Hi Tom,
Attached is a haskell file I wrote when I was learning how to use the
directory functions. It builds a tree structure corresponding to the directory
tree and finds the files that end in ".txt". It then sorted the files in order
of modification time. As you can guess from the program, it was for managing
weblog entries in Blosxom.
It's beginner-ish code, but you can probably adapt it to your needs.
Note that the top level directory name "dir" is hardcoded into the program.
Best Wishes,
Greg
On Jun 22, 2004, at 5:20 AM, Tom Hofte wrote:
Hi,
�
I'm looking for a way to iteratively read all the files in a directory and
its subdirectories, given the filepath of the top-level dir.
For example, I want to find a file, corresponding to a�given filename,�in a directory and its subdirectories.
�
Is there a way to implement this in Haskell?
�
Kind regards,
�
Tom Hofte
�
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dirtree.hs:
--
-- walk a directory tree and find all of the files ending in .txt
--
module Main (main) where
import Monad
import Directory
import Text.Regex
import List
--
-- dirTree returns a tree with nodes containing file
-- information or directory information and a subdirectory.
--
data DTree = FileNode String | DirNode String [DTree]
addPrefix d str = do return (d ++ str)
addSuffix d str = do return (str ++ d)
scanDir d = do
dentries <- getDirectoryContents d
files <- mapM (addPrefix d) dentries
ffiles <- filterM doesFileExist files
-- directory names require extra processing: we must delete the "." and ".." entries
-- and add a trailing "/"
dirs <- filterM (\x -> do return (x /= "." && x /= "..")) dentries
ddirs <- mapM (addPrefix d) dirs
dddirs <- mapM (addSuffix "/") ddirs
subdirs <- filterM doesDirectoryExist dddirs
subDTrees <- mapM scanDir subdirs
return (DirNode d ((map (\f -> FileNode f) ffiles) ++ subDTrees))
-- walk a directory tree, printing the contents
showDTree (FileNode fname) = do print fname
showDTree (DirNode dname ds) = do
print dname
mapM showDTree ds
return ()
-- given a directory tree, find the files that end in ".txt"
findTxt (DirNode dname ds) = concat (map findTxt ds)
findTxt (FileNode fname) = if (isTextFile fname) then [fname] else []
-- given a file name, see if it ends in ".txt"
isTextFile f = (matchRegex regexp f) /= Nothing where regexp = mkRegex ".*txt"
printIfMatched f = if (isTextFile f) then do print f else do return ()
dir = "/Users/gwright/Desktop/Blosxom/docs/"
timeSortedFiles d = do
directoryTree <- scanDir d
showDTree directoryTree
textFiles <- do return (findTxt directoryTree)
modTimes <- mapM getModificationTime textFiles
fs <- do return (sortBy (\(f1,t1) (f2,t2) -> compare t1 t2) (zip textFiles modTimes))
return (map fst fs)
main = do
fs <- timeSortedFiles dir
fs' <- do return (take 1 fs)
mapM (\f -> do c <- readFile f; putStr c) fs'
return ()
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