Select all unique third octet in a list of IP addresses with PowerShell - powershell

Question

I have a list of IP addresses. They all start with 10.10. I want all the unique values of the third octet. This way I can count how many of that unique value there are.
10.10.26.251
10.10.27.221
10.10.26.55
10.10.31.12
10.10.12.31
10.10.31.11
10.10.27.15
10.10.26.5
When I am done I want to know that I have 3 .26 network devices, 2 27, and so on so forth. Other than breaking down the octet with a split and looping through each one, I can't think of any single liners. Any suggestions?

Answer 1

here's a small variant. [grin] i already had this before noticing the other answers - and it is a tad different.
what it does ...
creates a collection of IPv4 address objects to work with
groups them by a calculated property [the 3rd octet]
creates a [PSCustomObject] for each resulting group
sends it to the $Octet3_Report variable
shows it on screen
output to a CSV file would be easy at that point. here's the code ...
$IP_List = #(
[ipaddress]'10.10.26.251'
[ipaddress]'10.10.27.221'
[ipaddress]'10.10.26.55'
[ipaddress]'10.10.31.12'
[ipaddress]'10.10.12.31'
[ipaddress]'10.10.31.11'
[ipaddress]'10.10.27.15'
[ipaddress]'10.10.26.5'
)
$Octet3_Report = $IP_List |
Group-Object -Property {$_.ToString().Split('.')[2]} |
ForEach-Object {
[PSCustomObject]#{
Octet_3 = $_.Name
Count = $_.Count
}
}
$Octet3_Report
on screen output ...
Octet_3 Count
------- -----
26 3
27 2
31 2
12 1

Answer 2

It's like me to figure it out after the fact.
The Return contains the dns records. The IP address are stored inside recorddata. I pull the end of the IP address off. Then loop through grabbing only the range and count with a foreach loop to make it cleaner.
$DNSRecordCounts = #()
$Ranges = ($Return | where-object {$_.recorddata -like "10.10.*"}).recorddata -replace "\.\d{1,3}$" | select -Unique
foreach ($range in $Ranges) {
$DNSRecordCounts += [pscustomobject][ordered]#{
IPRange = $range
Count = ($Return | Where-Object {$_.recorddata -like "$($range).*"}).Count
}
}

Answer 3

Based on your question and what I can infer from your own answer, if you are looking for something a little more like "idiomatic" PowerShell you want the following:
$Return `
| Select-Object -ExpandProperty recorddata `
| ForEach-Object {
$_ -match "\d+\.\d+\.(?<octet>\d+)\.\d+" | Out-Null
$Matches.octet
} `
| Group-Object `
| ForEach-Object {
[PSCustomObject]#{
Octet = $_.Name
Count = $_.Count
}
}