routine dir_mkfile ( directory: file_t; RPT flags: int; mode: mode_t; out newnode: mach_port_send_t);
Create a new file without linking it into the filesystem. You still must have
write permission on the specified directory, even though it will not actually
be written. Return in
newnode a port to the file.
flags are the same as
dir lookup, but
O_TRUNC are assumed even
if not specified.