UNIX Shell Scripting

Duration: 3 days
Type: intermediate

Description

This course enables programmers to write UNIX Shell Scripts. Delegates incrementally build scripts of increasing complexity, which perform tasks such as console I/O, text manipulation, arithmetic, process control and signal handling.

By default the Korn shell is used for examples and exercises, although the Bourne and C shells are also discussed. The course can be delivered on any version of UNIX, but typically Red Hat or Ubuntu Linux is used. Tools specific to particular flavors of UNIX (e.g. DTrace on Solaris) are not covered by default, but can usually be included if required.

Prerequisites

Delegates should be experienced UNIX/Linux users and have some previous programming experience, preferably in C, Perl, Ruby, C# or Java.

List of Modules

Review of Core Concepts

The history and evolution of UNIX
The filesystem, mounting devices and inodes
Processes, threads, scheduling and signals
Using the essential UNIX commands
Comparing the different UNIX shells
Picking the right shell for the job

Starting Shell Programming

Why shell scripts are an essential tool
Using the shebang line to pick an interpreter
Declaring and working with shell variables
Built in operators for testing and arithmetic
Evaluating expresisons using the expr command
Testing variables with if and case
Creating and controlling for, while and until loops
Debugging your shell scripts

Regular Expressions

How a Regular Expression Engine operates
The difference between basic and extended regular expressions
Options for using regular expressions in shell scripts
Creating character classes and specifying multiplicities
Meta-characters for specifying positions in the input
Using parenthesis for grouping and submatches
The non greedy versions of *, + and ?
Using parenthesis that do not capture
Applying modifiers to only part of the expression
Using look-around assertions to match without capturing

Creating Useful Scripts

Creating formatted output with printf
Working with environment variables
Testing the exit status of a command
Looping till a command is successful
Discarding command output using /dev/null
Using /dev/zero to create test files
Testing the attributes of files
Returning an exit status from your script
Processing command line arguments
Reading and parsing input from the keyboard
Processing files one line at a time
Creating and working with arrays

Using the Sed Tool in Shell Scripts

Understanding how Sed transforms text input
Working with commands and addresses
Manipulating the contents of the pattern space
Using the hold buffer to copy and paste text
Sed commands for selection and iteration

Using the Awk Tool in Shell Scripts

Understanding how Awk processes text
Breaking up input into records and fields
Writing actions to processes records
Using regular expressions in actions
Awk commands for selection and iteration
Adding functions to Awk scripts

Advanced Shell Programming

Trapping and handling signals
Running other programs via exec
Starting, monitoring and deleting processes
Breaking up scripts into functions
Security issues with shell scripts

Alternatives to Shell Scripting

How Perl improves and extends shell scripting
Object oriented scripting using Ruby and Python