From: Joe Van Dyk <joevandyk@...>
Date: 2005-11-17T13:37:54+09:00
Subject: Improving code...

It should be fairly obvious as to what I'm doing (getting information
about a process -- right now just cpu percentage).

Any ideas on how I can improve this code?  I'm not a big fan of how
the scanf stuff works.

This is also heavily *nix-biased, and I'm not sure how to properly
work with Windows.



require 'scanf'

class ProcessInfo

  def initialize pid
    @pid = pid
  end

  def cpu_percentage
    # if we don't know the previous time, return 0.0
    if @previous_cpu_time.nil? || @previous_time.nil?
      @previous_cpu_time = get_process_cpu_time
      @previous_time = Time.now
      0.0
    else
      # Get current and elapsed time
      current_time = Time.now
      elapsed_time = current_time - @previous_time

      # Get current and elapsed cpu time
      current_cpu_time = get_process_cpu_time
      elapsed_cpu_time = current_cpu_time - @previous_cpu_time

      # Calculate the percentage used
      percentage = elapsed_cpu_time / elapsed_time

      # Save the current time
      @previous_time = current_time
      @previous_cpu_time = current_cpu_time

      percentage
    end
  end

  private
  # Need to get the process stats
  def get_process_cpu_time
    stats = get_process_stats
    stats[:system_cpu_time] + stats[:user_cpu_time]
  end

  # See 'man proc' for details.
  def get_process_stats
    proc_stats = File.read("/proc/#{ @pid }/stat")

    # EEWWWW -- gets the stuff from /proc/<pid>/stat and puts it into vars
    pid, comm, state, ppid, pgrp, session, tty_nr, tpgid, flags,
      minflt, cminflt, majflt, cmajflt, utime, stime, cutime,
      cstime, priority, nice, who_cares, itrealvade,
      starttime, vsize, rss, rlim, startcode, endcode, startstack,
      kstkesp, kstkeip, signal, blocked, sigignore, sigcatch,
      wchan, nswap, cnswap, exit_signal, processor =
    proc_stats.scanf("%d %s %c %d %d %d %d %d %d %d \
%d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d \
%d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d")

    # Just put the ones I need into the hash
    stats = {}
    stats[:system_cpu_time] = stime
    stats[:user_cpu_time] = utime
    stats[:processor] = processor
    stats
  end
end


 # example usage

fail "hey, specify a process id please!" if ARGV.size != 1
pid = ARGV.shift
c = ProcessInfo.new pid

loop do
  puts "current cpu percentage = #{ c.cpu_percentage }"
  sleep 3
end