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LWP::UserAgent(3)     User Contributed Perl Documentation    LWP::UserAgent(3)

       LWP::UserAgent - Web user agent class

        require LWP::UserAgent;

        my $ua = LWP::UserAgent->new;

        my $response = $ua->get('');

        if ($response->is_success) {
            print $response->decoded_content;  # or whatever
        else {
            die $response->status_line;

       The "LWP::UserAgent" is a class implementing a web user agent.  "LWP::UserAgent" objects can be used to dis-
       patch web requests.

       In normal use the application creates an "LWP::UserAgent" object, and then configures it with values for time-
       outs, proxies, name, etc. It then creates an instance of "HTTP::Request" for the request that needs to be per-
       formed. This request is then passed to one of the request method the UserAgent, which dispatches it using the
       relevant protocol, and returns a "HTTP::Response" object.  There are convenience methods for sending the most
       common request types: get(), head() and post().  When using these methods then the creation of the request
       object is hidden as shown in the synopsis above.

       The basic approach of the library is to use HTTP style communication for all protocol schemes.  This means that
       you will construct "HTTP::Request" objects and receive "HTTP::Response" objects even for non-HTTP resources
       like gopher and ftp.  In order to achieve even more similarity to HTTP style communications, gopher menus and
       file directories are converted to HTML documents.

       The following constructor methods are available:

       $ua = LWP::UserAgent->new( %options )
           This method constructs a new "LWP::UserAgent" object and returns it.  Key/value pair arguments may be pro-
           vided to set up the initial state.  The following options correspond to attribute methods described below:

              KEY                     DEFAULT
              -----------             --------------------
              agent                   "libwww-perl/#.###"
              from                    undef
              conn_cache              undef
              cookie_jar              undef
              default_headers         HTTP::Headers->new
              max_size                undef
              max_redirect            7
              parse_head              1
              protocols_allowed       undef
              protocols_forbidden     undef
              requests_redirectable   ['GET', 'HEAD']
              timeout                 180

           The following additional options are also accepted: If the "env_proxy" option is passed in with a TRUE
           value, then proxy settings are read from environment variables (see env_proxy() method below).  If the
           "keep_alive" option is passed in, then a "LWP::ConnCache" is set up (see conn_cache() method below).  The
           "keep_alive" value is passed on as the "total_capacity" for the connection cache.

           Returns a copy of the LWP::UserAgent object.

       The settings of the configuration attributes modify the behaviour of the "LWP::UserAgent" when it dispatches
       requests.  Most of these can also be initialized by options passed to the constructor method.

       The following attributes methods are provided.  The attribute value is left unchanged if no argument is given.
       The return value from each method is the old attribute value.

       $ua->agent( $product_id )
           Get/set the product token that is used to identify the user agent on the network.  The agent value is sent
           as the "User-Agent" header in the requests.  The default is the string returned by the _agent() method (see

           If the $product_id ends with space then the _agent() string is appended to it.

           The user agent string should be one or more simple product identifiers with an optional version number sep-
           arated by the "/" character.  Examples are:

             $ua->agent('Checkbot/0.4 ' . $ua->_agent);
             $ua->agent('Checkbot/0.4 ');    # same as above
             $ua->agent("");                 # don't identify

           Returns the default agent identifier.  This is a string of the form "libwww-perl/#.###", where "#.###" is
           substituted with the version number of this library.

       $ua->from( $email_address )
           Get/set the e-mail address for the human user who controls the requesting user agent.  The address should
           be machine-usable, as defined in RFC 822.  The "from" value is send as the "From" header in the requests.


           The default is to not send a "From" header.  See the default_headers() method for the more general inter-
           face that allow any header to be defaulted.

       $ua->cookie_jar( $cookie_jar_obj )
           Get/set the cookie jar object to use.  The only requirement is that the cookie jar object must implement
           the extract_cookies($request) and add_cookie_header($response) methods.  These methods will then be invoked
           by the user agent as requests are sent and responses are received.  Normally this will be a "HTTP::Cookies"
           object or some subclass.

           The default is to have no cookie_jar, i.e. never automatically add "Cookie" headers to the requests.

           Shortcut: If a reference to a plain hash is passed in as the $cookie_jar_object, then it is replaced with
           an instance of "HTTP::Cookies" that is initialized based on the hash.  This form also automatically loads
           the "HTTP::Cookies" module.  It means that:

             $ua->cookie_jar({ file => "$ENV{HOME}/.cookies.txt" });

           is really just a shortcut for:

             require HTTP::Cookies;
             $ua->cookie_jar(HTTP::Cookies->new(file => "$ENV{HOME}/.cookies.txt"));

       $ua->default_headers( $headers_obj )
           Get/set the headers object that will provide default header values for any requests sent.  By default this
           will be an empty "HTTP::Headers" object.

       $ua->default_header( $field )
       $ua->default_header( $field => $value )
           This is just a short-cut for $ua->default_headers->header( $field => $value ). Example:

             $ua->default_header('Accept-Encoding' => scalar HTTP::Message::decodable());
             $ua->default_header('Accept-Language' => "no, en");

       $ua->conn_cache( $cache_obj )
           Get/set the "LWP::ConnCache" object to use.  See LWP::ConnCache for details.

       $ua->credentials( $netloc, $realm )
       $ua->credentials( $netloc, $realm, $uname, $pass )
           Get/set the user name and password to be used for a realm.

           The $netloc is a string of the form "<host>:<port>".  The username and password will only be passed to this
           server.  Example:

             $ua->credentials("", "Some Realm", "foo", "secret");

       $ua->max_size( $bytes )
           Get/set the size limit for response content.  The default is "undef", which means that there is no limit.
           If the returned response content is only partial, because the size limit was exceeded, then a
           "Client-Aborted" header will be added to the response.  The content might end up longer than "max_size" as
           we abort once appending a chunk of data makes the length exceed the limit.  The "Content-Length" header, if
           present, will indicate the length of the full content and will normally not be the same as

       $ua->max_redirect( $n )
           This reads or sets the object's limit of how many times it will obey redirection responses in a given
           request cycle.

           By default, the value is 7. This means that if you call request() method and the response is a redirect
           elsewhere which is in turn a redirect, and so on seven times, then LWP gives up after that seventh request.

       $ua->parse_head( $boolean )
           Get/set a value indicating whether we should initialize response headers from the <head> section of HTML
           documents. The default is TRUE.  Do not turn this off, unless you know what you are doing.

       $ua->protocols_allowed( \@protocols )
           This reads (or sets) this user agent's list of protocols that the request methods will exclusively allow.
           The protocol names are case insensitive.

           For example: "$ua->protocols_allowed( [ 'http', 'https'] );" means that this user agent will allow only
           those protocols, and attempts to use this user agent to access URLs with any other schemes (like
           "ftp://...") will result in a 500 error.

           To delete the list, call: "$ua->protocols_allowed(undef)"

           By default, an object has neither a "protocols_allowed" list, nor a "protocols_forbidden" list.

           Note that having a "protocols_allowed" list causes any "protocols_forbidden" list to be ignored.

       $ua->protocols_forbidden( \@protocols )
           This reads (or sets) this user agent's list of protocols that the request method will not allow. The proto-
           col names are case insensitive.

           For example: "$ua->protocols_forbidden( [ 'file', 'mailto'] );" means that this user agent will not allow
           those protocols, and attempts to use this user agent to access URLs with those schemes will result in a 500

           To delete the list, call: "$ua->protocols_forbidden(undef)"

       $ua->requests_redirectable( \@requests )
           This reads or sets the object's list of request names that "$ua->redirect_ok(...)" will allow redirection
           for.  By default, this is "['GET', 'HEAD']", as per RFC 2616.  To change to include 'POST', consider:

              push @{ $ua->requests_redirectable }, 'POST';

       $ua->show_progress( $boolean )
           Get/set a value indicating whether a progress bar should be displayed on on the terminal as requests are
           processed. The default is FALSE.

       $ua->timeout( $secs )
           Get/set the timeout value in seconds. The default timeout() value is 180 seconds, i.e. 3 minutes.

           The requests is aborted if no activity on the connection to the server is observed for "timeout" seconds.
           This means that the time it takes for the complete transaction and the request() method to actually return
           might be longer.

       Proxy attributes

       The following methods set up when requests should be passed via a proxy server.

       $ua->proxy(\@schemes, $proxy_url)
       $ua->proxy($scheme, $proxy_url)
           Set/retrieve proxy URL for a scheme:

            $ua->proxy(['http', 'ftp'], '');
            $ua->proxy('gopher', '');

           The first form specifies that the URL is to be used for proxying of access methods listed in the list in
           the first method argument, i.e. 'http' and 'ftp'.

           The second form shows a shorthand form for specifying proxy URL for a single access scheme.

       $ua->no_proxy( $domain, ... )
           Do not proxy requests to the given domains.  Calling no_proxy without any domains clears the list of
           domains. Eg:

            $ua->no_proxy('localhost', 'no', ...);

           Load proxy settings from *_proxy environment variables.  You might specify proxies like this (sh-syntax):

             export gopher_proxy wais_proxy no_proxy

           csh or tcsh users should use the "setenv" command to define these environment variables.

           On systems with case insensitive environment variables there exists a name clash between the CGI environ-
           ment variables and the "HTTP_PROXY" environment variable normally picked up by env_proxy().  Because of
           this "HTTP_PROXY" is not honored for CGI scripts.  The "CGI_HTTP_PROXY" environment variable can be used


       Handlers are code that injected at various phases during the processing of requests.  The following methods are
       provided to manage the active handlers:

       $ua->add_handler( $phase => \&cb, %matchspec )
           Add handler to be invoked in the given processing phase.  For how to specify %matchspec see "Matching" in

           The possible values $phase and the corresponding callback signatures are:

           request_preprepare => sub { my($request, $ua, $h) = @_; ... }
               The handler is called before the "request_prepare" and other standard initialization of of the request.
               This can be used to set up headers and attributes that the "request_prepare" handler depends on.  Proxy
               initialization should take place here; but in general don't register handlers for this phase.

           request_prepare => sub { my($request, $ua, $h) = @_; ... }
               The handler is called before the request is sent and can modify the request any way it see fit.  This
               can for instance be used to add certain headers to specific requests.

               The method can assign a new request object to $_[0] to replace the request that is sent fully.

               The return value from the callback is ignored.  If an exceptions is raised it will abort the request
               and make the request method return a "400 Bad request" response.

           request_send => sub { my($request, $ua, $h) = @_; ... }
               This handler get a chance of handling requests before it's sent to the protocol handlers.  It should
               return an HTTP::Response object if it wishes to terminate the processing; otherwise it should return

               The "response_header" and "response_data" handlers will not be invoked for this response, but the
               "response_done" will be.

           response_header => sub { my($response, $ua, $h) = @_; ... }
               This handler is called right after the response headers have been received, but before any content
               data.  The handler might set up handlers for data and might croak to abort the request.

               The handler might set the $response->{default_add_content} value to control if any received data should
               be added to the response object directly.  This will initially be false if the $ua->request() method
               was called with a ':content_filename' or ':content_callbak' argument; otherwise true.

           response_data => sub { my($response, $ua, $h, $data) = @_; ... }
               This handlers is called for each chunk of data received for the response.  The handler might croak to
               abort the request.

               This handler need to return a TRUE value to be called again for subsequent chunks for the same request.

           response_done => sub { my($response, $ua, $h) = @_; ... }
               The handler is called after the response has been fully received, but before any redirect handling is
               attempted.  The handler can be used to extract information or modify the response.

           response_redirect => sub { my($response, $ua, $h) = @_; ... }
               The handler is called in $ua->request after "response_done".  If the handler return an HTTP::Request
               object we'll start over with processing this request instead.

       $ua->remove_handler( undef, %matchspec )
       $ua->remove_handler( $phase, %matchspec )
           Remove handlers that match the given %matchspec.  If $phase is not provided remove handlers from all

           Be careful as calling this function with %matchspec that is not not specific enough can remove handlers not
           owned by you.  It's probably better to use the set_my_handler() method instead.

           The removed handlers are returned.

       $ua->set_my_handler( $phase, $cb, %matchspec )
           Set handlers private to the executing subroutine.  Works by defaulting an "owner" field to the %matchhspec
           that holds the name of the called subroutine.  You might pass an explicit "owner" to override this.

           If $cb is passed as "undef", remove the handler.

       $ua->get_my_handler( $phase, %matchspec )
       $ua->get_my_handler( $phase, %matchspec, $init )
           Will retrieve the matching handler as hash ref.

           If $init is passed passed as a TRUE value, create and add the handler if it's not found.  If $init is a
           subroutine reference, then it's called with the created handler hash as argument.  This sub might populate
           the hash with extra fields; especially the callback.  If $init is a hash reference, merge the hashes.

       $ua->handlers( $phase, $request )
       $ua->handlers( $phase, $response )
           Returns the handlers that apply to the given request or response at the given processing phase.

       The methods described in this section are used to dispatch requests via the user agent.  The following request
       methods are provided:

       $ua->get( $url )
       $ua->get( $url , $field_name => $value, ... )
           This method will dispatch a "GET" request on the given $url.  Further arguments can be given to initialize
           the headers of the request. These are given as separate name/value pairs.  The return value is a response
           object.  See HTTP::Response for a description of the interface it provides.

           Fields names that start with ":" are special.  These will not initialize headers of the request but will
           determine how the response content is treated.  The following special field names are recognized:

               :content_file   => $filename
               :content_cb     => \&callback
               :read_size_hint => $bytes

           If a $filename is provided with the ":content_file" option, then the response content will be saved here
           instead of in the response object.  If a callback is provided with the ":content_cb" option then this func-
           tion will be called for each chunk of the response content as it is received from the server.  If neither
           of these options are given, then the response content will accumulate in the response object itself.  This
           might not be suitable for very large response bodies.  Only one of ":content_file" or ":content_cb" can be
           specified.  The content of unsuccessful responses will always accumulate in the response object itself,
           regardless of the ":content_file" or ":content_cb" options passed in.

           The ":read_size_hint" option is passed to the protocol module which will try to read data from the server
           in chunks of this size.  A smaller value for the ":read_size_hint" will result in a higher number of call-
           back invocations.

           The callback function is called with 3 arguments: a chunk of data, a reference to the response object, and
           a reference to the protocol object.  The callback can abort the request by invoking die().  The exception
           message will show up as the "X-Died" header field in the response returned by the get() function.

       $ua->head( $url )
       $ua->head( $url , $field_name => $value, ... )
           This method will dispatch a "HEAD" request on the given $url.  Otherwise it works like the get() method
           described above.

       $ua->post( $url, \%form )
       $ua->post( $url, \@form )
       $ua->post( $url, \%form, $field_name => $value, ... )
       $ua->post( $url, $field_name => $value,... Content => \%form )
       $ua->post( $url, $field_name => $value,... Content => \@form )
       $ua->post( $url, $field_name => $value,... Content => $content )
           This method will dispatch a "POST" request on the given $url, with %form or @form providing the key/value
           pairs for the fill-in form content. Additional headers and content options are the same as for the get()

           This method will use the POST() function from "HTTP::Request::Common" to build the request.  See
           HTTP::Request::Common for a details on how to pass form content and other advanced features.

       $ua->mirror( $url, $filename )
           This method will get the document identified by $url and store it in file called $filename.  If the file
           already exists, then the request will contain an "If-Modified-Since" header matching the modification time
           of the file.  If the document on the server has not changed since this time, then nothing happens.  If the
           document has been updated, it will be downloaded again.  The modification time of the file will be forced
           to match that of the server.

           The return value is the the response object.

       $ua->request( $request )
       $ua->request( $request, $content_file )
       $ua->request( $request, $content_cb )
       $ua->request( $request, $content_cb, $read_size_hint )
           This method will dispatch the given $request object.  Normally this will be an instance of the
           "HTTP::Request" class, but any object with a similar interface will do.  The return value is a response
           object.  See HTTP::Request and HTTP::Response for a description of the interface provided by these classes.

           The request() method will process redirects and authentication responses transparently.  This means that it
           may actually send several simple requests via the simple_request() method described below.

           The request methods described above; get(), head(), post() and mirror(), will all dispatch the request they
           build via this method.  They are convenience methods that simply hides the creation of the request object
           for you.

           The $content_file, $content_cb and $read_size_hint all correspond to options described with the get()
           method above.

           You are allowed to use a CODE reference as "content" in the request object passed in.  The "content" func-
           tion should return the content when called.  The content can be returned in chunks.  The content function
           will be invoked repeatedly until it return an empty string to signal that there is no more content.

       $ua->simple_request( $request )
       $ua->simple_request( $request, $content_file )
       $ua->simple_request( $request, $content_cb )
       $ua->simple_request( $request, $content_cb, $read_size_hint )
           This method dispatches a single request and returns the response received.  Arguments are the same as for
           request() described above.

           The difference from request() is that simple_request() will not try to handle redirects or authentication
           responses.  The request() method will in fact invoke this method for each simple request it sends.

       $ua->is_protocol_supported( $scheme )
           You can use this method to test whether this user agent object supports the specified "scheme".  (The
           "scheme" might be a string (like 'http' or 'ftp') or it might be an URI object reference.)

           Whether a scheme is supported, is determined by the user agent's "protocols_allowed" or "protocols_forbid-
           den" lists (if any), and by the capabilities of LWP.  I.e., this will return TRUE only if LWP supports this
           protocol and it's permitted for this particular object.

       Callback methods

       The following methods will be invoked as requests are processed. These methods are documented here because sub-
       classes of "LWP::UserAgent" might want to override their behaviour.

       $ua->prepare_request( $request )
           This method is invoked by simple_request().  Its task is to modify the given $request object by setting up
           various headers based on the attributes of the user agent. The return value should normally be the $request
           object passed in.  If a different request object is returned it will be the one actually processed.

           The headers affected by the base implementation are; "User-Agent", "From", "Range" and "Cookie".

       $ua->redirect_ok( $prospective_request, $response )
           This method is called by request() before it tries to follow a redirection to the request in $response.
           This should return a TRUE value if this redirection is permissible.  The $prospective_request will be the
           request to be sent if this method returns TRUE.

           The base implementation will return FALSE unless the method is in the object's "requests_redirectable"
           list, FALSE if the proposed redirection is to a "file://..."  URL, and TRUE otherwise.

       $ua->get_basic_credentials( $realm, $uri, $isproxy )
           This is called by request() to retrieve credentials for documents protected by Basic or Digest Authentica-
           tion.  The arguments passed in is the $realm provided by the server, the $uri requested and a boolean flag
           to indicate if this is authentication against a proxy server.

           The method should return a username and password.  It should return an empty list to abort the
           authentication resolution attempt.  Subclasses can override this method to prompt the user for the informa-
           tion. An example of this can be found in "lwp-request" program distributed with this library.

           The base implementation simply checks a set of pre-stored member variables, set up with the credentials()

       $ua->progress( $status, $request_or_response )
           This is called frequently as the response is received regardless of how the content is processed.  The
           method is called with $status "begin" at the start of processing the request and with $state "end" before
           the request method returns.  In between these $status will be the fraction of the response currently
           received or the string "tick" if the fraction can't be calculated.

           When $status is "begin" the second argument is the request object, otherwise it is the response object.

       See LWP for a complete overview of libwww-perl5.  See lwpcook and the scripts lwp-request and lwp-download for
       examples of usage.

       See HTTP::Request and HTTP::Response for a description of the message objects dispatched and received.  See
       HTTP::Request::Common and HTML::Form for other ways to build request objects.

       See WWW::Mechanize and WWW::Search for examples of more specialized user agents based on "LWP::UserAgent".

       Copyright 1995-2008 Gisle Aas.

       This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

perl v5.8.8                       2008-12-05                 LWP::UserAgent(3)