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542Re: [NTS] Can a Reg Exp handle 123 AND not a|b|c followed by x?

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  • flo.gehrke
    May 10, 2012
      --- In ntb-scripts@yahoogroups.com, "John Shotsky" <jshotsky@...> wrote:
      > I am not understanding something here – The criteria was:
      > three characters that are *NOT* MON|TUE|WED|THU|FRI|SAT|SUN
      > How is this avoiding those strings? I've wanted to do this text
      > that didn't contain a certain string on multiple occasions.


      The second part of that RegEx...


      matches an opening and a closing literal bracket '(...)' embracing three digits '.{3}' that are NOT 'Mon', 'Tue' etc, as Joy demanded.

      The 3-digit-days are excluded with a Negative Lookahead. Since a Lookahead doesn't consume any character, any different 3-digit-string will match at the same position between the opening and the closing bracket. That's why, for example,..

      'John' is matched with '(?!Mary)John'

      that is: Find 'John' at a position where you don't see 'Mary' when looking ahead.

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