iTP Secure WebServer System Administrator's Guide (iTPWebSvr 5.1+)

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Using Common Gateway Interface (CGI) Programs

iTP Secure WebServer System Administrator’s Guide—522659-001

8-27

Server Headers

A web client cannot properly interpret CGI program output unless it knows the output

data (MIME) type. Therefore, every response generated by a CGI program must contain

a Content-type: header. For example:

Content-type: text/html

Clients ignore any headers they are unable to interpret.

Server Headers

Two headers (Location: and Status:) are used by CGI programs to pass information

to the server rather than directly to the web client. These headers cause the server to

modify its response to the web client.

The

Location: header instructs the server to redirect the web client to another URL.

This redirection consists of a specific URL the web client should access in place of the

original URL. For example, a CGI program returning the header

Location: http://www.foo.com/home.html

is instructing the server to redirect the web client to a URL

http://www.foo.com/home.html

The Status: header instructs the server to return a specific status response to the web

client. This status information consists of a numeric HTTP status code followed by text

explaining the code. For example, a CGI program might cause the server to return a bad-

request response to the web client:

Status: 400 Bad Request

Content-type: text/html

<TITLE>Bad Request</TITLE>

</HEAD><BODY>

You sent this server a bad request.

</BODY></HTML>

For a complete list of the HTTP status codes, see Table C-2, HTTP Status Codes, on

page C-3.

Nonparsed Headers

CGI programs can use the nonparsed header feature to return responses directly to the

web client.

To use this feature, the CGI program must have a file name that begins with nph- (for

example, nph-payment.cgi). This marker tells the server not to process any of the CGI

program’s output.

A CGI program using the nonparsed feature must construct a complete HTTP response,

including all status and header information.