Re: Avoid unportable nested double-quotes and backquotes.

[Eric Blake]

On 05/23/2010 05:54 AM, Ralf Wildenhues wrote:
> Hi Bruno,
> 
> * Bruno Haible wrote on Sun, May 23, 2010 at 01:37:41PM CEST:
>>> noticed this small shell unportability in gnulib coming from gettext.
>>> ...
>>>          ac_dir=`echo "$ac_file"|sed 's%/[^/][^/]*$%%'`
>>> -        ac_dir_suffix="/`echo "$ac_dir"|sed 's%^\./%%'`"
>>> +        ac_dir_suffix=/`echo "$ac_dir"|sed 's%^\./%%'`
>>
>> There is no unportability here. I tested these statements
> [...]
>> In summary, I did find a shell that does not understand "`...\"...\"...`"
>> but I did not find a shell that does not understand "`..."..."...`". That
>> paragraph in autoconf.texi dates back to 2000-05-19 12:17:29. It may have
>> referred to shells that were in common use between 1995 and 2000 and have
>> disappeared by now.
> 
> Thanks for testing.  I'm fairly sure I've come across a shell that
> doesn't like this in the last few years, but don't remember which, and
> it might have been on an old system.  ATM some of my test systems aren't
> reachable though, so I can't confirm this.

I'm not sure which systems are affected, but I do know that you will
have issues with "`...\"...\"...`".  There is an ambiguity of whether
the \" will be interpolated by the outer "" or by the ``, so some shells
will pass \" to the `` while others pass just " to the ``.

But yes, it would be nice to have an actual counterexample from a modern
machine, to update that section in the autoconf manual about why we
should still worry about that failure.

-- 
Eric Blake   address@hidden    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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