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

Providing parameter defaults

Within bash parameters, there are named spaces in the memory that allow us access to stored values. There are two types of parameters:

  • Variables

  • Special parameters

Special parameters are read-only and are pre-set by the shell. Variables are maintained by ourselves as well as bash. In general, when talking about syntax, bash will refer to variables by their family name of parameters.


Variables are one type of parameter. These can be set by the system or by ourselves. For example, $USER is a variable parameter that is set by the system but can be written by us. As such, it is not a read-only requisite of special parameters.

Special parameters

Special parameters are the second parameter type and are managed by the shell itself and are presented as read-only. We have come across these before in parameters, such as $0 but let's take a look at another $-. We can expand these parameters to gain an understanding of their use, using the echo command:

$ echo "My shell...