#!/bin/bash
{ 
sed -f /dev/fd/10 10<<-EOD
/^[^#][^ ]* www dot example dot com$/    s/^/#/   
$ a\
127.0.0.1 insertion dot this dot that
EOD
} | sort | uniq

#!/usr/bin/env ruby

require 'set'

YourDownloadedFile = "/home/hello/hosts-mods"
HostsFile = "/etc/hosts"

#This will contain the whole hosts file, as a set of lines
aHosts = File.read(HostsFile).lines.collect
#Clean trailing spaces, line endings etc and drop empty lines
aHosts.collect! {|s| s.chomp.strip}.select! {|s| s.length > 0}

#Here we put the lines you want to add...
aAddLines = File.read(YourDownloadedFile).lines.collect
#As before, but also only take lines starting by "+"
aAddLines.select! {|s| s[0] == "+"}.collect! {|s| s.chomp.strip}.select! {|s| s.length > 0}

#...and here we put the lines you want to blacklist
aRemoveLines = File.read(YourDownloadedFile).lines.collect
aRemoveLines.select! {|s| s[0] = "-"}.collect! {|s| s.chomp.strip}.select! {|s| s.length > 0}

#We have three Arrays so far, but Sets would be better suited to our task, so let's convert data
#Note that Set can't contain duplicates in the same list, so they will be stripped away here if any.
sHosts = Set.new(aHosts)
sAddLines = Set.new(aAddLines)
sRemoveLines = Set.new(aRemoveLines)

#Do as said in my previous post
a = sHosts.intersection sRemoveLines
b = sHosts.union sAddLines
c = b.difference sRemoveLines
d = Set.new(a).collect! {|s| "#" + s}
e = c.union d

#Print the result on stdout
e.each {|s| puts s}

#!/bin/bash
{ 
sed -f /dev/fd/10 10<<-'EOD'

# don't blackhole these hosts:

/.*127.0.0.1 googlesyndication.com$/            s/^#* */#/
/.*127.0.0.1 pagead.googlesyndication.com$/     s/^#* */#/
/.*127.0.0.1 pagead2.googlesyndication.com$/    s/^#* */#/
/.*127.0.0.1 searchportal.information.com$/     s/^#* */#/
/.*127.0.0.1 www.thepiratebay.org$/             s/^#* */#/

# do blackhole these hosts:

$ a\
127.0.0.1 www.exscn.com\
127.0.0.1 forums.exscn.com\
127.0.0.1 freezonesurvivors.to\
127.0.0.1 www.dd-wrt.org\
127.0.0.1 www.openwrt.com
EOD
} | sort | uniq

# cat /path/to/newly/downloaded/blackhole/file /etc/hosts | edithosts > /etc/hosts.new
# ln -f /etc/hosts /etc/hosts.old
# mv -f /etc/hosts.new /etc/hosts

#!/bin/bash

# Load file names from /etc/blackhole.conf if any.
[ -r /etc/blackhole.conf ] && . /etc/blackhole.conf

# Set defaults.
[ -n "$BLACKHOLE_ALWAYS"  ] || BLACKHOLE_ALWAYS="/etc/blackhole.always"
[ -n "$BLACKHOLE_NEVER"   ] || BLACKHOLE_NEVER="/etc/blackhole.never"
[ -n "$BLACKHOLE_LISTS"   ] || BLACKHOLE_LISTS="/etc/blackhole.urls"
[ -n "$BLACKHOLE_ADDRESS" ] || BLACKHOLE_ADDRESS="127.0.0.254"
[ -n "$HOSTS_FILE"        ] || HOSTS_FILE="/etc/hosts"

# Make sure we use POSIX locale, so we handle all input charsets as-is.
export LANG=C LC_ALL=C

# Create a temporary working directory.
WORK="$(mktemp -d)" || exit $?
trap "rm -rf '$WORK'" EXIT

# Copy non-blackhole items from the current hosts file.
awk -v "addr=$BLACKHOLE_ADDRESS" '
    BEGIN {
        RS="[\t\v\f ]*(\r\n|\n\r|[\r\n])"
        FS="[\t\v\f ]+"
    }

    ($1 != addr) { printf("%s\n", $0) }
' "$HOSTS_FILE" > "$WORK/header" || exit $?

(
    # List the host names from the blackhole lists
    if [ -r "$BLACKHOLE_LISTS" ]; then
        while read URL ; do

            # Skip comment lines.
            [ "$URL" = "${URL##[#;]}" ] || continue

            echo -n "Downloading $URL: " >&2

            # Get the list, but filter to keep just the host names.
            wget -q -O - "$URL" | awk '
                (NF >= 2 && $1 !~ /[^.:0-9A-Fa-f]/) {
                    if (index($0, "#") > 0)
                        sub(/#.*$/, "")
                    for (i = 2; i <= NF; i++)
                        if (length($i) > 0)
                            printf("%s\n", $i)
                }
            ' && echo "Success" >&2 || echo "Error [$?]" >&2

        done < "$BLACKHOLE_LISTS"
    fi

) | (
    # Omit those that should never be blackholed.
    # Start domains with a dot.
    if [ -r "$BLACKHOLE_NEVER" ]; then
        awk -v "file=$BLACKHOLE_NEVER" '
            BEGIN {
                split("", host)
                split("", domain)
                while ((getline < file) > 0) {
                    if (index($0, "#") > 0)
                        sub(/#.*$/, "")
                    for (i = 1; i <= NF; i++)
                        if (length($i) > 1 && substr($i, 1, 1) == ".")
                            domain[substr($i, 1)] = 1
                        else if (length($i) > 0)
                            host[$i] = 1
                }
                domains = length(domain)
            }

            ($0 in host) { next }
            (domains > 0) {
                temp = $0
                while ((i = index(temp, ".")) > 0) {
                    temp = substr(temp, i + 1)
                    if (temp in domain)
                        next
                }
            }
            { print }
        '
    else
        cat
    fi

    # Add the always-blackholed host names
    if [ -r "$BLACKHOLE_ALWAYS" ]; then
        awk '   (NF >= 2 && $1 !~ /[^.:0-9A-Fa-f]/) {
                    if (index($0, "#") > 0)
                        sub(/#.*$/, "")
                    for (i = 2; i <= NF; i++)
                        if (length($i) > 0)
                            printf("%s\n", $i)
                }' "$BLACKHOLE_ALWAYS"
    fi

) | awk -v "to=$BLACKHOLE_ADDRESS" '
    ($0 in listed) { next }
    {
        listed[$0] = 1
        printf("%s %s\n", to, $0)
    }
' > "$WORK/footer" || exit $?

# Combine into a new hosts file..
HOSTS_TEMP="$HOSTS_FILE.$(hostname -s).$$"
if ! cat "$WORK/header" "$WORK/footer" > "$HOSTS_TEMP" ; then
    rm -f "$HOSTS_TEMP"
    rm -rf "$WORK"
    exit 1
fi

# .. create a hardlink (so the file will exist at all times) ..
if ! ln -f "$HOSTS_FILE" "$HOSTS_FILE.old" ; then
    rm -f "$HOSTS_TEMP"
    rm -rf "$WORK"
    exit 1
fi

# .. and try to replace the hosts file.
if ! mv -f "$HOSTS_TEMP" "$HOSTS_FILE" ; then
    rm -f "$HOSTS_TEMP"
    rm -rf "$WORK"
    exit 1
fi

# Success.
rm -rf "$WORK"
trap - EXIT

echo "$HOSTS_FILE updated successfully."
exit 0

cp /etc/hosts hosts
env HOSTS_FILE=hosts ./this-script