#!/bin/bash

#

# tm_switcher -- a backup volume switchr for Apple's TimeMachine

#

# ####################################################################

# This script will help to automatically switch backup destination

# on Apple's TimeMachine according to available destination volumes.

# You can have one or more of both USB and network devices, of which

# the first available destination is used

# ####################################################################

# released to the public "as-is" under the terms of the GPL Version 2

# ####################################################################

# r0.1 2012/01/25

# - initial release 



# specify zero or more USB volumes as backup destinations

# you must give only the volume label

# specify multiple volumes like this:

# USB_Volumes=("Volume1" "Volume2")

#

USB_Volumes=("My Passport")



# specify zero or more NETWORK volumes as backup destinations

# you must give the full AFP volume path

# specify multiple volumes identically as described

# in the "USB Volumes" section above

#

NET_Volumes=("afp://TMUsername:TMPassword@HOSTorIPAddress/TMShare")



# get current TimeMachine directory

#

current_tm_dir=`/usr/bin/tmutil machinedirectory`



# check if we are disconnected

#

[ "$current_tm_dir" == "" ] && tm_status=CONNECT_NONE



# check if we are connected to an USB disk

#

for volume in "${USB_Volumes[@]}"; do

	echo $current_tm_dir | grep -e "$volume" > /dev/null 2>&1

	[ "$?" == "0" ] && tm_status=CONNECT_USB 

done



# check if we are connected to an Network Volume (TimeCapsule) 

#

for volume in "${NET_Volumes[@]}"; do

	_volume_basename=`basename ${volume}`

	/sbin/mount | grep " on /Volumes/${_volume_basename}" > /dev/null 2>&1	

	[ "$?" == "0" ] && tm_status=CONNECT_NET 

done





# check if we need to switch TimeMachine locations

#

if [ "${tm_status}" == "CONNECT_NONE" ]; then

	echo "NOTICE: TimeMachine is disconnected, current status is: ${tm_status}"



	# check if we can reach any of the NET_Volumes hosts given

	#

	for volume in "${NET_Volumes[@]}"; do

		_dest_server=`echo $volume | grep -P -o '@([[:digit:]]{1,3}.[[:digit:]]{1,3}.[[:digit:]]{1,3}.[[:digit:]]{1,3}|(b.*b.?)+)/' | sed -E 's:(@|/)::g'`

 

		# always recheck that TimeMachine is not yet connected

		#

		if [ "${tm_status}" == "CONNECT_NONE" ]; then

			# perform a simple connectivity test

			ping -c 1 $_dest_server > /dev/null 2>&1

			if [ "$?" == "0" ]; then

				echo "NOTICE: We found this volume to be available for backups: $volume"

				echo "        We will be switching TimeMachine volumes now ..."

				sudo tmutil setdestination "$volume" 

				tm_status=CONNECT_NET

			fi

		fi

	done





	# check if we can reach any of the NET_Volumes hosts given

	#

	for volume in "${USB_Volumes[@]}"; do

		# always recheck that TimeMachine is not yet connected

		#

		if [ "${tm_status}" == "CONNECT_NONE" ]; then

			# check if the volume is available 

			diskutil info "$volume" > /dev/null 2>&1

			if [ "$?" == "0" ]; then

				# try to mount the volume

				diskutil mount "/Volumes/$volume" > /dev/null 2>&1

				if [ "$?" == "0" ]; then	

					sleep 5

					echo "NOTICE: We found this volume to be available for backups: $volume"

					echo "        We will be switching TimeMachine volumes now ..."

					sudo tmutil setdestination "/Volumes/$volume" 

					tm_status=CONNECT_USB

				fi

			fi

		fi

	done





	# bail out if we failed on finding a proper backup volume

	#

	if [ "${tm_status}" == "CONNECT_NONE" ]; then

		echo "ERROR: Failed in finding a TimeMachine Voloume on USB or on the LAN available for backups."

		echo "       Exiting now."

		exit

	else

		echo "NOTICE: A suitable backup volume has been located for TimeMachine backups."

		echo "        Starting backup now ..."

		tmutil startbackup

	fi

else

	if [ "${tm_status}" == "CONNECT_USB" -o "${tm_status}" == "CONNECT_NET" ]; then

		echo "NOTICE: TimeMachine is already connected, current status is: ${tm_status}"

		echo "        TimeMachine destinations will not be switched!"

	else

		echo "ERROR: Unable to figure current TimeMachine status."

	fi

fi



exit