I've made this script to automate blocking some deviant hosts on my router, and was curious if there's anything much else that can be done to make it quicker and more efficient.

Presently I'm restricted to using packages available on the Entware repository and the latest Busybox/ash shell environment. So, for example, I can't use commands like sort -S 25% --parallel=4 adblock.sources (though found awk/gawk to be faster and more memory efficient anyway).

Any help is greatly appreciated!

curl -GOs https://raw.githubusercontent.com/T145/packages/master/net/adblock/files/adblock.sources

for key in $(jq -r 'keys[]' adblock.sources); do
        case $key in
        gaming | osid_basic )
                # Ignore these lists
                ;;
        * )
                url=$(jq -r ".$key.url" adblock.sources)
                rule=$(jq -r ".$key.rule" adblock.sources)

                case $url in
                *.tar.gz )
                        curl -s $url | \
                        tar -xOzf - | \
                        gawk "$rule" | \
                        sed "s/\r//g" | \
                        sed 's/^/0.0.0.0 /' >> the_blacklist.temp.txt
                        ;;
                * )
                        curl -s $url | \
                        gawk "$rule" | \
                        sed "s/\r//g" | \
                        sed 's/^/0.0.0.0 /' >> the_blacklist.temp.txt
                esac

                unset url
                unset rule
        esac
done

# Filter duplicate hosts
gawk '!a[$0]++' the_blacklist.temp.txt > the_blacklist.txt

rm the_blacklist.temp.txt
rm adblock.sources