Run ping, netcat, host (or any other) commands on multiple hosts or IPs or both. Also run many procresses at a time!

healthcheck.sh

#!/usr/bin/env bash

set -euo pipefail

# In some commands, I've used the full parameter names just for the sake of learning/debugging/memorizing.

# From $ man xargs:
# --max-procs 
#        Run up to max-procs processes at a time; the default is 1.  
#        If max-procs is 0, xargs will run as many processes as possible at a time.

if [[ ! -r hosts.txt ]]; then
    echo 'No input "hosts.txt" file found'
    exit 1
fi

echo 'TEST: ping hosts'
xargs --arg-file=hosts.txt -L 1 --max-procs=1 --no-run-if-empty --verbose -- ping -q -c1

echo 'TEST: run DNS lookup'
xargs --arg-file=hosts.txt -L 1 --max-procs=1 --no-run-if-empty --verbose -- host

echo 'TEST: check if TCP port (443) is listening for connections'
xargs --arg-file=hosts.txt -L 1 --max-procs=1 --no-run-if-empty --verbose -I{} -- /bin/nc -zv {} 443

hosts.txt

8.8.8.8
8.8.4.4

google.com
github.com

1.1.1.1
1.0.0.1