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Mastering Linux Shell Scripting

You're reading from   Mastering Linux Shell Scripting Master the complexities of Bash shell scripting and unlock the power of shell for your enterprise

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Product type Paperback
Published in Dec 2015
Publisher
ISBN-13 9781784396978
Length 198 pages
Edition 1st Edition
Tools
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Author (1):
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Andrew Mallett Andrew Mallett
Author Profile Icon Andrew Mallett
Andrew Mallett
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Table of Contents (16) Chapters Close

Preface 1. What and Why of Scripting with Bash FREE CHAPTER 2. Creating Interactive Scripts 3. Conditions Attached 4. Creating Code Snippets 5. Alternative Syntax 6. Iterating with Loops 7. Creating Building Blocks with Functions 8. Introducing sed 9. Automating Apache Virtual Hosts 10. Awk Fundamentals 11. Summarizing Logs with Awk 12. A Better lastlog with Awk 13. Using Perl as a Bash Scripting Alternative 14. Using Python as a Bash Scripting Alternative Index

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...

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