Added 'executing ruby' and minor fixes

Ruby/001_article.adoc

@@ -8,8 +8,6 @@ Fabian Pfaff (c) 2016 vogella GmbH
 Version 0.1, 01.11.2016		
 :docinfodir: ../
 :vgwort: Ruby
-
-Some notes about Ruby
 
 include::010_overview.adoc[]
 include::020_installation.adoc[]

Ruby/010_overview.adoc

@@ -1,4 +1,52 @@
 == Ruby
 
-A dynamic, reflective, object-oriented, general-purpose programming language.
+Ruby is a dynamic, reflective, object-oriented, general-purpose programming language.
 
+=== "Hello, World!" Ruby program
+
+[source, ruby]
+----
+include::res/hello_world/hello.rb[]
+----
+
+=== Executing Ruby source files
+
+Ruby source files are by convention marked with the `.rb` extension.
+To execute the hello world program you have to save it into a file, e.g. `hello.rb`.
+You can then run it from the command line.
+
+[source, terminal]
+----
+include::res/terminal/hello[]
+----
+
+If you want to omit the `ruby` before your file name you have to add a shebang line as the first line in your file.
+
+[source, ruby]
+----
+include::res/shebang/shebang_line[]
+----
+
+If you are using a Unix-like operating system you also have to make the file executable with `chmod`.
+
+[source, terminal]
+----
+include::res/terminal/chmod[]
+----
+
+=== The Ruby console
+The Ruby console offers a quick way to execute Ruby code. It allows you to type in Ruby commands and evaluates them.
+You can call it from your terminal by issuing the command `irb`. Type in our hello world program:
+
+[source, ruby]
+----
+include::res/hello_world/hello.rb[]
+----
+Press enter-> and the code will be executed.
+
+You can even prototype methods and classes inside the console.
+
+[source, ruby]
+----
+include::res/irb/method_prototyping[]
+----

Ruby/030_debugging.adoc

@@ -33,7 +33,7 @@ pp ary
 => [1, 2, [3, 4]]
 ----
 
-Some useful methods to use in conjunction with puts are
+Some useful methods to use in conjunction with 'puts' are
 
 * instance_variables: all instance variables of the object
 * methods: all available methods of the class instance
@@ -82,7 +82,7 @@ a
 [TIP]
 ====
 If your program makes use of a framework like Rails or Sinatra your stacktrace might be quite convoluted.
-It can help to filter the stack trace for your project name.
+It might be useful to filter the stack trace by your project name.
 [source, ruby]
 ----
 puts caller.select { |line| line.include? 'project_name' }
@@ -98,9 +98,10 @@ puts caller.select { |line| line['project_name'] }
 === Debugging with pry-byebug
 Interactive step-by-step debugging can be done with pry-byebug, which adds debugging and stack navigation to the ruby console pry.
 To use it you have to add it as a dependency to your project.
-If your project uses bundler you add it to your Gemfile.
+If your project uses bundler must you add it to your Gemfile.
 // TODO(fap): should move to general gem installation guide?
 
+[source, ruby]
 ----
 group :development do
   # your other dev dependencies
@@ -139,33 +140,33 @@ Once you have entered pry you can execute statements like you would normally do
 
 [source, ruby]
 ----
-	2:  def factorial(n, acc = 1)
-	3:  	binding.pry
-=>	4:  	return acc if n <= 1
-	5:  	fact(n - 1, n * acc)
-	6:  end
+    2:  def factorial(n, acc = 1)
+    3:    binding.pry
+=>  4:    return acc if n <= 1
+    5:    fact(n - 1, n * acc)
+    6:  end
 	
 pry(#<Math>)> n
 => 4
 pry(#<Math>)> acc
 => 1
 pry(#<Math>)> next
 
-	2:  def factorial(n, acc = 1)
-	3:  	binding.pry
-	4:  	return acc if n <= 1
-=>	5:  	fact(n - 1, n * acc)
-	6:  end
+    2:  def factorial(n, acc = 1)
+    3:    binding.pry
+    4:    return acc if n <= 1
+=>  5:    fact(n - 1, n * acc)
+    6:  end
 	
 pry(#<Math>)> n
 => 4
 pry(#<Math>)> continue
 
-	2:  def factorial(n, acc = 1)
-	3:  	binding.pry
-=>	4:  	return acc if n <= 1
-	5:  	fact(n - 1, n * acc)
-	6:  end
+    2:  def factorial(n, acc = 1)
+    3:    binding.pry
+=>  4:    return acc if n <= 1
+    5:    fact(n - 1, n * acc)
+    6:  end
 	
 pry(#<Math>)> n
 => 3

Ruby/res/hello_world/hello.rb

@@ -0,0 +1 @@
+puts 'Hello, World!'

Ruby/res/irb/method_prototyping

@@ -0,0 +1,6 @@
+irb(main):001:0> def reverse(ary)
+irb(main):002:1> ary.reduce([]) { |a, e| a.unshift(e) }
+irb(main):003:1> end
+=> :reverse
+irb(main):004:0> reverse([1, 2, 3, 4])
+=> [4, 3, 2, 1]

Ruby/res/shebang/shebang_line

@@ -0,0 +1 @@
+#!/usr/bin/ruby

Ruby/res/terminal/chmod

@@ -0,0 +1 @@
+chmod +x hello.rb

Ruby/res/terminal/hello

@@ -0,0 +1,2 @@
+ruby hello.rb
+Hello, World!