Copyright	© 2016 Julian Ospald
License	BSD3
Maintainer	Julian Ospald <hasufell@posteo.de>
Stability	experimental
Portability	portable
Safe Haskell	None
Language	Haskell2010

HPath.IO

Contents

Types
File copying
File deletion
File opening
File creation
File renaming/moving
File permissions
Directory reading
Filetype operations
Others

Description

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.

Synopsis

Types

data FileType Source

Constructors

Directory
RegularFile
SymbolicLink
BlockDevice
CharacterDevice
NamedPipe
Socket

Instances

Eq FileType
Show FileType

data RecursiveErrorMode Source

The error mode for any recursive operation.

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 Source

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 Source

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 Source

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 file already exists

Throws in Overwrite mode only:

UnsatisfiedConstraints if destination file is non-empty directory

Note: calls symlink

copyFile Source

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 () Source

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 () Source

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 () Source

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 () Source

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 () Source

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 Source

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

executeFile Source

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 () Source

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 file already exists
NoSuchThing if any of the parent components of the path do not exist

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

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

Throws:

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

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

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 /destination/somedir

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 Source

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 () Source

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
FileDoesExist if destination file already exists (HPathIOException)
DirDoesExist if destination directory already exists (HPathIOException)
SameFile if destination and source are the same file (HPathIOException)

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

moveFile Source

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