From: Junio C Hamano <gitster@pobox.com>
Date: Sat, 01 Mar 2008 20:52:43 GMT
Subject: Re: [PATCH v2 1/3] git-submodule: New subcommand 'summary' (1) - code framework
Message-ID: <7vejauxj38.fsf@gitster.siamese.dyndns.org>
In-Reply-To: <46dff0320803010227r5024d152g259a6a07a2441351@mail.gmail.com>

"Ping Yin" <pkufranky@gmail.com> writes:

>>  > +             grep '^:160000\|:[0-9]\+ 160000' |
>>
>>  This looks troublesome.
>>
>>   - [0-9] is obviously wrong and [0-7] is what you meant;
>>   - \| and \+ are not BRE but GNU.
>>
> man grep says
>  In  basic regular expressions the metacharacters ?, +, {, |, (, and )
> lose their special meaning; instead use the backslashed versions \?,
> \+, \{, \|, \(, and \).
>
> Doen't it mean that '\|' is BRE ?

It just says unlike in ERE, these characters are not special in BRE; it
does not at all say using backslash like \?, \+, and \| makes them so.

And they are not.  \(...\), \{m\}, \{m,\} and \{m,n\} are part of BRE, but
the two you used (\+ and \|) are not.  GNU accept these two as extensions,
but other POSIX implementations may have troubles with them.

  http://www.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap09.html

Please be gentle to porters to non GNU systems.  Either stay inside BRE
(which I think we have managed to do with our usage of grep) or explicitly
ask for ERE with "grep -E".