Bash function to convert bytes to human readable size

human_readable.sh

# Copyright 2015 Andrew Gunnerson <andrewgunnerson@gmail.com>
# Copyright 2024 antiops@github
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.


# Convert bytes to human readable size
# $1: Size in bytes
# $2: Floating point precision (digits after dot)
# Return: Nothing
# Prints: Human readable size
#
# Example: "$(human_readable 6390759424 2)" == "5.95 GiB"
human_readable() {
  local abbrevs=(
    $((1 << 60)):ZiB
    $((1 << 50)):EiB
    $((1 << 40)):TiB
    $((1 << 30)):GiB
    $((1 << 20)):MiB
    $((1 << 10)):KiB
    $((1)):Bytes
  )

  local no_input=$([[ -z "$1" ]] && echo " (No Input)")
  local bytes=$((10#${1:-0}))
  local precision=$((10#${2:-2}))

  if [[ "${bytes}" == "0" ]]; then
    echo "0 Bytes$no_input"
  elif [[ "${bytes}" == "1" ]]; then
    echo "1 Byte"
  else
    for item in "${abbrevs[@]}"; do
      local factor="${item%:*}"
      local abbrev="${item#*:}"
      if [[ "${bytes}" -ge "${factor}" ]]; then
        local size="$(bc -l <<< "${bytes} / ${factor}")"
        local size_floating="$(printf "%.*f" "${precision}" "${size}")"
        printf "%g %s\n" "${size_floating}" "${abbrev}"
        break
      fi
    done
  fi
}

Changelog

• Set default values to input variables

  • Bytes: 0
  • Precision: 2

• Handle strings bash would percieve as octals ¹

$ human_readable 09999999
9.54 MiB

• Handle 0 or no input

$ human_readable 0
0 Bytes

$ human_readable
0 Bytes (No Input)

• Normalize floating point to decimal after precision application (ie 5.00000001 -> 5.00 -> 5) ^{2 3}

$ human_readable 5
5 Bytes

Footnotes

1. StackOverflow: Convert string into integer in bash script ↩

2. StackOverflow: Use printf to format floats without decimal places if only trailing 0s ↩

3. Python 3 Documentation: string Format Specification ↩