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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

Traps


When a process is running and in between we kill the process, the process terminates instantly without doing anything further. A programmer who writes a program may want to do some tasks before a program actually terminates; for example, a clean up of the temporary directories created, saving applications' state, saving logs, and so on. In such a case, a programmer would like to listen to signals and do the required task before actually allowing you to terminate the process.

Consider the following shell script example:

#!/bin/bash
# Filename: my_app.sh
# Description: Reverse a file

echo "Enter file to be reversed"
read filename

tmpfile="/tmp/tmpfile.txt"
# tac command is used to print a file in reverse order
tac $filename > $tmpfile
cp $tmpfile $filename
rm $tmpfile

This program takes an input from a user file and then reverses the file content. This script creates a temporary file to keep the reversed content of the file and later copies it to the original file. At the end, it deletes...

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