LWP::UserAgent(3) User Contributed Perl Documentation LWP::UserAgent(3)
NAME
LWP::UserAgent - Web user agent class
SYNOPSIS
use strict;
use warnings;
use LWP::UserAgent ();
my $ua = LWP::UserAgent->new(timeout => 10);
$ua->env_proxy;
my $response = $ua->get('http://example.com');
if ($response->is_success) {
print $response->decoded_content;
}
else {
die $response->status_line;
}
Extra layers of security (note the "cookie_jar" and
"protocols_allowed"):
use strict;
use warnings;
use HTTP::CookieJar::LWP ();
use LWP::UserAgent ();
my $jar = HTTP::CookieJar::LWP->new;
my $ua = LWP::UserAgent->new(
cookie_jar => $jar,
protocols_allowed => ['http', 'https'],
timeout => 10,
);
$ua->env_proxy;
my $response = $ua->get('http://example.com');
if ($response->is_success) {
print $response->decoded_content;
}
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" in LWP::UserAgent, "head"
in LWP::UserAgent, "post" in LWP::UserAgent, "put" in LWP::UserAgent
and "delete" in LWP::UserAgent. When using these methods, 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:
clone
my $ua2 = $ua->clone;
Returns a copy of the LWP::UserAgent object.
CAVEAT: Please be aware that the clone method does not copy or clone
your "cookie_jar" attribute. Due to the limited restrictions on what
can be used for your cookie jar, there is no way to clone the
attribute. The "cookie_jar" attribute will be "undef" in the new object
instance.
new
my $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/#.###"
conn_cache undef
cookie_jar undef
cookie_jar_class HTTP::Cookies
default_headers HTTP::Headers->new
from undef
local_address undef
max_redirect 7
max_size undef
no_proxy []
parse_head 1
protocols_allowed undef
protocols_forbidden undef
proxy {}
requests_redirectable ['GET', 'HEAD']
send_te 1
show_progress undef
ssl_opts { verify_hostname => 1 }
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" in LWP::UserAgent). If
"env_proxy" isn't provided, the "PERL_LWP_ENV_PROXY" environment
variable controls if "env_proxy" in LWP::UserAgent is called during
initialization. If the "keep_alive" option value is defined and non-
zero, then an "LWP::ConnCache" is set up (see "conn_cache" in
LWP::UserAgent). The "keep_alive" value is passed on as the
"total_capacity" for the connection cache.
"proxy" must be set as an arrayref of key/value pairs. "no_proxy" takes
an arrayref of domains.
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.
agent
my $agent = $ua->agent;
$ua->agent('Checkbot/0.4 '); # append the default to the end
$ua->agent('Mozilla/5.0');
$ua->agent(""); # don't identify
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 a string of the form "libwww-perl/#.###", where "#.###"
is substituted with the version number of this library.
If the provided string ends with space, the default "libwww-perl/#.###"
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.
conn_cache
my $cache_obj = $ua->conn_cache;
$ua->conn_cache( $cache_obj );
Get/set the LWP::ConnCache object to use. See LWP::ConnCache for
details.
cookie_jar
my $jar = $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. You are, however, encouraged to use HTTP::CookieJar::LWP
instead. See "BEST PRACTICES" for more information.
use HTTP::CookieJar::LWP ();
my $jar = HTTP::CookieJar::LWP->new;
my $ua = LWP::UserAgent->new( cookie_jar => $jar );
# or after object creation
$ua->cookie_jar( $cookie_jar );
The default is to have no cookie jar, i.e. never automatically add
"Cookie" headers to the requests.
If $jar contains an unblessed hash reference, a new cookie jar object
is created for you automatically. The object is of the class set with
the "cookie_jar_class" constructor argument, which defaults to
HTTP::Cookies.
$ua->cookie_jar({ file => "$ENV{HOME}/.cookies.txt" });
is really just a shortcut for:
require HTTP::Cookies;
$ua->cookie_jar(HTTP::Cookies->new(file => "$ENV{HOME}/.cookies.txt"));
As described above and in "BEST PRACTICES", you should set
"cookie_jar_class" to "HTTP::CookieJar::LWP" to get a safer cookie jar.
my $ua = LWP::UserAgent->new( cookie_jar_class => 'HTTP::CookieJar::LWP' );
$ua->cookie_jar({}); # HTTP::CookieJar::LWP takes no args
These can also be combined into the constructor, so a jar is created at
instantiation.
my $ua = LWP::UserAgent->new(
cookie_jar_class => 'HTTP::CookieJar::LWP',
cookie_jar => {},
);
credentials
my $creds = $ua->credentials();
$ua->credentials( $netloc, $realm );
$ua->credentials( $netloc, $realm, $uname, $pass );
$ua->credentials("www.example.com:80", "Some Realm", "foo", "secret");
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.
default_header
$ua->default_header( $field );
$ua->default_header( $field => $value );
$ua->default_header('Accept-Encoding' => scalar HTTP::Message::decodable());
$ua->default_header('Accept-Language' => "no, en");
This is just a shortcut for "$ua->default_headers->header( $field =>
$value )".
default_headers
my $headers = $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.
from
my $from = $ua->from;
$ua->from('foo@bar.com');
Get/set the email address for the human user who controls the
requesting user agent. The address should be machine-usable, as
defined in RFC2822 <https://tools.ietf.org/html/rfc2822>. The "from"
value is sent as the "From" header in the requests.
The default is to not send a "From" header. See "default_headers" in
LWP::UserAgent for the more general interface that allow any header to
be defaulted.
local_address
my $address = $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.
max_redirect
my $max = $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" in
LWP::UserAgent 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.
max_size
my $size = $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)".
parse_head
my $bool = $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.
protocols_allowed
my $aref = $ua->protocols_allowed; # get allowed protocols
$ua->protocols_allowed( \@protocols ); # allow ONLY these
$ua->protocols_allowed(undef); # delete the list
$ua->protocols_allowed(['http',]); # ONLY allow http
By default, an object has neither a "protocols_allowed" list, nor a
"protocols_forbidden" in LWP::UserAgent list.
This reads (or sets) this user agent's list of protocols that the
request methods will exclusively allow. The protocol names are case
insensitive.
For example: "$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.
Note that having a "protocols_allowed" list causes any
"protocols_forbidden" in LWP::UserAgent list to be ignored.
protocols_forbidden
my $aref = $ua->protocols_forbidden; # get the forbidden list
$ua->protocols_forbidden(\@protocols); # do not allow these
$ua->protocols_forbidden(['http',]); # All http reqs get a 500
$ua->protocols_forbidden(undef); # delete the list
This reads (or sets) this user agent's list of protocols that the
request method will not allow. The protocol names are case insensitive.
For example: "$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.
requests_redirectable
my $aref = $ua->requests_redirectable;
$ua->requests_redirectable( \@requests );
$ua->requests_redirectable(['GET', 'HEAD',]); # the default
This reads or sets the object's list of request names that
"redirect_ok" in LWP::UserAgent will allow redirection for. By default,
this is "['GET', 'HEAD']", as per RFC 2616
<https://tools.ietf.org/html/rfc2616>. To change to include "POST",
consider:
push @{ $ua->requests_redirectable }, 'POST';
send_te
my $bool = $ua->send_te;
$ua->send_te( $boolean );
If true, will send a "TE" header along with the request. The default is
true. Set it to false to disable the "TE" header for systems who can't
handle it.
show_progress
my $bool = $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.
ssl_opts
my @keys = $ua->ssl_opts;
my $val = $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" => $bool
When TRUE LWP will for secure protocol schemes ensure it connects
to servers that have a valid certificate matching the expected
hostname. If FALSE no checks are made and you can't be sure that
you communicate with the expected peer. The no checks behaviour
was the default for libwww-perl-5.837 and earlier releases.
This option is initialized from the "PERL_LWP_SSL_VERIFY_HOSTNAME"
environment variable. If this environment variable isn't set; then
"verify_hostname" defaults to 1.
Please note that that recently the overall effect of this option
with regards to SSL handling has changed. As of version 6.11 of
LWP::Protocol::https, which is an external module, SSL certificate
verification was harmonized to behave in sync with IO::Socket::SSL.
With this change, setting this option no longer disables all SSL
certificate verification, only the hostname checks. To disable all
verification, use the "SSL_verify_mode" option in the "ssl_opts"
attribute. For example: "$ua-"ssl_opts(SSL_verify_mode =>
IO::Socket::SSL::SSL_VERIFY_NONE);>
"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.
timeout
my $secs = $ua->timeout;
$ua->timeout( $secs );
Get/set the timeout value in seconds. The default value is 180 seconds,
i.e. 3 minutes.
The request 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" in LWP::UserAgent method
to actually return might be longer.
When a request times out, a response object is still returned. The
response will have a standard HTTP Status Code (500). This response
will have the "Client-Warning" header set to the value of "Internal
response". See the "get" in LWP::UserAgent method description below
for further details.
PROXY ATTRIBUTES
The following methods set up when requests should be passed via a proxy
server.
env_proxy
$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.
no_proxy
$ua->no_proxy( @domains );
$ua->no_proxy('localhost', 'example.com');
$ua->no_proxy(); # clear the list
Do not proxy requests to the given domains, including subdomains.
Calling "no_proxy" without any domains clears the list of domains.
proxy
$ua->proxy(\@schemes, $proxy_url)
$ua->proxy(['http', 'ftp'], 'http://proxy.sn.no:8001/');
# For a single scheme:
$ua->proxy($scheme, $proxy_url)
$ua->proxy('gopher', 'http://proxy.sn.no:8001/');
# To set multiple proxies at once:
$ua->proxy([
ftp => 'http://ftp.example.com:8001/',
[ 'http', 'https' ] => 'http://http.example.com:8001/',
]);
Set/retrieve proxy URL for a scheme.
The first form specifies that the URL is to be used as a proxy for
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.
The third form demonstrates setting multiple proxies at once. This is
also the only form accepted by the constructor.
HANDLERS
Handlers are code that injected at various phases during the processing
of requests. The following methods are provided to manage the active
handlers:
add_handler
$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 $phase and the corresponding callback signatures
are as follows. Note that the handlers are documented in the order in
which they will be run, which is:
request_preprepare
request_prepare
request_send
response_header
response_data
response_done
response_redirect
request_preprepare => sub { my($request, $ua, $handler) = @_; ... }
The handler is called before the "request_prepare" and other
standard initialization of the request. This can be used to set up
headers and attributes that the "request_prepare" handler depends
on. Proxy initialization should take place here; but in general
don't register handlers for this phase.
request_prepare => sub { my($request, $ua, $handler) = @_; ... }
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, $handler) = @_; ... }
This handler gets a chance of handling requests before they're sent
to the protocol handlers. It should return an HTTP::Response
object if it wishes to terminate the processing; otherwise it
should return nothing.
The "response_header" and "response_data" handlers will not be
invoked for this response, but the "response_done" will be.
response_header => sub { my($response, $ua, $handler) = @_; ... }
This handler is called right after the response headers have been
received, but before any content data. The handler might set up
handlers for data and might croak to abort the request.
The handler might set the "$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, $handler, $data) = @_; ... }
This handler is called for each chunk of data received for the
response. The handler might croak to abort the request.
This handler needs to return a TRUE value to be called again for
subsequent chunks for the same request.
response_done => sub { my($response, $ua, $handler) = @_; ... }
The handler is called after the response has been fully received,
but before any redirect handling is attempted. The handler can be
used to extract information or modify the response.
response_redirect => sub { my($response, $ua, $handler) = @_; ... }
The handler is called in "$ua->request" after "response_done". If
the handler returns an HTTP::Request object we'll start over with
processing this request instead.
For all of these, $handler is a code reference to the handler that is
currently being run.
get_my_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.
handlers
$ua->handlers( $phase, $request )
$ua->handlers( $phase, $response )
Returns the handlers that apply to the given request or response at the
given processing phase.
remove_handler
$ua->remove_handler( undef, %matchspec );
$ua->remove_handler( $phase, %matchspec );
$ua->remove_handler(); # REMOVE ALL HANDLERS IN ALL PHASES
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" in LWP::UserAgent method instead.
The removed handlers are returned.
set_my_handler
$ua->set_my_handler( $phase, $cb, %matchspec );
$ua->set_my_handler($phase, undef); # remove handler for phase
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.
REQUEST METHODS
The methods described in this section are used to dispatch requests via
the user agent. The following request methods are provided:
delete
my $res = $ua->delete( $url );
my $res = $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" in
LWP::UserAgent 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.
get
my $res = $ua->get( $url );
my $res = $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 # or $filehandle
':content_cb' => \&callback
':read_size_hint' => $bytes
If a $filename or $filehandle is provided with the ":content_file"
option, then the response content will be saved here instead of in the
response object. The $filehandle may also be an object with an open
file descriptor, such as a File::Temp object. If a callback is
provided with the ":content_cb" option then this function will be
called for each chunk of the response content as it is received from
the server. If neither of these options are given, then the response
content will accumulate in the response object itself. This might not
be suitable for very large response bodies. Only one of
":content_file" or ":content_cb" can be specified. The content of
unsuccessful responses will always accumulate in the response object
itself, regardless of the ":content_file" or ":content_cb" options
passed in. Note that errors writing to the content file (for example
due to permission denied or the filesystem being full) will be reported
via the "Client-Aborted" or "X-Died" response headers, and not the
"is_success" method.
The ":read_size_hint" option is passed to the protocol module which
will try to read data from the server in chunks of this size. A
smaller value for the ":read_size_hint" will result in a higher number
of callback invocations.
The callback function is called with 3 arguments: a chunk of data, a
reference to the response object, and a reference to the protocol
object. The callback can abort the request by invoking "die()". The
exception message will show up as the "X-Died" header field in the
response returned by the "$ua->get()" method.
head
my $res = $ua->head( $url );
my $res = $ua->head( $url , $field_name => $value, ... );
This method will dispatch a "HEAD" request on the given URL. Otherwise
it works like the "get" in LWP::UserAgent method described above.
is_protocol_supported
my $bool = $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.
is_online
my $bool = $ua->is_online;
Tries to determine if you have access to the Internet. Returns 1 (true)
if the built-in heuristics determine that the user agent is able to
access the Internet (over HTTP) or 0 (false).
See also LWP::Online.
mirror
my $res = $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.
Uses "move" in File::Copy to attempt to atomically replace the
$filename.
The return value is an HTTP::Response object.
patch
# Any version of HTTP::Message works with this form:
my $res = $ua->patch( $url, $field_name => $value, Content => $content );
# Using hash or array references requires HTTP::Message >= 6.12
use HTTP::Request 6.12;
my $res = $ua->patch( $url, \%form );
my $res = $ua->patch( $url, \@form );
my $res = $ua->patch( $url, \%form, $field_name => $value, ... );
my $res = $ua->patch( $url, $field_name => $value, Content => \%form );
my $res = $ua->patch( $url, $field_name => $value, Content => \@form );
This method will dispatch a "PATCH" 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" in LWP::UserAgent method.
CAVEAT:
This method can only accept content that is in key-value pairs when
using HTTP::Request::Common prior to version 6.12. Any use of hash or
array references will result in an error prior to version 6.12.
This method will use the "PATCH" 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.
post
my $res = $ua->post( $url, \%form );
my $res = $ua->post( $url, \@form );
my $res = $ua->post( $url, \%form, $field_name => $value, ... );
my $res = $ua->post( $url, $field_name => $value, Content => \%form );
my $res = $ua->post( $url, $field_name => $value, Content => \@form );
my $res = $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" in
LWP::UserAgent 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.
put
# Any version of HTTP::Message works with this form:
my $res = $ua->put( $url, $field_name => $value, Content => $content );
# Using hash or array references requires HTTP::Message >= 6.07
use HTTP::Request 6.07;
my $res = $ua->put( $url, \%form );
my $res = $ua->put( $url, \@form );
my $res = $ua->put( $url, \%form, $field_name => $value, ... );
my $res = $ua->put( $url, $field_name => $value, Content => \%form );
my $res = $ua->put( $url, $field_name => $value, Content => \@form );
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" in
LWP::UserAgent method.
CAVEAT:
This method can only accept content that is in key-value pairs when
using HTTP::Request::Common prior to version 6.07. Any use of hash or
array references will result in an error prior to version 6.07.
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.
request
my $res = $ua->request( $request );
my $res = $ua->request( $request, $content_file );
my $res = $ua->request( $request, $content_cb );
my $res = $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 an HTTP::Response
object.
The "request" method will process redirects and authentication
responses transparently. This means that it may actually send several
simple requests via the "simple_request" in LWP::UserAgent method
described below.
The request methods described above; "get" in LWP::UserAgent, "head" in
LWP::UserAgent, "post" in LWP::UserAgent and "mirror" in LWP::UserAgent
will all dispatch the request they build via this method. They are
convenience methods that simply hide 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" in LWP::UserAgent method above. Note
that errors writing to the content file (for example due to permission
denied or the filesystem being full) will be reported via the
"Client-Aborted" or "X-Died" response headers, and not the "is_success"
method.
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.
simple_request
my $request = HTTP::Request->new( ... );
my $res = $ua->simple_request( $request );
my $res = $ua->simple_request( $request, $content_file );
my $res = $ua->simple_request( $request, $content_cb );
my $res = $ua->simple_request( $request, $content_cb, $read_size_hint );
This method dispatches a single request and returns the response
received. Arguments are the same as for the "request" in
LWP::UserAgent described above.
The difference from "request" in LWP::UserAgent is that
"simple_request" will not try to handle redirects or authentication
responses. The "request" in LWP::UserAgent method will, in fact,
invoke this method for each simple request it sends.
CALLBACK METHODS
The following methods will be invoked as requests are processed. These
methods are documented here because subclasses of LWP::UserAgent might
want to override their behaviour.
get_basic_credentials
# This checks wantarray and can either return an array:
my ($user, $pass) = $ua->get_basic_credentials( $realm, $uri, $isproxy );
# or a string that looks like "user:pass"
my $creds = $ua->get_basic_credentials($realm, $uri, $isproxy);
This is called by "request" in LWP::UserAgent 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" in LWP::UserAgent method.
prepare_request
$request = $ua->prepare_request( $request );
This method is invoked by "simple_request" in LWP::UserAgent. 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".
progress
my $prog = $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 HTTP::Request
object, otherwise it is the HTTP::Response object.
redirect_ok
my $bool = $ua->redirect_ok( $prospective_request, $response );
This method is called by "request" in LWP::UserAgent 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.
BEST PRACTICES
The default settings can get you up and running quickly, but there are
settings you can change in order to make your life easier.
Handling Cookies
You are encouraged to install Mozilla::PublicSuffix and use
HTTP::CookieJar::LWP as your cookie jar. HTTP::CookieJar::LWP provides
a better security model matching that of current Web browsers when
Mozilla::PublicSuffix is installed.
use HTTP::CookieJar::LWP ();
my $jar = HTTP::CookieJar::LWP->new;
my $ua = LWP::UserAgent->new( cookie_jar => $jar );
See "cookie_jar" for more information.
Managing Protocols
"protocols_allowed" gives you the ability to allow arbitrary protocols.
my $ua = LWP::UserAgent->new(
protocols_allowed => [ 'http', 'https' ]
);
This will prevent you from inadvertently following URLs like
"file:///etc/passwd". See "protocols_allowed".
"protocols_forbidden" gives you the ability to deny arbitrary
protocols.
my $ua = LWP::UserAgent->new(
protocols_forbidden => [ 'file', 'mailto', 'ssh', ]
);
This can also prevent you from inadvertently following URLs like
"file:///etc/passwd". See "protocols_forbidden".
SEE ALSO
See LWP(3) for a complete overview of libwww-perl5. See lwpcook(3) and
the scripts lwp-request(1) and lwp-download(1) for examples of
usage.
See HTTP::Request(3) and HTTP::Response(3) for a description of the
message objects dispatched and received. See HTTP::Request::Common(3)
and HTML::Form(3) for other ways to build request objects.
COPYRIGHT AND LICENSE
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 v5.34.3 2024-03-11 LWP::UserAgent(3)
libwww-perl 6.770.0 - Generated Mon Mar 11 07:46:02 CDT 2024