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.

My current regex for this is "\^.*"

The problem with that is that it does not match characters as planned ... but for one match it does work. The string that make it not work is ^@jj (basically anything that has ^ ... ).

What would be the best way to not match any characters now ? I was thinking of removing the \  but only doing this will transform the "not" into a "start with" ...

Answer 1

Have you tried this simple regex? [^.]*

Answer 2

The ^ character doesn't mean "not" except inside a character class ([]). If you want to not match anything, you could use a negative lookahead that matches anything: (?!.*).

Answer 3

You want to match nothing at all? Neg lookarounds seems obvious, but can be slow, perhaps ^$ (matches empty string only) as an alternative?

Answer 4

^ is only not when it's in class (such as [^a-z] meaning anything but a-z). You've turned it into a literal ^ with the backslash.

What you're trying to do is [^]*, but that's not legal. You could try something like

" {10000}"

which would match exactly 10,000 spaces, if that's longer than your maximum input, it should never be matched.

Answer 5

Instead of trying to not match any characters, why not just match all characters? ^.*$ should do the trick. If you have to not match any characters then try ^\j$ (Assuming of course, that your regular expression engine will not throw an error when you provide it an invalid character class. If it does, try ^()$. A quick test with RegexBuddy suggests that this might work.

Answer 6

What about no regex (empty string)?

Answer 7

A simple and cheap regex that will never match anything is to match against something that is simply unmatchable, for example: \b\B.

It's simply impossible for this regex to match, since it's a contradiction.

References

• regular-expressions.info\Word Boundaries
  • \B is the negated version of \b. \B matches at every position where \b does not.

Answer 8

Eh I know this is a little late, but you could simply not read any input if the regex is empty