Question

I have an application that runs in Citrix environment. The application can be run simultaneously by several users in different user sessions. In my application I am writing to a file which should be mutually exclusive across all the user sessions. I tried Mutex to avoid writing to a file from different user sessions but using Mutex failed as in some scenarios different user sessions could not detect whether the Mutex object was already created.

Could any one tell me which of the below approach is better to achieve mutual exclusion across all the user sessions:

1. Using Named pipes :
   If named pipe already exists then application will wait till the pipe gets closed by the application instance which had opened it. Otherwise create the named pipe to indicate the acquiring of lock.
2. Using a lock file:
   Create a normal file on disk to indicate the acquiring of lock and delete when unlock needs to be done.

Answer 1

You don’t need to use a lock file. You can use the built in file system sharing mechanism.

When you open the file by calling CreateFile() you determine the sharing access for subsequent attempts to open the file with the dwShareMode parameter. For example, set this to 0 and no other process will be able to open the file.