Book Image

Mastering Linux Shell Scripting

By : Andrew Mallett
Book Image

Mastering Linux Shell Scripting

By: Andrew Mallett

Overview of this book

Shell scripting is a quick method to prototype a complex application or a problem by automating tasks when working on Linux-based systems. Using both simple one-line commands and command sequences complex problems can be solved with ease, from text processing to backing up sysadmin tools. In this book, you’ll discover everything you need to know to master shell scripting and make informed choices about the elements you employ. Get to grips with the fundamentals of creating and running a script in normal mode, and in debug mode. Learn about various conditional statements' code snippets, and realize the power of repetition and loops in your shell script. Implement functions and edit files using the Stream Editor, script in Perl, program in Python – as well as complete coverage of other scripting languages to ensure you can choose the best tool for your project.
Table of Contents (21 chapters)
Mastering Linux Shell Scripting
About the Author
About the Reviewer

Significant whitespace

A major difference between Python and most other languages is that additional whitespace can mean something. The indent level of your code defines the block of code to which it belongs. So far, we have not indented the code we have created past the start of the line. This means that all of the code is at the same indent level and belongs to the same code block. Rather than using brace brackets or do and done keywords to define the code block, we use indents. If we indent with four spaces, then we must stick to those four spaces. When we return to the previous indent level, we return to the previous code block.

This seems complex but it is really quite simple and keeps your code clean and uncluttered. If we edit the file to prevent unwelcomed errors, if an argument is not supplied, we can see this in action:

import sys
count = len(sys.argv)
if ( count > 1 ):
    print("Arguments supplied: " + str(count))
    print("Hello " + sys.argv[1])