Remove random items from `Get-ChildItem` output-CodePudding

I'd like to ask a question about removing lines from a variable that has strings obtained from get-childitem. Right now, I'm extracing lines indicating files with this :

$FolderToOpen= Get-ChildItem -Path $SrcDir -Filter *.$ExtLst

That gets the files from a specified folder and specified extensions Then, I get 4 random lines from that variable

$FourFiles = $FolderToOpen | Get-Random -Count 4

But then, here's my problem, I'd like to delete those 4 lines from the first variable. However I can't get to do that, doing

$FolderToOpen -replace "$FourFiles",""

for exemple doesn't do anything. Could someone help me please? Thank you in advance :)

CodePudding user response：

Yet another way of doing that is to take advantage of Compare-Object that compares arrays element-wise:

Compare-Object -ReferenceObject $FolderToOpen -DifferenceObject $FourFiles -PassThru

CodePudding user response：

The Get-ChildItem cmdlet returns an array of objects by default and as such is of a fixed size (see Everything you wanted to know about arrays for further information on this)

If we cast the results of the Get-ChildItem call to a list first, we'll then be able to add and remove items (without the need to create new arrays to hold the updated data)

Updated code below should give you what you're looking for:

# Call Get-ChildItem but store the results as a list of objects
# rather than a standard array of objects
[Collections.Generic.List[Object]]$FolderToOpen= Get-ChildItem -Path $SrcDir -Filter *.$ExtLst

# Get your random selection of 4 files
$FourFiles = $FolderToOpen | Get-Random -Count 4

# Remove them from the list 
$FolderToOpen.RemoveAll({ param($folder) $folder -in $FourFiles })

The RemoveAll function above will return the total number of entries removed from the list (in this example, 4).

CodePudding user response：

The problem with your approach is that PowerShell prefers operating on objects instead of strings. The output of Get-ChildItem is a stream of objects, what can be proven by piping it to Get-Member:

PS> dir | Get-Member 
TypeName: System.IO.DirectoryInfo
...
TypeName: System.IO.FileInfo
...

Since you are interested in particularly filtering strings, you can cast all the objects to strings beforehand and then perform filtering:

$FourFiles = $FolderToOpen | Get-Random -Count 4 | % {$_.ToString()}
$FolderToOpen | Where {$_.ToString() -inotin $FourFiles}

Note that $FolderToOpen is a stream of strings, instead of one big string like you would have in Bash. Therefore I used Where to filter the entries.