برنامه‌نویسی پرو بش: اسکریپت‌نویسی در شل GNU/Linux

Considering the critical role Bash has in the installation and operation of Linux distributions and thereby its ubiquity, Bash as a programming language is frequently overlooked by programmers. The author of Pro Bash Programming has done a creditable job in providing the wherewithal for everyone from beginners to expert shell programmers to write more powerful and efficient scripts using Bash, as he takes you through a fast paced coverage of bash's capabilities. Along the way, many useful, well explained and commented practical scripts are provided, many of which can be used to build and test your own scripts. The author claims that while he used to use C when he needed extra speed, that was several years ago and he now does everything in the shell. This book shows how.The 230 page book is divided into the 15 chapters below, with each chapter ending with a summary of the commands covered and some well chosen exercises. 1 Hello, World! Your first Shell Program - how to create and run a script and establish good scripting habits 2 Input, Output and Throughput - echo, printf, read and IO streams 3 Looping and Branching - tests, conditional execution, looping constructs 4 Command-Line Parsing and Expansion - quoting, brace, tilde, parameter, variable arithmetic and pathname expansion, command and process substitution, word splitting and parsing with getops 5 Parameters and Variables - variable scope (essential reading), positional parameters and expansion using patterns, arrays - indexed and associative 6 Shell Functions - how to define, use and set exit codes, use of compound commands, creation and use of function libraries 7 String Manipulation - concatenation, processing character by character, case conversion, inserting, overlaying and trimming strings 8 File Operations and Commands - reading, use of external commands, regular expressions with grep, sed and awk, file name expansion options 9 Reserved Words and Builtin Commands - good coverage of builtin commands, particularly read (including into arrays) plus a very informative section on how to use builtin commands correctly 10 Writing Bug-Free Scripts and Debugging the Rest - good scripting programming recommendations for bug free code plus a test and debug example 11 Programming for the Command Line - manipulating the directory stack, filesystem and miscellaneous functions, managing man pages, games! 12 Runtime Configuration - command line options and arguments, menus, configuration files, scripts with several names, using environment variables 13 Data Processing - sorting and searching arrays, various ways of reading arrays into memory, grids (string and two dimensional), data file formats 14 Scripting the Screen - using the screen as a blackboard or canvas, rendition modes and colours, text scrolling - rolling dice example 15 Entry-Level Programming - single key entry, use of author's key-funcs library, sanity checking, form entry, reading the mouse!Appendix: Shell Variables - alphabetic listing of (1) variables set by bash and (2) variables used by bashOne of the strengths of this book is that the author explains the fastest way to accomplish many standard programming tasks through the appropriate choice of one of the many different bash methods available, including the choice between builtin bash commands and external commands. I found chapter 9 particularly interesting here. Chapter 7 shows how effective bash is at string manipulation with the right techniques - amazing! While the book covers bash 4.0 and often uses non POSIX extensions, those unable to use bash 4.0 or constrained to POSIX compliant code are not forgotten, with the author providing alternatives that work within these constraints.Where a subject is introduced in an early chapter and expanded on later, the author thoughtfully provides the forward reference. Source code for the included scripts is available from the publisher's webpage for this book at [...]The 10 page index works reasonably well, but you may find it worthwhile grabbing the companion eBook so you can directly search through the book to make the best use of it as a reference source. If you buy the dead tree version, the eBook is available on-line for $10 until April 2010 direct from the publisher.I can recommend this book to anyone that can benefit from automating repetitive shell based tasks in Linux but isn't sure how best to go about it. The included scripts and wealth of tips on how to avoid common bash coding problems will provide you with a quick return on your investment. Neil Matthews Apress - Pro Bash Programming Scripting the GNULinux Shell (10-2009) (ATTiCA)......Page 1 Books for Professionals......Page 2 Contents at a Glance......Page 6 Contents......Page 8 About the Author......Page 19 About the Technical Reviewer......Page 20 Introduction......Page 22 The Code......Page 26 The File......Page 27 Choosing and Using a Text Editor......Page 28 Summary......Page 30 Parameters and Variables......Page 32 Arguments and Options......Page 33 printf: Formatting and Printing Data......Page 34 Standard Input/Output Streams and Redirection......Page 38 Reading Input......Page 40 Summary......Page 41 Testing an Expression......Page 44 Lists......Page 47 Looping......Page 50 Summary......Page 52 Command-Line Parsing and Expansion......Page 54 Quoting......Page 55 Brace Expansion......Page 56 Tilde Expansion......Page 57 Parameter and Variable Expansion......Page 58 Command Substitution......Page 60 Word Splitting......Page 61 Process Substitution......Page 62 Parsing Options......Page 63 Summary......Page 66 The Scope of a Variable: Can You See It from Here?......Page 68 Shell Variables......Page 69 Parameter Expansion......Page 71 Positional Parameters......Page 78 Arrays......Page 79 Summary......Page 81 Definition Syntax......Page 84 Compound Commands......Page 86 Getting Results......Page 87 Sample Script......Page 89 Summary......Page 91 Concatenation......Page 92 Processing Character by Character......Page 94 Case Conversion......Page 95 Comparing Contents Without Regard to Case......Page 97 Check for Valid Variable Name......Page 98 Overlay......Page 99 Summary......Page 100 Reading a File......Page 104 External Commands......Page 106 Regular Expressions......Page 110 File Name Expansion Options......Page 114 Summary......Page 119 help, Display Information About Builtin Commands......Page 122 time, Print Time Taken for Execution of a Command......Page 123 read, Read a Line from an Input Stream......Page 124 type, Display Information About Commands......Page 131 builtin, Execute a Builtin Command......Page 133 Summary......Page 135 Prevention Is Better Than Cure......Page 138 Debugging a Script......Page 145 Summary......Page 148 Manipulating the Directory Stack......Page 150 Filesystem Functions......Page 154 Miscellaneous Functions......Page 157 Managing Man Pages......Page 158 Games......Page 159 Defining Variables......Page 166 Menus......Page 167 Configuration Files......Page 168 Scripts with Several Names......Page 169 All Together Now......Page 171 Summary......Page 181 Arrays......Page 182 Data File Formats......Page 196 Summary......Page 201 Teletypewriter vs. Canvas......Page 204 Moving the Cursor......Page 206 Changing Rendition Modes and Colors......Page 207 Placing a Block of Text on the Screen......Page 208 Scrolling Text......Page 211 Rolling Dice......Page 212 Single-Key Entry......Page 216 History in Scripts......Page 222 Sanity Checking......Page 223 Form Entry......Page 224 Reading the Mouse......Page 225 Shell Variables......Page 230 Index......Page 246

The bash shell is a complete programming language, not merely a glue to combine external Linux commands. By taking full advantage of shell internals, shell programs can perform as snappily as utilities written in C or other compiled languages. And you will see how, without assuming Unix lore, you can write professional bash 4.0 programs through standard programming techniques.

• Complete bash coverage
• Teaches bash as a programming language
• Helps you master bash 4.0 features

What you’ll learn

• Use the shell to write new utilities and accomplish most programming tasks.
• Use shell parameter expansion to replace many external commands, making scripts very fast.
• Learn to avoid many common mistakes that cause scripts to fail.
• Learn how bash’s readline and history libraries can save typing when getting user input.
• Learn to use features new to bash 4.0.
• Build shell scripts that get information from the Web.

Who this book is for

Beginning Linux and Unix system administrators who want to be in full command of their systems.

Table of Contents

1. Hello, World! Your First Shell Program
2. Input, Output, and Throughput
3. Looping and Branching
4. Command-Line Parsing and Expansion
5. Parameters and Variables
6. Shell Functions
7. String Manipulation
8. File Operations and Commands
9. Reserved Words and Builtin Commands
10. Writing Bug-Free Scripts and Debugging the Rest
11. Programming for the Command Line
12. Runtime Configuration
13. Data Processing
14. Scripting the Screen
15. Entry-Level Programming