stuff to add to FilePath or System.directory?

10 Jan 2005

      Here's some stuff that I have in the cabal Utils module that might be
useful in System.FilePath or System.Directory...

What would folks think of adding them? I find createIfNotExists to be
especially useful, though maybe it should be createDirectoryAndParents
or something.

peace,

  isaac

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module PathStuff (createIfNotExists, currentDir, removeFileRecursive) where

import Control.Monad    (unless, liftM, mapM)
import Data.Maybe       (Maybe, catMaybes)
import System.IO.Error  (try)
import System.FilePath  (pathParents)
import System.Directory (getDirectoryContents, removeDirectory,
                         setCurrentDirectory, getCurrentDirectory,
                         doesDirectoryExist, removeFile, 
                         createDirectory)

createIfNotExists :: Bool     -- ^Create its parents too?
		  -> FilePath -- ^The path to the directory you want to make
		  -> IO ()
createIfNotExists parents file
    = do b <- doesDirectoryExist file
	 case (b,parents, file) of 
		  (_, _, "")    -> return ()
		  (True, _, _)  -> return ()
		  (_, True, _)  -> createDirectoryParents file
		  (_, False, _) -> createDirectory file

-- |like mkdir -p.  Create this directory and its parents
createDirectoryParents :: FilePath -> IO()
createDirectoryParents file
    = mapM_ (createIfNotExists False) (tail (pathParents file))

-- |The path name that represents the current directory.  May be
-- system-specific.  In Unix, it's "." FIX: What about other arches?
currentDir :: FilePath
currentDir = "."

-- |Probably follows symlinks, be careful.
removeFileRecursive :: FilePath -> IO ()
removeFileRecursive startLoc
    = do cont' <- getDirectoryContents startLoc
         let cont = filter (\x -> x /= "." && x /= "..") cont'
         curDir <- getCurrentDirectory
         setCurrentDirectory startLoc
         dirs <- removeFiles cont
         mapM removeFileRecursive dirs
         setCurrentDirectory curDir
         removeDirectory startLoc

-- |Remove a list of files; if it encounters a directory, it doesn't
-- remove it, but returns it.  Throws everything that removeFile
-- throws unless the file is a directory.
removeFiles :: [FilePath]    -- ^Files and directories to remove
            -> IO [FilePath]
            {- ^The ones we were unable to remove because they were of
                an inappropriate type (directory) removeFiles -}
removeFiles files = liftM catMaybes (mapM rm' files)
      where
       rm' :: FilePath -> IO (Maybe FilePath)
       rm' f = do  temp <- try (removeFile f)
                   case temp of
                    Left e  -> do isDir <- doesDirectoryExist f
                                  -- If f is not a directory, re-throw the error
                                  unless isDir $ ioError e
                                  return (Just f)
                    Right _ -> return Nothing

Isaac Jones

Krasimir Angelov

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