Bash Command Line and Shell Scripts Pocket Primer PDF
Preview Bash Command Line and Shell Scripts Pocket Primer
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B C L ash ommand ine and s s heLL Cripts P P ocket rimer Oswald Campesato MERCURY LEARNING AND INFORMATION Dulles, Virginia Boston, Massachusetts New Delhi Copyright © 2020 by Mercury Learning and inforMation LLC. All rights reserved. This publication, portions of it, or any accompanying software may not be reproduced in any way, stored in a retrieval system of any type, or transmitted by any means, media, electronic display or mechanical display, including, but not limited to, photocopy, record- ing, Internet postings, or scanning, without prior permission in writing from the publisher. Publisher: David Pallai Mercury Learning and inforMation 22841 Quicksilver Drive Dulles, VA 20166 [email protected] www.merclearning.com (800) 232-0223 O. Campesato. Bash Command Line and Shell Scripts Pocket Primer. ISBN: 978-1-68392-504-0 The publisher recognizes and respects all marks used by companies, manufacturers, and developers as a means to distinguish their products. 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I’d like to dedicate this book to my parents – may this bring joy and happiness into their lives. CONTENTS Preface xv Chapter 1: Introduction 1 What is Unix? 2 Available Shell Types 2 What is bash? 3 Getting help for Commands 4 bash Navigating Around Directories 4 The Command 4 history Listing Filenames with the Command 5 ls Displaying Contents of Files 8 The Command 8 cat The and Commands 9 head tail The Pipe Symbol 10 The Command 11 fold File Ownership: Owner, Group, and World 11 Hidden Files 12 Handling Problematic Filenames 13 Working with Environment Variables 13 The Command 13 env Useful Environment Variables 14 Setting the Environment Variable 14 PATH Specifying Aliases and Environment Variables 15 Finding Executable Files 16 The Command and the echo Command 17 printf The Command 17 cut viii • Bash Command Line and Shell Scripts The echo Command and Whitespaces 18 Command Substitution (“backtick”) 20 The “pipe” Symbol and Multiple Commands 20 Using a Semicolon to Separate Commands 21 The Command 22 paste Inserting Blank Lines with the Command 22 paste A Simple Use Case with the Command 23 paste A Simple Use Case with and Commands 24 cut paste What about zsh? 25 Switching between bash and zsh 26 Configuring zsh 26 Summary 26 Chapter 2: Files and Directories 29 Create, Copy, Remove, and Move Files 29 Creating Text Files 29 Copying Files 30 Copy Files with Command Substitution 30 Deleting Files 31 Moving Files 32 The Command 32 ln The basename, dirname, and file Commands 33 The Command 33 wc The Command 34 cat The Command and the Command 34 more less The Command 35 head The tail Command 36 Comparing File Contents 38 The Parts of a Filename 38 Working with File Permissions 39 The Command 40 chmod Changing owner, permissions, and groups 40 The umask and ulimit Commands 41 Working with Directories 41 Absolute and Relative Directories 41 Absolute/Relative Pathnames 41 Creating Directories 42 Removing Directories 43 Navigating to Directories 43 Moving Directories 44 Using Quote Characters 44 Streams and Redirection Commands 45 Working with Metacharacters 46 Working with Character Classes 47 Contents • ix MetaCharacters and Character Classes 48 Digits and Characters 48 Working with “^” and “\” and “!” 49 Filenames and Metacharacters 49 Summary 50 Chapter 3: Useful Commands 51 The join Command 52 The Command 52 fold The Command 53 split The Command 53 sort The Command 56 uniq How to Compare Files 56 The Command 57 od The Command 57 tr A Simple Use Case 60 The Command 61 find The Command 62 tee File Compression Commands 63 The command 63 tar The Command 63 cpio The gzip and gunzip Commands 64 The bunzip2 Command 64 The zip Command 65 Commands for zip Files and bz Files 65 Internal Field Separator (IFS) 65 Data From a Range of Columns in a Dataset 66 Working with Uneven Rows in Datasets 68 Summary 68 Chapter 4: Conditional Logic and Loops 71 Quick Overview of Operators in bash 71 Arithmetic Operations and Operators 72 The expr Command 72 Arithmetic Operators 73 Boolean and Numeric Operators 73 Compound Operators and Numeric Operators 74 Working with Variables 74 Assigning Values to Variables 75 The Command for User Input 76 read Boolean Operators and String Operators 76 Compound Operators and String Operators 77 File Test Operators 78 Compound Operators and File Operators 79
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