Appends a /etc/hosts style file onto your existing /etc/hosts file after backing it up

sync-hosts-file.sh

#!/bin/bash

# USAGE
# $> sudo ./sync-hosts-file
# Run this command in a directory where you have a hosts.append file
# which has hosts in the /etc/hosts style.

if [ "$(id -u)" != "0" ]; then
    echo "You need to be root to execute this script"
    exit 1
fi

HOSTS_BACKUP="/etc/hosts.sync.bak"
HOSTS_FILE="/etc/hosts"
ADDITIONAL_HOSTS="hosts.append"

if [ ! -f $HOSTS_BACKUP ];
then
    echo "This is the first sync attempt. Copying over $HOSTS_FILE to $HOSTS_BACKUP";
    cp $HOSTS_FILE $HOSTS_BACKUP
fi

cat $HOSTS_BACKUP > $HOSTS_FILE
cat $ADDITIONAL_HOSTS >> $HOSTS_FILE

echo "Done. Added original and typeset hosts to $HOSTS_FILE"