Book Image

Learning Linux Shell Scripting

By : Ganesh Sanjiv Naik
Book Image

Learning Linux Shell Scripting

By: Ganesh Sanjiv Naik

Overview of this book

Linux is the one of the most powerful and universally adopted OSes. Shell is a program that gives the user direct interaction with the operating system. Scripts are collections of commands that are stored in a file. The shell can read this file and act on the commands as if they were typed on the keyboard. Shell scripting is used to automate day-to-day administration, and for testing or product development tasks. This book covers Bash, GNU Bourne Again SHell, preparing you to work in the exciting world of Linux shell scripting. We start with an introduction to the Shell environment and explain basic commands used in Shell. Next we move on to check, kill, and control the execution of processes in Linux OS. Further, we teach you about the filter tools available in Linux and explain standard output and standard errors devices. Then we will ensure you understand Shell’s interpretation of commands and get a firmer grasp so you use them in practice. Next, you’ll experience some real-world essentials such as debugging and perform Shell arithmetic fluently. Then you’ll take a step ahead and learn new and advanced topics in Shell scripting, such as starting up a system and customizing a Linux system. Finally, you’ll get to understand the capabilities of scripting and learn about Grep, Stream Editor, and Awk.
Table of Contents (20 chapters)
Learning Linux Shell Scripting
Credits
About the Author
Acknowledgments
About the Reviewers
www.PacktPub.com
Preface
Index

User initialization scripts


Till now, we have seen different scripts, these scripts initialize the operating system, prior to the login of any user. Once the basic operating system in initialized, the user login process starts. This process is explained in the following topics.

Systemwide settings scripts

In the /etc/ folder, the following files are related to the user level initialization:

  • /etc/profile: Few distributions will have additional folder /etc/profile.d/. All the scripts from the profile.d folder will be executed.

  • /etc/bash.bashrc

The preceding scripts are called by all the users, including root and normal users. Initially, the /etc/profile script will be called. This script creates system-wide environment settings. Few distributions will have the /etc/profile.d/ folder. SuSE Linux has additional /etc/profile.local script. The scripts in this folder will also be called. Then, the /etc/bash.bachrc script will be executed.

User level settings – default files

Scripts in the /etc/ folder...