book

Linux Shell Scripting Essentials

by Sinny Kumari

November 2015

Beginner

282 pages

5h 5m

English

Packt Publishing

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What this book covers

Downloading the example codeErrataPiracyQuestions
Hello World in shellInteracting with shellLet's make it scripted
NomenclatureAssigning a valueAccessing a valueConstant variablesReading variables from a user input
The assignment operatorArithmetic operatorsLogical operatorsComparison operators
~ (Tilde)* (Asterisk)? (Question mark)[ ] (Square brackets){ } (Curly brackets)
Exit on the first failureEnabling/disabling symbolic link's resolution pathSetting/unsetting variables
Standard I/O and error streamsFile descriptors
Redirecting standard outputRedirecting standard inputRedirecting standard errorsMultiple redirection
PipePipeline
Regular expression metacharactersCharacter ranges and classesCharacter rangesMatching dates in mm-dd-yyyy formatMatching a valid monthMatching a valid dayMatching the valid year in a dateCombining valid months, days, and years regex to form valid datesRegex for a valid shell variable
SyntaxLooking for a pattern in a fileLooking for a pattern in multiple filesA few more grep usagesSearching in a binary fileSearching in a directoryExcluding files/directories from a searchDisplay a filename with a matching patternMatching an exact word
String substitution using sMultiple substitutions
Writing an output to stdout and appending to a fileSending an output to multiple commands
Sorting an input textSorting a single fileRedirecting output to sortFiltering unique elementsUnique elements in a file
Deleting input charactersSqueezing to a single occurrenceInverting a character set to be translated
Printing lines using headPrinting the first few linesPrinting the first few bytesPrinting lines using tailChecking log entriesFinding any line in a file
Cutting across columnsText selection in files
Exiting from scripts and exit codesExit codesExit codes with a special meaningScript with exit codes
File checksArithmetic checksString checksExpression checks
Simple if and elseThe if, elif, and else statementsNested if
Indexed arraysArray declaration and value assignmentOperations on arraysThe associative arrayThe declaration and value assignmentOperations on arrays
Simple iterationIterating over a command outputSpecifying a range to the for loopSmall and sweet for loop
Loop using selectThe while loopThe until loop
Basic operations with xargsUsing xargs to find a file with the maximum sizeArchiving files with a given pattern
Calling a function in bashPassing parameters to functions
Creating aliasListing all aliasesRemoving an alias
Modularizing your scriptsSource to a script fileSyntaxCreating a shell script libraryLoading a shell script libraryCalling a shell library in bashCalling shell library in another shell script
Reading arguments in scriptsShifting command line argumentsProcessing command line options in a script
Debugging using echoDebugging an entire script using -xDebugging sections of a script using the set options
Managing bash completion with completeViewing the existing bash completionModifying default bash completion behaviorRemoving bash completion specificationWriting bash completion for your own applicationAn example of bash completionRunning the created bash completion
Knowing the default environmentViewing a shell environmentprintenvenvDifferences between shell and environment variables
Creating environment variablesModifying environment variablesDeleting environment variables
.bashrc.bash_profile.bash_logout
Shell variables controlling the historyThe history builtin commandModifying the default history behaviorHandy shortcuts for seeing the history[Ctrl + r]Up and down arrow key!!!(search_string)!?(search_string)
Running tasks in the backgroundSending a running task to the backgroundListing background tasksMoving tasks to the foregroundTerminating tasks
Performing basic file operationsCreating filesDirectory fileRegular fileTouch commandUsing the command line editorsUsing the cat commandRedirecting the command's outputModifying filesViewing filesViewing content using catmore and lessDeleting filesDeleting a regular fileDeleting a directory
Moving filesMoving a directory to a new locationRenaming a fileCopying filesCopying files locallyCopying a file to another locationCopying files remotelyCopying files to a remote server
Files comparison using diffExample
Searching files according to use caseFinding and deleting a file based on inode number
Soft linkHard linkDifference between hard link and soft link
The block device fileNamed pipe fileSocket file
Creating a temporary file using mktemp
Viewing the ownership and permission of filesChanging permissionChanging the owner and groupChanging a file's ownerChanging group ownership
Knowing the files opened by a specific applicationListing the applications that opened a fileKnowing the files opened by a user
Viewing and modifying configuration files
Process managementProcess creation and executionProcess terminationUsing the kill commandUsing the killall commandUsing the pkill command
Listing processesSyntaxSimple process selectionProcess selection by listOutput format controlListing all processes with detailsListing all processes run by a userProcesses running in the current terminalListing processes by a command nameTree format display of processesMonitoring processes
Diffing the output of two processes
Changing scheduling prioritiesUsing niceUsing renice
Available signals
Information on IPC using ipcsListing information provided by IPCsKnowing processes' PID who recently did IPCs
Running tasks at a specific timeExecuting scripts using atScheduling commandsScheduling a script fileListing scheduled tasksRemoving scheduled tasks
Cron daemonCron configurationCrontab entriesSpecial strings in Crontab
Listing crontab entriesEditing crontab entriesRemoving crontab entries
systemd unitsManaging servicesStatus of a serviceEnabling and disabling servicesStart and stop a serviceViewing system logsViewing the latest log entriesViewing logs of a particular time interval
Embedding Python languageEmbedding AWK language

Overview

This hands-on guide, 'Linux Shell Scripting Essentials', walks you through the fundamentals of shell scripting with a focus on how to automate day-to-day tasks and solve complex problems efficiently. You'll gain practical experience writing scripts that interact with Linux-based environments effectively and reliably.

What this Book will help me do

Efficiently write shell scripts to automate repetitive tasks and solve problems.
Manipulate large text data files and perform streamlined search operations.
Debug scripts effectively using robust debugging techniques for faultless execution.
Understand and use environment variables and processes within your scripts.
Embed other programming languages into shell scripts to extend their functionality.

Author(s)

Sinny Kumari, a seasoned Linux professional and expert in shell scripting, brings years of terminal troubleshooting and programming expertise to this authoring project. With a passion for sharing knowledge, she presents complex technical concepts clearly and adopts a hands-on instructional style. Sinny aims to empower developers and system administrators to unlock the full potential of shell scripting.

Who is it for?

This book is aimed at developers, system administrators, and Linux enthusiasts who are familiar with basic command-line tools and have a fundamental understanding of scripting. It best suits individuals looking to streamline their workflows and develop a deeper understanding of shell scripting for task automation. If you're keen to improve your problem-solving skills through scripts that integrate seamlessly with Linux environments, this book is for you.