Yep, common use case for what I work on is BLAH_BLAH_THINGY_CONFIG_FILE in the environment being a path to some file that the library will open to read config,

Yep, common use case for what I work on is BLAH_BLAH_THINGY_CONFIG_FILE in the environment being a path to some file that the library will open to read config, instead of having the config itself in the environment (maybe it's a large unwieldy JSON thing). https://github.com/DataDog/dd-trace-cpp/blob/6dacac2922d08f455f10807f22aa0e98832d20d5/test/test_tracer_config.cpp#L91-L93 https://github.com/DataDog/dd-trace-cpp/blob/6dacac2922d08f4... It's not secure, but I'm not worried about bad actors monitoring /tmp in my test container so they can make my tests fail anyway. It would be nice if there were a "file paths that start with a null character belong to an ad hoc in memory file system specific to the process," or something. /tmp/tmp.eJaVgxtV0x/ is close enough. Open to code golfing suggestions on the code linked above.