array=([1]=one [2]= two)

array=([1]=one [2]=two)

You have an array element on the form [index]=. The shell will interpret this as an independent element with index index and value <empty string>.

This may happen as part of the expression [index]= value, where the space is not allowed and causes the shell to interpret it as [index]="" [index+1]=value.

If you wanted the element to have a value, remove the spaces after =, e.g. [index]=value.

If you wanted to assign an empty string, explicitly use empty quotes: [index]="". This makes no difference to the shell, but will make your intention clear to shellcheck and other humans.

None.