A practical guide to Linux commands, editors, and shell ... - GBV

A Practical Guide to Linux®

Editors,

and

Commands,

Shell Programming

SECOND EDITION

Mark G. Sobell

• • PRENTICE HALL

Upper Saddle River, NJ New York

Capetown

Toronto

• •

Sydney

• •

•

Boston

Montreal

Tokyo

•

•

•

Indianapolis

London

Singapore

•

San Francisco

•

Munich

•

Mexico

•

Paris

City

•

Madrid

Contents xxxi

Preface

Chapter l: Welcome to Linux and Mac OS X The

History of UNIX and GNU-Linux The Heritage of Linux: UNIX Fade to 1983 3 Next

2

2

4

Scene, 1991

The Code Is Free Have Fun!

5

5

What Is So Good About Linux?

6

Why Linux Is Popular with Hardware Companies Linux Is Portable

The C

Linux Can

Linux Can Run

Many Tasks

Linux Provides

a

11

12

Secure Hierarchical

Filesystem

12

The Shell: Command Interpreter and Programming A Large Collection of Useful Utilities 15

Interprocess Communication System Administration 16 Additional Features of Linux GUIs:

Language

13

15

16

Graphical User Interfaces (Inter)Networking Utilities 17 Software Development 17 Exercises

9

10

Kernel

Chapter Summary

Developers

11

Programming Interface Support Many Users 12

a

and

9

Programming Language

Overview of Linux

Linux Has

1

16

18

18

xiii

xiv

Contents

PART I

The Linux and Mac OS X

Operating Systems

21

Chapter 2: Getting Started Conventions Used in This Book

Logging

In from

a

Terminal

Working with the Shell Which Shell

or

23

24

Terminal Emulator

28

Are You

28

Running?

Correcting Mistakes 29 Repeating/Editing Command Lines su/sudo:

Curbing

26

Your Power (root

Where to Find Documentation

31

Privileges)

31

33

The

—help Option 33 33 man: Displays the System Manual for a Searches 35 Keyword apropos:

Displays Information About

info:

HOWTOs:

Utilities

Out How

Finding Things Getting Help with the System 38 More About

Chapter Summary

41

41

43

44

Advanced Exercises

44

Chapter 3: The Utilities Special Characters Basic Utilities Is: Lists

45

46

47

the Names of Files Text File

cat:

Displays

a

rm:

Deletes

File

a

47

48

48

less Is more:

hostname:

Display a Text File One Screen Displays the System Name 49

Working with Files 49 49 cp: Copies a File mv:

Ipr:

38

41

Logging Changing Your Password Exercises

36

40

Logging In

Using Virtual Consoles 40 What to Do If You Cannot Log In Out

Work

Changes Prints a

the Name of

File

a

File

50

51

grep: Searches for a String 52 head: Displays the Beginning of

a

File

52

at a

Time

48

Contents

Displays the End of a File 53 Displays a File in Order 54 uniq: Removes Duplicate Lines from 54 diff: Compares Two Files

xv

tail:

sort:

file: Identifies the Contents of

I

(Pipe):

a

a

File

File

56

Communicates Between Processes

Four More Utilities echo: date:

54

56

57

Displays Text 57 Displays the Time and Date

58

58 script: Records a Shell Session todos/unix2dos: Converts Linux and Mac OS X Files

Compressing and Archiving Files 60 bzip2: Compresses a File 60 bunzip2 and bzcat: Decompress a File 61 gzip: Compresses a File 62 62 tar: Packs and Unpacks Archives Locating Commands

65

which and whereis: Locate siocate/locate: Searches for

a

Utility

a

File

65 66

Obtaining User and System Information 67 who: Lists Users on the System

67

68 finger: Lists Users on the System 69 w: Lists Users on the System

Communicating with Other Users 70 write: Sends a Message 70 Denies or Accepts Messages mesg: Email

71

72

Chapter Summary Exercises

72

75

Advanced Exercises

75

Chapter 4: The Filesystem The Hierarchical

Filesystem

78

Directory Files and Ordinary Files Filenames The

77

78

79

Working Directory 82 Directory 82

Your Home Pathnames

83

Absolute Pathnames Relative Pathnames

83 84

Working with Directories 85 86 mkdir: Creates a Directory cd: Changes to Another Working Directory

87

to

Windows Format

59

xvi

Contents

rmdir: Deletes

Using

mv, cp: Move Moves

mv:

a

88

Directory

a

89

Pathnames

or Copy Files Directory 90

90

Important Standard Directories and Files Is -1:

Displays Permissions

93 94

Access Permissions

Changes Setgid Permissions Access Permissions Directory chmod:

Setuid and

ACLs: Access Control Lists

96 98

99

Enabling ACLs 100 "Working with Access Rules 100 Setting Default Rules for a Directory Links

103

104

Hard Links

106 108

Symbolic Links rm:

91

93

Access Permissions

Removes

a

Link 111

Chapter Summary Exercises

110

112

Advanced Exercises

114

Chapter 5: The Shell The Command Line

117

118

Syntax 118 Processing the Command

Line

120

Executing the Command Line 123 Editing the Command Line 123 Standard Input and Standard Output The Screen The

as a

File

Keyboard and Screen

Redirection

123

124 as

Standard

Input and Standard Output

126

Pipes 131 Running a Command in the Background Filename Generation/Pathname

134

Expansion

136

The ? Special Character 137 The f" Special Character 138 The Builtins

[ ] Special Characters

139

141

Chapter Summary

142

Utilities and Builtins Introduced in This Exercises

143

Advanced Exercises

144

Chapter

142

125

PART II

The Editors

147

Chapter 6: The vim Editor History

149

150

Tutorial: Using vim

Starting

vim

Create and Edit

to

a

File

151

151

Command and Input Modes 153 Entering Text 154 Getting Help 155 Ending the Editing Session 158 The

compatible Parameter

Introduction Online

to vim Features

Help

158

Terminology

159

158 158

Modes of

Operation 159 The Display 160 Correcting Text as You Insert Work Buffer Line

Length and File Size

Windows File Locks

Text After

a

an

Editing Session

Crash

by

Cursor to

Characters a

162

163

Moving the Cursor

the Cursor

Moving the

161

161

Command Mode:

Moving

160

161

Abnormal Termination of Recovering

It

161

164 165

Specific Character

165

Moving the Cursor by Words 166 Moving the Cursor by Lines 166 Moving the Cursor by Sentences and Paragraphs Moving the Cursor Within the Screen 167 Viewing Different Parts of the Work Buffer

Input Mode 168 Inserting Text 168 Appending Text 168 Opening a Line for Text 168 Replacing Text 169 Quoting Special Characters in Input Mode Command Mode: Deleting and Changing Text Undoing Changes 169 Deleting Characters 170 Deleting Text 170

Changing Text

171

Replacing Text Changing Case

172

173

167

169 169

167

xviii

Contents

Searching and Substituting 173 Searching for a Character 173 Searching for a String 174 Substituting One String for Another Miscellaneous Commands

Join

180

180

Status .

176

180

180

(Period)

Deleting Text 181 The General-Purpose Buffer

Copyingj Moving, and

180

Named Buffers 182 Numbered Buffers 182 Reading and Writing Files

183

Reading Files 183 Writing Files 183 Identifying the Current File Setting

Parameters

Setting Setting

Parameters from Within vim

184

Parameters in

185

The .vimrc

a

185

185

Advanced Editing

Techniques

Using Markers

190

Macros and Shortcuts

190

Shell Commands from Within vim

Units of Measure

Character

191

193

193

193

Blank-Delimited Word Line

194

194

Sentence

194

Paragraph 195 Screen (Window)

196

Factor

196

Chapter Summary

196

Repeat Exercises

201

Advanced Exercises

202

Chapter 7: The History

189

189

Editing Other Files Executing

File

Startup

Startup File

Parameters

Word

184

184

emacs

Editor

205

206

Evolution emacs

206

Versus vim

Command-Line

207

emacs

Versus

Graphical

emacs

208

Contents

Tutorial: Getting Started with

208

emacs

Starting emacs 208 Exiting 210 Inserting Text 210 Deleting Characters 210 Moving the Cursor 211 Editing at the Cursor Position 214 Saving and Retrieving the Buffer 214 The

emacs

Basic

GUI

Editing

215

Commands

216

Notation and Use

216 Keys: Key Sequences and Commands 217 MFTA-x: Running a Command Without a Key Binding Numeric Arguments 218 Point and the Cursor 218 Scrolling Through a Buffer Text

218

219

Erasing Searching for Text 219 Using the Menubar from the Keyboard Online

Help

221

223

Advanced

Editing 225 Undoing Changes 225 Point, Mark, and Region Cut

and Paste:

226

Yanking Killed

Inserting Special Characters Global Buffer Commands

Visiting and Saving Files Buffers 235 Windows

Text

228

230 230

232

236

Foreground Shell Commands

238

Shell Commands

239

Background

Major Modes: Language-Sensitive Editing Selecting a Major Mode 240 Human-Language Modes 240 CMode

243

Customizing Indention Comments

Special-Purpose Customizing

246

247

emacs

Modes

247

249

The .emacs Startup File 250 Remapping Keys 251 A Sample .emacs File 253 More Information Access to

emacs

Chapter Summary Exercises

Advanced

254 254 254

262 Exercises

264

239

217

xix

xx

Contents

PART III

The Shells

267

Chapter 8: The Bourne Again Shell

269

270

Background Shell Basics

271

Startup Files

271

Commands That Are

Symbols 275 Redirecting Standard Error 275 Writing a Simple Shell Script 278 Separating and Grouping Commands Job Control

281

285

Manipulating the Directory Stack Parameters and Variables

288

290

User-Created Variables 292 Variable Attributes 295 Keyword Variables 296

Special Characters Processes

304

306

Process

Structure

306

Process Identification

Executing History

a

306

Command

308

308

Variables That Control

History 308 Reexecuting and Editing Commands 310 The Readline Libra ry Aliases

318

324

Single Versus Double Quotation Marks Examples of Aliases 326 Functions

327

Controlling

bash: Features and

Command-Line

Options

Shell Features

330

Options

in

330

330

Processing the Command Line 334 History Expansion 334 Alias Substitution 334 Parsing and Scanning the Command Line Command-Line Expansion

Chapter Summary

343

Aliases

335

334

325

Contents

Exercises

345

Advanced Exercises

347

Chapter 9: The TC Shell Shell

350

Scripts and

Entering

Startup

349

Leaving the

Files

TC Shell

351

352

Features Common

Again and TC Shells

the Bourne

to

Command-Line Expansion (Substitution)

Job Control

358

Filename Substitution

Manipulating

the

358

Directory Stack

Command Substitution

359

Redirecting Standard Error

359

"Working with the Command Line Word

Completion

360

Editing the Command Line Correcting Spelling 364 Variables

360 363

365

Variable Substitution

366

String Variables Arrays of String Variables 366

Numeric Variables

Braces

370

Special Variable Forms Shell Variables

371

Control Structures

378

if

371

378

381

goto

In terrupt

Handling

if...then...else foreach while

381

382

383 385

break and continue switch Builtins

3 86

387

Chapter Summary Exercises

367

368

391

392

Advanced Exercises

394

385

359

354

353

xxi

xxii

Contents

PART IV

Programming Tools

395

Chapter 10: Programming the Bourne Again Shell 398

Control Structures iL.then

398

iL.then...else

402

iL.then...elif

405

for...in

for

411

412

while until

414 418

break and continue 427

select

Here Document File

420

421

case

Descriptors

429

431

Parameters and Variables

Array Variables

434

434

Locality of Variables 436 Special Parameters 438 Positional Parameters

440

Expanding Null and Unset Variables Builtin Commands type:

Displays Information

About

read:

Accepts User Input

447

exec:

Executes

trap: Catches kill: Aborts

a

a

Command

a

Process

or

a

Command

Redirects File

Descriptors

456

A Partial List of Builtins

456 459

460

Arithmetic Evaluation

460

Logical Evaluation (Conditional Expressions) String Pattern Matching 462 Operators 463 Shell

Programs

468

A Recursive Shell The

Script 469 quiz Shell Script 472

Chapter Summary Exercises

447

453

Signal

getopts: Parses Options

Expressions

445

446

478

480

Advanced Exercises

482

461

450

397

Contents

Chapter 11: The Perl Scripting Language Introduction

to

Perl

485

486

More Information

486

487

Help

perldoc

487

Terminology 489 Running a Perl Program Variables

490

491

Syntax

493

Scalar Variables

495

Variables

497

Array

Hash Variables

500

Control Structures

if/unless

501

501

if...else

503

if...elsif...else

504

foreach/for last and

505

506

next

while/until

508

Working with Files Sort

xxiil

510

513

Subroutines

515

517

Regular Expressions Syntax and the CPAN Modules

=~

Operator

518

523

525

Examples

Chapter Summary Exercises

529

529

Advanced Exercises

530

Chapter 12: The AWK Pattern Processing Language Syntax

532

Arguments Options Notes

532

533 534

Language Basics Patterns Actions

534

534 535

Comments Variables Functions Arithmetic

535

535 536

Operators

537

531

xxlv

Contents

538

Associative Arrays 538

printf

Control Structures

Examples

539

541

gawk Programming

Advanced

getline: Controlling Input Coprocess: Two-Way I/O Getting Input from

558 558

560

Network

a

562

563

Chapter Summary 563

Exercises

Advanced Exercises

564

Chapter 13: Thesed Editor Syntax

565

566 566

Arguments

566

Options

Editor Basics

567

Addresses

567

Instructions

568

Control Structures The Hold

Examples

569 570

Space

570

Chapter Summary Exercises

581

581

Chapter 14: The rsync Secure Copy Utility Syntax

584

Arguments

Options Notes

584

584

586

More Information

586

Examples Using a Trailing Slash (/) on source-file 587 Removing Files 588 Copying Files to and from a Remote System Mirroring a Directory 590 Making Backups 591 587

Chapter Summary Exercises

594

594

590

583

Contents

PARTV Standard

Command Reference

Multiplicative Suffixes

Common

Options Utility

The sample

597

602

603 604

sample Brief description of what the utility does 607 aspell Checks a file for spelling errors at

Executes commands

at a

specified time

bzip2 Compresses or decompresses files 617 cal Displays a calendar cat

cd

chgrp chmod chown

Joins and displays files another

605 611

615

618

working directory

620

Changes

to

Changes

the group associated with a file 622 the access mode (permissions) of a file

Changes Changes the

owner

of

associated with

a

626

file and/or the group the file is

631

Compares two files 634 Compares sorted files 636 configure Configures source code automatically 640 cp Copies files cmp

comm

cpio Creates

archive,

an

directory hierarchy crontab cut date dd

df diff

or

archive,

an

input

lines

or sets the system time and date 658 Converts and copies a file

Displays

copies

a

649

fields from

652

655

Displays

Displays disk

or

644

Maintains crontab files

Selects characters

files from

restores

638

661

space usage

the differences between

two text

files

663

Checks, modifies, and repairs local volumes C3© 668 671 ditto Copies files and creates and unpacks archives BD 673 kernel dmesg Displays messages dscl Displays and manages Directory Service information GED

diskutil

du

Displays information and/or file

echo expr file find

Displays

a

Evaluates

Displays

on

680

expression

682

the classification of

Finds files based

on

criteria

a

file

Displays

information about users

fmt

Formats

text

Checks and

very

simply

686

688

finger fsck

by directory hierarchy

677

message

an

disk usage

695

697

repairs a filesystem

699

ftp Transfers files over a network 704 gawk Searches for and processes patterns in gcc

Compiles

C and C++ programs

712

a

file

711

674

xxv

xxvi

Contents

GetFilelnfo

Displays file

attributes 6E©

grep

Searches for

a

717

pattern in files

719 files

gzip Compresses or decompresses head Displays the beginning of a file kill

Terminates

killall

Terminates

launchctl less In

make man

Displays text files,

740

printers

742

Displays information

about

link

a

Keeps

a set

Displays

mkfs

Creates

a

nohup od open otool

time

one or more

plutil pr ps rep renice

rlogin rm

files

745

753

current

759

Renames

a

Dumps

file

or moves a

the

Changes Runs

763

priority of

command that the

keeps

of

contents

file

a

773

running after

you

Manipulates property

list files @©

Paginates files for printing

Displays process Copies

the

Changes Logs in on

a

files

Removes

file

a

priority

of

Removes directories

rsh

Executes commands

an

archive,

or

copies

system

800

792

a

to or

a

from

a remote

802

process 803

link)

804

806 on

a remote

system

807

rsync Copies files and directory hierarchies securely scp Securely copies one or more files to or from a SetFile

Edits

a

file

split Divides

a

ssh stat

network

remote

system

813

process that sleeps for 817 sort Sorts and/or merges files a

over a

812

noninteractively

Sets file attributes G3J Creates

sleep

a

794

remote system

(deletes

782

796

status

one or more

775

out

784

archive, restores files from directory hierarchy 786 an

rmdir

sed

log

776

Opens files, directories, and URLs