hostcomplete

#!/bin/bash
# FLAG: headupcommands

arg=$1
result=()

lookupWithnmap() {
	local interface=`ip address | grep -i "state UP"`
	interface=($(echo $interface | tr " " "\n"))
	interface=${interface[1]}
	interface=${interface//\:/}
	regexp="inet (.+?) brd (.+?) $interface"
	interface=`ip address | grep -iE "$regexp"`
	if [[ $interface =~ $regexp ]];
	then
		interface=()
		interface=${BASH_REMATCH[1]}
		interface=`nmap -sL $interface | grep -i "$arg"`
		set -f
		IFS=$'\t\n'
		regexp="scan report for (.+?) \("
		for i in ${interface[@]}
		do
			if [[ $i =~ $regexp ]];
			then
				local elem=${BASH_REMATCH[1]}
				if ! [[ -z "$elem" ]];
				then
					result+=("$elem")
				fi;
			fi;
		done;
	fi;
	
	return 0
}

lookupWitharp() {
	local res=`arp | grep -i "$arg"`
	set -f
	old_ifs=$IFS
	IFS=$'\t\n'
	for i in ${res[@]}
	do
		IFS=$' '
		for u in ${i[@]}
		do
			if ! [[ -z "$u" ]];
			then
				result+=("$u")
			fi
			break
		done
		IFS=$'\t\n'
	done
}

if ! [ -z $(which arp) ];
then
	lookupWitharp
	#echo "hi"
elif ! [ -z $(which nmap) ];
then
	#echo "blib"
	lookupWithnmap
fi;

echo ${result[*]}