Question

I have a file stream opened in writeshare and append mode from multiple processes.
Does anybody know if a single unbuffered write operation can be considered atomic?

Or have i to develop a way to synchronize different writes to ensure my data are safe?

Answer 1

I found my way.

You can open a filestream using this constructor.

new FileStream(FileName,
    FileMode.Append,
    System.Security.AccessControl.FileSystemRights.AppendData,
    FileShare.ReadWrite, 4096, FileOptions.None);

using System.Security.AccessControl.FileSystemRights.AppendData parameter to open the stream, with FileMode.Append, the OS will try to write the buffer in atomic way.

If your write is bigger than buffer size, the operation will not be atomic, so you have to check your buffer size.