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#!/bin/bash

pretty(){
  # Digest a single number into a pretty number
  num=${1:-0}
  zero=0

  tera=$(( $num / 1099511627776 ))
  num=$(( $num % 1099511627776 ))
  giga=$(( $num / 1073741824 ))
  num=$(( $num % 1073741824 ))
  mega=$(( $num / 1048576 ))
  num=$(( $num % 1048576 ))
  kilo=$(( $num / 1024 ))
  num=$(( $num % 1024 ))
  byte=${num:-0}

  one=byte && two=zero && sign=B
  [ $kilo -gt 0 ] && one=kilo && two=byte && sign=kB
  [ $mega -gt 0 ] && one=mega && two=kilo && sign=MB
  [ $giga -gt 0 ] && one=giga && two=mega && sign=GB
  [ $tera -gt 0 ] && one=tera && two=giga && sign=TB

  fmt="%0.2f%s\n"
  [ "${sign}" = "B" ] && fmt="%0d%s\n"
  num=$(eval echo \$$one.\$$two)
  [ "$two" = "zero" ] && num=$(eval echo \$$one)
  printf "${fmt}" ${num} $sign
}

digest(){
  dev="${1}"
  if [ ! -d "/sys/block/${dev}" ]
  then
    return 1
  fi
  eval $(printf 'old_r=$old_r_%s old_w=$old_w_%s' "${dev}" "${dev}")
  [ -z "${old_r}" ] && old_r=0
  [ -z "${old_w}" ] && old_w=0
  eval $(awk '{print "cur_r=" $3 " cur_w=" $7}' /sys/block/${dev}/stat)
  dif_r=$(( (${cur_r} - ${old_r}) * 512 ))
  dif_w=$(( (${cur_w} - ${old_w}) * 512 ))
  eval $(printf "old_r_%s=%u old_w_%s=%u" "${dev}" "${cur_r}" "${dev}" "${cur_w}")
  printf "%s: R: %s W: %s \033[K\n" "${dev}" "$(pretty ${dif_r})" "$(pretty ${dif_w})"
}

while true
do
  printf "\033[0;0H" # Cursor to upper left
  for I in /sys/block/sd?
  do
    digest "$(basename "${I}")"
  done
  printf "\033[0J" # Clear the rest of the page
  sleep 1
done