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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

Exiting from scripts and exit codes

We are now well familiar with shell script files, commands, and running them in bash to get the desired output. Until now, whatever shell script examples we have seen, they run line by line until the end of the file. While writing real-world shell scripts, it may not always be the case. We may need to exit a script in between, for example, when some error occurs, doesn't satisfy a certain condition, and so on. To exit from the script, the exit shell builtin is used with an optional return value. The return value tells the exit code, which is also known as return status or exit status.

Exit codes

Every command returns an exit code when it gets executed. Exit code is one of the ways to know whether a command is executed successfully or if some error has occurred. As per the POSIX (Portable Operating System Interface) standard convention, a command or program with successful execution returns 0, and 1 or a higher value for failed execution.

In bash,...

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