before do
  puts "I will run all the time..."
end

Here’s a module that will allow you to run code only before certain routes:

module Sinatra

  module BeforeOnlyFilter
    def before_only(routes, &block)
      before do
        routes.map!{|x| x = x.gsub(/\*/, '\w+')}
        routes_regex = routes.map{|x| x = x.gsub(/\//, '\/')}
        instance_eval(&block) if routes_regex.any? {|route| (request.path =~ /^#{route}$/) != nil}
      end
    end
  end

  register BeforeOnlyFilter

end

Use it like below, note that you insert ‘*’ for routes that use variable placeholders like ‘:id’…

before_only(['/post', '/comment/*/user/*']) do
  puts "I will only run before the routes '/post' & '/comment/*/user/*'..."
end