Dynamic dns update script

#!/bin/bash
# +-----------------------------------------------------------------------------------------+
# | Update dynamic dns zone                                                                 |
# | Jan 2012 flip hess [email protected]                                                  |
# +-----------------------------------------------------------------------------------------+
# generate a key: dnssec-keygen -a hmac-md5 -b 128 -n USER dnsupdate

# Global variables:

PATH='/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin'
SCRIPT_PATH="${0}"
ARGS="${#}"
ARG1="${1}"
ARG2="${2}"
ARG3="${3}"

DNSSERVERS="10.8.2.2 10.8.3.3 10.8.4.4"
KEY="INSERTYOURKEY"

# Functions:

  # exit function
  function die()
  {
    echo -e "Error in script: ${SCRIPT_PATH}:\n${1}"
    exit 1
  }

  # Shows usage function.
  function fUsage()
  {
    echo -e "Usage: ${SCRIPT_PATH} [add|delete|usage] [hostname] [ipaddress]"
    return 0
  }

  # check for.......
  function fCheck()
  {
    # user must be root:
    [ $(whoami) = root ] || die "User must be root!"

    [ -x /usr/bin/nsupdate ] || die "This script depends on nsupdate! Install it by typing: \"sudo apt-get install dnsutils\""

    # check for arguments:
    [ ${ARGS} = 3 ] || { fUsage ; exit 1; }

    # check for vars
    { [ ${ARG1} != add ] || [ ${ARG1} != 'delete' ]; } || { fUsage ; exit 1; }
    { [ -n ${ARG2} ] || [ -n ${ARG3} ]; } || { fUsage ; exit 1; }

    # set finishing dot
    if ( echo "${ARG2}" |grep -qE '.+\.$' ) ; then
      HOST="${ARG2}"
    else
      HOST="${ARG2}."
    fi

    # check for valid ip
    if ( echo ${ARG3} | grep -Eq '^[ 0-9 ]+\.[ 0-9 ]+\.[ 0-9 ]+\.[ 0-9 ]+$') ; then
      IP="${ARG3}"
    else
      die "Please use a VALID IP address"
    fi

    ZONE="$( echo ${HOST} | awk -F. '{ print $2"."$3"."$4" }' )"
    ARPA="$( echo ${IP} | awk -F. '{ print $4"."$3"."$2"."$1".in-addr.arpa."}' )"
    ARPAZONE="$( echo ${IP} | awk -F. '{ print $3"."$2"."$1".in-addr.arpa."}')"

    return 0
  }

  # add forward
  function fAddForward()
  {
    for SERVER in ${DNSSERVERS} ; do
      echo -e "server ${SERVER}\nkey dnsupdate ${KEY}\nzone ${ZONE}\nupdate add ${HOST} 600 IN A ${IP}\nsend\n" | nsupdate
      [ ${?} = 0 ] || { echo  "Failed to update Forward for ${HOST} on ${SERVER}"; continue; }
    done

    return 0
  }

  # add reverse
  function fAddReverse()
  {
    for SERVER in ${DNSSERVERS} ; do
      echo -e "server ${SERVER}\nkey dnsupdate ${KEY}\nzone ${ARPAZONE}\nupdate add ${ARPA} 600 IN PTR ${HOST}\nsend\n" | nsupdate
      [ ${?} = 0 ] || {  echo  "Failed to update Reverse for ${HOST} on ${SERVER}"; continue; }
    done

    return 0
  }

  # delete forward
  function fDelForward()
  {
    for SERVER in ${DNSSERVERS} ; do
      echo -e "server ${SERVER}\nkey dnsupdate ${KEY}\nzone ${ZONE}\nupdate delete ${HOST} 600 IN A ${IP}\nsend\n" | nsupdate
      [ ${?} = 0 ] || { echo  "Failed to update Forward for ${HOST} on ${SERVER}"; continue; }
    done

    return 0
  }

  # delete reverse
  function fDelReverse()
  {
    for SERVER in ${DNSSERVERS} ; do
      echo -e "server ${SERVER}\nkey dnsupdate ${KEY}\nzone ${ARPAZONE}\nupdate delete ${ARPA} IN PTR ${HOST}\nsend\n" | nsupdate
      [ ${?} = 0 ] || { echo  "Failed to delete Reverse for ${HOST} on ${SERVER}"; continue; }
    done

    return 0
  }

  # The main function.
  function fMain()
  {
    case "${ARG1}"
    in
      usage)
        fUsage
        exit 1
        ;;
      delete)
        fDelForward && fDelReverse
        ;;
      add)
        fAddForward && fAddReverse
        ;;
      *)
        fUsage
        exit 1
        ;;
    esac

    return 0
  }

 # check environment:
  fCheck

 # Start the program:
  fMain "${@}"

 # Exit with previous return code:
  exit "${?}"