Learning Linux Shell Scripting

Cover
Title Page
Copyright and Credits
Dedication
Packt Upsell
Contributors
Table of Contents
Preface
Chapter 1: Getting Started and Working with Shell Scripting
	Comparison of shells
	Tasks done by the shell
	Working in the shell
	Learning basic Linux commands
	Our first script – Hello World
	When not to use scripts
	Various directories
	Working with permissions
		Changing file permissions
		The chmod command
			Technique one – the symbolic method
			Technique two – the numeric method
		Setting umask
		Setuid
		Setgid
		Sticky bit
	Summary
Chapter 2: Drilling Deep into Process Management, Job Control, and Automation
	Introducing process basics
	Monitoring processes using ps
	Process management
	Process monitoring tools – top, iostat, and vmstat
	Understanding "at"
	Understanding crontab
	Summary
Chapter 3: Using Text Processing and Filters in Your Scripts
	Text filtering tools
		Head and tail
		The diff command
		The cut command
		The paste command
		The join command
		The uniq command
		The comm command
		The tr command
		The sort command
	IO redirection
		File descriptors
		Redirection
		Brace expansion
	Pattern matching with the vi editor
	Pattern searching using grep
	Summary
Chapter 4: Working with Commands
	Learning shell interpretation of commands
		Checking and disabling shell internal commands
		The exit status
	Command substitution
	Command separators
		Command1; command2
		Command grouping
	Logical operators
		Command1 & command2
		Command1 && command2
		Command1 || command2
	Pipes
	Summary
Chapter 5: Exploring Expressions and Variables
	Understanding variables
	Working with environment variables
		The local variable and its scope
		Exporting variables
	Working with read-only variables
	Working with command-line arguments (special variables, set and shift, getopt)
		Understanding set
		Understanding shift
			Resetting positional parameters
	Understanding getopts
	Understanding default parameters
	Working with arrays
		Creating an array and initializing it
		Accessing array values
	Summary
Chapter 6: Neat Tricks with Shell Scripting
	Interactive shell scripts – reading user input
		Summarizing the read command with options
	The here document and the << operator
		The here operator with the sort command
			The here operator with the wc command
			The utility ed and here operator
			A script for sending messages to all logged-in users
			Using the << here operator for FTP usage and data transfer
		Turning off variable substitution
	The here string and the <<< operator
	File handling
		Introducing file handling
			Using exec to assign a file descriptor (fd) to file
		Understanding the opening, writing, and closing of a file
		Understanding reading from a file
		Understanding reading and writing to a file
		Using the read command on a file descriptor (fd)
		Reading from one file and writing to another file
			Displaying the file descriptor information from the /proc folder
			File handling - reading line by line
		Summarizing usage of the exec command
	Debugging
		Debugging mode – disabling the shell (option -n)
		Debugging mode - displaying commands (option -v)
		Debugging mode – the tracing execution (option -x)
		Using the set command
			Summary of debugging options for the set command
			The vi editor setting for debugging
		Good practices for Shell scripts
	Summary
Chapter 7: Performing Arithmetic Operations in Shell Scripts
	Using a declare command for arithmetic
		Listing integers
	Using the let command for arithmetic
	Using the expr command for arithmetic
		Using an arithmetic expansion
	Binary, octal, and hex arithmetic operations
	Floating-point arithmetic
	Summary
Chapter 8: Automating Decision-Making in Scripts
	Checking the exit status of commands
	Understanding the test command
		Using the test command
		Using the test command with double brackets
		String comparison options for the test command
		Numerical comparison operators for the test command
		File test options for the test command
		File-testing binary operators
		Logical test operators
	Conditional constructs – if else
		Numerical handling if constructs
		Using the exit command and the ? variable
		String handling with the if construct
		Checking for null values
		File handling with the if command
		Multiple test commands and if constructs
		The if/elif/else command
		The null command
	Switching case
	Implementing simple menus with select
	Summary
Chapter 9: Automating Repetitive Tasks
	Looping with the for command
	Exiting from the current loop iteration with the continue command
	Exiting from a loop with a break
	Working with the do – while loop
	Using until
	Piping the output of a loop to a Linux command
	Running loops in the background
	The IFS and loops
	Summary
Chapter 10: Working with Functions
	Understanding functions
		Displaying functions
		Removing functions
	Passing arguments or parameters to functions
	Sharing the data with many functions
	Declaring local variables in functions
	Returning information from functions
		Returning a word or string from a function
	Running functions in the background
		Command source and period (.)
	Creating a library of functions
	Summary
Chapter 11: Using Advanced Functionality in Scripts
	Understanding signals and traps
	Using the trap command
	Ignoring signals
		Resetting signals
		Listing traps
	Using traps inside a function
	Running scripts or processes even if the user logs out
	Creating dialog boxes with the dialog utility
		Creating a message box (msgbox)
		Creating a message box (msgbox) with a title
		The yes/no box (yesno)
		The input box (inputbox)
		The textbox (textbox)
		A password box
		The checklist box (checklist)
		The menu box (menu)
		The radiolist box (radiolist)
		The progress meter box (gauge)
	Summary
Chapter 12: System Startup and Customizing a Linux System
	System startup, inittab, and run levels
		The kernel startup and init process
		Understanding run levels
		System initialization boot scripts
	User initialization scripts
		System-wide setting scripts
		User level settings – default files
	Summary
Chapter 13: Pattern Matching and Regular Expressions with sed and awk
	The basics of regular expressions
	sed – non-interactive stream editor
		Understanding sed
		Addressing in sed
		How to modify a file with sed
		Printing – the p command
		Deleting – the d command
		Substitution – the s command
		Range of selected lines the comma
		Multiple edits – the e command
		Reading from files – the r command
		Writing to files – the w command
		Appending – the a command
		Inserting – the i command
		Changing – the c command
		Transform – the y command
		Quit – the q command
		Holding and getting – the h and g commands
		Holding and exchanging – the h and x commands
		sed scripting
	Using awk
		The meaning of awk
		Using awk
			Input from files
		Input from commands
		How awk works
		awk commands from within a file
		Records and fields
			Records
				The record separator
				The $0 variable
				The NR variable
			Fields
			Field separators
				The input field separator
		Patterns and actions
			Patterns
			Actions
		Regular expressions
		Writing the awk script file
		Using variables in awk
		Decision-making using an if statement
		Using the for loop
		Using the while loop
		Using the do while loop
	Summary
Chapter 14: Taking Backup and Embedding Other Languages in Shell Scripts
	Backup of files from command line
		Backup command rsync
		Backup across the network
		Automating backup activity
	Embedding other language codes or scripts in Bash shell scripts
		Embedding other language code in Bash shell script
		Sending output to Bash Script
		Storing other language output to Bash variable
		Sending data to an embedded language code
		Using data from file by embedded language
		Sending user input to the embedded code
		Embedding Python code in Bash shell Script
		Embedding Ruby code
		Embedding other language code in Bash – comparative study
	Summary
Chapter 15: Database Administration Using Shell Scripts
	Introduction to database administration
	Working with a MySQL Database
		Checking the version of MySQL database
		Creating a database
		Show databases
		Creating a user
		Creating a table in MySQL
		Inserting data into table
		Retrieving data from the table
		Updating data
		Deleting data
		Altering a table
		Describing a table
		Drop the table
		Drop the database
	Working with Oracle Database
		Switching to an Oracle user
		Creating a user in Oracle SQL command line
		The Grant statement
		The Define command
		Predefined variables
		Create user through a shell script
		Creating a table
		Inserting the data into table
		Retrieving data from a table
		Update the data
		Delete the data
		Drop the table
	Summary
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Index