Think I've found the worst way to do this:
$ip = "192.168.13.1"
$a,$b,$c,$d = $ip.Split(".")
[int]$c = $c
$c = $c+1
[string]$c = $c
$newIP = $a+"."+$b+"."+$c+"."+$d
$newIP
But what is the best way? Has to be string when completed. Not bothered about validating its a legit IP.
Using your example for how you want to modify the third octet, I'd do it pretty much the same way, but I'd compress some of the steps together:
$IP = "192.168.13.1"
$octets = $IP.Split(".") # or $octets = $IP -split "\."
$octets[2] = [string]([int]$octets[2] + 1) # or other manipulation of the third octet
$newIP = $octets -join "."
$newIP
You can simply use the -replace operator of PowerShell and a look ahead pattern. Look at this script below
Set-StrictMode -Version "2.0"
$ErrorActionPreference="Stop"
cls
$ip1 = "192.168.13.123"
$tests=@("192.168.13.123" , "192.168.13.1" , "192.168.13.12")
foreach($test in $tests)
{
$patternRegex="\d{1,3}(?=\.\d{1,3}$)"
$newOctet="420"
$ipNew=$test -replace $patternRegex,$newOctet
$msg="OLD ip={0} NEW ip={1}" -f $test,$ipNew
Write-Host $msg
}
This will produce the following:
OLD ip=192.168.13.123 NEW ip=192.168.420.123
OLD ip=192.168.13.1 NEW ip=192.168.420.1
OLD ip=192.168.13.12 NEW ip=192.168.420.12
How to use the -replace operator?
https://powershell.org/2013/08/regular-expressions-are-a-replaces-best-friend/
Understanding the pattern that I have used
The (?=) in \\d{1,3}(?=.\\d{1,3}$) means look behind.
The (?=.\\d{1,3}$ in \\d{1,3}(?=.\\d{1,3}$) means anything behind a DOT and 1-3 digits.
The leading \\d{1,3} is an instruction to specifically match 1-3 digits
All combined in plain english " Give me 1-3 digits which is behind a period and 1-3 digits located towards the right side boundary of the string "
Look ahead regex
CORRECTION
The regex pattern is a look ahead and not look behind .
If you have PowerShell Core (v6.1 or higher), you can combine -replace
with a script block -based replacement :
PS> '192.168.13.1' -replace '(?<=^(\d+\.){2})\d+', { 1 + $_.Value }
192.168.14.1
Negative look-behind assertion (?<=^(\\d+\\.){2})
matches everything up to, but not including, the 3rd octet - without considering it part of the overall match to replace.
(?<=...)
is the look-behind assertion, \\d+
matches one or more ( +
) digits ( \\d
), \\.
a literal .
, and {2}
matches the preceding subexpression ( (...)
) 2 times. \\d+
then matches just the 3rd octet; since nothing more is matched, the remainder of the string ( .
and the 4th octet) is left in place.
Inside the replacement script block ( { ... }
), $_
refers to the results of the match, in the form of a [MatchInfo]
instance; its .Value
is the matched string, ie the 3rd octet, to which 1
can be added.
1
, an implicit [int]
, as the LHS , the RHS (the .Value
string ) is implicitly coerced to [int]
(you may choose to use an explicit cast). If you must remain compatible with Windows PowerShell , consider Jeff Zeitlin's helpful answer .
For complete your method but shortly :
$a,$b,$c,$d = "192.168.13.1".Split(".")
$IP="$a.$b.$([int]$c+1).$d"
function Replace-3rdOctet {
Param(
[string]$GivenIP,
[string]$New3rdOctet
)
$GivenIP -match '(\d{1,3}).(\d{1,3}).(\d{1,3}).(\d{1,3})' | Out-Null
$Output = "$($matches[1]).$($matches[2]).$New3rdOctet.$($matches[4])"
Return $Output
}
Copy to a ps1 file and dot source it from command line, then type
Replace-3rdOctet -GivenIP '100.201.190.150' -New3rdOctet '42'
Output: 100.201.42.150
From there you could add extra error handling etc for random input etc.
here's a slightly different method. [ grin ] i managed to not notice the answer by JeffZeitlin until after i finished this.
[edit - thanks to JeffZeitlin for reminding me that the OP wants the final result as a string. oops! [*blush*]]
what it does ...
here's the code ...
$OriginalIPv4 = '1.1.1.1'
$TargetOctet = 3
$OctetList = [int[]]$OriginalIPv4.Split('.')
$OctetList[$TargetOctet - 1]++
$NewIPv4 = [ipaddress]($OctetList -join '.')
$NewIPv4
'=' * 30
$NewIPv4.IPAddressToString
output ...
Address : 16908545
AddressFamily : InterNetwork
ScopeId :
IsIPv6Multicast : False
IsIPv6LinkLocal : False
IsIPv6SiteLocal : False
IsIPv6Teredo : False
IsIPv4MappedToIPv6 : False
IPAddressToString : 1.1.2.1
==============================
1.1.2.1
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