Wednesday, May 9, 2012

A better way to expand hosts in a subnet

Before i mentioned that you could expand the hosts in a subnet by using bash brace expansion. While that works fine, if you have a file with 40 different CIDR subnets in them it can be REALLY annoying. In walks nmap.
Nmap has a scan feature called list scan that will output the IPs to be tested. All you need to do is supply it with a range/file-with-ranges and it will output the IPs, one in a line. The output may be a little ugly so i created a quick function to parse out just the IPs
expandrange() {
    if [[ -z $1 ]]; then
        echo 'Expands the subnets/ranges provided in the first argument to output in the second argument (file)'
        echo 'Usage: expandrange range.cidr.txt range.long.txt'
        nmap -sL -n -iL $1 | grep 'Nmap scan' | cut -d ' ' -f 5 > $2
    fi; }

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