Adblock using /etc/hosts (need no stupid browser plugin)

adhostsblock.sh

#!/bin/sh
#
# (c) 2013 "nyov"

set -e

#
# Script to download, update and append blocklist to /etc/hosts
# for more info, visit http://winhelp2002.mvps.org/hosts.htm
#

# Must run as root to edit /etc/hosts (dangerous)
# or allow /etc/hosts to be edited by some other group
# (e.g. chgrp adm /etc/hosts; adduser xyz adm)
#
# Best backup your hosts file before first run!

# Define local blackhole IP
#   On a proxy server this may point to a webserver which
#   serves a cheery "This page is blocked" message.
#   As a 404 error page of course, so nothing breaks.
#
BLACKHOLE_IP='127.0.0.254'

# Magic lines between which the script will operate
#  Add those two lines somewhere in your /etc/hosts
#  before running the script.
#  Otherwise nothing will happen.
#  # echo -e '# [START OF SCRIPT-GENERATED BLOCKLIST]\n# [END OF SCRIPT-GENERATED BLOCKLIST]' >> /etc/hosts
#
MAGIC_HEADER='# [START OF SCRIPT-GENERATED BLOCKLIST]'
MAGIC_FOOTER='# [END OF SCRIPT-GENERATED BLOCKLIST]'

# Work in a temporary location
cd /tmp

hostsblock () {
        # fetch the file, if newer
        wget -N -nv "http://winhelp2002.mvps.org/hosts.txt"

        # check return value
        # (sadly doesnt differ whether we downloaded anything or not, with wget)
        if [ ${?} != 0 ]; then
                return ${?}
        fi

        # work on a copy (to not break update checking)
        cp -a hosts.txt tmphosts

        # needs a dos2unix conversion
        dos2unix tmphosts
        # alternatively...
        #sed -i 's/^M$//' tmphosts

        # remove file header
        sed -i -e '/./{H;$!d;}' -e 'x;/Disclaimer/d;' tmphosts

        # strip default localhost entries (we have our own!)
        sed -i -e '/127\.0\.0\.1  localhost/d' -e '/::1/d' tmphosts
        sed -i -e '/127\.0\.0\.1 localhost/d' -e '/::1/d' tmphosts

        # convert 0.0.0.0 to local blackhole ip
        sed -i -e "s/^0\.0\.0\.0/$BLACKHOLE_IP/" tmphosts

        # and lastly remove all empty lines left
        sed -i -e '/^$/d' -e '/./!d' tmphosts


        # now clean a previous blocklist from /etc/hosts
        #sed -i '/^# \[Start of entries generated by WinHelp2002\]/,/^# \[end of entries generated by WinHelp2002\]/d' /etc/hosts
        #sed -i '/^# \[Start of entries generated by MVPS HOSTS\]/,/^# \[end of entries generated by MVPS HOSTS\]/d' /etc/hosts

        # and add the new list at the end of it
        #cat tmphosts >> /etc/hosts


        # Safer solution, using our own magic header

        # delete everything between those two lines
        sed -i '/^# \[START OF SCRIPT-GENERATED BLOCKLIST\]/,/^# \[END OF SCRIPT-GENERATED BLOCKLIST\]/{/^# \[START/!{/^# \[END/!d}}' /etc/hosts

        # and add the new list after the magic header
        sed -i '/^# \[START OF SCRIPT-GENERATED BLOCKLIST\]/r tmphosts' /etc/hosts

        rm tmphosts
        # possibly remove the file to force fresh download
        #rm hosts.txt

        echo "Done"
}

hostsblock