You'll Be Seeing Ruby

An Introduction to the Ruby Programming Language

Mission Data

Chuck Fouts and Darren Day

You'll Be Seeing Ruby...

• in scripting situations, where you'd see bash and perl
• powering web applications on the server side
• soon

What is Ruby?

• An object-oriented scripting language
• Perl-like in the toolset and problems it was intended to address
• Smalltalk-like in its fundamental OO design principles

I, as a language maniac and OO fan for 15 years, really really wanted a genuine object-oriented, easy-to-use scripting language.

- Matz, [ruby-talk:00382] Re: history of ruby

Very Brief Ruby Timeline

• 1993: Yukihiro "Matz" Matsumoto begins development on Ruby
• 1995: Ruby officially released in Japan
• 1998: Matz's first official Ruby announcement in English on comp.lang.misc
• 2000: Programming Ruby: A Pragmatic Programmer's Guide, by Dave Thomas and Andy Hunt, is published
• 2004: 2nd Edition of Programming Ruby, now referred to as "the Pickaxe book"

Ruby Fundamentals

The Principle of (Matz's) Least Surprise

Understand these fundamentals, and not much in Ruby will surprise you.

• Interpreted execution
• Everything (that can be assigned to a variable) is an object
• Variables are dynamically typed
• Objects respond to method calls, returning object responses
• Blocks of code can be passed as a parameter in method calls

Try Ruby without Ruby

tryruby.hobix.com

• interactive Ruby environment with built in tutorial mode
• think of it as IM session with Ruby
• created by why the lucky stiff, enigmatic Rubyist

Ruby Releases

• The current release is 1.8.x (1.8.4 as I write this)
• Current development release is 1.9.x
• See the pattern? Even numbers (1.8.x) are production releases
• Odd numbers are development releases

Installing Ruby

• *nix Systems: vary by distribution...check the package manager
• Apple includes Ruby with Mac OS X
• Windows: One-click Ruby Installer @ rubyinstaller.rubyforge.org
• Use the Source! ruby-lang.org

What Do You Get?

• ruby: executable command interpreter
• irb: interactive Ruby shell
• ri: ruby information; think manpages for classes
• rdoc: ruby documentation compiler; think javadoc for ruby
• erb: templating engine for ruby; think jsp
• the standard class library: ranging from Object, Hash, and Array to Zlib

Default Library

• By default, Ruby includes many classes

$ ruby -e 'puts Module.constants.join(" ")'

ARGF ARGV ArgumentError Array Bignum Binding Class Comparable Continuation Data Dir ENV EOFError Enumerable Errno Exception FALSE FalseClass File FileTest Fixnum Float FloatDomainError GC Hash IO IOError IndexError Integer Interrupt Kernel LoadError LocalJumpError Marshal MatchData MatchingData Math Method Module NIL NameError NilClass NoMemoryError NoMethodError NotImplementedError Numeric Object ObjectSpace PLATFORM Precision Proc Process RELEASE_DATE RUBY_PLATFORM RUBY_RELEASE_DATE RUBY_VERSION Range RangeError Regexp RegexpError RuntimeError STDERR STDIN STDOUT ScriptError SecurityError Signal SignalException StandardError String Struct Symbol SyntaxError SystemCallError SystemExit SystemStackError TOPLEVEL_BINDING TRUE Thread ThreadError ThreadGroup Time TrueClass TypeError UnboundMethod VERSION ZeroDivisionError

Standard Library

• Many useful classes ship with Ruby, but must be included specifically in your program with the require command.

abbrev base64 benchmark bigdecimal cgi complex csv curses date dbm delegate digest dl drb English enumerator erb etc fcntl fileutils finalize find forwardable ftools gdbm generator getoptlong gserver iconv importenv io/wait ipaddr jcode logger mailread mathn matrix mkmf monitor mutex_m net/ftp net/http net/imap net/pop net/smtp net/telnet nkf observer open-uri open3 openssl optparse ostruct parsedate pathname ping pp prettyprint profile profiler pstore pty racc racc/parser rational rdoc readbytes readline resolv resolv-replace rexml rinda rss runit scanf sdbm set singleton soap socket stringio strscan syck sync syslog tcltklib tempfile test/unit thread thwait time timeout tk tmpdir tracer tsort un uri weakref webrick Win32API win32ole wsdl xmlrpc xsd yaml zlib

Need More Classes?

• Ruby Application Archive: central listing for Ruby projects
  raa.ruby-lang.org
• RubyForge: hosting for open-source Ruby projects
  rubyforge.org
• RubyGems: the CPAN of the Ruby world; package management for Ruby classes
  docs.rubygems.org

irb

• irb is the interactive Ruby shell
• like a conversation with the Ruby runtime
• type a line of code and see the results immediately
• you'll see lots of nil returns from calls with no return value, like puts

irb(main):001:0> puts "Hello Ruby" Hello Ruby => nil irb(main):002:0> 3 + 5 => 8

ruby command

• ruby interpets a file's (or stream's) worth of Ruby code
• supports shebang (#! /usr/bin/ruby) syntax in *nix shell commands
• ruby -e [command] on the commandline

ruby hello.rb howdy there
ruby -e "a = 3" -e "b = 5" -e "puts a + b" 8