Really? Escaping, people! This code isn't practical or useful; it's dangerous and sloppy.

    cout << "<body>\n";
    ...
    cout << getenv("QUERY_STRING");     
    cout << "</body>\n";

FWIW I wrote an article about HTML escaping and shell here: http://www.oilshell.org/blog/2017/09/19.html

Followup: http://www.oilshell.org/blog/2017/09/29.html

Also if you want to use a native language for web sites (which I don't), Go is a better choice, as the standard library has html/template which protects you from naive injections:

https://golang.org/pkg/html/template/