A pure-Ruby 'tree' utility

tree.rb

#!/usr/bin/ruby

=begin
Changelog for 1.7
 * Fixed a bug where bottom-level directories did not, in fact, have their '/'
 * Allowed the specification of flags and directories in any order. Thus, the
   results of `tree -depth 1 test` and `tree test -depth 1` are identical, and
   either can be used.

Changelog for 1.6.2
 * Added a '/' for the very first, root directory

Changelog for 1.6.1
 * Removed the extra, trailing '/' on symlinks

Changelog for 1.6
 * Fixed the bug where even the last folder in a list would have '|' under it
   for sub-items

Changelog for 1.5
 * Added the -sym flag to follow symlinks
 * Cleaned up the display_directory method to only execute the list.each block,
   instead of treating the last entry differently in a separate but similar
   chunk of code
 * Made sure every folder had a '/' after it to clear up confusion

Changelog for 1.4
 * Added the -depth flag to limit the depth of the tree
 * Improved the flag system to allow for non-truth values

Changelog for 1.3
 * Added the flag/config system
 * Implemented the -app and -help flags
=end

USAGE = "\
A 'tree' replacement utility for systems.  It displays a textual filesystem tree
of either the current directory, or one supplied via command-line argument.  It
is not as featured as the UNIX version (no 'ls' colors, etc) but it works too.

usage: tree [options] path
options:
  -app      Display the inside of .app folders (Mac applications)
  -depth N  Limits the tree to N directories (0 being top-level)
  -help     Shows this message
  -sym      Follow symlinks instead of displaying their targets

example:
	user@host$ tree path
	path/
	|-- file.txt
	|-- link -> location
	`-- folder/
	    `-- subfile1

Version 1.7.  All code is released under the MIT license. Anybody can use it,
copy it, give it away, modify it, and so on.  (c) 2010 Chris 'hr4dish' Sz."

def display_directory(path,offset='',depth=0)
	list = Dir[path+'/*'] # Glob
	return if list.length == 0
	list.each { |f|
		delim = (f == list.last) ? '`' : '|'
		link = File.symlink? f
		checkf = (link) ? File.readlink(f) : f
		checkdir = File.directory? checkf
		print offset+delim+'-- '+f.split('/').last # Just the name, thanks
		print '/' if checkdir
		dir = if checkdir then
			if $config['depth'] == -1 or depth < $config['depth'] then
				if f =~ /\.app$/ then
					not $config['app']
				elsif link then
					$config['sym']
				else
					true
				end
			else
				false
			end
		end
		if dir then
			delim = (delim == '`') ? ' ' : '|'
			print "\n"
			display_directory(f,offset+delim+'   ',depth+1)
		else
			# Symlinked directories get a / too
			print(' -> '+File.readlink(f)) if link
			print "\n"
			#print(( (checkdir) ? '/' : '' )+' -> '+File.readlink(f)) if link
		end
	}
end

$config = {
	'app' => true,
	'help' => false,
	'depth' => -1,
	'sym' => false
}

# Parse options
ARGV.each_with_index { |opt, i|
	next unless opt[0] == 45
	opt = opt[1..opt.length] # drop the -
	if [true, false].include? $config[opt] then
		$config[opt] = !$config[opt] # toggle
	else
		arg = ARGV[i + 1]
		case $config[opt].class.to_s
			when "Fixnum"
				$config[opt] = arg.to_i
			when "String"
				$config[opt] = arg
		end
		ARGV.delete_at i+1
	end
	ARGV.delete_at i
}

if $config['help'] then
	puts USAGE
	exit 0
end

ARGV << '.' unless ARGV.length > 0
ARGV.each { |dir|
	puts dir+"/"
	display_directory dir
	print "\n" unless ARGV.last == dir
}