PowerShell Error Handling

last modified February 15, 2025

Effective error handling ensures scripts fail gracefully and provide meaningful feedback. PowerShell offers multiple mechanisms to handle exceptions and errors during script execution.

Terminating errors halt execution, while non-terminating errors allow scripts to continue. Use try/catch blocks, $Error variable, and ErrorAction to manage different error types in PowerShell.

Try/Catch Blocks

Basic exception handling uses try/catch blocks to capture terminating errors. This example attempts to read a non-existent file.

try_catch.ps1

try { Get-Content “missing.txt” -ErrorAction Stop } catch { Write-Output “Error encountered: $_” }

The script forces a terminating error with -ErrorAction Stop. The catch block captures the exception using the $_ automatic variable.

Get-Content “missing.txt” -ErrorAction Stop

Forces a terminating error when file isn’t found. Without -ErrorAction Stop, Get-Content produces a non-terminating error.

PS C:> .\try_catch.ps1 Error encountered: Cannot find path ‘C:\missing.txt’…

ErrorAction Parameter

Control error behavior using -ErrorAction. This converts non-terminating errors to terminating ones for capture in try/catch blocks.

error_action.ps1

try { Remove-Item “nonexistent.txt” -ErrorAction Stop } catch [System.Management.Automation.ItemNotFoundException] { Write-Output “Specific error: File not found” } catch { Write-Output “General error: $_” }

This script handles specific exception types first, then general errors. ItemNotFoundException catches missing file scenarios specifically.

PS C:> .\error_action.ps1 Specific error: File not found

$Error Variable

PowerShell maintains $Error array containing recent errors. Access the latest error with $Error[0].

error_var.ps1

Get-ChildItem “invalid_path” -ErrorAction SilentlyContinue if ($Error.Count -gt 0) { Write-Output “Last error: $($Error[0].Exception.Message)” }

SilentlyContinue suppresses error output while still populating $Error. We check for errors and display the most recent message.

PS C:> .\error_var.ps1 Last error: Cannot find path ‘C:\invalid_path’…

Finally Block

Use finally to execute cleanup code regardless of errors. This example demonstrates resource cleanup after file operations.

finally_block.ps1

$file = $null try { $file = [System.IO.File]::OpenRead(“test.txt”) } catch { Write-Output “Error opening file: $_” } finally { if ($file) { $file.Close() } Write-Output “Cleanup completed” }

The finally block ensures file handles get closed even if an error occurs during file opening.

PS C:> .\finally_block.ps1 Cleanup completed

Custom Errors

Generate custom errors using Write-Error and handle them in scripts. This allows controlled error propagation.

custom_error.ps1

function Test-Value { param($val) if ($val -lt 10) { Write-Error “Value too low” -ErrorAction Stop } }

try { Test-Value -val 5 } catch { Write-Output “Custom error caught: $_” }

Write-Error with -ErrorAction Stop creates a terminating error caught by the catch block. This enables structured error reporting.

PS C:> .\custom_error.ps1 Custom error caught: Value too low

Source

Microsoft PowerShell Documentation

These examples demonstrate essential error handling techniques for creating robust PowerShell scripts.

Author

Jan Bodnar is a professional developer and technical writer with expertise in system administration and automation. Author of multiple programming manuals and maintainer of PowerShell-focused educational resources.

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