State of the file

#1 Have you tried checking the boolean return from the openForWrite(), openForRead(), or openForAppend() functions? I haven't had the situation you have, but they should probably return false if they can't open the file.

#2 That was the first I've thought about. I've tried to check openForRead() return value - it doesn't work with .jpg files, only with text files.

#3 Okey then..
May be somebody knows another way how to read the image file which is rewriting 25 times in minute?

#4 I think we need more information on what you need to have happen.

You have two applications trying to read and write to the same jpg file? Or is one file reading while the other one is writing?

Sounds like you're looking for a File Locking solution: http://en.wikipedia.org/wiki/File_locking

#5 If my memory serves me, each platform handles file locking differently. I think the 'LockFile' is the command you're looking for on Win32: http://msdn.microsoft.com/en-us/library/aa365202%28VS.85%29.aspx

Let me know if that works for you.

#6 I have two applications trying to access one .jpg file: one Win32 app writes (and rewrites) this file (about 9-25 times in minute) and Torque app reads it with the same frequency.

Thank you for the links, I read it. But I suppose that there it's another situation: functions LockFile and UnlockFile are using when you need to spread different regions within one file between two processes.

And in my situation I need to create the scheme where two processes can access one whole file. Consistently or in parallel. That's why I asked about checking the state of file, because as far as I understand it's the easiest way to create this scheme.