Hello, There is something I don't get with mapped_file from the IOStreams library. Here is an example: // Code snippet #include <iostream> #include <boost/iostreams/device/mapped_file.hpp> #include <boost/iostreams/stream.hpp> using namespace boost::iostreams; int main(int argc, char **argv) { if (argc != 2) return 1; try { stream <mapped_file_sink> out; mapped_file_params p(argv[1]); p.new_file_size = 1024 * sizeof (char); out.open(mapped_file_sink(p)); } catch (const std::exception &e) { std::cout << e.what() << std::endl; return 2; } return 0; } // Code snippet When compiled, the execution goes like: c:\>test_shmem somefile c:\>test_shmem somefile failed setting file size: The handle is invalid. I tried without the new_file_size, I tried with a mapped_file... Is there something I don't get? Why are we not able to open a file that already exist? Thanks for your help. JD