| directory-1.0.0.0: library for directory handling | Contents | Index

System.Directory |

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

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
makeRelativeToCurrentDirectory :: FilePath -> IO FilePath
findExecutable :: String -> IO (Maybe FilePath)
doesFileExist :: FilePath -> IO Bool
doesDirectoryExist :: FilePath -> IO Bool
data Permissions = Permissions {

readable, writable, executable, searchable :: Bool

}
getPermissions :: FilePath -> IO Permissions
setPermissions :: FilePath -> Permissions -> IO ()
getModificationTime :: FilePath -> IO ClockTime

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/007904975/toc.htm), 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

:: 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 content and all subdirectories. Be careful, if the directory contains symlinks, the function will follow them.
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]`

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.

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
Given path referring to a file or directory, returns a canonicalized path, with the intent that two paths referring to the same file/directory will map to the same canonicalized path. Note that it is impossible to guarantee that the implication (same file/dir <=> same canonicalizedPath) holds in either direction: this function can make only a best-effort attempt.
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 there isn't such executable. For example (findExecutable "ghc") gives you the path to GHC.
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 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

Constructors

Permissions |

readable, writable, executable, searchable :: Bool |

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.

Timestamps
getModificationTime :: FilePath -> IO ClockTime
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.

Produced by Haddock version 0.8