b=' b '
e=''
echo 1 a $b c
echo 2 a +$b c
echo 3 a $e$b c
echo 4 a "$e"$b c
echo 5 a ""$b c
echo 6 a $b+ c
echo 7 a $b$e c
echo 8 a $b"$e" c
echo 9 a $b"" c