bash vi mode: What does # -*- mode: ruby -*- # vi: set ft=ruby : mean?

Question

I'm looking through some random code, and at the top of it, it says this:

# -*- mode: ruby -*-
# vi: set ft=ruby :

What does this mean?

I know it's a simple question, but I couldn't find it out online because a) I don't even know what language this code is written in, and b) I'm very new to bash and vi.

Solution

Those lines are modelines which tell an editor (e.g. emacs or vi) to choose a specific editing mode for a file. An editing mode affects how editor e.g. higlights and indents contents of the file.

You can read more about modelines for emacs (which are called file-local variables) here and modelines for vim here.

Comments

[Michał Politowski]

This question doesn't seem to have anything to do with bash.

[romainl]

It's modeline not magical line.

[Admin]

Actually it's most often called magical modeline where I come from, just to distinguish it from modeline of emacs which is entirely different thing.

[romainl]

Well, in Vim, it's called "modeline" and in Emacs it's called "file-local variables".

[Admin]

I suggest an edit then.