Re: pattern substitution expands "~" even in quoted variables

[Lars Wendler]

On Fri, 7 Mar 2014 16:15:05 -0800 Eduardo A. Bustamante López wrote:

>On Fri, Mar 07, 2014 at 05:21:53PM +0100, Lars Wendler wrote:
>> Configuration Information 
>> [Automatically generated, do not change]:
>> Machine: x86_64
>> OS: linux-gnu
>> Compiler: x86_64-pc-linux-gnu-gcc
>> Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64'
>> -DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-pc-linux-gnu'
>> -DCONF_VENDOR='pc' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash'
>> -DSHELL -DHAVE_CONFIG_H   -I. -I./include -I. -I./include -I./lib
>> -DDEFAULT_PATH_VALUE='/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin'
>> -DSTANDARD_UTILS_PATH='/bin:/usr/bin:/sbin:/usr/sbin'
>> -DSYS_BASHRC='/etc/bash/bashrc'
>> -DSYS_BASH_LOGOUT='/etc/bash/bash_logout'
>> -DNON_INTERACTIVE_LOGIN_SHELLS -DSSH_SOURCE_BASHRC -march=barcelona
>> -mtune=barcelona -O2 -pipe uname output: Linux shanghai 3.12.13 #2
>> SMP PREEMPT Wed Mar 5 17:26:09 CET 2014 x86_64 Quad-Core AMD
>> Opteron(tm) Processor 2389 AuthenticAMD GNU/Linux Machine Type:
>> x86_64-pc-linux-gnu
>> 
>> Bash Version: 4.3
>> Patch Level: 0
>> Release Status: release
>> 
>> Description:
>> 
>> bash-4.3 seems to expand a "~" (tilde character) with full homepath
>> in a pattern substitution even when the variable is embraced by
>> double quotes.
>> 
>> Repeat-By:
>> 
>> replace_with_tilde() { P="foo_bar" ; echo ${P/_/~} ;  echo
>> "${P/_/~}" ; }
>> 
>> 
>> bash-4.2.45:
>> 
>> ~% replace_with_tilde
>> foo/home/polynomial-cbar
>> foo~bar
>> 
>> 
>> bash-4.3.0:
>> 
>> ~% replace_with_tilde
>> foo/home/polynomial-cbar
>> foo/home/polynomial-cbar
>
>(1) You're not quoting it right:
>
>dualbus@debian:~$ for shell in /bin/bash ~/local/bin/bash; do "$shell"
>-c 'p=foo_bar; echo "${p/_/\~} $BASH_VERSION"'; done foo\~bar
>4.2.37(1)-release foo~bar 4.3.0(2)-release
>
>(2) In fact, this change in 4.3 is a fix to an old (and a bit weird)
>behavior, see:
>
>- http://lists.gnu.org/archive/html/bug-bash/2012-02/msg00106.html
>- http://lists.gnu.org/archive/html/bug-bash/2013-03/msg00099.html
>
>If you want the old behavior:
>
>dualbus@debian:~$ ~/local/bin/bash -c 'shopt -s compat42; p=foo_bar;
>echo "${p/_/\~} $BASH_VERSION"' foo\~bar 4.3.0(2)-release
>

Thank you very much for your thorough explanation :)

-- 
Lars Wendler
Gentoo package maintainer
GPG: 4DD8 C47C CDFA 5295 E1A6 3FC8 F696 74AB 981C A6FC

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