cpufreqctl

#!/usr/bin/env bash
CPU_LAST_FILE=/tmp/noahhuppert-alligator-cpufreq-last

CPUS_DIR=/sys/devices/system/cpu
CPU_FREQ_FILE=cpufreq/scaling_governor

check() {
    if [[ "$?" != "0" ]]; then
	   die "$@"
    fi
}

bold() {
    echo "$(tput bold)$@$(tput sgr0)"
}

die() {
    echo "Error: $@" >&2
    exit 1
}

# Sets all CPU frequencies
set_cpu_freq() { # ( freq_value )
    freq_value="$1"

    now_freq=$(cat "${CPUS_DIR}/cpu0/${CPU_FREQ_FILE}")
    check "Failed to get CPU0's frequency to save as previous frequency"

    prev_freq=$(get_last_cpu_freq)
    check "Failed to get previous frequency"

    if [[ "$now_freq" != "$prev_freq" ]]; then
	   echo "$now_freq" > "$CPU_LAST_FILE"
	   check "Failed to save previous CPU frequency"
    fi

    echo "$freq_value" | tee "${CPUS_DIR}/"cpu*/"${CPU_FREQ_FILE}"
    check "Failed to set CPUs to \"$freq_value\" mode"
    
    bold "Set CPU's frequency scaling to \"$freq_value\" mode"
}

# Gets last CPU frequency
get_last_cpu_freq() {
    cat "$CPU_LAST_FILE"
}

while getopts "hpsgu" opt; do
    case "$opt" in
	   h)
		  cat <<EOF
cpufreqctl - Adjusts the linux Kernel's CPU frequency scaling mechanism

USAGE

    cpufreqctl [-h] -p|-r|-s

OPTIONS

    -h    Show help text
    -p    Set CPU frequency scale to performance mode
    -s    Set CPU frequency scale to powersave mode
    -g    Get CPU frequency scale values
    -u    Undo to last CPU frequency mode

BEHAVIOR

    Options -p, -s, -g, and -u cannot be provided at the
    same time.

    Stores the state of the CPU frequency before making
    any change in

        $CPU_LAST_FILE

    Uses the file

        ${CPUS_DIR}/cpu*/${CPU_FREQ_FILE}

    to control the Kernel CPU frequency scaling.

EOF
		  exit 0
		  ;;
	   p) opt_perf=true ;;
	   s) opt_save=true ;;
	   g) opt_get=true ;;
	   u) opt_undo=true ;;
	   '?') die "Unknown option" ;;
    esac
done

if [ -n "$opt_perf" ] && [ -n "$opt_save" ] && ["$opt_undo" ]; then
    die "Options -p, -s, and -u cannot both be provided"
fi

if [ -n "$opt_perf" ]; then
    set_cpu_freq performance
elif [ -n "$opt_save" ]; then
    set_cpu_freq powersave
elif [ -n "$opt_undo" ]; then
    last=$(get_last_cpu_freq)
    check "Failed to get last CPU frequency"

    set_cpu_freq "$last"

    bold "Reverted CPU's frequency"
elif [ -n "$opt_get" ]; then
    cat "${CPUS_DIR}/"cpu*/"${CPU_FREQ_FILE}"
    check "Failed to get CPU frequencies"
else
    die "Must specify options -p, -s, and -u"
fi