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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

Looping around with for


The for loop can be used to iterate over the items in a list or till the condition is true.

The syntax of using the for loop in bash is as follows:

for item in [list]
do
   #Tasks
done

Another way of writing the for loop is the way C does, as follows:

for (( expr1; expr2; expr3 ))
  # Tasks
done

Here, expr1 is initialization, expr2 is condition, and expr3 is increment.

Simple iteration

The following shell script explains how we can use the for loop to print the values of a list:

#!/bin/bash
# Filename: for_loop.sh
# Description: Basic for loop in bash

declare -a names=(Foo Bar Tom Jerry)
echo "Content of names array is:"
for name in ${names[@]}
do
   echo -n "$name "
done
echo

The output of the script is as follows:

Content of names array is:
Foo Bar Tom Jerry

Iterating over a command output

We know that a lot of commands give multiline output such as ls, cat, grep, and so on. In many cases, it makes sense to loop over each line of output and do further processing on them.

The...

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