Rev Your Ruby With RVM

What’s this RVM thing?

Simply: RVM is Ruby Version Manager.

There you go all done, see you back here next week!

Ok, in all seriousness RVM is a fantastic tool when you are working with multiple ruby projects. It allows you to install multiple versions (and implementations) of the ruby interpreter and use different ones for different projects. It also extends all the way down to your gems, allowing you to have completely different sets of gems installed for different projects.

I’m not going to go into deep technical details here. If you want to go in depth, check out the RVM website.

Ok, but why do I need it?

RVM sounds kinda interesting and maybe it might conceivably be useful, but you don’t see how you could ever have an actual use for it right? Wrong!

Let’s take 2 projects that I have right now:

Shiny new Rails 3 app that acts as an OpenID provider
Legacy Rails 2.3.8 project management app that is too big to migrate at the moment

Rubies of many shades and varieties

This Rails 3 app that I’m working on was written specifically with Ruby 1.9 in mind and takes advantage of a couple of new things so it won’t even run on 1.8.7.

Meanwhile my Rails 2.3.8 app has a lot going on in it involving time tracking and we all know that date handling changed from 1.8 to 1.9. Some would say, well just go fix that 2.3.8 app to run on 1.9. Unfortunately this is not an option because there are a lot of other things going on that are different from 1.8 to 1.9 and I just don’t have the time right now.

So I clearly have to have both 1.8.7 and 1.9.2 installed, but how? Here is where RVM comes in.

Using RVM I can install both versions and switch between them. Here’s what I mean:

# The system-provided ruby
$ ruby -v
ruby 1.8.7 (2010-01-10 patchlevel 249) [universal-darwin11.0]

# Now let's use RVM's ruby 1.8.7
$ rvm use 1.8.7
Using /Users/vongrippen/.rvm/gems/ruby-1.8.7-p334
$ ruby -v
ruby 1.8.7 (2011-02-18 patchlevel 334) [i686-darwin10.7.0]

# Now lets use ruby 1.9.2
$ rvm use 1.9.2
Using /Users/vongrippen/.rvm/gems/ruby-1.9.2-p180
$ ruby -v
ruby 1.9.2p180 (2011-02-18 revision 30909) [x86_64-darwin11.1.0]

# I could even switch to another variety of ruby even, like JRuby
$ rvm use jruby
Using /Users/vongrippen/.rvm/gems/jruby-1.6.2
$ ruby -v
jruby 1.6.2 (ruby-1.8.7-p330) (2011-05-23 e2ea975) (Java HotSpot(TM) 64-Bit Server VM 1.6.0_26) [darwin-x86_64-java]

As I work I can change ruby versions at will, pretty useful isn't it?

Gems of every shape and size

Rubygems allows me to install multiple versions of a gem so I should be good, right? Alas, no.

My Rails 3 app has a dependency on rubygems 1.7 or higher, but the rails 2.3 app will only run if rubygems is version 1.4.2 or lower! This is more than just a slight problem for me since I’m doing development work in both and can’t be reinstalling rubygems all day long when I switch. Not to mention that they require different versions of rack that interfere with each other.

Here, RVM saves the day again with gemsets. RVM includes another feature called gemsets, which are complete rubygems environments all bottled up and separated.

Let me show you an example:

The gemset for my Rails 2.3.8 app

$ rvm use 1.8.7@rails2.3.8
Using /Users/vongrippen/.rvm/gems/ruby-1.8.7-p334 with gemset rails2.3.8
$ gem -v
1.4.2
$ gem list -l

*** LOCAL GEMS ***

actionmailer (2.3.8)
actionpack (2.3.8)
activerecord (2.3.8)
activeresource (2.3.8)
activesupport (2.3.8)
rack (1.1.2)
rails (2.3.8)
rake (0.8.7)
sqlite3 (1.3.4)
sqlite3-ruby (1.3.3)

Using the rails3.1 gemset I’ve created

$ rvm use 1.9.2@rails3.1
Using /Users/vongrippen/.rvm/gems/ruby-1.9.2-p180 with gemset rails3.1
$ gem -v
1.8.10
$ gem list -l

*** LOCAL GEMS ***

actionmailer (3.1.0)
actionpack (3.1.0)
activemodel (3.1.0)
activerecord (3.1.0)
activeresource (3.1.0)
activesupport (3.1.0)
arel (2.2.1)
bcrypt-ruby (3.0.1)
builder (3.0.0)
bundler (1.0.20)
erubis (2.7.0)
hike (1.2.1)
i18n (0.6.0)
mail (2.3.0)
mime-types (1.16)
multi_json (1.0.3)
polyglot (0.3.2)
rack (1.3.3)
rack-cache (1.0.3)
rack-mount (0.8.3)
rack-ssl (1.3.2)
rack-test (0.6.1)
rails (3.1.0)
railties (3.1.0)
rake (0.8.7)
rdoc (3.9.4)
sprockets (2.0.0)
thor (0.14.6)
tilt (1.3.3)
treetop (1.4.10)
tzinfo (0.3.29)

So now I can even switch the entire set of gems from one project to the next without them interfering! Life just got a little bit easier when doing ruby development.

Sounds useful, let’s install it!

Installing it is pretty easy, especially if you are on a Mac. Even still it’s easy on Linux too, you just have to install some extra libraries that most distributions don’t include by default. If you are on Windows? Sorry, but I’m not much help there. I don’t use Windows at all anymore, so I haven’t the slightest idea how to install rvm there or if it is even possible. Your best bet is RVM’s official documentation.

Got a shiny Mac here, where to start?

First things first, do you have Xcode installed?

If not you will need to install it. On 10.6 (Snow Leopard) or earlier, look for Xcode 3 since it is free. 10.6 can also run Xcode 4.0, but it costs $5 from the App Store. I’m using OS X 10.7 Lion, which means I’ll be using Xcode 4.1 which is free from the Mac App Store.

Also, if you are running Xcode 3 you will need to install Git.

Now that you have Xcode installed it’s time to get our hands dirty in a terminal.

Let’s download and run the RVM installer all in one simple command

bash -s stable < <(curl -s https://raw.github.com/wayneeseguin/rvm/master/binscripts/rvm-installer)

Now, we need to add RVM to the end of your bash .profile using your favorite text editor (if you are using zsh, this file is ~/.zshrc)

~/.profile

  [[ -s "$HOME/.rvm/scripts/rvm" ]] && . "$HOME/.rvm/scripts/rvm" # This loads RVM into a shell session.

Now, either reload your profile by running source ~/.profile or restart your shell to load RVM.

Alright, RVM is installed but we still need to install a few rubies, skip past the part on installing RVM in Linux and lets get some rubies.

Sometimes I like to get down with a little Linux

There is a decent sized list of dependencies that may or may not be installed on your system already, I’ve listed the install commands for some of the most common distributions below. If your distro is not on the list, after running the base RVM install (before installing any ruby versions), run rvm requirements to see the list of dependencies.

The absolute bare minimum just to get RVM installed is a system copy of ruby and git, but that’s still not a necessarily functional RVM.

openSUSE

sudo zypper install -y patterns-openSUSE-devel_basis ruby git gcc-c++ bzip2 readline-devel zlib-devel libxml2-devel libxslt-devel libyaml-devel libopenssl-devel libffi45-devel libtool bison

Debian/Ubuntu

sudo apt-get install ruby-full build-essential openssl libreadline6 libreadline6-dev curl git-core zlib1g zlib1g-dev libssl-dev libyaml-dev libsqlite3-0 libsqlite3-dev sqlite3 libxml2-dev libxslt-dev autoconf libc6-dev ncurses-dev automake libtool bison

Fedora/CentOS

yum install -y ruby git-core gcc-c++ patch readline readline-devel zlib zlib-devel libyaml-devel libffi-devel openssl-devel
yum install -y make bzip2 autoconf automake libtool bison
yum install -y iconv-devel

Arch

pacman -Sy --noconfirm ruby git gcc patch curl zlib readline libxml2 libxslt git autoconf diffutils make libtool bison

Gentoo

emerge ruby libiconv readline zlib openssl curl git libyaml sqlite libxslt libtool bison

Now that you have all of your depedencies and libraries all installed we can go about installing RVM.

bash -s stable < <(curl -s https://raw.github.com/wayneeseguin/rvm/master/binscripts/rvm-installer)

Now, we need to add RVM to the end of your bash .profile using your favorite text editor (if you are using zsh, this file is ~/.zshrc)

~/.profile

  [[ -s "$HOME/.rvm/scripts/rvm" ]] && . "$HOME/.rvm/scripts/rvm" # This loads RVM into a shell session.

Now, either reload your profile by running source ~/.profile or restart your shell to load RVM.

Let’s pick out some rubyies

Now that you have RVM itself installed we still need to install at least 1 ruby interpreter. Since I’m using OS X Lion, I’m going to install 1.8.7, 1.9.2, and macruby. MacRuby is a little bit special, because it is Mac only and requires that the LLVM compiler suite be installed.

A full list of available rubies for installation can be found by running rvm list known

$ rvm install 1.8.7
Installing Ruby from source to: /Users/vongrippen/.rvm/rubies/ruby-1.8.7-p352, this may take a while depending on your cpu(s)...

ruby-1.8.7-p352 - #fetching 
ruby-1.8.7-p352 - #downloading ruby-1.8.7-p352, this may take a while depending on your connection...
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 4108k  100 4108k    0     0   180k      0  0:00:22  0:00:22 --:--:--  235k
100 4108k  100 4108k    0     0   178k      0  0:00:22  0:00:22 --:--:--  178kruby-1.8.7-p352 - #extracting ruby-1.8.7-p352 to /Users/vongrippen/.rvm/src/ruby-1.8.7-p352
ruby-1.8.7-p352 - #extracted to /Users/vongrippen/.rvm/src/ruby-1.8.7-p352
ruby-1.8.7-p352 - #configuring 
ruby-1.8.7-p352 - #compiling 
ruby-1.8.7-p352 - #installing 
Removing old Rubygems files...
Installing rubygems-1.8.10 for ruby-1.8.7-p352 ...
Installation of rubygems completed successfully.
ruby-1.8.7-p352 - adjusting #shebangs for (gem irb erb ri rdoc testrb rake).
ruby-1.8.7-p352 - #importing default gemsets (/Users/vongrippen/.rvm/gemsets/)
Install of ruby-1.8.7-p352 - #complete

$ rvm install 1.9.2
Installing Ruby from source to: /Users/vongrippen/.rvm/rubies/ruby-1.9.2-p290, this may take a while depending on your cpu(s)...

ruby-1.9.2-p290 - #fetching 
ruby-1.9.2-p290 - #downloading ruby-1.9.2-p290, this may take a while depending on your connection...
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 8604k  100 8604k    0     0   695k      0  0:00:12  0:00:12 --:--:--  939k
ruby-1.9.2-p290 - #extracting ruby-1.9.2-p290 to /Users/vongrippen/.rvm/src/ruby-1.9.2-p290
ruby-1.9.2-p290 - #extracted to /Users/vongrippen/.rvm/src/ruby-1.9.2-p290
Fetching yaml-0.1.4.tar.gz to /Users/vongrippen/.rvm/archives
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  460k  100  460k    0     0   409k      0  0:00:01  0:00:01 --:--:--  435k
Extracting yaml-0.1.4.tar.gz to /Users/vongrippen/.rvm/src
Configuring yaml in /Users/vongrippen/.rvm/src/yaml-0.1.4.
Compiling yaml in /Users/vongrippen/.rvm/src/yaml-0.1.4.
Installing yaml to /Users/vongrippen/.rvm/usr
ruby-1.9.2-p290 - #configuring 
ruby-1.9.2-p290 - #compiling 
 ruby-1.9.2-p290 - #installing 
Removing old Rubygems files...
Installing rubygems-1.8.10 for ruby-1.9.2-p290 ...
Installation of rubygems completed successfully.
ruby-1.9.2-p290 - adjusting #shebangs for (gem irb erb ri rdoc testrb rake).
ruby-1.9.2-p290 - #importing default gemsets (/Users/vongrippen/.rvm/gemsets/)
Install of ruby-1.9.2-p290 - #complete

$ rvm install macruby
Retrieving MacRuby 0.10 ...
Archive:  /Users/vongrippen/.rvm/archives/MacRuby%200.10.zip
  inflating: /Users/vongrippen/.rvm/src/macruby-0.10/MacRuby 0.10.pkg  
Password: <Your administrative password>

Pretty easy wasn’t it? Now you have several versions of ruby installed and available to you.

But wait, there’s more!

You’ve only gotten started on the capabilities here, there’s still gemsets, rvmrc, and more that I’m not going to cover in depth here. For more information on those huge timesavers, checkout RVM’s website.

Mike Cochran