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URI(3) - URI - Uniform Resource Identifiers (absolute and relative) - man 3 URI

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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(1,5)("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(1,8) RFC 2396
       (and updated by RFC 2732).

       A Uniform Resource Identifier is a compact string(3,n) 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(1,8) 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(7,n,1 builtins) 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(3,n) 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(3,n) that denotes the scheme, a string(3,n)
           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(7,n,1 builtins) of characters available for building URI references is
           restricted (see URI::Escape).  Characters outside this set(7,n,1 builtins) 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(1,n) URI from a file(1,n) name.  See URI::file.

       $uri = URI::file->new_abs( $filename )
       $uri = URI::file->new_abs( $filename, $os )
           Constructs a new absolute file(1,n) URI from a file(1,n) name.  See
           URI::file.

       $uri = URI::file->cwd
           Returns the current working directory as a file(1,n) URI.  See
           URI::file.

       $uri->clone
           Returns a copy of the $uri.

COMMON METHODS
       The methods described in(1,8) this section are available for all "URI"
       objects.

       Methods that give access(2,5) to components of a URI always return the old
       value of the component.  The value returned is "undef" if(3,n) 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(1,8) addition to returning the old
       value of the component.  Passing an undefined argument removes the com-
       ponent (if(3,n) 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(3,n) 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(3,n) possible).

           Letter case does not matter for scheme names.  The string(3,n) returned
           by $uri->scheme is always lowercase.  If you want the scheme just
           as it was written in(1,8) the URI in(1,8) 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(7,n,1 builtins) and return the part of the
           URI between the host(1,5) 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(1,8) most Perl con-
           structs.

       $uri->canonical
           Returns a normalized version(1,3,5) of the URI.  The rules for normaliza-
           tion are scheme-dependent.  They usually involve lowercasing the
           scheme and Internet host(1,5) name components, removing the explicit
           port specification if(3,n) 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(3,n) the $uri is already in(1,8) 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(3,n) are considered equal.  The method can
           also be used as a plain function which can also test two string(3,n)
           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(3,n) 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(1,5) 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(3,n) too, but this string(3,n) does not
           include the parameters.

       $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(7,n,1 builtins) 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(3,n) 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(7,n,1 builtins) 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(1,5), the
       following methods are available in(1,8) 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(1,8)
           clear(1,3x,3x clrtobot) text (such as URI) has proven to be a security risk in(1,8) almost
           every case where it has been used.

       $uri->host(1,5)
       $uri->host(1,5)( $new_host )
           Sets and returns the unescaped hostname.

           If the $new_host string(3,n) 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(1,8) 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(1,5) and port as a single unit.  The returned
           value includes a port, even if(3,n) it matches the default port.  The
           host(1,5) 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(1,8) RFC 2397.  It allows inclusion
           of small data items as "immediate" data, as if(3,n) it had been included
           externally.

           "URI" objects belonging to the data scheme support the common meth-
           ods and two new methods to access(2,5) their scheme-specific components:
           $uri->media_type and $uri->data.  See URI::data for details.

       file(1,n):
           An old specification of the file(1,n) URI scheme is found in(1,8) RFC 1738.
           A new RFC 2396 based specification in(1,8) not available yet, but file(1,n)
           URI references are in(1,8) common use.

           "URI" objects belonging to the file(1,n) scheme support the common and
           generic methods.  In addition, they provide two methods for mapping
           file(1,n) URIs back to local file(1,n) names; $uri->file(1,n) and $uri->dir.  See
           URI::file for details.

       ftp:
           An old specification of the ftp URI scheme is found in(1,8) RFC 1738.  A
           new RFC 2396 based specification in(1,8) not available yet, but ftp URI
           references are in(1,8) 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(1,8)
           <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(1,8) 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(3,5,n):
           The ldap(3,5,n) URI scheme is specified in(1,8) RFC 2255.  LDAP is the Light-
           weight Directory Access Protocol.  An ldap(3,5,n) URI describes an LDAP
           search operation to perform to retrieve information from an LDAP
           directory.

           "URI" objects belonging to the ldap(3,5,n) scheme support the common,
           generic and server methods as well as ldap-specific methods:
           $uri->dn, $uri->attributes, $uri->scope, $uri->filter(1,3x,3x curs_util), $uri->exten-
           sions.  See URI::ldap for details.

       ldapi:
           Like the ldap(3,5,n) URI scheme, but uses a UNIX domain socket.  The
           server methods are not supported, and the local socket(2,7,n) 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(1,8) various OpenLDAP manual pages.

       ldaps:
           Like the ldap(3,5,n) 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(1,8) RFC 2368.  The scheme was
           originally used to designate the Internet mailing address of an
           individual or service.  It has (in(1,8) RFC 2368) been extended to allow
           setting of other mail(1,8) 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(1,8)
           <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(2,5) the path: $uri->group and $uri->message.

       nntp:
           See news scheme.

       pop:
           The pop URI scheme is specified in(1,8) 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(2,5) the userinfo components: $uri->user and $uri->auth

       rlogin:
           An old specification of the rlogin URI scheme is found in(1,8) 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(1,8) 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(2,5) the userinfo sub-components: $uri->user and $uri->password.

       sip:
           The sip URI specification is described in(1,8) 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(7,n,1 builtins) 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(1,8) 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(2,5) the userinfo sub-components: $uri->user and $uri->password.

       urn:
           The syntax of Uniform Resource Names is specified in(1,8) 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(1,8) lower case by the $uri->nid method.  The
           $uri->_nid method can be used if(3,n) you want it in(1,8) its original case.

       urn:isbn:
           The "urn:isbn:" namespace contains International Standard Book Num-
           bers (ISBNs) and is described in(1,8) RFC 3187.  A "URI" object belong-
           ing to this namespace has the following extra methods (if(3,n) 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(1,8) 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(7,n,1 builtins) 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(1,8)
           the relative URL if(3,n) 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(1,5)/a/b")
                 ==>  "http:foo"

             local $URI::ABS_ALLOW_RELATIVE_SCHEME = 1;
             URI->new("http:foo")->abs("http://host(1,5)/a/b")
                 ==>  "http:/host(1,5)/a/foo"

       $URI::ABS_REMOTE_LEADING_DOTS
           You can also have the abs() method ignore excess ".."  segments in(1,8)
           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(1,5)/a/b")
                 ==> "http://host(1,5)/../../foo"

             local $URI::ABS_REMOTE_LEADING_DOTS = 1;
             URI->new("../../../foo")->abs("http://host(1,5)/a/b")
                 ==> "http://host(1,5)/foo"

BUGS
       Using regexp(3,n) 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(1,8) 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(1,8) turn was (dis-
       tantly) based on the "wwwurl.pl" code in(1,8) 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 v5.8.5                       2004-01-14                            URI(3)

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