Classic Shell Scripting. Hidden Commands that Unlock the Power of Unix (e-book)

Classic Shell Scripting. Hidden Commands that Unlock the Power of Unix (e-book) - Opis

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. Spis treści:
Classic Shell Scripting
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A Note Regarding Supplemental (...) więcej Files
Foreword
Preface
Intended Audience
What You Should Already Know
Chapter Summary
Conventions Used in This Book
Code Examples
Unix Tools for Windows Systems
Cygwin
DJGPP
MKS Toolkit
AT&T UWIN
Safari Enabled
Wed Like to Hear from You
Acknowledgments
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
2.5.1. Commands and Arguments
2.5.2. Variables
2.5.3. Simple Output with echo
2.5.4. Fancier Output with printf
2.5.5. Basic I/O Redirection
2.5.5.1. Redirection and pipelines
2.5.5.2. Special files: /dev/null and /dev/tty
2.5.6. Basic Command Searching
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
3.1.1. Simple grep
3.2. Regular Expressions
3.2.1. What Is a Regular Expression?
3.2.1.1. POSIX bracket expressions
3.2.2. Basic Regular Expressions
3.2.2.1. Matching single characters
3.2.2.2. Backreferences
3.2.2.3. Matching multiple characters with one expression
3.2.2.4. Anchoring text matches
3.2.2.5. BRE operator precedence
3.2.3. Extended Regular Expressions
3.2.3.1. Matching single characters
3.2.3.2. Backreferences don't exist
3.2.3.3. Matching multiple regular expressions with one expression
3.2.3.4. Alternation
3.2.3.5. Grouping
3.2.3.6. Anchoring text matches
3.2.3.7. ERE operator precedence
3.2.4. Regular Expression Extensions
3.2.5. Which Programs Use Which Regular Expressions?
3.2.6. Making Substitutions in Text Files
3.2.7. Basic Usage
3.2.7.1. Substitution details
3.2.8. sed Operation
3.2.8.1. To print or not to print
3.2.9. Matching Specific Lines
3.2.10. How Much Text Gets Changed?
3.2.11. Lines Versus Strings
3.3. Working with Fields
3.3.1. Text File Conventions
3.3.2. Selecting Fields with cut
3.3.3. Joining Fields with join
3.3.4. Rearranging Fields with awk
3.3.4.1. Patterns and actions
3.3.4.2. Fields
3.3.4.3. Setting the field separators
3.3.4.4. Printing lines
3.3.4.5. Startup and cleanup actions
3.4. Summary
4. Text Processing Tools
4.1. Sorting Text
4.1.1. Sorting by Lines
4.1.2. Sorting by Fields
4.1.3. Sorting Text Blocks
4.1.4. Sort Efficiency
4.1.5. Sort Stability
4.1.6. Sort Wrap-Up
4.2. Removing Duplicates
4.3. Reformatting Paragraphs
4.4. Counting Lines, Words, and Characters
4.5. Printing
4.5.1. Evolution of Printing Technology
4.5.2. Other Printing Software
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
6.1.1. Variable Assignment and the Environment
6.1.2. Parameter Expansion
6.1.2.1. Expansion operators
6.1.2.2. Positional parameters
6.1.2.3. Special variables
6.1.3. Arithmetic Expansion
6.2. Exit Statuses
6.2.1. Exit Status Values
6.2.2. if-elif-else-fi
6.2.3. Logical NOT, AND, and OR
6.2.4. The test Command
6.3. The case Statement
6.4. Looping
6.4.1. for Loops
6.4.2. while and until Loops
6.4.3. break and continue
6.4.4. shift and Option Processing
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
7.3.1. Additional Redirection Operators
7.3.2. File Descriptor Manipulation
7.4. The Full Story on printf
7.5. Tilde Expansion and Wildcards
7.5.1. Tilde Expansion
7.5.2. Wildcarding
7.5.2.1. Hidden files
7.6. Command Substitution
7.6.1. Using sed for the head Command
7.6.2. Creating a Mailing List
7.6.3. Simple Math: expr
7.7. Quoting
7.8. Evaluation Order and eval
7.8.1. The eval Statement
7.8.2. Subshells and Code Blocks
7.9. Built-in Commands
7.9.1. The set Command
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
9.3.1. Comments and Whitespace
9.3.2. Strings and String Expressions
9.3.3. Numbers and Numeric Expressions
9.3.4. Scalar Variables
9.3.5. Array Variables
9.3.6. Command-Line Arguments
9.3.7. Environment Variables
9.4. Records and Fields
9.4.1. Record Separators
9.4.2. Field Separators
9.4.3. Fields
9.5. Patterns and Actions
9.5.1. Patterns
9.5.2. Actions
9.6. One-Line Programs in awk
9.7. Statements
9.7.1. Sequential Execution
9.7.2. Conditional Execution
9.7.3. Iterative Execution
9.7.4. Array Membership Testing
9.7.5. Other Control Flow Statements
9.7.6. User-Controlled Input
9.7.7. Output Redirection
9.7.8. Running External Programs
9.8. User-Defined Functions
9.9. String Functions
9.9.1. Substring Extraction
9.9.2. Lettercase Conversion
9.9.3. String Searching
9.9.4. String Matching
9.9.5. String Substitution
9.9.6. String Splitting
9.9.7. String Reconstruction
9.9.8. String Formatting
9.10. Numeric Functions
9.11. Summary
10. Working with Files
10.1. Listing Files
10.1.1. Long File Listings
10.1.2. Listing File Metadata
10.2. Updating Modification Times with touch
10.3. Creating and Using Temporary Files
10.3.1. The $$ Variable
10.3.2. The mktemp Program
10.3.3. The /dev/random and /dev/urandom Special Files
10.4. Finding Files
10.4.1. Finding Files Quickly
10.4.2. Finding Where Commands Are Stored
10.4.3. The find Command
10.4.3.1. Using the find command
10.4.3.2. A simple find script
10.4.3.3. A complex find script
10.4.4. Finding Problem Files
10.5. Running Commands: xargs
10.6. Filesystem Space Information
10.6.1. The df Command
10.6.2. The du Command
10.7. Comparing Files
10.7.1. The cmp and diff Utilities
10.7.2. The patch Utility
10.7.3. File Checksum Matching
10.7.4. Digital Signature Verification
10.8. Summary
11. Extended Example: Merging User Databases
11.1. The Problem
11.2. The Password Files
11.3. Merging Password Files
11.3.1. Separating Users by Manageability
11.3.2. Managing UIDs
11.3.3. Creating User-Old UID-New UID Triples
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
12.3.1. Private Spelling Dictionaries
12.3.2. ispell and aspell
12.4. A Spellchecker in awk
12.4.1. Introductory Comments
12.4.2. Main Body
12.4.3. initialize( )
12.4.4. get_dictionaries( )
12.4.5. scan_options( )
12.4.6. load_dictionaries( )
12.4.7. load_suffixes( )
12.4.8. order_suffixes( )
12.4.9. spell_check_line( )
12.4.10. spell_check_word( )
12.4.11. strip_suffixes( )
12.4.12. report_exceptions( )
12.4.13. Retrospective on Our Spellchecker
12.4.14. Efficiency of awk Programs
12.5. Summary
13. Processes
13.1. Process Creation
13.2. Process Listing
13.3. Process Control and Deletion
13.3.1. Deleting Processes
13.3.2. Trapping Process Signals
13.4. Process System-Call Tracing
13.5. Process Accounting
13.6. Delayed Scheduling of Processes
13.6.1. sleep: Delay Awhile
13.6.2. at: Delay Until Specified Time
13.6.3. batch: Delay for Resource Control
13.6.4. crontab: Rerun at Specified Times
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
14.3.1. The select Loop
14.3.2. Extended Test Facility
14.3.3. Extended Pattern Matching
14.3.4. Brace Expansion
14.3.5. Process Substitution
14.3.6. Indexed Arrays
14.3.7. Miscellaneous Extensions
14.4. Download Information
14.4.1. bash
14.4.2. ksh93
14.5. Other Extended Bourne-Style Shells
14.6. Shell Versions
14.7. Shell Initialization and Termination
14.7.1. Bourne Shell (sh) Startup
14.7.2. Korn Shell Startup
14.7.3. Bourne-Again Shell Startup and Termination
14.7.4. Z-Shell Startup 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
A.1. Manual Pages for pathfind
A.2. Manual-Page Syntax Checking
A.3. Manual-Page Format Conversion
A.4. Manual-Page Installation
B. Files and Filesystems
B.1. What Is a File?
B.2. How Are Files Named?
B.3. What's in a Unix File?
B.4. The Unix Hierarchical Filesystem
B.4.1. Filesystem Structure
B.4.2. Layered Filesystems
B.4.3. Filesystem Implementation Overview
B.4.4. Devices as Unix Files
B.5. How Big Can Unix Files Be?
B.6. Unix File Attributes
B.6.1. File Ownership and Permissions
B.6.1.1. Ownership
B.6.1.2. Permissions
B.6.1.3. Default permissions
B.6.1.4. Permissions in action
B.6.1.5. Directory permissions
B.6.2. File Timestamps
B.6.3. File Links
B.6.4. File Size and Timestamp Variations
B.6.5. Other File Metadata
B.7. Unix File Ownership and Privacy Issues
B.8. Unix File Extension Conventions
B.9. Summary
C. Important Unix Commands
C.1. Shells and Built-in Commands
C.2. Text Manipulation
C.3. Files
C.4. Processes
C.5. Miscellaneous Programs
16. Bibliography
16.1. Unix Programmer's Manuals
16.2. Programming with the Unix Mindset
16.3. Awk and Shell
16.4. Standards
16.5. Security and Cryptography
16.6. Unix Internals
16.7. O'Reilly Books
16.8. Miscellaneous Books
About the Authors
Colophon
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