fanspeed

#!/bin/bash
# Set Mac fan speed according to CPU temperature. 
# Use without arguments or see README for help.
#
# Copyright (C) 2015, https://github.com/4gra/smc-hd-shim
# This program comes with ABSOLUTELY NO WARRANTY; for details see included LICENCE.
# This is free software, and you are welcome to redistribute it under certain
# conditions; view the included file LICENCE for details.
#
# I wrote this for my MacBookPro4,1; your mileage WILL vary on other hardware,
# and might even vary on idential hardware depending on upgrades, load, etc. 
#
# Requires the smc tool:
#   https://github.com/hholtmann/smcFanControl/tree/master/smc-command
# Thrown together using awk, bc, cut, printf.  Could be improved.
# What do you mean, "should've written it in C"?
#
# Essential reference:
#   http://www.parhelia.ch/blog/statics/k3_keys.html
#
mode="$1"; shift
smc="/usr/local/bin/smc"

# Acceptable Min / Max values
min=1440
max=6000
# Sleep timer - ONLY for test daemon mode.
zzz=30
# Fan formula.  Works for me.  No guarantees.  
# Stays a little higher, and cooler, than firmware used to, on my MBP4,1.
formula='(i^2)+(i*3)+350'

# Set back to auto.
function safemode() {
    logger "Returning to automatic mode."
    echo "Returning to automatic mode." >&2
    $smc -k 'FS! ' -w 0000
    exit 1
}

# IS fan speed forced?
function is_forced() {
    ${smc} -f | awk '
        /^Total fans/{TOTAL=$5;}
        /Mode *: *forced$/{FORCED++;}
        END{if(FORCED==TOTAL && TOTAL>0){exit 0;}exit 1;}'
    echo $?
}

# Convert to hex and shift as required by SMC
function hexspeed() {
    printf "%02x\n" $(( $1 << 2 ))
}

# Get the integer part of the temperature and convert to decimal degrees C.
# If the output from smc changes, this WILL break, so I put in a basic sanity check.
function dectemp() {
    # note we're ignoring the low bits
    temp=$($smc -k Th0H -r | cut -c 24,25)
    dec=$((16#${temp}))
    if [[ -n $dec && $dec -ge 0 ]]; then
        echo $dec
    else
        logger "Couldn't read temperature."
        echo "Couldn't read temperature." >&2
        safemode
        exit 1
    fi
}

# Sets fans to the given speed(s).
# $1: fan1, and fan2 if $2 is unset.
# $2: fan2
function setspeed() {
    trap safemode ERR
    # auto mode
    if [[ $1 == 'auto' ]]; then
        [[ $(is_forced) == 0 ]] && $smc -k 'FS! ' -w 0000
        return 0
    fi
    # everything else:
    [[ $2 -ne 0 ]] && s2=$2 || s2=$1
    echo "Setting $1 $s2" >&2
    fan1=$(hexspeed $1)
    fan2=$(hexspeed $s2)
    # Set the force bit if not already set. 
    if [[ $(is_forced) != 0 ]]; then
        $smc -k 'FS! ' -w 0003
    fi
    # TODO: check / fix errors from SMC, since it outputs 0 on failure :(
    $smc -k F0Tg -w $fan1 
    $smc -k F1Tg -w $fan2
}

# Calculate the speed and limit it.
function calcspeed() {
    ispd=$(echo "i=$(dectemp); $formula" | bc)
    [[ $ispd -gt $max ]] && ispd=$max
    [[ $ispd -lt $min ]] && ispd=$min
    echo $ispd 
}

# Guess commandline intentions from this point on!
if [[ $mode == 'update' ]]; then
    echo "Starting at $(date)" >&2
    setspeed $(calcspeed)

elif [[ $mode == 'daemon' ]]; then
    echo "Starting at $(date)" >&2
    trap safemode QUIT 
    while true; do
        setspeed $(calcspeed)
        sleep $zzz
    done
    exit 0

elif [[ $mode == 'auto' ]]; then
    setspeed auto
    $smc -f

elif [[ $mode == 'set' ]]; then
    setspeed $(printf '%d' $1) $(printf '%d' $2)
    $smc -f

elif [[ $mode == 'info' ]]; then
    $smc -f | awk 'BEGIN{printf("Fans: ");}/Actual/{printf $4" ";}END{print "";}'
    echo "Monitored temperature: $(dectemp)"
    echo "Suggested speed: $(calcspeed)"

else
    echo "Usage: $0 [info|auto|set <RPM [RPM2]>|update|daemon]"
    echo "  See $0 source for details."
    echo "  $0 info"
    echo "    print some temperature / fan information"
    echo "  $0 auto | set <RPM [RPM2]>"
    echo "    sets / unsets fan speed using $smc"
    echo "    auto: removes the force bit, allowing firmware (non-)control."
    echo "  $0 update" 
    echo "    sets fan speed automatically, once, and quit"
    echo "    designed to be called by launchd on a schedule."
    echo "  $0 daemon" 
    echo "    sets fan speed automatically on a ${zzz} second loop"
    echo "    for testing purposes only."
    exit 1

fi