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

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) ?
I'm using :

get-content myfile.txt | select-string -pattern "my_string" -encoding ASCII | select -last 1
But it's very very long (about 16-18 seconds).
I did tests without the last pipe "`select -last 1`", but it's the same time.

Is there **a faster way** to get the **last occurence** (or all occurences) of a specific string in huge file?

Perhaps it's the needed time ...
Or it there any possiblity to read the file faster from the end as I want the last occurence?
Thanks

Have you tried using `[System.IO.File]::ReadAllLines();`? This method is more "raw" than the PowerShell-esque method, since we're plugging directly into the Microsoft .NET Framework types.

$Lines = [System.IO.File]::ReadAllLines();
[Regex]::Matches($Lines, 'my_string_pattern');

Try this:

get-content myfile.txt -ReadCount 1000 |
foreach { $_ -match "my_string" }

That will read your file in chunks of 1000 records at a time, and find the matches in each chunk. This gives you better performance because you aren't wasting a lot of cpu time on memory management, since there's only 1000 lines at a time in the pipeline.

Have you tried:

gc myfile.txt | % { if($_ -match "my_string") {write-host $_}}

Or, you can create a "grep"-like function:

function grep($f,$s) {
gc $f | % {if($_ -match $s){write-host $_}}
}

Then you can just issue: `grep $myfile.txt $my_string`

$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

I wanted to extract the lines that contained failed and also write this lines to a new file, I will add the full command for this

get-content log.txt -ReadCount 1000 |
>> foreach { $_ -match "failed" } | Out-File C:\failes.txt