> I believe there are actually several different issues here, Yes. - I agree.
> perhaps it's worth stating them explicitly to ensure we're > on the same page. I thank you for your very detailed answer. > Grep's default coloring is red text and default background. This setting can be fine in several use cases. > But TAB (and space) are empty characters - they do not have text. I know this detail also. > Because the default background color is not changed, Can this display detail be adjusted anyhow (like it is provided by the tool “ack” by default)? > you will not see them highlighted with a color. This can trigger questionable interpretations of the involved software behaviour. > This is an unexpected "gotcha" - some terminal programs > do NOT color tab characters at all! I am curious if such a situation should become better known. > they just move the cursor, Indentation is performed then at least. > while others print multiple spaces which are colored. This would be nice if you could actually see a different colour. > You might see different results on your terminal This can happen because of variations in involved programming interfaces and supported display capabilities. > - which means "grep" is not the problem at all here. There are additional constraints to consider. > You asked about replacing non-printable characters. > This is easy enough to do with existing programs, Do you know any approach which provides a complete replacement for an usable visual representation already? > so not likely to be added as a new option to grep. The match colouring evolved. So I imagine that a corresponding character replacement could be performed by a companion tool (similar to your command examples). > Hope this helps, I am also curious on how the application knowledge will evolve further for regular expressions in recent software versions. Patch code filtering might become safer and easier. Regards, Markus