Book Image

Linux Shell Scripting Essentials

By : Sinny Kumari, Khem Raj
Book Image

Linux Shell Scripting Essentials

By: Sinny Kumari, Khem Raj

Overview of this book

Table of Contents (15 chapters)
Linux Shell Scripting Essentials
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Debugging your scripts


We write different shell scripts to perform different tasks. Have you ever encountered any errors while executing a shell script? The answer would be mostly yes! This is to be expected as it is practically impossible to always write perfect shell scripts, without errors or bugs.

For example, the following shell script is a buggy script while execution:

#!/bin/bash
# Filename: buggy_script.sh
# Description: Demonstrating a buggy script

a=12 b=8
if [ a -gt $b ]
then
  echo "a is greater than b"
else
  echo "b is greater than a"
fi

The following output is obtained after executing buggy_script.sh:

$ sh buggy_script.sh 
buggy_script.sh: line 6: [: a: integer expression expected
b is greater than a

From the output, we see that the error [: a: integer expression expected occurred at line 6. It's not always possible to know the reason of the error by just looking into an error message, especially when seeing an error for the first time. Also, looking manually into the code and...