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Re^3: Rename unreliable on Windows

by Corion (Pope)
on Apr 04, 2012 at 11:22 UTC ( #963416=note: print w/replies, xml ) Need Help??

in reply to Re^2: Rename unreliable on Windows
in thread Rename unreliable on Windows

Maybe your virus scanner, maybe your backup application, maybe some other program. How would we know? think that the Sysinternals Tools have some program to show what programs hold a filehandle to a file, but I don't know.

If in doubt, I would talk to the system administrator for the machines in question.

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Re^4: Rename unreliable on Windows
by BrowserUk (Pope) on Apr 04, 2012 at 11:36 UTC
    think that the Sysinternals Tools have some program to show what programs hold a filehandle to a file,

    Yes. it is called handle.exe:

    C:\test>handle /? Handle v3.42 Copyright (C) 1997-2008 Mark Russinovich Sysinternals - usage: handle [[-a [-l]] [-u] | [-c <handle> [-y]] | [-s]] [-p <proces +s>|<pid>] [name] -a Dump all handle information. -l Just show pagefile-backed section handles. -c Closes the specified handle (interpreted as a hexadecimal nu +mber). You must specify the process by its PID. WARNING: Closing handles can cause application or system ins +tability. -y Don't prompt for close handle confirmation. -s Print count of each type of handle open. -u Show the owning user name when searching for handles. -p Dump handles belonging to process (partial name accepted). name Search for handles to objects with <name> (fragment accepted +). No arguments will dump all file references.

    With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority".
    In the absence of evidence, opinion is indistinguishable from prejudice.

    The start of some sanity?

Re^4: Rename unreliable on Windows
by elef (Friar) on Apr 04, 2012 at 11:44 UTC
    Thanks for that one!
    It was indeed my backup sw (WD anywhere backup). After disabling it, the test script runs to 10000 loops without errors.

    Followup question: why does this happen and is there an easy workaround (apart from disabling the backup sw)? I mean, I don't think I've had problems with deleting or modifying files, only renaming... And I don't think I've had issues outside of perl.

      This is how Windows as an operating system works. A file cannot be renamed while it is held open.

      A good backup software would request the backup privilege, and use the Windows Backup API. But even then, I'm not sure whether that would allow renaming a file while it is held open.

        elef should file a bug report / complaint against this backup software. It doesn't even have to use the Backup API. It can simply specify full sharing when opening the file. Simply add in the FILE_SHARE_DELETE bit (which also allows renaming) when opening the file (though, the Backup API likely provides other benefits).

        - tye        

      is there an easy workaround (apart from disabling the backup sw)?

      You could just keep trying to rename it...

      1 until rename $file1, $file2;

      Of course, if a file can genuinely never be renamed, this will cause your script to keep trying forever. Better to limit to a finite number of attempts at renaming.

      my $attempts; while (not rename $file1, $file2) { $attempts++; die "Could not rename file: $!" if $attempts > 7; sleep $attempts; }
      perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'

        You could also throw it into a queue of items "to deal with later".


        Thanks. Hoping that copying is more robust than renaming, I tried this:
        unlink "rename2.txt" or die "Can't delete file: $!"; copy ("rename1.txt", "rename2.txt") or die "Can't copy file: $!"; unlink "rename1.txt" or die "Can't delete file: $!";

        Errors became less frequent, but they're still there. I'll try your suggestion. I really like the idea of sleeping increasing intervals between attempts, too.

        Edit: did the test, and the solution works. I also added some reporting to see how many extra attempts are needed for the renamings to succeed. The second attempt was sufficient every time, and it was needed ~50 times before the script got to 10000 loops. I'll implement this with 5 attempts max (just in case the backup sw spends more time on larger files) and forget about the issue. Thanks.

      One of the solutions that you could use in conjunction with your script is Unlocker. Although the screen shots highlight the GUI, there's also a command line version. If you used that, your script should then be able to do the rename.

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