Book Image

Tcl/Tk 8.5 Programming Cookbook

Book Image

Tcl/Tk 8.5 Programming Cookbook

Overview of this book

With Tcl/Tk, you can create full-featured cross-platform applications in a simple and easy-to-understand way without any expensive development package; the only tools required are a simple text editor and your imagination. This practical cookbook will help you to efficiently interact with editors, debuggers, and shell type interactive programs using Tcl/Tk 8. This cookbook will comprehensively guide you through practical implementation of Tcl/Tk 8.5 commands and tools. This book will take you through all the steps needed to become a productive programmer in Tcl/Tk 8. Right from guiding you through the basics to creating a stand-alone application, it provides complete explanation of all the steps along with handy tips and tricks. The book begins with an introduction to the Tcl shell, syntax, variables, and programming best practices in the language. It then explores procedures and the flow of events with control constructs followed by advanced error trapping and recovery. From Chapter 4, a detailed study of string expressions and handling enables you to handle various string functions and use lists to expand the string functionality. The book then discusses in-depth the Tcl Dictionary and how to utilize it to store and retrieve data. File operations and Tk GUI handling are covered extensively along with a developing a real-world address book application to practice the concepts learned.
Table of Contents (20 chapters)
Tcl/Tk 8.5 Programming Cookbook
About the Author
About the Reviewers

Getting a record

While the dict for command is generally used for processing multiple key/value pairs, Tcl provides the dict get command to obtain the value assigned to a specific key. The syntax is as follows:

dict get dictionaryValue key

How to do it…

In the following example, we will create a dictionary containing a set of key/value pairs and then, using the dict get command, obtain the value associated with the specified key. Return values from the commands are provided for clarity. Enter the following command:

% set names [dict create 1 John 2 Mary 3 Paul]
1 John 2 Mary 3 Paul
% dict get $names 3

How it works…

The dict get command will retrieve the value associated with the argument contained in the key for the dictionary defined by dictionaryValue.