docs/70507: RE in BUG section of re_format(7) in obsolete notation

[Marian Cerny]

The following reply was made to PR docs/70507; it has been noted by GNATS.

From: Marian Cerny <jojo at matfyz.cz>
To: Giorgos Keramidas <keramida at freebsd.org>
Cc: "Daniel C. Sobral" <dcs at newsguy.com>, bug-followup at freebsd.org,
	"Daniel C. Sobral" <dcs at freebsd.org>,
	Ruslan Ermilov <ru at freebsd.org>, David O'Brien <obrien at freebsd.org>
Subject: Re: docs/70507: RE in BUG section of re_format(7) in obsolete notation
Date: Sun, 10 Jul 2005 17:08:15 +0200

 On 2005-07-10 15:05 +0300, Giorgos Keramidas wrote:
 > On 2005-07-09 23:01, "Daniel C. Sobral" <dcs at newsguy.com> wrote:
 > >Giorgos Keramidas wrote:
 > >>On 2004-08-16 01:30, Marian Cerny <jojo at matfyz.cz> wrote:
 > >>> Shouldn't this paragraph in BUGS section in manual page of re_format:
 > >>>
 > >>>    Back references are a dreadful botch, posing major problems for
 > >>>    efficient implementations.  They are also somewhat vaguely
 > >>>    defined (does `a\(\(b\)*\2\)*d' match `abbbd'?).
 > >>>    Avoid using them.
 > >>>
 > >>> be
 > >>>
 > >>>    Back references are a dreadful botch, posing major problems for
 > >>>    efficient implementations.  They are also somewhat vaguely
 > >>>    defined (does `a((b)*\2)*d' match `abbbd'?).
 > >>>    Avoid using them.
 > >>>
 > >>> because `a\(\(b\)*\2\)*d' is in obsolete notation? Or does this bug
 > >>> concern only the obsolete REs?
 > >>
 > >> You're probably right that we should change the syntax to look like a
 > >> modern RE.  The basic RE syntax is still used by many utils in the base
 > >> system though.  This is probably why the regexp has remained as you see
 > >> it now.
 > >>
 > >> Daniel, Ruslan and David... what do you think?  Is this change ok?
 > >
 > > Old, OLD messages... This was lost in a number of spams I'm happing to
 > > be clearing right now. Thing about back references is... they didn't
 > > work with Extended Regex, only with basic Regex, which is the obsolete
 > > notation.
 > >
 > > So I'm guessing the rewritten example wouldn't work, because back
 > > references is not supported with that syntax. So, if this change was
 > > done, could someone check if back references are actually supported in
 > > extended regex (the modern syntax), and, if not, undone this change? :-)
 > 
 > Nothing was changed, since I wasn't sure of what to do.
 > 
 > Thanks for the clarification :-)
 
 Now, when I am reading the manpage once again, i noticed that back
 references are not supported in modern REs. But implementation in
 FreeBSD (egrep) supports them and the modified example works.
 
 > Does this mean we can close this PR now?
 
 Yes, if back references are not supported by POSIX in modern RE, the PR
 can be IMHO closed.
 
 -- 
 Marian Cerny <jojo at matfyz.cz>
 Jabber: jojo at njs.netlab.cz
 
 [ UNIX is user friendly. It's just selective about who its friends are. ]