Is there a minor mode to highlight regular expressions in a buffer?

Example of desired behavior: #!/bin/sh sed 's/^[1-9]*\.\s(.*)$/\1/g' file.txt Where the `[1-9]` is one color, the `(.*)` is another color, and the `\1` is the same color. Or something similar. Web searches seem to inevitably assume we're talking about _finding matches_ for the regex. Is this a thing, or am I crazy for even wanting it? EDIT: Apparently I am. Thanks for the suggestions anyway, folks.

M-s h r `highlight-regexp` You will write a regular expression to highlight regular expressions. :-)

> Is this a thing I don't think so. > am I crazy for even wanting it? Maybe :) Is this just for `sed` commands in shell scripts? If not, what is it for (specifically), and what is your method for identifying regular expressions in each case? (Your example is already complicated -- you want Emacs, while editing a shell script, to recognise that part of the shell script represents (in shell syntax) a sed script, and then to know how to add syntax highlighting (for the sed dialect of regular expressions) to the portion of that shell-escaped sed-script string which happens to be a regexp.)

Beside highlight-regexp mentioned by /u/KonpakuYoumu there is also a package "symbol overlay" that can highlight symbols: https://github.com/wolray/symbol-overlay. It doesn't use font-lock, but overlay-put, so it coexists with normal font locking. I use it for a subfeature: moving from symbol to an identical named symbols, even when I don't have eglot on. This is an excerpt from my keyboard mapping: "M-<up>" #'symbol-overlay-jump-prev "M-<down>" #'symbol-overlay-jump-next

I set the `hi-lock-file-patterns` to highlight different strings with different colors in a file by setting that as file local variable or in a .dir-locals.el. I set that variable as safe [in my emacs config][1] so that I don't get the "is it safe?" prompt each time I tweak the regexp for highlighting. --- Seems like you are trying to highlight regexp strings in a file. So it might be a tough one to robustly write a regexp that correctly highlights the regexp groups consistently. [1]: https://github.com/kaushalmodi/.emacs.d/blob/c643684ad675753c69df602d7298241d05173255/setup-files/setup-highlight.el#L47-L49

It's not exactly what you're asking for, but you could create an indirect buffer (`clone-indirect-buffer`, `C-x 4 c` by default), narrow it to the regexp, and then switch to a mode for editing regex.

> Is this just for `sed` commands in shell scripts? Ideally no. The idea is it would be possible to enable for any `prog-mode` buffer or anything. I use regular expressions a lot for sh scripts, interactively, and for tweaking the editor. Sadly, Emacs seems to just put anything in "quotes" as `font-lock-string-face` which is boring. It's not a big deal. It would just be nice to see a little more contextual color in the buffer. I was asking here because Google and co. absolutely refuse to interpret the question correctly.

I am not sure that this is what Mitchell means. What he seems to be looking for is a semantic highlighting that would highlight matching groups of regular expression _itself_, not a match of said expression.

I'd be honestly surprised if anything out there does this. The highlighter has to not only parse multiple different regexp dialects and multiple different programming languages, but also understand *how* the code will be executed (e.g. *this* shell string (or sub-string) winds up being used in sed code as a sed regexp, *this* shell string winds up being used in perl code as a perl regexp. It's a huge woolly task involving lots of static analysis of multiple languages simultaneously, and I doubt that the benefits would justify the effort.

symbol-overlay: great find !