book

Learning Linux Shell Scripting

by Ganesh Sanjiv Naik

December 2015

Beginner

306 pages

5h 2m

English

Packt Publishing

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What this book covers

Downloading the color images of this bookErrataPiracyQuestions
Comparison of shells
Changing file permissionsCommand chmodTechnique one – the symbolic methodTechnique two – the numeric methodSetting umaskSetuidSetgidSticky bit
Introducing process basics
Text filtering toolsHead and tailThe diff commandThe cut commandThe paste commandThe join commandThe uniq commandThe comm commandThe tr command
File descriptorsRedirectionBrace expansion
Learning shell interpretation of commandsChecking and disabling shell internal commandsThe exit status
Command1; command2Command grouping
Command1 & command2Command1 && command2Command1 || command2
Understanding variables
The local variable and its scopeExporting variables
Understanding setUnderstanding shiftResetting positional parameters
Creating an array and initializing itAccessing array values
Interactive Shell scripts – reading user inputSummarizing the read command with options
The here operator with the sort commandThe here operator with the wc commandThe utility ed and here operatorA script for sending messages to all logged-in usersUsing the << here operator for FTP usage and data transferTurning off variable substitution
Introducing file handlingUsing exec to assign file descriptor (fd) to fileUnderstanding the opening, writing, and closing of a fileUnderstanding reading from a fileUnderstanding reading and writing to a fileUsing command read on file descriptor (fd)Reading from one file and writing to another fileDisplaying the file descriptor information from the /proc folderFile handling – reading line by lineExecuting the command and storing the results in a fileSummarizing usage of the exec command
Debugging mode – disabling the shell (option -n)Debugging mode – displaying commands (option -v)Debugging mode – the tracing execution (option -x)Summarizing the debugging options for the Bash shellUsing the set commandSummary of debugging options for set commandThe vi editor setting for debuggingGood practices for Shell scripts
Using a command declare for arithmeticListing integers
Using an arithmetic expansion
Checking the exit status of commands
Using the test command with single bracketsUsing the test command with double bracketsString comparison options for the test commandNumerical comparison operators for the test commandFile test options for the test commandFile testing binary operatorsLogical test operators
Numerical handling if constructsUsing the command exit and the ? variableString handling with the if constructChecking for null valuesFile handling with the if commandMultiple test commands and if constructsThe if/elif/else commandThe null command
Understanding functionsDisplaying functionsRemoving functions
Returning a word or string from a function
Command source and period (.)
Understanding signals and traps
Resetting signalsListing traps
Creating a message box (msgbox)Creating a message box (msgbox) with a titleThe yes/no box (yesno)The input box (inputbox)The textbox (textbox)A password boxThe menu box (menu)The checklist box (checklist)The radiolist box (radiolist)The progress meter box (gauge)
System startup, inittab, and run levelsThe kernel startup and init processUnderstanding run levelsSystem initialization boot scripts
Systemwide settings scriptsUser level settings – default files
The basics of regular expressions
Understanding sedUnderstanding regular expression usage in sedAddressing in sedHow to modify a file with sedPrinting – the p commandDeleting – the d commandSubstitution – the s commandRange of selected lines: the commaMultiple edits – the e commandReading from files – the r commandWriting to files – the w commandAppending – the a commandInserting – the i commandChanging – the c commandTransform – the y commandQuit – the q commandHolding and getting – the h and g commandsHolding and exchanging – the h and x commandssed scripting
The meaning of awkUsing awkInput from filesInput from commandsHow awk worksawk commands from within a fileRecords and fieldsRecordsThe record separatorThe $0 variableThe NR variableFieldsField separatorsThe input field separatorPatterns and actionsPatternsActionsRegular expressionsWriting the awk script fileUsing variables in awkDecision making using an if statementUsing the for loopUsing the while loopUsing the do while loop

Overview

"Learning Linux Shell Scripting" provides a structured guide to mastering the art of writing effective and sophisticated shell scripts for Unix/Linux systems. By learning these skills, you will be able to automate tasks, handle system administration efficiently, and develop advanced scripting applications in a practical and hands-on manner.

What this Book will help me do

Understand and utilize GNU Bash to write and execute Linux shell scripts efficiently.
Automate common tasks and system administration processes, saving time and reducing manual effort.
Gain proficiency in working with variables, expressions, and conditionals within scripts.
Debug and improve shell scripts by learning advanced tools and techniques, such as Shell tracing.
Explore advanced scripting topics like system initialization, customization, and integration with tools like sed and awk.

Author(s)

Ganesh Sanjiv Naik is an industry expert in Linux systems and scripting, with years of experience in technical training and consulting. Ganesh's approach to writing combines clarity with practical application, ensuring readers gain valuable skills that apply directly to real-world scenarios.

Who is it for?

This book is perfect for Linux enthusiasts looking to expand their proficiency in system tasks through scripting. It suits those with a basic knowledge of Linux who aim to delve into automation and performance optimization. If your goal is to become proficient in Bash scripting and handle real-world tasks effectively, this book is designed for you. Whether you're an IT professional, developer, or system administrator, you'll find "Learning Linux Shell Scripting" a valuable addition to your learning resources.