URI - Uniform Resource Identifiers (absolute and relative)
$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/");
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 that
identifies an abstract or physical resource. A Uniform Resource
Identifier can be further classified as 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 URIs 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 into which a URI reference can be divided depend on the
scheme. The URI class provides methods to get and set the
individual components. The methods available for a specific
URI object depend on the scheme.
The following methods construct new URI objects:
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 be either 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 URI::Escape). Characters outside this set are automatically escaped by the URI constructor.
The methods described in this section are available for all URI
objects.
Methods that give access to components of a URI always return the
old value of the component. The value returned is 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 updates the corresponding component in addition to
returning the old value of the component. Passing an undefined
argument removes the component (if possible). The description of
each accessor method indicates whether the component is passed as
an escaped or an unescaped string. A component that can be further
divided into sub-parts are usually passed escaped, as unescaping might
change its semantics.
The common methods available for all URI are:
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 updates the scheme of $uri, possibly changing the
class of $uri, and returns the old scheme value. The method croaks
if the new scheme name is illegal; a scheme name must begin with a
letter and must consist of only US-ASCII letters, numbers, and a few
special marks: ".", "+", "-". This restriction effectively means
that the scheme must be passed unescaped. Passing an undefined
argument to the scheme method makes 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.
Returns a normalized version of the URI. The rules for normalization are scheme-dependent. They usually involve lowercasing the scheme and 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 is already in normalized form, then a reference to it is returned instead of a copy.
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.
The following methods are available to schemes that use the common/generic syntax for hierarchical namespaces. The descriptions of schemes below indicate which these are. Unknown schemes are assumed to support the generic syntax, and therefore the following methods:
Sets and returns the path. In a scalar context, it returns the same value as $uri->path. In a list context, it returns 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.
Note that absolute paths have the empty string as their first
path_segment, i.e. the path /foo/bar have 3
path_segments; "", "foo" and "bar".
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 by a "=" character.
The form can be set either by passing separate key/value pairs, or via an array or hash reference. Passing an empty array or an empty hash removes the query component, whereas passing no arguments at all leaves the component unchanged. The order of keys is undefined if a hash reference is passed. The old value is always returned as a list of separate key/value pairs. Assigning this list to a hash is unwise as the keys returned might repeat.
The values passed when setting the form can be plain strings or references to arrays of strings. Passing an array of values has the same effect as passing the key repeatedly with one value at a time. All the following statements have the same effect:
$uri->query_form(foo => 1, foo => 2);
$uri->query_form(foo => [1, 2]);
$uri->query_form([ foo => 1, foo => 2 ]);
$uri->query_form([ foo => [1, 2] ]);
$uri->query_form({ foo => [1, 2] });
The URI::QueryParam module can be loaded to add further methods to
manipulate the form of a URI. See URI::QueryParam for details.
Sets and returns query components that use the keywords separated by "+" format.
The keywords can be set either by passing separate keywords directly or by passing a reference to an array of keywords. Passing an empty array removes the query component, whereas passing no arguments at all leaves the component unchanged. The old value is always returned as a list of separate words.
For schemes where the authority component denotes an Internet host, the following methods are available in addition to the generic methods.
Sets and returns the escaped userinfo part of the authority component.
For some schemes this is a user name and a password separated by a colon. This practice is not recommended. Embedding passwords in clear text (such as URI) has proven to be a security risk in almost every case where it has been used.
Sets and returns the unescaped hostname.
If the $new_host string ends with a colon and a number, then this number also sets the port.
Sets and returns the port. The port is a simple integer that should be greater than 0.
If a port is not specified explicitly in the URI, then the URI scheme's default port is returned. If you don't want the default port substituted, then you can use the $uri->_port method instead.
Scheme-specific support is provided for the following URI schemes. For URI
objects that do not belong to one of these, you can only use the common and
generic methods.
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 URI::data for details.
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 for mapping file URIs
back to local file names; $uri->file and $uri->dir. See URI::file
for details.
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 for
accessing the userinfo sub-components: $uri->user and $uri->password.
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 for
accessing gopher-specific path components: $uri->gopher_type,
$uri->selector, $uri->search, $uri->string.
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.
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 ldap-specific methods: $uri->dn,
$uri->attributes, $uri->scope, $uri->filter, $uri->extensions. See
URI::ldap for details.
The mailto URI scheme is specified in RFC 2368. The scheme was originally used to designate the Internet 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.
URI objects belonging to the mms scheme support the common,
generic, and server methods, with the exception of userinfo and
query-related sub-components.
The news, nntp and snews URI schemes are specified in <draft-gilman-news-url-01> and will hopefully be available as an 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.
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
URI objects belonging to the rlogin scheme support the
common, generic and server methods.
URI objects belonging to the rtsp scheme support the common,
generic, and server methods, with the exception of userinfo and
query-related sub-components.
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.
URI objects belonging to the sip scheme support the
common, generic, and server methods with the exception of path related
sub-components. In addition, they provide two methods to get and set
sip parameters: $uri->params_form and $uri->params.
URI objects belonging to the telnet scheme support the
common, generic and server methods.
URI objects belonging to the tn3270 scheme support the
common, generic and server methods.
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.
The syntax of Uniform Resource Names is specified in RFC 2141. URI
objects belonging to the urn scheme provide the common methods, and also the
methods $uri->nid and $uri->nss, which return the Namespace Identifier
and the Namespace-Specific String respectively.
The Namespace Identifier basically works like the Scheme identifier of URIs, and further divides the URN namespace. Namespace Identifier assignments are maintained at <http://www.iana.org/assignments/urn-namespaces>.
Letter case is not significant for the Namespace Identifier. It is always returned in lower case by the $uri->nid method. The $uri->_nid method can be used if you want it in its original case.
urn:isbn: namespace contains International Standard Book
Numbers (ISBNs) and is described in RFC 3187. A URI object belonging
to this namespace has the following extra methods (if the
Business::ISBN module is available): $uri->isbn,
$uri->isbn_publisher_code, $uri->isbn_country_code, $uri->isbn_as_ean.
urn:oid: namespace contains Object Identifiers (OIDs) and is
described in RFC 3061. An object identifier consists of sequences of digits
separated by dots. A URI object belonging to this namespace has an
additional method called $uri->oid that can be used to get/set the oid
value. In a list context, oid numbers are returned as separate elements.
The following configuration variables influence how the class and its methods behave:
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"
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::ABS_REMOTE_LEADING_DOTS = 1;
URI->new("../../../foo")->abs("http://host/a/b")
==> "http://host/foo"
Using regexp variables like $1 directly as arguments to the URI methods does 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. Example:
/(...)/ || die;
$u->query("$1");
As an alternative to this module, the following (official) regular expression can be used to decode a URI:
my($scheme, $authority, $path, $query, $fragment) = $uri =~ m|(?:([^:/?#]+):)?(?://([^/?#]*))?([^?#]*)(?:\?([^#]*))?(?:#(.*))?|;
The URI::Split module provides the function uri_split() as a
readable alternative.
URI::file, URI::WithBase, URI::QueryParam, URI::Escape, URI::Split, URI::Heuristic
RFC 2396: "Uniform Resource Identifiers (URI): Generic Syntax", Berners-Lee, Fielding, Masinter, August 1998.
http://www.iana.org/assignments/uri-schemes
http://www.iana.org/assignments/urn-namespaces
http://www.w3.org/Addressing/
Copyright 1995-2003 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.
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.