What regular expressions do cx cf (open file) accept in Emacs?

Question

I know that it will accept '*' in file names, but standard regular expression operators such as '.' or character classes do not work. I thought it would be something that I could easily find on the Internet, but after about 15 minutes of searching I could not find the answer to my question, much to my dismay.

Answer 1

In the Emacs "Visiting Files" User Guide :

If the specified file name contains shell-style wildcards, Emacs visits all files matching that. (In case-insensitive file systems, Emacs matches wildcards without the case letter.) Wildcards include the sequences "?", "*" And "[...].

So these are not regular expressions; they are simple shell wildcards . ? matches any single character, * matches zero or more characters, and [abc] matches any of the characters a, b or c.