removing the last line of files using PowerShell command - powershell

Question

I would like to remove last line of few files using PowerShell command. I saw the following which does the same thing for the first line of the files. How can I modify that to remove the last line of the files?
gci *.txt | % { (gc $_) | ? { (1) -notcontains $_.ReadCount } | sc -path $_ }
I will appreciate it if I also get the explanation for the commands.
Cheers,
Siavoush
I haven't try anything yet.

Answer 1

Undoubtedly there are a number of solutions for this.
The below one should perform quite fast:
# create a List object to store the contents of the files
$list = [System.Collections.Generic.List[string]]::new()
Get-ChildItem -Path 'X:\Where\The\Files\Are' -Filter '*.txt' -File | ForEach-Object {
$list.AddRange([System.IO.File]::ReadAllLines($_.FullName))
$list.RemoveAt($list.Count - 1)
[System.IO.File]::WriteAllLines($_.FullName, $list)
$list.Clear()
}
Some explanation to the code above:
Because an array is static, adding or removing elements from it is a time and memory consuming thing to do because the entire array would need to be recreated in memory.
This is why I chose to wrk with the System.Collections.Generic.List object that is optimized for adding or removing elements.
Instead of using Get-Content, I chose to use .Net [System.IO.File]::ReadAllLines() method because that has less overhead and performs faster when reading an entire text file as array of lines
$list.RemoveAt($list.Count - 1) takes away the last element (line) from the array of lines
[System.IO.File]::WriteAllLines($_.FullName, $list) rewrites the lines (minus the last because we removed that) back to the file, overwriting the original content
finally, $list.Clear() empties the List object to get it ready for the next file