IP Validator

This is a simple script, which validates IP addresses, converts them into binary form and assign to an IP class.
Usage: ./ipvalidator <IP address>
Example: ./ipvalidator 192.168.15.16

This script is using bc (bash calculator) to convert octets to binary number and a simple while loop to scale the binary number to 8 digits.
TIP: If you want to convert any numeral system to decimal number in bash you can use following command:
echo $(( 2#101011 )) to convert binary number to decimal
echo $(( 16#5E3 )) to convert hex number to decimal


Here's the script:

#!/bin/bash

echo INPUT IP: $1

OCT=0;
for OCTSUB in $( echo $1 | sed -e 's/\./ /g' ); do

  let OCT=$OCT+1;
  if [ $OCT -gt 4 ]; then
    echo The address is too long!
    exit 1
  fi

  if [[ $OCTSUB != [0-9]* ]] || [ $OCTSUB -gt 255 ]; then
    echo The $OCT. octet is out of range \($OCTSUB is not valid number\);
    exit 1
  fi

done

if [ $OCT -lt 4 ]; then
  echo The address is too short!
  exit 1
fi

echo -e IP Address: $1 is valid!

echo -n "Binary Address: "
for BINNUM in $( echo $1 | sed -e 's/\./ /g' ); do
  BINNUM="`echo "ibase=10; obase=2; $BINNUM" | bc`";

  while [ "`echo "${#BINNUM}"`" -lt 8 ]; do
    BINNUM=0$BINNUM
  done

   BINRES=$BINRES.$BINNUM
done

BINRES="`echo -e $BINRES | sed -e 's/\.//'`"
echo $BINRES

CLASS=(`echo $BINRES | tr '.' "\n" | head -n 1 | sed -e 's/[0-1]/& /g'`)
if [ ${CLASS[0]} -eq 0 ]; then
  VALID=A
elif [ ${CLASS[1]} -eq 0 ]; then
  VALID=B
elif [ ${CLASS[2]} -eq 0 ]; then
  VALID=C
elif [ ${CLASS[3]} -eq 0 ]; then
  VALID=D
else VALID=E
fi
echo This is valid $VALID class address.
echo ""

exit 0