ruby - Watch/read a growing log file

Question

I have a log file that is constantly growing. How can I watch and parse it via a Ruby script?

The script will parse each new line as it is written to the file and output something to the screen when the new line contains the string 'ERROR'

Answer 1

def watch_for(file, pattern)
  f = File.open(file,"r")
  f.seek(0,IO::SEEK_END)
  while true do
    select([f])
    line = f.gets
    puts "Found it! #{line}" if line=~pattern
  end
end

watch_for("g.txt",/ERROR/)

Thanks for the ezpz's idea, using the select method you get get what you want. The select method is listening the IO's stream, read the bytes what comes 'late'.