Hostname resolving

#!/bin/bash

# Comment this if statement if you don't want to clean address file each time
if [ -s addresses.txt ]
    then
        rm -f addresses.txt
        touch addresses.txt
fi

while read line
do
    result=$(dig "$line" +short)
    if [ -n "$result" ];
        then
            echo "$result" >> addresses.txt
            echo "$result"
        else
            echo "$line" >> addresses.txt
            echo "$line"
    fi
done < hostnames.txt

# Comment these lines if you don't want to clean hostname file each time
rm -f hostnames.txt
touch hostnames.txt