network scan script using nc

scan.sh

#!/bin/bash

echo "First 3 IP octets: "
read net

echo "Start IP (last octet): "
read start_octet

echo "End IP (last octet): "
read end_octet

echo "[b]readth (a few ports) or [d]epth (large port range) port scan? Enter 'b' or 'd': "
read bdport

# default port list
bp_arr=(21 22 23 25 53 80 8080)

if [ -z $bdport ] || [[ $bdport == "b" ]] ; then
    bdport="b" # default to breadth
elif [[ $bdport == "d" ]] ; then
    echo "Start port: "
    read sport

    echo "End port: "
    read eport
fi

echo "IP addr direction. 'r' for reverse. Enter for default (sequential): "
read direction

if [ -z $direction ] ; then
    :
elif [[ $direction == "r" ]] ; then
    tmp_octet=$start_octet
    start_octet=$end_octet
    end_octet=$tmp_octet
fi

if [[ $bdport == "b" ]] ; then
    outfile="nc_${net}.${start_octet}-${end_octet}_bports"
elif [[ $bdport == "d" ]] ; then
    outfile="nc_${net}.${start_octet}-${end_octet}_ports_${sport}-${eport}"
fi

echo "Output: $outfile"
echo "Scan range: $net .$start_octet - $end_octet"

for ((i=$start_octet; $i <=$end_octet; i++))
do
    if [[ $(($i % 10)) == 0 ]]; then
        echo "Scanning $net.$i ..."
    fi
    if [ -z $bdport ] || [[ $bdport == "b" ]] ; then
        for bport in "${bp_arr[@]}"; do
            nc -nvzw 1 $net.$i $bport 2>&1 | grep -E '[Oo]pen|[Ss]ucce' >> $outfile
        done
    elif [[ $bdport == "d" ]] ; then
        for ((p=$sport; p <= $eport; p++))
        do
            nc -nvzw 1 $net.$i $p 2>&1 | grep -E '[Oo]pen|[Ss]ucce' >> $outfile
        done
    fi
done