book

Ruby Cookbook

by Lucas Carlson, Leonard Richardson

July 2006

Intermediate to advanced

906 pages

23h

English

O'Reilly Media, Inc.

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Dedication
A Note Regarding Supplemental Files
Preface
1. Life Is Short2. Audience3. The Structure of This Book4. How the Code Listings Work5. Installing the Software6. Platform Differences, Version Differences, and Other Headaches7. Other Resources8. Conventions Used in This Book9. Using Code Examples10. Comments and Questions11. Acknowledgments
1. Strings
1.1. Building a String from Parts1.2. Substituting Variables into Strings1.3. Substituting Variables into an Existing String1.4. Reversing a String by Words or Characters1.5. Representing Unprintable Characters1.6. Converting Between Characters and Values1.7. Converting Between Strings and Symbols1.8. Processing a String One Character at a Time1.9. Processing a String One Word at a Time1.10. Changing the Case of a String1.11. Managing Whitespace1.12. Testing Whether an Object Is String-Like1.13. Getting the Parts of a String You Want1.14. Handling International Encodings1.15. Word-Wrapping Lines of Text1.16. Generating a Succession of Strings1.17. Matching Strings with Regular Expressions1.18. Replacing Multiple Patterns in a Single Pass1.19. Validating an Email Address1.20. Classifying Text with a Bayesian Analyzer
2. Numbers
2.1. Parsing a Number from a String2.2. Comparing Floating-Point Numbers2.3. Representing Numbers to Arbitrary Precision2.4. Representing Rational Numbers2.5. Generating Random Numbers2.6. Converting Between Numeric Bases2.7. Taking Logarithms2.8. Finding Mean, Median, and Mode2.9. Converting Between Degrees and Radians2.10. Multiplying Matrices2.11. Solving a System of Linear Equations2.12. Using Complex Numbers2.13. Simulating a Subclass of Fixnum2.14. Doing Math with Roman Numbers2.15. Generating a Sequence of Numbers2.16. Generating Prime Numbers2.17. Checking a Credit Card Checksum
3. Date and Time
3.1. Finding Today’s Date3.2. Parsing Dates, Precisely or Fuzzily3.3. Printing a Date3.4. Iterating Over Dates3.5. Doing Date Arithmetic3.6. Counting the Days Since an Arbitrary Date3.7. Converting Between Time Zones3.8. Checking Whether Daylight Saving Time Is in Effect3.9. Converting Between Time and DateTime Objects3.10. Finding the Day of the Week3.11. Handling Commercial Dates3.12. Running a Code Block Periodically3.13. Waiting a Certain Amount of Time3.14. Adding a Timeout to a Long-Running Operation
4. Arrays
4.1. Iterating Over an Array4.2. Rearranging Values Without Using Temporary Variables4.3. Stripping Duplicate Elements from an Array4.4. Reversing an Array4.5. Sorting an Array4.6. Ignoring Case When Sorting Strings4.7. Making Sure a Sorted Array Stays Sorted4.8. Summing the Items of an Array4.9. Sorting an Array by Frequency of Appearance4.10. Shuffling an Array4.11. Getting the N Smallest Items of an Array4.12. Building Up a Hash Using Injection4.13. Extracting Portions of Arrays4.14. Computing Set Operations on Arrays4.15. Partitioning or Classifying a Set
5. Hashes
5.1. Using Symbols as Hash Keys5.2. Creating a Hash with a Default Value5.3. Adding Elements to a Hash5.4. Removing Elements from a Hash5.5. Using an Array or Other Modifiable Object as a Hash Key5.6. Keeping Multiple Values for the Same Hash Key5.7. Iterating Over a Hash5.8. Iterating Over a Hash in Insertion Order5.9. Printing a Hash5.10. Inverting a Hash5.11. Choosing Randomly from a Weighted List5.12. Building a Histogram5.13. Remapping the Keys and Values of a Hash5.14. Extracting Portions of Hashes5.15. Searching a Hash with Regular Expressions
6. Files and Directories
6.1. Checking to See If a File Exists6.2. Checking Your Access to a File6.3. Changing the Permissions on a File6.4. Seeing When a File Was Last Used Problem6.5. Listing a Directory6.6. Reading the Contents of a File6.7. Writing to a File6.8. Writing to a Temporary File6.9. Picking a Random Line from a File6.10. Comparing Two Files6.11. Performing Random Access on “Read-Once” Input Streams6.12. Walking a Directory Tree6.13. Locking a File6.14. Backing Up to Versioned Filenames6.15. Pretending a String Is a File6.16. Redirecting Standard Input or Output6.17. Processing a Binary File6.18. Deleting a File6.19. Truncating a File6.20. Finding the Files You Want6.21. Finding and Changing the Current Working Directory
7. Code Blocks and Iteration
7.1. Creating and Invoking a Block7.2. Writing a Method That Accepts a Block7.3. Binding a Block Argument to a Variable7.4. Blocks as Closures: Using Outside Variables Within a Code Block7.5. Writing an Iterator Over a Data Structure7.6. Changing the Way an Object Iterates7.7. Writing Block Methods That Classify or Collect7.8. Stopping an Iteration7.9. Looping Through Multiple Iterables in Parallel7.10. Hiding Setup and Cleanup in a Block Method7.11. Coupling Systems Loosely with Callbacks

8. Objects and Classes
8.1. Managing Instance Data8.2. Managing Class Data8.3. Checking Class or Module Membership8.4. Writing an Inherited Class8.5. Overloading Methods8.6. Validating and Modifying Attribute Values8.7. Defining a Virtual Attribute8.8. Delegating Method Calls to Another Object8.9. Converting and Coercing Objects to Different Types8.10. Getting a Human-Readable Printout of Any Object8.11. Accepting or Passing a Variable Number of Arguments8.12. Simulating Keyword Arguments8.13. Calling a Superclass’s Method8.14. Creating an Abstract Method8.15. Freezing an Object to Prevent Changes8.16. Making a Copy of an Object8.17. Declaring Constants8.18. Implementing Class and Singleton Methods8.19. Controlling Access by Making Methods Private
9. Modules and Namespaces
9.1. Simulating Multiple Inheritance with Mixins9.2. Extending Specific Objects with Modules9.3. Mixing in Class Methods9.4. Implementing Enumerable: Write One Method, Get 22 Free9.5. Avoiding Naming Collisions with Namespaces9.6. Automatically Loading Libraries as Needed9.7. Including Namespaces9.8. Initializing Instance Variables Defined by a Module9.9. Automatically Initializing Mixed-In Modules
10. Reflection and Metaprogramming
10.1. Finding an Object’s Class and Superclass10.2. Listing an Object’s Methods10.3. Listing Methods Unique to an Object10.4. Getting a Reference to a Method10.5. Fixing Bugs in Someone Else’s Class10.6. Listening for Changes to a Class10.7. Checking Whether an Object Has Necessary Attributes10.8. Responding to Calls to Undefined Methods10.9. Automatically Initializing Instance Variables10.10. Avoiding Boilerplate Code with Metaprogramming10.11. Metaprogramming with String Evaluations10.12. Evaluating Code in an Earlier Context10.13. Undefining a Method10.14. Aliasing Methods10.15. Doing Aspect-Oriented Programming10.16. Enforcing Software Contracts
11. XML and HTML
11.1. Checking XML Well-Formedness11.2. Extracting Data from a Document’s Tree Structure11.3. Extracting Data While Parsing a Document11.4. Navigating a Document with XPath11.5. Parsing Invalid Markup11.6. Converting an XML Document into a Hash11.7. Validating an XML Document11.8. Substituting XML Entities11.9. Creating and Modifying XML Documents11.10. Compressing Whitespace in an XML Document11.11. Guessing a Document’s Encoding11.12. Converting from One Encoding to Another11.13. Extracting All the URLs from an HTML Document11.14. Transforming Plain Text to HTML11.15. Converting HTML Documents from the Web into Text11.16. A Simple Feed Aggregator
12. Graphics and Other File Formats
12.1. Thumbnailing Images12.2. Adding Text to an Image12.3. Converting One Image Format to Another12.4. Graphing Data12.5. Adding Graphical Context with Sparklines12.6. Strongly Encrypting Data12.7. Parsing Comma-Separated Data12.8. Parsing Not-Quite-Comma-Separated Data12.9. Generating and Parsing Excel Spreadsheets12.10. Compressing and Archiving Files with Gzip and Tar12.11. Reading and Writing ZIP Files12.12. Reading and Writing Configuration Files12.13. Generating PDF Files12.14. Representing Data as MIDI Music
13. Databases and Persistence
13.1. Serializing Data with YAML13.2. Serializing Data with Marshal13.3. Persisting Objects with Madeleine13.4. Indexing Unstructured Text with SimpleSearch13.5. Indexing Structured Text with Ferret13.6. Using Berkeley DB Databases13.7. Controlling MySQL on Unix13.8. Finding the Number of Rows Returned by a Query13.9. Talking Directly to a MySQL Database13.10. Talking Directly to a PostgreSQL Database13.11. Using Object Relational Mapping with ActiveRecord13.12. Using Object Relational Mapping with Og13.13. Building Queries Programmatically13.14. Validating Data with ActiveRecord13.15. Preventing SQL Injection Attacks13.16. Using Transactions in ActiveRecord13.17. Adding Hooks to Table Events13.18. Adding Taggability with a Database Mixin
14. Internet Services
14.1. Grabbing the Contents of a Web Page14.2. Making an HTTPS Web Request14.3. Customizing HTTP Request Headers14.4. Performing DNS Queries14.5. Sending Mail14.6. Reading Mail with IMAP14.7. Reading Mail with POP314.8. Being an FTP Client14.9. Being a Telnet Client14.10. Being an SSH Client14.11. Copying a File to Another Machine14.12. Being a BitTorrent Client14.13. Pinging a Machine14.14. Writing an Internet Server14.15. Parsing URLs14.16. Writing a CGI Script14.17. Setting Cookies and Other HTTP Response Headers14.18. Handling File Uploads via CGI14.19. Running Servlets with WEBrick14.20. A Real-World HTTP Client
15. Web Development: Ruby on Rails
15.1. Writing a Simple Rails Application to Show System Status15.2. Passing Data from the Controller to the View15.3. Creating a Layout for Your Header and Footer15.4. Redirecting to a Different Location15.5. Displaying Templates with Render15.6. Integrating a Database with Your Rails Application15.7. Understanding Pluralization Rules15.8. Creating a Login System15.9. Storing Hashed User Passwords in the Database15.10. Escaping HTML and JavaScript for Display15.11. Setting and Retrieving Session Information15.12. Setting and Retrieving Cookies15.13. Extracting Code into Helper Functions15.14. Refactoring the View into Partial Snippets of Views15.15. Adding DHTML Effects with script.aculo.us15.16. Generating Forms for Manipulating Model Objects15.17. Creating an Ajax Form15.18. Exposing Web Services on Your Web Site15.19. Sending Mail with Rails15.20. Automatically Sending Error Messages to Your Email15.21. Documenting Your Web Site15.22. Unit Testing Your Web Site15.23. Using breakpoint in Your Web Application
16. Web Services and Distributed Programming
16.1. Searching for Books on Amazon16.2. Finding Photos on Flickr16.3. Writing an XML-RPC Client16.4. Writing a SOAP Client16.5. Writing a SOAP Server16.6. Searching the Web with Google’s SOAP Service16.7. Using a WSDL File to Make SOAP Calls Easier16.8. Charging a Credit Card16.9. Finding the Cost to Ship Packages via UPS or FedEx16.10. Sharing a Hash Between Any Number of Computers16.11. Implementing a Distributed Queue16.12. Creating a Shared “Whiteboard”16.13. Securing DRb Services with Access Control Lists16.14. Automatically Discovering DRb Services with Rinda16.15. Proxying Objects That Can’t Be Distributed16.16. Storing Data on Distributed RAM with MemCached16.17. Caching Expensive Results with MemCached16.18. A Remote-Controlled Jukebox
17. Testing, Debugging, Optimizing, and Documenting
17.1. Running Code Only in Debug Mode17.2. Raising an Exception17.3. Handling an Exception17.4. Rerunning After an Exception17.5. Adding Logging to Your Application17.6. Creating and Understanding Tracebacks17.7. Writing Unit Tests17.8. Running Unit Tests17.9. Testing Code That Uses External Resources17.10. Using breakpoint to Inspect and Change the State of Your Application17.11. Documenting Your Application17.12. Profiling Your Application17.13. Benchmarking Competing Solutions17.14. Running Multiple Analysis Tools at Once17.15. Who’s Calling That Method? A Call Graph Analyzer
18. Packaging and Distributing Software
18.1. Finding Libraries by Querying Gem Respositories18.2. Installing and Using a Gem18.3. Requiring a Specific Version of a Gem18.4. Uninstalling a Gem18.5. Reading Documentation for Installed Gems18.6. Packaging Your Code as a Gem18.7. Distributing Your Gems18.8. Installing and Creating Standalone Packages with setup.rb
19. Automating Tasks with Rake
19.1. Automatically Running Unit Tests19.2. Automatically Generating Documentation19.3. Cleaning Up Generated Files19.4. Automatically Building a Gem19.5. Gathering Statistics About Your Code19.6. Publishing Your Documentation19.7. Running Multiple Tasks in Parallel19.8. A Generic Project Rakefile
20. Multitasking and Multithreading
20.1. Running a Daemon Process on Unix20.2. Creating a Windows Service20.3. Doing Two Things at Once with Threads20.4. Synchronizing Access to an Object20.5. Terminating a Thread20.6. Running a Code Block on Many Objects Simultaneously20.7. Limiting Multithreading with a Thread Pool20.8. Driving an External Process with popen20.9. Capturing the Output and Error Streams from a Unix Shell Command20.10. Controlling a Process on Another Machine20.11. Avoiding Deadlock
21. User Interface
21.1. 21.2. Getting Input One Line at a Time21.3. Getting Input One Character at a Time21.4. Parsing Command-Line Arguments21.5. Testing Whether a Program Is Running Interactively21.6. Setting Up and Tearing Down a Curses Program21.7. Clearing the Screen21.8. Determining Terminal Size21.9. Changing Text Color21.10. Reading a Password21.11. Allowing Input Editing with Readline21.12. Making Your Keyboard Lights Blink21.13. Creating a GUI Application with Tk21.14. Creating a GUI Application with wxRuby21.15. Creating a GUI Application with Ruby/GTK21.16. Creating a Mac OS X Application with RubyCocoa21.17. Using AppleScript to Get User Input
22. Extending Ruby with Other Languages
22.1. Writing a C Extension for Ruby22.2. Using a C Library from Ruby22.3. Calling a C Library Through SWIG22.4. Writing Inline C in Your Ruby Code22.5. Using Java Libraries with JRuby
23. System Administration
23.1. Scripting an External Program23.2. Managing Windows Services23.3. Running Code as Another User23.4. Running Periodic Tasks Without cron or at23.5. Deleting Files That Match a Regular Expression23.6. Renaming Files in Bulk23.7. Finding Duplicate Files23.8. Automating Backups23.9. Normalizing Ownership and Permissions in User Directories23.10. Killing All Processes for a Given User
Index
About the Authors
Colophon
Copyright

Overview

Do you want to push Ruby to its limits? The Ruby Cookbook is the most comprehensive problem-solving guide to today's hottest programming language. It gives you hundreds of solutions to real-world problems, with clear explanations and thousands of lines of code you can use in your own projects.

From data structures and algorithms, to integration with cutting-edge technologies, the Ruby Cookbook has something for every programmer. Beginners and advanced Rubyists alike will learn how to program with:

Strings and numbers
Arrays and hashes
Classes, modules, and namespaces
Reflection and metaprogramming
XML and HTML processing
Ruby on Rails (including Ajax integration)
Databases
Graphics
Internet services like email, SSH, and BitTorrent
Web services
Multitasking
Graphical and terminal interfaces

If you need to write a web application, this book shows you how to get started with Rails. If you're a system administrator who needs to rename thousands of files, you'll see how to use Ruby for this and other everyday tasks. You'll learn how to read and write Excel spreadsheets, classify text with Bayesian filters, and create PDF files. We've even included a few silly tricks that were too cool to leave out, like how to blink the lights on your keyboard.

The Ruby Cookbook is the most useful book yet written about Ruby. When you need to solve a problem, don't reinvent the wheel: look it up in the Cookbook.

Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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