Compare nmap two different scan file

npdiff.sh

#!/bin/bash
#
# (N)map(P)ort diff -- yeah there is `ndiff` command already but it fail to compare between `-sC` and `-p-` output format
# intended just for comparing between initial scan: `-sC -sV target-ipaddr` with allport scan `-p- target-ipaddr`
# use option `-n` to remove newline
# then run `-sC -sV -p{copy-and-paste-new-ports}`
#
# requirements: `pip install yq`
#

initial=$1
allport=$2
progname=$(awk -F'/' '{print $NF}' <<< $0)

usage() {
  echo "Usage: $progname [scan-1.xml] [scan-2.xml]"
  echo "Example: $progname enumeration/nmap/initial.xml enumeration/nmap/allports.xml"
}

[ -z "$initial" ] || [ -z "$allport" ] && usage && exit 0
[ ! -f "$initial" ] && echo "$progname: $initial: No such scan file" && exit 1
[ ! -f "$allport" ] && echo "$progname: $allport: No such scan file" && exit 1

cat $initial | xq -rcM '.nmaprun.host.ports.port[]."@portid"' > /tmp/npdiff-initial.txt
cat $allport | xq -rcM '.nmaprun.host.ports.port[]."@portid"' > /tmp/npdiff-allport.txt
out=$(comm -23 <(sort /tmp/npdiff-allport.txt) <(sort /tmp/npdiff-initial.txt))
rm /tmp/npdiff-*

[ "$1" == "-n" ] || [ "$3" == "-n" ] && echo $out | sed 's/ /,/g' && exit 0
[ -z "$out" ] && echo "no new open ports" && exit 0
echo "$out"