Shell script to toggle a device using a smart switch

ifttt_toggle_device_state.sh

# In IFTTT create two webhooks named using the pattern, "$DEVICE_on" and "$DEVICE_off"
DEVICE="desk_fan"

# This is where the state of the device is kept
DEVICE_STATE_FILE=~/.${DEVICE}.state

IFTTT_KEY=""

# Set the default state of the device to "off" if the status file does not exist
[ -s $DEVICE_STATE_FILE ] || echo "off" > $DEVICE_STATE_FILE

# Get the current state of the device
DEVICE_STATE=$(<$DEVICE_STATE_FILE)

# Toggle the state of the device
DEVICE_STATE=$([ "$DEVICE_STATE" = "on" ] && echo "off" || echo "on")

# Tell IFTTT to toggle the device
curl -s https://maker.ifttt.com/trigger/${DEVICE}_${DEVICE_STATE}/with/key/${IFTTT_KEY} > /dev/null

# Update the device state
echo "${DEVICE_STATE}" > $DEVICE_STATE_FILE

# Capitalizes the first letter of the state
echo "$(tr '[:lower:]' '[:upper:]' <<< ${DEVICE_STATE:0:1})${DEVICE_STATE:1}"