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The Ultimate Linux Shell Scripting Guide

The Ultimate Linux Shell Scripting Guide

By : Donald A. Tevault
4.8 (5)
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The Ultimate Linux Shell Scripting Guide

The Ultimate Linux Shell Scripting Guide

4.8 (5)
By: Donald A. Tevault

Overview of this book

Embark on a comprehensive journey through command shells with this hands-on manual. While Bash is a Linux staple, Z shell and PowerShell are rising stars, applicable to Linux, macOS, and Unix. Progress seamlessly through chapters, each building on the last, creating a solid foundation. Learn through a unique approach: concepts, examples, and interactive labs. These labs, nearly a hundred strong, form the core of experiential learning, essential for script creation. Focusing on Linux commands and their scripting applications, this manual is universally relevant across Linux and select Unix-like systems. It goes beyond theory, offering practical scripts for real-world Linux administration. Scripts are designed for manageability, aiding learning and troubleshooting. The goal is to nurture the ability to craft intelligent, functional shell scripts. While centered on Bash, this book offers a peek into the future with Z Shell and PowerShell, expanding your skills and adaptability. This book is systematically structured and engaging so that it will guide you to master command shells, equipping you for real-world Linux challenges.
Table of Contents (26 chapters)
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24
Other Books You May Enjoy
25
Index

Performing Tests

There will be times when your scripts will need to test for a certain condition before making a decision on which action to take. You might need to check for the existence of a certain file or directory, whether certain permissions are set on a file or directory, or for a myriad of other things. There are three ways to perform a test, which are:

  • Use the keyword test followed by a test condition, with another command joined to it with either a && or a || construct.
  • Enclose the test condition within a set of square brackets.
  • Use an if. . .then construct

Let’s start by looking at the test keyword.

Using the test Keyword

For our first example, let’s test to see whether a certain directory exists, and then create it if it doesn’t. Here’s how that works:

[donnie@fedora ~]$ test -d graphics || mkdir graphics
[donnie@fedora ~]$ ls -ld graphics/
drwxr-xr-x. 1 donnie donnie 0 Sep 26 15:41 graphics...

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