Book Image

Linux Shell Scripting Bootcamp

By : James K Lewis
Book Image

Linux Shell Scripting Bootcamp

By: James K Lewis

Overview of this book

Linux Shell Scripting Bootcamp is all about learning the essentials of script creation, validating parameters, and checking for the existence of files and other items needed by the script. We will use scripts to explore iterative operations using loops and learn different types of loop statements, with their differences. Along with this, we will also create a numbered backup script for backup files. Further, you will get well-versed with how variables work on a Linux system and how they relate to scripts. You’ll also learn how to create and call subroutines in a script and create interactive scripts. The most important archive commands, zip and tar, are also discussed for performing backups. Later, you will dive deeper by understanding the use of wget and curl scripts and the use of checksum and file encryption in further chapters. Finally, you will learn how to debug scripts and scripting best practices that will enable you to write a great code every time! By the end of the book, you will be able to write shell scripts that can dig data from the web and process it efficiently.
Table of Contents (19 chapters)
Linux Shell Scripting Bootcamp
Credits
About the Author
Acknowledgement
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface
Index

Environment variables


So far we have only talked about variables that are local to a script. There are also system wide environment variables (env vars) which play a very important part of any Linux system. Here are a few, some of which the reader may already be aware of:

Variable

Role

HOME

user's home directory

PATH

directories which are searched for commands

PS1

command line prompt

HOSTNAME

hostname of the machine

SHELL

shell that is being used

USER

user of this session

EDITOR

text editor to use for crontab and other programs

HISTSIZE

number of commands that will be shown by the history command

TERM

type of command line terminal that is being used

Most of these are self-explanatory, however, I will mention a few.

The PS1 environment variable controls what the shell prompt displays as part of the command line. The default setting is usually something like [guest1@big1 ~]$, which is not as useful as it could be. At a minimum, a good prompt shows at least...