Using Linux scripting I need to modify this program so that it can also compute << (left shift), >> (right shift) and ** (exponent).

#!/bin/bash

if [ $# -ne 2 ]; then echo Illegal input

elif [ $1 gt $2 ]; then echo $1 is greater

elif [ $1 -eq $2 ]; then echo $1 and $2 are equal

else echo $2 is greater

fi