Answer:

In Ruby, a class constant has a name starting with an uppercase character, e.g.

Foo = 'bar'
puts Foo

Where you try to re-define the constant, a warning message will be shown, e.g.

Foo = 'bar'
Foo = '123'

(irb):18: warning: already initialized constant Foo

Answer:

In Ruby, global variable has a name beginning with $, e.g.

$foo = 'bar'
puts $foo

In contrast, local variable has a name start with a lower case letter or an underscore character, e.g.

foo = 'bar'
puts foo

Answer:

To print a string of "Hello World" to the standard output in different scripting languages

1. Perl

print "Hello, World!";

2. Python

print('Hello, World!')

3. PHP

echo "Hello, World!";

4. Ruby

puts "Hello, World!"

Answer:

To list all the available gems on rubyforge.org, use this command:

# gem list --remote

For example, to search for all rails related gems, use

# gem list --remote | grep "\-rails"

Answer:

To list all the installed gems on your machine, simply execute the following command:

# gem list --local

*** LOCAL GEMS ***

abstract (1.0.0)
actionmailer (3.0.9)
actionpack (3.0.9)
activemodel (3.0.9)
activerecord (3.0.9)
activeresource (3.0.9)
activesupport (3.0.9)
arel (2.0.10)
builder (2.1.2)
erubis (2.6.6)
i18n (0.5.0)
mail (2.2.19)
mime-types (1.16)
polyglot (0.3.1)
rack (1.2.3)
rack-mount (0.6.14)
rack-test (0.5.7)
rake (0.9.2)
treetop (1.4.9)
tzinfo (0.3.28)

Answer:

To update the the RubyGems installed in Ubuntu, enter the command below:

# sudo gem update --systemNow

That's it.

Answer:

In the last article, we talked how to install Ruby in Ubuntu. Now, we are going to install a very popular web framework for Ruby - RubyOnRails.

Firstly, you need to install RubyGems, a gem is a packaged Ruby application or library.

# sudo apt-get install rubygems

Then, we use the gem command to install rails.

# sudo gem install rails

That's all.

Answer:

To install Ruby under Ubuntu, you need to type the commands below:

# sudo apt-get install ruby-full build-essential

The above command will install more than the Ruby interpreter, but they are useful when you want to play with RubyOnRails later.

Answer:

To declare a multi-line string in Ruby, it is as easy as the following.

sql = "
        SELECT *
            FROM `user` AS u
            JOIN `company` AS c
                ON u.cid = c.id
             WHERE u.id = 8
"

puts sql