diff --git a/clean_files.txt b/clean_files.txt
index a70a44c2..069d7ae5 100644
--- a/clean_files.txt
+++ b/clean_files.txt
@@ -103,6 +103,7 @@ plugins/available/jump.plugin.bash
 plugins/available/less-pretty-cat.plugin.bash
 plugins/available/node.plugin.bash
 plugins/available/nodenv.plugin.bash
+plugins/available/osx-timemachine.plugin.bash
 plugins/available/osx.plugin.bash
 plugins/available/percol.plugin.bash
 plugins/available/plenv.plugin.bash
diff --git a/plugins/available/osx-timemachine.plugin.bash b/plugins/available/osx-timemachine.plugin.bash
index 3d7ff00c..2eef14bd 100644
--- a/plugins/available/osx-timemachine.plugin.bash
+++ b/plugins/available/osx-timemachine.plugin.bash
@@ -1,84 +1,94 @@
-cite about-plugin
+# shellcheck shell=bash
 about-plugin 'OS X Time Machine functions'
 
-function time-machine-destination() {
-  group "osx-timemachine"
-  about "Shows the OS X Time Machine destination/mount point"
+if [[ "${OSTYPE}" != 'darwin'* ]]; then
+	_log_warning "This plugin only works with Mac OS X"
+	return 1
+fi
 
-  echo $(tmutil destinationinfo | grep "Mount Point" | sed -e 's/Mount Point   : \(.*\)/\1/g')
+function time-machine-destination() {
+	group "osx-timemachine"
+	about "Shows the OS X Time Machine destination/mount point"
+
+	tmutil destinationinfo | grep "Mount Point" | sed -e 's/Mount Point   : \(.*\)/\1/g'
 }
 
 function time-machine-list-machines() {
-  group "osx-timemachine"
-  about "Lists the OS X Time Machine machines on the backup volume"
+	group "osx-timemachine"
+	about "Lists the OS X Time Machine machines on the backup volume"
 
-  local tmdest="$(time-machine-destination)/Backups.backupdb"
+	local tmdest
+	tmdest="$(time-machine-destination)/Backups.backupdb"
 
-  find "$tmdest" -maxdepth 1 -mindepth 1 -type d | grep -v "/\." | while read line ; do
-    echo "${line##*/}"
-  done
+	find "$tmdest" -maxdepth 1 -mindepth 1 -type d | grep -v "/\." | while read -r line; do
+		echo "${line##*/}"
+	done
 }
 
 function time-machine-list-all-backups() {
-  group "osx-timemachine"
-  about "Shows all of the backups for the specified machine"
-  param "1: Machine name (optional)"
-  example "time-machine-list-all-backups my-laptop"
+	group "osx-timemachine"
+	about "Shows all of the backups for the specified machine"
+	param "1: Machine name (optional)"
+	example "time-machine-list-all-backups my-laptop"
 
-  # Use the local hostname if none provided
-  local COMPUTERNAME=${1:-$(scutil --get ComputerName)}
-  local BACKUP_LOCATION="$(time-machine-destination)/Backups.backupdb/$COMPUTERNAME"
+	# Use the local hostname if none provided
+	local COMPUTERNAME BACKUP_LOCATION
+	COMPUTERNAME=${1:-$(scutil --get ComputerName)}
+	BACKUP_LOCATION="$(time-machine-destination)/Backups.backupdb/$COMPUTERNAME"
 
-  find "$BACKUP_LOCATION" -maxdepth 1 -mindepth 1 -type d | while read line ; do
-    echo "$line"
-  done
+	find "$BACKUP_LOCATION" -maxdepth 1 -mindepth 1 -type d | while read -r line; do
+		echo "$line"
+	done
 }
 
 function time-machine-list-old-backups() {
-  group "osx-timemachine"
-  about "Shows all of the backups for the specified machine, except for the most recent backup"
-  param "1: Machine name (optional)"
-  example "time-machine-list-old-backups my-laptop"
+	group "osx-timemachine"
+	about "Shows all of the backups for the specified machine, except for the most recent backup"
+	param "1: Machine name (optional)"
+	example "time-machine-list-old-backups my-laptop"
 
-  # Use the local hostname if none provided
-  local COMPUTERNAME=${1:-$(scutil --get ComputerName)}
-  local BACKUP_LOCATION="$(time-machine-destination)/Backups.backupdb/$COMPUTERNAME"
+	# Use the local hostname if none provided
+	local COMPUTERNAME BACKUP_LOCATION
+	COMPUTERNAME=${1:-$(scutil --get ComputerName)}
+	BACKUP_LOCATION="$(time-machine-destination)/Backups.backupdb/$COMPUTERNAME"
 
-  # List all but the most recent one
-  find "$BACKUP_LOCATION" -maxdepth 1 -mindepth 1 -type d -name 2\* | sed \$d | while read line ; do
-    echo "$line"
-  done
+	# List all but the most recent one
+	find "$BACKUP_LOCATION" -maxdepth 1 -mindepth 1 -type d -name 2\* | sed \$d | while read -r line; do
+		echo "$line"
+	done
 }
 
 # Taken from here: http://stackoverflow.com/a/30547074/1228454
 function _tm_startsudo() {
-    sudo -v
-    ( while true; do sudo -v; sleep 50; done; ) &
-    SUDO_PID="$!"
-    trap _tm_stopsudo SIGINT SIGTERM
+	sudo -v # validate without running a command.
+	(while sudo "-${SUDO_ASKPASS:+A}v"; do
+		sleep 50
+	done) &
+	SUDO_PID="$!"
+	trap _tm_stopsudo SIGINT SIGTERM
 }
 function _tm_stopsudo() {
-    kill "$SUDO_PID"
-    trap - SIGINT SIGTERM
-    sudo -k
+	kill "$SUDO_PID"
+	trap - SIGINT SIGTERM
+	sudo -k
 }
 
 function time-machine-delete-old-backups() {
-  group "osx-timemachine"
-  about "Deletes all of the backups for the specified machine, with the exception of the most recent one"
-  param "1: Machine name (optional)"
-  example "time-machine-delete-old-backups my-laptop"
+	group "osx-timemachine"
+	about "Deletes all of the backups for the specified machine, with the exception of the most recent one"
+	param "1: Machine name (optional)"
+	example "time-machine-delete-old-backups my-laptop"
 
-  # Use the local hostname if none provided
-  local COMPUTERNAME=${1:-$(scutil --get ComputerName)}
+	# Use the local hostname if none provided
+	local COMPUTERNAME=${1:-$(scutil --get ComputerName)} _old_backup
 
-  # Ask for sudo credentials only once
-  _tm_startsudo
+	# Ask for sudo credentials only once
+	_tm_startsudo
 
-  echo "$(time-machine-list-old-backups "$COMPUTERNAME")" | while read i ; do
-    # Delete the backup
-    sudo tmutil delete "$i"
-  done
+	while read -r _old_backup; do
+		# Delete the backup
+		sudo tmutil delete "$_old_backup"
+	done <<< "$(time-machine-list-old-backups "$COMPUTERNAME")"
 
-  _tm_stopsudo
+	_tm_stopsudo
 }