Checks if LAN hosts are up in parallel

hostsup.fast

#!/bin/bash
# parallel port check via nc. Takes ~1 s per scanned service, but
# should almost not depend on the number of hosts.
# by silverweed
# FIXME: echo-ing lines from check_host may result in more lines
#+ bloated together.

# file containing the IPs to scan
HOSTLIST="$HOME/.hostlist.txt"
NC="/bin/nc"

# map of default services -> ports to scan
declare -A TO_CHECK
TO_CHECK[ssh]=22
TO_CHECK[http]=80

# preliminary checks
[[ -r $HOSTLIST ]] || {
	echo "$HOSTLIST not readable: exiting." >&2
	exit 1
}
[[ -x $NC ]] || {
	echo "$NC not executable: exiting." >&2
	exit 2
}

# given a host IP, checks all services in TO_CHECK and returns an associative
# array IS_UP with the results (0 = up, 1 = not up)
check_host() {
	[[ -n $1 ]] || {
		echo "Warning: invalid argument for check_host(): $1" >&2
		return 1
	}

	ping -c 1 -w 1 $1 &> /dev/null || {
		[[ $1 =~ ^([0-9]{1,3}\.){3}([0-9]{1,3})$ ]] || {
			echo -en "\033[1;31m"
			printf "%-16s " "$1:"
			echo -e "down\033[0;0m"
		}
		return
	}

	declare -A IS_UP
	for SERVICE in ${!TO_CHECK[@]}; do
		$NC -w 1 $1 ${TO_CHECK[$SERVICE]} &> /dev/null
		IS_UP[$SERVICE]=$?
	done

	echo -en "\033[1;32m"
	printf "%-16s " "$1:"
	for SERVICE in ${!IS_UP[@]}; do
		if [[ ${IS_UP[$SERVICE]} == 0 ]]; then
			echo -en "\033[1;32m"
		else
			echo -en "\033[1;31m"
		fi
		echo -en "$SERVICE \033[0;0m"
	done
	echo ""
}

add_service() {
	SRV=$(awk -v FS=':' '{ print $1 }' <(echo $1))
	PORT=$(awk -v FS=':' '{ print $2 }' <(echo $1))
	if [[ $PORT ]]; then
		TO_CHECK["${SRV:-?}"]=$PORT
	else
		# try to resolve port number from service name
		TO_CHECK["$SRV"]=$(awk "/^\s*[^#]/ && /$SRV/ { print \$2; exit }" /etc/services | cut -f1 -d'/')
		if [[ ${TO_CHECK["$SRV"]} ]]; then
			echo "[INFO] Scanning service $SRV on port ${TO_CHECK[$SRV]}." >&2
		else
			echo -n "[ERR] Failed to resolve port for service $SRV. "
			echo "Please specify it with '-s $SRV:<port>'." >&2
		fi
	fi
}

SORT='sort -g'
while [[ $# -gt 0 ]]; do
	case $1 in
	-s)
		unset TO_CHECK
		declare -A TO_CHECK
		shift
		while [[ $# -gt 0 && ! $1 =~ -.* ]]; do
			add_service "$1"
			shift
		done
		;;
	-n)
		DONTRESOLVE=true
		SORT="sort -g -k4 -t'.'"
		shift
		;;
	*)
		echo "Usage: $0 [-n] [-s <service1[:port]> [service2[:port] ...] ]" >&2
		exit 0
		;;
	esac
done

declare -a PIDS
i=0

echo "Checking $(wc -l $HOSTLIST | awk '{print $1}') hosts..." >&2
STARTTIME=$(date +%s)
for HOST in $(< $HOSTLIST); do
	if [[ $DONTRESOLVE != true ]]; then
		RESOLVE=$(grep $HOST /etc/hosts | awk '{print $2}')
		[[ -n $RESOLVE ]] && HOST=$RESOLVE
	fi
	# parallel scan
	check_host $HOST & PIDS[$i]=$!
	let i++
done | eval "$SORT"

for ((j = 0; j < i; j++)); do
	wait ${PIDS[$j]}
done

echo "Elapsed time: $(($(date +%s) - STARTTIME)) s" >&2