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GHC 9.10.3 · lts/ghc-9.10.x · c74966e · 2026-09-27

Modulefilepath-1.5.4.0Haskell2010

System.OsPath

An implementation of the Abstract FilePath Proposal, which aims to supersede type FilePath = String for various reasons:

  1. it is more efficient and avoids memory fragmentation (uses unpinned ShortByteString under the hood)

  2. it is more type-safe (newtype over ShortByteString)

  3. avoids round-tripping issues by not converting to String (which is not total and loses the encoding)

  4. abstracts over unix and windows while keeping the original bytes

It is important to know that filenames/filepaths have different representations across platforms:

  • On Windows, filepaths are expected to be encoded as UTF16-LE as per the documentation, but may also include invalid surrogate pairs, in which case UCS-2 can be used. They are passed as wchar_t* to syscalls. OsPath only maintains the wide character invariant.

  • On Unix, filepaths don't have a predefined encoding (although they are often interpreted as UTF8) as per the POSIX specification and are passed as char[] to syscalls. OsPath maintains no invariant here.

Apart from encoding, filepaths have additional restrictions per platform:

Use isValid to check for these restrictions (OsPath doesn't maintain this invariant).

Also note that these restrictions are not exhaustive and further filesystem specific restrictions may apply on all platforms. This library makes no attempt at satisfying these. Library users may need to account for that, depending on what filesystems they want to support.

It is advised to follow these principles when dealing with filepaths/filenames:

  1. Avoid interpreting filenames that the OS returns, unless absolutely necessary. For example, the filepath separator is usually a predefined Word8/Word16, regardless of encoding. So even if we need to split filepaths, it might still not be necessary to understand the encoding of the filename.

  2. When interpreting OS returned filenames consider that these might not be UTF8 on unix or at worst don't have an ASCII compatible encoding. The are 3 available strategies fer decoding/encoding: a) pick the best UTF (UTF-8 on unix, UTF-16LE on windows), b) decode with an explicitly defined TextEncoding, c) mimic the behavior of the base library (permissive UTF16 on windows, current filesystem encoding on unix).

  3. Avoid comparing String based filepaths, because filenames of different encodings may have the same String representation, although they're not the same byte-wise.

  • 3 types
  • 63 values
  • Packagefilepath-1.5.4.0
  • Exports66
  • LanguageHaskell2010
  • LicenceBSD-3-Clause
  • SourceOsPath.hs

Types

3 declarations
typetype OsPath = OsString
#

Type representing filenames/pathnames.

This type doesn't add any guarantees over OsString.

newtypenewtype OsString
#

Newtype representing short operating system specific strings.

Internally this is either WindowsString or PosixString, depending on the platform. Both use unpinned ShortByteString for efficiency.

The constructor is only exported via System.OsString.Internal.Types, since dealing with the internals isn't generally recommended, but supported in case you need to write platform specific code.

Instances9Eq, Ord, Show, Generic, Semigroup, Monoid, …
newtypenewtype OsChar
#

Newtype representing a code unit.

On Windows, this is restricted to two-octet codepoints Word16, on POSIX one-octet (Word8).

Instances6Eq, Ord, Show, Generic, NFData, Rep

Filepath construction

6 declarations
valueencodeUtf :: MonadThrow m => FilePath -> m OsPath
#

Partial unicode friendly encoding.

On windows this encodes as UTF16-LE (strictly), which is a pretty good guess. On unix this encodes as UTF8 (strictly), which is a good guess.

Throws an EncodingException if encoding fails. If the input does not contain surrogate chars, you can use unsafeEncodeUtf.

valueosp :: QuasiQuoter
#

QuasiQuote an OsPath. This accepts Unicode characters and encodes as UTF-8 on unix and UTF-16LE on windows. Runs isValid on the input. If used as a pattern, requires turning on the ViewPatterns extension.

valuepack :: [OsChar] -> OsPath
#

Pack a list of OsChar to an OsPath.

Note that using this in conjunction with unsafeFromChar to convert from [Char] to OsPath is probably not what you want, because it will truncate unicode code points.

Filepath deconstruction

4 declarations
valuedecodeUtf :: MonadThrow m => OsPath -> m FilePath
#

Partial unicode friendly decoding.

On windows this decodes as UTF16-LE (strictly), which is a pretty good guess. On unix this decodes as UTF8 (strictly), which is a good guess.

Throws a EncodingException if decoding fails.

Word construction

1 declaration

Word deconstruction

1 declaration

Separator predicates

7 declarations
valuepathSeparator :: OsChar
#

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

Windows: pathSeparator == '\\'S
Posix:   pathSeparator ==  '/'
valuepathSeparators :: [OsChar]
#

The list of all possible separators.

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

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

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

$PATH methods

1 declaration
valuesplitSearchPath :: OsString -> [OsPath]
#

Take a string, split it on the searchPathSeparator character.

On Windows, blank items are ignored on Windows, and path elements are stripped of quotes.

On Posix, blank items are converted to . on Posix, and quotes are not treated specially.

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

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

Extension functions

14 declarations
valuesplitExtension :: OsPath -> (OsPath, OsString)
#

Split on the extension. addExtension is the inverse.

splitExtension "/directory/path.ext" == ("/directory/path",".ext")
uncurry (<>) (splitExtension x) == x
Valid 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/","")
valuetakeExtension :: OsPath -> OsString
#

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

takeExtension "/directory/path.ext" == ".ext"
takeExtension x == snd (splitExtension x)
Valid x => takeExtension (addExtension x "ext") == ".ext"
Valid x => takeExtension (replaceExtension x "ext") == ".ext"
valuereplaceExtension :: OsPath -> OsString -> OsPath
#

Set the extension of a file, overwriting one if already present, equivalent to -<.>.

replaceExtension "/directory/path.txt" "ext" == "/directory/path.ext"
replaceExtension "/directory/path.txt" ".ext" == "/directory/path.ext"
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"
replaceExtension x y == addExtension (dropExtension x) y
value(-<.>) :: OsPath -> OsString -> OsPath
#

Remove the current extension and add another, equivalent to replaceExtension.

"/directory/path.txt" -<.> "ext" == "/directory/path.ext"
"/directory/path.txt" -<.> ".ext" == "/directory/path.ext"
"foo.o" -<.> "c" == "foo.c"
valuedropExtension :: OsPath -> OsPath
#

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

dropExtension "/directory/path.ext" == "/directory/path"
dropExtension x == fst (splitExtension x)
valueaddExtension :: OsPath -> OsString -> OsPath
#

Add an extension, even if there is already one there, equivalent to <.>.

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

Add an extension, even if there is already one there, equivalent to <.>.

addExtension "/directory/path" "ext" == "/directory/path.ext"
addExtension "file.txt" "bib" == "file.txt.bib"
addExtension "file." ".bib" == "file..bib"
addExtension "file" ".bib" == "file.bib"
addExtension "/" "x" == "/.x"
addExtension x "" == x
Valid x => takeFileName (addExtension (addTrailingPathSeparator x) "ext") == ".ext"
Windows: addExtension "\\\\share" ".txt" == "\\\\share\\.txt"
valuehasExtension :: OsPath -> Bool
#

Does the given filename have an extension?

hasExtension "/directory/path.ext" == True
hasExtension "/directory/path" == False
null (takeExtension x) == not (hasExtension x)
value(<.>) :: OsPath -> OsString -> OsPath
#

Add an extension, even if there is already one there, equivalent to addExtension.

"/directory/path" <.> "ext" == "/directory/path.ext"
"/directory/path" <.> ".ext" == "/directory/path.ext"
valuesplitExtensions :: OsPath -> (OsPath, OsString)
#

Split on all extensions.

splitExtensions "/directory/path.ext" == ("/directory/path",".ext")
splitExtensions "file.tar.gz" == ("file",".tar.gz")
uncurry (<>) (splitExtensions x) == x
Valid x => uncurry addExtension (splitExtensions x) == x
splitExtensions "file.tar.gz" == ("file",".tar.gz")
valuedropExtensions :: OsPath -> OsPath
#

Drop all extensions.

dropExtensions "/directory/path.ext" == "/directory/path"
dropExtensions "file.tar.gz" == "file"
not $ hasExtension $ dropExtensions x
not $ any isExtSeparator $ takeFileName $ dropExtensions x
valuetakeExtensions :: OsPath -> OsString
#

Get all extensions.

takeExtensions "/directory/path.ext" == ".ext"
takeExtensions "file.tar.gz" == ".tar.gz"
valuereplaceExtensions :: OsPath -> OsString -> OsPath
#

Replace all extensions of a file with a new extension. Note that replaceExtension and addExtension both work for adding multiple extensions, so only required when you need to drop all extensions first.

replaceExtensions "file.fred.bob" "txt" == "file.txt"
replaceExtensions "file.fred.bob" "tar.gz" == "file.tar.gz"
valueisExtensionOf :: OsString -> OsPath -> Bool
#

Does the given filename have the specified extension?

"png" `isExtensionOf` "/directory/file.png" == True
".png" `isExtensionOf` "/directory/file.png" == True
".tar.gz" `isExtensionOf` "bar/foo.tar.gz" == True
"ar.gz" `isExtensionOf` "bar/foo.tar.gz" == False
"png" `isExtensionOf` "/directory/file.png.jpg" == False
"csv/table.csv" `isExtensionOf` "/data/csv/table.csv" == False
valuestripExtension :: OsString -> OsPath -> Maybe OsPath
#

Drop the given extension from a filepath, and the "." preceding it. Returns Nothing if the filepath does not have the given extension, or Just and the part before the extension if it does.

This function can be more predictable than dropExtensions, especially if the filename might itself contain . characters.

stripExtension "hs.o" "foo.x.hs.o" == Just "foo.x"
stripExtension "hi.o" "foo.x.hs.o" == Nothing
dropExtension x == fromJust (stripExtension (takeExtension x) x)
dropExtensions x == fromJust (stripExtension (takeExtensions x) x)
stripExtension ".c.d" "a.b.c.d"  == Just "a.b"
stripExtension ".c.d" "a.b..c.d" == Just "a.b."
stripExtension "baz"  "foo.bar"  == Nothing
stripExtension "bar"  "foobar"   == Nothing
stripExtension ""     x          == Just x

Filename/directory functions

13 declarations
valuesplitFileName :: OsPath -> (OsPath, OsPath)
#

Split a filename into directory and file. </> is the inverse. The first component will often end with a trailing slash.

splitFileName "/directory/file.ext" == ("/directory/","file.ext")
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:","")
valuetakeFileName :: OsPath -> OsPath
#

Get the file name.

takeFileName "/directory/file.ext" == "file.ext"
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)
valuereplaceFileName :: OsPath -> OsString -> OsPath
#

Set the filename.

replaceFileName "/directory/other.txt" "file.ext" == "/directory/file.ext"
Valid x => replaceFileName x (takeFileName x) == x
valuedropFileName :: OsPath -> OsPath
#

Drop the filename. Unlike takeDirectory, this function will leave a trailing path separator on the directory.

dropFileName "/directory/file.ext" == "/directory/"
dropFileName x == fst (splitFileName x)
valuetakeBaseName :: OsPath -> OsPath
#

Get the base name, without an extension or path.

takeBaseName "/directory/file.ext" == "file"
takeBaseName "file/test.txt" == "test"
takeBaseName "dave.ext" == "dave"
takeBaseName "" == ""
takeBaseName "test" == "test"
takeBaseName (addTrailingPathSeparator x) == ""
takeBaseName "file/file.tar.gz" == "file.tar"
valuereplaceBaseName :: OsPath -> OsString -> OsPath
#

Set the base name.

replaceBaseName "/directory/other.ext" "file" == "/directory/file.ext"
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
valuetakeDirectory :: OsPath -> OsPath
#

Get the directory name, move up one level.

          takeDirectory "/directory/other.ext" == "/directory"
          takeDirectory x `isPrefixOf` x || takeDirectory x == "."
          takeDirectory "foo" == "."
          takeDirectory "/" == "/"
          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:\\"
valuereplaceDirectory :: OsPath -> OsPath -> OsPath
#

Set the directory, keeping the filename the same.

replaceDirectory "root/file.ext" "/directory/" == "/directory/file.ext"
Valid x => replaceDirectory x (takeDirectory x) `equalFilePath` x
value(</>) :: OsPath -> OsPath -> OsPath
#

Combine two paths with a path separator. If the second path starts with a path separator or a drive letter, then it returns the second. The intention is that readFile (dir </> file) will access the same file as setCurrentDirectory dir; readFile file.

Posix:   "/directory" </> "file.ext" == "/directory/file.ext"
Windows: "/directory" </> "file.ext" == "/directory\\file.ext"
         "directory" </> "/file.ext" == "/file.ext"
Valid x => (takeDirectory x </> takeFileName x) `equalFilePath` x

Combined:

Posix:   "/" </> "test" == "/test"
Posix:   "home" </> "bob" == "home/bob"
Posix:   "x:" </> "foo" == "x:/foo"
Windows: "C:\\foo" </> "bar" == "C:\\foo\\bar"
Windows: "home" </> "bob" == "home\\bob"

Not combined:

Posix:   "home" </> "/bob" == "/bob"
Windows: "home" </> "C:\\bob" == "C:\\bob"

Not combined (tricky):

On Windows, if a filepath starts with a single slash, it is relative to the root of the current drive. In [1], this is (confusingly) referred to as an absolute path. The current behavior of </> is to never combine these forms.

Windows: "home" </> "/bob" == "/bob"
Windows: "home" </> "\\bob" == "\\bob"
Windows: "C:\\home" </> "\\bob" == "\\bob"

On Windows, from [1]: "If a file name begins with only a disk designator but not the backslash after the colon, it is interpreted as a relative path to the current directory on the drive with the specified letter." The current behavior of </> is to never combine these forms.

Windows: "D:\\foo" </> "C:bar" == "C:bar"
Windows: "C:\\foo" </> "C:bar" == "C:bar"
valuesplitPath :: OsPath -> [OsPath]
#

Split a path by the directory separator.

splitPath "/directory/file.ext" == ["/","directory/","file.ext"]
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"]
valuejoinPath :: [OsPath] -> OsPath
#

Join path elements back together.

joinPath z == foldr (</>) "" z
joinPath ["/","directory/","file.ext"] == "/directory/file.ext"
Valid x => joinPath (splitPath x) == x
joinPath [] == ""
Posix: joinPath ["test","file","path"] == "test/file/path"
valuesplitDirectories :: OsPath -> [OsPath]
#

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

         splitDirectories "/directory/file.ext" == ["/","directory","file.ext"]
         splitDirectories "test/file" == ["test","file"]
         splitDirectories "/test/file" == ["/","test","file"]
Windows: splitDirectories "C:\\test\\file" == ["C:\\", "test", "file"]
         Valid x => joinPath (splitDirectories x) `equalFilePath` x
         splitDirectories "" == []
Windows: splitDirectories "C:\\test\\\\\\file" == ["C:\\", "test", "file"]
         splitDirectories "/test///file" == ["/","test","file"]

Drive functions

6 declarations
valuesplitDrive :: OsPath -> (OsPath, OsPath)
#

Split a path into a drive and a path. On Posix, / 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")
valuejoinDrive :: OsPath -> OsPath -> OsPath
#

Join a drive and the rest of the path.

Valid x => 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"

Join a drive and the rest of the path.

Valid x => 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"
valuehasDrive :: OsPath -> Bool
#

Does a path have a drive.

not (hasDrive x) == null (takeDrive x)
Posix:   hasDrive "/foo" == True
Windows: hasDrive "C:\\foo" == True
Windows: hasDrive "C:foo" == True
         hasDrive "foo" == False
         hasDrive "" == False
valueisDrive :: OsPath -> Bool
#

Is an element a drive

Posix:   isDrive "/" == True
Posix:   isDrive "/foo" == False
Windows: isDrive "C:\\" == True
Windows: isDrive "C:\\foo" == False
         isDrive "" == False

Trailing slash functions

3 declarations
valuehasTrailingPathSeparator :: OsPath -> Bool
#

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

hasTrailingPathSeparator "test" == False
hasTrailingPathSeparator "test/" == True
valueaddTrailingPathSeparator :: OsPath -> OsPath
#

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/"
valuedropTrailingPathSeparator :: OsPath -> OsPath
#

Remove any trailing path separators

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

File name manipulations

7 declarations
valuenormalise :: OsPath -> OsPath
#

Normalise a file

  • // outside of the drive can be made blank

  • / -> pathSeparator

  • ./ -> ""

Does not remove "..", because of symlinks.

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 "/a/../c" == "/a/../c"
Posix:   normalise "./bob/fred/" == "bob/fred/"
Windows: normalise "c:\\file/bob\\" == "C:\\file\\bob\\"
Windows: normalise "c:\\" == "C:\\"
Windows: normalise "C:.\\" == "C:"
Windows: normalise "\\\\server\\test" == "\\\\server\\test"
Windows: normalise "//server/test" == "\\\\server\\test"
Windows: normalise "c:/file" == "C:\\file"
Windows: normalise "/file" == "\\file"
Windows: normalise "\\" == "\\"
Windows: normalise "/./" == "\\"
         normalise "." == "."
Posix:   normalise "./" == "./"
Posix:   normalise "./." == "./"
Posix:   normalise "/./" == "/"
Posix:   normalise "/" == "/"
Posix:   normalise "bob/fred/." == "bob/fred/"
Posix:   normalise "//home" == "/home"
valueequalFilePath :: OsPath -> OsPath -> Bool
#

Equality of two filepaths. 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.

Similar to normalise, this does not expand "..", because of symlinks.

         x == y ==> equalFilePath x y
         normalise x == normalise y ==> equalFilePath x y
         equalFilePath "foo" "foo/"
         not (equalFilePath "/a/../c" "/c")
         not (equalFilePath "foo" "/foo")
Posix:   not (equalFilePath "foo" "FOO")
Windows: equalFilePath "foo" "FOO"
Windows: not (equalFilePath "C:" "C:/")
valuemakeRelative :: OsPath -> OsPath -> OsPath
#

Contract a filename, based on a relative path. Note that the resulting path will never introduce .. paths, as the presence of symlinks means ../b may not reach a/b if it starts from a/c. For a worked example see this blog post.

The corresponding makeAbsolute function can be found in System.Directory.

         makeRelative "/directory" "/directory/file.ext" == "file.ext"
         Valid x => makeRelative (takeDirectory x) x `equalFilePath` takeFileName x
         makeRelative x x == "."
         Valid x y => equalFilePath x y || (isRelative x && makeRelative y x == x) || equalFilePath (y </> makeRelative y x) 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"
Windows: makeRelative "/" "//" == "//"
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"
valueisRelative :: OsPath -> 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:\\" == False
Windows: isRelative "c:/" == False
Windows: isRelative "c:" == True
Windows: isRelative "\\\\foo" == False
Windows: isRelative "\\\\?\\foo" == False
Windows: isRelative "\\\\?\\UNC\\foo" == False
Windows: isRelative "/foo" == True
Windows: isRelative "\\foo" == True
Posix:   isRelative "test/path" == True
Posix:   isRelative "/test" == False
Posix:   isRelative "/" == False

According to [1]:

  • "A UNC name of any format [is never relative]."

  • "You cannot use the "\?" prefix with a relative path."

valueisValid :: OsPath -> Bool
#

Is a filepath valid, i.e. could you create a file like it? This function checks for invalid names, and invalid characters, but does not check if length limits are exceeded, as these are typically filesystem dependent.

         isValid "" == False
         isValid "\0" == 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
Windows: isValid "\\\\\\foo" == False
Windows: isValid "\\\\?\\D:file" == False
Windows: isValid "foo\tbar" == False
Windows: isValid "nul .txt" == False
Windows: isValid " nul.txt" == True
valuemakeValid :: OsPath -> OsPath
#

Take a filepath and make it valid; does not change already valid filepaths.

isValid (makeValid x)
isValid x ==> makeValid x == x
makeValid "" == "_"
makeValid "file\0name" == "file_name"
Windows: makeValid "c:\\already\\/valid" == "c:\\already\\/valid"
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"
Windows: makeValid "\\\\\\foo" == "\\\\drive"
Windows: makeValid "\\\\?\\D:file" == "\\\\?\\D:\\file"
Windows: makeValid "nul .txt" == "nul _.txt"