Learning Perl: Making Easy Things Easy and Hard Things Possible

Description

If you're just getting started with Perl, this is the book you want—whether you're a programmer, system administrator, or web hacker. Nicknamed "the Llama" by two generations of users, this best seller closely follows the popular introductory Perl course taught by the authors since 1991. This eighth edition covers recent changes to the language up to version 5.34. Perl is suitable for almost any task on almost any platform, from short fixes to complete web applications. Learning Perl teaches you the basics and shows you how to write simple, single-file programs—roughly 90% of the Perl programs in use today. And each chapter includes exercises to help you practice what you've just learned. Other books may teach you to program in Perl, but this book will turn you into a Perl programmer. Topics include: Perl data and variable types Subroutines File operations Regular expressions String manipulation (including Unicode) Lists and sorting Process management Use of third-party modules Cover Copyright Table of Contents Preface Typographical Conventions Code Examples O’Reilly Online Learning How to Contact Us History of This Book Changes from the Previous Edition Acknowledgments From Randal From brian From Tom From All of Us Chapter 1. Introduction Questions and Answers Is This the Right Book for You? What About the Exercises and Their Answers? What If I’m a Perl Course Instructor? What Does “Perl” Stand For? Why Did Larry Create Perl? Why Didn’t Larry Just Use Some Other Language? Is Perl Easy or Hard? How Did Perl Get to Be So Popular? What’s Happening with Perl Now? What’s Perl Really Good For? What Is Perl Not Good For? How Can I Get Perl? What Is CPAN? Is There Any Kind of Support? What If I Find a Bug in Perl? How Do I Make a Perl Program? A Simple Program What’s Inside That Program? How Do I Compile My Perl Program? A Whirlwind Tour of Perl Exercises Chapter 2. Scalar Data Numbers All Numbers Have the Same Format Internally Integer Literals Nondecimal Integer Literals Floating-Point Literals Numeric Operators Strings Single-Quoted String Literals Double-Quoted String Literals String Operators Automatic Conversion Between Numbers and Strings Perl’s Built-in Warnings Interpreting Nondecimal Numerals Scalar Variables Choosing Good Variable Names Scalar Assignment Compound Assignment Operators Output with print Interpolation of Scalar Variables into Strings Creating Characters by Code Point Operator Precedence and Associativity Comparison Operators The if Control Structure Boolean Values Getting User Input The chomp Operator The while Control Structure The undef Value The defined Function Exercises Chapter 3. Lists and Arrays Accessing Elements of an Array Special Array Indices List Literals The qw Shortcut List Assignment The pop and push Operators The shift and unshift Operators The splice Operator Interpolating Arrays into Strings The foreach Control Structure Perl’s Favorite Default: $_ The reverse Operator The sort Operator The each Operator Scalar and List Context Using List-Producing Expressions in Scalar Context Using Scalar-Producing Expressions in List Context Forcing Scalar Context in List Context Exercises Chapter 4. Subroutines Defining a Subroutine Invoking a Subroutine Return Values Arguments Private Variables in Subroutines Variable-Length Parameter Lists A Better &max Routine Empty Parameter Lists Notes on Lexical (my) Variables The use strict Pragma The return Operator Omitting the Ampersand Nonscalar Return Values Persistent, Private Variables Subroutine Signatures Prototypes Exercises Chapter 5. Input and Output Input from Standard Input Input from the Diamond Operator The Double Diamond The Invocation Arguments Output to Standard Output Formatted Output with printf Arrays and printf Filehandles Opening a Filehandle Binmoding Filehandles Bad Filehandles Closing a Filehandle Fatal Errors with die Warning Messages with warn Automatically die-ing Using Filehandles Changing the Default Output Filehandle Reopening a Standard Filehandle Output with say Filehandles in a Scalar Exercises Chapter 6. Hashes What Is a Hash? Why Use a Hash? Hash Element Access The Hash as a Whole Hash Assignment The Big Arrow Hash Functions The keys and values Functions The each Function Typical Use of a Hash The exists Function The delete Function Hash Element Interpolation The %ENV Hash Exercises Chapter 7. Regular Expressions Sequences Practice Some Patterns The Wildcard Quantifiers Grouping in Patterns Alternation Character Classes Character Class Shortcuts Negating the Shortcuts Unicode Properties Anchors Word Anchors Exercises Chapter 8. Matching with Regular Expressions Matches with m// Match Modifiers Case-Insensitive Matching with /i Matching Any Character with /s Adding Whitespace with /x Combining Option Modifiers Choosing a Character Interpretation Beginning- and End-of-Line Anchors Other Options The Binding Operator =~ The Match Variables The Persistence of Captures Captures in Alternations Noncapturing Parentheses Named Captures The Automatic Match Variables Precedence Examples of Precedence And There’s More A Pattern Test Program Exercises Chapter 9. Processing Text with Regular Expressions Substitutions with s/// Global Replacements with /g Different Delimiters Substitution Modifiers The Binding Operator Nondestructive Substitutions Case Shifting Metaquoting The split Operator The join Function m// in List Context More Powerful Regular Expressions Nongreedy Quantifiers Fancier Word Boundaries Matching Multiple-Line Text Updating Many Files In-Place Editing from the Command Line Exercises Chapter 10. More Control Structures The unless Control Structure The else Clause with unless The until Control Structure Statement Modifiers The Naked Block Control Structure The elsif Clause Autoincrement and Autodecrement The Value of Autoincrement The for Control Structure The Secret Connection Between foreach and for Loop Controls The last Operator The next Operator The redo Operator Labeled Blocks The Conditional Operator Logical Operators The Value of a Short-Circuit Operator The defined-or Operator Control Structures Using Partial-Evaluation Operators Exercises Chapter 11. Perl Modules Finding Modules Installing Modules Using Your Own Directories Using Simple Modules The File::Basename Module Using Only Some Functions from a Module The File::Spec Module Path::Class Databases and DBI Dates and Times Exercises Chapter 12. File Tests File Test Operators Testing Several Attributes of the Same File Stacked File Test Operators The stat and lstat Functions The localtime Function Bitwise Operators Using Bitstrings Exercises Chapter 13. Directory Operations The Current Working Directory Changing the Directory Globbing An Alternate Syntax for Globbing Directory Handles Manipulating Files and Directories Removing Files Renaming Files Links and Files Making and Removing Directories Modifying Permissions Changing Ownership Changing Timestamps Exercises Chapter 14. Strings and Sorting Finding a Substring with index Manipulating a Substring with substr Formatting Data with sprintf Using sprintf with “Money Numbers” Advanced Sorting Sorting a Hash by Value Sorting by Multiple Keys Exercises Chapter 15. Process Management The system Function Avoiding the Shell The Environment Variables The exec Function Using Backquotes to Capture Output Using Backquotes in a List Context External Processes with IPC::System::Simple Processes as Filehandles Getting Down and Dirty with fork Sending and Receiving Signals Exercises Chapter 16. Some Advanced Perl Techniques Slices Array Slice Hash Slice Key-Value Slices Trapping Errors Using eval More Advanced Error Handling Picking Items from a List with grep Transforming Items from a List with map Fancier List Utilities Exercises Appendix A. Exercise Answers Answers to Chapter 1 Exercises Answers to Chapter 2 Exercises Answers to Chapter 3 Exercises Answers to Chapter 4 Exercises Answers to Chapter 5 Exercises Answers to Chapter 6 Exercises Answers to Chapter 7 Exercises Answers to Chapter 8 Exercises Answers to Chapter 9 Exercises Answers to Chapter 10 Exercises Answers to Chapter 11 Exercises Answers to Chapter 12 Exercises Answers to Chapter 13 Exercises Answers to Chapter 14 Exercises Answers to Chapter 15 Exercises Answers to Chapter 16 Exercises Appendix B. Beyond the Llama Further Documentation Regular Expressions Packages Extending Perl’s Functionality Writing Your Own Modules Databases Mathematics Lists and Arrays Bits and Pieces Formats Networking and IPC System V IPC Sockets Security Debugging Command-Line Options Built-in Variables References Complex Data Structures Object-Oriented Programming Anonymous Subroutines and Closures Tied Variables Operator Overloading Using Other Languages Inside Perl Embedding Converting find Command Lines to Perl Command-Line Options in Your Programs Embedded Documentation More Ways to Open Filehandles Graphical User Interfaces (GUIs) And More… Appendix C. A Unicode Primer Unicode UTF-8 and Friends Getting Everyone to Agree Fancy Characters Using Unicode in Your Source Fancier Characters Dealing with Unicode in Perl Fancier Characters by Name Reading from STDIN or Writing to STDOUT or STDERR Reading from and Writing to Files Dealing with Command-Line Arguments Dealing with Databases Further Reading Appendix D. Experimental Features A Short History of Perl Development Perl 5.10 and Beyond Installing a Recent Perl Experimental Features Turning Off Experimental Warnings Enable or Disable Features Lexically Don’t Rely on Experimental Features Index About the Authors Colophon