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LWP::UserAgent(3pm) - phpMan

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



NAME
       LWP::UserAgent - Web user agent class

SYNOPSIS
        require LWP::UserAgent;

        my $ua = LWP::UserAgent->new;
        $ua->timeout(10);
        $ua->env_proxy;

        my $response = $ua->get('http://search.cpan.org/');

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

DESCRIPTION
       The "LWP::UserAgent" is a class implementing a web user agent.  "LWP::UserAgent" objects
       can be used to dispatch web requests.

       In normal use the application creates an "LWP::UserAgent" object, and then configures it
       with values for timeouts, proxies, name, etc. It then creates an instance of
       "HTTP::Request" for the request that needs to be performed. 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(), post(), put() and delete().  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.

CONSTRUCTOR METHODS
       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 provided 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
              local_address           undef
              ssl_opts                { verify_hostname => 1 }
              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 "env_proxy" isn't provided the
           "PERL_LWP_ENV_PROXY" environment variable controls if env_proxy() is called during
           initialization.  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.

       $ua->clone
           Returns a copy of the LWP::UserAgent object.

ATTRIBUTES
       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 attribute 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
       $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 below).

           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 separated by the "/" character.  Examples are:

             $ua->agent('Checkbot/0.4 ' . $ua->_agent);
             $ua->agent('Checkbot/0.4 ');    # same as above
             $ua->agent('Mozilla/5.0');
             $ua->agent("");                 # don't identify

       $ua->_agent
           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
       $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.  Example:

             $ua->from('gaas AT cpan.org');

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

       $ua->cookie_jar
       $ua->cookie_jar( $cookie_jar_obj )
           Get/set the cookie jar object to use.  The only requirement is that the cookie jar
           object must implement the extract_cookies($response) and add_cookie_header($request)
           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
       $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
       $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("www.example.com:80", "Some Realm", "foo", "secret");

       $ua->local_address
       $ua->local_address( $address )
           Get/set the local interface to bind to for network connections.  The interface can be
           specified as a hostname or an IP address.  This value is passed as the "LocalAddr"
           argument to IO::Socket::INET.

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

       $ua->max_redirect
       $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
       $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
       $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
       $ua->protocols_forbidden( \@protocols )
           This reads (or sets) this user agent's list of protocols that the request method will
           not allow. The protocol 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 error.

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

       $ua->requests_redirectable
       $ua->requests_redirectable( \@requests )
           This reads or sets the object's list of request names that "$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
       $ua->show_progress( $boolean )
           Get/set a value indicating whether a progress bar should be displayed on the terminal
           as requests are processed. The default is FALSE.

       $ua->timeout
       $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.

       $ua->ssl_opts
       $ua->ssl_opts( $key )
       $ua->ssl_opts( $key => $value )
           Get/set the options for SSL connections.  Without argument return the list of options
           keys currently set.  With a single argument return the current value for the given
           option.  With 2 arguments set the option value and return the old.  Setting an option
           to the value "undef" removes this option.

           The options that LWP relates to are:

           "verify_hostname" => $bool
               When TRUE LWP will for secure protocol schemes ensure it connects to servers that
               have a valid certificate matching the expected hostname.  If FALSE no checks are
               made and you can't be sure that you communicate with the expected peer.  The no
               checks behaviour was the default for libwww-perl-5.837 and earlier releases.

               This option is initialized from the PERL_LWP_SSL_VERIFY_HOSTNAME environment
               variable.  If this environment variable isn't set; then "verify_hostname" defaults
               to 1.

           "SSL_ca_file" => $path
               The path to a file containing Certificate Authority certificates.  A default
               setting for this option is provided by checking the environment variables
               "PERL_LWP_SSL_CA_FILE" and "HTTPS_CA_FILE" in order.

           "SSL_ca_path" => $path
               The path to a directory containing files containing Certificate Authority
               certificates.  A default setting for this option is provided by checking the
               environment variables "PERL_LWP_SSL_CA_PATH" and "HTTPS_CA_DIR" in order.

           Other options can be set and are processed directly by the SSL Socket implementation
           in use.  See IO::Socket::SSL or Net::SSL for details.

           The libwww-perl core no longer bundles protocol plugins for SSL.  You will need to
           install LWP::Protocol::https separately to enable support for processing https-URLs.

   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'], 'http://proxy.sn.no:8001/');
            $ua->proxy('gopher', 'http://proxy.sn.no:8001/');

           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', 'example.com');

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

             gopher_proxy=http://proxy.my.place/
             wais_proxy=http://proxy.my.place/
             no_proxy="localhost,example.com"
             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 environment 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 instead.

   Handlers
       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 HTTP::Config.

           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 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 exception 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 gets a chance of handling requests before they're sent to the
               protocol handlers.  It should return an HTTP::Response object if it wishes to
               terminate the processing; otherwise it should return nothing.

               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_file or
               $content_cb argument; otherwise true.

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

               This handler needs 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
               returns 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 phases.

           Be careful as calling this function with %matchspec that is 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 %matchspec 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 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.

REQUEST METHODS
       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.

           There will still be a response object returned when LWP can't connect to the server
           specified in the URL or when other failures in protocol handlers occur.  These
           internal responses use the standard HTTP status codes, so the responses can't be
           differentiated by testing the response status code alone.  Error responses that LWP
           generates internally will have the "Client-Warning" header set to the value "Internal
           response".  If you need to differentiate these internal responses from responses that
           a remote server actually generates, you need to test this header value.

           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 function 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 callback 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() method.

           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->put( $url, \%form )
       $ua->put( $url, \@form )
       $ua->put( $url, \%form, $field_name => $value, ... )
       $ua->put( $url, $field_name => $value,... Content => \%form )
       $ua->put( $url, $field_name => $value,... Content => \@form )
       $ua->put( $url, $field_name => $value,... Content => $content )
           This method will dispatch a "PUT" 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() method.

           This method will use the PUT() 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->delete( $url )
       $ua->delete( $url, $field_name => $value, ... )
           This method will dispatch a "DELETE" request on the given $url.  Additional headers
           and content options are the same as for the get() method.

           This method will use the DELETE() 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 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" function 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_online
           Tries to determine if you have access to the Internet.  Returns TRUE if the built-in
           heuristics determine that the user agent is able to access the Internet (over HTTP).
           See also LWP::Online.

       $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_forbidden" 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 subclasses 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 Authentication.  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 information. 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() method.

       $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 ALSO
       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
       Copyright 1995-2009 Gisle Aas.

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



perl v5.18.2                                2014-07-26                        LWP::UserAgent(3pm)


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