Ubuntu Manpage: URI - Uniform Resource Identifiers (absolute and relative)

NAME

       URI - Uniform Resource Identifiers (absolute and relative)

SYNOPSIS

        use URI ();

        $u1 = URI->new("http://www.example.com");
        $u2 = URI->new("foo", "http");
        $u3 = $u2->abs($u1);
        $u4 = $u3->clone;
        $u5 = URI->new("HTTP://WWW.example.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.example.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 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.

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.

           If  the  scheme isn't one of those that URI recognizes, you still get an URI object back that you can
           access the generic methods on.  The "$uri->has_recognized_scheme" method can  be  used  to  test  for
           this.

           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.

       $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 (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 (percent-
encoded) 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 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.

$uri->has_recognized_scheme
Returns TRUE if the URI scheme is one that URI recognizes.

It will also be TRUE for relative URLs where a recognized scheme was provided to the constructor,
even if "$uri->scheme" returns "undef" for these.

$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 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
$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 ASCII 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->as_iri
Returns a Unicode string representing the URI. Escaped UTF-8 sequences representing non-ASCII
characters are turned into their corresponding Unicode code point.

$uri->canonical
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.

$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 relative, 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.

$uri->secure
Returns a TRUE value if the URI is considered to point to a resource on a secure channel, such as an
SSL or TLS encrypted one.

GENERIC METHODS

       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.  Unrecognized 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 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".

       $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( $key1 => $val1, $key2 => $val2, ..., $delim )
       $uri->query_form( \@key_value_pairs )
       $uri->query_form( \@key_value_pairs, $delim )
       $uri->query_form( \%hash )
       $uri->query_form( \%hash, $delim )
           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 $delim parameter can be passed as ";" to force the key/value pairs to be delimited by ";" instead
           of "&" in the query string.  This practice is often recommended for URLs  embedded  in  HTML  or  XML
           documents  as  this  avoids  the  trouble  of  escaping  the  "&"  character.  You might also set the
           $URI::DEFAULT_QUERY_FORM_DELIMITER variable to ";" for the same global effect.

           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.  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.

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 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.

$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.

For IPv6 addresses the brackets around the raw address is removed in the return value from
$uri->host. When setting the host attribute to an IPv6 address you can use a raw address or one
enclosed in brackets. The address needs to be enclosed in brackets if you want to pass in a new port
value as well.

$uri->ihost
Returns the host in Unicode form. Any IDNA A-labels are turned into U-labels.

$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: ":".

For IPv6 addresses the bracketing is preserved; thus URI->new("http://[::1]/")->host_port returns
"[::1]:80". Contrast this with $uri->host which will remove the brackets.

$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 methods 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
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.

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 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.

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 OpenLDAP
package. There is no real specification for it, but it is mentioned 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 mechanism.

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.

Note that the "foo@example.com" part of a mailto is not the "userinfo" and "host" but instead the
"path". This allows a mailto URI to contain multiple comma separated email addresses.

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. (Update: as of April 2010, they are in RFC 5538
<https://tools.ietf.org/html/rfc5538>.

"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.

nntps:
See news scheme and RFC 5538 <https://tools.ietf.org/html/rfc5538>.

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.

sftp:
"URI" objects belonging to the sftp 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 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:
The "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_group_code
(formerly isbn_country_code, which is still supported by issues a deprecation warning),
$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"

       $URI::DEFAULT_QUERY_FORM_DELIMITER
           This value can be set to ";" to have the query form "key=value" pairs delimited by ";" instead of "&"
           which is the default.

BUGS

       There are some things that are not quite right:

       •   Using  regexp  variables  like $1 directly as arguments to the URI accessor 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");

       •   The  escaping  (percent  encoding)  of chars in the 128 .. 255 range passed to the URI constructor or
           when setting URI parts using the accessor methods depend on the state of the internal UTF8 flag  (see
           utf8::is_utf8)  of  the  string  passed.   If  the  UTF8 flag is set the UTF-8 encoded version of the
           character is percent encoded.  If the UTF8 flag isn't set the Latin-1 version (byte) of the character
           is percent encoded.  This basically exposes the internal encoding of Perl strings.

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.

COPYRIGHT

       Copyright 1995-2009 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.

perl v5.32.1                                       2021-10-26                                           URI(3pm)