convert bytes to human readble size

convert_human.sh

#!/bin/bash -e

math_calc() {
  local format="$1"
  local equation="$2"

  echo | awk "{printf \"$format\", $equation}"
}

convert_to_bytes() {
  local v=$1
  local s=${v%%[^0-9.]*}
  local u=${v##$s}
  local inbytes=0
  case $u in
    KB)
      inbytes=$(math_calc "%d" "$s * 1000")
      ;;
    MB)
      inbytes=$(math_calc "%d" "$s * 1000 * 1000")
      ;;
    GB)
      inbytes=$(math_calc "%d" \
        "$s * 1000 * 1000 * 1000")
      ;;
    K|KiB)
      inbytes=$(math_calc "%d" "$s * 1024")
      ;;
    M|MiB)
      inbytes=$(math_calc "%d" "$s * 1024 * 1024")
      ;;
    G|GiB)
      inbytes=$(math_calc "%d" \
        "$s * 1024 * 1024 * 1024")
      ;;
    B|"")
      if [ -n "$s" ]; then
        inbytes=$(printf "%d" $s)
      fi
      ;;
    -)
      #special case
      inbytes=0
      ;;
    *)
      log_err "unit not support: $u"
      ;;
  esac
  echo $inbytes
}


convert_to_human() {
  local v=$1
  local h=0
  local unitidx=0
  local unitNames=("B" "K" "M" "G" "T")
  while true; do
    h=$(math_calc "%.2f" "$v / 1024")
    if expr $h \< 1.0 > /dev/null; then
      break
    else
      v=$h
    fi
    let unitidx=unitidx+1
  done

  echo ${v%%.00}${unitNames[$unitidx]}
}

convert_to_human $(expr 1024 \* 1024 \* 30 \* 30)
convert_to_human $(expr 1024 \* 1024 \* 30 \* 30 \* 3)
convert_to_human $(expr 102 \* 4)