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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

Running tasks at a specific time


In general, when we run a command or script, it starts executing instantly. However, what if we want it to run later at a specific time? For example, I want to download large data from the Internet, but don't want to slow down my Internet bandwidth while I am working. So, I would like to run my download script at 1:00 AM since I won't be using the Internet for any kind of work after 1:00 AM. It is possible to schedule download scripts or commands later at a specified time using the at command. We can also list scheduled tasks using the atq command or remove any scheduled tasks using the atrm command.

Executing scripts using at

We will use the at command to run tasks at a given time. The syntax of using the at command is as follows:

at [Option] specified_time

In the preceding syntax, specified_time refers to the time at which a command or script should run. The time can be in the following format:

Time format

Description

HH:MM

The specific time of the day...

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