Powershell ignoring looking behind the regular expression to return the entire line


A simple enough question I hope.

I have a text log file that includes the following line:


I want to search through the log file and return the "00000000926" section of the above text. So I wrote a regular expression: (?<=123.{17}).{11}

So when the look behind text equals '123' with 17 characters, return the next 11. This works fine when tested on online regex editors. However in Powershell the entire line is returned instead of the 11 characters I want and I can't understand why.

$InputFile = get-content logfile.log
$regex = '(?<=123.{17}).{11}'
$Inputfile | select-string $regex

(entire line is returned).

Why is powershell returning the entire line?

It's because you're using Select-String which returns the line that matches (think grep).

$InputFile = get-content logfile.log | ForEach-Object {
    if ($_ -match '(?<=123.{17})(.{11})') {

Haven't tested this, but it should work (or something similar).