You should specify a URL for the <IMG>
's src
attribute that can be reached from the browser.
/home/zaman/ssdggraph/SSDGhistory.png
is unlikely to to satisfy that requirement. (You should probably have someting like http://path_known_to_webserver/SSDGhistory.png
).
You should probably also read up on the concepts of web pages and cgi scripts. I would call a CGI "that displays an image", some program that would be referenced in the above URL and dynamically streams out the image data once the web pages refers to it and a browser asks for it. That might be what you mean, but it is kind of unclear.