Erlang Programming/Creating Web Applications with yaws/Arg structure

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The arg data structure is the main mechanism which the server uses to forward essential information to the web application. The #arg recored is defined in yaws_api.hrl and is defined as:

-record(arg, {
          clisock,        %% the socket leading to the peer client
          client_ip_port, %% {Ip, Port} for the client
          headers,        %% headers
          req,            %% request
          clidata,        %% The client data (as a binary in POST requests)
          server_path,    %% The normalized server path
          querydata,      %% Was the URL on the form of ...?query (GET reqs)
          appmoddata,     %% the remainder of the path leading up to the query
          docroot,        %% where's the data
          fullpath,       %% full deep path to yaws file
          cont,           %% Continuation for chunked multipart uploads
          state,          %% State for use by users of the out/1 callback
          pid,            %% pid of the yaws worker process
          opaque,         %% useful to pass static data
          appmod_prepath, %% path in front of: <appmod><appmoddata>
          pathinfo        %% Set to 'd/e' when calling c.yaws for the request
                          %% http://some.host/a/b/c.yaws/d/e
         }).

Some of the parameters in the Arg structure contain additional information as shown below.

-record(headers, {
          connection,
          accept,
          host,
          if_modified_since,
          if_match,
          if_none_match,
          if_range,
          if_unmodified_since,
          range,
          referer,
          user_agent,
          accept_ranges,
          cookie = [],
          keep_alive,
          content_length,
          authorization,
          other = []   %% misc other headers
         }).