PowerShell Test-Path

PowerShell Test-Path Cmdlet

If there is a problem finding a file, or checking for a container object, then call for PowerShell's Test-Path; it will respond with a 'True or False'.

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Classic Example:  PowerShell Checks If a File Exist

Start with a simple script to check the existence of your file.

# PowerShell Check If File Exists
$WantFile = "C:\Windows\explorer.exe"
Test-Path $WantFile

Note 1: The only result that PowerShell can return is a true or a false.  However, Test-Path cries out for an 'if' statement to act upon the output, thus:-

# PowerShell  Checks If a File Exists
$WantFile = "C:\Windows\explorer.exe"
$FileExists = Test-Path $WantFile
If ($FileExists -eq $True) {Write-Host "Yippee"}
Else {Write-Host "No file at this location"}

Note 2: As with all these scripts, please amend my examples to fit your environment.

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Test-Path Environmental Variables

In addition to physical file locations, you can also employ Test-Path to interrogate the registry or as here, Environmental Variables.

# PowerShell Test-Path for Environmental Variables
Test-Path env:\PathExt

Challenge: Which of these are really Environment variables?
Public, Private, Temp, Tump and Tmp

PowerShell Test-Path -IsValid

One of the under-rated jobs for Test-Path is to validate that the path part of a script really exists.

# PowerShell script to check a valid path
Clear-Host
$ImageFiles = "H:\Sports\fun_pictures\"
$ValidPath = Test-Path $ImageFiles -IsValid
If ($ValidPath -eq $True) {Write-Host "Path is OK"}
Else {Write-Host "Mistake in ImageFiles variable"}

PowerShell Test-Path -Exclude

Here is a real-life problem, I wanted to see if there were any files which are not .gif, pnp, bmp or .jpg, that have got mixed up with my photo collection.  Assumption: the files I (we) are interested in are stored in H:\Sports\fun_pictures\

# Script to check for rogue picture format.
Clear-Host
$ImageFiles = "H:\Sports\fun_pictures\*.*"
$RogueExists = Test-Path $ImageFiles `
-exclude *.jpg, *.gif, *.png, *.bmp
If ($RogueExists -eq $True) {Write-Host ` "Non .jpg .gif .png .bmp images"}
Else {Write-Host "There are no unknown formats."}

Note 3: You will have to edit the above file radically if you want it to work on your computer.  Change the values for $ImageFiles and also tweak the -exclude file extensions.  See more on PowerShell Else.

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A Test-Path Example To Make You Think

# PowerShell Test-Path Cmdlet -Exclude
Clear-Host
$WantFile = "C:\Windows\.*"
$FileExists = Test-Path -Path $WantFile -Exclude *.*
If ($FileExists -eq $True) {Write-Host "Yippee"}
Else {Write-Host "No file at this location"}

Note 4: I created this script deliberately.  It makes no sense in practical terms.  Please adjust the value of Exclude *.* to *.exe or *.dll.  As you can see wildcards are allowed in the path an in the extensions.

Note 5: Here I have explicitly used the -Path parameter, however, any value after Test-Path is assumed to be the location, thus  -Path is optional.

Note 6: I often find that experimenting with Get-ChildItem alongside Test-Path reveals the strengths and weaknesses of these two cmdlets.

 

Research The PowerShell Test-Path Cmdlet

# Find out more about PowerShell Test-Path cmdlet
Clear-Host
Get-Help Test-Path -full

Note 7: By interrogating Test-Path with Get-Help we can unearth useful parameters such as -IsValid to check the path.  There are also -Include and -exclude, which refine the contents of your search. It was thanks to Get-Help that I discovered -PathType.

Test-Path -PathType

The main purpose of the -PathType parameter is to check if the object is a file or a folder.  However, it can also be used in the registry to check for keys or data.

Clear-Host
$Location = 'HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon'
Test-Path $Location -PathType container

Trap:  HKLM: needs that colon.  If you simply export areas of the registry, then copy as:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
there are problems.

HKEY_LOCAL_MACHINE is fine, the space between Windows and NT is no problem, but the lack of a colon is a show-stopper, it should be:
HKEY_LOCAL_MACHINE:\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon

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The Rest of the Path Family

Here is a simple technique to find more cmdlets.  Get-Command -Noun often throws up interesting results, for example Resolve-Path.

# PowerShell Path Cmdlet Research
Clear-Host
Get-Command -Noun Path

Convert-Path
Join-Path
Resolve-Path
Split-Path
Test-Path

Join-Path Example

Here is a beautiful script to find which drive hosts a particular folder.

Clear-Host
$Folder = "Stuff"
Get-PSDrive | Where-Object {
$_.root -match "[C-Z]:\\" -and (Test-Path $(Join-Path $_.root $Folder))
}

Note 8: Please change "Stuff" to the name of the folder you are looking for.
For example: $Folder = "Program Files"

See more real-life tasks for PowerShell »

Summary of PowerShell Test-Path Cmdlet

The classic job for PowerShell Test-Path is to check that a file exists.  However, you can extend its usefulness by testing registry paths, or to search for files with a particular extension.

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See more Microsoft PowerShell tutorials:

PowerShell Home   • Test-ServerHealth  • Test-SystemHealth   • Test-Connection  • Test-Path

PowerShell Logon Script  • PowerShell add printer  • PowerShell Schedule Task  • Free CSVDE Tool

Map Network Drive  • Exchange 2010 PowerShell Cmdlets   • Exchange 2010 Performance Monitor

Please email me if you have a better script examples. Also please report any factual mistakes, grammatical errors or broken links, I will be happy to correct the fault.

 

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