Custom error messages in PowerShell - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this PowerShell script with custom error?

Consider the following script that tries to divide two numbers and shows a custom error message if division by zero occurs. What will be the output?

PowerShell

try {
  $a = 10
  $b = 0
  $result = $a / $b
  Write-Output "Result: $result"
} catch {
  Write-Output "Error: Cannot divide by zero!"
}

A Divide by zero exception thrown, script stops

B Result: Infinity

C Result: 0

D Error: Cannot divide by zero!

💡 Hint

Think about what happens when you divide by zero in PowerShell inside a try block.

Dividing by zero in PowerShell throws a runtime exception. The catch block catches it and prints the custom error message.

💻 Command Output

intermediate

What does this script output when input is invalid?

This script reads a number and throws a custom error if the input is not a number. What is the output if the user inputs 'abc'?

PowerShell

try {
  $input = 'abc'
  if (-not ($input -as [int])) {
    throw "Input is not a valid number"
  }
  Write-Output "Input is valid: $input"
} catch {
  Write-Output "Error: $_"
}

A Error: Input is not a valid number

B Error: System.Management.Automation.RuntimeException: Input is not a valid number

C Input is valid: abc

D No output

💡 Hint

Check how the script throws and catches the error with a custom message.

The script throws a string error which is caught and printed as a custom error message without the full exception details.

📝 Syntax

advanced

Which option correctly defines a function that throws a custom error with a message?

You want to create a PowerShell function that throws a custom error with the message 'Invalid operation'. Which option is syntactically correct?

A function Test-Error { throw Invalid operation }

B function Test-Error { throw "Invalid operation" }

C function Test-Error { throw ('Invalid operation') }

D function Test-Error { throw [string]'Invalid operation' }

💡 Hint

Remember how to throw a string error message in PowerShell.

Option B correctly throws a string error message. Option B misses quotes causing syntax error. Option B uses parentheses unnecessarily but is valid syntax. Option B tries to cast but is invalid syntax for throw.

🔧 Debug

advanced

Why does this script not show the custom error message?

This script is supposed to catch an error and show a custom message, but it shows the default error instead. Why?

PowerShell

try {
  Write-Output "Start"
  throw "Something went wrong"
} catch {
  Write-Output $_.Exception.Message
}

A Because Write-Output cannot print error messages

B Because throw does not create an exception object

C Because $_ is a string, not an object with Exception property

D Because catch block is missing curly braces

💡 Hint

Check what $_ contains when throwing a string error.

When throwing a string, $_ in catch is the string itself, not an exception object, so $_.Exception is null causing no custom message.

🚀 Application

expert

How to create a custom error object with a specific message and error ID?

You want to throw a custom error in PowerShell with message 'File not found' and error ID 'FileMissing'. Which code snippet correctly creates and throws this error?

A $err = New-Object System.Management.Automation.ErrorRecord (New-Object System.IO.FileNotFoundException 'File not found'), 'FileMissing', 'ObjectNotFound', $null; throw $err

B throw New-Object System.Management.Automation.ErrorRecord ('File not found', 'FileMissing', 'ObjectNotFound', $null)

C throw New-Object System.IO.FileNotFoundException('File not found', 'FileMissing')

D $err = New-Object System.Management.Automation.ErrorRecord ('File not found', 'FileMissing', 'ObjectNotFound', $null); throw $err

💡 Hint

ErrorRecord requires an Exception object as first argument.

Option A correctly creates an ErrorRecord with a FileNotFoundException and throws it. Option A passes a string instead of Exception causing error. Option A throws an Exception but misses ErrorRecord wrapper. Option A passes string instead of Exception to ErrorRecord constructor causing error.