Using "notin" with matching groups - regex

Question

Using powershell, I am trying to determine which perl scripts in a directory are not called from any other script. In my Select-String I am grouping the matches because there is some other logic I use to filter out results where the line is commented, and a bunch of other scenarios I want to exclude(for simplicity I excluded that from the code posted below). My main problem is in the "-notin" part.
I can get this to work if I remove the grouping from Select-string and only match the filename itself. So this works.
$searchlocation = "C:\Temp\"
$allresults = Select-String -Path "$searchlocation*.pl" -Pattern '\w+\.pl'
$allperlfiles = Get-Childitem -Path "$searchlocation*.pl"
$allperlfiles | foreach-object -process{
$_ | where {$_.name -notin $allresults.matches.value} | Select -expandproperty name | Write-Host
}
However I cannot get the following to work. The only difference between this and above is the value for the "-Pattern" and the value after "-notin". I'm not sure how to use "notin" along with matching groups.
$searchlocation = "C:\Temp\"
$allresults = Select-String -Path "$searchlocation*.pl" -Pattern '(.*?)(\w+\.pl)'
$allperlfiles = Get-Childitem -Path "$searchlocation*.pl"
$allperlfiles | foreach-object -process{
$_ | where {$_.name -notin $allresults.matches.groups[2].value} | Select -expandproperty name | Write-Host}
At a high level the code should search all perl scripts in a directory for any lines that execute any other perl script. With that I now have $allresults which basically gives me a list of all perl scripts called from other files. To get the inverse of that(files that are NOT called from any other file) I get a list of all perl scripts in the directory, cycle through those and list out the ones that DONT show up in $allresults.

Answer 1

When you select a grouping you need to do so using a Select statement, or iteratively in a loop, otherwise you are only going to select the value from the Nth match.
IE if your $Allresults object contains
File.pl, File 2.pl, File 3.pl
Then $allresults.Matches.Groups[2].value Only Returns File2.pl
Instead, you need to select those values!
$allresults | select #{N="Match";E={ $($_.Matches.Groups[2].value) } }
Which will return:
Match
-----
File1.pl
File2.pl
File3.pl
In your specific example, each match has three sub-items, the results will be completely sequential, so what you would term "match 1, group 1" is groups[0] while "match 2, group 1" is groups[3]
This means the matches you care about (those with grouping 2) are in the array values contained in the set {2,5,8,11,...,etc.} or can be described as (N*3-1) Where N is the number of the match. So For Match 1 = (1*3)-1 = [2]; while For Match 13 = (13*3)-1 = [38]
You can iterate through them using a loop to check:
for($i=0; $i -le ($allresults.Matches.groups.count-1); $i++){
"Group[$i] = ""$($allresults.Matches.Groups[$i].value)"""
}
I noticed that you took the time to avoid loops in collecting your data, but then accidentally seem to have fallen prey to using one in matching your data.
Not-In and other compares when used by the select and where clauses don't need a loop structure and are faster if not looped, so you can forego the Foreach-object loop and have a better process just by using a simple Where (?).
$SearchLocation = "C:\Temp\"
$FileGlob = "*.pl"
$allresults = Select-String -Path "$SearchLocation$FileGlob" -Pattern '(.*?)([\w\.]+\.bat)'
$allperlfiles = Get-Childitem -Path "$SearchLocation$FileGlob"
$allperlfiles | ? {
$_.name -notin $(
$allresults | select #{N="Match";E={ $($_.Matches.Groups[2].value) } }
)
} | Select -expandproperty name | Write-Host
Now, that should be faster and simpler code to maintain, but, as you may have noticed, it still has some redundancies now that you are not looping.
As you are piping it all into a Select which can do the work of the where, and what's more you only are looking to match the NAME property here so you can either for-go the last select by only piping the name of the file in the first place, or you can forgo the where and select exactly what you want.
I think the former is far simpler, and the latter is useful if you are going to actually do something with those other values inside the loop that we don't know yet.
Finally, Write-host is likely redundant as any object output will echo to the console.
Here is that version which incorporates the removal of the unnecessary loops and removes redundancies related to the output of the info you wanted, all together.
$SearchLocation = "C:\Temp\"
$FileGlob = "*.pl"
$allresults = Select-String -Path "$SearchLocation$FileGlob" -Pattern ('(.*?)([\w\.]+\'+$FileGlob+')')
$allperlfiles = Get-Childitem -Path "$SearchLocation$FileGlob"
$allperlfiles.name | ? {
$_ -notin $(
$allresults | select #{
N="Match";E={
$($_.Matches.Groups[2].value)
}
}
)
}