Script Debugging Tutorial

Introduction to Script Debugging

Debugging is a crucial part of the development process. It allows you to identify and fix errors in your scripts. This tutorial will guide you through various techniques and tools for debugging scripts from the command line.

Common Debugging Techniques

There are several techniques that you can use to debug scripts:

• Using print statements
• Using a debugger
• Checking log files
• Using error messages

Using Print Statements

Print statements are one of the simplest ways to debug a script. By inserting print statements at various points in your code, you can track the flow of execution and the values of variables.

                    #!/bin/bash
                    echo "Starting script..."
                    var1="Hello"
                    echo "var1: $var1"
                    var2="World"
                    echo "var2: $var2"
                    echo "Script finished."
                

Using a Debugger

A debugger is a powerful tool that allows you to step through your code, inspect variables, and control the execution flow. One of the most commonly used debuggers for shell scripts is bashdb.

                    # Install bashdb
                    sudo apt-get install bashdb

                    # Debug a script
                    bashdb myscript.sh
                

Checking Log Files

Many scripts generate log files that contain detailed information about their execution. Checking these log files can help you identify errors and understand the behavior of your script.

                    # View the last 10 lines of a log file
                    tail -n 10 /var/log/myscript.log
                

Using Error Messages

Error messages can provide valuable information about what went wrong in your script. Make sure to read and understand these messages to quickly identify and fix issues.

                    #!/bin/bash
                    echo "Starting script..."
                    non_existing_command
                    echo "Script finished."
                

                        Starting script...
                        myscript.sh: line 3: non_existing_command: command not found
                        Script finished.
                    

Conclusion

Debugging is an essential skill for any developer. By using print statements, debuggers, log files, and error messages, you can effectively identify and fix errors in your scripts. Practice these techniques regularly to improve your debugging skills.