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Environment Variables

Environment Variables. Overview. Your CGI or ASP Programs may make use of a “Collection” of variables, variously called ENVIRONMENT or SERVER VARIABLES. Different variables may be set on different servers. Your server logs may be set to record these variables. To see actual examples:.

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Environment Variables

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  1. Environment Variables

  2. Overview • Your CGI or ASP Programs may make use of a “Collection” of variables, variously called ENVIRONMENT or SERVER VARIABLES. • Different variables may be set on different servers. • Your server logs may be set to record these variables.

  3. To see actual examples: • http://parana.ecs.csus.edu/fall02/servervariables.asp • http://sequoia.ecs.csus.edu/~harville/cgi-bin/environment.cgi

  4. CONTENT_LENGTH • The length in bytes of the returned document. • USE: Perhaps the programmer wants to limit the size of the response.

  5. CONTENT_TYPE • The type of information returned. • Ex: text/html • USE: Perhaps the programmer wants to have different parts of the program activate depending on the content type.

  6. DOCUMENT_ROOT • The main site directory. • USE: Setting up paths for dynamically generated URLs.

  7. GATEWAY_INTERFACE • The CGI version number. • USE: Perhaps certain program features require a certain CGI version.

  8. HTTP_ACCEPT • Media types the client accepts.

  9. HTTP_ACCEPT_ENCODING Methods of compression the browser understands. HTTP_ACCEPT_ENCODING = gzip, deflate

  10. HTTP_ACCEPT_LANGUAGE HTTP_ACCEPT_LANGUAGE = en-us • USE: Perhaps different files are to be served up depending on the language of the user.

  11. HTTP_CONNECTION HTTP_CONNECTION = Keep-Alive Every request made requires that the server and client re-introduce each other. Keep-Alive is a switch that allows requests sent within a very short time to avoid this server-client bureaucracy.

  12. HTTP_COOKIE • A list of cookies the particular site (or advertising group) has control over. • USE: Customer tracking, customization and other honorable or questionable activities.

  13. HTTP_HOST The name of the machine on which the script resides. HTTP_HOST = parana

  14. HTTP_REFERER • The page that requested the current document or program. • Note the correct misspelling. • Referrer would be more correct, but the mistake was made and not corrected. • USE: Redirection to a previous page.

  15. HTTP_USER_AGENT • The client browser version. • Use: Customization or redirection based on browser type (and thus capabilities).

  16. PATH_INFO • The current virtual path. PATH_INFO = /chat/servervariables.asp • Use: Recording a page name for redirection.

  17. PATH_TRANSLATED • The full absolute path on the server. PATH_INFO = /chat/servervariables.asp PATH_TRANSLATED = C:\csc123\chat\servervariables.asp ALSO: APPL_PHYSICAL_PATH = C:\csc123\chat\

  18. QUERY_STRING • This variable returns the query string: • ?example=Kevin%20Harville • USE: Using form or Querystring information.

  19. REMOTE_ADDR • The remote IP making the request. • USE: Serving up unique pages based on the user. Companies have actually served different pages to their competitors than to their clients.

  20. REMOTE_HOST • The remote hostname or IP of the requestor.

  21. REQUEST_METHOD • I.e. GET or POST.

  22. SCRIPT_NAME • The virtual path of the current script.

  23. SERVER_NAME • Server hostname or IP

  24. SERVER_PORT • Usually 80 • The “channel” incoming requests come in on.

  25. SERVER_PROTOCOL SERVER_PROTOCOL = HTTP/1.1

  26. SERVER_SOFTWARE SERVER_SOFTWARE = Microsoft-IIS/5.0

  27. URL URL = /chat/servervariables.asp

  28. Others • Numerous ones exist for SSL • HTTP_RAW and ALL_HTTP give long lists of the variables.

  29. Summary • Server or Environment Variables are a useful means of site customization. • They allow for customers to be tracked, which may or may not be in the customer’s best interest. • The allow logging of information.

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