System.EasyFile

easy-file-0.2.1: Cross-platform File handling

Safe Haskell | Safe
Language | Haskell98

System.EasyFile

Contents

- Actions on directories
- Pre-defined directories
- Actions on files
- Existence tests
- Permissions
- Timestamps
- Size
- File/directory information
- Separator predicates
- Extension methods
- Drive methods
- Operations on a FilePath, as a list of directories
- Low level FilePath operators
- File name manipulators

Description

This is a module of cross-platform file handling for Unix/Mac/Windows.

The standard module System.Directory and System.FilePath have following shortcomings:

- getModificationTime exists in System.Directory. But getAccessTime, getChangeTime, getCreationTime do not exist.
- getModificationTime returns obsoleted type, `ClockTime`. It should return modern type, `UTCTime`, I believe.
- Some file functions are missing. A function to tell the link counter, for instance.
- Path separator is not unified. Even though Windows accepts '/' as a file separator, getCurrentDirectory in System.Directory returns '\' as a file separator. So, we need to specify regular expression like this: "[/\\]foo[/\\]bar[/\\]baz".
- getHomeDirectory returns `HOMEDRIVE`/`HOMEPATH` instead of the `HOME` environment variable on Windows.

This module aims to resolve these problems and provides:

- `getModificationTime`, `getAccessTime`, `getChangeTime`, and `getCreationTime`. They return `UTCTime`.
- `isSymlink`, `getLinkCount`, and `hasSubDirectories`.
- '/' as the single `pathSeparator`. For instance, `getCurrentDirectory` returns a path whose separator is '/' even on Windows.
- `getHomeDirectory2` which refers the `HOME` environment variable.
- Necessary functions in System.Directory and System.FilePath.

Synopsis

- createDirectory :: FilePath -> IO ()
- createDirectoryIfMissing :: Bool -> FilePath -> IO ()
- removeDirectory :: FilePath -> IO ()
- removeDirectoryRecursive :: FilePath -> IO ()
- renameDirectory :: FilePath -> FilePath -> IO ()
- getDirectoryContents :: FilePath -> IO [FilePath]
- getCurrentDirectory :: IO FilePath
- setCurrentDirectory :: FilePath -> IO ()
- getHomeDirectory :: IO FilePath
- getHomeDirectory2 :: IO (Maybe FilePath)
- getAppUserDataDirectory :: String -> IO FilePath
- getUserDocumentsDirectory :: IO FilePath
- getTemporaryDirectory :: IO FilePath
- removeFile :: FilePath -> IO ()
- renameFile :: FilePath -> FilePath -> IO ()
- copyFile :: FilePath -> FilePath -> IO ()
- canonicalizePath :: FilePath -> IO FilePath
- doesFileExist :: FilePath -> IO Bool
- doesDirectoryExist :: FilePath -> IO Bool
- data Permissions :: *
- getPermissions :: FilePath -> IO Permissions
- setPermissions :: FilePath -> Permissions -> IO ()
- copyPermissions :: FilePath -> FilePath -> IO ()
- getCreationTime :: FilePath -> IO (Maybe UTCTime)
- getChangeTime :: FilePath -> IO (Maybe UTCTime)
- getModificationTime :: FilePath -> IO UTCTime
- getAccessTime :: FilePath -> IO UTCTime
- getFileSize :: FilePath -> IO Word64
- isSymlink :: FilePath -> IO Bool
- getLinkCount :: FilePath -> IO (Maybe Int)
- hasSubDirectories :: FilePath -> IO (Maybe Bool)
- type FilePath = String
- pathSeparator :: Char
- pathSeparators :: [Char]
- isPathSeparator :: Char -> Bool
- extSeparator :: Char
- isExtSeparator :: Char -> Bool
- 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

# Actions on directories

createDirectory :: FilePath -> IO ()

``createDirectory` dir` creates a new directory `dir` which is initially empty, or as near to empty as the operating system allows.

The operation may fail with:

- `isPermissionError` / `PermissionDenied` The process has insufficient privileges to perform the operation. `[EROFS, EACCES]`
- `isAlreadyExistsError` / `AlreadyExists` The operand refers to a directory that already exists. `[EEXIST]`
- `HardwareFault` A physical I/O error has occurred. `[EIO]`
- `InvalidArgument` The operand is not a valid directory name. `[ENAMETOOLONG, ELOOP]`
- `NoSuchThing` There is no path to the directory. `[ENOENT, ENOTDIR]`
- `ResourceExhausted` Insufficient resources (virtual memory, process file descriptors, physical disk space, etc.) are available to perform the operation. `[EDQUOT, ENOSPC, ENOMEM, EMLINK]`
- `InappropriateType` The path refers to an existing non-directory object. `[EEXIST]`

createDirectoryIfMissing

Arguments

:: Bool | Create its parents too?
-> FilePath | The path to the directory you want to make
-> IO () |

``createDirectoryIfMissing` parents dir` creates a new directory `dir` if it doesn't exist. If the first argument is `True` the function will also create all parent directories if they are missing.

removeDirectory :: FilePath -> IO ()

``removeDirectory` dir` removes an existing directory dir. The implementation may specify additional constraints which must be satisfied before a directory can be removed (e.g. the directory has to be empty, or may not be in use by other processes). It is not legal for an implementation to partially remove a directory unless the entire directory is removed. A conformant implementation need not support directory removal in all situations (e.g. removal of the root directory).

The operation may fail with:

- `HardwareFault` A physical I/O error has occurred. `[EIO]`
- `InvalidArgument` The operand is not a valid directory name. `[ENAMETOOLONG, ELOOP]`
- `isDoesNotExistError` / `NoSuchThing` The directory does not exist. `[ENOENT, ENOTDIR]`
- `isPermissionError` / `PermissionDenied` The process has insufficient privileges to perform the operation. `[EROFS, EACCES, EPERM]`
- `UnsatisfiedConstraints` Implementation-dependent constraints are not satisfied. `[EBUSY, ENOTEMPTY, EEXIST]`
- `UnsupportedOperation` The implementation does not support removal in this situation. `[EINVAL]`
- `InappropriateType` The operand refers to an existing non-directory object. `[ENOTDIR]`

removeDirectoryRecursive :: FilePath -> IO ()

``removeDirectoryRecursive` dir` removes an existing directory dir together with its contents and subdirectories. Symbolic links are removed without affecting their the targets.

renameDirectory :: FilePath -> FilePath -> IO ()

``renameDirectory` old new` changes the name of an existing directory from old to new. If the new directory already exists, it is atomically replaced by the old directory. If the new directory is neither the old directory nor an alias of the old directory, it is removed as if by `removeDirectory`. A conformant implementation need not support renaming directories in all situations (e.g. renaming to an existing directory, or across different physical devices), but the constraints must be documented.

On Win32 platforms, `renameDirectory` fails if the new directory already exists.

The operation may fail with:

- `HardwareFault` A physical I/O error has occurred. `[EIO]`
- `InvalidArgument` Either operand is not a valid directory name. `[ENAMETOOLONG, ELOOP]`
- `isDoesNotExistError` / `NoSuchThing` The original directory does not exist, or there is no path to the target. `[ENOENT, ENOTDIR]`
- `isPermissionError` / `PermissionDenied` The process has insufficient privileges to perform the operation. `[EROFS, EACCES, EPERM]`
- `ResourceExhausted` Insufficient resources are available to perform the operation. `[EDQUOT, ENOSPC, ENOMEM, EMLINK]`
- `UnsatisfiedConstraints` Implementation-dependent constraints are not satisfied. `[EBUSY, ENOTEMPTY, EEXIST]`
- `UnsupportedOperation` The implementation does not support renaming in this situation. `[EINVAL, EXDEV]`
- `InappropriateType` Either path refers to an existing non-directory object. `[ENOTDIR, EISDIR]`

getDirectoryContents :: FilePath -> IO [FilePath]

``getDirectoryContents` dir` returns a list of all entries in dir.

The operation may fail with:

- `HardwareFault` A physical I/O error has occurred. `[EIO]`
- `InvalidArgument` The operand is not a valid directory name. `[ENAMETOOLONG, ELOOP]`
- `isDoesNotExistError` / `NoSuchThing` The directory does not exist. `[ENOENT, ENOTDIR]`
- `isPermissionError` / `PermissionDenied` The process has insufficient privileges to perform the operation. `[EACCES]`
- `ResourceExhausted` Insufficient resources are available to perform the operation. `[EMFILE, ENFILE]`
- `InappropriateType` The path refers to an existing non-directory object. `[ENOTDIR]`

getCurrentDirectory :: IO FilePath

If the operating system has a notion of current directories, `getCurrentDirectory` returns an absolute path to the current directory of the calling process.

The operation may fail with:

- `HardwareFault` A physical I/O error has occurred. `[EIO]`
- `isDoesNotExistError` / `NoSuchThing` There is no path referring to the current directory. `[EPERM, ENOENT, ESTALE...]`
- `isPermissionError` / `PermissionDenied` The process has insufficient privileges to perform the operation. `[EACCES]`
- `ResourceExhausted` Insufficient resources are available to perform the operation.
- `UnsupportedOperation` The operating system has no notion of current directory.

setCurrentDirectory :: FilePath -> IO ()

If the operating system has a notion of current directories, ``setCurrentDirectory` dir` changes the current directory of the calling process to dir.

The operation may fail with:

- `HardwareFault` A physical I/O error has occurred. `[EIO]`
- `InvalidArgument` The operand is not a valid directory name. `[ENAMETOOLONG, ELOOP]`
- `isDoesNotExistError` / `NoSuchThing` The directory does not exist. `[ENOENT, ENOTDIR]`
- `isPermissionError` / `PermissionDenied` The process has insufficient privileges to perform the operation. `[EACCES]`
- `UnsupportedOperation` The operating system has no notion of current directory, or the current directory cannot be dynamically changed.
- `InappropriateType` The path refers to an existing non-directory object. `[ENOTDIR]`

Note that in a concurrent program, the current directory is global state shared between all threads of the process. When using filesystem operations from multiple threads, it is therefore highly recommended to use absolute rather than relative `FilePath`s.

# Pre-defined directories

getHomeDirectory :: IO FilePath

Returns the current user's home directory.

The directory returned is expected to be writable by the current user, but note that it isn't generally considered good practice to store application-specific data here; use `getAppUserDataDirectory` instead.

On Unix, `getHomeDirectory` returns the value of the `HOME` environment variable. On Windows, the system is queried for a suitable path; a typical path might be `C:Documents And Settingsuser`.

The operation may fail with:

- `UnsupportedOperation` The operating system has no notion of home directory.
- `isDoesNotExistError` The home directory for the current user does not exist, or cannot be found.

getHomeDirectory2 :: IO (Maybe FilePath)

Returns the current user's home directory from the `HOME` environment variable.

getAppUserDataDirectory :: String -> IO FilePath

Returns the pathname of a directory in which application-specific data for the current user can be stored. The result of `getAppUserDataDirectory` for a given application is specific to the current user.

The argument should be the name of the application, which will be used to construct the pathname (so avoid using unusual characters that might result in an invalid pathname).

Note: the directory may not actually exist, and may need to be created first. It is expected that the parent directory exists and is writable.

On Unix, this function returns `$HOME/.appName`. On Windows, a typical path might be

    C:/Documents And Settings/user/Application Data/appName

The operation may fail with:

- `UnsupportedOperation` The operating system has no notion of application-specific data directory.
- `isDoesNotExistError` The home directory for the current user does not exist, or cannot be found.

getUserDocumentsDirectory :: IO FilePath

Returns the current user's document directory.

The directory returned is expected to be writable by the current user, but note that it isn't generally considered good practice to store application-specific data here; use `getAppUserDataDirectory` instead.

On Unix, `getUserDocumentsDirectory` returns the value of the `HOME` environment variable. On Windows, the system is queried for a suitable path; a typical path might be `C:/Documents and Settings/user/My Documents`.

The operation may fail with:

- `UnsupportedOperation` The operating system has no notion of document directory.
- `isDoesNotExistError` The document directory for the current user does not exist, or cannot be found.

getTemporaryDirectory :: IO FilePath

Returns the current directory for temporary files.

On Unix, `getTemporaryDirectory` returns the value of the `TMPDIR` environment variable or "/tmp" if the variable isn't defined. On Windows, the function checks for the existence of environment variables in the following order and uses the first path found:

- TMP environment variable.
- TEMP environment variable.
- USERPROFILE environment variable.
- The Windows directory

The operation may fail with:

- `UnsupportedOperation` The operating system has no notion of temporary directory.

The function doesn't verify whether the path exists.

# Actions on files

removeFile :: FilePath -> IO ()

`removeFile` file removes the directory entry for an existing file file, where file is not itself a directory. The implementation may specify additional constraints which must be satisfied before a file can be removed (e.g. the file may not be in use by other processes).

The operation may fail with:

- `HardwareFault` A physical I/O error has occurred. `[EIO]`
- `InvalidArgument` The operand is not a valid file name. `[ENAMETOOLONG, ELOOP]`
- `isDoesNotExistError` / `NoSuchThing` The file does not exist. `[ENOENT, ENOTDIR]`
- `isPermissionError` / `PermissionDenied` The process has insufficient privileges to perform the operation. `[EROFS, EACCES, EPERM]`
- `UnsatisfiedConstraints` Implementation-dependent constraints are not satisfied. `[EBUSY]`
- `InappropriateType` The operand refers to an existing directory. `[EPERM, EINVAL]`

renameFile :: FilePath -> FilePath -> IO ()

``renameFile` old new` changes the name of an existing file system object from old to new. If the new object already exists, it is atomically replaced by the old object. Neither path may refer to an existing directory. A conformant implementation need not support renaming files in all situations (e.g. renaming across different physical devices), but the constraints must be documented.

The operation may fail with:

- `HardwareFault` A physical I/O error has occurred. `[EIO]`
- `InvalidArgument` Either operand is not a valid file name. `[ENAMETOOLONG, ELOOP]`
- `isDoesNotExistError` / `NoSuchThing` The original file does not exist, or there is no path to the target. `[ENOENT, ENOTDIR]`
- `isPermissionError` / `PermissionDenied` The process has insufficient privileges to perform the operation. `[EROFS, EACCES, EPERM]`
- `ResourceExhausted` Insufficient resources are available to perform the operation. `[EDQUOT, ENOSPC, ENOMEM, EMLINK]`
- `UnsatisfiedConstraints` Implementation-dependent constraints are not satisfied. `[EBUSY]`
- `UnsupportedOperation` The implementation does not support renaming in this situation. `[EXDEV]`
- `InappropriateType` Either path refers to an existing directory. `[ENOTDIR, EISDIR, EINVAL, EEXIST, ENOTEMPTY]`

copyFile :: FilePath -> FilePath -> IO ()

``copyFile` old new` copies the existing file from old to new. If the new file already exists, it is atomically replaced by the old file. Neither path may refer to an existing directory. The permissions of old are copied to new, if possible.

canonicalizePath :: FilePath -> IO FilePath

Canonicalize the path of an existing file or directory. The intent is that two paths referring to the same file/directory will map to the same canonicalized path.

Note: if you only require an absolute path, consider using ``makeAbsolute`` instead, which is more reliable and does not have unspecified behavior on nonexistent paths.

It is impossible to guarantee that the implication (same file/dir <=> same canonicalized path) holds in either direction: this function can make only a best-effort attempt.

The precise behaviour is that of the POSIX `realpath` function (or `GetFullPathNameW` on Windows). In particular, the behaviour on paths that don't exist can vary from platform to platform. Some platforms do not alter the input, some do, and some throw an exception.

An empty path is considered to be equivalent to the current directory.

Known bug(s): on Windows, this function does not resolve symbolic links.

# Existence tests

doesFileExist :: FilePath -> IO Bool

The operation `doesFileExist` returns `True` if the argument file exists and is not a directory, and `False` otherwise.

doesDirectoryExist :: FilePath -> IO Bool

The operation `doesDirectoryExist` returns `True` if the argument file exists and is either a directory or a symbolic link to a directory, and `False` otherwise.

# Permissions

data Permissions :: *

Instances

Eq Permissions |
Ord Permissions |
Read Permissions |
Show Permissions |

getPermissions :: FilePath -> IO Permissions

The `getPermissions` operation returns the permissions for the file or directory.

The operation may fail with:

- `isPermissionError` if the user is not permitted to access the permissions; or
- `isDoesNotExistError` if the file or directory does not exist.

setPermissions :: FilePath -> Permissions -> IO ()

The `setPermissions` operation sets the permissions for the file or directory.

The operation may fail with:

- `isPermissionError` if the user is not permitted to set the permissions; or
- `isDoesNotExistError` if the file or directory does not exist.

copyPermissions :: FilePath -> FilePath -> IO ()

This function copy the permission of the first file to the second.

# Timestamps

getCreationTime :: FilePath -> IO (Maybe UTCTime)

The `getCreationTime` operation returns the UTC time at which the file or directory was created. The time is only available on Windows.

getChangeTime :: FilePath -> IO (Maybe UTCTime)

The `getChangeTime` operation returns the UTC time at which the file or directory was changed. The time is only available on Unix and Mac. Note that Unix's rename() does not change ctime but MacOS's rename() does.

getModificationTime :: FilePath -> IO UTCTime

The `getModificationTime` operation returns the UTC time at which the file or directory was last modified.

The operation may fail with:

- `isPermissionError` if the user is not permitted to access the modification time; or
- `isDoesNotExistError` if the file or directory does not exist.

getAccessTime :: FilePath -> IO UTCTime

The `getModificationTime` operation returns the UTC time at which the file or directory was last accessed.

# Size

getFileSize :: FilePath -> IO Word64

Getting the size of the file.

# File/directory information

isSymlink :: FilePath -> IO Bool

This function tells whether or not a file/directory is symbolic link.

getLinkCount :: FilePath -> IO (Maybe Int)

This function returns the link counter of a file/directory.

hasSubDirectories :: FilePath -> IO (Maybe Bool)

This function returns whether or not a directory has sub-directories.

# Separator predicates

type FilePath = String

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.

    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)

extSeparator :: Char

File extension character

    extSeparator == '.'

isExtSeparator :: Char -> Bool

Is the character an extension character?

    isExtSeparator a == (a == extSeparator)

# 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 infixr 7

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

splitExtensions :: FilePath -> (FilePath, String)

Split on all extensions

    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 "\\\\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") -- xxx
    Posix:   splitDrive "/test" == ("/","test") -- xxx
    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" -- xxx
    Windows: joinDrive "/:" "foo" == "/:/foo" -- xxx

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.

    uncurry (++) (splitFileName x) == x
    Valid x => uncurry combine (splitFileName x) == 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"
    replaceBaseName x (takeBaseName x) == x

takeDirectory :: FilePath -> FilePath

Get the directory name, move up one level.

              takeDirectory x `isPrefixOf` 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\\bar" -- xxx
    Windows:  takeDirectory "C:/" == "C:/"

replaceDirectory :: FilePath -> String -> FilePath

Set the directory, keeping the filename the same.

    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
    combine "/" "test" == "/test"
    combine "home" "bob" == "home/bob"

(</>) :: FilePath -> FilePath -> FilePath infixr 5

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
    addTrailingPathSeparator "test/rest" == "test/rest/"

dropTrailingPathSeparator :: FilePath -> FilePath

Remove any trailing path separators

    dropTrailingPathSeparator "file/test/" == "file/test"
    not (hasTrailingPathSeparator (dropTrailingPathSeparator x)) || isDrive x
    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" -- xxx
    Windows: 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" "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)