Powershell Nested Foreach loop giving incorrect results

Question

i have two arrays $newUsers and $oldUsers already populated with userid's in the script i've written. My next goal is to check whether the userid from $newUsers exists in $oldUsers. if yes, then display statement Write-Host "New User_id $rowNew found in Old user list" else display Write-Host "New User_id $rowNew Notfound in Old user list"

below is the logic i used and the output i'am getting.

foreach ($rowNew in $newusers){ 
           foreach ($rowOld in $oldusers){
                 if ($rowNew -ieq $rowOld){ 
                      Write-Host "New User_id $rowNew found in Old user list"
                 } else {
                   Write-Host "New User_id $rowNew Notfound in Old user list"   
                 }
            }
        }

--Result

New User_id fadb274 found in Old user list
New User_id fadb274 Notfound in Old user list
New User_id fadb274 Notfound in Old user list
New User_id fadb274 Notfound in Old user list
New User_id fadb274 Notfound in Old user list
New User_id fadb274 Notfound in Old user list
New User_id fadb274 Notfound in Old user list
New User_id fadb274 Notfound in Old user list
New User_id fad8878 found in Old user list
New User_id fad8878 Notfound in Old user list
New User_id fad8878 Notfound in Old user list
New User_id fad8878 Notfound in Old user list

Not sure why i'am getting the above results, should'nt i be getting one result for each userid. could anyone help me as to what i need to change in code snippet above?

I suggest to use compare-object cmdlet.

CB.
– CB.

2013-06-26 15:53:25 +00:00
Commented Jun 26, 2013 at 15:53 — CB.
– CB., Commented Jun 26, 2013 at 15:53

Dave Sexton · Accepted Answer · 2013-06-26 16:05:12Z

3

I think the problem is that you are trying to match every item in one file to every other item in the other file so each run of the outer loop wil result in one possible and lots of non matches.

Why not use the Compare-Object instead like so:

Compare-Object -ReferenceObject $oldusers -DifferenceObject $newusers -IncludeEqual | % {
  if($_.SideIndicator -eq '==') {$f = 'found'} else {$f = 'NotFound'}
  if($_.SideIndicator -eq '<=') {$a = 'Old'} 
  if($_.SideIndicator -eq '=>') {$a = 'New'}
  "New User_id $($_.InputObject) $f in $a user list"
}

Another alternative would be to just do one loop and use -contains instead of -ieq.

answered Jun 26, 2013 at 16:05

Dave Sexton

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4 Comments

user1411254 Over a year ago

Thanks Dave!! it worked, for further analysis on these userid's in my script how would i go by assigning found userid's into one array and not found ones into another array while being in the foreach-object loop?

user1411254 Over a year ago

i tried using one loop by using -contains and the result came out as no userid's found, below is the code snippet

user1411254 Over a year ago

foreach ($id in $newUsers){ if ( $id -contains $oldUsers){ Write-Host "$id Found in New user list" } else { Write-Host "$id Not Found in New user list" } }

Dave Sexton Over a year ago

Looks good but you just need to make a change: $id -contains $oldUsers should be $oldUsers -contains $id

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