Check whether a given file is open or closed

[Little John]

Hi all,

I need to know, whether or not a particular file is opened by another process.
So I wrote the following small function, which works correctly as far as I can see (tested on Windows XP x86):

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Procedure.i FileIsClosed (fileName$)
   ; returns #False if the file does not exist, or if it is opened by another process;
   ;         #True otherwise
   ;
   ; Note: By passing zero as 3rd parameter for CreateFile_(),
   ;       we request *exclusive* access to the respective file.
   ;       This fails if the file is already open.
   ; <http://msdn.microsoft.com/en-us/library/aa363858%28v=vs.85%29.aspx>
   ; <http://msdn.microsoft.com/en-us/library/aa363874%28v=vs.85%29.aspx>
   Protected handle
   
   handle = CreateFile_(@fileName$, #GENERIC_READ, 0, #Null, #OPEN_EXISTING, #FILE_ATTRIBUTE_NORMAL, #Null)
   If handle = #INVALID_HANDLE_VALUE
      ProcedureReturn #False
   Else
      CloseHandle_(handle)
      ProcedureReturn #True
   EndIf   
EndProcedure


;-- Demo
Define TestFile$ = "Test.txt"
   
; Test #1
CreateFile(0, TestFile$)
Debug FileIsClosed(TestFile$)   ; should display 0
   
; Test #2
CloseFile(0)
Debug FileIsClosed(TestFile$)   ; should display 1

Any suggestions for improvement are welcome (if necessary).

Regards, Little John

[Marco2007]

Works fine!

[Little John]

Thanks for the feedback!

Regards, Little John

[A M S]

Work fine, that's useful

[Little John]

Thanks, I'm happy that it is useful for some of you.

Regards, Little John

[mskuma]

I think this is another (similar) solution
http://www.purebasic.fr/english/viewtop ... 13&t=44269

if you add a filesize() call you can determine existence also.

[Kiffi]

i know, the Thread is old, but what about this?

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Procedure.i FileIsClosed2 (fileName$)
  ProcedureReturn RenameFile(fileName$, fileName$)
EndProcedure

;-- Demo
Define TestFile$ = "Test.txt"
   
; Test #1
CreateFile(0, TestFile$)
Debug FileIsClosed2(TestFile$)   ; should display 0
   
; Test #2
CloseFile(0)
Debug FileIsClosed2(TestFile$)   ; should display 1

Greetings ... Kiffi

[SFSxOI]

that would work kiffi, until the application that was using the file crashed because it expected a file with a certain name and your procedure changed it to a different name.

[Kiffi]

... and your procedure changed it to a different name.

my procedure doesn't change the name.

Greetings ... Kiffi

[Little John]

Code: Select all

[...]
RenameFile(fileName$, fileName$)
[...]

Hehe ... great idea, thank you!
This should even work cross-platform.

Regards, Lttle John

[SFSxOI]

... and your procedure changed it to a different name.

my procedure doesn't change the name.

Greetings ... Kiffi

Oki dokee then, i guess the early morning and not enough coffee made me think it did, but I see now that it doesn't so I stand corrected. Thanks for posting it Kiffi

[IdeasVacuum]

That is a brilliant method Kiffi

[yrreti]

That is a brilliant method Kiffi

I second that! and it works great.

Thanks for sharing it.

[luis]

But what's the practical use for something like this ?

I'm asking because:

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if FileIsClosed ("file.txt") ; ok the file was not in use, some time ago, inside that proc
    ; but now ? 
endif

[yrreti]

Hi luis

As quoted above:

Code: Select all

I need to know, whether or not a particular file is opened by another process.

I had a problem with the following.
CopyFile in a loop, CopyDirectory, DeleteFile in a loop, and DeleteDirectory intermittently failing.
Result = 0 with no reason that I could see.
The above code could possibly be useful to help with troubleshooting why the failure was occurring.
(Possible file still in use.)
The weird thing is that since I added the check, I haven't seen any files still in use, but the intermittently failing stopped?
If it does occur again, then maybe I'll have more of an idea why these commands intermittently fail.
At least I'll know whether it is being caused by a file still in use or not.

In truth, I don't have much confidence in all four of those commands, and will possible post some code later if it does
occur again. It does seem to occur much more when copying files to and from a usb drive.
But again, not since adding that check? Weird isn't it.

P.S. I don't use it in that procedure. I just use that check line in the loop itself.
And in the case of CopyDirectory and DeleteDirectory, I use an ExamineDirectory loop method to check the files first.

(I have to leave for a bit, so can't reply for awhile)

yrreti