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Mastering Linux Shell Scripting

You're reading from   Mastering Linux Shell Scripting A practical guide to Linux command-line, Bash scripting, and Shell programming

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Product type Paperback
Published in Apr 2018
Publisher
ISBN-13 9781788990554
Length 284 pages
Edition 2nd Edition
Languages
Tools
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Authors (2):
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Mokhtar Ebrahim Mokhtar Ebrahim
Author Profile Icon Mokhtar Ebrahim
Mokhtar Ebrahim
Andrew Mallett Andrew Mallett
Author Profile Icon Andrew Mallett
Andrew Mallett
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Toc

Table of Contents (17) Chapters Close

Preface 1. The 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 the Stream Editor 9. Automating Apache Virtual Hosts 10. AWK Fundamentals 11. Regular Expressions 12. Summarizing Logs with AWK 13. A Better lastlog with AWK 14. Using Python as a Bash Scripting Alternative 15. Assessments 16. Other Books You May Enjoy

Formatting output

We have remained faithful to the print command so far, as we have been limited in what we require from the output. If we want to print out, say, the username, UID, and default shell, we need to start formatting the output just a little. In this case, we can organize the output in well-shaped columns. Without formatting, the command we use will look similar to the following example, where we use commas to separate the field that we want to print:

$ awk ' BEGIN { FS=":" } { print $1,$3,$7 } ' /etc/passwd  

We use the BEGIN block here, as we can make use of it to print column headers later.

To understand the problem a little better, take a look at the following screenshot, which illustrates uneven column widths:

The issue that we have in the output is that the columns do not align, as the username is an inconsistent length. To improve on this...

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