Check drive letter map and replace it only if it doesn't match (Powershell)

Question

In powershell, how to check drive letter mapping and replace it only if it doesn't match the path, I don't want to delete it and add it again because this could kill other processes that are using the drive letter, but I don't mind checking it everytime.

Set-MapDrive "Z:" "//MyServer/Stuff1"

Here's what I have so far.

How to implement the Get-DriveMap Function?

function Set-MapDrive {
    param(
        [string]$letter, 
        [string]$shar_path
    )

    $curr_path = Get-DriveMap($letter)

    # Letter Not Mapped
    if ($curr_path -eq $null) {
        net use $letter $share_path
    }
    else {
        $dir1 = Get-Item $user_path
        $dir2 = Get-Item $share_path

        # Letter Map has changed
        if($dir1.GetHashCode() -eq $dir2.GetHashCode()) {
            net use $letter \delete
            net use $letter $share_path
        }

        # No Change
        else {
             write-host "Note: Driver $letter already mapped to $share_path"
        }
    }
}

function Get-DriveMap {
    param(
        [string]$letter
    )
     
    $x = Get-PSDrive $letter
    #^^^^ This produces error if letter doesn't exist?!
    # need it to set $x to null if it doesn't exist.

    return $x.DisplayRoot
}

As an aside: PowerShell functions, cmdlets, scripts, and external programs must be invoked _like shell commands_ - `foo arg1 arg2` - _not_ like C# methods - `foo('arg1', 'arg2')`. If you use `,` to separate arguments, you'll construct an _array_ that a command sees as a _single argument_. To prevent _accidental_ use of method syntax, use [`Set-StrictMode -Version 2`](https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/set-strictmode) or higher, but note its other effects. See [this answer](https://stackoverflow.com/a/65208621/45375) for more information. — mklement0, Oct 19 '21 at 13:34

score 2 · Answer 1 · answered Oct 19 '21 at 13:32

Use Get-PSDrive to fetch any existing drive:

function Set-MapDrive {
  param(
    [string]$Letter,
    [string]$RootPath
  )

  $existingDrive = Get-PSDrive -Name $Letter.TrimEnd(':') -ErrorAction SilentlyContinue
  if($existingDrive){
    if($existingDrive.Root -eq $RootPath){
      # nothing more to do, drive already exists with correct root path
      return
    }

    # remove existing drive mapping here
  }

  # create new drive mapping here
}

score 0 · Answer 2 · answered Oct 19 '21 at 16:44

function my_drive_map {
    param(
        [string]$letter, 
        [string]$share_path
    )
    #example: my_map_drive "Z:" "\\MyServer\MyDir"

    write-host "my_drive_map $letter $share_path"

    $L  = $letter.TrimEnd(':')
    $LL = "${L}:"

    if (-not (Test-Path $share_path)) {
        write-host "    ERROR: Network share path is inaccessable"
        exit 1
    }

    $map = Get-SmbMapping -LocalPath $LL -ErrorAction SilentlyContinue  
            
    #$map | select *

    if ($map -eq $null) {
            write-host "    # case1: Drive Not Mapped Yet"
            write-host "    PS> Remove-SmbMapping -LocalPath $LL -Force -ErrorAction SilentlyContinue (case3)"
            Remove-SmbMapping -LocalPath $LL -Force -ErrorAction SilentlyContinue | out-null

            write-host "    PS> New-SmbMapping -LocalPath $LL -RemotePath $share_path -Persistent"
            New-SmbMapping -LocalPath $LL -RemotePath $share_path -Persistent $true | out-null
    }
    
    # Drive-Letter Already Mapped
    else  {    
        $dir1 = $map.RemotePath
        $dir2 = $share_path
      

        # Drive-Letter Map has changed, Remap it
        if($dir1 -ne $dir2) {
            write-host "    # case2: Drive-Letter already mapped to wrong Path, Change it"
            write-host "    # comparing path1($dir1) to path2($dir2)"
                
            write-host "    PS> Remove-SmbMapping -LocalPath $LL -Force -ErrorAction SilentlyContinue | out-null"
            Remove-SmbMapping -LocalPath $LL -Force -ErrorAction SilentlyContinue | out-null        

            write-host "    PS> New-SmbMapping -LocalPath $LL -RemotePath $share_path -Persistent"
            New-SmbMapping -LocalPath $LL -RemotePath $share_path -Persistent $true | out-null
        }
        else {
            write-host "    # case3: Drive-Letter already mapped and is correct"
            write-host "    # comparing path1($dir1) to path2($dir2)"
        }
    }       
    
    # Check that Drive-Letter is available
    if (-not (Test-Path "${L}:\")) {
        write-host "    ERROR: Drive-Letter ${L}: is still inaccessable"
        exit 1
    }
    
    write-host  "    (OK) ${L}: accessable as $share_path"
}

function my_drive_list {
    Get-SmbMapping
}

function my_drive_remove {
    param(
        [string]$letter
    )

    write-host "my_drive_remove $letter $share_path"

    $L  = $letter.TrimEnd(':')
    $LL = "${L}:"

    Remove-SmbMapping -LocalPath $LL -Force -ErrorAction SilentlyContinue | out-null
    
    $map = Get-SmbMapping -LocalPath $LL -ErrorAction SilentlyContinue  
            
    if ($map -eq $null) {
        write-host "    (OK) Drive sucessfully removed"
    }
    else {
        write-host "    (err) Drive still attached"
    }
    
}

Check drive letter map and replace it only if it doesn't match (Powershell)

2 Answers2