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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

Working with e-mail logs

We have worked with logs from the Apache HTTP web server. The reality is that we can apply the same ideals and methodology to any log file. We will take a look at Postfix mail logs. The mail log holds all activity from the SMTP server and we can then see who has been sending e-mails to whom. The log file is usually located at /var/log/mail.log. I will access this on my Ubuntu 15.10 server that has a local e-mail delivery. All this means is that the STMP server is listening only to the localhost interface of 127.0.0.1.

The log format will change a little depending on the type of message. For example, $7 will contain from logs on outbound message, whereas inbound messages will contain to.

If we want to list all the inbound messages to the SMTP server, we can use the following command:

# awk '  ( $7 ~ /^to/ ) ' /var/log/mail.log

As the string to is very short, we can add identification to it by ensuring that the field begins with to using the ^. The command...

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