We already implemented a tool that works like ls on Linux/MacOS, or dir on Windows, but just as these tools, it doesn't print the file size for directories.

In order to get the size equivalent of a directory, we would have to descend down into it and sum up the size of all files that it contains.

In this recipe, we will implement a tool that does just that. The tool can be run on any folder and will summarize the accumulated size of all directory entries.