teach yourself perl 5 in 21 days

Teach Yourself Perl 5 in 21 days
David Till
Table of Contents:
Introduction
Who Should Read This Book?●
Special Features of This Book●
Programming Examples●
End-of-Day Q& A and Workshop●
Conventions Used in This Book●
What You'll Learn in 21 Days●
Week 1 Week at a Glance
Where You're Going●
Day 1 Getting Started
What Is Perl?●
How Do I Find Perl?
Where Do I Get Perl?❍
Other Places to Get Perl❍
●
A Sample Perl Program●
Running a Perl Program
If Something Goes Wrong❍
●
The First Line of Your Perl Program: How Comments Work
Comments❍
●
Line 2: Statements, Tokens, and <STDIN>
Statements and Tokens❍
Tokens and White Space❍
What the Tokens Do: Reading from Standard Input❍
●
Line 3: Writing to Standard Output

Function Invocations and Arguments❍
●
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Error Messages●
Interpretive Languages Versus Compiled Languages●
Summary●
Q&A●
Workshop
Quiz❍
Exercises❍
●
Day 2 Basic Operators and Control Flow
Storing in Scalar Variables Assignment
The Definition of a Scalar Variable❍
Scalar Variable Syntax❍
Assigning a Value to a Scalar Variable❍
●
Performing Arithmetic
Example of Miles-to-Kilometers Conversion❍
The chop Library Function❍
●
Expressions
Assignments and Expressions❍
●
Other Perl Operators●
Introduction to Conditional Statements●
The if Statement
The Conditional Expression❍
The Statement Block❍

Testing for Equality Using ==❍
Other Comparison Operators❍
●
Two-Way Branching Using if and else●
Multi-Way Branching Using elsif●
Writing Loops Using the while Statement●
Nesting Conditional Statements●
Looping Using the until Statement●
Summary●
Q&A●
Workshop
Quiz❍
Exercises❍
●
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Day 3 Understanding Scalar Values
What Is a Scalar Value?●
Integer Scalar Values
Integer Scalar Value Limitations❍
●
Floating-Point Scalar Values
Floating-Point Arithmetic and Round-Off Error❍
●
Using Octal and Hexadecimal Notation
Decimal Notation❍
Octal Notation❍
Hexadecimal Notation❍
Why Bother?❍
●

Character Strings
Using Double-Quoted Strings❍
Escape Sequences❍
Single-Quoted Strings❍
●
Interchangeability of Strings and Numeric Values
Initial Values of Scalar Variables❍
●
Summary●
Q&A●
Workshop
Quiz❍
Exercises❍
●
Day 4 More Operators
Using the Arithmetic Operators
Exponentiation❍
The Remainder Operator❍
Unary Negation❍
●
Using Comparison Operators
Integer-Comparison Operators❍
String-Comparison Operators❍
String Comparison Versus Integer Comparison❍
Comparison and Floating-Point Numbers❍
●
Using Logical Operators●
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Evaluation Within Logical Operators❍

Logical Operators as Subexpressions❍
Using Bit-Manipulation Operators
What Bits Are and How They Are Used❍
The Bit-Manipulation Operators❍
●
Using the Assignment Operators
Assignment Operators as Subexpressions❍
●
Using Autoincrement and Autodecrement
The Autoincrement Operator Pre-Increment❍
The Autoincrement Operator Post-Increment❍
The Autodecrement Operator❍
Using Autoincrement With Strings❍
●
The String Concatenation and Repetition Operators
The String-Concatenation Operator❍
The String-Repetition Operator❍
Concatenation and Assignment❍
●
Other Perl Operators
The Comma Operator❍
The Conditional Operator❍
●
The Order of Operations
Precedence❍
Associativity❍
Forcing Precedence Using Parentheses❍
●
Summary●
Q&A●

Workshop
Quiz❍
Exercises❍
●
Day 5 Lists and Array Variables
Introducing Lists●
Scalar Variables and Lists
Lists and String Substitution❍
●
Storing Lists in Array Variables●
Accessing an Element of an Array Variable●
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More Details on Array Element Names❍
Using Lists and Arrays in Perl Programs
Using Brackets and Substituting for Variables❍
●
Using List Ranges
Expressions and List Ranges❍
●
More on Assignment and Array Variables
Copying from One Array Variable to Another❍
Using Array Variables in Lists❍
Substituting for Array Variables in Strings❍
Assigning to Scalar Variables from Array Variables❍
●
Retrieving the Length of a List●
Using Array Slices
Using List Ranges in Array-Slice Subscripts❍
Using Variables in Array-Slice Subscripts❍

Assigning to Array Slices❍
Overlapping Array Slices❍
Using the Array-Slice Notation as a Shorthand❍
●
Reading an Array from the Standard Input File●
Array Library Functions
Sorting a List or Array Variable❍
Reversing a List or Array Variable❍
Using chop on Array Variables❍
Creating a Single String from a List❍
Splitting a String into a List❍
Other List-Manipulation Functions❍
●
Summary●
Q&A●
Workshop
Quiz❍
Exercises❍
●
Day 6 Reading from and Writing to Files
Opening a File
The File Variable❍
The Filename❍
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The File Mode❍
Checking Whether the Open Succeeded❍
Reading from a File
File Variables and the Standard Input File❍

Terminating a Program Using die❍
Reading into Array Variables❍
●
Writing to a File
The Standard Output File Variable❍
Merging Two Files into One❍
●
Redirecting Standard Input and Standard Output●
The Standard Error File●
Closing a File●
Determining the Status of a File
File-Test Operator Syntax❍
Available File-Test Operators❍
More on the -e Operator❍
Testing for Read Permission-the -r Operator❍
Checking for Other Permissions❍
Checking for Empty Files❍
Using File-Test Operators with File Variables❍
●
Reading from a Sequence of Files
Reading into an Array Variable❍
●
Using Command-Line Arguments as Values
ARGV and the <> Operator❍
●
Opening Pipes●
Summary●
Q&A●
Workshop
Quiz❍

Exercises❍
●
Day 7 Pattern Matching
Introduction●
The Match Operators
Match-Operator Precedence❍
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Special Characters in Patterns
The + Character❍
The [] Special Characters❍
The * and ? Special Characters❍
Escape Sequences for Special Characters❍
Matching Any Letter or Number❍
Anchoring Patterns❍
Variable Substitution in Patterns❍
Excluding Alternatives❍
Character-Range Escape Sequences❍
Matching Any Character❍
Matching a Specified Number of Occurrences❍
Specifying Choices❍
Reusing Portions of Patterns❍
Pattern-Sequence Scalar Variables❍
Special-Character Precedence❍
Specifying a Different Pattern Delimiter❍
●
Pattern-Matching Options
Matching All Possible Patterns❍
Ignoring Case❍

Treating the String as Multiple Lines❍
Evaluating a Pattern Only Once❍
Treating the String as a Single Line❍
Using White Space in Patterns❍
●
The Substitution Operator
Using Pattern-Sequence Variables in Substitutions❍
Options for the Substitution Operator❍
Evaluating a Pattern Only Once❍
Treating the String as Single or Multiple Lines❍
Using White Space in Patterns❍
Specifying a Different Delimiter❍
●
The Translation Operator
Options for the Translation Operator❍
●
Extended Pattern-Matching
Parenthesizing Without Saving in Memory❍
Embedding Pattern Options❍
●
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Positive and Negative Look-Ahead❍
Pattern Comments❍
Summary●
Q&A●
Workshop
Quiz❍
Exercises❍
●

Week 1 Week 1 in Review
Week 2 Week 2 at a Glance
Where You're Going●
Day 8 More Control Structures
Using Single-Line Conditional Statements
Problems with Single-Line Conditional Statements❍
●
Looping Using the for Statement
Using the Comma Operator in a for Statement❍
●
Looping Through a List: The foreach Statement
The foreach Local Variable❍
Changing the Value of the Local Variable❍
Using Returned Lists in the foreach Statement❍
●
The do Statement●
Exiting a Loop Using the last Statement●
Using next to Start the Next Iteration of a Loop●
The redo Statement●
Using Labeled Blocks for Multilevel Jumps
Using next and redo with Labels❍
●
The continue Block●
The goto Statement●
Summary●
Q&A●
Workshop
Quiz❍
Exercises❍
●

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Day 9 Using Subroutines
What Is a Subroutine?●
Defining and Invoking a Subroutine
Forward References to Subroutines❍
●
Returning a Value from a Subroutine
Return Values and Conditional Expressions❍
●
The return Statement●
Using Local Variables in Subroutines
Initializing Local Variables❍
●
Passing Values to a Subroutine
Passing a List to a Subroutine❍
●
Calling Subroutines from Other Subroutines●
Recursive Subroutines●
Passing Arrays by Name Using Aliases●
Using the do Statement with Subroutines●
Specifying the Sort Order●
Predefined Subroutines
Creating Startup Code Using BEGIN❍
Creating Termination Code Using END❍
Handling Non-Existent Subroutines Using AUTOLOAD❍
●
Summary●
Q&A●
Workshop

Quiz❍
Exercises❍
●
Day 10 Associative Arrays
Limitations of Array Variables●
Definition●
Referring to Associative Array Elements●
Adding Elements to an Associative Array●
Creating Associative Arrays●
Copying Associative Arrays from Array Variables●
Adding and Deleting Array Elements●
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Listing Array Indexes and Values●
Looping Using an Associative Array●
Creating Data Structures Using Associative Arrays
Linked Lists❍
Structures❍
Trees❍
Databases❍
Example: A Calculator Program❍
●
Summary●
Q&A●
Workshop
Quiz❍
Exercises❍
●
Day 11 Formatting Your Output
Defining a Print Format●

Displaying a Print Format●
Displaying Values in a Print Format
Creating a General-Purpose Print Format❍
Choosing a Value-Field Format❍
Printing Value-Field Characters❍
Using the Multiline Field Format❍
●
Writing to Other Output Files
Saving the Default File Variable❍
●
Specifying a Page Header
Changing the Header Print Format❍
●
Setting the Page Length
Using print with Pagination❍
●
Formatting Long Character Strings
Eliminating Blank Lines When Formatting❍
Supplying an Indefinite Number of Lines❍
●
Formatting Output Using printf●
Summary●
Q&A●
Workshop●
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Quiz❍
Exercises❍
Day 12 Working with the File System
File Input and Output Functions

Basic Input and Output Functions❍
Skipping and Rereading Data❍
System Read and Write Functions❍
Reading Characters Using getc❍
Reading a Binary File Using binmode❍
●
Directory-Manipulation Functions
The mkdir Function❍
The chdir Function❍
The opendir Function❍
The closedir Function❍
The readdir Function❍
The telldir and seekdir Functions❍
The rewinddir Function❍
The rmdir Function❍
●
File-Attribute Functions
File-Relocation Functions❍
Link and Symbolic Link Functions❍
File-Permission Functions❍
Miscellaneous Attribute Functions❍
●
Using DBM Files
The dbmopen Function❍
The dbmclose Function❍
●
Summary●
Q&A●
Workshop
Quiz❍

Exercises❍
●
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Day 13 Process, String, and Mathematical
Functions
Process- and Program-Manipulation Functions
Starting a Process❍
Terminating a Program or Process❍
Execution Control Functions❍
Miscellaneous Control Functions❍
●
Mathematical Functions
The sin and cos Functions❍
The atan2 Function❍
The sqrt Function❍
The exp Function❍
The log Function❍
The abs Function❍
The rand and srand Functions❍
●
String-Manipulation Functions
The index Function❍
The rindex Function❍
The length Function❍
Retrieving String Length Using tr❍
The pos Function❍
The substr Function❍
The study Function❍
Case Conversion Functions❍

The quotemeta Function❍
The join Function❍
The sprintf Function❍
●
Summary●
Q&A●
Workshop
Quiz❍
Exercises❍
●
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Day 14 Scalar-Conversion and List-Manipulation
Functions
The chop Function●
The chomp Function●
The crypt Function●
The hex Function●
The int Function●
The oct Function
The oct Function and Hexadecimal Integers❍
●
The ord and chr Functions●
The scalar Function●
The pack Function
The pack Function and C Data Types❍
●
The unpack Function
Unpacking Strings❍
Skipping Characters When Unpacking❍

The unpack Function and uuencode❍
●
The vec Function●
The defined Function●
The undef Function●
Array and List Functions
The grep Function❍
The splice Function❍
The shift Function❍
The unshift Function❍
The push Function❍
The pop Function❍
Creating Stacks and Queues❍
The split Function❍
The sort and reverse Functions❍
The map Function❍
The wantarray Function❍
●
Associative Array Functions
The keys Function❍
The values Function❍
●
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The each Function❍
The delete Function❍
The exists Function❍
Summary●
Q&A●
Workshop

Quiz❍
Exercises❍
●
Week 2 Week 2 in Review
Week 3 Week 3 at a Glance
Where You're Going●
Day 15 System Functions
System Library Emulation Functions
The getgrent Function❍
The setgrent and endgrent Functions❍
The getgrnam Function❍
The getgrid Function❍
The getnetent Function❍
The getnetbyaddr Function❍
The getnetbyname Function❍
The setnetent and endnetent Functions❍
The gethostbyaddr Function❍
The gethostbyname Function❍
The gethostent, sethostent, and endhostent Functions❍
The getlogin Function❍
The getpgrp and setpgrp Functions❍
The getppid Function❍
The getpwnam Function❍
The getpwuid Function❍
The getpwent Function❍
The setpwent and endpwent Functions❍
The getpriority and setpriority Functions❍
●
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The getprotoent Function❍
The getprotobyname and getprotobynumber Functions❍
The setprotoent and endprotoent Functions❍
The getservent Function❍
The getservbyname and getservbyport Functions❍
The setservent and endservent Functions❍
The chroot Function❍
The ioctl Function❍
The alarm Function❍
Calling the System select Function❍
The dump Function❍
Socket-Manipulation Functions
The socket Function❍
The bind Function❍
The listen Function❍
The accept Function❍
The connect Function❍
The shutdown Function❍
The socketpair Function❍
The getsockopt and setsockopt Functions❍
The getsockname and getpeername Functions❍
●
The UNIX System V IPC Functions
IPC Functions and the require Statement❍
The msgget Function❍
The msgsnd Function❍
The msgrcv Function❍
The msgctl Function❍
The shmget Function❍
The shmwrite Function❍

The shmread Function❍
The shmctl Function❍
The semget Function❍
The semop Function❍
The semctl Function❍
●
Summary●
Q&A●
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Workshop
Quiz❍
Exercises❍
●
Day 16 Command-Line Options
Specifying Options
Specifying Options on the Command Line❍
Specifying an Option in the Program❍
●
The -v Option: Printing the Perl Version Number●
The -c Option: Checking Your Syntax●
The -w Option: Printing Warnings
Checking for Possible Typos❍
Checking for Redefined Subroutines❍
Checking for Incorrect Comparison Operators❍
●
The -e Option: Executing a Single-Line Program●
The -s Option: Supplying Your Own Command-Line Options
The -s Option and Other Command-Line Arguments❍
●

The -P Option: Using the C Preprocessor
The C Preprocessor: A Quick Overview❍
●
The -I Option: Searching for C Include Files●
The -n Option: Operating on Multiple Files●
The -p Option: Operating on Files and Printing●
The -i Option: Editing Files
Backing Up Input Files Using the -i Option❍
●
The -a Option: Splitting Lines●
The -F Option: Specifying the Split Pattern●
The -0 Option: Specifying Input End-of-Line●
The -l Option: Specifying Output End-of-Line●
The -x Option: Extracting a Program from a Message●
Miscellaneous Options
The -u Option❍
The -U Option❍
The -S Option❍
The -D Option❍
The -T Option: Writing Secure Programs❍
●
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The -d Option: Using the Perl Debugger●
Summary●
Q&A●
Workshop
Quiz❍
Exercises❍
●

Day 17 System Variables
Global Scalar Variables
The Default Scalar Variable: $_❍
The Program Name: $0❍
The User ID: $< and $>❍
The Group ID: $( and $)❍
The Version Number: $]❍
The Input Line Separator: $/❍
The Output Line Separator: $❍
The Output Field Separator: $,❍
The Array Element Separator: $"❍
The Number Output Format: $#❍
The eval Error Message: $@❍
The System Error Code: $?❍
The System Error Message: $!❍
The Current Line Number: $.❍
Multiline Matching: $*❍
The First Array Subscript: $[❍
Multidimensional Associative Arrays and the $; Variable❍
The Word-Break Specifier: $:❍
The Perl Process ID: $$❍
The Current Filename: $ARGV❍
The Write Accumulator: $^A❍
The Internal Debugging Value: $^D❍
The System File Flag: $^F❍
Controlling File Editing Using $^I❍
The Format Form-Feed Character: $^L❍
Controlling Debugging: $^P❍
●
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The Program Start Time: $^T❍
Suppressing Warning Messages: $^W❍
The $^X Variable❍
Pattern System Variables
Retrieving Matched Subpatterns❍
Retrieving the Entire Pattern: $&❍
Retrieving the Unmatched Text: the $` and $' Variables❍
The $+ Variable❍
●
File System Variables
The Default Print Format: $~❍
Specifying Page Length: $=❍
Lines Remaining on the Page: $-❍
The Page Header Print Format: $^❍
Buffering Output: $|❍
The Current Page Number: $%❍
●
Array System Variables
The @_ Variable❍
The @ARGV Variable❍
The @F Variable❍
The @INC Variable❍
The %INC Variable❍
The %ENV Variable❍
The %SIG Variable❍
●
Built-In File Variables
STDIN, STDOUT, and STDERR❍
ARGV❍

DATA❍
The Underscore File Variable❍
●
Specifying System Variable Names as Words●
Summary●
Q&A●
Workshop
Quiz❍
Exercises❍
●
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Day 18 References in Perl 5
Introduction to References●
Using References●
Using the Backslash Operator●
References and Arrays●
Multidimensional Arrays●
References to Subroutines
Using Subroutine Templates❍
●
Using Subroutines to Work with Multiple Arrays
Pass By Value or By Reference?❍
●
References to File Handles
What Does the *variable Operator Do?❍
●
Using Symbolic References… Again
Declaring Variables with Curly Braces❍
●

More on Hard Versus Symbolic References●
For More Information●
Summary●
Q&A●
Workshop
Quiz❍
●
Exercises●
Day 19 Object-Oriented Programming in Perl
An Introduction to Modules
The Three Important Rules❍
●
Classes in Perl●
Creating a Class●
Blessing a Constructor
Instance Variables❍
●
Methods●
Exporting Methods●
Invoking Methods●
Overrides●
Destructors●
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Inheritance●
Overriding Methods●
A Few Comments About Classes and Objects in Perl●
Summary●
Q&A●
Workshop

Quiz❍
Exercises❍
●
Day 20 Miscellaneous Features of Perl
The require Function
The require Function and Subroutine Libraries❍
Using require to Specify a Perl Version❍
●
The $#array Variables
Controlling Array Length Using $#array❍
●
Alternative String Delimiters
Defining Strings Using <<❍
●
Special Internal Values●
Using Back Quotes to Invoke System Commands●
Pattern Matching Using ?? and the reset Function
Using reset with Variables❍
●
Other Features of the <> Operator
Scalar Variable Substitution and <>❍
Creating a List of Filenames❍
●
Global Indirect References and Aliases●
Packages
Defining a Package❍
Switching Between Packages❍
The main Package❍
Referring to One Package from Another❍
Specifying No Current Package❍

Packages and Subroutines❍
Defining Private Data Using Packages❍
Packages and System Variables❍
Accessing Symbol Tables❍
●
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Modules
Creating a Module❍
Importing Modules Into Your Program❍
Using Predefined Modules❍
●
Using Perl in C Programs●
Perl and CGI Scripts●
Translators and Other Supplied Code●
Summary●
Q&A●
Workshop
Quiz❍
Exercises❍
●
Day 21 The Perl Debugger
Entering and Exiting the Perl Debugger
Entering the Debugger❍
Exiting the Debugger❍
●
Listing Your Program
The l command❍
The - Command❍
The w Command❍

The // and ?? Commands❍
The S Command❍
●
Stepping Through Programs
The s Command❍
The n Command❍
The f command❍
The Carriage-Return Command❍
The r Command❍
●
Displaying Variable Values
The X Command❍
The V Command❍
●
Breakpoints
The b Command❍
The c Command❍
●
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The L Command and Breakpoints❍
The d and D Commands❍
Tracing Program Execution●
Line Actions
The a Command❍
The A Command❍
The < and > Commands❍
Displaying Line Actions Using the L Command❍
●
Other Debugging Commands

Executing Other Perl Statements❍
The H Command: Listing Preceding Commands❍
The ! Command: Executing Previous Commands❍
The T Command: Stack Tracing❍
The p Command: Printing an Expression❍
The = Command: Defining Aliases❍
Predefining Aliases❍
The h Command: Debugger Help❍
●
Summary●
Q&A●
Workshop
Quiz❍
●
Week 3 Week 3 in Review
Appendix A Answers
Answers for Day 1, "Getting Started"
Quiz❍
Exercises❍
●
Answers for Day 2, "Basic Operators and Control Flow"
Quiz❍
Exercises❍
●
Answers for Day 3, "Understanding Scalar Values"
Quiz❍
Exercises❍
●
Answers for Day 4, "More Operators"●
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Quiz❍
Exercises❍
Answers for Day 5, "Lists and Array Variables"
Quiz❍
Exercises❍
●
Answers for Day 6, "Reading from and Writing to Files"
Quiz❍
Exercises❍
●
Answers for Day 7, "Pattern Matching"
Quiz❍
Exercises❍
●
Answers for Day 8, "More Control Structures"
Quiz❍
Exercises❍
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Answers for Day 9, "Using Subroutines"
Quiz❍
Exercises❍
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Answers for Day 10, "Associative Arrays"
Quiz❍
Exercises❍
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Answers for Day 11, "Formatting Your Output"
Quiz❍
Exercises❍

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Answers for Day 12, "Working with the File System"
Quiz❍
Exercises❍
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Answers for Day 13, "Process, String, and Mathematical Functions"
Quiz❍
Exercises❍
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Answers for Day 14, "Scalar-Conversion and List-Manipulation Functions"
Quiz❍
Exercises❍
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Answers for Day 15, "System Functions"
Quiz❍
Exercises❍
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Answers for Day 16, "Command-Line Options"●
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Quiz❍
Exercises❍
Answers for Day 17, "System Variables"
Quiz❍
Exercises❍
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Answers for Day 18, "References in
Perl 5"
Quiz❍
Exercises❍

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Answers for Day 19, "Object-Oriented Programming in Perl"
Quiz❍
Exercises❍
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Answers for Day 20, "Miscellaneous Features of Perl"
Quiz❍
Exercises❍
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Answers for Day 21, "The Perl Debugger"
Quiz❍
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Appendix B ASCII Character Set
Credits
Copyright © 1996 by Sams Publishing
SECOND EDITION
All rights reserved. No part of this book shall be reproduced, stored in a retrieval system, or transmitted by
any means, electronic, mechanical, photocopying, recording, or otherwise, without written permission from
the publisher. No patent liability is assumed with respect to the use of the information contained herein.
Although every precaution has been taken in the preparation of this book, the publisher and author assume
no responsibility for errors or omissions. Neither is any liability assumed for damages resulting from the use
of the information contained herein. For information, address Sams Publishing, 201 W. 103rd St.,
Indianapolis, IN 46290.
International Standard Book Number: 0-672-30894-0 HTML conversion by :
M/s. LeafWriters (India) Pvt. Ltd.
Website :
e-mail :
Publisher and President Richard K. Swadley Acquisitions Manager Greg Wiegand
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Development Manager Dean Miller Managing Editor Cindy Morrow
Marketing Manager John Pierce Assistant Marketing
Manager
Kristina Perry
Acquisitions Editor Chris Denny Development Editors Angelique Brittingham,
Keith Davenport
Software Development
Specialist
Steve Straiger Production Editor Tonya R. Simpson
Copy Editor Kimberly K. Hannel Technical Reviewer Elliotte Rusty Harold
Editorial Coordinator Bill Whitmer Technical Edit
Coordinator
Lynette Quinn
Formatter Frank Sinclair Editorial Assistants Carol Ackerman, Andi
Richter Rhonda,
Tinch-Mize
Cover Designer Tim Amrhein Book Designer Gary Adair
Copy Writer Peter Fuller Production Team
Supervisor
Brad Chinn
Production Michael Brumitt, Charlotte Clapp, Jason Hand, Sonja Hart, Louisa Klucznik,
Ayanna Lacey, Clint Lahnen, Paula Lowell, Laura Robbins, Bobbi Satterfield,
Carol Sheehan, Chris Wilcox
Acknowledgments
I would like to thank the following people for their help:
David Macklem at Sietec Open Systems for allowing me to take the time off to work on the first
edition of this book
●
Everyone at Sams Publishing, for their efforts and encouragement●
Jim Gardner, for telling the people at Sams Publishing about me●

I'd also like to thank all those friends of mine (you know who you are) who tolerated my going stir-crazy as
my deadlines approached.
About the Authors
David Till
David Till is a technical writer working in Toronto, Ontario, Canada. He holds a master's degree in
computer science from the University of Waterloo; programming languages was his major field of study.
He also has worked in compiler development and on version-control software. He lists his hobbies as
"writing, comedy, walking, duplicate bridge, and fanatical support of the Toronto Blue Jays."
He can be reached via e-mail at or , or on the
World Wide Web at />Kamran Husain
Kamran Husain is a software consultant with experience in UNIX system programming. He has dabbled in
all sorts of software for real-time systems applications, telecommunications, seismic data acquisition and
navigation, X Window/Motif and Microsoft Windows applications. He refuses to divulge any more of his
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