Convert File Size Output in Pure BASH

#!/bin/bash
# Created By Marc Gilligan
# https://github.com/ulfnic
# BSD-0 or CC-0

print_size() {
  local -a types=(B KiB MiB GiB TiB PiB EiB ZiB YiB)
  local num=$1
  local \
    num_len=${#num} \
    thousands digits

  thousands=$(((num_len - 1) / 3))
  ((thousands >= ${#types[@]})) && return 1
  digits=$((num_len - (thousands * 3) + 1))

  if ((thousands > 0)); then
    printf '  %*s%s %s\n' 4 "${num:0:digits}" ".${num:digits:1}" "${types[thousands]}"
  else
    printf '  %*s %s\n' 6 "${num:0:digits}" "${types[thousands]}  "
  fi
}

print_size 1
print_size 12
print_size 123
print_size 1234
print_size 12345
print_size 123456
print_size 1234567
print_size 12345678
print_size 123456789
print_size 1234567890
print_size 12345678901
print_size 123456789012
print_size 1234567890123
print_size 12345678901234
print_size 123456789012345
print_size 1234567890123456
print_size 12345678901234567
print_size 123456789012345678
print_size 1234567890123456789
print_size 12345678901234567890
print_size 123456789012345678901
print_size 1234567890123456789012
print_size 12345678901234567890123
print_size 123456789012345678901234
print_size 1234567890123456789012345
print_size 12345678901234567890123456
print_size 123456789012345678901234567