Script to generate a blocklist zone file for unbound DNS server

unbound_blocklist.sh

#!/bin/sh

# Inspired by:
# https://old.reddit.com/r/PFSENSE/comments/9mipe0/unboundbased_dnsblacklisting/
# https://news.ycombinator.com/item?id=22854209
#
# With lotsa code stolen from:
# https://www.tumfatig.net/20190405/blocking-ads-using-unbound8-on-openbsd/
#
# Comment filter syntax from:
# https://unix.stackexchange.com/questions/157328/how-can-i-remove-all-comments-from-a-file/157619#157619
#
# Using redirect vs. static/always_nxdomain in unbound:
# https://github.com/NLnetLabs/unbound/issues/55

stevenblacks="https://raw.githubusercontent.com/StevenBlack/hosts/master/alternates/gambling/hosts"
frellwits="https://raw.githubusercontent.com/lassekongo83/Frellwits-filter-lists/master/Frellwits-Swedish-Hosts-File.txt"

################################################################################

# Test for internet connectivity before doing anything else
if ! nc -zw1 google.com 80 >/dev/null 2>&1; then
    echo "No internet connection, quitting..." 1>&2
    exit 1
fi

tmpfile="$(mktemp)"
trap 'rm -f $tmpfile' 0 HUP INT QUIT TERM # 0 = regular exit

# Get and filter StevenBlack's hosts file
curl -s "$stevenblacks" | \
sed -n '/Start StevenBlack/,$p' | \
sed -e '/^[[:blank:]]*#/d;s/#.*//' -e '/^[[:space:]]*$/d' | \
awk '/^0.0.0.0/ { print $2 }' >> "$tmpfile"

# Get and filter Frellwit's swedish hosts file
curl -s "$frellwits" | \
sed -e '/^[[:blank:]]*#/d;s/#.*//' -e '/^[[:space:]]*$/d' | \
awk '/^127.0.0.1/ { print $2 }' >> "$tmpfile"

# Output header
cat << EOF
################################################################################
#
# Personal DNS blocklist for unbound
#
# Public entries: $(sort -fu "$tmpfile" | wc -l | tr -d ' ')
# Timestamp:      $(date "+%Y-%m-%d %H:%M")
# Source:         https://gist.github.com/lmas/f04efe1a96c1d6d388ac990655453ec5
#
################################################################################

# Custom domains
# These two are mostly used for scams, see: https://fosstodon.org/@suprjami/110381691990708727
local-zone: "zip." always_nxdomain
local-zone: "mov." always_nxdomain

# Public lists
EOF

# Output entries
sort -fu "$tmpfile" | awk '{print "local-zone: \"" $1 "\" always_nxdomain"}'