Pasted

#!/usr/bin/bash
 
CIDR=192.168.0
STARTOCTET=0
ENDOCTET=1
 
while getopts O:o: flag
do
    case "${flag}" in
        O) filename=${OPTARG};;
        o) filename=${OPTARG};;
    esac
done
 
echo "Please enter the starting octet..."
read STARTOCTET
 
echo "Please enter the ending octet..."
read ENDOCTET
 
[ -n "$STARTOCTET" ] && [ "$STARTOCTET" -eq "$STARTOCTET" ] 2>/dev/null
if [ $? -ne 0 ]; then
   echo $STARTOCTET is not number
   exit 1
fi
 
[ -n "$ENDOCTET" ] && [ "$ENDOCTET" -eq "$ENDOCTET" ] 2>/dev/null
if [ $? -ne 0 ]; then
   echo $ENDOCTET is not number
   exit 1
fi
 
if (( $ENDOCTET < $STARTOCTET)); 
then
    echo "Start octect must be earlier than ending octet"
    exit 1
fi
 
for i in $(seq $STARTOCTET $ENDOCTET)
do
    echo "scanning $i"
    nmap -Pn -F $CIDR.$i >> $filename
done