ps_lsof.rb

class Prcss
  attr_accessor :pid, :ppid, :command
  attr_reader :done

  def initialize(pid, ppid, command)
    @pid = pid.to_i
    @ppid = ppid.to_i
    @command = command
  end

  def children
    Prcss.list_by(pid.to_s).select{|p| p.ppid == pid }
  end

  def fd_count
    `lsof -p #{pid} | wc -l`.strip.to_i
  end

  def print
    return if done
    fd = fd_count
    puts '%d %d %d %s' % [pid, ppid, fd, command[0..150]] if fd > 0
    done = true
  end

  def print_as_tree
    return if done
    print
    children.each{|c| c.print_as_tree }
  end

  class << self
    def process_map
      @process_map ||= {}
    end

    def find_or_new(pid, ppid, command)
      process_map[pid.to_i] || Prcss.new(pid, ppid, command)
    end

    def list_by(str)
      cmd = "ps -e -o pid,ppid,command"
      cmd << "| grep '#{str}'" if str
      result = `#{cmd}`
      r = result.split("\n").map do |line|
        parts = line.split(/\s+/, 3)
        parts.length == 3 ? Prcss.find_or_new(*parts) : nil
      end
      r.reject{|p| p == nil || p.command =~ /\Agrep\s|\Aps \-e/}
    end

  end
end

if ARGV.length > 0
  ARGV.each do |arg|
    Prcss.list_by(arg).each(&:print_as_tree)
  end
else
  Prcss.list_by(nil).each(&:print)
end