From: Robert Klemme <shortcutter@...>
Date: 2008-08-12T15:37:53+09:00
Subject: Re: Sigh! I'm depressed. Debian vs Ruby and the backtick and subshells

On 12.08.2008 07:48, John Carter wrote:
> I have just strace'd weird bug to it's root cause.
> 
> For decades bash was the "sh" of choice for linux systems.
> 
> Then somebody threw some money at the Debian foundation to make Debian
> boot faster.
> 
> The solution was to tweak the init scripts to be perfectly POSIX
> Lowest Common Denominator "sh" compatible, and then make dash the
> default "sh".
> 
> To allow for legacy scripts that expect /bin/sh === /bin/bash you can
>    sudo dpkg-reconfigure dash
> and switch back to sh === bash
> 
> Thus on Debian (and Debian derivatives like Ubuntu) Rubies backtick
> (iff there is a glob or a redirection present) is HARDCODED to /bin/sh
> but will (depending on the users whim) give you dash or bash.
> 
> For example the &> redirection is a bashism...
> ls -l /bin/sh
> lrwxrwxrwx 1 root root 4 2008-08-12 16:54 /bin/sh -> dash
> build@ws1419:~/AutomatedBuild/test$ ruby -e 'system("ls NOFILEWITHTHISNAME&>foo")'
> ls: cannot access NOFILEWITHTHISNAME: No such file or directory
> build@ws1419:~/AutomatedBuild/test$ cat foo
> build@ws1419:~/AutomatedBuild/test$ sudo dpkg-reconfigure dash 
> Removing `diversion of /bin/sh to /bin/sh.distrib by dash'
> Removing `diversion of /usr/share/man/man1/sh.1.gz to /usr/share/man/man1/sh.distrib.1.gz by dash'
> build@ws1419:~/AutomatedBuild/test$ ruby -e 'system("ls NOFILEWITHTHISNAME&>foo")'
> build@ws1419:~/AutomatedBuild/test$ cat foo
> ls: cannot access NOFILEWITHTHISNAME: No such file or directory
> 
> AAARGH!
> 
> As I always say... if a bug is hard to find... you won't know what to
> do with it once you find it.

You should probably mention that the bug is actually in _your_ code: if 
you rely on bash features present in /bin/sh then that's the error.

:-)

Kind regards

	robert