how to get the value in a string using regex - regex

Question

I am confused on how to get the number in the string below. I crafted a regex
$regex = '(?s)^.+\bTotal Members in Group: ([\d.]+).*$'
I need only the number part 2 inside a long string a line reads Total Members in Group: 2.
My $regex returns me the entire line but what i really need is the number.
The number is random

Answer 1

cls
$string = 'Total Members in Group: 2'
$membersCount = $string -replace "\D*"
$membersCount
One more way:
cls
$string = 'Total Members in Group: 2'
$membersCount = [Regex]::Match($string, "(?<=Group:\s*)\d+").Value
$membersCount

Answer 2

Fors1k's helpful answer shows elegant solutions that bypass the need for a capture group ((...)) - they are the best solutions for the specific example in the question.
To answer the general question as to how to extract substrings
if and when capture groups are needed, the PowerShell-idiomatic way is to:
Either: Use -match, the regular-expression matching operator with a single input string: if the -match operation returns $true, the automatic $Matches variable reflects what the regex captured, with property (key) 0 containing the full match, 1 the first capture group's match, and so on.
$string = 'Total Members in Group: 2'
if ($string -match '(?s)^.*\bTotal Members in Group: (\d+).*$') {
# Output the first capture group's match
$Matches.1
}
Note:
-match only ever looks for one match in the input.
Direct use of the underlying .NET APIs is required to look for all matches, via [regex]::Matches() - see this answer for an example.
While -match only populates $Matches with a single input string (with an array, it acts as a filter and returns the sub-array of matching input strings), you can use a switch statement with -Regex to apply -match behavior to an array of input strings; here's a simplified example (outputs '1', '2', '3'):
switch -Regex ('A1', 'A2', 'A3') {
'A(.)' { $Matches.1 }
}
Or: Use -replace, the regular-expression-based string replacement operator, to match the entire input string and replace it with a reference to what the capture group(s) of interest captured; e.g, $1 refers to the first capture group's value.
$string = 'Total Members in Group: 2'
$string -replace '(?s)^.*\bTotal Members in Group: (\d+).*$', '$1'
Note:
-replace, unlike -match, looks for all matches in the input
-replace also supports an array of input strings, in which case each array element is processed separately (-match does too, but in that case it does not populate $Matches; as stated, switch can remedy that).
A caveat re -replace is that if the regex does not match, the input string is returned as-is