How can you tell defined and undefined elements apart?

• This expression returns FALSE for a defined element:

(( ${newArray[0]:-"null"} == "null" ))

• And it also returns TRUE for an undefined element:

(( ${newArray[1]:-"null"} == "null" ))

For example, if we fix it and try again with:

if (( ${newArray[$i]:-"null"} == "null" )); then

val="undef"

else

val=${newArray[$i]}

fi

printf "[%d]=%s " $i $val

On stdout:

newArray has 2 elements

[0]=1 [1]=undef [2]=undef [3]=99 [4]=undef