Remove entries of one text file present in another - powershell

Question

I have 2 text file like below
exclude.txt
10.1.1.3
10.1.1.4
10.1.1.5
10.1.1.6
free.txt
10.1.1.3
10.1.1.4
10.1.1.5
10.1.1.6
10.1.1.7
10.1.1.8
10.1.1.9
10.1.1.10
I want to write exclude the entries of exclude.txt from free.txt and write to another file
10.1.1.7
10.1.1.8
10.1.1.9
10.1.1.10
I tried :
compare-object (get-content $freeips) (get-content $excludeip) -PassThru | format-list | Out-File $finalips
Here in the final output I am always getting the first IP of the exclude.txt
10.1.1.7
10.1.1.8
10.1.1.9
10.1.1.10
10.1.1.3
and another way I tried
$exclude = Get-Content "C:\exclude.txt"
foreach($ip in $exclude)
{
get-content "C:\free.txt" | select-string -pattern $ip -notmatch | Out-File "C:\diff.txt"
}
But in this case also I am getting the entries of exclude.txt in the final output.
Please let me know where I am doing wrong here

Answer 1

The Select-String solution is probably faster. Besides it doesn't require the iteration through the IP addresses as the -Pattern parameters accepts a string array (String[]). The point is thou that by default the pattern(s) repressent a regular expression where a dot (.) is a place holder for any character. To search for a literal pattern you should use the -SimpleMatch switch:
$exclude = Get-Content .\exclude.txt
get-content .\free.txt |Select-String -pattern $exclude -NotMatch -SimpleMatch
Note: The space in top of the displayed exclude.txt file suggests that there might be an empty line in top of the file (which regex matches any string). To get rid of any empty lines, use:
$exclude = Get-Content .\exclude.txt |Where-Object { $_ }

Answer 2

When comparing, $excludeip should be the referenceObject and $freeips comes after, like this:
compare-object (get-content $excludeip) (get-content $freeips) -PassThru | Out-File $finalips