Question

I’m trying to parse a string with regex. I need to get the first part before a clean &. A clean & does not have + right before or after it.

Clean &:

• 47&78
• a+bc&gsd+f

Not Clean &:

• fA+&71
• nap&+sys

For Matisse+&+Sadko&sendtemp=1 the regex should return Matisse+&+Sadko.

I’ve tried to do it that way, but I it doesn’t work:

.*(?!\+)&(?!\+).*

Thanks.

Answer 1

The (?!...) is a (negative) lookahead expression, it checks whether the next characters do (not) match. So, you would need to add that one character to your regex, because the & is never a +:

(?!\+).&(?!\+)

But that would need at least one character before the &. Better use (negative) lookbehind:

(?<!\+)&(?!\+)

Read more on Regex Lookaround.

If your & is never at the string beginning or end, you could also just use a negated character class:

.*[^+]&[^+].*

…or, if it could, let that be optional:

^(?:.*[^+])?&(?:[^+].*)?$