Date: Sun, 10 Jul 2005 15:10:14 GMT From: Marian Cerny <jojo@matfyz.cz> To: freebsd-doc@FreeBSD.org Subject: Re: docs/70507: RE in BUG section of re_format(7) in obsolete notation Message-ID: <200507101510.j6AFAEsV028469@freefall.freebsd.org>
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The following reply was made to PR docs/70507; it has been noted by GNATS. From: Marian Cerny <jojo@matfyz.cz> To: Giorgos Keramidas <keramida@freebsd.org> Cc: "Daniel C. Sobral" <dcs@newsguy.com>, bug-followup@freebsd.org, "Daniel C. Sobral" <dcs@freebsd.org>, Ruslan Ermilov <ru@freebsd.org>, David O'Brien <obrien@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@newsguy.com> wrote: > >Giorgos Keramidas wrote: > >>On 2004-08-16 01:30, Marian Cerny <jojo@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@matfyz.cz> Jabber: jojo@njs.netlab.cz [ UNIX is user friendly. It's just selective about who its friends are. ]
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