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             <PRE>


            Coar, et al.               CGI/1.1 Specification                     May, 1998

            
            INTERNET-DRAFT             Expires 1 December 1998                    [Page 2]


             </PRE>

            
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                  INTERNET-DRAFT&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

            
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                  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Ken A L Coar

            
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                  draft-coar-cgi-v11-03.{html,txt}&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

            
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                  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;IBM Corporation

            
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                  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

            
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                  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;D.R.T. Robinson

            
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                  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

            
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                  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;E*TRADE&nbsp;UK&nbsp;Ltd.

            
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                  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

            
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                  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;25 June 1999

            
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              <H1 ALIGN="CENTER">

            
               The WWW Common Gateway Interface

            
               <BR>

            
               Version 1.1

            
              </H1>


            <!--#include virtual="I-D-statement" -->


              <H2>

            
               <A NAME="Abstract">

            
                Abstract

            
               </A>

            
              </H2>

            
              <P>

            
              The Common Gateway Interface (CGI) is a simple interface for running

            
              external programs, software or gateways under an information server

            
              in a platform-independent manner. Currently, the supported information

            
              servers are HTTP servers.

            
              </P>

            
              <P>

            
              The interface has been in use by the World-Wide Web since 1993. This

            
              specification defines the

            
              "current practice" parameters of the

            
              'CGI/1.1' interface developed and documented at the U.S. National

            
              Centre for Supercomputing Applications [NCSA-CGI].

            
              This document also defines the use of the CGI/1.1 interface

            
              on the Unix and AmigaDOS(tm) systems.

            
              </P>

            
              <P>

            
              Discussion of this draft occurs on the CGI-WG mailing list; see the

            
              project Web page at

            
              <SAMP>&lt;URL:<A HREF="http://CGI-Spec.Golux.Com/"

            
                            >http://CGI-Spec.Golux.Com/</A>&gt;</SAMP>

            
              for details on the mailing list and the status of the project.

            
              </P>


            <!--#if expr="$GUI" -->

            
              <H2>

            
               Revision History

            
              </H2>

            
              <P>

            
              The revision history of this draft is being maintained using Web-based

            
              GUI notation, such as struck-through characters and colour-coded

            
              sections.  The following legend describes how to determine the origin

            
              of a particular revision according to the colour of the text:

            
              </P>

            
              <DL COMPACT>

            
               <DT>Black

            
               </DT>

            
               <DD>Revision 00, released 28 May 1998

            
               </DD>

            
               <DT>Green

            
               </DT>

            
               <DD>Revision 01, released 28 December 1998

            
                <BR>

            
                Major structure change: Section 4, "Request Metadata (Meta-Variables)"

            
                was moved entirely under <A HREF="#7.0">Section 7</A>, "Data Input to the

            
                CGI Script."

            
                Due to the size of this change, it is noted here and the text in its

            
                former location does <EM>not</EM> appear as struckthrough.  This has

            
                caused major <A HREF="#6.0">sections 5</A> and following to decrement

            
                by one.  Other

            
                large text movements are likewise not marked up.  References to RFC

            
                1738 were changed to 2396 (1738's replacement).

            
               </DD>

            
               <DT>Red

            
               </DT>

            
               <DD>Revision 02, released 2 April, 1999

            
                <BR>

            
                Added text to <A HREF="#8.3">section 8.3</A> defining correct handling

            
                of HTTP/1.1

            
                requests using "chunked" Transfer-Encoding.  Labelled metavariable

            
                names in <A HREF="#8.0">section 8</A> with the appropriate detail section

            
                numbers.

            
                Clarified allowed usage of <SAMP>Status</SAMP> and

            
                <SAMP>Location</SAMP> response header fields.  Included new

            
                Internet-Draft language.

            
               </DD>

            
               <DT>Fuchsia

            
               </DT>

            
               <DD>Revision 03, released 25 June 1999

            
                <BR>

            
                Changed references from "HTTP" to "Protocol-Specific" for the listing of

            
                things like HTTP_ACCEPT.  Changed 'entity-body' and 'content-body' to

            
                'message-body.'  Added a note that response headers must comply with

            
                requirements of the protocol level in use.  Added a lot of stuff about

            
                security (section 11).  Clarified a bunch of productions.  Pointed out

            
                that zero-length and omitted values are indistinguishable in this

            
                specification.  Clarified production describing order of fields in

            
                script response header.  Clarified issues surrounding encoding of

            
                data.  Acknowledged additional contributors, and changed one of

            
                the authors' addresses.

            
               </DD>

            
              </DL>

            
            <!--#endif -->


              <H2>

            
               <A NAME="Contents">

            
                Table of Contents

            
               </A>

            
              </H2>

            
              <DIV ALIGN="CENTER">

            
               <PRE>

            
              1 Introduction..............................................<A

            
                                                                           HREF="#1.0"

            
                                                                          >TBD</A>

            
               1.1 Purpose................................................<A

            
                                                                           HREF="#1.1"

            
                                                                          >TBD</A>

            
               1.2 Requirements...........................................<A

            
                                                                           HREF="#1.2"

            
                                                                          >TBD</A>

            
               1.3 Specifications.........................................<A

            
                                                                           HREF="#1.3"

            
                                                                          >TBD</A>

            
               1.4 Terminology............................................<A

            
                                                                           HREF="#1.4"

            
                                                                          >TBD</A>

            
              2 Notational Conventions and Generic Grammar................<A

            
                                                                           HREF="#2.0"

            
                                                                          >TBD</A>

            
               2.1 Augmented BNF..........................................<A

            
                                                                           HREF="#2.1"

            
                                                                          >TBD</A>

            
               2.2 Basic Rules............................................<A

            
                                                                           HREF="#2.2"

            
                                                                          >TBD</A>

            
              3 Protocol Parameters.......................................<A

            
                                                                           HREF="#3.0"

            
                                                                          >TBD</A>

            
               3.1 URL Encoding...........................................<A

            
                                                                           HREF="#3.1"

            
                                                                          >TBD</A>

            
               3.2 The Script-URI.........................................<A

            
                                                                           HREF="#3.2"

            
                                                                          >TBD</A>

            
              4 Invoking the Script.......................................<A

            
                                                                           HREF="#4.0"

            
                                                                          >TBD</A>

            
              5 The CGI Script Command Line...............................<A

            
                                                                           HREF="#5.0"

            
                                                                          >TBD</A>

            
              6 Data Input to the CGI Script..............................<A

            
                                                                           HREF="#6.0"

            
                                                                          >TBD</A>

            
               6.1 Request Metadata (Metavariables).......................<A

            
                                                                           HREF="#6.1"

            
                                                                          >TBD</A>

            
                6.1.1 AUTH_TYPE...........................................<A

            
                                                                           HREF="#6.1.1"

            
                                                                          >TBD</A>

            
                6.1.2 CONTENT_LENGTH......................................<A

            
                                                                           HREF="#6.1.2"

            
                                                                          >TBD</A>

            
                6.1.3 CONTENT_TYPE........................................<A

            
                                                                           HREF="#6.1.3"

            
                                                                          >TBD</A>

            
                6.1.4 GATEWAY_INTERFACE...................................<A

            
                                                                           HREF="#6.1.4"

            
                                                                          >TBD</A>

            
                6.1.5 Protocol-Specific Metavariables.....................<A

            
                                                                           HREF="#6.1.5"

            
                                                                          >TBD</A>

            
                6.1.6 PATH_INFO...........................................<A

            
                                                                           HREF="#6.1.6"

            
                                                                          >TBD</A>

            
                6.1.7 PATH_TRANSLATED.....................................<A

            
                                                                           HREF="#6.1.7"

            
                                                                          >TBD</A>

            
                6.1.8 QUERY_STRING........................................<A

            
                                                                           HREF="#6.1.8"

            
                                                                          >TBD</A>

            
                6.1.9 REMOTE_ADDR.........................................<A

            
                                                                           HREF="#6.1.9"

            
                                                                          >TBD</A>

            
                6.1.10 REMOTE_HOST........................................<A

            
                                                                           HREF="#6.1.10"

            
                                                                          >TBD</A>

            
                6.1.11 REMOTE_IDENT.......................................<A

            
                                                                           HREF="#6.1.11"

            
                                                                          >TBD</A>

            
                6.1.12 REMOTE_USER........................................<A

            
                                                                           HREF="#6.1.12"

            
                                                                          >TBD</A>

            
                6.1.13 REQUEST_METHOD.....................................<A

            
                                                                           HREF="#6.1.13"

            
                                                                          >TBD</A>

            
                6.1.14 SCRIPT_NAME........................................<A

            
                                                                           HREF="#6.1.14"

            
                                                                          >TBD</A>

            
                6.1.15 SERVER_NAME........................................<A

            
                                                                           HREF="#6.1.15"

            
                                                                          >TBD</A>

            
                6.1.16 SERVER_PORT........................................<A

            
                                                                           HREF="#6.1.16"

            
                                                                          >TBD</A>

            
                6.1.17 SERVER_PROTOCOL....................................<A

            
                                                                           HREF="#6.1.17"

            
                                                                          >TBD</A>

            
                6.1.18 SERVER_SOFTWARE....................................<A

            
                                                                           HREF="#6.1.18"

            
                                                                          >TBD</A>

            
                6.2 Request Message-Bodies................................<A

            
                                                                           HREF="#6.2"

            
                                                                          >TBD</A>

            
              7 Data Output from the CGI Script...........................<A

            
                                                                           HREF="#7.0"

            
                                                                          >TBD</A>

            
               7.1 Non-Parsed Header Output...............................<A

            
                                                                           HREF="#7.1"

            
                                                                          >TBD</A>

            
               7.2 Parsed Header Output...................................<A

            
                                                                           HREF="#7.2"

            
                                                                          >TBD</A>

            
                7.2.1 CGI header fields...................................<A

            
                                                                           HREF="#7.2.1"

            
                                                                          >TBD</A>

            
                 7.2.1.1 Content-Type.....................................<A

            
                                                                           HREF="#7.2.1.1"

            
                                                                          >TBD</A>

            
                 7.2.1.2 Location.........................................<A

            
                                                                           HREF="#7.2.1.2"

            
                                                                          >TBD</A>

            
                 7.2.1.3 Status...........................................<A

            
                                                                           HREF="#7.2.1.3"

            
                                                                          >TBD</A>

            
                 7.2.1.4 Extension header fields..........................<A

            
                                                                           HREF="#7.2.1.3"

            
                                                                          >TBD</A>

            
                7.2.2 HTTP header fields..................................<A

            
                                                                           HREF="#7.2.2"

            
                                                                          >TBD</A>

            
              8 Server Implementation.....................................<A

            
                                                                           HREF="#8.0"

            
                                                                          >TBD</A>

            
               8.1 Requirements for Servers...............................<A

            
                                                                           HREF="#8.1"

            
                                                                          >TBD</A>

            
                8.1.1 Script-URI..........................................<A

            
                                                                           HREF="#8.1"

            
                                                                          >TBD</A>

            
                8.1.2 Request Message-body Handling.......................<A

            
                                                                           HREF="#8.1.2"

            
                                                                          >TBD</A>

            
                8.1.3 Required Metavariables..............................<A

            
                                                                           HREF="#8.1.3"

            
                                                                          >TBD</A>

            
                8.1.4 Response Compliance.................................<A

            
                                                                           HREF="#8.1.4"

            
                                                                          >TBD</A>

            
               8.2 Recommendations for Servers............................<A

            
                                                                           HREF="#8.2"

            
                                                                          >TBD</A>

            
               8.3 Summary of Metavariables...............................<A

            
                                                                           HREF="#8.3"

            
                                                                          >TBD</A>

            
              9 Script Implementation.....................................<A

            
                                                                           HREF="#9.0"

            
                                                                          >TBD</A>

            
               9.1 Requirements for Scripts...............................<A

            
                                                                           HREF="#9.1"

            
                                                                          >TBD</A>

            
               9.2 Recommendations for Scripts............................<A

            
                                                                           HREF="#9.2"

            
                                                                          >TBD</A>

            
              10 System Specifications....................................<A

            
                                                                           HREF="#10.0"

            
                                                                          >TBD</A>

            
               10.1 AmigaDOS..............................................<A

            
                                                                           HREF="#10.1"

            
                                                                          >TBD</A>

            
               10.2 Unix..................................................<A

            
                                                                           HREF="#10.2"

            
                                                                          >TBD</A>

            
              11 Security Considerations..................................<A

            
                                                                           HREF="#11.0"

            
                                                                          >TBD</A>

            
               11.1 Safe Methods..........................................<A

            
                                                                           HREF="#11.1"

            
                                                                          >TBD</A>

            
               11.2 HTTP Header Fields Containing Sensitive Information...<A

            
                                                                           HREF="#11.2"

            
                                                                          >TBD</A>

            
               11.3 Script Interference with the Server...................<A

            
                                                                           HREF="#11.3"

            
                                                                          >TBD</A>

            
               11.4 Data Length and Buffering Considerations..............<A

            
                                                                           HREF="#11.4"

            
                                                                          >TBD</A>

            
               11.5 Stateless Processing..................................<A

            
                                                                           HREF="#11.5"

            
                                                                          >TBD</A>

            
              12 Acknowledgments..........................................<A

            
                                                                           HREF="#12.0"

            
                                                                          >TBD</A>

            
              13 References...............................................<A

            
                                                                           HREF="#13.0"

            
                                                                          >TBD</A>

            
              14 Authors' Addresses.......................................<A

            
                                                                           HREF="#14.0"

            
                                                                          >TBD</A>

            
                 </PRE>

            
              </DIV>


              <H2>

            
               <A NAME="1.0">

            
                1. Introduction

            
               </A>

            
              </H2>


              <H3>

            
               <A NAME="1.1">

            
                1.1. Purpose

            
               </A>

            
              </H3>

            
              <P>

            
              Together the HTTP [<A HREF="#[3]">3</A>,<A HREF="#[8]">8</A>] server

            
              and the CGI script are responsible

            
              for servicing a client

            
              request by sending back responses. The client

            
              request comprises a Universal Resource Identifier (URI)

            
              [<A HREF="#[1]">1</A>], a

            
              request method, and various ancillary

            
              information about the request

            
              provided by the transport mechanism.

            
              </P>

            
              <P>

            
              The CGI defines the abstract parameters, known as

            
              metavariables,

            
              which describe the client's

            
              request. Together with a

            
              concrete programmer interface this specifies a platform-independent

            
              interface between the script and the HTTP server.

            
              </P>


              <H3>

            
               <A NAME="1.2">

            
                1.2. Requirements

            
               </A>

            
              </H3>

            
              <P>

            
              This specification uses the same words as RFC 1123

            
              [<A HREF="#[5]">5</A>] to define the

            
              significance of each particular requirement. These are:

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <DL>

            
               <DT><EM>MUST</EM>

            
               </DT>

            
               <DD>

            
                <P>

            
                This word or the adjective 'required' means that the item is an

            
                absolute requirement of the specification.

            
                </P>

            
               </DD>

            
               <DT><EM>SHOULD</EM>

            
               </DT>

            
               <DD>

            
                <P>

            
                This word or the adjective 'recommended' means that there may

            
                exist valid reasons in particular circumstances to ignore this

            
                item, but the full implications should be understood and the case

            
                carefully weighed before choosing a different course.

            
                </P>

            
               </DD>

            
               <DT><EM>MAY</EM>

            
               </DT>

            
               <DD>

            
                <P>

            
                This word or the adjective 'optional' means that this item is

            
                truly optional. One vendor may choose to include the item because

            
                a particular marketplace requires it or because it enhances the

            
                product, for example; another vendor may omit the same item.

            
                </P>

            
               </DD>

            
              </DL>

            
              <P>

            
              An implementation is not compliant if it fails to satisfy one or more

            
              of the 'must' requirements for the protocols it implements. An

            
              implementation that satisfies all of the 'must' and all of the

            
              'should' requirements for its features is said to be 'unconditionally

            
              compliant'; one that satisfies all of the 'must' requirements but not

            
              all of the 'should' requirements for its features is said to be

            
              'conditionally compliant.'

            
              </P>


              <H3>

            
               <A NAME="1.3">

            
                1.3. Specifications

            
               </A>

            
              </H3>

            
              <P>

            
              Not all of the functions and features of the CGI are defined in the

            
              main part of this specification. The following phrases are used to

            
              describe the features which are not specified:

            
              </P>

            
              <DL>

            
               <DT><EM>system defined</EM>

            
               </DT>

            
               <DD>

            
                <P>

            
                The feature may differ between systems, but must be the same for

            
                different implementations using the same system. A system will

            
                usually identify a class of operating-systems. Some systems are

            
                defined in

            
                <A HREF="#10.0"

            
                >section 10</A> of this document.

            
                New systems may be defined

            
                by new specifications without revision of this document.

            
                </P>

            
               </DD>

            
               <DT><EM>implementation defined</EM>

            
               </DT>

            
               <DD>

            
                <P>

            
                The behaviour of the feature may vary from implementation to

            
                implementation, but a particular implementation must document its

            
                behaviour.

            
                </P>

            
               </DD>

            
              </DL>


              <H3>

            
               <A NAME="1.4">

            
                1.4. Terminology

            
               </A>

            
              </H3>

            
              <P>

            
              This specification uses many terms defined in the HTTP/1.1

            
              specification [<A HREF="#[8]">8</A>]; however, the following terms are

            
              used here in a

            
              sense which may not accord with their definitions in that document,

            
              or with their common meaning.

            
              </P>


              <DL>

            
               <DT><EM>metavariable</EM>

            
               </DT>

            
               <DD>

            
                <P>

            
                A named parameter that carries information from the server to the

            
                script. It is not necessarily a variable in the operating-system's

            
                environment, although that is the most common implementation.

            
                </P>

            
               </DD>


               <DT><EM>script</EM>

            
               </DT>

            
               <DD>

            
                <P>

            
                The software which is invoked by the server <EM>via</EM> this

            
                interface. It

            
                need not be a standalone program, but could be a

            
                dynamically-loaded or shared library, or even a subroutine in the

            
                server.  It <EM>may</EM> be a set of statements

            
                interpreted at run-time, as the term 'script' is frequently

            
                understood, but that is not a requirement and within the context

            
                of this specification the term has the broader definition stated.

            
                </P>

            
               </DD>

            
               <DT><EM>server</EM>

            
               </DT>

            
               <DD>

            
                <P>

            
                The application program which invokes the script in order to service

            
                requests.

            
                </P>

            
               </DD>

            
              </DL>


              <H2>

            
               <A NAME="2.0">

            
                2. Notational Conventions and Generic Grammar

            
               </A>

            
              </H2>


              <H3>

            
               <A NAME="2.1">

            
                2.1. Augmented BNF

            
               </A>

            
              </H3>

            
              <P>

            
              All of the mechanisms specified in this document are described in

            
              both prose and an augmented Backus-Naur Form (BNF) similar to that

            
              used by RFC 822 [<A HREF="#[6]">6</A>]. This augmented BNF contains

            
              the following constructs:

            
              </P>

            
              <DL>

            
               <DT>name = definition

            
               </DT>

            
               <DD>

            
                <P>

            
                The

            
                definition by the equal character ("="). Whitespace is only

            
                significant in that continuation lines of a definition are

            
                indented.

            
                </P>

            
               </DD>

            
               <DT>"literal"

            
               </DT>

            
               <DD>

            
                <P>

            
                Quotation marks (") surround literal text, except for a literal

            
                quotation mark, which is surrounded by angle-brackets ("&lt;" and "&gt;").

            
                Unless stated otherwise, the text is case-sensitive.

            
                </P>

            
               </DD>

            
               <DT>rule1 | rule2

            
               </DT>

            
               <DD>

            
                <P>

            
                Alternative rules are separated by a vertical bar ("|").

            
                </P>

            
               </DD>

            
               <DT>(rule1 rule2 rule3)

            
               </DT>

            
               <DD>

            
                <P>

            
                Elements enclosed in parentheses are treated as a single element.

            
                </P>

            
               </DD>

            
               <DT>*rule

            
               </DT>

            
               <DD>

            
                <P>

            
                A rule preceded by an asterisk ("*") may have zero or more

            
                occurrences. A rule preceded by an integer followed by an asterisk

            
                must occur at least the specified number of times.

            
                </P>

            
               </DD>

            
               <DT>[rule]

            
               </DT>

            
               <DD>

            
                <P>

            
                An element enclosed in square

            
                brackets ("[" and "]") is optional.

            
                </P>

            
               </DD>

            
              </DL>


              <H3>

            
               <A NAME="2.2">

            
                2.2. Basic Rules

            
               </A>

            
              </H3>

            
              <P>

            
              The following rules are used throughout this specification to

            
              describe basic parsing constructs.

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                alpha         = lowalpha | hialpha

            
                alphanum      = alpha | digit

            
                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"

            
                hex           = digit | "A" | "B" | "C" | "D" | "E" | "F" | "a"

            
                                | "b" | "c" | "d" | "e" | "f"

            
                escaped       = "%" hex hex

            
                OCTET         = &lt;any 8-bit sequence of data&gt;

            
                CHAR          = &lt;any US-ASCII character (octets 0 - 127)&gt;

            
                CTL           = &lt;any US-ASCII control character

            
                                (octets 0 - 31) and DEL (127)&gt;

            
                CR            = &lt;US-ASCII CR, carriage return (13)&gt;

            
                LF            = &lt;US-ASCII LF, linefeed (10)&gt;

            
                SP            = &lt;US-ASCII SP, space (32)&gt;

            
                HT            = &lt;US-ASCII HT, horizontal tab (9)&gt;

            
                NL            = CR | LF

            
                LWSP          = SP | HT | NL

            
                tspecial      = "(" | ")" | "@" | "," | ";" | ":" | "\" | &lt;"&gt;

            
                                | "/" | "[" | "]" | "?" | "&lt;" | "&gt;" | "{" | "}"

            
                                | SP | HT | NL

            
                token         = 1*&lt;any CHAR except CTLs or tspecials&gt;

            
                quoted-string = ( &lt;"&gt; *qdtext &lt;"&gt; ) | ( "&lt;" *qatext "&gt;")

            
                qdtext        = &lt;any CHAR except &lt;"&gt; and CTLs but including LWSP&gt;

            
                qatext        = &lt;any CHAR except "&lt;", "&gt;" and CTLs but

            
                                including LWSP&gt;

            
                mark          = "-" | "_" | "." | "!" | "~" | "*" | "'" | "(" | ")"

            
                unreserved    = alphanum | mark

            
                reserved      = ";" | "/" | "?" | ":" | "@" | "&amp;" | "=" |

            
                                "$" | ","

            
                uric          = reserved | unreserved | escaped

            
              </PRE>

            
              <P>

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

            
              character sequence.

            
              </P>


              <H2>

            
               <A NAME="3.0">

            
                3. Protocol Parameters

            
               </A>

            
              </H2>


              <H3>

            
               <A NAME="3.1">

            
                3.1. URL Encoding

            
               </A>

            
              </H3>

            
              <P>

            
              Some variables and constructs used here are described as being

            
              'URL-encoded'. This encoding is described in section

            
              2 of RFC

            
              2396

            
              [<A HREF="#[4]">4</A>].

            
              </P>

            
              <P>

            
              An alternate "shortcut" encoding for representing the space

            
              character exists and is in common use.  Scripts MUST be prepared to

            
              recognise both '+' and '%20' as an encoded space in a

            
              URL-encoded value.

            
              </P>

            
              <P>

            
              Note that some unsafe characters may have different semantics if

            
              they are encoded. The definition of which characters are unsafe

            
              depends on the context.

            
              For example, the following two URLs do not

            
              necessarily refer to the same resource:

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                http://somehost.com/somedir%2Fvalue

            
                http://somehost.com/somedir/value

            
              </PRE>

            
              <P>

            
              See section

            
              2 of RFC

            
              2396 [<A HREF="#[4]">4</A>]

            
              for authoritative treatment of this issue.

            
              </P>


              <H3>

            
               <A NAME="3.2">

            
                3.2. The Script-URI

            
               </A>

            
              </H3>

            
              <P>

            
              The 'Script-URI' is defined as the URI of the resource identified

            
              by the metavariables.   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.

            
              </P>

            
              <P>

            
              The Script-URI has the syntax of generic-RL as defined in section 2.1

            
              of RFC 1808 [<A HREF="#[7]">7</A>], with the exception that object

            
              parameters and

            
              fragment identifiers are not permitted:

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                &lt;scheme&gt;://&lt;host&gt;&lt;port&gt;/&lt;path&gt;?&lt;query&gt;

            
              </PRE>

            
              <P>

            
              The various components of the

            
              Script-URI

            
              are defined by some of the

            
              metavariables (see

            
              <A HREF="#4.0">section 4</A>

            
              below);

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                script-uri = protocol "://" SERVER_NAME ":" SERVER_PORT enc-script

            
                             enc-path-info "?" QUERY_STRING

            
              </PRE>

            
              <P>

            
              where 'protocol' is obtained

            
              from SERVER_PROTOCOL, 'enc-script' is a

            
              URL-encoded version of SCRIPT_NAME and 'enc-path-info' is a

            
              URL-encoded version of PATH_INFO.  See

            
              <A HREF="#4.6">section 4.6</A> for more information about the PATH_INFO

            
              metavariable.

            
              </P>

            
              <P>

            
              Note that the scheme and the protocol are <EM>not</EM> identical;

            
              for instance, a resource accessed <EM>via</EM> an SSL mechanism

            
              may have a Client-URI with a scheme of "<SAMP>https</SAMP>"

            
              rather than "<SAMP>http</SAMP>".   CGI/1.1 provides no means

            
              for the script to reconstruct this, and therefore

            
              the Script-URI includes the base protocol used.

            
              </P>


              <H2>

            
               <A NAME="4.0">

            
                4. Invoking the Script

            
               </A>

            
              </H2>

            
              <P>

            
              The

            
              script is invoked in a system defined manner. Unless specified

            
              otherwise, the file containing the script will be invoked as an

            
              executable program.

            
              </P>


              <H2>

            
               <A NAME="5.0">

            
                5. The CGI Script Command Line

            
               </A>

            
              </H2>

            
              <P>

            
              Some systems support a method for supplying an array of strings to

            
              the CGI script. This is only used in the case of an 'indexed' query.

            
              This is identified by a "GET" or "HEAD" HTTP request with a URL

            
              query

            
              string not containing any unencoded "=" characters. For such a

            
              request,

            
              servers SHOULD parse the search string

            
              into words, using the following rules:

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                search-string = search-word *( "+" search-word )

            
                search-word   = 1*schar

            
                schar         = xunreserved | escaped | xreserved

            
                xunreserved   = alpha | digit | xsafe | extra

            
                xsafe         = "$" | "-" | "_" | "."

            
                xreserved     = ";" | "/" | "?" | ":" | "@" | "&"

            
              </PRE>

            
              <P>

            
              After parsing, each word is URL-decoded, optionally encoded in a

            
              system defined manner,

            
              and then the argument list is set to the list

            
              of words.

            
              </P>

            
              <P>

            
              If the server cannot create any part of the argument list, then the

            
              server SHOULD NOT generate any command line information. For example, the

            
              number of arguments may be greater than operating system or server

            
              limitations permit, or one of the words may not be representable as an

            
              argument.

            
              </P>

            
              <P>

            
              Scripts SHOULD check to see if the QUERY_STRING value contains an

            
              unencoded "=" character, and SHOULD NOT use the command line arguments

            
              if it does.

            
              </P>


              <H2>

            
               <A NAME="6.0">

            
                6. Data Input to the CGI Script

            
               </A>

            
              </H2>

            
              <P>

            
              Information about a request comes from two different sources: the

            
              request header, and any associated

            
              message-body.

            
              Servers MUST

            
              make portions of this information available to

            
               scripts.

            
              </P>


              <H3>

            
               <A NAME="6.1">

            
                6.1. Request Metadata

            
                (Metavariables)

            
               </A>

            
              </H3>

            
              <P>

            
              Each CGI server

            
              implementation MUST define a mechanism

            
              to pass data about the request from

            
              the server to the script.

            
              The metavariables containing these

            
              data

            
              are accessed by the script in a system

            
              defined manner.

            
              The

            
              representation of the characters in the

            
              metavariables is

            
              system defined.

            
              </P>

            
              <P>

            
              This specification does not distinguish between the representation of

            
              null values and missing ones.  Whether null or missing values

            
              (such as a query component of "?" or "", respectively) are represented

            
              by undefined metavariables or by metavariables with values of "" is

            
              implementation-defined.

            
              </P>

            
              <P>

            
              Case is not significant in the

            
              metavariable

            
              names, in that there cannot be two

            
              different variables

            
              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

            
              than this.

            
              </P>

            
              <P>

            
              Metavariable

            
              values MUST be

            
              considered case-sensitive except as noted

            
              otherwise.

            
              </P>

            
              <P>

            
              The canonical

            
              metavariables

            
              defined by this specification are:

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                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

            
              </PRE>

            
              <P>

            
              Metavariables with names beginning with the protocol name (<EM>e.g.</EM>,

            
              "HTTP_ACCEPT") are also canonical in their description of request header

            
              fields.  The number and meaning of these fields may change independently

            
              of this specification.  (See also <A HREF="#6.1.5">section 6.1.5</A>.)

            
              </P>


              <H4>

            
               <A NAME="6.1.1">

            
                6.1.1. AUTH_TYPE

            
               </A>

            
              </H4>

            
              <P>

            
              This variable is specific to requests made

            
              <EM>via</EM> the

            
              "<CODE>http</CODE>"

            
              scheme.

            
              </P>

            
              <P>

            
              If the Script-URI

            
              required access authentication for external

            
              access, then the server

            
              MUST set

            
              the value of

            
              this variable

            
              from the '<SAMP>auth-scheme</SAMP>' token in

            
              the request's "<SAMP>Authorization</SAMP>" header

            
              field.

            
              Otherwise

            
              it is

            
              set to NULL.

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                AUTH_TYPE   = "" | auth-scheme

            
                auth-scheme = "Basic" | "Digest" | token

            
              </PRE>

            
              <P>

            
              HTTP access authentication schemes are described in section 11 of the

            
              HTTP/1.1 specification [<A HREF="#[8]">8</A>]. The auth-scheme is

            
              not case-sensitive.

            
              </P>

            
              <P>

            
              Servers

            
              MUST

            
              provide this metavariable

            
              to scripts if the request

            
              header included an "<SAMP>Authorization</SAMP>" field

            
              that was authenticated.

            
              </P>


              <H4>

            
               <A NAME="6.1.2">

            
                6.1.2. CONTENT_LENGTH

            
               </A>

            
              </H4>

            
              <P>

            
              This

            
              metavariable

            
              is set to the

            
              size of the message-body

            
              entity attached to the request, if any, in decimal

            
              number of octets. If no data are attached, then this

            
              metavariable

            
              is either NULL or not

            
              defined. The syntax is

            
              the same as for

            
              the HTTP "<SAMP>Content-Length</SAMP>" header field (section 14.14, HTTP/1.1

            
              specification [<A HREF="#[8]">8</A>]).

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                CONTENT_LENGTH = "" | 1*digit

            
              </PRE>

            
              <P>

            
              Servers MUST provide this metavariable

            
              to scripts if the request

            
              was accompanied by a

            
              message-body entity.

            
              </P>


              <H4>

            
               <A NAME="6.1.3">

            
                6.1.3. CONTENT_TYPE

            
               </A>

            
              </H4>

            
              <P>

            
              If the request includes a

            
              message-body,

            
              CONTENT_TYPE is set

            
              to

            
              the Internet Media Type

            
              [<A HREF="#[9]">9</A>] of the attached

            
              entity if the type was provided <EM>via</EM>

            
              a "<SAMP>Content-type</SAMP>" field in the

            
              request header, or if the server can determine it in the absence

            
              of a supplied "<SAMP>Content-type</SAMP>" field. The syntax is the

            
              same as for the HTTP

            
              "<SAMP>Content-Type</SAMP>" header field.

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                CONTENT_TYPE = "" | media-type

            
                media-type   = type "/" subtype *( ";" parameter)

            
                type         = token

            
                subtype      = token

            
                parameter    = attribute "=" value

            
                attribute    = token

            
                value        = token | quoted-string

            
              </PRE>

            
              <P>

            
              The type, subtype,

            
              and parameter attribute names are not

            
              case-sensitive. Parameter values MAY be case sensitive.

            
              Media types and their use in HTTP are described

            
              in section 3.7 of the

            
              HTTP/1.1 specification [<A HREF="#[8]">8</A>].

            
              </P>

            
              <P>

            
              Example:

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                application/x-www-form-urlencoded

            
              </PRE>

            
              <P>

            
              There is no default value for this variable. If and only if it is

            
              unset, then the script MAY attempt to determine the media type from

            
              the data received. If the type remains unknown, then

            
              the script MAY choose to either assume a

            
              content-type of

            
              <SAMP>application/octet-stream</SAMP>

            
              or reject the request with  a 415 ("Unsupported Media Type")

            
              error.  See <A HREF="#7.2.1.3">section 7.2.1.3</A>

            
              for more information about returning error status values.

            
              </P>

            
              <P>

            
              Servers MUST provide this metavariable

            
              to scripts if

            
              a "<SAMP>Content-Type</SAMP>" field was present

            
              in the original request header.  If the server receives a request

            
              with an attached entity but no "<SAMP>Content-Type</SAMP>"

            
              header field, it MAY attempt to

            
              determine the correct datatype, or it MAY omit this

            
              metavariable when

            
              communicating the request information to the script.

            
              </P>


              <H4>

            
               <A NAME="6.1.4">

            
                6.1.4. GATEWAY_INTERFACE

            
               </A>

            
              </H4>

            
              <P>

            
              This

            
              metavariable

            
              is set to

            
              the dialect of CGI being used

            
              by the server to communicate with the script.

            
              Syntax:

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                GATEWAY_INTERFACE = "CGI" "/" major "." minor

            
                major             = 1*digit

            
                minor             = 1*digit

            
              </PRE>

            
              <P>

            
              Note that the major and minor numbers are treated as separate

            
              integers and hence each may be

            
              more than a single

            
              digit. Thus CGI/2.4 is a lower version than CGI/2.13 which in turn

            
              is lower than CGI/12.3. Leading zeros in either

            
              the major or the minor number MUST be ignored by scripts and

            
              SHOULD NOT be generated by servers.

            
              </P>

            
              <P>

            
              This document defines the 1.1 version of the CGI interface

            
              ("CGI/1.1").

            
              </P>

            
              <P>

            
              Servers MUST provide this metavariable

            
              to scripts.

            
              </P>


              <H4>

            
               <A NAME="6.1.5">

            
                6.1.5. Protocol-Specific Metavariables

            
               </A>

            
              </H4>

            
              <P>

            
              These metavariables are specific to

            
              the protocol

            
              <EM>via</EM> which the request is made.

            
              Interpretation of these variables depends on the value of

            
              the

            
              SERVER_PROTOCOL

            
              metavariable

            
              (see

            
              <A HREF="#6.1.17">section 6.1.17</A>).

            
              </P>

            
              <P>

            
              Metavariables

            
              with names beginning with "HTTP_" contain

            
              values from the request header, if the

            
              scheme used was HTTP.

            
              Each

            
              HTTP header field name is converted to upper case, has all occurrences of

            
              "-" replaced with "_",

            
              and has "HTTP_" prepended to  form

            
              the metavariable name.

            
              Similar transformations are applied for other

            
              protocols.

            
              The header data MAY be presented as sent

            
              by the client, or MAY be rewritten in ways which do not change its

            
              semantics. If multiple header fields with the same field-name are received

            
              then  the server

            
              MUST  rewrite them as though they

            
              had been received as a single header field having the same

            
              semantics before being represented in a

            
              metavariable.

            
              Similarly, a header field that is received on more than one line

            
              MUST be merged into a single line. The server MUST, if necessary,

            
              change the representation of the data (for example, the character

            
              set) to be appropriate for a CGI

            
              metavariable.

            
              <!-- ###NOTE: See if 2068 describes this thoroughly, and

            
              point there if so. -->

            
              </P>

            
              <P>

            
              Servers are

            
              not required to create

            
              metavariables for all

            
              the request

            
              header fields that they

            
              receive. In particular,

            
              they MAY

            
              decline to make available any

            
              header fields carrying authentication information, such as

            
              "<SAMP>Authorization</SAMP>", or

            
              which are available to the script

            
              <EM>via</EM> other metavariables,

            
              such as "<SAMP>Content-Length</SAMP>" and "<SAMP>Content-Type</SAMP>".

            
              </P>


              <H4>

            
               <A NAME="6.1.6">

            
                6.1.6. PATH_INFO

            
               </A>

            
              </H4>

            
              <P>

            
              The PATH_INFO

            
              metavariable

            
              specifies

            
              a path to be interpreted by the CGI script. It identifies the

            
              resource or sub-resource to be returned

            
              by the CGI

            
              script, and it is derived from the portion

            
              of the URI path following the script name but preceding

            
              any query data.

            
              The syntax

            
              and semantics are similar to a decoded HTTP URL

            
              'path' token

            
              (defined in

            
              RFC 2396

            
              [<A HREF="#[4]">4</A>]), with the exception

            
              that a PATH_INFO of "/"

            
              represents a single void path segment.

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                PATH_INFO = "" | ( "/" path )

            
                path      = segment *( "/" segment )

            
                segment   = *pchar

            
                pchar     = &lt;any CHAR except "/"&gt;

            
              </PRE>

            
              <P>

            
              The PATH_INFO string is the trailing part of the &lt;path&gt; component of

            
              the Script-URI

            
              (see <A HREF="#3.2">section 3.2</A>)

            
              that follows the SCRIPT_NAME

            
              portion of the path.

            
              </P>

            
              <P>

            
              Servers MAY impose their own restrictions and

            
              limitations on what values they will accept for PATH_INFO, and MAY

            
              reject or edit any values they

            
              consider objectionable before passing

            
              them to the script.

            
              </P>

            
              <P>

            
              Servers MUST make this URI component available

            
              to CGI scripts.  The PATH_INFO

            
              value is case-sensitive, and the

            
              server MUST preserve the case of the PATH_INFO element of the URI

            
              when making it available to scripts.

            
              </P>


              <H4>

            
               <A NAME="6.1.7">

            
                6.1.7. PATH_TRANSLATED

            
               </A>

            
              </H4>

            
              <P>

            
              PATH_TRANSLATED is derived by taking any path-info component of the

            
              request URI (see

            
              <A HREF="#6.1.6">section 6.1.6</A>), decoding it

            
              (see <A HREF="#3.1">section 3.1</A>), parsing it as a URI in its own

            
              right, and performing any virtual-to-physical

            
              translation appropriate to map it onto the

            
              server's document repository structure.

            
              If the request URI includes no path-info

            
              component, the PATH_TRANSLATED metavariable SHOULD NOT be defined.

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                PATH_TRANSLATED = *CHAR

            
              </PRE>

            
              <P>

            
              For a request such as the following:

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                http://somehost.com/cgi-bin/somescript/this%2eis%2epath%2einfo

            
              </PRE>

            
              <P>

            
              the PATH_INFO component would be decoded, and the result

            
              parsed as though it were a request for the following:

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                http://somehost.com/this.is.the.path.info

            
              </PRE>

            
              <P>

            
              This would then be translated to a

            
              location in the server's document repository,

            
              perhaps a filesystem path something

            
              like this:

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                /usr/local/www/htdocs/this.is.the.path.info

            
              </PRE>

            
              <P>

            
              The result of the translation is the value of PATH_TRANSLATED.

            
              </P>

            
              <P>

            
              The value of PATH_TRANSLATED may or may not map to a valid

            
              repository

            
              location.

            
              Servers MUST preserve the case of the path-info

            
              segment if and only if the underlying

            
              repository

            
              supports case-sensitive

            
              names.  If the

            
              repository

            
              is only case-aware, case-preserving, or case-blind

            
              with regard to

            
              document names,

            
              servers are not required to preserve the

            
              case of the original segment through the translation.

            
              </P>

            
              <P>

            
              The

            
              translation

            
              algorithm the server uses to derive PATH_TRANSLATED is

            
              implementation defined; CGI scripts which use this variable may

            
              suffer limited portability.

            
              </P>

            
              <P>

            
              Servers SHOULD provide this metavariable

            
              to scripts if and only if the request URI includes a

            
              path-info component.

            
              </P>


              <H4>

            
               <A NAME="6.1.8">

            
                6.1.8. QUERY_STRING

            
               </A>

            
              </H4>

            
              <P>

            
              A URL-encoded

            
              string; the &lt;query&gt; part of the

            
              Script-URI.

            
              (See

            
              <A HREF="#3.2">section 3.2</A>.)

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                QUERY_STRING = query-string

            
                query-string = *uric

            
              </PRE>

            
              <P>

            
              The URL syntax for a  query

            
              string is described in

            
              section 3 of

            
              RFC 2396

            
              [<A HREF="#[4]">4</A>].

            
              </P>

            
              <P>

            
              Servers MUST supply this value to scripts.

            
              The QUERY_STRING value is case-sensitive.

            
              If the Script-URI does not include a query component,

            
              the QUERY_STRING metavariable MUST be defined as an empty string ("").

            
              </P>


              <H4>

            
               <A NAME="6.1.9">

            
                6.1.9. REMOTE_ADDR

            
               </A>

            
              </H4>

            
              <P>

            
              The IP address of the client

            
              sending the request to the server. This

            
              is not necessarily that of the user

            
              agent

            
              (such as if the request came through a proxy).

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                REMOTE_ADDR  = hostnumber

            
                hostnumber   = ipv4-address | ipv6-address

            
              </PRE>

            
              <P>

            
              The definitions of <SAMP>ipv4-address</SAMP> and <SAMP>ipv6-address</SAMP>

            
              are provided in Appendix B of RFC 2373 [<A HREF="#[13]">13</A>].

            
              </P>

            
              <P>

            
              Servers MUST supply this value to scripts.

            
              </P>


              <H4>

            
               <A NAME="6.1.10">

            
                6.1.10. REMOTE_HOST

            
               </A>

            
              </H4>

            
              <P>

            
              The fully qualified domain name of the

            
              client sending the request to

            
              the server, if available, otherwise NULL.

            
              (See <A HREF="#6.1.9">section 6.1.9</A>.)

            
              Fully qualified domain names take the form as described in

            
              section 3.5 of RFC 1034 [<A HREF="#[10]">10</A>] and section 2.1 of

            
              RFC 1123 [<A HREF="#[5]">5</A>].  Domain names are not case sensitive.

            
              </P>

            
              <P>

            
              Servers SHOULD provide this information to

            
              scripts.

            
              </P>


              <H4>

            
               <A NAME="6.1.11">

            
                6.1.11. REMOTE_IDENT

            
               </A>

            
              </H4>

            
              <P>

            
              The identity information reported about the connection by a

            
              RFC 1413 [<A HREF="#[11]">11</A>] request to the remote agent, if

            
              available. Servers

            
              MAY choose not

            
              to support this feature, or not to request the data

            
              for efficiency reasons.

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                REMOTE_IDENT = *CHAR

            
              </PRE>

            
              <P>

            
              The data returned

            
              may be used for authentication purposes, but the level

            
              of trust reposed in them should be minimal.

            
              </P>

            
              <P>

            
              Servers MAY supply this information to scripts if the

            
              RFC1413 [<A HREF="#[11]">11</A>] lookup is performed.

            
              </P>


              <H4>

            
               <A NAME="6.1.12">

            
                6.1.12. REMOTE_USER

            
               </A>

            
              </H4>

            
              <P>

            
              If the request required authentication using the "Basic"

            
              mechanism (<EM>i.e.</EM>, the AUTH_TYPE

            
              metavariable is set

            
              to "Basic"), then the value of the REMOTE_USER

            
              metavariable is set to the

            
              user-ID supplied.  In all other cases

            
              the value of this metavariable

            
              is undefined.

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                REMOTE_USER = *OCTET

            
              </PRE>

            
              <P>

            
              This variable is specific to requests made <EM>via</EM> the

            
              HTTP protocol.

            
              </P>

            
              <P>

            
              Servers SHOULD provide this metavariable

            
              to scripts.

            
              </P>


              <H4>

            
               <A NAME="6.1.13">

            
                6.1.13. REQUEST_METHOD

            
               </A>

            
              </H4>

            
              <P>

            
              The REQUEST_METHOD

            
              metavariable

            
              is set to the

            
              method with which the request was made, as described in section

            
              5.1.1 of the HTTP/1.0 specification [<A HREF="#[3]">3</A>] and

            
              section 5.1.1 of the

            
              HTTP/1.1 specification [<A HREF="#[8]">8</A>].

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                REQUEST_METHOD   = http-method

            
                http-method      = "GET" | "HEAD" | "POST" | "PUT" | "DELETE"

            
                                   | "OPTIONS" | "TRACE" | extension-method

            
                extension-method = token

            
              </PRE>

            
              <P>

            
              The method is case sensitive.

            
              CGI/1.1 servers MAY choose to process some methods

            
              directly rather than passing them to scripts.

            
              </P>

            
              <P>

            
              This variable is specific to requests made with HTTP.

            
              </P>

            
              <P>

            
              Servers MUST provide this metavariable

            
              to scripts.

            
              </P>


              <H4>

            
               <A NAME="6.1.14">

            
                6.1.14. SCRIPT_NAME

            
               </A>

            
              </H4>

            
              <P>

            
              The SCRIPT_NAME

            
              metavariable

            
              is

            
              set to a URL path that could identify the CGI script (rather than the

            
              script's

            
              output). The syntax and semantics are identical to a

            
              decoded HTTP URL 'path' token

            
              (see RFC 2396

            
              [<A HREF="#[4]">4</A>]).

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                SCRIPT_NAME = "" | ( "/" [ path ] )

            
              </PRE>

            
              <P>

            
              The SCRIPT_NAME string is some leading part of the &lt;path&gt; component

            
              of the Script-URI derived in some

            
              implementation defined manner.

            
              No PATH_INFO or QUERY_STRING segments

            
              (see sections <A HREF="#6.1.6">6.1.6</A> and

            
              <A HREF="#6.1.8">6.1.8</A>) are included

            
              in the SCRIPT_NAME value.

            
              </P>

            
              <P>

            
              Servers MUST provide this metavariable

            
              to scripts.

            
              </P>


              <H4>

            
               <A NAME="6.1.15">

            
                6.1.15. SERVER_NAME

            
               </A>

            
              </H4>

            
              <P>

            
              The SERVER_NAME

            
              metavariable

            
              is set to the

            
              name  of the

            
              server, as

            
              derived from the &lt;host&gt; part of the

            
              Script-URI

            
              (see <A HREF="#3.2">section 3.2</A>).

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                SERVER_NAME = hostname | hostnumber

            
              </PRE>

            
              <P>

            
              Servers MUST provide this metavariable

            
              to scripts.

            
              </P>


              <H4>

            
               <A NAME="6.1.16">

            
                6.1.16. SERVER_PORT

            
               </A>

            
              </H4>

            
              <P>

            
              The SERVER_PORT

            
              metavariable

            
              is set to the

            
              port on which the

            
              request was received, as used in the &lt;port&gt;

            
              part of the Script-URI.

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                SERVER_PORT = 1*digit

            
              </PRE>

            
              <P>

            
              If the &lt;port&gt; portion of the script-URI is blank, the actual

            
              port number upon which the request was received MUST be supplied.

            
              </P>

            
              <P>

            
              Servers MUST provide this metavariable

            
              to scripts.

            
              </P>


              <H4>

            
               <A NAME="6.1.17">

            
                6.1.17. SERVER_PROTOCOL

            
               </A>

            
              </H4>

            
              <P>

            
              The SERVER_PROTOCOL

            
              metavariable

            
              is set to

            
              the

            
              name and revision of the information protocol with which

            
              the

            
              request

            
              arrived.  This is not necessarily the same as the protocol version used by

            
              the server in its response to the client.

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                SERVER_PROTOCOL   = HTTP-Version | extension-version

            
                                    | extension-token

            
                HTTP-Version      = "HTTP" "/" 1*digit "." 1*digit

            
                extension-version = protocol "/" 1*digit "." 1*digit

            
                protocol          = 1*( alpha | digit | "+" | "-" | "." )

            
                extension-token   = token

            
              </PRE>

            
              <P>

            
              'protocol' is a version of the &lt;scheme&gt; part of the

            
              Script-URI, but is

            
              not identical to it.  For example, the scheme of a request may be

            
              "<SAMP>https</SAMP>" while the protocol remains "<SAMP>http</SAMP>".

            
              The protocol is not case sensitive, but

            
              by convention, 'protocol' is in

            
              upper case.

            
              </P>

            
              <P>

            
              A well-known extension token value is "INCLUDED",

            
              which signals that the current document is being included as part of

            
              a composite document, rather than being the direct target of the

            
              client request.

            
              </P>

            
              <P>

            
              Servers MUST provide this metavariable

            
              to scripts.

            
              </P>


              <H4>

            
               <A NAME="6.1.18">

            
                6.1.18. SERVER_SOFTWARE

            
               </A>

            
              </H4>

            
              <P>

            
              The SERVER_SOFTWARE

            
              metavariable

            
              is set to the

            
              name and version of the information server software answering the

            
              request (and running the gateway).

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                SERVER_SOFTWARE = 1*product

            
                product         = token [ "/" product-version ]

            
                product-version = token

            
              </PRE>

            
              <P>

            
              Servers MUST provide this metavariable

            
              to scripts.

            
              </P>


              <H3>

            
               <A NAME="6.2">

            
                6.2. Request Message-Bodies

            
               </A>

            
              </H3>

            
              <P>

            
              As there may be a data entity attached to the request, there MUST be

            
              a system defined method for the script to read

            
              these data. Unless

            
              defined otherwise, this will be <EM>via</EM> the 'standard input' file

            
              descriptor.

            
              </P>

            
              <P>

            
              If the CONTENT_LENGTH value (see <A HREF="#6.1.2">section 6.1.2</A>)

            
              is non-NULL, the server MUST supply at least that many bytes to

            
              scripts on the standard input stream.

            
              Scripts are

            
              not obliged to read the data.

            
              Servers MAY signal an EOF condition after CONTENT_LENGTH bytes have been

            
              read, but are

            
              not obligated to do so.  Therefore, scripts

            
              MUST NOT

            
              attempt to read more than CONTENT_LENGTH bytes, even if more data

            
              are available.

            
              </P>

            
              <P>

            
              For non-parsed header (NPH) scripts (see

            
              <A HREF="#7.1">section 7.1</A>

            
              below),

            
              servers SHOULD

            
              attempt to ensure that the data

            
              supplied to the script are precisely

            
              as supplied by the client and unaltered by

            
              the server.

            
              </P>

            
              <P>

            
              <A HREF="#8.1.2">Section 8.1.2</A> describes the requirements of

            
              servers with regard to requests that include

            
              message-bodies.

            
              </P>


              <H2>

            
               <A NAME="7.0">

            
                7. Data Output from the CGI Script

            
               </A>

            
              </H2>

            
              <P>

            
              There MUST be a system defined method for the script to send data

            
              back to the server or client; a script MUST always return some data.

            
              Unless defined otherwise, this will be <EM>via</EM> the 'standard

            
              output' file descriptor.

            
              </P>

            
              <P>

            
              There are two forms of output that  scripts can supply to servers: non-parsed

            
              header (NPH) output, and parsed header output.

            
              Servers MUST support parsed header

            
              output and MAY support NPH output.  The method of

            
              distinguishing between the two

            
              types of output (or scripts) is implementation defined.

            
              </P>

            
              <P>

            
              Servers MAY implement a timeout period within which data must be

            
              received from scripts.  If a server implementation defines such

            
              a timeout and receives no data from a script within the timeout

            
              period, the server MAY terminate the script process and SHOULD

            
              abort the client request with

            
              either a

            
              '504 Gateway Timed Out' or a

            
              '500 Internal Server Error' response.

            
              </P>


              <H3>

            
               <A NAME="7.1">

            
                7.1. Non-Parsed Header Output

            
               </A>

            
              </H3>

            
              <P>

            
              Scripts using the NPH output form

            
              MUST return a complete HTTP response message, as described

            
              in Section 6 of the HTTP specifications

            
              [<A HREF="#[3]">3</A>,<A HREF="#[8]">8</A>].

            
               NPH scripts

            
              MUST use the SERVER_PROTOCOL variable to determine the appropriate format

            
              for a response.

            
              </P>

            
              <P>

            
              Servers

            
              SHOULD attempt to ensure that the script output is sent

            
              directly to the client, with minimal

            
              internal and no transport-visible

            
              buffering.

            
              </P>


              <H3>

            
               <A NAME="7.2">

            
                7.2. Parsed Header Output

            
               </A>

            
              </H3>

            
              <P>

            
              Scripts using the parsed header output form MUST supply

            
              a CGI response message to the server

            
              as follows:

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                CGI-Response   = *optional-field CGI-Field *optional-field NL [ Message-Body ]

            
                optional-field = ( CGI-Field | HTTP-Field )

            
                CGI-Field      = Content-type

            
                               | Location

            
                               | Status

            
                               | extension-header

            
              </PRE>

            
              <P><!-- ##### If HTTP defines x-headers, remove ours except x-cgi- -->

            
              The response comprises a header and a body, separated by a blank line.

            
              The body may be NULL.

            
              The header fields are either CGI header fields to be interpreted by

            
              the server, or HTTP header fields

            
              to be included in the response returned

            
              to the client

            
              if the request method is HTTP. At least one

            
              CGI-Field MUST be

            
              supplied, but no CGI  field name may be used more than once

            
              in a response.

            
              If a body is supplied, then a "<SAMP>Content-type</SAMP>"

            
              header field MUST be

            
              supplied by the script,

            
              otherwise the script MUST send a "<SAMP>Location</SAMP>"

            
              or "<SAMP>Status</SAMP>" header field. If a

            
              <SAMP>Location</SAMP> CGI-Field

            
              is returned, then the script MUST NOT supply

            
              any HTTP-Fields.

            
              </P>

            
              <P>

            
              Each header field in a CGI-Response MUST be specified on a single line;

            
              CGI/1.1 does not support continuation lines.

            
              </P>


              <H4>

            
               <A NAME="7.2.1">

            
                7.2.1. CGI header fields

            
               </A>

            
              </H4>

            
              <P>

            
              The CGI header fields have the generic syntax:

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                generic-field  = field-name ":" [ field-value ] NL

            
                field-name     = token

            
                field-value    = *( field-content | LWSP )

            
                field-content  = *( token | tspecial | quoted-string )

            
              </PRE>

            
              <P>

            
              The field-name is not case sensitive; a NULL field value is

            
              equivalent to the header field not being sent.

            
              </P>


              <H4>

            
               <A NAME="7.2.1.1">

            
                7.2.1.1. Content-Type

            
               </A>

            
              </H4>

            
              <P>

            
              The Internet Media Type [<A HREF="#[9]">9</A>] of the entity

            
              body, which is to be sent unmodified to the client.

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                Content-Type = "Content-Type" ":" media-type NL

            
              </PRE>

            
              <P>

            
              This is actually an HTTP-Field

            
              rather than a CGI-Field, but

            
              it is listed here because of its importance in the CGI dialogue as

            
              a member of the "one of these is required" set of header

            
              fields.

            
              </P>


              <H4>

            
               <A NAME="7.2.1.2">

            
                7.2.1.2. Location

            
               </A>

            
              </H4>

            
              <P>

            
              This is used to specify to the server that the script is returning a

            
              reference to a document rather than an actual document.

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                Location         = "Location" ":"

            
                                   ( fragment-URI | rel-URL-abs-path ) NL

            
                fragment-URI     = URI [ # fragmentid ]

            
                URI              = scheme ":" *qchar

            
                fragmentid       = *qchar

            
                rel-URL-abs-path = "/" [ hpath ] [ "?" query-string ]

            
                hpath            = fpsegment *( "/" psegment )

            
                fpsegment        = 1*hchar

            
                psegment         = *hchar

            
                hchar            = alpha | digit | safe | extra

            
                                   | ":" | "@" | "& | "="

            
              </PRE>

            
              <P>

            
              The Location

            
              value is either an absolute URI with optional fragment,

            
              as defined in RFC 1630 [<A HREF="#[1]">1</A>], or an absolute path

            
              within the server's URI space (<EM>i.e.</EM>,

            
              omitting the scheme and network-related fields) and optional

            
              query-string. If an absolute URI is returned by the script,

            
              then the

            
              server MUST generate a

            
              '302 redirect' HTTP response

            
              message unless the script has supplied an

            
              explicit Status response header field.

            
              Scripts returning an absolute URI MAY choose to

            
              provide a message-body.  Servers MUST make any appropriate modifications

            
              to the script's output to ensure the response to the user-agent complies

            
              with the response protocol version.

            
              If the Location value is a path, then the server

            
              MUST generate

            
              the response that it would have produced in response to a request

            
              containing the URL

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                scheme "://" SERVER_NAME ":" SERVER_PORT rel-URL-abs-path

            
              </PRE>

            
              <P>

            
              Note: If the request was accompanied by a

            
              message-body

            
              (such as for a POST request), and the script

            
              redirects the request with a Location field, the

            
              message-body

            
              may not be

            
              available to the resource that is the target of the redirect.

            
              </P>


              <H4>

            
               <A NAME="7.2.1.3">

            
                7.2.1.3. Status

            
               </A>

            
              </H4>

            
              <P>

            
              The "<SAMP>Status</SAMP>" header field is used to indicate to the server what

            
              status code the server MUST use in the response message.

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                Status        = "Status" ":" digit digit digit SP reason-phrase NL

            
                reason-phrase = *&lt;CHAR, excluding CTLs, NL&gt;

            
              </PRE>

            
              <P>

            
              The valid status codes are listed in section 6.1.1 of the HTTP/1.0

            
              specifications [<A HREF="#[3]">3</A>]. If the SERVER_PROTOCOL is

            
              "HTTP/1.1", then the status codes defined in the HTTP/1.1

            
              specification [<A HREF="#[8]">8</A>] may

            
              be used. If the script does not return a "<SAMP>Status</SAMP>" header

            
              field, then "200 OK" SHOULD be assumed by the server.

            
              </P>

            
              <P>

            
              If a script is being used to handle a particular error or condition

            
              encountered by the server, such as a '404 Not Found' error, the script

            
              SHOULD use the "<SAMP>Status</SAMP>" CGI header field to propagate the error

            
              condition back to the client.  <EM>E.g.</EM>, in the example mentioned it

            
              SHOULD include a "Status:&nbsp;404&nbsp;Not&nbsp;Found" in the

            
              header data returned to the server.

            
              </P>


              <H4>

            
               <A NAME="7.2.1.4">

            
                7.2.1.4. Extension header fields

            
               </A>

            
              </H4>

            
              <P>

            
              Scripts MAY include in their CGI response header additional fields

            
              not defined in this or the HTTP specification.

            
              These are called "extension" fields,

            
              and have the syntax of a <SAMP>generic-field</SAMP> as defined in

            
              <A HREF="#7.2.1">section 7.2.1</A>.  The name of an extension field

            
              MUST NOT conflict with a field name defined in this or any other

            
              specification; extension field names SHOULD begin with "X-CGI-"

            
              to ensure uniqueness.

            
              </P>


              <H4>

            
               <A NAME="7.2.2">

            
                7.2.2. HTTP header fields

            
               </A>

            
              </H4>

            
              <P>

            
              The script MAY return any other header fields defined by the

            
              specification

            
              for the SERVER_PROTOCOL (HTTP/1.0 [<A HREF="#[3]">3</A>] or HTTP/1.1

            
              [<A HREF="#[8]">8</A>]).

            
              Servers MUST resolve conflicts beteen CGI header

            
              and HTTP header formats or names (see <A HREF="#8.0">section 8</A>).

            
              </P>


              <H2>

            
               <A NAME="8.0">

            
                8. Server Implementation

            
               </A>

            
              </H2>

            
              <P>

            
              This section defines the requirements that must be met by HTTP

            
              servers in order to provide a coherent and correct CGI/1.1

            
              environment in which scripts may function.  It is intended

            
              primarily for server implementors, but it is useful for

            
              script authors to be familiar with the information as well.

            
              </P>


              <H3>

            
               <A NAME="8.1">

            
                8.1. Requirements for Servers

            
               </A>

            
              </H3>

            
              <P>

            
              In order to be considered CGI/1.1-compliant, a server must meet

            
              certain basic criteria and provide certain minimal functionality.

            
              The details of these requirements are described in the following sections.

            
              </P>


              <H3>

            
               <A NAME="8.1.1">

            
                8.1.1. Script-URI

            
               </A>

            
              </H3>

            
              <P>

            
              Servers MUST support the standard mechanism (described below) which

            
              allows

            
              script authors to determine

            
              what URL to use in documents

            
              which reference the script;

            
              specifically, what URL to use in order to

            
              achieve particular settings of the

            
              metavariables. This

            
              mechanism is as follows:

            
              </P>

            
              <P>

            
              The server

            
              MUST translate the header data from the CGI header field syntax to

            
              the HTTP

            
              header field syntax if these differ. For example, the character

            
              sequence for

            
              newline (such as Unix's ASCII NL) used by CGI scripts may not be the

            
              same as that used by HTTP (ASCII CR followed by LF). The server MUST

            
              also resolve any conflicts between header fields returned by the script

            
              and header fields that it would otherwise send itself.

            
              </P>


              <H3>

            
               <A NAME="8.1.2">

            
                8.1.2. Request Message-body Handling

            
               </A>

            
              </H3>

            
              <P>

            
              These are the requirements for server handling of message-bodies directed

            
              to CGI/1.1 resources:

            
              </P>

            
              <OL>

            
               <LI>The message-body the server provides to the CGI script MUST

            
                have any transfer encodings removed.

            
               </LI>

            
               <LI>The server MUST derive and provide a value for the CONTENT_LENGTH

            
                metavariable that reflects the length of the message-body after any

            
                transfer decoding.

            
               </LI>

            
               <LI>The server MUST leave intact any content-encodings of the message-body.

            
               </LI>

            
              </OL>


              <H3>

            
               <A NAME="8.1.3">

            
                8.1.3. Required Metavariables

            
               </A>

            
              </H3>

            
              <P>

            
              Servers MUST provide scripts with certain information and

            
              metavariables

            
              as described in <A HREF="#8.3">section 8.3</A>.

            
              </P>


              <H3>

            
               <A NAME="8.1.4">

            
                8.1.4. Response Compliance

            
               </A>

            
              </H3>

            
              <P>

            
              Servers MUST ensure that responses sent to the user-agent meet all

            
              requirements of the protocol level in effect.  This may involve

            
              modifying, deleting, or augmenting any header

            
              fields and/or message-body supplied by the script.

            
              </P>


              <H3>

            
               <A NAME="8.2">

            
                8.2. Recommendations for Servers

            
               </A>

            
              </H3>

            
              <P>

            
              Servers SHOULD provide the "<SAMP>query</SAMP>" component of the script-URI

            
              as command-line arguments to scripts if it does not

            
              contain any unencoded '=' characters and the command-line arguments can

            
              be generated in an unambiguous manner.

            
              (See <A HREF="#5.0">section 5</A>.)

            
              </P>

            
              <P>

            
              Servers SHOULD set the AUTH_TYPE

            
              metavariable to the value of the

            
              '<SAMP>auth-scheme</SAMP>' token of the "<SAMP>Authorization</SAMP>"

            
              field if it was supplied as part of the request header.

            
              (See <A HREF="#6.1.1">section 6.1.1</A>.)

            
              </P>

            
              <P>

            
              Where applicable, servers SHOULD set the current working directory

            
              to the directory in which the script is located before invoking

            
              it.

            
              </P>

            
              <P>

            
              Servers MAY reject with error '404 Not Found'

            
              any requests that would result in

            
              an encoded "/" being decoded into PATH_INFO or SCRIPT_NAME, as this

            
              might represent a loss of information to the script.

            
              </P>

            
              <P>

            
              Although the server and the CGI script need not be consistent in

            
              their handling of URL paths (client URLs and the PATH_INFO data,

            
              respectively), server authors may wish to impose consistency.

            
              So the server implementation SHOULD define its behaviour for the

            
              following cases:

            
              </P>

            
              <OL>

            
               <LI>define any restrictions on allowed characters, in particular

            
                whether ASCII NUL is permitted;

            
               </LI>

            
               <LI>define any restrictions on allowed path segments, in particular

            
                whether non-terminal NULL segments are permitted;

            
               </LI>

            
               <LI>define the behaviour for <SAMP>"."</SAMP> or <SAMP>".."</SAMP> path

            
                segments; <EM>i.e.</EM>, whether they are prohibited, treated as

            
                ordinary path

            
                segments or interpreted in accordance with the relative URL

            
                specification [<A HREF="#[7]">7</A>];

            
               </LI>

            
               <LI>define any limits of the implementation, including limits on path or

            
                search string lengths, and limits on the volume of header data the server

            
                will parse.

            
               </LI><!-- ##### Move the field resolution/translation para below here -->

            
              </OL>

            
              <P>

            
              Servers MAY generate the

            
              Script-URI in

            
              any way from the client URI,

            
              or from any other data (but the behaviour SHOULD be documented).

            
              </P>

            
              <P>

            
              For non-parsed header (NPH) scripts (see

            
              <A HREF="#7.1">section 7.1</A>), servers SHOULD

            
              attempt to ensure that the script input comes directly from the

            
              client, with minimal buffering. For all scripts the data will be

            
              as supplied by the client.

            
              </P>


              <H3>

            
               <A NAME="8.3">

            
                8.3. Summary of

            
                MetaVariables

            
               </A>

            
              </H3>

            
              <P>

            
              Servers MUST provide the following

            
              metavariables to

            
              scripts.  See the individual descriptions for exceptions and semantics.

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                CONTENT_LENGTH (section <A HREF="#6.1.2">6.1.2</A>)

            
                CONTENT_TYPE (section <A HREF="#6.1.3">6.1.3</A>)

            
                GATEWAY_INTERFACE (section <A HREF="#6.1.4">6.1.4</A>)

            
                PATH_INFO (section <A HREF="#6.1.6">6.1.6</A>)

            
                QUERY_STRING (section <A HREF="#6.1.8">6.1.8</A>)

            
                REMOTE_ADDR (section <A HREF="#6.1.9">6.1.9</A>)

            
                REQUEST_METHOD (section <A HREF="#6.1.13">6.1.13</A>)

            
                SCRIPT_NAME (section <A HREF="#6.1.14">6.1.14</A>)

            
                SERVER_NAME (section <A HREF="#6.1.15">6.1.15</A>)

            
                SERVER_PORT (section <A HREF="#6.1.16">6.1.16</A>)

            
                SERVER_PROTOCOL (section <A HREF="#6.1.17">6.1.17</A>)

            
                SERVER_SOFTWARE (section <A HREF="#6.1.18">6.1.18</A>)

            
              </PRE>

            
              <P>

            
              Servers SHOULD define the following

            
              metavariables for scripts.

            
              See the individual descriptions for exceptions and semantics.

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                AUTH_TYPE (section <A HREF="#6.1.1">6.1.1</A>)

            
                REMOTE_HOST (section <A HREF="#6.1.10">6.1.10</A>)

            
              </PRE>

            
              <P>

            
              In addition, servers SHOULD provide

            
              metavariables for all fields present

            
              in the HTTP request header, with the exception of those involved with

            
              access control.  Servers MAY at their discretion provide

            
              metavariables

            
              for access control fields.

            
              </P>

            
              <P>

            
              Servers MAY define the following

            
              metavariables.  See the individual

            
              descriptions for exceptions and semantics.

            
              </P><!--#if expr="! $GUI" -->

            
              <P></P><!--#endif -->

            
              <PRE>

            
                PATH_TRANSLATED (section <A HREF="#6.1.7">6.1.7</A>)

            
                REMOTE_IDENT (section <A HREF="#6.1.11">6.1.11</A>)

            
                REMOTE_USER (section <A HREF="#6.1.12">6.1.12</A>)

            
              </PRE>

            
              <P>

            
              Servers MAY

            
              at their discretion define additional implementation-specific

            
              extension metavariables

            
              provided their names do not

            
              conflict with defined header field names.  Implementation-specific

            
              metavariable names SHOULD

            
              be prefixed with "X_" (<EM>e.g.</EM>,

            
              "X_DBA") to avoid the potential for such conflicts.

            
              </P>


              <H2>

            
               <A NAME="9.0">

            
                9.

            
                Script Implementation

            
               </A>

            
              </H2>

            
              <P>

            
              This section defines the requirements and recommendations for scripts

            
              that are intended to function in a CGI/1.1 environment.  It is intended

            
              primarily as a reference for script authors, but server implementors

            
              should be familiar with these issues as well.

            
              </P>


              <H3>

            
               <A NAME="9.1">

            
                9.1. Requirements for Scripts

            
               </A>

            
              </H3>

            
              <P>

            
              Scripts using the parsed-header method to communicate with servers

            
              MUST supply a response header to the server.

            
              (See <A HREF="#7.0">section 7</A>.)

            
              </P>

            
              <P>

            
              Scripts using the NPH method to communicate with servers MUST

            
              provide complete HTTP responses, and MUST use the value of the

            
              SERVER_PROTOCOL metavariable

            
              to determine the appropriate format.

            
              (See <A HREF="#7.1">section 7.1</A>.)

            
              </P>

            
              <P>

            
              Scripts MUST check the value of the REQUEST_METHOD

            
              metavariable in order

            
              to provide an appropriate response.

            
              (See <A HREF="#6.1.13">section 6.1.13</A>.)

            
              </P>

            
              <P>

            
              Scripts MUST be prepared to handled URL-encoded values in

            
              metavariables.

            
              In addition, they MUST recognise both "+" and "%20" in URL-encoded

            
              quantities as representing the space character.

            
              (See <A HREF="#3.1">section 3.1</A>.)

            
              </P>

            
              <P>

            
              Scripts MUST ignore leading zeros in the major and minor version numbers

            
              in the GATEWAY_INTERFACE

            
              metavariable value. (See

            
              <A HREF="#6.1.4">section 6.1.4</A>.)

            
              </P>

            
              <P>

            
              When processing requests that include a

            
              message-body, scripts

            
              MUST NOT read more than CONTENT_LENGTH bytes from the input stream.

            
              (See sections <A HREF="#6.1.2">6.1.2</A> and <A HREF="#6.2">6.2</A>.)

            
              </P>


              <H3>

            
               <A NAME="9.2">

            
                9.2. Recommendations for Scripts

            
               </A>

            
              </H3>

            
              <P>

            
              Servers may interrupt or terminate script execution at any time

            
              and without warning, so scripts SHOULD be prepared to deal with

            
              abnormal termination.

            
              </P>

            
              <P>

            
              Scripts MUST

            
              reject with

            
              error '405 Method Not

            
              Allowed' requests

            
              made using methods that they do not support. If the script does

            
              not intend

            
              processing the PATH_INFO data, then it SHOULD reject the request with

            
              '404 Not

            
              Found' if PATH_INFO is not NULL.

            
              </P>

            
              <P>

            
              If a script is processing the output of a form, it SHOULD

            
              verify that the CONTENT_TYPE

            
              is "<SAMP>application/x-www-form-urlencoded</SAMP>" [<A HREF="#[2]">2</A>]

            
              or whatever other media type is expected.

            
              </P>

            
              <P>

            
              Scripts parsing PATH_INFO,

            
              PATH_TRANSLATED, or SCRIPT_NAME

            
              SHOULD be careful

            
              of void path segments ("<SAMP>//</SAMP>") and special path segments

            
              (<SAMP>"."</SAMP> and

            
              <SAMP>".."</SAMP>). They SHOULD either be removed from the path before

            
              use in OS

            
              system calls, or the request SHOULD be rejected with

            
              '404 Not Found'.

            
              </P>

            
              <P>

            
              As it is impossible for

            
              scripts to determine the client URI that

            
              initiated  a

            
              request without knowledge of the specific server in

            
              use, the script SHOULD NOT return "<SAMP>text/html</SAMP>"

            
              documents containing

            
              relative URL links without including a "<SAMP>&lt;BASE&gt;</SAMP>"

            
              tag in the document.

            
              </P>

            
              <P>

            
              When returning header fields,

            
              scripts SHOULD try to send the CGI

            
              header fields (see section

            
              <A HREF="#7.2">7.2</A>) as soon as possible, and

            
              SHOULD send them

            
              before any HTTP header fields. This may

            
              help reduce the server's memory requirements.

            
              </P>


              <H2>

            
               <A NAME="10.0">

            
                10. System Specifications

            
               </A>

            
              </H2>


              <H3>

            
               <A NAME="10.1">

            
                10.1. AmigaDOS

            
               </A>

            
              </H3>

            
              <P>

            
              The implementation of the CGI on an AmigaDOS operating system platform

            
              SHOULD use environment variables as the mechanism of providing

            
              request metadata to CGI scripts.

            
              </P>

            
              <DL>

            
               <DT><STRONG>Environment variables</STRONG>

            
               </DT>

            
               <DD>

            
                <P>

            
                These are accessed by the DOS library routine <SAMP>GetVar</SAMP>. The

            
                flags argument SHOULD be 0. Case is ignored, but upper case is

            
                recommended for compatibility with case-sensitive systems.

            
                </P>

            
               </DD>

            
               <DT><STRONG>The current working directory</STRONG>

            
               </DT>

            
               <DD>

            
                <P>

            
                The current working directory for the script is set to the directory

            
                containing the script.

            
                </P>

            
               </DD>

            
               <DT><STRONG>Character set</STRONG>

            
               </DT>

            
               <DD>

            
                <P>

            
                The US-ASCII character set is used for the definition of environment

            
                variable names and header

            
                field names; the newline (NL) sequence is LF;

            
                servers SHOULD also accept CR LF as a newline.

            
                </P>

            
               </DD>

            
              </DL>


              <H3>

            
               <A NAME="10.2">

            
                10.2. Unix

            
               </A>

            
              </H3>

            
              <P>

            
              The implementation of the CGI on a UNIX operating system platform

            
              SHOULD use environment variables as the mechanism of providing

            
              request metadata to CGI scripts.

            
              </P>

            
              <P>

            
              For Unix compatible operating systems, the following are defined:

            
              </P>

            
              <DL>

            
               <DT><STRONG>Environment variables</STRONG>

            
               </DT>

            
               <DD>

            
                <P>

            
                These are accessed by the C library routine <SAMP>getenv</SAMP>.

            
                </P>

            
               </DD>

            
               <DT><STRONG>The command line</STRONG>

            
               </DT>

            
               <DD>

            
                <P>

            
                This is accessed using the

            
                <SAMP>argc</SAMP> and <SAMP>argv</SAMP>

            
                arguments to <SAMP>main()</SAMP>. The words have any characters

            
                that

            
                are 'active' in the Bourne shell escaped with a backslash.

            
                If the value of the QUERY_STRING

            
                metavariable

            
                contains an unencoded equals-sign '=', then the command line

            
                SHOULD NOT be used by the script.

            
                </P>

            
               </DD>

            
               <DT><STRONG>The current working directory</STRONG>

            
               </DT>

            
               <DD>

            
                <P>

            
                The current working directory for the script

            
                SHOULD be set to the directory

            
                containing the script.

            
                </P>

            
               </DD>

            
               <DT><STRONG>Character set</STRONG>

            
               </DT>

            
               <DD>

            
                <P>

            
                The US-ASCII character set is used for the definition of environment

            
                variable names and header field names; the newline (NL) sequence is LF;

            
                servers SHOULD also accept CR LF as a newline.

            
                </P>

            
               </DD>

            
              </DL>


              <H2>

            
               <A NAME="11.0">

            
                11. Security Considerations

            
               </A>

            
              </H2>


              <H3>

            
               <A NAME="11.1">

            
                11.1. Safe Methods

            
               </A>

            
              </H3>

            
              <P>

            
              As discussed in the security considerations of the HTTP

            
              specifications [<A HREF="#[3]">3</A>,<A HREF="#[8]">8</A>], the

            
              convention has been established that the

            
              GET and HEAD methods should be 'safe'; they should cause no

            
              side-effects and only have the significance of resource retrieval.

            
              </P>

            
              <P>

            
              CGI scripts are responsible for enforcing any HTTP security considerations

            
              [<A HREF="#[3]">3</A>,<A HREF="#[8]">8</A>]

            
              with respect to the protocol version level of the request and

            
              any side effects generated by the scripts on behalf of

            
              the server.  Primary

            
              among these

            
              are the considerations of safe and idempotent methods.  Idempotent

            
              requests are those that may be repeated an arbitrary number of times

            
              and produce side effects identical to a single request.

            
              </P>


              <H3>

            
               <A NAME="11.2">

            
                11.2. HTTP Header

            
                Fields Containing Sensitive Information

            
               </A>

            
              </H3>

            
              <P>

            
              Some HTTP header fields may carry sensitive information which the server

            
              SHOULD NOT pass on to the script unless explicitly configured to do

            
              so. For example, if the server protects the script using the

            
              "<SAMP>Basic</SAMP>"

            
              authentication scheme, then the client will send an

            
              "<SAMP>Authorization</SAMP>"

            
              header field containing a username and password. If the server, rather

            
              than the script, validates this information then the password SHOULD

            
              NOT be passed on to the script <EM>via</EM> the HTTP_AUTHORIZATION

            
              metavariable

            
              without careful consideration.

            
              This also applies to the

            
              Proxy-Authorization header field and the corresponding

            
              HTTP_PROXY_AUTHORIZATION

            
              metavariable.

            
              </P>


              <H3>

            
               <A NAME="11.3">

            
                11.3. Script

            
                Interference with the Server

            
               </A>

            
              </H3>

            
              <P>

            
              The most common implementation of CGI invokes the script as a child

            
              process using the same user and group as the server process. It

            
              SHOULD therefore be ensured that the script cannot interfere with the

            
              server process, its configuration, or documents.

            
              </P>

            
              <P>

            
              If the script is executed by calling a function linked in to the

            
              server software (either at compile-time or run-time) then precautions

            
              SHOULD be taken to protect the core memory of the server, or to

            
              ensure that untrusted code cannot be executed.

            
              </P>


              <H3>

            
               <A NAME="11.4">

            
                11.4. Data Length and Buffering Considerations

            
               </A>

            
              </H3>

            
              <P>

            
              This specification places no limits on the length of message-bodies

            
              presented to the script.  Scripts should not assume that statically

            
              allocated buffers of any size are sufficient to contain the entire

            
              submission at one time.  Use of a fixed length buffer without careful

            
              overflow checking may result in an attacker exploiting 'stack-smashing'

            
              or 'stack-overflow' vulnerabilities of the operating system.

            
              Scripts may spool large submissions to disk or other buffering media,

            
              but a rapid succession of large submissions may result in denial of

            
              service conditions.  If the CONTENT_LENGTH of a message-body is larger

            
              than resource considerations allow, scripts should respond with an

            
              error status appropriate for the protocol version; potentially applicable

            
              status codes include '503 Service Unavailable' (HTTP/1.0 and HTTP/1.1),

            
              '413 Request Entity Too Large' (HTTP/1.1), and

            
              '414 Request-URI Too Long' (HTTP/1.1).

            
              </P>


              <H3>

            
               <A NAME="11.5">

            
                11.5. Stateless Processing

            
               </A>

            
              </H3>

            
              <P>

            
              The stateless nature of the Web makes each script execution and resource

            
              retrieval independent of all others even when multiple requests constitute a

            
              single conceptual Web transaction.  Because of this, a script should not

            
              make any assumptions about the context of the user-agent submitting a

            
              request.  In particular, scripts should examine data obtained from the client

            
              and verify that they are valid, both in form and content, before allowing

            
              them to be used for sensitive purposes such as input to other

            
              applications, commands, or operating system services.  These uses

            
              include, but are not

            
              limited to: system call arguments, database writes, dynamically evaluated

            
              source code, and input to billing or other secure processes.  It is important

            
              that applications be protected from invalid input regardless of whether

            
              the invalidity is the result of user error, logic error, or malicious action.

            
              </P>

            
              <P>

            
              Authors of scripts involved in multi-request transactions should be

            
              particularly cautios about validating the state information;

            
              undesirable effects may result from the substitution of dangerous

            
              values for portions of the submission which might otherwise be

            
              presumed safe.  Subversion of this type occurs when alterations

            
              are made to data from a prior stage of the transaction that were

            
              not meant to be controlled by the client (<EM>e.g.</EM>, hidden

            
              HTML form elements, cookies, embedded URLs, <EM>etc.</EM>).

            
              </P>


              <H2>

            
               <A NAME="12.0">

            
                12. Acknowledgements

            
               </A>

            
              </H2>

            
              <P>

            
              This work is based on a draft published in 1997 by David R. Robinson,

            
              which in turn was based on the original CGI interface that arose out of

            
              discussions on the <EM>www-talk</EM> mailing list. In particular,

            
              Rob McCool, John Franks, Ari Luotonen,

            
              George Phillips and

            
              Tony Sanders deserve special recognition for their efforts in

            
              defining and implementing the early versions of this interface.

            
              </P>

            
              <P>

            
              This document has also greatly benefited from the comments and

            
              suggestions made by  Chris Adie, Dave Kristol,

            
              Mike Meyer, David Morris, Jeremy Madea,

            
              Patrick M<SUP>c</SUP>Manus, Adam Donahue,

            
              Ross Patterson, and Harald Alvestrand.

            
              </P>


              <H2>

            
               <A NAME="13.0">

            
                13. References

            
               </A>

            
              </H2>

            
              <DL COMPACT>

            
               <DT><A NAME="[1]">[1]</A>

            
               </DT>

            
               <DD>Berners-Lee, T., 'Universal Resource Identifiers in WWW: A

            
                   Unifying Syntax for the Expression of Names and Addresses of

            
                   Objects on the Network as used in the World-Wide Web', RFC 1630,

            
                   CERN, June 1994.

            
                   <P>

            
                   </P>

            
               </DD>

            
               <DT><A NAME="[2]">[2]</A>

            
               </DT>

            
               <DD>Berners-Lee, T. and Connolly, D., 'Hypertext Markup Language -

            
                    2.0', RFC 1866, MIT/W3C, November 1995.

            
                   <P>

            
                   </P>

            
               </DD>

            
               <DT><A NAME="[3]">[3]</A>

            
               </DT>

            
               <DD>Berners-Lee, T., Fielding, R. T. and Frystyk, H.,

            
                      'Hypertext Transfer Protocol -- HTTP/1.0', RFC 1945, MIT/LCS,

            
                      UC Irvine, May 1996.

            
                   <P>

            
                   </P>

            
               </DD>


              <DT><A NAME="[4]">[4]</A>

            
              </DT>

            
              <DD>Berners-Lee, T., Fielding, R., and Masinter, L., Editors,

            
               'Uniform Resource Identifiers (URI): Generic Syntax', RFC 2396,

            
               MIT, U.C. Irvine, Xerox Corporation, August 1996.

            
               <P>

            
               </P>

            
              </DD>


              <DT><A NAME="[5]">[5]</A>

            
              </DT>

            
              <DD>Braden, R., Editor, 'Requirements for Internet Hosts --

            
                      Application and Support', STD 3, RFC 1123, IETF, October 1989.

            
                   <P>

            
                   </P>

            
               </DD>

            
               <DT><A NAME="[6]">[6]</A>

            
               </DT>

            
               <DD>Crocker, D.H., 'Standard for the Format of ARPA Internet Text

            
                      Messages', STD 11, RFC 822, University of Delaware, August 1982.

            
                   <P>

            
                   </P>

            
               </DD>

            
              <DT><A NAME="[7]">[7]</A>

            
              </DT>

            
              <DD>Fielding, R., 'Relative Uniform Resource Locators', RFC 1808,

            
                      UC Irvine, June 1995.

            
                   <P>

            
                   </P>

            
               </DD>

            
               <DT><A NAME="[8]">[8]</A>

            
               </DT>

            
               <DD>Fielding, R., Gettys, J., Mogul, J., Frystyk, H. and

            
                      Berners-Lee, T., 'Hypertext Transfer Protocol -- HTTP/1.1',

            
                      RFC 2068, UC Irvine, DEC,

            
            	  MIT/LCS, January 1997.

            
                   <P>

            
                   </P>

            
               </DD>

            
               <DT><A NAME="[9]">[9]</A>

            
               </DT>

            
               <DD>Freed, N. and Borenstein N., 'Multipurpose Internet Mail

            
                      Extensions (MIME) Part Two: Media Types', RFC 2046, Innosoft,

            
                      First Virtual, November 1996.

            
                   <P>

            
                   </P>

            
               </DD>

            
               <DT><A NAME="[10]">[10]</A>

            
               </DT>

            
               <DD>Mockapetris, P., 'Domain Names - Concepts and Facilities',

            
                      STD 13, RFC 1034, ISI, November 1987.

            
                   <P>

            
                   </P>

            
               </DD>

            
               <DT><A NAME="[11]">[11]</A>

            
               </DT>

            
               <DD>St. Johns, M., 'Identification Protocol', RFC 1431, US

            
                      Department of Defense, February 1993.

            
                   <P>

            
                   </P>

            
               </DD>

            
               <DT><A NAME="[12]">[12]</A>

            
               </DT>

            
               <DD>'Coded Character Set -- 7-bit American Standard Code for

            
                      Information Interchange', ANSI X3.4-1986.

            
                   <P>

            
                   </P>

            
               </DD>

            
               <DT><A NAME="[13]">[13]</A>

            
               </DT>

            
               <DD>Hinden, R. and Deering, S.,

            
                      'IP Version 6 Addressing Architecture', RFC 2373,

            
            	  Nokia, Cisco Systems,

            
                      July 1998.

            
                   <P>

            
                   </P>

            
               </DD>

            
              </DL>


              <H2>

            
               <A NAME="14.0">

            
                14. Authors' Addresses

            
               </A>

            
              </H2>

            
              <ADDRESS>

            
               <P>

            
               Ken A L Coar

            
               <BR>

            
               MeepZor Consulting

            
               <BR>

            
               7824 Mayfaire Crest Lane, Suite 202

            
               <BR>

            
               Raleigh, NC   27615-4875

            
               <BR>

            
               U.S.A.

            
               </P>

            
               <P>

            
               Tel: +1 (919) 254.4237

            
               <BR>

            
               Fax: +1 (919) 254.5250

            
               <BR>

            
               Email:

            
               <A

            
                HREF="mailto:Ken.Coar@Golux.Com"

            
               ><SAMP>Ken.Coar@Golux.Com</SAMP></A>

            
               </P>

            
              </ADDRESS>

            
              <ADDRESS>

            
               <P>

            
               David Robinson

            
               <BR>

            
               E*TRADE UK Ltd

            
               <BR>

            
               Mount Pleasant House

            
               <BR>

            
               2 Mount Pleasant

            
               <BR>

            
               Huntingdon Road

            
               <BR>

            
               Cambridge CB3 0RN

            
               <BR>

            
               UK

            
               </P>

            
               <P>

            
               Tel: +44 (1223) 566926

            
               <BR>

            
               Fax: +44 (1223) 506288

            
               <BR>

            
               Email:

            
               <A

            
                HREF="mailto:drtr@etrade.co.uk"

            
               ><SAMP>drtr@etrade.co.uk</SAMP></A>

            
              </ADDRESS>


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