gets,readlineは行の途中まででもも読んじゃう

tailっぽく1行づつ読みたい

gets.rb

output = open("file.txt","w")
output.sync = true

Thread.new do
  open("file.txt") do |f|
    loop do
      if f.eof?
        sleep 0.01
      else
        s = f.gets #readline
        puts "gets: #{s.inspect}"
      end
    end
  end
end

output.puts("line01")
sleep(0.1)

output.write("line02\nline03\nline04\n")
sleep(0.1)

output.write("lin")
sleep(0.1)
output.write("e05\n")
sleep(0.1)

output.flush
sleep(1)

=begin
gets: "line01\n"
gets: "line02\n"
gets: "line03\n"
gets: "line04\n"
gets: "lin"
gets: "e05\n"
=end

tailer

def tailer(input)
  Enumerator.new do |y|
    buf = ""
    loop do
      if input.eof?
        sleep 0.1
      else
        buf << input.read(4*1024)
        while buf =~ /(.*?\n)(.*)/m
          y << $1
          buf = $2
        end
      end
    end
  end
end

open(ARGV[0]) do |f|
  tailer(f).each do |line|
    puts line
  end
end