alpha         = lowalpha | hialpha
      lowalpha      = "a" | "b" | "c" | "d" | "e" | "f" | "g" | "h"
                    | "i" | "j" | "k" | "l" | "m" | "n" | "o" | "p"
                    | "q" | "r" | "s" | "t" | "u" | "v" | "w" | "x"
                    | "y" | "z"
      hialpha       = "A" | "B" | "C" | "D" | "E" | "F" | "G" | "H"
                    | "I" | "J" | "K" | "L" | "M" | "N" | "O" | "P"
                    | "Q" | "R" | "S" | "T" | "U" | "V" | "W" | "X"
                    | "Y" | "Z"
      digit         = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7"
                    | "8" | "9"
      OCTET         = <any 8-bit byte>
      CHAR          = <any character>
      CTL           = <any control character>
      SP            = <space character>
      NL            = 
      LWSP          = SP | NL | <horizontal-tab>




 
INTERNET-DRAFT       Common Gateway Interface - 1.1     15 February 1996


      tspecial      = "(" | ")" | "@" | "," | ";" | ":" | "\" | <">
                    | "/" | "[" | "]" | "?" | SP
      token         = 1*<any CHAR except CTLs or tspecials>
      quoted-string = ( <"> *qdtext <"> ) | ( "<" *qatext ">")
      qdtext        = <any CHAR except <"> and CTLs but including LWSP>
      qatext        = <any CHAR except "<", ">" and CTLs but
                      including LWSP>

   Note that newline (NL) need not be a single character, but can be a
   character sequence.

3. URL Encoding

   Some variables and constructs used here are described as being
   `URL-encoded'. This encoding is described in section 2.2 of RFC 1738
   [4]. In a URL encoded string an escape sequence consists of a percent
   character ("%") followed by two hexadecimal digits, where the two
   hexadecimal digits form an octet. An escape sequence represents the
   graphic character which has the octet as its code within the US-ASCII
   [11] coded character set, if it exists. If no such graphic character
   exists, then the escape sequence represents the octet value itself.

   Note that some unsafe characters may have different semantics if they
   are encoded. The definition of which characters are unsafe depends on
   the context.

4. The Script URI

   A `Script URI' can be defined; this describes the resource identified
   by the environment variables. Often, this URI will be the same as the
   URI requested by the client (the `Client URI'); however, it need not
   be. Instead, it could be a URI invented by the server, and so it can
   only be used in the context of the server and its CGI interface.

   The script URI has the syntax of generic-RL as defined in section 2.1
   of RFC 1808 [7], with the exception that object parameters and
   fragment identifiers are not permitted:

      ://:/?

   The various components of the script URI are defined by some of the
   environment variables (see below);

      script-uri = protocol "://" SERVER_NAME ":" SERVER_PORT enc-script
                   enc-path-info "?" QUERY_STRING

   where `protocol' is found from SERVER_PROTOCOL, `enc-script' is a
   URL-encoded version of SCRIPT_NAME and `enc-path-info' is a




 
INTERNET-DRAFT       Common Gateway Interface - 1.1     15 February 1996


   URL-encoded version of PATH_INFO.

5. Environment variables

   Environment variables are used to pass data about the request from
   the server to the script. They are accessed by the script in a system
   defined manner. In all cases, a missing environment variable is
   equivalent to a zero-length (NULL) value, and vice versa. The
   representation of the characters in the environment variables is
   system defined.

   Case is not significant in the names, in that there cannot be two
   different variable whose names differ in case only. Here they are
   shown using a canonical representation of capitals plus underscore
   ("_"). The actual representation of the names is system defined; for
   a particular system the representation may be defined differently to
   this.

   The variables are: