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Troubleshooting Common Errors

Note

Quick guide to understanding, diagnosing, and fixing the most common PowerShell errors you'll encounter.

Overview

Every PowerShell user encounters errors. The key is knowing how to read error messages, understand what went wrong, and fix the problem. This guide covers the most common errors and their solutions.

How to Read Error Messages

PowerShell error messages contain valuable information:

Get-Item : Cannot find path 'C:\NonExistent\file.txt' because it does not exist.
At line:1 char:1
+ Get-Item "C:\NonExistent\file.txt"
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (C:\NonExistent\file.txt:String) [Get-Item], ItemNotFoundException
    + FullyQualifiedErrorId : PathNotFound,Microsoft.PowerShell.Commands.GetItemCommand

Breaking it down:

  • First line: What command failed and why
  • At line:X char:Y: Where in your script the error occurred
  • CategoryInfo: Type of error (ObjectNotFound, InvalidArgument, etc.)
  • FullyQualifiedErrorId: Technical error identifier

Focus on the First Line

The first line usually tells you everything you need to know. The rest provides technical details for deeper debugging.

Common Error Categories

1. File Not Found / Path Not Found

Error Message

Cannot find path 'C:\file.txt' because it does not exist.

What It Means

PowerShell can't find the file or folder you specified.

Common Causes

  • Typo in the path
  • File doesn't exist
  • Using forward slashes instead of backslashes on Windows
  • Relative path when you need absolute path

How to Fix

# BAD - Path doesn't exist
Get-Content "C:\NonExistent\file.txt"

# GOOD - Check if path exists first
$path = "C:\Temp\file.txt"
if (Test-Path $path) {
    Get-Content $path
} else {
    Write-Warning "File not found: $path"
}

# GOOD - Use error handling
try {
    Get-Content "C:\Temp\file.txt" -ErrorAction Stop
} catch {
    Write-Error "Could not read file: $_"
}

Always Use Test-Path

Before working with files, verify they exist using Test-Path.

2. Access Denied / UnauthorizedAccessException

Error Message

Access to the path 'C:\Windows\System32\config.sys' is denied.

What It Means

You don't have permission to access the file/folder.

Common Causes

  • Trying to access system files without admin rights
  • File is locked by another process
  • Insufficient NTFS permissions

How to Fix

# Solution 1: Run PowerShell as Administrator
# Right-click PowerShell → "Run as Administrator"

# Solution 2: Check permissions
Get-Acl "C:\SecureFolder" | Format-List

# Solution 3: Use -Force (when appropriate)
Remove-Item "C:\file.txt" -Force

# Solution 4: Check if file is in use
$file = "C:\file.txt"
try {
    [System.IO.File]::Open($file, 'Open', 'Read', 'None').Dispose()
    Write-Output "File is not locked"
} catch {
    Write-Warning "File is in use by another process"
}

3. Cannot Bind Parameter / Parameter Not Found

Error Message

A parameter cannot be found that matches parameter name 'Invalid'.

What It Means

You used a parameter name that doesn't exist for that cmdlet.

Common Causes

  • Typo in parameter name
  • Using wrong cmdlet
  • Parameter doesn't exist in your PowerShell version

How to Fix

# BAD - Wrong parameter name
Get-Process -ProcessName "powershell"  # Should be -Name

# GOOD - Use correct parameter
Get-Process -Name "powershell"

# Check available parameters
Get-Help Get-Process -Parameter *

# Use Tab completion to avoid typos
Get-Process -N<Tab>  # Auto-completes to -Name

Use Get-Help to Find Parameters

Get-Help CommandName -Parameter * shows all available parameters.

4. Execution Policy Error

Error Message

File C:\Scripts\script.ps1 cannot be loaded because running scripts is disabled on this system.

What It Means

Your system's execution policy prevents scripts from running.

Common Causes

  • Default security settings block scripts
  • Group Policy restrictions

How to Fix

# Check current policy
Get-ExecutionPolicy

# Set for current user only (doesn't require admin)
Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser

# Temporarily bypass for one script
PowerShell.exe -ExecutionPolicy Bypass -File "C:\Scripts\script.ps1"

# Check if Group Policy is blocking
Get-ExecutionPolicy -List

Security Note

Only run scripts you trust! Changing execution policy can expose you to malicious scripts.

5. Cannot Convert Value to Type

Error Message

Cannot convert value "abc" to type "System.Int32". Error: "Input string was not in a correct format."

What It Means

PowerShell can't convert the data to the requested type.

Common Causes

  • Trying to convert text to a number
  • Invalid date format
  • Type mismatch

How to Fix

# BAD - Can't convert text to number
[int]"abc"  # ERROR

# GOOD - Validate before converting
$input = "123"
if ($input -match '^\d+$') {
    $number = [int]$input
} else {
    Write-Warning "Input is not a valid number"
}

# GOOD - Use try/catch for conversion
try {
    $number = [int]"abc"
} catch {
    Write-Error "Conversion failed: $_"
}

# GOOD - Use -as operator (returns $null on failure)
$number = "abc" -as [int]
if ($null -eq $number) {
    Write-Warning "Conversion failed"
}

6. Property Does Not Exist

Error Message

The property 'InvalidProperty' cannot be found on this object.

What It Means

You're trying to access a property that doesn't exist on the object.

Common Causes

  • Typo in property name
  • Object type is different than expected
  • Property was removed in newer PowerShell versions

How to Fix

# Find available properties
$process = Get-Process | Select-Object -First 1
$process | Get-Member -MemberType Property

# BAD - Property doesn't exist
$process.InvalidProperty

# GOOD - Use correct property name
$process.Name

# GOOD - Check if property exists
if ($process.PSObject.Properties['CPU']) {
    Write-Output $process.CPU
}

7. Object Reference Not Set to an Instance

Error Message

You cannot call a method on a null-valued expression.

What It Means

You're trying to use an object that is $null.

Common Causes

  • Variable was never set
  • Command returned no results
  • Property doesn't exist

How to Fix

# BAD - Variable is null
$result = $null
$result.ToString()  # ERROR

# GOOD - Check for null first
if ($null -ne $result) {
    $result.ToString()
} else {
    Write-Warning "Result is null"
}

# GOOD - Use null-conditional operator (PowerShell 7+)
$result?.ToString()

# GOOD - Provide default value
$value = $result ?? "Default"

8. The Term Is Not Recognized

Error Message

The term 'Get-FakeCommand' is not recognized as the name of a cmdlet, function, script file, or operable program.

What It Means

PowerShell doesn't know what command you're trying to run.

Common Causes

  • Typo in command name
  • Module not loaded
  • Command doesn't exist

How to Fix

# Check if command exists
Get-Command Get-Process

# Search for partial name
Get-Command *Process*

# Load required module
Import-Module ActiveDirectory
Get-ADUser -Filter *

# Check available modules
Get-Module -ListAvailable

# BAD - Typo
Get-Proces

# GOOD - Correct spelling
Get-Process

9. Index Out of Range

Error Message

Index was outside the bounds of the array.

What It Means

You're trying to access an array element that doesn't exist.

Common Causes

  • Array is smaller than you think
  • Using wrong index number
  • Array is empty

How to Fix

# BAD - Array only has 3 items (index 0, 1, 2)
$array = @("one", "two", "three")
$array[5]  # ERROR

# GOOD - Check array size
if ($array.Count -gt 5) {
    $array[5]
} else {
    Write-Warning "Array doesn't have 6 items"
}

# GOOD - Use safe indexing
$index = 5
if ($index -lt $array.Count) {
    $array[$index]
}

10. Pipeline Input Error

Error Message

The input object cannot be bound to any parameters for the command.

What It Means

Pipeline is sending wrong type of object to the command.

Common Causes

  • Format cmdlet used too early in pipeline
  • Wrong object type
  • Misunderstanding how pipeline binding works

How to Fix

# BAD - Format-Table breaks pipeline
Get-Process | Format-Table | Where-Object {$_.CPU -gt 50}  # ERROR

# GOOD - Format at the end
Get-Process | Where-Object {$_.CPU -gt 50} | Format-Table

# Check what's in the pipeline
Get-Process | Get-Member  # Shows object type

Debugging Techniques

Use -WhatIf to Preview

# See what would happen without actually doing it
Remove-Item "C:\Important\*" -WhatIf
Stop-Service "ImportantService" -WhatIf

Use -Verbose for Details

# See detailed information about what's happening
Copy-Item -Path "C:\source" -Destination "C:\dest" -Verbose

Use Write-Host for Debugging

# Add debug output to see what's happening
foreach ($file in Get-ChildItem) {
    Write-Host "Processing: $($file.Name)" -ForegroundColor Yellow
    # Your code here
}

Check Variable Values

# See what's in a variable
$myVariable | Format-List *

# See variable type
$myVariable.GetType()

# See if variable is null
if ($null -eq $myVariable) {
    Write-Output "Variable is null!"
}

Use Try-Catch for Error Details

try {
    # Your code here
    Get-Content "C:\file.txt"
} catch {
    Write-Error "Error occurred: $($_.Exception.Message)"
    Write-Error "Error type: $($_.Exception.GetType().FullName)"
    Write-Error "Line number: $($_.InvocationInfo.ScriptLineNumber)"
}

Use $Error Variable

# View recent errors
$Error[0]  # Most recent error
$Error[1]  # Second most recent

# View full error details
$Error[0] | Format-List * -Force

# Clear error history
$Error.Clear()

Common Mistakes

Not Checking if File Exists

# BAD - Assumes file exists
$content = Get-Content "C:\file.txt"

# GOOD - Check first
if (Test-Path "C:\file.txt") {
$content = Get-Content "C:\file.txt"
} else {
Write-Warning "File not found"
}

Ignoring Error Messages

# BAD - Suppressing errors you should handle
Get-Process -Name "fake" -ErrorAction SilentlyContinue

# GOOD - Capture and handle errors
$process = Get-Process -Name "fake" -ErrorAction SilentlyContinue
if ($null -eq $process) {
Write-Warning "Process not found"
}

Assuming Command Succeeds

# BAD - Doesn't check if copy worked
Copy-Item "C:\source.txt" "D:\backup.txt"
Remove-Item "C:\source.txt"  # Deletes even if copy failed!

# GOOD - Verify operation succeeded
try {
Copy-Item "C:\source.txt" "D:\backup.txt" -ErrorAction Stop
if (Test-Path "D:\backup.txt") {
    Remove-Item "C:\source.txt"
}
} catch {
Write-Error "Copy failed: $_"
}

Tips & Tricks

Use -ErrorAction to Control Behavior

# Stop on error (throw exception)
Get-Item "C:\fake.txt" -ErrorAction Stop

# Ignore errors silently
Get-Item "C:\fake.txt" -ErrorAction SilentlyContinue

# Show warning but continue
Get-Item "C:\fake.txt" -ErrorAction Continue

# Ask user what to do
Get-Item "C:\fake.txt" -ErrorAction Inquire

Save Errors to a Variable

# Capture errors without displaying them
Get-ChildItem C:\Restricted -ErrorVariable myErrors -ErrorAction SilentlyContinue

# Check if errors occurred
if ($myErrors) {
Write-Warning "Encountered $($myErrors.Count) errors"
$myErrors | Export-Csv "C:\Logs\errors.csv"
}

Use -Debug for Step-by-Step Execution

# Pause before each step
$DebugPreference = "Inquire"
Get-Process

# See debug messages
Write-Debug "Processing file: $fileName"

Quick Reference: Error Action Preference

ErrorAction What Happens
Stop Throws terminating error, stops execution
Continue Displays error, continues (default)
SilentlyContinue Suppresses error, continues
Inquire Asks user how to proceed
Ignore Completely ignores error (doesn't log it)

When to Ask for Help

If you're still stuck:

  1. Use Get-Help 

    Get-Help Get-Process -Full
Get-Help Get-Process -Examples

  2. Search Online

  3. Copy the error message
  4. Search: "PowerShell [error message]"

  5. Check Microsoft Docs, Stack Overflow, Reddit r/PowerShell

  6. Check PowerShell Version 

    $PSVersionTable.PSVersion
    Some errors occur only in specific versions.

  7. Ask the Community

  8. Reddit: r/PowerShell
  9. Stack Overflow: [powershell] tag
  10. PowerShell Discord/Slack

Additional Resources