where is bin directory in rails3?

I am trying to place the wkhtml开发者_JAVA技巧topdf executable in the "bin directory" of my rails project so that it works with heroku, as mentioned here.

dumb question....where is the "bin" folder in the rails project? I placed the executable in root of my executable, however, heroku gives an error saying:

No wkhtmltopdf executable found at /app/bin/wkhtmltopdf-i386

And the following code is used to provide path for wkhtmltopdf

config.wkhtmltopdf = Rails.root.join('bin', 'wkhtmltopdf-i386');

You need to create the bin folder under the app/ folder and add it in there.

mkdir app/bin