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Date: Mon, 20 Sep 2010 09:16:08 -0600
From: Eric Blake <eblake AT redhat DOT com>
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Subject: Re: awk gsub problem
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On 09/19/2010 02:33 PM, Lee wrote:
>> If LANG is "en_US" or "en_US.utf8", then the regular expression "[a-z]"
>> does *not* correspond anymore to the ASCII codes.  Rather it corresponds
>> to something like "[aAbBcCdD...zZ]", independent of the actual character
>> encoding ISO-8859-1 or UTF-8.

In glibc, [a-z] gets translated according to locale collation order.  If 
A collates before a, then it maps to [aBbCc..Zz], if A collates after a, 
then it maps to [aAbB...yYz] (notice that in either case, one of the two 
capital letters is omitted, so it is NOT the same as all 26 letters in 
both cases).

This has been a MUCH complained-about feature of glibc, which has in 
turn been copied by bash, awk, grep, etc.

Note that POSIX explicitly states that [a-z] has unspecified results in 
any locale except C.  So the glibc behavior is permitted, but so is the 
traditional behavior of just the 26 lowercase letters.

If you can convince the glibc folks that [a-z] should have the 
traditional behavior, more power to you.

http://lists.gnu.org/archive/html/bug-grep/2010-09/msg00030.html

-- 
Eric Blake   eblake AT redhat DOT com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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