cgi - Common Gateway Interface

The Common Gateway Interface is a way to create dynamic web pages. It defines rules for interaction between a program and the web server while the server talks to the client. There are some ways to use it.

Normally the webserver sets several environment variables to give some information to the CGI program so it can determine various stuff.

AUTH_TYPE

This reflects the authentification method used to validate a user.

CONTENT_LENGTH

The length of the data in bytes passed to the CGI program through standard input. This is used by the POST method.

CONTENT_TYPE

The MIME type of the query data, such as "text/html", optional.

DOCUMENT_ROOT

This reflects the document root directory of the webserver.

GATEWAY_INTERFACE

Reflects the version of the Common Gateway Interface that the server is using

HTTP_ACCEPT

A comma separated list of MIME type that the client is willing to accept.

HTTP_FROM

The email address of the user issuing the information request. This is not supported by most browsers.

HTTP_REFERER

Reflects the URL from which tis CGI program was accessed.

HTTP_USER_AGENT

The name, version and libraries of the browser making the request. This information can be used to determine if the browser is capable of graphics and is able to display frames and tables.

PATH_INFO

This shows extra information that was passed to the CGI program via command line. Normally it's empty or non-existant.

PATH_TRANSLATED

The translated path on the local filesystem.

QUERY_STRING

This variable refers to additional arguments that were appended to the CGI programm - normally with the '?' sign.

REMOTE_ADDR

This refers to the host from which the information request was issued, as ip number.

REMOTE_HOST

This refers to the host from which the information request was issued.

REMOTE_USER

The authenticated name of the user.

REQUEST_METHOD

This refers to the method with which the information request was issued. Normally this is either GET or POST.

SCRIPT_NAME

The virtual name of the script being executed.

SERVER_NAME

The server's hostname or ip number. This may be used to determine the correct paths or resulting HTML code for CGI programs that are used on the same machine for several servers.

SERVER_PROTOCOL

This is the name and version of the information protocol the request came in with. Normally this is "HTTP/1.0" or "HTTP/1.1".

SERVER_PORT

This refers to the TCP/IP port on which the webserver is running.

SERVER_SOFTWARE

This reflects the name and revision of the webserver software.

This CGI library is written by Martin Schulze <joey@infodrom.north.de>. If you have additions or improvements please get in touch with him.

cgiDebug(3), cgiHeader(3), cgiSetType(3), cgiSetHeader(3), cgiGetValue(3), cgiGetVariables(3).