The Linux Command Line

The Linux Command Line

Fifth Internet Edition

William Shotts

A Book

Copyright ?2008-2019, William E. Shotts, Jr.

This work is licensed under the Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License. To view a copy of this license, visit the link above or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042.

A version of this book is also available in printed form, published by No Starch Press. Copies may be purchased wherever fine books are sold. No Starch Press also offers electronic formats for popular e-readers. They can be reached at: .

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This book is part of the project, a site for Linux education and advocacy devoted to helping users of legacy operating systems migrate into the future. You may contact the project at .

Release History

Version 19.01A 19.01 17.10 16.07 13.07 09.12

Date January 28, 2019 January 17, 2019 October 19, 2017 July 28, 2016 July 6, 2013 December 14, 2009

Description Fifth Internet Edition (Corrected TOC) Fifth Internet Edition. Fourth Internet Edition. Third Internet Edition. Second Internet Edition. First Internet Edition.

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................................................................................................xix

Prerequisites............................................................................................................xix Why I Don't Call It "GNU/Linux"...........................................................................xix

What's New in the Fifth Internet Edition.........................................................................xx Acknowledgments..........................................................................................................xx

First Internet Edition..................................................................................................xx Second Internet Edition............................................................................................xxi Third Internet Edition................................................................................................xxi Fourth Internet Edition..............................................................................................xxi Fifth Internet Edition.................................................................................................xxi Your Feedback Is Needed!............................................................................................xxi Further Reading............................................................................................................xxi Colophon......................................................................................................................xxii

Part 1 ? Learning the Shell...............................................................1

1 ? What Is the Shell?......................................................................................2

Terminal Emulators..........................................................................................................2 Making 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

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Changing the Current Working Directory........................................................................9 Absolute Pathnames..................................................................................................9 Relative Pathnames...................................................................................................9 Some Helpful Shortcuts............................................................................................11 Important Facts About Filenames........................................................................11

Summing Up..................................................................................................................12

3 ? Exploring the System..............................................................................13

Having 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 Taking 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..................................................................................32 Be Careful with rm!..............................................................................................33

ln ? Create Links............................................................................................................33 Hard Links................................................................................................................33 Symbolic Links..........................................................................................................34

Let's Build a Playground................................................................................................34 Creating Directories..................................................................................................34 Copying Files............................................................................................................35 Moving and Renaming Files.....................................................................................36 Creating Hard Links..................................................................................................37 Creating Symbolic Links...........................................................................................38 Removing Files and Directories...............................................................................39 Creating Symlinks With The GUI.........................................................................41

Summing Up..................................................................................................................41 Further Reading.............................................................................................................41

5 ? Working with Commands........................................................................42

What Exactly Are Commands?......................................................................................42 Identifying Commands...................................................................................................43

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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 man ? Display a Program's Manual Page................................................................46 apropos ? Display Appropriate Commands..............................................................47 whatis ? Display One-line Manual Page Descriptions..............................................48

The Most Brutal Man Page Of Them All..............................................................48 info ? Display a Program's Info Entry.......................................................................48 README and Other Program Documentation Files................................................50 Creating Our Own Commands with alias......................................................................50 Summing Up..................................................................................................................52 Further Reading.............................................................................................................52

6 ? Redirection................................................................................................54

Standard Input, Output, and Error.................................................................................54 Redirecting Standard Output.........................................................................................55 Redirecting Standard Error............................................................................................57

Redirecting Standard Output and Standard Error to One File.................................57 Disposing of Unwanted Output.................................................................................58

/dev/null In Unix Culture......................................................................................58 Redirecting Standard Input............................................................................................58

cat ? Concatenate Files............................................................................................59 Pipelines........................................................................................................................61

The Difference Between > and |..........................................................................61 Filters........................................................................................................................62 uniq - Report or Omit Repeated Lines......................................................................62 wc ? Print Line, Word, and Byte Counts...................................................................63 grep ? Print Lines Matching a Pattern......................................................................63 head / tail ? Print First / Last Part of Files................................................................64 tee ? Read from Stdin and Output to Stdout and Files............................................65 Summing Up..................................................................................................................66

Linux Is About Imagination..................................................................................66

7 ? Seeing the World as the Shell Sees It....................................................68

Expansion......................................................................................................................68 Pathname Expansion...............................................................................................69 Pathname Expansion of Hidden Files.................................................................70 Tilde Expansion........................................................................................................70 Arithmetic Expansion................................................................................................71 Brace Expansion......................................................................................................72 Parameter Expansion...............................................................................................73 Command Substitution.............................................................................................74

Quoting..........................................................................................................................75 Double Quotes..........................................................................................................76 Single Quotes...........................................................................................................78 Escaping Characters................................................................................................78 Backslash Escape Sequences............................................................................79

Summing Up..................................................................................................................79

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