It sounds complex but its not, Comparing Files in PowerShell - powershell

Question

I have a folder with a huge amount of files in it with lots of different extensions (abc, abc_trg, def, def_trg, ghi, ghi_trg, jkl, mno).
You will see that there are some files that have a matching 'trigger' file, but not all files in this folder need to have a trigger file, it is just the following extensions that must have a trigger file: abc, def, ghi.
filename1.abc
filename1.abc_trg
filename2.def
filename2.def_trg
filename3.abc
filename4.def_trg
filename5.ghi
filename6.jkl
filename7.mno
filename8.ghi
filename8.ghi_trg
filename9.jkl
i.e. The extension types that do have Trigger files (abc, abc_trg, def, def_trg, ghi, ghi_trg) must have a matching filename.
I need a PowerShell script that will analyse the and compare files that are meant to exist with a trigger filetype (abc, abc_trg, def, def_trg, ghi, ghi_trg) and if a match is found (e.g. filename1, filename2, filename8) or if there are files that have extensions not in this list, e.g. jkl & mno (filename6.jkl, filename7.mno, filename9.jkl) then those files are left/not touched.
If there are files that are meant to have a matching extension & trigger file, but do not, i.e. they have become orphaned, then these need to be deleted (e.g. filename3.abc, filename4.def_trg, filename5.ghi)
So the resultant file list should look like this:
filename1.abc
filename1.abc_trg
filename2.def
filename2.def_trg
filename6.jkl
filename7.mno
filename8.ghi
filename8.ghi_trg
filename9.jkl
Here is my code so far:
$strDir = "D:\Temp\FileCompareTest\"
$strFileTypesToIgnore = ".jkl",".mno"
$strExtABC = ".abc"
$strExtABC_Trigger = ".abc_trg"
$strExtDEF = ".def"
$strExtDEF_Trigger = ".def_trg"
$strExtGHI = ".ghi"
$strExtGHI_Trigger = ".ghi_trg"
$arrFiles = Get-ChildItem $strDir -exclude $strFileTypesToIgnore
ForEach ($objFile in $arrFiles) {
$strFilename = $objFile.BaseName
$strExtension = $objFile.Extension
If ($strExtension -eq ".abc") {
$arrFiles2 = Get-ChildItem $strDir -exclude $strFileTypesToIgnore
ForEach ($objFile2 in $arrFiles2) {
$strFilename2 = $objFile2.BaseName
$strExtension2 = $objFile2.Extension
If ($strExtension2 -eq ".abc_trg") {
If (Compare-Object $strFilename $strFilename2) {
Write-Host "match is: $strFilename$strExtension and $strFilename2$strExtension2"
} Else {
Write-Host "Not a match: $strFilename$strExtension and $strFilename2$strExtension2"
}
}
}
}
}
Can you help please?
Regards
Darren

Answer 1

Thanks for including your code. You have the right idea of comparing names and and extensions but lets try a different approach.
We loop each file and check its extension. Depending on if the file is a trg file or not we have a similar mean to check for its partner. Since we use a Where-Object clause the output files are passed onto the pipe to Remove-Item for deletion. Test with the -WhatIf switch to verify it is working.
I tried to use simple cmdlets and methods for string manipulation.
$path = "C:\temp\test"
$extension = "_trg"
$files = Get-ChildItem -Path $path
$fileNames = $files | Select-Object -ExpandProperty Name
$files | Where-Object{
# Check what extension this file is so we can find the appropriate partner
if($_.Extension.Contains($extension)){
# Attempt to find a matching non trg file
$fileNames -notcontains $_.Name.Substring(0, $_.Name.LastIndexOf($extension))
} else {
# Attempt to find a matching trg file
$fileNames -notcontains "$($_.Name)$extension"
}
} | Remove-Item -Force -Confirm:$false -WhatIf
We save all the file names in $fileNames and use -notcontains to see if the file in the loop has its partner in the list. If not it passed through the pipe.