powershell to resolve junction target path

问题:

In PowerShell, I need resolve the target path of a junction (symlink).

for example, say I have a junction c:\someJunction whose target is c:\temp\target

I tried variations of $junc = Get-Item c:\someJunction, but was only able to get c:\someJunction

How do I find the target path of the junction, in this example c:\temp\target, of a given junction?

回答1:

You can get the path by doing the following:

Get-ChildItem -Path C:\someJunction

Edit for finding the path and not the contents of the folder

Add-Type -MemberDefinition @"
private const int FILE_SHARE_READ = 1;
private const int FILE_SHARE_WRITE = 2;

private const int CREATION_DISPOSITION_OPEN_EXISTING = 3;
private const int FILE_FLAG_BACKUP_SEMANTICS = 0x02000000;

[DllImport("kernel32.dll", EntryPoint = "GetFinalPathNameByHandleW", CharSet = CharSet.Unicode, SetLastError = true)]
 public static extern int GetFinalPathNameByHandle(IntPtr handle, [In, Out] StringBuilder path, int bufLen, int flags);

[DllImport("kernel32.dll", EntryPoint = "CreateFileW", CharSet = CharSet.Unicode, SetLastError = true)]
 public static extern SafeFileHandle CreateFile(string lpFileName, int dwDesiredAccess, int dwShareMode,
 IntPtr SecurityAttributes, int dwCreationDisposition, int dwFlagsAndAttributes, IntPtr hTemplateFile);

 public static string GetSymbolicLinkTarget(System.IO.DirectoryInfo symlink)
 {
     SafeFileHandle directoryHandle = CreateFile(symlink.FullName, 0, 2, System.IntPtr.Zero, CREATION_DISPOSITION_OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, System.IntPtr.Zero);
     if(directoryHandle.IsInvalid)
     throw new Win32Exception(Marshal.GetLastWin32Error());

     StringBuilder path = new StringBuilder(512);
     int size = GetFinalPathNameByHandle(directoryHandle.DangerousGetHandle(), path, path.Capacity, 0);
     if (size<0)
     throw new Win32Exception(Marshal.GetLastWin32Error());
     // The remarks section of GetFinalPathNameByHandle mentions the return being prefixed with "\\?\"
     // More information about "\\?\" here -> http://msdn.microsoft.com/en-us/library/aa365247(v=VS.85).aspx
     if (path[0] == '\\' && path[1] == '\\' && path[2] == '?' && path[3] == '\\')
     return path.ToString().Substring(4);
     else
     return path.ToString();
 }
"@ -Name Win32 -NameSpace System -UsingNamespace System.Text,Microsoft.Win32.SafeHandles,System.ComponentModel

$dir = Get-Item D:\1
[System.Win32]::GetSymbolicLinkTarget($dir)

回答2:

New-Item, Remove-Item, and Get-ChildItem have been enhanced to support creating and managing symbolic links. The -ItemType parameter for New-Item accepts a new value, SymbolicLink. Now you can create symbolic links in a single line by running the New-Item cmdlet.

What's New in Windows PowerShell v5

I've checked the symlink support on the my Windows 7 machine, it's works fine.

> New-Item -Type SymbolicLink -Target C: -Name TestSymlink


    Directory: C:\Users\skokhanovskiy\Desktop


Mode                LastWriteTime         Length Name
----                -------------         ------ ----
d----l       06.09.2016     18:27                TestSymlink

Get target of the symbolic link as easy as to create it.

> Get-Item .\TestSymlink | Select-Object -ExpandProperty Target
C:\

回答3:

This does the trick with less work, and works even for junctions on a remote server:

fsutil reparsepoint query "M:\Junc"

If you want just the target name:

fsutil reparsepoint query "M:\Junc" | where-object { $_ -imatch 'Print Name:' } | foreach-object { $_ -replace 'Print Name\:\s*','' }

so

function Get_JunctionTarget($p_path)
{
    fsutil reparsepoint query $p_path | where-object { $_ -imatch 'Print Name:' } | foreach-object { $_ -replace 'Print Name\:\s*','' }
}

Also, the code below is a slight modification of the code that Josh provided above. It can be put in a file that is read multiple times, and it handles the leading \\?\ correctly in the case of a network drive:

function Global:Get_UNCPath($l_dir)
{
    if( ( ([System.Management.Automation.PSTypeName]'System.Win32').Type -eq $null)  -or ([system.win32].getmethod('GetSymbolicLinkTarget') -eq $null) )
    {
        Add-Type -MemberDefinition @"
private const int CREATION_DISPOSITION_OPEN_EXISTING = 3;
private const int FILE_FLAG_BACKUP_SEMANTICS = 0x02000000;

[DllImport("kernel32.dll", EntryPoint = "GetFinalPathNameByHandleW", CharSet = CharSet.Unicode, SetLastError = true)]
 public static extern int GetFinalPathNameByHandle(IntPtr handle, [In, Out] StringBuilder path, int bufLen, int flags);

[DllImport("kernel32.dll", EntryPoint = "CreateFileW", CharSet = CharSet.Unicode, SetLastError = true)]
 public static extern SafeFileHandle CreateFile(string lpFileName, int dwDesiredAccess, int dwShareMode,
 IntPtr SecurityAttributes, int dwCreationDisposition, int dwFlagsAndAttributes, IntPtr hTemplateFile);

 public static string GetSymbolicLinkTarget(System.IO.DirectoryInfo symlink)
 {
     SafeFileHandle directoryHandle = CreateFile(symlink.FullName, 0, 2, System.IntPtr.Zero, CREATION_DISPOSITION_OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, System.IntPtr.Zero);
     if(directoryHandle.IsInvalid)
     {
         throw new Win32Exception(Marshal.GetLastWin32Error());
     }
     StringBuilder path = new StringBuilder(512);
     int size = GetFinalPathNameByHandle(directoryHandle.DangerousGetHandle(), path, path.Capacity, 0);
     if (size<0)
     {
         throw new Win32Exception(Marshal.GetLastWin32Error());
     }
     // The remarks section of GetFinalPathNameByHandle mentions the return being prefixed with "\\?\"
     // More information about "\\?\" here -> http://msdn.microsoft.com/en-us/library/aa365247(v=VS.85).aspx
     string sPath = path.ToString();
     if( sPath.Length>8 && sPath.Substring(0,8) == @"\\?\UNC\" )
     {
         return @"\" + sPath.Substring(7);
     }
     else if( sPath.Length>4 && sPath.Substring(0,4) == @"\\?\" )
     {
         return sPath.Substring(4);
     }
     else
     {
         return sPath;
     }
 }
"@ -Name Win32 -NameSpace System -UsingNamespace System.Text,Microsoft.Win32.SafeHandles,System.ComponentModel
    }
    [System.Win32]::GetSymbolicLinkTarget($l_dir)
}

and given the function Get_UNCPath above, we can improve the function Get_JunctionTarget as follows:

function Global:Get_JunctionTarget([string]$p_path)
{
    $l_target = fsutil reparsepoint query $p_path | where-object { $_ -imatch 'Print Name\:' } | foreach-object { $_ -replace 'Print Name\:\s*','' }
    if( $l_target -imatch "(^[A-Z])\:\\" )
    {
        $l_drive = $matches[1]
        $l_uncPath = Get_UncPath $p_path
        if( $l_uncPath -imatch "(^\\\\[^\\]*\\)" )
        {
            $l_machine = $matches[1]
            $l_target = $l_target -replace "^$l_drive\:","$l_machine$l_drive$"
        }
    }
    $l_target
}

回答4:

We end up using this function

function Get-SymlinkTargetDirectory {           
    [cmdletbinding()]
    param(
        [string]$SymlinkDir
    )
    $basePath = Split-Path $SymlinkDir
    $folder = Split-Path -leaf $SymlinkDir
    $dir = cmd /c dir /a:l $basePath | Select-String $folder
    $dir = $dir -join ' '
    $regx = $folder + '\ *\[(.*?)\]'
    $Matches = $null
    $found = $dir -match $regx
    if ($found) {
        if ($Matches[1]) {
            Return $Matches[1]
        }
    }
    Return '' 
}