Advanced Bash Shell Scripting

Course Description

In this two-day hands-on course students learn how to read, write, and debug complex Bash shell scripts.

Course Objectives

Upon successful completion of this course, students will be able to:

• Read and understand Bash shell scripts
• Debug Bash shell scripts
• Customize and extend their user environment with Bash shell scripts
• Create interactive menus with Bash shell scripts
• Use all key language features of the Bash shell: variables, arrays, branches, loops and functions
• Write Bash shell scripts that perform complex file handling, string manipulations and mathematics

Course Benefits

Bash is the default shell for Linux. Students will increase their productivity by taking full advantage of the Bash shell.

Who Should Attend

This course is valuable for system administrators, developers and other computer professionals involved with Linux.

Prerequisite

To ensure your success, we recommend you first take either our Introduction To UNIX course or our Introduction To Linux course, or have the equivalent knowledge. Familiarity with Web browsers, the vi editor, and Linux command line interface is assumed. Prior programming experience is highly recommended.

Method Of Instruction

Lecture, demonstrations, questions and answers, and numerous hands-on exercises.

Hands-on Exercises

Throughout this course, students perform a series of extensive hands-on exercises including:

• Creating loops and making decisions using while and for loops
• Writing scripts to perform matematical calculations
• Using eval for dynamic commands
• Handling errors with default values
• Working with arrays
• Breaking a large program into reusable modules using functions
• Manipulating multiple files
• Handling unexpected events with trap
• Processing command line options
• Building an interactive menu interface using case constructs and read
• Building colorful and sophisticated menu interfaces using dialog

Course Outline

Chapter 1: Using Structured Commands

• if, then, elif, fi
• The test command
• Compount condition testing
• The case command
• The for command
• The while command
• The until command
• Nesting Loops
• The break command
• The continue command
• Processing the output of a loop
• Specifying default values and error conditions
• Shell arithmetic
• The select statement
• The eval command

Chapter 2: Handling User Input

• $$ - PID of the shell
• $# - Number of arguments
• $* - All arguments
• Getting Options
• Reading in command arguments
• The read command
• The IFS command
• The shift command
• The set command
• Parameter expansion

Chapter 3: Presenting Data

• File descriptors
• Redirecting input and output
• Using temporary files

Chapter 4: Script Control

• Signals
• Running scripts in the background
• Running scripts without a terminal
• The at and batch commands
• The nice command
• Having cron run scripts
• Runnings scripts when booting

Chapter 5: Functions

• Calling a function
• Passing arguments to functions
• Setting and unsetting parameters
• Defining global and local variables
• Specifying default values and error conditions
• Returning values from functions
• Function declarations
• Passing and returning arrays
• Creating and using libraries
• Using functions on the command line

Chapter 6: Interactive Graphics

• Creating text menus
• Adding color
• The dialog command
• Integrating GNOME and KDE into scripts

Chapter 7: sed and awk

• Multiline commands
• Inserting and appending text
• Pattern replacemnt
• Extracting fields
• String manipulation
• Formatting output
• Using functions

Chapter 8: Debugging Techniques

• Using echo and printf
• Using Standard Error
• Script Tracing
• Options for Debugging
• Conditional Debugging