vendor/rails/railties/lib/rails/rack/log_tailer.rb

   1 module Rails
   2   module Rack
   3     class LogTailer
   4       EnvironmentLog = "#{File.expand_path(Rails.root)}/log/#{Rails.env}.log"
   5
   6       def initialize(app, log = nil)
   7         @app = app
   8
   9         path = Pathname.new(log || EnvironmentLog).cleanpath
  10         @cursor = ::File.size(path)
  11         @last_checked = Time.now.to_f
  12
  13         @file = ::File.open(path, 'r')
  14       end
  15
  16       def call(env)
  17         response = @app.call(env)
  18         tail_log
  19         response
  20       end
  21
  22       def tail_log
  23         @file.seek @cursor
  24
  25         mod = @file.mtime.to_f
  26         if mod > @last_checked
  27           contents = @file.read
  28           @last_checked = mod
  29           @cursor += contents.size
  30           $stdout.print contents
  31         end
  32       end
  33     end
  34   end
  35 end