Junio C Hamano <gitster@xxxxxxxxx> writes:
> "Ping Yin" <pkufranky@xxxxxxxxx> writes:
> ...
>> 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".
I think this would help people new to our codebase.
Also
Message-ID: <7v4pdtgjf0.fsf@xxxxxxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [PATCH] git-filter-branch could be confused by similar names
Date: Fri, 04 Jan 2008 17:17:39 -0800
aka
http://article.gmane.org gmane.comp.version-control.git/69630
---
Documentation/CodingGuidelines | 12 ++++++++++++
1 files changed, 12 insertions(+), 0 deletions(-)
diff --git a/Documentation/CodingGuidelines b/Documentation/CodingGuidelines
index 3b042db..994eb91 100644
--- a/Documentation/CodingGuidelines
+++ b/Documentation/CodingGuidelines
@@ -53,6 +53,18 @@ For shell scripts specifically (not exhaustive):
- We do not write the noiseword "function" in front of shell
functions.
+ - As to use of grep, stick to a subset of BRE (namely, no \{m,n\},
+ [::], [==], nor [..]) for portability.
+
+ - We do not use \{m,n\};
+
+ - We do not use -E;
+
+ - We do not use ? nor + (which are \{0,1\} and \{1,\}
+ respectively in BRE) but that goes without saying as these
+ are ERE elements not BRE (note that \? and \+ are not even part
+ of BRE -- making them accessible from BRE is a GNU extension).
+
For C programs:
- We use tabs to indent, and interpret tabs as taking up to
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