external table - cheeyoung/sqlplus-public GitHub Wiki

...
ORACLE_LOADER
...
ACCESS PARAMETERS
( ...
  PREPROCESSOR directory_spec:file_spec
  ...
)

15.3.7 PREPROCESSOR

The preprocessor program converts the data to a record format supported by the access driver and then writes the converted record data to standard output (stdout), which the access driver reads as input.

15.3.8 PREPROCESSOR_TIMEOUT