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

Displaying data from web logs

We have already had a preview of how we can use awk to view the logs files from the Apache web server; however, we will now move onto our demonstration file that has a greater and more varied content.

Selecting entries by date

Having seen how we can display the date, we should perhaps look at how we print entries from just one day. To do this, we can use the match operator in awk. This is denoted by the tilde or squiggly line, if you prefer. As we only need the date element, there is no need for us to use both the date and time-zone field. The following command shows how to print entries from 10th September 2014:

$ awk ' ( $4 ~ /10\/Sep\/2014/ ) ' access.log

For completeness, this command and partial output is shown in the following screenshot:

The round brackets or parentheses embrace the range of lines that we are looking for and we have omitted the main block, which ensures that we print the complete matching lines from the range. There is nothing stopping us...