Tcl and the Tk Toolkit, Second Edition

John K. Ousterhout's Definitive Introduction to Tcl/Tk-Now Fully Updated for Tcl/Tk 8.5 Tcl and the Tk Toolkit, Second Edition, is the fastest way for newcomers to master Tcl/Tk and is the most authoritative resource for experienced programmers seeking to gain from Tcl/Tk 8.5's powerful enhancements. Written by Tcl/Tk creator John K. Ousterhout and top Tcl/Tk trainer Ken Jones, this updated volume provides the same extraordinary clarity and careful organization that made the first edition the world's number one Tcl/Tk tutorial. Part I introduces Tcl/Tk through simple scripts that demonstrate its value and offer a flavor of the Tcl/Tk scripting experience. The authors then present detailed, practical guidance on every feature necessary to build effective, efficient production applications-including variables, expressions, strings, lists, dictionaries, control flow, procedures, namespaces, file and directory management, interprocess communication, error and exception handling, creating and using libraries, and more. Part II turns to the Tk extension and Tk 8.5's new themed widgets, showing how to organize sophisticated user interface elements into modern GUI applications for Tcl. Part III presents incomparable coverage of Tcl's C functions, which are used to create new commands and packages and to integrate Tcl with existing C software-thereby leveraging Tcl's simplicity while accessing C libraries or executing performance-intensive tasks. Throughout, the authors illuminate all of Tcl/Tk 8.5's newest, most powerful improvements. You'll learn how to use new Starkits and Starpacks to distribute run-time environments and applications through a single file; how to take full advantage of the new virtual file system support to treat entities such as zip archives and HTTP sites as mountable file systems; and more. From basic syntax to simple Tcl commands, user interface development to C integration, this fully updated classic covers it all. Whether you're using Tcl/Tk to automate system/network administration, streamline testing, control hardware, or even build desktop or Web applications, this is the one Tcl/Tk book you'll always turn to for answers. Cover......Page 1 Contents......Page 6 Preface......Page 26 Preface to the First Edition......Page 28 Introduction......Page 32 PART I: The Tcl Language......Page 36 1.1 Getting Started......Page 38 1.2 “Hello, World!” with Tk......Page 41 1.3 Script Files......Page 43 1.4 Variables and Substitutions......Page 46 1.5 Control Structures......Page 47 1.6 On the Tcl Language......Page 49 1.7 Event Bindings......Page 50 1.8 Additional Features of Tcl and Tk......Page 54 2.1 Scripts, Commands, and Words......Page 56 2.2 Evaluating a Command......Page 57 2.3 Variable Substitution......Page 59 2.5 Backslash Substitution......Page 61 2.6 Quoting with Double Quotes......Page 63 2.7 Quoting with Braces......Page 64 2.8 Argument Expansion......Page 65 2.9 Comments......Page 67 2.10 Normal and Exceptional Returns......Page 70 2.11 More on Substitutions......Page 71 3.1 Commands Presented in This Chapter......Page 74 3.3 Tcl’s Internal Storage of Data......Page 76 3.4 Arrays......Page 77 3.5 Variable Substitution......Page 78 3.6 Multidimensional Arrays......Page 80 3.7 Querying the Elements of an Array......Page 81 3.8 The incr and append Commands......Page 82 3.10 Predefined Variables......Page 84 3.11 Preview of Other Variable Facilities......Page 85 4.1 Commands Presented in This Chapter......Page 88 4.2 Numeric Operands......Page 89 4.3 Operators and Precedence......Page 90 4.4 Math Functions......Page 93 4.5 Substitutions......Page 95 4.6 String Manipulation......Page 97 4.8 Types and Conversions......Page 98 4.9 Precision......Page 99 5.1 Commands Presented in This Chapter......Page 100 5.2 Extracting Characters: string index and string range......Page 104 5.4 Simple Searching......Page 105 5.5 String Comparisons......Page 106 5.6 String Replacements......Page 107 5.7 Determining String Types......Page 108 5.8 Generating Strings with format......Page 109 5.9 Parsing Strings with scan......Page 111 5.10 Glob-Style Pattern Matching......Page 113 5.11 Pattern Matching with Regular Expressions......Page 114 5.12 Using Regular Expressions for Substitutions......Page 122 5.13 Character Set Issues......Page 124 5.14 Message Catalogs......Page 126 5.15 Binary Strings......Page 130 6.1 Commands Presented in This Chapter......Page 136 6.2 Basic List Structure and the lindex and llength Commands......Page 138 6.3 Creating Lists: list, concat, and lrepeat......Page 140 6.4 Modifying Lists: lrange, linsert, lreplace, lset, and lappend......Page 141 6.5 Extracting List Elements: lassign......Page 144 6.6 Searching Lists: lsearch......Page 145 6.8 Converting between Strings and Lists: split and join......Page 146 6.9 Creating Commands as Lists......Page 148 Chapter 7 Dictionaries......Page 150 7.1 Commands Presented in This Chapter......Page 151 7.2 Basic Dictionary Structure and the dict get Command......Page 153 7.3 Creating and Updating Dictionaries......Page 155 7.4 Examining Dictionaries: The size, exists, keys, and for Subcommands......Page 157 7.5 Updating Dictionary Values......Page 158 7.6 Working with Nested Dictionaries......Page 161 8.1 Commands Presented in This Chapter......Page 166 8.2 The if Command......Page 167 8.3 The switch Command......Page 168 8.4 Looping Commands: while, for, and foreach......Page 171 8.5 Loop Control: break and continue......Page 173 8.6 The eval Command......Page 174 8.7 Executing from Files: source......Page 175 9.1 Commands Presented in This Chapter......Page 178 9.2 Procedure Basics: proc and return......Page 179 9.4 Defaults and Variable Numbers of Arguments......Page 181 9.5 Call by Reference: upvar......Page 183 9.6 Creating New Control Structures: uplevel......Page 185 9.7 Applying Anonymous Procedures......Page 186 10.1 Commands Presented in This Chapter......Page 190 10.2 Evaluating Tcl Code in a Namespace......Page 193 10.3 Manipulating Qualified Names......Page 196 10.4 Exporting and Importing Namespace Commands......Page 197 10.5 Inspecting Namespaces......Page 198 10.6 Working with Ensemble Commands......Page 199 10.7 Accessing Variables from Other Namespaces......Page 204 10.8 Controlling the Name Resolution Path......Page 205 11.1 Commands Presented in This Chapter......Page 208 11.2 Manipulating File and Directory Names......Page 211 11.4 Listing Directory Contents......Page 214 11.5 Working with Files on Disk......Page 216 11.6 Reading and Writing Files......Page 220 11.7 Virtual File Systems......Page 229 11.8 Errors in System Calls......Page 231 12.1 Commands Presented in This Chapter......Page 232 12.3 Invoking Subprocesses with exec......Page 234 12.4 I/O to and from a Command Pipeline......Page 238 12.5 Configuring Channel Options......Page 239 12.6 Event-Driven Channel Interaction......Page 241 12.7 Process IDs......Page 244 12.9 TCP/IP Socket Communication......Page 245 12.10 Sending Commands to Tcl Programs......Page 249 13.1 Commands Presented in This Chapter......Page 254 13.2 What Happens after an Error?......Page 255 13.4 Trapping Errors with catch......Page 257 13.5 Exceptions in General......Page 258 13.6 Background Errors and bgerror......Page 262 Chapter 14 Creating and Using Tcl Script Libraries......Page 264 14.1 Commands Presented in This Chapter......Page 265 14.3 Using Libraries......Page 267 14.4 Autoloading......Page 268 14.5 Packages......Page 269 14.6 Tcl Modules......Page 274 14.7 Packaging Your Scripts as Starkits......Page 277 15.1 Commands Presented in This Chapter......Page 282 15.2 Time Delays......Page 288 15.3 Time and Date Manipulation......Page 289 15.5 The info Command......Page 294 15.6 Tracing Operations on Simple Variables......Page 299 15.7 Tracing Array Variables......Page 303 15.8 Renaming and Deleting Commands......Page 304 15.9 Tracing Commands......Page 305 15.10 Unknown Commands......Page 307 15.11 Slave Interpreters......Page 309 16.1 Commands Presented in This Chapter......Page 318 16.2 The History List......Page 319 16.4 Re-executing Commands from the History List......Page 320 16.5 Shortcuts Implemented by unknown......Page 321 16.6 Current Event Number: history nextid......Page 322 PART II: Writing Scripts for Tk......Page 324 Chapter 17 An Introduction to Tk......Page 326 17.1 A Brief Introduction to Windowing Systems......Page 327 17.2 Widgets......Page 329 17.3 Applications, Toplevel Widgets, and Screens......Page 331 17.5 Creating and Destroying Widgets......Page 332 17.6 Geometry Managers......Page 333 17.7 Widget Commands......Page 334 17.8 Commands for Interconnection......Page 335 Chapter 18 A Tour of the Tk Widgets......Page 338 18.1 Widget Basics......Page 339 18.2 Frames......Page 341 18.3 Color Options......Page 342 18.4 Toplevels......Page 343 18.5 Labels......Page 344 18.7 Buttons......Page 347 18.8 Listboxes......Page 352 18.9 Scrollbars......Page 353 18.10 Scales......Page 356 18.11 Entries......Page 358 18.12 Menus......Page 362 18.13 Panedwindow......Page 369 18.14 Standard Dialogs......Page 372 18.15 Other Common Options......Page 374 19.1 Comparing Classic and Themed Widgets......Page 378 19.2 Combobox......Page 380 19.3 Notebook......Page 381 19.4 Progressbar......Page 384 19.7 Treeview......Page 385 19.8 Themed Widget States......Page 393 19.9 Themed Widget Styles......Page 395 19.10 Other Standard Themed Widget Options......Page 399 20.1 Commands Presented in This Chapter......Page 402 20.2 The font Command......Page 404 20.3 The image Command......Page 410 Chapter 21 Geometry Managers......Page 420 21.1 Commands Presented in This Chapter......Page 421 21.2 An Overview of Geometry Management......Page 422 21.3 The Gridder......Page 424 21.4 The Packer......Page 431 21.5 Padding......Page 439 21.7 Hierarchical Geometry Management......Page 440 21.8 Widget Stacking Order......Page 442 21.9 Other Geometry Manager Options......Page 443 21.10 Other Geometry Managers in Tk......Page 444 22.1 Commands Presented in This Chapter......Page 448 22.2 Events......Page 449 22.3 An Overview of the bind Command......Page 451 22.4 Event Patterns......Page 452 22.6 Substitutions in Scripts......Page 454 22.7 Conflict Resolution......Page 456 22.8 Event-Binding Hierarchy......Page 457 22.9 When Are Events Processed?......Page 458 22.10 Named Virtual Events......Page 460 22.11 Generating Events......Page 462 22.12 Logical Actions......Page 463 22.13 Other Uses of Bindings......Page 466 23.1 Canvas Basics: Items and Types......Page 468 23.2 Manipulating Items with Identifiers and Tags......Page 471 23.3 Bindings......Page 474 23.4 Canvas Scrolling......Page 479 23.5 PostScript Generation......Page 480 24.1 Text Widget Basics......Page 482 24.2 Text Indices and Marks......Page 485 24.3 Search and Replace......Page 486 24.4 Text Tags......Page 488 24.5 Virtual Events......Page 493 24.6 Embedded Windows......Page 494 24.7 Embedded Images......Page 495 24.8 Undo......Page 497 24.9 Peer Text Widgets......Page 499 Chapter 25 Selection and the Clipboard......Page 502 25.1 Commands Presented in This Chapter......Page 503 25.2 Selections, Retrievals, and Types......Page 504 25.3 Locating and Clearing the Selection......Page 505 25.4 Supplying the Selection with Tcl Scripts......Page 506 25.5 The clipboard Command......Page 508 25.6 Drag and Drop......Page 509 Chapter 26 Window Managers......Page 512 26.1 Commands Presented in This Chapter......Page 513 26.2 Window Sizes......Page 516 26.3 Window Positions......Page 517 26.4 Gridded Windows......Page 518 26.5 Window States......Page 519 26.6 Decorations......Page 520 26.7 Special Handling: Transients, Groups, and Override-Redirect......Page 521 26.8 System-Specific Window Attributes......Page 522 26.9 Dockable Windows......Page 523 26.10 Window Close......Page 524 26.11 Session Management......Page 525 27.1 Commands Presented in This Chapter......Page 526 27.2 Input Focus......Page 528 27.3 Modal Interactions......Page 530 27.4 Custom Dialogs......Page 534 28.1 Commands Presented in This Chapter......Page 540 28.2 The Option Database......Page 541 28.3 Option Database Entries......Page 542 28.4 The RESOURCE_MANAGER Property and .Xdefaults File......Page 543 28.5 Priorities in the Option Database......Page 544 28.6 The option Command......Page 545 28.7 The configure Widget Command......Page 546 28.8 The cget Widget Command......Page 547 29.1 Commands Presented in This Chapter......Page 548 29.3 The update Command......Page 549 29.5 The tk Command......Page 551 29.6 Variables Managed by Tk......Page 552 29.7 Ringing the Bell......Page 553 PART III: Writing Tcl Applications in C......Page 554 Chapter 30 Tcl and C Integration Philosophy......Page 556 30.1 Tcl versus C: Where to Draw the Line......Page 558 30.2 Resource Names—Connecting C Constructs to Tcl......Page 559 30.3 “Action-Oriented” versus “Object-Oriented”......Page 560 30.4 Representing Information......Page 561 31.1 Functions Presented in This Chapter......Page 562 31.2 Interpreters......Page 564 31.3 A Simple Tcl Application......Page 565 31.5 Multiple Interpreters......Page 566 Chapter 32 Tcl Objects......Page 568 32.1 Functions Presented in This Chapter......Page 569 32.3 Numerical Objects......Page 572 32.4 Fetching C Values from Objects......Page 573 32.5 The Dynamic Nature of a Tcl Object......Page 574 32.8 Reference Counting......Page 575 32.9 Shared Objects......Page 576 32.10 New Object Types......Page 577 32.11 Parsing Strings......Page 578 32.12 Memory Allocation......Page 579 33.1 Functions Presented in This Chapter......Page 580 33.2 Evaluating Tcl Code......Page 581 33.3 Dynamically Building Scripts......Page 583 33.4 Tcl Expressions......Page 584 34.1 Functions Presented in This Chapter......Page 586 34.2 Setting Variable Values......Page 588 34.3 Reading Variables......Page 590 34.5 Linking Tcl and C Variables......Page 591 34.6 Setting and Unsetting Variable Traces......Page 593 34.7 Trace Callbacks......Page 594 34.9 Multiple Traces......Page 596 34.10 Unset Callbacks......Page 597 35.1 Functions Presented in This Chapter......Page 598 35.2 Command Functions......Page 601 35.3 Registering Commands......Page 602 35.5 Tcl_AppendResult......Page 604 35.6 Tcl_SetResult and interp->result......Page 605 35.7 clientData and Deletion Callbacks......Page 607 35.8 Deleting Commands......Page 610 35.9 Fetching and Setting Command Parameters......Page 611 35.10 How Tcl Procedures Work......Page 613 35.11 Command Traces......Page 614 36.1 Functions Presented in This Chapter......Page 616 36.2 The Init Function......Page 617 36.3 Packages......Page 618 36.5 Tcl Stubs......Page 619 36.6 The ifconfig Extension......Page 620 37.1 Functions Presented in This Chapter......Page 628 37.2 Adding Tcl to an Application......Page 629 37.3 Initialize Tcl......Page 630 37.4 Creating New Tcl Shells......Page 631 38.1 Functions Presented in This Chapter......Page 634 38.2 Completion Codes......Page 635 38.3 Setting errorCode......Page 638 38.4 Managing the Return Options Dictionary......Page 639 38.5 Adding to the Stack Trace in errorInfo......Page 640 38.6 Tcl_Panic......Page 643 39.1 Functions Presented in This Chapter......Page 646 39.2 Dynamic Strings......Page 652 39.3 String Matching......Page 656 39.4 Regular Expression Matching......Page 657 39.5 Working with Character Encodings......Page 659 39.6 Handling Unicode and UTF-8 Strings......Page 660 39.7 Command Completeness......Page 662 Chapter 40 Hash Tables......Page 664 40.1 Functions Presented in This Chapter......Page 665 40.2 Keys and Values......Page 666 40.3 Creating and Deleting Hash Tables......Page 667 40.4 Creating Entries......Page 668 40.5 Finding Existing Entries......Page 670 40.6 Searching......Page 671 40.7 Deleting Entries......Page 672 40.8 Statistics......Page 673 41.1 Functions Presented in This Chapter......Page 674 41.2 Lists......Page 677 41.3 Dictionaries......Page 679 42.1 Functions Presented in This Chapter......Page 684 42.2 Channel Operations......Page 691 42.3 Registering Channels......Page 693 42.4 Standard Channels......Page 695 42.5 Creating a New Channel Type......Page 696 43.1 Functions Presented in This Chapter......Page 706 43.2 Channel Events......Page 707 43.3 Timer Events......Page 711 43.4 Idle Callbacks......Page 712 43.5 Invoking the Event Dispatcher......Page 713 44.1 Tcl File System Functions......Page 716 44.2 Virtual File Systems......Page 718 45.1 Functions Presented in This Chapter......Page 720 45.2 Processes......Page 722 45.3 Reaping Child Processes......Page 724 45.4 Asynchronous Events......Page 725 45.6 Exiting and Cleanup......Page 728 45.7 Miscellaneous......Page 729 46.1 Functions Presented in This Chapter......Page 730 46.4 Creating Threads......Page 732 46.6 Mutexes......Page 733 46.7 Condition Variables......Page 734 46.8 Miscellaneous......Page 736 47.1 Building Tcl and Tk......Page 738 47.2 The Tcl Extension Architecture (TEA)......Page 742 47.3 Building Embedded Tcl......Page 749 Appendixes......Page 750 A.1 Versions......Page 752 A.3 ActiveTcl......Page 753 A.5 Compiling Tcl/Tk from Source Distributions......Page 754 B.1 Obtaining and Installing Extensions......Page 756 B.2 TkCon Extended Console......Page 759 B.5 Sound Support with Snack......Page 760 B.6 Object-Oriented Tcl......Page 761 B.8 XML Programming......Page 762 B.10 Integrating Tcl and Java......Page 763 B.12 Expect......Page 764 B.13 Extended Tcl......Page 765 C.1 Online Resources......Page 766 C.2 Books......Page 767 Appendix D: Tcl Source Distribution License......Page 770 Index......Page 772 A......Page 773 B......Page 775 C......Page 776 D......Page 780 E......Page 781 F......Page 784 G......Page 786 I......Page 787 L......Page 789 M......Page 791 N......Page 792 P......Page 793 Q......Page 795 R......Page 796 S......Page 797 T......Page 801 U......Page 804 V......Page 805 W......Page 806 Z......Page 808 Tcl was born of frustration. In the early 1980s my students and I developed a num-ber of interactive tools at the University of California at Berkeley, mostly for inte-grated circuit design, and we found ourselves spending a lot of time building badcommand languages. Each tool needed to have a command language of some sort,but our main interest was in the tool rather than its command language. We spentas little time as possible on the command language and always ended up with a lan-guage that was weak and quirky. Furthermore, the command language for one toolwas never quite right for the next tool, so we ended up building a new bad com-mand language for each tool. This became increasingly frustrating. In the fall of 1987 it occurred to me that the solution was to build a reusable com-mand language. If a general-purpose scripting language could be built as a C librarypackage, then perhaps it could be reused for many different purposes in many dif-ferent applications. Of course, the language would need to be extensible so that eachapplication could add its own specific features to the core provided by the library. Inthe spring of 1988 I decided to implement such a language, and the result was Tcl.Tk was also born of frustration. The basic idea for Tk arose in response to Apple'€™sannouncement of HyperCard in the fall of 1987. HyperCard generated tremendousexcitement because of the power of the system and the way in which it allowed manydifferent interactive elements to be scripted and work together. However, I was discour-aged. The HyperCard system had obviously taken a large development effort, and itseemed unlikely to me that a small group such as a university research projectcould ever mount such a massive effort. This suggested that we would not be able toparticipate in the development of new forms of interactive software in the future. The Tcl scripting language and the Tk toolkit, a programming environment for creating graphical user interfaces under X Windows together represent one of the most exciting innovations in X Window System programming. Because Tcl and Tk are so easy to learn, extremely powerful, and contain sophisticated features, they have dramatically reduced development time for thousands of X programmers. Written by the creator of Tcl and Tk, this book is the single authoritative resource for anyone who wants to work with this extraordinary environment. The book offers an introduction and overview of Tcl and Tk and then presents detailed instructions for script writing in Tcl and working with the Tk toolkit. You will discover how Tk's windowing shell, wish, enables you to develop window-based applications with amazingly few lines of code. You will also find information on Tk's novel and powerful facility for linking applications. Many other features are also described, such as Tk's hypertext and hypergraphics widgets and Tcl's facilities for procedures, list management, and subprocess execution. For interested readers, the book also describes the C interfaces for Tcl and Tk, showing how to extend their built-in features by writing new C commands. Upon reading this book, you will learn how to produce far more powerful X Windows System applications in a fraction of the time that used to be required.