Regex for numbers after a certain string part

Question

I'm trying to extract numbers inside an URL with regex.

Example Input: http://localhost:23089/generic-url-segment-c?p=5

Expected Output : 5

Example Input: http://localhost:23089/generic-url-segment-c?p=12&sort=5

Expected Output: 12

First I tried to look for the numbers with a mixture of string.replace,string.indexof and substring but thought Regex would be easier.

So far I tried using ((p=)?=.) but can't get the 5 only.

And also as shown in second example, this value might be a two digit value or there even might be other parameters after it. So maybe a search between p= and & is necessary but I don't know how Regex behaves in absence of parameters.

If you have linked to System.Web it might be more reliable to use the following: HttpUtility.ParseQueryString(new Uri("your url here").Query)["p"] — Martin Brown
– Martin Brown, Commented Aug 21, 2017 at 16:29

Wiktor Stribiżew · Accepted Answer · 2018-10-10 11:10:16Z

3

Try the below pattern. The plus matches 1 or more so you can get 1 or more digits -

 p=(\d+)

The brackets are a group so to get the value of the match within the group use

match.Groups[1].Value

edited Oct 10, 2018 at 11:10

Wiktor Stribiżew

631k41 gold badges502 silver badges632 bronze badges

answered Aug 21, 2017 at 15:24

David Lindon

3653 silver badges10 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

David Lindon Over a year ago

What language are you using? Look at the 'group' under match info on regex101, you will see only the 5 is matched

user8478480 Over a year ago

@EgeBayrak You need to match group 1 rather than the full match.

Ege Bayrak Over a year ago

Ok I managed to get 5 by using match.Groups[Index].Value, if you can modift your answer to include this I can accept it as correct answer

Toto Over a year ago

@EgeBayrak: Be aware that regex matches 5 in group=5 or anythingThatEndWith_p=5

Toto · Accepted Answer · 2017-08-21 16:20:40Z

2

You could use lookbehind:

(?<=\bp=)\d+

or

(?<=[?&]p=)\d+

Usage:

Regex.Match(str, @"(?<=[?&]p=)\d+").Value;

edited Aug 21, 2017 at 16:20

answered Aug 21, 2017 at 15:42

Toto

91.7k63 gold badges97 silver badges135 bronze badges

2 Comments

shA.t Over a year ago

Or (?<=\b\?p=)\d+ to be more specific => C# usage: Regex.Match(str, @"(?<=\b\?p=)\d+").Value; ;).

Toto Over a year ago

@shA.t: Thanks edited, 've added the possibility of &

Collectives™ on Stack Overflow

Regex for numbers after a certain string part

2 Answers 2

4 Comments

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

4 Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related