Interactive Ruby (irb)

Interactive Ruby or irb is an interactive programming environment that comes with Ruby. It was written by Keiju Ishitsuka.

Usage Syntax

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.

$ irb[.rb] [options] [programfile] [arguments]

Here is a complete list of options −

Sr.No. Command & Description
1

-f

Suppress reading of the file ~/.irbrc.
2

-m

bc mode (load mathn library so fractions or matrix are available).
3

-d

Sets $DEBUG to true (same as ruby -d).
4

-r load-module

Same as ruby -r.
5

-I path

Specify $LOAD_PATH directory.
6

--inspect

Use inspect for output (default except for bc mode).
7

--noinspect

Don't use inspect for output.
8

--readline

Use Readline extension module.
9

--noreadline

Don't use Readline extension module.
10

--prompt prompt-mode (--prompt-mode prompt-mode)

Switch prompt mode. Predefined prompt modes are default, simple, xmp, and inf-ruby.
11

--inf-ruby-mode

Use prompt appropriate for inf-ruby-mode on Emacs. Suppresses --readline.
12

--simple-prompt

Simple prompt mode.
13

--noprompt

No prompt mode.
14

--tracer

Display trace for each execution of commands.
15

--back-trace-limit n

Display backtrace top n and tail n. The default value is 16.
16

--irb_debug n

Set internal debug level to n (not for popular use).
17

-v (--version).

Print the version of irb.

Example

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):006:0> x = 1
=> 1
irb(main):007:0> x + 59
=> 60
irb(main):005:0> 50 / 5
=> 10
irb(main):008:0> hi = "Hello, Mac!"
=> "Hello, Mac!"

You can also invoke a single program with irb. After running the program, irb exits. Let's call our hello.rb program −

$ 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> def initialize( hello )
hello.rb(main):005:2> @hello = hello
hello.rb(main):006:2> end
hello.rb(main):007:1> def hello
hello.rb(main):008:2> @hello
hello.rb(main):009:2> end
hello.rb(main):010:1> end
=> nil
hello.rb(main):011:0>
hello.rb(main):012:0* salute = Hello.new( "Hello, Mac!" )
=> #<Hello:0x319f20 @hello = "Hello, Mac!">
hello.rb(main):013:0> puts salute.hello
Hello, Mac!
=> nil
hello.rb(main):014:0> $
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