book

Learning Perl, 3rd Edition

by Tom Phoenix, Randal L. Schwartz

July 2001

Beginner

334 pages

9h 54m

English

O'Reilly Media, Inc.

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A Note Regarding Supplemental Files
Preface
Typographical ConventionsHow to Contact UsCode ExamplesHistory of This BookAcknowledgments
1. Introduction
1.1. Questions and Answers1.1.1. Is This the Right Book for You?1.1.2. Why Are There So Many Footnotes?1.1.3. What About the Exercises and Their Answers?1.1.4. What Do Those Numbers Mean at the Start of the Exercise?1.1.5. What If I’m a Perl Course Instructor?1.2. What Does “Perl” Stand For?1.2.1. Why Didn’t Larry Just Use Some Other Language?1.2.2. Is Perl Easy or Hard?1.2.3. How Did Perl Get to Be So Popular?1.2.4. What’s Happening with Perl Now?1.2.5. What’s Perl Really Good For?1.2.6. What Is Perl Not Good For?1.3. How Can I Get Perl?1.3.1. What Is CPAN?1.3.2. How Can I Get Support for Perl?1.3.3. Are There Any Other Kinds of Support?1.3.4. What If I Find a Bug in Perl?1.4. How Do I Make a Perl Program?1.4.1. A Simple Program1.4.2. What’s Inside That Program?1.4.3. But How Do I Compile Perl?1.5. A Whirlwind Tour of Perl1.6. Exercises
2. Scalar Data
2.1. What Is Scalar Data?2.2. Numbers2.2.1. All Numbers Are the Same Format Internally2.2.2. Floating-Point Literals2.2.3. Integer Literals2.2.4. Nondecimal Integer Literals2.2.5. Numeric Operators2.3. Strings2.3.1. Single-Quoted String Literals2.3.2. Double-Quoted String Literals2.3.3. String Operators2.3.4. Automatic Conversion Between Numbers and Strings2.4. Perl’s Built-in Warnings2.5. Scalar Variables2.5.1. Choosing Good Variable Names2.5.2. Scalar Assignment2.5.3. Binary Assignment Operators2.6. Output with print 2.6.1. Interpolation of Scalar Variables into Strings2.6.2. Operator Precedence and Associativity2.6.3. Comparison Operators2.7. The if Control Structure2.7.1. Boolean Values2.8. Getting User Input2.9. The chomp Operator2.10. The while Control Structure2.11. The undef Value2.12. The defined Function2.13. Exercises
3. Lists and Arrays
3.1. Accessing Elements of an Array3.2. Special Array Indices3.3. List Literals3.3.1. The qw Shortcut3.4. List Assignment3.4.1. The pop and push Operators3.4.2. The shift and unshift Operators3.5. Interpolating Arrays into Strings3.6. The foreach Control Structure3.7. Perl’s Favorite Default: $_3.7.1. The reverse Operator3.7.2. The sort Operator3.8. Scalar and List Context3.8.1. Using List-Producing Expressions in Scalar Context3.8.2. Using Scalar-Producing Expressions in List Context3.8.3. Forcing Scalar Context3.9. <STDIN> in List Context3.10. Exercises
4. Subroutines
4.1. System and User Functions4.2. Defining a Subroutine4.3. Invoking a Subroutine4.4. Return Values4.5. Arguments4.6. Private Variables in Subroutines4.7. The local Operator4.7.1. The Difference Between local and my4.8. Variable-length Parameter Lists4.8.1. A Better &max Routine4.8.2. Empty Parameter Lists4.9. Notes on Lexical (my) Variables4.10. The use strict Pragma4.11. The return Operator4.11.1. Omitting the Ampersand4.12. Exercises
5. Hashes
5.1. What Is a Hash?5.1.1. Why Use a Hash?5.2. Hash Element Access5.2.1. The Hash as a Whole5.2.2. Hash Assignment5.2.3. The Big Arrow5.3. Hash Functions5.3.1. The keys and values Functions5.3.2. The each Function5.4. Typical Use of a Hash5.4.1. The exists Function5.4.2. The delete Function5.4.3. Hash Element Interpolation5.5. Exercises
6. I/O Basics
6.1. Input from Standard Input6.2. Input from the Diamond Operator6.3. The Invocation Arguments6.4. Output to Standard Output6.5. Formatted Output with printf6.5.1. Arrays and printf6.6. Exercises
7. Concepts of Regular Expressions
7.1. What Are Regular Expressions?7.2. Using Simple Patterns7.2.1. About Metacharacters7.2.2. Simple Quantifiers7.2.3. Grouping in Patterns7.2.4. Alternatives7.3. A Pattern Test Program7.4. Exercises
8. More About Regular Expressions
8.1. Character Classes8.1.1. Character Class Shortcuts8.1.2. Negating the Shortcuts8.2. General Quantifiers8.3. Anchors8.3.1. Word Anchors8.4. Memory Parentheses8.4.1. Backreferences8.4.2. Memory Variables8.5. Precedence8.5.1. Examples of Precedence8.5.2. And There’s More8.6. Exercises

9. Using Regular Expressions
9.1. Matches with m//9.2. Option Modifiers9.2.1. Case-insensitive Matching with /i9.2.2. Matching Any Character with /s9.2.3. Combining Option Modifiers9.2.4. Other Options9.3. The Binding Operator, =~9.4. Interpolating into Patterns9.5. The Match Variables9.5.1. The Persistence of Memory9.5.2. The Automatic Match Variables9.6. Substitutions with s///9.6.1. Global Replacements with /g9.6.2. Different Delimiters9.6.3. Option Modifiers9.6.4. The Binding Operator9.6.5. Case Shifting9.7. The split Operator9.8. The join Function9.9. Exercises
10. More Control Structures
10.1. The unless Control Structure10.1.1. The else Clause with unless10.2. The until Control Structure10.3. Expression Modifiers10.4. The Naked Block Control Structure10.5. The elsif Clause10.6. Autoincrement and Autodecrement10.6.1. The Value of Autoincrement10.7. The for Control Structure10.7.1. The Secret Connection Between foreach and for10.8. Loop Controls10.8.1. The last Operator10.8.2. The next Operator10.8.3. The redo Operator10.8.4. Labeled Blocks10.9. Logical Operators10.9.1. The Value of a Short-Circuit Operator10.9.2. The Ternary Operator, ?:10.9.3. Control Structures Using Partial-Evaluation Operators10.10. Exercise
11. Filehandles and File Tests
11.1. What Is a Filehandle?11.2. Opening a Filehandle11.2.1. Closing a Filehandle11.2.2. Bad Filehandles11.3. Fatal Errors with die11.3.1. Warning Messages with warn11.4. Using Filehandles11.4.1. Changing the Default Output Filehandle11.5. Reopening a Standard Filehandle11.6. File Tests11.6.1. The stat and lstat Functions11.6.2. The localtime Function11.6.3. Bitwise Operators11.6.4. Using Bitstrings11.6.5. Using the Special Underscore Filehandle11.7. Exercises
12. Directory Operations
12.1. Moving Around the Directory Tree12.2. Globbing12.3. An Alternate Syntax for Globbing12.4. Directory Handles12.5. Recursive Directory Listing12.6. Exercises
13. Manipulating Files and Directories
13.1. Removing Files13.2. Renaming Files13.3. Links and Files13.4. Making and Removing Directories13.5. Modifying Permissions13.6. Changing Ownership13.7. Changing Timestamps13.8. Using Simple Modules13.8.1. The File::Basename Module13.8.2. Using Only Some Functions from a Module13.8.3. The File::Spec Module13.9. Exercises
14. Process Management
14.1. The system Function14.1.1. Avoiding the Shell14.2. The exec Function14.3. The Environment Variables14.4. Using Backquotes to Capture Output14.4.1. Using Backquotes in a List Context14.5. Processes as Filehandles14.6. Getting Down and Dirty with Fork14.7. Sending and Receiving Signals14.8. Exercises
15. Strings and Sorting
15.1. Finding a Substring with index15.2. Manipulating a Substring with substr15.3. Formatting Data with sprintf15.3.1. Using sprintf with “Money Numbers”15.4. Advanced Sorting15.4.1. Sorting a Hash by Value15.4.2. Sorting by Multiple Keys15.5. Exercises
16. Simple Databases
16.1. DBM Files and DBM Hashes16.1.1. Opening and Closing DBM Hashes16.1.2. Using a DBM Hash16.2. Manipulating Data with pack and unpack16.3. Fixed-length Random-access Databases16.4. Variable-length (Text) Databases16.4.1. In-place Editing from the Command Line16.5. Exercises
17. Some Advanced Perl Techniques
17.1. Trapping Errors with eval17.2. Picking Items from a List with grep17.3. Transforming Items from a List with map17.4. Unquoted Hash Keys17.5. More Powerful Regular Expressions17.5.1. Non-greedy Quantifiers17.5.2. Matching Multiple-line Text17.6. Slices17.6.1. Array Slice17.6.2. Hash Slice17.7. Exercise
A. Exercise Answers
A.1. Answers to Chapter 2 Exercises A.2. Answers to Chapter 3 ExercisesA.3. Answers to Chapter 4 ExercisesA.4. Answers to Chapter 5 ExercisesA.5. Answers to Chapter 6 ExercisesA.6. Answers to Chapter 7 ExercisesA.7. Answers to Chapter 8 ExercisesA.8. Answers to Chapter 9 ExercisesA.9. Answer to Chapter 10 ExerciseA.10. Answers to Chapter 11 ExercisesA.11. Answers to Chapter 12 ExercisesA.12. Answers to Chapter 13 ExercisesA.13. Answers to Chapter 14 ExercisesA.14. Answers to Chapter 15 ExercisesA.15. Answers to Chapter 16 ExercisesA.16. Answer to Chapter 17 Exercises
B. Beyond the Llama
B.1. Further DocumentationB.2. Regular expressionsB.3. PackagesB.4. Extending Perl’s FunctionalityB.4.1. LibrariesB.4.2. ModulesB.4.3. Finding and Installing ModulesB.4.4. Writing Your Own ModulesB.5. Some Important ModulesB.5.1. The CGI and CGI_Lite ModulesB.5.2. The Cwd ModuleB.5.3. The Fatal ModuleB.5.4. The File::Basename ModuleB.5.5. The File::Copy ModuleB.5.6. The File::Spec ModuleB.5.7. The Image::Size ModuleB.5.8. The Net::SMTP ModuleB.5.9. The POSIX ModuleB.5.10. The Sys::Hostname ModuleB.5.11. The Text::Wrap ModuleB.5.12. The Time::Local ModuleB.6. PragmasB.6.1. The constant PragmaB.6.2. The diagnostics PragmaB.6.3. The lib PragmaB.6.4. The strict PragmaB.6.5. The vars PragmaB.6.6. The warnings PragmaB.7. DatabasesB.7.1. Direct System Database AccessB.7.2. Flat-file Database AccessB.7.3. Relational Database AccessB.8. Other Operators and FunctionsB.8.1. Transliteration with tr///B.8.2. Here documentsB.9. MathematicsB.9.1. Advanced Math FunctionsB.9.2. Imaginary and Complex NumbersB.9.3. Large and High-Precision NumbersB.10. Lists and ArraysB.10.1. map and grepB.10.2. The splice OperatorB.11. Bits and PiecesB.12. FormatsB.13. Networking and IPCB.13.1. System V IPCB.13.2. SocketsB.14. SecurityB.15. DebuggingB.16. The Common Gateway Interface (CGI)B.17. Command-Line OptionsB.18. Built in VariablesB.19. Syntax ExtensionsB.20. ReferencesB.20.1. Complex Data StructuresB.20.2. Object-Oriented ProgrammingB.20.3. Anonymous Subroutines and ClosuresB.21. Tied VariablesB.22. Operator OverloadingB.23. Dynamic LoadingB.24. EmbeddingB.25. Converting Other Languages to PerlB.26. Converting find Command Lines to PerlB.27. Command-line Options in Your ProgramsB.28. Embedded DocumentationB.29. More Ways to Open FilehandlesB.30. Locales and UnicodeB.31. Threads and ForkingB.32. Graphical User Interfaces (GUIs)B.33. And More...
Index
About the Authors
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Copyright

Content preview from Learning Perl, 3rd Edition

Colophon

Our look is the result of reader comments, our own experimentation, and feedback from distribution channels. Distinctive covers complement our distinctive approach to technical topics, breathing personality and life into potentially dry subjects.

The animal featured on the cover of Learning Perl, Third Edition, is the llama, a relation of the camel native to the Andean range. Also included in this llamoid group is the domestic alpaca and their wild ancestors, the guanaco and the vicuna. Bones found in ancient human settlements suggest that domestication of the alpaca and llama dates back 4,500 years. In 1531, when Spanish conquistadors overran the Inca Empire in the high Andes, they found both animals present in great numbers. These llamas are suited for high mountain life; their hemoglobin can take in more oxygen than that of other mammals.

Llamas can weigh up to 300 pounds and are mainly used as beasts of burden. A packtrain may contain several hundred animals and can travel up to twenty miles per day. Llamas will carry loads up to fifty pounds, but have a tendency to be short-tempered and resort to spitting and biting to demonstrate displeasure. To the people of the Andes, llamas also provide meat, wool for clothing, hides for leather, and fat for candles. Their wool can also be braided into rope and rugs, and their dried dung is used for fuel.

Sarah Jane Shangraw and Ann Schirmer were the production editors for Learning Perl, Third Edition. Nicole Arigo copyedited the ...

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Learning Perl, 3rd Edition

by Tom Phoenix, Randal L. Schwartz

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