The default file association for an unrecognized file extension is TextEdit. I'd rather it use Emacs. How can this be changed? High-Sierra and Mojave, if it makes a difference.
Note: This is not about changing the default for a given file-type. I'm asking about the fall-back for any file that has no assigned default.
What do you mean by unrecognised file type?
That description was perhaps misleading; I've updated the title. A couple of examples from my files are 'a.out', "#AtoD.ino#", "cookies.sqlite". BTW, I'm not asking what these files are, where they came from, or why they don't have a file-association that plays nicely. I'd just like to choose which tool opens them by default.