"Ping Yin" <pkufranky@xxxxxxxxx> 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".
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