Robots Text Script

I am just checking into robots text. Haven't any experience with them.

Was wondering what to write, html php or java, I prefer not to use java.

I would like to make one that allows friendly bots google yahoo etc, and dissallows everybody elses bots. (spambots)

Will this work if on the main page and protect all the others or does it have to be on all pages, and on php for my forum and blog?

Thanks for your input and experiences with robots text

I believe that a single file, robots.txt, can specify everything for the site. I'm not sure on the details, but google should help, or perhaps someone else will know.