title: What is the C++ iostream to creating a file with O_EXCL?
body: <p>I want to create an output file in a threadsafe manner, and only if it does not exist. I want to use the file system for synchronization. With <code>open()</code> I would use the flags <code>O_RWRONLY|O_CREAT|O_EXCL</code>. Is there a way to do this in C++17 using the <code>iostream</code> or <code>fstream</code> ?</p>