Book Image

Learning Linux Shell Scripting

By : Ganesh Sanjiv Naik
Book Image

Learning Linux Shell Scripting

By: Ganesh Sanjiv Naik

Overview of this book

Linux is the one of the most powerful and universally adopted OSes. Shell is a program that gives the user direct interaction with the operating system. Scripts are collections of commands that are stored in a file. The shell can read this file and act on the commands as if they were typed on the keyboard. Shell scripting is used to automate day-to-day administration, and for testing or product development tasks. This book covers Bash, GNU Bourne Again SHell, preparing you to work in the exciting world of Linux shell scripting. We start with an introduction to the Shell environment and explain basic commands used in Shell. Next we move on to check, kill, and control the execution of processes in Linux OS. Further, we teach you about the filter tools available in Linux and explain standard output and standard errors devices. Then we will ensure you understand Shell’s interpretation of commands and get a firmer grasp so you use them in practice. Next, you’ll experience some real-world essentials such as debugging and perform Shell arithmetic fluently. Then you’ll take a step ahead and learn new and advanced topics in Shell scripting, such as starting up a system and customizing a Linux system. Finally, you’ll get to understand the capabilities of scripting and learn about Grep, Stream Editor, and Awk.
Table of Contents (20 chapters)
Learning Linux Shell Scripting
Credits
About the Author
Acknowledgments
About the Reviewers
www.PacktPub.com
Preface
Index

Debugging


In the very old days of computer technology, the initial problems with computers were due to real insects. Due to this, fault finding was later called as finding a bug. Therefore, the process of finding and fixing the problems in computers was called debugging.

The process of debugging involves the following:

  • Finding out what has gone wrong

  • Fixing the problem

In the actual debugging process, you will need to do the following:

  • Understand the error message and find out what is the problem with the script.

  • Find the error location in the script.

  • Locate the line number from the error message. The following are a few error messages:

    • debug_sp: line 11: [7: command not found]

    • file: line 6: unexpected EOF while looking for matching `"'

    These messages inform the user about the line numbers of script which contain errors.

  • Correct the issue or problematic part of code. We may have to read the line as well as look backward from this line number for any possible reason for the error.

Debugging mode...