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

Further filtering to display users by UID

We have been able to build our skills with awk piece by piece and what we have learned has been useful. We can take these tiny steps and add them to start creating something a little more usable. Perhaps, we want to print just the standard users; these are usually users higher than 500 or 1000 depending on your particular distribution.

On the Raspbian distribution that I am using for this book, standard users start with UID 1000. The UID is the third field. This is really a simple matter of using the value of the third field as the range operator. We can see this in the following example:

$ awk -F":" '$3 > 999 ' /etc/passwd

We can show users with UID 101 with the following command:

$ awk -F":" '$3 < 101 ' /etc/passwd

These just give you an idea of some of the possibilities available with awk. The reality is that we can play all day with our arithmetic comparison operators.

We have also seen that with some of these examples, the awk statements become...