Welcome Forums General PowerShell Q&A manipulating a line (IP) of a CSV to only use first 3 octets

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    • #168760
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      I have a CSV file that is sent to me (lets say it is called NetInput.csv).  Each line is a subnet in CIDR format and appears like this example here…

      192.168.10.0/24

      192.168.13.0/24

      192.168.20.0/24

      I am writing a ping sweep script using the following powershell one-liner that I will foreach through each subnet

      1..254 | % {“$first3octet.$($_): $(Test-Connection -count 1 -comp $first3octet.$($_) -quiet)”} | Out-File -FilePath C:\temp\pingtest.txt

      How would I take the first 3 octets of each line and put them in to a variable (the variable being $first3octet  in the line above).  essentially stripping off the .0/24 portion.

      I am pretty sure I would need to do something like

      # get the content of the csv

      $netlist = gc c:\temp\NetInput.csv

      # then do a ‘foreach’  to each line of the file with some command to only use the first 3 octets in to a new variable

      foreach ($subnet in $netlist) {do something here that drops the .0/24 from the subnet and put in to $first3octet variable}

      Any help or suggestions would be greatly appreciated.  I am very new to powershell and eager to put it to good use !

       

       

       

    • #168802
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      Hello,
      Here is one way to skin this cat..

      $cidr = '192.168.10.0/24'
      # split the network ip on '.', select the first 3 items in the result object and join them back together with a '.' delimiter
      $First3Octets = ($cidr -split [regex]::Escape('.') | Select-Object -First 3) -join '.'
      

      Also, for future posts, it helps when you format the code in your post. Makes it easier to read.

      HTH,
      Steve

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