Module Fpath

File system paths, file extensions, path sets and maps.

A (file system) path specifies a file or a directory in a file system hierarchy. A path has three parts:

  1. An optional, platform-dependent, volume.
  2. An optional root directory separator dir_sep whose presence distinguishes absolute paths ("/a") from relative ones ("a")
  3. A non-empty list of dir_sep separated segments. Segments are non empty strings except for maybe the last one. The latter distinguishes directory paths ("a/b/") from file paths ("a/b").

The path segments "." and ".." are relative path segments that respectively denote the current and parent directory. The basename of a path is its last non-empty segment if it is not a relative path segment or the empty string otherwise.

Consult a few important tips.

Note. Fpath processes paths without accessing the file system.

v0.7.3 - homepage

Separators and segments

val dir_sep : string

dir_sep is the platform dependent natural directory separator. This is "/" on POSIX and "\\" on Windows.

val is_seg : string -> bool

is_seg s is true iff s does not contain dir_sep or '/' or a 0x00 byte.

val is_rel_seg : string -> bool

is_rel_seg s is true iff s is a relative segment, that is "." or "..".

Paths

type t

The type for paths.

val v : string -> t

v s is the string s as a path.

  • raises Invalid_argument

    if s is not a valid path. Use of_string to deal with untrusted input.

val add_seg : t -> string -> t

add_seg p seg adds segment seg to the segments of p if p's last segment is non-empty or replaces the last empty segment with seg. Examples.

  • raises Invalid_argument

    if is_seg seg is false.

val (/) : t -> string -> t

p / seg is add_seg p seg. Left associative.

val append : t -> t -> t

append p q appends q to p as follows:

  • If q is absolute or has a non-empty volume then q is returned.
  • Otherwise appends q's segments to p using add_seg.

Examples.

val (//) : t -> t -> t

p // p' is append p p'. Left associative.

val split_volume : t -> string * t

split_volume p is the pair (vol, q) where vol is the platform dependent volume of p or the empty string if there is none and q the path p without its volume, that is its optional root dir_sep and segments.

On POSIX if vol is non-empty then it can only be "/" (e.g. in v "//a/b"). On Windows vol may be one of the following prefixes parsed before an absolute root dir_sep, except in the first case where a relative path can follow:

$(drive):
\\$(server)\$(share)
\\?\$(drive):
\\?\$(server)\$(share)
\\?\UNC\$(server)\$(share)
\\.\$(device)

The following invariant holds:

  • equal p (v @@ vol ^ (to_string q))
val segs : t -> string list

segs p is p's non-empty list of segments. Absolute paths have an initial empty string added, this allows to recover the path's string with concat ~sep:dir_sep. Examples.

The following invariant holds:

  • equal p (v @@ (fst @@ split_volume p) ^ (String.concat ~sep:dir_sep (segs p)))

File and directory paths

Note. The following functions use syntactic semantic properties of paths. Given a path, these properties can be different from the one your file system attributes to it.

val is_dir_path : t -> bool

is_dir_path p is true iff p represents a directory. This means that p's last segment is either empty ("") or relative. The property is invariant with respect to normalization. Examples.

val is_file_path : t -> bool

is_file_path p is true iff p represents a file. This is the negation of is_dir_path. This means that p's last segment is neither empty ("") nor relative. The property is invariant with respect to normalization. Examples.

val to_dir_path : t -> t

to_dir_path p is add_seg p "". It ensure that the result represents a directory and, if converted to a string, that it ends with a dir_sep. Examples.

val filename : t -> string

filename p is the file name of p. This is the last segment of p if p is a file path and the empty string otherwise. The result is invariant with respect to normalization. See also basename. Examples.

Base and parent paths

val split_base : t -> t * t

split_base p splits p into a directory d and a relative base path b such that:

  • b is a relative path that contains the segments of p that start at the last non-empty segment. This means that b has a single non-empty segment, and preserves directoryness of p. If p is a root path there are no such segments and b is "./".
  • d is a directory such that d // b represents the same path as p. They may however differ syntactically when converted to a string.

Examples.

Note. Normalizing p before using the function ensures that b is a relative segment iff p cannot be named (like in ".", "../../", "/", etc.).

val base : t -> t

base p is snd (split_base p).

val basename : t -> string

basename p is p's last non-empty segment if non-relative or the empty string otherwise. The latter occurs only on root paths and on paths whose last non-empty segment is a relative segment. See also filename and base. Examples.

Note. Normalizing p before using the function ensures the empty string is only returned iff p cannot be named (like in ".", "../../", "/", etc.)

val parent : t -> t

parent p is a directory path that contains p. If p is a root path this is p itself. Examples.

Warning. parent p // base p may not represent p, use split_base for this.

Normalization

val rem_empty_seg : t -> t

rem_empty_seg p removes an existing last empty segment of p if p is not a root path. This ensure that if p is converted to a string it will not have a trailing dir_sep unless p is a root path. Note that this may affect p's directoryness. Examples.

val normalize : t -> t

normalize p is a path that represents the same path as p, directoryness included, and that has the following properties:

  • If p is absolute the resulting path has no "." and ".." segments.
  • If p is relative the resulting path is either "./" or it has no "." segments and ".." segments may only appear as initial segments.
  • If p is a directory it always end with an empty segment; this means it doesn't end with "." or "..".

Examples.

Warning. Like file and directory path functions this function does not consult the file system and is purely based on the syntactic semantic of paths which can be different from the one of your concrete file system attributes. For example in presence of symbolic links the resulting path may not point to the same entity. Use the normalization functions of your OS system library to ensure correct behaviour with respect to a concrete file system.

Prefixes

Warning. The syntactic prefix relation between paths does not, in general, entail directory containement. The following examples show this:

is_prefix (v "..") (v "../..") = true
is_prefix (v "..") (v ".") = false

However, on normalized, absolute paths, the prefix relation does entail directory containement. See also is_rooted.

val is_prefix : t -> t -> bool

is_prefix prefix p is true if prefix is a prefix of p. This checks that:

  • prefix has the same optional volume as p.
  • prefix has the same optional root directory separator as p.
  • The list of segments of prefix is a prefix of those of p, ignoring the last empty segment of prefix if the number of non-empty segments of p is strictly larger than those of prefix. This means that is_prefix (v "a/") (v "a/b") is true but is_prefix (v "a/") (v "a") is false

Examples.

val find_prefix : t -> t -> t option

find_prefix p p' is Some prefix if there exists prefix such that prefix is the longest path with is_prefix prefix p && is_prefix prefix p' = true and None otherwise. Note that if both p and p' are absolute and have the same volume then a prefix always exists: the root path of their volume. Examples.

val rem_prefix : t -> t -> t option

rem_prefix prefix p is:

  • None if prefix is not a prefix of p or if prefix and p are equal.
  • Some q otherwise where q is p without the prefix prefix and preserves p's directoryness. This means that q is a always relative and that the path prefix // q and p represent the same paths. They may however differ syntactically when converted to a string.

Examples.

Roots and relativization

val relativize : root:t -> t -> t option

relativize ~root p is:

  • Some q if there exists a relative path q such that root // q and p represent the same paths, directoryness included. They may however differ syntactically when converted to a string. Note that q is normalized.
  • None otherwise.

Examples.

val is_rooted : root:t -> t -> bool

is_rooted root p is true iff the path p is the directory root or contained in root and that p can be relativized w.r.t. root (the normalized relative path will have no parent directory segments). Examples.

Predicates and comparison

val is_rel : t -> bool

is_rel p is true iff p is a relative path, i.e. the root directory separator is missing in p.

val is_abs : t -> bool

is_abs p is true iff p is an absolute path, i.e. the root directory separator is present in p.

val is_root : t -> bool

is_root p is true iff p is a root directory, i.e. p has the root directory separator and a single, empty, segment. Examples.

Warning. By definition this is a syntactic test. For example it will return false on "/a/.." or "/..". Normalizing the path before testing avoids this problem.

val is_current_dir : ?prefix:bool -> t -> bool

is_current_dir p is true iff p is the current relative directory, i.e. either "." or "./". If prefix is true (defaults to false) simply checks that p is relative and its first segment is ".".

Warning. By definition this is a syntactic test. For example it will return false on "./a/.." or "./.". Normalizing the path before testing avoids this problem.

val is_parent_dir : ?prefix:bool -> t -> bool

is_parent_dir p is true iff p is the relative parent directory, i.e. either ".." or "../". If prefix is true (defaults to false), simply checks that p is relative and its first segment is "..".

Warning. By definition this is a syntactic test. For example it will return false on "./a/../.." or "./..". Normalizing the path before testing avoids this problem.

val is_dotfile : t -> bool

is_dotfile p is true iff p's basename is non empty and starts with a '.'.

Warning. By definition this is a syntactic test. For example it will return false on ".ssh/.". Normalizing the path before testing avoids this problem.

val equal : t -> t -> bool

equal p p' is true if p and p' have the same volume are both relative or absolute and have the same segments.

Warning. By definition this is a syntactic test. For example equal (v "./") (v "a/..") is false. Normalizing the paths before testing avoids this problem.

val compare : t -> t -> int

compare p p' is a total order on paths compatible with equal.

Conversions and pretty printing

val to_string : t -> string

to_string p is the path p as a string. The result can be safely converted back with v.

val of_string : string -> (t, [ `Msg of string ]) result

of_string s is the string s as a path. The following transformations are performed on the string:

  • On Windows any '/' occurence is converted to '\\' before any processing occurs.
  • Non-initial empty segments are suppressed; "a//b" becomes "a/b", "//a////b//" becomes "//a/b/", etc.
  • On Windows empty absolute UNC paths are completed to their root. For example "\\\\server\\share" becomes "\\\\server\\share\\", but incomplete UNC volumes like "\\\\a" return Error.

Error (`Msg (strf "%S: invalid path" s)) is returned if

  • s or the path following the volume is empty (""), except on Windows UNC paths, see above.
  • s has null byte ('\x00').
  • On Windows, s is an invalid UNC path (e.g. "\\\\" or "\\\\a")
val pp : Format.formatter -> t -> unit

pp ppf p prints path p on ppf using to_string.

val dump : Format.formatter -> t -> unit

dump ppf p prints path p on ppf using String.dump.

File extensions

The file extension (resp. multiple file extension) of a path segment is the suffix that starts at the last (resp. first) occurence of a '.' that is preceeded by at least one non '.' character. If there is no such occurence in the segment, the extension is empty. With these definitions, ".", "..", "..." and dot files like ".ocamlinit" or "..ocamlinit" have no extension, but ".emacs.d" and "..emacs.d" do have one.

Warning. The following functions act on paths whose basename is non empty and do nothing otherwise. Normalizing p before using the functions ensures that the functions do nothing iff p cannot be named, see basename.

type ext = string

The type for file extensions.

val get_ext : ?multi:bool -> t -> ext

get_ext p is p's basename file extension or the empty string if there is no extension. If multi is true (defaults to false), returns the multiple file extension. Examples.

val has_ext : ext -> t -> bool

has_ext e p is true iff get_ext p = e || get_ext ~multi:true p = e. If e doesn't start with a '.' one is prefixed before making the test. Examples.

val mem_ext : ext list -> t -> bool

mem_ext exts p is List.mem (get_ext p) exts || List.mem (get_ext ~multi:true p) exts.

val exists_ext : ?multi:bool -> t -> bool

exists_ext ~multi p is true iff p's basename file extension is not empty. If multi is true (default to false) returns true iff p has more than one extension. Examples.

val add_ext : ext -> t -> t

add_ext ext p is p with the string ext concatenated to p's basename, if non empty. If ext doesn't start with a '.' one is prefixed to it before concatenation except if ext is "". Examples.

  • raises Invalid_argument

    if is_seg ext is false.

val rem_ext : ?multi:bool -> t -> t

rem_ext p is p with the extension of p's basename removed. If multi is true (default to false), the multiple file extension is removed. Examples.

val set_ext : ?multi:bool -> ext -> t -> t

set_ext ?multi ext p is add_ext ext (rem_ext ?multi p).

val split_ext : ?multi:bool -> t -> t * ext

split_ext ?multi p is (rem_ext ?multi p, get_ext ?multi p). If this is (q, ext) the following invariant holds:

  • equal p (add_ext q ext)
val (+) : t -> ext -> t

p + ext is add_ext ext p. Left associative.

val (-+) : t -> ext -> t

p -+ ext is set_ext ext p. Left associative.

Path sets and maps

type path = t
type set

The type for path sets. Membership is determined according to equal.

module Set : sig ... end

Path sets.

module Map : sig ... end

Path maps.

type +'a map = 'a Map.t

The type for maps from paths to values of type 'a. Paths are compared with compare.

Tips

Examples