Heuristic(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 repre-
sent "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 Iden-
tifier 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.
CONSTRUCTORS
The following methods construct new "URI" objects:
$uri = URI->new( $str )
$uri = URI->new( $str, $scheme )
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 avail-
able).
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.
$uri = URI->new_abs( $str, $base_uri )
Constructs a new absolute URI object. The $str argument can denote
a relative or absolute URI. If relative, then it is absolutized
using $base_uri as base. The $base_uri must be an absolute URI.
$uri = URI::file->new( $filename )
$uri = URI::file->new( $filename, $os )
Constructs a new file URI from a file name. See URI::file.
$uri = URI::file->new_abs( $filename )
$uri = URI::file->new_abs( $filename, $os )
Constructs a new absolute file URI from a file name. See
URI::file.
$uri = URI::file->cwd
Returns the current working directory as a file URI. See
URI::file.
$uri->clone
Returns a copy of the $uri.
COMMON METHODS
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 (rep-
resented 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 com-
ponent (if possible). The description of each accessor method indi-
cates 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:
$uri->scheme
$uri->scheme( $new_scheme )
Sets and returns the scheme part of the $uri. If the $uri is rela-
tive, then $uri->scheme returns "undef". If called with an argu-
ment, 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 spe-
cial 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.
$uri->opaque
$uri->opaque( $new_opaque )
Sets and returns the scheme-specific part of the $uri (everything
between the scheme and the fragment) as an escaped string.
$uri->path
$uri->path( $new_path )
Sets and returns the same value as $uri->opaque unless the URI sup-
ports 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
$uri->fragment( $new_frag )
Returns the fragment identifier of a URI reference as an escaped
string.
$uri->as_string
Returns a URI object to a plain string. URI objects are also con-
verted to plain strings automatically by overloading. This means
that $uri objects can be used as plain strings in most Perl con-
structs.
$uri->canonical
Returns a normalized version of the URI. The rules for normaliza-
tion 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 repre-
sented 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.
$uri->eq( $other_uri )
URI::eq( $first_uri, $other_uri )
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 )
Returns an absolute URI reference. If $uri is already absolute,
then a reference to it is simply returned. If the $uri is rela-
tive, then a new absolute URI is constructed by combining the $uri
and the $base_uri, and returned.
$uri->rel( $base_uri )
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 com-
mon/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:
$uri->authority
$uri->authority( $new_authority )
Sets and returns the escaped authority component of the $uri.
$uri->path
$uri->path( $new_path )
Sets and returns the escaped path component of the $uri (the part
between the host name and the query or fragment). The path can
never be undefined, but it can be the empty string.
$uri->path_query
$uri->path_query( $new_path_query )
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
$uri->path_segments( $segment, ... )
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 ele-
ment is the unescaped path segment proper; subsequent elements are
escaped parameter strings. Such an anonymous array uses overload-
ing 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".
$uri->query
$uri->query( $new_query )
Sets and returns the escaped query component of the $uri.
$uri->query_form
$uri->query_form( $key1 => $val1, $key2 => $val2, ... )
$uri->query_form( \@key_value_pairs )
$uri->query_form( \%hash )
Sets and returns query components that use the applica-
tion/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.
$uri->query_keywords
$uri->query_keywords( $keywords, ... )
$uri->query_keywords( \@keywords )
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. Pass-
ing 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.
SERVER METHODS
For schemes where the authority component denotes an Internet host, the
following methods are available in addition to the generic methods.
$uri->userinfo
$uri->userinfo( $new_userinfo )
Sets and returns the escaped userinfo part of the authority compo-
nent.
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.
$uri->host
$uri->host( $new_host )
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.
$uri->port
$uri->port( $new_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.
$uri->host_port
$uri->host_port( $new_host_port )
Sets and returns the host and port as a single unit. The returned
value includes a port, even if it matches the default port. The
host part and the port part are separated by a colon: ":".
$uri->default_port
Returns the default port of the URI scheme to which $uri belongs.
For http this is the number 80, for ftp this is the number 21, etc.
The default port for a scheme can not be changed.
SCHEME-SPECIFIC SUPPORT
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.
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 meth-
ods and two new methods to access their scheme-specific components:
$uri->media_type and $uri->data. See URI::data 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 for mapping
file URIs back to local file names; $uri->file and $uri->dir. See
URI::file 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
for accessing 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 avail-
able 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.
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. Its 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 Light-
weight 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->exten-
sions. See URI::ldap for details.
ldapi:
Like the ldap URI scheme, but uses a UNIX domain socket. The
server methods are not supported, and the local socket path is
available as $uri->un_path. The ldapi scheme is used by the OpenL-
DAP package. There is no real specification for it, but it is men-
tioned in various OpenLDAP manual pages.
ldaps:
Like the ldap URI scheme, but uses an SSL connection. This scheme
is deprecated, as the preferred way is to use the start_tls mecha-
nism.
mailto:
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.
mms:
The mms URL specification can be found at <http://sdp.ppona.com/>
"URI" objects belonging to the mms scheme support the common,
generic, and server methods, with the exception of userinfo and
query-related sub-components.
news:
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.
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 specification of the rlogin URI scheme is found in RFC 1738.
"URI" objects belonging to the rlogin scheme support the common,
generic and server methods.
rtsp:
The rtsp URL specification can be found in section 3.2 of RFC 2326.
"URI" objects belonging to the rtsp scheme support the common,
generic, and server methods, with the exception of userinfo and
query-related sub-components.
rtspu:
The rtspu URI scheme is used to talk to RTSP servers over UDP
instead of TCP. The syntax is the same as rtsp.
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.
sip:
The sip URI specification is described in sections 19.1 and 25 of
RFC 3261. "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.
sips:
See sip scheme. Its syntax is the same as sip, but the default
port is different.
snews:
See news scheme. Its syntax is the same as news, but the default
port is different.
telnet:
An old specification of the telnet URI scheme is found in RFC 1738.
"URI" objects belonging to the telnet scheme support the common,
generic and server methods.
tn3270:
These URIs are used like telnet URIs but for connections to IBM
mainframes. "URI" objects belonging to the tn3270 scheme support
the common, generic and server methods.
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.
urn:
The syntax of Uniform Resource Names is specified in RFC 2141.
"URI" objects belonging to the urn scheme provide the common meth-
ods, and also the methods $uri->nid and $uri->nss, which return the
Namespace Identifier and the Namespace-Specific String respec-
tively.
The Namespace Identifier basically works like the Scheme identifier
of URIs, and further divides the URN namespace. Namespace Identi-
fier assignments are maintained at <http://www.iana.org/assign-
ments/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:
The "urn:isbn:" namespace contains International Standard Book Num-
bers (ISBNs) and is described in RFC 3187. A "URI" object belong-
ing to this namespace has the following extra methods (if the Busi-
ness::ISBN module is available): $uri->isbn, $uri->isbn_pub-
lisher_code, $uri->isbn_country_code, $uri->isbn_as_ean.
urn:oid:
The "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.
CONFIGURATION VARIABLES
The following configuration variables influence how the class and its
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::ABS_REMOTE_LEADING_DOTS = 1;
URI->new("../../../foo")->abs("http://host/a/b")
==> "http://host/foo"
BUGS
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("$1");
PARSING URIs WITH REGEXP
As an alternative to this module, the following (official) regular
expression can be used to decode a URI:
my($scheme, $authority, $path, $query, $fragment) =
$uri =~ m|(?:([^:/?#]+):)?(?://([^/?#]*))?([^?#]*)(?:\?([^#]*))?(?:#(.*))?|;
The "URI::Split" module provides the function uri_split() as a readable
alternative.
SEE ALSO
URI::file, URI::WithBase, URI::QueryParam, URI::Escape, URI::Split,
URI::Heuristic
RFC 2396: "Uniform Resource Identifiers (URI): Generic Syntax", Bern-
ers-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
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.
AUTHORS / ACKNOWLEDGMENTS
This module is based on the "URI::URL" module, which in turn was (dis-
tantly) based on the "wwwurl.pl" code in the libwww-perl for perl4
developed by Roy Fielding, as part of the Arcadia project at the Uni-
versity of California, Irvine, with contributions from Brooks Cutter.
"URI::URL" was developed by Gisle Aas, Tim Bunce, Roy Fielding and Mar-
tijn Koster with input from other people on the libwww-perl mailing
list.
"URI" and related subclasses was developed by Gisle Aas.
perl v5.8.8 2004-01-14 URI(3)
See also Apache::URI(3)
See also URI::Escape(3)
See also URI::Heuristic(3)
See also URI::QueryParam(3)
See also URI::Split(3)
See also URI::URL(3)
See also URI::WithBase(3)
See also URI::data(3)
See also URI::file(3)
See also URI::ldap(3)
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