set scaling_max_freq for all cpu in system

set_freq

#!/bin/bash -eu

# set max cpu scaling frequency

# get limits in MHz
declare -r MIN_KHZ=$( cat /sys/devices/system/cpu/cpufreq/policy0/cpuinfo_min_freq )
declare -r MAX_KHZ=$( cat /sys/devices/system/cpu/cpufreq/policy0/cpuinfo_max_freq )
declare -r MIN_MHZ=$(( MIN_KHZ / 1000 ))
declare -r MAX_MHZ=$(( MAX_KHZ / 1000 ))

# func used in errors
fatal() {
    echo "$1" 1>&2
    exit 1
}

# echo usage and limits if no parameters
[[ $# > 0 ]] || {
    declare -r CURR=$( cat /sys/devices/system/cpu/cpufreq/policy0/scaling_max_freq )
    declare -r CURR_MHZ=$(( $CURR / 1000 ))
    echo "Usage: $0 <max_freq_in_MHz>"
    echo "Min freq: $MIN_MHZ MHz"
    echo "Max freq: $MAX_MHZ MHz"
    echo "Current freq: $CURR_MHZ MHz"
    exit 0
}

# get freq parameter
declare -r FREQ_MHZ="${1:0}"

# non-numeric parameter?
[[ $FREQ_MHZ =~ ^[0-9]+$ ]] || fatal "Input frequency not a number !"

# frequency greater then max?
[[ $FREQ_MHZ -le $MAX_MHZ ]] || fatal "Input frequency > $MAX_MHZ !"

# frequency lower than min?
[[ $FREQ_MHZ -ge $MIN_MHZ ]] || fatal "Input frequency < $MIN_MHZ !"

# set frequency
declare -r FREQ=$(( FREQ_MHZ * 1000 ))
for i in /sys/devices/system/cpu/cpufreq/policy*/scaling_max_freq; do
    echo "$FREQ" > $i
done