PowerShell scripts

Error / Exception handling in PowerShell scripts

Diagram showing PowerShell script flow with try block, catch block for error handling, and finally block for cleanup.

Hello All,

Greetings and welcome to PowerShell Hub. Today, we will discuss one of the most important aspects of PowerShell scripting: Error and Exception Handling.

What is an Exception? OR what is an error?

As per Microsoft – An exception is the an event that is created when normal error handling can’t deal with the issue.

Details

In PowerShell we will use Try {} Catch {} Finally {} blocks to capture, handle and manage terminating errors effectively.
What are terminating errors in PowerShell?
- Terminating errors are the errors / exception which immediately halt the execution of a PowerShell script.
- These error triggers a catch block naturally.

Basic Try-Catch-Finally Structure

			
Try {
      # Code
      Get-Content -Path "C:\NonExistentFile.txt" -ErrorAction Stop
} Catch {
      # Handles the error if something breaks
      Write-Warning "Failed to read the file. Reason: $_"
} Finally {
      # Always runs, useful for cleanup tasks like closing sessions
      Write-Host "Cleanup operations completed."
}

		

Here, in above code block, variable “$_” in catch block represent the error / exception object.
We can use multiple catch blocks to capture different types of error separately.
For example: In example below we are catching two exceptions
- One specific to – DivideByZero – Exception occurs when we divide any number by Zero (0).
- Other one is generic – catching any type of exception.

			
Try {
    $Num = 9 / 0
} 
Catch [System.DivideByZeroException] {
    Write-Host "Error: Cannot divide by zero." -ForegroundColor Red
}
Catch {
    Write-Host "Error occurred: $_"
}

		

Other option to write exception is in text file . We can use the PowerShell CMDLET – Add-Content .
- Add-Content appends data to an existing file without overwriting its current contents. If the specified file does not exist, the cmdlet will automatically create new file.

Throw keyword

Throw keyword is used to throw or to create our own terminating errors.
Consider example below – we are throwing our own exception in case $price mentioned is below zero.

			
if($price -lt 0)
{
    Throw "Price can not be less than 0"
}

References

Thank you for reading.

Feel free to discuss about PowerShell.

Have a great time ahead ! LIFE IS BEAUTIFUL :)

Error / Exception handling in PowerShell scripts

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