Returns the names of all devices that match a specified set of
    search criteria.

    Format

      SYS$DEVICE_SCAN  return_devnam ,retlen ,[search_devnam]

                       ,[itmlst] ,[contxt]

    C Prototype

      int sys$device_scan  (void *return_devnam, unsigned short

                           int *retlen, void *search_devnam, void

                           *itmlst, struct _generic_64 *contxt);