!7

p-typewriter {
  long PREV_TOTAL = 0, PREV_IDLE = 0;
  
  repeat with sleep 1 {
    S line = first(toLines(loadTextFile("/proc/stat")));
    print(line);
    S[] CPU = line.split("\\s+");
  
    long IDLE = Long.parseLong(CPU[4]); //Get the idle CPU time.
    long TOTAL = Long.parseLong(CPU[1]) + Long.parseLong(CPU[2]) + Long.parseLong(CPU[3]) + Long.parseLong(CPU[4]);
  
    long DIFF_IDLE = IDLE - PREV_IDLE;
    long DIFF_TOTAL = TOTAL - PREV_TOTAL;
    long DIFF_USAGE = DIFF_TOTAL == 0 ? 0 : (1000 * (DIFF_TOTAL - DIFF_IDLE) / DIFF_TOTAL + 5) / 10;
    print("CPU: " + DIFF_USAGE + "%");
  
    PREV_TOTAL = TOTAL;
    PREV_IDLE = IDLE;
    //return (float) DIFF_USAGE;
  }
}

Thanks to http://stackoverflow.com/questions/28787946/get-cpu-load-per-core-using-java