Re: printf(1), sh(1), POSIX.2 and octal escape sequences

[RVP <rvp%SDF.ORG@localhost>]

On Wed, 28 Jun 2023, tlaronde%polynum.com@localhost wrote:

> But you can't: from the syntax given, \777 is a perfectly valid \77
> octal sequence followed by the character '7'.

That would be a very surprising way to resolve the ambiguity which is
present here. There are others when it comes to octal notation:

Single-digit octal escapes can be confused with regexp back-references, so
POSIX says octal escapes must have at least 2 digits in certain situations.

As for resolving \777 as \777 and not \77'7 is this note in the EXTENDED
DESCRIPTION for tr(1) (I knew I had read this somewhere in my travels through
POSIX-land):

   \octal
          Octal sequences can be used to represent characters with specific
          coded values. An octal sequence shall consist of a <backslash>
          followed by the _longest_ sequence of one, two, or three-octal-digit
          characters (01234567).

   (my emphasis)

What's good for the goose is also good for the gander, I say.

Cheers!
-RVP