Help with Using PowerShell to split a file by a particular string and saving as specific name

richardsmc 

Hi, Marvin.

Here's a basic working template to get you started, where I've assumed the example data you've provided is consistently formed.

If, for example, "MessageA" could in fact feature a space, such as "Message A", then some logic would have to be added to the script to allow for that.

Input data file

Script

$SourceFile = "D:\Data\Temp\Forum\forum.txt";

$SourceDirectory = [System.IO.Path]::GetDirectoryName($SourceFile) + "\";
$FileOpen = $false;
$Timestamp = [datetime]::MinValue;

Get-Content -Path $SourceFile |
    ForEach-Object {
        $Line = $_;

        # Check this isn't empty space in between files. If so, skip it.
        if ((-not $FileOpen) -and [string]::IsNullOrWhiteSpace($Line))
        {
            # We do nothing here, meaning we skip the empty space between files.
        }
        # Check if we've hit a well-formed line that indicates the start of a new message-aligned file.
        elseif ((-not $FileOpen) -and
                ($Line.Length -gt 10) -and
                ([datetime]::TryParse($Line.Substring(0, 10), [ref] $Timestamp) -and
                (4 -eq ($Parts = [regex]::Split($Line, "\s+")).Count)))
        {
            $NewFileName = [string]::Concat($SourceDirectory, $Parts[1], ".txt");

            Out-File -FilePath $NewFileName -InputObject $Line -ErrorAction:Stop;
            $FileOpen = $true;
        }
        # Check if we've hit a well-formed line indicating the end of a file.
        elseif ("*End of message" -eq $Line)
        {
            # This is more of a safety check, since outside of an error condition, $FileOpen should always be $true.
            if ($FileOpen)
            {
                Out-File -FilePath $NewFileName -InputObject $Line -Append;
            }

            $FileOpen = $false;
            $NewFileName = $null;
        }
        # Otherwise, if a file is considered "open", weite the line to it. (Mechanically, the file isn't really open - it's just easier to conceptualise it that way.)
        elseif ($FileOpen)
        {
            Out-File -FilePath $NewFileName -InputObject $Line -Append;
        }
    }

Output

Cheers,

Lain