remove last n characters of a file using batch

Question

I am having around 500 files in a folder. I am trying to concatenate a 4KB data(stored as a file) to all the files using batch " for /r %i in (*) do type 4KB file.txt >> %i

Now I want them to revert to orignal state. Few files are around 14GB . While trying to read , it takes a lot of time to open.

Please let me know how can I revert them back to original state.

Answer 1

First off, the difficulty of this task depends on the actual string you appended to the file.

Get-ChildItem [your path here] | ForEach-Object {
$TempVar = Get-Content $_ | Select-string -Exclude "Something that uniquely matches the string you want to remove"
$TempVar | Set-Content $_ }

Alternatively:

Get-ChildItem [your path here] | ForEach-Object {
$Length = ($_.ToCharArray) - 4096 #As you have 4KB, exactly?
$Newfile = ($_.ToCharArray() | Select -first $Length) -join ""
$NewFile | Set-content $_ 

}

Both attempts can be considered harmful as this may affect encoding, file structure etc - I just don't have enough time to check on that. If the files are of any importance, better back them up.