Learning Perl: Making Easy Things Easy and Hard Things Possible [8 ed.] 9781492094951

If you're just getting started with Perl, this is the book you want—whether you're a programmer, system admini

2,488 545 3MB

English Pages 398 Year 2021

Report DMCA / Copyright


Learning Perl: Making Easy Things Easy and Hard Things Possible [8 ed.]

Table of contents :
Table of Contents
Typographical Conventions
Code Examples
O’Reilly Online Learning
How to Contact Us
History of This Book
Changes from the Previous Edition
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
Chapter 2. Scalar Data
All Numbers Have the Same Format Internally
Integer Literals
Nondecimal Integer Literals
Floating-Point Literals
Numeric Operators
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
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
Chapter 4. Subroutines
Defining a Subroutine
Invoking a Subroutine
Return Values
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
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
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
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
Chapter 7. Regular Expressions
Practice Some Patterns
The Wildcard
Grouping in Patterns
Character Classes
Character Class Shortcuts
Negating the Shortcuts
Unicode Properties
Word Anchors
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
Examples of Precedence
And There’s More
A Pattern Test Program
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
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
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
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
Databases and DBI
Dates and Times
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
Chapter 13. Directory Operations
The Current Working Directory
Changing the Directory
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
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
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
Chapter 16. Some Advanced Perl Techniques
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
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
Extending Perl’s Functionality
Writing Your Own Modules
Lists and Arrays
Bits and Pieces
Networking and IPC
System V IPC
Command-Line Options
Built-in Variables
Complex Data Structures
Object-Oriented Programming
Anonymous Subroutines and Closures
Tied Variables
Operator Overloading
Using Other Languages Inside Perl
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
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
About the Authors

Polecaj historie