URI(3) User Contributed Perl Documentation URI(3)
NAME
URI - Uniform Resource Identifiers (absolute and relative)
SYNOPSIS
$u1 = URI->new("http://www.perl.com");
$u2 = URI->new("foo", "http");
$u3 = $u2->abs($u1);
$u4 = $u3->clone;
$u5 = URI->new("HTTP://WWW.perl.com:80")->canonical;
$str = $u->as_string;
$str = "$u";
$scheme = $u->scheme;
$opaque = $u->opaque;
$path = $u->path;
$frag = $u->fragment;
$u->scheme("ftp");
$u->host("ftp.perl.com");
$u->path("cpan/");
DESCRIPTION
This module implements the URI class. Objects of this
class represent "Uniform Resource Identifier references"
as specified in RFC 2396 (and updated by RFC 2732).
A Uniform Resource Identifier is a compact string of
characters for identifying an abstract or physical
resource. A Uniform Resource Identifier can be further
classified either a Uniform Resource Locator (URL) or a
Uniform Resource Name (URN). The distinction between URL
and URN does not matter to the URI class interface. A
"URI-reference" is a URI that may have additional
information attached in the form of a fragment identifier.
An absolute URI reference consists of three parts. A
scheme, a scheme specific part and a fragment identifier.
A subset of URI references share a common syntax for
hierarchical namespaces. For these the scheme specific
part is further broken down into authority, path and query
components. These URI can also take the form of relative
URI references, where the scheme (and usually also the
authority) component is missing, but implied by the
context of the URI reference. The three forms of URI
reference syntax are summarized as follows:
<scheme>:<scheme-specific-part>#<fragment>
<scheme>://<authority><path>?<query>#<fragment>
<path>?<query>#<fragment>
The components that a URI reference can be divided into
depend on the scheme. The URI class provides methods to
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get and set the individual components. The methods
available for a specific URI object depend on the scheme.
CONSTRUCTORS
The following methods construct new URI objects:
$uri = URI->new( $str, [$scheme] )
This class method constructs a new URI object. The
string representation of a URI is given as argument
together with an optional scheme specification.
Common URI wrappers like "" and <>, as well as leading
and trailing white space, are automatically removed
from the $str argument before it is processed further.
The constructor determines the scheme, maps this to an
appropriate URI subclass, constructs a new object of
that class and returns it.
The $scheme argument is only used when $str is a
relative URI. It can either be a simple string that
denotes the scheme, a string containing an absolute
URI reference or an absolute URI object. If no
$scheme is specified for a relative URI $str, then
$str is simply treated as a generic URI (no scheme
specific methods available).
The set of characters available for building URI
references is restricted (see the URI::Escape
manpage). Characters outside this set are
automatically escaped by the URI constructor.
$uri = URI->new_abs( $str, $base_uri )
This constructs a new absolute URI object. The $str
argument can denote a relative or absolute URI. If
relative, then it will be absolutized using $base_uri
as base. The $base_uri must be an absolute URI.
$uri = URI::file->new( $filename, [$os] )
This constructs a new file URI from a file name. See
the URI::file manpage.
$uri = URI::file->new_abs( $filename, [$os] )
This constructs a new absolute file URI from a file
name. See the URI::file manpage.
$uri = URI::file->cwd
This returns the current working directory as a file
URI. See the URI::file manpage.
$uri->clone
This method returns a copy of the $uri.
COMMON METHODS
The methods described in this section are available for
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all URI objects.
Methods that give access to components of a URI will
always return the old value of the component. The value
returned will be undef if the component was not present.
There is generally a difference between a component that
is empty (represented as "") and a component that is
missing (represented as undef). If an accessor method is
given an argument it will update the corresponding
component in addition to returning the old value of the
component. Passing an undefined argument will remove the
component (if possible). The description of the various
accessor methods will tell if the component is passed as
an escaped or an unescaped string. Components that can be
futher divided into sub-parts are usually passed escaped,
as unescaping might change its semantics.
The common methods available for all URI are:
$uri->scheme( [$new_scheme] )
This method sets and returns the scheme part of the
$uri. If the $uri is relative, then $uri->scheme
returns undef. If called with an argument, it will
update the scheme of $uri, possibly changing the class
of $uri, and return the old scheme value. The method
croaks if the new scheme name is illegal; scheme names
must begin with a letter and must consist of only
US-ASCII letters, numbers, and a few special marks:
".", "+", "-". This restriction effectively means
that scheme have to be passed unescaped. Passing an
undefined argument to the scheme method will make the
URI relative (if possible).
Letter case does not matter for scheme names. The
string returned by $uri->scheme is always lowercase.
If you want the scheme just as it was written in the
URI in its original case, you can use the
$uri->_scheme method instead.
$uri->opaque( [$new_opaque] )
This method sets and returns the scheme specific part
of the $uri (everything between the scheme and the
fragment) as an escaped string.
$uri->path( [$new_path] )
This method sets and returns the same value as
$uri->opaque unless the URI supports the generic
syntax for hierarchical namespaces. In that case the
generic method is overridden to set and return the
part of the URI between the host name and the
fragment.
$uri->fragment( [$new_frag] )
This method returns the fragment identifier of a URI
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reference as an escaped string.
$uri->as_string
This method returns a URI object to a plain string.
URI objects are also converted to plain strings
automatically by overloading. This means that $uri
objects can be used as plain strings in most Perl
constructs.
$uri->canonical
This method will return a normalized version of the
URI. The rules for normalization are scheme
dependent. It usually involves lowercasing of the
scheme and the Internet host name components, removing
the explicit port specification if it matches the
default port, uppercasing all escape sequences, and
unescaping octets that can be better represented as
plain characters.
For efficiency reasons, if the $uri already was in
normalized form, then a reference to it is returned
instead of a copy.
$uri->eq( $other_uri )
URI::eq( $first_uri, $other_uri )
This method tests whether two URI references are
equal. URI references that normalize to the same
string are considered equal. The method can also be
used as a plain function which can also test two
string arguments.
If you need to test whether two URI object references
denote the same object, use the '==' operator.
$uri->abs( $base_uri )
This method returns an absolute URI reference. If
$uri already is absolute, then a reference to it is
simply returned. If the $uri is relative, then a new
absolute URI is constructed by combining the $uri and
the $base_uri, and returned.
$uri->rel( $base_uri )
This method returns a relative URI reference if it is
possible to make one that denotes the same resource
relative to $base_uri. If not, then $uri is simply
returned.
GENERIC METHODS
The following methods are available to schemes that use
the common/generic syntax for hierarchical namespaces.
The description of schemes below will tell which one these
are. Unknown schemes are assumed to support the generic
syntax, and therefore the following methods:
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$uri->authority( [$new_authority] )
This method sets and returns the escaped authority
component of the $uri.
$uri->path( [$new_path] )
This method sets and returns the escaped path
component of the $uri (the part between the host name
and the query or fragment). The path will never be
undefined, but it can be the empty string.
$uri->path_query( [$new_path_query] )
This method sets and returns the escaped path and
query components as a single entity. The path and the
query are separated by a "?" character, but the query
can itself contain "?".
$uri->path_segments( [$segment,...] )
This method sets and returns the path. In scalar
context it returns the same value as $uri->path. In
list context it will return the unescaped path
segments that make up the path. Path segments that
have parameters are returned as an anonymous array.
The first element is the unescaped path segment
proper. Subsequent elements are escaped parameter
strings. Such an anonymous array uses overloading so
it can be treated as a string too, but this string
does not include the parameters.
$uri->query( [$new_query] )
This method sets and returns the escaped query
component of the $uri.
$uri->query_form( [$key => $value,...] )
This method sets and returns query components that use
the application/x-www-form-urlencoded format.
Key/value pairs are separated by "&" and the key is
separated from the value with a "=" character.
$uri->query_keywords( [$keywords,...] )
This method sets and returns query components that use
the keywords separated by "+" format.
SERVER METHODS
Schemes where the authority component denotes a Internet
host will have the following methods available in addition
to the generic methods.
$uri->userinfo( [$new_userinfo] )
This method sets and returns the escaped userinfo part
of the authority componenent.
For some schemes this will be a user name and a
password separated by a colon. This practice is not
recommended. Embedding passwords in clear text (such
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as URI) has proven to be a security risk in almost
every case where it has been used.
$uri->host( [$new_host] )
This method sets and returns the unescaped hostname.
If the $new_host string ends with a colon and a
number, then this number will also set the port.
$uri->port( [ $new_port] )
This method sets and returns the port. The port is
simple integer that should be greater than 0.
If no explicit port is specified in the URI, then the
default port of the URI scheme is returned. If you
don't want the default port substituted, then you can
use the $uri->_port method instead.
$uri->host_port( [ $new_host_port ] )
This method sets and returns the host and port as a
single unit. The returned value will include a port,
even if it matches the default port. The host part
and the port part is separated with a colon; ":".
$uri->default_port
This method returns the default port of the URI scheme
that $uri belongs to. For http this will be the
number 80, for ftp this will be the number 21, etc.
The default port for a scheme can not be changed.
SCHEME SPECIFIC SUPPORT
The following URI schemes are specifically supported. For
URI objects not belonging to one of these you can only use
the common and generic methods.
data:
The data URI scheme is specified in RFC 2397. It
allows inclusion of small data items as "immediate"
data, as if it had been included externally.
URI objects belonging to the data scheme support the
common methods and two new methods to access their
scheme specific components; $uri->media_type and
$uri->data. See the URI::data manpage for details.
file:
An old specification of the file URI scheme is found
in RFC 1738. A new RFC 2396 based specification in
not available yet, but file URI references are in
common use.
URI objects belonging to the file scheme support the
common and generic methods. In addition they provide
two methods to map file URI back to local file names;
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$uri->file and $uri->dir. See the URI::file manpage
for details.
ftp:
An old specification of the ftp URI scheme is found in
RFC 1738. A new RFC 2396 based specification in not
available yet, but ftp URI references are in common
use.
URI objects belonging to the ftp scheme support the
common, generic and server methods. In addition they
provide two methods to access the userinfo sub-
components: $uri->user and $uri->password.
gopher:
The gopher URI scheme is specified in <draft-murali-
url-gopher-1996-12-04> and will hopefully be available
as a RFC 2396 based specification.
URI objects belonging to the gopher scheme support the
common, generic and server methods. In addition they
support some methods to access gopher specific path
components: $uri->gopher_type, $uri->selector,
$uri->search, $uri->string.
http:
The http URI scheme is specified in RFC 2616. The
scheme is used to reference resources hosted by HTTP
servers.
URI objects belonging to the http scheme support the
common, generic and server methods.
https:
The https URI scheme is a Netscape invention which is
commonly implemented. The scheme is used to reference
HTTP servers through SSL connections. It's syntax is
the same as http, but the default port is different.
ldap:
The ldap URI scheme is specified in RFC 2255. LDAP is
the Lightweight Directory Access Protocol. An ldap
URI describes an LDAP search operation to perform to
retrieve information from an LDAP directory.
URI objects belonging to the ldap scheme support the
common, generic and server methods as well as specific
ldap methods; $uri->dn, $uri->attributes, $uri->scope,
$uri->filter, $uri->extensions. See the URI::ldap
manpage for details.
mailto:
The mailto URI scheme is specified in RFC 2368. The
scheme was originally used to designate the Internet
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mailing address of an individual or service. It has
(in RFC 2368) been extended to allow setting of other
mail header fields and the message body.
URI objects belonging to the mailto scheme support the
common methods and the generic query methods. In
addition they support the following mailto specific
methods: $uri->to, $uri->headers.
news:
The news, nntp and snews URI schemes are specified in
<draft-gilman-news-url-01> and will hopefully be
available as a RFC 2396 based specification soon.
URI objects belonging to the news scheme support the
common, generic and server methods. In addition they
provide some methods to access the path: $uri->group
and $uri->message.
nntp:
See news scheme.
pop:
The pop URI scheme is specified in RFC 2384. The
scheme is used to reference a POP3 mailbox.
URI objects belonging to the pop scheme support the
common, generic and server methods. In addition they
provide two methods to access the userinfo components:
$uri->user and $uri->auth
rlogin:
An old speficication of the rlogin URI scheme is found
in RFC 1738. URI objects belonging to the rlogin
scheme support the common, generic and server methods.
rsync:
Information about rsync is available from
http://rsync.samba.org. URI objects belonging to the
rsync scheme support the common, generic and server
methods. In addition they provide methods to access
the userinfo sub-components: $uri->user and
$uri->password.
snews:
See news scheme. It's syntax is the same as news, but
the default port is different.
telnet:
An old speficication of the telnet URI scheme is found
in RFC 1738. URI objects belonging to the telnet
scheme support the common, generic and server methods.
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ssh:
Information about ssh is available at
http://www.openssh.com/. URI objects belonging to the
ssh scheme support the common, generic and server
methods. In addition they provide methods to access
the userinfo sub-components: $uri->user and
$uri->password.
CONFIGURATION VARIABLES
The following configuration variables influence how the
class and it's methods behave:
$URI::ABS_ALLOW_RELATIVE_SCHEME
Some older parsers used to allow the scheme name to be
present in the relative URL if it was the same as the
base URL scheme. RFC 2396 says that this should be
avoided, but you can enable this old behaviour by
setting the $URI::ABS_ALLOW_RELATIVE_SCHEME variable
to a TRUE value. The difference is demonstrated by
the following examples:
URI->new("http:foo")->abs("http://host/a/b")
==> "http:foo"
local $URI::ABS_ALLOW_RELATIVE_SCHEME = 1;
URI->new("http:foo")->abs("http://host/a/b")
==> "http:/host/a/foo"
$URI::ABS_REMOTE_LEADING_DOTS
You can also have the abs() method ignore excess ".."
segments in the relative URI by setting
$URI::ABS_REMOTE_LEADING_DOTS to a TRUE value. The
difference is demonstrated by the following examples:
URI->new("../../../foo")->abs("http://host/a/b")
==> "http://host/../../foo"
local $URI::URL::ABS_REMOTE_LEADING_DOTS = 1;
URI->new("../../../foo")->abs("http://host/a/b")
==> "http://host/foo"
BUGS
Using regexp variables like $1 directly as argument to the
URI methods do not work too well with current perl
implementations. I would argue that this is actually a
bug in perl. The workaround is to quote them. E.g.:
/(...)/ || die;
$u->query("$1");
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PARSING URIs WITH REGEXP
As an alternative to this module, the following (official)
regular expression can be used to decode a URI:
my($scheme, $authority, $path, $query, $fragment) =
$uri =~ m|^(?:([^:/?#]+):)?(?://([^/?#]*))?([^?#]*)(?:\?([^#]*))?(?:#(.*))?|;
SEE ALSO
the URI::file manpage, the URI::WithBase manpage, the
URI::Escape manpage, the URI::Heuristic manpage
RFC 2396: "Uniform Resource Identifiers (URI): Generic
Syntax", Berners-Lee, Fielding, Masinter, August 1998.
COPYRIGHT
Copyright 1995-2001 Gisle Aas.
Copyright 1995 Martijn Koster.
This program is free software; you can redistribute it
and/or modify it under the same terms as Perl itself.
AUTHORS / ACKNOWLEDGMENTS
This module is based on the URI::URL module, which in turn
was (distantly) based on the wwwurl.pl code in the libwww-
perl for perl4 developed by Roy Fielding, as part of the
Arcadia project at the University of California, Irvine,
with contributions from Brooks Cutter.
URI::URL was developed by Gisle Aas, Tim Bunce, Roy
Fielding and Martijn Koster with input from other people
on the libwww-perl mailing list.
URI and related subclasses was developed by Gisle Aas.
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