#!/bin/sh
# Script to display CPU usage

RED="\e[31m"
GREEN="\e[32m"
YELLOW="\e[33m"
CYAN="\e[36m"
ENDCOLOR="\e[0m"

# Cache in tmpfs to improve speed and reduce SSD load
cache=/tmp/cpu-script-cache
rm /tmp/cpu-script-cache 2>/dev/null
while true; do
    sleep 1
    cpu_stats=$(awk '/^cpu / {print $2 + $3 + $4 + $5, $5}' /proc/stat)
    if [ ! -f "$cache" ]; then
        echo -n "   ${CYAN}--%${ENDCOLOR}   \r"
        echo "$cpu_stats" >"$cache"
        continue
    fi
    prev_stats=$(cat "$cache")
    total=$(echo "$prev_stats" | awk '{print $1}')
    prev_idle=$(echo "$prev_stats" | awk '{print $2}')
    curr_total=$(echo "$cpu_stats" | awk '{print $1}')
    curr_idle=$(echo "$cpu_stats" | awk '{print $2}')
    total_diff=$((curr_total - total))
    idle_diff=$((curr_idle - prev_idle))

    if [ "$total_diff" -eq 0 ]; then
        usage=0 # Avoid division by zero
    else
        usage=$((100 * (total_diff - idle_diff) / total_diff))
    fi

    if [ "$usage" -lt 50 ]; then
        echo -n "   ${GREEN}${usage}%${ENDCOLOR}   \r"
    elif [ "$usage" -lt 70 ]; then
        echo -n "   ${YELLOW}${usage}%${ENDCOLOR}   \r"
    else
        echo -n "   ${RED}${usage}%${ENDCOLOR}   \r"
    fi
    echo "$cpu_stats" >"$cache"
done