Ruby Pocket Reference

Interactive Ruby (irb)

Interactive Ruby or irb is an interactive programming environment that comes with Ruby. It was written by Keiju Ishitsuka. To invoke it, type irb at a shell or command prompt, and begin entering Ruby statements and expressions. Use exit or quit to exit irb. Here is a sample of irb evaluating a variety of expressions:

$ irb
irb(main):001:0> 23 + 27
=> 50
irb(main):002:0> 50 - 23
=> 27
irb(main):003:0> 10 * 5
=> 50
irb(main):004:0> 10**5
=> 100000
irb(main):005:0> 50 / 5
=> 10
irb(main):006:0> x = 1
=> 1
irb(main):007:0> x + 59
=> 60
irb(main):008:0> hi = "Hello, Matz!"
=> "Hello, Matz!"
irb(main):009:0> hi.each { |s| print s }
Hello, Matz!=> "Hello, Matz!"
irb(main):010:0> 1.upto( 10 ) { |n| print n, " " }
1 2 3 4 5 6 7 8 9 10 => 1
irb(main):011:0> 100 < 1_000
=> true
irb(main):012:0> class Hello
irb(main):013:1>   attr :hi, true
irb(main):014:1> end
=> nil
irb(main):015:0> h = Hello.new
=> #<Hello:0x3602cc>
irb(main):016:0> h.hi="Hello, Matz!"
=> "Hello, Matz!"
irb(main):017:0> h.hi
=> "Hello, Matz!"
irb(main):018:0> self
=> main
irb(main):019:0> self.class
=> Object
irb(main):020:0> exit

You can also invoke a single program with irb. After running the program, irb exits:

$ cat hello.rb
#!/usr/bin/env ruby

class Hello
  def initialize( hello )
    @hello = hello
  end
  def hello
    @hello
  end
end

salute = Hello.new( "Hello, Matz!" )
puts salute.hello
$ irb hello.rb hello.rb(main):001:0> #!/usr/bin/env ruby hello.rb(main):002:0* hello.rb(main):003:0* class Hello hello.rb(main):004:1> ...