batch identify files filled with zeros

Question

I have some folders which contain files (old temp P2P files saved wrongly apparently) which are just filled with zeros - any program/batch that can verify this ? I do not want to open each one with a hex editor

Answer 1

Though it runs the risk of false positives (like most CRC-based solutions), if PowerShell and a Java runtime environment are installed, it is possible to do approximately what you're asking for after downloading and extracting Jacksum.

Adapt the following command (the $jacksum_root_directory variable should have no trailing slash), then open PowerShell and run it to get a listing of files with a checksum of zero:

$jacksum_root_directory = 'drive:\path\to\directory'
$jacksum_jar_location = 'drive:\path\to\jacksum.jar'
java -jar $jacksum_jar_location -E dec -F "#CHECKSUM #FILENAME" -a crc64 -p -r -f $jacksum_root_directory | where { $_.StartsWith('0 ') } | foreach { get-item $_.Remove(0, 2) }

All zeroed-out and empty files will have a checksum of zero and should show in the listing, but it's possible that other, non-zeroed files may also have a zero checksum.

When you feel confident that the files listed can be safely deleted, they can be deleted automatically by replacing get-item with remove-item in the third line and re-running the command.