4.1.18. Protocol-Specific Meta-Variables . . . . . . . .  19
       4.2. Request Message-Body . . . . . . . . . . . . . . . . . .  20
       4.3. Request Methods  . . . . . . . . . . . . . . . . . . . .  20
            4.3.1.  GET. . . . . . . . . . . . . . . . . . . . . . .  20
            4.3.2.  POST . . . . . . . . . . . . . . . . . . . . . .  21
            4.3.3.  HEAD . . . . . . . . . . . . . . . . . . . . . .  21
            4.3.4.  Protocol-Specific Methods. . . . . . . . . . . .  21
       4.4. The Script Command Line. . . . . . . . . . . . . . . . .  21






 
RFC 3875                    CGI Version 1.1                 October 2004


   5.  NPH Scripts . . . . . . . . . . . . . . . . . . . . . . . . .  22
       5.1. Identification . . . . . . . . . . . . . . . . . . . . .  22
       5.2. NPH Response . . . . . . . . . . . . . . . . . . . . . .  22

   6.  CGI Response. . . . . . . . . . . . . . . . . . . . . . . . .  23
       6.1. Response Handling. . . . . . . . . . . . . . . . . . . .  23
       6.2. Response Types . . . . . . . . . . . . . . . . . . . . .  23
            6.2.1.  Document Response. . . . . . . . . . . . . . . .  23
            6.2.2.  Local Redirect Response. . . . . . . . . . . . .  24
            6.2.3.  Client Redirect Response . . . . . . . . . . . .  24
            6.2.4.  Client Redirect Response with Document . . . . .  24
       6.3. Response Header Fields . . . . . . . . . . . . . . . . .  25
            6.3.1.  Content-Type . . . . . . . . . . . . . . . . . .  25
            6.3.2.  Location . . . . . . . . . . . . . . . . . . . .  26
            6.3.3.  Status . . . . . . . . . . . . . . . . . . . . .  26
            6.3.4.  Protocol-Specific Header Fields. . . . . . . . .  27
            6.3.5.  Extension Header Fields. . . . . . . . . . . . .  27
       6.4. Response Message-Body. . . . . . . . . . . . . . . . . .  28

   7.  System Specifications . . . . . . . . . . . . . . . . . . . .  28
       7.1. AmigaDOS . . . . . . . . . . . . . . . . . . . . . . . .  28
       7.2. UNIX . . . . . . . . . . . . . . . . . . . . . . . . . .  28
       7.3. EBCDIC/POSIX . . . . . . . . . . . . . . . . . . . . . .  29

   8.  Implementation. . . . . . . . . . . . . . . . . . . . . . . .  29
       8.1. Recommendations for Servers. . . . . . . . . . . . . . .  29
       8.2. Recommendations for Scripts. . . . . . . . . . . . . . .  30

   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  30
       9.1. Safe Methods . . . . . . . . . . . . . . . . . . . . . .  30
       9.2. Header Fields Containing Sensitive Information . . . . .  31
       9.3. Data Privacy . . . . . . . . . . . . . . . . . . . . . .  31
       9.4. Information Security Model . . . . . . . . . . . . . . .  31
       9.5. Script Interference with the Server. . . . . . . . . . .  31
       9.6. Data Length and Buffering Considerations . . . . . . . .  32
       9.7. Stateless Processing . . . . . . . . . . . . . . . . . .  32
       9.8. Relative Paths . . . . . . . . . . . . . . . . . . . . .  33
       9.9. Non-parsed Header Output . . . . . . . . . . . . . . . .  33

   10. Acknowledgements. . . . . . . . . . . . . . . . . . . . . . .  33

   11. References. . . . . . . . . . . . . . . . . . . . . . . . . .  33
       11.1. Normative References. . . . . . . . . . . . . . . . . .  33
       11.2. Informative References. . . . . . . . . . . . . . . . .  34

   12. Authors' Addresses. . . . . . . . . . . . . . . . . . . . . .  35

   13. Full Copyright Statement. . . . . . . . . . . . . . . . . . .  36




 
RFC 3875                    CGI Version 1.1                 October 2004


1.  Introduction

1.1.  Purpose

   The Common Gateway Interface (CGI) [22] allows an HTTP [1], [4]
   server and a CGI script to share responsibility for responding to
   client requests.  The client request comprises a Uniform Resource
   Identifier (URI) [11], a request method and various ancillary
   information about the request provided by the transport protocol.

   The CGI defines the abstract parameters, known as meta-variables,
   which describe a client's request.  Together with a concrete
   programmer interface this specifies a platform-independent interface
   between the script and the HTTP server.

   The server is responsible for managing connection, data transfer,
   transport and network issues related to the client request, whereas
   the CGI script handles the application issues, such as data access
   and document processing.

1.2.  Requirements

   The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT',
   'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY' and 'OPTIONAL' in this
   document are to be interpreted as described in BCP 14, RFC 2119 [3].