Shell scripting skills never go out of style. It's the shell that unlocks the real potential of Unix. Shell scripting is essential for Unix users and system administrators-a way to quickly harness and customize the full power of any Unix system. With shell scripts, you can combine the fundamental Unix text and file processing commands to crunch data and automate repetitive tasks. But beneath this simple promise lies a treacherous ocean of variations in Unix commands and standards. Classic Shell Scripting is written to help you reliably navigate these tricky waters. Writing shell scripts requires more than just a knowledge of the shell language, it also requires familiarity with the individual Unix programs: why each one is there, how to use them by themselves, and in combination with the other programs. The authors are intimately familiar with the tips and tricks that can be used to create excellent scripts, as well as the traps that can make your best effort a bad shell script. With Classic Shell Scripting you'll avoid hours of wasted effort. You'll learn not only write useful shell scripts, but how to do it properly and portably. The ability to program and customize the shell quickly, reliably, and portably to get the best out of any individual system is an important skill for anyone operating and maintaining Unix or Linux systems. Classic Shell Scripting gives you everything you need to master these essential skills.

Table of Contents:
Foreword Preface 1. Background 1.1 Unix History 1.2 Software Tools Principles 1.3 Summary 2. Getting Started 2.1 Scripting Languages Versus Compiled Languages 2.2 Why Use a Shell Script? 2.3 A Simple Script 2.4 Self-Contained Scripts: The #! First Line 2.5 Basic Shell Constructs 2.6 Accessing Shell Script Arguments 2.7 Simple Execution Tracing 2.8 Internationalization and Localization 2.9 Summary 3. Searching and Substitutions 3.1 Searching for Text 3.2 Regular Expressions 3.3 Working with Fields 3.4 Summary 4. Text Processing Tools 4.1 Sorting Text 4.2 Removing Duplicates 4.3 Reformatting Paragraphs 4.4 Counting Lines, Words, and Characters 4.5 Printing 4.6 Extracting the First and Last Lines 4.7 Summary 5. Pipelines Can Do Amazing Things 5.1 Extracting Data from Structured Text Files 5.2 Structured Data for the Web 5.3 Cheating at Word Puzzles 5.4 Word Lists 5.5 Tag Lists 5.6 Summary 6. Variables, Making Decisions, and Repeating Actions 6.1 Variables and Arithmetic 6.2 Exit Statuses 6.3 The case Statement 6.4 Looping 6.5 Functions 6.6 Summary 7. Input and Output, Files, and Command Evaluation 7.1 Standard Input, Output, and Error 7.2 Reading Lines with read 7.3 More About Redirections 7.4 The Full Story on printf 7.5 Tilde Expansion and Wildcards 7.6 Command Substitution 7.7 Quoting 7.8 Evaluation Order and eval 7.9 Built-in Commands 7.10 Summary 8. Production Scripts 8.1 Path Searching 8.2 Automating Software Builds 8.3 Summary 9. Enough awk to Be Dangerous 9.1 The awk Command Line 9.2 The awk Programming Model 9.3 Program Elements 9.4 Records and Fields 9.5 Patterns and Actions 9.6 One-Line Programs in awk 9.7 Statements 9.8 User-Defined Functions 9.9 String Functions 9.10 Numeric Functions 9.11 Summary 10. Working with Files 10.1 Listing Files 10.2 Updating Modification Times with touch 10.3 Creating and Using Temporary Files 10.4 Finding Files 10.5 Running Commands: xargs 10.6 Filesystem Space Information 10.7 Comparing Files 10.8 Summary 11. Extended Example: Merging User Databases 11.1 The Problem 11.2 The Password Files 11.3 Merging Password Files 11.4 Changing File Ownership 11.5 Other Real-World Issues 11.6 Summary 12. Spellchecking 12.1 The spell Program 12.2 The Original Unix Spellchecking Prototype 12.3 Improving ispell and aspell 12.4 A Spellchecker in awk 12.5 Summary 13. Processes 13.1 Process Creation 13.2 Process Listing 13.3 Process Control and Deletion 13.4 Process System-Call Tracing 13.5 Process Accounting 13.6 Delayed Scheduling of Processes 13.7 The /proc Filesystem 13.8 Summary 14. Shell Portability Issues and Extensions 14.1 Gotchas 14.2 The bash shopt Command 14.3 Common Extensions 14.4 Download Information 14.5 Other Extended Bourne-Style Shells 14.6 Shell Versions 14.7 Shell Initialization and Termination 14.8 Summary 15. Secure Shell Scripts: Getting Started 15.1 Tips for Secure Shell Scripts 15.2 Restricted Shell 15.3 Trojan Horses 15.4 Setuid Shell Scripts: A Bad Idea 15.5 ksh93 and Privileged Mode 15.6 Summary A. Writing Manual Pages B. Files and Filesystems C. Important Unix Commands Bibliography Glossary Index