The Linux Command Line

内容简介：

You've experienced the shiny, point-and-click surface of your Linux computer-now dive below and explore its depths with the power of the command line. The Linux Command Line takes you from your very first terminal keystrokes to writing full programs in Bash, the most popular Linux shell. Along the way you'll learn the timeless skills handed down by generations of gray-bearded, mouse-shunning gurus: file navigation, environment configuration, command chaining, pattern matching with regular expressions, and more. In addition to that practical knowledge, author William Shotts reveals the philosophy behind these tools and the rich heritage that your desktop Linux machine has inherited from Unix supercomputers of yore. As you make your way through the book's short, easily-digestible chapters, you'll learn how to: * Create and delete files, directories, and symlinks * Administer your system, including networking, package installation, and process management * Use standard input and output, redirection, and pipelines * Edit files with Vi, the world's most popular text editor * Write shell scripts to automate common or boring tasks * Slice and dice text files with cut, paste, grep, patch, and sed Once you overcome your initial "shell shock," you'll find that the command line is a natural and expressive way to communicate with your computer. Just don't be surprised if your mouse starts to gather dust.

目录：

Part 1 – Introduction.........................................................................1

1 – Introduction................................................................................................2

Why Use The Command Line?.......................................................................................2

What This Book Is About.................................................................................................3

Who Should Read This Book..........................................................................................3

What's In This Book.........................................................................................................4

How To Read This Book..................................................................................................5

Prerequisites...............................................................................................................5

Why I Don't Call It “GNU/Linux”.............................................................................5

Acknowledgments...........................................................................................................6

Your Feedback Is Needed!..............................................................................................7

Further Reading...............................................................................................................7

Colophon.........................................................................................................................7

Part 2 – Learning The Shell..............................................................9

2 – What Is The Shell?...................................................................................10

Terminal Emulators........................................................................................................10

Your First Keystrokes....................................................................................................10

Command History.....................................................................................................11

Cursor Movement.....................................................................................................11

A Few Words About Mice And Focus...................................................................11

Try Some Simple Commands........................................................................................12

Ending A Terminal Session............................................................................................13

The Console Behind The Curtain........................................................................13

Further Reading.............................................................................................................13

3 – Navigation.................................................................................................14

Understanding The File System Tree............................................................................14

The Current Working Directory......................................................................................14

Listing The Contents Of A Directory..............................................................................15

Changing The Current Working Directory.....................................................................16

Absolute Pathnames................................................................................................16

Relative Pathnames.................................................................................................16

Some Helpful Shortcuts............................................................................................18

Important Facts About Filenames........................................................................18

4 – Exploring The System.............................................................................20

More Fun With ls...........................................................................................................20

Options And Arguments............................................................................................21

A Longer Look At Long Format.................................................................................22

Determining A File's Type With file................................................................................23

Viewing File Contents With less....................................................................................24

What Is “Text”?.....................................................................................................24

Less Is More........................................................................................................26

A Guided Tour................................................................................................................26

Symbolic Links...............................................................................................................29

Hard Links.....................................................................................................................30

Further Reading.............................................................................................................30

5 – Manipulating Files And Directories........................................................31

Wildcards.......................................................................................................................31

Character Ranges................................................................................................33

Wildcards Work In The GUI Too..........................................................................33

mkdir – Create Directories.............................................................................................34

cp – Copy Files And Directories....................................................................................34

Useful Options And Examples..................................................................................35

mv – Move And Rename Files......................................................................................36

Useful Options And Examples..................................................................................36

rm – Remove Files And Directories...............................................................................37

Useful Options And Examples..................................................................................37

Be Careful With rm!.............................................................................................38

ln – Create Links............................................................................................................39

Hard Links................................................................................................................39

Symbolic Links..........................................................................................................40

Let's Build A Playground................................................................................................40

Creating Directories..................................................................................................40

Copying Files............................................................................................................41

Moving And Renaming Files.....................................................................................42

Creating Hard Links..................................................................................................43

Creating Symbolic Links...........................................................................................44

Removing Files And Directories...............................................................................45

Creating Symlinks With The GUI.........................................................................47

Summing Up.............................................................................................................47

6 – Working With Commands........................................................................48

What Exactly Are Commands?......................................................................................48

Identifying Commands...................................................................................................49

type – Display A Command's Type...........................................................................49

which – Display An Executable's Location...............................................................49

Getting A Command's Documentation..........................................................................50

help – Get Help For Shell Builtins............................................................................50

--help – Display Usage Information..........................................................................51

man – Display A Program's Manual Page................................................................51

apropos – Display Appropriate Commands..............................................................53

whatis – Display A Very Brief Description Of A Command.......................................53

The Most Brutal Man Page Of Them All..............................................................53

info – Display A Program's Info Entry.......................................................................54

README And Other Program Documentation Files................................................55

Creating Your Own Commands With alias....................................................................56

Revisiting Old Friends...................................................................................................58

Further Reading.............................................................................................................58

7 – Redirection................................................................................................59

Standard Input, Output, And Error.................................................................................59

Redirecting Standard Output.........................................................................................60

Redirecting Standard Error............................................................................................61

Redirecting Standard Output And Standard Error To One File................................62

Disposing Of Unwanted Output................................................................................63

/dev/null In Unix Culture......................................................................................63

Redirecting Standard Input............................................................................................63

cat – Concatenate Files............................................................................................63

Pipelines........................................................................................................................65

Filters........................................................................................................................66

uniq - Report Or Omit Repeated Lines....................................................................66

wc – Print Line, Word, And Byte Counts..................................................................67

grep – Print Lines Matching A Pattern......................................................................67

head / tail – Print First / Last Part Of Files................................................................68

tee – Read From Stdin And Output To Stdout And Files..........................................69

Summing Up..................................................................................................................70

Linux Is About Imagination..................................................................................70

8 – Seeing The World As The Shell Sees It..................................................72

Expansion......................................................................................................................72

Pathname Expansion...............................................................................................73

Pathname Expansion Of Hidden Files.................................................................74

Tilde Expansion........................................................................................................74

Arithmetic Expansion................................................................................................75

Brace Expansion......................................................................................................76

Parameter Expansion...............................................................................................77

Command Substitution.............................................................................................78

Quoting..........................................................................................................................79

Double Quotes..........................................................................................................79

Single Quotes...........................................................................................................81

Escaping Characters................................................................................................82

Backslash Escape Sequences............................................................................82

Summing Up..................................................................................................................83

Further Reading.............................................................................................................83

9 – Advanced Keyboard Tricks.....................................................................84

Command Line Editing..................................................................................................84

Cursor Movement.....................................................................................................84

Modifying Text...........................................................................................................85

Cutting And Pasting (Killing And Yanking) Text........................................................85

The Meta Key......................................................................................................86

Completion....................................................................................................................86

Programmable Completion..................................................................................88

Using History.................................................................................................................88

Searching History.....................................................................................................89

History Expansion.....................................................................................................91

script....................................................................................................................91

Summing Up..................................................................................................................92

Further Reading.............................................................................................................92

10 – Permissions............................................................................................93

Owners, Group Members, And Everybody Else............................................................94

Reading, Writing, And Executing...................................................................................95

chmod – Change file mode.......................................................................................97

What The Heck Is Octal?.....................................................................................98

Setting File Mode With The GUI.............................................................................100

umask – Set Default Permissions..........................................................................101

Some Special Permissions................................................................................103

Changing Identities......................................................................................................104

su – Run A Shell With Substitute User And Group IDs..........................................105

sudo – Execute A Command As Another User.......................................................106

Ubuntu And sudo...............................................................................................107

chown – Change File Owner And Group................................................................107

chgrp – Change Group Ownership.........................................................................109

Exercising Our Privileges............................................................................................109

Changing Your Password.............................................................................................111

Further Reading...........................................................................................................112

11 – Processes..............................................................................................113

How A Process Works.................................................................................................113

Viewing Processes......................................................................................................114

Viewing Processes Dynamically With top...............................................................116

Controlling Processes..................................................................................................118

Interrupting A Process.............................................................................................119

Putting A Process In The Background....................................................................119

Returning A Process To The Foreground...............................................................120

Stopping (Pausing) A Process................................................................................121

Signals.........................................................................................................................122

Sending Signals To Processes With kill.................................................................122

Sending Signals To Multiple Processes With killall................................................125

More Process Related Commands.............................................................................125

Part 3 – Configuration And The Environment.............................127

12 – The Environment..................................................................................128

What Is Stored In The Environment?..........................................................................128

Examining The Environment..................................................................................128

Some Interesting Variables.....................................................................................130

How Is The Environment Established?.......................................................................131

What's In A Startup File?........................................................................................132

Modifying The Environment.........................................................................................134

Which Files Should We Modify?.............................................................................134

Text Editors.............................................................................................................134

Using A Text Editor.................................................................................................135

Why Comments Are Important..........................................................................138

Activating Our Changes..........................................................................................139

Summing Up................................................................................................................139

Further Reading..........................................................................................................139

13 – A Gentle Introduction To vi.................................................................140

Why We Should Learn vi.............................................................................................140

A Little Background ....................................................................................................141

Starting And Stopping vi..............................................................................................141

Compatibility Mode............................................................................................142

Editing Modes..............................................................................................................143

Entering Insert Mode..............................................................................................144

Saving Our Work....................................................................................................144

Moving The Cursor Around.........................................................................................145

Basic Editing................................................................................................................146

Appending Text.......................................................................................................146

Opening A Line.......................................................................................................147

Deleting Text...........................................................................................................148

Cutting, Copying And Pasting Text.........................................................................149

Joining Lines...........................................................................................................151

Search And Replace....................................................................................................151

Searching Within A Line..........................................................................................151

Searching The Entire File.......................................................................................151

Global Search And Replace...................................................................................152

Editing Multiple Files...................................................................................................154

Switching Between Files.........................................................................................155

Opening Additional Files For Editing......................................................................155

Copying Content From One File Into Another........................................................156

Inserting An Entire File Into Another.......................................................................157

Saving Our Work.........................................................................................................158

Further Reading..........................................................................................................159

14 – Customizing The Prompt.....................................................................160

Anatomy Of A Prompt..................................................................................................160

Trying Some Alternate Prompt Designs......................................................................162

Adding Color................................................................................................................163

Terminal Confusion............................................................................................163

Moving The Cursor......................................................................................................166

Saving The Prompt......................................................................................................167

Summing Up................................................................................................................167

Further Reading..........................................................................................................168

Part 4 – Common Tasks And Essential Tools.............................169

15 – Package Management..........................................................................170

Packaging Systems.....................................................................................................170

How A Package System Works...................................................................................171

Package Files.........................................................................................................171

Repositories............................................................................................................171

Dependencies.........................................................................................................172

High And Low-level Package Tools........................................................................172

Common Package Management Tasks.......................................................................173

Finding A Package In A Repository........................................................................173

Installing A Package From A Repository.................................................................173

Installing A Package From A Package File.............................................................174

Removing A Package.............................................................................................174

Updating Packages From A Repository..................................................................175

Upgrading A Package From A Package File...........................................................175

Listing Installed Packages......................................................................................176

Determining If A Package Is Installed.....................................................................176

Displaying Info About An Installed Package...........................................................177

Finding Which Package Installed A File.................................................................177

Summing Up................................................................................................................177

The Linux Software Installation Myth.................................................................178

Further Reading..........................................................................................................179

16 – Storage Media.......................................................................................180

Mounting And Unmounting Storage Devices..............................................................180

Viewing A List Of Mounted File Systems................................................................182

Why Unmounting Is Important...........................................................................185

Determining Device Names....................................................................................186

Creating New File Systems.........................................................................................189

Manipulating Partitions With fdisk..........................................................................189

Creating A New File System With mkfs..................................................................192

Testing And Repairing File Systems............................................................................193

What The fsck?..................................................................................................193

Formatting Floppy Disks..............................................................................................193

Moving Data Directly To/From Devices.......................................................................194

Creating CD-ROM Images..........................................................................................195

Creating An Image Copy Of A CD-ROM.................................................................195

Creating An Image From A Collection Of Files.......................................................195

A Program By Any Other Name.........................................................................196

Writing CD-ROM Images.............................................................................................196

Mounting An ISO Image Directly............................................................................196

Blanking A Re-Writable CD-ROM...........................................................................197

Writing An Image....................................................................................................197

Further Reading..........................................................................................................197

Extra Credit..................................................................................................................197

17 – Networking............................................................................................199

Examining And Monitoring A Network.........................................................................200

ping.........................................................................................................................200

traceroute...............................................................................................................201

netstat.....................................................................................................................202

Transporting Files Over A Network..............................................................................203

ftp............................................................................................................................204

lftp – A Better ftp.....................................................................................................206

wget........................................................................................................................206

Secure Communication With Remote Hosts...............................................................206

ssh..........................................................................................................................207

Tunneling With SSH..........................................................................................210

scp And sftp............................................................................................................211

An SSH Client For Windows?............................................................................212

Further Reading..........................................................................................................212

18 – Searching For Files..............................................................................213

locate – Find Files The Easy Way...............................................................................213

Where Does The locate Database Come From?..............................................215

find – Find Files The Hard Way...................................................................................215

Tests.......................................................................................................................216

Operators................................................................................................................218

Predefined Actions..................................................................................................221

User Defined Actions..............................................................................................223

Improving Efficiency...............................................................................................224

xargs.......................................................................................................................224

Dealing With Funny Filenames..........................................................................225

A Return To The Playground..................................................................................226

Options...................................................................................................................228

Further Reading..........................................................................................................229

19 – Archiving And Backup.........................................................................230

Compressing Files.......................................................................................................230

gzip.........................................................................................................................231

bzip2.......................................................................................................................233

Don’t Be Compressive Compulsive...................................................................234

Archiving Files.............................................................................................................234

tar............................................................................................................................234

zip...........................................................................................................................240

Synchronizing Files And Directories............................................................................242

Using rsync Over A Network...................................................................................245

Further Reading..........................................................................................................246

20 – Regular Expressions...........................................................................247

What Are Regular Expressions?............................................................................247

grep.............................................................................................................................247

Metacharacters And Literals........................................................................................249

The Any Character......................................................................................................250

Anchors.......................................................................................................................251

A Crossword Puzzle Helper...............................................................................251

Bracket Expressions And Character Classes..............................................................252

Negation.................................................................................................................252

Traditional Character Ranges.................................................................................253

POSIX Character Classes......................................................................................254

Reverting To Traditional Collation Order............................................................257

POSIX Basic Vs. Extended Regular Expressions.......................................................258

POSIX................................................................................................................258

Alternation...................................................................................................................259

Quantifiers...................................................................................................................260

? - Match An Element Zero Or One Time...............................................................260

* - Match An Element Zero Or More Times............................................................261

+ - Match An Element One Or More Times............................................................262

{ } - Match An Element A Specific Number Of Times..............................................262

Putting Regular Expressions To Work.........................................................................263

Validating A Phone List With grep...........................................................................263

Finding Ugly Filenames With find...........................................................................264

Searching For Files With locate.............................................................................265

Searching For Text In less And vim........................................................................265

Summing Up................................................................................................................267

Further Reading..........................................................................................................267

21 – Text Processing....................................................................................268

Applications Of Text.....................................................................................................268

Documents.............................................................................................................269

Web Pages.............................................................................................................269

Email.......................................................................................................................269

Printer Output.........................................................................................................269

Program Source Code............................................................................................269

Revisiting Some Old Friends.......................................................................................269

cat...........................................................................................................................270

MS-DOS Text Vs. Unix Text...............................................................................271

sort..........................................................................................................................271

uniq.........................................................................................................................279

Slicing And Dicing........................................................................................................280

cut...........................................................................................................................280

Expanding Tabs.................................................................................................283

paste.......................................................................................................................284

join..........................................................................................................................285

Comparing Text...........................................................................................................287

comm......................................................................................................................288

diff...........................................................................................................................288

patch.......................................................................................................................291

Editing On The Fly.......................................................................................................292

tr..............................................................................................................................292

ROT13: The Not-So-Secret Decoder Ring........................................................294

sed..........................................................................................................................295

People Who Like sed Also Like.........................................................................303

aspell......................................................................................................................303

Summing Up................................................................................................................307

Further Reading..........................................................................................................307

Extra Credit..................................................................................................................308

22 – Formatting Output................................................................................309

Simple Formatting Tools..............................................................................................309

nl – Number Lines..................................................................................................309

fold – Wrap Each Line To A Specified Length........................................................313

fmt – A Simple Text Formatter................................................................................313

pr – Format Text For Printing..................................................................................317

printf – Format And Print Data................................................................................318

Document Formatting Systems...................................................................................321

groff.........................................................................................................................322

Summing Up................................................................................................................328

Further Reading..........................................................................................................328

23 – Printing..................................................................................................330

A Brief History Of Printing............................................................................................330

Printing In The Dim Times......................................................................................330

Character-based Printers.......................................................................................331

Graphical Printers...................................................................................................332

Printing With Linux......................................................................................................333

Preparing Files For Printing.........................................................................................333

pr – Convert Text Files For Printing........................................................................333

Sending A Print Job To A Printer..................................................................................335

lpr – Print Files (Berkeley Style).............................................................................335

lp – Print Files (System V Style).............................................................................336

Another Option: a2ps..............................................................................................337

Monitoring And Controlling Print Jobs.........................................................................340

lpstat – Display Print System Status......................................................................340

lpq – Display Printer Queue Status........................................................................341

lprm / cancel – Cancel Print Jobs..........................................................................342

Summing Up................................................................................................................342

Further Reading..........................................................................................................342

24 – Compiling Programs............................................................................344

What Is Compiling?.....................................................................................................344

Are All Programs Compiled?..................................................................................345

Compiling A C Program...............................................................................................346

Obtaining The Source Code...................................................................................346

Examining The Source Tree...................................................................................348

Building The Program.............................................................................................350

Installing The Program...........................................................................................354

Summing Up................................................................................................................354

Further Reading..........................................................................................................355

Part 5 – Writing Shell Scripts.......................................................357

25 – Writing Your First Script......................................................................358

What Are Shell Scripts?...............................................................................................358

How To Write A Shell Script.........................................................................................358

Script File Format........................................................................................................359

Executable Permissions..............................................................................................360

Script File Location......................................................................................................360

Good Locations For Scripts....................................................................................362

More Formatting Tricks................................................................................................362

Long Option Names................................................................................................362

Indentation And Line Continuation.........................................................................362

Configuring vim For Script Writing.....................................................................363

Summing Up................................................................................................................364

Further Reading..........................................................................................................364

26 – Starting A Project.................................................................................365

First Stage: Minimal Document...................................................................................365

Second Stage: Adding A Little Data............................................................................367

Variables And Constants.............................................................................................368

Assigning Values To Variables And Constants.......................................................371

Here Documents.........................................................................................................372

Summing Up................................................................................................................375

Further Reading..........................................................................................................375

27 – Top-Down Design.................................................................................376

Shell Functions............................................................................................................377

Local Variables............................................................................................................380

Keep Scripts Running..................................................................................................381

Shell Functions In Your .bashrc File..................................................................384

Summing Up................................................................................................................384

Further Reading..........................................................................................................384

28 – Flow Control: Branching With if.........................................................385

if...................................................................................................................................385

Exit Status...................................................................................................................386

test...............................................................................................................................388

File Expressions.....................................................................................................388

String Expressions..................................................................................................391

Integer Expressions................................................................................................392

A More Modern Version Of test...................................................................................393

(( )) - Designed For Integers........................................................................................395

Combining Expressions...............................................................................................396

Portability Is The Hobgoblin Of Little Minds.......................................................398

Control Operators: Another Way To Branch................................................................399

Summing Up................................................................................................................399

Further Reading..........................................................................................................400

29 – Reading Keyboard Input......................................................................401

read – Read Values From Standard Input...................................................................402

Options...................................................................................................................404

IFS..........................................................................................................................406

You Can’t Pipe read...........................................................................................407

Validating Input............................................................................................................408

Menus..........................................................................................................................409

Summing Up................................................................................................................411

Extra Credit.............................................................................................................411

Further Reading...........................................................................................................411

30 – Flow Control: Looping With while / until...........................................412

Looping........................................................................................................................412

while........................................................................................................................412

Breaking Out Of A Loop...............................................................................................415

until.........................................................................................................................416

Reading Files With Loops...........................................................................................417

Summing Up................................................................................................................418

Further Reading..........................................................................................................418

31 – Troubleshooting...................................................................................419

Syntactic Errors...........................................................................................................419

Missing Quotes.......................................................................................................420

Missing Or Unexpected Tokens..............................................................................420

Unanticipated Expansions......................................................................................421

Logical Errors .............................................................................................................423

Defensive Programming.........................................................................................423

Verifying Input.........................................................................................................425

Design Is A Function Of Time............................................................................425

Testing.........................................................................................................................425

Test Cases..............................................................................................................426

Debugging...................................................................................................................427

Finding The Problem Area......................................................................................427

Tracing....................................................................................................................427

Examining Values During Execution......................................................................430

Summing Up................................................................................................................430

Further Reading..........................................................................................................431

32 – Flow Control: Branching With case...................................................432

case.............................................................................................................................432

Patterns..................................................................................................................434

Summing Up................................................................................................................436

Further Reading..........................................................................................................436

33 – Positional Parameters.........................................................................437

Accessing The Command Line...................................................................................437

Determining The Number of Arguments.................................................................438

shift – Getting Access To Many Arguments............................................................439

Simple Applications................................................................................................440

Using Positional Parameters With Shell Functions................................................441

Handling Positional Parameters En Masse.................................................................442

A More Complete Application......................................................................................444

Summing Up................................................................................................................447

Further Reading..........................................................................................................450

34 – Flow Control: Looping With for..........................................................451

for: Traditional Shell Form...........................................................................................451

Why i?................................................................................................................453

for: C Language Form.................................................................................................454

Summing Up................................................................................................................455

Further Reading..........................................................................................................456

35 – Strings And Numbers..........................................................................457

Parameter Expansion..................................................................................................457

Basic Parameters...................................................................................................457

Expansions To Manage Empty Variables...............................................................458

Expansions That Return Variable Names..............................................................460

String Operations....................................................................................................460

Arithmetic Evaluation And Expansion.........................................................................463

Number Bases........................................................................................................464

Unary Operators.....................................................................................................464

Simple Arithmetic....................................................................................................464

Assignment.............................................................................................................466

Bit Operations.........................................................................................................468

Logic.......................................................................................................................469

bc – An Arbitrary Precision Calculator Language........................................................472

Using bc..................................................................................................................473

An Example Script..................................................................................................473

Summing Up................................................................................................................475

Extra Credit..................................................................................................................475

Further Reading..........................................................................................................475

36 – Arrays....................................................................................................476

What Are Arrays?........................................................................................................476

Creating An Array........................................................................................................476

Assigning Values To An Array......................................................................................477

Accessing Array Elements...........................................................................................478

Array Operations.........................................................................................................480

Outputting The Entire Contents Of An Array..........................................................480

Determining The Number Of Array Elements.........................................................480

Finding The Subscripts Used By An Array.............................................................481

Adding Elements To The End Of An Array.............................................................481

Sorting An Array......................................................................................................482

Deleting An Array....................................................................................................482

Summing Up................................................................................................................483

Further Reading..........................................................................................................484

37 – Exotica...................................................................................................485

Group Commands And Subshells...............................................................................485

Process Substitution...............................................................................................486

Traps............................................................................................................................488

Temporary Files.................................................................................................491

Asynchronous Execution.............................................................................................492

wait.........................................................................................................................492

Named Pipes...............................................................................................................493

Setting Up A Named Pipe.......................................................................................494

Using Named Pipes................................................................................................494

Summing Up................................................................................................................495

Further Reading..........................................................................................................495