meta-variables.  The SCRIPT_NAME and PATH_INFO values, URL-encoded
   with ";", "=" and "?"  reserved, give <script-path> and .




 
RFC 3875                    CGI Version 1.1                 October 2004


   See section 4.1.5 for more information about the PATH_INFO
   meta-variable.

   The scheme and the protocol are not identical as the scheme
   identifies the access method in addition to the application protocol.
   For example, a resource accessed using Transport Layer Security (TLS)
   [14] would have a request URI with a scheme of https when using the
   HTTP protocol [19].  CGI/1.1 provides no generic means for the script
   to reconstruct this, and therefore the Script-URI as defined includes
   the base protocol used.  However, a script MAY make use of
   scheme-specific meta-variables to better deduce the URI scheme.

   Note that this definition also allows URIs to be constructed which
   would invoke the script with any permitted values for the path-info
   or query-string, by modifying the appropriate components.

3.4.  Execution

   The script is invoked in a system-defined manner.  Unless specified
   otherwise, the file containing the script will be invoked as an
   executable program.  The server prepares the CGI request as described
   in section 4; this comprises the request meta-variables (immediately
   available to the script on execution) and request message data.  The
   request data need not be immediately available to the script; the
   script can be executed before all this data has been received by the
   server from the client.  The response from the script is returned to
   the server as described in sections 5 and 6.

   In the event of an error condition, the server can interrupt or
   terminate script execution at any time and without warning.  That
   could occur, for example, in the event of a transport failure between
   the server and the client; so the script SHOULD be prepared to handle
   abnormal termination.

4.  The CGI Request

   Information about a request comes from two different sources; the
   request meta-variables and any associated message-body.

4.1.  Request Meta-Variables

   Meta-variables contain data about the request passed from the server
   to the script, and are accessed by the script in a system-defined
   manner.  Meta-variables are identified by case-insensitive names;
   there cannot be two different variables whose names differ in case
   only.  Here they are shown using a canonical representation of
   capitals plus underscore ("_").  A particular system can define a
   different representation.




 
RFC 3875                    CGI Version 1.1                 October 2004


      meta-variable-name = "AUTH_TYPE" | "CONTENT_LENGTH" |
                           "CONTENT_TYPE" | "GATEWAY_INTERFACE" |
                           "PATH_INFO" | "PATH_TRANSLATED" |
                           "QUERY_STRING" | "REMOTE_ADDR" |
                           "REMOTE_HOST" | "REMOTE_IDENT" |
                           "REMOTE_USER" | "REQUEST_METHOD" |
                           "SCRIPT_NAME" | "SERVER_NAME" |
                           "SERVER_PORT" | "SERVER_PROTOCOL" |
                           "SERVER_SOFTWARE" | scheme |
                           protocol-var-name | extension-var-name
      protocol-var-name  = ( protocol | scheme ) "_" var-name
      scheme             = alpha *( alpha | digit | "+" | "-" | "." )
      var-name           = token
      extension-var-name = token

   Meta-variables with the same name as a scheme, and names beginning
   with the name of a protocol or scheme (e.g., HTTP_ACCEPT) are also
   defined.  The number and meaning of these variables may change
   independently of this specification.  (See also section 4.1.18.)

   The server MAY set additional implementation-defined extension meta-
   variables, whose names SHOULD be prefixed with "X_".

   This specification does not distinguish between zero-length (NULL)
   values and missing values.  For example, a script cannot distinguish
   between the two requests http://host/script and http://host/script?
   as in both cases the QUERY_STRING meta-variable would be NULL.

      meta-variable-value = "" | 1*<TEXT, CHAR or tokens of value>

   An optional meta-variable may be omitted (left unset) if its value is
   NULL.  Meta-variable values MUST be considered case-sensitive except
   as noted otherwise.  The representation of the characters in the
   meta-variables is system-defined; the server MUST convert values to