Hidden Gems

How to Fix Ruby 1.9.3 "It seems your ruby installation is missing psych" Error

2011-11-04T22:59:00.000-07:00

If you see this:

/usr/local/lib/ruby/1.9.1/yaml.rb:56:in `<top (required)>':
It seems your ruby installation is missing psych (for YAML output).
To eliminate this warning, please install libyaml and reinstall your ruby.
Latest version currently installed. Aborting.

First do this:

sudo apt-get install libyaml-dev

Then rebuild/reinstall your Ruby.

Getting Current EC2 Instance Id in Ruby

2011-02-18T15:28:00.000-08:00

How to Strip All Non-Alphanumeric Characters from a String in Ruby

2011-01-17T18:22:00.000-08:00

x.gsub(/[^[:alnum:]]/, '')

Installing Ruby 1.9 from Source on Ubuntu in Five Minutes

2010-08-18T18:01:00.000-07:00

This is on a clean Ubuntu Lucid Lynx image.

sudo apt-get install gcc libzlib-ruby libssl-dev libxslt-dev libxml2-dev libmemcached-dev libsasl2-dev libmemcached-dbg libpq-dev libcurl4-gnutls-dev libyaml-dev make
wget LINK_TO_RUBY_TAR

Find tar link here: http://www.ruby-lang.org/en/downloads/

tar -zxvf rubyXXXX.tar.gz
cd rubyXXXX
./configure
make
sudo make install

That's it, try running "ruby -v" to see the ruby version.

I recommend doing the following to enable SSL support (only takes a few seconds):

cd ext/openssl
ruby extconf.rb
make
sudo make install

And lastly, update the gem system:

sudo gem update --system

Git For Noobs - The first few commands you must know to start working on a git project

2010-07-21T18:55:00.000-07:00

This is the minimum set of things you need to know to contribute to a git repository.

git clone

This is the first thing you need to do to get the code. Find the git repository URL and then clone it, for example:


git clone http://github.com/appoxy/simple_record

Now you have the code and can start working on it. When you're done with your modifications and tested them, you then need to commit.

git commit

This will commit to your local repository, the keyword being local. And by local, I mean your hard drive, NOT the remote repository that you cloned above. This is different than subversion where a commit will commit to the remote repository.


git commit -am "I just modified some stuff... I'm not a noob anymore!"

Now that's committed to your local repo. Let's get that commit onto the remote repo.

git push

This will take your local commits that you made with git commit and push them up to the remote git repository that you cloned above.


git push

Now your changes are on the remote repository for all to see.

Delete a Local Git Branch

2010-06-08T18:30:00.000-07:00

Use git push to the remote branch with a colon in front of the name, eg:


git branch -D bigbadbranch

Delete a Remote Git Branch

2010-06-08T09:44:00.000-07:00

Use git push to the remote branch with a colon in front of the name, eg:


git push origin :nolongerneededbranch

Write a String to a File in Ruby

2010-05-11T09:44:00.000-07:00


File.open(path_to_file, 'w') {|f| f.write(content) }

Read a File into a String in Ruby

2010-05-10T10:43:00.000-07:00

My favorite way (simplest):


s = IO.read(filename)

There are other ways too:


s = File.open(filename) { |f| f.read }

MD5 Hash of a File in Ruby

2010-05-08T10:41:00.000-07:00

md5 = Digest::MD5.hexdigest(File.read('path_to_file'))

.nil? .blank? .present? .empty? and self

2010-05-06T12:49:00.000-07:00

Here is a script to check all the usages:


require 'active_support'

my_stuff = [
nil,
true,
false,
"",
"hi",
0,
1,
{},
{:something=>"or other"},
[],
["hello"]
]

my_stuff.each do |x|
puts "x=" + x.to_s
puts "nil? " + x.nil?.to_s
puts "blank? " + x.blank?.to_s
puts "present? " + x.present?.to_s
puts "empty? " + (x.respond_to?(:empty?) ? x.empty?.to_s : "not defined")
puts "self " + (x ? "true" : "false")
puts ""
end

And here is the output:


x=
nil? true
blank? true
present? false
empty? not defined
self false

x=true
nil? false
blank? false
present? true
empty? not defined
self true

x=false
nil? false
blank? true
present? false
empty? not defined
self false

x=
nil? false
blank? true
present? false
empty? true
self true

x=hi
nil? false
blank? false
present? true
empty? false
self true

x=0
nil? false
blank? false
present? true
empty? not defined
self true

x=1
nil? false
blank? false
present? true
empty? not defined
self true

x={}
nil? false
blank? true
present? false
empty? true
self true

x={:something=>"or other"}
nil? false
blank? false
present? true
empty? false
self true

x=[]
nil? false
blank? true
present? false
empty? true
self true

x=["hello"]
nil? false
blank? false
present? true
empty? false
self true

Blog for our Developers

2010-05-06T12:17:00.000-07:00

This blog will feature posts from our developers about the things they are working on and tips and tricks about Ruby on Rails and Cloud insfrastructure, Amazon in particular.