Function init_file_logging 

pub fn init_file_logging(
    path: &Path,
    debug: bool,
    scope: LogScope,
) -> Result<LogHandle, Error>

Open path as a non-blocking, ANSI-free file log. Global installs the process subscriber with try_init (a second call returns a handle and leaves the first subscriber in place); Scoped installs a thread-local default whose guard lives in the handle.