Professional Perl Programming Peter Wainwright with Aldo Calpini Arthur Corliss Simon Cozens Juan Julián Merelo Guervós Chris Nandor Aalhad Saraf Wrox Press Ltd. TEAMFLY Team-Fly ® Professional Perl Programming © 2001 Wrox Press All rights reserved. No part of this book may be reproduced, stored in a retrieval system or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embodied in critical articles or reviews. The author and publisher have made every effort in the preparation of this book to ensure the accuracy of the information. However, the information contained in this book is sold without warranty, either express or implied. Neither the authors, Wrox Press nor its dealers or distributors will be held liable for any damages caused or alleged to be caused either directly or indirectly by this book. Published by Wrox Press Ltd, Arden House, 1102 Warwick Road, Acocks Green, Birmingham, B27 6BH, UK Printed in the United States ISBN 1-861004-49-4 Trademark Acknowledgements Wrox has endeavored to provide trademark information about all the companies and products mentioned in this book by the appropriate use of capitals. However, Wrox cannot guarantee the accuracy of this information. Credits Author Technical Reviewers Peter Wainwright Simon Cozens Carl Culvett Contributing Authors David Fannin Aldo Calpini Iain Georgeson Arthur Corliss Terry Gliedt Simon Cozens Jim Harle Juan Julián Merelo Guervós Chris Lightfoot Chris Nandor Mark Mamone Aalhad Saraf Neil Matthews Bill Moss Technical Architect Nathan Neulinger Louay Fatoohi Gavin Smyth Rick Stones Technical Editors Paul Warren Mankee Cheng Andrew Yourtchenko David Mercer Philips Yuson Andrew Polshaw Dan Robotham Production Manager Simon Hardware Additional Editorial Mohammed Rfaquat Production Project Coordinator Mark Burdett Author Agents Julia Gilbert Illustrations Velimir Ilic Shabnam Hussain Project Administrator Cover Nicola Phillips Shelley Frazier Indexers Proof Readers Alessandro Ansa Chris Smith Adrian Axinte Keith Westmoreland Bill Johncocks Diana Skeldon Category Managers Viv Emery Paul Cooper About the Authors Peter Wainwright Peter Wainwright is a freelance developer and software consultant. He got his first taste of programming on a BBC Micro and gained most of his early programming experience writing applications in C on Solaris. He then discovered Linux, shortly followed by Perl and Apache, and has been happily programming there ever since. Outside of the software industry, he is a partner of Space Future Consulting, an international space tourism consultancy firm. He spends much of his free time maintaining the non-profit Space Future website at www.spacefuture.com and writes the occasional article on space tourism. He is also an advisor to the board of one or two companies engaged in space tourism and vehicle development. If you have $50m to spare, he would like to have a word with you. As well as being the primary author of Professional Perl Programming, he is the author of Professional Apache (ISBN: 1861003021), also published by Wrox Press, as well as a contributing author to Beginning Per l (ISBN: 1861003145). Formerly based in London, he recently moved from England to the Upper West Side of New York to be with his new wife, a professional editor, whom he met through a mutual interest in space tourism and low-rent apartments. Aldo Calpini Aldo Calpini is well known in the Perl community for his many important Win32 modules. His active participation on several mailing lists has helped the Perl language grow in the Win32 community. He began programming twenty years ago and still enjoys hacking every kind of computer he can put his hands on. He works today as lead programmer in an Italian Internet startup company. Arthur Corliss Arthur Corliss has been programming since buying his first home computer a Timex Sinclair 1000 with a whopping 2K of RAM (which he still has). Having worked his way through several languages, Perl has become his most frequent language of choice at his latest venture, Gallant Technologies, Inc., a software development company. On his own time he continues the madness by working on the Curses::Widgets and Curses::Forms modules, which he authored and is available on CPAN. Simon Cozens Simon Cozens is an Open Source programmer and author; he writes for the Perl Journal, www.perl.com, and other sites, and is the author of Wrox Press' Beginning Perl (ISBN: 1861003145). He is a member of the Perl development team, and his hobbies include reading, typography and the Greek language and culture. Juan Julián Merelo Guervós Juan Julián Merelo Guervós was born in Ubeda, Jaén, Spain, the 10th of March of 1965. Juan received a degree in Theoretical Physics by the University of Granada in 1989, and a PhD in Physics in 1994. He has been hacking PERL since 1993 or 1994, and is the author of a widely popular (and pioneer) web tutorial of PERL in Spanish (available from http://www.granavenida.com/perl). Currently Juan is an associate professor at Granada University, in Spain. He is married and has three wonderful daughters, two of whom are fraternal twins, born in 1998 and 1999. He can be reached at jmerelo@geneura.ugr.es, and his homepage (which is, so far, in Spanish) is at http://geneura.ugr.es/~jmerelo Chris Nandor Chris Nandor, pudge@pobox.com, is a programmer for OSDN, working on theSlashdot code. He co-authored the book MacPerl: Power and Ease (ISBN : 1881957322) from Prime Time Freeware, writes the Perl News column for the Perl Journal, and runs the web sites http://use.perl.org/ and http://news.perl.org/. Chris lives in Massachusetts with his three dogs, two cats, and one wonderful and supportive wife, Jennifer. I'd like to dedicate this book to my wife, my parents, and my in-laws who've all given me encouragement & put up with me during deadlines. Aalhad Saraf Aalhad Saraf is in the Systems Software Group in IBM Labs. He has been with Linux since 1995. Perl, C, and C++ are his favorite tools. Has a Bachelors degree in Electronics Engineering from the University of Pune, a Post Graduate Diploma awarded by the national resource center of the 'Center for Development of Advanced Computing' (a scientific society of the Ministry of IT, Govt. of India). He worked on microcontrollers/embedded systems and hand-held computing devices in Syslab Automation and on an interactive gaming server for DishnetDSL – one of India's leading ISPs. He also teaches Perl, Software Engineering and Quality systems during his spare time. He Takes his table tennis seriously, fiddles around with a guitar, juggles tennis balls and is an omnivore when it comes to reading. He likes networks. He dreams of traveling through space sitting in a packet; playing with the civilization of Data, providing the subjects – bytes, with new worlds and increasingly better means of transport. Aalhad is 22 years old and aspires to get a Ph.D. in Computer Science some day. Table of Contents Introduction 1 Chapter 1: Introduction 7 Introduction 7 Key Features 8 Supported Platforms 9 Perl History and Versions 10 Essential Information 10 Building and Installing Perl 12 Installing Pre-built Perl Distributions 12 Installing Perl on UNIX 13 Installing Perl on Windows 13 Installing Perl on Macintosh 14 Building Perl from Source 14 Building a Threaded Perl Interpreter 17 Differences for Windows and Macintosh 17 Other Platforms 17 Building and Installing Modules 18 Installing Modules with the 'CPAN' Module 18 Starting and Configuring CPAN 19 Installing Modules 20 Listing and Searching CPAN 21 Reading Module Documentation Without Installing 23 Reloading CPAN 23 Configuring CPAN Options 24 Installing Modules by Hand 24 Running Perl 27 Starting Perl Applications 27 Perl on UNIX 28 Perl on Windows 28 Perl on Macintosh 29 The Command Line 29 Command Line Syntax 30 Supplying Arguments to Perl Scripts 30 Using Perl as a Generic Command Line Utility 31 The Perl Environment 32 General Environment Variables Used by Perl 32 Perl Specific Environment Variables 32 Summary 33 Table of Contents ii Chapter 2: Basic Concepts 35 Values and Variables 35 Whitespace 36 Data Types 36 Special Variables 39 Interpolation 39 Context 40 Scalar and List Context 41 Void Context 42 Operators 42 Blocks 43 Control Constructs 43 Loop Modifiers 45 Subroutines 46 Functions 47 Scoping 47 Chapter 3: Scalars 51 Value Conversion and Caching 51 Numbers 52 Integers 53 Integer Range and Big Integers 53 Converting Integers into Floating-Point Numbers 54 Converting Integers into Strings 54 Handling Different Number Bases 55 Floating-Point Numbers 56 Converting Floats into Integers 58 Converting Floats into Strings 58 The 'use integer' Pragma 60 Mathematical Functions 61 Strings 62 Quotes and Quoting 62 'Here' Documents 65 Bareword Strings and Version Numbers 67 Converting Strings into Numbers 68 Converting Strings into Lists and Hashes 69 Functions For Manipulating Strings 71 Print 71 Line Terminator Termination 72 Characters and Character Codes 73 Length and Position 73 Substrings and Vectors 74 Upper and Lower Case 75 Interpolation 75 Pattern Matching and Transliteration 75 Password Encryption 76 Low Level String Conversions 76 String Formatting 80 Summary 84 Table of Contents iii Chapter 4: Operators 87 Operators Versus Functions 87 Operator Types and Categories 88 Assignment 89 Arithmetic 89 Shift 91 String and List 91 Logical 93 Bitwise 94 Combination Assignment 97 Increment and Decrement 98 Comparison 99 Regular Expression Binding 101 Comma and Relationship 101 Reference and Dereference 102 The Arrow 102 Range 103 Ternary 105 Precedence and Associativity 106 Precedence and Parentheses 107 Disabling Functions and Operators 110 Overriding Operators 113 Summary 114 Chapter 5: Beyond Scalars – More Data Types 117 Lists and Arrays 117 Manipulating Arrays 119 Modifying the Contents of an Array 119 Counting an Array 121 Adding Elements to an Array 122 Resizing and Truncating an Array 123 Removing Elements from an Array 123 Removing All Elements from an Array 125 Sorting and Reversing Lists and Arrays 125 Changing the Starting Index Value 127 Converting Lists and Arrays into Scalars 127 Taking References 127 Converting Lists into Formatted Strings 127 Hashes 129 Manipulating Hashes 131 Adding and Modifying Hash Values 131 Removing Hash Keys and Values 132 Converting Lists and Arrays into Hashes 132 Reversing Hashes 133 Accessing and Iterating Over Hashes 134 Converting Hashes into Scalars 137 Converting Hashes into Arrays 138 The Special Hash '%ENV' 138 Configuring Programs via '%ENV' 140 Handling Tainted Input from '%ENV' 140 'Env.pm' 141 Table of Contents iv References 142 Hard References 142 Creating References 143 Comparing References 144 Dereferencing 145 Working with References 146 Passing References to Subroutines 147 Finding the Type of a Reference 148 Complex Data Structures 151 The Problem with Nesting – My Lists Went Flat! 151 Lists of Lists and Multidimensional Arrays 151 Hashes of Hashes and Other Animals 153 Adding to and Modifying Complex Data Structures 154 Creating Complex Data Structures Programmatically 155 Traversing Complex Data Structures 158 Typeglobs 161 Defining Typeglobs 161 Manipulating Typeglobs 162 Accessing Typeglobs 163 The Undefined Value 164 Tests of Existence 166 Using the Undefined Value 167 Using 'undef' as a Function 168 Constants 169 Declaring Scalar Constants with the 'constant' Pragma 169 Declaring List and Hash Constants 171 Constant References 171 Listing and Checking for the Existence of Constants 172 Summary 172 Chapter 6: Structure, Flow, and Control 175 Expressions, Statements, and Blocks 175 Declarations 176 Expressions and Simple Statements 176 Blocks and Compound Statements 177 Blocks in Perl Statements 178 Naked Blocks 178 Defining the Main Program as a Block 179 Blocks as Loops 180 The 'do' Block 181 Special Blocks 182 Conditional Statements 183 What Is Truth? 184 'if', 'else', and 'elsif' 185 'unless' 187 Writing Conditions with Logical Operators 188 The Ternary Operator 189 Switches and Multi-Branched Conditions 192 Returning Values from Multi-Branched Conditions 194 [...]... 'Win32::API' module Using Perl from C First Steps 872 874 875 875 875 Building a Program (The Hard Way) Building a Program (The Easy Way) 876 877 Implementing the Perl Interpreter Embedding Perl Code Getting Perl Values Using Perl Subroutines Working with Perl Internals Using Modules 877 880 881 882 884 886 The Java -Perl Lingo 888 xvii Table of Contents Perl and COM PerlCOM 'PerlCtrl' Miscellaneous Languages... of Perl programmers, this is a good thing; in the eyes of advocates of some other languages, it isn't Perl' s anti-motto really ought to be 'Just Because You Can Do It, Doesn't Mean You Should.'; Perl does not impose good programming practices, so it is also easy to write badly constructed and hard-to-read code through sloppy programming Perl is a very practically-minded language, and takes a no-frills... code on non-UNIX ports of Perl, notably ActivePerl's PPM package tool Finally, we look at the various ways of running Perl, and setting up the operating system to recognize Perl scripts as Perl scripts We also take a look at the Perl command line together with special environment variables, and examine one way to create stand-alone Perl applications that can run without the benefit of a Perl installation... of Perl is its implementation of libraries with modules, which has made it a genuinely extensible language With its clarity, logical structure, and practical approach, Professional Perl Programming is the ideal guide and companion into the world of Perl programming Who Is This Book For? The breadth and depth of this book make it immensely useful for both the newcomer to Perl and the experienced Perl. .. Over Reading Detecting the End-of-File Reading a Single Character Writing to Filehandles Buffering and Autoflush Mode Alternatives to 'print' Handling Binary and Text Files The 'binmode' Function The 'open' Pragma Random Access 'seek' to a Specific Place within a File Clearing the End-of-File Condition with 'seek' Writing at the End-of-File Finding the Current Position Object-Oriented Random Access 426... of professional developers sharing their hard earned knowledge Following in the Wrox tradition, this book goes beyond merely reprising the original (and free) documentation supplied with the language and applies a pragmatic, example based approach to every subject that it covers Whether Perl is an old acquaintance or a new frontier, any Perl developer will find plenty to discover in Professional Perl. .. programming with Perl objects We are shown how to write object classes and are given a detailed look at inheritance and subclassing The chapter covers keeping data private, destroying objects, and operator overloading The last section discusses a special feature of Perl: ties and tied objects Chapter 20 stops looking at Perl from the surface and takes us inside the Perl interpreter We examine how Perl. .. Chapter 14: Command-Line and Shell Interaction Parsing-Command Line Arguments Command-Line Conventions The '@ARGV' Array Passing Arguments to Perl Itself Setting Variables from '@ARGV' Reading Files from '@ARGV' '@ARGV' and Standard Input Simple Command-Line Processing with 'Getopt::Std' Basic Processing with 'getopt' Slightly Smarter Processing with 'getopts' More Complex Command-line Processing with... An Example Tied Hash Class An Example Class Using 'Tie::StdHash' Summary Chapter 20: Inside Perl Analyzing the Perl Binary – 'Config.pm' 'perl -V' How It Works Platform Compiler Linker and Libraries Dynamic Linking Under the Hood Around the Source Tree Building Perl 'metaconfig' Rather than 'autoconf'? How Perl Works Parsing Compiling Interpreting Internal Variable Types PVs IVs NVs Arrays and Hashes... create simple Perl shells and how to integrate the underlying shell into our Perl scripts The next chapter discusses programming terminal input and output We show different ways of writing to terminals, including using the Term::ReadKey and Term::ReadLine modules The chapter then addresses how to write to the screen and introduces high-level terminal modules Finally, Chapter 15 shows us the low-level interface . 24 Running Perl 27 Starting Perl Applications 27 Perl on UNIX 28 Perl on Windows 28 Perl on Macintosh 29 The Command Line 29 Command Line Syntax 30 Supplying Arguments to Perl Scripts 30 Using Perl. Platforms 9 Perl History and Versions 10 Essential Information 10 Building and Installing Perl 12 Installing Pre-built Perl Distributions 12 Installing Perl on UNIX 13 Installing Perl on Windows. Team-Fly ® Professional Perl Programming © 2001 Wrox Press All rights reserved. No part of this book may be reproduced, stored