lib::URI::URL(3User Contributed Perl Documentatiolib::URI::URL(3)NAMEURI::URL - Uniform Resource Locators (absolute and
relative)
SYNOPSIS
use URI::URL;
# Constructors
$url1 = new URI::URL 'http://www.perl.com/%7Euser/gisle.gif';
$url2 = new URI::URL 'gisle.gif', 'http://www.com/%7Euser';
$url3 = url 'http://www.sn.no/'; # handy constructor
$url4 = $url2->abs; # get absolute url using base
$url5 = $url2->abs('http:/other/path');
$url6 = newlocal URI::URL 'test';
# Stringify URL
$str1 = $url->as_string; # complete escaped URL string
$str2 = $url->full_path; # escaped path+params+query
$str3 = "$url"; # use operator overloading
# Retrieving Generic-RL components:
$scheme = $url->scheme;
$netloc = $url->netloc; # see user,password,host,port below
$path = $url->path;
$params = $url->params;
$query = $url->query;
$frag = $url->frag;
# Accessing elements in their escaped form
$path = $url->epath;
$params = $url->eparams;
$query = $url->equery;
# Retrieving Network location (netloc) components:
$user = $url->user;
$password = $url->password;
$host = $url->host;
$port = $url->port; # returns default if not defined
# Retrieve escaped path components as an array
@path = $url->path_components;
# HTTP query-string access methods
@keywords = $url->keywords;
@form = $url->query_form;
# All methods above can set the field values, e.g:
$url->scheme('http');
$url->host('www.w3.org');
$url->port($url->default_port);
$url->base($url5); # use string or object
$url->keywords(qw(dog bones));
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# File methods
$url = new URI::URL "file:/foo/bar";
open(F, $url->local_path) or die;
# Compare URLs
if ($url->eq("http://www.sn.no")) or die;
DESCRIPTION
This module implements the URI::URL class representing
Uniform Resource Locators (URL). URLs provide a compact
string representation for resources available via the
Internet. Both absolute (RFC 1738) and relative (RFC 1808)
URLs are supported.
URI::URL objects are created by calling new(), which takes
as argument a string representation of the URL or an
existing URL object reference to be cloned. Specific
individual elements can then be accessed via the scheme(),
user(), password(), host(), port(), path(), params(),
query() and frag() methods. In addition escaped versions
of the path, params and query can be accessed with the
epath(), eparams() and equery() methods. Note that some
URL schemes will support all these methods.
The object constructor new() must be able to determine the
scheme for the URL. If a scheme is not specified in the
URL itself, it will use the scheme specified by the base
URL. If no base URL scheme is defined then new() will
croak if URI::URL::strict(1) has been invoked, otherwise
http is silently assumed. Once the scheme has been
determined new() then uses the implementor() function to
determine which class implements that scheme. If no
implementor class is defined for the scheme then new()
will croak if URI::URL::strict(1) has been invoked,
otherwise the internal generic URL class is assumed.
Internally defined schemes are implemented by the
URI::URL::scheme_name module. The URI::URL::implementor()
function can be used to explicitly set the class used to
implement a scheme if you want to override this.
HOW AND WHEN TO ESCAPE
This is an edited extract from a URI specification:
The printability requirement has been met by specifying
a safe set of characters, and a general escaping scheme
for encoding "unsafe" characters. This "safe" set is
suitable, for example, for use in electronic mail.
This is the canonical form of a URI.
There is a conflict between the need to be able to
represent many characters including spaces within a URI
directly, and the need to be able to use a URI in
environments which have limited character sets or in
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which certain characters are prone to corruption. This
conflict has been resolved by use of an hexadecimal
escaping method which may be applied to any characters
forbidden in a given context. When URLs are moved
between contexts, the set of characters escaped may be
enlarged or reduced unambiguously. The canonical form
for URIs has all white spaces encoded.
Notes:
A URL string must, by definition, consist of escaped
components. Complete URLs are always escaped.
The components of a URL string must be individually
escaped. Each component of a URL may have a separate
requirements regarding what must be escaped, and those
requirements are also dependent on the URL scheme.
Never escape an already escaped component string.
This implementation expects an escaped URL string to be
passed to new() and will return a fully escaped URL string
from as_string() and full_path().
Individual components can be manipulated in unescaped or
escaped form. The following methods return/accept
unescaped strings:
scheme path
user params
password query
host frag
port
The following methods return/accept partial escaped
strings:
netloc eparams
epath equery
Partial escaped means that only reserved characters (i.e.
':', '@', '/', ';', '?', '=', '&' in addition to '%', '.'
and '#') needs to be escaped when they are to be treated
as normal characters. Fully escaped means that all unsafe
characters are escaped. Unsafe characters are all all
control characters (%00-%1F and %7F), all 8-bit characters
(%80-%FF) as well as '{', '}', '|', '\', '^', '[', ']'
'`', '"', '<' and '>'. Note that the character '~' is not
considered unsafe by this library as it is common practice
to use it to reference personal home pages, but it is
still unsafe according to RFC 1738.
ADDING NEW URL SCHEMES
New URL schemes or alternative implementations for
existing schemes can be added to your own code. To create
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a new scheme class use code like:
package MYURL::foo;
@ISA = (URI::URL::implementor()); # inherit from generic scheme
The 'URI::URL::implementor()' function call with no
parameters returns the name of the class which implements
the generic URL scheme behaviour (typically
URI::URL::_generic). All hierarchical schemes should be
derived from this class.
Your class can then define overriding methods (e.g.,
new(), _parse() as required).
To register your new class as the implementor for a
specific scheme use code like:
URI::URL::implementor('x-foo', 'MYURL::foo');
Any new URL created for scheme 'x-foo' will be implemented
by your MYURL::foo class. Existing URLs will not be
affected.
FUNCTIONS
new URI::URL $url_string [, $base_url]
This is the object constructor. It will create a new
URI::URL object, initialized from the URL string. To
trap bad or unknown URL schemes use:
$obj = eval { new URI::URL "snews:comp.lang.perl.misc" };
or set URI::URL::strict(0) if you do not care about bad
or unknown schemes.
newlocal URI::URL $path;
Returns an URL object that denotes a path within the
local filesystem. Paths not starting with '/' are
interpreted relative to the current working directory.
This constructor always return an absolute 'file' URL.
url($url_string, [, $base_url])
Alternative constructor function. The url() function
is exported by the URI::URL module and is easier both
to type and read than calling URI::URL->new directly.
Useful for constructs like this:
$h = url($str)->host;
This function is just a wrapper for URI::URL->new.
URI::URL::strict($bool)
If strict is true then we croak on errors. The
function returns the previous value.
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URI::URL::implementor([$scheme, [$class]])
Use this function to get or set implementor class for a
scheme. Returns '' if specified scheme is not
supported. Returns generic URL class if no scheme
specified.
METHODS
This section describes the methods available for an
URI::URL object. Note that some URL schemes will disallow
some of these methods and will croak if they are used.
Some URL schemes add additional methods that are described
in the sections to follow.
Attribute access methods marked with (*) can take an
optional argument to set the value of the attribute, and
they always return the old value.
$url->abs([$base, [$allow_scheme_in_relative_urls]])
The abs() method attempts to return a new absolute
URI::URL object for a given URL. In order to convert a
relative URL into an absolute one, a base URL is
required. You can associate a default base with a URL
either by passing a base to the new() constructor when
a URI::URL is created or using the base() method on the
object later. Alternatively you can specify a one-off
base as a parameter to the abs() method.
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. RFC1808 says that this should be
avoided, but you can enable this old behaviour by
passing a TRUE value as the second argument to the
abs() method. The difference is demonstrated by the
following examples:
url("http:foo")->abs("http://host/a/b") ==> "http:foo"
url("http:foo")->abs("http://host/a/b", 1) ==> "http:/host/a/foo"
The rel() method will do the opposite transformation.
$url->as_string
Returns a string representing the URL in its canonical
form. All unsafe characters will be escaped. This
method is overloaded as the perl "stringify" operator,
which means that URLs can be used as strings in many
contexts.
$url->base (*)
Get/set the base URL associated with the current
URI::URL object. The base URL matters when you call
the abs() method.
$url->clone
Returns a copy of the current URI::URL object.
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$url->crack
Return a 9 element array with the following content:
0: $url->scheme *)
1: $url->user
2: $url->password
3: $url->host
4: $url->port
5: $url->epath
6: $url->eparams
7: $url->equery
8: $url->frag
All elements except scheme will be undefined if the
corresponding URL part is not available.
Note: The scheme (first element) returned by crack will
aways be defined. This is different from what the
$url->scheme returns, since it will return undef for
relative URLs.
$url->default_port
Returns the default port number for the URL scheme that
the URI::URL belongs too.
$url->eparams (*)
Get/set the URL parameters in escaped form.
$url->epath (*)
Get/set the URL path in escaped form.
$url->eq($other_url)
Compare two URLs to decide if they match or not. The
rules for how comparison is made varies for different
parts of the URLs; scheme and netloc comparison is
case-insensitive, and escaped chars match their %XX
encoding unless they are "reserved" or "unsafe".
$url->equery (*)
Get/set the URL query string in escaped form.
$url->full_path
Returns the string "/path;params?query". This is the
string that is passed to a remote server in order to
access the document.
$url->frag (*)
Get/set the fragment (unescaped)
$url->host (*)
Get/set the host (unescaped)
$url->netloc (*)
Get/set the network location in escaped form. Setting
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the network location will affect 'user', 'password',
'host' and 'port'.
$url->params (*)
Get/set the URL parameters (unescaped)
$url->password (*)
Get/set the password (unescaped)
$url->path (*)
Get/set the path (unescaped). This method will croak
if any of the path components in the return value
contain the "/" character. You should use the epath()
method to be safe.
$url->path_components (*)
Get/set the path using a list of unescaped path
components. The return value will loose the
distinction beween '.' and '%2E'. When setting a
value, a '.' is converted to be a literal '.' and is
therefore encoded as '%2E'.
$url->port (*)
Get/set the network port (unescaped)
$url->rel([$base])
Return a relative URL if possible. This is the
opposite of what the abs() method does. For instance:
url("http://www.math.uio.no/doc/mail/top.html",
"http://www.math.uio.no/doc/linux/")->rel
will return a relative URL with path set to
"../mail/top.html" and with the same base as the
original URL.
If the original URL already is relative or the scheme
or netloc does not match the base, then a copy of the
original URL is returned.
$url->print_on(*FILEHANDLE);
Prints a verbose presentation of the contents of the
URL object to the specified file handle (default
STDOUT). Mainly useful for debugging.
$url->scheme (*)
Get/set the scheme for the URL.
$url->query (*)
Get/set the query string (unescaped). This method will
croak if the string returned contains both '+' and
'%2B' or '=' together with '%3D' or '%26'. You should
use the equery() method to be safe.
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$url->user (*)
Get/set the URL user name (unescaped)
HTTP METHODS
For http URLs you may also access the query string using
the keywords() and the query_form() methods. Both will
croak if the query is not of the correct format. The
encodings look like this:
word1+word2+word3.. # keywords
key1=val1&key2=val2... # query_form
Note: These functions does not return the old value when
they are used to set a value of the query string.
$url->keywords (*)
The keywords() method returns a list of unescaped
strings. The method can also be used to set the query
string by passing in the keywords as individual
arguments to the method.
$url->query_form (*)
The query_form() method return a list of unescaped
key/value pairs. If you assign the return value to a
hash you might loose some values if the key is repeated
(which it is allowed to do).
This method can also be used to set the query sting of
the URL like this:
$url->query_form(foo => 'bar', foo => 'baz', equal => '=');
If the value part of a key/value pair is a reference to
an array, then it will be converted to separate
key/value pairs for each value. This means that these
two calls are equal:
$url->query_form(foo => 'bar', foo => 'baz');
$url->query_form(foo => ['bar', 'baz']);
FILE METHODS
The file URLs implement the local_path() method that
returns a path suitable for access to files within the
current filesystem. These methods can not be used to set
the path of the URL.
$url->local_path
This method is really just an alias for one of the
methods below depending on what system you run on.
$url->unix_path
Returns a path suitable for use on a Unix system. This
method will croak if any of the path segments contains
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a "/" or a NULL character.
$url->dos_path
Returns a path suitable for use on a MS-DOS or
MS-Windows system.
$url->mac_path
Returns a path suitable for use on a Macintosh system.
$url->vms_path
Returns a path suitable for use on a VMS system. VMS
is a trademark of Digital.
GOPHER METHODS
The methods access the parts that are specific for the
gopher URLs. These methods access different parts of the
$url->path.
$url->gtype (*)
$url->selector (*)
$url->search (*)
$url->string (*)
NEWS METHODS
$url->group (*)
$url->article (*)
WAIS METHODS
The methods access the parts that are specific for the
wais URLs. These methods access different parts of the
$url->path.
$url->database (*)
$url->wtype (*)
$url->wpath (*)
MAILTO METHODS
$url->address (*)
The mail address can also be accessed with the netloc()
method.
WHAT A URL IS NOT
URL objects do not, and should not, know how to 'get' or
'put' the resources they specify locations for, anymore
than a postal address 'knows' anything about the postal
system. The actual access/transfer should be achieved by
some form of transport agent class (see the LWP::UserAgent
manpage). The agent class can use the URL class, but
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should not be a subclass of it.
COMPATIBILITY
This is a listing incompatibilities with URI::URL version
3.x:
unsafe(), escape() and unescape()
These methods not supported any more.
full_path() and as_string()
These methods does no longer take a second argument
which specify the set of characters to consider as
unsafe.
'+' in the query-string
The '+' character in the query part of the URL was
earlier considered to be an encoding of a space. This
was just bad influence from Mosaic. Space is now
encoded as '%20'.
path() and query()
This methods will croak if they loose information. Use
epath() or equery() instead. The path() method will
for instance loose information if any path segment
contain an (encoded) '/' character.
The path() now consider a leading '/' to be part of the
path. If the path is empty it will default to '/'.
You can get the old behaviour by setting
$URI::URL::COMPAT_VER_3 to TRUE before accessing the
path() method.
netloc()
The string passed to netloc is now assumed to be
escaped. The string returned will also be (partially)
escaped.
sub-classing
The path, params and query is now stored internally in
unescaped form. This might affect sub-classes of the
URL scheme classes.
AUTHORS / ACKNOWLEDGMENTS
This module is (distantly) based on the wwwurl.pl code in
the libwww-perl distribution developed by Roy Fielding
<fielding@ics.uci.edu>, as part of the Arcadia project at
the University of California, Irvine, with contributions
from Brooks Cutter.
Gisle Aas <aas@sn.no>, Tim Bunce <Tim.Bunce@ig.co.uk>, Roy
Fielding <fielding@ics.uci.edu> and Martijn Koster
<m.koster@webcrawler.com> (in English alphabetical order)
have collaborated on the complete rewrite for Perl 5, with
input from other people on the libwww-perl mailing list.
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If you have any suggestions, bug reports, fixes, or
enhancements, send them to the libwww-perl mailing list at
<libwww-perl@ics.uci.edu>.
COPYRIGHT
Copyright 1995-1996 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.
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