1URI::file(3) User Contributed Perl Documentation URI::file(3)
2
6 URI::file - URI that maps to local file names
7
9 use URI::file;
10 $u1 = URI->new("file:/foo/bar");
12 $u2 = URI->new("foo/bar", "file");
13 $u3 = URI::file->new($path);
15 $u4 = URI::file->new("c:\\windows\\", "win32");
16 $u1->file;
18 $u1->file("mac");
19
21 The "URI::file" class supports "URI" objects belonging to the file URI
22 scheme. This scheme allows us to map the conventional file names found
23 on various computer systems to the URI name space, see RFC 8089
24 <https://www.rfc-editor.org/rfc/rfc8089.html>.
25 If you simply want to construct file URI objects from URI strings, use
27 the normal "URI" constructor. If you want to construct file URI
28 objects from the actual file names used by various systems, then use
29 one of the following "URI::file" constructors:
30 $u = URI::file->new( $filename, [$os] )
32 Maps a file name to the file: URI name space, creates a URI object
33 and returns it. The $filename is interpreted as belonging to the
34 indicated operating system ($os), which defaults to the value of
35 the $^O variable. The $filename can be either absolute or
36 relative, and the corresponding type of URI object for $os is
37 returned.
38 $u = URI::file->new_abs( $filename, [$os] )
40 Same as URI::file->new, but makes sure that the URI returned
41 represents an absolute file name. If the $filename argument is
42 relative, then the name is resolved relative to the current
43 directory, i.e. this constructor is really the same as:
44 URI::file->new($filename)->abs(URI::file->cwd);
46 $u = URI::file->cwd
48 Returns a file URI that represents the current working directory.
49 See Cwd.
50 The following methods are supported for file URI (in addition to the
52 common and generic methods described in URI):
53 $u->file( [$os] )
55 Returns a file name. It maps from the URI name space to the file
56 name space of the indicated operating system.
57 It might return "undef" if the name can not be represented in the
59 indicated file system.
60 $u->dir( [$os] )
62 Some systems use a different form for names of directories than for
63 plain files. Use this method if you know you want to use the name
64 for a directory.
65 The "URI::file" module can be used to map generic file names to names
67 suitable for the current system. As such, it can work as a nice
68 replacement for the "File::Spec" module. For instance, the following
69 code translates the UNIX-style file name Foo/Bar.pm to a name suitable
70 for the local system:
71 $file = URI::file->new("Foo/Bar.pm", "unix")->file;
73 die "Can't map filename Foo/Bar.pm for $^O" unless defined $file;
74 open(FILE, $file) || die "Can't open '$file': $!";
75 # do something with FILE
76
78 Most computer systems today have hierarchically organized file systems.
79 Mapping the names used in these systems to the generic URI syntax
80 allows us to work with relative file URIs that behave as they should
81 when resolved using the generic algorithm for URIs (specified in RFC
82 3986 <https://www.rfc-editor.org/rfc/rfc3986.html>). Mapping a file
83 name to the generic URI syntax involves mapping the path separator
84 character to "/" and encoding any reserved characters that appear in
85 the path segments of the file name. If path segments consisting of the
86 strings "." or ".." have a different meaning than what is specified for
87 generic URIs, then these must be encoded as well.
88 If the file system has device, volume or drive specifications as the
90 root of the name space, then it makes sense to map them to the
91 authority field of the generic URI syntax. This makes sure that
92 relative URIs can not be resolved "above" them, i.e. generally how
93 relative file names work in those systems.
94 Another common use of the authority field is to encode the host on
96 which this file name is valid. The host name "localhost" is special
97 and generally has the same meaning as a missing or empty authority
98 field. This use is in conflict with using it as a device
99 specification, but can often be resolved for device specifications
100 having characters not legal in plain host names.
101 File name to URI mapping in normally not one-to-one. There are usually
103 many URIs that map to any given file name. For instance, an authority
104 of "localhost" maps the same as a URI with a missing or empty
105 authority.
106 Example 1: The Mac classic (Mac OS 9 and earlier) used ":" as path
108 separator, but not in the same way as a generic URI. ":foo" was a
109 relative name. "foo:bar" was an absolute name. Also, path segments
110 could contain the "/" character as well as the literal "." or "..". So
111 the mapping looks like this:
112 Mac classic URI
114 ---------- -------------------
115 :foo:bar <==> foo/bar
116 : <==> ./
117 ::foo:bar <==> ../foo/bar
118 ::: <==> ../../
119 foo:bar <==> file:/foo/bar
120 foo:bar: <==> file:/foo/bar/
121 .. <==> %2E%2E
122 <undef> <== /
123 foo/ <== file:/foo%2F
124 ./foo.txt <== file:/.%2Ffoo.txt
125 Note that if you want a relative URL, you *must* begin the path with a
127 :. Any path that begins with [^:] is treated as absolute.
128 Example 2: The UNIX file system is easy to map, as it uses the same
130 path separator as URIs, has a single root, and segments of "." and ".."
131 have the same meaning. URIs that have the character "\0" or "/" as
132 part of any path segment can not be turned into valid UNIX file names.
133 UNIX URI
135 ---------- ------------------
136 foo/bar <==> foo/bar
137 /foo/bar <==> file:/foo/bar
138 /foo/bar <== file://localhost/foo/bar
139 file: ==> ./file:
140 <undef> <== file:/fo%00/bar
141 / <==> file:/
142
144 The following configuration variables influence how the class and its
145 methods behave:
146 %URI::file::OS_CLASS
148 This hash maps OS identifiers to implementation classes. You might
149 want to add or modify this if you want to plug in your own file
150 handler class. Normally the keys should match the $^O values in
151 use.
152 If there is no mapping then the "Unix" implementation is used.
154 $URI::file::DEFAULT_AUTHORITY
156 This determines what "authority" string to include in absolute file
157 URIs. It defaults to "". If you prefer verbose URIs you might set
158 it to be "localhost".
159 Setting this value to "undef" forces behaviour compatible to URI
161 v1.31 and earlier. In this mode host names in UNC paths and drive
162 letters are mapped to the authority component on Windows, while we
163 produce authority-less URIs on Unix.
164
166 URI, File::Spec, perlport
167
169 Copyright 1995-1998,2004 Gisle Aas.
170 This library is free software; you can redistribute it and/or modify it
172 under the same terms as Perl itself.
173perl v5.36.0 2022-11-03 URI::file(3)