RegExp for matching three letters, but not text "BUY"

Question

I have two buttons on form, one of the buttons contain currency code (EUR, USD, GBP,CHF,..) and another one - trade direction (BUY or SELL). And some utility recognize buttons by it's text. To recognize button with currencies, I use Regular expression ":[A-Z]{3}", but it don't work properly when second button contain text "BUY" (regex description returns more than one object).

Question: how can I write pattern for Regular expression, which means: match only when text contain three upper letters, but not text "BUY"?

Thanks!

You can also try to just match the content of the first button only. That way you don't care if some third button `YAY` or `NAY` is added. — polygenelubricants, Jul 08 '10 at 11:04

score 72 · Accepted Answer · edited May 23 '17 at 11:46

72

^(?!BUY)[A-Z]{3}$

(?!BUY) is negative lookahead that would fail if it matches the regex BUY

edited May 23 '17 at 11:46

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answered Jul 07 '10 at 13:04

Amarghosh

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score 16 · Answer 2 · answered Jul 07 '10 at 13:04

16

You can use a negative look-behind assertion to verify that the text just matched does not equal BUY.

[A-Z]{3}(?<!BUY)

answered Jul 07 '10 at 13:04

Daniel Brückner

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the look ahead version is more widely supported in different regex implementations, and has better performance (I think). – Jens Jul 07 '10 at 13:16
this worked for me in a (simulation) of java8 regex, while the accepted answer didn't – ycomp Nov 05 '17 at 05:19

RegExp for matching three letters, but not text "BUY"

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