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 max_size undef
62 max_redirect 7
63 parse_head 1
64 protocols_allowed undef
65 protocols_forbidden undef
66 requests_redirectable ['GET', 'HEAD']
67 timeout 180
68 The following additional options are also accepted: If the
70 "env_proxy" option is passed in with a TRUE value, then proxy
71 settings are read from environment variables (see env_proxy()
72 method below). If the "keep_alive" option is passed in, then a
73 "LWP::ConnCache" is set up (see conn_cache() method below). The
74 "keep_alive" value is passed on as the "total_capacity" for the
75 connection cache.
76 $ua->clone
78 Returns a copy of the LWP::UserAgent object.
79
81 The settings of the configuration attributes modify the behaviour of
82 the "LWP::UserAgent" when it dispatches requests. Most of these can
83 also be initialized by options passed to the constructor method.
84 The following attribute methods are provided. The attribute value is
86 left unchanged if no argument is given. The return value from each
87 method is the old attribute value.
88 $ua->agent
90 $ua->agent( $product_id )
91 Get/set the product token that is used to identify the user agent
92 on the network. The agent value is sent as the "User-Agent" header
93 in the requests. The default is the string returned by the
94 _agent() method (see below).
95 If the $product_id ends with space then the _agent() string is
97 appended to it.
98 The user agent string should be one or more simple product
100 identifiers with an optional version number separated by the "/"
101 character. Examples are:
102 $ua->agent('Checkbot/0.4 ' . $ua->_agent);
104 $ua->agent('Checkbot/0.4 '); # same as above
105 $ua->agent('Mozilla/5.0');
106 $ua->agent(""); # don't identify
107 $ua->_agent
109 Returns the default agent identifier. This is a string of the form
110 "libwww-perl/#.###", where "#.###" is substituted with the version
111 number of this library.
112 $ua->from
114 $ua->from( $email_address )
115 Get/set the e-mail address for the human user who controls the
116 requesting user agent. The address should be machine-usable, as
117 defined in RFC 822. The "from" value is send as the "From" header
118 in the requests. Example:
119 $ua->from('gaas@cpan.org');
121 The default is to not send a "From" header. See the
123 default_headers() method for the more general interface that allow
124 any header to be defaulted.
125 $ua->cookie_jar
127 $ua->cookie_jar( $cookie_jar_obj )
128 Get/set the cookie jar object to use. The only requirement is that
129 the cookie jar object must implement the extract_cookies($request)
130 and add_cookie_header($response) methods. These methods will then
131 be invoked by the user agent as requests are sent and responses are
132 received. Normally this will be a "HTTP::Cookies" object or some
133 subclass.
134 The default is to have no cookie_jar, i.e. never automatically add
136 "Cookie" headers to the requests.
137 Shortcut: If a reference to a plain hash is passed in as the
139 $cookie_jar_object, then it is replaced with an instance of
140 "HTTP::Cookies" that is initialized based on the hash. This form
141 also automatically loads the "HTTP::Cookies" module. It means
142 that:
143 $ua->cookie_jar({ file => "$ENV{HOME}/.cookies.txt" });
145 is really just a shortcut for:
147 require HTTP::Cookies;
149 $ua->cookie_jar(HTTP::Cookies->new(file => "$ENV{HOME}/.cookies.txt"));
150 $ua->default_headers
152 $ua->default_headers( $headers_obj )
153 Get/set the headers object that will provide default header values
154 for any requests sent. By default this will be an empty
155 "HTTP::Headers" object.
156 $ua->default_header( $field )
158 $ua->default_header( $field => $value )
159 This is just a short-cut for $ua->default_headers->header( $field
160 => $value ). Example:
161 $ua->default_header('Accept-Encoding' => scalar HTTP::Message::decodable());
163 $ua->default_header('Accept-Language' => "no, en");
164 $ua->conn_cache
166 $ua->conn_cache( $cache_obj )
167 Get/set the "LWP::ConnCache" object to use. See LWP::ConnCache for
168 details.
169 $ua->credentials( $netloc, $realm )
171 $ua->credentials( $netloc, $realm, $uname, $pass )
172 Get/set the user name and password to be used for a realm.
173 The $netloc is a string of the form "<host>:<port>". The username
175 and password will only be passed to this server. Example:
176 $ua->credentials("www.example.com:80", "Some Realm", "foo", "secret");
178 $ua->max_size
180 $ua->max_size( $bytes )
181 Get/set the size limit for response content. The default is
182 "undef", which means that there is no limit. If the returned
183 response content is only partial, because the size limit was
184 exceeded, then a "Client-Aborted" header will be added to the
185 response. The content might end up longer than "max_size" as we
186 abort once appending a chunk of data makes the length exceed the
187 limit. The "Content-Length" header, if present, will indicate the
188 length of the full content and will normally not be the same as
189 "length($res->content)".
190 $ua->max_redirect
192 $ua->max_redirect( $n )
193 This reads or sets the object's limit of how many times it will
194 obey redirection responses in a given request cycle.
195 By default, the value is 7. This means that if you call request()
197 method and the response is a redirect elsewhere which is in turn a
198 redirect, and so on seven times, then LWP gives up after that
199 seventh request.
200 $ua->parse_head
202 $ua->parse_head( $boolean )
203 Get/set a value indicating whether we should initialize response
204 headers from the <head> section of HTML documents. The default is
205 TRUE. Do not turn this off, unless you know what you are doing.
206 $ua->protocols_allowed
208 $ua->protocols_allowed( \@protocols )
209 This reads (or sets) this user agent's list of protocols that the
210 request methods will exclusively allow. The protocol names are
211 case insensitive.
212 For example: "$ua->protocols_allowed( [ 'http', 'https'] );" means
214 that this user agent will allow only those protocols, and attempts
215 to use this user agent to access URLs with any other schemes (like
216 "ftp://...") will result in a 500 error.
217 To delete the list, call: "$ua->protocols_allowed(undef)"
219 By default, an object has neither a "protocols_allowed" list, nor a
221 "protocols_forbidden" list.
222 Note that having a "protocols_allowed" list causes any
224 "protocols_forbidden" list to be ignored.
225 $ua->protocols_forbidden
227 $ua->protocols_forbidden( \@protocols )
228 This reads (or sets) this user agent's list of protocols that the
229 request method will not allow. The protocol names are case
230 insensitive.
231 For example: "$ua->protocols_forbidden( [ 'file', 'mailto'] );"
233 means that this user agent will not allow those protocols, and
234 attempts to use this user agent to access URLs with those schemes
235 will result in a 500 error.
236 To delete the list, call: "$ua->protocols_forbidden(undef)"
238 $ua->requests_redirectable
240 $ua->requests_redirectable( \@requests )
241 This reads or sets the object's list of request names that
242 "$ua->redirect_ok(...)" will allow redirection for. By default,
243 this is "['GET', 'HEAD']", as per RFC 2616. To change to include
244 'POST', consider:
245 push @{ $ua->requests_redirectable }, 'POST';
247 $ua->show_progress
249 $ua->show_progress( $boolean )
250 Get/set a value indicating whether a progress bar should be
251 displayed on on the terminal as requests are processed. The default
252 is FALSE.
253 $ua->timeout
255 $ua->timeout( $secs )
256 Get/set the timeout value in seconds. The default timeout() value
257 is 180 seconds, i.e. 3 minutes.
258 The requests is aborted if no activity on the connection to the
260 server is observed for "timeout" seconds. This means that the time
261 it takes for the complete transaction and the request() method to
262 actually return might be longer.
263 $ua->ssl_opts
265 $ua->ssl_opts( $key )
266 $ua->ssl_opts( $key => $value )
267 Get/set the options for SSL connections. Without argument return
268 the list of options keys currently set. With a single argument
269 return the current value for the given option. With 2 arguments
270 set the option value and return the old. Setting an option to the
271 value "undef" removes this option.
272 The options that LWP relates to are:
274 "verify_hostname" => $bool
276 When TRUE LWP will for secure protocol schemes ensure it
277 connects to servers that have a valid certificate matching the
278 expected hostname. If FALSE no checks are made and you can't
279 be sure that you communicate with the expected peer. The no
280 checks behaviour was the default for libwww-perl-5.837 and
281 earlier releases.
282 This option is initialized from the
284 PERL_LWP_SSL_VERIFY_HOSTNAME environment variable. If this
285 envirionment variable isn't set; then "verify_hostname"
286 defaults to 0.
287 "SSL_ca_file" => $path
289 The path to a file containing Certificate Authority
290 certificates. A default setting for this option is provided by
291 checking the environment variables "PERL_LWP_SSL_CA_FILE" and
292 "HTTPS_CA_FILE" in order. Last resort value is built-in value
293 /etc/pki/tls/certs/ca-bundle.crt.
294 "SSL_ca_path" => $path
296 The path to a directory containing files containing Certificate
297 Authority certificates. A default setting for this option is
298 provided by checking the environment variables
299 "PERL_LWP_SSL_CA_PATH" and "HTTPS_CA_DIR" in order.
300 Other options can be set and are processed directly by the SSL
302 Socket implementation in use. See IO::Socket::SSL or Net::SSL for
303 details.
304 SSL Socket implementation can be selected by environment variable
306 "PERL_NET_HTTPS_SSL_SOCKET_CLASS". IO::Socket::SSL is preferred by
307 default.
308 Proxy attributes
310 The following methods set up when requests should be passed via a proxy
311 server.
312 $ua->proxy(\@schemes, $proxy_url)
314 $ua->proxy($scheme, $proxy_url)
315 Set/retrieve proxy URL for a scheme:
316 $ua->proxy(['http', 'ftp'], 'http://proxy.sn.no:8001/');
318 $ua->proxy('gopher', 'http://proxy.sn.no:8001/');
319 The first form specifies that the URL is to be used for proxying of
321 access methods listed in the list in the first method argument,
322 i.e. 'http' and 'ftp'.
323 The second form shows a shorthand form for specifying proxy URL for
325 a single access scheme.
326 $ua->no_proxy( $domain, ... )
328 Do not proxy requests to the given domains. Calling no_proxy
329 without any domains clears the list of domains. Eg:
330 $ua->no_proxy('localhost', 'example.com');
332 $ua->env_proxy
334 Load proxy settings from *_proxy environment variables. You might
335 specify proxies like this (sh-syntax):
336 gopher_proxy=http://proxy.my.place/
338 wais_proxy=http://proxy.my.place/
339 no_proxy="localhost,example.com"
340 export gopher_proxy wais_proxy no_proxy
341 csh or tcsh users should use the "setenv" command to define these
343 environment variables.
344 On systems with case insensitive environment variables there exists
346 a name clash between the CGI environment variables and the
347 "HTTP_PROXY" environment variable normally picked up by
348 env_proxy(). Because of this "HTTP_PROXY" is not honored for CGI
349 scripts. The "CGI_HTTP_PROXY" environment variable can be used
350 instead.
351 Handlers
353 Handlers are code that injected at various phases during the processing
354 of requests. The following methods are provided to manage the active
355 handlers:
356 $ua->add_handler( $phase => \&cb, %matchspec )
358 Add handler to be invoked in the given processing phase. For how
359 to specify %matchspec see "Matching" in HTTP::Config.
360 The possible values $phase and the corresponding callback
362 signatures are:
363 request_preprepare => sub { my($request, $ua, $h) = @_; ... }
365 The handler is called before the "request_prepare" and other
366 standard initialization of of the request. This can be used to
367 set up headers and attributes that the "request_prepare"
368 handler depends on. Proxy initialization should take place
369 here; but in general don't register handlers for this phase.
370 request_prepare => sub { my($request, $ua, $h) = @_; ... }
372 The handler is called before the request is sent and can modify
373 the request any way it see fit. This can for instance be used
374 to add certain headers to specific requests.
375 The method can assign a new request object to $_[0] to replace
377 the request that is sent fully.
378 The return value from the callback is ignored. If an
380 exceptions is raised it will abort the request and make the
381 request method return a "400 Bad request" response.
382 request_send => sub { my($request, $ua, $h) = @_; ... }
384 This handler get a chance of handling requests before it's sent
385 to the protocol handlers. It should return an HTTP::Response
386 object if it wishes to terminate the processing; otherwise it
387 should return nothing.
388 The "response_header" and "response_data" handlers will not be
390 invoked for this response, but the "response_done" will be.
391 response_header => sub { my($response, $ua, $h) = @_; ... }
393 This handler is called right after the response headers have
394 been received, but before any content data. The handler might
395 set up handlers for data and might croak to abort the request.
396 The handler might set the $response->{default_add_content}
398 value to control if any received data should be added to the
399 response object directly. This will initially be false if the
400 $ua->request() method was called with a ':content_filename' or
401 ':content_callbak' argument; otherwise true.
402 response_data => sub { my($response, $ua, $h, $data) = @_; ... }
404 This handlers is called for each chunk of data received for the
405 response. The handler might croak to abort the request.
406 This handler need to return a TRUE value to be called again for
408 subsequent chunks for the same request.
409 response_done => sub { my($response, $ua, $h) = @_; ... }
411 The handler is called after the response has been fully
412 received, but before any redirect handling is attempted. The
413 handler can be used to extract information or modify the
414 response.
415 response_redirect => sub { my($response, $ua, $h) = @_; ... }
417 The handler is called in $ua->request after "response_done".
418 If the handler return an HTTP::Request object we'll start over
419 with processing this request instead.
420 $ua->remove_handler( undef, %matchspec )
422 $ua->remove_handler( $phase, %matchspec )
423 Remove handlers that match the given %matchspec. If $phase is not
424 provided remove handlers from all phases.
425 Be careful as calling this function with %matchspec that is not not
427 specific enough can remove handlers not owned by you. It's
428 probably better to use the set_my_handler() method instead.
429 The removed handlers are returned.
431 $ua->set_my_handler( $phase, $cb, %matchspec )
433 Set handlers private to the executing subroutine. Works by
434 defaulting an "owner" field to the %matchhspec that holds the name
435 of the called subroutine. You might pass an explicit "owner" to
436 override this.
437 If $cb is passed as "undef", remove the handler.
439 $ua->get_my_handler( $phase, %matchspec )
441 $ua->get_my_handler( $phase, %matchspec, $init )
442 Will retrieve the matching handler as hash ref.
443 If $init is passed passed as a TRUE value, create and add the
445 handler if it's not found. If $init is a subroutine reference,
446 then it's called with the created handler hash as argument. This
447 sub might populate the hash with extra fields; especially the
448 callback. If $init is a hash reference, merge the hashes.
449 $ua->handlers( $phase, $request )
451 $ua->handlers( $phase, $response )
452 Returns the handlers that apply to the given request or response at
453 the given processing phase.
454
456 The methods described in this section are used to dispatch requests via
457 the user agent. The following request methods are provided:
458 $ua->get( $url )
460 $ua->get( $url , $field_name => $value, ... )
461 This method will dispatch a "GET" request on the given $url.
462 Further arguments can be given to initialize the headers of the
463 request. These are given as separate name/value pairs. The return
464 value is a response object. See HTTP::Response for a description
465 of the interface it provides.
466 There will still be a response object returned when LWP can't
468 connect to the server specified in the URL or when other failures
469 in protocol handlers occur. These internal responses use the
470 standard HTTP status codes, so the responses can't be
471 differentiated by testing the response status code alone. Error
472 responses that LWP generates internally will have the "Client-
473 Warning" header set to the value "Internal response". If you need
474 to differentiate these internal responses from responses that a
475 remote server actually generates, you need to test this header
476 value.
477 Fields names that start with ":" are special. These will not
479 initialize headers of the request but will determine how the
480 response content is treated. The following special field names are
481 recognized:
482 :content_file => $filename
484 :content_cb => \&callback
485 :read_size_hint => $bytes
486 If a $filename is provided with the ":content_file" option, then
488 the response content will be saved here instead of in the response
489 object. If a callback is provided with the ":content_cb" option
490 then this function will be called for each chunk of the response
491 content as it is received from the server. If neither of these
492 options are given, then the response content will accumulate in the
493 response object itself. This might not be suitable for very large
494 response bodies. Only one of ":content_file" or ":content_cb" can
495 be specified. The content of unsuccessful responses will always
496 accumulate in the response object itself, regardless of the
497 ":content_file" or ":content_cb" options passed in.
498 The ":read_size_hint" option is passed to the protocol module which
500 will try to read data from the server in chunks of this size. A
501 smaller value for the ":read_size_hint" will result in a higher
502 number of callback invocations.
503 The callback function is called with 3 arguments: a chunk of data,
505 a reference to the response object, and a reference to the protocol
506 object. The callback can abort the request by invoking die(). The
507 exception message will show up as the "X-Died" header field in the
508 response returned by the get() function.
509 $ua->head( $url )
511 $ua->head( $url , $field_name => $value, ... )
512 This method will dispatch a "HEAD" request on the given $url.
513 Otherwise it works like the get() method described above.
514 $ua->post( $url, \%form )
516 $ua->post( $url, \@form )
517 $ua->post( $url, \%form, $field_name => $value, ... )
518 $ua->post( $url, $field_name => $value,... Content => \%form )
519 $ua->post( $url, $field_name => $value,... Content => \@form )
520 $ua->post( $url, $field_name => $value,... Content => $content )
521 This method will dispatch a "POST" request on the given $url, with
522 %form or @form providing the key/value pairs for the fill-in form
523 content. Additional headers and content options are the same as for
524 the get() method.
525 This method will use the POST() function from
527 "HTTP::Request::Common" to build the request. See
528 HTTP::Request::Common for a details on how to pass form content and
529 other advanced features.
530 $ua->mirror( $url, $filename )
532 This method will get the document identified by $url and store it
533 in file called $filename. If the file already exists, then the
534 request will contain an "If-Modified-Since" header matching the
535 modification time of the file. If the document on the server has
536 not changed since this time, then nothing happens. If the document
537 has been updated, it will be downloaded again. The modification
538 time of the file will be forced to match that of the server.
539 The return value is the the response object.
541 $ua->request( $request )
543 $ua->request( $request, $content_file )
544 $ua->request( $request, $content_cb )
545 $ua->request( $request, $content_cb, $read_size_hint )
546 This method will dispatch the given $request object. Normally this
547 will be an instance of the "HTTP::Request" class, but any object
548 with a similar interface will do. The return value is a response
549 object. See HTTP::Request and HTTP::Response for a description of
550 the interface provided by these classes.
551 The request() method will process redirects and authentication
553 responses transparently. This means that it may actually send
554 several simple requests via the simple_request() method described
555 below.
556 The request methods described above; get(), head(), post() and
558 mirror(), will all dispatch the request they build via this method.
559 They are convenience methods that simply hides the creation of the
560 request object for you.
561 The $content_file, $content_cb and $read_size_hint all correspond
563 to options described with the get() method above.
564 You are allowed to use a CODE reference as "content" in the request
566 object passed in. The "content" function should return the content
567 when called. The content can be returned in chunks. The content
568 function will be invoked repeatedly until it return an empty string
569 to signal that there is no more content.
570 $ua->simple_request( $request )
572 $ua->simple_request( $request, $content_file )
573 $ua->simple_request( $request, $content_cb )
574 $ua->simple_request( $request, $content_cb, $read_size_hint )
575 This method dispatches a single request and returns the response
576 received. Arguments are the same as for request() described above.
577 The difference from request() is that simple_request() will not try
579 to handle redirects or authentication responses. The request()
580 method will in fact invoke this method for each simple request it
581 sends.
582 $ua->is_protocol_supported( $scheme )
584 You can use this method to test whether this user agent object
585 supports the specified "scheme". (The "scheme" might be a string
586 (like 'http' or 'ftp') or it might be an URI object reference.)
587 Whether a scheme is supported, is determined by the user agent's
589 "protocols_allowed" or "protocols_forbidden" lists (if any), and by
590 the capabilities of LWP. I.e., this will return TRUE only if LWP
591 supports this protocol and it's permitted for this particular
592 object.
593 Callback methods
595 The following methods will be invoked as requests are processed. These
596 methods are documented here because subclasses of "LWP::UserAgent"
597 might want to override their behaviour.
598 $ua->prepare_request( $request )
600 This method is invoked by simple_request(). Its task is to modify
601 the given $request object by setting up various headers based on
602 the attributes of the user agent. The return value should normally
603 be the $request object passed in. If a different request object is
604 returned it will be the one actually processed.
605 The headers affected by the base implementation are; "User-Agent",
607 "From", "Range" and "Cookie".
608 $ua->redirect_ok( $prospective_request, $response )
610 This method is called by request() before it tries to follow a
611 redirection to the request in $response. This should return a TRUE
612 value if this redirection is permissible. The $prospective_request
613 will be the request to be sent if this method returns TRUE.
614 The base implementation will return FALSE unless the method is in
616 the object's "requests_redirectable" list, FALSE if the proposed
617 redirection is to a "file://..." URL, and TRUE otherwise.
618 $ua->get_basic_credentials( $realm, $uri, $isproxy )
620 This is called by request() to retrieve credentials for documents
621 protected by Basic or Digest Authentication. The arguments passed
622 in is the $realm provided by the server, the $uri requested and a
623 boolean flag to indicate if this is authentication against a proxy
624 server.
625 The method should return a username and password. It should return
627 an empty list to abort the authentication resolution attempt.
628 Subclasses can override this method to prompt the user for the
629 information. An example of this can be found in "lwp-request"
630 program distributed with this library.
631 The base implementation simply checks a set of pre-stored member
633 variables, set up with the credentials() method.
634 $ua->progress( $status, $request_or_response )
636 This is called frequently as the response is received regardless of
637 how the content is processed. The method is called with $status
638 "begin" at the start of processing the request and with $state
639 "end" before the request method returns. In between these $status
640 will be the fraction of the response currently received or the
641 string "tick" if the fraction can't be calculated.
642 When $status is "begin" the second argument is the request object,
644 otherwise it is the response object.
645
647 See LWP for a complete overview of libwww-perl5. See lwpcook and the
648 scripts lwp-request and lwp-download for examples of usage.
649 See HTTP::Request and HTTP::Response for a description of the message
651 objects dispatched and received. See HTTP::Request::Common and
652 HTML::Form for other ways to build request objects.
653 See WWW::Mechanize and WWW::Search for examples of more specialized
655 user agents based on "LWP::UserAgent".
656
658 Copyright 1995-2009 Gisle Aas.
659 This library is free software; you can redistribute it and/or modify it
661 under the same terms as Perl itself.
662perl v5.10.1 2017-03-22 LWP::UserAgent(3)