How can I check for files opened externally to my application ?

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I need to check if certain files have been opened externally to my application i.e by clicking on the file in windows explorer, and then the file opens in an application like notepad. But I can't to find a way to do this.

I have tried CFile::Open() with modeWrite, and CFile::Write(), and these do not fail if the file has been opened elsewhere.

Is there another way?

Posted 17-Nov-11 22:44pm

Jackie Lloyd

Updated 18-Nov-11 20:38pm

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Timberbird 18-Nov-11 4:52am

In which way are they opened? The file may be opened by an application exclusively, when write access to that file is blocked, or it may be just loaded in memory. For example, when you open a file with notepad, the latter loads file content into memory and then closes the file, so it can be viewed and edited by other programs.
I know this is quite obvious, just in case

Sergey Alexandrovich Kryukov 18-Nov-11 14:16pm

And also, a file which seems to be open may be not actually open. This is even more trivial that what you point out, but it needs to be checked up. Please see my solution.
--SA

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Sergey Alexandrovich Kryukov · Answer 1 · 2011-11-18T08:14:00

Your method is basically correct and should work, but it is destructive, you may want to use read instead or check stream size. The problem is that the file could be opened for non-exclusive access, which is not very typical but your method of detection won't detect it.

You can try this: http://read.pudn.com/downloads36/sourcecode/windows/111597/NtSystemInfo/NtSystemInfoTest/NtSystemInfoTest.cpp__.htm[^].

Also, it may happen that you think the file is opened but actually it is not. Please check it up. For example, many text editor do not keep a file handle open. They open a file, read it all into the application's memory and close immediately. File is read and not opened. You can check up what really happens using Sysinternals Process Explorer: see Sysinternals Suite: http://technet.microsoft.com/en-us/sysinternals/bb842062[^].

—SA