From: Brad Volz <bradv@...>
Date: 2008-12-16T19:17:48+09:00
Subject: implementing python's os.walk

Hello,

I seem to be having some difficulty creating a version of python's  
os.walk() for ruby, and I was hoping for some pointers.

As some background, python's os.walk() [1] is a generator function.   
It is passed the top of a directory tree and it returns the following  
for each subdirectory that it encounters:
   . the working directory
   . an Array of subdirectories
   . an Array of non-directory files

Here is some truncated output for my use case:

 >>> import os
 >>> repo = '/usr/local/nfsen/profiles-data/live/lax1er1'
 >>> for root, dirs, files in os.walk(repo):
...     if len(files) == 288:
...         print root
...
/usr/local/nfsen/profiles-data/live/lax1er1/2008/11/11
  ..
/usr/local/nfsen/profiles-data/live/lax1er1/2008/12/13

Essentially, when there are exactly 288 files in a subdirectory, I  
want to print or otherwise do something with the working directory.

Here is my attempt at simply translating this library function to ruby:

#! /usr/bin/env ruby

require 'pp'

dirs = [ '/usr/local/nfsen/profiles-data/live/lax1er1' ]

def find_dirs(top)
   dirs = []
   nondirs = []
   Dir.entries(top).each do |f|
     next if f =~ /(\.$|\.\.$)/
     full_path = [top, f].join('/')
     if File.directory?(full_path)
       dirs.push(full_path)
     else
       nondirs.push(full_path)
     end
   end

   yield top, dirs, nondirs

   dirs.each do |d|
     if File.directory?(d)
       for o in find_dirs(d) { |a,b,c| puts "#{a} #{b} #{c}"}
         yield o
       end
     end
   end
end

find_dirs(dirs[0]) do |top,dirs,nondirs|
   if nondirs.length == 288
     puts "#{top}"
   end
end

There are some things that I know are wrong or missing, but that is  
due to trying to get something to run at all without throwing an  
exception.

The part that I think is totally wrong is:

	for o in find_dirs(d) { |a,b,c| puts "#{a} #{b} #{c}"}

It's really only in there currently to keep the from getting  
'LocalJumpError: no block given.'  Unfortunately, I have no idea what  
the correct way to deal with this would be.

The missing part would be including the directory contents in addition  
to the working directory and the Array of subdirectories.

So, I guess my main questions would be:  What do I need to do to get  
this sort of a generator to work?  Do I need to wrap this up in a  
'class' or is a 'def' sufficient?  What should the block look like,  
and where should it be in the code?

Thanks for reading,

Brad

[1]  http://svn.python.org/view/python/branches/release25-maint/Lib/os.py?rev=62757&view=auto