Generate directory tree-like graphs, based on https://web.archive.org/web/20171105234622/http://www.graphviz.org:80/content/generate-directory-tree-dot

treedot.rb

# Based on http://www.graphviz.org/content/generate-directory-tree-dot
def treedot(tree)
  nodes = Hash.new {|h,k| h[k] = "node#{h.size}"}
  dot = 'digraph tree{
  fixedsize=true
  splines=ortho
  node [style="rounded,filled", fillcolor="#E5E5E5", concentrate=true]'
  tree.each {|name,subtree| add(dot, name, subtree, nodes)}
  dot << "\n}"
end

def add(dot, name, tree, nodes)
  node = nodes[name]
  dot << "\n  #{node}[label=\"#{name}\" shape=box]"
  size = 1
  if tree
    previous = node
    previous_size = 1
    tree.each {|name2,subtree|
      node2 = nodes[name2]
      # Vertical
      dot << "\n\n  #{previous} -> #{node}_to_#{node2} [arrowhead=none, minlen=#{previous_size}]"
      # Horizontal
      dot << "\n  #{previous = "#{node}_to_#{node2}"} -> #{node2} {rank=same #{previous} [shape=point] #{node2} [label=\"#{name2}\"] }"
      size += previous_size = add(dot, name2, subtree, nodes)
    }
  end
  size
end

tree = {
  'a1(a)' => {
    'b1(a)' => {
      'c1(a)' => {
        'd1(a)' => nil
      },
      'c2(a)' => {
        'd2(a)' => nil,
        'd3(a)' => nil
      }
    },
    'b2(a)' => nil
  }
}

#puts treedot({}), '---'
#puts treedot({'a' => nil}), '---'
#puts treedot({'a' => {'b' => nil}}), '---'
puts dot = treedot(tree)

IO.write('treedot.dot', dot)
`graphviz/bin/dot.exe treedot.dot -O -Tpdf`