Grep the nmap output - linux

Question

I have output my nmap result to a file called test.txt and it looks like this:
Nmap scan report for 192.168.1.5
Host is up (0.13s latency).
PORT STATE SERVICE VERSION
23/tcp open telnet Linux telnetd
--
Nmap scan report for 192.168.1.7
Host is up (0.13s latency).
PORT STATE SERVICE VERSION
80/tcp open http Popper
--
Nmap scan report for 192.168.1.20
Host is up (0.13s latency).
PORT STATE SERVICE VERSION
110/tcp open pop3 Dove
I want to output the results from the file in my terminal using grep and pipe that displays the result in format: IP address followed by the open ports like this:
192.168.10.2
80
223
53
192.168.10.7
80
223

Answer 1

You probably want:
cat test.txt | sed 's/Nmap scan report for //' | sed '/Host is/d' | sed '/Not shown/d' | sed '/All/d' | sed '/PORT /d' | cut -f1 -d"/" | sed '/^$/d' | sed '/--/d'
For nmap -F 192.168.0.1/24 > test.txt:
cat test.txt | tail -n+3 | sed '/Nmap done/d' | awk 'NR>1{print l}{l=$0}' | sed 's/Nmap scan report for //' | sed '/Host is/d' | sed '/Not shown/d' | sed '/All/d' | sed '/PORT /d' | cut -f1 -d"/" | sed '/^$/d'
Joke. It does not make sense... Use nmap with XML Output -oX.
Read: https://nmap.org/book/output-formats-xml-output.html

Answer 2

I'd do the following:
Get a regular expression to match ip's and ports for the nmap output. You can take advantage of the positions of both, i.e ports are at the beginning of the line(^) and end with a '/' character, and ip's are the last item on the line($).
Use grep -o to look for any of that regular expressions (look at the OR operator on the regex (|)). This will reduce the output to just the matches.