bug#26576: -v when used with -C

[Assaf Gordon]

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