Re: converting octal escape sequences to utf-8 and back

[Eli Zaretskii <eliz@gnu.org>]

> From: Roland Winkler <winkler@gnu.org>
> Date: Sun, 29 May 2011 01:58:30 -0500
> 
> > IOW, encode-coding-string produces the encoding specified by its 3rd
> > argument, not its ASCII representation.
> 
> ...So it seems that emacs knows already what I would like to have (at
> least its display engine).

Nitpicking: It's not the display engine that does that, it's
eval-last-sexp.

> How can I achieve that I actually get this in an output file, too?
> Are there some formulas that allow one to calculate these octal
> sequences?

This should do what you want:

  (with-output-to-string (princ (encode-coding-string STRING 'utf-8)))

(the STRING argument should be the entire string that you want to send
to that program of yours).

But this is crazy, IMO: Lisp code should not need to jump through the
hoops like that to produce such an octal representation.  TRT is to
have a special encoding for this, then you could simply say

  (encode-coding-string STRING 'foo)

or even just

  (encode-coding-region START END 'foo)

because I presume that your original text comes from some buffer.