walking a directory tree

["Ken Smith" <kgsmith@...>]

I have found myself in a position where I must use Lua to walk a
directory tree and performing some operation on every file.  Is there
an idiomatic way to do this in Lua?  Ideally, I would like something
like Python's os.walk(dir).  Right now, I'm doing this.

for file in io.popen('/usr/bin/find dir -type f') do
  -- deal with file
end

This seems rather heavy-handed and a program that uses this construct
runs out of memory although it is not yet clear if this construct is
the cause.  Thanks in advance for any suggestions.

environment details:
Darwin 8.8.1 (Mac OS X 10.4.8)
Lua 5.1.1

 Ken Smith