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268 lines
8.2 KiB
268 lines
8.2 KiB
package URI::file;
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use strict;
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use vars qw(@ISA);
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require URI::_generic;
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@ISA = qw(URI::_generic);
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# Map from $^O values to implementation classes. The Unix
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# class is the default.
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my %os_class = (
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os2 => "OS2",
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mac => "Mac",
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MacOS => "Mac",
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MSWin32 => "Win32",
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win32 => "Win32",
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msdos => "FAT",
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dos => "FAT",
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qnx => "QNX",
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);
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sub os_class
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{
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my($OS) = shift || $^O;
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my $class = "URI::file::" . ($os_class{$OS} || "Unix");
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no strict 'refs';
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unless (%{"$class\::"}) {
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eval "require $class";
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die $@ if $@;
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}
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$class;
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}
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sub path { shift->path_query(@_) }
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sub host { shift->authority(@_) }
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sub new
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{
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my($class, $path, $os) = @_;
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os_class($os)->new($path);
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}
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sub new_abs
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{
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my $class = shift;
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my $file = $class->new(shift);
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return $file->abs($class->cwd) unless $$file =~ /^file:/;
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$file;
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}
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sub cwd
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{
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my $class = shift;
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require Cwd;
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my $cwd = Cwd::cwd();
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$cwd = VMS::Filespec::unixpath($cwd) if $^O eq 'VMS';
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$cwd = $class->new($cwd);
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$cwd .= "/" unless substr($cwd, -1, 1) eq "/";
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$cwd;
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}
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sub file
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{
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my($self, $os) = @_;
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os_class($os)->file($self);
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}
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sub dir
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{
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my($self, $os) = @_;
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os_class($os)->dir($self);
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}
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1;
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__END__
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=head1 NAME
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URI::file - URI that map to local file names
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=head1 SYNOPSIS
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use URI::file;
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$u1 = URI->new("file:/foo/bar");
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$u2 = URI->new("foo/bar", "file");
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$u3 = URI::file->new($path);
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$u4 = URI::file->new("c:\\windows\\", "win32");
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$u1->file;
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$u1->file("mac");
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=head1 DESCRIPTION
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The C<URI::file> class supports C<URI> objects belonging to the I<file>
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URI scheme. This scheme allows us to map the conventional file names
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found on various computer systems to the URI name space. An old
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specification of the I<file> URI scheme is found in RFC 1738. Some
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older background information is also in RFC 1630. There are no newer
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specifications as far as I know.
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If you want simply to construct I<file> URI objects from URI strings,
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use the normal C<URI> constructor. If you want to construct I<file>
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URI objects from the actual file names used by various systems, then
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use one of the following C<URI::file> constructors:
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=over 4
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=item $u = URI::file->new( $filename, [$os] )
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Maps a file name to the I<file:> URI name space, creates an URI object
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and returns it. The $filename is interpreted as one belonging to the
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indicated operating system ($os), which defaults to the value of the
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$^O variable. The $filename can be either absolute or relative, and
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the corresponding type of URI object for $os is returned.
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=item $u = URI::file->new_abs( $filename, [$os] )
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Same as URI::file->new, but will make sure that the URI returned
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represents an absolute file name. If the $filename argument is
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relative, then the name is resolved relative to the current directory,
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i.e. this constructor is really the same as:
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URI::file->new($filename)->abs(URI::file->cwd);
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=item $u = URI::file->cwd
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Returns a I<file> URI that represents the current working directory.
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See L<Cwd>.
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=back
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The following methods are supported for I<file> URI (in addition to
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the common and generic methods described in L<URI>):
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=over 4
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=item $u->file( [$os] )
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This method return a file name. It maps from the URI name space
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to the file name space of the indicated operating system.
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It might return C<undef> if the name can not be represented in the
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indicated file system.
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=item $u->dir( [$os] )
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Some systems use a different form for names of directories than for plain
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files. Use this method if you know you want to use the name for
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a directory.
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=back
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The C<URI::file> module can be used to map generic file names to names
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suitable for the current system. As such, it can work as a nice
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replacement for the C<File::Spec> module. For instance the following
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code will translate the Unix style file name F<Foo/Bar.pm> to a name
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suitable for the local system.
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$file = URI::file->new("Foo/Bar.pm", "unix")->file;
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die "Can't map filename Foo/Bar.pm for $^O" unless defined $file;
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open(FILE, $file) || die "Can't open '$file': $!";
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# do something with FILE
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=head1 MAPPING NOTES
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Most computer systems today have hierarchically organized file systems.
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Mapping the names used in these systems to the generic URI syntax
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allows us to work with relative file URIs that behave as they should
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when resolved using the generic algorithm for URIs (specified in RFC
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2396). Mapping a file name to the generic URI syntax involves mapping
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the path separator character to "/" and encoding of any reserved
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characters that appear in the path segments of the file names. If
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path segments consisting of the strings "." or ".." have a
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different meaning than what is specified for generic URIs, then these
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must be encoded as well.
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If the file system has device, volume or drive specifications as
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the root of the name space, then it makes sense to map them to the
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authority field of the generic URI syntax. This makes sure that
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relative URI can not be resolved "above" them , i.e. generally how
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relative file names work in those systems.
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Another common use of the authority field is to encode the host that
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this file name is valid on. The host name "localhost" is special and
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generally have the same meaning as an missing or empty authority
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field. This use will be in conflict with using it as a device
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specification, but can often be resolved for device specifications
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having characters not legal in plain host names.
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File name to URI mapping in normally not one-to-one. There are
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usually many URI that map to the same file name. For instance an
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authority of "localhost" maps the same as a URI with a missing or empty
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authority.
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Example 1: The Mac use ":" as path separator, but not in the same way
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as generic URI. ":foo" is a relative name. "foo:bar" is an absolute
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name. Also path segments can contain the "/" character as well as be
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literal "." or "..". It means that we will map like this:
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Mac URI
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---------- -------------------
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:foo:bar <==> foo/bar
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: <==> ./
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::foo:bar <==> ../foo/bar
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::: <==> ../../
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foo:bar <==> file:/foo/bar
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foo:bar: <==> file:/foo/bar/
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.. <==> %2E%2E
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<undef> <== /
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foo/ <== file:/foo%2F
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./foo.txt <== file:/.%2Ffoo.txt
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Note that if you want a relative URL, you *must* begin the path with a :. Any
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path that begins with [^:] will be treated as absolute.
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Example 2: The Unix file system is easy to map as it use the same path
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separator as URIs, have a single root, and segments of "." and ".."
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have the same meaning. URIs that have the character "\0" or "/" as
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part of any path segment can not be turned into valid Unix file names.
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Unix URI
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---------- ------------------
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foo/bar <==> foo/bar
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/foo/bar <==> file:/foo/bar
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/foo/bar <== file://localhost/foo/bar
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file: ==> ./file:
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<undef> <== file:/fo%00/bar
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/ <==> file:/
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=cut
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RFC 1630
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[...]
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There is clearly a danger of confusion that a link made to a local
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file should be followed by someone on a different system, with
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unexpected and possibly harmful results. Therefore, the convention
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is that even a "file" URL is provided with a host part. This allows
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a client on another system to know that it cannot access the file
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system, or perhaps to use some other local mechanism to access the
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file.
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The special value "localhost" is used in the host field to indicate
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that the filename should really be used on whatever host one is.
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This for example allows links to be made to files which are
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distribted on many machines, or to "your unix local password file"
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subject of course to consistency across the users of the data.
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A void host field is equivalent to "localhost".
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=head1 SEE ALSO
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L<URI>, L<File::Spec>, L<perlport>
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=head1 COPYRIGHT
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Copyright 1995-1998 Gisle Aas.
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This library is free software; you can redistribute it and/or
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modify it under the same terms as Perl itself.
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=cut
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