Re: Regex negative word

/^(?!cat)\s+dog/

This is called "A zero-width negative lookahead assertion." ... See why so many people like Perl for obfuscation :)

--
-- GhodMode

Blessed is he who has found his work; let him ask no other blessedness.
-- Thomas Carlyle

Comment on Re: Regex negative word Download Code

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Re^2: Regex negative word by Roy Johnson (Monsignor) on Mar 30, 2006 at 14:07 UTC
Note that your example is not entirely sensible, though. The expression you give must begin with whitespace, so of course it doesn't begin cat. You have to remember that the lookahead is zero-width, so after it, you're in the same position in the string as before it. Perhaps something like `/^(?!cat).\sdog/` [download] as the most general case to consume the non-cat, before-the-dog portion of the string. Caution:* Contents may have been coded under pressure.	[reply] [d/l]
Re^3: Regex negative word by GhodMode (Pilgrim) on Mar 30, 2006 at 15:42 UTC
You are absolutely right! But, rereading the question, the whitespace and the `dog` aren't necessary, either. zer just asked for a regex that matches a string which does not begin with `cat`. So, I think `/^(?!cat)/` should do it. That would match any line with a beginning which is not followed by a cat, right? -- -- GhodMode Blessed is he who has found his work; let him ask no other blessedness. -- Thomas Carlyle	[reply]
Re^4: Regex negative word by GhodMode (Pilgrim) on Mar 30, 2006 at 15:48 UTC
Incidentally, due to my only skimming the replies, I've wasted everyone's time. My apologies to GrandFather who gave the correct answer first. -- -- GhodMode Blessed is he who has found his work; let him ask no other blessedness. -- Thomas Carlyle	[reply]