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Asked: 2026-06-17T17:05:37+00:00

I’m working with a piece of code that applies a regex to a string

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I’m working with a piece of code that applies a regex to a string and returns the first match. I don’t have access to modify the code to return all matches, nor do I have the ability to implement alternative code.

I have the following example target string:

usera,userb,,userc,,userd,usere,userf,

This is a list of comma delimited usernames joined from multiple sources, some of which were blank resulting in two commas in some places. I’m trying to write a regex that will return all of the comma delimited usernames except for specific values.

For example, consider the following expression:

[^,]\w{1,},(?<!(userb|userc|userd),)

This results in three matches:

usera,

usere,

userf,

Is there any way to get these results as a single match, instead of a match collection, e.g. a single match having the text ‘usera,usere,userf,’ ?

If I could write code in any language this would be trivial, but I’m limited to input of only the target string and the pattern, and I need a single match that has all items except for the ones I’m omitting. I’m not sure if this is even possible, everything I’ve ever done with regex’s involves processing multiple items in a match collection.

Here is an example in Regex Coach. This image shows that there are the three matches I want, but my requirement is to have the text in a single match, not three separate matches.

enter image description here

EDIT1:
To clarify this ticket is specifically intended to solve the use case using only regular expression syntax. Solving this problem in code is trivial but solving it using only a regex was the requirement given the fact that the executing code is part of a 3rd party product that I didn’t want to reverse engineer, wrap, or replace.

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1 Answer

  1. Editorial Team

    Is there any way to get these results as a single match, instead of a match collection, e.g. a single match having the text 'usera,usere,userf,'?

    No. Regex matches are consecutive.

    A regular expression matches a (sub)string from start to finish. You cannot drop the middle part, this is not how regex engines work. But you can apply the expression again to find another matching substring (incremental search – that’s what Regex Coach does). This would result in a match collection.

    That being said, you could also just match everything you don’t want to keep and remove it, e.g.

    ,(?=[\s,]+)|(userb|userc|userd)[\s,]*

    http://rubular.com/r/LOKOg6IeBa

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