Rex Swain's
CGI Environment Variable Demo

Variable	Value
	Description
AUTH_TYPE	[undefined]
	Protocol-specific authentication method used to validate the user.
CONTENT_LENGTH	[undefined]
	Length of the data passed to the CGI program through STDIN; implies REQUEST_METHOD is "POST".
CONTENT_TYPE	[undefined]
	For queries which have attached information, such as HTTP POST and PUT, this is the MIME content type of the data.
DOCUMENT_ROOT	[undefined]
	The directory from which web documents are served.
GATEWAY_INTERFACE	CGI/1.1
	CGI specification revision number to which server complies.
HTTP_ACCEPT	*/*
	List of the MIME types that the client can accept.
HTTP_CONNECTION	close
	[unanticipated]
HTTP_COOKIE	[undefined]
	Cookie values. [See Cookie Demo.]
HTTP_FROM	[undefined]
	The Email address of the user making the request. [Most browsers do not support this variable.]
HTTP_HOST	cgi-int.tripod.com
	[unanticipated]
HTTP_REFERER	https://ruevs2.tripod.com/cgi-bin/ environment.cgi?foo=1&bar=2
	The URL of the document that the client pointed to before accessing the CGI program.
HTTP_USER_AGENT	claudebot
	The browser the client is using.
PATH_INFO	[undefined]
	Extra path information, as given by the client.
PATH_TRANSLATED	[undefined]
	Server-provided version of PATH_INFO (with virtual-to-physical mapping).
QUERY_STRING	foo=1&bar=2
	Query information passed to the program following URL and "?"; implies REQUEST_METHOD is "GET".
REMOTE_ADDR	10.126.24.9
	IP address of remote host making the request.
REMOTE_HOST	[undefined]
	Remote hostname making the request.
REMOTE_IDENT	[undefined]
	If the HTTP server supports RFC 931 identification, then this variable will be set to the remote username retrieved from the server. Usage of this variable should be limited to logging only.
REMOTE_USER	[undefined]
	Authenticated username (see AUTH_TYPE).
REQUEST_METHOD	GET
	The method with which the request was made (e.g., "GET" or "POST" or "HEAD").
REQUEST_URI	/ruevs2/cgi-bin/ environment.cgi?foo=1&bar=2
	[unanticipated]
SCRIPT_NAME	/environment.cgi
	Virtual path to the script being executed (used for self-referencing URLs).
SERVER_ADMIN	ops@tripod.com
	[unanticipated]
SERVER_NAME	cgi-int.tripod.com
	Server host name, DNS alias, or IP address (as it would appear in self-referencing URLs).
SERVER_PORT	80
	Port number the request was sent to (i.e., the host on which the server is running).
SERVER_PROTOCOL	HTTP/1.1
	Name and revision of the information protocol this request came in with.
SERVER_SOFTWARE	[undefined]
	Name and version of the server software answering the request.

GET

One way to invoke a Perl program is with an HTML <A HREF=...>...</A> link. Parameters are passed to Perl after the URL and a ?. Try it...

Hit me: /cgi-bin/environment.cgi?foo=1&bar=2

When this page reappears, you should see REQUEST_METHOD of "GET". The parameter names and values arrive via QUERY_STRING, and should be "foo=1&bar=2".

POST

Another way to invoke a Perl program is with an HTML <FORM METHOD=post> tag, one or more <INPUT> tags, and an <INPUT TYPE=submit> tag. Try it...

When this page reappears, you should see REQUEST_METHOD of "POST". The parameter names and values arrive via STDIN, and would be something like "foo=1&bar=2". CONTENT_LENGTH will be set to the length of that string. CONTENT_TYPE will be something like "application/x-www-form-urlencoded".

See Also

• Common Gateway Interface documentation and examples (from NCSA)
• CGI Environment Variables specification and examples (from NCSA)

Other Summaries and Demos

• See my home page for other summaries and demos: APL, REXX, XEDIT, Perl, HTML, RGB Colors, HTTP Cookies, Email Forms, CGI Environment Variables, Server Side Includes, etc...