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Questions tagged [negative-lookbehind]

In regular expressions, negative lookbehind checks if the character before the current character does NOT match a certain character.

In regular expressions, negative lookbehind checks if the character before the current character does NOT match a certain character. For example, (?<!a)b matches a "b" that is not preceded by an "a", using the negative lookbehind.

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Negative lookbehind equivalent in JavaScript

Is there a way to achieve the equivalent of a negative lookbehind in JavaScript regular expressions? I need to match a string that does not start with a specific set of characters. It seems I am unable to find a regex that does this without failing…
Andrew Ensley
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Regex Negative Lookbehind works in PCRE but not in Python

The pattern (?
Matt Elson
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Regular expression using negative lookbehind not working in Notepad++

I have a source file with literally hundreds of occurrences of strings flecha.jpg and flecha1.jpg, but I need to find occurrences of any other .jpg image (i.e. casa.jpg, moto.jpg, whatever) I have tried using a regular expression with negative…
DiegoDD
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How to use Negative Lookahead in Regex to Delete unwanted Lines

I need help regarding using negative lookahead. I am using Notepad++ and I want to delete all lines except the lines that contain (.*) I tried a couple of things but that didnt work. ^.*(?!).* ^.*(?!.*)
Atif
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What's the easiest way to get an equivalent to GNU grep that supports negative lookbehinds?

I'm trying to grep through a bunch of files in nested subdirectories to look for regular expression matches; my regex requires negative lookbehind. Perl has negative lookbehind, but as far as I can tell GNU grep doesn't support negative…
Dan Fabulich
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Lookbehind in regex for VBA?

Is there a way to do negative and positive lookbehind in VBA regex? I want to not match if the string starts with "A", so I am currently doing ^A at the start of the pattern, then removing the first character of match(0). Obviously not the best…
Rich Tier
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Regular Expression in R with a negative lookbehind

So I have the following data, let's say called "my_data": Storm.Type TYPHOON SEVERE STORM TROPICAL STORM SNOWSTORM AND HIGH WINDS What I want is to classify whether or not each element in my_data$Storm.Type is a storm, BUT I don't want to include…
Jonathan Charlton
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RegEx: Look-behind to avoid odd number of consecutive backslashes

I have user input where some tags are allowed inside square brackets. I've already wrote the regex pattern to find and validate what's inside the brackets. In user input field opening-bracket could ([) be escaped with backslash, also backslash could…
Wh1T3h4Ck5
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Regex negative lookbehind and lookahead: equivalence and performance

I need a regex that will select only those URL strings NOT ending with specific extensions like .png or .css. I tested the following: 1) this one using negative lookbehind: (?
Timido
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Javascript regex: find a word NOT followed by space character

I need javascript regex that will match words that are NOT followed by space character and has @ before, like this: @bug - finds "@bug", because no space afer it @bug and me - finds nothing because there is space after "@bug" @bug and @another …
Zeljko
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Java regex error - Look-behind with group reference

I'm trying to build a regex that matches exactly two occurrences of a char in a class. This is the regex I made: (?
user2402372
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Regex negative lookbehind in Ruby doesn't seem to work

Making an argument parser. I want to split a string into an array where the delimiter is ", " except when preceded by "|". That means string "foo, ba|, r, arg" should result in `["foo", "ba|, r", "arg"]` I'm trying to use this regex: (?
tybro0103
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Are negative lookbehind in regex searches possible in Geany?

Geany's documentation on negative assertions makes it look like they're possible. For reference, this works and gives me results: pcregrep -r "(?
Denys Séguret
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php regex: Alternative to backreference in negative lookbehind

I want to find instances where a captured group does not appear later in the string: aaaBbb = CccBbb <- format is valid, skip aaaDddd = CccDddd <- format is valid, skip aaaEeee = CccFfff <- format is not valid, match this one only So this matches…
Redzarf
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Regex - Match words in pattern, except within email address

I'm looking to find words in a string that match a specific pattern. Problem is, if the words are part of an email address, they should be ignored. To simplify, the pattern of the "proper words" \w+\.\w+ - one or more characters, an actual period,…
alon
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