Include filename in output - powershell

Question

I would like to get content from files in a folder (ignoring the header lines, since some file may ONLY contain the header). But in the output, I would like to include the filename from which the line is read. So far, I have the following:
Get-ChildItem | Get-Content | Where { $_ -notlike "HEADER_LINE_TEXT" } | Out-File -FilePath output_text.txt
I've tried to work with creating a variable in the Where block, $filename=$_.BaseName, and using it in the output, but this didn't work.
EDIT:
I ended up with the following:
Get-ChildItem -Path . |
Where-Object { $_.FullName -like "*records.txt"; $fname=$_FullName; } |
Get-Content |
Select-Object { ($fname + "|" + $_.Trim()) } |
Where { $_ -notlike "*HEADER_LINE_TEXT*" } |
Format-Table -HideTableHeaders |
Out-File -FilePath output_text.txt
This looks lengthy, and can probably be made shorter and clearer. Can someone help with cleaning this up a bit? I'll either post the solution, or vote for a cleaner solution, if one is posted. Thanks.

Answer 1

This looks like a case where it would make it more readable to not make it a one liner at cost of a little additional memory usage.
$InputFolder = "C:\example"
$OutputFile = "C:\example\output_text.txt"
$Files = Get-ChildItem $InputFolder | Where-Object { $_.FullName -like "*records.txt"}
Foreach ($File in $Files) {
$FilteredContent = Get-Content $File.FullName | Where-Object {$_ -notlike "*HEADER_LINE_TEXT*"}
$Output = $FilteredContent | Foreach-Object { "$($File.FullName)|$($_.Trim())" }
$Output | Out-File $OutputFile -Append
}
If you are going to go oneliner style for brevity, you could cut down on length by using position for parameters and using aliases.
Here are a couple other changes:
No need for the second semicolon in your first where block.
I think your variable wasn't working because you were missing the period between $_ and fullname.
Format-Table isn't needed because you already have the string you want to output
You can optimize a little by moving the second where earlier so that you don't trim() on lines you are just going to filter
Looks like you want to use foreach instead of select
Removed the + operator for string concatenation, instead using $() to evaluate inside parenthesis
gci . |
? { $_.FullName -like "*records.txt"; $fname=$_.FullName } |
% { gc $_.FullName } |
? { $_ -notlike "*HEADER_LINE_TEXT*" } |
% { "$fname|$($_.Trim())" } |
Out-File output_text.txt