fsiorate.rb

#!/usr/bin/env ruby
usg = []
loop {
    begin
        usg = ([IO.popen(["df", "--output=used", "--block-size=1024", "."]).readlines[1].to_i] + usg)[0, 5]
        if usg.length > 4
            STDOUT << "\r" << (->(x){x.sum / x.length}).call(usg[0..-2].zip(usg[1..-1]).collect {|x, y| x - y}) << " KiB/s       "
        end
        sleep 0.5
    rescue Interrupt
        break
    end
}