ptyvim.rb

require 'pty'
require 'io/console'

STDIN.raw do
  File.open('keylog.txt', 'a') do |log|
    PTY.spawn('vim wtf') do |r, w, pid|
      w.winsize = STDIN.winsize
      rs = { STDIN => w, r => STDOUT }
      rs.compare_by_identity
      loop do
        x = IO.select(rs.keys)
        if x
          x[0].each do |io|
            data = io.read_nonblock(4096)
            rs[io].write(data)
            if io == STDIN
              log.write(data)
              log.flush
            end
          end
        end
      end
    end
  end
end