Ruby tutorial

i
AbouttheTutorial
Ruby is a scripting language designed by Yukihiro Matsumoto, also known as Matz. It
runs on a variety of platforms, such as Windows, Mac OS, and the various versions of
UNIX.
This tutorial gives a complete understanding on Ruby.
Audience
This tutorial has been prepared for beginners to help them understand the basic to
advanced concepts related to Ruby Scripting languages.
Prerequisites
Before you start practicing with various types of examples given in this tutorial, we are
making an assumption that you are already aware of computer programs and
programming languages in general.
Copyright&Disclaimer
 Copyright 2015 by Tutorials Point (I) Pvt. Ltd.
All the content and graphics published in this e-book are the property of Tutorials Point
(I) Pvt. Ltd. The user of this e-book is prohibited to reuse, retain, copy, distribute or
republish any contents or a part of contents of this e-book in any manner without written
consent of the publisher.
We strive to update the contents of our website and tutorials as timely and as precisely
as possible, however, the contents may contain inaccuracies or errors. Tutorials Point (I)
Pvt. Ltd. provides no guarantee regarding the accuracy, timeliness or completeness of
our website or its contents including this tutorial. If you discover any errors on our
website or in this tutorial, please notify us at contact@tutorialspoint.com

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TableofContents
About the Tutorial ......................................................................................................................................
Audience....................................................................................................................................................i
Prerequisites..............................................................................................................................................i
Copyright & Disclaimer ..............................................................................................................................i
Table of Contents......................................................................................................................................ii
1. RUBY – OVERVIEW..................................................................................................................1
Features of Ruby.......................................................................................................................................1
Tools You Will Need..................................................................................................................................2
What is Next? ...........................................................................................................................................2
2. RUBY – ENVIRONMENT SETUP................................................................................................3
Try it Option Online ..................................................................................................................................3
Local Environment Setup ..........................................................................................................................3
Ruby Installation on Linux/Unix................................................................................................................3
Using yum to Install Ruby .........................................................................................................................4
Ruby Installation on Windows ..................................................................................................................4
Ruby Command Line Options....................................................................................................................5
Ruby Environment Variables.....................................................................................................................7
Popular Ruby Editors ................................................................................................................................9
Interactive Ruby (IRb) ...............................................................................................................................9
What is Next? .........................................................................................................................................10
3. RUBY – SYNTAX .....................................................................................................................11
Whitespace in Ruby Program..................................................................................................................11
Line Endings in Ruby Program.................................................................................................................11
Ruby Identifiers ......................................................................................................................................11

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Reserved Words......................................................................................................................................12
Here Document in Ruby..........................................................................................................................12
Ruby BEGIN Statement...........................................................................................................................13
Ruby END Statement ..............................................................................................................................14
Ruby Comments......................................................................................................................................15
4. RUBY – CLASSES AND OBJECTS..............................................................................................16
Defining a Class in Ruby ..........................................................................................................................17
Variables in a Ruby Class.........................................................................................................................17
Creating Objects in Ruby Using new Method..........................................................................................18
Custom Method to Create Ruby Objects.................................................................................................18
Member Functions in Ruby Class ............................................................................................................19
Simple Case Study...................................................................................................................................20
5. RUBY – VARIABLES, CONSTANTS AND LITERALS ....................................................................24
Ruby Global Variables.............................................................................................................................24
Ruby Instance Variables..........................................................................................................................25
Ruby Class Variables ...............................................................................................................................26
Ruby Local Variables ...............................................................................................................................27
Ruby Constants.......................................................................................................................................27
Ruby Pseudo-Variables ...........................................................................................................................28
Ruby Basic Literals ..................................................................................................................................28
Integer Numbers.....................................................................................................................................28
Floating Numbers....................................................................................................................................29
String Literals..........................................................................................................................................29
Backslash Notations................................................................................................................................30
Ruby Arrays ............................................................................................................................................31
Ruby Hashes ...........................................................................................................................................31

iv
Ruby Ranges ...........................................................................................................................................32
6. RUBY – OPERATORS ..............................................................................................................33
Ruby Arithmetic Operators.....................................................................................................................33
Ruby Comparison Operators...................................................................................................................33
Ruby Assignment Operators ...................................................................................................................35
Ruby Parallel Assignment........................................................................................................................35
Ruby Bitwise Operators ..........................................................................................................................36
Ruby Logical Operators ...........................................................................................................................37
Ruby Ternary Operator ...........................................................................................................................38
Ruby Range Operators............................................................................................................................38
Ruby defined? Operators........................................................................................................................38
Ruby Dot "." and Double Colon "::" Operators........................................................................................40
Ruby Operators Precedence....................................................................................................................41
7. RUBY – COMMENTS..............................................................................................................43
Ruby Multiline Comments ......................................................................................................................43
8. RUBY – IF…ELSE, CASE, UNLESS.............................................................................................45
Ruby if...else Statement .........................................................................................................................45
Ruby if modifier......................................................................................................................................46
Ruby unless Statement...........................................................................................................................46
Ruby unless modifier..............................................................................................................................47
Ruby case Statement..............................................................................................................................47
9. RUBY – LOOPS.......................................................................................................................50
Ruby while Statement ............................................................................................................................50
Ruby while modifier ...............................................................................................................................51
Ruby until Statement..............................................................................................................................51

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Ruby until modifier.................................................................................................................................52
Ruby for Statement ................................................................................................................................53
Ruby break Statement............................................................................................................................54
Ruby next Statement..............................................................................................................................55
Ruby redo Statement .............................................................................................................................56
Ruby retry Statement .............................................................................................................................56
10. RUBY – METHODS...............................................................................................................58
Return Values from Methods..................................................................................................................59
Ruby return Statement...........................................................................................................................59
Variable Number of Parameters .............................................................................................................60
Class Methods.........................................................................................................................................61
Ruby alias Statement..............................................................................................................................62
Ruby undef Statement............................................................................................................................62
11. RUBY – BLOCKS ...................................................................................................................64
The yield Statement ...............................................................................................................................64
Blocks and Methods................................................................................................................................66
BEGIN and END Blocks ............................................................................................................................66
12. RUBY – MODULES AND MIXINS...........................................................................................68
Ruby require Statement .........................................................................................................................69
Ruby include Statement .........................................................................................................................70
Mixins in Ruby ........................................................................................................................................71
13. RUBY – STRINGS..................................................................................................................73
Expression Substitution ..........................................................................................................................73
General Delimited Strings .......................................................................................................................73
Escape Characters...................................................................................................................................74

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Character Encoding.................................................................................................................................75
String Built-in Methods...........................................................................................................................75
String unpack Directives..........................................................................................................................85
14. RUBY – ARRAYS ...................................................................................................................89
Creating Arrays .......................................................................................................................................89
Array Built-in Methods ...........................................................................................................................91
Array pack Directives ..............................................................................................................................99
15. RUBY – HASHES.................................................................................................................103
Creating Hashes ....................................................................................................................................103
Hash Built-in Methods ..........................................................................................................................104
16. RUBY – DATE AND TIME....................................................................................................109
Getting Current Date and Time .............................................................................................................109
Getting Components of a Date & Time..................................................................................................109
Time.utc, Time.gm and Time.local Functions .......................................................................................110
Timezones and Daylight Savings Time...................................................................................................112
Formatting Times and Dates .................................................................................................................112
Time Formatting Directives...................................................................................................................113
Time Arithmetic ....................................................................................................................................114
17. RUBY – RANGES ................................................................................................................116
Ranges as Sequences ............................................................................................................................116
Ranges as Conditions ............................................................................................................................118
Ranges as Intervals ...............................................................................................................................118
18. RUBY – ITERATORS............................................................................................................120
Ruby each Iterator................................................................................................................................120
Ruby collect Iterator.............................................................................................................................121

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19. RUBY – FILE I/O .................................................................................................................123
The puts Statement ..............................................................................................................................123
The gets Statement ..............................................................................................................................123
The putc Statement..............................................................................................................................124
The print Statement .............................................................................................................................124
Opening and Closing Files .....................................................................................................................125
The File.new Method............................................................................................................................125
The File.open Method ..........................................................................................................................125
Reading and Writing Files .....................................................................................................................126
The sysread Method.............................................................................................................................126
The syswrite Method............................................................................................................................127
The each_byte Method.........................................................................................................................127
The IO.readlines Method......................................................................................................................128
The IO.foreach Method ........................................................................................................................128
Renaming and Deleting Files.................................................................................................................128
File Modes and Ownership ...................................................................................................................129
File Inquiries .........................................................................................................................................130
Directories in Ruby................................................................................................................................132
Navigating Through Directories.............................................................................................................132
Creating a Directory..............................................................................................................................132
Deleting a Directory..............................................................................................................................133
Creating Files & Temporary Directories.................................................................................................133
Built-in Functions..................................................................................................................................133
File Class and Methods .........................................................................................................................134
Directory Class and Methods ................................................................................................................139
20. RUBY – EXCEPTIONS..........................................................................................................142

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Using retry Statement ..........................................................................................................................143
Using raise Statement ..........................................................................................................................144
Using ensure Statement .......................................................................................................................146
Using else Statement............................................................................................................................147
Catch and Throw...................................................................................................................................148
Class Exception .....................................................................................................................................149
21. RUBY OBJECT ORIENTED ...................................................................................................151
Ruby Class Definition ............................................................................................................................151
Define Ruby Objects .............................................................................................................................151
The initialize Method............................................................................................................................151
The instance Variables ..........................................................................................................................152
The accessor & setter Methods.............................................................................................................152
The instance Methods...........................................................................................................................155
The class Methods and Variables ..........................................................................................................155
The to_s Method...................................................................................................................................156
Access Control ......................................................................................................................................157
Class Inheritance...................................................................................................................................159
Methods Overriding..............................................................................................................................160
Operator Overloading...........................................................................................................................161
Freezing Objects....................................................................................................................................162
Class Constants .....................................................................................................................................164
Create Object Using Allocate.................................................................................................................165
Class Information..................................................................................................................................166
22. RUBY – REGULAR EXPRESSIONS ........................................................................................167
Regular-Expression Modifiers ...............................................................................................................167
Regular-Expression Patterns .................................................................................................................168

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Regular-Expression Examples................................................................................................................171
Anchors.................................................................................................................................................173
Special Syntax with Parentheses...........................................................................................................174
Search and Replace...............................................................................................................................174
23. RUBY – DBI........................................................................................................................177
Architecture of a DBI Application..........................................................................................................177
Prerequisites.........................................................................................................................................178
Obtaining and Installing Ruby/DBI........................................................................................................178
Database Connection............................................................................................................................179
INSERT Operation .................................................................................................................................180
Using do Statement ..............................................................................................................................180
Using prepare and execute...................................................................................................................181
READ Operation....................................................................................................................................183
Fetching the Result ...............................................................................................................................184
Update Operation.................................................................................................................................190
DELETE Operation .................................................................................................................................191
Performing Transactions.......................................................................................................................192
COMMIT Operation ..............................................................................................................................193
ROLLBACK Operation ............................................................................................................................193
Disconnecting Database........................................................................................................................193
Handling Errors .....................................................................................................................................194
Code Blocks with Methods....................................................................................................................195
Driver-specific Functions and Attributes ...............................................................................................196
24. RUBY – WEB APPLICATIONS ..............................................................................................199
Writing CGI Scripts................................................................................................................................199
Using cgi.rb ...........................................................................................................................................199

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Form Processing....................................................................................................................................200
Creating Forms and HTML.....................................................................................................................201
Quoting Strings .....................................................................................................................................203
Useful Methods in CGI Class..................................................................................................................203
Ruby CGI ...............................................................................................................................................204
Cookies and Sessions ............................................................................................................................210
Ruby CGI Cookies ..................................................................................................................................210
Ruby CGI Sessions .................................................................................................................................212
Web Hosting Servers.............................................................................................................................214
25. RUBY – SENDING EMAIL....................................................................................................215
Sending an HTML e-mail using Ruby .....................................................................................................216
Sending Attachments as an e-mail ........................................................................................................217
26. RUBY – SOCKET PROGRAMMING ......................................................................................220
What are Sockets? ................................................................................................................................220
A Simple Client......................................................................................................................................221
A Simple Server.....................................................................................................................................221
Multi-Client TCP Servers .......................................................................................................................222
A Tiny Web Browser .............................................................................................................................223
Further Readings...................................................................................................................................224
27. RUBY – XML, XSLT, XPATH.................................................................................................225
What is XML?........................................................................................................................................225
XML Parser Architectures and APIs .......................................................................................................225
Parsing and Creating XML using Ruby ...................................................................................................225
DOM-like Parsing ..................................................................................................................................227
SAX-like Parsing ....................................................................................................................................228
XPath and Ruby ....................................................................................................................................230

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XSLT and Ruby ......................................................................................................................................231
Further Reading ....................................................................................................................................232
28. RUBY – WEB SERVICES ......................................................................................................233
What is SOAP? ......................................................................................................................................233
Installing SOAP4R..................................................................................................................................233
Writing SOAP4R Servers........................................................................................................................233
Writing SOAP4R Clients.........................................................................................................................237
29. RUBY – TK GUIDE ..............................................................................................................240
Introduction..........................................................................................................................................240
Installation............................................................................................................................................240
Simple Tk Application ...........................................................................................................................240
Ruby/Tk Widget Classes........................................................................................................................241
TkFrame................................................................................................................................................242
TkButton...............................................................................................................................................245
TkLabel .................................................................................................................................................248
TkEntry .................................................................................................................................................251
TkCheckButton......................................................................................................................................256
TkRadioButton......................................................................................................................................261
TkListbox...............................................................................................................................................265
TkComboBox.........................................................................................................................................272
TkMenu ................................................................................................................................................274
TkMenubutton......................................................................................................................................280
Tk.messageBox .....................................................................................................................................284
TkScrollbar............................................................................................................................................286
TkCanvas...............................................................................................................................................291
TkScale..................................................................................................................................................300

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TkText...................................................................................................................................................305
TkToplevel ............................................................................................................................................310
TkSpinbox .............................................................................................................................................312
TkProgressBar.......................................................................................................................................318
Dialog Box.............................................................................................................................................321
Tk::Tile::Notebook ................................................................................................................................323
Tk::Tile::Paned ......................................................................................................................................326
Tk::Tile::Separator ................................................................................................................................328
Ruby/Tk Font, Colors, and Images.........................................................................................................330
Standard Configuration Options ...........................................................................................................334
Ruby/Tk Geometry Management .........................................................................................................339
grid .......................................................................................................................................................339
Pack ......................................................................................................................................................340
Place .....................................................................................................................................................342
Ruby/Tk Event Handling .......................................................................................................................343
The configure Method..........................................................................................................................345
The cget Method ..................................................................................................................................346
30. RUBY – LDAP .....................................................................................................................347
Ruby/LDAP Installation.........................................................................................................................347
Establish LDAP Connection....................................................................................................................347
Adding an LDAP Entry ...........................................................................................................................348
Modifying an LDAP Entry ......................................................................................................................350
Deleting an LDAP Entry .........................................................................................................................351
Modifying the Distinguished Name.......................................................................................................352
Performing a Search..............................................................................................................................353
Handling Errors .....................................................................................................................................355

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Further Reading ....................................................................................................................................355
31. RUBY – MULTITHREADING ................................................................................................356
Creating Ruby Threads..........................................................................................................................356
Thread Lifecycle ....................................................................................................................................357
Threads and Exceptions ........................................................................................................................358
Thread Variables...................................................................................................................................358
Thread Priorities ...................................................................................................................................359
Thread Exclusion...................................................................................................................................359
Handling Deadlock................................................................................................................................361
Thread States........................................................................................................................................362
Thread Class Methods...........................................................................................................................363
Thread Instance Methods .....................................................................................................................365
32. RUBY – BUILT-IN FUNCTIONS............................................................................................368
Functions for Numbers..........................................................................................................................374
Functions for Float................................................................................................................................377
Functions for Math ...............................................................................................................................378
Conversion Field Specifier.....................................................................................................................379
Test Function Arguments ......................................................................................................................381
33. RUBY – PREDEFINED VARIABLES........................................................................................384
34. RUBY – PREDEFINED CONSTANTS .....................................................................................388
35. RUBY – ASSOCIATED TOOLS ..............................................................................................390
Standard Ruby Tools.............................................................................................................................390
RubyGems.............................................................................................................................................390
Ruby Debugger .....................................................................................................................................394
Interactive Ruby....................................................................................................................................398

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Ruby Profiler.........................................................................................................................................401
Additional Ruby Tools...........................................................................................................................402
eRuby: Embeded Ruby..........................................................................................................................402
ri: Ruby Interactive Reference...............................................................................................................403

Ruby
1
Ruby is a pure object-oriented programming language. It was created in 1993 by
Yukihiro Matsumoto of Japan.
You can find the name Yukihiro Matsumoto on the Ruby mailing list at www.ruby-
lang.org. Matsumoto is also known as Matz in the Ruby community.
Ruby is "A Programmer's Best Friend".
Ruby has features that are similar to those of Smalltalk, Perl, and Python. Perl, Python,
and Smalltalk are scripting languages. Smalltalk is a true object-oriented language.
Ruby, like Smalltalk, is a perfect object-oriented language. Using Ruby syntax is much
easier than using Smalltalk syntax.
FeaturesofRuby
 Ruby is an open-source and is freely available on the Web, but it is subject to a
license.
 Ruby is a general-purpose, interpreted programming language.
 Ruby is a true object-oriented programming language.
 Ruby is a server-side scripting language similar to Python and PERL.
 Ruby can be used to write Common Gateway Interface (CGI) scripts.
 Ruby can be embedded into Hypertext Markup Language (HTML).
 Ruby has a clean and easy syntax that allows a new developer to learn very
quickly and easily.
 Ruby has similar syntax to that of many programming languages such as C++
and Perl.
 Ruby is very much scalable and big programs written in Ruby are easily
maintainable.
 Ruby can be used for developing Internet and intranet applications.
 Ruby can be installed in Windows and POSIX environments.
 Ruby support many GUI tools such as Tcl/Tk, GTK, and OpenGL.
 Ruby can easily be connected to DB2, MySQL, Oracle, and Sybase.
 Ruby has a rich set of built-in functions, which can be used directly into Ruby
scripts.
1. RUBY – OVERVIEW

Ruby
2
ToolsYouWillNeed
For performing the examples discussed in this tutorial, you will need a latest computer
like Intel Core i3 or i5 with a minimum of 2GB of RAM (4GB of RAM recommended). You
also will need the following software:
 Linux or Windows 95/98/2000/NT or Windows 7 operating system
 Apache 1.3.19-5 Web server
 Internet Explorer 5.0 or above Web browser
 Ruby 1.8.5
This tutorial will provide the necessary skills to create GUI, networking, and Web
applications using Ruby. It also will talk about extending and embedding Ruby
applications.
WhatisNext?
The next chapter guides you to where you can obtain Ruby and its documentation.
Finally, it instructs you on how to install Ruby and prepare an environment to develop
Ruby applications.

Ruby
3
TryitOptionOnline
We already have set up Ruby Programming environment online, so that you can execute
almost all the tutorial examples online at the same time when you are doing your theory
work. This gives you confidence in what you are reading and to check the result with
different options. Feel free to modify any example and execute it online.
Try the following example using the Try it option available on our website at the top
right corner of the sample code box given below:
#!/usr/bin/ruby -w
puts "Hello, Ruby!";
For most of the examples given in this tutorial, you will find a Try it option on our
website code sections at the top right corner that will take you to the online compiler. So
just make use of it and enjoy your learning.
LocalEnvironmentSetup
If you are still willing to set up your environment for Ruby programming language, then
let's proceed. This tutorial will teach you all the important topics related to environment
setup. We would recommend you to go through the following topics first and then
proceed further:
 Ruby Installation on Linux/Unix : If you are planning to have your
development environment on Linux/Unix Machine, then go through this chapter.
 Ruby Installation on Windows : If you are planning to have your development
environment on Windows Machine, then go through this chapter.
 Ruby Command Line Options : This chapter list out all the command line
options, which you can use along with Ruby interpreter.
 Ruby Environment Variables : This chapter has a list of all the important
environment variables to be set to make Ruby Interpreter works.
RubyInstallationonLinux/Unix
Here are the steps to be followed to install Ruby on a Unix machine:
NOTE: Before proceeding, make sure you have root privilege.
 Download a zipped file having latest version of Ruby. Follow Download Link.
2. RUBY – ENVIRONMENT SETUP

Ruby
4
 After having downloaded the Ruby archive, unpack it and change into the newly
created directory:
$ tar -xvzf ruby-1.6.7.tgz
$ cd ruby-1.6.7
 Now, configure and compile the source code as follows:
$ ./configure
$ make
 Finally, install Ruby interpreter as follows:
$ su -l root # become a root user
$ make install
$ exit # become the original user again
 After installation, make sure everything is working fine by issuing the following
command on the command-line:
$ruby -v
ruby 1.6.7 (2002-06-04) [i386-netbsd]
 If everything is fine, this should output the version of the installed Ruby
interpreter as shown above. You may have installed different version, so it will
display a different version.
UsingyumtoInstallRuby
If your computer is connected to the Internet, then the easiest way to install Ruby or
any other other RPM is using the yum utility. Give the following command at the
command prompt and you will find Ruby gets installed on your computer.
$ yum install ruby
RubyInstallationonWindows
Here are the steps to install Ruby on a Windows machine.
NOTE: You may have different versions available at the time of installation.
 Download a zipped file having latest version of Ruby. Follow Download Link.
 After having downloaded the Ruby archive, unpack it and change into the newly
created directory:
 Double-click the Ruby1.6.7.exe file. The Ruby installation wizard starts.

Ruby
5
 Click Next to move to the Important Information page of the wizard and keep
moving till Ruby installer completes installing Ruby.
You may need to set some environment variables if your installation has not setup them
appropriately.
 If you use Windows 9x, add the following lines to your c:autoexec.bat: set
PATH="D:(ruby install directory)bin;%PATH%"
 Windows NT/2000 users need to modify their registries.
o Click Control Panel | System Properties | Environment Variables.
o Under System Variables, select Path and click EDIT.
o Add your Ruby directory to the end of the Variable Value list and click OK.
o Under System Variables, select PATHEXT and click EDIT.
o Add .RB and .RBW to the Variable Value list and click OK.
 After installation, make sure everything is working fine by issuing the following
command on the command-line:
$ruby -v
ruby 1.6.7
 If everything is fine, this should output the version of the installed Ruby
interpreter as shown above. You may have installed different version, so it will
display a different version.
RubyCommandLineOptions
Ruby is generally run from the command line in the following way:
$ ruby [ options ] [.] [ programfile ] [ arguments ... ]
The interpreter can be invoked with any of the following options to control the
environment and behavior of the interpreter.
Option Description
-a Used with -n or -p to split each line. Check -n and -p options.
-c Checks syntax only, without executing program.
-C dir Changes directory before executing (equivalent to -X).
-d Enables debug mode (equivalent to -debug).

Ruby
6
-F pat Specifies pat as the default separator pattern ($;) used by split.
-e prog Specifies prog as the program from the command line. Specify multiple
-e options for multiline programs.
-h Displays an overview of command-line options.
-i [ ext] Overwrites the file contents with program output. The original file is
saved with the extension ext. If ext isn't specified, the original file is
deleted.
-I dir Adds dir as the directory for loading libraries.
-K [ kcode] Specifies the multibyte character set code (e or E for EUC (extended
Unix code); s or S for SJIS (Shift-JIS); u or U for UTF-8; and a, A, n, or
N for ASCII).
-l Enables automatic line-end processing. Chops a newline from input
lines and appends a newline to output lines.
-n Places code within an input loop (as in while gets; ... end).
-0[ octal] Sets default record separator ($/) as an octal. Defaults to 0 if octal not
specified.
-p Places code within an input loop. Writes $_ for each iteration.
-r lib Uses require to load lib as a library before executing.
-s Interprets any arguments between the program name and filename
arguments fitting the pattern -xxx as a switch and defines the
corresponding variable.
-T [level] Sets the level for tainting checks (1 if level not specified).
-v Displays version and enables verbose mode
-w Enables verbose mode. If program file not specified, reads from STDIN.
-x [dir] Strips text before #!ruby line. Changes directory to dir before
executing if dir is specified.

Ruby
7
-X dir Changes directory before executing (equivalent to -C).
-y Enables parser debug mode.
--copyright Displays copyright notice.
--debug Enables debug mode (equivalent to -d).
--help Displays an overview of command-line options (equivalent to -h).
--version Displays version.
--verbose Enables verbose mode (equivalent to -v). Sets $VERBOSE to true.
--yydebug Enables parser debug mode (equivalent to -y).
Single character command-line options can be combined. The following two lines express
the same meaning:
$ruby -ne 'print if /Ruby/' /usr/share/bin
$ruby -n -e 'print if /Ruby/' /usr/share/bin
RubyEnvironmentVariables
Ruby interpreter uses the following environment variables to control its behavior. The
ENV object contains a list of all the current environment variables set.
Variable Description
DLN_LIBRARY_PATH Search path for dynamically loaded modules.
HOME Directory moved to when no argument is passed to
Dir::chdir. Also used by File::expand_path to expand "~".
LOGDIR Directory moved to when no arguments are passed to

Ruby
8
Dir::chdir and environment variable HOME isn't set.
PATH Search path for executing subprocesses and searching for
Ruby programs with the -S option. Separate each path with a
colon (semicolon in DOS and Windows).
RUBYLIB Search path for libraries. Separate each path with a colon
(semicolon in DOS and Windows).
RUBYLIB_PREFIX Used to modify the RUBYLIB search path by replacing prefix
of library path1 with path2 using the format path1;path2 or
path1path2.
RUBYOPT Command-line options passed to Ruby interpreter. Ignored in
taint mode (Where $SAFE is greater than 0).
RUBYPATH With -S option, search path for Ruby programs. Takes
precedence over PATH. Ignored in taint mode (where $SAFE
is greater than 0).
RUBYSHELL Specifies shell for spawned processes. If not set, SHELL or
COMSPEC are checked.
For Unix, use env command to see a list of all the environment variables.
HOSTNAME=ip-72-167-112-17.ip.secureserver.net
RUBYPATH=/usr/bin
SHELL=/bin/bash
TERM=xterm
HISTSIZE=1000
SSH_CLIENT=122.169.131.179 1742 22
SSH_TTY=/dev/pts/1
USER=amrood
JRE_HOME=/usr/java/jdk/jre
J2RE_HOME=/usr/java/jdk/jre
PATH=/usr/local/bin:/bin:/usr/bin:/home/guest/bin
MAIL=/var/spool/mail/guest
PWD=/home/amrood
INPUTRC=/etc/inputrc

Ruby
9
JAVA_HOME=/usr/java/jdk
LANG=C
HOME=/root
SHLVL=2
JDK_HOME=/usr/java/jdk
LOGDIR=/usr/log/ruby
LOGNAME=amrood
SSH_CONNECTION=122.169.131.179 1742 72.167.112.17 22
LESSOPEN=|/usr/bin/lesspipe.sh %s
RUBYLIB=/usr/lib/ruby
G_BROKEN_FILENAMES=1
_=/bin/env
PopularRubyEditors
To write your Ruby programs, you will need an editor:
 If you are working on Windows machine, then you can use any simple text editor
like Notepad or Edit plus.
 VIM (Vi IMproved) is a very simple text editor. This is available on almost all Unix
machines and now Windows as well. Otherwise, your can use your favorite vi
editor to write Ruby programs.
 RubyWin is a Ruby Integrated Development Environment (IDE) for Windows.
 Ruby Development Environment (RDE) is also a very good IDE for windows
users.
InteractiveRuby(IRb)
Interactive Ruby (IRb) provides a shell for experimentation. Within the IRb shell, you
can immediately view expression results, line by line.
This tool comes along with Ruby installation so you have nothing to do extra to have IRb
working.
Just type irb at your command prompt and an Interactive Ruby Session will start as
given below:
$irb
irb 0.6.1(99/09/16)
irb(main):001:0> def hello
irb(main):002:1> out = "Hello World"
irb(main):003:1> puts out

Ruby
10
irb(main):004:1> end
nil
irb(main):005:0> hello
Hello World
nil
irb(main):006:0>
Do not worry about what we did here. You will learn all these steps in subsequent
chapters.
WhatisNext?
We assume now you have a working Ruby Environment and you are ready to write the
first Ruby Program. The next chapter will teach you how to write Ruby programs.

Ruby
11
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