Auto-formatting a source file in emacs

Question

How do I apply a set of formatting rules to an existing source file in emacs?

Specifically I have an assembly (*.s) file, but I would like a generic command

Answer 1

The major mode it's using for your .s files won't be cc-mode hence c-set-style makes no sense. However you can always manually enter cc-mode (M-x cc-mode) and then do the c-set-style you want. However as the C styles are keyed for C source code and not assembler this is almost certainly not what you want to do.