How to compare numbers in a string variable?

Question

I have a powershell script that is grabbing the output of a website and storing it into a string variable. What I would like to do is check a line in the output which contains two numbers - the number of emails sent out of the total number of emails.
I have not come up with a way to do this that works. I was thinking of maybe using a regex, but there are other numbers I don't care about that keep getting caught.
Here is a sample of what is contained in the string variable:
Email ID: 46862270 : Succeded. Time Taken: 00:00:00.0924511
Email ID: 46862272 : Succeded. Time Taken: 00:00:00.0493887
-- Sent 250 of 250 emails successfully. Total Dispatch Time: 00:00:08.1406995
--State Written to DB. Time Taken for DB Write: 00:00:00.4611053
Here is another sample:
Email ID: 46865840 : Succeded. Time Taken: 00:00:00.9333887
-- Sent 17 of 17 emails successfully. Total Dispatch Time: 00:00:01.2416905
--State Written to DB. Time Taken for DB Write: 00:00:00.0402957
So if I have the above contained in a variable called $httpResponse how can I find only the line that starts with -- Sent
and then subtract the first number from the second number?
So for example if I have this:
Email ID: 46865840 : Succeded. Time Taken: 00:00:00.9333887
-- Sent 207 of 217 emails successfully. Total Dispatch Time: 00:00:01.2416905
--State Written to DB. Time Taken for DB Write: 00:00:00.0402957
I would want the check to return 10. Is this even possible?
Any help is appreciated!

Answer 1

Sure.
$String = @'
Email ID: 46865840 : Succeded. Time Taken: 00:00:00.9333887
-- Sent 207 of 217 emails successfully. Total Dispatch Time: 00:00:01.2416905
--State Written to DB. Time Taken for DB Write: 00:00:00.0402957
if ( $string -match 'Sent (\d+) of (\d+) emails .+' )
{ $FailedEmailCount = [int]$matches[2] - $matches[1] }
$FailedEmailCount
10
Each set of parens will designate a capture group, and those can be referenced from $Matches after a successful -match.
Just remember that they will all be strings, and to do a math operation you have to cast at least the one on the LH side to a numeric type first.
[string](0..33|%{[char][int](46+("686552495351636652556262185355647068516270555358646562655775 0645570").substring(($_*2),2))})-replace " "