CTL_STREAM_t ctl_ms_open_file_relative(const char *base, const char *name, CTL_MS_MODE_t mode);
ctl_ms_open_file_relative opens the file name name relative to the directory base on the volume vol for reading or writing according to the parameter mode.
The effect of this is to open the file whose path is the concatenation of base, a directory separator, and name.
ctl_ms_open_file_relative returns a standard status code.
ctl_ms_open_file_relative is thread-safe.