{
"mode": "perldoc",
"parameter": "LWP",
"section": "",
"url": "https://www.chedong.com/phpMan.php/perldoc/LWP/json",
"generated": "2026-06-15T18:52:46Z",
"synopsis": "use LWP;\nprint \"This is libwww-perl-$LWP::VERSION\\n\";",
"sections": {
"NAME": {
"content": "LWP - The World-Wide Web library for Perl\n",
"subsections": []
},
"SYNOPSIS": {
"content": "use LWP;\nprint \"This is libwww-perl-$LWP::VERSION\\n\";\n",
"subsections": []
},
"DESCRIPTION": {
"content": "The libwww-perl collection is a set of Perl modules which provides a simple and consistent\napplication programming interface (API) to the World-Wide Web. The main focus of the library is\nto provide classes and functions that allow you to write WWW clients. The library also contain\nmodules that are of more general use and even classes that help you implement simple HTTP\nservers.\n\nMost modules in this library provide an object oriented API. The user agent, requests sent and\nresponses received from the WWW server are all represented by objects. This makes a simple and\npowerful interface to these services. The interface is easy to extend and customize for your own\nneeds.\n\nThe main features of the library are:\n\n* Contains various reusable components (modules) that can be used separately or together.\n\n* Provides an object oriented model of HTTP-style communication. Within this framework we\ncurrently support access to \"http\", \"https\", \"gopher\", \"ftp\", \"news\", \"file\", and \"mailto\"\nresources.\n\n* Provides a full object oriented interface or a very simple procedural interface.\n\n* Supports the basic and digest authorization schemes.\n\n* Supports transparent redirect handling.\n\n* Supports access through proxy servers.\n\n* Provides parser for robots.txt files and a framework for constructing robots.\n\n* Supports parsing of HTML forms.\n\n* Implements HTTP content negotiation algorithm that can be used both in protocol modules and\nin server scripts (like CGI scripts).\n\n* Supports HTTP cookies.\n\n* Some simple command line clients, for instance \"lwp-request\" and \"lwp-download\".\n",
"subsections": []
},
"HTTP STYLE COMMUNICATION": {
"content": "The libwww-perl library is based on HTTP style communication. This section tries to describe\nwhat that means.\n\nLet us start with this quote from the HTTP specification document\n:\n\n* The HTTP protocol is based on a request/response paradigm. A client establishes a connection\nwith a server and sends a request to the server in the form of a request method, URI, and\nprotocol version, followed by a MIME-like message containing request modifiers, client\ninformation, and possible body content. The server responds with a status line, including the\nmessage's protocol version and a success or error code, followed by a MIME-like message\ncontaining server information, entity meta-information, and possible body content.\n\nWhat this means to libwww-perl is that communication always take place through these steps:\nFirst a *request* object is created and configured. This object is then passed to a server and\nwe get a *response* object in return that we can examine. A request is always independent of any\nprevious requests, i.e. the service is stateless. The same simple model is used for any kind of\nservice we want to access.\n\nFor example, if we want to fetch a document from a remote file server, then we send it a request\nthat contains a name for that document and the response will contain the document itself. If we\naccess a search engine, then the content of the request will contain the query parameters and\nthe response will contain the query result. If we want to send a mail message to somebody then\nwe send a request object which contains our message to the mail server and the response object\nwill contain an acknowledgment that tells us that the message has been accepted and will be\nforwarded to the recipient(s).\n\nIt is as simple as that!\n",
"subsections": [
{
"name": "The Request Object",
"content": "The libwww-perl request object has the class name HTTP::Request. The fact that the class name\nuses \"HTTP::\" as a prefix only implies that we use the HTTP model of communication. It does not\nlimit the kind of services we can try to pass this *request* to. For instance, we will send\nHTTP::Requests both to ftp and gopher servers, as well as to the local file system.\n\nThe main attributes of the request objects are:\n\n* method is a short string that tells what kind of request this is. The most common methods are\nGET, PUT, POST and HEAD.\n\n* uri is a string denoting the protocol, server and the name of the \"document\" we want to\naccess. The uri might also encode various other parameters.\n\n* headers contains additional information about the request and can also used to describe the\ncontent. The headers are a set of keyword/value pairs.\n\n* content is an arbitrary amount of data.\n"
},
{
"name": "The Response Object",
"content": "The libwww-perl response object has the class name HTTP::Response. The main attributes of\nobjects of this class are:\n\n* code is a numerical value that indicates the overall outcome of the request.\n\n* message is a short, human readable string that corresponds to the *code*.\n\n* headers contains additional information about the response and describe the content.\n\n* content is an arbitrary amount of data.\n\nSince we don't want to handle all possible *code* values directly in our programs, a libwww-perl\nresponse object has methods that can be used to query what kind of response this is. The most\ncommonly used response classification methods are:\n"
},
{
"name": "is_success",
"content": "The request was successfully received, understood or accepted.\n"
},
{
"name": "is_error",
"content": "The request failed. The server or the resource might not be available, access to the resource\nmight be denied or other things might have failed for some reason.\n"
},
{
"name": "The User Agent",
"content": "Let us assume that we have created a *request* object. What do we actually do with it in order\nto receive a *response*?\n\nThe answer is that you pass it to a *user agent* object and this object takes care of all the\nthings that need to be done (like low-level communication and error handling) and returns a\n*response* object. The user agent represents your application on the network and provides you\nwith an interface that can accept *requests* and return *responses*.\n\nThe user agent is an interface layer between your application code and the network. Through this\ninterface you are able to access the various servers on the network.\n\nThe class name for the user agent is LWP::UserAgent. Every libwww-perl application that wants to\ncommunicate should create at least one object of this class. The main method provided by this\nobject is request(). This method takes an HTTP::Request object as argument and (eventually)\nreturns a HTTP::Response object.\n\nThe user agent has many other attributes that let you configure how it will interact with the\nnetwork and with your application.\n\n* timeout specifies how much time we give remote servers to respond before the library\ndisconnects and creates an internal *timeout* response.\n\n* agent specifies the name that your application uses when it presents itself on the network.\n\n* from can be set to the e-mail address of the person responsible for running the application.\nIf this is set, then the address will be sent to the servers with every request.\n\n* parsehead specifies whether we should initialize response headers from the \"\" section\nof HTML documents.\n\n* proxy and noproxy specify if and when to go through a proxy server.\n\n\n* credentials provides a way to set up user names and passwords needed to access certain\nservices.\n\nMany applications want even more control over how they interact with the network and they get\nthis by sub-classing LWP::UserAgent. The library includes a sub-class, LWP::RobotUA, for robot\napplications.\n"
},
{
"name": "An Example",
"content": "This example shows how the user agent, a request and a response are represented in actual perl\ncode:\n\n# Create a user agent object\nuse LWP::UserAgent;\nmy $ua = LWP::UserAgent->new;\n$ua->agent(\"MyApp/0.1 \");\n\n# Create a request\nmy $req = HTTP::Request->new(POST => 'http://search.cpan.org/search');\n$req->contenttype('application/x-www-form-urlencoded');\n$req->content('query=libwww-perl&mode=dist');\n\n# Pass request to the user agent and get a response back\nmy $res = $ua->request($req);\n\n# Check the outcome of the response\nif ($res->issuccess) {\nprint $res->content;\n}\nelse {\nprint $res->statusline, \"\\n\";\n}\n\nThe $ua is created once when the application starts up. New request objects should normally\ncreated for each request sent.\n"
}
]
},
"NETWORK SUPPORT": {
"content": "This section discusses the various protocol schemes and the HTTP style methods that headers may\nbe used for each.\n\nFor all requests, a \"User-Agent\" header is added and initialized from the \"$ua->agent\" attribute\nbefore the request is handed to the network layer. In the same way, a \"From\" header is\ninitialized from the $ua->from attribute.\n\nFor all responses, the library adds a header called \"Client-Date\". This header holds the time\nwhen the response was received by your application. The format and semantics of the header are\nthe same as the server created \"Date\" header. You may also encounter other \"Client-XXX\" headers.\nThey are all generated by the library internally and are not received from the servers.\n\nHTTP Requests\nHTTP requests are just handed off to an HTTP server and it decides what happens. Few servers\nimplement methods beside the usual \"GET\", \"HEAD\", \"POST\" and \"PUT\", but CGI-scripts may\nimplement any method they like.\n\nIf the server is not available then the library will generate an internal error response.\n\nThe library automatically adds a \"Host\" and a \"Content-Length\" header to the HTTP request before\nit is sent over the network.\n\nFor a GET request you might want to add an \"If-Modified-Since\" or \"If-None-Match\" header to make\nthe request conditional.\n\nFor a POST request you should add the \"Content-Type\" header. When you try to emulate HTML