I would like to validate that a user-provided string is a path to a file or directory.

$Path = 'some input string'

if (!(Test-Path -LiteralPath $Path)) {
  Write-Error "${Path}: No such file or directory"
  exit 1
}

The problem is that Test-Path cannot differentiate between for eg. a directory and a registry key...

How can I do it?

I would like to validate that a user-provided string is a path to a file or directory.

$Path = 'some input string'

if (!(Test-Path -LiteralPath $Path)) {
  Write-Error "${Path}: No such file or directory"
  exit 1
}

The problem is that Test-Path cannot differentiate between for eg. a directory and a registry key...

How can I do it?

• powershell

2 Answers 2

You can use Get-Item, probably with -LiteralPath instead of -Path if you do not want it to interpret wildcards. Based on the output you can determine:

1. If the cmdlet produces output you can be sure the path exists. Here you could change error action from SilentlyContinue to Stop if you wanted the cmdlet to throw a terminating error instead of you manually throwing the error.
2. To which provider the item belongs to by looking at the .PSProvider property.
3. If the path belongs to the FileSystem, you can determine if the path is a file or directory by looking at the .PSIsContainer property.

In summary you could do:

$item = Get-Item -LiteralPath $path -ErrorAction SilentlyContinue

# if the path can't be resolved
if (-not $item) {
    throw [System.Management.Automation.ItemNotFoundException]::new(
        "Cannot find path '$path' because it does not exist.")
}

# if the path exists but is not a FileSystem path
if ($item.PSProvider.Name -ne 'FileSystem') {
    throw [System.ArgumentException]::new(
        "The resolved path '$path' is not a FileSystem path but '$($item.PSProvider.Name)'.")
}

# here you know the path exists and belongs to FileSystem,
# you can use `$item.PSIsContainer` to know if its a File or Folder

You can use Resolve-Path to discover provider information about a given item path:

if(!(Test-Path -LiteralPath $Path) -or (Resolve-Path -LiteralPath $Path).Provider.Name -ne 'FileSystem') {
  # path might be valid, but it's not a file system path
}