Regex to *not* match any characters

Question

I know it is quite some weird goal here but for a quick and dirty fix for one of our system we do need to not filter any input and let the corruption go into the system.

Answer 1

Empty regex

The best regex to never match anything is an empty regex. But I'm not sure all regex engine will accept that.

Impossible regex

The other solution is to create an impossible regex. I found that $-^ only takes two steps to compute regardless of the size of your text (https://regex101.com/r/yjcs1Z/1).

For reference:

• $^ and $. take 36 steps to compute -> O(1)
• \b\B takes 1507 steps on my sample and increase with the number of character in your string -> O(n)