Regex Query Help - Lookbehind

问题

This is somewhat related to: Regular Expression - Formatting text in a block - IM but a different problem.

Looking for -'s wrapping text with the following conditions:

Conditions:

• token can be at start or end of line
• token must be surround by space or one or more symbols: {.,!@#$....}.
  • must not be a normal character [a-zA-Z] surrounding the - pair in question.
  • See Sample test 3 ...w-thank you-
  • Test 4 and 5 succeed because the - is wrapped with [^a-zA-Z]
• token must not be followed by a space on the first - or a space preceding the last -
  • "-Wow -" will not be a match as the closing - was preceded by a space.
  • See Sample test 6 and 7

For the front of the regular expression I would need: (^|[\s\W]+)
and the end would be: ($|[\s\W]+)

I have the current expression, but it is failing due to the escape condition being stop after finding the first -

   (^|[\s\W]+)-([^\s][^-]*)-($|[\s\W]+)

Sample test strings would be:

1. (all.): -Wow-thank you-.
2. (Wow): -Wow- thank you-!
3. (NIL): - Wow-thank you-.
4. (thank you): - Wow!-thank you-
5. (thank you): - Wow -thank you-
6. (all): -Wow - thank you-
7. (NIL): -Wow - thank you -

Does this require look behind? (I'm a regex newbie so please bear with me) Or is my middle condition totally wrong.

Thank you much!
mwolfe.

回答1:

Try a simpler middle expression.

(^|[\s\W]+)-(.*?)-($|[\s\W]+)
             ^^^

The non-greedy wildcard match would capture the minimum string necessary to match the following -($|[\s\W]+).

---

Edit. Okay, I see why that's wrong. You want a non-space character to immediately follow and succeed the opening and closing dashes, respectively. So try this:

(^|[\s\W]+)-(\S.*?\S)-($|[\s\W]+)
             ^^   ^^

来源：https://stackoverflow.com/questions/15288276/regex-query-help-lookbehind