file save completed

i have a file saved from an external program, i have to open and read, i need to know when the writing of that file is completed

previously i have been using a simple loop

Code:

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Do While FileLen(myfile) = 0
    DoEvents
    l = l + 1
    If l > 10000 Then MsgBox inv & " timed out": Exit Sub
Loop

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this has been working for several years, but on a new, faster machine, the code continues before the file saving has completed, i can obviously extend the loop or use a sleep, but i would like some way to actually test, when the code should continue

What type of file is this?

One possible idea:

1. Check to see if the file exists. If no, not created yet, else if yes, then go to step 2.

2. Get the length/size of the file. Wait 1-3 seconds, then check the size/length again. If it is not the same, file is still being built, wait again and re-check.

This is assuming that the file is not locked/unavailable while it is being created.

Quote:

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Originally Posted by westconn1

... i need to know when the writing of that file is completed

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You might be able to detect that via ReadDirectoryChangesW. This thread has some examples of that API and the accepted answer is actually an example you posted yourself.

This can be a solution: use a loop to see if the file is exclusively accessible
1. Open file with Lock Write
2. if it fails, repeat
3. if it does not fail, continue

Quote:

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You might be able to detect that via ReadDirectoryChangesW. This thread has some examples of that API and the accepted answer is actually an example you posted yourself.

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that is how i know the file is created, but the file exists even before writing is complete

Quote:

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2. Get the length/size of the file. Wait 1-3 seconds, then check the size/length again. If it is not the same, file is still being built, wait again and re-check.

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a 3 second wait should be more than adequate, but i was trying to avoid such a long delay unless required, many of the files are quite small, but this appears to have determined the cause of the problem, the files written on the new machine are bigger than previous systems, more than 10x the size

Quote:

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This can be a solution: use a loop to see if the file is exclusively accessible

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this would probably be the best solution for the current situation, but i was not keen to implement it

i will have to look at the file size and reconsider what utilities i should use, i just assumed that as windows 10 had a built in PDF printer driver i should just use it, but it looks like i should change to using the free one i was using previously
20Kb against >300Kb

Quote:

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Originally Posted by westconn1

that is how i know the file is created, but the file exists even before writing is complete

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According to my tests, applications (or perhaps the OS?) updates the last modified timestamp of a file when they are done writing and have closed the file. ReadDirectoryChangesW can detect when that happens if you specify FILE_NOTIFY_CHANGE_LAST_WRITE for the dwNotifyFilter argument. You could also specify FILE_NOTIFY_CHANGE_SIZE if the size of the file is guaranteed to change after it's modified.

hi,

here a function to check if the File is open, it will return True or False if open

Code:

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Public Function FileIsOpened(Filename As String) As Boolean
'prüft ob eine Datei (von einem anderen Programm) geöffnet ist

  Dim FNr As Integer
 
      If Not ExistFile(Filename) Then
        Exit Function
      End If
     
      On Error GoTo Fehler
      FNr = FreeFile
      Open Filename For Input Lock Read Write As #FNr
      Close #FNr
      Exit Function
       
Fehler:
      FileIsOpened = True
End Function


Public Function ExistFile(Filename As String, _
                          Optional Hidden As Boolean = False) _
                          As Boolean
'prüft die Existenz einer Datei

      If Hidden Then
        If Len(Dir(Filename, vbHidden)) > 0 Then
            ExistFile = True
        End If
      Else
        If Len(Dir(Filename)) > 0 Then
            ExistFile = True
        End If
      End If
End Function

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more or less what Gibra had in mind

Quote:

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ReadDirectoryChangesW can detect when that happens if you specify FILE_NOTIFY_CHANGE_LAST_WRITE for the dwNotifyFilter argument.

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i have been using FILE_ACTION_ADDED, which returns as soon as the file starts to write, i will have to look at changing to FILE_NOTIFY_CHANGE_LAST_WRITE, although i never had a problem in the past with a different pdf printer driver

Quote:

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here a function to check if the File is open, it will return True or False if open

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thanks for the function, i had been considering using something like that, but probably inline, rather than a separate function