CODEWITHSUNDEEP
phpregexescaping
Joel
Joel

Reputation: 2824

Regex to match possibly-escaped quotes

I'm trying to write a regex to match single quotes, which may be escaped. A matched quote should have an even number of backslashes before it (an odd number means that the quote is escaped). For example, in these five strings:

'quotes should be matched'
\'quotes should NOT be matched\'
\\'quotes should be matched\\'
\\\'quotes should NOT be matched\\\'
\\\\'quotes should be matched\\\\'

Here is the regex that I have:

(?<=[^\\](?:\\\\)*)'

However, this does not match anything in the above example. I find this strange because removing the * from the regex matches the quotes with two backslashes, as it should:

(?<=[^\\](?:\\\\))' matches \\'

Upvotes: 1

Views: 145

Answers (1)

rvalvik
rvalvik

Reputation: 1559

As far as I can see, it's not possible to match just the '. This is because you can't have dynamic length lookbehinds as Wiseguy pointed out.

The following regex would match the correct ' AND any \s leading up to it however. Not sure if this will be of any use..

(?<!\\)(?:\\\\)*'

Matches an arbitrary number of double \s not preceded by a \ and followed by a '.

Upvotes: 3

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