#!/usr/bin/env bash
size_re='^[[:space:]]*([[:digit:]]+)[[:space:]]*([kmg])b?[[:space:]]*$'
 
declare -A multipliers=(
  [k]=$(( 1024 ))
  [m]=$(( 1024 * 1024 ))
  [g]=$(( 1024 * 1024 * 1024 ))
)
 
to_bytes() {
  result=$1
  if [[ $1 =~ $size_re ]] && { units=${BASH_REMATCH[2]}; [[ $units && ${multipliers[$units]} ]]; }; then
    result=$(( ${BASH_REMATCH[1]} * ${multipliers[${BASH_REMATCH[2]}]} ))
  elif (( $1 )); then
    result=$(( $1 ))
  else
    echo "ERROR: $1 could not be parsed as a number" >&2
    return 1
  fi
  echo "$result"
}
 
Var1='25 MB'
Var2=1G
Var1_bytes=$(to_bytes "${Var1,,}") || exit
Var2_bytes=$(to_bytes "${Var2,,}") || exit
if (( Var1_bytes > Var2_bytes )); then
  echo "Var1 (${Var1_bytes} bytes) is larger than Var2 (${Var2_bytes} bytes)"
else
  echo "Var1 (${Var1_bytes} bytes) is NOT larger than Var2 (${Var2_bytes} bytes)"
fi
 

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