Le 20/05/2018 à 18h03, Paul Eggert a écrit :
> Garreau, Alexandre wrote:
>> I believe context options used in conjonction with invert-match option
>> should specify which lines*not to show*  along with matched then not
>> shown lines.
>
> I can see it the other way. For example, "show all lines that lack
> signed integers, plus their context" can be done via a command like
> "grep -C1 -v -E 
> '[-+][0-9]+([^.e]|$)'", and I don't see any easy way to do the same
> search under the changes you're proposing.

Oh in fact, I didn’t notice it actually had this effect… in fact when
only a few lines don’t match, especially when they’re not contiguous,
using -v with context options nearly equals not using grep at all… turns
out I narrowed enough my mind to miss this.

> In essence you're proposing a new feature that I'd call "negative
> context"; i.e., if a line is not selected, then suppress the output of
> nearby lines that are selected. grep already has a lot of features and
> it's not clear this one is important enough to add.

My memory is bad, but grepping at looking at my history for when I made
up this example says me I needed this feature for something like this: