Classic Shell Scripting (Paperback)

Arnold Robbins, Nelson H.F. Beebe




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:



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