In this quick reference, you'll find everything you need to know about the bash shell. Whether you print it out or read it on the screen, this PDF gives you the answers to the annoying questions that always come up when you're writing shell scripts: What characters do you need to quote? How do you get variable substitution to do exactly what you want? How do you use arrays? It's also helpful for interactive use. If you're a Unix user or programmer, or if you're using bash on Windows, you'll find this quick reference indispensable.

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 to not only to 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

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 Chapter 1: Background Chapter 2: Getting Started Chapter 3: Searching and Substitutions Chapter 4: Text Processing Tools Chapter 5: Pipelines Can Do Amazing Things Chapter 6: Variables, Making Decisions, and Repeating Actions Chapter 7: Input and Output, Files, and Command Evaluation Chapter 8: Production Scripts Chapter 9: Enough awk to Be Dangerous Chapter 10: Working with Files Chapter 11: Extended Example: Merging User Databases Chapter 12: Spellchecking Chapter 13: Processes Chapter 14: Shell Portability Issues and Extensions Chapter 15: Secure Shell Scripts: Getting Started Appendix A: Writing Manual Pages Appendix B: Files and Filesystems Appendix C: Important Unix Commands Chapter 16: Bibliography Colophon 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: 1Background1 2Getting started8 3Searching and substitutions30 4Text processing tools67 5Pipelines can do amazing things87 6Variables, making decisions, and repeating actions109 7Input and output, files, and command evaluation140 8Production scripts177 9Enough awk to be dangerous223 10Working with files267 11Extended example : merging user databases308 12Spellchecking325 13Processes352 14Shell portability issues and extensions381 15Secure shell scripts : getting started413 Non-Fiction,Science,COMPUTERS / Operating Systems / UNIX,Reference

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 to not only to 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

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.About the AuthorArnold Robbins, an Atlanta native, is a professional programmer and technical author. He has worked with Unix systems since 1980, when he was introduced to a PDP-11 running a version of Sixth Edition Unix. He has been a heavy AWK user since 1987, when he became involved with gawk, the GNU project's version of AWK. As a member of the POSIX 1003.2 balloting group, he helped shape the POSIX standard for AWK. He is currently the maintainer of gawk and its documentation. He is also coauthor of the sixth edition of O'Reilly's Learning the vi Editor. Since late 1997, he and his family have been living happily in Israel.Nelson Beebe is a long time Unix user and system administrator, and has helped for years on Usenet newsgroups.

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 to not only to 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

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 to not only to 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

Describes how to create and customize shell scrips for UNIX.

xxii, 534 p. : 24 cm Includes bibliographical references (p. 478-483) and index

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 to not only to 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

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 to not only to 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

Classic Shell Scripting - 2005

Table of Contents 5 Foreword 11 Preface 13 Intended Audience 14 What You Should Already Know 16 Chapter Summary 16 Conventions Used in This Book 19 Code Examples 21 Unix Tools for Windows Systems 21 Cygwin 21 DJGPP 22 MKS Toolkit 22 AT&T UWIN 22 Safari Enabled 23 We’d Like to Hear from You 23 Acknowledgments 24 Chapter 1. Background 25 1.1 Unix History 25 1.2 Software Tools Principles 28 1.3 Summary 30 Chapter 2. Getting Started 32 2.1 Scripting Languages Versus Compiled Languages 32 2.2 Why Use a Shell Script? 33 2.3 A Simple Script 33 2.4 Self-Contained Scripts: The #! First Line 34 2.5 Basic Shell Constructs 36 2.5.1 Commands and Arguments 36 2.5.2 Variables 38 2.5.3 Simple Output with echo 39 2.5.4 Fancier Output with printf 41 2.5.5 Basic I/O Redirection 42 2.5.5.1 Redirection and pipelines 43 2.5.5.2 Special files: /dev/null and /dev/tty 45 2.5.6 Basic Command Searching 46 2.6 Accessing Shell Script Arguments 47 2.7 Simple Execution Tracing 48 2.8 Internationalization and Localization 49 2.9 Summary 52 Chapter 3. Searching and Substitutions 54 3.1 Searching for Text 54 3.1.1 Simple grep 55 3.2 Regular Expressions 55 3.2.1 What Is a Regular Expression? 57 3.2.1.1 POSIX bracket expressions 59 3.2.2 Basic Regular Expressions 61 3.2.2.1 Matching single characters 61 3.2.2.2 Backreferences 63 3.2.2.3 Matching multiple characters with one expression 64 3.2.2.4 Anchoring text matches 65 3.2.2.5 BRE operator precedence 66 3.2.3 Extended Regular Expressions 66 3.2.3.1 Matching single characters 66 3.2.3.2 Backreferences don’t exist 66 3.2.3.3 Matching multiple regular expressions with one expression 67 3.2.3.4 Alternation 67 3.2.3.5 Grouping 68 3.2.3.6 Anchoring text matches 69 3.2.3.7 ERE operator precedence 69 3.2.4 Regular Expression Extensions 69 3.2.5 Which Programs Use Which Regular Expressions? 70 3.2.6 Making Substitutions in Text Files 72 3.2.7 Basic Usage 72 3.2.7.1 Substitution details 74 3.2.8 sed Operation 76 3.2.8.1 To print or not to print 76 3.2.9 Matching Specific Lines 77 3.2.10 How Much Text Gets Changed? 79 3.2.11 Lines Versus Strings 80 3.3 Working with Fields 80 3.3.1 Text File Conventions 81 3.3.2 Selecting Fields with cut 82 3.3.3 Joining Fields with join 84 3.3.4 Rearranging Fields with awk 86 3.3.4.1 Patterns and actions 86 3.3.4.2 Fields 86 3.3.4.3 Setting the field separators 87 3.3.4.4 Printing lines 88 3.3.4.5 Startup and cleanup actions 88 3.4 Summary 89 Chapter 4. Text Processing Tools 91 4.1 Sorting Text 91 4.1.1 Sorting by Lines 91 4.1.2 Sorting by Fields 94 4.1.3 Sorting Text Blocks 96 4.1.4 Sort Efficiency 98 4.1.5 Sort Stability 98 4.1.6 Sort Wrap-Up 99 4.2 Removing Duplicates 99 4.3 Reformatting Paragraphs 100 4.4 Counting Lines, Words, and Characters 101 4.5 Printing 102 4.5.1 Evolution of Printing Technology 104 4.5.2 Other Printing Software 104 4.6 Extracting the First and Last Lines 107 4.7 Summary 110 Chapter 5. Pipelines Can Do Amazing Things 111 5.1 Extracting Data from Structured Text Files 111 5.2 Structured Data for the Web 118 5.3 Cheating at Word Puzzles 124 5.4 Word Lists 126 5.5 Tag Lists 129 5.6 Summary 131 Chapter 6. Variables, Making Decisions, and Repeating Actions 133 6.1 Variables and Arithmetic 133 6.1.1 Variable Assignment and the Environment 133 6.1.2 Parameter Expansion 137 6.1.2.1 Expansion operators 137 6.1.2.2 Positional parameters 139 6.1.2.3 Special variables 141 6.1.3 Arithmetic Expansion 142 6.2 Exit Statuses 144 6.2.1 Exit Status Values 144 6.2.2 if–elif–else–fi 145 6.2.3 Logical NOT, AND, and OR 146 6.2.4 The test Command 148 6.3 The case Statement 153 6.4 Looping 154 6.4.1 for Loops 154 6.4.2 while and until Loops 154 6.4.3 break and continue 155 6.4.4 shift and Option Processing 156 6.5 Functions 159 6.6 Summary 162 Chapter 7. Input and Output, Files, and Command Evaluation 164 7.1 Standard Input, Output, and Error 164 7.2 Reading Lines with read 164 7.3 More About Redirections 167 7.3.1 Additional Redirection Operators 167 7.3.2 File Descriptor Manipulation 169 7.4 The Full Story on printf 171 7.5 Tilde Expansion and Wildcards 176 7.5.1 Tilde Expansion 176 7.5.2 Wildcarding 177 7.5.2.1 Hidden files 179 7.6 Command Substitution 179 7.6.1 Using sed for the head Command 181 7.6.2 Creating a Mailing List 181 7.6.3 Simple Math: expr 183 7.7 Quoting 185 7.8 Evaluation Order and eval 186 7.8.1 The eval Statement 190 7.8.2 Subshells and Code Blocks 191 7.9 Built-in Commands 192 7.9.1 The set Command 196 7.10 Summary 199 Chapter 8. Production Scripts 201 8.1 Path Searching 201 8.2 Automating Software Builds 216 8.3 Summary 246 Chapter 9. Enough awk to Be Dangerous 247 9.1 The awk Command Line 248 9.2 The awk Programming Model 249 9.3 Program Elements 250 9.3.1 Comments and Whitespace 250 9.3.2 Strings and String Expressions 250 9.3.3 Numbers and Numeric Expressions 252 9.3.4 Scalar Variables 256 9.3.5 Array Variables 257 9.3.6 Command-Line Arguments 258 9.3.7 Environment Variables 260 9.4 Records and Fields 260 9.4.1 Record Separators 260 9.4.2 Field Separators 261 9.4.3 Fields 262 9.5 Patterns and Actions 262 9.5.1 Patterns 262 9.5.2 Actions 263 9.6 One-Line Programs in awk 264 9.7 Statements 268 9.7.1 Sequential Execution 268 9.7.2 Conditional Execution 268 9.7.3 Iterative Execution 269 9.7.4 Array Membership Testing 271 9.7.5 Other Control Flow Statements 272 9.7.6 User-Controlled Input 273 9.7.7 Output Redirection 274 9.7.8 Running External Programs 275 9.8 User-Defined Functions 276 9.9 String Functions 279 9.9.1 Substring Extraction 280 9.9.2 Lettercase Conversion 280 9.9.3 String Searching 280 9.9.4 String Matching 281 9.9.5 String Substitution 281 9.9.6 String Splitting 282 9.9.7 String Reconstruction 284 9.9.8 String Formatting 285 9.10 Numeric Functions 288 9.11 Summary 290 Chapter 10. Working with Files 291 10.1 Listing Files 291 10.1.1 Long File Listings 295 10.1.2 Listing File Metadata 296 10.2 Updating Modification Times with touch 297 10.3 Creating and Using Temporary Files 298 10.3.1 The $$ Variable 300 10.3.2 The mktemp Program 300 10.3.3 The /dev/random and /dev/urandom Special Files 301 10.4 Finding Files 303 10.4.1 Finding Files Quickly 303 10.4.2 Finding Where Commands Are Stored 304 10.4.3 The find Command 304 10.4.3.1 Using the find command 304 10.4.3.2 A simple find script 311 10.4.3.3 A complex find script 312 10.4.4 Finding Problem Files 316 10.5 Running Commands: xargs 317 10.6 Filesystem Space Information 319 10.6.1 The df Command 319 10.6.2 The du Command 321 10.7 Comparing Files 323 10.7.1 The cmp and diff Utilities 323 10.7.2 The patch Utility 324 10.7.3 File Checksum Matching 325 10.7.4 Digital Signature Verification 327 10.8 Summary 331 Chapter 11. Extended Example: Merging User Databases 332 11.1 The Problem 332 11.2 The Password Files 333 11.3 Merging Password Files 334 11.3.1 Separating Users by Manageability 335 11.3.2 Managing UIDs 337 11.3.3 Creating User–Old UID–New UID Triples 339 11.4 Changing File Ownership 341 11.5 Other Real-World Issues 345 11.6 Summary 347 Chapter 12. Spellchecking 349 12.1 The spell Program 349 12.2 The Original Unix Spellchecking Prototype 350 12.3 Improving ispell and aspell 351 12.3.1 Private Spelling Dictionaries 352 12.3.2 ispell and aspell 353 12.4 A Spellchecker in awk 355 12.4.1 Introductory Comments 357 12.4.2 Main Body 357 12.4.3 initialize() 357 12.4.4 get_dictionaries() 358 12.4.5 scan_options() 359 12.4.6 load_dictionaries() 360 12.4.7 load_suffixes() 361 12.4.8 order_suffixes() 363 12.4.9 spell_check_line() 364 12.4.10 spell_check_word() 364 12.4.11 strip_suffixes() 365 12.4.12 report_exceptions() 366 12.4.13 Retrospective on Our Spellchecker 371 12.4.14 Efficiency of awk Programs 373 12.5 Summary 374 Chapter 13. Processes 376 13.1 Process Creation 377 13.2 Process Listing 378 13.3 Process Control and Deletion 384 13.3.1 Deleting Processes 385 13.3.2 Trapping Process Signals 387 13.4 Process System-Call Tracing 392 13.5 Process Accounting 396 13.6 Delayed Scheduling of Processes 397 13.6.1 sleep: Delay Awhile 397 13.6.2 at: Delay Until Specified Time 398 13.6.3 batch: Delay for Resource Control 398 13.6.4 crontab: Rerun at Specified Times 399 13.7 The /proc Filesystem 402 13.8 Summary 403 Chapter 14. Shell Portability Issues and Extensions 405 14.1 Gotchas 405 14.2 The bash shopt Command 409 14.3 Common Extensions 413 14.3.1 The select Loop 413 14.3.2 Extended Test Facility 416 14.3.3 Extended Pattern Matching 417 14.3.4 Brace Expansion 419 14.3.5 Process Substitution 419 14.3.6 Indexed Arrays 420 14.3.7 Miscellaneous Extensions 423 14.4 Download Information 426 14.4.1 bash 426 14.4.2 ksh93 428 14.5 Other Extended Bourne-Style Shells 429 14.6 Shell Versions 429 14.7 Shell Initialization and Termination 430 14.7.1 Bourne Shell (sh) Startup 431 14.7.2 Korn Shell Startup 432 14.7.3 Bourne-Again Shell Startup and Termination 432 14.7.4 Z-Shell Startup and Termination 434 14.8 Summary 436 Chapter 15. Secure Shell Scripts: Getting Started 437 15.1 Tips for Secure Shell Scripts 437 15.2 Restricted Shell 440 15.3 Trojan Horses 442 15.4 Setuid Shell Scripts: A Bad Idea 443 15.5 ksh93 and Privileged Mode 445 15.6 Summary 446 Appendix A. Writing Manual Pages 447 Manual Pages for pathfind 448 Manual-Page Syntax Checking 459 Manual-Page Format Conversion 460 Manual-Page Installation 460 Appendix B. Files and Filesystems 461 What Is a File? 461 How Are Files Named? 462 What’s in a Unix File? 465 The Unix Hierarchical Filesystem 467 Filesystem Structure 467 Layered Filesystems 469 Filesystem Implementation Overview 471 Devices as Unix Files 474 How Big Can Unix Files Be? 474 Unix File Attributes 476 File Ownership and Permissions 476 Ownership 476 Permissions 477 Default permissions 479 Permissions in action 479 Directory permissions 482 File Timestamps 484 File Links 485 File Size and Timestamp Variations 487 Other File Metadata 490 Unix File Ownership and Privacy Issues 491 Unix File Extension Conventions 493 Summary 495 Appendix C. Important Unix Commands 497 Shells and Built-in Commands 497 Text Manipulation 498 Files 499 Processes 500 Miscellaneous Programs 500 Bibliography 502 Unix Programmer’s Manuals 502 Programming with the Unix Mindset 502 Awk and Shell 504 Standards 504 Security and Cryptography 505 Unix Internals 506 O’Reilly Books 506 Miscellaneous Books 507 Glossary 508 Index 533

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 to not only to 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

Who does "classic shell scripting" nowadays?Maybe some IT geek, hackers, linux distribution developers... and embedded engineers!If you develop embedded system based on linux, you will have to do with sh scripts & friends.You can do a lot of things with a good script, better than writing your-own-cross-compiled-c-code.This book can help you in going deep and use the power you have immediately available even on the smallest linux busybox installation. I liked it, I enjoyed reading it, and it helped (and helps) me in my work.I found the awk chapter a bit less good, but this is not a book on awk.

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 to not only to 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

Classic Shell Scripting Preface What You Should Already Know Chapter Summary Conventions Used in This Book Code Examples Unix Tools for Windows Systems DJGPP MKS Toolkit AT & T UWIN Safari Enabled We & d Like to Hear from You Acknowledgments 1. Background 1.2. Software Tools Principles 1.3. Summary 2. Getting Started 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 2.5.2. Variables 2.5.3. Simple Output with echo 2.5.4. Fancier Output with printf 2.5.5. Basic I/O Redirection. 2.5.5.2. Special files: /dev/null and /dev/tty2.5.6. 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 3.2. Regular Expressions 3.2.2. Basic Regular Expressions 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. Ext.

Classic Shell Scripting Preface What You Should Already Know Chapter Summary Conventions Used in This Book Code Examples Unix Tools for Windows Systems DJGPP MKS Toolkit AT & T UWIN Safari Enabled We & d Like to Hear from You Acknowledgments 1. Background 1.2. Software Tools Principles 1.3. Summary 2. Getting Started 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 2.5.2. Variables 2.5.3. Simple Output with echo 2.5.4. Fancier Output with printf 2.5.5. Basic I/O Redirection. 2.5.5.2. Special files: /dev/null and /dev/tty2.5.6. 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 3.2. Regular Expressions 3.2.2. Basic Regular Expressions 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. Ext.