Display info about ram shared between Linux processes

cowstat.rb

#!/usr/bin/env ruby

require 'ostruct'

class LinuxProcess < OpenStruct

  def initialize(args)
    super
    read_status!
  end

  def read_status!
    status = read_proc_file("status").scan(/(.*):[\t ]+(.*)/)
    self.name = status.find { |i| i.first == 'Name' }.last
    self.ppid = status.find { |i| i.first == 'PPid' }.last.to_i
    self.vm_size = status.find { |i| i.first == 'VmSize' }.last.split(' ').first.to_i rescue nil
    self.vm_rss = status.find { |i| i.first == 'VmRSS' }.last.split(' ').first.to_i rescue nil
    self.cmdline = self.read_proc_file("cmdline")
  end

  def read_smaps!
    smaps = read_proc_file("smaps").scan(/(.*):[\t ]+(.*)/)
    private_dirty = smaps.find_all { |i| i.first == 'Private_Dirty' }
    self.private_dirty = private_dirty.inject(0) { |i, pd| i + pd.last.split(' ').first.to_i }
    shared_dirty = smaps.find_all { |i| i.first == 'Shared_Dirty' }
    self.shared_dirty = shared_dirty.inject(0) { |i, sc| i + sc.last.split(' ').first.to_i }
  end

  def pid
    @pid ||= procfile.split('/').last.to_i
  end

  def read_proc_file(name)
    begin
      File.read(File.join("/proc/#{pid}", name))
    rescue Errno::EACCES
      ""
    end
  end

  def self.all
    Dir.glob("/proc/[0-9]*").collect do |procfile|
      LinuxProcess.new :procfile => procfile
    end
  end

end

if !ARGV.empty? and ARGV.first =~ /[^0-9]+/
  pid_name_selector = Regexp.new(ARGV.first)
  pid_selection = []
else
  pid_selection = ARGV.collect { |i| i.to_i }
end

LinuxProcess.all.each do |p|

  if pid_name_selector and pid_name_selector.match(p.cmdline)
    next if p.pid == Process.pid
    pid_selection << p.pid
  elsif (pid_selection & [p.pid, p.ppid]).empty?
    next
  else
    pid_selection << p.pid
  end

  p.read_smaps!

  puts "#{p.pid}: #{p.name} #{p.cmdline}"
  puts "  vm_size:#{p.vm_size} kB  vm_rss:#{p.vm_rss} kB  private_dirty: #{p.private_dirty} kB  shared_dirty: #{p.shared_dirty} kB"

end