System.Directory

directory-1.2.2.0: Platform-agnostic library for filesystem operations

Copyright | (c) The University of Glasgow 2001
License | BSD-style (see the file libraries/base/LICENSE)
Maintainer | libraries@haskell.org
Stability | stable
Portability | portable
Safe Haskell | Trustworthy
Language | Haskell2010

System.Directory

Contents

- Actions on directories
- Pre-defined directories
- Actions on files
- Existence tests
- Permissions
- Timestamps

Description

System-independent interface to directory manipulation.

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
- 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
- makeAbsolute :: FilePath -> IO FilePath
- makeRelativeToCurrentDirectory :: FilePath -> IO FilePath
- findExecutable :: String -> IO (Maybe FilePath)
- findExecutables :: String -> IO [FilePath]
- findFile :: [FilePath] -> String -> IO (Maybe FilePath)
- findFiles :: [FilePath] -> String -> IO [FilePath]
- findFilesWith :: (FilePath -> IO Bool) -> [FilePath] -> String -> IO [FilePath]
- doesFileExist :: FilePath -> IO Bool
- doesDirectoryExist :: FilePath -> IO Bool
- data Permissions
- emptyPermissions :: Permissions
- readable :: Permissions -> Bool
- writable :: Permissions -> Bool
- executable :: Permissions -> Bool
- searchable :: Permissions -> Bool
- setOwnerReadable :: Bool -> Permissions -> Permissions
- setOwnerWritable :: Bool -> Permissions -> Permissions
- setOwnerExecutable :: Bool -> Permissions -> Permissions
- setOwnerSearchable :: Bool -> Permissions -> Permissions
- getPermissions :: FilePath -> IO Permissions
- setPermissions :: FilePath -> Permissions -> IO ()
- copyPermissions :: FilePath -> FilePath -> IO ()
- getModificationTime :: FilePath -> IO UTCTime

# Documentation

A directory contains a series of entries, each of which is a named reference to a file system object (file, directory etc.). Some entries may be hidden, inaccessible, or have some administrative function (e.g. `.` or `..' under POSIX http://www.opengroup.org/onlinepubs/009695399/), but in this standard all such entries are considered to form part of the directory contents. Entries in sub-directories are not, however, considered to form part of the directory contents.

Each file system object is referenced by a path. There is normally at least one absolute path to each file system object. In some operating systems, it may also be possible to have paths which are relative to the current directory.

# 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.

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.

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 Settings/user`.

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.

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:/Users/user/AppData/Roaming/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.

makeAbsolute :: FilePath -> IO FilePath

Make a path absolute by prepending the current directory (if it isn't already absolute) and applying ``normalise`` to the result.

The operation may fail with the same exceptions as ``getCurrentDirectory``.

Since: 1.2.2.0

makeRelativeToCurrentDirectory :: FilePath -> IO FilePath

`makeRelative` the current directory.

findExecutable :: String -> IO (Maybe FilePath)

Given an executable file name, searches for such file in the directories listed in system PATH. The returned value is the path to the found executable or Nothing if an executable with the given name was not found. For example (findExecutable "ghc") gives you the path to GHC.

The path returned by `findExecutable` corresponds to the program that would be executed by `createProcess` when passed the same string (as a RawCommand, not a ShellCommand).

On Windows, `findExecutable` calls the Win32 function `SearchPath`, which may search other places before checking the directories in `PATH`. Where it actually searches depends on registry settings, but notably includes the directory containing the current executable. See http://msdn.microsoft.com/en-us/library/aa365527.aspx for more details.

findExecutables :: String -> IO [FilePath]

Given a file name, searches for the file and returns a list of all occurences that are executable.

Since: 1.2.2.0

findFile :: [FilePath] -> String -> IO (Maybe FilePath)

Search through the given set of directories for the given file. Used by `findExecutable` on non-windows platforms.

findFiles :: [FilePath] -> String -> IO [FilePath]

Search through the given set of directories for the given file and returns a list of paths where the given file exists.

Since: 1.2.1.0

findFilesWith :: (FilePath -> IO Bool) -> [FilePath] -> String -> IO [FilePath]

Search through the given set of directories for the given file and with the given property (usually permissions) and returns a list of paths where the given file exists and has the property.

Since: 1.2.1.0

# 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

The `Permissions` type is used to record whether certain operations are permissible on a file/directory. `getPermissions` and `setPermissions` get and set these permissions, respectively. Permissions apply both to files and directories. For directories, the executable field will be `False`, and for files the searchable field will be `False`. Note that directories may be searchable without being readable, if permission has been given to use them as part of a path, but not to examine the directory contents.

Note that to change some, but not all permissions, a construct on the following lines must be used.

     makeReadable f = do
        p <- getPermissions f
        setPermissions f (p {readable = True})

data Permissions

Instances

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

emptyPermissions :: Permissions

readable :: Permissions -> Bool

writable :: Permissions -> Bool

executable :: Permissions -> Bool

searchable :: Permissions -> Bool

setOwnerReadable :: Bool -> Permissions -> Permissions

setOwnerWritable :: Bool -> Permissions -> Permissions

setOwnerExecutable :: Bool -> Permissions -> Permissions

setOwnerSearchable :: Bool -> Permissions -> 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 ()

# Timestamps

getModificationTime :: FilePath -> IO UTCTime

The `getModificationTime` operation returns the clock 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.

Note: This function returns a timestamp with sub-second resolution only if this package is compiled against `unix-2.6.0.0` or later for unix systems, and `Win32-2.3.1.0` or later for windows systems. Of course this also requires that the underlying file system supports such high resolution timestamps.