file.

      The arguments of any CWD commands are successive segment parts of
      the URL delimited by slash, and the final segment is suitable as
      the filename argument to the RETR command for retrieval or the
      directory argument to NLIST.

      For some file systems (Unix in particular), the "/" used to denote
      the hierarchical structure of the URL corresponds to the delimiter
      used to construct a file name hierarchy, and thus, the filename
      will look the same as the URL path.  This does NOT mean that the
      URL is a Unix filename.

         Note: Retrieving subsequent URLs from the same host

      There is no common hierarchical model to the FTP protocol, so if a
      directory change command has been given, it is impossible in
      general to deduce what sequence should be given to navigate to
      another directory for a second retrieval, if the paths are
      different.  The only reliable algorithm is to disconnect and
      reestablish the control connection.

   Data type

      The data content type of a file can only, in the general FTP case,
      be deduced from the name, normally the suffix of the name.  This
      is not standardized. An alternative is for it to be transferred in
      information outside the URL.  A suitable FTP transfer type (for
      example binary "I" or text "A") must in turn be deduced from the
      data content type.  It is recommended that conventions for
      suffixes of public archives be established, but it is outside the
      scope of this standard.

      An FTP URL may optionally specify the FTP data transfer type by
      which an object is to be retrieved. Most of the methods correspond
      to the FTP "Data Types" ASCII and IMAGE for the retrieval of a
      document, as specified in FTP by the TYPE command.  One method
      indicates directory access.




 
RFC 1630                      URIs in WWW                      June 1994


      The data type is specified by a suffix to the URL.  Possible
      suffixes are:

       ;type =      Use FTP type as given to perform data
                               transfer.

       /                       Use FTP directory list commands to read
                               directory

      The type code is in the format defined in RFC 959 except that THE
      SPACE IS OMITTED FROM THE URL.

   Transfer Mode

      Stream Mode is always used.

Gopher

   The gopher URL specifies the host and optionally the port to which
   the client should connect. This is followed by a slash and a single
   gopher type code. This type code is used by the client to determine
   how to interpret the server's reply and is is not for sending to
   server.  The command string to be sent to the server immediately
   follows the gopher type character.  It consists of the gopher
   selector string followed by any "Gopher plus" syntax, but always
   omitting the trainling CR LF pair.

   When the gopher command string contains characters (such a embedded
   CR LF and HT characters) not allowed in a URL, these are encoded
   using the conventional encoding.

   Note that some gopher selector strings begin with a copy of the
   gopher type character, in which case that character will occur twice
   consecutively.  Also note that the gopher selector string may be an
   empty string since this is how gopher clients refer to the top-level
   directory on a gopher server.

   If the encoded command string (with trailing CR LF stripped) would be
   void then the gopher type character may be omiited and "1" (ASCII 31
   hex) is assumed.

   Note that slash "/" in gopher selector strings may not correspond to
   a level in a hierarchical structure.









 
RFC 1630                      URIs in WWW                      June 1994