CODEWITHSUNDEEP
powershell
user6591241
user6591241

Reputation: 11

Powershell - I want to return only empty records from ipconfig /displaydns

The subject is my ultimate goal. Using Powershell I have managed to return the contents of "ipconfig /displaydns" formatted into a table but I used some publicly posted code and I am new to powershell so I don't fully understand how it all works. The problem with what I am using is that it only returns the results that begin with the text "Record Name". This means that any entry that has no A record or where a record doesn't exist will not be returned. I'm using this code to try and get these records:

Function Get-FailedDNSClientCache{ 
    Invoke-Expression "IPConfig /DisplayDNS" | Select-String -Pattern "-----" -Context 2,1 |

        ForEach-Object{
            "" + $_.Context.PreContext[1]
            "" + $_.Line
            "" + $_.Context.Postcontext[0]
            "" + $_.Context.PreContext[2]
           }
       }

The code above gives me some output that looks like this:

pagead.l.doubleclick.net
----------------------------------------
No records of type AAAA

s0-2mdn-net.l.google.com
----------------------------------------
Record Name . . . . . : s0-2mdn-net.l.google.com    

www.redditstatic.com
----------------------------------------
No records exist

s0-2mdn-net.l.google.com
----------------------------------------
Record Name . . . . . : s0-2mdn-net.l.google.com

I've been trying all the different filtering methods I have found but I end up returning no data, null fields or I filter out just the text line that starts with "Record Name" but not the entire record. I think the problem is that I need to create each returned record as an object rather than each line but my attempts at that have failed as well. I'd basically like for my output to look like this:

pagead.l.doubleclick.net
----------------------------------------
No records of type AAAA

www.redditstatic.com
----------------------------------------
No records exist

I've seen bits and pieces of my question answered throughout the forum and I have tried most of the solutions provided but I think I am not understanding something fundamental allowing me to put it all together correctly. Please keep in mind I am truly trying to understand what I am doing so the more information the better. TIA

Upvotes: 1

Views: 878

Answers (3)

woxxom
woxxom

Reputation: 73746

Using a simple regex:

  • oneliner

    ([regex]'(?s)(\S+)\n\s+-+\s+(.+?)\n').matches((ipconfig /displayDNS) -join "`n") | ?{ $_.groups[2].value -notlike 'Record Name*' } | %{ $orphans = @{} } { $orphans[$_.groups[1].value] = $_.Groups[2].value } { $orphans }

  • more readable, using PS2 SortedDictionary

    $output = (ipconfig /displayDNS) -join "`n"
$rx = [regex]'(?s)(\S+)\n\s+-+\s+(.+?)\n'
$orphansSorted = [Collections.Generic.SortedDictionary[string,string]]::new()

forEach ($match in $rx.matches($output)) {
    $url = $match.groups[1].value
    $msg = $match.groups[2].value
    if ($msg -notlike 'Record Name*') {
        $orphansSorted[$url] = $msg
    }
}
$orphansSorted

Output:

Key                                          Value                  
---                                          -----                  
mpa.one.microsoft.com                        No records of type AAAA
my.router                                    No records exist
onlineconfigservice.ubi.com                  No records of type AAAA
static3.cdn.ubi.com                          No records of type AAAA
ubisoft-orbit.s3.amazonaws.com               No records of type AAAA
ubisoft-orbit-savegames.s3.amazonaws.com     No records of type AAAA

Upvotes: 0

Mathias R. Jessen
Mathias R. Jessen

Reputation: 174815

Use Where-Object to filter on matches where the PostContext[0] value contains the string "No records":

Function Get-FailedDNSClientCache{ 
Invoke-Expression "IPConfig /DisplayDNS" | Select-String -Pattern "-----" -Context 2,1 | Where-Object {$_.Context.Postcontext[0] -like "*No records*"} |ForEach-Object {
        "" + $_.Context.PreContext[1]
        "" + $_.Line
        "" + $_.Context.Postcontext[0]
        "" + $_.Context.PreContext[2]
       }
   }

Upvotes: 0

morgb
morgb

Reputation: 2312

You can use the Get-DnsClientCache cmdlet and pass in the status flag you wish to search for. For example:

Get-DnsClientCache -Status NotExist

Or

Get-DnsClientCache -Status NoRecords

If you don't have this function, you can create your own based on https://gallery.technet.microsoft.com/scriptcenter/ad12dc1c-b0c7-44d6-97c7-1a537b0b4fef

The code for the above cited function is:

Function Get-DNSClientCache{ 
$DNSCache = @() 

Invoke-Expression "IPConfig /DisplayDNS" | 
Select-String -Pattern "Record Name" -Context 0,5 | 
    %{ 
        $Record = New-Object PSObject -Property @{ 
        Name=($_.Line -Split ":")[1] 
        Type=($_.Context.PostContext[0] -Split ":")[1] 
        TTL=($_.Context.PostContext[1] -Split ":")[1] 
        Length=($_.Context.PostContext[2] -Split ":")[1] 
        Section=($_.Context.PostContext[3] -Split ":")[1] 
        HostRecord=($_.Context.PostContext[4] -Split ":")[1] 
        } 
        $DNSCache +=$Record 
    } 
    return $DNSCache 
}

Either of these methods will return an object that you can manipulate further as needed.

Upvotes: 1

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