Table Of Content

The Linux Command Line Second Internet Edition William E. Shotts, Jr. A LinuxCommand.org Book Copyright ©2008-2013, William E. Shotts, Jr. This work is licensed under the Creative Commons Attribution-Noncommercial-No De- rivative Works 3.0 United States License. To view a copy of this license, visit the link above or send a letter to Creative Commons, 171 Second Street, Suite 300, San Fran- cisco, California, 94105, USA. Linux® is the registered trademark of Linus Torvalds. All other trademarks belong to their respective owners. This book is part of the LinuxCommand.org project, a site for Linux education and advo- cacy devoted to helping users of legacy operating systems migrate into the future. You may contact the LinuxCommand.org project at http://linuxcommand.org. This book is also available in printed form, published by No Starch Press and may be purchased wherever fine books are sold. No Starch Press also offers this book in elec- tronic formats for most popular e-readers: http://nostarch.com/tlcl.htm Release History Version Date Description 13.07 July 6, 2013 Second Internet Edition. 09.12 December 14, 2009 First Internet Edition. 09.11 November 19, 2009 Fourth draft with almost all reviewer feedback incorporated and edited through chapter 37. 09.10 October 3, 2009 Third draft with revised table formatting, partial application of reviewers feedback and edited through chapter 18. 09.08 August 12, 2009 Second draft incorporating the first editing pass. 09.07 July 18, 2009 Completed first draft. Table of Contents Introduction....................................................................................................xvi Why Use The Command Line?.....................................................................................xvi What This Book Is About..............................................................................................xvii Who Should Read This Book.......................................................................................xvii What's In This Book.....................................................................................................xviii How To Read This Book..............................................................................................xviii Prerequisites............................................................................................................xix Why I Don't Call It “GNU/Linux”...........................................................................xix Acknowledgments..........................................................................................................xx Your Feedback Is Needed!............................................................................................xx What's New In The Second Internet Edition.................................................................xxi Further Reading............................................................................................................xxi Colophon.......................................................................................................................xxi Part 1 – Learning The Shell..............................................................1 1 – What Is The Shell?.....................................................................................2 Terminal Emulators..........................................................................................................2 Your First Keystrokes......................................................................................................2 Command History.......................................................................................................3 Cursor Movement.......................................................................................................3 A Few Words About Mice And Focus....................................................................3 Try Some Simple Commands..........................................................................................4 Ending A Terminal Session..............................................................................................5 The Console Behind The Curtain..........................................................................5 Summing Up....................................................................................................................5 Further Reading...............................................................................................................6 2 – Navigation...................................................................................................7 Understanding The File System Tree..............................................................................7 The Current Working Directory........................................................................................7 Listing The Contents Of A Directory................................................................................8 Changing The Current Working Directory.......................................................................9 Absolute Pathnames..................................................................................................9 Relative Pathnames...................................................................................................9 Some Helpful Shortcuts............................................................................................11 Important Facts About Filenames........................................................................11 i Summing Up..................................................................................................................12 3 – Exploring The System.............................................................................13 More Fun With ls...........................................................................................................13 Options And Arguments............................................................................................14 A Longer Look At Long Format.................................................................................16 Determining A File's Type With file................................................................................17 Viewing File Contents With less....................................................................................17 What Is “Text”?.....................................................................................................17 Less Is More........................................................................................................19 A Guided Tour................................................................................................................19 Symbolic Links...............................................................................................................23 Hard Links.....................................................................................................................24 Summing Up..................................................................................................................24 Further Reading.............................................................................................................24 4 – Manipulating Files And Directories........................................................25 Wildcards.......................................................................................................................25 Character Ranges................................................................................................27 Wildcards Work In The GUI Too..........................................................................27 mkdir – Create Directories.............................................................................................28 cp – Copy Files And Directories....................................................................................28 Useful Options And Examples..................................................................................29 mv – Move And Rename Files......................................................................................30 Useful Options And Examples..................................................................................30 rm – Remove Files And Directories...............................................................................31 Useful Options And Examples..................................................................................31 Be Careful With rm!.............................................................................................32 ln – Create Links............................................................................................................33 Hard Links................................................................................................................33 Symbolic Links..........................................................................................................33 Let's Build A Playground................................................................................................34 Creating Directories..................................................................................................34 Copying Files............................................................................................................34 Moving And Renaming Files.....................................................................................35 Creating Hard Links..................................................................................................37 Creating Symbolic Links...........................................................................................38 Removing Files And Directories...............................................................................39 Creating Symlinks With The GUI.........................................................................40 Summing Up..................................................................................................................41 Further Reading.............................................................................................................41 5 – Working With Commands........................................................................42 What Exactly Are Commands?......................................................................................42 Identifying Commands...................................................................................................43 type – Display A Command's Type...........................................................................43 which – Display An Executable's Location...............................................................43 Getting A Command's Documentation..........................................................................44 help – Get Help For Shell Builtins............................................................................44 --help – Display Usage Information..........................................................................45 ii man – Display A Program's Manual Page................................................................45 apropos – Display Appropriate Commands..............................................................47 whatis – Display A Very Brief Description Of A Command.......................................47 The Most Brutal Man Page Of Them All..............................................................48 info – Display A Program's Info Entry.......................................................................48 README And Other Program Documentation Files................................................49 Creating Your Own Commands With alias....................................................................50 Summing Up..................................................................................................................52 Further Reading.............................................................................................................52 6 – Redirection................................................................................................53 Standard Input, Output, And Error.................................................................................53 Redirecting Standard Output.........................................................................................54 Redirecting Standard Error............................................................................................55 Redirecting Standard Output And Standard Error To One File................................56 Disposing Of Unwanted Output................................................................................57 /dev/null In Unix Culture......................................................................................57 Redirecting Standard Input............................................................................................57 cat – Concatenate Files............................................................................................57 Pipelines........................................................................................................................59 The Difference Between > and |..........................................................................60 Filters........................................................................................................................61 uniq - Report Or Omit Repeated Lines.....................................................................61 wc – Print Line, Word, And Byte Counts..................................................................62 grep – Print Lines Matching A Pattern......................................................................62 head / tail – Print First / Last Part Of Files................................................................63 tee – Read From Stdin And Output To Stdout And Files..........................................64 Summing Up..................................................................................................................65 Linux Is About Imagination..................................................................................65 7 – Seeing The World As The Shell Sees It..................................................67 Expansion......................................................................................................................67 Pathname Expansion...............................................................................................68 Pathname Expansion Of Hidden Files.................................................................69 Tilde Expansion........................................................................................................69 Arithmetic Expansion................................................................................................70 Brace Expansion......................................................................................................71 Parameter Expansion...............................................................................................72 Command Substitution.............................................................................................73 Quoting..........................................................................................................................74 Double Quotes..........................................................................................................75 Single Quotes...........................................................................................................76 Escaping Characters................................................................................................77 Backslash Escape Sequences............................................................................77 Summing Up..................................................................................................................78 Further Reading.............................................................................................................78 8 – Advanced Keyboard Tricks.....................................................................79 Command Line Editing..................................................................................................79 Cursor Movement.....................................................................................................79 iii Modifying Text...........................................................................................................80 Cutting And Pasting (Killing And Yanking) Text........................................................80 The Meta Key......................................................................................................81 Completion....................................................................................................................81 Programmable Completion..................................................................................83 Using History.................................................................................................................83 Searching History.....................................................................................................84 History Expansion.....................................................................................................86 script....................................................................................................................86 Summing Up..................................................................................................................86 Further Reading.............................................................................................................87 9 – Permissions..............................................................................................88 Owners, Group Members, And Everybody Else............................................................89 Reading, Writing, And Executing...................................................................................90 chmod – Change File Mode.....................................................................................92 What The Heck Is Octal?.....................................................................................93 Setting File Mode With The GUI...............................................................................95 umask – Set Default Permissions............................................................................96 Some Special Permissions..................................................................................98 Changing Identities........................................................................................................99 su – Run A Shell With Substitute User And Group IDs............................................99 sudo – Execute A Command As Another User.......................................................101 Ubuntu And sudo...............................................................................................101 chown – Change File Owner And Group................................................................102 chgrp – Change Group Ownership.........................................................................103 Exercising Our Privileges............................................................................................103 Changing Your Password............................................................................................106 Summing Up................................................................................................................107 Further Reading..........................................................................................................107 10 – Processes.............................................................................................108 How A Process Works.................................................................................................108 Viewing Processes......................................................................................................109 Viewing Processes Dynamically With top..............................................................111 Controlling Processes.................................................................................................113 Interrupting A Process............................................................................................114 Putting A Process In The Background....................................................................114 Returning A Process To The Foreground...............................................................115 Stopping (Pausing) A Process................................................................................116 Signals.........................................................................................................................117 Sending Signals To Processes With kill.................................................................117 Sending Signals To Multiple Processes With killall................................................120 More Process Related Commands.............................................................................120 Summing Up................................................................................................................121 Part 2 – Configuration And The Environment.............................123 11 – The Environment..................................................................................124 iv What Is Stored In The Environment?..........................................................................124 Examining The Environment..................................................................................124 Some Interesting Variables.....................................................................................126 How Is The Environment Established?.......................................................................127 What's In A Startup File?........................................................................................128 Modifying The Environment.........................................................................................130 Which Files Should We Modify?.............................................................................130 Text Editors.............................................................................................................130 Using A Text Editor.................................................................................................131 Why Comments Are Important..........................................................................134 Activating Our Changes..........................................................................................135 Summing Up................................................................................................................135 Further Reading..........................................................................................................135 12 – A Gentle Introduction To vi.................................................................136 Why We Should Learn vi.............................................................................................136 A Little Background ....................................................................................................137 Starting And Stopping vi..............................................................................................137 Compatibility Mode............................................................................................138 Editing Modes..............................................................................................................139 Entering Insert Mode..............................................................................................140 Saving Our Work....................................................................................................140 Moving The Cursor Around.........................................................................................141 Basic Editing................................................................................................................142 Appending Text.......................................................................................................142 Opening A Line.......................................................................................................143 Deleting Text...........................................................................................................144 Cutting, Copying, And Pasting Text........................................................................145 Joining Lines...........................................................................................................147 Search-And-Replace...................................................................................................147 Searching Within A Line..........................................................................................147 Searching The Entire File.......................................................................................147 Global Search-And-Replace...................................................................................148 Editing Multiple Files...................................................................................................150 Switching Between Files.........................................................................................151 Opening Additional Files For Editing......................................................................151 Copying Content From One File Into Another........................................................152 Inserting An Entire File Into Another.......................................................................153 Saving Our Work.........................................................................................................154 Summing Up................................................................................................................155 Further Reading..........................................................................................................155 13 – Customizing The Prompt.....................................................................156 Anatomy Of A Prompt..................................................................................................156 Trying Some Alternative Prompt Designs....................................................................158 Adding Color................................................................................................................159 Terminal Confusion............................................................................................160 Moving The Cursor......................................................................................................162 Saving The Prompt......................................................................................................163 Summing Up................................................................................................................164 v Further Reading..........................................................................................................164 Part 3 – Common Tasks And Essential Tools.............................165 14 – Package Management..........................................................................166 Packaging Systems.....................................................................................................166 How A Package System Works...................................................................................167 Package Files.........................................................................................................167 Repositories............................................................................................................167 Dependencies.........................................................................................................168 High And Low-level Package Tools........................................................................168 Common Package Management Tasks.......................................................................169 Finding A Package In A Repository........................................................................169 Installing A Package From A Repository.................................................................169 Installing A Package From A Package File.............................................................170 Removing A Package.............................................................................................170 Updating Packages From A Repository..................................................................171 Upgrading A Package From A Package File...........................................................171 Listing Installed Packages......................................................................................172 Determining If A Package Is Installed.....................................................................172 Displaying Info About An Installed Package...........................................................173 Finding Which Package Installed A File.................................................................173 Summing Up................................................................................................................173 The Linux Software Installation Myth.................................................................174 Further Reading..........................................................................................................175 15 – Storage Media.......................................................................................176 Mounting And Unmounting Storage Devices..............................................................176 Viewing A List Of Mounted File Systems................................................................178 Why Unmounting Is Important...........................................................................181 Determining Device Names....................................................................................182 Creating New File Systems.........................................................................................185 Manipulating Partitions With fdisk..........................................................................185 Creating A New File System With mkfs..................................................................188 Testing And Repairing File Systems............................................................................189 What The fsck?..................................................................................................189 Formatting Floppy Disks..............................................................................................189 Moving Data Directly To/From Devices.......................................................................190 Creating CD-ROM Images..........................................................................................191 Creating An Image Copy Of A CD-ROM.................................................................191 Creating An Image From A Collection Of Files.......................................................191 A Program By Any Other Name.........................................................................192 Writing CD-ROM Images.............................................................................................192 Mounting An ISO Image Directly............................................................................192 Blanking A Re-Writable CD-ROM...........................................................................193 Writing An Image....................................................................................................193 Summing Up................................................................................................................193 Further Reading..........................................................................................................193 Extra Credit..................................................................................................................193 vi 16 – Networking............................................................................................195 Examining And Monitoring A Network.........................................................................196 ping.........................................................................................................................196 traceroute...............................................................................................................197 netstat.....................................................................................................................198 Transporting Files Over A Network..............................................................................199 ftp............................................................................................................................199 lftp – A Better ftp.....................................................................................................202 wget........................................................................................................................202 Secure Communication With Remote Hosts...............................................................202 ssh..........................................................................................................................203 Tunneling With SSH..........................................................................................206 scp And sftp............................................................................................................207 An SSH Client For Windows?............................................................................208 Summing Up................................................................................................................208 Further Reading..........................................................................................................208 17 – Searching For Files..............................................................................209 locate – Find Files The Easy Way...............................................................................209 Where Does The locate Database Come From?..............................................211 find – Find Files The Hard Way...................................................................................211 Tests.......................................................................................................................212 Operators................................................................................................................214 Predefined Actions..................................................................................................217 User-Defined Actions..............................................................................................219 Improving Efficiency...............................................................................................220 xargs.......................................................................................................................220 Dealing With Funny Filenames..........................................................................221 A Return To The Playground..................................................................................221 Options...................................................................................................................224 Summing Up................................................................................................................225 Further Reading..........................................................................................................225 18 – Archiving And Backup.........................................................................226 Compressing Files.......................................................................................................226 gzip.........................................................................................................................227 bzip2.......................................................................................................................229 Don’t Be Compressive Compulsive...................................................................230 Archiving Files.............................................................................................................230 tar............................................................................................................................230 zip...........................................................................................................................236 Synchronizing Files And Directories............................................................................238 Using rsync Over A Network...................................................................................240 Summing Up................................................................................................................241 Further Reading..........................................................................................................241 19 – Regular Expressions...........................................................................243 What Are Regular Expressions?............................................................................243 grep.............................................................................................................................243 vii Metacharacters And Literals........................................................................................245 The Any Character......................................................................................................246 Anchors.......................................................................................................................247 A Crossword Puzzle Helper...............................................................................247 Bracket Expressions And Character Classes..............................................................248 Negation.................................................................................................................248 Traditional Character Ranges.................................................................................249 POSIX Character Classes......................................................................................250 Reverting To Traditional Collation Order............................................................253 POSIX Basic Vs. Extended Regular Expressions.......................................................254 POSIX................................................................................................................254 Alternation...................................................................................................................255 Quantifiers...................................................................................................................256 ? - Match An Element Zero Or One Time...............................................................256 * - Match An Element Zero Or More Times............................................................257 + - Match An Element One Or More Times............................................................258 { } - Match An Element A Specific Number Of Times..............................................258 Putting Regular Expressions To Work.........................................................................259 Validating A Phone List With grep...........................................................................259 Finding Ugly Filenames With find...........................................................................260 Searching For Files With locate.............................................................................261 Searching For Text With less And vim....................................................................261 Summing Up................................................................................................................263 Further Reading..........................................................................................................263 20 – Text Processing....................................................................................264 Applications Of Text.....................................................................................................264 Documents.............................................................................................................265 Web Pages.............................................................................................................265 Email.......................................................................................................................265 Printer Output.........................................................................................................265 Program Source Code............................................................................................265 Revisiting Some Old Friends.......................................................................................265 cat...........................................................................................................................266 MS-DOS Text Vs. Unix Text...............................................................................267 sort..........................................................................................................................267 uniq.........................................................................................................................275 Slicing And Dicing........................................................................................................276 cut...........................................................................................................................276 Expanding Tabs.................................................................................................279 paste.......................................................................................................................280 join..........................................................................................................................281 Comparing Text...........................................................................................................283 comm......................................................................................................................284 diff...........................................................................................................................284 patch.......................................................................................................................287 Editing On The Fly.......................................................................................................288 tr..............................................................................................................................288 ROT13: The Not-So-Secret Decoder Ring........................................................290 sed..........................................................................................................................290 viii

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The Linux Command Line Second Internet Edition William E. Shotts, Jr. A LinuxCommand.org Book Copyright ©2008-2013, William E. Shotts, Jr. This work is licensed under the Creative Commons Attribution-Noncommercial-No De- rivative Works 3.0 United States License. To view a copy of this license, visit the link above or send a letter to Creative Commons, 171 Second Street, Suite 300, San Fran- cisco, California, 94105, USA. Linux® is the registered trademark of Linus Torvalds. All other trademarks belong to their respective owners. This book is part of the LinuxCommand.org project, a site for Linux education and advo- cacy devoted to helping users of legacy operating systems migrate into the future. You may contact the LinuxCommand.org project at http://linuxcommand.org. This book is also available in printed form, published by No Starch Press and may be purchased wherever fine books are sold. No Starch Press also offers this book in elec- tronic formats for most popular e-readers: http://nostarch.com/tlcl.htm Release History Version Date Description 13.07 July 6, 2013 Second Internet Edition. 09.12 December 14, 2009 First Internet Edition. 09.11 November 19, 2009 Fourth draft with almost all reviewer feedback incorporated and edited through chapter 37. 09.10 October 3, 2009 Third draft with revised table formatting, partial application of reviewers feedback and edited through chapter 18. 09.08 August 12, 2009 Second draft incorporating the first editing pass. 09.07 July 18, 2009 Completed first draft. Table of Contents Introduction....................................................................................................xvi Why Use The Command Line?.....................................................................................xvi What This Book Is About..............................................................................................xvii Who Should Read This Book.......................................................................................xvii What's In This Book.....................................................................................................xviii How To Read This Book..............................................................................................xviii Prerequisites............................................................................................................xix Why I Don't Call It “GNU/Linux”...........................................................................xix Acknowledgments..........................................................................................................xx Your Feedback Is Needed!............................................................................................xx What's New In The Second Internet Edition.................................................................xxi Further Reading............................................................................................................xxi Colophon.......................................................................................................................xxi Part 1 – Learning The Shell..............................................................1 1 – What Is The Shell?.....................................................................................2 Terminal Emulators..........................................................................................................2 Your First Keystrokes......................................................................................................2 Command History.......................................................................................................3 Cursor Movement.......................................................................................................3 A Few Words About Mice And Focus....................................................................3 Try Some Simple Commands..........................................................................................4 Ending A Terminal Session..............................................................................................5 The Console Behind The Curtain..........................................................................5 Summing Up....................................................................................................................5 Further Reading...............................................................................................................6 2 – Navigation...................................................................................................7 Understanding The File System Tree..............................................................................7 The Current Working Directory........................................................................................7 Listing The Contents Of A Directory................................................................................8 Changing The Current Working Directory.......................................................................9 Absolute Pathnames..................................................................................................9 Relative Pathnames...................................................................................................9 Some Helpful Shortcuts............................................................................................11 Important Facts About Filenames........................................................................11 i Summing Up..................................................................................................................12 3 – Exploring The System.............................................................................13 More Fun With ls...........................................................................................................13 Options And Arguments............................................................................................14 A Longer Look At Long Format.................................................................................16 Determining A File's Type With file................................................................................17 Viewing File Contents With less....................................................................................17 What Is “Text”?.....................................................................................................17 Less Is More........................................................................................................19 A Guided Tour................................................................................................................19 Symbolic Links...............................................................................................................23 Hard Links.....................................................................................................................24 Summing Up..................................................................................................................24 Further Reading.............................................................................................................24 4 – Manipulating Files And Directories........................................................25 Wildcards.......................................................................................................................25 Character Ranges................................................................................................27 Wildcards Work In The GUI Too..........................................................................27 mkdir – Create Directories.............................................................................................28 cp – Copy Files And Directories....................................................................................28 Useful Options And Examples..................................................................................29 mv – Move And Rename Files......................................................................................30 Useful Options And Examples..................................................................................30 rm – Remove Files And Directories...............................................................................31 Useful Options And Examples..................................................................................31 Be Careful With rm!.............................................................................................32 ln – Create Links............................................................................................................33 Hard Links................................................................................................................33 Symbolic Links..........................................................................................................33 Let's Build A Playground................................................................................................34 Creating Directories..................................................................................................34 Copying Files............................................................................................................34 Moving And Renaming Files.....................................................................................35 Creating Hard Links..................................................................................................37 Creating Symbolic Links...........................................................................................38 Removing Files And Directories...............................................................................39 Creating Symlinks With The GUI.........................................................................40 Summing Up..................................................................................................................41 Further Reading.............................................................................................................41 5 – Working With Commands........................................................................42 What Exactly Are Commands?......................................................................................42 Identifying Commands...................................................................................................43 type – Display A Command's Type...........................................................................43 which – Display An Executable's Location...............................................................43 Getting A Command's Documentation..........................................................................44 help – Get Help For Shell Builtins............................................................................44 --help – Display Usage Information..........................................................................45 ii man – Display A Program's Manual Page................................................................45 apropos – Display Appropriate Commands..............................................................47 whatis – Display A Very Brief Description Of A Command.......................................47 The Most Brutal Man Page Of Them All..............................................................48 info – Display A Program's Info Entry.......................................................................48 README And Other Program Documentation Files................................................49 Creating Your Own Commands With alias....................................................................50 Summing Up..................................................................................................................52 Further Reading.............................................................................................................52 6 – Redirection................................................................................................53 Standard Input, Output, And Error.................................................................................53 Redirecting Standard Output.........................................................................................54 Redirecting Standard Error............................................................................................55 Redirecting Standard Output And Standard Error To One File................................56 Disposing Of Unwanted Output................................................................................57 /dev/null In Unix Culture......................................................................................57 Redirecting Standard Input............................................................................................57 cat – Concatenate Files............................................................................................57 Pipelines........................................................................................................................59 The Difference Between > and |..........................................................................60 Filters........................................................................................................................61 uniq - Report Or Omit Repeated Lines.....................................................................61 wc – Print Line, Word, And Byte Counts..................................................................62 grep – Print Lines Matching A Pattern......................................................................62 head / tail – Print First / Last Part Of Files................................................................63 tee – Read From Stdin And Output To Stdout And Files..........................................64 Summing Up..................................................................................................................65 Linux Is About Imagination..................................................................................65 7 – Seeing The World As The Shell Sees It..................................................67 Expansion......................................................................................................................67 Pathname Expansion...............................................................................................68 Pathname Expansion Of Hidden Files.................................................................69 Tilde Expansion........................................................................................................69 Arithmetic Expansion................................................................................................70 Brace Expansion......................................................................................................71 Parameter Expansion...............................................................................................72 Command Substitution.............................................................................................73 Quoting..........................................................................................................................74 Double Quotes..........................................................................................................75 Single Quotes...........................................................................................................76 Escaping Characters................................................................................................77 Backslash Escape Sequences............................................................................77 Summing Up..................................................................................................................78 Further Reading.............................................................................................................78 8 – Advanced Keyboard Tricks.....................................................................79 Command Line Editing..................................................................................................79 Cursor Movement.....................................................................................................79 iii Modifying Text...........................................................................................................80 Cutting And Pasting (Killing And Yanking) Text........................................................80 The Meta Key......................................................................................................81 Completion....................................................................................................................81 Programmable Completion..................................................................................83 Using History.................................................................................................................83 Searching History.....................................................................................................84 History Expansion.....................................................................................................86 script....................................................................................................................86 Summing Up..................................................................................................................86 Further Reading.............................................................................................................87 9 – Permissions..............................................................................................88 Owners, Group Members, And Everybody Else............................................................89 Reading, Writing, And Executing...................................................................................90 chmod – Change File Mode.....................................................................................92 What The Heck Is Octal?.....................................................................................93 Setting File Mode With The GUI...............................................................................95 umask – Set Default Permissions............................................................................96 Some Special Permissions..................................................................................98 Changing Identities........................................................................................................99 su – Run A Shell With Substitute User And Group IDs............................................99 sudo – Execute A Command As Another User.......................................................101 Ubuntu And sudo...............................................................................................101 chown – Change File Owner And Group................................................................102 chgrp – Change Group Ownership.........................................................................103 Exercising Our Privileges............................................................................................103 Changing Your Password............................................................................................106 Summing Up................................................................................................................107 Further Reading..........................................................................................................107 10 – Processes.............................................................................................108 How A Process Works.................................................................................................108 Viewing Processes......................................................................................................109 Viewing Processes Dynamically With top..............................................................111 Controlling Processes.................................................................................................113 Interrupting A Process............................................................................................114 Putting A Process In The Background....................................................................114 Returning A Process To The Foreground...............................................................115 Stopping (Pausing) A Process................................................................................116 Signals.........................................................................................................................117 Sending Signals To Processes With kill.................................................................117 Sending Signals To Multiple Processes With killall................................................120 More Process Related Commands.............................................................................120 Summing Up................................................................................................................121 Part 2 – Configuration And The Environment.............................123 11 – The Environment..................................................................................124 iv What Is Stored In The Environment?..........................................................................124 Examining The Environment..................................................................................124 Some Interesting Variables.....................................................................................126 How Is The Environment Established?.......................................................................127 What's In A Startup File?........................................................................................128 Modifying The Environment.........................................................................................130 Which Files Should We Modify?.............................................................................130 Text Editors.............................................................................................................130 Using A Text Editor.................................................................................................131 Why Comments Are Important..........................................................................134 Activating Our Changes..........................................................................................135 Summing Up................................................................................................................135 Further Reading..........................................................................................................135 12 – A Gentle Introduction To vi.................................................................136 Why We Should Learn vi.............................................................................................136 A Little Background ....................................................................................................137 Starting And Stopping vi..............................................................................................137 Compatibility Mode............................................................................................138 Editing Modes..............................................................................................................139 Entering Insert Mode..............................................................................................140 Saving Our Work....................................................................................................140 Moving The Cursor Around.........................................................................................141 Basic Editing................................................................................................................142 Appending Text.......................................................................................................142 Opening A Line.......................................................................................................143 Deleting Text...........................................................................................................144 Cutting, Copying, And Pasting Text........................................................................145 Joining Lines...........................................................................................................147 Search-And-Replace...................................................................................................147 Searching Within A Line..........................................................................................147 Searching The Entire File.......................................................................................147 Global Search-And-Replace...................................................................................148 Editing Multiple Files...................................................................................................150 Switching Between Files.........................................................................................151 Opening Additional Files For Editing......................................................................151 Copying Content From One File Into Another........................................................152 Inserting An Entire File Into Another.......................................................................153 Saving Our Work.........................................................................................................154 Summing Up................................................................................................................155 Further Reading..........................................................................................................155 13 – Customizing The Prompt.....................................................................156 Anatomy Of A Prompt..................................................................................................156 Trying Some Alternative Prompt Designs....................................................................158 Adding Color................................................................................................................159 Terminal Confusion............................................................................................160 Moving The Cursor......................................................................................................162 Saving The Prompt......................................................................................................163 Summing Up................................................................................................................164 v Further Reading..........................................................................................................164 Part 3 – Common Tasks And Essential Tools.............................165 14 – Package Management..........................................................................166 Packaging Systems.....................................................................................................166 How A Package System Works...................................................................................167 Package Files.........................................................................................................167 Repositories............................................................................................................167 Dependencies.........................................................................................................168 High And Low-level Package Tools........................................................................168 Common Package Management Tasks.......................................................................169 Finding A Package In A Repository........................................................................169 Installing A Package From A Repository.................................................................169 Installing A Package From A Package File.............................................................170 Removing A Package.............................................................................................170 Updating Packages From A Repository..................................................................171 Upgrading A Package From A Package File...........................................................171 Listing Installed Packages......................................................................................172 Determining If A Package Is Installed.....................................................................172 Displaying Info About An Installed Package...........................................................173 Finding Which Package Installed A File.................................................................173 Summing Up................................................................................................................173 The Linux Software Installation Myth.................................................................174 Further Reading..........................................................................................................175 15 – Storage Media.......................................................................................176 Mounting And Unmounting Storage Devices..............................................................176 Viewing A List Of Mounted File Systems................................................................178 Why Unmounting Is Important...........................................................................181 Determining Device Names....................................................................................182 Creating New File Systems.........................................................................................185 Manipulating Partitions With fdisk..........................................................................185 Creating A New File System With mkfs..................................................................188 Testing And Repairing File Systems............................................................................189 What The fsck?..................................................................................................189 Formatting Floppy Disks..............................................................................................189 Moving Data Directly To/From Devices.......................................................................190 Creating CD-ROM Images..........................................................................................191 Creating An Image Copy Of A CD-ROM.................................................................191 Creating An Image From A Collection Of Files.......................................................191 A Program By Any Other Name.........................................................................192 Writing CD-ROM Images.............................................................................................192 Mounting An ISO Image Directly............................................................................192 Blanking A Re-Writable CD-ROM...........................................................................193 Writing An Image....................................................................................................193 Summing Up................................................................................................................193 Further Reading..........................................................................................................193 Extra Credit..................................................................................................................193 vi 16 – Networking............................................................................................195 Examining And Monitoring A Network.........................................................................196 ping.........................................................................................................................196 traceroute...............................................................................................................197 netstat.....................................................................................................................198 Transporting Files Over A Network..............................................................................199 ftp............................................................................................................................199 lftp – A Better ftp.....................................................................................................202 wget........................................................................................................................202 Secure Communication With Remote Hosts...............................................................202 ssh..........................................................................................................................203 Tunneling With SSH..........................................................................................206 scp And sftp............................................................................................................207 An SSH Client For Windows?............................................................................208 Summing Up................................................................................................................208 Further Reading..........................................................................................................208 17 – Searching For Files..............................................................................209 locate – Find Files The Easy Way...............................................................................209 Where Does The locate Database Come From?..............................................211 find – Find Files The Hard Way...................................................................................211 Tests.......................................................................................................................212 Operators................................................................................................................214 Predefined Actions..................................................................................................217 User-Defined Actions..............................................................................................219 Improving Efficiency...............................................................................................220 xargs.......................................................................................................................220 Dealing With Funny Filenames..........................................................................221 A Return To The Playground..................................................................................221 Options...................................................................................................................224 Summing Up................................................................................................................225 Further Reading..........................................................................................................225 18 – Archiving And Backup.........................................................................226 Compressing Files.......................................................................................................226 gzip.........................................................................................................................227 bzip2.......................................................................................................................229 Don’t Be Compressive Compulsive...................................................................230 Archiving Files.............................................................................................................230 tar............................................................................................................................230 zip...........................................................................................................................236 Synchronizing Files And Directories............................................................................238 Using rsync Over A Network...................................................................................240 Summing Up................................................................................................................241 Further Reading..........................................................................................................241 19 – Regular Expressions...........................................................................243 What Are Regular Expressions?............................................................................243 grep.............................................................................................................................243 vii Metacharacters And Literals........................................................................................245 The Any Character......................................................................................................246 Anchors.......................................................................................................................247 A Crossword Puzzle Helper...............................................................................247 Bracket Expressions And Character Classes..............................................................248 Negation.................................................................................................................248 Traditional Character Ranges.................................................................................249 POSIX Character Classes......................................................................................250 Reverting To Traditional Collation Order............................................................253 POSIX Basic Vs. Extended Regular Expressions.......................................................254 POSIX................................................................................................................254 Alternation...................................................................................................................255 Quantifiers...................................................................................................................256 ? - Match An Element Zero Or One Time...............................................................256 * - Match An Element Zero Or More Times............................................................257 + - Match An Element One Or More Times............................................................258 { } - Match An Element A Specific Number Of Times..............................................258 Putting Regular Expressions To Work.........................................................................259 Validating A Phone List With grep...........................................................................259 Finding Ugly Filenames With find...........................................................................260 Searching For Files With locate.............................................................................261 Searching For Text With less And vim....................................................................261 Summing Up................................................................................................................263 Further Reading..........................................................................................................263 20 – Text Processing....................................................................................264 Applications Of Text.....................................................................................................264 Documents.............................................................................................................265 Web Pages.............................................................................................................265 Email.......................................................................................................................265 Printer Output.........................................................................................................265 Program Source Code............................................................................................265 Revisiting Some Old Friends.......................................................................................265 cat...........................................................................................................................266 MS-DOS Text Vs. Unix Text...............................................................................267 sort..........................................................................................................................267 uniq.........................................................................................................................275 Slicing And Dicing........................................................................................................276 cut...........................................................................................................................276 Expanding Tabs.................................................................................................279 paste.......................................................................................................................280 join..........................................................................................................................281 Comparing Text...........................................................................................................283 comm......................................................................................................................284 diff...........................................................................................................................284 patch.......................................................................................................................287 Editing On The Fly.......................................................................................................288 tr..............................................................................................................................288 ROT13: The Not-So-Secret Decoder Ring........................................................290 sed..........................................................................................................................290 viii

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