How does pygments guess lexer?

Question

I'm using middleman-syntax to highlight code in my blog

I'm writing my templates in markdown... and was wondering, how does pygments guess lexer?

  if I write

  ´´´ruby
  ruby code here
  ```

  it doesnt work

  if I write

  ```      
  #!ruby
  ruby here
  ```

  it does

  If I write

  ```
  <?php
  php code here
  ```

  It does

Is there a list of how pygments guess it?

Answer 1

As far as I know, Pygments does not guess.

Linguist does.