HTTP Monitor Script for Bash

If you run a web application, or want to know when a web server goes up or down. There’s a range of products you can use to do this, such as Nagios (URL monitoring is only one aspect of server monitoring that Nagios can perform). There are times however when configuring a full blown monitoring system like Nagios is way over the scope of what you want to do right now.

Here’s a script I use to monitor URL’s. I put this in my cron to run every 5 minutes. It only emails you when the HTTP status of the URL has changed since last time you requested it. This should avoid heaps of emails in your inbox, unless you have a bouncy server.

#!/bin/bash
# Simple HTTP monitor script
# Monitors a URL and sends an email when the status of it changes

NOTIFY_EMAIL=youremailhere@yourdomainname.com

if [ -z $1 ]; then
  echo Usage: $0 url_to_monitor
  echo Example: $0 http://www.google.com/
  exit 1
fi

URL=$1
STATUS_FILE_PREFIX=.`echo $URL | sed -s 's/[\/\.:]/-/g'`
RESULT_TEXT=`HEAD $URL | head -n 1`
STATUS_FILE_SUFFIX=`echo $RESULT_TEXT | sed -s 's/ /-/g'`
if [ ! -f $STATUS_FILE_PREFIX.$STATUS_FILE_SUFFIX ]; then
  rm "$STATUS_FILE_PREFIX.*" > /dev/null 2>&1
  touch $STATUS_FILE_PREFIX.$STATUS_FILE_SUFFIX
  echo $URL returned $RESULT_TEXT | mail -s "[$0]: $URL returned $RESULT_TEXT" $NOTIFY_EMAIL
fi
exit $RESULT

This should work on a stock Ubuntu/Debian system. To actually use this script:

  1. Save the above as monitor.sh in your favourite directory.
  2. Edit it and change the NOTIFY_EMAIL address to your own
  3. chmod u+x monitor.sh
  4. Invoke it like this: ./monitor.sh http://www.google.com/

What you do with it is up to you. Note that to track the status this script will create hidden files in the current directory. For example, if Google returns a 200 OK status, a hidden file called .http—www-google-com-.200-OK will be created.

categories Uncategorized | | datetime August 28, 2008 10:32 pm

4 Comments

  • By Frank, September 6, 2008 @ 6:23 am

    Handy! How would you tie something like this in with an alert on your ubuntu desktop say? I’m new to bash scripting and I think that would be very cool.

  • By Omer, July 15, 2011 @ 10:37 pm

    Hello,

    the script you created works perfectly for me. I am using it to monitor multiple website urls.

    Great job! nice script!

    Thanks
    Omer

  • By Joel Thompson, September 14, 2011 @ 4:54 pm

    Hi, thanks for the script, we tried to use this script for our new external webserver but found it wasnt deleting the hidden files in the folder. This resulted in it not warning you when the site went up/down untill these hidden files were deleted.

    The fix was to move the .* out of the double qoutes when checking for the hidden files to remove, like so.

    rm “$STATUS_FILE_PREFIX”.* > /dev/null 2>&1

    After that it has been working brilliantly, thanks.

  • By GuruBob, October 25, 2011 @ 1:09 pm

    Cheers Joel – I hadn’t spotted that :)

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