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Re: Expanding an undefined array


From: Chet Ramey
Subject: Re: Expanding an undefined array
Date: Wed, 24 Sep 2008 23:57:54 -0400
User-agent: Thunderbird 2.0.0.16 (Macintosh/20080707)

Bernd Eggink wrote:
> Is the following difference intentional, a bug, or do I miss something?
> 
>   unset a
>   set -- "address@hidden"
>   echo $#
> 
> Output: 0

This is correct.

>   typeset a
>   set -- "address@hidden"
>   echo $#
> 
> Output: 1

The question is how to treat the variable created by `typeset'.  Bash
has traditionally treated `typeset a' as equivalent to `typeset a=""'
instead of creating a `placeholder' variable that exists in a sort of
limbo.  That's different from things like `export a' or `readonly a',
and probably inconsistent enough to be worth changing for bash-4.0.
That's the difference between the examples, not the expansion of
"address@hidden".

Chet

Chet
> 
> The man page says, "If the word is double-quoted, ... address@hidden expands
> each element of name to a separate word. When there are no array
> members, address@hidden expands  to  nothing." It doesn't mention a
> difference between an empty and an unset variable in this context. As a
> quoted 'nothing' normally counts 1 word, the 'nothing' in the first
> example appears to be some kind of 'super-nothing'.
> 
> Regards,
> Bernd
> 


-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer

Chet Ramey, ITS, CWRU    address@hidden    http://cnswww.cns.cwru.edu/~chet/




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