Provided by: liburi-perl_5.27-1_all 
NAME
URI::file - URI that maps to local file names
SYNOPSIS
use URI::file;
$u1 = URI->new("file:/foo/bar");
$u2 = URI->new("foo/bar", "file");
$u3 = URI::file->new($path);
$u4 = URI::file->new("c:\\windows\\", "win32");
$u1->file;
$u1->file("mac");
DESCRIPTION
The "URI::file" class supports "URI" objects belonging to the file URI scheme. This scheme allows us to
map the conventional file names found on various computer systems to the URI name space, see RFC 8089
<https://www.rfc-editor.org/rfc/rfc8089.html>.
If you simply want to construct file URI objects from URI strings, use the normal "URI" constructor. If
you want to construct file URI objects from the actual file names used by various systems, then use one
of the following "URI::file" constructors:
$u = URI::file->new( $filename, [$os] )
Maps a file name to the file: URI name space, creates a URI object and returns it. The $filename is
interpreted as belonging to the indicated operating system ($os), which defaults to the value of the
$^O variable. The $filename can be either absolute or relative, and the corresponding type of URI
object for $os is returned.
$u = URI::file->new_abs( $filename, [$os] )
Same as URI::file->new, but makes sure that the URI returned represents an absolute file name. If
the $filename argument is relative, then the name is resolved relative to the current directory, i.e.
this constructor is really the same as:
URI::file->new($filename)->abs(URI::file->cwd);
$u = URI::file->cwd
Returns a file URI that represents the current working directory. See Cwd.
The following methods are supported for file URI (in addition to the common and generic methods described
in URI):
$u->file( [$os] )
Returns a file name. It maps from the URI name space to the file name space of the indicated
operating system.
It might return "undef" if the name can not be represented in the indicated file system.
$u->dir( [$os] )
Some systems use a different form for names of directories than for plain files. Use this method if
you know you want to use the name for a directory.
The "URI::file" module can be used to map generic file names to names suitable for the current system.
As such, it can work as a nice replacement for the "File::Spec" module. For instance, the following code
translates the UNIX-style file name Foo/Bar.pm to a name suitable for the local system:
$file = URI::file->new("Foo/Bar.pm", "unix")->file;
die "Can't map filename Foo/Bar.pm for $^O" unless defined $file;
open(FILE, $file) || die "Can't open '$file': $!";
# do something with FILE
MAPPING NOTES
Most computer systems today have hierarchically organized file systems. Mapping the names used in these
systems to the generic URI syntax allows us to work with relative file URIs that behave as they should
when resolved using the generic algorithm for URIs (specified in RFC 3986 <https://www.rfc-
editor.org/rfc/rfc3986.html>). Mapping a file name to the generic URI syntax involves mapping the path
separator character to "/" and encoding any reserved characters that appear in the path segments of the
file name. If path segments consisting of the strings "." or ".." have a different meaning than what is
specified for generic URIs, then these must be encoded as well.
If the file system has device, volume or drive specifications as the root of the name space, then it
makes sense to map them to the authority field of the generic URI syntax. This makes sure that relative
URIs can not be resolved "above" them, i.e. generally how relative file names work in those systems.
Another common use of the authority field is to encode the host on which this file name is valid. The
host name "localhost" is special and generally has the same meaning as a missing or empty authority
field. This use is in conflict with using it as a device specification, but can often be resolved for
device specifications having characters not legal in plain host names.
File name to URI mapping in normally not one-to-one. There are usually many URIs that map to any given
file name. For instance, an authority of "localhost" maps the same as a URI with a missing or empty
authority.
Example 1: The Mac classic (Mac OS 9 and earlier) used ":" as path separator, but not in the same way as
a generic URI. ":foo" was a relative name. "foo:bar" was an absolute name. Also, path segments could
contain the "/" character as well as the literal "." or "..". So the mapping looks like this:
Mac classic URI
---------- -------------------
:foo:bar <==> foo/bar
: <==> ./
::foo:bar <==> ../foo/bar
::: <==> ../../
foo:bar <==> file:/foo/bar
foo:bar: <==> file:/foo/bar/
.. <==> %2E%2E
<undef> <== /
foo/ <== file:/foo%2F
./foo.txt <== file:/.%2Ffoo.txt
Note that if you want a relative URL, you *must* begin the path with a :. Any path that begins with [^:]
is treated as absolute.
Example 2: The UNIX file system is easy to map, as it uses the same path separator as URIs, has a single
root, and segments of "." and ".." have the same meaning. URIs that have the character "\0" or "/" as
part of any path segment can not be turned into valid UNIX file names.
UNIX URI
---------- ------------------
foo/bar <==> foo/bar
/foo/bar <==> file:/foo/bar
/foo/bar <== file://localhost/foo/bar
file: ==> ./file:
<undef> <== file:/fo%00/bar
/ <==> file:/
CONFIGURATION VARIABLES
The following configuration variables influence how the class and its methods behave:
%URI::file::OS_CLASS
This hash maps OS identifiers to implementation classes. You might want to add or modify this if you
want to plug in your own file handler class. Normally the keys should match the $^O values in use.
If there is no mapping then the "Unix" implementation is used.
$URI::file::DEFAULT_AUTHORITY
This determines what "authority" string to include in absolute file URIs. It defaults to "". If you
prefer verbose URIs you might set it to be "localhost".
Setting this value to "undef" forces behaviour compatible to URI v1.31 and earlier. In this mode
host names in UNC paths and drive letters are mapped to the authority component on Windows, while we
produce authority-less URIs on Unix.
SEE ALSO
URI, File::Spec, perlport
COPYRIGHT
Copyright 1995-1998,2004 Gisle Aas.
This library is free software; you can redistribute it and/or modify it under the same terms as Perl
itself.
perl v5.38.2 2024-02-14 URI::file(3pm)