Replace until a pattern is found in PowerShell - regex

Question

I have been trying to transform the following string:
CN=John Doe,OU=IT,OU=Support,OU=Department,OU=HQ,DC=FR,DC=CONTOSO,DC=COM
to:
FR.CONTOSO.COM
As a first step, I tried to remove everything until ",DC" pattern.
I thought I could use the un-greedy ".+?" to match everything until the first ",DC" pattern:
$str = 'CN=John Doe,OU=IT,OU=Support,OU=Department,OU=HQ,DC=FR,DC=CONTOSO,DC=COM'
$str -replace '.+?,DC', ''
This returns:
=COM
Any idea why it's getting only the last one even with the un-greedy version?
How could I do this?

Answer 1

Just split the string:
$parts = ('CN=John Doe,OU=IT,OU=Support,OU=Department,OU=HQ,DC=FR,DC=CONTOSO,DC=COM' -split ',')
$newString = '{0}.{1}.{2}' -f $parts[-3].split('=')[1], $parts[-2].split('=')[1], $parts[-1].split('=')[1]

Answer 2

OK, so I took #EBGreen's advice and decided to make a function that does all the work:
#Requires -Version 4
Function ConvertFrom-DistinguishedName
{
[CmdletBinding()]
[OutputType('System.Management.Automation.PSCustomObject')]
Param(
[Parameter(Position = 0, Mandatory)]
[Alias('DistinguishedName', 'Name')]
[ValidatePattern('^CN=.+?,(OU=.+?,)+DC=.+$')]
[string]
$Path
)
$local:ErrorActionPreference = [System.Management.Automation.ActionPreference]::Stop
$WS = $Path -split ',' # working set
$User = $WS[0] -replace 'CN='
$Domain = $WS.Where({$PSItem.StartsWith('DC=')}).ToLower() -replace 'dc=' -join '.'
$OU = $WS.Where({$PSItem.StartsWith('OU=')}) -replace 'OU='
[array]::Reverse($OU)
[pscustomobject]#{
'User' = $User
'Domain' = $Domain
'OU' = $OU -join '\'
}
}
PS C:\> ConvertFrom-DistinguishedName 'CN=John Doe,OU=IT,OU=Support,OU=Department,OU=HQ,DC=FR,DC=CONTOSO,DC=COM'
User Domain OU
---- ------ --
John Doe fr.contoso.com HQ\Department\Support\IT
The end result? This converts your distinguished AD name to a PSCustomObject you can easily work with.

Answer 3

To get the domain out of the Distinguishedname, you will want to use -Split. Finally we can use -join to insert '.' between the DCs
This will store your domain string to $domain:
$dn = "CN=John Doe,OU=IT,OU=Support,OU=Department,OU=HQ,DC=FR,DC=CONTOSO,DC=COM"
$domain = $dn -Split "," | ? {$_ -like "DC=*"}
$domain = $domain -join "." -replace ("DC=", "")
Write-Host "Current Domain: " $domain

Answer 4

You should use the ^ to start from the beginning.
$str = 'CN=John Doe,OU=IT,OU=Support,OU=Department,OU=HQ,DC=FR,DC=CONTOSO,DC=COM'
$str = $str -replace '^.+?,DC',''
$str = $str -replace 'DC=',''
$str -replace ',','.'

Answer 5

Since nobody bothered explaining the behavior yet:
The replacement operation replaces every occurrence of the pattern .+?,DC in the string, so it first removes CN=John Doe,OU=IT,OU=Support,OU=Department,OU=HQ,DC, then continues where that replacement left off and removes =FR,DC, and then =CONTOSO,DC, leaving you with just =COM.
To avoid this behavior you need to anchor the expression at the beginning of the string (^), as others have already suggested. The second replacement for substituting the remaining ,DC= with dots can be daisy-chained to the first one, so you need just one statement:
$str -replace '^.*?,dc=' -replace ',dc=', '.'