CLUSTERfoo!

Managing Multiple Computers with One bashrc/zshrc

Here is a simple way to share the same .bashrc / .zshrc / .bash_profile across multiple computers, while still retaining unique settings in between computers.

Suppose you want some special setting to apply only to your laptop.

First, create an empty file called .setup_00:

$ touch ~/.setup_00

Next, in your rc file, add the following if statement. Anything inside that if statement will only apply to your laptop:

if [ -f '.setup_00' ]; then
    echo "This message only shows on my laptop!"
fi

You can use this method to run any shell script uniquely on computers that contain the .setup_00 file.

That’s it. It’s not fancy, but it works.

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Rails Cheatsheet

Updated: Instad of .rvmrc, I now use .ruby-version and .ruby-gemset.

A little cheatsheet of Rails stuff I don’t want to forget. Many of these tips come from Michael Hartl’s Rails tutorial.

Setting Up Environment

Install RVM, Ruby, Bundler

Install RVM through instructions on rvm.io. RVM now also eliminates the need to use bundle exec when used with bundler.

Install latest ruby. The following OpenSSL option is needed on Ubuntu:

$ rvm install 1.9.3-head --with-openssl-dir=$HOME/.rvm/

Aside:

If you ever get the following warning:

make: /usr/bin/gcc-4.2: No such file or directory

You will also need to run

$ rvm reinstall 1.9.3-head --with-gcc=clang

Create project gemset and be in it before installing Rails:

$ rvm use 1.9.3-head@projectname --create

Project-specific gemsets prevent big headaches. Don’t forget to set a project rvmrc file after Rail app is generated (see below).

Install Rails

$ gem install rails

And if on Linux, also run:

$ sudo apt-get install libxslt-dev libxml2-dev libsqlite3-dev

Install node.js so that rails server can run properly in your development environment.

Initialize Rails App

Set up Rails App Directory

Skip TestUnit if you’re using rspec:

$ rails new project_name --skip-test-unit

Now create two files: .ruby-version and .ruby-gemset. These files will ensure that rvm, or whatever ruby envelope you use, know to switch to the correct Ruby version (and gemset, in rvm). For example, if you’re using Ruby 2.0.0 and a gemset called my-project, create a .ruby-version file with the following content:

2.0.0

And a .ruby-gemset file with:

my-project

Now cd in and out of the directory and make sure that rvm is switching to the correct gemset with:

$ rvm gemset list

Set up Rspec

Add rspec, guard and spork to development / test environment in Gemfile:

group :development, :test do
  gem 'rspec-rails', '~> 2'

  # If using guard and spork:
  gem 'guard-rspec', '~> 2'
  gem 'guard-spork', '~> 1'
  gem 'spork', '~> 0.9'
end

Make Rails use rspec instead of TestUnit:

$ rails g rspec:install

Speeding up Tests with Spork and Guard

Follow these instructions.

Heroku / Deployment

Add PostgreSQL gem and production-environment-specific gems. In gem file:

group :production do
  gem 'pg'
end

To run bundler without production gems

$ bundle install --without production

Bundler remembers this setting, no need to use it again.

Initialize Heroku:

$ heroku login
$ heroku create

Push to Heroku and rename:

$ git push heroku
$ heroku rename project_name

Maintenance

After Migrations

After running

$ rake db:migrate

The following come in handy:

Stop the Rails server. This is obvious, but forgetting to restart the server after a migration is a sure way to waste time wondering why half your tests are suddenly failing.

Annotate models and migrations (requires the annotate gem):

$ annotate

Tell the test database about the migration too:

$ rake db:test:prepare

Restart the Rails server.

Sometimes you want to reset your test database:

$ rake db:reset
$ rake db:test:prepare

Run Console in Sandbox Mode!

Don’t break things:

$ rails console --sandbox

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MathJax RSS

Yesterday I started using MathJax to render mathematical equations on my blog. MathJax uses a Javascript library to render LaTex on the client side, as a result, mathematical equations will not render if you are reading this blog through an RSS feed or email.

I toyed with the idea of rendering equations as .pngs, but I like the convenience of MathJax. From now on, posts that include mathematical equations will include a warning, so readers on RSS know to check the original post.

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