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    Linux Shell Scripting Cookbook, Second Edition
    Linux Shell Scripting Cookbook, Second Edition
    Linux Shell Scripting Cookbook, Second Edition
    Ebook1,042 pages6 hours

    Linux Shell Scripting Cookbook, Second Edition

    By Shantanu Tushar and Sarath Lakshman

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    About this ebook

    This book is written in a Cookbook style and it offers learning through recipes with examples and illustrations. Each recipe contains step-by-step instructions about everything necessary to execute a particular task. The book is designed so that you can read it from start to end for beginners, or just open up any chapter and start following the recipes as a reference for advanced users.If you are a beginner or an intermediate user who wants to master the skill of quickly writing scripts to perform various tasks without reading the entire manual, this book is for you. You can start writing scripts and one-liners by simply looking at the similar recipe and its descriptions without any working knowledge of shell scripting or Linux. Intermediate/advanced users as well as system administrators/ developers and programmers can use this book as a reference when they face problems while coding.
    LanguageEnglish
    PublisherPackt Publishing
    Release dateMay 21, 2013
    ISBN9781782162759
    Linux Shell Scripting Cookbook, Second Edition

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      Linux Shell Scripting Cookbook, Second Edition - Shantanu Tushar

      Table of Contents

      Linux Shell Scripting Cookbook

      Credits

      About the Authors

      About the Reviewers

      www.PacktPub.com

      Support files, eBooks, discount offers and more

      Why Subscribe?

      Free Access for Packt account holders

      Preface

      What this book covers

      What you need for this book

      Who this book is for

      Conventions

      Reader feedback

      Customer support

      Downloading the example code

      Errata

      Piracy

      Questions

      1. Shell Something Out

      Introduction

      Printing in the terminal

      How to do it...

      How it works...

      There's more...

      Escaping newline in echo

      Printing a colored output

      Playing with variables and environment variables

      Getting ready

      How to do it...

      There's more...

      Finding the length of a string

      Identifying the current shell

      Checking for super user

      Modifying the Bash prompt string (username@hostname:~$)

      Function to prepend to environment variables

      How to do it...

      How it works...

      Math with the shell

      Getting ready

      How to do it...

      Playing with file descriptors and redirection

      Getting ready

      How to do it...

      How it works...

      There's more...

      Redirection from a file to a command

      Redirecting from a text block enclosed within a script

      Custom file descriptors

      Arrays and associative arrays

      Getting ready

      How to do it...

      There's more...

      Defining associative arrays

      Listing of array indexes

      Visiting aliases

      How to do it...

      There's more...

      Escaping aliases

      Grabbing information about the terminal

      Getting ready

      How to do it...

      Getting and setting dates and delays

      Getting ready

      How to do it...

      How it works...

      There's more...

      Producing delays in a script

      Debugging the script

      How to do it...

      How it works...

      There's more...

      Shebang hack

      Functions and arguments

      How to do it...

      There's more...

      The recursive function

      Exporting functions

      Reading the return value (status) of a command

      Passing arguments to commands

      Reading the output of a sequence of commands in a variable

      Getting ready

      How to do it...

      There's more...

      Spawning a separate process with subshell

      Subshell quoting to preserve spacing and the newline character

      Reading n characters without pressing the return key

      How to do it...

      Running a command until it succeeds

      How to do it...

      How it works...

      There's more...

      A faster approach

      Adding a delay

      Field separators and iterators

      Getting ready

      How to do it...

      Comparisons and tests

      How to do it...

      2. Have a Good Command

      Introduction

      Concatenating with cat

      How to do it...

      How it works…

      There's more...

      Getting rid of extra blank lines

      Displaying tabs as ^I

      Line numbers

      Recording and playing back of terminal sessions

      Getting ready

      How to do it...

      How it works...

      Finding files and file listing

      Getting ready

      How to do it...

      There's more...

      Search based on filename or regular expression match

      Negating arguments

      Search based on the directory depth

      Search based on file type

      Search on file times

      Search based on file size

      Deleting based on the file matches

      Match based on the file permissions and ownership

      Executing commands or actions with find

      Skipping specified directories when using the find command

      Playing with xargs

      Getting ready

      How to do it...

      How it works…

      There's more...

      Passing formatted arguments to a command by reading stdin

      Using xargs with find

      Counting the number of lines of C code in a source code directory

      While and subshell trick with stdin

      Translating with tr

      Getting ready

      How to do it...

      How it works…

      There's more...

      Deleting characters using tr

      Complementing character set

      Squeezing characters with tr

      Character classes

      Checksum and verification

      Getting ready

      How to do it...

      How it works...

      There's more...

      Checksum for directories

      Cryptographic tools and hashes

      How to do it...

      Sorting unique and duplicates

      Getting ready

      How to do it...

      How it works…

      There's more...

      Sorting according to the keys or columns

      uniq

      Temporary file naming and random numbers

      How to do it...

      How it works…

      Splitting files and data

      How to do it...

      There's more…

      Specifying a filename prefix for the split files

      Slicing filenames based on extension

      How to do it…

      How it works…

      Renaming and moving files in bulk

      Getting ready

      How to do it...

      How it works…

      Spell checking and dictionary manipulation

      How to do it...

      How it works...

      Automating interactive input

      Getting ready

      How to do it...

      How it works…

      There's more...

      Automating with expect

      Making commands quicker by running parallel processes

      How to do it...

      How it works...

      3. File In, File Out

      Introduction

      Generating files of any size

      How to do it...

      The intersection and set difference (A-B) on text files

      Getting ready

      How to do it...

      How it works...

      Finding and deleting duplicate files

      Getting ready

      How to do it...

      How it works...

      Working with file permissions, ownership, and the sticky bit

      How to do it...

      There's more...

      Changing ownership

      Setting sticky bit

      Applying permissions recursively to files

      Applying ownership recursively

      Running an executable as a different user (setuid)

      Making files immutable

      Getting ready

      How to do it...

      Generating blank files in bulk

      Getting ready

      How to do it...

      Finding symbolic links and their targets

      How to do it...

      How it works...

      Enumerating file type statistics

      Getting ready

      How to do it...

      How it works...

      Using loopback files

      How to do it...

      How it works...

      There's more...

      Creating partitions inside loopback images

      Quicker way to mount loopback disk images with partitions

      Mounting ISO files as loopback

      Flush changing immediately with sync

      Creating ISO files and hybrid ISO

      Getting ready

      How to do it...

      There's more...

      Hybrid ISO that boots off a flash drive or hard disk

      Burning an ISO from the command line

      Playing with the CD-ROM tray

      Finding the difference between files, patching

      How to do it...

      There's more...

      Generating difference against directories

      Using head and tail for printing the last or first 10 lines

      How to do it...

      Listing only directories – alternative methods

      Getting ready

      How to do it...

      How it works...

      Fast command-line navigation using pushd and popd

      Getting ready

      How to do it...

      There's more...

      Most frequently used directory switching

      Counting the number of lines, words, and characters in a file

      How to do it...

      Printing the directory tree

      Getting ready

      How to do it...

      There's more...

      HTML output for tree

      4. Texting and Driving

      Introduction

      Using regular expressions

      How to do it...

      How it works...

      There's more...

      Treatment of special characters

      Visualizing regular expressions

      Searching and mining a text inside a file with grep

      How to do it...

      There's more...

      Recursively search many files

      Ignoring case of pattern

      grep by matching multiple patterns

      Including and excluding files in a grep search

      Using grep with xargs with zero-byte suffix

      Silent output for grep

      Printing lines before and after text matches

      Cutting a file column-wise with cut

      How to do it...

      There's more

      Specifying the range of characters or bytes as fields

      Using sed to perform text replacement

      How to do it…

      There's more...

      Removing blank lines

      Performing replacement directly in the file

      Matched string notation (&)

      Substring match notation (\1)

      Combination of multiple expressions

      Quoting

      Using awk for advanced text processing

      Getting ready...

      How to do it…

      How it works…

      There's more…

      Special variables

      Passing an external variable to awk

      Reading a line explicitly using getline

      Filtering lines processed by awk with filter patterns

      Setting delimiter for fields

      Reading the command output from awk

      Using loop inside awk

      String manipulation functions in awk

      Finding the frequency of words used in a given file

      Getting ready

      How to do it...

      How it works...

      See also

      Compressing or decompressing JavaScript

      Getting ready

      How to do it...

      How it works...

      See also

      Merging multiple files as columns

      How to do it...

      See also

      Printing the nth word or column in a file or line

      How to do it...

      See also

      Printing text between line numbers or patterns

      Getting ready

      How to do it...

      See also

      Printing lines in the reverse order

      Getting ready

      How to do it...

      How it works...

      Parsing e-mail addresses and URLs from text

      How to do it...

      How it works...

      See also

      Removing a sentence in a file containing a word

      Getting ready

      How to do it...

      How it works...

      See also

      Replacing a pattern with text in all the files in a directory

      How to do it...

      How it works...

      There's more...

      Text slicing and parameter operations

      How to do it...

      See also

      5. Tangled Web? Not At All!

      Introduction

      Downloading from a web page

      Getting ready

      How to do it...

      How it works...

      There's more...

      Restricting the download speed

      Resume downloading and continue

      Copying a complete website (mirroring)

      Accessing pages with HTTP or FTP authentication

      Downloading a web page as plain text

      How to do it...

      A primer on cURL

      Getting ready

      How to do it…

      How it works...

      There's more...

      Continuing and resuming downloads

      Setting the referer string with cURL

      Cookies with cURL

      Setting a user agent string with cURL

      Specifying a bandwidth limit on cURL

      Specifying the maximum download size

      Authenticating with cURL

      Printing response headers excluding the data

      See also

      Accessing Gmail e-mails from the command line

      How to do it...

      How it works...

      See also

      Parsing data from a website

      How to do it...

      How it works...

      See also

      Image crawler and downloader

      How to do it...

      How it works...

      See also

      Web photo album generator

      Getting ready

      How to do it...

      How it works...

      See also

      Twitter command-line client

      Getting ready

      How to do it...

      How it works...

      See also

      Creating a define utility by using the Web backend

      Getting ready

      How to do it...

      How it works...

      See also

      Finding broken links in a website

      Getting ready

      How to do it...

      How it works...

      See also

      Tracking changes to a website

      Getting ready

      How to do it...

      How it works...

      See also

      Posting to a web page and reading the response

      Getting ready

      How to do it...

      How it works...

      See also

      6. The Backup Plan

      Introduction

      Archiving with tar

      Getting ready

      How to do it...

      How it works...

      There's more...

      Appending files to an archive

      Extracting files and folders from an archive

      stdin and stdout with tar

      Concatenating two archives

      Updating files in an archive with a timestamp check

      Comparing files in the archive and file system

      Deleting files from the archive

      Compression with the tar archive

      Excluding a set of files from archiving

      Excluding version control directories

      Printing total bytes

      See also

      Archiving with cpio

      How to do it...

      How it works...

      Compressing data with gzip

      How to do it...

      There's more...

      Gzip with tarball

      zcat - reading gzipped files without extracting

      Compression ratio

      Using bzip2

      Using lzma

      See also

      Archiving and compressing with zip

      How to do it...

      How it works...

      Faster archiving with pbzip2

      Getting ready

      How to do it...

      How it works...

      There's more...

      Manually specifying the number of CPUs

      Specifying the compression ratio

      Creating filesystems with compression

      Getting ready

      How to do it...

      There's more...

      Excluding files while creating a squashfs file

      Backup snapshots with rsync

      How to do it...

      How it works...

      There's more...

      Excluding files while archiving with rsync

      Deleting non-existent files while updating rsync backup

      Scheduling backups at intervals

      Version control-based backup with Git

      Getting ready

      How to do it...

      Creating entire disk images using fsarchiver

      Getting ready

      How to do it...

      How it works...

      7. The Old-boy Network

      Introduction

      Setting up the network

      Getting ready

      How to do it...

      There's more...

      Printing the list of network interfaces

      Displaying IP addresses

      Spoofing the hardware address (MAC address)

      Name server and DNS (Domain Name Service)

      DNS lookup

      Showing routing table information

      See also

      Let us ping!

      How to do it...

      There's more

      Round trip time

      Limiting the number of packets to be sent

      Return status of the ping command

      Traceroute

      Listing all the machines alive on a network

      Getting ready

      How to do it...

      How it works...

      There's more...

      Parallel pings

      Using fping

      See also

      Running commands on a remote host with SSH

      Getting ready

      How to do it...

      There's more...

      SSH with compression

      Redirecting data into stdin of remote host shell commands

      Running graphical commands on a remote machine

      See also

      Transferring files through the network

      Getting ready

      How to do it...

      There's more...

      Automated FTP transfer

      SFTP (Secure FTP)

      The rsync command

      SCP (secure copy program)

      Recursive copying with SCP

      See also

      Connecting to a wireless network

      Getting ready

      How to do it...

      How it works...

      See also

      Password-less auto-login with SSH

      Getting ready

      How to do it...

      Port forwarding using SSH

      How to do it...

      There's more...

      Non-interactive port forward

      Reverse port forwarding

      Mounting a remote drive at a local mount point

      Getting ready

      How to do it...

      See also

      Network traffic and port analysis

      Getting ready

      How to do it...

      How it works...

      There's more...

      Opened port and services using netstat

      Creating arbitrary sockets

      Getting ready

      How to do it...

      There's more...

      Quickly copying files over the network

      Sharing an Internet connection

      Getting ready

      How to do it...

      Basic firewall using iptables

      How to do it...

      How it works...

      There's more...

      8. Put on the Monitor's Cap

      Introduction

      Monitoring disk usage

      Getting ready

      How to do it...

      There's more...

      Displaying disk usage in KB, MB, or Blocks

      Displaying the grand total sum of disk usage

      Printing files in specified units

      Excluding files from the disk usage calculation

      Finding the 10 largest size files from a given directory

      Disk free information

      Calculating the execution time for a command

      How to do it...

      How it works...

      Collecting information about logged in users, boot logs, and boot failures

      Getting ready

      How to do it...

      Listing the top 10 CPU consuming processes in an hour

      Getting ready

      How to do it...

      How it works...

      See also

      Monitoring command outputs with watch

      How to do it...

      There's more

      Highlighting the differences in the watch output

      Logging access to files and directories

      Getting ready

      How to do it...

      How it works...

      Logfile management with logrotate

      Getting ready

      How to do it...

      How it works...

      Logging with syslog

      Getting ready

      How to do it...

      See also

      Monitoring user logins to find intruders

      Getting ready

      How to do it…

      How it works…

      Remote disk usage health monitor

      Getting ready

      How to do it…

      How it works…

      See also

      Finding out active user hours on a system

      Getting ready

      How to do it…

      How it works…

      Measuring and optimizing power usage

      Getting ready

      How to do it...

      Monitoring disk activity

      Getting ready

      How to do it...

      Checking disks and filesystems for errors

      Getting ready

      How to do it...

      How it works...

      9. Administration Calls

      Introduction

      Gathering information about processes

      Getting ready

      How to do it...

      How it works...

      There's more...

      top

      Sorting the ps output with respect to a parameter

      Finding the process ID when given command names

      Filters with ps for real user or ID, effective user or ID

      TTY filter for ps

      Information about process threads

      Specifying output width and columns to be displayed

      Showing environment variables for a process

      About which, whereis, file, whatis, and load average

      See also

      Killing processes and send or respond to signals

      Getting ready

      How to do it...

      There's more...

      The kill family of commands

      Capturing and responding to signals

      Sending messages to user terminals

      Getting ready

      How to do it...

      How it works...

      Gathering system information

      How to do it...

      Using /proc for gathering information

      How to do it...

      Scheduling with cron

      Getting ready

      How to do it…

      How it works...

      There's more…

      Specifying environment variables

      Running commands at system start up/boot

      Viewing the cron table

      Removing the cron table

      Writing and reading the MySQL database from Bash

      Getting ready

      How to do it…

      How it works…

      User administration script

      How to do it…

      How it works…

      Bulk image resizing and format conversion

      Getting ready

      How to do it..

      How it works…

      See also

      Taking screenshots from the terminal

      Getting ready

      How to do it...

      Managing multiple terminals from one

      Getting ready

      How to do it...

      Index

      Linux Shell Scripting Cookbook

      Second Edition

      Linux Shell Scripting Cookbook

      Second Edition

      Copyright © 2013 Packt Publishing

      All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

      Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the authors, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.

      Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.

      First published: January 2011

      Second edition: May 2013

      Production Reference: 1140513

      Published by Packt Publishing Ltd.

      Livery Place

      35 Livery Street

      Birmingham B3 2PB, UK.

      ISBN 978-1-78216-274-2

      www.packtpub.com

      Cover Image by Parag Kadam (<[email protected]>)

      Credits

      Authors

      Shantanu Tushar

      Sarath Lakshman

      Reviewers

      Rajeshwari K.

      John C. Kennedy

      Anil Kumar

      Sudhendu Kumar

      Aravind SV

      Acquisition Editor

      Kartikey Pandey

      Lead Technical Editor

      Ankita Shashi

      Technical Editors

      Jalasha D'costa

      Amit Ramadas

      Lubna Shaikh

      Project Coordinator

      Shiksha Chaturvedi

      Proofreader

      Linda Morris

      Indexer

      Hemangini Bari

      Production Coordinator

      Shantanu Zagade

      Cover Work

      Shantanu Zagade

      About the Authors

      Shantanu Tushar is an advanced GNU/Linux user since his college days. He works as an application developer and contributes to the software in the KDE projects.

      Shantanu has been fascinated by computers since he was a child, and spent most of his high school time writing C code to perform daily activities. Since he started using GNU/Linux, he has been using shell scripts to make the computer do all the hard work for him. He also takes time to visit students at various colleges to introduce them to the power of Free Software, including its various tools. Shantanu is a well-known contributor in the KDE community and works on Calligra, Gluon and the Plasma subprojects. He looks after maintaining Calligra Active – KDE's office document viewer for tablets, Plasma Media Center, and the Gluon Player. One day, he believes, programming will be so easy that everybody will love to write programs for their computers.

      Shantanu can be reached by e-mail on <[email protected]>, shantanutushar on identi.ca/twitter, or his website http://www.shantanutushar.com.

      I would like to thank my friends and family for the support and encouragement they've given me, especially to my sweet sister for her patience when I couldn't get time to talk to her. I am particularly thankful to Sinny Kumari for patiently testing the scripts to make sure they function properly and Sudhendu Kumar for helping me with the recipe on GNU Screen.

      I must also thank Krishna, Madhusudan, and Santosh who introduced me to the wonderful world of GNU/Linux and Free Software. Also, a big thanks to all the reviewers of the book for taking the time to painfully go through every minute detail in the book and help me in improving it. I am also thankful to the whole team at Packt Publishing, without whose efforts and experience, this second edition wouldn't have happened.

      Sarath Lakshman is a 23 year old who was bitten by the Linux bug during his teenage years. He is a software engineer working in ZCloud engineering group at Zynga, India. He is a life hacker who loves to explore innovations. He is a GNU/Linux enthusiast and hactivist of free and open source software. He spends most of his time hacking with computers and having fun with his great friends. Sarath is well known as the developer of SLYNUX (2005)—a user friendly GNU/Linux distribution for Linux newbies. The free and open source software projects he has contributed to are PiTiVi Video editor, SLYNUX GNU/Linux distro, Swathantra Malayalam Computing, School-Admin, Istanbul, and the Pardus Project. He has authored many articles for the Linux For You magazine on various domains of FOSS technologies. He had made a contribution to several different open source projects during his multiple Google Summer of Code projects. Currently, he is exploring his passion about scalable distributed systems in his spare time. Sarath can be reached via his website http://www.sarathlakshman.com.

      About the Reviewers

      Rajeshwari K. received her B.E degree (Information Science and Engineering) from VTU in 2004 and M. Tech degree (Computer Science and Engineering) from VTU in 2009. From 2004 to 2007 she handled a set of real-time projects and did some freelancing. Since 2010 she has being working as Assistant Professor at BMS College of Engineering in the department of Information Science and Engineering. She has a total of five years' experience in teaching in Computer Science subjects.

      BMS College of Engineering, Bangalore is one of the autonomous colleges running under VTU with high acclamation nationwide.

      Her research interests include operating systems and system-side programming.

      John C. Kennedy has been administering Unix and Linux servers and workstations since 1997. He has experience with Red Hat, SUSE, Ubuntu, Debian, Solaris, and HP-UX. John is also experienced in Bash shell scripting and is currently teaching himself Python and Ruby. John has also been a Technical Editor for various publishers for over 10 years specializing in books related to open source technologies.

      When John is not geeking out in front of either a home or work computer, he helps out with a German Shepherd Rescue in Virginia by fostering some great dogs or helping with their IT needs.

      I would like to thank my family (my wonderful wife, Michele, my intelligent and caring daughter Denise, and my terrific and smart son, Kieran) for supporting the (sometimes) silly things and not so silly things I do. I'd also like to thank my current foster dogs for their occasional need to keep their legs crossed a little longer while I test things out from the book and forget they are there.

      Anil Kumar is a software developer. He received his Computer Science undergraduate degree from BITS Pilani. He has work experience of more than two years in the field of Web Development and Systems. Besides working as a software developer, Anil is an open source evangelist and a blogger. He currently resides in Bangalore. He can be contacted at <[email protected]>.

      Sudhendu Kumar has been a GNU/Linux user for more than five years. Presently being a software developer for a networking giant, in free time, he also contributes to KDE.

      I would like to thank the publishers for giving me this opportunity to review the book. I hope readers find the book useful and they enjoy reading it.

      Aravind SV has worked with various Unix-like systems and shells over many years. You can contact him at <[email protected]>.

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      Dedicated to my parents who taught me how to think and reason, and to be optimistic in every situation in life

      —Shantanu Tushar

      Preface

      GNU/Linux is one of the most powerful and flexible operating systems in the world. In modern computing, there is absolutely no space where it is not used—from servers, portable computers, mobile phones, tablets to supercomputers, everything runs Linux. While there are beautiful and modern graphical interfaces available for it, the shell still remains the most flexible way of interacting with the system.

      In addition to executing individual commands, a shell can follow commands from a script, which makes it very easy to automate tasks. Examples of such tasks are preparing reports, sending e-mails, performing maintenance, and so on. This book is a collection of chapters which contain recipes to demonstrate real-life usages of commands and shell scripts. You can use these as a reference, or an inspiration for writing your own scripts. The tasks will range from text manipulation to performing network operations to administrative tasks.

      As with everything, the shell is only as awesome as you make it. When you become an expert at shell scripting, you can use the shell to the fullest and harness its true power. Linux Shell Scripting Cookbook shows you how to do exactly that!

      What this book covers

      Chapter 1, Shell Something Out, is an introductory chapter for understanding the basic concepts and features in Bash. We discuss printing text in the terminal, doing mathematical calculations, and other simple functionalities provided by Bash.

      Chapter 2, Have a Good Command, shows commonly used commands that are available with GNU/Linux. This chapter travels through different practical usage examples that users may come across and that they could make use of. In addition to essential commands, this second edition talks about cryptographic hashing commands and a recipe to run commands in parallel, wherever possible.

      Chapter 3, File In, File Out, contains a collection of recipes related to files and filesystems. This chapter explains how to generate large-size files, installing a filesystem on files, mounting files, and creating ISO images. We also deal with operations such as finding and removing duplicate files, counting lines in a file collecting details about files, and so on.

      Chapter 4, Texting and Driving, has a collection of recipes that explains most of the command-line text processing tools well under GNU/Linux with a number of task examples. It also has supplementary recipes for giving a detailed overview of regular expressions and commands such as sed and awk. This chapter goes through solutions to most of the frequently used text processing tasks in a variety of recipes. It is an essential read for any serious task.

      Chapter 5, Tangled Web? Not At All!, has a collection of shell-scripting recipes that talk to services on the Internet. This chapter is intended to help readers understand how to interact with the Web using shell scripts to automate tasks such as collecting and parsing data from web pages. This is discussed using POST and GET to web pages, writing clients to web services. The second edition uses new authorization mechanisms such as OAuth for services such as Twitter.

      Chapter 6, The Backup Plan, shows several commands used for performing data back up, archiving, compression, and so on. In addition to faster compression techniques, this second edition also talks about creating entire disk images.

      Chapter 7, The Old-boy Network, has a collection of recipes that talks about networking on Linux and several commands useful for writing network-based scripts. The chapter starts with an introductory basic networking primer and goes on to cover usages of ssh – one of the most powerful commands on any modern GNU/Linux system. We discuss advanced port forwarding, setting up raw communication channels, configuring the firewall, and much more.

      Chapter 8, Put on the Monitor's Cap, walks through several recipes related to monitoring activities on the Linux system and tasks used for logging and reporting. The chapter explains tasks such as calculating disk usage, monitoring user access, and CPU usage. In this second edition, we also learn how to optimize power consumption, monitor disks, and check their filesystems for errors.

      Chapter 9, Administration Calls, has a collection of recipes for system administration. This chapter explains different commands to collect details about the system and user management using scripting. We also discuss bulk image resizing and accessing MySQL databases from the shell. New in this edition is that we learn how to use the GNU Screen to manage multiple terminals without needing a window manager.

      What you need for this book

      Basic user experience with any GNU/Linux platform will help you easily follow the book. We have tried to keep all the recipes in the book precise and as simple to follow as possible. Your curiosity for learning with the Linux platform is the only prerequisite for the book. Step-by-step explanations are provided for solving the scripting problems explained in the book. In order to run and test the examples in the book, a Ubuntu/Debian Linux installation is recommended, however, any other Linux distribution is enough for most of the tasks. You will find the book to be a straightforward reference to essential shell-scripting tasks, as well as a learning aid to code real-world efficient scripts.

      Who this book is for

      If you

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