Switch to SpeakEasy.net DSL

The Modular Manual Browser

Home Page
Manual: (Debian-5.0)
Apropos / Subsearch:
optional field

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

       LWP::UserAgent - Web user agent class

        require LWP::UserAgent;

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

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

        if ($response->is_success) {
            print $response->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 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() 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 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
              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 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("");                 # 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.  Example:


           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( $cookie_jar_obj )
           Get/set the cookie jar object to use.  The only requirement is that
           the cookie jar object must implement the extract_cookies($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

           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

             $ua->cookie_jar({ file => "$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.  Example:

             $ua->default_headers->push_header('Accept-Language' => "no, en");

       $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-Language' => "no, en");

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

       $ua->credentials( $netloc, $realm, $uname, $pass )
           Set the user name and password to be used for a realm.  It is often
           more useful to specialize the get_basic_credentials() method

           The $netloc 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->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 protocol names are case

           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)"

       $ua->requests_redirectable( \@requests )
           This reads or sets the object's list of request names that
           "$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->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

       $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', '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 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

       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

               :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->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

           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

       $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

       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

           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 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 v5.10.0                      2008-06-17               LWP::UserAgent(3pm)