Request Parameters

Request parameters must be either a variable (in which case the request is considered to not have special parameters) or a list. The following terms are allowed in that list:

• timeout(+Secs) - request timeout. If it is not specified, a default value (5 seconds) is used. Only the first request in a list should have the timeout value set. Timeouts that appear in subsequent requests are ignored.
• authentication([c(+Realm,+Username,+Pasword),...]) - If the site requires authentication, you should specify it in a list as an argument to the authentication/1 functor. Realm is a string that the servers return to let applications know which username/password pair to send (in case the application works with several pages that require different authentication). They are used as page identifiers for the authentication purposes. If Realm is an atom (e.g., authentication('FooSite', boo, moo)), then when a Web server requests authentication for the FooSite realm, the Libwww package will send the foo/moo user-password pair.

  If Realm is a variable, then it is considered to match every realm. The Libwww package searches for matching authentication triples in the order they appear in the authentication list. Thus, the triple where Realm is a variable should appear last and serve as a default username/password pair.

• formdata([attval_pair1, attval_pair2, ...]) -- list of attribute/value pairs to fill out a form (in case URL is a CGI script). Each attribute/value pair must be an atom of the form attr=val.
• selection(Taglist1,Taglist2,Taglist3) -- if the request is htmlparse or xmlparse, then this term provides control over which tags to parse. Taglist1 is a list of tags that specifies inside which tags to parse. For instance, if it is [ul,form] than parsing will be done only inside these elements. Other elements will be ignored. Taglist2 tells the system to stop parsing inside the corresponding elements. For instance, [table] means that parsing should be done only inside ul and form elements. However, if we hit a table during parsing, then parsing should stop unless we hit ul or form inside the table element. This switching of parsing on and off can continue to arbitrary depth. Taglist3 is a list of tags that are to be ignored completely. That is, the parsing process will simply strip these tags (but not the text inside them). For instance, if Taglist3 is [p,i] and the page contains ``<p>foo <i>moo</i>'' then parsing will be done as if the page contained just ``foo moo''.
• if_modified_since(Date) -- fetch the document only if it has been modified after the specified date. The date must be given as an atom string in the GMT format, e.g., 'Tue, 21 Sep 1999 14:46:36 GMT'. Otherwise, the status code WWW_EXPIRED_DOC is returned.