Powershell - If Folder Exists, Increment Folder Name

I'm trying to see if a folder exists, and if it does, add an increment to the folder name, like this.

FolderName

• If FolderName exists, name the folder FolderName_1
• If FolderName_1 exists, name the folder FolderName_2

This is what I have so far, but it doesn't work.

$i = 1
if (Test-Path -Path $FolderName) {
    $FolderName  = $FolderName + '_'+ $i
    $i++
 } 
 else {
}

I know I am missing logic, just not sure how to make this work. Thanks for your help!

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For a robust solution you must examine all currently existing folders that match the name pattern and extract the highest embedded number from them, then add 1 to that number:

# Get the highest number embedded in the names of any existing folders.
$highestExistingNum = 
  Get-ChildItem -ErrorAction Ignore -Directory $FolderName, $FolderName_* |
  ForEach-Object { if ($_.Name -match '_(\d+)$') { [int] $Matches.1 } else { 0 } }
  Sort-Object -Descending |
  Select-Object -First 1

if ($null -ne $highestExistingNum) { # At least 1 preexisting folder?
  $FolderName = $FolderName + '_' + (1 + $highestExistingNum)
}

Note:

• If you expect more than 10 folders, consider zero-padding the embedded numbers, so that their Get-ChildItem output order reflects the embedded numbers; e.g., for 3-digit 0 padding (e.g., 001), use: (1 + $highestExistingNum).ToString('D3')

• The Get-ChildItem call finds all existing folders that fit the original name and the name pattern, if any; the -Directory switch limits processing to folders (directories only)

  • Note: If no existing folders are found, the whole pipeline outputs nothing. This case is later detected by comparing the value of $highestExistingNum to $null.

• The ForEach-Object call:

  • uses the -match operator with a regex to see if a given folder name ends with ($) a _ followed by one or more (+) digits (\d), and captures ((...)) the latter.

  • accesses the captured string of digits via the automatic $Matches variable and converts it to an integer ([int]).

  • if the folder name doesn't end in _ followed by a number, 0 is returned.

• Sort-Object sorts the resulting integers in descending order (-Descending), i.e. the highest number is output first.

• Select-Object is used to select only that highest number -First 1.

  • Note: In PowerShell (Core) 7+, you can streamline the above by using -Top 1 with Sort-Object (i.e. Sort-Object -Descending -Top 1), which obviates the need for the Select-Object call.

You are missing the use of Rename-Item, as well as some extra logic for detecting/updating the _i part:

$FolderName = 'foo'
$Target = "C:\"
Get-ChildItem -Path $Target -Directory `
| Where-Object { $_.Name -match "$FolderName`_(\d+)|$FolderName"} `
| ForEach-Object {
  if ($_ -match "$FolderName`_(\d+)"){
    $NewName = $FolderName + "_$([int]$matches[1] + 1)"
  } else {
    $NewName = $FolderName + '_1'
  }
  $OldName = $_.FullName
  $NewName = Join-Path $Target $NewName
  Write-Host "Found '$($_.FullName)', renaming to '$NewName'"
  Rename-Item -Path $OldName -NewName $NewName
}

To elaborate: $FolderName is presumably a string, but we want to interact with a file object. We use the Rename-Item cmdlet to do so, using the string path. We also use a simple regex to account for the _i counter.

You're quite close, but you need to use another variable to store the 'base name' of your directory: otherwise you're adding _1 and then adding _2 on top of that (getting something_1_2), instead of adding _2 instead of _1.

Something like this:

$BaseName = 'MyDir'
$FullName = $BaseName
$i = 0
while (Test-Path $FullName)
{
  $FullName = "$BaseName_$i"
  $i++
}

Try a while loop as follows:

$i = 0
$Suffix=''
while (Test-Path -Path "$FolderName$Suffix" -PathType Container) {
    $i++
    $suffix="_$i"
}
$FolderName  = "$FolderName$Suffix"
$FolderName

Supposing the following scenario:

Get-ChildItem -Path . -Directory | Select-Object -ExpandProperty Name

> folder
> folder_1
> folder_2

then (a folder exists, script returns a new name):

$FolderName = 'folder'
D:\PShell\SO583976.ps1

> folder_3

or (a folder does not exist, script returns the same name):

$FolderName = 'anotherfolder'
D:\PShell\SO583976.ps1

> anotherfolder