Subject: Re: bug#26576: -v when used with -C

From: Assaf Gordon <[email-masked]>
Date: Fri, 21 Apr 2017 15:34:57 +0000

On Thu, Apr 20, 2017 at 02:34:47PM -0500, Eric Blake wrote:
>On 04/20/2017 11:51 AM, Assaf Gordon wrote:
>
>> If I may suggest the following sed program:
>>
>>  $ sed -n ':x 1,2{N;bx} ; /UGLY/{ N;N;z;bx }; /./P;N;D' file
>
>Works as long as lines 1 and 2 do not contain UGLY. But misbehaves if
>UGLY appears early:
[...]
>Also misbehaves if two occurrences of UGLY appear with overlapping context:
>
[...]
>May be fixable with even more magic, perhaps by using the hold buffer to
>track the status of the last three lines, and suppressing output if any
>of the last three inputs were UGLY.  But more complicated than I want to
>spend time on for the sake of this email.
>

Good catch, thanks for pointing this out.

Indeed, that was an ad-hoc script, suitible for some limited scenarios
but not robust as a general solution.

-assaf