Test in PowerShell code if a folder is a junction

问题:

How can I test in PowerShell code if a folder is a junction point?

回答1:

Take a look at this blog: http://blogs.msdn.com/powershell/archive/2010/02/10/viewing-junctions-with-dir.aspx

the way to do it is to copy the built in file system formatting file, modify it so that junctions are indicated, then load it with Update-FormatData:

From the Blog:

The file system formatting rules are in $pshome\FileSystem.Format.ps1xml. I copied this, then in the element [ViewDefinitions –> View –> TableControl –> TableRowEntries –> TableRowEntry –> TableColumnItems –> TableColumnItem] I changed the content of PropertyName with value of 'Mode' to the following:

<ScriptBlock> 
   "$($_.Mode)$(if($_.Attributes -band [IO.FileAttributes]::ReparsePoint)
{'J'})" </ScriptBlock> 

This does a bitwise AND on the DirectoryInfo object Attributes property ($_.Attributes) against the .Net System.IO.FileAttributes.ReparsePoint enum value. If the result is not zero, it displays a ‘J’ next to the other file mode attributes. Next, load the new formatting file like this:

 PS> Update-FormatData -PrependPath myFilesystem.format.ps1xml

The PrependPath parameter ensures that the new formatting file is loaded before the built-in formatting files.

Directory alink has a ‘J’ in the mode column, seems to work!

It's in the Mode column J for Junction.

回答2:

If (Get-Item Test Folder).Attributes.ToString().Contains("ReparsePoint"){Code}

回答3:

Since at least PowerShell v5.0, there is better support for links (or as MS calls them: Reparse Points)

improved Item cmdlets - LinkType property

Linked article is under WMF 5.0 category, which might mean that the method was available since PS v5.0.
These features were included in standard Get-Item, Get-ChildItem, so there are no additional steps required. It can be used on any current PS.

LinkType is a String property on an Object, returned by Get-Item and Get-ChildItem,
it can have one of the following four values: '', 'Junction', 'SymbolicLink', 'HardLink'.

To answer OP's question, you can check if a folder is a junction point using:

if ((Get-Item -Path $Target -Force).LinkType -eq "Junction") { }

To check if a file/folder is a "ReparsePoint", of any kind (Junction, SymbolicLink or HardLink):

if ((Get-Item -Path $Target -Force).LinkType) { }

LinkType value on ordinary file/folder is an empty String, which when used as if condition in PS resolves to False

Get-ChildItem can be used to list all Junction folders:

(Get-ChildItem -Path $Target -Force) | Where-Object { $_.LinkType -eq "Junction" }

Note that value 'SymbolicLink' is the same for both file or folder, so to list only Symbolic links to folders:

(Get-ChildItem -Path $Target -Directory -Force) | Where-Object { $_.LinkType -eq "SymbolicLink" }

Cmdlet Get-ChildItem (alias: dir, ls, gci) now shows ReparsePoint attribute, as l in Mode column, without any extension. But it will not show 'HardLink' and shows l for both Junction and SymbolicLink:

> Get-ChildItem -Path $Target -Force


    Directory: C:\Users


Mode                LastWriteTime         Length Name                          
----                -------------         ------ ----                          
d--hsl       2018-04-12     01:45                All Users                     
d-rh--       2018-05-09     06:12                Default                       
d--hsl       2018-04-12     01:45                Default User                  
d-----       2018-06-24     03:05                Papo                          
d-r---       2018-07-27     07:12                Public

• LinkType does not work on folders with special permissions inside \Users and \Users\, even though Get-ChildItem as seen above does work and shows l on them.
• Remove-Item has issues. It can't remove Junction, and if Forced, will remove original contents with it. This is said to be fixed in future version PS v6

---

Using these improved, or today's standard Cmdlets, has some advantages over previous methods, described in older answers here.

• It does differentiate between Junction and Symbolic Link
  If OP wanted to test if folder is a Junction, checking by Attribute property would result in false positive for folder Symbolic Link.

• detects Hard Link.

• LinkType is [String] as opposed to Attributes property, which is [FileAttributes] type and needs .ToString() or a use of -band

回答4:

FYI, if you happen to be running PowerShell Community Extensions, this info is available as output (and as a note property) on output of Get-ChildItem:

21> gci .\Roaming\Microsoft\eHome


    Directory: Microsoft.PowerShell.Core\FileSystem::C:\Users...


Mode           LastWriteTime       Length Name
----           -------------       ------ ----
d----     2/15/2010 12:18 AM        <DIR> DvdCoverCache
d----      8/9/2009  1:10 AM    <SYMLINK> DvdInfoCache [\...
d----      8/8/2009 11:51 PM        <DIR> DvdInfoCache.orig
d----    10/22/2009  7:12 PM        <DIR> mcl_images

However for programmatic access I would access the info via the Attributes property as the other poster suggests.

回答5:

If you have the PowerShell Community Extensions which I would recommend if you are working with junctions you can do the following to determine if a folder is a junction or not:

Import-Module pscx
if ((Get-Item *test_folder*).ReparsePoint){
    Write-Host "YES"
}

回答6:

Try this:

$TargetAttributes = (Get-Item -Path $Target -Force).Attributes.ToString()
if ($TargetAttributes -match "ReparsePoint") {
    if ($TargetAttributes -match "Archive") {
        Write-Output ("Link to a file.")
    } else {
        Write-Output ("Link to a folder.")
    }
} else {
    Write-Output ("Normal File or Folder.")
}