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I'm having the following problem:

Some text files (also some binary files) on my system are listed with the correct file size but when I open them, they appear empty.

>ls -la
-rw-rw-r--  1 user user   652 Mar 12 16:17 summary.txt
>cat summary.txt
>

If I display them in midnight commander I get a list of dots (......) and in vi a list of ^@. I'm not sure when it happened, but I guess since the last reboot.

System:

  • Linux ubuntu 3.8.0-37-generic #53~precise1-Ubuntu SMP Wed Feb 19 21:37:54 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
  • ext4

Is there a way to fix it?

Edit: I guess it most be somehow correlated with a system reboot. Can I somehow find out by looking at the log files what happened?

Thanks.

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    Could perhaps be a partially transferred/downloaded file? I know that at least several BitTorrent-clients creates files of the size it need for the file it's downloading, and then fill it with NUL - and if the download fails, NUL will be all the file contain. Don't think it's much you can do; you may have reserved space for the file, but you obviously haven't actually downloaded/transferred it. Commented Apr 8, 2014 at 10:54
  • Did you neglect to mention that your system crashed/lost power shortly after you wrote that file? Commented Apr 8, 2014 at 14:22
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    The file is corrupted. If the system crashed before you saved the file or just as the file was being written, this is to be expected. Otherwise do a memory test (reboot and choose “memory test” at the Grub prompt, let it run for at least one full pass). Commented Apr 8, 2014 at 22:59
  • @BaardKopperud - thanks for the hint, but the file was there the left time I logged into the system, now it's corrupted. I don't know exactly when the problem occurred. Commented Apr 9, 2014 at 14:36
  • @psusi - it's a virtual machine on our institutes server infrastructure. I saw that it was rebooted but I don't know if it crashed - definitely right after it was written. Commented Apr 9, 2014 at 14:37

1 Answer 1

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^@ is a representation of the null byte. You can get a better picture from xxd or od.

If the contents of the file has been lost, the fix would be to restore it from the version control system or backups.

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  • Thanks for your help. I just executed xxd and it seems that only null bytes are in the file: 0000000: 0000 0000 0000 0000 0000 0000 0000 0000 ................ 0000010: 0000 0000 0000 0000 0000 0000 0000 0000 ................ ----- Do you have any idea why that happened - or could I somehow find it out. It would be great if it was only a "one time" thing. Commented Apr 8, 2014 at 10:57
  • These things can happen e.g. if two processes write to the same file. Commented Apr 8, 2014 at 11:22
  • or if the file has been scrubbed with dd from /dev/zero Commented Jul 24, 2015 at 3:03

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