Bash case-modifying word expansions and locales

[Tomasz Tomasik]

Hello.

I have problem with case-modifying word expansions in bash.
http://wiki.bash-hackers.org/syntax/pe#case_modification

bash -c 'foo="żółw"; echo ${foo^^}'
żółW

Characters with diacritical marks are not affected.

However, it works in zsh:
zsh -c 'foo="żółw"; echo ${(U)foo}'
ŻÓŁW

Terminal character encoding: UTF-8

# locale
LANG=en_US.utf8
LC_CTYPE="pl_PL.utf8"
LC_NUMERIC="pl_PL.utf8"
LC_TIME="pl_PL.utf8"
LC_COLLATE="pl_PL.utf8"
LC_MONETARY="pl_PL.utf8"
LC_MESSAGES="pl_PL.utf8"
LC_PAPER="pl_PL.utf8"
LC_NAME="pl_PL.utf8"
LC_ADDRESS="pl_PL.utf8"
LC_TELEPHONE="pl_PL.utf8"
LC_MEASUREMENT="pl_PL.utf8"
LC_IDENTIFICATION="pl_PL.utf8"
LC_ALL=pl_PL.utf8

I tried also LC_ALL=en_US.utf8

# locale -a | grep -E "^pl_"
pl_PL
pl_PL.iso88592
pl_PL.utf8

# bash --version
GNU bash, version 4.1.2(1)-release (x86_64-redhat-linux-gnu)
Copyright (C) 2009 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html
>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

# echo "$BASH_VERSION"
4.1.2(1)-release

Package: bash-4.1.2-14.el6.x86_64.rpm from sl

I also tried bash-4.2.37-1.el6.x86_64.rpm compiled
from bash-4.2.37-1.fc16.src.rpm.
http://koji.fedoraproject.org/koji/buildinfo?buildID=343762

# uname -r
2.6.32-358.11.1.el6.x86_64

# grep "" /etc/*-release
/etc/lsb-release:LSB_VERSION=base-4.0-amd64:base-4.0-ia32:base-4.0-noarch:core-4.0-amd64:core-4.0-ia32:core-4.0-noarch:graphics-4.0-amd64:graphics-4.0-ia32:graphics-4.0-noarch:printing-4.0-amd64:printing-4.0-ia32:printing-4.0-noarch
/etc/redhat-release:Scientific Linux release 6.4 (Carbon)
/etc/system-release:Scientific Linux release 6.4 (Carbon)

I really appreciate any help you can provide.

-- 
Tomasz Tomasik