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Re: 4.4 change in behavior from 4.3: how to catch unset when using ${#le


From: Chet Ramey
Subject: Re: 4.4 change in behavior from 4.3: how to catch unset when using ${#length}
Date: Wed, 9 Nov 2016 13:22:26 -0500
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:45.0) Gecko/20100101 Thunderbird/45.4.0

On 11/7/16 4:49 AM, Dan Douglas wrote:
> On Sun, Nov 6, 2016 at 3:46 PM, Chet Ramey <address@hidden> wrote:
>> On 11/1/16 5:57 AM, Dan Douglas wrote:
>>> On a possibly related note, would you consider adjusting +, :+, -, :-,
>>> as in "address@hidden" to align with the meaning of [[ -v address@hidden ]] 
>>> as
>>> discussed in 
>>> https://lists.gnu.org/archive/html/bug-bash/2014-11/msg00099.html
>>> ?
>>
>> There's not a compelling reason to break backwards compatibility or to be
>> unnecessarily incompatible with other shells that implement that construct,
>> like ksh93.
> 
> I kind of doubt anybody would know what to expect with them. :+ and :-
> are particularly weird (they don't quite have to do with testing for
> defined variable admittedly).

This is probably true.  I think all the shells with arrays try to treat
address@hidden in the same way as $@, which gets strange in a "scalar" context.
There was a pretty extensive discussion of the $@ issue on the austin-
group mailing list, which revealed big differences in how shells expand
$@ in a "non-list" context.  I think those differences are reflected in
how those shells expand address@hidden

Chet

-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    address@hidden    http://cnswww.cns.cwru.edu/~chet/



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