having trouble walking into subdirectories

Question

To familiarize myself with <filesystem>, I wrote a simple recursive function that walks a directory tree:

#include <filesystem>

namespace fs = std::tr2::sys;
const fs::directory_iterator fs_end;

void walk(fs::path root)
{
    std::cout << "ENTERING " << root << '\n';
    for (auto it = fs::directory_iterator(root); it != fs_end; ++it)
    {
        if (is_directory(it->status()))
        {
            walk(it->path());
        }
        else
        {
            std::cout << it->path() << " is not a directory\n";
        }
    }
    std::cout << "LEAVING " << root << '\n';
}

int main()
{
    walk("d:/a");
}

Unfortunately, this will only visit the immediate directories inside the directory specified in main. The subdirectories are not visited. To illustrate, I made a very simple directory structure:

The output of the program is as follows:

ENTERING d:/a
ENTERING b
LEAVING b
ENTERING c
LEAVING c
LEAVING d:/a

As you can see, d is not visited. Apparently, the for loop is run zero times inside c. Why?

Answer 1

From the output it looks like it->path() is giving you the relative path, not the absolute path. While iterating, your current directory does not change, so trying to iterate over a directory with path 'b' or 'c' won't work and no subdirectories will be found in that non-existent directory. In your for-loop, try the following recursive call:

walk(root/it->path());

Now, when your program examines directory c, it should output:

ENTERING d:/a/c 
ENTERING d:/a/c/d
etc...