System.Directory.ListTree

Monadic directory tree.

-- List of files under "." or subfolders with ".markdown" extension,
-- except for those with a name starting with "_" somewhere in their path. (like "_cache/index.markdown")
markdownFiles :: ListT IO FilePath
markdownFiles
    = filter ((== ".markdown") . takeExtension) -- only take files with a ".markdown" extension
    . lastL                                     -- get the leaves of the tree (files, not directories)
    . scanl1 appendPath                         -- transform tree nodes to filenames including path
    . prune (not . isPrefixOf "_")              -- ignore directories or files whose name starts with "_"
    $ directoryTree "."                         -- directory tree starting at "."

Module name System.Directory.Tree is a better fit but it is taken by "directory-tree", a read-directory-tree-in-bulk module.

Documentation

directoryTree :: MonadIO m => FilePath -> ListT (ListT m) FilePath

appendPath :: FilePath -> FilePath -> FilePath

When used with scanl or scanl1, transforms tree of filenames to tree of filenames with the paths