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Module Netglob


module Netglob: sig .. end
Globbing


Globbing resolves shell wildcards like "*" and "?". For example,

    let files = Netglob.glob (`String "*.cm[iox]")
    

would return all files matching this pattern (e.g. module.cmi, module.cmo).

The main user function is Netglob.glob. Globbing accesses the local filesystem by default, but one can also run the globbing algorithm on any other filesystem, provided the access primitives of Netglob.glob_fsys are available.

Types and exceptions


type glob_expr = glob_expr_atom list 
type glob_expr_atom = [ `Brace of glob_expr list
| `Bracket of bool * glob_set
| `Literal of string
| `Qmark
| `Star
| `Tilde of string ]
Atoms:

  • `Literal s: Matches the string literally. The string must not be empty. The backslash is not an escape character, but matches the backslash character.
  • `Star: The "*" operator
  • `Qmark: The "?" operator
  • `Bracket(negated,set): The [...] operator. The set argument describes the characters that are matched. The negated argument is true when the expression is negated (i.e. [^...]).
  • `Brace l: The {e1,e2,...} operator
  • `Tilde t: The ~username operator. If t="" the current user is meant. The `Tilde atom may only occur at the beginning of the list. The `Tilde atom always matches a directory, and must be followed by a literal slash (if anything follows).
Compatibility: Conforms to POSIX with extensions (braces). Shells often implement brace expressions in a slightly different way (braces are parsed and expanded in a separate step before the other pattern constructors are handled). The cases where this leads to different results are quite exotic (e.g. "{~g,~h}1" would mean "~g1 ~h1", but this implementation rejects the pattern).
type glob_set = < set : (int * int) list > 
A set of code points is given as a list of ranges (from,to), with from <= to. It is allowed that ranges overlap.
type valid_glob_expr 
A validated glob_expr
class type user_info = object .. end
Access to the user database
class type glob_fsys = object .. end
Filesystem primitives.
type glob_mode = [ `All_paths | `All_words | `Existing_paths ] 
Modes:
  • `Existing_paths: Only paths are returned that really exist
  • `All_paths: Generated paths not including *, ? and bracket expressions are returned even if they do not exist. For example, globbing for "fictive{1,2,3}" would return ["ficitve1";"fictive2";"fictive3"] independent of whether these files exist.
  • `All_words: Patterns that cannot be resolved are returned as-is (like the shell does)

type pattern = [ `Expr of valid_glob_expr | `String of string ] 
Input for Netglob.glob
exception Bad_glob_expr of string
An syntax error in the glob expression; the argument is the bad expression
exception Unsupported_expr of string
The notations :class:, .symbol., =eqclass= inside ... are not supported by this implementation. If they are found, this exception will be raised, and the argument is the whole glob expression

Parsing and printing


val parse_glob_expr : ?encoding:Netconversion.encoding ->
?enable_star:bool ->
?enable_qmark:bool ->
?enable_brackets:bool ->
?enable_braces:bool ->
?enable_tilde:bool ->
?enable_escape:bool -> string -> valid_glob_expr
Parses the glob expression. By default, all syntax features are enabled. May raise Bad_glob_expr or Unsupported_expr.

The glob expressions are POSIX-compliant with the extension of brace expressions, and tildes, and the omission of internationalized bracket expressions:

  • *: Matches a sequence of zero or more arbitrary characters
  • ?: Matches one arbitrary character
  • [abc]: Matches one of the mentioned characters
  • [a-z]: Matches one of the characters of the range. This is here only permitted when the range falls into the ASCII set. (Otherwise the interpretation would be dependent on the encoding.) Note that the ASCII restriction does not comply to POSIX.
  • [!expr] or [^expr]: Negates the bracket expression
  • {expr,expr,...}: Generates a string for each of the alternatives. A brace expression is even recognized if there is no comma, or even no contents (i.e. "{expr}" and "{}"). The elements of brace expressions may be again glob expressions; nested brace expressions are allowed.
  • ~username: Generates the home directory of this user
  • ~: Generates the home directory of the current user
  • If enabled, the backslash character is the escape character. Within bracket expressions, the backslash character never escapes.
  • Not supported: Collating symbols [.a.], equivalence classes [=a=], and character classes [:name:]. If they are found, the exception Unsupported_expr will be raised.
Glob expressions have a character encoding. This defaults to `Enc_iso88591. Encodings must be ASCII-compatible.
val validate_glob_expr : Netconversion.encoding -> glob_expr -> valid_glob_expr
Checks whether the passed expression is syntactically valid. If so, a validated expression is returned. Otherwise, this function fails.
val recover_glob_expr : valid_glob_expr -> glob_expr
Returns the explicit representation
val encoding_of_glob_expr : valid_glob_expr -> Netconversion.encoding
Returns the encoding
val literal_glob_expr : Netconversion.encoding -> string -> valid_glob_expr
Returns an expression that matches literally the passed string
val print_glob_expr : ?escape_in_literals:bool -> valid_glob_expr -> string
Prints the glob expression as string. Meta characters are escaped by a backslash when possible. Meta characters are: "*", "?", "["], ["]", "{", "}", ",", "~" and "\\"

  • escape_in_literals: Whether meta characters in `Literal subexpressions are escaped. This is true by default.


Operations on valid_glob_expr


val expand_glob_expr : ?user_info:user_info ->
?expand_brace:bool ->
?expand_tilde:bool -> valid_glob_expr -> valid_glob_expr list
Resolve generative sub expressions by expanding them. The returned list of glob expr no longer contains the expanded constructions.

  • expand_brace: Expands `Brace subexpressions.
  • expand_tilde: Expands `Tilde subexpressions.
  • user_info: The subset of file system operations needed for tilde expansion. Defaults to Netglob.local_user_info (see below).
Both expand_* options are enabled by default.
val match_glob_expr : ?protect_period:bool ->
?protect_slash:bool ->
?encoding:Netconversion.encoding -> valid_glob_expr -> string -> bool
Matches the glob_expr against a string.

The input must neither contain brace expressions nor tildes (i.e. call expand_glob_expr first). The function fails if it encounters such an expression.

  • protect_period: If true, a leading period cannot be not matched by *, ?, [...], but only by a literal .. A leading period is a . at the beginning of the string to be matched against, or if also protect_slash a . after a /
  • protect_slash: If true, a slash cannot be matched by *, ?, [...], but only by a literal /
Both options are enabled by default.

  • encoding: The encoding of the string argument. Defaults to the encoding of the glob pattern.

val split_glob_expr : valid_glob_expr -> valid_glob_expr list
Splits the glob expression into filename components separated by literal / characters. For example, for the glob expression "a*b/c/d?", the list ["a*b"; "c"; "d?"] is returned.

If the first component begins with a slash, the slash is not removed from the first returned list element, e.g. for "/ab/c*", the list [ "/ab"; "c*" ] is computed. Use check_rooted_glob_expr to test this case.

Several adjacent slashes are handled like a single slash. E.g. for "a//b", the list ["a"; "b"] is returned.

If the last component ends with a slash, it is not removed from the returned list element, e.g. for "a/b/", the list [ "a"; "b/" ] is returned. Use check_directory_glob_expr to test this case.

The glob expression passed to this function must not contain brace or tilde expressions.

val check_rooted_glob_expr : valid_glob_expr -> valid_glob_expr option
If the glob expression matches the root directory (i.e. the expression begins with a literal /), the function returns Some expr', where expr' matches the path relative to the root directory (i.e. the expression without the / at the beginning).

Otherwise, None is returned.

Example: For "/a/b*", the expression "a/b*" is returned.

Special case: for "/", the expression "" (only matching the empty string) is returned.

The glob expression passed to this function must not contain brace or tilde expressions.

val check_directory_glob_expr : valid_glob_expr -> valid_glob_expr option
If the last component of the glob expression matches only directories because it ends with a literal / character, the value Some expr' is returned where expr' matches the same path without the trailing /.

Otherwise, None is returned.

Example: For "a/b*/", the expression "a/b*" is returned.

Special case: for "/", the expression "" (only matching the empty string) is returned.

The glob expression passed to this function must not contain brace or tilde expressions.


Globbing


val glob : ?encoding:Netconversion.encoding ->
?base_dir:string ->
?protect_period:bool ->
?fsys:glob_fsys ->
?user_info:user_info ->
?mode:glob_mode -> pattern -> string list
Forms a set of filenames as described below, and matches this set against the pattern. The pattern can be given as a `String s in which case s is parsed (with all features enabled, and it is assumed it has the passed encoding). Alternatively, an already parsed `Expr e can be given. (Note that encoding is ignored in this case.)

Slashes must be explicitly matched: "/" must literally occur in order to be a candidate for matching. It is not matched by * or ? or a bracket expression.

Periods: The leading period is protected if protect_period. It must then also literally occur to be matched.

Anchoring: If the glob_expr begins with a literal "/", the set of filenames is anchored at the root directory; otherwise the set is anchored at the current directory or, if base_dir is passed, at this directory. (If fsys is passed, it is required to also set base_dir.)

Initially, the set contains all files of the anchor directory (for the root directory, a "/" is prepended).

After that, the set is extended by adding the paths of subdirectories relative to the anchor directory. Note that the constructed set is always infinite, because "." and ".." are not handled specially, and are also regarded as "subdirectories". However, after applying the matching criterion, the returned list is always finite.

Note that the anchor directory itself is not part of the generated set. For example, for the expression "/*" the root directory "/" is not returned. As an exception of this rule, for the glob expression "/" the file "/" is returned.

Braces: Brace expressions are handled by expanding them first, even before filename generation starts.

Mode: By default, only existing paths are returned (mode=`Existing_paths). If no files match, the empty list is returned (and not the pattern as the shell does). By passing a different mode, this can be changed:

  • `All_paths: It is allowed that non-existing paths are returned when the paths do not contain *, ?, or [ metacharacters after the brace expansion. Path expressions with these metacharacters are still checked for existence.
  • `All_words: When an expression does not refer to existing paths, it is returned as such, leaving the metacharacters *, ?, [ unexpanded (i.e., what the Bourne shell does). Note that either all metacharacters are resolved, or none, but not a subset of them.
Encodings: Often, only the pattern has an encoding, but not the filesystem (as in Unix). In this case, no conversion is attempted, and the byte representation of the pattern is matched with the byte representation of the filenames. Good luck.

If the filesystem has an encoding, however, conversions may be required, and this can cause problems. Usually, network filesystems provide an encoding, and the Win32 local filesystem. (For Unix, one can pass a custom fsys with encoding knowledge.) Conversion problems can be avoided if (1) the encoding of the pattern is a superset of the filename encoding. Also, (2) one should not use literals in the pattern that cannot be represented in the filename encoding. If (2) cannot be satisfied, ensure you have at least mode=`Existing_paths, i.e. the default mode (this removes results from the returned list when a conversion problem occurs).

The return value of glob is encoded in the encoding of the filesystem if the filesystem provides an encoding. (If you want to check this encoding, pass fsys, e.g. as local_fsys(), and call the path_encoding method of fsys.)


Remarks



Examples demonstrating the effect of encodings: (Linux)

       let fsys = local_fsys ~encoding:`Enc_utf8()
       let l = glob ~fsys (`String "\214*")
    

The byte 214 is O-umlaut in ISO-8859-1 (the default encoding for patterns). By passing an fsys argument we change the encoding for filenames to UTF-8. For example, if

"\195\150ffentlich"

was a file in the current directory, it would be found and returned in l.

Conversions: For example, assume we have a file "\226\130\172uro" (EUR-uro in UTF-8). The glob

       let fsys = local_fsys ~encoding:`Enc_utf8()
       let l = glob ~fsys (`String "*")
    

finds it although the euro sign cannot be represented in ISO-8859-1, the default pattern encoding.

We run into a problem, however, if we want to generate the euro sign even if the file is not present, and the filesystem uses an encoding that does not include this sign:

       let fsys = local_fsys ~encoding:`Enc_iso88591()
       let l = glob ~fsys ~encoding:`Enc_utf8 ~mode:`All_paths 
                  (`String "\226\130\172uro")
    

This raises an exception Netconversion.Cannot_represent 8364.

Notes for Win32:

  • Globbing only supports forward slashes, not backslashes as path separators
  • Globbing does neither recognize drive letters nor UNC paths as special cases. This may lead to subtle bugs. Glob expressions like "c:/file.*" may or may not work depending on the context.
  • The usually case-insensitive file system is not taken into account. (To be fixed.)


Default access objects


class local_user_info : unit -> user_info
val local_user_info : unit -> user_info
Get the home directory of a user from the local user database.
class local_fsys : ?encoding:Netconversion.encoding -> unit -> glob_fsys
val local_fsys : ?encoding:Netconversion.encoding -> unit -> glob_fsys
Accesses the local filesystem
class of_stream_fs : Netfs.stream_fs -> glob_fsys
val of_stream_fs : Netfs.stream_fs -> glob_fsys
Use an arbitrary network filesystem for globbing

Compatibility

This implementation is not fully compatible with the POSIX specs. The differences:

  • Missing support for character classes, equivalence classes and collating symbols.
  • Ranges in brackets are restricted to ASCII.
  • Unparseable patterns are indicated by exceptions. POSIX, however, requires that such patterns are taken literally. E.g. a pattern "[" would match a left bracket in POSIX, but this module throws a syntax error.
  • If the slash character is protected, it is still allowed inside brackets. POSIX, however, requires that the pattern is scanned for slashes before brackets. For instance, the pattern "[a/b*]" is scanned as [`Literal "[a/b]"; `Star] following the POSIX rules while this implementation sees a bracket expression with "a", "b", "/" and "*" characters.
  • The "^" character negates the set if used at the beginning of bracket expressions. POSIX leaves this unspecified.
  • Brace expresions are an extension (although commonly implemented in shells).
  • The default globbing mode is `Existing_paths which is not defined by POSIX. Use `All_paths for getting POSIX behavior.
Compared with popular shells, there are some subtle differences in how the various syntax elements (wildcards, braces, tildes) are parsed and processed. Shells do it in this order:
  • Parse and expand brace expressions
  • Parse and expand tildes
  • Split the paths at slashes into path components
  • Parse and expand wildcards
For example, after expanding braces it is possible to see totally new tilde or wildcard expressions, e.g. "~user{1,2}/file" would be legal. This implementation here does not support this - we first parse the expression, and then interpret it. However, users interested in a higher degree of compatibility can call the Netglob parsing, processing and printing functions in the required order, and emulate the shell behavior. For example,

  let alt_glob pat =
    let g1 = 
       parse_glob_expr 
         ~enable_star:false ~enable_qmark:false ~enable_brackets:false
         ~enable_tilde:false        (* only braces remain enabled *)
          pat in
    let g2_list = 
       expand_glob_expr g1 in
    let pat2_list = 
       List.map (print_glob_expr ~escape_in_literals:false) g2_list in
    let g3_list =
       List.map
         (fun pat2 -> parse_glob_expr ~enable_braces:false pat2) 
         pat2_list in
    List.flatten
      (List.map (fun g3 -> glob (`Expr g3)) g3_list)
    

would parse and expand brace expressions in a separate step before running glob on the remaining syntactic elements.

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