Linux / UNIX Bash Scripting - Shell Scripting

Course Description

This course is to help users of Linux / Unix systems to automate the repetitive tasks they encounter during their daily work using "Shell Scripts" or "Bash Scripts". It is a hands-on course with lots of examples and the goal is to encourage and empower participants to "work smarter not harder". One of the best techniques to employ in this effort is to write a script to carry out repetitive tasks.
2 Days
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Prerequisites

Participants should have attended the Linux / Unix User Essentials course or have equivalent skills. The course is aimed at Linux / Unix users, programmers and system administrators.

Linux / UNIX Processes

What is a Process?
Process Structure
The ps Utility
Options to the ps Utility
Background Commands (&)
Killing Background Processes
Redirecting the Standard Error

Combining Linux commands

Redirecting input, output and error streams
Pipe operator
Command substitutions (``)
And operator
Or operator
Creating a script

Getting Started

What is a Shell?
Running Scripts
Specifying the Script’s Interpreter
The PATH Environment Variable
Sub-shells
chmod +x
Adding a "shebang" to your script
Returning a value from your script

Variables

Shell Variables
The read Command
The export Command
The Shell Environment
Variable Substitution
Command Substitution
Creating an array

Conditional Statements

The Exit Status of Commands
Command Line Examples
The test Command
The if-then-else Construct
The elif Construct
case Statements

Loops

The for Loop
The while Loop
Reading Lines From Files
Using Arrays with Loops

Functions

Shell Functions
Passing Arguments to Functions
Returning Values from Functions
Function Libraries

Special Variables

$$ - PID of Shell
Command-Line Arguments
$# - Number of Arguments
$* - All Arguments
The shift Command
The set Command
Getting Options

Quoting Mechanisms

Single vs. Double Quotes
What is a Here Document?
Using a Here Document
Here Document Quoting
Ignoring Leading Tabs

.bashrc

The Login Process
Scripts that are run at startup
Making changes persist a reboot

Advanced Programming

Shell Arithmetic
The select Statement
Terminal Independence in Scripts
The eval Command

Debugging techniques

Using echo
Using Standard Error
Options for Debugging
Script Tracing
Conditional Debugging

Shell Scripting Alternatives

If you are working on very difficult automation tasks, utilising a different language such as Perl or Python could be beneficial. This lesson will demonstrate how some of the techniques encountered so far can be applied to scripts that are written in a different programming language.
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