How do I regex split with variable values?

Question

I have the following string:

21>Please be specific. What do you mean by that?21>Hello are you there623>Simon?

I want to split it into:

21>Please be specific. What do you mean by that?
21>Hello are you there
623>Simon?

Basically the splitter is the numeric value (21 and 623 in this case) followed by the >.

My implementation is that I find the > char, then walk back until I find a non-numeric value.

So basically using sub-string and the like. But it's ugly and I am certain there is a better Regex implementation, but I don't know enough about it.

So can Regex be used here?

Maybe something like \d{1,3}>? Or maybe even \d+>? First one would look for 1 to 3 digits followed by >, and the second would look for one or more digits followed by >. — Tim
– Tim, Commented Apr 7, 2016 at 17:22

Community · Accepted Answer · 2020-06-20 09:12:55Z

5

You can achieve that with look ahead and look behind, so that your match is the zero length area between what you want to split.

string s = "21>Please be specific. What do you mean by that?21>Hello are you there623>Simon?";
Regex reg = new Regex(@"(?<=\D)(?=\d+>)");
var r = reg.Split(s);
foreach(var i in r)
    Console.WriteLine(i);

Will output

21>Please be specific. What do you mean by that?

21>Hello are you there

623>Simon?

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Apr 7, 2016 at 17:28

juharr

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1 Comment

juharr Over a year ago

@noob Yep, and I think our answers complement each other.

user2705585 · Accepted Answer · 2016-04-07 17:28:27Z

3

Try with following regex. It matches the zero width between something and number>

Regex: (?<=\D)(?=\d+>) replaced with \n for demo.

Explanation:

(?<=\D) looks behind to see if it's not a number.
(?=\d+>) looks ahead to see if it's a number>.

And matched the zer0-width between them.

Regex101 Demo

answered Apr 7, 2016 at 17:28

user2705585

Comments

Laurel · Accepted Answer · 2016-04-07 17:32:00Z

0

Try: [0-9]+>

Explanation:

[0-9]+ At least 1 digit
> followed by >

It might make sense to replace the matches with \n$0, which will move them to individual lines.

edited Apr 7, 2016 at 17:32

answered Apr 7, 2016 at 17:22

Laurel

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3 Comments

Tim Over a year ago

Wouldn't \d+> be equivalent?

juharr Over a year ago

If you use that with Regex.Split it's going to remove the matches. I think the OP's asking how to keep the matches.

Laurel Over a year ago

@Tim \d includes any unicode digit, and will be slower. It's better to use [0-9] unless you need to find Persian digits or something.

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