O'Reilly - Learning The Bash Shell.pdf - system LINUX - rav022

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Learning the bash Shell, Second Edition

By Cameron Newham , Bill Rosenblatt

• Table of

Contents

• Index

• Reviews

• Examples

• Reader

Reviews

• Errata

Publisher: O'Reilly

Pub Date: January 1998

ISBN: 1−56592−347−2

Pages: 334

Ripped by Caudex 2003

This second edition covers all of the features of bash Version 2.0, while still

applying to bash Version 1.x. It includes one−dimensional arrays, parameter

expansion, more pattern−matching operations, new commands, security

improvements, additions to ReadLine, improved configuration and installation,

and an additional programming aid, the bash shell debugger.

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Printed in the United States of America.

Published by O'Reilly & Associates, Inc., 101 Morris Street, Sebastopol, CA 95472.

The O'Reilly logo is a registered trademark of O'Reilly & Associates, Inc. Many of the designations used by

manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations

appear in this book, and O'Reilly & Associates, Inc. was aware of a trademark claim, the designations have

been printed in caps or initial caps. The use of the fish image in association with the bash shell is a trademark

of O'Reilly & Associates, Inc.

While every precaution has been taken in the preparation of this book, the publisher assumes no responsibility

for errors or omissions, or for damages resulting from the use of the information contained herein.

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Preface

The first thing users of the UNIX or Linux operating systems come face to face with is the shell. "Shell" is the

UNIX term for a user interface to the system—something that lets you communicate with the computer via

the keyboard and the display. Shells are just separate programs that encapsulate the system, and, as such, there

are many to choose from.

Systems are usually set up with a "standard" shell that new users adopt without question. However, some of

these standard shells are rather old and lack many features of the newer shells. This is a shame, because shells

have a large bearing on one's working environment. Since changing shells is as easy as changing hats, there is

no reason not to change to the latest and greatest in shell technology.

Of the many shells to choose from, this book introduces the Bourne Again shell (bash for short), a modern

general−purpose shell. Other useful modern shells are the Korn shell (ksh) and the "Tenex C shell" (tcsh);

both are also the subjects of O'Reilly handbooks.

Preface

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bash Versions

This book is relevant to all versions of bash, although older versions lack some of the features of the most

recent version. [] You can easily find out which version you are using by typing echo $BASH_VERSION. The

earliest public version of bash was 1.0, and the most recent is 2.01 (released in May 1997). If you have an

older version, you might like to upgrade to the latest one. Chapter 11 , shows you how to go about it.

[] Even though version 2.0 has been out for a while, bash version 1.14.x is still in widespread use. Throughout

this book we have clearly marked with footnotes the features that are not present in the earlier versions.

bash Versions

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Summary of bash Features

bash is a backward−compatible evolutionary successor to the Bourne shell that includes most of the C shell's

major advantages as well as features from the Korn shell and a few new features of its own. Features

appropriated from the C shell include:

· Directory manipulation, with the pushd, popd, and dirs commands.

· Job control, including the fg and bg commands and the ability to stop jobs with CTRL−Z.

· Brace expansion, for generating arbitrary strings.

· Tilde expansion, a shorthand way to refer to directories.

· Aliases, which allow you to define shorthand names for commands or command lines.

· Command history, which lets you recall previously entered commands.

bash's major new features include:

· Command−line editing, allowing you to use vi− or emacs−style editing commands on your command

lines.

· Key bindings that allow you to set up customized editing key sequences.

· Integrated programming features: the functionality of several external UNIX commands, including test,

expr, getopt, and echo, has been integrated into the shell itself, enabling common programming tasks to be

done more cleanly and efficiently.

· Control structures, especially the select construct, which enables easy menu generation.

· New options and variables that give you more ways to customize your environment.

· One dimensional arrays that allow easy referencing and manipulation of lists of data.

· Dynamic loading of built−ins, plus the ability to write your own and load them into the running shell.

Summary of bash Features

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