System.FilePath.Posix

filepath-1.2.0.0: Library for manipulating FilePaths in a cross platform way.

Portability | portable
Stability | stable
Maintainer | libraries@haskell.org

System.FilePath.Posix

Contents

- Separator predicates
- Path methods (environment $PATH)
- Extension methods
- Drive methods
- Operations on a FilePath, as a list of directories
- Low level FilePath operators
- File name manipulators

Description

A library for FilePath manipulations, using Posix style paths on all platforms. Importing System.FilePath is usually better.

Synopsis

- type FilePath = String
- pathSeparator :: Char
- pathSeparators :: [Char]
- isPathSeparator :: Char -> Bool
- searchPathSeparator :: Char
- isSearchPathSeparator :: Char -> Bool
- extSeparator :: Char
- isExtSeparator :: Char -> Bool
- splitSearchPath :: String -> [FilePath]
- getSearchPath :: IO [FilePath]
- splitExtension :: FilePath -> (String, String)
- takeExtension :: FilePath -> String
- replaceExtension :: FilePath -> String -> FilePath
- dropExtension :: FilePath -> FilePath
- addExtension :: FilePath -> String -> FilePath
- hasExtension :: FilePath -> Bool
- (<.>) :: FilePath -> String -> FilePath
- splitExtensions :: FilePath -> (FilePath, String)
- dropExtensions :: FilePath -> FilePath
- takeExtensions :: FilePath -> String
- splitDrive :: FilePath -> (FilePath, FilePath)
- joinDrive :: FilePath -> FilePath -> FilePath
- takeDrive :: FilePath -> FilePath
- hasDrive :: FilePath -> Bool
- dropDrive :: FilePath -> FilePath
- isDrive :: FilePath -> Bool
- splitFileName :: FilePath -> (String, String)
- takeFileName :: FilePath -> FilePath
- replaceFileName :: FilePath -> String -> FilePath
- dropFileName :: FilePath -> FilePath
- takeBaseName :: FilePath -> String
- replaceBaseName :: FilePath -> String -> FilePath
- takeDirectory :: FilePath -> FilePath
- replaceDirectory :: FilePath -> String -> FilePath
- combine :: FilePath -> FilePath -> FilePath
- (</>) :: FilePath -> FilePath -> FilePath
- splitPath :: FilePath -> [FilePath]
- joinPath :: [FilePath] -> FilePath
- splitDirectories :: FilePath -> [FilePath]
- hasTrailingPathSeparator :: FilePath -> Bool
- addTrailingPathSeparator :: FilePath -> FilePath
- dropTrailingPathSeparator :: FilePath -> FilePath
- normalise :: FilePath -> FilePath
- equalFilePath :: FilePath -> FilePath -> Bool
- makeRelative :: FilePath -> FilePath -> FilePath
- isRelative :: FilePath -> Bool
- isAbsolute :: FilePath -> Bool
- isValid :: FilePath -> Bool
- makeValid :: FilePath -> FilePath

# Separator predicates

type FilePath = String Source

File and directory names are values of type `String`, whose precise meaning is operating system dependent. Files can be opened, yielding a handle which can then be used to operate on the contents of that file.

pathSeparator :: Char

The character that separates directories. In the case where more than one character is possible, `pathSeparator` is the 'ideal' one.

     Windows: pathSeparator == '\\'
     Posix:   pathSeparator ==  '/'
     isPathSeparator pathSeparator

pathSeparators :: [Char]

The list of all possible separators.

     Windows: pathSeparators == ['\\', '/']
     Posix:   pathSeparators == ['/']
     pathSeparator `elem` pathSeparators

isPathSeparator :: Char -> Bool

Rather than using `(== `pathSeparator`)`, use this. Test if something is a path separator.

     isPathSeparator a == (a `elem` pathSeparators)

searchPathSeparator :: Char

The character that is used to separate the entries in the $PATH environment variable.

     Windows: searchPathSeparator == ';'
     Posix:   searchPathSeparator == ':'

isSearchPathSeparator :: Char -> Bool

Is the character a file separator?

     isSearchPathSeparator a == (a == searchPathSeparator)

extSeparator :: Char

File extension character

     extSeparator == '.'

isExtSeparator :: Char -> Bool

Is the character an extension character?

     isExtSeparator a == (a == extSeparator)

# Path methods (environment $PATH)

splitSearchPath :: String -> [FilePath]

Take a string, split it on the `searchPathSeparator` character.

Follows the recommendations in http://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap08.html

     Posix:   splitSearchPath "File1:File2:File3"  == ["File1","File2","File3"]
     Posix:   splitSearchPath "File1::File2:File3" == ["File1",".","File2","File3"]
     Windows: splitSearchPath "File1;File2;File3"  == ["File1","File2","File3"]
     Windows: splitSearchPath "File1;;File2;File3" == ["File1","File2","File3"]

getSearchPath :: IO [FilePath]

Get a list of filepaths in the $PATH.

# Extension methods

splitExtension :: FilePath -> (String, String)

Split on the extension. `addExtension` is the inverse.

     uncurry (++) (splitExtension x) == x
     uncurry addExtension (splitExtension x) == x
     splitExtension "file.txt" == ("file",".txt")
     splitExtension "file" == ("file","")
     splitExtension "file/file.txt" == ("file/file",".txt")
     splitExtension "file.txt/boris" == ("file.txt/boris","")
     splitExtension "file.txt/boris.ext" == ("file.txt/boris",".ext")
     splitExtension "file/path.txt.bob.fred" == ("file/path.txt.bob",".fred")
     splitExtension "file/path.txt/" == ("file/path.txt/","")

takeExtension :: FilePath -> String

Get the extension of a file, returns `""` for no extension, `.ext` otherwise.

     takeExtension x == snd (splitExtension x)
     Valid x => takeExtension (addExtension x "ext") == ".ext"
     Valid x => takeExtension (replaceExtension x "ext") == ".ext"

replaceExtension :: FilePath -> String -> FilePath

Set the extension of a file, overwriting one if already present.

     replaceExtension "file.txt" ".bob" == "file.bob"
     replaceExtension "file.txt" "bob" == "file.bob"
     replaceExtension "file" ".bob" == "file.bob"
     replaceExtension "file.txt" "" == "file"
     replaceExtension "file.fred.bob" "txt" == "file.fred.txt"

dropExtension :: FilePath -> FilePath

Remove last extension, and the "." preceding it.

     dropExtension x == fst (splitExtension x)

addExtension :: FilePath -> String -> FilePath

Add an extension, even if there is already one there. E.g. `addExtension "foo.txt" "bat" -> "foo.txt.bat"`.

     addExtension "file.txt" "bib" == "file.txt.bib"
     addExtension "file." ".bib" == "file..bib"
     addExtension "file" ".bib" == "file.bib"
     addExtension "/" "x" == "/.x"
     Valid x => takeFileName (addExtension (addTrailingPathSeparator x) "ext") == ".ext"
     Windows: addExtension "\\\\share" ".txt" == "\\\\share\\.txt"

hasExtension :: FilePath -> Bool

Does the given filename have an extension?

     null (takeExtension x) == not (hasExtension x)

(<.>) :: FilePath -> String -> FilePath

Alias to `addExtension`, for people who like that sort of thing.

splitExtensions :: FilePath -> (FilePath, String)

Split on all extensions

     uncurry (++) (splitExtensions x) == x
     uncurry addExtension (splitExtensions x) == x
     splitExtensions "file.tar.gz" == ("file",".tar.gz")

dropExtensions :: FilePath -> FilePath

Drop all extensions

     not $ hasExtension (dropExtensions x)

takeExtensions :: FilePath -> String

Get all extensions

     takeExtensions "file.tar.gz" == ".tar.gz"

# Drive methods

splitDrive :: FilePath -> (FilePath, FilePath)

Split a path into a drive and a path. On Unix, / is a Drive.

     uncurry (++) (splitDrive x) == x
     Windows: splitDrive "file" == ("","file")
     Windows: splitDrive "c:/file" == ("c:/","file")
     Windows: splitDrive "c:\\file" == ("c:\\","file")
     Windows: splitDrive "\\\\shared\\test" == ("\\\\shared\\","test")
     Windows: splitDrive "\\\\shared" == ("\\\\shared","")
     Windows: splitDrive "\\\\?\\UNC\\shared\\file" == ("\\\\?\\UNC\\shared\\","file")
     Windows: splitDrive "\\\\?\\UNCshared\\file" == ("\\\\?\\","UNCshared\\file")
     Windows: splitDrive "\\\\?\\d:\\file" == ("\\\\?\\d:\\","file")
     Windows: splitDrive "/d" == ("","/d")
     Posix:   splitDrive "/test" == ("/","test")
     Posix:   splitDrive "//test" == ("//","test")
     Posix:   splitDrive "test/file" == ("","test/file")
     Posix:   splitDrive "file" == ("","file")

joinDrive :: FilePath -> FilePath -> FilePath

Join a drive and the rest of the path.

              uncurry joinDrive (splitDrive x) == x
     Windows: joinDrive "C:" "foo" == "C:foo"
     Windows: joinDrive "C:\\" "bar" == "C:\\bar"
     Windows: joinDrive "\\\\share" "foo" == "\\\\share\\foo"
     Windows: joinDrive "/:" "foo" == "/:\\foo"

takeDrive :: FilePath -> FilePath

Get the drive from a filepath.

     takeDrive x == fst (splitDrive x)

hasDrive :: FilePath -> Bool

Does a path have a drive.

     not (hasDrive x) == null (takeDrive x)

dropDrive :: FilePath -> FilePath

Delete the drive, if it exists.

     dropDrive x == snd (splitDrive x)

isDrive :: FilePath -> Bool

Is an element a drive

# Operations on a FilePath, as a list of directories

splitFileName :: FilePath -> (String, String)

Split a filename into directory and file. `combine` is the inverse.

     Valid x => uncurry (</>) (splitFileName x) == x || fst (splitFileName x) == "./"
     Valid x => isValid (fst (splitFileName x))
     splitFileName "file/bob.txt" == ("file/", "bob.txt")
     splitFileName "file/" == ("file/", "")
     splitFileName "bob" == ("./", "bob")
     Posix:   splitFileName "/" == ("/","")
     Windows: splitFileName "c:" == ("c:","")

takeFileName :: FilePath -> FilePath

Get the file name.

     takeFileName "test/" == ""
     takeFileName x `isSuffixOf` x
     takeFileName x == snd (splitFileName x)
     Valid x => takeFileName (replaceFileName x "fred") == "fred"
     Valid x => takeFileName (x </> "fred") == "fred"
     Valid x => isRelative (takeFileName x)

replaceFileName :: FilePath -> String -> FilePath

Set the filename.

     Valid x => replaceFileName x (takeFileName x) == x

dropFileName :: FilePath -> FilePath

Drop the filename.

     dropFileName x == fst (splitFileName x)

takeBaseName :: FilePath -> String

Get the base name, without an extension or path.

     takeBaseName "file/test.txt" == "test"
     takeBaseName "dave.ext" == "dave"
     takeBaseName "" == ""
     takeBaseName "test" == "test"
     takeBaseName (addTrailingPathSeparator x) == ""
     takeBaseName "file/file.tar.gz" == "file.tar"

replaceBaseName :: FilePath -> String -> FilePath

Set the base name.

     replaceBaseName "file/test.txt" "bob" == "file/bob.txt"
     replaceBaseName "fred" "bill" == "bill"
     replaceBaseName "/dave/fred/bob.gz.tar" "new" == "/dave/fred/new.tar"
     Valid x => replaceBaseName x (takeBaseName x) == x

takeDirectory :: FilePath -> FilePath

Get the directory name, move up one level.

               takeDirectory x `isPrefixOf` x || takeDirectory x == "."
               takeDirectory "foo" == "."
               takeDirectory "/foo/bar/baz" == "/foo/bar"
               takeDirectory "/foo/bar/baz/" == "/foo/bar/baz"
               takeDirectory "foo/bar/baz" == "foo/bar"
     Windows:  takeDirectory "foo\\bar" == "foo"
     Windows:  takeDirectory "foo\\bar\\\\" == "foo\\bar"
     Windows:  takeDirectory "C:\\" == "C:\\"

replaceDirectory :: FilePath -> String -> FilePath

Set the directory, keeping the filename the same.

     Valid x => replaceDirectory x (takeDirectory x) `equalFilePath` x

combine :: FilePath -> FilePath -> FilePath

Combine two paths, if the second path `isAbsolute`, then it returns the second.

     Valid x => combine (takeDirectory x) (takeFileName x) `equalFilePath` x
     Posix:   combine "/" "test" == "/test"
     Posix:   combine "home" "bob" == "home/bob"
     Windows: combine "home" "bob" == "home\\bob"
     Windows: combine "home" "/bob" == "/bob"

(</>) :: FilePath -> FilePath -> FilePath

A nice alias for `combine`.

splitPath :: FilePath -> [FilePath]

Split a path by the directory separator.

     concat (splitPath x) == x
     splitPath "test//item/" == ["test//","item/"]
     splitPath "test/item/file" == ["test/","item/","file"]
     splitPath "" == []
     Windows: splitPath "c:\\test\\path" == ["c:\\","test\\","path"]
     Posix:   splitPath "/file/test" == ["/","file/","test"]

joinPath :: [FilePath] -> FilePath

Join path elements back together.

     Valid x => joinPath (splitPath x) == x
     joinPath [] == ""
     Posix: joinPath ["test","file","path"] == "test/file/path"

splitDirectories :: FilePath -> [FilePath]

Just as `splitPath`, but don't add the trailing slashes to each element.

     splitDirectories "test/file" == ["test","file"]
     splitDirectories "/test/file" == ["/","test","file"]
     Valid x => joinPath (splitDirectories x) `equalFilePath` x
     splitDirectories "" == []

# Low level FilePath operators

hasTrailingPathSeparator :: FilePath -> Bool

Is an item either a directory or the last character a path separator?

     hasTrailingPathSeparator "test" == False
     hasTrailingPathSeparator "test/" == True

addTrailingPathSeparator :: FilePath -> FilePath

Add a trailing file path separator if one is not already present.

     hasTrailingPathSeparator (addTrailingPathSeparator x)
     hasTrailingPathSeparator x ==> addTrailingPathSeparator x == x
     Posix:    addTrailingPathSeparator "test/rest" == "test/rest/"

dropTrailingPathSeparator :: FilePath -> FilePath

Remove any trailing path separators

     dropTrailingPathSeparator "file/test/" == "file/test"
     Posix:    not (hasTrailingPathSeparator (dropTrailingPathSeparator x)) || isDrive x
     Posix:    dropTrailingPathSeparator "/" == "/"
     Windows:  dropTrailingPathSeparator "\\" == "\\"

# File name manipulators

normalise :: FilePath -> FilePath

Normalise a file

- // outside of the drive can be made blank
- / -> `pathSeparator`
- ./ -> ""

     Posix:   normalise "/file/\\test////" == "/file/\\test/"
     Posix:   normalise "/file/./test" == "/file/test"
     Posix:   normalise "/test/file/../bob/fred/" == "/test/file/../bob/fred/"
     Posix:   normalise "../bob/fred/" == "../bob/fred/"
     Posix:   normalise "./bob/fred/" == "bob/fred/"
     Windows: normalise "c:\\file/bob\\" == "C:\\file\\bob\\"
     Windows: normalise "c:\\" == "C:\\"
     Windows: normalise "\\\\server\\test" == "\\\\server\\test"
     Windows: normalise "c:/file" == "C:\\file"
              normalise "." == "."
     Posix:   normalise "./" == "./"

equalFilePath :: FilePath -> FilePath -> Bool

Equality of two `FilePath`s. If you call `System.Directory.canonicalizePath` first this has a much better chance of working. Note that this doesn't follow symlinks or DOSNAM~1s.

              x == y ==> equalFilePath x y
              normalise x == normalise y ==> equalFilePath x y
     Posix:   equalFilePath "foo" "foo/"
     Posix:   not (equalFilePath "foo" "/foo")
     Posix:   not (equalFilePath "foo" "FOO")
     Windows: equalFilePath "foo" "FOO"

makeRelative :: FilePath -> FilePath -> FilePath

Contract a filename, based on a relative path.

There is no corresponding `makeAbsolute` function, instead use `System.Directory.canonicalizePath` which has the same effect.

              Valid y => equalFilePath x y || (isRelative x && makeRelative y x == x) || equalFilePath (y </> makeRelative y x) x
              makeRelative x x == "."
              null y || equalFilePath (makeRelative x (x </> y)) y || null (takeFileName x)
     Windows: makeRelative "C:\\Home" "c:\\home\\bob" == "bob"
     Windows: makeRelative "C:\\Home" "c:/home/bob" == "bob"
     Windows: makeRelative "C:\\Home" "D:\\Home\\Bob" == "D:\\Home\\Bob"
     Windows: makeRelative "C:\\Home" "C:Home\\Bob" == "C:Home\\Bob"
     Windows: makeRelative "/Home" "/home/bob" == "bob"
     Posix:   makeRelative "/Home" "/home/bob" == "/home/bob"
     Posix:   makeRelative "/home/" "/home/bob/foo/bar" == "bob/foo/bar"
     Posix:   makeRelative "/fred" "bob" == "bob"
     Posix:   makeRelative "/file/test" "/file/test/fred" == "fred"
     Posix:   makeRelative "/file/test" "/file/test/fred/" == "fred/"
     Posix:   makeRelative "some/path" "some/path/a/b/c" == "a/b/c"

isRelative :: FilePath -> Bool

Is a path relative, or is it fixed to the root?

     Windows: isRelative "path\\test" == True
     Windows: isRelative "c:\\test" == False
     Windows: isRelative "c:test" == True
     Windows: isRelative "c:" == True
     Windows: isRelative "\\\\foo" == False
     Windows: isRelative "/foo" == True
     Posix:   isRelative "test/path" == True
     Posix:   isRelative "/test" == False

isAbsolute :: FilePath -> Bool

    not . isRelative

     isAbsolute x == not (isRelative x)

isValid :: FilePath -> Bool

Is a FilePath valid, i.e. could you create a file like it?

              isValid "" == False
     Posix:   isValid "/random_ path:*" == True
     Posix:   isValid x == not (null x)
     Windows: isValid "c:\\test" == True
     Windows: isValid "c:\\test:of_test" == False
     Windows: isValid "test*" == False
     Windows: isValid "c:\\test\\nul" == False
     Windows: isValid "c:\\test\\prn.txt" == False
     Windows: isValid "c:\\nul\\file" == False
     Windows: isValid "\\\\" == False

makeValid :: FilePath -> FilePath

Take a FilePath and make it valid; does not change already valid FilePaths.

     isValid (makeValid x)
     isValid x ==> makeValid x == x
     makeValid "" == "_"
     Windows: makeValid "c:\\test:of_test" == "c:\\test_of_test"
     Windows: makeValid "test*" == "test_"
     Windows: makeValid "c:\\test\\nul" == "c:\\test\\nul_"
     Windows: makeValid "c:\\test\\prn.txt" == "c:\\test\\prn_.txt"
     Windows: makeValid "c:\\test/prn.txt" == "c:\\test/prn_.txt"
     Windows: makeValid "c:\\nul\\file" == "c:\\nul_\\file"