A means to test whether or not the user has an SSH key installed for a remote system

test_ssh_key.sh

#!/bin/bash

USER=$1
HOST=$2

function test_ssh_key_setup() {
  ssh -q -q -o "BatchMode=yes" -o "ConnectTimeout 5" ${USER}@${HOST} "echo 2>1"
  [ $? ] && return 0 || return 1
}

if [ -z "${USER}" ]; then
  echo "You need to provide a username for the remote host"
  exit 1
fi

if [ -z "${HOST}" ]; then
  echo "You need to provide a hostname or IP for the sensor to update"
  exit 2
fi

if [ ! $(test_ssh_key_setup) ]; then
  echo "Your SSH key doesn't appear to be installed for ${USER} on ${HOST}."
  echo "Please install your SSH key and run this script again."
  exit 3
fi

# Do stuff on remote system with SSH safely knowing you won't be prompted for a password