Powershell write array using StreamWriter

Question

I'm new to PowerShell and am trying to write a script that will allow me to read through a very large text file and extract certain lines if they begin with "2020".

When a match is found, it should write to an array ($Lines), then I'm trying to output this filtered content to another text file using StreamWriter.

Here is what I have so far:

$reader = New-Object System.IO.StreamReader 'C:\Users\PSTest\Years.txt'
$writer = New-Object System.IO.StreamWriter 'C:\Users\PSTest\Data.txt'

$lines = @()

        Foreach ($line in $reader) {

             if ($reader -ne $null) {
             while (!$reader.EndOfStream) {
             $line = $reader.ReadLine()

                   if ($line.StartsWith("2020")) { 
                   $lines += $line }

                         $writer.writeline($lines) }      
    }
  }  

 $reader.dispose()
 $writer.dispose()

When I write to the console I can tell there are hundreds of matches, but nothing ever gets written to the output file (Data.txt).

What am I missing? Thank you in advance.

Answer 1

if you want really use an array try this :

try
{
$reader = New-Object System.IO.StreamReader 'C:\temp\test.txt'
$lines = @()

while (($line = $reader.ReadLine()) -ne $null)  
{  
if ($line.StartsWith("2020")) { $lines += $line }
}

#not necessary to keep file open
$reader.Close() 

$writer = New-Object System.IO.StreamWriter 'C:\temp\test2.txt'
$lines | %{$writer.WriteLine($_)}

}
finally
{

    if ($reader -ne $null)
    {
        $reader.Close()
        $reader.Dispose()
    }

    if ($writer -ne $null)
    {
        $writer.Close()
        $writer.Dispose()
    }
}

otherwise :

try
{
$reader = New-Object System.IO.StreamReader 'C:\temp\test.txt'
$writer = New-Object System.IO.StreamWriter 'C:\temp\test2.txt'

while (($line = $reader.ReadLine()) -ne $null)  
{  
if ($line.StartsWith("2020")) { $writer.WriteLine($line)}
}

}
finally
{

    if ($reader -ne $null)
    {
        $reader.Close()
        $reader.Dispose()
    }

    if ($writer -ne $null)
    {
        $writer.Close()
        $writer.Dispose()
    }
}