URI::file(3pm) User Contributed Perl Documentation URI::file(3pm)
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)
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