keeps multiplying by powers of 2 until it finds the widest bitness your system supports

bitness.bash

#!/bin/bash

# related to bytesToHuman.bash
# 64-bibt checks at https://superuser.com/questions/1030122/what-is-the-maximum-value-of-a-numeric-bash-shell-variable/1030129#1030129

# perpetual while loop: https://stackoverflow.com/questions/10797835/while-vs-while-true
# expressions: http://tldp.org/LDP/abs/html/arithexp.html
# comparisons: http://tldp.org/LDP/abs/html/comparison-ops.html

b=1
n=1
while :
do
  # loop infinitely
  printf "%3s %40s\n" "$b" "$n"
  b=$(( 1+$b ))
  t=$n
  n=$(( 2*$n ))
  if (( $n < $t )); then
    exit
  fi
done
echo "the final number on the left is the largest bitness; on the right the largest power of 2 your system supports"