All the CGI programs have access to the following environment variables. These variables play an important role while writing any CGI program.
| Sr.No. | Variable Name & Description |
|---|---|
| 1 | CONTENT_TYPE The data type of the content. Used when the client is sending attached content to the server. For example, file upload. |
| 2 | CONTENT_LENGTH The length of the query information. It is available only for POST requests. |
| 3 | HTTP_COOKIE Returns the set cookies in the form of key & value pair. |
| 4 | HTTP_USER_AGENT The User-Agent request-header field contains information about the user agent originating the request. It is name of the web browser. |
| 5 | PATH_INFO The path for the CGI script. |
| 6 | QUERY_STRING The URL-encoded information that is sent with GET method request. |
| 7 | REMOTE_ADDR The IP address of the remote host making the request. This is useful logging or for authentication. |
| 8 | REMOTE_HOST The fully qualified name of the host making the request. If this information is not available, then REMOTE_ADDR can be used to get IR address. |
| 9 | REQUEST_METHOD The method used to make the request. The most common methods are GET and POST. |
| 10 | SCRIPT_FILENAME The full path to the CGI script. |
| 11 | SCRIPT_NAME The name of the CGI script. |
| 12 | SERVER_NAME The server's hostname or IP Address |
| 13 | SERVER_SOFTWARE The name and version of the software the server is running. |
Here is small CGI program to list out all the CGI variables.
#!/usr/bin/python import os print "Content-type: text/html\r\n\r\n"; print "<font size=+1>Environment</font><\br>"; for param in os.environ.keys(): print "<b>%20s</b>: %s<\br>" % (param, os.environ[param])