Generate a graph of the process tree

process_tree.rb

#!/usr/bin/env ruby

class UnixProcess
  attr_reader :uid, :pid, :ppid, :cmd

  def initialize(uid:, pid:, ppid:, cmd:)
    @uid = uid
    @pid = pid
    @ppid = ppid
    @cmd = cmd
  end

  def to_s
    "#{pid}: #{cmd}"
  end
end

class ProcessTree
  def initialize(processes)
    @processes_hash = processes.inject({}) do |hash, process|
      hash[process.pid] = process
      hash
    end
  end

  def processes
    @processes_hash.values
  end

  def parent(process)
    @processes_hash[process.ppid]
  end
end

class ProcessGraphGenerator
  def generate(filetype, filename)
    File.open(dot_filename, "w") do |file|
      write_dot_graph(file, processes(ps_output))
    end

    `dot -T#{filetype} #{dot_filename} > #{filename}`
  end

  private

  def ps_output
    `ps -e -f`.lines[1..-1]
  end

  def processes(ps_output)
    procs = ps_output.map do |process_line|
      fields = process_line.split
      UnixProcess.new(
        uid: fields[0].to_i,
        pid: fields[1].to_i,
        ppid: fields[2].to_i,
        cmd: fields[7..-1].join(" "),
      )
    end
    ProcessTree.new(procs)
  end

  def write_dot_graph(file, process_tree)
    file.puts "digraph G {"
    file.puts "  graph [rankdir=LR];"
    file.puts "  node [shape=rectangle];"
    process_tree.processes.each do |process|
      if process.pid != 1
        file.puts "  \"#{process_tree.parent(process)}\" -> \"#{process}\";"
      end
    end
    file.puts "}"
  end

  def dot_filename
    "/tmp/graph.dot"
  end
end

ProcessGraphGenerator.new.generate(:pdf, "graph.pdf")