Path.IO

This module provides interface to System.Directory for users of Path module. It also implements commonly used primitives like recursive scanning and copying of directories.

Actions on directories

createDir :: MonadIO m => Path b Dir -> m ()

createDir 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]

createDirIfMissing

Arguments

:: MonadIO m

=> Bool

Create its parents too?

-> Path b Dir

The path to the directory you want to make

-> m ()

createDirIfMissing 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.

removeDir :: MonadIO m => Path b Dir -> m ()

removeDir 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]

removeDirRecur :: MonadIO m => Path b Dir -> m ()

removeDirRecur dir removes an existing directory dir together with its contents and subdirectories. Within this directory, symbolic links are removed without affecting their the targets.

renameDir

Arguments

:: MonadIO m

=> Path b0 Dir

Old name

-> Path b1 Dir

New name

-> m ()

renameDir 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 removeDir. 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, renameDir 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]

listDir

Arguments

:: (MonadIO m, MonadThrow m)

=> Path b Dir

Directory to list

-> m ([Path Abs Dir], [Path Abs File])

Sub-directories and files

listDir dir returns a list of all entries in dir without the special entries (. and ..). Entries are not sorted.

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]

listDirRecur

Arguments

:: (MonadIO m, MonadThrow m)

=> Path b Dir

Directory to list

-> m ([Path Abs Dir], [Path Abs File])

Sub-directories and files

Similar to listDir, but recursively traverses every sub-directory, and collects all files and directories. This can fail with the same exceptions as listDir.

copyDirRecur

Arguments

:: (MonadIO m, MonadCatch m)

=> Path b0 Dir

Source

-> Path b1 Dir

Destination

-> m ()

Copy directory recursively. This is not smart about symbolic links, but tries to preserve permissions when possible. If destination directory already exists, new files and sub-directories will complement its structure, possibly overwriting old files if they happen to have the same name as the new ones.

Current working directory

getCurrentDir :: (MonadIO m, MonadThrow m) => m (Path Abs Dir)

Obtain the current working directory as an absolute path.

In a multithreaded program, the current working directory is a global state shared among all threads of the process. Therefore, when performing filesystem operations from multiple threads, it is highly recommended to use absolute rather than relative paths (see: makeAbsolute).

The operation may fail with:

• HardwareFault A physical I/O error has occurred. [EIO]
• isDoesNotExistError or NoSuchThing There is no path referring to the working directory. [EPERM, ENOENT, ESTALE...]
• isPermissionError or 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 working directory.

setCurrentDir :: MonadIO m => Path b Dir -> m ()

Change the working directory to the given path.

In a multithreaded program, the current working directory is a global state shared among all threads of the process. Therefore, when performing filesystem operations from multiple threads, it is highly recommended to use absolute rather than relative paths (see: makeAbsolute).

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 or NoSuchThing The directory does not exist. [ENOENT, ENOTDIR]
• isPermissionError or PermissionDenied The process has insufficient privileges to perform the operation. [EACCES]
• UnsupportedOperation The operating system has no notion of current working directory, or the working directory cannot be dynamically changed.
• InappropriateType The path refers to an existing non-directory object. [ENOTDIR]

withCurrentDir

Arguments

:: (MonadIO m, MonadMask m)

=> Path b Dir

Directory to execute in

-> m a

Action to be executed

-> m a

Run an IO action with the given working directory and restore the original working directory afterwards, even if the given action fails due to an exception.

The operation may fail with the same exceptions as getCurrentDir and setCurrentDir.

Pre-defined directories

getHomeDir :: (MonadIO m, MonadThrow m) => m (Path Abs Dir)

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 getAppUserDataDir instead.

On Unix, getHomeDir returns the value of the HOME environment variable. On Windows, the system is queried for a suitable path; a typical path might be C:/Users/<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.

getAppUserDataDir

Arguments

:: (MonadIO m, MonadThrow m)

=> Path File Dir

A relative path that is appended to the path

-> m (Path Abs Dir)

Obtain the path to a special directory for storing user-specific application data (traditional Unix location).

The argument is usually the name of the application. Since it will be integrated into the path, it must consist of valid path characters.

• On Unix-like systems, the path is ~/.<app>.
• On Windows, the path is %APPDATA%/<app> (e.g. C:/Users/<user>/AppData/Roaming/<app>)

Note: the directory may not actually exist, in which case you would need to create it. It is expected that the parent directory exists and is writable.

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.

getUserDocsDir :: (MonadIO m, MonadThrow m) => m (Path Abs Dir)

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 getAppUserDataDir instead.

On Unix, getUserDocsDir returns the value of the HOME environment variable. On Windows, the system is queried for a suitable path; a typical path might be C:/Users/<user>/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.

getTempDir :: (MonadIO m, MonadThrow m) => m (Path Abs Dir)

Returns the current directory for temporary files.

On Unix, getTempDir 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.

Path transformation

type family AbsPath path

Closed type-family describing how to get absolute version of given Path.

Equations

AbsPath (Path b File) = Path Abs File

AbsPath (Path b Dir) = Path Abs Dir

class AnyPath path where

Class of things (Paths) that can be canonicalized and made absolute.

Methods

canonicalizePath :: (MonadIO m, MonadThrow m) => path -> m (AbsPath path)

Make a path absolute and remove as many indirections from it as possible. Indirections include the two special directories . and .., as well as any symbolic links. The input path need not point to an existing file or directory.

Note: if you require only an absolute path, use makeAbsolute instead. Most programs need not care about whether a path contains symbolic links.

Due to the fact that symbolic links and .. are dependent on the state of the existing filesystem, the function can only make a conservative, best-effort attempt. Nevertheless, if the input path points to an existing file or directory, then the output path shall also point to the same file or directory.

Formally, symbolic links and .. are removed from the longest prefix of the path that still points to an existing file. The function is not atomic, therefore concurrent changes in the filesystem may lead to incorrect results.

(Despite the name, the function does not guarantee canonicity of the returned path due to the presence of hard links, mount points, etc.)

Similar to normalise, an empty path is equivalent to the current directory.

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

makeAbsolute :: (MonadIO m, MonadThrow m) => path -> m (AbsPath path)

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

If the path is already absolute, the operation never fails. Otherwise, the operation may fail with the same exceptions as getCurrentDirectory.

Instances

AnyPath (Path b Dir)

AnyPath (Path b File)

Actions on files

removeFile :: MonadIO m => Path b File -> m ()

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

Arguments

:: MonadIO m

=> Path b0 File

Original location

-> Path b1 File

New location

-> m ()

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

Arguments

:: MonadIO m

=> Path b0 File

Original location

-> Path b1 File

Where to put copy

-> m ()

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.

findExecutable

Arguments

:: MonadIO m

=> Path Rel File

Executable file name

-> m (Maybe (Path Abs File))

Path to found executable

Given an executable file name, search 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.

findFile

Arguments

:: (MonadIO m, MonadThrow m)

=> [Path b Dir]

Set of directories to search in

-> Path Rel File

Filename of interest

-> m (Maybe (Path Abs File))

Absolute path to file (if found)

Search through the given set of directories for the given file.

findFiles

Arguments

:: (MonadIO m, MonadThrow m)

=> [Path b Dir]

Set of directories to search in

-> Path Rel File

Filename of interest

-> m [Path Abs File]

Absolute paths to all found files

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

findFilesWith

Arguments

:: (MonadIO m, MonadThrow m)

=> (Path Abs File -> m Bool)

How to test the files

-> [Path b Dir]

Set of directories to search in

-> Path Rel File

Filename of interest

-> m [Path Abs File]

Absolute paths to all found files

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

Existence tests

doesFileExist :: MonadIO m => Path b File -> m Bool

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

doesDirExist :: MonadIO m => Path b Dir -> m Bool

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

isLocationOccupied :: MonadIO m => Path b t -> m Bool

Check if there is a file or directory on specified path.

Permissions

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 :: MonadIO m => Path b t -> m 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 :: MonadIO m => Path b t -> Permissions -> m ()

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

Arguments

:: MonadIO m

=> Path b0 t0

From where to copy

-> Path b1 t1

What to modify

-> m ()

Set permissions for the object found on second given path so they match permissions of the object on the first path.

Timestamps

getModificationTime :: MonadIO m => Path b t -> m UTCTime

Obtain the time at which the file or directory was last modified.

The operation may fail with:

• isPermissionError if the user is not permitted to read the modification time; or
• isDoesNotExistError if the file or directory does not exist.

Caveat for POSIX systems: This function returns a timestamp with sub-second resolution only if this package is compiled against unix-2.6.0.0 or later and the underlying filesystem supports them.