${string##substring}

    Strips longest match of $substring from front of $string.

       1 stringZ=abcABC123ABCabc
       2 #       |----|
       3 #       |----------|
       4
       5 echo ${stringZ#a*C}      # 123ABCabc
       6 # Strip out shortest match between 'a' and 'C'.
       7
       8 echo ${stringZ##a*C}     # abc
       9 # Strip out longest match between 'a' and 'C'.

${string%substring}

    Strips shortest match of $substring from back of $string.
${string%%substring}

    Strips longest match of $substring from back of $string.

       1 stringZ=abcABC123ABCabc
       2 #                    ||
       3 #        |------------|
       4
       5 echo ${stringZ%b*c}      # abcABC123ABCa
       6 # Strip out shortest match between 'b' and 'c', from back of $stringZ.
       7
       8 echo ${stringZ%%b*c}     # a
       9 # Strip out longest match between 'b' and 'c', from back of $stringZ.