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Re: typeset -p on an empty integer variable is an error. (plus -v test w

From: John Kearney
Subject: Re: typeset -p on an empty integer variable is an error. (plus -v test w/ array elements)
Date: Fri, 11 Jan 2013 21:48:32 +0100
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/17.0 Thunderbird/17.0

Am 11.01.2013 19:27, schrieb Dan Douglas:
> Bash treats the variable as essentially undefined until given at least an 
> empty value.
>     $ bash -c 'typeset -i x; [[ -v x ]]; echo "$?, ${x+foo}"; typeset -p x'
>     1,
>     bash: line 0: typeset: x: not found
>     $ ksh -c 'typeset -i x; [[ -v x ]]; echo "$?, ${x+foo}"; typeset -p x'
>     0,
>     typeset -i x
> Zsh implicitly gives integers a zero value if none are specified and the
> variable was previously undefined. Either the ksh or zsh ways are fine IMO.
> Also I'll throw this in:
>     $ arr[1]=test; [[ -v arr[1] ]]; echo $?
>     1
> This now works in ksh to test if an individual element is set, though it 
> hasn't always. Maybe Bash should do the same? -v is tricky because it adds 
> some extra nuances to what it means for something to be defined...

Personally I like the current behavior, disclaimer I use nounset.
I see no problem with getting people to initialize variables.

it is a more robust programming approach.


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