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Classic Shell Scripting
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.
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
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