HPath.IO

This module provides high-level IO related file operations like copy, delete, move and so on. It only operates on Path Abs which guarantees us well-typed paths which are absolute.

Some functions are just path-safe wrappers around unix functions, others have stricter exception handling and some implement functionality that doesn't have a unix counterpart (like copyDirRecursive).

Some of these operations are due to their nature not atomic, which means they may do multiple syscalls which form one context. Some of them also have to examine the filetypes explicitly before the syscalls, so a reasonable decision can be made. That means the result is undefined if another process changes that context while the non-atomic operation is still happening. However, where possible, as few syscalls as possible are used and the underlying exception handling is kept.

Note: BlockDevice, CharacterDevice, NamedPipe and Socket are ignored by some of the more high-level functions (like easyCopy). For other functions (like copyFile), the behavior on these file types is unreliable/unsafe. Check the documentation of those functions for details.

Types

data FileType

Constructors

Directory

RegularFile

SymbolicLink

BlockDevice

CharacterDevice

NamedPipe

Socket

Instances

Eq FileType

Methods

(==) :: FileType -> FileType -> Bool

(/=) :: FileType -> FileType -> Bool

Show FileType

Methods

showsPrec :: Int -> FileType -> ShowS

show :: FileType -> String

showList :: [FileType] -> ShowS

data RecursiveErrorMode

The error mode for recursive operations.

On FailEarly the whole operation fails immediately if any of the recursive sub-operations fail, which is sort of the default for IO operations.

On CollectFailures skips errors in the recursion and keeps on recursing. However all errors are collected in the RecursiveFailure error type, which is raised finally if there was any error. Also note that RecursiveFailure does not give any guarantees on the ordering of the collected exceptions.

Constructors

FailEarly

CollectFailures

data CopyMode

The mode for copy and file moves. Overwrite mode is usually not very well defined, but is a convenience shortcut.

Constructors

Strict

fail if any target exists

Overwrite

overwrite targets

File copying

copyDirRecursive

Arguments

:: Path Abs

source dir

-> Path Abs

destination (parent dirs are not automatically created)

-> CopyMode

-> RecursiveErrorMode

-> IO ()

Copies the contents of a directory recursively to the given destination, while preserving permissions. Does not follow symbolic links. This behaves more or less like the following, without descending into the destination if it already exists:

  cp -a /source/dir /destination/somedir

For directory contents, this will ignore any file type that is not RegularFile, SymbolicLink or Directory.

For Overwrite copy mode this does not prune destination directory contents, so the destination might contain more files than the source after the operation has completed. Permissions of existing directories are fixed.

Safety/reliability concerns:

• not atomic
• examines filetypes explicitly
• an explicit check throwDestinationInSource is carried out for the top directory for basic sanity, because otherwise we might end up with an infinite copy loop... however, this operation is not carried out recursively (because it's slow)

Throws:

• NoSuchThing if source directory does not exist
• PermissionDenied if source directory can't be opened
• SameFile if source and destination are the same file (HPathIOException)
• DestinationInSource if destination is contained in source (HPathIOException)

Throws in FailEarly RecursiveErrorMode only:

• PermissionDenied if output directory is not writable
• InvalidArgument if source directory is wrong type (symlink)
• InappropriateType if source directory is wrong type (regular file)

Throws in CollectFailures RecursiveErrorMode only:

• RecursiveFailure if any of the recursive operations that are not part of the top-directory sanity-checks fail (HPathIOException)

Throws in Strict CopyMode only:

• AlreadyExists if destination already exists

recreateSymlink

Arguments

:: Path Abs

the old symlink file

-> Path Abs

destination file

-> CopyMode

-> IO ()

Recreate a symlink.

In Overwrite copy mode only files and empty directories are deleted.

Safety/reliability concerns:

• Overwrite mode is inherently non-atomic

Throws:

• InvalidArgument if source file is wrong type (not a symlink)
• PermissionDenied if output directory cannot be written to
• PermissionDenied if source directory cannot be opened
• SameFile if source and destination are the same file (HPathIOException)

Throws in Strict mode only:

• AlreadyExists if destination already exists

Throws in Overwrite mode only:

• UnsatisfiedConstraints if destination file is non-empty directory

Note: calls symlink

copyFile

Arguments

:: Path Abs

source file

-> Path Abs

destination file

-> CopyMode

-> IO ()

Copies the given regular file to the given destination. Neither follows symbolic links, nor accepts them. For "copying" symbolic links, use recreateSymlink instead.

Note that this is still sort of a low-level function and doesn't examine file types. For a more high-level version, use easyCopy instead.

In Overwrite copy mode only overwrites actual files, not directories.

Safety/reliability concerns:

• Overwrite mode is not atomic
• when used on CharacterDevice, reads the "contents" and copies them to a regular file, which might take indefinitely
• when used on BlockDevice, may either read the "contents" and copy them to a regular file (potentially hanging indefinitely) or may create a regular empty destination file
• when used on NamedPipe, will hang indefinitely

Throws:

• NoSuchThing if source file does not exist
• NoSuchThing if source file is a a Socket
• PermissionDenied if output directory is not writable
• PermissionDenied if source directory can't be opened
• InvalidArgument if source file is wrong type (symlink or directory)
• SameFile if source and destination are the same file (HPathIOException)

Throws in Strict mode only:

• AlreadyExists if destination already exists

Note: calls sendfile and possibly read/write as fallback

easyCopy :: Path Abs -> Path Abs -> CopyMode -> RecursiveErrorMode -> IO ()

Copies a regular file, directory or symbolic link. In case of a symbolic link it is just recreated, even if it points to a directory. Any other file type is ignored.

Safety/reliability concerns:

• examines filetypes explicitly
• calls copyDirRecursive for directories

File deletion

deleteFile :: Path Abs -> IO ()

Deletes the given file. Raises eISDIR if run on a directory. Does not follow symbolic links.

Throws:

• InappropriateType for wrong file type (directory)
• NoSuchThing if the file does not exist
• PermissionDenied if the directory cannot be read

deleteDir :: Path Abs -> IO ()

Deletes the given directory, which must be empty, never symlinks.

Throws:

• InappropriateType for wrong file type (symlink to directory)
• InappropriateType for wrong file type (regular file)
• NoSuchThing if directory does not exist
• UnsatisfiedConstraints if directory is not empty
• PermissionDenied if we can't open or write to parent directory

Notes: calls rmdir

deleteDirRecursive :: Path Abs -> IO ()

Deletes the given directory recursively. Does not follow symbolic links. Tries deleteDir first before attemtping a recursive deletion.

On directory contents this behaves like easyDelete and thus will ignore any file type that is not RegularFile, SymbolicLink or Directory.

Safety/reliability concerns:

• not atomic
• examines filetypes explicitly

Throws:

• InappropriateType for wrong file type (symlink to directory)
• InappropriateType for wrong file type (regular file)
• NoSuchThing if directory does not exist
• PermissionDenied if we can't open or write to parent directory

easyDelete :: Path Abs -> IO ()

Deletes a file, directory or symlink. In case of directory, performs recursive deletion. In case of a symlink, the symlink file is deleted. Any other file type is ignored.

Safety/reliability concerns:

• examines filetypes explicitly
• calls deleteDirRecursive for directories

File opening

openFile :: Path Abs -> IO ProcessID

Opens a file appropriately by invoking xdg-open. The file type is not checked. This forks a process.

executeFile

Arguments

:: Path Abs

program

-> [ByteString]

arguments

-> IO ProcessID

Executes a program with the given arguments. This forks a process.

File creation

createRegularFile :: FileMode -> Path Abs -> IO ()

Create an empty regular file at the given directory with the given filename.

Throws:

• PermissionDenied if output directory cannot be written to
• AlreadyExists if destination already exists
• NoSuchThing if any of the parent components of the path do not exist

createDir :: FileMode -> Path Abs -> IO ()

Create an empty directory at the given directory with the given filename.

Throws:

• PermissionDenied if output directory cannot be written to
• AlreadyExists if destination already exists
• NoSuchThing if any of the parent components of the path do not exist

createDirRecursive :: FileMode -> Path Abs -> IO ()

Create an empty directory at the given directory with the given filename. All parent directories are created with the same filemode. This basically behaves like:

  mkdir -p /some/dir

Safety/reliability concerns:

• not atomic

Throws:

• PermissionDenied if any part of the path components do not exist and cannot be written to
• AlreadyExists if destination already exists and is not a directory

createSymlink

Arguments

:: Path Abs

destination file

-> ByteString

path the symlink points to

-> IO ()

Create a symlink.

Throws:

• PermissionDenied if output directory cannot be written to
• AlreadyExists if destination file already exists
• NoSuchThing if any of the parent components of the path do not exist

Note: calls symlink

File renaming/moving

renameFile :: Path Abs -> Path Abs -> IO ()

Rename a given file with the provided filename. Destination and source must be on the same device, otherwise eXDEV will be raised.

Does not follow symbolic links, but renames the symbolic link file.

Safety/reliability concerns:

• has a separate set of exception handling, apart from the syscall

Throws:

• NoSuchThing if source file does not exist
• PermissionDenied if output directory cannot be written to
• PermissionDenied if source directory cannot be opened
• UnsupportedOperation if source and destination are on different devices
• AlreadyExists if destination already exists
• SameFile if destination and source are the same file (HPathIOException)

Note: calls rename (but does not allow to rename over existing files)

moveFile

Arguments

:: Path Abs

file to move

-> Path Abs

destination

-> CopyMode

-> IO ()

Move a file. This also works across devices by copy-delete fallback. And also works on directories.

Does not follow symbolic links, but renames the symbolic link file.

Safety/reliability concerns:

• Overwrite mode is not atomic
• copy-delete fallback is inherently non-atomic
• since this function calls easyCopy and easyDelete as a fallback to renameFile, file types that are not RegularFile, SymbolicLink or Directory may be ignored
• for Overwrite mode, the destination will be deleted (not recursively) before moving

Throws:

• NoSuchThing if source file does not exist
• PermissionDenied if output directory cannot be written to
• PermissionDenied if source directory cannot be opened
• SameFile if destination and source are the same file (HPathIOException)

Throws in Strict mode only:

• AlreadyExists if destination already exists

Note: calls rename (but does not allow to rename over existing files)

File reading

readFile :: Path Abs -> IO ByteString

Read the given file at once into memory as a strict ByteString. Symbolic links are followed, no sanity checks on file size or file type. File must exist.

Note: the size of the file is determined in advance, as to only have one allocation.

Safety/reliability concerns:

• since amount of bytes to read is determined in advance, the file might be read partially only if something else is appending to it while reading
• the whole file is read into memory!

Throws:

• InappropriateType if file is not a regular file or a symlink
• PermissionDenied if we cannot read the file or the directory containting it
• NoSuchThing if the file does not exist

readFileEOF :: Path Abs -> IO ByteString

Read the given file in chunks of size `8192` into memory until fread returns 0. Returns a lazy ByteString, because it uses Builders under the hood.

Safety/reliability concerns:

• the whole file is read into memory!

Throws:

• InappropriateType if file is not a regular file or a symlink
• PermissionDenied if we cannot read the file or the directory containting it
• NoSuchThing if the file does not exist

File writing

writeFile :: Path Abs -> ByteString -> IO ()

Write a given ByteString to a file, truncating the file beforehand. The file must exist. Follows symlinks.

Throws:

• InappropriateType if file is not a regular file or a symlink
• PermissionDenied if we cannot read the file or the directory containting it
• NoSuchThing if the file does not exist

appendFile :: Path Abs -> ByteString -> IO ()

Append a given ByteString to a file. The file must exist. Follows symlinks.

Throws:

• InappropriateType if file is not a regular file or a symlink
• PermissionDenied if we cannot read the file or the directory containting it
• NoSuchThing if the file does not exist

File permissions

newFilePerms :: FileMode

Default permissions for a new file.

newDirPerms :: FileMode

Default permissions for a new directory.

Directory reading

getDirsFiles

Arguments

:: Path Abs

dir to read

-> IO [Path Abs]

Gets all filenames of the given directory. This excludes "." and "..". This version does not follow symbolic links.

The contents are not sorted and there is no guarantee on the ordering.

Throws:

• NoSuchThing if directory does not exist
• InappropriateType if file type is wrong (file)
• InappropriateType if file type is wrong (symlink to file)
• InappropriateType if file type is wrong (symlink to dir)
• PermissionDenied if directory cannot be opened

Filetype operations

getFileType :: Path Abs -> IO FileType

Get the file type of the file located at the given path. Does not follow symbolic links.

Throws:

• NoSuchThing if the file does not exist
• PermissionDenied if any part of the path is not accessible

Others

canonicalizePath :: Path Abs -> IO (Path Abs)

Applies realpath on the given absolute path.

Throws:

• NoSuchThing if the file at the given path does not exist
• NoSuchThing if the symlink is broken