What are all the ways to traverse directory trees?

Question

How do you traverse a directory tree in your favorite language?

What do you need to know to traverse a directory tree in different operating systems? On different f

Answer 1

C++

#include 
#include 
#include 

#define foreach BOOST_FOREACH
namespace fs = boost::filesystem;

fs::recursive_directory_iterator it(top), eod;
foreach (fs::path const & p, std::make_pair(it, eod)) {
    if (is_directory(p)) {
        ...
    } else if (is_regular_file(p)) {
        ...
    } else if (is_symlink(p)) {
        ...
    }
}