opennic or root nameservers for systemd-resolved

#!/bin/bash
# ~/bin/cron_systemd_resolved from https://pastebin.com/JBfYVVtG
# ...to pick either 10 random opennic nameservers, or all 13(usually) root nameservers
# sudo crontab -e, a root cron script
# Bob Dodds - cto at blockrippa dot com
#  https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=4UJD7RNRZNH7W

# set 13 root servers--
#
# cron_systemd_resolved --root
#
# or just set random 10 working opennic servers--
#
# cron_systemd_resolved

unset s str

if [[ "$0 $*" =~ root ]]
 then s=(
  `for h in $( host -tns . |\
   sed -n -e '/root-servers.net/{s/\(^.*[\t ]\)\(.*\.net\)\(\.$\)/\2/p;}' )
   do host -ta $h | sed -n -e 's/\(^.*[\t ]\)\([.0-9]\+$\)/\2/p'
  done`
 )
else
 s=(
 `wget -O- https://servers.opennic.org/ |\
   sed -n -e '/\(^.*>\)\([0-9]\+\.[0-9]\+\.[0-9]\+\.[0-9]\+\)\(<.*>Pass<.*$\)/{
    s//\2/;
    H;
   }' \
   -e '${
    g;
    /./p;
   }' | shuf -n10`
 )
fi

str=${s[@]}
if [ ${#s[@]} = 10 ]
 then sudo sed -i \
  -e 's/^#*Cache=.*/Cache=yes/' \
  -e '/^DNS=/d' \
  -e "\$s/.*/DNS=${str}\n/" \
   /etc/systemd/resolved.conf
 sudo systemctl restart systemd-resolved
 echo ${0##*/} opennic: ${s[@]} | logger --stderr
elif [ ${#s[@]} -gt 10 ]
 then sudo sed -i \
  -e 's/^#*Cache=.*/Cache=yes/' \
  -e '/^DNS=/d' \
  -e "\$s/.*/DNS=${str}\n/" \
   /etc/systemd/resolved.conf
 sudo systemctl restart systemd-resolved
 echo ${0##*/} root: ${s[@]} | logger --stderr
fi