By default * quantifier is greedy, which means that regex engine will try to match as much text as possible. *? matches all characters except newline (because we are not using RegexOptions.Singleline) in lazy (or non-greedy) mode thanks to question mark after asterisk. If you want to put part of the expression into a group but you don’t want to push results into Groups collection, you may use non-capturing group by adding a question mark and colon after opening parenthesis, like this: (?:something) Lazy wildcard http: but when I was running below code, I was seeing the 1st index of the returned array was containing the string http when I was thinking that http and colon : both will not get reported as they are inside a non-capturing group. ![]() Regex is awesome when your subject is precise, but as you can see in your case, the variable-length payload is difficult to deal with elegantly. ( \w+ ) is capturing group, which means that results of this group existence are added to Groups collection of Match object. The first group in my regex (:(A-Za-z+):) is a non-capturing group which matches the protocol scheme and colon : character i.e. The 'some stuff' part is something that regex is particularly bad for - unlimited quantifiers paired with dot or equivalent tend to be a sign that regex is the wrong tool. However, if the captured text is not used, then the capturing. That makes a capturing group quite similar to a variable in that its value (the captured text) is stored (by the regex engine) and can be accessed afterward (by the developer). Sometimes groups get created as a side effect of the parenthetical syntax used to isolate a part of the expression such that modifiers, operators, or quantifiers can act on the isolated part of the expression. A capturing group is intended to store its matched text so it can later be used, e.g. The regular expression engine will try to fill the leftmost. Non-Capturing Groups Groups are not always defined in order to create sub-matches. Actually it's the first (capturing) group being greedy that is the problem. + will try to match as many characters as possible before stopping, so it will stop at the last. We later use this group to find closing tag with the use of backreference. This will give the desired result.Your regex (.+) (. ![]() \w+ part is surrounded with parenthesis to create a group containing XML root name ( getName for sample log line). ![]() <(\w+) will match less-than sign followed by one or more characters from \w class (letters, digits or underscores). A true parser is written with the specific grammar of your subject in mind not necessarily foo, followed by some stuff, and maybe another foo like the regex is doing. Note: In some cases (like in our log examination example), instead of using positive lookaround we may use non-capturing group. Well, youre parsing with regex - its not the same thing as writing a parser. Check this awesome page if you want to learn more about lookarounds.
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