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System.Path.NameManip

Portability | portable
Stability | provisional
Maintainer | John Goerzen <jgoerzen@complete.org>

Description
Low-level path name manipulations. Written by Volker Wysk
Synopsis

slice_path :: String -> [String]
unslice_path :: [String] -> String
normalise_path :: String -> String
slice_filename :: String -> [String]
slice_filename' :: String -> [String]
unslice_filename :: [String] -> String
split_path :: String -> (String, String)
dir_part :: String -> String
filename_part :: String -> String
unsplit_path :: (String, String) -> String
split_filename :: String -> (String, String)
split_filename' :: String -> (String, String)
unsplit_filename :: (String, String) -> String
split3 :: String -> (String, String, String)
unsplit3 :: (String, String, String) -> String
test_suffix :: String -> String -> Maybe String
absolute_path :: String -> IO String
absolute_path_by :: String -> String -> String
absolute_path' :: String -> String -> String
guess_dotdot_comps :: [String] -> Maybe [String]
guess_dotdot :: String -> Maybe String

Documentation

slice_path | Source

:: String | The path to be broken to components.
-> [String] | List of path components.

Split a path in components. Repeated "`/`" characters don't lead to empty components. "`.`" path components are removed. If the path is absolute, the first component will start with "`/`". "`..`" components are left intact. They can't be simply removed, because the preceding component might be a symlink. In this case, realpath is probably what you need.

The case that the path is empty, is probably an error. However, it is treated like "`.`", yielding an empty path components list.

Examples:

    slice_path "/"        = ["/"]
    slice_path "/foo/bar" = ["/foo","bar"]
    slice_path "..//./"   = [".."]
    slice_path "."        = []

See `unslice_path`, realpath, realpath_s.

unslice_path | Source

:: [String] | List of path components
-> String | The path which consists of the supplied path components
Form a path from path components. This isn't the inverse of `slice_path`, since ``unslice_path` . `slice_path`` normalises the path. See `slice_path`.

normalise_path | Source

:: String | Path to be normalised
-> String | Path in normalised form

Normalise a path. This is done by reducing repeated `/` characters to one, and removing `.` path components. `..` path components are left intact, because of possible symlinks.

    normalise_path = unslice_path . slice_path

slice_filename | Source

:: String | Path
-> [String] | List of components the file name is made up of

Split a file name in components. This are the base file name and the suffixes, which are separated by dots. If the name starts with a dot, it is regarded as part of the base name. The result is a list of file name components. The filename may be a path. In this case, everything up to the last path component will be returned as part of the base file name. The path gets normalised thereby.

No empty suffixes are returned. If the file name contains several consecutive dots, they are regared as part of the preceding file name component.

Concateneting the name components and adding dots, reproduces the original name, with a normalised path: `concat . intersperse "." . `slice_filename` == normalise`.

Note that the last path component might be "`..`". Then it is not possible to deduce the refered directory's name from the path. An IO action for getting the real path is then necessary.

Examples:

    slice_filename "a.b//./.foo.tar.gz" == ["a.b/.foo","tar","gz"]
    slice_filename ".x..y."             == [".x.", "y."]

See `unslice_filename`, `slice_filename'`.

slice_filename' | Source

:: String | File name without path
-> [String] | List of components the file name is made up of
This is a variant of `slice_filename`. It is like `slice_filename`, except for being more efficient, and the filename must not contain any preceding path, since this case isn't considered. See `slice_filename`, `unslice_filename`.

unslice_filename | Source

:: [String] | List of file name components
-> String | Name of the file which consists of the supplied components

Form file name from file name components, interspersing dots. This is the inverse of `slice_filename`, except for normalisation of any path.

     unslice_filename = concat . intersperse "."

See `slice_filename`.

split_path | Source

:: String | Path to be split
-> (String, String) | Directory and file name components of the path. The directory path is normalized.

Split a path in directory and file name. Only in the case that the supplied path is empty, both parts are empty strings. Otherwise, `"."` is filled in for the corresponding part, if necessary. Unless the path is empty, concatenating the returned path and file name components with a slash in between, makes a valid path to the file.

`split_path` splits off the last path component. This isn't the same as the text after the last `/`.

Note that the last path component might be `".."`. Then it is not possible to deduce the refered directory's name from the path. Then an IO action for getting the real path is necessary.

Examples:

    split_path "/a/b/c"      == ("/a/b", "c")
    split_path "foo"         == (".", "foo")
    split_path "foo/bar"     == ("foo", "bar")
    split_path "foo/.."      == ("foo", "..")
    split_path "."           == (".", ".")
    split_path ""            == ("", "")
    split_path "/foo"        == ("/", "foo")
    split_path "foo/"        == (".", "foo")
    split_path "foo/."       == (".", "foo")
    split_path "foo///./bar" == ("foo", "bar")

See `slice_path`.

dir_part :: String -> String | Source

Get the directory part of a path.

    dir_part = fst . split_path

See `split_path`.

filename_part :: String -> String | Source

Get the last path component of a path.

    filename_part = snd . split_path

Examples:

    filename_part "foo/bar" == "bar"
    filename_part "."       == "."

See `split_path`.

unsplit_path | Source

:: (String, String) | Directory and file name
-> String | Path formed from the directory and file name parts

Inverse of `split_path`, except for normalisation.

This concatenates two paths, and takes care of `"."` and empty paths. When the two components are the result of `split_path`, then `unsplit_path` creates a normalised path. It is best documented by its definition:

    unsplit_path (".", "") = "."
    unsplit_path ("", ".") = "."
    unsplit_path (".", q)  = q
    unsplit_path ("", q)   = q
    unsplit_path (p, "")   = p
    unsplit_path (p, ".")  = p
    unsplit_path (p, q)    = p ++ "/" ++ q

Examples:

    unsplit_path ("", "")     == ""
    unsplit_path (".", "")    == "."
    unsplit_path (".", ".")   == "."
    unsplit_path ("foo", ".") == "foo"

See `split_path`.

split_filename | Source

:: String | Path including the file name to be split
-> (String, String) | The normalised path with the file prefix, and the file suffix.

Split a file name in prefix and suffix. If there isn't any suffix in the file name, then return an empty suffix. A dot at the beginning or at the end is not regarded as introducing a suffix.

The last path component is what is being split. This isn't the same as splitting the string at the last dot. For instance, if the file name doesn't contain any dot, dots in previous path component's aren't mistaken as introducing suffixes.

The path part is returned in normalised form. This means, `"."` components are removed, and multiple "`/`"s are reduced to one.

Note that there isn't any plausibility check performed on the suffix. If the file name doesn't have a suffix, but happens to contain a dot, then this dot is mistaken as introducing a suffix.

Examples:

    split_filename "path/to/foo.bar"                             = ("path/to/foo","bar")
    split_filename "path/to/foo"                                 = ("path/to/foo","")
    split_filename "/path.to/foo"                                = ("/path.to/foo","")
    split_filename "a///./x"                                     = ("a/x","")
    split_filename "dir.suffix/./"                               = ("dir","suffix")
    split_filename "Photographie, Das 20. Jahrhundert (300 dpi)" = ("Photographie, Das 20", " Jahrhundert (300 dpi)")

See `slice_path`, 'split_filename\''

split_filename' | Source

:: String | Filename to be split
-> (String, String) | Base name and the last suffix
Variant of `split_filename`. This is a more efficient version of `split_filename`, for the case that you know the string is is a pure file name without any slashes. See `split_filename`.

unsplit_filename | Source

:: (String, String) | File name prefix and suffix
-> String | Path
Inverse of `split_filename`. Concatenate prefix and suffix, adding a dot in between, iff the suffix is not empty. The path part of the prefix is normalised. See `split_filename`.

split3 | Source

:: String | Path to split
-> (String, String, String) | Directory part, base file name part and suffix part
Split a path in directory, base file name and suffix.

unsplit3 | Source

:: (String, String, String) | Directory part, base file name part and suffix part
-> String | Path consisting of dir, base and suffix
Form path from directory, base file name and suffix parts.

test_suffix | Source

:: String | Suffix to split off
-> String | Path to test
-> Maybe String | Prefix without the suffix or `Nothing`
Test a path for a specific suffix and split it off. If the path ends with the suffix, then the result is `Just prefix`, where `prefix` is the normalised path without the suffix. Otherwise it's `Nothing`.

absolute_path | Source

:: String | The path to be made absolute
-> IO String | Absulte path
Make a path absolute, using the current working directory. This makes a relative path absolute with respect to the current working directory. An absolute path is returned unmodified. The current working directory is determined with `getCurrentDirectory` which means that symbolic links in it are expanded and the path is normalised. This is different from `pwd`.

absolute_path_by | Source

:: String | The directory relative to which the path is made absolute
-> String | The path to be made absolute
-> String | Absolute path
Make a path absolute. This makes a relative path absolute with respect to a specified directory. An absolute path is returned unmodified.

absolute_path' | Source

:: String | The path to be made absolute
-> String | The directory relative to which the path is made absolute
-> String | Absolute path
Make a path absolute. This makes a relative path absolute with respect to a specified directory. An absolute path is returned unmodified. The order of the arguments can be confusing. You should rather use `absolute_path_by`. `absolute_path'` is included for backwards compatibility.

guess_dotdot_comps | Source

:: [String] | List of path components
-> Maybe [String] | In case the path could be transformed, the `".."`-component free list of path components.

Guess the `".."`-component free form of a path, specified as a list of path components, by syntactically removing them, along with the preceding path components. This will produce erroneous results when the path contains symlinks. If the path contains leading `".."` components, or more `".."` components than preceeding normal components, then the `".."` components can't be normalised away. In this case, the result is `Nothing`.

guess_dotdot | Source

:: String | Path to be normalised
-> Maybe String | In case the path could be transformed, the normalised, `".."`-component free form of the path.

Guess the `".."`-component free, normalised form of a path. The transformation is purely syntactic. `".."` path components will be removed, along with their preceding path components. This will produce erroneous results when the path contains symlinks. If the path contains leading `".."` components, or more `".."` components than preceeding normal components, then the `".."` components can't be normalised away. In this case, the result is `Nothing`.

    guess_dotdot = fmap unslice_path . guess_dotdot_comps . slice_path

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