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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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Toc

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

Using awk ranges to exclude data

So far in this book, we have predominately looked at including data with ranges either for sed or for awk. With both of these tools, we can negate the range so that we exclude the specified rows. This suits the need that we have been using the output from lastlog. This will print all the login data for all the users, including accounts that have never been logged in. These accounts that have never been logged in might be service accounts or for new users that have not logged into the system so far.

The lastlog command

If we look at the output from lastlog, when it is used without any options, we can begin to understand the issue. From the command line, we execute the command as a standard user. There is no requirement to run it as the root account. The command is shown in the following example:

$ lastlog

The partial output is shown within the following screenshot:

The lastlog command

We can see, even from this limited output that we have a cluttered output due to the virtual noise...

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