#!/bin/bash
#
# Get current HDD temperature. You need TemperatureMonitor by Marcel Bresink (thanks!)
# from http://www.bresink.de/osx/TemperatureMonitor.html
# Needs to be installed in Applications/Utilities
#
HDD_TEMP=`/Applications/Utilities/TemperatureMonitor.app/Contents/MacOS/tempmonitor -c -l -a | grep "SMART Disk" | sed "s/.*: *//" | sed "s/ C$//"`

#
# Assume 40C is normal temperature. Anything over that is overheat
#
OVERHEAT=$(($HDD_TEMP - 40))
if [ "$OVERHEAT" -le 0 ]; then OVERHEAT=0; fi 

#
# Scale the overheat to fan's RPM. Run 1000RPM at 40C, scale to 4000PRM at 70C
# Disclaimer: set yourself whatever you think is safe and/or reasonable. No claims, please.
#
RPM=$((1000 + $OVERHEAT * 100))
RPM4HEX=`printf "%04x" $(($RPM * 4))`

echo "TEMP=$HDD_TEMP OVERHEAT=$OVERHEAT RPM=$RPM RPM4HEX=$RPM4HEX"
#
# Set target PRM using smcFanControl by Hendrik Holtmann (thanks!)
# e.g. from http://www.macupdate.com/app/mac/23049/smcfancontrol
# Needs to be installed in Applications/Utilities
#
/Applications/Utilities/smcFanControl.app/Contents/Resources/smc -k F1Mx -w $RPM4HEX