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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 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.

	   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->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.
       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 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.

	   "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 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:

       o   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");

       o   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.

SEE ALSO
       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
       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 v5.16.3				    2012-03-25					   URI(3)
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