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...
--
Dan Douglas
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