Shell Programming and Scripting

echo "\nEnter first three quadrants of router address (must contain three periods) \nExample- xx.xxx.xx. :"
read PT1ADD
echo 'Enter beginning range of the fourth quadrant :'
read PT2ADD
echo 'Enter the end range of the forth quadrant :'
read PT3ADD
echo '\n--------------------------------------'
echo 'Running scan on '$PT1ADD$PT2ADD-$PT3ADD
echo '--------------------------------------\n'
jot -w  $PT1ADD $PT3ADD $PT2ADD $PT3ADD | uniq |
while read SRC
do ping -c1 -W1 $SRC &>/dev/null
STATUS=$(echo $?)
    if [ $STATUS == 0 ]; then
        echo $SRC '\tUsed' | tr '\n' '\t'
        host $SRC | awk '/pointer/ {print $5}' | grep -m1 '.com' || echo 'No Domain'

## ^ I know grep is redundant here but if awk failed to find "pointer" it did not trigger the || echo 'No Domain' command. 
Grep was my workaround ##

    elif [ $STATUS == 2 ]; then
    echo $SRC '\tNOT_Used'
    else echo '\tPing Error Occured'
    fi
done
echo '\n--------------------------------------'
echo 'Scan Complete'
echo '--------------------------------------\n'

function get_three_quad
{
   REPLY=""
   while [ -z "$REPLY" ]
   do
      printf "$1"
      read
      if [ "${REPLY//[0-9]/}" != ".." ]
      then
         echo "Illegal input"
         REPLY=""
      fi
    done
}

get_three_quad "
Enter first three quadrants of router address (must contain three periods)
Example- xx.xxx.xx. : "
echo "You entered: $REPLY"

if ! echo "$REPLY" | grep -qE "^((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)(\.|$)){3}$"

[ $REPLY -gt 0 -a $REPLY -lt 256 ] 2>/dev/null && return
echo "Illegal input"
REPLY=""

function get_three_quad
{
   REPLY=""
   while [ -z "$REPLY" ]
   do
      printf "$1"
      read     
      if ! echo "$REPLY" | grep -qE "^((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)(\.|$)){3}$"
      then
         echo "Illegal input"
         REPLY=""
      fi
    done
    [ $# -gt 1 ] && printf -v "$2" "%s" "$REPLY"
}

get_three_quad "
Enter first three quadrants of router address (must contain three periods)
Example- xx.xxx.xx. : " PT1ADD
echo "You entered: $PT1ADD"