Sort file base on line starting value

# file name is given as command line (First argument) "$1"
# reverse sort file content based on line start with value "$2" supplied as command line argument (Second Argument)

#!/bin/bash

if [ -z $1 ] || [ -z  $2  ]

then
    echo  "$0 : provide exact two argument "
    exit 1

else
    cat "$1" | grep "^$2"  | sort -r

fi