CGI Environment Variables

browser info | form info | program info | server info | visitor identity

Program and Form Information

SCRIPT_NAME

The virtual path of the CGI script relative to DOCUMENT_ROOT. It can be used in conjunction with DOCUMENT_ROOT to determine the physical disk location of the program or with SERVER_NAME to determine the URL of the program. For example:
$prg_location = "$ENV{'DOCUMENT_ROOT'}$ENV{'SCRIPT_NAME'}";
$prg_url = "http://$ENV{'SERVER_NAME'}$ENV{'SCRIPT_NAME'}";
Example: '/cgi-bin/myscript.cgi'

REQUEST_METHOD

POST or GET

CONTENT_LENGTH

For forms submitted with POST, the number of bytes in the standard input. You can then read the attached data from STDIN. (numeric)
Example: 382

CONTENT_TYPE

In a form submitted with POST, the MIME content type of the form data. In forms submitted with POST the value will be "application/x-www-form-urlencoded". In forms with file upload, the content-type will be "multipart/form-data".

QUERY_STRING

The arguments to the script. For forms submitted with GET, the form input. Bascially everything after the ? in the URL. There is a limit to how much info can be passed with GET. The amount varies from server to server.

PATH_INFO

Extra path information, as sent by the browser. For example:
http://www.domain.com/cgi-bin/myscript.cgi/users/username
PATH_INFO would be set to '/users/username'

PATH_TRANSLATED

The actual system-specific pathname of the path contained in PATH_INFO. This variable treats PATH_INFO as a relative path within your server's Web space and turns it into a full, absolute path on your server's hard drive.
Example: '/home/users/tina'

Visitor Identity and Browser Request Information

REMOTE_ADDR

The visitor's IP address. (string)
Example: '100.100.100.100'

REMOTE_HOST

The visitor's host name. Usually the same as the visitor's domain name, but some servers may set this variable to the visitor's IP address or even leave it empty. Note: this variable cannot be set.
Example: 'domain.com'

REMOTE_USER

The username of the visitor that called the script. This value will only be set if server authentication is turned on.

REMOTE_IDENT

If the web server is running Ident (a protocol to verify the user connecting to you) and the system that submitted the form or script is also running Ident, this variable contains the value returned by Ident.

HTTP_USER_AGENT

The browser that submitted the form. Usually includes the browser name, version number, and info about the visitor's operating system.
Example: 'Mozilla/4.0 (Macintosh; I; PPC)'

HTTP_ACCEPT

A list of content-types that the browser can accept directly, as defined by the HTTP Accept header. Basically, a list of the MIME types supported by the visitor's browser. Usually only contains an abbreviated list.
Example: 'image/gif, image/jpeg'

HTTP_REFERER

If the CGI script was called from a link within a Web page, the complete URL of the referring page. If a form submission, the URL of document that sent the form data, though not all browsers send this value.
Example: 'http://www.domain.com/myform.html'

HTTP_COOKIE

The value of any cookies that have been set in the visitor's browser and which are accessible by your site.

SERVER_PROTOCOL

The name and revision of the request protocol used to access the server. The HTTP protocol that the server is running.
Example: 'HTTP/1.1'

SERVER_PORT

The TCP port on which the server is running. The port to which the program was sent. Usually port 80 for web servers.
Example: 80

Server Information

SERVER_NAME

Host name or IP address on which the CGI script is running, as it appears in the URL.

SERVER_SOFTWARE

The name and version of the Web server software.
Example: 'NCSA/1.5.2'

GATEWAY_INTERFACE

The version of CGI running on the server.

DOCUMENT_ROOT

The absolute path of the root directory for the server. This is the directory that the server's domain name maps to.

SERVER_ADMIN

The email address for the server administrator.