Question

In windows-based OS, assuming there are several different processes that may read and/or write a file freqently by using fopen/fopen_s/fwrite etc, in such case, do I need to consider data-races, or the OS can handle this automatically to ensure the file can only be opened/updated by a single process here at any given time whilst the rest fopen attemp will fail? And what about linux-based OS on this matter?

Answer 1

In Windows it depends on how you open the file.

see some possible values for uStyle parameter in case of OpenFile and dwShareMode in case of CreateFile.

Please note that OpenFile is kind of deprecated though so better use CreateFile.