Web Server Health Script (./healthcheck.sh)

#!/bin/sh

##
# Server Health Script
# Executes Curl and checks the HTTP response code repeatedly. Sends an email if code is not 200 or 302.
#
# Example to check Google every 5 minutes silently, even after shell user logs out:
# $ ./healthcheck.sh http://google.com Google 300 > /dev/null &
##

if [ "$1" = "" ]; then
  echo -en "\nUsage: $0 <url> [title] [timer]\n\n"
  echo -en "  url  - Required. The page to target\n"
  echo -en "title  - Optional. The title of this check, used in emails;\n"
  echo -en "         if left blank, title will assume the url\n"
  echo -en "timer  - If set, sleep in [timer] seconds after a check,\n"
  echo -en "         otherwise execute checks back-to-back\n\n"
  echo -en "Exit codes:\n\n"
  echo -en "0 - success or canceled script\n"
  echo -en "1 - required parameters not provided\n\n"
  echo -en "Author: Carl Bennett\n"
  echo -en "License: CC-BY-SA 3.0\n\n"
  exit 1
else
  URL=$1
fi

if [ "$2" = "" ]; then
  TITLE=$URL
else
  TITLE=$2
fi

if [ "$3" = "" ]; then
  SLEEP_TIMER=0
else
  SLEEP_TIMER=$3
fi

EMAIL_ADDRESS_FROM="server-health"
EMAIL_ADDRESS_TO="noc"
EMAIL_SUBJECT="Failure status notification for $TITLE"
EMAIL_MESSAGE="Failed to retrieve a 200 OK status while checking $TITLE."

i=0
while true; do
  ((i++))
  echo -n "Check $i..."
  FIRSTLINE=`curl -s -D- -o/dev/null $URL | head -n 1`
  CODE=`echo -n "$FIRSTLINE" | awk '{print $2}'`
  if [ "$CODE" != "200" ] && [ "$CODE" != "302" ]; then
    echo "failed, sending email..."
    echo -ne "To: $EMAIL_ADDRESS_TO\nFrom: $EMAIL_ADDRESS_FROM\nSubject: $EMAIL_SUBJECT\n\n$EMAIL_MESSAGE\n\nURL: $URL\nStatus: $FIRSTLINE" | sendmail $EMAIL_ADDRESS_TO
  else
    echo "success."
  fi
  if [ $SLEEP_TIMER -ge 1 ]; then
    sleep $SLEEP_TIMER
  fi
done