A small shell script that will add and remove lines from the hosts file. Originally created by Claus Witt, http://clauswitt.com/319.html.

update-hosts.sh

#! /bin/sh
# @author: Claus Witt
# http://clauswitt.com/319.html

# Adding or Removing Items to hosts file
# Use -h flag for help

DEFAULT_IP=127.0.0.1
IP=${3:-$DEFAULT_IP}
HOST_FILE=${4:/etc/hosts}

case "$1" in
  add)
        sed -ie "\|\s{1,\}$2\$|d" $HOST_FILE
        echo "$IP $2" >> $HOST_FILE
        ;;
  remove)
        sed -ie "\|^$IP $2\$|d" $HOST_FILE
        ;;
  *)
        echo "Usage: "
        echo "hosts.sh [add|remove] [hostname] [ip] [host file]"
        echo 
        echo "Ip defaults to 127.0.0.1"
        echo "Host file defaults to /etc/hosts"
        echo "Examples:"
        echo "hosts.sh add testing.com"
        echo "hosts.sh remove testing.com 192.168.1.1"
        echo "hosts.sh add testing.com 192.168.1.1 ~/hosts"
        exit 1
        ;;
esac

exit 0