM, Pádraig Brady wrote:
On 02/11/2013 03:29 PM, Pádraig Brady wrote:
On 02/11/2013 02:56 AM, Tom Warzeka wrote:
Hello!  I sometimes use 'cat -E' as a quick check for lines with trailing
white space.  I understand that '$' was chosen as the end-of-line
character due to its usage in regular expressions.  However, I like to
use a more conspicuous character, such as '@'.  So, I thought, how about
letting the user specify the end-of-line character?  While doable with
'sed', it was quite easy to add an option to accomplish this.  My
proposed new syntax is:

cat -E -c @ ...


cat --show-ends --end-char=@ ...

It is minimally intrusive and does not affect backward compatibility:
when one of the new options is not specified, the end-of-line character
is still '$'.  Alternatively, use of one of these options could
automatically turn-on displaying an end-of-line character
(just add "show_ends = true;" within the new case).

Here's my patch submitted for your perusal.  It is applied to
coreutils-8.20, the current latest stable release.  If you decide to
include it, feel free to make any changes you see fit.  Thanks!

-- Tom

Why is @ (or any char) better than $ ?
If you wanted to highlight stuff you'd be better with grep or sed:

cat -E < the/file | GREP_COLOR='30;41' grep --color '[[:space:]]*\$$'

I don't think there is enough benefit for including this change.

BTW if you're only interested in looking at trailing whitespace,
then the trailing $, and thus `cat` is redundant anyway:

# Show all lines with trailing whitespace highlighted
$ GREP_COLOR='41' grep --color '[[:blank:]]*$'

# Show lines with trailing whitespace highlighted
$ GREP_COLOR='41' grep --color '[[:blank:]]\+$'


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