wait_ssh

#!/usr/bin/env bash

# Author: Curtis K - http://www.centosblog.com/sshwait-script-waits-ssh-available-connecting/
# Github: https://www.github.com/centosblog
# Description: a script that waits for SSH on a remote host to become available before connecting.

# Check if nc is available
CHECK_NC="$( which nc 2>/dev/null )"
if [ -n "$CHECK_NC" ]; then
	NC="nc"
else
	echo "Error: netcat or nc not found. Please install this first. Eg:"
	echo "yum install nc"
	exit 1
fi

# Check arguements are present
if [ -z "$1" ]; then
        echo
        echo "Script usage:"
	echo "sshwait <SSH_OPTIONS> <SSH_USER@SSH_HOST>"
        exit 1
fi

# The actual connection string should be the last arguement
CONN_STRING="$( echo "$@" | awk '{ print $NF }' )"

if [ $# -gt 1 ]; then
	SSH_OPTS="$( echo "$@" | sed "s/$CONN_STRING//g" )"
fi

# Determine SSH username
SSH_USER_CHECK="$( echo "$CONN_STRING" | grep "\@" )"

if [ -n "$SSH_USER_CHECK" ]; then
	SSH_USER="$( echo "$CONN_STRING" | cut -d"@" -f1 )"
	SSH_HOST="$( echo "$CONN_STRING" | cut -d"@" -f2 )"
else
	SSH_USER="$(whoami)"
	SSH_HOST="$CONN_STRING"
fi

# Show parameters
echo "SSH user: $SSH_USER"
echo "SSH host: $SSH_HOST"
[ -n $SSH_OPTS ] && echo "SSH options: $SSH_OPTS"

echo

stop_and_fail() {
	echo "Timeout after 10s"
	exit 1
}

# Check SSH function
check_ssh () {

	echo "Waiting for SSH connection"
	START_WAIT="$( date +%s )"
	while [ $( $NC -w 5 -z $SSH_HOST 22 > /dev/null ; echo $? ) -ne 0 ]; do
		sleep 1
	done

	echo
	STOP_WAIT="$( date +%s )"

	TOTAL_WAIT="$( echo "scale=2; $STOP_WAIT - $START_WAIT" | bc )"

	tput bel
	tput bel
	echo "SSH ready (waited for $TOTAL_WAIT seconds)"
	echo
}

check_ssh