They used colon instead, back in pre OS X days. That’s >20 years ago. Admittedly some obscure cases carried that over and remain but you’ll rarely come across them today.

Oh it's even weirder than that: whether or not paths are separated by colons or slashes is specific to the app you're using, even in modern macOS versions.

To see this in action, open a terminal, type:

  touch test:file.txt

Then open Finder and browse to whatever folder you were in and you'll see a file called test/file.txt.

I'm not sure which is the native representation, but I do know that every API I've used to interact with the filesystem on macOS has used slashes as the path separator, so GP should be fine. But it's definitely a fun party trick to pull out around unsuspecting Mac users.

Heh, memory is foggy but I think one colleague occasionally ran it on his Mac without issues. I guess your linked thread is good advice, just dont't do it – like using spaces in filenames sooner or later makes a random shell script go haywire.

yes, if by 'mac' you mean macos 9 or earlier, which was a consideration when java was designed but generally not anymore