Read file line by line in PowerShell

Not much documentation on PowerShell loops.

Documentation on loops in PowerShell is plentiful, and you might want to check out the following help topics: about_For, about_ForEach, about_Do, about_While.

foreach($line in Get-Content .\file.txt) {
    if($line -match $regex){
        # Work here
    }
}

Another idiomatic PowerShell solution to your problem is to pipe the lines of the text file to the ForEach-Object cmdlet:

Get-Content .\file.txt | ForEach-Object {
    if($_ -match $regex){
        # Work here
    }
}

Instead of regex matching inside the loop, you could pipe the lines through Where-Object to filter just those you’re interested in:

Get-Content .\file.txt | Where-Object {$_ -match $regex} | ForEach-Object {
    # Work here
}