c# regex - matching optionals after a named group

Question

I'm sure this has been quite numerous times but though i've checked all similar questions, i couldn't come up with a solution.

The problem is that i've an input urls similar to;

I want to match the slug part of it (in above examples, it's peacefuljay).

Regex i've tried so far are;

 http://.*\.justin\.tv/(?<Slug>.*)(?:#.)?
 http://.*\.justin\.tv/(?<Slug>.*)(?:#.)

But i can't come with a solution. Either it fails in the first url or in others.

Help appreciated.

Kobi · Accepted Answer · 2011-03-21 09:51:51Z

3

The easiest way of parsing a Uri is by using the Uri class:

string justin = "http://www.justin.tv/peacefuljay#/w/778713616/3";
Uri uri = new Uri(justin);
string s1 = uri.LocalPath; // "/peacefuljay"
string s2 = uri.Segments[1]; // "peacefuljay"

If you insisnt on a regex, you can try someting a bit more specific:

Match mate = Regex.Match(str, @"http://(\w+\.)*justin\.tv(?:/(?<Slug>[^#]*))?");

(\w+\.)* - Ensures you match the domain, not anywhere else in the string (eg, hash or query string).
(?:/(?<Slug>[^#]*))? - Optional group with the string you need. [^#] limits the characters you expect to see in your slug, so it should eliminate the need of the extra group after it.

edited Mar 21, 2011 at 9:51

answered Mar 21, 2011 at 9:39

Kobi

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3 Comments

HuseyinUslu Over a year ago

Thanks for this which is actually a way to solve but in my situation i've to implement this with regexes -- cause i've far more urls to parse which i can't parse them all with uri segments.

Kobi Over a year ago

Actually, the more you have, the more complex the regex will be. Unless you're doing URL rewriting, which is sometimes confined to regex, this should be the better option. This will also handle tricky urls, like http://www.justin.tv /warandhate?source=justin.tv/peacefuljay , which currently fail on your regex. Either way, I've added a regex alternative.

HuseyinUslu Over a year ago

Thanks for the regex method. Actually the urls i've are one fore livestream, one for ustream and so on. So each will have specific regex to process.

yellowblood · Accepted Answer · 2011-03-21 09:47:53Z

2

As I see it there's no reason to treat to the parts after the "slug".

Therefore you only need to match all characters after the host that aren't "/" or "#".

http://.*\.justin\.tv/(?<Slug>[^/#]+)

answered Mar 21, 2011 at 9:47

yellowblood

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Comments

sipsorcery · Accepted Answer · 2011-03-21 09:40:47Z

0

http://.*\.justin\.tv/(?<Slug>.*)#*?

or

http://.*\.justin\.tv/(?<Slug>.*)(#|$)

answered Mar 21, 2011 at 9:40

sipsorcery

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