tangetools/w4it-for-port-open/w4it-for-port-open

#!/bin/bash

quiet=false

while getopts ":q" opt; do
    case $opt in
	q)
	    quiet=true
	    shift
	    ;;
	\?)
	    echo "Invalid option: -$OPTARG" >&2
	    ;;
    esac
done

host=$1
port=$2

nc=$( which nc )

SECONDS=0
next=10

usage () {
    (
	echo "Usage:" 
	echo "  $0 host [port]"
	echo "  port defaults to 22 (ssh)"
    ) >&2
    exit 1
}

print_not_reachable () {
    if [ $SECONDS -ge $next ] ; then
	$quiet || echo -n $SECONDS >&2
	next=$((next + 10))
    else
	$quiet || echo -n . >&2
    fi
}

is_port_open () {
    $nc -z -w 2 $host $port >&2
    return $?
}

if [ -z "$host" ] ; then
  usage
fi
if [ -z "$port" ] ; then
  port=22
fi
if [ -z "$nc" ] ; then
  echo "Error, 'nc' not installed."
  exit 2
fi

while ! is_port_open ; do
  sleep 1
  print_not_reachable
done
echo >&2