Re: Confusing/unclear documentation of Sed back references

Eric Blake wrote:
> Bob Proulx wrote:
> > The invocation section documents the -r option.
> > 
> >   https://www.gnu.org/software/sed/manual/sed.html#Invoking-sed
> > 
> >   -r
> >   --regexp-extended
> >       Use extended regular expressions rather than basic regular
> >       expressions.  Extended regexps are those that egrep accepts;
> >       they can be clearer because they usually have less backslashes,
> >       but are a GNU extension and hence scripts that use them are not
> >       portable.  See [Extended regular expressions].
> 
> This is no longer entirely true.  POSIX has proposed standardizing the
> -E synonym of -r, which means that it IS portable to use 'sed -E' to get
> extended regular expressions in modern sed implementations, and that it
> is no longer a GNU-only extension:
> http://austingroupbugs.net/view.php?id=528
> (However, it is still true that the spelling 'sed -r' is still a GNU
> extension, and you should get used to 'sed -E' instead)

I don't see how you can see that isn't entirely true.  As I read
things the -E is still a proposal.  At this time no sed -E option yet
exists in GNU sed.  

  https://www.gnu.org/software/sed/manual/sed.html#Invoking-sed

And that doesn't even mention the traditional Unix systems.  Not even
in the current standards docs.

  http://pubs.opengroup.org/onlinepubs/009695399/utilities/sed.html

It certainly can't be considered portable.  Not even in bleeding edge
systems.

Bob