I would like to use FastCGI with shell scripts. I have found several tutorials about writing CGI scripts in shell, but nothing about FastCGI, and I guess this is not the same thing.
Is it possible, and how?
The whole point of FastCGI is to avoid spawning a new process for each incoming connection. By the very nature of the language, a shell script will spawn many processes during its execution, unless you want to restrict yourself greatly. (No cat, awk, sed, grep, etc, etc). So from the start, if you're going to use shellscript, you may as well use regular CGI instead of FastCGI.
If you're determined anyway, the first big hurdle is that you have to accept() connections on a listening socket provided by the webserver. As far as I know, there is no UNIX tool that does this. Now, you could write one in some other language, and it could run your shellscript once for each incoming connection. But this is exactly what normal CGI does, and I guarantee it does it better than the custom program you or I would write. So again, stick with normal CGI if you want to use shellscript.