Flush file buffers in on non-Windows platforms

Question

I have a logging component that uses a TByteStream for storing log contents and TFileStream for writing them to disk periodically. I need to ensure after writing to the file stream the file is updated immediately. So far I know only of FlushFileBuffers(), a Windows-specific function for that. How to do it on other supported by XE8 platforms?

Answer 1

The RTL has no function for flushing a file without closing it. You have to use platform-specific functions instead. On Windows, TFileStream uses the Win32 CreateFile() function to open/create a file, so you can use FlushFileBuffers() to flush it. On other platforms, TFileStream uses the POSIX open() function to open/create a file, so you can use the POSIX fsync() function to flush it.

Try this:

uses
  ...
  {$IFDEF MSWINDOWS}
  , Winapi.Windows
  {$ELSE}
  , Posix.Unistd
  {$ENDIF}
  ;

...

{$IFDEF MSWINDOWS}
FlushFileBuffers(MyFileStream.Handle);
{$ELSE}
fsync(Integer(MyFileStream.Handle));
{$ENDIF}