Compare contents of 6 objects and delete which are not matching - powershell

Question

I have some 6 files which are created dynamically (so,I dont know the contents). I need to compare these 6 files (exactly speaking compare one file with 5 others) and see what all contents in the file 1 are matching with the other 5. The contents which are matching should be saved, others need to be deleted.
I coded something like below, but is deleting everything (which are matching too).
$lines = Get-Content "C:\snaps.txt"
$check1 = Get-Content "C:\Previous_day_latest.txt"
$check2 = Get-Content "C:\this_week_saved_snaps.txt"
$check3 = Get-Content "C:\all_week_latest_snapshots.txt"
$check4 = Get-Content "C:\each_month_latest.txt"
$check5 = Get-Content "C:\exclusions.txt"
foreach($l in $lines)
{
if(($l -notmatch $check1) -and ($l -notmatch $check2) -and ($l -notmatch $check3) -and ($l -notmatch $check4))
{
Remove-Item -Path "C:\$l.txt"
}else
{
#nothing
}
}
foreach($ch in $check5)
{
Remove-Item -Path "C:\$ch.txt"
}
Contents of 6 files will be as shown below:
$lines
testinstance-01-07-15-08-00
testinstance-10-07-15-23-00
testinstance-13-02-15-13-00
testinstance-15-06-15-23-00
testinstance-19-01-15-23-00
testinstance-23-05-15-20-00
testinstance-27-03-15-23-00
testinstance-28-02-15-23-00
testinstance-29-07-15-08-00
testinstance-30-04-15-23-00
testinstance-30-06-15-23-00
testinstance-31-01-15-23-00
testinstance-31-12-14-23-00
$check1
testinstance-29-07-15-08-00
$check2
testinstance-23-05-15-20-00
testinstance-27-03-15-23-00
$check3
testinstance-01-07-15-23-00
testinstance-13-02-15-13-00
testinstance-19-01-15-23-00
$check4
testinstance-28-02-15-23-00
testinstance-30-04-15-23-00
testinstance-30-06-15-23-00
testinstance-31-01-15-23-00
$check5
testinstance-31-12-14-23-00
I've read about compare-object. But not sure how that can be implemented in my case as contents of all 5 files will be different and all those contents should be saved from deletion. Can someone please guide me to achieve what I said.? Any help would be really appreciated.

Answer 1

I would create an array of the files to check so you can simply add new files without modifying other parts of your script.
I use the where cmdlet which filters all lines that are in the reference file using -in condition and finally overwrite the file:
$referenceFile = 'C:\snaps.txt'
$compareFiles = #(
'C:\Previous_day_latest.txt',
'C:\this_week_saved_snaps.txt',
'C:\all_week_latest_snapshots.txt',
'C:\each_month_latest.txt',
'C:\exclusions.txt'
)
# get the content of the reference file
$referenceContent = (gc $referenceFile)
foreach ($file in $compareFiles)
{
# get the content of the file to check
$content = (gc $file)
# filter all contents from the file to check which are in the reference file and save it
$content | where { $_ -in $referenceContent } | sc $file
}

Answer 2

You can use the -contains operator to compare array contents. If you open all the files you want to check and store into an array, you can compare that with the reference file:
$lines = Get-Content "C:\snaps.txt"
$check1 = "C:\Previous_day_latest.txt"
$check2 = "C:\this_week_saved_snaps.txt"
$check3 = "C:\all_week_latest_snapshots.txt"
$check4 = "C:\each_month_latest.txt"
$check5 = "C:\exclusions.txt"
$checklines = #()
(1..5) | ForEach-Object {
$comp = Get-Content $(Get-Variable check$_).value
$checklines += $comp
}
$matches = $lines | ? { $checklines -contains $_ }
If you switch the -contains to -notcontains you'll see the three lines that don't match

Answer 3

The other answers here are great but I wanted to show you that Compare-Object could still work. You need to use it in a loop however. Just to try and show something else I included a simple use of Join-Path for building the array of checks. Basically we are saving some typing when you move your files to a production area. Update one path instead of more.
$rootPath = "C:\"
$fileNames = "Previous_day_latest.txt", "this_week_saved_snaps.txt", "all_week_latest_snapshots.txt", "each_month_latest.txt", "exclusions.txt"
$lines = Get-Content (Join-path $rootPath "snaps.txt")
$checks = $fileNames | ForEach-Object{Join-Path $rootPath $_}
ForEach($check in $checks){
Compare-Object -ReferenceObject $lines -DifferenceObject (Get-Content $check) -IncludeEqual |
Where-Object{$_.SideIndicator -eq "=="} |
Select-Object -ExpandProperty InputObject |
Set-Content $check
}
So we take each file path and use Compare-Object in a loop comparing each to the $lines array. Using -IncludeEqual we find the lines that both files share and write those back to the file.
Depending on how many checks you have and where they are it might be easier to have this line to build the array $checks
$checks = Get-ChildItem "C:\" -Filter "*.txt" | Select-Object -Expand FullName