1LWP::UserAgent(3) User Contributed Perl Documentation LWP::UserAgent(3)
2
6 LWP::UserAgent - Web user agent class
7
9 require LWP::UserAgent;
10 my $ua = LWP::UserAgent->new;
12 $ua->timeout(10);
13 $ua->env_proxy;
14 my $response = $ua->get('http://search.cpan.org/');
16 if ($response->is_success) {
18 print $response->decoded_content; # or whatever
19 }
20 else {
21 die $response->status_line;
22 }
23
25 The "LWP::UserAgent" is a class implementing a web user agent.
26 "LWP::UserAgent" objects can be used to dispatch web requests.
27 In normal use the application creates an "LWP::UserAgent" object, and
29 then configures it with values for timeouts, proxies, name, etc. It
30 then creates an instance of "HTTP::Request" for the request that needs
31 to be performed. This request is then passed to one of the request
32 method the UserAgent, which dispatches it using the relevant protocol,
33 and returns a "HTTP::Response" object. There are convenience methods
34 for sending the most common request types: get(), head() and post().
35 When using these methods then the creation of the request object is
36 hidden as shown in the synopsis above.
37 The basic approach of the library is to use HTTP style communication
39 for all protocol schemes. This means that you will construct
40 "HTTP::Request" objects and receive "HTTP::Response" objects even for
41 non-HTTP resources like gopher and ftp. In order to achieve even more
42 similarity to HTTP style communications, gopher menus and file
43 directories are converted to HTML documents.
44
46 The following constructor methods are available:
47 $ua = LWP::UserAgent->new( %options )
49 This method constructs a new "LWP::UserAgent" object and returns
50 it. Key/value pair arguments may be provided to set up the initial
51 state. The following options correspond to attribute methods
52 described below:
53 KEY DEFAULT
55 ----------- --------------------
56 agent "libwww-perl/#.###"
57 from undef
58 conn_cache undef
59 cookie_jar undef
60 default_headers HTTP::Headers->new
61 local_address undef
62 max_size undef
63 max_redirect 7
64 parse_head 1
65 protocols_allowed undef
66 protocols_forbidden undef
67 requests_redirectable ['GET', 'HEAD']
68 timeout 180
69 The following additional options are also accepted: If the
71 "env_proxy" option is passed in with a TRUE value, then proxy
72 settings are read from environment variables (see env_proxy()
73 method below). If the "keep_alive" option is passed in, then a
74 "LWP::ConnCache" is set up (see conn_cache() method below). The
75 "keep_alive" value is passed on as the "total_capacity" for the
76 connection cache.
77 $ua->clone
79 Returns a copy of the LWP::UserAgent object.
80
82 The settings of the configuration attributes modify the behaviour of
83 the "LWP::UserAgent" when it dispatches requests. Most of these can
84 also be initialized by options passed to the constructor method.
85 The following attribute methods are provided. The attribute value is
87 left unchanged if no argument is given. The return value from each
88 method is the old attribute value.
89 $ua->agent
91 $ua->agent( $product_id )
92 Get/set the product token that is used to identify the user agent
93 on the network. The agent value is sent as the "User-Agent" header
94 in the requests. The default is the string returned by the
95 _agent() method (see below).
96 If the $product_id ends with space then the _agent() string is
98 appended to it.
99 The user agent string should be one or more simple product
101 identifiers with an optional version number separated by the "/"
102 character. Examples are:
103 $ua->agent('Checkbot/0.4 ' . $ua->_agent);
105 $ua->agent('Checkbot/0.4 '); # same as above
106 $ua->agent('Mozilla/5.0');
107 $ua->agent(""); # don't identify
108 $ua->_agent
110 Returns the default agent identifier. This is a string of the form
111 "libwww-perl/#.###", where "#.###" is substituted with the version
112 number of this library.
113 $ua->from
115 $ua->from( $email_address )
116 Get/set the e-mail address for the human user who controls the
117 requesting user agent. The address should be machine-usable, as
118 defined in RFC 822. The "from" value is send as the "From" header
119 in the requests. Example:
120 $ua->from('gaas@cpan.org');
122 The default is to not send a "From" header. See the
124 default_headers() method for the more general interface that allow
125 any header to be defaulted.
126 $ua->cookie_jar
128 $ua->cookie_jar( $cookie_jar_obj )
129 Get/set the cookie jar object to use. The only requirement is that
130 the cookie jar object must implement the extract_cookies($request)
131 and add_cookie_header($response) methods. These methods will then
132 be invoked by the user agent as requests are sent and responses are
133 received. Normally this will be a "HTTP::Cookies" object or some
134 subclass.
135 The default is to have no cookie_jar, i.e. never automatically add
137 "Cookie" headers to the requests.
138 Shortcut: If a reference to a plain hash is passed in as the
140 $cookie_jar_object, then it is replaced with an instance of
141 "HTTP::Cookies" that is initialized based on the hash. This form
142 also automatically loads the "HTTP::Cookies" module. It means
143 that:
144 $ua->cookie_jar({ file => "$ENV{HOME}/.cookies.txt" });
146 is really just a shortcut for:
148 require HTTP::Cookies;
150 $ua->cookie_jar(HTTP::Cookies->new(file => "$ENV{HOME}/.cookies.txt"));
151 $ua->default_headers
153 $ua->default_headers( $headers_obj )
154 Get/set the headers object that will provide default header values
155 for any requests sent. By default this will be an empty
156 "HTTP::Headers" object.
157 $ua->default_header( $field )
159 $ua->default_header( $field => $value )
160 This is just a short-cut for $ua->default_headers->header( $field
161 => $value ). Example:
162 $ua->default_header('Accept-Encoding' => scalar HTTP::Message::decodable());
164 $ua->default_header('Accept-Language' => "no, en");
165 $ua->conn_cache
167 $ua->conn_cache( $cache_obj )
168 Get/set the "LWP::ConnCache" object to use. See LWP::ConnCache for
169 details.
170 $ua->credentials( $netloc, $realm )
172 $ua->credentials( $netloc, $realm, $uname, $pass )
173 Get/set the user name and password to be used for a realm.
174 The $netloc is a string of the form "<host>:<port>". The username
176 and password will only be passed to this server. Example:
177 $ua->credentials("www.example.com:80", "Some Realm", "foo", "secret");
179 $ua->local_address
181 $ua->local_address( $address )
182 Get/set the local interface to bind to for network connections.
183 The interface can be specified as a hostname or an IP address.
184 This value is passed as the "LocalAddr" argument to
185 IO::Socket::INET.
186 $ua->max_size
188 $ua->max_size( $bytes )
189 Get/set the size limit for response content. The default is
190 "undef", which means that there is no limit. If the returned
191 response content is only partial, because the size limit was
192 exceeded, then a "Client-Aborted" header will be added to the
193 response. The content might end up longer than "max_size" as we
194 abort once appending a chunk of data makes the length exceed the
195 limit. The "Content-Length" header, if present, will indicate the
196 length of the full content and will normally not be the same as
197 "length($res->content)".
198 $ua->max_redirect
200 $ua->max_redirect( $n )
201 This reads or sets the object's limit of how many times it will
202 obey redirection responses in a given request cycle.
203 By default, the value is 7. This means that if you call request()
205 method and the response is a redirect elsewhere which is in turn a
206 redirect, and so on seven times, then LWP gives up after that
207 seventh request.
208 $ua->parse_head
210 $ua->parse_head( $boolean )
211 Get/set a value indicating whether we should initialize response
212 headers from the <head> section of HTML documents. The default is
213 TRUE. Do not turn this off, unless you know what you are doing.
214 $ua->protocols_allowed
216 $ua->protocols_allowed( \@protocols )
217 This reads (or sets) this user agent's list of protocols that the
218 request methods will exclusively allow. The protocol names are
219 case insensitive.
220 For example: "$ua->protocols_allowed( [ 'http', 'https'] );" means
222 that this user agent will allow only those protocols, and attempts
223 to use this user agent to access URLs with any other schemes (like
224 "ftp://...") will result in a 500 error.
225 To delete the list, call: "$ua->protocols_allowed(undef)"
227 By default, an object has neither a "protocols_allowed" list, nor a
229 "protocols_forbidden" list.
230 Note that having a "protocols_allowed" list causes any
232 "protocols_forbidden" list to be ignored.
233 $ua->protocols_forbidden
235 $ua->protocols_forbidden( \@protocols )
236 This reads (or sets) this user agent's list of protocols that the
237 request method will not allow. The protocol names are case
238 insensitive.
239 For example: "$ua->protocols_forbidden( [ 'file', 'mailto'] );"
241 means that this user agent will not allow those protocols, and
242 attempts to use this user agent to access URLs with those schemes
243 will result in a 500 error.
244 To delete the list, call: "$ua->protocols_forbidden(undef)"
246 $ua->requests_redirectable
248 $ua->requests_redirectable( \@requests )
249 This reads or sets the object's list of request names that
250 "$ua->redirect_ok(...)" will allow redirection for. By default,
251 this is "['GET', 'HEAD']", as per RFC 2616. To change to include
252 'POST', consider:
253 push @{ $ua->requests_redirectable }, 'POST';
255 $ua->show_progress
257 $ua->show_progress( $boolean )
258 Get/set a value indicating whether a progress bar should be
259 displayed on on the terminal as requests are processed. The default
260 is FALSE.
261 $ua->timeout
263 $ua->timeout( $secs )
264 Get/set the timeout value in seconds. The default timeout() value
265 is 180 seconds, i.e. 3 minutes.
266 The requests is aborted if no activity on the connection to the
268 server is observed for "timeout" seconds. This means that the time
269 it takes for the complete transaction and the request() method to
270 actually return might be longer.
271 $ua->ssl_opts
273 $ua->ssl_opts( $key )
274 $ua->ssl_opts( $key => $value )
275 Get/set the options for SSL connections. Without argument return
276 the list of options keys currently set. With a single argument
277 return the current value for the given option. With 2 arguments
278 set the option value and return the old. Setting an option to the
279 value "undef" removes this option.
280 The options that LWP relates to are:
282 "verify_hostname" => $bool
284 When TRUE LWP will for secure protocol schemes ensure it
285 connects to servers that have a valid certificate matching the
286 expected hostname. If FALSE no checks are made and you can't
287 be sure that you communicate with the expected peer. The no
288 checks behaviour was the default for libwww-perl-5.837 and
289 earlier releases.
290 This option is initialized from the
292 PERL_LWP_SSL_VERIFY_HOSTNAME environment variable. If this
293 envirionment variable isn't set; then "verify_hostname"
294 defaults to 1.
295 "SSL_ca_file" => $path
297 The path to a file containing Certificate Authority
298 certificates. A default setting for this option is provided by
299 checking the environment variables "PERL_LWP_SSL_CA_FILE" and
300 "HTTPS_CA_FILE" in order. Last resort value is built-in value
301 /etc/pki/tls/certs/ca-bundle.crt.
302 "SSL_ca_path" => $path
304 The path to a directory containing files containing Certificate
305 Authority certificates. A default setting for this option is
306 provided by checking the environment variables
307 "PERL_LWP_SSL_CA_PATH" and "HTTPS_CA_DIR" in order.
308 Other options can be set and are processed directly by the SSL
310 Socket implementation in use. See IO::Socket::SSL or Net::SSL for
311 details.
312 SSL Socket implementation can be selected by environment variable
314 "PERL_NET_HTTPS_SSL_SOCKET_CLASS". IO::Socket::SSL is preferred by
315 default.
316 Proxy attributes
318 The following methods set up when requests should be passed via a proxy
319 server.
320 $ua->proxy(\@schemes, $proxy_url)
322 $ua->proxy($scheme, $proxy_url)
323 Set/retrieve proxy URL for a scheme:
324 $ua->proxy(['http', 'ftp'], 'http://proxy.sn.no:8001/');
326 $ua->proxy('gopher', 'http://proxy.sn.no:8001/');
327 The first form specifies that the URL is to be used for proxying of
329 access methods listed in the list in the first method argument,
330 i.e. 'http' and 'ftp'.
331 The second form shows a shorthand form for specifying proxy URL for
333 a single access scheme.
334 $ua->no_proxy( $domain, ... )
336 Do not proxy requests to the given domains. Calling no_proxy
337 without any domains clears the list of domains. Eg:
338 $ua->no_proxy('localhost', 'example.com');
340 $ua->env_proxy
342 Load proxy settings from *_proxy environment variables. You might
343 specify proxies like this (sh-syntax):
344 gopher_proxy=http://proxy.my.place/
346 wais_proxy=http://proxy.my.place/
347 no_proxy="localhost,example.com"
348 export gopher_proxy wais_proxy no_proxy
349 csh or tcsh users should use the "setenv" command to define these
351 environment variables.
352 On systems with case insensitive environment variables there exists
354 a name clash between the CGI environment variables and the
355 "HTTP_PROXY" environment variable normally picked up by
356 env_proxy(). Because of this "HTTP_PROXY" is not honored for CGI
357 scripts. The "CGI_HTTP_PROXY" environment variable can be used
358 instead.
359 Handlers
361 Handlers are code that injected at various phases during the processing
362 of requests. The following methods are provided to manage the active
363 handlers:
364 $ua->add_handler( $phase => \&cb, %matchspec )
366 Add handler to be invoked in the given processing phase. For how
367 to specify %matchspec see "Matching" in HTTP::Config.
368 The possible values $phase and the corresponding callback
370 signatures are:
371 request_preprepare => sub { my($request, $ua, $h) = @_; ... }
373 The handler is called before the "request_prepare" and other
374 standard initialization of of the request. This can be used to
375 set up headers and attributes that the "request_prepare"
376 handler depends on. Proxy initialization should take place
377 here; but in general don't register handlers for this phase.
378 request_prepare => sub { my($request, $ua, $h) = @_; ... }
380 The handler is called before the request is sent and can modify
381 the request any way it see fit. This can for instance be used
382 to add certain headers to specific requests.
383 The method can assign a new request object to $_[0] to replace
385 the request that is sent fully.
386 The return value from the callback is ignored. If an
388 exceptions is raised it will abort the request and make the
389 request method return a "400 Bad request" response.
390 request_send => sub { my($request, $ua, $h) = @_; ... }
392 This handler get a chance of handling requests before it's sent
393 to the protocol handlers. It should return an HTTP::Response
394 object if it wishes to terminate the processing; otherwise it
395 should return nothing.
396 The "response_header" and "response_data" handlers will not be
398 invoked for this response, but the "response_done" will be.
399 response_header => sub { my($response, $ua, $h) = @_; ... }
401 This handler is called right after the response headers have
402 been received, but before any content data. The handler might
403 set up handlers for data and might croak to abort the request.
404 The handler might set the $response->{default_add_content}
406 value to control if any received data should be added to the
407 response object directly. This will initially be false if the
408 $ua->request() method was called with a $content_file or
409 $content_cb argument; otherwise true.
410 response_data => sub { my($response, $ua, $h, $data) = @_; ... }
412 This handlers is called for each chunk of data received for the
413 response. The handler might croak to abort the request.
414 This handler need to return a TRUE value to be called again for
416 subsequent chunks for the same request.
417 response_done => sub { my($response, $ua, $h) = @_; ... }
419 The handler is called after the response has been fully
420 received, but before any redirect handling is attempted. The
421 handler can be used to extract information or modify the
422 response.
423 response_redirect => sub { my($response, $ua, $h) = @_; ... }
425 The handler is called in $ua->request after "response_done".
426 If the handler return an HTTP::Request object we'll start over
427 with processing this request instead.
428 $ua->remove_handler( undef, %matchspec )
430 $ua->remove_handler( $phase, %matchspec )
431 Remove handlers that match the given %matchspec. If $phase is not
432 provided remove handlers from all phases.
433 Be careful as calling this function with %matchspec that is not not
435 specific enough can remove handlers not owned by you. It's
436 probably better to use the set_my_handler() method instead.
437 The removed handlers are returned.
439 $ua->set_my_handler( $phase, $cb, %matchspec )
441 Set handlers private to the executing subroutine. Works by
442 defaulting an "owner" field to the %matchspec that holds the name
443 of the called subroutine. You might pass an explicit "owner" to
444 override this.
445 If $cb is passed as "undef", remove the handler.
447 $ua->get_my_handler( $phase, %matchspec )
449 $ua->get_my_handler( $phase, %matchspec, $init )
450 Will retrieve the matching handler as hash ref.
451 If $init is passed passed as a TRUE value, create and add the
453 handler if it's not found. If $init is a subroutine reference,
454 then it's called with the created handler hash as argument. This
455 sub might populate the hash with extra fields; especially the
456 callback. If $init is a hash reference, merge the hashes.
457 $ua->handlers( $phase, $request )
459 $ua->handlers( $phase, $response )
460 Returns the handlers that apply to the given request or response at
461 the given processing phase.
462
464 The methods described in this section are used to dispatch requests via
465 the user agent. The following request methods are provided:
466 $ua->get( $url )
468 $ua->get( $url , $field_name => $value, ... )
469 This method will dispatch a "GET" request on the given $url.
470 Further arguments can be given to initialize the headers of the
471 request. These are given as separate name/value pairs. The return
472 value is a response object. See HTTP::Response for a description
473 of the interface it provides.
474 There will still be a response object returned when LWP can't
476 connect to the server specified in the URL or when other failures
477 in protocol handlers occur. These internal responses use the
478 standard HTTP status codes, so the responses can't be
479 differentiated by testing the response status code alone. Error
480 responses that LWP generates internally will have the "Client-
481 Warning" header set to the value "Internal response". If you need
482 to differentiate these internal responses from responses that a
483 remote server actually generates, you need to test this header
484 value.
485 Fields names that start with ":" are special. These will not
487 initialize headers of the request but will determine how the
488 response content is treated. The following special field names are
489 recognized:
490 :content_file => $filename
492 :content_cb => \&callback
493 :read_size_hint => $bytes
494 If a $filename is provided with the ":content_file" option, then
496 the response content will be saved here instead of in the response
497 object. If a callback is provided with the ":content_cb" option
498 then this function will be called for each chunk of the response
499 content as it is received from the server. If neither of these
500 options are given, then the response content will accumulate in the
501 response object itself. This might not be suitable for very large
502 response bodies. Only one of ":content_file" or ":content_cb" can
503 be specified. The content of unsuccessful responses will always
504 accumulate in the response object itself, regardless of the
505 ":content_file" or ":content_cb" options passed in.
506 The ":read_size_hint" option is passed to the protocol module which
508 will try to read data from the server in chunks of this size. A
509 smaller value for the ":read_size_hint" will result in a higher
510 number of callback invocations.
511 The callback function is called with 3 arguments: a chunk of data,
513 a reference to the response object, and a reference to the protocol
514 object. The callback can abort the request by invoking die(). The
515 exception message will show up as the "X-Died" header field in the
516 response returned by the get() function.
517 $ua->head( $url )
519 $ua->head( $url , $field_name => $value, ... )
520 This method will dispatch a "HEAD" request on the given $url.
521 Otherwise it works like the get() method described above.
522 $ua->post( $url, \%form )
524 $ua->post( $url, \@form )
525 $ua->post( $url, \%form, $field_name => $value, ... )
526 $ua->post( $url, $field_name => $value,... Content => \%form )
527 $ua->post( $url, $field_name => $value,... Content => \@form )
528 $ua->post( $url, $field_name => $value,... Content => $content )
529 This method will dispatch a "POST" request on the given $url, with
530 %form or @form providing the key/value pairs for the fill-in form
531 content. Additional headers and content options are the same as for
532 the get() method.
533 This method will use the POST() function from
535 "HTTP::Request::Common" to build the request. See
536 HTTP::Request::Common for a details on how to pass form content and
537 other advanced features.
538 $ua->mirror( $url, $filename )
540 This method will get the document identified by $url and store it
541 in file called $filename. If the file already exists, then the
542 request will contain an "If-Modified-Since" header matching the
543 modification time of the file. If the document on the server has
544 not changed since this time, then nothing happens. If the document
545 has been updated, it will be downloaded again. The modification
546 time of the file will be forced to match that of the server.
547 The return value is the the response object.
549 $ua->request( $request )
551 $ua->request( $request, $content_file )
552 $ua->request( $request, $content_cb )
553 $ua->request( $request, $content_cb, $read_size_hint )
554 This method will dispatch the given $request object. Normally this
555 will be an instance of the "HTTP::Request" class, but any object
556 with a similar interface will do. The return value is a response
557 object. See HTTP::Request and HTTP::Response for a description of
558 the interface provided by these classes.
559 The request() method will process redirects and authentication
561 responses transparently. This means that it may actually send
562 several simple requests via the simple_request() method described
563 below.
564 The request methods described above; get(), head(), post() and
566 mirror(), will all dispatch the request they build via this method.
567 They are convenience methods that simply hides the creation of the
568 request object for you.
569 The $content_file, $content_cb and $read_size_hint all correspond
571 to options described with the get() method above.
572 You are allowed to use a CODE reference as "content" in the request
574 object passed in. The "content" function should return the content
575 when called. The content can be returned in chunks. The content
576 function will be invoked repeatedly until it return an empty string
577 to signal that there is no more content.
578 $ua->simple_request( $request )
580 $ua->simple_request( $request, $content_file )
581 $ua->simple_request( $request, $content_cb )
582 $ua->simple_request( $request, $content_cb, $read_size_hint )
583 This method dispatches a single request and returns the response
584 received. Arguments are the same as for request() described above.
585 The difference from request() is that simple_request() will not try
587 to handle redirects or authentication responses. The request()
588 method will in fact invoke this method for each simple request it
589 sends.
590 $ua->is_protocol_supported( $scheme )
592 You can use this method to test whether this user agent object
593 supports the specified "scheme". (The "scheme" might be a string
594 (like 'http' or 'ftp') or it might be an URI object reference.)
595 Whether a scheme is supported, is determined by the user agent's
597 "protocols_allowed" or "protocols_forbidden" lists (if any), and by
598 the capabilities of LWP. I.e., this will return TRUE only if LWP
599 supports this protocol and it's permitted for this particular
600 object.
601 Callback methods
603 The following methods will be invoked as requests are processed. These
604 methods are documented here because subclasses of "LWP::UserAgent"
605 might want to override their behaviour.
606 $ua->prepare_request( $request )
608 This method is invoked by simple_request(). Its task is to modify
609 the given $request object by setting up various headers based on
610 the attributes of the user agent. The return value should normally
611 be the $request object passed in. If a different request object is
612 returned it will be the one actually processed.
613 The headers affected by the base implementation are; "User-Agent",
615 "From", "Range" and "Cookie".
616 $ua->redirect_ok( $prospective_request, $response )
618 This method is called by request() before it tries to follow a
619 redirection to the request in $response. This should return a TRUE
620 value if this redirection is permissible. The $prospective_request
621 will be the request to be sent if this method returns TRUE.
622 The base implementation will return FALSE unless the method is in
624 the object's "requests_redirectable" list, FALSE if the proposed
625 redirection is to a "file://..." URL, and TRUE otherwise.
626 $ua->get_basic_credentials( $realm, $uri, $isproxy )
628 This is called by request() to retrieve credentials for documents
629 protected by Basic or Digest Authentication. The arguments passed
630 in is the $realm provided by the server, the $uri requested and a
631 boolean flag to indicate if this is authentication against a proxy
632 server.
633 The method should return a username and password. It should return
635 an empty list to abort the authentication resolution attempt.
636 Subclasses can override this method to prompt the user for the
637 information. An example of this can be found in "lwp-request"
638 program distributed with this library.
639 The base implementation simply checks a set of pre-stored member
641 variables, set up with the credentials() method.
642 $ua->progress( $status, $request_or_response )
644 This is called frequently as the response is received regardless of
645 how the content is processed. The method is called with $status
646 "begin" at the start of processing the request and with $state
647 "end" before the request method returns. In between these $status
648 will be the fraction of the response currently received or the
649 string "tick" if the fraction can't be calculated.
650 When $status is "begin" the second argument is the request object,
652 otherwise it is the response object.
653
655 See LWP for a complete overview of libwww-perl5. See lwpcook and the
656 scripts lwp-request and lwp-download for examples of usage.
657 See HTTP::Request and HTTP::Response for a description of the message
659 objects dispatched and received. See HTTP::Request::Common and
660 HTML::Form for other ways to build request objects.
661 See WWW::Mechanize and WWW::Search for examples of more specialized
663 user agents based on "LWP::UserAgent".
664
666 Copyright 1995-2009 Gisle Aas.
667 This library is free software; you can redistribute it and/or modify it
669 under the same terms as Perl itself.
670perl v5.12.4 2011-10-13 LWP::UserAgent(3)