Get all lines containing a string in a huge text file - as fast as possible?

Question

In Powershell, how to read and get as fast as possible the last line (or all the lines) which contains a specific string in a huge text file (about 200000 lines / 30 MBytes) ?

Answer 1

$reader = New-Object System.IO.StreamReader("myfile.txt")

$lines = @()

if ($reader -ne $null) {
    while (!$reader.EndOfStream) {
        $line = $reader.ReadLine()
        if ($line.Contains("my_string")) {
            $lines += $line
        }
    }
}

$lines | Select-Object -Last 1