How to get info from a file when it is being used by another process?

[Vivek Narayanan]

I need this to update a progress bar.First a DOS service is run in the background , which writes a log file as it runs , the percentage info can be retrieved (there is no other way to get the percentage since this is a dos service) from the log file,but i get an error that the file is being used by another process(the DOS one).Its pointless to get info from the log file after the DOS process completes,as i need it to update a progress bar.Is there any solution to this? Thanks in Advance, Regards, Vivek

[Luc Pattyn]

Hi, two attempts: 1. I think the following code works even when the file is still open (and being written to) by another process: FileInfo fi=new FileInfo(filename); log("size="+fi.Length); 2. there is a solution if the other process has created the file with a share mode of read or readwrite, meaning it allows other processes to simultaneously read or readwrite the same file. If it did, you now can open the same file with FileMode.Read and FileShare.ReadWrite (i.e. "I want to read" and "I allow others to read and write"). And one remark: files get buffered, the buffer gets written to disk for sure only when one closes the file, or performs a flush operation (forcing the physical write). So for small files that dont flush, watching the size might not be a good progress indication. :)

Luc Pattyn

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[Dave Kreskowiak]

If the other process opens and writes to it's file, denying shared read, there's nothing you can do. If it allows shared read by other applications while it's writing, then you can open the file using:

Dim fs As New FileStream(_filepath_, FileMode.Open, FileAccess.Read, FileShare.ReadWrite)

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Dave Kreskowiak Microsoft MVP Visual Developer - Visual Basic
     2006, 2007

[Vivek Narayanan]

Thanks a lot for giving the idea of using the file's length. Vivek