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"text": "# LWP (man)\n\n## NAME\n\nLWP - The World-Wide Web library for Perl\n\n## SYNOPSIS\n\nuse LWP;\nprint \"This is libwww-perl-$LWP::VERSION\\n\";\n\n## DESCRIPTION\n\nThe libwww-perl collection is a set of Perl modules which provides a simple and consistent\napplication programming interface (API) to the World-Wide Web. The main focus of the library\nis to provide classes and functions that allow you to write WWW clients. The library also\ncontain modules that are of more general use and even classes that help you implement simple\nHTTP servers.\n\n## Sections\n\n- **NAME**\n- **SYNOPSIS**\n- **DESCRIPTION**\n- **HTTP STYLE COMMUNICATION** (6 subsections)\n- **NETWORK SUPPORT** (8 subsections)\n- **OVERVIEW OF CLASSES AND PACKAGES**\n- **MORE DOCUMENTATION**\n- **ENVIRONMENT**\n- **AUTHORS**\n- **COPYRIGHT**\n- **AVAILABILITY**\n\nUse structuredContent.sections for detailed options, examples, and full documentation.\n"
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"summary": "LWP - The World-Wide Web library for Perl",
"synopsis": "use LWP;\nprint \"This is libwww-perl-$LWP::VERSION\\n\";",
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{
"name": "NAME",
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},
{
"name": "SYNOPSIS",
"lines": 3,
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},
{
"name": "DESCRIPTION",
"lines": 38,
"subsections": []
},
{
"name": "HTTP STYLE COMMUNICATION",
"lines": 30,
"subsections": [
{
"name": "The Request Object",
"lines": 18
},
{
"name": "The Response Object",
"lines": 15
},
{
"name": "is_success()",
"lines": 2
},
{
"name": "is_error()",
"lines": 3
},
{
"name": "The User Agent",
"lines": 42
},
{
"name": "An Example",
"lines": 27
}
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},
{
"name": "NETWORK SUPPORT",
"lines": 13,
"subsections": [
{
"name": "HTTP Requests",
"lines": 22
},
{
"name": "HTTPS Requests",
"lines": 12
},
{
"name": "FTP Requests",
"lines": 32
},
{
"name": "News Requests",
"lines": 21
},
{
"name": "Gopher Request",
"lines": 12
},
{
"name": "File Request",
"lines": 11
},
{
"name": "Mailto Request",
"lines": 10
},
{
"name": "CPAN Requests",
"lines": 14
}
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{
"name": "OVERVIEW OF CLASSES AND PACKAGES",
"lines": 37,
"subsections": []
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{
"name": "MORE DOCUMENTATION",
"lines": 5,
"subsections": []
},
{
"name": "ENVIRONMENT",
"lines": 30,
"subsections": []
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{
"name": "AUTHORS",
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{
"name": "COPYRIGHT",
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{
"name": "AVAILABILITY",
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"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\nis to provide classes and functions that allow you to write WWW clients. The library also\ncontain modules that are of more general use and even classes that help you implement simple\nHTTP servers.\n\nMost modules in this library provide an object oriented API. The user agent, requests sent\nand responses received from the WWW server are all represented by objects. This makes a\nsimple and powerful interface to these services. The interface is easy to extend and\ncustomize for your own needs.\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\nand in 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\nconnection with a server and sends a request to the server in the form of a request\nmethod, URI, and protocol version, followed by a MIME-like message containing request\nmodifiers, client information, and possible body content. The server responds with a\nstatus line, including the message's protocol version and a success or error code,\nfollowed by a MIME-like message containing server information, entity meta-information,\nand 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\nany previous requests, i.e. the service is stateless. The same simple model is used for any\nkind of service we want to access.\n\nFor example, if we want to fetch a document from a remote file server, then we send it a\nrequest that contains a name for that document and the response will contain the document\nitself. If we access a search engine, then the content of the request will contain the query\nparameters and the response will contain the query result. If we want to send a mail message\nto somebody then we send a request object which contains our message to the mail server and\nthe response object will contain an acknowledgment that tells us that the message has been\naccepted and will be forwarded 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\nname uses \"HTTP::\" as a prefix only implies that we use the HTTP model of communication. It\ndoes not limit the kind of services we can try to pass this request to. For instance, we\nwill send HTTP::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\nare GET, 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\nthe content. 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-\nperl response object has methods that can be used to query what kind of response this is.\nThe most commonly 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\nresource might 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\nresponse 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\nthis interface 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\nwants to communicate should create at least one object of this class. The main method\nprovided by this object is request(). This method takes an HTTP::Request object as argument\nand (eventually) returns 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\nnetwork.\n\n• from can be set to the e-mail address of the person responsible for running the\napplication. If this is set, then the address will be sent to the servers with every\nrequest.\n\n• parsehead specifies whether we should initialize response headers from the \"\"\nsection of 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\nrobot applications.\n"
},
{
"name": "An Example",
"content": "This example shows how the user agent, a request and a response are represented in actual\nperl code:\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 $ua is created once when the application starts up. New request objects should normally\ncreated for each request sent.\n"
}
]
},
"NETWORK SUPPORT": {
"content": "This section discusses the various protocol schemes and the HTTP style methods that headers\nmay be used for each.\n\nFor all requests, a \"User-Agent\" header is added and initialized from the \"$ua->agent\"\nattribute before the request is handed to the network layer. In the same way, a \"From\"\nheader is initialized from the $ua->from attribute.\n\nFor all responses, the library adds a header called \"Client-Date\". This header holds the\ntime when the response was received by your application. The format and semantics of the\nheader are the same as the server created \"Date\" header. You may also encounter other\n\"Client-XXX\" headers. They are all generated by the library internally and are not received\nfrom the servers.\n",
"subsections": [
{
"name": "HTTP Requests",
"content": "HTTP 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\nbefore it 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\nmake the request conditional.\n\nFor a POST request you should add the \"Content-Type\" header. When you try to emulate HTML\n