A bit ago I was debugging a failing script at work. It turns out that
when you say
FOO=(x y z)
then the variable FOO is an array and is defined. But when you say
FOO=()
then the variable FOO is an array (because ${#FOO[*]} substitutes an
integer viz. 0) but it is *not* defined (because ${FOO[*]} generates an
error when "set -u" is in effect).
I really don't like this. But it is according to the manual (because
FOO has no index that has a value), and no doubt there are scripts out
there that depend subtly on this case.
It turns out that this can matter, if you do something like this:
set -u # for safety
...
if ...
then
FOO=(...)
else
FOO=()
fi
...
FOO_PLUS=("${FOO[@]}" x y z w)
Dale
