BTW As can be seen from the documentation of 'safer-file-handles', I'm currently not satisfied at all about my implementation of the standard files (stdin, stdout and stderr). To quote the docs: BIG WARNING: I'm not satisfied with my current implementation of the standard handles (stdin, stdout and stderr)! Currently the standard handles are regional computations that return the regional file handles to the respected standard handles. There are 4 problems with this approach: * When the region terminates in which you call one of the standard handles the respected handle will be closed. I think this is not the expected behaviour. I would expect the standard handles to always remain open. * In System.IO the standard handles are pure values. My standard handles are monadic computations which makes them harder to work with. * There is no way to explicitly close a standard handle. Indeed, the whole purpose of lightweight monadic regions is to automatically close handles. However, when writing a Unix daemon for example, you need to be able to explicitly close the standard handles. * When reading 'man stdin' I'm confused if the standard handles are always open on program startup: quote 'man stdin': "...Under normal circumstances every Unix program has three streams opened for it when it starts up, one for input, one for output, and one for printing diagnostic or error messages..." "...The stdin, stdout, and stderr macros conform to C89 and this standard also stipulates that these three streams shall be open at program startup...." So now I'm confused... are these standard file handles always open on program startup or are there abnormal situations when they are closed? Maybe I just have to believe the documentation in System.IO which specifies that they are always initially open. If the standard handles are closed on startup using a handle returned from one of the standard handles will result in an exception! This would be a violation of my safety guarantees which is unacceptable. Does anyone have a solution or an rough idea how to solve it? Thanks, Bas