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’.
- Classic Example: PowerShell Checks If a File Exist
- PowerShell Test-Path -IsValid
- PowerShell Test-Path -Exclude
- A Test-Path Example To Make You Think
- Test-Path -PathType
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
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.
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.
