i want to know how can i handle the file changing when the file is opened and i'm reading from it or make any operation on it.
Thanks

 

Read this tutorial about opening closing and reading from files This will help you http://www.cplusplus.com/doc/tutorial/files/

 

I suggest you read up on the concept of file locking. I haven't played with it in 10-15 years, so I don't remember much. But, IIRC, on UNIX, it was a "suggested" behavior that applications pay attention to file locks, but not required. Thus, the technique may or may not work for you. You didn't bother saying what OS you're using and these things can be very OS specific. A Windows programmer will have to speak up about Windows techniques, as I don't do Windows.

Another technique, if you have appropriate permissions, is to lock out other users from accessing the file by changing permissions. This may or may not be usable. Another trick is to rename the file while you're using it, then restore the old name. But you have to be careful about problems interrupting this process -- you have to be damn sure that your program always renames the file no matter what happens. And this exception handling type stuff isn't easy for beginning programmers.