Standard environment variables

The following are some of the more standard CGI environment variables. Note that:

• Some of these environment variables may not be supported by your server;
• Even if some of these environment variables are supported by your server, they may be implemented differently; and
• Your server may support more environment variables than those listed here.

To find out what environment variables your server does support, and how it implements them, take a look at the environment variables CGI example.

Server Specific Environment Variables

DOCUMENT_ROOT

Absolute path on server machine of root web folder (e.g. /usr/httpd/htdocs/)

GATEWAY_INTERFACE

Version of CGI supported by the server (e.g. CGI/1.1)

SERVER_ADDR

IP address of the server

SERVER_ADMIN

Email address of server administrator

SERVER_NAME

Host name of the server (e.g. www.paulgriffiths.net)

SERVER_PORT

Listening port of the server (usually 80)

SERVER_PROTOCOL

Name and version of protocol used by the server (e.g. HTTP 1/1)

SERVER_SOFTWARE

Name (and version, usually) of server software (e.g. Apache/2.2.4)

Request Specific Environment Variables

AUTH_TYPE

Type of authentication used by the server (e.g. basic)

CONTENT_LENGTH

Number of characters passed to STDIN from a POST request (e.g. 220)

CONTENT_TYPE

Type of data sent to the server, if applicable (e.g. application/x-www-form-urlencoded)

HTTP_REFERER

URI of web page that called the script

PATH_INFO

Relative path information included in the URI after the script name, but before the query string (e.g. if http://www.paulgriffiths.net/cgi-bin/envvars.pl/more/path/info?var1=red&var2=herring is called then PATH_INFO would contain /more/path/info).

PATH_TRANSLATED

Same as PATH_INFO but with the virtual path translated into an absolute path on the server machine, i.e. not a URI (e.g. /usr/httpd/htdocs/more/path/info/)

QUERY_STRING

The part of the URI after the ? character (e.g. var1=red&var2=herring))

REMOTE_ADDR

User's IP address

REMOTE_PORT

User's port

REMOTE_USER

User's identified name, if authorisation was used.

REQUEST_METHOD

The HTTP request method used, usually GET or POST, but can be different.

REQUEST_URI

Full relative URI of request (e.g. /cgi-bin/envvars.pl/more/path/info?var1=red&var2=herring)

SCRIPT_NAME

Name of script before any additional path info or query string (e.g. /cgi-bin/envvars.pl)

SCRIPT_FILENAME

Absolute path on the server machine of the script (e.g. /usr/httpd/htdocs/cgi-bin/envvars.pl)