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
Credits
About the Author
Acknowledgment
About the Reviewers
www.PacktPub.com
Preface

Parsing a string using conversion specifiers


To parse a string in Tcl using conversion specifiers we will be using the scan command. The scan command parses the string in a similar manner as in the ANSI C sscanf procedure. As the scan command does not accept switches such as the regexp and regsub commands, we will proceed directly to the command. The syntax of the command is as follows:

scan string format variable variable variable…

The scan command accepts a string to parse and based on the format provided, it will convert the string. If variables are provided, they will be updated to the output of the conversions.

The scan command supports the following conversion characters:

Character

Description

d

The input string must be a decimal integer.

o

The input string must be an octal integer.

u

The input string must be a decimal integer (as in the case of d).

The output is assigned to the variable as an unsigned decimal string.

s

The input substring consists of all the characters...