[tmottabr]

in regex this is correct, but in many other contexts * is used as wildcard.

ie.: in most OSes you can use * as wildcard for filename.

file.*

will refer to all files named "file" with any extension

.zip

will refer to all files with any name as long as they have the zip extension

is a wildcard in most contexts while "." is wildcard only in regex that i know.

[elygre]

True. But in the article, the full paragraph reads like this:

Perhaps this is where the use of * as the wild-card character comes from. I find regular expressions can induce swearing, occasionally.

[chrisseaton]

* is the wildcard in some forms of regular expressions, such as file name globs.

[elygre]

I know that * is the wildcard in many expressions, such as some query languages and (as you say) file name globs. However, I don't actually think a wildcard glob is a regular expression. Wikipedia, always a risky source :-), makes that point, with a reference to further reading.

The article is about the asterisk character, and the connection to the wild-card seems legit. But the sentence "I find regular expressions can induce swearing, occasionally" (which I agree fully with!) hints towards the idea that the * is used as a wildcard in regular expressions, which I think isn't quite true.

[1] https://en.wikipedia.org/wiki/Glob_(programming)#Compared_to...

[tialaramex]

A glob isn't a regular expression, and indeed one of the reasons it isn't is that it lacks the Kleene star - which is the thing an asterisk does in the typical regular expression syntax.

[chrisseaton]

I don't think you need the Kleene star to be regular.

Star-free languages are regular languages without the Kleene star.

https://en.wikipedia.org/wiki/Star-free_language

But I'm not an expert in formal languages and maybe you are.

[denotational]

I think you're slightly at cross-purposes: GP is saying that since globs lack the Kleene star, they cannot be used to define all regular languages.

Star-free languages are a strict subset of the set of regular languages, so there exist regular languages that require the Kleene star to be represented as a regular expression; indeed the Wikipedia article you linked gives an example.

It's perhaps worth noting that neither regular expressions nor globs are themselves regular languages: they are just used to define regular languages. Consider that regular expressions usually require some form of parenthetical notation, and that languages with matched parentheses cannot be regular as a trivial consequence of the pumping lemma.