I found myself having to construct a series of near-identical directory structures, and wanted a quick visualization of their contents. Was too lazy to open a file manager, and was happy for the excuse to code some Ruby. This was the result.

tree

#!/usr/bin/env ruby

TAB_STOP = 2

$directories_only = false
$use_color = true

class Tree
  attr_reader :word, :branches

  def initialize(word = '/')
    @word = word
    @branches = {}
  end

  def branch(word)
    branches[word] ||= Tree.new(word)
  end

  def to_s(indent = 0)
    lines = []
    lines << (" "*TAB_STOP*indent) + word

    branches.each do |name, branch|
      lines << branch.to_s(indent+1)
    end

    lines.join "\n"
  end
end

def help
  puts "Usage: tree [-d]"
  puts "\t d : list directories only"
  puts "\t c : disable color"
  exit
end

help if ARGV.include? "--help"

ARGV.each do |arg|
  if arg[0] == ?-
    arg.bytes.each do |opt|
      case opt
        when ?d then $directories_only = true
        when ?c then $use_color = false
        when ?h then help
        when ?- then ;
        else raise "Unrecognized option: "+opt.chr
      end
    end
  end
end

def blue(str)
  $use_color ? "\e[0;34m#{str}\e[0;0m" : str
end

base = Dir.pwd
tree = Tree.new(blue(File.basename(base)+"/"))
Dir[File.join(Dir.pwd, "**", "*")].each do |fi|
  next if $directories_only &&  !(File.directory? fi)
  relative = fi.gsub(/^#{Regexp::escape File.join(base, '')}/, '')
  nest = relative.split(/\//)

  trunk = tree
  nest.each_with_index do |word, i|
    if i != nest.length-1 || File.directory?(fi)
      word = blue(word + "/")
    end
    trunk = trunk.branch word
  end
end

puts tree