I am happy to report that I have this script running as a daemon, logging every ElkM1 event into my database. And it runs for months without issue.

I will keep these instructions brief. If you have detailed questions, please ask in the comments and I’ll help the best I can.

Download

You can download all the scirpts, just click here.

Notables

1. If you don’t know a least a little perl and some MySQL basics, you may want to look elsewhere.
2. The script and accompanying files are designed to work in concert as a daemonized process.
3. Everything is logged into ‘elk_monitor.log’ in the same directory (or directory of your choosing) as the script. If you have a lot of passive infra-red motion detectors, you will want to monitor the log size.

Basic File Structure

elk_monitor.pl

This is the main script, it runs in a loop checking for new messages every second. You will need edit the %zonelist, %outputs, %areas near the top. Also, you will need to set some paths, look near the top of the file.

Required: ElkM1::Control, Log4perl

elk_monitor.sh

This is the shell script that controls elk_monitor.pl as a daemon. Setting up daemons can be complex as each system is different, so google around for some help.

elkm1.sql

A MySQL script to setup the tables and fields that the elk_monitor.pl script uses. You will need to add a database named ‘elkm1′. After that you can execute this script to create everything else for you.

lib/elkm1_db.pl

The database setting and basic sql commands are abstracted into this library. This is where you will need to set MySQL’s host, name, password, etc.

lib/file_tickler.pl

I use a custom ruby script to monitor the daemon. This library just touches a file every minute to let us know the elk_monitor.pl script is still running. Why? Well, I have had the script ‘freeze’ without exiting and most monitoring applications do not detect this. Obviously, this part is optional.

Conclusion

If you get all the settings right, she should run all day/week/month for you.

I and not a perl expert. Far from it. So I’m sure everything could use some tidying. If you do, please let me know and I’ll incorporate your changes.

But it got me thinking, there is another think I like to keep an eye on on our servers… log files. Oh, and I was looking for good excuse to play around with Sinatra. So, “with a one, and-a-two, and-a-three…” we have Sinatra-Tailer.

You can read all about it on the github page, but in short it simply performs a tail and displays the last X lines of the log file.

tail -n /path/to/my/log/file.log

Features

1. refreshes the list every X seconds, set by the user
2. only one config.yml file to edit
3. supports file globs, so you can grab a whole list of file with one line
4. specify the number of lines to show
5. completely unobtrusive js, because I’m cool?

Requirements

Sinatra framework (tested on 0.9.1.1, earlier may work)

I whipped this up pretty quickly so I’m sure there are a few bugs. There is some testing for a few unit tests, but nothing functional.

One word of warning, if you want to put this on a production server my recommendation is to put it on a separate port (like 9876) and for heaven’s sake, at a minimum use http basic authentication. From the sinatra readme:

 use Rack::Auth::Basic do |username, password|
    username == 'admin' && password == 'secret'
  end

Enjoy!

The Problem

Here in my development palace I have a couple of laptops that I use for development and an Ubuntu (hardy) server as a Rails/Rack sandbox that I run with Passenger. While I have always been able to serve up either a Rails or Sinatra project, I typically have 3 or 4 going at the same time. But I had to access them with urls like: http://192.168.0.2/project1 and http://192.168.0.2/project2.

So, what’s the problem, eh?

Well, for starters, you can’t do anything concerning subdomains. That’s a show stopper for many apps.

Second, it really messes with your environment variables like ["PATH_INFO"]. So if you do any routing and you expect the base url to be ‘/’, it won’t be. The root url will be ‘/projectx’. Bummer.

The Solution

To remedy the issues with non-tld virtual hosts (also called sub URIs?) we need to add the domains to the laptops and server, then add the virtualhosts on the server for apache. This means that I can now goto http://project1.ubuntu.remote url to get to my rails/rack app.

For reference, I am using the following:

• Laptops: Mac OS X, 10.5.7 and 10.4.11
• Server: Ubuntu Desktop 8.04LTS, Apache/2.2.8 (Ubuntu) mod_fastcgi/2.4.6 PHP/5.2.4-2ubuntu5.5 with Suhosin-Patch Phusion_Passenger/2.0.6

On Each Laptop

These instructions are for Mac OS X, but should be identical for your favorite flavor of *nix. We are going to add some friendly names to our ubuntu server using it’s ip address (192.168.0.2). In this example we will be able to access the root web documents using http://ubuntu.remote, and one of our Sinatra projects using http://project1.ubuntu.remote.

Important! Don’t use a name ending in ‘.local’. While it did work for me, I read about a few instances where some systems will not resolve domain names ending in .local outside the local machine. Also, don’t change anything else in your /etc/hosts file except to add the lines at the end.

mate /etc/hosts

# add the following line to the END of your /etc/hosts file and save
# note: there is a <space> character between the ip address and each host name
192.168.0.2 ubuntu.remote project1.ubuntu.remote

On The Server: Hosts File

Nothing will work until we tell the server machine that it can accept incoming traffic from our new friendly names. Similar to on the mac, we need to edit our /etc/hosts file but we will add a slightly different line. In this case we are telling the server that incoming traffic from ‘ubuntu.remote’ and ‘gems.ubuntu.remote’ are just names for the localhost (127.0.0.1).

sudo pico /etc/hosts

# add the following line to the end of our /etc/hosts file and save
# you can added after your existing 127.0.0.1 line if you wish
127.0.0.1 ubuntu.remote project1.ubuntu.remote

On The Server: VirtualHosts

As a final step we will need to add or change the virtual host definitions for your rails/rack project. Depending on your Apache setup or Linux distro, the default enabled site may be slightly different and you may have to adapt your virtual host file to your default setup.

First, in my /etc/apache2/apache.conf file, I have the following line near the end of the file. This was to eliminate a warning every time apache was started/restarted. It may affect your virtual host default, but shouldn’t, so add it if you get errors.

#added near end of /etc/apache2/apache.conf
ServerName localhost

Next we need to check our default virtual host setup to see how the NameVirtualHost is defined. We will duplicate that in each new virtual host that we add. The parts we are looking is the NameVirtualHost and VirtualHost near the top. They could be ‘NameVirtualHost *’ and ‘<VirtualHost *>’ or ‘NameVirtualHost *:80′ and ‘<VirtualHost *:80>’. See the pattern? We need to use the same definition in our new virtual files.

Let’s check our default virtual host setup:

cd /etc/apache2/sites-enabled
ls # your are looking for the name of your default site file

  total 0

  lrwxrwxrwx 1 root root 36 2009-02-27 18:49 000-default -> /etc/apache2/sites-available/default

cat /etc/apache2/sites-enabled/000-default

  NameVirtualHost *
  <VirtualHost *>
    ServerAdmin webmaster@localhost
  # snipped several lines #
  </VirtualHost>

On my system the NameVirtualHost is ‘*’, so that is what we need to use for the new virtual host. In this case, I am going to add a virtual host file for a rack based project. It’s a Sinatra app, but that doesn’t matter as this will work for any rack based project, even a rails/rack project (since rails 2.2.2?).

Also, I like using the Apache2 system to enable and disable sites. It’s clean, easy to use, and if any apache admin comes along they will know exactly what is going on.

It’s also work mentioning that you should disable or delete any existing virtual host files that you were using previously.

cd /etc/apache2/sites-available
sudo pico gems

# enter this as your virtual host setup
<VirtualHost *>
  ServerName project1.ubuntu.remote

  DocumentRoot "/path/to/your/application/project/public"

  RackEnv production
  <directory "/path/to/your/application/project/public">
    Order allow,deny
    Allow from all
  </directory>
</VirtualHost>

# save the file and reload apache

sudo /etc/init.d/apache2 reload

The Fun Part

Assuming you saw no errors when you reloaded apache, you should be able to go to your new urls see both the root files and your rack application.

http://ubuntu.remote

http://project1.ubuntu.remote

Dyn-O-Mite!

Bonus Points!

For extra credit, let’s say you have admin access to your router, and you are one of those gotta-have-control-of-everything dudes (or dudettes) so you installed a 3rd party firmware. You’re in luck! You can probably add some custom entries in your DNS and you don’t have to edit the /etc/hosts files on your laptop.

I installed Tomato firmware on my Linksys wireless router. Tomato uses Dnsmasq with allows you to set internal host names.

Maybe I’ll cover that in another post.

About a year ago, James Russo released a script on Cocoontech to monitor and control your Elk M1 from a perl script. You can read the forum post for more details. Thanks to James and other Cocoontech members, it works fairly well.

But there have been no updates or bug fixes in over a year. Not wanting to relive my perl days (sorry, I never really liked perl), I decided to revive the project and give it a new home. I asked James for permission to take over the project and he gracefully agreed.

ElkM1::Control New Home on Github

Go check it out! ElkM1::Control on github.

Why github? First, I have stopped using SVN. And sourceforge, ElkM1::Control’s original home, doesn’t support git. Second, github makes it too easy to fork a project and make changes yourself, then push them back up so that I can integrate those changes. You really should try git if you haven’t before. And you don’t need git to download ElkM1::Control and install it.

Updates and Bug Fixes!

You read that right, I have made a few bug fixes and added a couple of new features. I have been running ElkM1::Control on my Ubuntu Hardy server for about a month with no problems. I have also run and do some debugging on OS X (10.5.x).

I also changed the version numbering system to the more common major.minor.release notation. We are not at version 0.1.0.

Quick Installation Instructions

1. Goto the project home page and click the download button. Select the ZIP version (for some reason the TAR doesn’t work sometimes).
2. Follow the README file, don’t forget the PREREQUISITES section. For those who don’t rtfm…
3. From your favorite shell, you may need to add sudo in front of each: ‘perl Makefile.PL’
4. ‘make’
5. ‘make test’
6. Then to install: ‘make install’

Next, you’ll need a little script to get going. There are several scripts posted on Cocoontech, but this one should get you started:

# Example 2: Display all M1 messages
use ElkM1::Control;
    my $elk = ElkM1::Control->new(host => '192.168.0.251', port => 2101);
    while (1) {  # Loop forever
        while (my $msg = $elk->readMessage) { # Read the M1's messages
                print $msg->toString;  # Print the messages
        }
    }

I shouldn’t disrespect restful authentication much as she has been with me for over a year now. But every time I had to install, setup, and get the basics working in RA I couldn’t help gnashing my teeth. I jumped on the RA bandwagon like so many other Rails developers looking for an authentication system that just and move on to more important things.

Enter Authlogic by Ben Johnson of BinaryLogic. By luck, I was starting a new rails app this week, so I decided to take Authlogic out for a test drive. Following Ben’s Tutorial: Authlogic Basic Setup I had a basic login/logout/session management system up and running in a ridiculously little amount of code. The best part of Authlogic is that it truly get’s out of my way and provides me with what I need… a robust and secure methodology of authentication and session management.

The benefits of Authlogic are:

• It’s a plugin and a gem. When Ben pushes an update, getting the latest release is super simple.
• It’s a plugin and a gem. This keeps the authentication code separate from your codes, the way it should be.
• Session are treated like ActiveRecord objects. This is just as cools as it sounds and is very Rails-like.
• Better security. Authlogic uses a non-reversible token that is changed on every session initiation and password change, thus virtually eliminating session persistence and brute force session attacks.
• Ben Johnson. Ben knows what he is doing and has been quickly releasing updates.
• Ben Johnson. Sorry for the repetition, but Ben also has a nice series of tutorials with supporting project code you can download.
  • Tutorial: Reset passwords with Authlogic the RESTful way
  • Tutorial: Authlogic Basic Setup

I had several years of photos that I needed to identify and remove the duplicate. Instead of manually combing through 12,000 (read Long Story below) and before carpal tunnel set in, I needed a script to help me out. My situation may or may not be unique, so this script may not work 100% out-of-the-box for you, but it should get you started.

To use:

1. Download and unzip the script
2. Double-click the script to open in Script Editor
3. Go into iPhoto and select a group of photos you want to compare
4. Switch back to Script Editor and run the script
5. Don’t Touch Anything! Just let the script finish, it could take a while if you are comparing a lot of photos
6. After the script is done, go back into iphoto and search for “duplicate”
7. You can highlight all the duplicates and delete them or move them some place safe

Photos are considered a duplicate if:

1. both heights match
2. both widths match
3. the photo date in iPhoto match, this is typically the EXIF creation date

Long Story:

Breakfast from a Can? WTF!

At first, I honestly thought it was a joke, but I was compelled to stop and pick up the can and watch our demo maven squirt batter out of a can onto the griddle. I did try one, and it tasted OK, but nothing better than what I make for the kids on weekends. That’s when the whole thing really started to bother me.

Ridiculously High Cost!

I doubt one can could hold its own against my two boys. And the three pack can was something like $7.00 (please comment if you know the real price). Geeze Louise that is expensive. According to the label each can will make 28 – 4in. pancakes. I have some pretty serious doubts about that claim. Those must be some darn thin pancakes.

By their own admission, there is only 2.25 cups of batter in each can. When I make pancakes, I use a ladle that is 6oz. which I reckon results in 4oz. per pancake. And each of my boys will eat 3 to 4 of those suckers, without batting an eye. That comes out to ONE CAN per child. And my kids are not the video game, boob tube species either. In fact both are a tad on the skinny side.

Could You Be More Environmentally Unfriendly or What?

Don’t prattle on to me about how steel cans are recyclable. The amount of energy to produce and recycle those cans, the extra weight of shipping, the added shelf space, not to mention that you must keep it refrigerated are all energy wastes. And completely unnecessary.

My pancakes come in paper bags… um, flour, pinch of baking soda and baking powder, maybe some buttermilk if I have it around, , dash of salt, and an egg or two. Not much to recycle there. Even if you go the pancake mix route, all you have is one small box or plastic (recyclable) bag. Even better, Elise has a great recipe for Blueberry Buttermilk Pancakes over at Simply Recipes. Yum.

All that steel in the name of convenience is a shameful waste.

Are People Really That Lazy?

That was probably my first thought. Have people become so darn lazy that can’t mix a little water with some batter mix and make semi-homemade pancakes? I hope not. For crying in a bucket, how hard is it to mix up a little batter!

If you poke around on the blaster site, they have so-called testimonials from overly exuberant customers espousing how much time Batter Blaster has saved them and how convenient it was. All I can picture is one of those self-absorbed parents, squirting goo out of a can, while yapping on their cell phone, kids with permanent carpel tunnel jamming out on their NDS,  while cooking some pancakes. Woot, ain’t multi-tasking great. America, we sure have come a long way baby.

Let me put a better vision in your mind… you take a box of Krusteaz Pancake & Waffle Mix out of your cupboard, let your son or daughter measure out a couple of cups of mix, show them how to calculate the appropriate amount of water to add, topping it off with a short mixing lesson. You just made something together, and they enjoyed spending time with you, and they will enjoy cooking because they actually did something useful.

Wow, educating your kids about cooking and math all while you develop a real relationship with your kids FTW! Flipping amazing.

BTW, they sell the Krusteaz mix in big bags at Costco for around the same price as the blasters. I can only guess the hundreds of pancakes you can make with that bag, plus you’ll forgo chucking enough steel to build a Yugo.

Please, Please, Please…

Don’t by this product. It exists for only the wrong reasons. Do what is better for your wallet, your planet, and your family by exercising your brain and hands. Trust me, your kids will like you better for it.

If you have a favorite pancake or waffle recipe, please add it in the comments below.

I feel better now℠

Update 12/2/08: Fixed in Rails 2.2! (read more)

The error that I received was thus:

ActionView::TemplateError (undefined method `length' for #) on line #83 of dashboard/index.html.erb:


Fortunately, someone has submitted a ticket to Rails core. I hope it’s applied in the Rails 2.2.0 release.

Current Method, Done Busted

As of Rails 2.1.0, this is the current method (Rails 2.0.2 is similar, and also broken).

<br />
# File actionpack/lib/action_view/helpers/text_helper.rb, line 49<br />
def truncate(text, length = 30, truncate_string = "...")<br />
if text<br />
l = length - truncate_string.chars.length<br />
chars = text.chars<br />
(chars.length > length ? chars[0...l] + truncate_string : text).to_s<br />
end<br />
end<br />

The problem is that chars method called on the string object (truncate_string) returns an <Enumerable::Enumerator> object. And according to the Ruby 1.8.7 RDoc, there is no ‘length’ method in Enumerable::Enumerator. To be honest, I can’t find the ‘chars’ method in any of the Ruby 1.8.6 docs or 1.8.7 docs. I guessing that it may have been Rails method at some time.

Fix #1

The fix is to get rid of all the chars methods. On the bug ticket, the author gives his fix, but you are going to have to monkey-patch rails, or change the method name.

<br />
def truncate(text, length = 30, truncate_string = "...")<br />
if text<br />
l = length - truncate_string.chars.to_a.length<br />
chars = text.chars<br />
(chars.to_a.length > length ? chars.to_a[0...l].to_s + truncate_string : text).to_s<br />
end<br />
end<br />

Fix #2 (mine, tiny bit better?)

I’m not exactly sure why the string needs to be converted to an array, when the length function works just dandy on string objects. So I added this to my application_helper.rb file. Also, in the submitted patch, the result of the ternary is converted to a string (.to_s), when all the resulting methods of the ternary return strings. Unnecessary IMHO and probably left over from when the string object was converted to an enumerable. Note that I started with the Rail 2.0.1 version, so it’s slightly different than if I started with the 2.1.0 version.

<br />
def truncate_string(text, length = 30, truncate_string = '...')<br />
if text.nil? then return end<br />
l = length - truncate_string.length<br />
text.length > length ? text[0...l] + truncate_string : text<br />
end<br />

Yeah, yeah, I could have monkey-patched the TextHelper module, but why tempt fate if you don’t have to. A quick find/replace on ‘truncate’ to ‘truncate_string’ is all that was necessary. Works for me.

• A production server, not a development server, with only what is necessary
• A virtual machine that runs under VMware Player
• Ubuntu Server, 8.04 is the current, referred to as Hardy Heron
• Apache2 with Phusion Passenger to handle Rails applications
• Ruby, Rubygems, Ruby on Rails, a full Rails stack
• MySQL Server and SQLite, with phpMyAdmin to admin MySQL server
• All native drivers for Rails (MySQL and SQLite)
• OpenSSH server to access the server
• Postfix to send (only) emails

What you need to start:

1. VMware Player installed. Download it from VMware directly and follow their instructions (aptitude has older version 1.x)
2. Download the Ubuntu 8.04 Server ISO file for your machine. For torrent users, download the current i386 torrent file.
3. Download my VMX and VMDK files (vmplayer config and empty virtual disk).

Step 1: Setup Directory and Config File

Create a new directory somwhere (I called mine ‘Ubuntu840Server’) and copy the Ubuntu ISO file and the VMX and VMDK (don’t forget to unzip) files into it. You will need to do some quick editing to the Ubuntu840Server.vmx file, so fire up your favorite editor (in Ubuntu Desktop, right-click and Open with “Text Editor”). The only sections you may need to edit are:

• ide1:1.filename, make sure it matches the name of your ISO file, something like “ubuntu-8.04.1-serverr-i386.iso”
• fileSearchPath, change to the path of the directory you created

Step 2: Run VMWare Player

Run VMware Player and open the Ubuntu840Server.vmx. If all the config settings are correct and the ISO files is in the directory, you should boot into Ubuntu Installer.

Step 3: Install Ubuntu Server

I won’t go into details here because Ubuntu has step-by-step instructions on how to install. But the short story is: accept the defaults.

There is one selection that will make installation easier, select LAMP Server when asked for the Software selection. LAMP stands for Linux/Apache/MySQL/PHP. It will install all those packages and configure them automatically for you.

Note: even though I selected a LAMP server, for some reason it did not install Apache/Mysql/PHP. If this happens to you, just do the following after the server re-boots:

sudo apt-get install apache mysql-server php5 libapache2-mod-php5 php5-mysql


Step 4: Get the Latest Updates

If everything went well, you should reboot into Ubuntu Server and see the login: prompt. Go ahead and login with the username and password you supplied during the installation. Make sure you have the latest updates for Ubuntu by running (this may take a while):

sudo apt-get update
sudo apt-get upgrade


Step 5: Install OpenSSH

I like to administer my VMs from the terminal via SSH. Ubuntu Server does not come preconfigured with an SSH server, so lets install one:

sudo apt-get install openssh-client
sudo apt-get install openssh-server


You don’t really need the openssh-client, but I like to have it in case I ever need to ssh from the server to somewhere else. I can’t recommend enough that you secure your SSH server. If you server is exposed to the internet, it will be attacked, and one of the favorite vulnerabilities is SSH. Read this article on how to Secure an OpenSSH Server!

Step 6: Install phpMyAdmin

Since we are using MySQL, having a graphic administration program is nice and it’s hard to beat phpMyAdmin. I installed it from aptitude, but it did not set the proper aliases for apache2, so there are a few extra steps:

sudo apt-get install phpmyadmin

# close and save pico, then enter this to enable the phpmyadmin site
sudo a2ensite phpmyadmin
sudo /etc/init.d/apache2 restart


Step 7: Install Ruby

Next we need to install ruby. We’ll use the aptitude pre-built binaries to save time and make it easier to update in the future, but you may wish to install it from source. We also install the sqlite3 database because it is the default used by Rails 2.X and many test packages, but you can omit if you want.

sudo aptitude install ruby1.8-dev ruby1.8 ri1.8 rdoc1.8 irb1.8 libreadline-ruby1.8 libruby1.8 libopenssl-ruby sqlite3 libsqlite3-ruby1.8 build-essential mysql-client libmysqlclient15-dev postfix


Note that we installed the ‘build-essential’ package. This package is necessary for you to install any other software from source (like native msql drivers and phusion passenger). We also install the postfix package, you can just accept the defaults.

Next you will need to set some symlinks so that the libraries will be located when needed.

sudo ln -s /usr/bin/ruby1.8 /usr/bin/ruby
sudo ln -s /usr/bin/ri1.8 /usr/bin/ri
sudo ln -s /usr/bin/rdoc1.8 /usr/bin/rdoc
sudo ln -s /usr/bin/irb1.8 /usr/bin/irb


Now, when you should see your ruby package when you check the version from the terminal.

karl@ubuntuserver:~$ ruby -v
ruby 1.8.6 (2007-09-24 patchlevel 111) [i486-linux]


Step 8: Install RubyGems

RubyGems is a package manager like aptitude that makes is trivial to add/update/delete resources that ruby (and Rails) will need. It’s also how you will install and update Rails. We are going to install RubyGems from source as the aptitude package is quite out-of-date. RubyGems is a self-updating application, and when installed from aptitude, aptitude will complain and you may accidentally downgrade RubyGems.

# create a sources directory in your home
mkdir ~/sources
cd ~/sources

#update rubygems
sudo gem update --system
sudo gem update


Step 9: Install Ruby on Rails

All this work, and we are finally here. Too bad installing Rails is so easy. Just this one line.

sudo gem install rails
and a couple more gems you will probably need…
# install the native (faster) mysql driver
sudo gem install mysql

# if you want native (faster) sqlite3 drivers, for production
sudo apt-get install libsqlite3-dev
sudo gem install sqlite3-ruby

You can install any more gems you may need at this time with ’sudo gem install package-name‘, but if you are using rails 2.1 or greater, you can now add rubygem requirements to your environment.rb file and use rake to automatically installed gem dependencies.

Step 10: Install Phusion Passenger

There are many ways to host a Rails application, but at this time, Phusion Passenger gets the nod for the easiest to deploy and our experience has been rock-solid in reliability. These install steps are from the Passenger website installation instructions:

sudo gem install passenger
sudo apt-get install apache2-prefork-dev
sudo passenger-install-apache2-module
# and follow the instructions

# restart apache webserver
sudo /etc/init.d/apache2 restart


You will also be given a sample virtual host file to setup your Rails application. At this point you can copy an existing Rails app over to the new server, or follow along for a quick setup of a new Rails app.

Step 11: Create a Rails Application (optional)

We are going to create a very quick Rails application to test that our installation is working.

cd ~/
rails tester
script/generate scaffold Blog name:string content:text
rake db:migrate RAILS_ENV=production

# activate this site
sudo a2ensite tester
sudo /etc/init.d/apache2 restart


Now you can visit your site by going to http://address_of_server/ and you should see your rails application!

Problem: Our Cub Scout den leader sends email reminders to all the parent about upcoming events. I decided to setup a gCal (google calendar) will all the events so that other parents could just check the calendar as they wish, or subscribe to the ical file to integrate with their own calendar. But several of the parents don’t have calendars (shame, shame) and everyone still liked the idea of receiving email reminders. So I decided to write a ruby script to email reminders automatically two days before the event.

Solution: Ruby is a great language to handle this. Especially since there are gems to handle many of the functions we need. Some of the gems we will be using are as follows:

• open-uri: to get the ical file via http
• net/smtp: to send the email, you could use ActionMailer as well
• erb: email body is in a template.html.erb file for easy editing, erb processes the file
• yaml: a list of sent notifications are logged in a yaml file
• icalendar: the superb ical manipulation gem from Jeff Rose

All you need to do is setup a cron job to run this script. I chose to run the script at 8pm every evening.

I’m going to break this script apart by methods for easier commenting. You can download the complete script file and templates to follow along. In the single script file is logging and some formatting methods that don’t really need explanation here.

The script all assembled with some nice logging: notification_script.rb
A sample email template file: mail_template.html.erb
A sample recipient groupt list: group_list.txt

Setup and Requires

First, you are going to need the icalendar gem (documentation), which you can install with:

sudo gem install icalendar

For the beginning of our script, we’ll need a few other libraries to be required, and set a constant or two.

require 'rubygems'
require 'open-uri'
require 'icalendar'
require 'date'
require 'net/smtp'
require 'erb'
require 'yaml'

ICAL_URL = 'http://www.google.com/calendar/ical...path_to_your_ical_file'
FROM_EMAIL = 'your_email_address@domain.com'
MAIL_TEMPLATE_FILE = 'mail_template.html.erb'
SENT_NOTIFICATIONS_FILE = 'sent_notifications.yml'
GROUP_LIST_FILE = 'group_list.txt'
DAYS_BEFORE_TO_SEND = 2

All of these requires should already be installed in your standard ruby library. Following the requires are some constants you need to edit. The ICAL_URL constant is the url that you can look up from google calendars by going to your Calendar Settings, and selecting Calendar Details. You should see the ICAL (green) button that when you click, it shows you the url for the ical file of your calendar. Copy and paste this url into the ICAL_URL constant. You will also want to change the FROM_EMAIL to your email address, or the one you want notifications to be from.

The other constants are the names of the files that should be in the same directory as the script. You can rename them or change the paths as necessary.

The Main Event

I like to wrap my main events in a method called ‘init()’ and place it near the top of the script file so that it is quick and easy to find. You don’t have to do this, but supporting methods will have to come before your code.

def init
  begin
  myFile = open(ICAL_URL).read

  cals = Icalendar.parse(myFile)
  cal = cals.first

  cal.events.each{ |e|
    time_diff = e.dtstart - DateTime.now
    if time_diff < (DAYS_BEFORE_TO_SEND * 24 * 60 * 60) &amp;amp;&amp;amp; time_diff > 0

      if notified?(e.uid)
        #log '    notification previousy sent.'

      else
        send_to = group_list
        msg = ERB.new(File.read( MAIL_TEMPLATE_FILE )).result( binding )

        send_email('Den 4 Notifications', 'your_email@domain.com', send_to, e.summary, msg)

        add_notification_to_list(e.uid)
      end
    end
    }

  rescue
    #log the error
  end
end

Pretty easy, huh? Let start breaking this down in greater detail:

Step 1: Read the iCal File

Read the contents of the ical file at the ICAL_URL location. Using the open-uri library, the content of the ical file is read into a string object.

Step 2: Parse the iCal File with Icalendar

The Icalendar gem first requires that we parse the ical file, so that it can create the representative ’calendar’ and ‘event’ objects for reading. There is the potential of more than one calendar in the ics file. But in our case, we know there is only one, so we need to get that first ‘calendar’ object.

Step 3: Loop Through the Calendar Events

We need to look at every calendar ‘event’ object in the calendar so that we can look at the start date (e.dtstart) so see if it’s within the DAYS_BEFORE_TO_SEND.

Step 4: Previous Notification Sent? Ready Email Template

The ‘notified?’ method will tell us if this event has received previous notification. The e.uid attribute is a unique identifier associated with every event (an event id, if you will). We check that e.uid against a list of saved uid’s.

Then we can read the MAIL_TEMPLATE_FILE and use erb to process the file, substituting the various object attributes (variables). This makes it easy to change the email template without editing our script file.

Step 5: Send the Email Message

A Couple of things happen here that we’ll discuss in the ’send_email’ method, but suffice it to say that this sends the email to all the addresses in the GROUP_LIST_FILE.

Step 6: Add Notification to List

We save a list of the event uids (e.uid) that have been notified so that we don’t send a notification again.

Pretty spiffy, huh?

Now lets show some of the supporting methods and discuss.

Method: notified?

This method reads the SENT_NOTIFICATIONS_FILE yaml file to see if the passed ‘uid’ exists in the list of events with previous notification. The loop looks at each item in the ‘y_content’ array to see if the ‘uid’ is a match. If there is a match, return true (I like the explicitness of using return here). You can see how the yaml file is structured in the ‘add_notification_to_list’ method.

def notified?(uid)
  if File.exist?( SENT_NOTIFICATIONS_FILE )
    File.open( SENT_NOTIFICATIONS_FILE ) { |yf|
      y_content = YAML.load( yf )

      if y_content.is_a? Array
        y_content.each{ |e| return true if e[:uid] == uid }
      end
    }
  end

  return false  #not found
end

Method: group_list

The GROUP_LIST_FILE is a text file with the address of whom we want to send the notification emails to, separated by a linefeed. You can change this to suit your needs, like comma or pipe separation. It returns the list of email addresses in an array.

If the GROUP_LIST_FILE does not exist or there is an error reading the file, a default email address is returned so that at least someone gets notified. I would normally not do it his way and let the rescue raise an error and halt the script.

def group_list
  begin
    IO.read( GROUP_LIST_FILE ).split(/\n/)
  rescue
    return Array['default_email@domain.com']
  end
end

Method: send_email

Here we get to use the net/smtp gem to send the email. I chose this because it has fairly low overhead and it actually pretty easy to use. I’m not sure you can use it to send attachments, but in our case, we are just sending HTML emails.

A heredoc is used to create the string for the message header. I’m not such a fan of heredoc, so this is my one and only time I’ll use it.

Notice that the ‘Content-Type: text/html’ is set so that the receive recognizes this as an HTML email and not plain text. Use ‘Content-Type: text/plain’ if you’re sending a text only email.

You will have to set your SMTP server setting were you see ‘mail.my_server.com’. For more information on this, see the NET::SMTP documentation. Because there are many configurations for this, I didn’t place constants at the beginning of the script. The NET::SMTP docs pretty much cover it.

I would have liked to send all the messages using BCC, but alas I could find no documentation in NET::SMTP supporting BCC. In my case, everyone know everyone else, so it’s no big whoop.

def send_email(from_alias, from, to_array, subject, message)
	msg = <<END_OF_MESSAGE
From: #{from_alias} <#{from}>
To: #{to_array.collect{ |item| '<' + item + '>' }.join(',')}
Subject: [CUB SCOUTS]#{subject}
Content-Type: text/html

#{message}
END_OF_MESSAGE

	Net::SMTP.start( 'mail.my_server.com', 25 ) do |smtp|
		smtp.send_message msg, from, to_array
	end
end

Method: add_notification_to_list

Here we add an event uid to a yaml file and timestamp it. I’m sure there are a million ways to do this, but I just wanted to play around reading/writing yaml files.

There is one thing I don’t like about this though… the entire yaml file is read in, the new event is added to the end, and the resulting yaml replaces the entire existing file. I could not find a reliable way to append a yaml object to an existing yaml file. Well, sort of, but it creates an new array object hash for each append, instead of having all events in one array of hashes. Yeah, yeah, I’m being picky.

def add_notification_to_list(uid)
  if File.exists?( SENT_NOTIFICATIONS_FILE )
    y_content = YAML.load( File.open( SENT_NOTIFICATIONS_FILE ) )
  end

  y_content = [] unless y_content.is_a?( Array )

  File.open( SENT_NOTIFICATIONS_FILE, 'w+' ) { |yf|
    y_content.concat [ :date => Time.now, :uid => "#{uid}" ]
    YAML.dump( y_content, yf )
  }
end

Put it All Together…

The script all assembled with some nice logging: notification_script.rb
A sample email template file: mail_template.html.erb
A sample recipient groupt list: group_list.txt

All that’s left is to put all the files in a directory that has read/write access (for the log file and notification list file) and setup a cron job. Now you have automated notifications from your calendar.