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Linux Shell Scripting Essentials

Linux Shell Scripting Essentials

By : Sinny Kumari
4.5 (2)
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Linux Shell Scripting Essentials

Linux Shell Scripting Essentials

4.5 (2)
By: Sinny Kumari

Overview of this book

Shell scripting is a quick method to prototype complex applications or problems. Shell scripts are a collection of commands to automate tasks, usually those for which the user has a repeated need, when working on Linux-based systems. Using simple commands or a combination of them in a shell can solve complex problems easily. This book starts with the basics, including essential commands that can be executed on Linux systems to perform tasks within a few nanoseconds. You’ll learn to use outputs from commands and transform them to show the data you require. Discover how to write shell scripts easily, execute script files, debug, and handle errors. Next, you’ll explore environment variables in shell programming and learn how to customize them and add a new environment. Finally, the book walks you through processes and how these interact with your shell scripts, along with how to use scripts to automate tasks and how to embed other languages and execute them.
Table of Contents (10 chapters)
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9
Index

Configuration files


Configuration or config files are regular files that contain settings for an application. During the initial stage of execution, many applications in Linux and UNIX read settings from config file(s) and configure the application accordingly.

Viewing and modifying configuration files

Configuration files are generally present in the /etc/ directory and can be viewed using the cat command.

For example, consider viewing the resolv.conf config file:

$ cat /etc/resolv.conf
# Generated by NetworkManager
search WirelessAP
nameserver 192.168.1.1

The resolv.conf file contains the order in which to contact DNS servers.

We can also modify a configuration file to meet our requirements. For example, we can add another DNS entry in the /etc/resolv.conf file with the DNS value 8.8.8.8, if some of network URLs are accessible via 192.168.1.1. The modified cat /etc/resolv.conf will look like the following:

$ cat /etc/resolv.conf
# Generated by NetworkManager
search WirelessAP
nameserver 192...
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